In this study, we examined the effect of tomatidine on tumor necrosis factor (TNF)-α-induced apoptosis in C2C12 myoblasts. TNF-α treatment increased cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase (PARP) protein levels in a dose- and time-dependent manner. Pretreatment of cells with 10 μM tomatidine prevented TNF-α-induced apoptosis, caspase 3 cleavage, and PARP cleavage. Cells were treated with 100 ng/mL TNF-α for 24 h, and flow cytometry was utilized to assess apoptosis using annexin-V and 7-aminoactinomycin D. TNF-α up-regulated activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP) expression. This effect was suppressed by pretreatment with tomatidine. Pretreatment with 4-phenylbutyric acid (a chemical chaperone) also inhibited TNF-α-induced cleavage of caspase 3 and PARP and up-regulation of ATF4 and CHOP expression. In addition, tomatidine-mediated inhibition of phosphorylation of c-Jun amino terminal kinase (JNK) attenuated TNF-α-induced cleavage of PARP and caspase 3. However, tomatidine did not affect NF-κB activation in TNF-α-treated C2C12 myoblast cells. Taken together, the present study demonstrates that tomatidine attenuates TNF-α-induced apoptosis through down-regulation of CHOP expression and inhibition of JNK activation.
Keywords: Apoptosis; C2C12 myoblast; ER stress; TNF-α; Tomatidine.