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The long-term effects of a single episode of acute kidney injury (AKI) induced by bilateral ischemia-reperfusion injury (BIRI) on kidney lymphatic dynamics are not known. The purpose of this study was to determine if alterations in kidney lymphatics are sustained in the long term and how they relate to inflammation and injury. Mice underwent BIRI as a model of AKI and were followed up to 9 mo. Although kidney function markers normalized following initial injury, histological analysis revealed sustained tissue damage and inflammation for up to 9 mo. Transcriptional analysis showed both acute and late-stage lymphangiogenesis, supported by increased expression of lymphatic markers, with unique signatures at each phase. Expression of Ccl21a was distinctly upregulated during late-stage lymphangiogenesis. Three-dimensional tissue cytometry confirmed increased lymphatic vessel abundance, particularly in the renal cortex, at early and late timepoints postinjury. In addition, the study identified the formation of tertiary lymphoid structures composed of CCR7+ lymphocytes and observed changes in immune cell composition over time, suggesting a complex and dynamic response to AKI involving tissue remodeling and immune cell involvement. This study provides new insights into the role of lymphatics in the progression of AKI to chronic kidney disease. NEW & NOTEWORTHY: Here, we perform the first, comprehensive study of long-term lymphatic dynamics following a single acute kidney injury (AKI) event. Using improved three-dimensional image analysis and an expanded panel of transcriptional markers, we identify multiple stages of lymphatic responses with distinct transcriptional signatures, associations with the immune microenvironment, and collagen deposition. This research advances kidney lymphatic biology, emphasizing the significance of longitudinal studies in understanding AKI and the transition to chronic kidney disease. [ABSTRACT FROM AUTHOR]

Resident memory T cells (TRMs), which are memory T cells that are retained locally within tissues, have recently been described as antigen-specific frontline defenders against pathogens in barrier and nonbarrier epithelial tissues. They have also been noted for perpetuating chronic inflammation. The conditions responsible for TRM differentiation are still poorly understood, and their contributions, if any, to sterile models of chronic kidney disease (CKD) remain a mystery. In this study, we subjected male C57BL/6J mice and OT-1 transgenic mice to five consecutive days of 2 mg/kg aristolochic acid (AA) injections intraperitoneally to induce CKD or saline injections as a control. We evaluated their kidney immune profiles at 2 wk, 6 wk, and 6 mo after treatment. We identified a substantial population of TRMs in the kidneys of mice with AA-induced CKD. Flow cytometry of injured kidneys showed T cells bearing TRM surface markers and single-cell (sc) RNA sequencing revealed these cells as expressing well-known TRM transcription factors and receptors responsible for TRM differentiation and maintenance. Although kidney TRMs expressed Cd44, a marker of antigen experience and T cell activation, their derivation was independent of cognate antigen-T cell receptor interactions, as the kidneys of transgenic OT-1 mice still harbored considerable proportions of TRMs after injury. Our results suggest a nonantigen-specific or antigen-independent mechanism capable of generating TRMs in the kidney and highlight the need to better understand TRMs and their involvement in CKD. [ABSTRACT FROM AUTHOR]

Acute kidney injury (AKI) is a common finding in hospitalized patients, particularly those who are critically ill. The development of AKI is associated with several adverse outcomes including mortality, morbidity, progression to chronic kidney disease, and an increase in healthcare expenditure. Despite the well-established negative impact of AKI and rigorous efforts to better define, identify, and implement targeted therapies, the overall approach to the treatment of AKI continues to principally encompass supportive measures. This enduring challenge is primarily due to the heterogeneous nature of insults that activate many independent and overlapping molecular pathways. Consequently, it is evident that the identification of common mechanisms that mediate the pathogenesis of AKI, independent of etiology and engaged pathophysiological pathways, is of paramount importance and could lead to the identification of novel therapeutic targets. To better distinguish the commonly modulated mechanisms of AKI, we explored the transcriptional characteristics of human kidney biopsies from patients with acute tubular necrosis (ATN), and acute interstitial nephritis (AIN) using a NanoString inflammation panel. Subsequently, we used publicly available single-cell transcriptional resources to better interpret the generated transcriptional findings. Our findings identify robust acute kidney injury (AKI-induced) developmental reprogramming of macrophages (MΦ) with the expansion of C1Q+, CD163+ MΦ that is independent of the etiology of AKI and conserved across mouse and human species. These results would expand the current understanding of the pathophysiology of AKI and potentially offer novel targets for additional studies to enhance the translational transition of AKI research. NEW & NOTEWORTHY: Our findings identify robust acute kidney injury (AKI)-induced developmental reprogramming of macrophages (MΦ) with the expansion of C1Q+, CD163+ MΦ that is independent of the etiology of AKI and conserved across mouse and human species. [ABSTRACT FROM AUTHOR]

