TGF-\u03b21 reduces the oxidative stress-induced autophagy and apoptosis in rat annulus fibrosus cells through the ERK signaling pathway

Abstract

BackgroundThe aim of this study is to explore the effects of TGF-β1 on autophagy and apoptosis induced by exogenous hydrogen peroxide (H2O2) in annulus fibrosus (AF) cells and possible signal pathways involved in this process.MethodsAF cells were isolated from rat lumbar discs and subjected to different concentrations of exogenous H2O2 (50, 100, 200 μmol/L) for different time periods (0.5, 1, 2, and 4 h). Cell viability was determined by CCK-8 assay, and the levels of autophagy and apoptosis were evaluated by Western blotting and caspase 3, 8, 9 activity assay. By administration with different concentrations of TGF-β1 (5, 10, 20 ng/mL), the effects of TGF-β1 on autophagy and apoptosis induced by H2O2 were observed, and the possible signaling pathways were also investigated by using various apoptosis inhibitors or an autophagy inhibitor Bafilomycin A (Baf A) in AF cells.ResultsH2O2 significantly impaired cell viability in a dose- and time-dependent manner. H2O2 also induced a sudden and the highest level of autophagy at 1 h, and gradually increased apoptosis through ERK pathway. The mitochondrial pathway was involved in H2O2-induced apoptosis in AF cells. TGF-β1 reduced the expression of p-ERK and downregulated the expressions of Beclin-1, LC3 II/I, and mitochondrial-related apoptotic proteins (Bax/Bcl-2, caspase-9). Meanwhile, TGF-β1 downregulated the level of intracellular H2O2 through upregulating the expression level of glutathione peroxidase-1 (GPx-1).ConclusionsTGF-β1 reduced autophagy and apoptosis induced by exogenous H2O2 through downregulating the expression of ERK in AF cells. TGF-β1 could downregulate the level of ERK and intracellular H2O2 by upregulating GPx-1.