Autolysosomal degradation of cytosolic chromatin fragments antagonizes oxidative stress–induced senescence

Xiaojuan Han,Honghan Chen,Hui Gong,Xiaoqiang Tang,Ning Huang,Weitong Xu,Haoran Tai,Gongchang Zhang,Tingting Zhao,Chuhui Gong,Shuang Wang,Yu Yang,Hengyi Xiao

doi:10.1074/jbc.ra119.010734

Abstract

Oxidative stress-induced DNA damage, the senescence-associated secretory phenotype (SASP), and impaired autophagy all are general features of senescent cells. However, the cross-talk among these events and processes is not fully understood. Here, using NIH3T3 cells exposed to hydrogen peroxide stress, we show that stress-induced DNA damage provokes the SASP largely via cytosolic chromatin fragment (CCF) formation, which activates a cascade comprising cGMP-AMP synthase (cGAS), stimulator of interferon genes protein (STING), NF-κB, and SASP, and that autolysosomal function inhibits this cascade. We found that CCFs accumulate in senescent cells with activated cGAS-STING-NF-κB signaling, promoting SASP and cellular senescence. We also present evidence that the persistent accumulation of CCFs in prematurely senescent cells is partially associated with a defect in DNA-degrading activity in autolysosomes and reduced abundance of activated DNase 2α. Intriguingly, we found that metformin- or rapamycin-induced activation of autophagy significantly lessened the size and levels of CCFs and repressed the activation of the cGAS-STING-NF-κB-SASP cascade and cellular senescence. These effects of autophagy activators indicated that autolysosomal function contributes to CCF clearance and SASP suppression, further supported by the fact that the lysosome inhibitor bafilomycin A1 blocked the role of autophagy-mediated CCF clearance and senescence repression.

Highlights

Oxidative stress-induced DNA damage, the senescence-associated secretory phenotype (SASP), and impaired autophagy all are general features of senescent cells
We confirmed the increase in the mRNA of interferon ␤ (Ifn␤) and C-X-C chemokine ligand 10 (Cxcl10), two genes known widely as the downstream targets of the cGMP-AMP synthase (cGAS)-stimulator of interferon genes protein (STING) pathway, in senescent cells (Fig. 1I). These results suggest that oxidative DNA damage, cytosolic chromatin fragment (CCF) accumulation, and activation of the cGAS-STING signaling are collectively provoked in senescent cells, and these events were accompanied by SASP expression
Our findings demonstrated that oxidative stress causes CCF accumulation in premature senescent cells, which is associated with the defective DNA degeneration activity of autolysosome

Summary

Introduction

Oxidative stress-induced DNA damage, the senescence-associated secretory phenotype (SASP), and impaired autophagy all are general features of senescent cells. We show that autolysosomal dysfunction in DNA degeneration contributes to CCF accumulation in oxidative SIPS cells, where CCFs provoke SASP production through the aberrant activation of the cGAS-STING pathway. DNA damage, CCF accumulation, and cGAS-STING pathway activation occur in senescent cells

Results

Conclusion