Autophagy induction and CHOP under-expression promotes survival of fibroblasts from rheumatoid arthritis patients under endoplasmic reticulum stress

Abstract

IntroductionSynovial fibroblasts from rheumatoid arthritis show resistance to apoptotic stimuli, indicating they may be difficult to treat. To clearly understand these mechanisms of resistance, rheumatoid and osteoarthritis synovial fibroblasts (RASF and OASF) were exposed to endoplasmic reticulum (ER) stress such as thapsigargin, Ca2+-ATPase inhibitor.MethodsFibroblasts were assessed microscopically for cell viability by trypan blue exclusion and for autophagic cells by LC-3II formation. Caspase-3 activity was measured as aminomethyl-coumarin (AMC) liberated from AC-DEVD-AMC. Immunoblotting was performed to compare protein expression in OASF and RASF.ResultsER stress caused cell death in OASF but not in RASF. Thapsigargin, a Ca2+-ATPase inhibitor, did not change the expression of GRP78, an ER chaperone in OASF and RASF, but induced another ER stress protein, CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) differently, showing high levels in OASF and low levels in RASF. Thapsigargin increased the autophagy response in RASF, with autophagosome formation, beclin expression, and LC3-II conversion. Transfection with beclin siRNA inhibited autophagy and increased the susceptibility to ER stress-induced cell death. On the other hand, CHOP siRNA increased autophagy and improved cell survival, especially in RASF, indicating that CHOP is involved in regulation of autophagy and cell death, but that low expression of CHOP protects RASF from apoptosis.ConclusionsAutophagy induction and CHOP under-expression increases cell resistance against ER stress-induced cell death in fibroblasts from rheumatoid arthritis patients.

Thrombin Increases Lung Fibroblast Survival while Promoting Alveolar Epithelial Cell Apoptosis via the Endoplasmic Reticulum Stress Marker, CCAAT Enhancer–Binding Homologous Protein

“…These data suggest that thrombin increases survival of lung fibroblasts via down-regulation of CHOP expression in these cells, which may be another potential mechanism of the increased numbers of lung fibroblasts in pulmonary fibrosis. Our results are in agreement with recent work reported by Shin and colleagues (35), demonstrating that CHOP underexpression promotes survival of synovial fibroblasts from patients with rheumatoid arthritis under ER stress.…”

Obtain osteoarthritis related molecular signature genes through regulation network

“…It is crucial to the regulation of genes involved in immune and inflammatory responses and may be involved in the regulation of genes associated with the activation and differentiation of macrophages (22). C/EBP TFs are involved in the activation of OA cells, and endoplasmic reticulum stress causes cell death in OA (23).…”

Nutrient signaling pathways and rheumatic diseases

“…Хотя роль аутофагии при РА практически не изучена, действие одного из модифицирующих заболе-вание антиревматических препаратов -хлорохина -осно-вано на ингибировании аутофагии и усилении апоптоза [160]. Кроме того, показано, что индукция аутофагии в си-новиальных фибробластах при РА усиливает устойчивость этих клеток к гибели посредством апоптоза [161].…”