Rapamycin Induces Autophagy and Reduces the Apoptosis of Podocytes Under a Stimulated Condition of Immunoglobulin A Nephropathy

Abstract

Backgroud/Aims: The aim of this study was to investigate the potential renoprotective effect of rapamycin on the autophagy of podocytes treated with the supernatant of mesangial cells cultured with aggregated IgA1 (aIgA1) from immunoglobulin A nephropathy (IgAN) patients. Methods: Monomeric IgA1 (mIgA1) was isolated from the serum of IgAN patients or healthy volunteers, and then transformed to aIgA1 by heating. Subsequently, the aIgA1-mesangial cell supernatant was prepared by collecting the medium of mouse mesangial cells (MSC1097) cultured with aIgA1 (100 mg/L) from different IgAN patients or healthy volunteers for 48 h. Subsequently mouse podocytes (MPC5) were exposed to the supernatant of the aIgA1-mesangial cells for 24 h, using 100 mg/L aIgA1 from healthy volunteers as the control group or 100 mg/L aIgA1 from IgAN patients as the IgANs group, in RPMI 1640 medium. The MPC5 cells in the IgANs+Rap group were cultured with rapamycin (10 nmol/L) and the supernatant of MSC-1097 cells cultured with aIgA1 from IgAN patients in RPMI 1640 medium. Autophagy was assessed by western blot analysis (LC3, p62), electron microscopy, and immunofluorescence staining (LC3, p62, and CD63). The apoptosis of podocytes was evaluated by flow cytometry, and the expression of apoptosis-associated proteins cleaved-caspase-3 and caspase-3 were determined by western blot analysis. Results: Deficient autophagy, which was evident by decreased LC3-II and CD63 levels, caused accumulation of p62, and fewer autophagosomes were observed in the MPC5 cells cultured with the IgAN supernatant, along with stronger expression of cleaved caspase-3 and a higher apoptosis rate. Inhibition of autophagy was alleviated in the IgANs+Rap group. The LC3-II/LC3-I ratio increased by almost 30%, the accumulated p62 amount was reduced by 50%, and the number of autophagosomes per podocyte increased to about 7 times that of the IgAN groups. These results were confirmed by immunofluorescence staining. In addition, the apoptosis rate of MPC5 cells decreased from 19.88% in the IgAN group to 16.78% in the IgANs+Rap group, which was accompanied by a weaker expression level of cleaved caspase-3. Conclusions: Rapamycin can reduce the apoptosis of podocytes by inducing autophagy in IgAN.

Palmitic Acid-Induced Podocyte Apoptosis via the Reactive Oxygen Species-Dependent Mitochondrial Pathway

“…Podocytes form an important cellular layer of the glomerular filtration barrier, which is involved in the regulation of glomerular permselectivity [34]. Podocyte injury or dysfunction plays a pivotal role in the development of proteinuria in all forms of glomerular nephritis and DN [35, 36].…”

The protective effect of the TUG1/miR‑197/MAPK1 axis on lipopolysaccharide‑induced podocyte injury

“…Autophagy serves a vital role in keeping the balance between anabolism and catabolism, maintaining protein quality control and removing impaired proteins, organelles and lipids (30). The results obtained from the current studies have demonstrated that the dysfunction of podocyte autophagy taken responsibility for the development of various kidney diseases, including diabetic nephropathy (31), immunoglobulin A nephropathy (32) and proteinuric kidney disease (33). Besides, Tan et al (15) pointed out that the podocytes autophagy was remarkably suppressed by LPS, which result in LPS-induced injury of podocytes.…”

Inhibition of high mobility group box 1 (HMGB1) attenuates podocyte apoptosis and epithelial‐mesenchymal transition by regulating autophagy flux

“…It has been confirmed that impairment of podocyte autophagy is the key determinant of podocyte apoptosis . Upregulation of autophagy moderately rescues podocyte homeostasis that is important for glomerular filtration in DN . Previous studies have indicated that HMGB1‐mediated autophagy participates in the development of various types of cancer, renal ischemia‐reperfusion injury.…”

“…12 Upregulation of autophagy moderately rescues podocyte homeostasis that is important for glomerular filtration in DN. 33 Previous studies have indicated that HMGB1-mediated autophagy participates in the development of various types of cancer, renal ischemia-reperfusion injury. and DN, 25,34,35 indicating that HMGB1-induced autophagy could have a protective role in renal function.…”