MicroRNAs (miRNAs) are short non-coding RNA species which are important post-transcriptional regulators of gene expression and play an important role in the pathogenesis of diabetic nephropathy. ...miRNAs are present in urine in a remarkably stable form packaged in extracellular vesicles, predominantly exosomes. In the present study, urinary exosomal miRNA profiling was conducted in urinary exosomes obtained from 8 healthy controls (C), 8 patients with type II diabetes (T2D) and 8 patients with type II diabetic nephropathy (DN) using Agilent´s miRNA microarrays. In total, the expression of 16 miRNA species was deregulated (>2-fold) in DN patients compared to healthy donors and T2D patients: the expression of 14 miRNAs (miR-320c, miR-6068, miR-1234-5p, miR-6133, miR-4270, miR-4739, miR-371b-5p, miR-638, miR-572, miR-1227-5p, miR-6126, miR-1915-5p, miR-4778-5p and miR-2861) was up-regulated whereas the expression of 2 miRNAs (miR-30d-5p and miR-30e-5p) was down-regulated. Most of the deregulated miRNAs are involved in progression of renal diseases. Deregulation of urinary exosomal miRNAs occurred in micro-albuminuric DN patients but not in normo-albuminuric DN patients. We used qRT-PCR based analysis of the most strongly up-regulated miRNAs in urinary exosomes from DN patients, miRNAs miR-320c and miR-6068. The correlation of miRNA expression and micro-albuminuria levels could be replicated in a confirmation cohort. In conclusion, urinary exosomal miRNA content is altered in type II diabetic patients with DN. Deregulated miR-320c, which might have an impact on the TGF-β-signaling pathway via targeting thrombospondin 1 (TSP-1) shows promise as a novel candidate marker for disease progression in type II DN that should be evaluated in future studies.
African Americans have a heightened risk of developing chronic and end-stage kidney disease, an association that is largely attributed to two common genetic variants, termed G1 and G2, in the APOL1 ...gene. Direct evidence demonstrating that these APOL1 risk alleles are pathogenic is still lacking because the APOL1 gene is present in only some primates and humans; thus it has been challenging to demonstrate experimental proof of causality of these risk alleles for renal disease. Here we generated mice with podocyte-specific inducible expression of the APOL1 reference allele (termed G0) or each of the risk-conferring alleles (G1 or G2). We show that mice with podocyte-specific expression of either APOL1 risk allele, but not of the G0 allele, develop functional (albuminuria and azotemia), structural (foot-process effacement and glomerulosclerosis) and molecular (gene-expression) changes that closely resemble human kidney disease. Disease development was cell-type specific and likely reversible, and the severity correlated with the level of expression of the risk allele. We further found that expression of the risk-variant APOL1 alleles interferes with endosomal trafficking and blocks autophagic flux, which ultimately leads to inflammatory-mediated podocyte death and glomerular scarring. In summary, this is the first demonstration that the expression of APOL1 risk alleles is causal for altered podocyte function and glomerular disease in vivo.
Coding variants in apolipoprotein L1 (APOL1), termed G1 and G2, can explain most excess kidney disease risk in African Americans; however, the molecular pathways of APOL1-induced kidney dysfunction ...remain poorly understood. Here, we report that expression of G2 APOL1 in the podocytes of Nphs1rtTA/TRE-G2APOL1 (G2APOL1) mice leads to early activation of the cytosolic nucleotide sensor, stimulator of interferon genes (STING), and the NLR family pyrin domain-containing 3 (NLRP3) inflammasome. STING and NLRP3 expression was increased in podocytes from patients with high-risk APOL1 genotypes, and expression of APOL1 correlated with caspase-1 and gasdermin D (GSDMD) levels. To demonstrate the role of NLRP3 and STING in APOL1-associated kidney disease, we generated transgenic mice with the G2 APOL1 risk variant and genetic deletion of Nlrp3 (G2APOL1/Nlrp3 KO), Gsdmd (G2APOL1/Gsdmd KO), and STING (G2APOL1/STING KO). Knockout mice displayed marked reduction in albuminuria, azotemia, and kidney fibrosis compared with G2APOL1 mice. To evaluate the therapeutic potential of targeting NLRP3, GSDMD, and STING, we treated mice with MCC950, disulfiram, and C176, potent and selective inhibitors of NLRP3, GSDMD, and STING, respectively. G2APOL1 mice treated with MCC950, disulfiram, and C176 showed lower albuminuria and improved kidney function even when inhibitor treatment was initiated after the development of albuminuria.
