miR-664a-5p promotes experimental membranous nephropathy progression through HIPK2/Calpain1/GSα-mediated autophagy inhibition

Abstract

Abstract [Background] We previously found that miR-664a-5p is specifically expressed in urinary exosomes of idiopathic membranous nephropathy (IMN) patients, but its function and mechanism in MN progression are unclear. [Objective] To investigate the function and mechanism of miR-664a-5p in MN. [Methods] The miR-664a-5p expression in HK-2 cells, exosomes, human podocytes and renal tissues were studied, as well as the activity and apoptosis of these cells, the binding of miR-664a-5p to HIPK2 mRNA, the levels of several relative proteins and autophagy, several relative characteristics of exosomes. The MN progression in MN mice model was also studied. [Results] Albumin increased the miR-664a-5p content and apoptosis of HK-2 cells, which was blocked by miR-664a-5p antagomir. miR-664a-5p bound to the 3’ UTR of HIPK2 mRNA and reduced its expression. miR-664a-5p antagomir restored albumin-mediated Calpain1 up-regulation, GSα shear and autophagy decline. Autophagy inhibitor CQ blocked the protective effect of miR-664a-5p antagomir, HIPK2 overexpression, and Calpain inhibitor SJA6017 on albumin-mediated injury. The miR-664a-5p level increased in exosomes from albumin-treated HK-2 cells, and it could be horizontally transported to podocytes through exosomes. In MN mice, exosomes from albumin-treated HK-2 cells promoted the pathological MN symptoms, and AAV-Anti-miR-664-5p (mouse homology miRNA) could improve them. [Conclusion] Albumin increases the miR-664a-5p level and causes changes in the HIPK2/Calpain1/GSα pathway, which leads to autophagy inhibition and apoptosis up-regulation of renal tubular epithelial cells. miR-664a-5p can horizontally enter podocytes through exosomes. Targeted inhibition of miR-664a-5p can reduce the apoptosis of renal tubule cells and podocytes, and may improve the MN progression.