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Chemokine receptor (CCR5) expression in human kidneys and in the HIV infected macaque. Background. The chemokine receptor, CCR5, has been identified as an essential co-receptor with CD4, which permits entry of human immunodeficiency virus (HIV) into mammalian cells. This receptor may also mediate leukocyte and parenchymal responses to injury by virtue of its binding to locally released chemokines such as RANTES, MIP-1α and MIP-1β during inflammation. The localization of CCR5 in human or primate kidney is unknown. In this study we sought to identify sites of CCR5 synthesis through localization of mRNA coding for this peptide. Methods. CCR5 cDNA cloned into an expression vector was transcribed into a 1.1 Kb antisense riboprobe that was utilized for in situ hybridization (ISH) and Northern blotting studies. Results. Northern analysis demonstrated positive hybridization for CCR5 mRNA in total RNA isolated from allograft nephrectomy tissue with features of severe transplant rejection as well as in kidney tissue with focal interstitial nephritis. No comparable hybridization signal was achieved with human kidney tissue uninvolved by disease. CCR5 mRNA was not identified in intrinsic renal cell types by ISH in normal human (N = 6), normal macaque kidney (N = 5), in kidneys from macaques with established infection by HIV-2 (N = 9), kidneys from macaques infected with HIV-1 (N = 4), nor in kidneys from SIV-infected macaques (N = 5). CCR5 was identified by ISH in human kidneys with features of interstitial nephritis (N = 3) and in rejected human allograft kidneys (N = 14). The expression of CCR5 was restricted to infiltrating mononuclear leukocytes at sites of chronic tubulointerstitial injury and at sites of vascular and interstitial rejection, respectively. Conclusions. Understanding the localization of CCR5 as well as other chemokine receptors may help us understand how specificity in leukocyte trafficking is achieved in renal inflammatory processes such as... [ABSTRACT FROM AUTHOR]

The physiological function of free fatty acids (FFAs) has long been regarded as indirect in terms of their activities as educts and products in metabolic pathways. The observation that FFAs can also act as signaling molecules at FFA receptors (FFARs), a family of G protein-coupled receptors (GPCRs), has changed the understanding of the interplay of metabolites and host responses. Free fatty acids of different chain lengths and saturation statuses activate FFARs as endogenous agonists via binding at the orthosteric receptor site. After FFAR deorphanization, researchers from the pharmaceutical industry as well as academia have identified several ligands targeting allosteric sites of FFARs with the aim of developing drugs to treat various diseases such as metabolic, (auto)inflammatory, infectious, endocrinological, cardiovascular, and renal disorders. GPCRs are the largest group of transmembrane proteins and constitute the most successful drug targets in medical history. To leverage the rich biology of this target class, the drug industry seeks alternative approaches to address GPCR signaling. Allosteric GPCR ligands are recognized as attractive modalities because of their auspicious pharmacological profiles compared to orthosteric ligands. While the majority of marketed GPCR drugs interact exclusively with the orthosteric binding site, allosteric mechanisms in GPCR biology stay medically underexploited, with only several allosteric ligands currently approved. This review summarizes the current knowledge on the biology of FFAR1 (GPR40), FFAR2 (GPR43), FFAR3 (GPR41), FFAR4 (GPR120), and GPR84, including structural aspects of FFAR1, and discusses the molecular pharmacology of FFAR allosteric ligands as well as the opportunities and challenges in research from the perspective of drug discovery. [ABSTRACT FROM AUTHOR]

The authors comment on clinical trials of prednisone plus ramipril for preventing proteinuric immunoglobulin A nephropathy (IgAN) in patients at high risk of progressive renal damage. They agree that the trials strengthen the evidence that corticosteroid therapy is beneficial in proteinuric IgAN, even when administered with angiotensin-converting-enzyme inhibitor (ACEI). They recommend that corticosteroids should only be given to patients whose proteinuria level remains above one gram (g) per day following antihypertensive and antiproteinuric therapy.

The article focuses on the new Oxford classification of immunoglobulin A (IgA) nephropathy developed for predicting the risk of disease progression. It references the reports "The Oxford Classification of IgA Nephropathy: Pathology Definitions, Correlations and Reproducibility," by I. S. Roberts et al and "The Oxford Classification of IgA Nephropathy: Rationale, Clinicopathological Correlations and Classification," by D. C. Cattran et al, published in "Kidney International" in 2009. The need to study novel biomarkers of disease progression is tackled.

Background: The Oxford classification of IgA nephropathy (IgAN) defines histologic criteria (MEST-C) that provide prognostic information based on the kidney biopsy. There are few data on the predictive impact of this classification in randomized clinical trial settings.Methods: We performed an exploratory analysis of MEST-C scores in 70 available renal biopsies from 162 randomized STOP-IgAN trial participants and correlated the results with clinical outcomes. Analyses were performed by researchers blinded to the clinical outcome of the patients. Biopsies had been obtained 6.5 to 95 (median 9.4) months prior to randomization.Results: Mesangial hypercellularity (M1) associated with higher annual eGFR-loss during the 3-year trial (M1: - 5.06 ± 5.17 ml/min/1.73 m2, M0: - 0.79 ± 4.50 ml/min/1.73 m2, p = 0.002). An M0-score additionally showed a weak association with full clinical remission, whereas the percentage of patients losing ≥15 ml/min/1.73 m2 over the 3-year trial phase was higher among those scored as M1. Among patients with additional immunosuppression, ESRD occurred more frequently in patients when tubulointerstitial fibrosis (T1/2) was present (T1/2 = 33%, T0 = 0%, p = 0.008). In patients receiving supportive care only, ESRD frequencies were similar (T1/2 = 18%, T0 = 7%, p = 0.603). At randomization, eGFR was significantly lower when tubulointerstitial fibrosis was present (T1/2: 45.2 ± 15.7 ml/min/1.73 m2, T0: 74.6 ± 28.2 ml/min/1.73 m2, p < 0.0001). Endocapillary hypercellularity (E), and glomerular segmental sclerosis (S) were not associated with any clinical outcome parameter. In the analyzed cohort, patients with glomerular crescents (C1/2 scores) in their biopsies were more likely to develop ESRD during the 3-year trial phase, but this trend was only significant in patients under supportive care.Conclusions: This secondary analysis of STOP-IgAN biopsies indicates that M1, T1/2 and C1/2 scores associate with worse renal outcomes. [ABSTRACT FROM AUTHOR]

