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The TMEM16A (ANO1) Cl- channel is activated by Ca2+ in a voltage-dependent manner. It is broadly expressed and was shown to be also present in renal proximal tubule (RPT). KCNQ1 is an entirely different K+ selective channel that forms the cardiac IKS potassium channel together with its ß-subunit KCNE1. Surprisingly, KCNE1 has been claimed to interact with TMEM16A, and to be required for activation of TMEM16A in mouse RPT. Interaction with KCNE1 was reported to switch TMEM16A from a Ca22+-dependent to a voltage-dependent ion channel. Here we demonstrate that KCNE1 is not expressed in mouse RPT. TMEM16A expressed in RPT is activated by angiotensin II and ATP in a KCNE1-independent manner. Coexpression of KCNE1 does not change TMEM16A to a voltage gated Cl- channel and Ca2+-dependent regulation of TMEM16A is fully maintained in the presence of KCNE1. While overexpressed KCNE1 slightly affects Ca2+-dependent regulation of TMEM16A, the data provide no evidence for KCNE1 being an auxiliary functional subunit for TMEM16A. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, we investigated the long-term effects of COVID-19 on the kidneys using mice infected with a similar coronavirus. We examined markers in the kidneys related to inflammation, scarring, and damage. We identified that certain markers linked to scarring and inflammation remained high in the mice's kidneys even after the initial infection, suggesting kidney damage. However, other markers did not show significant changes (e.g., mRNA levels of TNFR-1, WFDC2, B2M, likely due to factors influencing their half-life and translation rate). To explore treatments, we tested a drug called SPIKENET (SPK), a 15-amino acid synthetic peptide, that blocks the virus from attaching and entering cells. When we gave SPK to the mice, it decreased the certain marker levels in their kidneys in both the group of mice that were treated shortly after infection and the group that received treatment a year after the infection. These findings indicate that kidney scarring may begin early in COVID-19 and that targeting specific markers and proteins with treatments like SPK could help prevent kidney damage in both early and long-term COVID-19 cases. Signs and symptoms involving multiple organ systems which persist for weeks or months to years after the initial SARS-CoV-2 infection (also known as PASC or long COVID) are common complications of individuals with COVID-19. We recently reported pathophysiological changes in various organs post-acute infection of mice with mouse hepatitis virus-1 (MHV-1, a coronavirus) (7 days) and after long-term post-infection (12 months). One of the organs severely affected in this animal model is the kidney, which correlated well with human studies showing kidney injury post-SARS-CoV-2 infection. Our long-term post-infection pathological observation in kidneys includes the development of edema and inflammation of the renal parenchyma, severe acute tubular necrosis, and infiltration of macrophages and lymphocytes, in addition to changes observed in both acute and long-term post-infection, which include tubular epithelial cell degenerative changes, peritubular vessel congestion, proximal and distal tubular necrosis, hemorrhage in the interstitial tissue, and vacuolation of renal tubules. These findings strongly suggest the possible development of renal fibrosis, in particular in the long-term post-infection. Accordingly, we investigated whether the signaling system that is known to initiate the above-mentioned changes in kidneys in other conditions is also activated in long-term post-MHV-1 infection. We found increased TGF-β1, FGF23, NGAL, IL-18, HIF1-α, TLR2, YKL-40, and B2M mRNA levels in long-term post-MHV-1 infection, but not EGFR, TNFR1, BCL3, and WFDC2. However, only neutrophil gelatinase-associated lipocalin (NGAL) increased in acute infection (7 days). Immunoblot studies showed an elevation in protein levels of HIF1-α, TLR-2, and EGFR in long-term post-MHV-1 infection, while KIM-1 and MMP-7 protein levels are increased in acute infection. Treatment with a synthetic peptide, SPIKENET (SPK), which inhibits spike protein binding, reduced NGAL mRNA in acute infection, and decreased TGF-β1, BCL3 mRNA, EGFR, HIF1-α, and TLR-2 protein levels long-term post-MHV-1 infection. These findings suggest that fibrotic events may initiate early in SARS-CoV-2 infection, leading to pronounced kidney fibrosis in long COVID. Targeting these factors therapeutically may prevent acute or long-COVID-associated kidney complications. [ABSTRACT FROM AUTHOR]

AIM: To observe the changes of renin-angiotensin system (RAS), including the angiotensin-converting enzyme (ACE)-angiotensin II (Ang II)-Ang II type 1 receptor (AT1) classic axis and the ACE2-Ang (1-7)-Mas receptor (MasR) new axis, in the proximal tubule of diabetic mice, and their effects on kidney structure and function in the early stage of diabetic kidney disease (DKD). METHODS: Male spontaneous type 1 diabetic Akita mice and type 2 diabetic db/db mice were used, and male nondiabetic mice with C57BL/6 background and db/m nondiabetic mice with C57BLKS/J background were used as controls, respectively. At 16 weeks of age, the mice were sacrificed to measure corresponding physiological parameters. Urine was collected, and the levels of Ang II and Ang (1-7) were measured by ELISA. Kidney tissue was collected for pathological section staining to evaluate morphological changes in kidney structure. Immunohistochemistry was used to observe the localization and changes of angiotensinogen (Agt), ACE, ACE2 and MasR in kidney tissues. Western blot and RT-qPCR were used to measure the changes of these proteins and mRNA in isolated proximal renal tubules. RESULTS: The glomerular filtration rate, urinary albumin/creatinine ratio, proximal tubular cell volume, tubular luminal dilation, tubular hypertrophy and tubular injury score were increased in type 1 and type 2 diabetic mice (P<0. 05). The Agt and ACE2 expression levels were increased in proximal tubules of diabetic mice compared with control mice (P<0. 01), while the ACE and MasR expression levels in proximal tubules of diabetic mice were lower than those in control mice (P<0. 01). Urinary Ang II excretion was increased, while urinary Ang (1-7) level was decreased in these 2 types of diabetic mice compared with control mice (P<0. 01). CONCLUSION: The proximal tubular RAS in spontaneously diabetic mice is activated in the early stage of DKD. Activation of RAS leads to glomerular hyperfiltration, glomerular and tubular hypertrophy, and proximal tubular injury in the early stage of DKD. [ABSTRACT FROM AUTHOR]

SGLT (sodium-glucose cotransporter) 2 inhibitors enhance urinary glucose excretion by inhibiting glucose reabsorption in the proximal renal tubule. In Japan, it has been administered for diabetes since 2014. Recently, the indication has been expanded to include chronic heart failure and chronic renal failure, and the number of prescriptions will be expected to increase in the future. Although urinary tract and genital tract infections are listed as adverse events of SGLT2 inhibitors, the discontinuation criteria of the drug and optimal follow-up methods are not still clear. Consequently, these are unmet needs within this field. We herein report a case of fungal infection which occurred while the patient was taking a SGLT2 inhibitor. A 77-year-old male with type 2 diabetes mellitus was admitted to our hospital in August 20XX complaining of fever and immobility. On the basis of further examination, he was diagnosed with acute pyelonephritis and underwent antibacterial therapy. Ipragliflozin, an SGLT2 inhibitor, was changed to insulin on admission day. Since Candida glabrata was detected in urine and blood cultures on the fifth day, antifungal therapy was added as antibacterial management. He was introduced to the ophthalmology department due to fungemia, and was diagnosed with fungal endophthalmitis. Due to an improvement of intraocular findings, the patient was discharged on the 42nd day after admission. Because urinary tract infections and genital infections such as necrotizing fasciitis (Fournier's gangrene) have been reported to be associated with SGLT2 inhibitors, urologists need to keep in mind the urological risks of SGLT2 inhibitors. [ABSTRACT FROM AUTHOR]

When sodium-glucose cotransporter-2 (SGLT2) inhibitors were first introduced a decade ago, no one expected them to have substantial effects beyond their known glucose-lowering effects, until the emergence of evidence of their robust renal and cardiovascular benefits showing that they could attenuate progression of kidney disease, irrespective of diabetes, as well as prevent the development of acute kidney injury. Still, the precise and elaborate mechanisms underlying the major organ protection of SGLT2 inhibitors remain unclear. SGLT2 inhibitors inhibit the reabsorption of sodium and glucose in the proximal tubule of the kidney and then recovers tubuloglomerular feedback, whereby SGLT2 inhibitors reduce glomerular hyperfiltration. This simple demonstration of their beneficial effects has perplexed experts in seeking more plausible and as yet undisclosed explanations for the whole effects of SGLT2 inhibitors, including metabolism reprogramming and the modulation of hypoxia, inflammation, and oxidative stress. Given that the renal benefits of SGLT2 inhibitors in patients with kidney disease but without diabetes were comparable to those seen in patients with diabetes, it may be reasonable to keep the emphasis on their hemodynamic actions. In this context, the aim of the present review is to provide a comprehensive overview of renal hemodynamics in individuals with diabetes who are treated with SGLT2 inhibitors, with a focus on natriuresis associated with the regulation of tubuloglomerular feedback and potential aquaresis. Throughout the discussion of alterations in renal sodium and water transports, particular attention will be given to the potential enhancement of adenosine and its receptors following SGLT2 inhibition. [ABSTRACT FROM AUTHOR]

