Proliferation and fibrosis of human Tenon's fibroblasts (HTFs) have significantly challenged the outcome of glaucoma filtration surgery. Hydroxycamptothecin (HCPT) is considered as a potential chemical to overcome this issue as it was previously shown that HCPT inhibited cell proliferation and induced apoptosis in fibroblasts. Here, we further dissected the molecular pathway, through which the HCPT inhibit the proliferation of HTFs. We showed that HCPT induced significant autophagy as well as apoptosis, two self-destructive processes, and down-regulated the expression of miR-216b in HTFs. Overexpression of miR-216b in HTFs suppressed the autophagy and apoptosis induced by HCPT, whereas silence of miR-216b led to effects that were similar to those caused by the treatment with HCPT. Further, we showed that miR-216b could directly target a specific fragment in the 3' untranslated region of Beclin 1 as demonstrated by luciferase assay, and consequently decreased the expression of Beclin 1. Consistently, knocking down Beclin 1 significantly decreased HCPT-triggered autophagy and apoptosis, and increased the viability of HTFs treated with HCPT, thus implicating that Beclin 1 functions as a pro-apoptotic molecule in this circumstance. Altogether, we concluded that miR-216b regulated both autophagy and apoptosis by modulating Beclin 1 in HTFs treated with HCPT. We also demonstrated that HCPT-induced autophagy is one of the agent's anti-proliferative effects.
Keywords: Beclin 1; apoptosis; autophagy; glaucoma; human Tenon's capsule fibroblasts; hydroxycamptothecin; microRNA-216b.
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