Angiostatin, a proteolytic fragment of plasminogen, is a potent anti-angiogenic factor recently shown also to have an inhibitory effect on leukocyte recruitment and macrophage migration. Because both angiogenesis and inflammation play key roles in the progression of chronic kidney disease, we evaluated the effect of angiostatin treatment in the rat remnant kidney model. Rats were pretreated for 4 wk with recombinant adeno-associated viruses expressing either angiostatin or green fluorescence protein. Chronic renal disease was then induced by a subtotal nephrectomy, and rats were killed 8 wk later for analysis. Angiostatin treatment was associated with significantly less proteinuria but no alterations in serum creatinine, creatinine clearance, and blood urea nitrogen levels. Treatment with angiostatin reduced renal peritubular capillary number and decreased urinary nitric oxide levels. Despite reducing capillary density, angiostatin diminished interstitial fibrosis in association with reduced macrophage and T-cell infiltration and renal monocyte chemoattractant protein-1 mRNA levels. In conclusion, angiostatin overexpression was associated with attenuated renal disease progression in a model of chronic kidney injury, likely because of its anti-inflammatory actions. However, its anti-angiogenic actions suggest countering effects that could partially offset its benefit in chronic kidney diseases. angiogenesis; gene therapy; inflammation; macrophage; vascular growth factors

The kidney is capable of regeneration following injury, particularly following acute insults. Although the mechanisms underlying cellular regeneration are incompletely understood, emerging evidence suggests a role for cells of renal origin in the repair and replacement of damaged renal tubule cells. The overall hypothesis of this study is that native kidney cells that reside in a niche in the kidney provide robust contribution to the repair of kidney tubules following injury. To test this hypothesis, we utilized a model of renal ischemia-reperfusion injury that results in extensive morphological changes, particularly in the outer medulla. Renal tissue obtained from mice constitutively expressing Escherichia coli [beta]-galactosidase (ROSA26) was dissected from the cortex, outer medulla, or papilla and implanted under the renal capsule of the injured mice. Mice were allowed to recover for 7 days. Sections through the injured kidney demonstrated the presence of implantderived cells in renal tubules in the outer medulla. The implanted renal region that exhibited the most robust response was the papilla, whereas tissue pieces from the cortex and outer medulla showed less contribution to recipient renal tubules. These results provide proofof-principle evidence that renal-derived reparative cells reside in all regions of the kidney, perhaps more predominantly in the renal papilla. A greater understanding of the cell biology of renal repair by native kidney cells will provide further insight into the design of novel therapies in acute kidney injury, and the subcapsular implant technique described in this study may offer unique advantages to evaluate renal repair mechanisms. epithelial repair; ischemia-reperfusion injury; progenitor cells

Accurate determination of renal function in mice is a major impediment to the use of murine models in acute kidney injury. The purpose of this study was to determine whether early changes in renal function could be detected using dynamic gamma camera imaging in a mouse model of ischemia-reperfusion (I/R) injury. C57BL/6 mice (n = 5/group) underwent a right nephrectomy, followed by either 30 min of I/R injury or sham surgery of the remaining kidney. Dynamic renal studies (21 min, 10 s/frame) were conducted before surgery (baseline) and at 5, 24, and 48 h by injection of [sup.99m]Tc-mercaptoacetyltriglycine (MAG3; ~1.0 mCi/mouse) via the tail vein. The percentage of injected dose (%ID) in the kidney was calculated for each 10-s interval after MAG3 injection, using standard region of interest analyses. A defect in renal function in I/R-treated mice was detected as early as 5 h after surgery compared with sham-treated mice, identified by the increased %ID (at peak) in the I/R-treated kidneys at 100 s (P < 0.01) that remained significantly higher than sham-treated mice for the duration of the scan until 600 s (P < 0.05). At 48 h, the renal scan demonstrated functional renal recovery of the I/R mice and was comparable to sham-treated mice. Our study shows that using dynamic imaging, renal dysfunction can be detected and quantified reliably as early as 5 h after I/R insult, allowing for evaluation of early treatment interventions. acute kidney injury; nuclear imaging; mice models of acute renal failure