Patients with end-stage kidney disease (ESKD) suffer from high levels of protein-bound uremic toxins (PBUTs) that contribute to various comorbidities. Conventional dialysis methods are ineffective in removing these PBUTs. A potential solution could be offered by a bioartificial kidney (BAK) composed of porous membranes covered by proximal tubule epithelial cells (PTECs) that actively secrete PBUTs. However, BAK development is currently being hampered by a lack of knowledge regarding the cytocompatibility of the dialysis fluid (DF) that comes in contact with the PTECs. Here, we conducted a comprehensive functional assessment of the DF on human conditionally immortalized PTECs (ciPTECs) cultured as monolayers in well plates, on Transwell® inserts, or on hollow fiber membranes (HFMs) that form functional units of a BAK. We evaluated cell viability markers, monolayer integrity, and PBUT clearance. Our results show that exposure to DF did not affect ciPTECs' viability, membrane integrity, or function. Seven anionic PBUTs were efficiently cleared from the perfusion fluid containing a PBUTs cocktail or uremic plasma, an effect which was enhanced in the presence of albumin. Overall, our findings support that the DF is cytocompatible and does not compromise ciPTECs function, paving the way for further advancements in BAK development and its potential clinical application. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model for the steady laminar, incompressible and Newtonian fluid flow in a proximal renal tubule is presented. In this, the tubule is considered as a tapered tube with double constriction and permeable boundary. The impact of the fluid reabsorption across the tubule wall is assumed as the occurrence of exponentially decreasing flow at each cross-section. The present model is formulated through the Navier–Stokes equations, under the appropriate boundary conditions. A regular perturbation technique is used to obtain the approximate solutions. This study brings out the significant impacts of reabsorption coefficient (α) and tapered angle (ϕ) on the flow variables such as velocities, the drop in pressure, and wall shear stress are discussed through graphs. The streamlines are also plotted to understand the influence of the reabsorption and tapering phenomena on the flow. [ABSTRACT FROM AUTHOR]

Transcriptomic analysis is a powerful method in the utilization of New Approach Methods (NAMs) for identifying mechanisms of toxicity and application to hazard characterization. With this regard, mapping toxicological events to time of exposure would be helpful to characterize early events. Here, we investigated time-dependent changes in gene expression levels in iPSC-derived renal proximal tubular-like cells (PTL) treated with five diverse compounds using TempO-Seq transcriptomics with the aims to evaluate the application of PTL for toxicity prediction and to report on temporal effects for the activation of cellular stress response pathways. PTL were treated with either 50 μM amiodarone, 10 μM sodium arsenate, 5 nM rotenone, or 300 nM tunicamycin over a temporal time course between 1 and 24 h. The TGFβ-type I receptor kinase inhibitor GW788388 (1 μM) was used as a negative control. Pathway analysis revealed the induction of key stress-response pathways, including Nrf2 oxidative stress response, unfolding protein response, and metal stress response. Early response genes per pathway were identified much earlier than 24 h and included HMOX1, ATF3, DDIT3, and several MT1 isotypes. GW788388 did not induce any genes within the stress response pathways above, but showed deregulation of genes involved in TGFβ inhibition, including downregulation of CYP24A1 and SERPINE1 and upregulation of WT1. This study highlights the application of iPSC-derived renal cells for prediction of cellular toxicity and sheds new light on the temporal and early effects of key genes that are involved in cellular stress response pathways. [ABSTRACT FROM AUTHOR]

SGLT2 (sodium-glucose cotransporter 2) inhibitors interfere with the reabsorption of glucose and sodium in the early proximal renal tubule, but the magnitude and duration of any ensuing natriuretic or diuretic effect are the result of an interplay between the degree of upregulation of SGLT2 and sodium-hydrogen exchanger 3, the extent to which downstream compensatory tubular mechanisms are activated, and (potentially) the volume set point in individual patients. A comprehensive review and synthesis of available studies reveals several renal response patterns with substantial variation across studies and clinical settings. However, the common observation is an absence of a large acute or chronic diuresis or natriuresis with these agents, either when given alone or combined with other diuretics. This limited response results from the fact that renal compensation to these drugs is rapid and nearly complete within a few days or weeks, preventing progressive volume losses. Nevertheless, the finding that fractional excretion of glucose and lithium (the latter being a marker of proximal sodium reabsorption) persists during long-term treatment with SGLT2 inhibitors indicates that pharmacological tolerance to the effects of these drugs at the level of the proximal tubule does not meaningfully occur. This persistent proximal tubular effect of SGLT2 inhibitors can be hypothesized to produce a durable improvement in the internal set point for volume homeostasis, which may become clinically important during times of fluid expansion. However, it is difficult to know whether a treatment-related change in the volume set point actually occurs or contributes to the effect of these drugs to reduce the risk of major heart failure events. SGLT2 inhibitors exert cardioprotective effects by a direct effect on cardiomyocytes that is independent of the presence of or binding to SGLT2 or the actions of these drugs on the proximal renal tubule. Nevertheless, changes in the volume set point mediated by SGLT2 inhibitors might potentially act cooperatively with the direct favorable molecular and cellular effects of these drugs on cardiomyocytes to mediate their benefits on the development and clinical course of heart failure. [ABSTRACT FROM AUTHOR]

Copper is an essential trace element for human health and, at the same time, a major industrial metal widely used both in its elemental form and in compounds. We conducted a dose-dependent assessment of the response of outbred albino male rats to subchronic low-dose exposure to copper oxide nanoparticles administered intraperitoneally at cumulative doses of 18 and 36 mg/kg during 6 weeks to exposure groups 1 and 2, respectively. We observed disorders at different levels of organization of the body in the exposed animals, from molecular to organismal. The observed decrease in the activity of succinate dehydrogenase in nucleated blood cells gave evidence of impaired bioenergetics processes. In view of the results of the metabolomics analysis, we assume mitochondrial damage and contribution of apoptotic processes to the pathology induced by copper poisoning. We also assume neurodegenerative effects based on the assessed morphological parameters of the nervous system, results of behavioral tests, and a decreased level of expression of genes encoding NMDA receptor subunits in the hippocampus. The hepatotoxic effect noted by a number of metabolomics-based, biochemical, and cytological indicators was manifested by the impaired protein-synthesizing function of the liver and enhanced degenerative processes in its cells. We also observed a nephrotoxic effect of nanosized copper oxide with a predominant lesion of proximal kidney tubules. At the same time, both doses tested demonstrated such positive health effects as a statistically significant decrease in the activity of alkaline phosphatase and the nucleated blood cell DNA fragmentation factor. Judging by the changes observed, the cumulative dose of copper oxide nanoparticles of 18 mg/kg body weight administered intraperitoneally approximates the threshold one for rats. The established markers of health impairments may serve as a starting point in the development of techniques of early diagnosis of copper poisoning. [ABSTRACT FROM AUTHOR]

Modelling proximal tubule physiology and pharmacology is essential to understand tubular biology and guide drug discovery. To date, multiple models have been developed; however, their relevance to human disease has yet to be evaluated. Here, we report a 3D vascularized proximal tubule-on-a-multiplexed chip (3DvasPT-MC) device composed of co-localized cylindrical conduits lined with confluent epithelium and endothelium, embedded within a permeable matrix, and independently addressed by a closed-loop perfusion system. Each multiplexed chip contains six 3DvasPT models. We performed RNA-seq and compared the transcriptomic profile of proximal tubule epithelial cells (PTECs) and human glomerular endothelial cells (HGECs) seeded in our 3D vasPT-MCs and on 2D transwell controls with and without a gelatin–fibrin coating. Our results reveal that the transcriptional profile of PTECs is highly dependent on both the matrix and flow, while HGECs exhibit greater phenotypic plasticity and are affected by the matrix, PTECs, and flow. PTECs grown on non-coated Transwells display an enrichment of inflammatory markers, including TNF-a, IL-6, and CXCL6, resembling damaged tubules. However, this inflammatory response is not observed for 3D proximal tubules, which exhibit expression of kidney signature genes, including drug and solute transporters, akin to native tubular tissue. Likewise, the transcriptome of HGEC vessels resembled that of sc-RNAseq from glomerular endothelium when seeded on this matrix and subjected to flow. Our 3D vascularized tubule on chip model has utility for both renal physiology and pharmacology. [ABSTRACT FROM AUTHOR]

High-throughput, rapid and non-invasive readouts of tissue health in microfluidic kidney co-culture models would expand their capabilities for pre-clinical assessment of drug-induced nephrotoxicity. Here, we demonstrate a technique for monitoring steady state oxygen levels in PREDICT96-O2, a high-throughput organ-on-chip platform with integrated optical-based oxygen sensors, for evaluation of drug-induced nephrotoxicity in a human microfluidic co-culture model of the kidney proximal tubule (PT). Oxygen consumption measurements in PREDICT96-O2 detected dose and time-dependent injury responses of human PT cells to cisplatin, a drug with known toxic effects in the PT. The injury concentration threshold of cisplatin decreased exponentially from 19.8 μM after 1 day to 2.3 μM following a clinically relevant exposure duration of 5 days. Additionally, oxygen consumption measurements resulted in a more robust and expected dose-dependent injury response over multiple days of cisplatin exposure compared to colorimetric-based cytotoxicity readouts. The results of this study demonstrate the utility of steady state oxygen measurements as a rapid, non-invasive, and kinetic readout of drug-induced injury in high-throughput microfluidic kidney co-culture models. [ABSTRACT FROM AUTHOR]