Chronic kidney disease (CKD) progression is associated with persisting oxidative stress, which impairs the NO-sGC-cGMP signaling cascade through the formation of oxidized and heme-free apo-sGC that cannot be activated by NO. Runcaciguat (BAY 1101042) is a novel, potent, and selective sGC activator that binds and activates oxidized and heme-free sGC and thereby restores NO-sGC-cGMP signaling under oxidative stress. Therefore, runcaciguat might represent a very effective treatment option for CKD/DKD. The potential kidney-protective effects of runcaciguat were investigated in ZSF1 rats as a model of CKD/DKD, characterized by hypertension, hyperglycemia, obesity, and insulin resistance. ZSF1 rats were treated daily orally for up to 12 weeks with runcaciguat (1, 3, 10 mg/kg/bid) or placebo. The study endpoints were proteinuria, kidney histopathology, plasma, urinary biomarkers of kidney damage, and gene expression profiling to gain information about relevant pathways affected by runcaciguat. Furthermore, oxidative stress was compared in the ZSF1 rat kidney with kidney samples from DKD patients. Within the duration of the 12-week treatment study, kidney function was significantly decreased in obese ZSF1 rats, indicated by a 20-fold increase in proteinuria, compared to lean ZSF1 rats. Runcaciguat dose-dependently and significantly attenuated the development of proteinuria in ZSF1 rats with reduced uPCR at the end of the study by −19%, −54%, and −70% at 1, 3, and 10 mg/kg/bid, respectively, compared to placebo treatment. Additionally, average blood glucose levels measured as HbA1C, triglycerides, and cholesterol were increased by five times, twenty times, and four times, respectively, in obese ZSF1 compared to lean rats. In obese ZSF1 rats, runcaciguat reduced HbA1c levels by −8%, −34%, and −76%, triglycerides by −42%, −55%, and −71%, and cholesterol by −16%, −17%, and −34%, at 1, 3, and 10 mg/kg/bid, respectively, compared to placebo. Concomitantly, runcaciguat also reduced kidney weights, morphological kidney damage, and urinary and plasma biomarkers of kidney damage. Beneficial effects were accompanied by changes in gene expression that indicate reduced fibrosis and inflammation and suggest improved endothelial stabilization. In summary, the sGC activator runcaciguat significantly prevented a decline in kidney function in a DKD rat model that mimics common comorbidities and conditions of oxidative stress of CKD patients. Thus, runcaciguat represents a promising treatment option for CKD patients, which is in line with recent phase 2 clinical study data, where runcaciguat showed promising efficacy in CKD patients (NCT04507061). [ABSTRACT FROM AUTHOR]

In addition to lymphomas, vascular tumors represent the most common neoplasms of the spleen. Littoral cell angiomas are benign vascular tumors originating from the littoral cells lining the splenic sinuses. In this report, we describe the case of a 63-year-old patient who developed night sweats 16 months after renal transplantation. Diagnostic workup showed multiple splenic masses believed to represent lymphoma infiltration to the spleen. Lymph nodes and bone marrow were unaffected, and diagnostic splenectomy was performed. Histological examination of the pathological specimen from the splenectomy specimen showed multiple littoral cell angiomas of the spleen. We recommend that physicians involved in the area of organ transplantation, especially kidneys, remain alert for other rarer splenic lesions in transplant recipients than posttransplantation lymphoma. More specific tools need to be developed to aid in the differential diagnosis of splenic masses to avoid splenectomy in patients with littoral cell angiomas. [ABSTRACT FROM AUTHOR]

Background and Purpose: Generation of cGMP via NO‐sensitive soluble guanylyl cyclase (sGC) has been implicated in the regulation of renal functions. Chronic kidney disease (CKD) is associated with decreased NO bioavailability, increased oxidative stress and oxidation of sGC to its haem‐free form, apo‐sGC. Apo‐sGC cannot be activated by NO, resulting in impaired cGMP signalling that is associated with chronic kidney disease progression. We hypothesised that sGC activators, which activate apo‐sGC independently of NO, increase renal cGMP production under conditions of oxidative stress, thereby improving renal blood flow (RBF) and kidney function. Experimental Approach Two novel sGC activators, runcaciguat and BAY‐543, were tested on murine kidney. We measured cGMP levels in real time in kidney slices of cGMP sensor mice, vasodilation of pre‐constricted glomerular arterioles and RBF in isolated perfused kidneys. Experiments were performed at baseline conditions, under L‐NAME‐induced NO deficiency, and in the presence of oxidative stress induced by ODQ. Key Results: Mouse glomeruli showed NO‐induced cGMP increases. Under baseline conditions, sGC activator did not alter glomerular cGMP concentration or NO‐induced cGMP generation. In the presence of ODQ, NO‐induced glomerular cGMP signals were markedly reduced, whereas sGC activator induced strong cGMP increases. L‐NAME and ODQ pretreated isolated glomerular arterioles were strongly dilated by sGC activator. sGC activator also increased cGMP and RBF in ODQ‐perfused kidneys. Conclusion and Implication: sGC activators increase glomerular cGMP, dilate glomerular arterioles and improve RBF under disease‐relevant oxidative stress conditions. Therefore, sGC activators represent a promising class of drugs for chronic kidney disease treatment. LINKED ARTICLES: This article is part of a themed issue on cGMP Signalling in Cell Growth and Survival. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.11/issuetoc [ABSTRACT FROM AUTHOR]