Recent studies in our laboratory using the Zucker obese (ZO) and Zucker diabetic fatty (ZDF) rat models resulted in unexpectedly high mortality rates in all genotypes including healthy homozygous lean Zucker rats, possibly because of renal dysfunction. Therefore, we evaluated left ventricular (LV) and kidney morphology and function in young ZO, Zucker diabetic fatty obese (ZDFO), homozygous Zucker/ZDF lean (ZL), and Sprague-Dawley (SD) rats. Hydronephrosis was evident in ZL, ZO, and ZDFO but not SD kidneys. ZDFO rats exhibited impaired LV shortening and relaxation with increased arterial stiffness. LV wall thickness was lower and LV end-systolic wall stress was higher in ZDFO compared with SD rats. Plasma ANG II was lower in ZO and ZDFO rats, which may be a result of reduced renal parenchyma with hydronephrosis; norepinephrine was higher in ZDFO rats than SD controls. Covariate analysis indicated that LV end-systolic wall stress was associated with renal dysfunction. The presence of hydronephrosis and its association with LV dysfunction potentially limits the ZDF model for study of the effects of diabetes on renal and cardiovascular function. diabetes; cardiac function; renal function doi:10.1152/ajpheart.01362.2006

Exogenous bilirubin (BR) substitutes for the protective effects of heme oxygenase (HO) in several organ systems. Our objective was to investigate the effects of exogenous BR in an in vivo model of ischemia-reperfusion injury (IRI) in the rat kidney. Four groups of male Sprague-Dawley rats were anesthetized using isoflurane in oxygen and treated with 1) 5 mg/kg intravenous (iv) BR, 1 h before ischemia and 6-h reperfusion; 2) vehicle 1 h before ischemia and 6-h reperfusion; 3) 20 mg/kg iv BR, 1 h before and during ischemia; and 4) vehicle 1 h before and during ischemia. Bilateral renal clamping (30 min) was followed by 6-h reperfusion. Infusion of 5 mg/kg iv BR achieved target levels in the serum at 6 h postischemia (31 [+ or -] 9 [micro]mol/l). Infusion of 20 mg/kg BR reached 50 [+ or -] 22 [micro]mol/1 at the end of ischemia, and a significant improvement was seen in serum creatinine at 6 h (1.07 [+ or -] 28 vs. 1.38 [+ or -] 0.18 mg/dl, P = 0.043). Glomerular filtration rate, estimated renal plasma flow, fractional excretion of electrolytes, and renal vascular resistance were not significantly improved in BR-treated groups. Histological grading demonstrated a trend toward preservation of cortical proximal tubules in rats receiving 20 mg/kg iv BR compared with control; however, neither BR dose provided protection against injury to the renal medulla. At the doses administered, iv BR did not provide complete protection against IRI in vivo. Combined supplementation of both BR and carbon monoxide may be required to preserve renal blood flow and adequately substitute for the protective effects of HO in vivo. heme oxygenase; carbon monoxide; biliverdin

Induction of heme oxygenase-1 (HO-1) in renal tubules occurs as an adaptive and beneficial response in acute renal failure (ARF) following ischemia and nephrotoxins. Using an in vitro model of polarized Madin-Darby canine kidney (MDCK) epithelial cells, we examined apical and basolateral cell surface sensitivity to HO-1 induction by heme. Basolateral exposure to 5 [micro]M hemin (heine chloride) resulted in higher HO-1 induction than did apical exposure. The peak induction of HO-1 by basolateral application of hemin occurred between 12 and 18 h of exposure and was dose dependent. Similar cell surface sensitivity to hemin-induced HO-1 expression was observed using a mouse cortical collecting duct cell line (94D cells). Hepatocyte growth factor (HGF) is known to decrease cell polarity of MDCK cells. Following pretreatment with HGF, apically applied hemin gave greater stimulation of HO-1 expression, whereas HGF alone did not induce HO-1. We also examined the effect of hypoxia on heroin-mediated HO-1 induction. MDCK cells were subjected to hypoxia (1% [O.sub.2]) for 24 h to simulate the effects of ischemic ARF. Under hypoxic conditions, both apical as well as basolateral surfaces of MDCK were more sensitive to HO-1 induction by hemin. Hypoxia alone did not induce HO-1 but appeared to potentiate both apical and basolateral sensitivity to hemin-mediated induction. These data demonstrate that the induction of HO-1 expression in polarized renal epithelia by heme is achieved primarily via basolateral exposure. However, under conditions of altered renal epithelial cell polarity and hypoxia, increased HO-1 induction occurs following apical exposure to heme. acute renal failure; kidney; hepatocyte growth factor

