Background: Anti-dsDNA antibodies play an important role in the pathogenesis of lupus nephritis (LN). Endoplasmic reticulum (ER) stress is a physical reaction under stressful condition and can cause inflammation when stimulation is sustained. This study investigated the roles of ER stress in anti-dsDNA antibody-induced inflammation response in human mesangial cells (HMCs).
Method: Anti-dsDNA antibodies isolated from LN patients were used to stimulate HMCs. The expression of GRP78, PERK, p-PERK, p-eIF2α, ATF4, p-IRE1α, ATF6 and CHOP in HMCs was measured by western blot. NF-κB activation was detected by examining nuclear translocation of NF-κB p65. The expression and production of IL-1β, TNF-α and MCP-1 were examined by qPCR and ELISA.
Results: Flow cytometry and cellular ELISA showed that anti-dsDNA antibodies can bind to HMCs. The binding was not inhibited by blockage of Fc receptor. Anti-dsDNA antibody stimulation significantly enhanced the expression of GRP78, p-PERK, p-eIF2α and ATF4 in HMCs. However, no significant increase in the expression of p-IRE1α and ATF6 was found. In addition, anti-dsDNA antibodies also significantly increased the activation of NF-κB and upregulated the expression of IL-1β, TNF-α and MCP-1, which were suppressed by pretreatment of HMCs with chemical ER stress inhibitor 4-PBA. Transfection of specific ATF4 siRNA also significantly reduced the activation of NF-κB and expression of proinflammatory cytokines.
Conclusion: Anti-dsDNA antibodies induce NF-κB activation and inflammation in HMCs via PERK-eIF2α-ATF4 ER stress pathway.