Introduction: Dotinurad is a newer urate-lowering agent that selectively inhibits urate transporter 1 in the renal proximal tubule and increases urinary urate excretion. Currently, little is known about the clinical efficacies of dotinurad in patients with hyperuricemia and hypertension. The aim of this study was to assess the clinical effects of a selective urate reabsorption inhibitor dotinurad on serum uric acid (SUA) levels and relevant vascular markers in patients with hyperuricemia and treated hypertension. Methods: This investigator-initiated, multicenter, prospective, single-arm, open-label, exploratory clinical trial in Japan enrolled patients with hyperuricemia and treated hypertension who received a 24-week dotinurad therapy (a starting dose at 0.5 mg once daily and up-titrated to 2 mg once daily). The primary endpoint was a percentage change in the SUA level from baseline to week 24. The secondary endpoints were cardiovascular and metabolic measurements, including changes in the cardio-ankle vascular index (CAVI) and derivatives of reactive oxygen metabolites (d-ROMs) concentration at week 24. Results: Fifty patients (mean age 70.5 ± 11.0 years, with 76.0% being men, and mean SUA level 8.5 ± 1.2 mg/dL) were included in the analysis. The percentage change from baseline in the SUA level at week 24 was − 35.8% (95% confidence interval [CI] − 39.7% to − 32.0%, P < 0.001), with approximately three quarters of patients achieving an SUA level of ≤ 6.0 mg/dL at week 24. The proportional changes from baseline in the geometric mean of CAVI and d-ROMs at week 24 were 0.96 (95% CI 0.92 to 1.00, P = 0.044) and 0.96 (95% CI 0.92 to 1.00, P = 0.044), respectively. Conclusion: In addition to meaningful SUA-lowering effects, 24 weeks of dotinurad therapy may favorably affect arterial stiffness and oxidative stress markers, suggesting off-target vascular protection of dotinurad. Further research is expected to verify our findings and elucidate the entire off-target effects of dotinurad. Trial registration jRCTs021210013, registration date June 24, 2021 [ABSTRACT FROM AUTHOR]

Differentiation is critical for cell fate decisions, but the signals involved remain unclear. The kidney proximal tubule (PT) cells reabsorb disulphide-rich proteins through endocytosis, generating cystine via lysosomal proteolysis. Here we report that defective cystine mobilization from lysosomes through cystinosin (CTNS), which is mutated in cystinosis, diverts PT cells towards growth and proliferation, disrupting their functions. Mechanistically, cystine storage stimulates Ragulator-Rag GTPase-dependent recruitment of mechanistic target of rapamycin complex 1 (mTORC1) and its constitutive activation. Re-introduction of CTNS restores nutrient-dependent regulation of mTORC1 in knockout cells, whereas cell-permeant analogues of L-cystine, accumulating within lysosomes, render wild-type cells resistant to nutrient withdrawal. Therapeutic mTORC1 inhibition corrects lysosome and differentiation downstream of cystine storage, and phenotypes in preclinical models of cystinosis. Thus, cystine serves as a lysosomal signal that tailors mTORC1 and metabolism to direct epithelial cell fate decisions. These results identify mechanisms and therapeutic targets for dysregulated homeostasis in cystinosis. Cystinosis is a lysosomal storage disease that affects the kidney. Here, the authors use preclinical models and advanced profiling techniques to discover the mechanism by which defective cystine mobilization from lysosomes disrupts kidney cell function, offering insights into potential therapies. [ABSTRACT FROM AUTHOR]

The kidney is critical in the human body's excretion of drugs and their metabolites. Renal transporters participate in actively secreting substances from the proximal tubular cells and reabsorbing them in the distal renal tubules. They can affect the clearance rates (CLr) of drugs and their metabolites, eventually influence the clinical efficiency and side effects of drugs, and may produce drug–drug interactions (DDIs) of clinical significance. Renal transporters and renal transporter-mediated DDIs have also been studied by many researchers. In this article, the main types of in vitro research models used for the study of renal transporter-mediated DDIs are membrane-based assays, cell-based assays, and the renal slice uptake model. In vivo research models include animal experiments, gene knockout animal models, positron emission tomography (PET) technology, and studies on human beings. In addition, in vitro–in vivo extrapolation (IVIVE), ex vivo kidney perfusion (EVKP) models, and, more recently, biomarker methods and in silico models are included. This article reviews the traditional research methods of renal transporter-mediated DDIs, updates the recent progress in the development of the methods, and then classifies and summarizes the advantages and disadvantages of each method. Through the sorting work conducted in this paper, it will be convenient for researchers at different learning stages to choose the best method for their own research based on their own subject's situation when they are going to study DDIs mediated by renal transporters. [ABSTRACT FROM AUTHOR]

Mitochondrial dysfunction is pivotal in drug-induced acute kidney injury (AKI), but the underlying mechanisms remain largely unknown. Transport proteins embedded in the mitochondrial inner membrane form a significant class of potential drug off-targets. So far, most transporter-drug interactions have been reported for the mitochondrial ADP/ATP carrier (AAC). Since it remains unknown to what extent AAC contributes to drug-induced mitochondrial dysfunction in AKI, we here aimed to better understand the functional role of AAC in the energy metabolism of human renal proximal tubular cells. To this end, CRISPR/Cas9 technology was applied to generate AAC3−/− human conditionally immortalized renal proximal tubule epithelial cells. This AAC3−/− cell model was characterized with respect to mitochondrial function and morphology. To explore whether this model could provide first insights into (mitochondrial) adverse drug effects with suspicion towards AAC-mediated mechanisms, wild-type and knockout cells were exposed to established AAC inhibitors, after which cellular metabolic activity and mitochondrial respiratory capacity were measured. Two AAC3−/− clones showed a significant reduction in ADP import and ATP export rates and mitochondrial mass, without influencing overall morphology. AAC3−/− clones exhibited reduced ATP production, oxygen consumption rates and metabolic spare capacity was particularly affected, mainly in conditions with galactose as carbon source. Chemical AAC inhibition was stronger compared to genetic inhibition in AAC3−/−, suggesting functional compensation by remaining AAC isoforms in our knockout model. In conclusion, our results indicate that ciPTEC-OAT1 cells have a predominantly oxidative phenotype that was not additionally activated by switching energy source. Genetic inhibition of AAC3 particularly impacted mitochondrial spare capacity, without affecting mitochondrial morphology, suggesting an important role for AAC in maintaining the metabolic spare respiration. [ABSTRACT FROM AUTHOR]

Clostridium perfringens (C. perfringens) is widely distributed in soil and in the human and animal intestines and is the causative agent of gas gangrene and enterotoxaemia in humans and animals. When C. perfringens infect domestic animals, it causes diarrhea, multiple-organ bleeding, and nervous system disorders by releasing toxins. In this study, to identify the etiology and pathology of the acute cause of death in a Suffolk ram, 12 different tissues including heart, liver, spleen, lung, kidney, testis, mesenteric lymph nodes, cecum, colon, middle colon, ileum, and rectum from the dead sheep were collected and pathogen isolation was performed by using identification medium of C. perfringens and 5% defibrated sheep blood agar medium. 16S rRNA gene of the isolated strain was amplified and sequenced. Phylogenetic trees of isolates were constructed based on 16S rRNA sequences and genetic evolution was analyzed. The specific primers for toxin typing of cpa, cpb, etx, itx, and cpe were used to identify the isolated strains. The pathological changes of tissues and organs were observed by histopathology. The results showed that 12 C. perfringens type D strains were isolated from different tissues. Histopathological observation showed endocardial hemorrhage and muscle fiber degeneration and necrosis, liver tissue capsule hemorrhage and liver sinusoids dilatation and congestion, white pulp atrophy and lymphocytopenia in spleen, renal glomerular necrosis with interstitial inflammatory cell infiltration and fibrous tissue hyperplasia in kidney, exfoliation of intestinal villous epithelial cells from the ileum tissue with inflammatory cell infiltration and vasodilation and congestion, mucosal layer extensive necrosis and hemorrhage of the colon tissue with necrosis and exfoliation of epithelial cell and inflammatory cell infiltration and vascular dilation and congestion, inflammatory cell infiltration and vasodilatation congestion in cecal tissue, spermatogenic tubule atrophy in testis tissue and necrosis and reduction of spermatogenic cells serous with exudation of serous substances and other pathological changes. The results showed that the pathogenic bacteria that caused the death of the flock was C. perfringens type D, which was found in all visceral tissues. This study also proved that C. perfringens could invade the reproductive organs of rams and cause pathological damage. [ABSTRACT FROM AUTHOR]

