Effect of miR-21 on Renal Fibrosis Induced by Nano-SiO2 in Diabetic Nephropathy Rats via PTEN/AKT Pathway.

MicroRNAs are a type of non-coding single-stranded RNA that can mediate target mRNA degradation or inhibit target mRNA translation, thereby regulating target gene expression and have an important role in physiological and pathological processes. At present, miRs have been confirmed to be closely related to kidneys and kidney diseases, and have been involved in the occurrence, development and prognosis of renal fibrosis. Now we review the research progress of miRs in renal fibrosis in recent years, and provide references for the future diagnosis and treatment of renal fibrosis. The incidence of diabetic nephropathy (DN) is increasing year by year, the pathogenesis is complicated, and renal fibrosis occurs during the progress of the disease, which is very difficult to treat. The protein encoded by the PTEN gene has lipid phosphatase and protein phosphatase activity and is the PTEN/AKT and FAK pathway important negative regulators. It can play an anti-fibrotic effect by negatively regulating the PTEN/AKT pathway. Studies show that during the pathogenesis of DN, the expression of PTEN protein is reduced, and the PI3K/AKT pathway is activated to exert multiple fibrotic effects, but affect PTEN. The regulatory factors of expression are still not clear; moreover, the specific mechanism of the decrease in PTEN protein expression in DN pathogenesis. Therefore, this study intends to Intervention of the expression level of miRs in renal tissues, to study its regulation of PTEN and its effect on renal fibrosis, and at the same time, observe the effects on renal tubular epithelial cell phenotype and fibrotic lesions under high glucose conditions by up-regulating and down-regulating PTEN expression. Further elucidate the pathogenesis of DN renal fibrosis, and explore new effective targets for the prevention and treatment of DN.

Dysregulated Expression of microRNA-21 and Disease-Related Genes in Human Patients and in a Mouse Model of Alport Syndrome.

Alport syndrome is a genetic disease caused by mutations in type IV collagen and is characterized by progressive kidney disease. The Col4α3-/- mouse model recapitulates the main features of human Alport syndrome. Previously, it was reported that kidney microRNA-21 (miR-21) expression is significantly increased in Col4α3-/- mice, and administration of anti-miR-21 oligonucleotides (anti-miR-21) attenuates kidney disease progression in Col4α3-/- mice, indicating that miR-21 is a viable therapeutic target for Alport syndrome. However, the expression pattern of miR-21 in the kidneys of patients with human Alport syndrome has not been evaluated. Paraffin-embedded kidney specimens were obtained from 27 patients with Alport syndrome and from 10 normal controls. They were evaluated for miR-21 expression and for in situ hybridization and mRNA expression by quantitative polymerase chain reaction. In addition, anti-miR-21 was administrated to Col4α3-/- mice at different stages of disease, and changes in proteinuria, kidney function, and survival were monitored. Transcriptomic analysis of mouse kidney was conducted using RNA sequencing. miR-21 expression was significantly elevated in kidney specimens from patients with Alport syndrome compared to normal controls. Elevated renal miR-21 expression positively correlated with 24 h urine protein, serum blood urea nitrogen, serum creatinine, and severity of kidney pathology. On histological evaluation, high levels of miR-21 were localized to damaged tubular epithelial cells and glomeruli. Kidney specimens from both humans and mice with Alport syndrome exhibited abnormal expression of genes involved in kidney injury, fibrosis, inflammation, mitochondrial function, and lipid metabolism. Administration of anti-miR-21 to Alport mice resulted in slowing of kidney function decline, partial reversal of abnormal gene expression associated with disease pathology, and improved survival. Increased levels of miR-21 in human Alport kidney samples showed a correlation with kidney disease severity measured by proteinuria, biomarkers of kidney function, and kidney histopathology scores. These human data, combined with the finding that a reduction of miR-21 in Col4α3-/- mice improves kidney phenotype and survival, support miR-21 as a viable therapeutic target for the treatment of Alport syndrome.

Calpain-Mediated Cleavage of Calcineurin in Puromycin Aminonucleoside-Induced Podocyte Injury.

The calcineurin inhibitors cyclosporine A (CsA) and tacrolimus are widely used in the treatment of proteinuria diseases. As the direct target of these drugs, calcineurin has previously been demonstrated to play a role in proteinuria diseases. However, aside from its immune-related effects, the local status of calcineurin in renal inherent cells has not been fully explored in the settings of proteinuria disease and podocyte injury. In this study, calcineurin activity and protein expression in the well-known puromycin aminonucleoside (PAN)-induced podocyte injury model were examined. Interestingly, we found that calcineurin activity was abnormally increased in PAN-treated podocytes, whereas the expression of the full-length 60-kDa calcineurin protein was decreased. This result suggests that there may be another activated form of calcineurin that is independent of the full-length phosphatase. To investigate whether calpain is involved in regulating calcineurin, we exposed PAN-treated podocytes to both pharmacological inhibitors of calpain and specific siRNAs against calpain. Calpain blockade reduced the enhanced calcineurin activity and restored the down-regulated expression of 60-kDa calcineurin. In addition, purified calpain protein was incubated with podocyte extracts, and a 45-kDa fragment of calcineurin was identified; this finding was confirmed in PAN-induced podocyte injury and calpain inhibition experiments. We conclude that calcineurin activity is abnormally increased during PAN-induced podocyte injury, whereas the expression of the full-length 60-kDa calcineurin protein is down-regulated due to over-activated calpain that cleaves calcineurin to form a 45-kDa fragment.