B7–1 Is Not Induced in Podocytes of Human and Experimental Diabetic Nephropathy

The incidence of progressive kidney disease associated with diabetes continues to rise worldwide. Current standard therapy with angiotensin–converting enzyme inhibitors and/or angiotensin receptor blockers achieves only partial renoprotection, increasing the need for novel therapeutic approaches. Previous studies described B7–1 induction in podocytes of patients with proteinuria, including those with FSGS and type 2 diabetic nephropathy (DN). These findings sparked great excitement in the renal community, implying that abatacept, a costimulatory inhibitor that targets B7–1, could be a novel therapy for diabetic renal disease. Given previous concerns over the value of B7–1 immunostaining and the efficacy of abatacept in patients with recurrent FSGS after renal transplantation, we investigated B7–1 expression in human and experimental DN before embarking on clinical studies of the use of B7–1 targeting strategies to treat proteinuria in DN. Immunohistochemical analysis of kidney specimens using different antibodies revealed that B7–1 is not induced in podocytes of patients with DN, independent of disease stage, or BTBR ob/ob mice, a model of type 2 diabetes. These results do not support the use of abatacept as a therapeutic strategy for targeting podocyte B7–1 for the prevention or treatment of DN.     

MicroRNA-21 in Glomerular Injury

TGF-β₁ is a pleotropic growth factor that mediates glomerulosclerosis and podocyte apoptosis, hallmarks of glomerular diseases. The expression of microRNA-21 (miR-21) is regulated by TGF-β₁, and miR-21 inhibits apoptosis in cancer cells. TGF-β₁–transgenic mice exhibit accelerated podocyte loss and glomerulosclerosis. We determined that miR-21 expression increases rapidly in cultured murine podocytes after exposure to TGF-β₁ and is higher in kidneys of TGF-β₁–transgenic mice than wild-type mice. miR-21–deficient TGF-β₁–transgenic mice showed increased proteinuria and glomerular extracellular matrix deposition and fewer podocytes per glomerular tuft compared with miR-21 wild-type TGF-β₁–transgenic littermates. Similarly, miR-21 expression was increased in streptozotocin-induced diabetic mice, and loss of miR-21 in these mice was associated with increased albuminuria, podocyte depletion, and mesangial expansion. In cultured podocytes, inhibition of miR-21 was accompanied by increases in the rate of cell death, TGF-β/Smad3-signaling activity, and expression of known proapoptotic miR-21 target genes p53, Pdcd4, Smad7, Tgfbr2, and Timp3. In American-Indian patients with diabetic nephropathy (n=48), albumin-to-creatinine ratio was positively associated with miR-21 expression in glomerular fractions (r=0.6; P<0.001) but not tubulointerstitial fractions (P=0.80). These findings suggest that miR-21 ameliorates TGF-β1 and hyperglycemia-induced glomerular injury through repression of proapoptotic signals, thereby inhibiting podocyte loss. This finding is in contrast to observations in murine models of tubulointerstitial kidney injury but consistent with findings in cancer models. The aggravation of glomerular disease in miR-21–deficient mice and the positive association with albumin-to-creatinine ratio in patients with diabetic nephropathy support miR-21 as a feedback inhibitor of TGF-β signaling and functions.     

Metabolomics Reveals a Key Role for Fumarate in Mediating the Effects of NADPH Oxidase 4 in Diabetic Kidney Disease

The NADPH oxidase (NOX) isoform NOX4 has been linked with diabetic kidney disease (DKD). However, a mechanistic understanding of the downstream effects of NOX4 remains to be established. We report that podocyte-specific induction of NOX4 in vivo was sufficient to recapitulate the characteristic glomerular changes noted with DKD, including glomerular hypertrophy, mesangial matrix accumulation, glomerular basement membrane thickening, albuminuria, and podocyte dropout. Intervention with a NOX1/NOX4 inhibitor reduced albuminuria, glomerular hypertrophy, and mesangial matrix accumulation in the F1 Akita model of DKD. Metabolomic analyses from these mouse studies revealed that tricarboxylic acid (TCA) cycle–related urinary metabolites were increased in DKD, but fumarate levels were uniquely reduced by the NOX1/NOX4 inhibitor. Expression of fumarate hydratase (FH), which regulates urine fumarate accumulation, was reduced in the diabetic kidney (in mouse and human tissue), and administration of the NOX1/NOX4 inhibitor increased glomerular FH levels in diabetic mice. Induction of Nox4 in vitro and in the podocyte-specific NOX4 transgenic mouse led to reduced FH levels. In vitro, fumarate stimulated endoplasmic reticulum stress, matrix gene expression, and expression of hypoxia-inducible factor-1α (HIF-1α) and TGF-β. Similar upregulation of renal HIF-1α and TGF-β expression was observed in NOX4 transgenic mice and diabetic mice and was attenuated by NOX1/NOX4 inhibition in diabetic mice. In conclusion, NOX4 is a major mediator of diabetes-associated glomerular dysfunction through targeting of renal FH, which increases fumarate levels. Fumarate is therefore a key link connecting metabolic pathways to DKD pathogenesis, and measuring urinary fumarate levels may have application for monitoring renal NOX4 activity.     