The functional interpretation of genome-wide association studies (GWAS) is challenging due to the cell-type-dependent influences of genetic variants. Here, we generated comprehensive maps of ...expression quantitative trait loci (eQTLs) for 659 microdissected human kidney samples and identified cell-type-eQTLs by mapping interactions between cell type abundances and genotypes. By partitioning heritability using stratified linkage disequilibrium score regression to integrate GWAS with single-cell RNA sequencing and single-nucleus assay for transposase-accessible chromatin with high-throughput sequencing data, we prioritized proximal tubules for kidney function and endothelial cells and distal tubule segments for blood pressure pathogenesis. Bayesian colocalization analysis nominated more than 200 genes for kidney function and hypertension. Our study clarifies the mechanism of commonly used antihypertensive and renal-protective drugs and identifies drug repurposing opportunities for kidney disease.
Transient receptor potential canonical type 6 (TRPC6) is a non-selective receptor-operated cation channel that regulates reactive fibrosis and growth signaling. Increased TRPC6 activity from enhanced ...gene expression or gain-of-function mutations contribute to cardiac and/or renal disease. Despite evidence supporting a pathophysiological role, no orally bioavailable selective TRPC6 inhibitor has yet been developed and tested in vivo in disease models. Here, we report an orally bioavailable TRPC6 antagonist (BI 749327; IC50 13 nM against mouse TRPC6, t1/2 8.5–13.5 hours) with 85- and 42-fold selectivity over the most closely related channels, TRPC3 and TRPC7. TRPC6 calcium conductance results in the stimulation of nuclear factor of activated T cells (NFAT) that triggers pathological cardiac and renal fibrosis and disease. BI 749327 suppresses NFAT activation in HEK293T cells expressing wild-type or gain-of-function TRPC6 mutants (P112Q, M132T, R175Q, R895C, and R895L) and blocks associated signaling and expression of prohypertrophic genes in isolated myocytes. In vivo, BI 749327 (30 mg/kg/day, yielding unbound trough plasma concentration ∼180 nM) improves left heart function, reduces volume/mass ratio, and blunts expression of profibrotic genes and interstitial fibrosis in mice subjected to sustained pressure overload. Additionally, BI 749327 dose dependently reduces renal fibrosis and associated gene expression in mice with unilateral ureteral obstruction. These results provide in vivo evidence of therapeutic efficacy for a selective pharmacological TRPC6 inhibitor with oral bioavailability and suitable pharmacokinetics to ameliorate cardiac and renal stress-induced disease with fibrosis.
Non-alcoholic fatty liver disease (NAFLD) affects about 24% of the world's population. Progression of early stages of NAFLD can lead to the more advanced form non-alcoholic steatohepatitis (NASH), ...and ultimately to cirrhosis or liver cancer. The current gold standard for diagnosis and assessment of NAFLD/NASH is liver biopsy followed by microscopic analysis by a pathologist. The Kleiner score is frequently used for a semi-quantitative assessment of disease progression. In this scoring system the features of active injury (steatosis, inflammation, and ballooning) and a separated fibrosis score are quantified. The procedure is time consuming for pathologists, scores have limited resolution and are subject to variation. We developed an automated deep learning method that provides full reproducibility and higher resolution. The system was established with 296 human liver biopsies and tested on 171 human liver biopsies with pathologist ground truth scores. The method is inspired by the way pathologist's analyze liver biopsies. First, the biopsies are analyzed microscopically for the relevant histopathological features. Subsequently, histopathological features are aggregated to a per-biopsy score. Scores are in the identical numeric range as the pathologist's ballooning, inflammation, steatosis, and fibrosis scores, but on a continuous scale. Resulting scores followed a pathologist's ground truth (quadratic weighted Cohen's κ on the test set: for steatosis 0.66, for inflammation 0.24, for ballooning 0.43, for fibrosis 0.62, and for the NAFLD activity score (NAS) 0.52. Mean absolute errors on a test set: for steatosis 0.29, for inflammation 0.53, for ballooning 0.61, for fibrosis 0.78, and for the NAS 0.77).