Steatosis, or ectopic lipid deposition, is the fundamental pathophysiology of non-alcoholic steatohepatitis and chronic kidney disease. Steatosis in the renal tubule causes endoplasmic reticulum (ER) stress, leading to kidney injury. Thus, ER stress could be a therapeutic target in steatonephropathy. Five-aminolevulinic acid (5-ALA) is a natural product that induces heme oxygenase (HO)-1, which acts as an antioxidant. This study aimed to investigate the therapeutic potential of 5-ALA in lipotoxicity-induced ER stress in human primary renal proximal tubule epithelial cells. Cells were stimulated with palmitic acid (PA) to induce ER stress. Cellular apoptotic signals and expression of genes involved in the ER stress cascade and heme biosynthesis pathway were analyzed. The expression of glucose-regulated protein 78 (GRP78), a master regulator of ER stress, increased significantly, followed by increased cellular apoptosis. Administration of 5-ALA induced a remarkable increase in HO-1 expression, thus ameliorating PA-induced GRP78 expression and apoptotic signals. BTB and CNC homology 1 (BACH1), a transcriptional repressor of HO-1, was significantly downregulated by 5-ALA treatment. HO-1 induction attenuates PA-induced renal tubular injury by suppressing ER stress. This study demonstrates the therapeutic potential of 5-ALA against lipotoxicity through redox pathway. [ABSTRACT FROM AUTHOR]

Loss of a kidney results in compensatory growth of the remaining kidney, a phenomenon of considerable clinical importance. However, the mechanisms involved are largely unknown. Here, we use a multi-omic approach in a unilateral nephrectomy model in male mice to identify signaling processes associated with renal compensatory hypertrophy, demonstrating that the lipid-activated transcription factor peroxisome proliferator-activated receptor alpha (PPARα) is an important determinant of proximal tubule cell size and is a likely mediator of compensatory proximal tubule hypertrophy. The authors used a multi-omic approach in a mouse unilateral nephrectomy model to identify signaling processes associated with compensatory hypertrophy of the renal proximal tubule. The results indicate that PPARα is an important determinant of proximal tubule cell size and is a likely mediator of compensatory proximal tubule hypertrophy. [ABSTRACT FROM AUTHOR]

PSMA theranostics: review of the current status of PSMA-targeted imaging and radioligand therapy. Astatine-211 for PSMA-targeted -radiation therapy of micrometastatic prostate cancer: a sustainable approach towards precision oncology Biodistribution and dosimetry for combined [177Lu]Lu-PSMA-I&T/[225Ac]Ac-PSMA-I&T therapy using multi-isotope quantitative SPECT imaging. Several peptidomimetic inhibitors of PSMA (such as PSMA-11, PSMA-617, PSMA I&T, MIP-1095, DCFPyL, etc.) typically having a Glu-ureido component that serves as the PSMA binding motif have been designed and translated for routine clinical use [[4], [7]-[9]]. [Extracted from the article]

Organic anion transporter 3 (OAT3), at the basolateral membrane of kidney proximal tubule cells, facilitates the elimination of numerous widely used drugs. Earlier investigation from our laboratory revealed that ubiquitin conjugation to OAT3 leads to OAT3 internalization from the cell surface, followed by degradation in the proteasome. In the current study, we examined the roles of chloroquine (CQ) and hydroxychloroquine (HCQ), two well-known anti-malarial drugs, in their action as proteasome inhibitors and their effects on OAT3 ubiquitination, expression, and function. We showed that in cells treated with CQ and HCQ, the ubiquitinated OAT3 was considerably enhanced, which correlated well with a decrease in 20S proteasome activity. Furthermore, in CQ- and HCQ-treated cells, OAT3 expression and OAT3-mediated transport of estrone sulfate, a prototypical substrate, were significantly increased. Such increases in OAT3 expression and transport activity were accompanied by an increase in the maximum transport velocity and a decrease in the degradation rate of the transporter. In conclusion, this study unveiled a novel role of CQ and HCQ in enhancing OAT3 expression and transport activity by preventing the degradation of ubiquitinated OAT3 in proteasomes. [ABSTRACT FROM AUTHOR]

Phosphoenolpyruvate carboxykinase 1 (PCK1 or PEPCK-C) is a cytosolic enzyme converting oxaloacetate to phosphoenolpyruvate, with a potential role in gluconeogenesis, ammoniagenesis, and cataplerosis in the liver. Kidney proximal tubule cells display high expression of this enzyme, whose importance is currently not well defined. We generated PCK1 kidney-specific knockout and knockin mice under the tubular cell-specific PAX8 promoter. We studied the effect of PCK1 deletion and overexpression at the renal level on tubular physiology under normal conditions and during metabolic acidosis and proteinuric renal disease. PCK1 deletion led to hyperchloremic metabolic acidosis characterized by reduced but not abolished ammoniagenesis. PCK1 deletion also resulted in glycosuria, lactaturia, and altered systemic glucose and lactate metabolism at baseline and during metabolic acidosis. Metabolic acidosis resulted in kidney injury in PCK1-deficient animals with decreased creatinine clearance and albuminuria. PCK1 further regulated energy production by the proximal tubule, and PCK1 deletion decreased ATP generation. In proteinuric chronic kidney disease, mitigation of PCK1 downregulation led to better renal function preservation. PCK1 is essential for kidney tubular cell acid-base control, mitochondrial function, and glucose/lactate homeostasis. Loss of PCK1 increases tubular injury during acidosis. Mitigating kidney tubular PCK1 downregulation during proteinuric renal disease improves renal function. [ABSTRACT FROM AUTHOR]

By preventing freezing, antifreeze proteins (AFPs) can permit cells and organs to be stored at subzero temperatures. As metabolic rates decrease with decreasing temperature, subzero static cold storage (SZ-SCS) could provide more time for tissue matching and potentially lead to fewer discarded organs. Human kidneys are generally stored for under 24 h and the tubule epithelium is known to be particularly sensitive to static cold storage (SCS). Here, telomerase-immortalized proximal-tubule epithelial cells from humans, which closely resemble their progenitors, were used as a proxy to assess the potential benefit of SZ-SCS for kidneys. The effects of hyperactive AFPs from a beetle and Cryostasis Storage Solution were compared to University of Wisconsin Solution at standard SCS temperatures (4 °C) and at −6 °C for up to six days. Although the AFPs helped guard against freezing, lower storage temperatures under these conditions were not beneficial. Compared to cells at 4 °C, those stored at −6 °C showed decreased viability as well as increased lactate dehydrogenase release and apoptosis. This suggests that this kidney cell type might be prone to chilling injury and that the addition of AFPs to enable SZ-SCS may not be effective for increasing storage times. • Cells can be stored unfrozen at subzero temperatures, using antifreeze proteins. • The antifreeze proteins from the beetle, Tenebrio molitor , are not harmful to cells. • Human kidney tubule cells are sensitive to chill injury at subzero temperatures. • Chill injury is not prevented by moderate concentrations of the antifreeze protein. [ABSTRACT FROM AUTHOR]

Diacylglycerol kinase (DGK) exerts balancing the intracellular level between two-second messengers, diacylglycerol and phosphatidic acid, by its phosphorylation activity. DGK z is often localized in cell nuclei, suggesting its involvement in the regulation of intranuclear activities, including mitosis and apoptosis. The present immunohistochemical study of rat kidneys first revealed no detection levels of DGK z -immunoreactivity in nuclei of most proximal tubule epithelia in contrast to its distinct occurrence in cell nuclei of collecting and distal tubules with the former more dominant. This finding suggests that DGK z is a key factor regulating vulnerability to acute kidney injury in various renal tubules: its low expression represents the high vulnerability of proximal tubule cells, and its distinct expression does the resistance of collecting and distal tubule cells. In addition, this isozyme was more or less localized in nuclei of cells forming glomeruli as well as in endothelial nuclei of peritubular capillaries and other intrarenal blood vessels, and epithelial nuclei of glomerular capsules (Bowman's capsules) and renal calyces, including intrarenal interstitial cells. [ABSTRACT FROM AUTHOR]

Proteinuria is an important risk factor for renal and cardiovascular disease. It is associated with a risk for glomerulonephritis, chronic kidney disease, and end-stage renal disease. Therefore, if persistent proteinuria is detected, kidney biopsy is considered to diagnose and treat the underlying disease. Recently, variants in the cubilin (CUBN) gene, which is associated with albuminuria, have been reported. This gene encodes cubilin, a membrane glycoprotein receptor expressed in the renal proximal tubules. Cubilin is a component of the megalin and cubilin-amnionless complex that mediates albumin reabsorption into the proximal tubules through endocytosis. A defect in cubilin leads to a reduction in albumin reuptake, resulting in albumin-dominant proteinuria. Although numerous controversies exist, several reports suggest that cubilin defects lead to proteinuria with a high portion of albuminuria but may not impair renal filtration function. If albuminuria due to reduced cubilin function is confirmed as a benign condition, we can consider using genetic studies to detect CUBN mutations in patients with proteinuria and they may not require any treatment or kidney biopsy. Here, we review recent papers on CUBN mutations and discuss the prognosis and management of individuals with this mutation. [ABSTRACT FROM AUTHOR]

