Chloroquine attenuates TLR3-mediated plasminogen activator inhibitor-1 expression in cultured human glomerular endothelial cells

BackgroundChloroquine, an antimalarial agent, has been reported to prevent the risk of thrombosis and decrease renal damage in patients with systemic lupus erythematosus (SLE); however, its detailed mechanisms remain unclear. Plasminogen activator inhibitor-1 (PAI-1) is an inhibitor of fibrinolysis and is involved in fibrin deposition in glomeruli. Since upregulation of glomerular Toll-like receptor 3 (TLR3) signaling reportedly plays a pivotal role in the pathogenesis of lupus nephritis (LN), we examined whether chloroquine affects TLR3-mediated expression of PAI-1 in cultured human glomerular endothelial cells (GECs).MethodsWe examined the effect of polyinosinic-polycytidylic acid (poly IC), an authentic double-stranded RNA, on PAI-1 and tissue plasminogen activator (t-PA) expression in GECs. Then, we analyzed whether pretreatment of chloroquine or dexamethasone inhibits poly IC-induced expression of these proteins using reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay.ResultsPoly IC increased PAI-1 expression in a time- and concentration-dependent manner, but did not affect t-PA expression in GECs. RNA interference against TLR3 inhibited poly IC-induced PAI-1 expression. Interestingly, pretreating cells with chloroquine, and also hydroxychloroquine, but not dexamethasone, attenuated poly IC-induced PAI-1 expression in GECs.ConclusionConsidering that TLR3 signaling is implicated in LN pathogenesis, our results suggest that chloroquine exert postulated renoprotective effects by inhibiting PAI-1 expression.