Therapies that restore renal cGMP levels are hypothesized to slow the progression of diabetic nephropathy. We investigated the effect of BI 703704, a soluble guanylate cyclase (sGC) activator, on ...disease progression in obese ZSF1 rats. BI 703704 was administered at doses of 0.3, 1, 3, and 10 mg/kg/d to male ZSF1 rats for 15 weeks, during which mean arterial pressure (MAP), heart rate (HR), and urinary protein excretion (UPE) were determined. Histologic assessment of glomerular and interstitial lesions was also performed. Renal cGMP levels were quantified as an indicator of target modulation. BI 703704 resulted in sGC activation, as evidenced by dose-dependent increases in renal cGMP levels. After 15 weeks of treatment, sGC activation resulted in dose-dependent decreases in UPE (from 463 ± 58 mg/d in vehicle controls to 328 ± 55, 348 ± 23, 283 ± 45, and 108 ± 23 mg/d in BI 703704-treated rats at 0.3, 1, 3, and 10 mg/kg, respectively). These effects were accompanied by a significant reduction in the incidence of glomerulosclerosis and interstitial lesions. Decreases in MAP and increases in HR were only observed at the high dose of BI 703704. These results are the first demonstration of renal protection with sGC activation in a nephropathy model induced by type 2 diabetes. Importantly, beneficial effects were observed at doses that did not significantly alter MAP and HR.
Chymase plays an important and diverse role in the homeostasis of a number of cardiovascular processes. Herein, we describe the identification of potent, selective chymase inhibitors, developed using ...fragment-based, structure-guided linking and optimization techniques. High-concentration biophysical screening methods followed by high-throughput crystallography identified an oxindole fragment bound to the S1 pocket of the protein exhibiting a novel interaction pattern hitherto not observed in chymase inhibitors. X-ray crystallographic structures were used to guide the elaboration/linking of the fragment, ultimately leading to a potent inhibitor that was >100-fold selective over cathepsin G and that mitigated a number of liabilities associated with poor physicochemical properties of the series it was derived from.
Gene mutations causing loss of dystrophin result in the severe muscle disease known as Duchenne muscular dystrophy (DMD). Despite efforts at genetic repair, DMD therapy remains largely palliative. ...Loss of dystrophin destabilizes the sarcolemmal membrane, inducing mechanosensitive cation channels to increase calcium entry and promote cell damage and, eventually, muscle dysfunction. One putative channel is transient receptor potential canonical 6 (TRPC6); we have shown that TRPC6 contributed to abnormal force and calcium stress-responses in cardiomyocytes from mice lacking dystrophin that were haplodeficient for utrophin (mdx/utrn+/- HET mice). Here, we show in both the HET mouse and the far more severe homozygous mdx/utrn-/- mouse that TRPC6 gene deletion or its selective pharmacologic inhibition (by BI 749327) prolonged survival 2- to 3-fold, improving skeletal and cardiac muscle and bone defects. Gene pathways reduced by BI 749327 treatment most prominently regulated fat metabolism and TGF-β1 signaling. These results support the testing of TRPC6 inhibitors in human trials for other diseases as a novel DMD therapy.
Tumor necrosis factor receptor superfamily members convey signals that promote diverse cellular responses. Receptor trimerization by extracellular ligands initiates signaling by recruiting members of ...the tumor necrosis factor receptor-associated factor (TRAF) family of adapter proteins to the receptor cytoplasmic domains. We report the 2.4- angstrom crystal structure of a 22-kDa, receptor-binding fragment of TRAF2 complexed with a functionally defined peptide from the cytoplasmic domain of the CD40 receptor. TRAF2 forms a mushroom-shaped trimer consisting of a coiled coil and a unique β -sandwich domain. Both domains mediate trimerization. The CD40 peptide binds in an extended conformation with every side chain in contact with a complementary groove on the rim of each TRAF monomer. The spacing between the CD40 binding sites on TRAF2 supports an elegant signaling mechanism in which trimeric, extracellular ligands preorganize the receptors to simultaneously recognize three sites on the TRAF trimer.
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