A combination of gene and cell-based therapies may provide significant advantages over existing treatments in terms of their effectiveness. However, long-term efficient gene delivery has been difficult to achieve in many cell types, including endothelial cells. We developed a freeze-thaw technique which significantly increases the transduction efficiency of recombinant adeno-associated virus vectors in human aortic endothelial cells (23-fold) and in human renal proximal tubular epithelial cells (128-fold) in comparison to current methods for transduction. Freeze-thaw resulted in a transient but significant increase in cell surface area by 1,174 [+ or -] 69.8 [micro][M.sup.2] per cell. Reduction of cryogenic medium volume and repeated freeze-thaw further increased transduction efficiency by 2.8- and 2.4-fold, respectively. Trypsinization, dimethylsulfoxide, and cold temperatures, which are also involved in cell preservation, had no significant impact on transduction efficiency. Increased transduction was also observed in mesenchymal stem cells (42-fold) by the freeze-thaw method. The potential mechanism of this novel technique likely involves an increase in the net permeable area of biological membranes caused by water crystallization. These findings provide a new approach for gene delivery in various cell types, particularly in those resistant to transduction by conventional methods. gene therapy; endothelial cells; stem cells; cell therapy doi:10.1152/ajpcell.00582.2005

The signaling pathways leading to high NaCl-induced activation of the transcription factor tonicity-responsive enhancer binding protein/osmotic response element binding protein (TonEBP/OREBP) remain incompletely understood. High NaCl has been reported to produce oxidative stress. Reactive oxygen species (ROS), which are a component of oxidative stress, contribute to regulation of transcription factors. The present study was undertaken to test whether the high NaCl-induced increase in ROS contributes to tonicity-dependent activation of TonEBP/OREBP. Human embryonic kidney 293 cells were used as a model. We find that raising NaCl increases ROS, including superoxide. N-acetylcysteine (NAC), an antioxidant, and MnTBAP, an inhibitor of superoxide, reduce high NaCl-induced superoxide activity and suppress both high NaCl-induced increase in TonEBP/OREBP transcriptional activity and high NaCl-induced increase in expression of BGT1mRNA, a transcriptional target of TonEBP/OREBP. Catalase, which decomposes hydrogen peroxide, does not have these effects, whether applied exogenously or overexpressed within the cells. Furthermore, NAC and MnTBAP, but not catalase, blunt high NaCl-induced increase in TonEBP/ OREBP transactivation. [N.sup.G]-monomethyl-L-arginine, a general inhibitor of nitric oxide synthase, has no significant effect on either high NaCl-induced increase in superoxide or TonEBP/OREBP transcriptional activity, suggesting that the effects of ROS do not involve nitric oxide. Ouabain, an inhibitor of Na-K-ATPase, attenuates high NaCl-induced superoxide activity and inhibits TonEBP/OREBP transcriptional activity. We conclude that the high NaCl-induced increase in ROS, including superoxide, contributes to activation of TonEBP/OREBP by increasing its transactivation. superoxides; nitric oxide; ouabain; transactivation; nuclear translocation

Heme oxygenase-1 (HO-1) is induced as an adaptive and protective response to tissue injury. HO-1 degrades heme into carbon monoxide (CO) and biliverdin; the latter is then converted to bilirubin. These reaction products have powerful antiapoptotic and antioxidant effects. Manipulation of the HO-1 system by administration of micromolar doses of exogenous CO or bilirubin has been performed in several organ systems, but the dose-related effects of these reaction products have not been investigated in the kidney. The purpose of this study was to evaluate the efficacy and dose-related protective effects of 1 or 10 [micro]M bilirubin flush before a 20-min period of warm ischemia. In an effort to minimize interactions with other chemical messengers or organ systems, we elected to use an isolated, perfused rat kidney model with an acellular, oxygenated perfusate. Using this model, we demonstrated that bilirubin treatment resulted in significant improvements in renal vascular resistance, urine output, glomerular filtration rate, tubular function, and mitochondrial integrity after ischemia-reperfusion injury (IRI). Beneficial effects on organ viability were achieved most consistently with a dose of 10 [micro]M bilirubin. We conclude that the protective effects of HO-1 activity during IRI in the kidney are mediated, at least in part, by bilirubin and that pretreatment with micromolar doses of bilirubin may offer a simple and inexpensive method to improve renal function after IRI. isolated; perfused kidney; heme oxygenase-1