Localization of fibroblast growth factor-2 (basic FGF) and FGF receptor-1 in adult human kidney. Background. The expression pattern of fibroblast growth factor-2 (FGF-2; basic FGF), a pleiotrophic growth factor, as well as one of its receptors (FGFR1), in the kidney is highly controversial. Methods. Using an approach that combines multiple antibodies for immunohistochemistry and correlative in situ hybridization, we assessed the intrarenal expression of both FGF-2 and FGFR1 in 13 specimens of adult kidney removed during tumor nephrectomy. Results. The FGF-2 expression pattern in the kidneys as detected by immunohistochemistry was variable and depended on the antibody used. The most consistent expression of FGF-2 protein was demonstrated in glomerular parietal epithelial cells, tubular cells (mainly of the distal nephron), as well as arterial endothelial cells. These locations also corresponded to areas of FGF-2 mRNA expression. Additionally, by immunohistochemistry, FGF-2 protein was detected in arterial smooth muscle cells and occasional podocytes. The expression of FGFR1 protein and mRNA was most consistently present in tubular cells of the distal nephron and in vascular smooth muscle cells. In situ hybridization, but not immunohistochemistry, also suggested FGFR1 expression in cells that could not be precisely identified within the glomerular tuft as well as some interstitial cells. Conclusion. These data suggest potential autocrine and paracrine pathways within the FGF-2 system, particularly within the vascular walls and in the distal nephron, and thereby provide information for further mechanistic understanding of the role of the FGF-2 system in human renal disease. [ABSTRACT FROM AUTHOR]

Mononuclear phagocytes (MNPs) participate in inflammation and repair after kidney injury, reflecting their complex nature. Dissection into refined functional subunits has been challenging and would benefit understanding of renal pathologies. Flow cytometric approaches are limited to classifications of either different MNP subsets or functional state. We sought to combine these two dimensions in one protocol that considers functional heterogeneity in each MNP subset. We identified five distinct renal MNP subsets based on a previously described strategy. In vitro polarization of bone marrow-derived macrophages (BMDM) into M1- and M2-like cells suggested functional distinction of CD86 + MHCII + CD206- and CD206 + cells. Combination of both distinction methods identified CD86 + MHCII + CD206- and CD206 + cells in all five MNP subsets, revealing their heterologous nature. Our approach revealed that MNP composition and their functional segmentation varied between different mouse models of kidney injury and, moreover, was dynamically regulated in a time-dependent manner. CD206 + cells from three analyzed MNP subsets had a higher ex vivo phagocytic capacity than CD86 + MHCII + CD206- counterparts, indicating functional uniqueness of each subset. In conclusion, our novel flow cytometric approach refines insights into renal MNP heterogeneity and therefore could benefit mechanistic understanding of renal pathology. [ABSTRACT FROM AUTHOR]

Sirolimus is an established immunosuppressant in renal transplantation with antineoplastic and antiviral features, but side effects like proteinuria limit its use. The aim of this retrospective multicenter observational study is to define predictors for determining which patients most likely benefit from a sirolimus-based therapy. All patients from 10 German centers that were switched to a sirolimus-containing maintenance immunosuppression in 2000 to 2008 after 3 months or later post-transplantation were enrolled (n = 726). Observation times after switching to sirolimus ranged from 4 days to 9 years (median: 24.3 months). With multinomial logistic regression, risk factors for the endpoints terminal graft failure and withdrawal of sirolimus therapy compared to successful therapy were identified. Successful sirolimus therapy was observed in 304 patients. Forty patients died with functioning graft. Therapy failures included graft loss (n = 106) and sirolimus-discontinuation for various reasons (n = 276). Successful sirolimus-use was predicted in 83% and graft failure in 65%, whereas prediction of deliberate sirolimus-discontinuation was poor (48%). Most favorable results for sirolimus-use were observed in patients switched in 2006 to 2008. Using ROC analysis, an estimated glomerular filtration rate (eGFR) below 32 mL/min was shown to be the cut-off in patients withdrawing from therapy as a result of renal reasons, as well as in patients with graft loss. Proteinuria above 151 mg/L was shown to be predictive for patients with graft failure. eGFR and proteinuria are the major determinants for successful sirolimus-therapy. Our findings help stratifying patients who will benefit most from this therapy and avoid toxicities in patients without potential benefits for this therapy. [ABSTRACT FROM AUTHOR]

A response from the author of the article "Intensive supportive care plus immunosuppression in IgA nephropathy" in the December 2, 2015 issue is presented.

The German Sirolimus Study Group has established a database among 10 transplant centers throughout Germany to study the outcomes in 726 renal transplant patients being converted to a sirolimus-containing therapy between 2000 and 2008 with a total of more than 1500 recorded patient years on therapy. In this study, we present a detailed description of the cohort, of characteristic changes over the observation period, proteinuria and graft survival, and new-onset proteinuria after conversion. Over the study period, age, graft function at the time of conversion, and the proportion of patients switched to sirolimus because of malignancy increased, whereas the proportion of patients with significant proteinuria at conversion decreased. Already modest proteinuria (151-268 mg/L) at conversion and new-onset proteinuria (>500 mg/L) after conversion were associated with inferior graft survival. Even mild proteinuria (>71 mg/L) at conversion was associated with new-onset proteinuria (>500 mg/L) post-conversion. Serum creatinine and urinary protein excretion at conversion together with age at transplantation had a significant impact on patient and graft survival. This large data set confirms and extends previous observations that proteinuria is an important indicator for graft outcome after conversion to sirolimus. We conclude that patients without any proteinuria have the greatest benefit from conversion to sirolimus. [ABSTRACT FROM AUTHOR]

The incidence of renal cell carcinoma ( RCC) after kidney transplantation is 15-fold increased. Acquired cystic kidney disease ( ACKD) is one of the known risk factors. We performed a small pilot study to assess the role of non-enhanced magnetic resonance imaging ( MRI) as a tool for intensified screening in renal transplant recipients with ACKD. Renal ultrasound was used to assess the native kidneys of 215 renal transplant recipients. Thirty patients with 54 kidneys, fulfilling the criteria of ACKD, underwent non-enhanced MRI at 1.5T using T2- and T1-weighed as well as diffusion-weighted sequences with a high spatial resolution. Among the 54 kidneys assessed by both methods, three RCCs were identified (6%). Of those, one RCC was detected by both imaging methods (33%), while two RCCs were diagnosed by MRI alone (67%). MRI identified an additional four proteinaceous or hemorrhagic cysts that did not fulfill the criteria for RCC but were classified as suspicious. All of these lesions were stable in size and appearance in follow-up studies. In conclusion, non-enhanced MRI was more sensitive than ultrasound in identifying RCCs and lesions suspicious for RCC and thus appears to be a useful secondary screening tool in patients with ACKD after renal transplantation. [ABSTRACT FROM AUTHOR]