Curtailing Endothelial TGF-β Signaling Is Sufficient to Reduce Endothelial-Mesenchymal Transition and Fibrosis in CKD

Excessive TGF-β signaling in epithelial cells, pericytes, or fibroblasts has been implicated in CKD. This list has recently been joined by endothelial cells (ECs) undergoing mesenchymal transition. Although several studies focused on the effects of ablating epithelial or fibroblast TGF-β signaling on development of fibrosis, there is a lack of information on ablating TGF-β signaling in the endothelium because this ablation causes embryonic lethality. We generated endothelium-specific heterozygous TGF-β receptor knockout (TβRII^endo+/−) mice to explore whether curtailed TGF-β signaling significantly modifies nephrosclerosis. These mice developed normally, but showed enhanced angiogenic potential compared with TβRII^endo+/+ mice under basal conditions. After induction of folic acid nephropathy or unilateral ureteral obstruction, TβRII^endo+/− mice exhibited less tubulointerstitial fibrosis, enhanced preservation of renal microvasculature, improvement in renal blood flow, and less tissue hypoxia than TβRII^endo+/+ counterparts. In addition, partial deletion of TβRII in the endothelium reduced endothelial-to-mesenchymal transition (EndoMT). TGF-β–induced canonical Smad2 signaling was reduced in TβRII^+/− ECs; however, activin receptor-like kinase 1 (ALK1)–mediated Smad1/5 phosphorylation in TβRII^+/− ECs remained unaffected. Furthermore, the S-endoglin/L-endoglin mRNA expression ratio was significantly lower in TβRII^+/− ECs compared with TβRII^+/+ ECs. These observations support the hypothesis that EndoMT contributes to renal fibrosis and curtailing endothelial TGF-β signals favors Smad1/5 proangiogenic programs and dictates increased angiogenic responses. Our data implicate endothelial TGF-β signaling and EndoMT in regulating angiogenic and fibrotic responses to injury.     

TNF-α-mediated podocyte injury via the apoptotic death receptor pathway in a mouse model of IgA nephropathy

BackgroundIgA nephropathy (IgAN) is the most common primary glomerular disease worldwide and it is characterized by mesangial IgA deposits. Proteinuria is a common clinical feature of IgAN, which has a critical connection to podocyte injury and has been used as a clinical prognostic factor for IgAN. Evidence has shown that TNF-α released from mesangial cells may lead to podocyte apoptosis.MethodsForty male BALB/c mouse were randomly divided into the control group and IgAN group. A mice model of IgAN was developed by oral administration of bovine serum albumin (BSA) combined with Staphylococcus Enterotoxin B (SEB) tail vein injection. Urinary protein concentrations, renal function, renal morphological, IgA deposition, apoptosis situation, and the mRNA and protein expression of nephrin, podocin, TNF-α, TNFR1, caspase-8 and caspase-3, were detected after 12 weeks.ResultsBSA and SEB can successfully establish an IgAN mouse model, and the main pathological changes are the IgA immune complex deposition in the mesangial area. The gene and protein expression levels of nephrin and podocin were found to be downregulated, and death receptor pathway-related indicators were upregulated, and they were involved in TNF-α-activated podocyte injury and apoptosis in IgAN mice.ConclusionTNF-α may play an important role in the pathogenesis of podocyte apoptosis in IgAN, and its effects may be mediated through the apoptotic death receptor pathway.     

