Sublytic C5b-9 triggers glomerular mesangial cell apoptosis via XAF1 gene activation mediated by p300-dependent IRF-1 acetylation.

W Qiu,G Zhu,Y Wang,T Yu,F He,L Liu,D Zhao,Y Lu,J Zhang,J Zhou

doi:10.1038/cddis.2014.153

Abstract

The apoptosis of glomerular mesangial cells (GMCs) in rat Thy-1 nephritis (Thy-1N), a model of human mesangioproliferative glomerulonephritis (MsPGN), is accompanied by sublytic C5b-9 deposition. However, the mechanism by which sublytic C5b-9 induces GMC apoptosis is unclear. In the present studies, the effect of X-linked inhibitor of apoptosis-associated factor 1 (XAF1) expression on GMC apoptosis and the role of p300 and interferon regulatory factor-1 (IRF-1) in mediating XAF1 gene activation were determined, both in the GMCs induced by sublytic C5b-9 (in vitro) and in the renal tissues of rats with Thy-1N (in vivo). The in vitro studies demonstrated that IRF-1-enhanced XAF1 gene activation and its regulation by p300-mediated IRF-1 acetylation were involved in GMC apoptosis induced by sublytic C5b-9. The element of IRF-1 binding to XAF1 promoter and two acetylated sites of IRF-1 protein were also revealed. In vivo, silence of p300, IRF-1 or XAF1 genes in the renal tissues diminished GMC apoptosis and secondary GMC proliferation as well as urinary protein secretion in Thy-1N rats. Together, these data implicate that sublytic C5b-9 induces the expression of both p300 and IRF-1, as well as p300-dependent IRF-1 acetylation that may contribute to XAF1 gene activation and subsequent GMC apoptosis in Thy-1N rats.

Highlights

Apoptosis and glomerular mesangial cell (GMC) proliferation and extracellular matrix (ECM) secretion.[1,2,3,4] Several studies have found that complement, especially C5b-9 complex, deposits in the glomeruli of patients with MsPGN,[5,6,7] leading to GMC apoptosis and eventual cellular damage
To further confirm that the above-mentioned effects were because of sublytic C5b-9 complexes, Cell Death and Disease control cells were treated with different media containing 5% Thy-1 antibody (Thy-1 Ab), 5% Thy-1 Ab þ 4% heat inactive serum (HIS), 5% Thy-1 Ab þ 4% complement C6-deficient serum (C6DS), 5% Thy-1 Ab þ 4% C6DS þ C6 (0.5 or 2 mg/l) and 5% Thy-1 Ab þ 4% C6DS þ PBS, respectively
The results showed that X-linked inhibitor of apoptosis-associated factor 1 (XAF1) expression was markedly upregulated only in the GMCs induced by sublytic C5b-9 (Figure 1d)

Summary

Introduction

Apoptosis and GMC proliferation and extracellular matrix (ECM) secretion.[1,2,3,4] Several studies have found that complement, especially C5b-9 complex, deposits in the glomeruli of patients with MsPGN,[5,6,7] leading to GMC apoptosis and eventual cellular damage. X-linked inhibitor of apoptosis-associated factor 1 (XAF1).[22,23] Reportedly, XAF1 was first identified as an interacting protein of X-linked inhibitor of apoptosis (XIAP) It functions as an antagonist of XIAP by rescuing XIAPsuppressed caspase-3 activity, promoting cellular apoptosis.[24,25] XAF1 is implicated as a tumor suppressor because XAF1 expression is downregulated in a variety of tumor cells including gastric and colon cancer cell lines, and transient expression of XAF1 sensitizes tumor cells to the proapoptotic effects of etoposide.[22,23,25] Our previous studies demonstrated that the expression of XAF1 was significantly increased in both renal tissues of Thy-1N rats (in vivo) and cultured rat GMCs stimulated with sublytic C5b-9 (in vitro). The role of XAF1 gene expression in sublytic C5b-9induced GMC apoptosis of the rats with Thy-1N and its regulation have not been clarified

Methods

Results

Conclusion