Background Platelet-derived growth factors (PDGF)-AA and -CC mediate renal fibroblast proliferation and/or renal fibrosis. Whereas PDGF-CC binds to both the PDGF receptors (PDGFRs)-αα- and -αβ, PDGF-AA binds more selectively to the αα-receptor, suggesting potential differences in the biological activities. Methods We compared signal transduction, gene expression as well as changes in the proteome induced by PDGF-AA and -CC in rat renal fibroblasts, which express both PDGFR subunits. The growth factor concentrations used were chosen based on their equipotency in inducing rat renal fibroblast proliferation. Results Both PDGF-AA and PDGF-CC induced phosphorylation and activation of extracellular signal-regulated kinase 1 (ERK1) and ERK2. Renal fibroblast proliferation induced by either PDGF-AA or -CC could be blocked by signal transduction inhibitors of the mitogen-activated protein kinase (MAPK)-, Janus-kinase (JAK)/signal transducers and activators of transcription (STAT) and phosphatidyl-inositol-3-kinase (PI3K) pathway, pointing to the involvement of all the three pathways. However, quantitative differences between both the stimulations were minor. Additive or synergistic effects by stimulating simultaneously with PDGF-AA and -CC were not observed. Using a proteomic approach we found eleven differentially expressed proteins, which were quantitatively altered after treatment with either PDGF-AA or PDGF-CC. The regulation of calreticulin and inorganic pyrophosphatase 1 could be verified by western blotting. Conclusions PDGF-AA and -CC exhibit almost identical biological effects on signal transduction and proteome in cultured renal fibroblasts, suggesting that the ligands exert their activity essentially through the commonly bound PDGFR-αα. Nonetheless, two differentially expressed proteins were identified which might be involved in the development of renal failure. [ABSTRACT FROM PUBLISHER]

Growth arrest-specific protein-1 (GAS1) is a GPI-anchored protein which is highly expressed in embryonic mouse fibroblasts and inhibits their proliferation. Glomerular mesangial cells release soluble GAS1 protein into the supernatant in vitro. Growth arrest led to GAS1 overexpression and increased release. Secretion involved disintegrin and metalloproteinase 10 and 17 as signified by inhibition experiments. Recombinant soluble GAS1 protein inhibited the proliferation of mesangial cells. Conversely, the induction of mesangial cell proliferation by PDGF-BB or -DD led to downregulation of GAS1 mRNA. Specific ligands of the PDGF α-receptor, PDGF-AA and -CC, had no effect. The GAS1 protein was localized in podocytes in kidneys from healthy rats. During the time course of mesangioproliferative glomerulonephritis in anti-Thy1.1-treated rats, glomerular GAS1 expression decreased prior to the onset of mesangial cell proliferation and increased at later stages during glomerular recovery. Finally, a plasmid expressing soluble GAS1 fused to an Fc fragment was systemically overexpressed in rats with mesangioproliferative glomerulonephritis. This ameliorated renal damage was indicated by decreased albuminuria and serum creatinine. Gas1/Fc-transfected rats also exhibited a reduction of the glomerular mesangial cell activation and proliferation. Thus, GAS1 is a novel endogenous inhibitor of glomerular mesangial cell proliferation and may be a novel therapeutic target in mesangioproliferative glomerular diseases. [ABSTRACT FROM AUTHOR]

Background. Chronic kidney disease (CKD) is increasingly recognized as a global health problem. The conditions leading to CKD, the health impact of CKD and the prognosis differ markedly between affected individuals. In particular, renal failure and cardiovascular mortality are competing risks for CKD patients. Opportunities for targeted intervention are very limited so far and require an improved understanding of the natural course of CKD, of the risk factors associated with various clinical end points and co-morbidities as well as of the underlying pathogenic mechanisms. Methods. The German Chronic Kidney Disease (GCKD) study is a prospective observational national cohort study. It aims to enrol a total of 5000 patients with CKD of various aetiologies, who are under nephrological care, and to follow them for up to 10 years. At the time of enrolment, male and female patients have an estimated glomerular filtration rate (eGFR) of 30–60 mL/min × 1.73m2 or overt proteinuria in the presence of an eGFR >60 mL/min × 1.73m2. Standardized collection of biomaterials, including DNA, serum, plasma and urine will allow identification and validation of biomarkers associated with CKD, CKD progression and related complications using hypothesis-driven and hypothesis-free approaches. Patient recruitment and follow-up is organized through a network of academic nephrology centres collaborating with practising nephrologists throughout the country. Conclusions. The GCKD study will establish one of the largest cohorts to date of CKD patients not requiring renal replacement therapy. Similarities in its design with other observational CKD studies, including cohorts that have already been established in the USA and Japan, will allow comparative and joint analyses to identify important ethnic and geographic differences and to enhance opportunities for identification of relevant risk factors and markers. [ABSTRACT FROM PUBLISHER]

Cognitive impairment is a common and largely undiagnosed finding in a significant number of dialysis patients. These alterations may result from concomitant cerebrovascular disease, hemodynamic instability, the uremic milieu, or changes induced by the dialysis process. In order to gain further insight into this, we recruited 12 stable chronic hemodialysis patients (without clinical neurological disease) and an age- and gender-matched cohort of 12 control individuals (without renal or neurological problems) in a prospective, single-center study. In order to disentangle the influence of dialysis itself on memory function, each dialysis patient was tested twice: once immediately before dialysis following a long weekend (t1) and again the day after this dialysis (t2). The control individuals were tested in the same time frame. Neuropsychological testing found that the control individuals performed significantly better in verbal learning, motor speed, task switching, verbal comprehension, word fluency, spatial visualization, spatial perception, and reasoning; all independent of the time point. Functional magnetic resonance imaging of the whole brain in seven hemodialysis patients found significantly more bilateral activation of the hippocampus during the verbal working memory task at t2 relative to t1 compared with their seven matched control counterparts. Thus, our study found differential and task-specific activation of memory-relevant brain areas during a dialysis cycle. [ABSTRACT FROM AUTHOR]