Heme oxygenases (HOs) catalyze the rate-limiting step in heme degradation resulting in the formation of iron, carbon monoxide, and biliverdin the latter of which is subsequently converted to bilirubin by biliverdin, reductase. Recent attention has focused on the biological effects of product(s) of this enzymatic reaction, which have important antioxidant, anti-inflammatory, and cytoprotective functions. Two major isoforms of the HO enzyme have been described: an inducible isoform, HO-1, and a constitutively expressed isoform, HO-2. A third isoform, HO-3, closely related to HO-2, has also been described. Several stimuli implicated in the pathogenesis of renal injury, such as heme, nitric oxide, growth factors, angiotensin II, cytokines, and nephrotoxins, induce HO-1. Induction of HO-1 occurs as an adaptive and beneficial response to these stimuli, as demonstrated by studies in renal and non-renal disease states. This review will focus on the molecular regulation of the HO-1 gene in renal injury and will highlight the interspecies differences, predominantly between the rodent and human HO-1 genes. gene transcription; oxidant stress; heme proteins

Heme oxygenase-1 (HO-1) catalyzes the rate-limiting step in heme degradation, releasing iron, carbon monoxide, and biliverdin. Induction of HO-1 is an adaptive and beneficial response in renal and nonrenal settings of tissue injury. The purpose of this study was to characterize the regulation of the human HO-1 gene in renal proximal tubule and aortic endothelial cells in response to heme and cadmium. Evaluation of multiple human HO-1 promoter-reporter constructs up to -9.1 kb demonstrated only a partial response to heme and cadmium. In an effort to mimic endogenous stimulus-dependent levels of HO-1 induction, we evaluated the entire 12.5 kb of the human HO-1 gene, including introns and exons, in conjunction with a -4.5-kb human HO-1 promoter and observed significant heme- and cadmium-mediated induction of the reporter gene, suggesting the presence of an internal enhancer. Enhancer function was orientation independent and required a region between -3.5 and -4.5 kb of the human HO-1 promoter. Our studies identified a novel enhancer internal to the human HO-1 gene that, in conjunction with the HO-1 promoter, recapitulates heme- and cadmium-mediated induction of the endogenous HO-1 gene. Elucidation of the molecular regulation of the human HO-1 gene will allow for the development of therapeutic strategies to manipulate HO-1 gene expression in pathological states. gene transcription; renal proximal tubule cells; endothelial cells; heme proteins; molecular regulation

The role of low-density lipoproteins (LDL) in promoting tubulointerstitial disease and renal cytotoxicity was analyzed in patients with proteinuric renal disease. Oxidized LDL contribute to tubulointerstitial disease by causing cytotoxicity in the renal tubular epithelium and endothelial cells. However, the cytotoxic effects of LDl was inhibited by alpha-tocopherol, ascorbic acid, butylated hydroxytoluene and deferoxamine.

Expansion of renal lymphatic networks, or lymphangiogenesis (LA), is well recognized during development and is now being implicated in kidney diseases. Although LA is associated with multiple pathological conditions, very little is known about its role in acute kidney injury. The purpose of this study was to evaluate the role of LA in a model of cisplatin-induced nephrotoxicity. LA is predominately regulated by vascular endothelial growth factor (VEGF)-C and VEGF-D, ligands that exert their function through their cognate receptor VEGF receptor 3 (VEGFR3). We demonstrated that use of MAZ51, a selective VEGFR3 inhibitor, caused significantly worse structural and functional kidney damage in cisplatin nephrotoxicity. Apoptotic cell death and inflammation were also increased in MAZ51-treated animals compared with vehicle-treated animals following cisplatin administration. Notably, MAZ51 caused significant upregulation of intrarenal phospho-NF-κB, phospho-JNK, and IL-6. Cisplatin nephrotoxicity is associated with vascular congestion due to endothelial dysfunction. Using three-dimensional tissue cytometry, a novel approach to explore lymphatics in the kidney, we detected significant vascular autofluorescence attributed to erythrocytes in cisplatin alone-treated animals. Interestingly, no such congestion was detected in MAZ51-treated animals. We found increased renal vascular damage in MAZ51-treated animals, whereby MAZ51 caused a modest decrease in the endothelial markers endomucin and von Willebrand factor, with a modest increase in VEGFR2. Our findings identify a protective role for de novo LA in cisplatin nephrotoxicity and provide a rationale for the development of therapeutic approaches targeting LA. Our study also suggests off-target effects of MAZ51 on the vasculature in the setting of cisplatin nephrotoxicity. [ABSTRACT FROM AUTHOR]