The current prevailing paradigm in the renin-angiotensin system dictates that most, if not all, biological, physiological, and pathological responses to its most potent peptide, angiotensin II (Ang II), are mediated by extracellular Ang II activating its cell surface receptors. Whether intracellular (or intracrine) Ang II and its receptors are involved remains incompletely understood. The present study tested the hypothesis that extracellular Ang II is taken up by the proximal tubules of the kidney by an AT1 (AT1a) receptor-dependent mechanism and that overexpression of an intracellular Ang II fusion protein (ECFP/Ang II) in mouse proximal tubule cells (mPTC) stimulates the expression of Na+/H+ exchanger 3 (NHE3), Na+/HCO3- cotransporter, and sodium and glucose cotransporter 2 (Sglt2) by AT1a/MAPK/ERK1/2/NF-kB signaling pathways. mPCT cells derived from male wild-type and type 1a Ang II receptor-deficient mice (Agtr1a-/-) were transfected with an intracellular enhanced cyan fluorescent protein-tagged Ang II fusion protein, ECFP/Ang II, and treated without or with AT1 receptor blocker losartan, AT2 receptor blocker PD123319, MEK1/MEK2 inhibitor U0126, NF-кB inhibitor RO 106-9920, or p38 MAP kinase inhibitor SB202196, respectively. In wild-type mPCT cells, the expression of ECFP/Ang II significantly increased NHE3, Na+/HCO3-, and Sglt2 expression (p < 0.01). These responses were accompanied by >3-fold increases in the expression of phospho-ERK1/2 and the p65 subunit of NF-кB (p < 0.01). Losartan, U0126, or RO 106-9920 all significantly attenuated ECFP/Ang II-induced NHE3 and Na+/HCO3- expression (p < 0.01). Deletion of AT1 (AT1a) receptors in mPCT cells attenuated ECFP/Ang II-induced NHE3 and Na+/HCO3- expression (p < 0.01). Interestingly, the AT2 receptor blocker PD123319 also attenuated ECFP/Ang II-induced NHE3 and Na+/HCO3- expression (p < 0.01). These results suggest that, similar to extracellular Ang II, intracellular Ang II may also play an important role in Ang II receptor-mediated proximal tubule NHE3, Na+/HCO3-, and Sglt2 expression by activation of AT1a/MAPK/ERK1/2/NF-kB signaling pathways. [ABSTRACT FROM AUTHOR]

A morphophysiological study of tubular reabsorption and mechanisms of protein endocytosis in the kidney of frogs (Rana temporaria L.) during parasitic infection was carried out. Pseudoplasmodia and spores of myxosporidia, beforehand assigned to the genus Sphaerospora, were detected in Bowman's capsules and in the lumen of individual renal tubules by light and electron microscopy. Remarkable morphological alteration and any signs of pathology in kidney tissue related to this myxosporean infection have not been noted. At the same time, significant changes in protein reabsorption and distribution of molecular markers of endocytosis in the proximal tubule (PT) cells in infected animals were detected by immunofluorescence confocal microscopy. In lysozyme injection experiments, the endocytosed protein and megalin expression in the infected PTs were not revealed. Tubular expression of cubilin and clathrin decreased, but endosomal recycling marker Rab11 increased or remained unchanged. Thus, myxosporean infection resulted in the alterations in lysozyme uptake and expression of the main molecular determinants of endocytosis. The inhibition of receptor-mediated clathrin-dependent protein endocytosis in amphibian kidneys due to myxosporidiosis was shown for the first time. Established impairment of the endocytic process is a clear marker of tubular cell dysfunction that can be used to assess the functioning of amphibian kidneys during adaptation to adverse environmental factors. [ABSTRACT FROM AUTHOR]

This study's goal was to assess the catfish's response to exposure to monoaromatic petroleum hydrocarbons (benzene, toluene, and xylene) and its recovery after exposure using oxidative stress, histopathological, and immunological changes as biomarkers. Four groups: one as control and other three exposed to benzene (0.762 ng/L), toluene (26.614 ng/L), and xylene (89.403 ng/L), respectively, for 30 days and then recovery period for 30 days. The levels of the cortisol, lipid peroxidation, and cytokines (IL-1β, IL-6) increased significantly (p < 0.05) after exposure to benzene and xylene compared to control. Superoxide dismutase (SOD), total antioxidant capacity (TAC), and acetylcholinstease (Ach) decreased significantly (p < 0.05) in fishes exposed to benzene only compared to control group. While glutathione-S-transferase (GST) did not show any change in different treatment groups compared to control group. The histopathological signs of liver exposed to benzene, toluene, and xylene displayed aggregation of melanomacrophages, congestion of sinusoids, vacuolar degeneration of hepatocytes, necrotic area with inflammatory cell infiltration, and thrombus of central vein. Kidney exposed to benzene, toluene, and xylene showed dilatation of Bowman's space with atrophy of glomerular tuft, lyses of RBCs with mononuclear cell infiltration, multifocal area of hemopoietic tissue necrosis, organized thrombus with perivascular hemorrhage, focal inflammatory cellular reaction, renal tubular necrosis, and thrombus of blood vessels. Spleen exposed to benzene, toluene, and xylene showed hyperplasia of lymphoid follicles in white pulp in a mild degree. These lesions appeared to a mild degree or disappeared completely after recovery period to BTX except spleen. In conclusion, monocyclic aromatic hydrocarbons (BTX) are hazardous to fish and the toxicity level was as benzene > xylene > toluene even though after recovery period. [ABSTRACT FROM AUTHOR]

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Progressive fibrosis is a feature of aging and chronic tissue injury in multiple organs, including the kidney and heart. Glioma-associated oncogene 1 expressing (Gli1+) cells are a major source of activated fibroblasts in multiple organs, but the links between injury, inflammation, and Gli1+ cell expansion and tissue fibrosis remain incompletely understood. We demonstrated that leukocyte-derived tumor necrosis factor (TNF) promoted Gli1+ cell proliferation and cardiorenal fibrosis through induction and release of Indian Hedgehog (IHH) from renal epithelial cells. Using single-cell–resolution transcriptomic analysis, we identified an "inflammatory" proximal tubular epithelial (iPT) population contributing to TNF- and nuclear factor κB (NF-κB)–induced IHH production in vivo. TNF-induced Ubiquitin D (Ubd) expression was observed in human proximal tubular cells in vitro and during murine and human renal disease and aging. Studies using pharmacological and conditional genetic ablation of TNF-induced IHH signaling revealed that IHH activated canonical Hedgehog signaling in Gli1+ cells, which led to their activation, proliferation, and fibrosis within the injured and aging kidney and heart. These changes were inhibited in mice by Ihh deletion in Pax8-expressing cells or by pharmacological blockade of TNF, NF-κB, or Gli1 signaling. Increased amounts of circulating IHH were associated with loss of renal function and higher rates of cardiovascular disease in patients with chronic kidney disease. Thus, IHH connects leukocyte activation to Gli1+ cell expansion and represents a potential target for therapies to inhibit inflammation-induced fibrosis. Editor's summary: Fibrosis and inflammation are closely linked in disease, but the mechanisms underlying this connection are not well understood. In this study, O'Sullivan and colleagues identify an epithelial population in human and murine renal fibrosis due to aging or ischemia-reperfusion injury, which they term inflammatory proximal tubular cells. They demonstrate how these cells release Indian hedgehog (IHH) in response to circulating TNF and thereby promote fibrosis through activation of Gli1-expressing cells. These results provide insight into circulating factors that regulate fibrosis and suggest that IHH signaling may be a potential therapeutic target. —Allison Williams [ABSTRACT FROM AUTHOR]

Cilia are essential for the ontogeny and function of many tissues, including the kidney. Here, we report that transcription factor ERRγ ortholog estrogen related receptor gamma a (Esrrγa) is essential for renal cell fate choice and ciliogenesis in zebrafish. esrrγa deficiency altered proximodistal nephron patterning, decreased the multiciliated cell populace and disrupted ciliogenesis in the nephron, Kupffer's vesicle and otic vesicle. These phenotypes were consistent with interruptions in prostaglandin signaling, and we found that ciliogenesis was rescued by PGE2 or the cyclooxygenase enzyme Ptgs1. Genetic interaction revealed that peroxisome proliferatoractivated receptor gamma, coactivator 1 alpha (Ppargc1a), which acts upstream of Ptgs1-mediated prostaglandin synthesis, has a synergistic relationship with Esrrγa in the ciliogenic pathway. These ciliopathic phenotypes were also observed in mice lacking renal epithelial cell (REC) ERRγ, where significantly shorter cilia formed on proximal and distal tubule cells. Decreased cilia length preceded cyst formation in REC-ERRγ knockout mice, suggesting that ciliary changes occur early during pathogenesis. These data position Esrrγa as a novel link between ciliogenesis and nephrogenesis through regulation of prostaglandin signaling and cooperation with Ppargc1a. [ABSTRACT FROM AUTHOR]