Y-box (YB) protein-1 is secreted by mesangial and immune cells after cytokine challenge, but extracellular functions are unknown. Here, we demonstrate that extracellular YB-1 associates with outer cell membrane components and interacts with extracellular Notch-3 receptor domains. The interaction appears to be specific for Notch-3, as YB-1-green fluorescent protein binds to the extracellular domains and full-length forms of Notch-3 but not to Notch-1. YB-1-green fluorescent protein and Notch-3 proteins co-localize at cell membranes, and extracellular YB-1 activates Notch-3 signaling, resulting in nuclear translocation of the Notch-3 intracellular domain and up-regulation of Notch target genes. The YB-1/Notch-3 interaction may be of particular relevance for inflammatory mesangioproliferative disease, as both proteins co-localize in an experimental nephritis model and receptor activation temporally and spatially correlates with YB-1 expression. [ABSTRACT FROM AUTHOR]

To the Editor: In their report on the Supportive versus Immunosuppressive Therapy for the Treatment of Progressive IgA Nephropathy (STOP-IgAN) trial, Rauen et al. (Dec. 3 issue)(1) provide an important contribution to therapeutic management in IgA nephropathy. The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines suggest the initiation of systemic glucocorticoids when proteinuria persists above 1 g of urinary protein excretion per day despite intensive supportive care. The investigators concluded that immunosuppressive treatment had many adverse effects without benefit in patients with moderate proteinuria and chronic kidney disease stages 1 through 3. Nevertheless, the trial was not designed to test . . . [ABSTRACT FROM AUTHOR]

Treatment resistant hypertension (TRH) appears of particular relevance in patients with chronic kidney disease (CKD). However, causes and consequences of TRH in CKD patients remain incompletely understood. Therefore, we analyzed the prevalence of apparent TRH (aTRH), and phenotypic characteristics and prognosis associated with aTRH among participants of the German Chronic Kidney Disease (GCKD) study. As insufficient medication adherence has been shown to be a frequent cause of pseudoresistance, we also assessed treatment adherence. Study participants were classified as having aTRH, controlled hypertension and uncontrolled hypertension based on study visit blood pressure and self-reported medication intake. Drug adherence was assessed by comparing self-reported antihypertensive medication with detectable urinary drug metabolites measured by mass spectroscopy. Out of 4901 individuals included in this study, 38% were classified as having aTRH. Male sex, older age, lower estimated glomerular filtration rate (eGFR), higher body mass index (BMI), higher urine albumin-to-creatinine ratio (UACR) and presence of diabetes mellitus were independently associated with higher prevalence of aTRH in a multivariable adjusted regression model. Patients classified as aTRH had higher risk for major adverse cardiovascular events and worsening of kidney disease compared to patients with no aTRH after multivariate adjustment for potential confounders. There was a high agreement between self-reported medication and detectable urinary drug metabolites. In conclusion, in a cohort of Caucasian patients with moderately severe CKD, aTRH was highly prevalent and, in most cases, likely not caused by low medication adherence. Furthermore, aTRH was linked to cardio-renal endpoints, emphasizing the need for improved management., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Diabetic kidney disease (DKD) is the most common cause of renal failure. Therapeutics development is hampered by our incomplete understanding of animal models on a cellular level. We show that ZSF1 rats recapitulate human DKD on a phenotypic and transcriptomic level. Tensor decomposition prioritizes proximal tubule (PT) and stroma as phenotype-relevant cell types exhibiting a continuous lineage relationship. As DKD features endothelial dysfunction, oxidative stress, and nitric oxide depletion, soluble guanylate cyclase (sGC) is a promising DKD drug target. sGC expression is specifically enriched in PT and stroma. In ZSF1 rats, pharmacological sGC activation confers considerable benefits over stimulation and is mechanistically related to improved oxidative stress regulation, resulting in enhanced downstream cGMP effects. Finally, we define sGC gene co-expression modules, which allow stratification of human kidney samples by DKD prevalence and disease-relevant measures such as kidney function, proteinuria, and fibrosis, underscoring the relevance of the sGC pathway to patients., Competing Interests: Declaration of interests A.F., J.V., I.M., K. Siudak, F.E., P.S., M.G., and M.P. are employees of Bayer AG. M.S.B. reports consultancy: Boehringer Ingelheim; editorial board membership: Journal of the American Society of Nephrology. K. Susztak reports research support: AstraZeneca, Bayer, Boehringer Ingelheim, Calico, Genentech, Gilead, GSK, Jnana, Lilly, Maze, Merck, Novartis, Novo Nordisk, Regeneron, Variant Bio, and Ventus; advisory board membership: Jnana Therapeutics and Pfizer; consultancy: AstraZeneca, Bayer, GSK, Jnana Therapeutics, Maze, Novo Nordisk, Pfizer, and Ventus; patents: Jag1- and Notch-based targeting of chronic kidney disease; editorial board membership: Cell Metabolism, eBioMedicine, Journal of the American Society of Nephrology, Journal of Clinical Investigation, Kidney International, and Med., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Immunoglobulin A (IgA) mediates mucosal responses to food antigens and the intestinal microbiome and is involved in susceptibility to mucosal pathogens, celiac disease, inflammatory bowel disease, and IgA nephropathy. We performed a genome-wide association study of serum IgA levels in 41,263 individuals of diverse ancestries and identified 20 genome-wide significant loci, including 9 known and 11 novel loci. Co-localization analyses with expression QTLs prioritized candidate genes for 14 of 20 significant loci. Most loci encoded genes that produced immune defects and IgA abnormalities when genetically manipulated in mice. We also observed positive genetic correlations of serum IgA levels with IgA nephropathy, type 2 diabetes, and body mass index, and negative correlations with celiac disease, inflammatory bowel disease, and several infections. Mendelian randomization supported elevated serum IgA as a causal factor in IgA nephropathy. African ancestry was consistently associated with higher serum IgA levels and greater frequency of IgA-increasing alleles compared to other ancestries. Our findings provide novel insights into the genetic regulation of IgA levels and its potential role in human disease., (© 2022. The Author(s).)

