Mitochondria-Associated Endoplasmic Reticulum Membranes Activating Mitochondrial Apoptosis through Rtn4b/P53/Ei24 Pathway in Podocytes under High-Glucose Condition

Background: Diabetic nephropathy (DKD) is a global health problem with complex pathogenesis and limited treatment options. The mitochondria-associated endoplasmic reticulum membrane (MAM) is essential for maintaining the normal function of both organelles. In our previous studies, we found the expression level of reticulon 4B (Rtn4b) in renal biopsy tissues of patients with DKD was significantly decreased. Methods: Here, we explore the underlying role and mechanism in deletion of RTN4B induces podocyte injury. Results: Results showed as the DKD progresses, the expression level of Rtn4b was gradually decreased in renal biopsy tissues (Fig 1). Altered expression was also observed in type 2 diabetes mice. As with the extension of time of high-glucose exposure, the expression level of Rtn4b in podocytes was gradually decreased. Inhibition of the expression of Rtn4b significantly down-regulated podocyte marker protein synaptopodin, nephrin and podocin.(Fig 2) In vivo, global knockout (KO) of Rtn4b deterioated renal function and pathology as presented by aggravated albuminuria, expanded glomerular mesangium and worsened podocyte injury in diabetic mice model (Fig 3). Mechanistically, p53 signaling pathway was among the top 10 enriched items, and mitoptosis related marker Ei24 ranked the highest score in the differential analysis in HG-cultured podocytes transfected with Rtn4b siRNA (Fig. 4). silencing Rtn4b promoted P53 activation via Ei24 mediated mitochondrial apoptotic pathway (Fig. 5). Conclusion: Altogether, these results suggest that Rtn4b protects podocytes from diabetic injuries by preventing ER-Mitochondrial crosstalk from mitoptosis and targeting Rtn4b may be a potential therapeutic approach in DN.