A small protein, Mitoregulin (Mtln), localizes in mitochondria and contributes to oxidative phosphorylation and fatty acid metabolism. Mtln knockout mice develop obesity on a high-fat diet, demonstrating elevated cardiolipin damage and suboptimal creatine kinase oligomerization in muscle tissue. Kidneys heavily depend on the oxidative phosphorylation in mitochondria. Here we report kidney-related phenotypes in aged Mtln knockout mice. Similar to Mtln knockout mice muscle mitochondria, those of the kidney demonstrate a decreased respiratory complex I activity and excessive cardiolipin damage. Aged male mice carrying Mtln knockout demonstrated an increased frequency of renal proximal tubules' degeneration. At the same time, a decreased glomerular filtration rate has been more frequently detected in aged female mice devoid of Mtln. An amount of Mtln partner protein, Cyb5r3, is drastically decreased in the kidneys of Mtln knockout mice. [ABSTRACT FROM AUTHOR]

Impaired mitochondrial function and dysregulated energy metabolism have been shown to be involved in the pathological progression of kidney diseases such as acute kidney injury (AKI) and diabetic nephropathy. Hence, improving mitochondrial function is a promising strategy for treating renal dysfunction. NADH: ubiquinone oxidoreductase core subunit V1 (NDUFV1) is an important subunit of mitochondrial complex I. In the present study, we found that NDUFV1 was reduced in kidneys of renal ischemia/reperfusion (I/R) mice. Meanwhile, renal I/R induced kidney dysfunction as evidenced by increases in BUN and serum creatinine, severe injury of proximal renal tubules, oxidative stress, and cell apoptosis. All these detrimental outcomes were attenuated by increased expression of NDUFV1 in kidneys. Moreover, knockdown of Ndufv1 aggravated cell insults induced by H2O2 in TCMK‐1 cells, which further confirmed the renoprotective roles of NDUFV1. Mechanistically, NDUFV1 improved the integrity and function of mitochondria, leading to reduced oxidative stress and cell apoptosis. Overall, our data indicate that NDUFV1 has an ability to maintain mitochondrial homeostasis in AKI, suggesting therapies by targeting mitochondria are useful approaches for dealing with mitochondrial dysfunction associated renal diseases such as AKI. [ABSTRACT FROM AUTHOR]

Of late, numerous microphysiological systems have been employed to model the renal proximal tubule. Yet there is lack of research on refining the functions of the proximal tubule epithelial layer—selective filtration and reabsorption. In this report, pseudo proximal tubule cells extracted from human-induced pluripotent stem cell-derived kidney organoids are combined and cultured with immortalized proximal tubule cells. It is shown that the cocultured tissue is an impervious epithelium that offers improved levels of certain transporters, extracellular matrix proteins collagen and laminin, and superior glucose transport and P-glycoprotein activity. mRNA expression levels higher than those obtained from each cell type were detected, suggesting an anomalous synergistic crosstalk between the two. Alongside, the improvements in morphological characteristics and performance of the immortalized proximal tubule tissue layer exposed, upon maturation, to human umbilical vein endothelial cells are thoroughly quantified and compared. Glucose and albumin reabsorption, as well as xenobiotic efflux rates through P-glycoprotein were all improved. The data presented abreast highlight the advantages of the cocultured epithelial layer and the non-iPSC-based bilayer. The in vitro models presented herein can be helpful in personalized nephrotoxicity studies. A microfluidic device can help analyse the functions of pseudo proximal tubule cells coming from hiPSC-derived kidney organoids, with the future potential for applications in personalized nephrotoxicity studies. [ABSTRACT FROM AUTHOR]

Simple Summary: This article presents new data on the histology and ultrastructure of the trunk kidney in two isolated populations of Atlantic salmon, from the Baltic and Barents Seas, covering both the freshwater and the seawater period of their life cycle. We studied juvenile salmon living in freshwater (parr), juvenile salmon running into the sea (smolts), adults feeding in the sea, adults returning to their natal river to spawn, and spawning individuals. According to the results obtained, the ultrastructural changes in the nephron, believed to affect the glomerular filtration rate and the amount of urine produced in salmon kidneys, occurred as early as the smolting stage. Such alterations reflect fundamental changes in the course of pre-adaptation to life in salt water. In the Barents Sea population, the adult salmon caught in the sea had the most pronounced ultrastructural changes, which are characteristic of marine fish. In the salmon that entered the river mouth and stayed in the fresh water for less than a day, structural rearrangements occurred only in the distal tubules of the nephron. The salmon from the Baltic Sea population had less pronounced differences in the morphometric characteristics of the nephron among the studied ontogenetic stages, apparently because of the low salinity in the sampling area. In both studied populations, the activation of cellular immunity was initiated during the parr–smolt transformation. Another distinct immune response was registered in the adults returning to the river for spawning. This article presents data on the mesonephros histology and ultrastructure in the Atlantic salmon from the Baltic Sea and Barents Sea populations, with an emphasis on comparisons between the following ontogenetic stages: parr, smolting, adult life at sea, the adults' return to their natal river to spawn, and spawning. The ultrastructural changes in the renal corpuscle and cells of the proximal tubules of the nephron occurred as early as the smolting stage. Such changes reflect fundamental alterations during the pre-adaptation to life in saltwater. In the Barents Sea population, the adult salmon sampled in the sea had the smallest diameters of the renal corpuscle and proximal and distal tubules, the most narrow urinary space, and the thickest basement membrane. In the group of salmon that entered the mouth of the river and spent less than 24 h in freshwater, the structural rearrangements occurred only in the distal tubules. Better development of the smooth endoplasmic reticulum and a greater abundance of mitochondria in the tubule cells were observed in the adult salmon from the Barents Sea compared to those from the Baltic Sea. Cell-immunity activation was initiated during the parr–smolt transformation. Another pronounced innate-immunity response was registered in the adults returning to the river to spawn. [ABSTRACT FROM AUTHOR]

Epidemiological studies show an association between low body selenium and the risk of hypertension. However, whether selenium deficiency causes hypertension remains unknown. Here, we report that Sprague-Dawley rats fed a selenium-deficient diet for 16 weeks developed hypertension, accompanied with decreased sodium excretion. The hypertension of selenium-deficient rats was associated with increased renal angiotensin II type 1 receptor (AT 1 R) expression and function that was reflected by the increase in sodium excretion after the intrarenal infusion of the AT 1 R antagonist candesartan. Selenium-deficient rats had increased systemic and renal oxidative stress; treatment with the antioxidant tempol for 4 weeks decreased the elevated blood pressure, increased sodium excretion, and normalized renal AT 1 R expression. Among the altered selenoproteins in selenium-deficient rats, the decrease in renal glutathione peroxidase 1 (GPx1) expression was most prominent. GPx1, via regulation of NF-κB p65 expression and activity, was involved in the regulation of renal AT 1 R expression because treatment with dithiocarbamate (PDTC), an NF-κB inhibitor, reversed the up-regulation of AT 1 R expression in selenium-deficient renal proximal tubule (RPT) cells. The up-regulation of AT 1 R expression with GPx1 silencing was restored by PDTC. Moreover, treatment with ebselen, a GPX1 mimic, reduced the increased renal AT 1 R expression, Na+-K+-ATPase activity, hydrogen peroxide (H 2 O 2) generation, and the nuclear translocation of NF-κB p65 protein in selenium-deficient RPT cells. Our results demonstrated that long-term selenium deficiency causes hypertension, which is due, at least in part, to decreased urine sodium excretion. Selenium deficiency increases H 2 O 2 production by reducing GPx1 expression, which enhances NF-κB activity, increases renal AT 1 R expression, causes sodium retention and consequently increases blood pressure. [Display omitted] • Long-term selenium deficiency causes hypertension. • Selenium deficiency increases renal AT 1 R expression and sodium retention. • Selenium deficiency elevates NF-κB activity via GPx1/H 2 O 2 pathway. [ABSTRACT FROM AUTHOR]

Background: Sodium-Glucose CoTransporter-2 (SGLT2) inhibitors, the -flozin group of drugs, which block glucose reuptake in the renal proximal tubule, are being increasingly used off-label to treat horses with refractory hyperinsulinemia. After 2 years of use by animals in our group, a horse on canagliflozin was incidentally noted to be hyperlipemic. Case Description: We have been following a cohort of equines (n = 20) treated with SGLT2 inhibitors due to refractory hyperinsulinemia. The animals are owned by members of the Equine Cushing's and Insulin Resistance Group and treated by their attending veterinarians. The index case was a 23 years old gelding with a 2 years history of recurring laminitis that began canagliflozin therapy to control hyperinsulinemia which was no longer responsive to metformin. Between 6 and 10 weeks post start of therapy, significant weight loss was noticed. Two days later he was hospitalized with colic symptoms and hyperlipemia but was bright, alert, and eating well throughout. Canagliflozin was discontinued and triglycerides returned to normal reference values within 10 days. A subsequent study of 19 other horses on SGLT2 inhibitors revealed varying degrees of hypertriglyceridemia, all asymptomatic. Conclusion: While this class of drugs holds great promise for cases of refractory hyperinsulinemia and laminitis that do not respond to diet or metformin therapy, hypertriglyceridemia is a potential side effect. In our experience, animals remained asymptomatic and eating well. Further study of hypertriglyceridemia in horses on SGLT2 inhibitors and the possible mitigating effect of diet is indicated. To our knowledge, this is the first report of hypertriglyceridemia with canagliflozin treatment in equines. [ABSTRACT FROM AUTHOR]

