Triptolide protects podocytes from IL-13 induced injury in vitro

Objective The injury or shedding of podocytes is the key component inducing glomerular sclerosis,and the abnormality of cytoskeleton and related-proteins are important reasons for focal segmental glomerular sclerosis.Triptolide shows dramatic effect in podocyte diseases.This study is to investigate the protective and treated effects and mechanism of triptolide on podocytes injury induced by IL-13.Methods Conditionally immortalized mouse podocytes were treated with IL-13(50ng/ml).For the protective experiments,the podocytes were pretreated for 30minutes with triptolide(3ng/ml) or dexamethasone(1 μmol/L) or both before IL-13 exposure for 24h,while for the recovery experiments,after 24h of IL-13 treatment,the culture medium was changed to medium with triptolide or dexamethasone or both for 72h.F-actin and ZO-1 patterns in podocytes were observed by confocal microscopy.In order to understand the underlying mechanism of IL-13 effect on podocytes,the activity of JAK-STAT6 signal pathway were analyzed by measuring the extent of phosphorylation of STAT6 using western blotting.Results In cultured mouse podocytes,we found that IL-13 almost completely disrupted the podocyte actin cytoskeleton,and prevent ZO-1 expression,while triptolide can obviously obstruct and alleviate the injury,stabilize the actin filments,and improve ZO-1 expression.Furthermore,triptolide can inhibit the activation of STAT6 phosphorylation induced by IL-13.Dexamethasone has the same effect with triptolide but they don′t have a synergistic effect.Conclusion Triptolide prevent and treat IL-13-induced podocyte injury.The above action of triptolide might be contributed to JAK-STAT6 signaling pathway.