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

Background: Chloroquine, 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).

Methods: We 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.

Results: Poly 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.

Conclusion: Considering that TLR3 signaling is implicated in LN pathogenesis, our results suggest that chloroquine exert postulated renoprotective effects by inhibiting PAI-1 expression.