Mitomycin C induces apoptosis in rheumatoid arthritis fibroblast-like synoviocytes via a mitochondrial-mediated pathway.

BACKGROUND/AIMS: Rheumatoid arthritis (RA) is a systemic chronic inflammatory disease characterised by prominent synoviocyte hyperplasia and a potential imbalance between the growth and death of fibroblast-like synoviocytes (FLS). Mitomycin C (MMC) has previously been demonstrated to inhibit fibroblast proliferation and to induce fibroblast apoptosis. However, the effects of MMC on the proliferation and apoptosis of human RA FLS and the potential mechanisms underlying its effects remain unknown. METHODS: Cell viability was determined using the Cell Counting Kit-8 assay. Apoptotic cell death was analysed via Annexin V-FITC/PI double staining and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling. The production of intracellular reactive oxygen species (ROS) was assessed via flow cytometry, and the changes in mitochondrial membrane potential (ΔΨm) were visualized based on JC-1 staining via fluorescence microscopy. The expression of apoptosis-related proteins was determined via Western blot. RESULTS: Treatment with MMC significantly reduced cell viability and induced apoptosis in RA FLS. Furthermore, MMC exposure was found to stimulate the production of ROS and to disrupt the ΔΨm compared to the control treatment. Moreover, MMC increased the release of mitochondrial cytochrome c, the ratio of Bax/Bcl-2, the activation of caspase-9 and caspase-3, and the subsequent cleavage of poly(ADP-ribose) polymerase. CONCLUSION: Our findings suggest that MMC inhibits cell proliferation and induces apoptosis in RA FLS, and the mechanism underlying this MMC-induced apoptosis may involve a mitochondrial signalling pathway.

MicroRNA-216b/Beclin 1 axis regulates autophagy and apoptosis in human Tenon's capsule fibroblasts upon hydroxycamptothecin exposure.

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.