Kidney resident macrophages (KRMs) are involved in maintaining renal homeostasis and in controlling the pathological outcome of acute kidney injury and cystic kidney disease in mice. In adult mice, KRMs maintain their population through self-renewal with little or no input from the peripheral blood. Despite recent data suggesting that a transcriptionally similar population of KRM-like cells is present across species, the idea that they are self-renewing and minimally dependent on peripheral blood input in other species has yet to be proven due to the lack of an appropriate model and cross-species expression markers. In this study, we used our recently identified cross-species KRM cell surface markers and parabiosis surgery in inbred Lewis rats to determine if rat KRMs are maintained independent of peripheral blood input, similar to their mouse counterparts. Flow cytometry analysis indicated that parabiosis surgery in the rat results in the establishment of chimerism of T/B cells, neutrophils, and monocytederived infiltrating macrophages in the blood, spleen, and kidney 3 wk after parabiosis surgery. Analysis of KRMs using the cell surface markers CD81 and C1q indicated that these cells have minimal chimerism and, therefore, receive little input from the peripheral blood. These data indicate that KRM properties are conserved in at least two different species. [ABSTRACT FROM AUTHOR]

Acute kidney injury (AKI) remains a significant clinical problem through its diverse etiologies, the challenges of robust measurements of injury and recovery, and its progression to chronic kidney disease (CKD). Bridging the gap in our knowledge of this disorder requires bringing together not only the technical resources for research but also the investigators currently endeavoring to expand our knowledge and those who might bring novel ideas and expertise to this important challenge. The University of Alabama at Birmingham-University of California-San Diego O'Brien Center for Acute Kidney Injury Research brings together technical expertise and programmatic and educational efforts to advance our knowledge in these diverse issues and the required infrastructure to develop areas of novel exploration. Since its inception in 2008, this O'Brien Center has grown its impact by providing state-of-the-art resources in clinical and preclinical modeling of AKI, a bioanalytical core that facilitates measurement of critical biomarkers, including serum creatinine via LC-MS/MS among others, and a biostatistical resource that assists from design to analysis. Through these core resources and with additional educational efforts, our center has grown its investigator base to include >200 members from 51 institutions. Importantly, this center has translated its pilot and catalyst funding program with a $37 return per dollar invested. Over 500 publications have resulted from the support provided with a relative citation ratio of 2.18 ± 0.12 (iCite). Through its efforts, this disease-centric O'Brien Center is providing the infrastructure and focus to help the development of the next generation of researchers in the basic and clinical science of AKI. This center creates the promise of the application at the bedside of the advances in AKI made by current and future investigators. [ABSTRACT FROM AUTHOR]

Cellular metabolic rates in the kidney are critical for maintaining normal renal function. In a hypoxic milieu, cells rely on glycolysis to meet energy needs, resulting in the generation of pyruvate and NADH. In the absence of oxidative phosphorylation, the continuation of glycolysis is dependent on the regeneration of NAD+ from NADH accompanied by the fermentation of pyruvate to lactate. This reaction is catalyzed by lactate dehydrogenase (LDH) isoform A (LDHA), whereas LDH isoform B (LDHB) catalyzes the opposite reaction. LDH is widely used as a potential injury marker as it is released from damaged cells into the urine and serum; however, the precise isoform-specific cellular localization of the enzyme along the nephron has not been characterized. By combining immunohistochemistry results and single-cell RNA-sequencing data on healthy mouse kidneys, we identified that LDHA is primarily expressed in proximal segments, whereas LDHB is expressed in the distal parts of the nephron. In vitro experiments in mouse and human renal proximal tubule cells showed an increase in LDHA following hypoxia with no change in LDHB. Using immunofluorescence, we observed that the overall expression of both LDHA and LDHB proteins decreased following renal ischemia-reperfusion injury as well as in the adenine-diet-induced model of chronic kidney disease. Single-nucleus RNA-sequencing analyses of kidneys following ischemia-reperfusion injury revealed a significant decline in the number of cells expressing detectable levels of Ldha and Ldhb; however, cells that were positive showed increased average expression postinjury, which subsided during the recovery phase. These data provide information on the cell-specific expression of LDHA and LDHB in the normal kidney as well as following acute and chronic kidney disease. [ABSTRACT FROM AUTHOR]