This study aimed to morphometrically examine the development of glomeruli and tubules in the kidney cortex of human foetuses at different gestational ages (GAs). We also investigated the expression of the proliferation marker Ki-67 and apoptosis-related markers Bcl-2 and Bax during nephrogenesis using immunohistochemistry. Kidney samples from 38 human foetuses of both sexes with GA ranging from 13 to 40 weeks were analysed. The samples were divided into 7 groups based on GA, each corresponding to 1 lunar month. Foetal kidneys showed a spatiotemporal gradient of nephron differentiation with the transient stages of nephron anlage located in the nephrogenic zone and immature nephrons located in the subjacent maturation zone. In the inner cortex, nephrons establish the morphological characteristics of definitive nephrons. The average area, perimeter, and Feret's diameter of the glomeruli formed within the kidney cortex gradually decreased up to a period of 29–32 weeks of gestation and subsequently increased until a period of 37–40 weeks. There was a weak negative correlation with GA. In contrast, the areal density of glomeruli increased up to a period of 21–24 weeks and then gradually decreased until a period of 37–40 weeks, showing a moderate negative correlation with GA. The average area of renal tubules slightly decreased until a period of 21–24 weeks of gestation and then gradually increased until a period of 36–40 weeks, showing a moderate positive correlation with GA. The average areal density of renal tubules increased significantly until a period of 21–24 weeks of gestation, remained relatively constant until a period of 33–36 weeks, and then increased significantly at 36–40 weeks. There was a strong positive correlation with GA. Our results showed that Ki-67 was expressed in numerous cells of the metanephric mesenchyme, pretubular aggregates, renal vesicles, comma-shaped bodies, and early S-shaped bodies. During subsequent development and the spatial expansion of nephrons towards the mature zone, the expression of Ki-67 was markedly reduced. Similarly, Bcl-2 was strongly expressed in induced nephrogenic progenitor cells, pretubular aggregates, renal vesicles, and comma-shaped bodies. As vascularisation and maturation of the nephron proceeded, Bcl-2 staining became less intense and limited to the parietal layer of the Bowman's capsule and renal tubules. Weak Bax expression was observed in individual scattered cells within segments of the nephrons at all developmental stages. In the mature zone, more intense Bax staining was observed in the renal tubules. [ABSTRACT FROM AUTHOR]

Urolithiasis is a complex and multifactorial disease characterized by the formation of calculi at the urinary tract level. Conventional therapeutic prophylaxis relies on the use of Ca-blockers, alkalis, diuretics, and anti-edema agents, but their prolonged utilization is often limited by several side effects. In this scenario, the aim of the present work was the design of an innovative multi-component nutraceutical formulation (NF) for the management of urinary stones consisting of a synergistic combination of natural aqueous extracts of Oreganum vulgare L. (1% of saponin), Urtica dioica (0.8% of β-sitosterol), Phyllanthus niruri (15% of tannins w/w), and Ceterach officinarum in association with bromelain, K, and Mg citrate. To assess the potential of NF also in the treatment of uric acid (UA) stones, the effects on the expression of the cellular UA transporters OAT1 and URAT1 were investigated in a renal tubular cell line. In addition, the myorelaxant effect of NF was investigated in a human pulmonary artery smooth muscle cell (HPASMC) model resulting in a decreased muscle contractility of −49.4% (p < 0.01) compared to the control. The treatment with NF also showed a valuable inhibition of in vitro calcium-oxalate crystal formation, both in prevention (−52.3% vs. control, p < 0.01) and treatment (−70.8% vs. control, p < 0.01) experiments. Finally, an ischemic reperfusion rat model was used to evaluate the NF anti-edema effects, resulting in a reduction in the edema-related vascular permeability (Normalized Gray Levels, NGL = 0.40 ± 0.09, p < 0.01, −67.1% vs. untreated rats). In conclusion, the present NF has shown to be a promising natural alternative for managing urinary tract stones. [ABSTRACT FROM AUTHOR]

The proximal tubule is the high-capacity reabsorptive powerhouse of the kidney. Two papers in recent issues of the JCI highlight mechanisms of more delicate effects of the proximal tubule. Yoon et al. demonstrated the intracellular mechanism by which parathyroid hormone (PTH) increases production of 1,25-vitamin D. Activation of PTH receptor 1/cAMP/PKA signaling inhibited salt-inducible kinase 2 (SIK2) and SIK3, which increased CYB27B1 transcription and 1,25-vitamin D production. Replication of these effects with small-molecule SIK inhibitors suggests possible therapeutic applications for patients with disorders characterized by 1,25-vitamin D deficiency. Zhou et al. discovered that proximal tubule glycolysis acts as a phosphate sensor that regulates fibroblast growth factor 23 production in bone. They described several kidney-specific metabolic modifications that enabled glycolysis to be deployed as a phosphate sensor. The provocative results raise intriguing questions with implications for patients with disorders of phosphate homeostasis, including chronic kidney disease. [ABSTRACT FROM AUTHOR]

(I) Heat map shows the expression of differentially expressed genes enriched in the cholesterol biosynthesis pathway, glycolysis pathway, fatty acid synthesis pathway, and cholesterol transport pathway in ccRCC. Among them, "C" means cholesterol biosynthesis pathway, "G" means glycolysis pathway, "F" means fatty acid synthesis pathway, and "CT" means cholesterol transport pathway. Among them, "C" means cholesterol biosynthesis pathway, "G" means glycolysis pathway, "F" means fatty acid synthesis pathway, and "CT" means cholesterol transport pathway. (T, U, W, X) Heat map shows the expression of differentially expressed genes enriched in the cholesterol biosynthesis pathway, glycolysis pathway, fatty acid synthesis pathway, and cholesterol transport pathway in ccRCC. [Extracted from the article]

Lead (Pb) intoxication is known to damage the proximal tubules of kidney. Autophagy and apoptosis have been shown to be involved in a variety of renal injuries, but the underlying mechanisms remain largely unknown. In this study, we constructed a mice model of Pb intoxication and validated it against lead concentrations in blood and urine. Electron microscopy revealed that Pb promoted the accumulation of autophagosomes. Subsequent immunofluorescence and western blotting revealed that Pb intoxication suppressed the autophagic flux. Next, exosomes were isolated and extracted through ultracentrifugation, and were further identified by diameter analysis and marker detection. We also demonstrated that autophagy and apoptosis were enhanced in renal cells with exosomes of Pb expose. Furthermore, the specific mechanisms were explored by RNA sequencing and it was found that several targeted genes regulated by differential exosomal miRNAs and lncRNAs. Target genes accumulated in several signaling pathways, especially the adenosine 5'‐monophosphate‐activated protein kinase (AMPK) signaling. We found that Pb intoxication‐induced exosomes activated the AMPK signaling in renal proximal tubule cells. Furthermore, autophagy and apoptosis assays showed that GSK‐690693, an AMPK inhibitor, significantly alleviated exosome‐induced renal injuries by Pb intoxication. In conclusion, Pb‐mediated exosome‐induced autophagy and apoptosis via activating the AMPK signaling contributing to Pb‐induced nephrotoxicity in renal cells. [ABSTRACT FROM AUTHOR]

N1‐methylnicotinamide (NMN) has been proposed as endogenous biomarker for drug–drug interactions mediated by inhibition of multidrug and toxin extrusion proteins (MATEs) at the renal proximal tubule. We analyzed NMN in plasma and urine samples of two clinical trials investigating a new probe drug cocktail (consisting of digoxin, metformin, furosemide, and rosuvastatin) dedicated to clinically relevant drug transporters. In trial 1, NMN was investigated after single‐dose treatment with individual cocktail components or after cocktail treatment. In trial 2, NMN was investigated after treatment with cocktail alone or with cocktail + inhibitor (cimetidine, a MATE inhibitor; or rifampin, verapamil, or probenecid, inhibitors of other transporters). In trial 1, NMN kinetics in plasma and urine were essentially not affected by individual cocktail components or after cocktail treatment. In trial 2, NMN renal clearance from 0 to 12 hours (CLR,0–12) geometric mean ratio (GMR) after cocktail + cimetidine vs. cocktail alone was 75% (90% confidence interval (CI): 65–87%). NMN CLR GMR after cocktail + verapamil, + rifampin, or + probenecid vs. cocktail alone was 99% (90% CI: 81–121%), 91% (90% CI: 75–111%), and 107% (90% CI: 91–126%), respectively. Compared with creatinine CLR and creatinine area under the plasma‐concentration time curve, NMN CLR was more specific and more sensitive for renal MATE inhibition. Absence of impact of the cocktail on NMN in trial 1 allows for utilization of NMN in studies using this transporter cocktail. Trial 2 data support that NMN CLR is a specific and sensitive marker for MATE‐mediated renal drug–drug interactions. [ABSTRACT FROM AUTHOR]