Multiple Genes of the Renin-Angiotensin System Are Novel Targets of Wnt/β-Catenin Signaling

Activation of the renin-angiotensin system (RAS) plays an essential role in the pathogenesis of CKD and cardiovascular disease. However, current anti-RAS therapy only has limited efficacy, partly because of compensatory upregulation of renin expression. Therefore, a treatment strategy to simultaneously target multiple RAS genes is necessary to achieve greater efficacy. By bioinformatics analyses, we discovered that the promoter regions of all RAS genes contained putative T-cell factor (TCF)/lymphoid enhancer factor (LEF)-binding sites, and β-catenin induced the binding of LEF-1 to these sites in kidney tubular cells. Overexpression of either β-catenin or different Wnt ligands induced the expression of all RAS genes. Conversely, a small-molecule β-catenin inhibitor ICG-001 abolished RAS induction. In a mouse model of nephropathy induced by adriamycin, either transient therapy or late administration of ICG-001 abolished established proteinuria and kidney lesions. ICG-001 inhibited renal expression of multiple RAS genes in vivo and abolished the expression of other Wnt/β-catenin target genes. Moreover, ICG-001 therapy restored expression of nephrin, podocin, and Wilms’ tumor 1, attenuated interstitial myofibroblast activation, repressed matrix expression, and inhibited renal inflammation and fibrosis. Collectively, these studies identify all RAS genes as novel downstream targets of Wnt/β-catenin. Our results indicate that blockade of Wnt/β-catenin signaling can simultaneously repress multiple RAS genes, thereby leading to the reversal of established proteinuria and kidney injury.     

Zinc-α2-Glycoprotein Exerts Antifibrotic Effects in Kidney and Heart

Zinc-α2-glycoprotein (AZGP1) is a secreted protein synthesized by epithelial cells and adipocytes that has roles in lipid metabolism, cell cycling, and cancer progression. Our previous findings in AKI indicated a new role for AZGP1 in the regulation of fibrosis, which is a unifying feature of CKD. Using two models of chronic kidney injury, we now show that mice with genetic AZGP1 deletion develop significantly more kidney fibrosis. This destructive phenotype was rescued by injection of recombinant AZGP1. Exposure of AZGP1-deficient mice to cardiac stress by thoracic aortic constriction revealed that antifibrotic effects were not restricted to the kidney but were cardioprotective. In vitro, recombinant AZGP1 inhibited kidney epithelial dedifferentiation and antagonized fibroblast activation by negatively regulating TGF-β signaling. Patient sera with high levels of AZGP1 similarly attenuated TGF-β signaling in fibroblasts. Taken together, these findings indicate a novel role for AZGP1 as a negative regulator of fibrosis progression, suggesting that recombinant AZGP1 may have translational effect for treating fibrotic disease.     

Klebsiella pneumoniae carrying blaNDM-1 gene in orthopedic practice

Emergence and spread of carbapenemases in Enterobacteriaceae is a cause of concern worldwide, the latest threat being New Delhi metallo-β-lactamase (NDM-1). This report is of an orthopedic case with fracture femur managed with internal fixation and bone grafting, who subsequently developed secondary infection with Klebsiella pneumoniae harboring bla_NDM-1 gene. Minimum inhibitory concentration (MIC) of imipenem was ≥8 μg/ml by E-test, suggestive of carbapenemase production. Phenotypic and further genotypic detection confirmed the presence of bla_NDM-1 gene. The isolate remained susceptible only to tigecycline, colistin, and polymyxin B.     

Effect of Angiotensin-Converting Enzyme Inhibition and Angiotensin II Type 1 Receptor Blockade on Streptozotocin-Induced Diabetic Nephropathy

The aim of this study was designed to investigate the possible beneficial effects of the angiotensin-converting enzyme (ACE) inhibitor, Quinapril (Q) and, the angiotensin (ang) II T₁ (AT1) receptor blocker, irbesartan (Irb), in streptozotocin (STZ)-induced diabetes in rats. The rats were randomly allotted into one of five experimental groups: A (control), B (diabetic untreated), C (diabetic treated with Q), D (diabetic treated with Irb), and E (diabetic treated with Q&Irb), each group containing 10 animals. Groups B–E received STZ. Diabetes was induced in four groups by a single intraperitoneal (i.p) injection of STZ (50 mg/kg, freshly dissolved in 5 mmol/L citrate buffer, pH 4.5). Two days after STZ treatment, development of diabetes in four experimental groups was confirmed by measuring blood glucose levels in a tail vein blood samples. Rats with blood glucose levels of 250 mg/dL or higher were considered to be diabetic. The rats in Q-, Irb-, and Q&Irb-treated groups were given Q (in a dose of 3 mg/kg body weight), Irb (5 mg/kg body weight), and Q&Irb (in a dose of 1.5 mg/kg + 2.5 mg/kg body weight) once a day orally by using intra-gastric intubation for 12 weeks starting two days after STZ injection. Treatment of Q and especially Irb reduced the glomerular size and thickening of capsular, glomerular, and tubular basement membranes; and increased amounts of mesangial matrix and tubular dilatation and renal function as compared with diabetics untreated. Notably, the better effects were obtained when Q and Irb given together. We conclude that Q, Irb, and especially Q+Irb therapy causes renal morphologic and functional improvement after STZ-induced diabetes in rats. We believe that further preclinical research into the utility of Q and Irb treatment, alone or its combination, may indicate its usefulness as a potential treatment in diabetic nephropathy (DNp).     