Heme oxygenase-1 gene ablation or expression modulates cisplatin-induced renal tubular apoptosis. Am J Physiol Renal Physiol 278: F726-F736, 2000.--Heme oxygenase-1 (HO-l) is a 32-kDa microsomal enzyme that catalyzes the conversion of heme to biliverdin, releasing iron and carbon monoxide. Induction of HO-1 occurs as a protective response in cells/tissues exposed to a wide variety of oxidant stimuli. The chemotherapeutic effects of cis-diamminedichloroplatinum(II) (cisplatin), a commonly used anticancer drug, are limited by significant nephrotoxicity, which is characterized by varying degrees of renal tubular apoptosis and necrosis. The purpose of this study was to evaluate the functional significance of HO-1 expression in cisplatin-induced renal injury. Our studies demonstrate that transgenic mice deficient in HO-1 (-/-), develop more severe renal failure and have significantly greater renal injury compared with wild-type (+/+) mice treated with cisplatin. In vitro studies in human renal proximal tubule cells demonstrate that hemin, an inducer of HO-l, significantly attenuated cisplatin-induced apoptosis and necrosis, whereas inhibition of HO-1 enzyme activity reversed the cytoprotective effect. Overexpression of HO-1 resulted in a significant reduction in cisplatin-induced cytotoxicity. These studies provide a basis for future studies using targeted gene expression of HO-1 as a therapeutic and preventive modality in high-risk settings of acute renal failure. acute renal failure; oxidative stress; cytoprotection; carbon monoxide; cancer chemotherapy

Lewisite (2-chlorovinyldichloroarsine) is an organic arsenical chemical warfare agent that was developed and weaponized during World Wars I/II. Stockpiles of lewisite still exist in many parts of the world and pose potential environmental and human health threat. Exposure to lewisite and similar chemicals causes intense cutaneous inflammatory response. However, morbidity and mortality in the exposed population is not only the result of cutaneous damage but is also a result of systemic injury. Here, we provide data delineating the pathogenesis of acute kidney injury (AKI) following cutaneous exposure to lewisite and its analog phenylarsine oxide (PAO) in a murine model. Both agents caused renal tubular injury, characterized by loss of brush border in proximal tubules and tubular cell apoptosis accompanied by increases in serum creatinine, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1. Interestingly, lewisite exposure enhanced production of reactive oxygen species (ROS) in the kidney and resulted in the activation of autophagic and DNA damage response (DDR) signaling pathways with increased expression of beclin-1, autophagy-related gene 7, and LC-3A/B-II and increased phosphorylation of γ-H2A.X and checkpoint kinase 1/2, respectively. Terminal deoxyribonucleotide-transferase-mediated dUTP nick-end labeling-positive cells were detected in renal tubules along with enhanced proapoptotic BAX/cleaved caspase-3 and reduced antiapoptotic BCL2. Scavenging ROS by cutaneous postexposure application of the antioxidant N-acetyl-L-cysteine reduced lewisite-induced autophagy and DNA damage. In summary, we provide evidence that topical exposure to lewisite causes AKI. The molecular mechanism underlying these changes involves ROSdependent activation of autophagy and DDR pathway associated with the induction of apoptosis. [ABSTRACT FROM AUTHOR]

Ferroptosis is an iron-dependent form of regulated nonapoptotic cell death, which contributes to damage in models of acute kidney injury (AKI). Heme oxygenase-1 (HO-1) is a cytoprotective enzyme induced in response to cellular stress, and is protective against AKI because of its antiapoptotic and anti-inflammatory properties. However, the role of HO-1 in regulating ferroptosis is unclear. The purpose of this study was to elucidate the role of HO-1 in regulating ferroptotic cell death in renal proximal tubule cells (PTCs). Immortalized PTCs obtained from HO-+/+ and HO--/- mice were treated with erastin or RSL3, ferroptosis inducers, in the presence or absence of antioxidants, an iron source, or an iron chelator. Cells were assessed for changes in morphology and metabolic activity as an indicator of cell viability. Treatment of HO-+/+ PTCs with erastin resulted in a time- and dose-dependent increase in HO-1 gene expression and protein levels compared with vehicle-treated controls. HO--/- cells showed increased dose-dependent erastin- or RSL3-induced cell death in comparison to HO-+/+ PTCs. Iron supplementation with ferric ammonium citrate in erastin-treated cells decreased cell viability further in HO--/- PTCs compared with HO--/- cells. Cotreatment with ferrostatin-1 (ferroptosis inhibitor), deferoxamine (iron chelator), or N-acetyl-L-cysteine (glutathione replenisher) significantly increased cell viability and attenuated erastin-induced ferroptosis in both HO-+/+ and HO--/- PTCs. These results demonstrate an important antiferroptotic role of HO-1 in renal epithelial cells. [ABSTRACT FROM AUTHOR]