Clear cell renal cell carcinomas (ccRCC) are characterized by arm-wide chromosomal alterations. Loss at 14q is associated with disease aggressiveness in ccRCC, which responds poorly to chemotherapeutics. The 14q locus contains one of the largest miRNA clusters in the human genome; however, little is known about the contribution of these miRNAs to ccRCC pathogenesis. In this regard, we investigated the expression pattern of selected miRNAs at the 14q32 locus in TCGA kidney tumors and in ccRCC cell lines. We demonstrated that the miRNA cluster is downregulated in ccRCC (and cell lines) as well as in papillary kidney tumors relative to normal kidney tissues (and primary renal proximal tubule epithelial (RPTEC) cells). We demonstrated that agents modulating expression of DNMT1 (e.g., 5-Aza-deoxycytidine) could modulate 14q32 miRNA expression in ccRCC cell lines. Lysophosphatidic acid (LPA, a lysophospholipid mediator elevated in ccRCC) not only increased labile iron content but also modulated expression of a 14q32 miRNA. Through an overexpression approach targeting a subset of 14q32 miRNAs (specifically at subcluster A: miR-431-5p, miR-432-5p, miR-127-3p, and miR-433-3p) in 769-P cells, we uncovered changes in cellular viability and claudin-1, a tight junction marker. A global proteomic approach was implemented using these miRNA overexpressing cell lines which uncovered ATXN2 as a highly downregulated target. Collectively, these findings support a contribution of miRNAs at 14q32 in ccRCC pathogenesis. [ABSTRACT FROM AUTHOR]

Nephrotoxicity is an important drug safety aspect to be assessed during drug discovery and development. To study renal toxicity, in vitro cell-based assays are often used. Unfortunately, translating the results of such cell assays to vertebrates including human remains challenging. Therefore, we aim to evaluate whether zebrafish larvae (ZFL) could serve as a vertebrate screening model to detect gentamicin-induced changes of kidney glomeruli and proximal tubules. To validate the model, we compared the results of ZFL with those obtained from kidney biopsies of gentamicin-treated mice. We used transgenic zebrafish lines expressing enhanced green fluorescent proteins in the glomerulus to visualize glomerular damage. Synchrotron radiation-based computed tomography (SRμCT) is a label-free approach providing three-dimensional representations of renal structures with micrometre resolution. Clinically used gentamicin concentrations induce nephrotoxicity and affect glomerular and proximal tubular morphology. Findings were confirmed in mice and ZFL. There was a strong correlation between fluorescent signals in ZFL, SRμCT- derived descriptors of glomerular and proximal tubular morphology and the histological analysis of mouse kidney biopsies. A combination of SRμCT and confocal microscopy provides unprecedented insights into anatomical structures of the zebrafish kidney. Based on our findings, we suggest to use ZFL as a predictive vertebrate screening model to study drug-induced nephrotoxicity and to bridge the gap between cell culture-based test systems and experiments in mammals. [ABSTRACT FROM AUTHOR]

Diabetes is a main risk factor for kidney disease, causing diabetic nephropathy in close to half of all patients with diabetes. Metabolism has recently been identified to be decisive in cell fate decisions and repair. Here we used mass spectrometry imaging (MSI) to identify tissue specific metabolic dysregulation, in order to better understand early diabetes-induced metabolic changes of renal cell types. In our experimental diabetes mouse model, early glomerular glycocalyx barrier loss and systemic metabolic changes were observed. In addition, MSI targeted at small molecule metabolites and glycero(phospho)lipids exposed distinct changes upon diabetes in downstream nephron segments. Interestingly, the outer stripe of the outer medullar proximal tubular segment (PT_S3) demonstrated the most distinct response compared to other segments. Furthermore, phosphatidylinositol lipid metabolism was altered specifically in PT_S3, with one of the phosphatidylinositol fatty acid tails being exchanged from longer unsaturated fatty acids to shorter, more saturated fatty acids. In acute kidney injury, the PT_S3 segment and its metabolism are already recognized as important factors in kidney repair processes. The current study exposes early diabetes-induced changes in membrane lipid composition in this PT_S3 segment as a hitherto unrecognized culprit in the early renal response to diabetes. [ABSTRACT FROM AUTHOR]

Autophagy is involved in the development of diabetic kidney disease (DKD), the leading cause of end-stage renal disease. The Fyn tyrosine kinase (Fyn) suppresses autophagy in the muscle. However, its role in kidney autophagic processes is unclear. Here, we examined the role of Fyn kinase in autophagy in proximal renal tubules both in vivo and in vitro. Phospho-proteomic analysis revealed that transglutaminase 2 (Tgm2), a protein involved in the degradation of p53 in the autophagosome, is phosphorylated on tyrosine 369 (Y369) by Fyn. Interestingly, we found that Fyn-dependent phosphorylation of Tgm2 regulates autophagy in proximal renal tubules in vitro, and that p53 expression is decreased upon autophagy in Tgm2-knockdown proximal renal tubule cell models. Using streptozocin (STZ)-induced hyperglycemic mice, we confirmed that Fyn regulated autophagy and mediated p53 expression via Tgm2. Taken together, these data provide a molecular basis for the role of the Fyn–Tgm2–p53 axis in the development of DKD. [ABSTRACT FROM AUTHOR]

Objective: To explore the improvement effect of Jiangzhuo Simiao Powder on hyperuricemia and renal injury in rats by reducing serum uric acid level and inhibiting NLRP3 inflammasome. Methods: Twenty-eight SD rats were randomly divided into control group, potassium oxyacid(OA) model group, OA+SMS group, and OA+allopurinol group, among them, the dose of SMS is based on laboratory animal substance management standards(10 times the adult dose per kilogram of body weight); Allopurinol was dissolved in the drinking water of the OA + allopurinol group(concentration, 150 mg/L); The control group and the OA group were given the same amount of distilled water(the intragastric volume was controlled at 2 m L/d) for 7 weeks. To investigate the mediating effect of SMS on renal mitochondrial reactive oxygen species(ROS) and oxidative stress(OS) products, protein expression of NLRP3-ASC-caspase-1axis. Results:(1) The data of control group, OA model and treatment group were significantly different(P＜0.05). At the end of the 7th week, the total uric acid excretion in the model group was significantly higher than that in the control group(P＜0.05), and the SZF group and allopurinol group were significantly higher than those in the OA group(P＜0.05).(2) Compared with the control group, the levels of BUN and Scr in the OA group were significantly increased(P＜0.05), while the levels of BUN and Scr in the rats treated with SMS and allopurinol decreased(P＜0.05).(3) In renal tissue structure, for the OA+SZF and OA+allopurinol groups, the epithelial cell swelling, vacuolar degeneration and inflammatory cell infiltration in the proximal renal tubules were reduced.(4) The oxidative stress indexes in renal tissue of OA-induced hyperuricemia rats were all increased(P＜0.05); namely, superoxide dismutase(SOD), catalase(CAT) and glutathione There was a significant imbalance between peroxidases, while SMS and allopurinol intervention could significantly restore the dynamic balance of the above oxidative stress response indicators(P＜0.05).(5) The expression of TXNIP m RNA and protein in kidney tissue of rats in OA group was significantly higher than that in other groups(P＜0.05), while SMS and allopurinol effectively inhibited the expression of TXNIP m RNA and protein(P＜0.05); m RNA and protein expression in the murine NLRP3-ASC-caspase-1 axis was elevated(P＜0.05). The activation of NLRP3-ASC-caspase-1 axis in the SMS group was significantly inhibited(P＜0.05). Conclusion: SMS attenuated tubular damage and inflammatory infiltration by reducing blood uric acid levels in reducing renal damage, while inhibiting the NLRP3 inflammasome activation triggered by mitochondrial ROS. [ABSTRACT FROM AUTHOR]

Fibroblast growth factor 23, parathyroid hormone, and 1,25-dihydroxyvitamin D are critical in phosphate homeostasis. Despite these factors' importance, regulators of phosphaturia in the acute postprandial phase remain largely unknown. This study investigated the mechanism of acute phosphate regulation in the postprandial phase in rats. Duodenal administration of radiolabeled phosphate (32P) showed that 32P levels in the inferior vena cava (IVC) blood were lower than those in the portal vein (PV) blood. Serum phosphate concentration transiently increased 5 min after phosphate solution administration through IVC, while it was maintained after the administration through PV. Phosphate administration through both IVC and PV resulted in increased fractional excretion of phosphate (FEPi) at 10 min without elevation of the known circulating factors, but urinary phosphate excretion during the period was 8% of the dose. Experiments using 32P or partial hepatectomy showed that the liver was one of the phosphate reservoirs. The elevation of FEPi and suppression of sodium-phosphate cotransporter 2a in the kidney at 10 min was attenuated in rats with SCH23390, hepatic denervation, or renal denervation, thus indicating that the liver communicated with the kidney via the nervous system to promote phosphaturia. These results revealed previously unknown mechanisms for serum phosphate maintenance. [ABSTRACT FROM AUTHOR]