Loss of Sirt1 promotes exosome secretion from podocytes by inhibiting lysosomal acidification in diabetic nephropathy.

Podocyte injury is a characteristic feature of diabetic nephropathy (DN). The secretion of exosomes in podocytes increases significantly in DN; however, the precise mechanisms remain poorly understood. Here, we demonstrated that Sirtuin1 (Sirt1) was significantly downregulated in podocytes in DN, which correlated negatively with increased exosome secretion. Similar results were observed in vitro. We found that lysosomal acidification in podocytes following high glucose administration was markedly inhibited, resulting in the decreased lysosomal degradation of multivesicular bodies. Mechanistically, we indicated that loss of Sirt1 contributed to the inhibited lysosomal acidification by decreasing the expression of the A subunit of the lysosomal vacuolar-type H+ ATPase proton pump (ATP6V1A) in podocytes. Overexpression of Sirt1 significantly improved lysosomal acidification with increased expression of ATP6V1A and inhibited exosome secretion. These findings suggest that dysfunctional Sirt1-mediated lysosomal acidification is the exact mechanism of increased secretion of exosomes in podocytes in DN, providing insights into potential therapeutic strategies for preventing DN progression.

Long noncoding RNA SNHG5 promotes podocyte injury via the microRNA-26a-5p/TRPC6 pathway in diabetic nephropathy.

Podocyte injury is a characteristic pathological hallmark of diabetic nephropathy (DN). However, the exact mechanism of podocyte injury in DN is incompletely understood. This study was conducted using db/db mice and immortalized mouse podocytes. High-throughput sequencing was used to identify the differentially expressed long noncoding RNAs in kidney of db/db mice. The lentiviral shRNA directed against long noncoding RNA small nucleolar RNA host gene 5 (SNHG5) or microRNA-26a-5p (miR-26a-5p) agomir was used to treat db/db mice to regulate the SNHG5/miR-26a-5p pathway. Here, we found that the expression of transient receptor potential canonical type 6 (TRPC6) was significantly increased in injured podocytes under the condition of DN, which was associated with markedly decreased miR-26a-5p. We determined that miR-26a-5p overexpression ameliorated podocyte injury in DN via binding to 3'-UTR of Trpc6, as evidenced by the markedly reduced activity of luciferase reporters by miR-26a-5p mimic. Then, the upregulated SNHG5 in podocytes and kidney in DN was identified, and it was proved to sponge to miR-26a-5p directly using luciferase activity, RNA immunoprecipitation, and RNA pull-down assay. Knockdown of SNHG5 attenuated podocyte injury in vitro, accompanied by an increased expression of miR-26a-5p and decreased expression of TRPC6, demonstrating that SNHG5 promoted podocyte injury by controlling the miR-26a-5p/TRPC6 pathway. Moreover, knockdown of SNHG5 protects against podocyte injury and progression of DN in vivo. In conclusion, SNHG5 promotes podocyte injury via the miR-26a-5p/TRPC6 pathway in DN. Our findings provide novel insights into the pathophysiology of podocyte injury and a potential new therapeutic strategy for DN.