Chronic kidney diseaQueryse (CKD) is associated with oxidative stress which can interrupt the nitric oxide (NO)/soluble guanylyl cyclase (sGC) signaling and decrease cyclic guanosine monophosphate (cGMP) production. Low cGMP concentrations can cause kidney damage and progression of CKD. The novel sGC activator runcaciguat targets the oxidized and heme-free form of sGC, restoring cGMP production under oxidative stress. The purpose of this study is to investigate if runcaciguat could provide an effective treatment for CKD. Runcaciguat was used for the treatment not only in rat CKD models with different etiologies and comorbidities, namely of hypertensive rats, the renin transgenic (RenTG) rat, and angiotensin-supplemented (ANG-SD) rat, but also in rats with diabetic and metabolic CKD, the Zucker diabetic fatty (ZDF) rat. The treatment duration was 2 to 42 weeks and runcaciguat was applied orally in doses from 1 to 10 mg/kg/bid. In these different rat CKD models, runcaciguat significantly reduced proteinuria (urinary protein to creatinine ratio; uPCR). These effects were also significant at doses which did not or only moderately decrease systemic blood pressure. Moreover, runcaciguat significantly decreased kidney injury biomarkers and attenuated morphological kidney damages. In RenTG rats, runcaciguat improved survival rates and markers of heart injury. These data demonstrate that the sGC activator runcaciguat exhibits cardio-renal protection at doses which did not reduce blood pressure and was effective in hypertensive as well as diabetic and metabolic CKD models. These data, therefore, suggest that runcaciguat, with its specific mode of action, represents an efficient treatment approach for CKD and associated CV diseases., (© 2021. The Author(s).)

TRPM2 is a Ca2 + -permeable cationic channel and serves as an oxidative stress sensor.TRPM2 deletion was harmful in renal ischemia-reperfusion injury, whereas TRPM2 deletion mitigated kidney fibrosis.Our findings suggest the role of TRPM2 in kidney diseases is context dependent., Competing Interests: H. Cernecka and F. Eitner report being employed by Bayer. M. Nangaku reports receiving research funding from Astellas, Bayer, Chugai, Daiichi-Sankyo, JT, Kyowa-Kirin, Mitsubishi Tanabe, Takeda, and Torii; reports receiving honoraria from Astellas, AstraZeneca, BI, Chugai, Daiichi-Sankyo, GSK, JT, Kyowa-Kirin, and Mitsubishi Tanabe; and reports being a scientific advisor or member of Akebia Kyowa-Kirin, Astellas, Bayer, BI, Daiichi-Sankyo, GSK, JT, and Mitsubishi Tanabe. T. Tanaka reports having consultancy agreements with AstraZeneca and Torii; reports receiving research funding from Chugai, Daiichi-Sankyo, and Kyowa-Kirin; and reports receiving honoraria from Astellas, AstraZeneca, Bayer, Kyowa-Kirin, Mitsubishi Tanabe, and Torii. The remaining author has nothing to disclose., (Copyright © 2022 by the American Society of Nephrology.)

Herein we describe the discovery, mode of action, and preclinical characterization of the soluble guanylate cyclase (sGC) activator runcaciguat. The sGC enzyme, via the formation of cyclic guanosine monophoshphate, is a key regulator of body and tissue homeostasis. sGC activators with their unique mode of action are activating the oxidized and heme-free and therefore NO-unresponsive form of sGC, which is formed under oxidative stress. The first generation of sGC activators like cinaciguat or ataciguat exhibited limitations and were discontinued. We overcame limitations of first-generation sGC activators and identified a new chemical class via high-throughput screening. The investigation of the structure-activity relationship allowed to improve potency and multiple solubility, permeability, metabolism, and drug-drug interactions parameters. This program resulted in the discovery of the oral sGC activator runcaciguat (compound 45 , BAY 1101042). Runcaciguat is currently investigated in clinical phase 2 studies for the treatment of patients with chronic kidney disease and nonproliferative diabetic retinopathy.

Introduction: The nonsteroidal mineralocorticoid receptor (MR) antagonist finerenone and sodium-glucose cotransporter-2 (SGLT2) inhibitors have demonstrated clinical benefits in chronic kidney disease patients with type 2 diabetes. Precise molecular mechanisms responsible for these benefits are incompletely understood. Here, we investigated potential direct anti-fibrotic effects and mechanisms of nonsteroidal MR antagonism by finerenone or SGLT2 inhibition by empagliflozin in 2 relevant mouse kidney fibrosis models: unilateral ureter obstruction and sub-chronic ischemia reperfusion injury., Methods: Kidney fibrosis was induced in mice via unilateral ureteral obstruction or ischemia. In a series of experiments, mice were treated orally with the MR antagonist finerenone (3 or 10 mg/kg), the SGLT2 inhibitor empagliflozin (10 or 30 mg/kg), or in a direct comparison of both drugs. Interstitial myofibroblast accumulation was quantified via alpha-smooth muscle actin and interstitial collagen deposition via Sirius Red/Fast Green staining in both models. Secondary analyses included the assessment of inflammatory cells, kidney mRNA expression of fibrotic markers as well as functional parameters (serum creatinine and albuminuria) in the ischemic model. Blood pressure was measured via telemetry in healthy conscious compound-treated animals., Results: Finerenone dose-dependently decreased pathological myofibroblast accumulation and collagen deposition with no effects on systemic blood pressure and inflammatory markers in the tested dose range. Reduced kidney fibrosis was paralleled by reduced kidney plasminogen activator inhibitor-1 (PAI-1) and naked cuticle 2 (NKD2) expression in finerenone-treated mice. In contrast, treatment with empagliflozin strongly increased urinary glucose excretion in both models and reduced ischemia-induced albuminuria but had no effects on kidney myofibroblasts or collagen deposition., Discussion/conclusion: Finerenone has direct anti-fibrotic properties resulting in reduced myofibroblast and collagen deposition accompanied by a reduction in renal PAI-1 and NKD2 expression in mouse models of progressive kidney fibrosis at blood pressure-independent dosages., (© 2021 The Author(s) Published by S. Karger AG, Basel.)