Mononuclear phagocytes are the most common cells in the kidney associated with immunity and inflammation. Although the presence of these cells in the kidney has been known for decades, the study of mononuclear phagocytes in the context of kidney function and dysfunction is still at an early stage. The purpose of this review is to summarize the present knowledge regarding classification of these cells in the mouse kidney and to identify relevant questions that would further advance the field and potentially lead to new opportunities for treatment of acute kidney injury and other kidney diseases. [ABSTRACT FROM AUTHOR]

Acute kidney injury (AKI) is one of the leading causes of in-hospital morbidity and mortality, particularly in critically ill patients. Although our understanding of AKI at the molecular level remains limited due to its complex pathophysiology, recent advances in both quantitative and spatial mass spectrometric approaches offer new opportunities to assess the significance of renal metabolomic changes in AKI models. In this study, we evaluated lipid changes in early ischemia-reperfusion (IR)-related AKI in mice by using sequential window acquisition of all theoretical spectra (SWATH)-mass spectrometry (MS) lipidomics. We found a significant increase in two abundant ether-linked phospholipids following IR at 6 h postinjury, a plasmanyl choline, phosphatidylcholine (PC) O-38:1 (O-18:0, 20:1), and a plasmalogen, phosphatidylethanolamine (PE) O-42:3 (O-20:1, 22:2). Both of these lipids correlated with the severity of AKI as measured by plasma creatinine. In addition to many more renal lipid changes associated with more severe AKI, PC O-38:1 elevations were maintained at 24 h post-IR, while renal PE O-42:3 levels decreased, as were all ether PEs detected by SWATH-MS at this later time point. To further assess the significance of this early increase in PC O-38:1, we used matrixassisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) to determine that it occurred in proximal tubules, a region of the kidney that is most prone to IR injury and also rich in the rate-limiting enzymes involved in ether-linked phospholipid biosynthesis. Use of SWATH-MS lipidomics in conjunction with MALDIIMS for lipid localization will help in elucidating the role of lipids in the pathobiology of AKI. [ABSTRACT FROM AUTHOR]

Heme oxygenase-1 (HO-1) is a cytoprotective enzyme that catalyzes the breakdown of heme to biliverdin, carbon monoxide, and iron. The beneficial effects of HO-1 expression are not merely due to degradation of the pro-oxidant heme but are also credited to the by-products that have potent, protective effects, including antioxidant, anti-inflammatory, and prosurvival properties. This is well reflected in the preclinical animal models of injury in both renal and nonrenal settings. However, excessive accumulation of the by-products can be deleterious and lead to mitochondrial toxicity and oxidative stress. Therefore, use of the HO system in alleviating injury merits a targeted approach. Based on the higher susceptibility of the proximal tubule segment of the nephron to injury, we generated transgenic mice using cre-lox technology to enable manipulation of HO-1 (deletion or overexpression) in a cell-specific manner. We demonstrate the validity and feasibility of these mice by breeding them with proximal tubule-specific Cre transgenic mice. Similar to previous reports using chemical modulators and global transgenic mice, we demonstrate that whereas deletion of HO-1, specifically in the proximal tubules, aggravates structural and functional damage during cisplatin nephrotoxicity, selective overexpression of HO-1 in proximal tubules is protective. At the cellular level, cleaved caspase-3 expression, a marker of apoptosis, and p38 signaling were modulated by HO-1. Use of these transgenic mice will aid in the evaluation of the effects of cell-specific HO-1 expression in response to injury and assist in the generation of targeted approaches that will enhance recovery with reduced, unwarranted adverse effects. [ABSTRACT FROM AUTHOR]