Hydroxycamptothecin prevents intraarticular scar adhesion by activating the PERK signal pathway

Intraarticular adhesion is one of the complications when the patients suffer from operations of knee-joint. Hydroxycamptothecin (HCPT) can selectively inhibit the activity of topoisomerase I and has shown anti-proliferative effect in previous researches. The aim of our experiment was to investigate the effect of topical application of HCPT on preventing intraarticular scar adhesion by activating the PERK signal pathway. As the results showed, HCPT could prevent the intraarticular scar adhesion and the inhibitory effect was in a dose-dependent manner. Furthermore, we assumed that ER stress mediated the suppression effect of the intraarticular scar adhesion. The results of immunohistochemistry showed that the expression of GRP78 and CHOP were increased together with the tendency of HCPT. When human fibroblasts were treated with HCPT in vitro, cell viability was inhibited according to the results of CCK-8 assay and Hoechst staining, and cell apoptosis was induced according to the results of AV/PI and western blot analysis. HCPT-induced apoptosis was correlated with elevation of GRP78 and CHOP, which were hallmarks of ER stress. Proteins associated with PERK signal pathway such as p-PERK and p-eIF2α were upregulated after treated by HCPT determined by western blot analysis. Knockdown of PERK decreased the ratio of Bax/Bcl-2, GRP78 and CHOP expression, suggesting that PERK signal pathway was involved in HCPT-induced fibroblast apoptosis. Our findings indicate that topical application of HCPT can prevent intraarticular scar adhesion. ER stress plays an important role in this effect by inducing fibroblasts apoptosis that may be mediated by PERK signal pathway.