Background: Renal transplant recipients have an increased cancer risk. The mammalian target of rapamycin inhibitor sirolimus (SRL) has immunosuppressive and antitumour activities but knowledge about its use in recipients with cancer is limited., Methods: We retrospectively analysed 726 renal allograft recipients converted to SRL from 10 German transplant centres. Patient and graft survival were analysed depending on malignancy status prior to conversion and tumour entity., Results: Malignancy before conversion to SRL was reported in 230 patients, with 137 patients having skin cancers and 101 having solid cancers. Cancer occurred 4.6 ± 9.4 (median 3.0) years after transplantation. Basal cell carcinoma, squamous cell carcinoma and Bowen's disease were the most prevalent skin cancers, while carcinomas of the kidney, colon and breast were the most prevalent solid cancers before conversion. Patients with prior malignancy were older and had better renal function at conversion compared with patients without a history of cancer. After conversion to SRL, cancer incidence rates (IRs) of all tumours were lower compared with rates before conversion. Cancer IRs after conversion were higher in patients with malignancy before conversion compared with those without. Patient survival was worse in patients with solid cancers compared with patients with skin cancers or without malignancies. Biopsy-proven acute rejections in the first year after conversion were less frequent in patients with malignancy compared with those without. Graft survival and renal function in all cancer types were better than in patients converted to SRL without cancers., Conclusions: Conversion to SRL in patients with a history of cancer is safe regarding renal function and graft survival, while patient survival is largely dependent on tumour entity., (© The Author(s) 2020. Published by Oxford University Press on behalf of ERA-EDTA.)

Background: Inhibitors of the renin-angiotensin system (RAS) are cornerstones of supportive therapy in patients with IgA nephropathy (IgAN). We analyzed the effects of single versus dual RAS blockaQueryde during our randomized STOP-IgAN trial., Methods: STOP-IgAN participants with available successive information on their RAS treatment regimen and renal outcomes during the randomized 3-year trial phase were stratified post hoc into two groups, i.e. patients under continuous single or dual RAS blocker therapy over the entire 3 years of the trial phase. Primary and secondary STOP-IgAN trial endpoints, i.e. frequencies of full clinical remission, eGFR-loss ≥ 15 and ≥ 30 ml/min/1.73 m 2 and ESRD onset, were analyzed by logistic regression and linear mixed effects models., Results: Among the 112 patients included in the present analysis, 82 (73%) were maintained on single and 30 (27%) on dual RAS inhibitor therapy throughout the trial. Neither RAS blocker strategy significantly affected full clinical remission, eGFR-loss rates, onset of ESRD. Proteinuria moderately increased in patients under dual RAS blockade by 0.1 g/g creatinine during the 3-year trial phase. This was particularly evident in patients without additional immunosuppression during the randomized trial phase, where proteinuria increased by 0.2 g/g creatinine in the dual RAS blockade group. In contrast, proteinuria decreased in patients under single RAS blocker therapy by 0.3 g/g creatinine. The course of eGFR remained stable and did not differ between the RAS treatment strategies., Conclusion: In the STOP-IgAN cohort, neither RAS blocker regimen altered renal outcomes. Patients on dual RAS blockade even exhibited higher proteinuria over the 3-year trial phase.

Platelet-derived growth factors (PDGF) have been implicated in kidney disease progression. We previously found that PDGF-C is upregulated at sites of renal fibrosis and that antagonism of PDGF-C reduces fibrosis in the unilateral ureteral obstruction model. We studied the role of PDGF-C in collagen 4A3 -/- ("Alport") mice, a model of progressive renal fibrosis with greater relevance to human kidney disease. Alport mice were crossbred with PDGF-C -/- mice or administered a neutralizing PDGF-C antibody. Both PDGF-C deficiency and neutralization reduced serum creatinine and blood urea nitrogen levels and mitigated glomerular injury, renal fibrosis, and renal inflammation. Unexpectedly, systolic blood pressure was also reduced in both Alport and wild-type mice treated with a neutralizing PDGF-C antibody. Neutralization of PDGF-C reduced arterial wall thickness in the renal cortex of Alport mice. Aortic rings isolated from anti-PDGF-C-treated wildtype mice exhibited reduced tension and faster relaxation than those of untreated mice. In vitro, PDGF-C upregulated angiotensinogen in aortic tissue and in primary hepatocytes and induced nuclear factor κB (NFκB)/p65-binding to the angiotensinogen promoter in hepatocytes. Neutralization of PDGF-C suppressed transcript expression of angiotensinogen in Alport mice and angiotensin II receptor type 1 in Alport and wildtype mice. Finally, administration of neutralizing PDGF-C antibodies ameliorated angiotensin II-induced hypertension in healthy mice. Thus, in addition to its key role in mediating renal fibrosis, we identified PDGF-C as a mediator of hypertension via effects on renal vasculature and on the renin-angiotensin system. The contribution to both renal fibrosis and hypertension render PDGF-C an attractive target in progressive kidney disease., (Copyright © 2019 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

The role of immunosuppression in IgA nephropathy (IgAN) is controversial. In the Supportive Versus Immunosuppressive Therapy for the Treatment of Progressive IgA Nephropathy (STOP-IgAN) Trial, 162 patients with IgAN and proteinuria >0.75 g/d after 6 months of optimized supportive care were randomized into two groups: continued supportive care or additional immunosuppression (GFR≥60 ml/min per 1.73 m 2 : 6-month corticosteroid monotherapy; GFR=30-59 ml/min per 1.73 m 2 : cyclophosphamide for 3 months followed by azathioprine plus oral prednisolone). Coprimary end points were full clinical remission and GFR loss ≥15 ml/min per 1.73 m 2 during the 3-year trial phase. In this secondary intention to treat analysis, we separately analyzed data from each immunosuppression subgroup and the corresponding patients on supportive care. Full clinical remission occurred in 11 (20%) patients receiving corticosteroid monotherapy and three (6%) patients on supportive care (odds ratio, 5.31; 95% confidence interval, 1.07 to 26.36; P =0.02), but the rate did not differ between patients receiving immunosuppressive combination and controls on supportive care (11% versus 4%, respectively; P =0.30). The end point of GFR loss ≥15 ml/min per 1.73 m 2 did not differ between groups. Only corticosteroid monotherapy transiently reduced proteinuria at 12 months. Severe infections, impaired glucose tolerance, and/or weight gain in the first year were more frequent with either immunosuppressive regimen than with supportive care. In conclusion, only corticosteroid monotherapy induced disease remission in a minority of patients who had IgAN with relatively well preserved GFR and persistent proteinuria. Neither immunosuppressive regimen prevented GFR loss, and both associated with substantial adverse events., (Copyright © 2018 by the American Society of Nephrology.)