Comparison of gene expression of the oncogenic Wnt/β-catenin signaling pathway components in the mouse and human epididymis

β-catenin is an integral part of the Wnt signaling pathway and has been linked to tumorigenesis and multiple developmental processes. The high β-catenin expression with low tumor incidence in the human epididymis is thus intriguing. In the present study, the β-catenin gene and protein was found to be highly expressed in the murine caput epididymidis, and the protein mainly localized along the lateral plasma membranes of adjacent epithelial cells throughout both human and mouse epididymides. Furthermore, the adult mouse epididymis was found to express almost all the Wnt/β-catenin signaling pathway genes that were determined previously by our group in the human organ. Despite the differences in epididymal structure, the similar location of β-catenin and the high concordance of this pathway''s components’ gene expression in both the adult human and mouse epididymides make the mouse a suitable animal model for studying the anti-tumor mechanism of the epididymis. In addition, both the mRNA and protein expression of β-catenin shared a similar spatial expression as the mRNA of Ros1, a proto-oncogene and a key developmental regulator of the initial segment of the mouse epididymis. The observations on the parallel temporal expression of β-catenin and Ros1 during postnatal development raise the possibility that the canonical Wnt signaling pathway has an additional role in the postnatal development of mouse epididymis.     

Transdifferentiation of pancreatic α-cells into insulinsecreting cells: From experimental models to underlying mechanisms

Pancreatic insulin-secreting β-cells are essential regulators of glucose metabolism. New strategies are cur-rently being investigated to create insulin-producing β cells to replace deficient β cells, including the differentiation of either stem or progenitor cells, and the newly uncovered transdifferentiation of mature non-β islet cell types. However, in order to correctly drive any cell to adopt a new β-cell fate, a better understanding of the in vivo mechanisms involved in the plasticity and biology of islet cells is urgently required. Here, we review the recent studies reporting the phenomenon of transdifferentiation of α cells into β cells by focusing on the major candidates and contexts revealed to be involved in adult β-cell regeneration through this process. The possible underlying mechanisms of transdifferentiation and the interactions between several key factors involved in the process are also addressed. We propose that it is of importance to further study the molecular and cellular mechanisms underlying α- to β-cell transdifferentiation, in order to make β-cell regeneration from α cells a relevant and realizable strategy for developing cell-replacement therapy.     

Genetic polymorphisms in HIF1A are associated with prostate cancer risk in a Chinese population

The hypoxia-inducible factor-1α (HIF-1α) plays an important role in regulating angiogenesis, which is essential for tumor growth and metastasis. Genetic variations of HIF1A (coding HIF-1α) have been shown to influence an individual''s susceptibility to many human tumors; however, evidence on associations between HIF1A single-nucleotide polymorphisms (SNPs) and prostate cancer (PCa) risk is conflicting. We genotyped three potentially functional polymorphisms in HIF1A (rs11549465, rs11549467 and rs2057482) using the TaqMan method and assessed their associations with PCa risk in a case–control study of 662 PCa patients and 716 controls in a Chinese Han population. Compared with rs11549467 GG genotype, the variant genotypes GA+AA had a significantly increased PCa risk (adjusted odds ratio (OR)=1.70; 95% confidence interval (CI)=1.06–2.72), particularly among older patients (OR=2.01; 95%CI=1.05–3.86), smokers (OR=2.06; 95%CI=1.07–3.99), never drinkers (OR=2.16; 95%CI=1.20–3.86) and patients without a family history of cancer (OR=1.71; 95%CI=1.02–2.89). Furthermore, patients with rs11549467 variant genotypes were associated with a higher Gleason score (OR=2.14; 95%CI=1.22–3.75). No altered PCa risk was associated with the rs11549465 and rs2057482 polymorphism. However, the combined variant genotypes of rs2057482 and rs11549467 were associated with increased PCa risk (OR=2.10; 95%CI=1.23–3.57 among subjects carrying three or more risk alleles). These results suggest that HIF1A polymorphisms may impact PCa susceptibility and progression in the Chinese Han population.