Role of podocyte autophagy in passive Heymann nephritis / 中华肾脏病杂志

ABSTRACT

Objective To investigate the role of autophagy in podocyte damage,and the intracellular mechanism of autophagy activation through passive Heymann nephritis (PHN) animal model.Methods Male Sprague-Dawley rats (n=40) were studied on day 0,2,4,7,and 21 after induction of PHN by injection of anti-Fx1A.Podocyte morphology and autophagosomes were observed by transmission electron microscopy.Podocyte numerical density was estimated by Weibel-Gomez =method.Cell apoptosis was detected by TUNEL assay and caspase-3 immunohistochemical staining.Expressions of autophagy markers and endoplasmic reticulum stress (ERS)-associated proteins were analyzed by Western blotting.Results (1) In PHN rats,immunohistochemical staining showed that C5b-9 deposited along glomerular basement membrane on day 4 to day 21.Small subepithelial electron -dense deposits and a part of foot process fusion were detected in the glomerulus of PHN rats on day 4 by transmission electron microscope,and podocyte damage was aggravated on day 21.Furthermore,compared with control,the urinary protein levels of PHN rats began to increase on day 3,and reached the top on day 21 [(50.6±6.0) mg/24 h].(2) The number of podocytes significantly decreased in PHN rats compared with control group on day 21(P ＜ 0.05).(3) In PHN rats,apoptotic podocytes were found by caspase-3 immunohistochemical staining and TUNEL assay on day 21.(4) The expression of autophagy marker LC3 Ⅱ was markedly increased on day 7 and 21,but down-regulated on day 21 compared with day 7.Moreover,accumulated autophagosomes in podocytes were detected on day 7 and 21 by transmission electron microscope.(5) The level of GRP78 was significantly increased on day 2 and 7 but reduced to baseline on day 21.At the same time,the downstream pathways (ATF6α,p-PERK and p-JNK) of unfolded protein response were also up-regulated in the early process of PHN and down-regulated later.Conclusions Autophagy is an important way to protect against immunemediated podocyte injury in membranous nephropathy.Autophagy activation is mainly related to endoplasmic reticulum stress induced by complement attack.This provides an important basis for a thorough understanding of the role of autophagy in the process of podocyte damage and the pathogenesis of membranous nephropathy.