Background: The outcomes of immunosuppressive therapy, when added to supportive care, in patients with IgA nephropathy are uncertain., Methods: We conducted a multicenter, open-label, randomized, controlled trial with a two-group, parallel, group-sequential design. During a 6-month run-in phase, supportive care (in particular, blockade of the renin-angiotensin system) was adjusted on the basis of proteinuria. Patients who had persistent proteinuria with urinary protein excretion of at least 0.75 g per day were randomly assigned to receive supportive care alone (supportive-care group) or supportive care plus immunosuppressive therapy (immunosuppression group) for 3 years. The primary end points in hierarchical order were full clinical remission at the end of the trial (protein-to-creatinine ratio <0.2 [with both protein and creatinine measured in grams] and a decrease in the estimated glomerular filtration rate [eGFR] of <5 ml per minute per 1.73 m(2) of body-surface area from baseline) and a decrease in the eGFR of at least 15 ml per minute per 1.73 m(2) at the end of the trial. The primary end points were analyzed with the use of logistic-regression models., Results: The run-in phase was completed by 309 of 337 patients. The proteinuria level decreased to less than 0.75 g of urinary protein excretion per day in 94 patients. Of the remaining 162 patients who consented to undergo randomization, 80 were assigned to the supportive-care group, and 82 to the immunosuppression group. After 3 years, 4 patients (5%) in the supportive-care group, as compared with 14 (17%) in the immunosuppression group, had a full clinical remission (P=0.01). A total of 22 patients (28%) in the supportive-care group and 21 (26%) in the immunosuppression group had a decrease in the eGFR of at least 15 ml per minute per 1.73 m(2) (P=0.75). There was no significant difference in the annual decline in eGFR between the two groups. More patients in the immunosuppression group than in the supportive-care group had severe infections, impaired glucose tolerance, and weight gain of more than 5 kg in the first year of treatment. One patient in the immunosuppression group died of sepsis., Conclusions: The addition of immunosuppressive therapy to intensive supportive care in patients with high-risk IgA nephropathy did not significantly improve the outcome, and during the 3-year study phase, more adverse effects were observed among the patients who received immunosuppressive therapy, with no change in the rate of decrease in the eGFR. (Funded by the German Federal Ministry of Education and Research; STOP-IgAN ClinicalTrials.gov number, NCT00554502.).

We have identified platelet-derived growth factor (PDGF)-CC as a potent profibrotic mediator in kidney fibrosis and pro-angiogenic mediator in glomeruli. Because renal fibrosis is associated with progressive capillary rarefaction, we asked whether PDGF-CC neutralization in fibrosis might have detrimental anti-angiogenic effects leading to aggravated peritubular capillary loss. We analyzed capillary rarefaction in mice with and without PDGF-CC neutralization (using genetically deficient mice and neutralizing antibodies), in three different models of renal interstitial fibrosis, unilateral ureteral obstruction, unilateral ischemia-reperfusion, Col4a3-deficient (Alport) mice, and healthy animals. Independent of the effect of PDGF-CC neutralization on renal fibrosis, we found no difference in capillary rarefaction between PDGF-CC-neutralized mice and mice with intact PDGF-CC. We also found no differences in microvascular leakage (determined by extravasation of Evans Blue Dye) and in renal relative blood volume quantified using in vivo microcomputed tomography. PDGF-CC neutralization had no effects on renal microvasculature in healthy animals. Capillary endothelium did not express PDGF receptor-α, suggesting that potential PDGF-CC effects would have to be indirect. PDGF-CC neutralization or deficiency was not associated with preservation or accelerated loss of peritubular capillaries, suggesting no significant pro-angiogenic effects of PDGF-CC during renal fibrosis. From a clinical perspective, the profibrotic effects of PDGF-CC outweigh the pro-angiogenic effects and, thus, do not limit a potential therapeutic use of PDGF-CC inhibition in renal fibrosis., (Copyright © 2015 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Mesangioproliferative glomerulonephritis is the most common nephritis worldwide. We examined the effects of low- and high-dose telmisartan, an angiotensin II receptor blocker, in rats with progressive anti-Thy1.1 mesangioproliferative glomerulonephritis in a clinically relevant situation of established renal damage. Uninephrectomized nephritic rats were randomized on day 28 to remain untreated (control treatment; CT), or to receive low- (0.1 mg/kg/day, LT) or high-dose telmisartan (10 mg/kg/day, HT), hydrochlorothiazide + hydralazine (8 + 32 mg/kg/day, HCT + H), or atenolol (100 mg/kg/day, AT). CT and LT rats were hypertensive, whereas HT, HCT + H and AT treatment normalized blood pressures. On day 131, despite similar blood lowering effects, only HT, but not AT or HCT + H, prevented loss of renal function and reduced proteinuria compared to CT. Only HT potently ameliorated glomerulosclerosis, tubulointerstitial damage, cortical matrix deposition, podocyte damage and macrophage infiltration. HT reduced cortical expression of platelet derived growth factor receptor-α and -β as well as transforming growth factor-β1. LT exhibited minor but significant efficacy even in the absence of antihypertensive effects. Transcript array analyses revealed a four-fold down-regulation of renal cortical chemokine (C-C motif) receptor 6 (CCR6) mRNA by HT, which was confirmed at the protein level. Silencing of CCR6 did not alter podocyte function in vitro, thus indicating a predominant role in the tubulo-interstitium. In human kidney biopsies, CCR6 mRNA and mRNA of its ligand chemokine (C-C motif) ligand 20 was up-regulated in patients with progressive IgA nephropathy compared to stable disease. Thus, delayed treatment with high-dose telmisartan exerted a pronounced benefit in progressive mesangioproliferative glomerulonephritis, which extended beyond that of equivalent blood pressure lowering. We identified down-regulation of platelet-derived growth factor receptors and CCR6 as potential mediators of telmisartan-related renoprotection. CCR6 may also regulate the renal outcome in human mesangioprolfierative glomerulonephritis., (Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)