Protective effect of interleukin-6 against the death of PC12 cells caused by serum deprivation or by the addition of a calcium ionophore

Interleukin-6 (IL-6) is known to differentiate the rat pheochromocytoma cell line PC12 to neuron-like cells. We examined the effect of IL-6 on the death of PC12 cells. IL-6 significantly blocked the death of PC12 cells by serum deprivation. The protective effect of IL-6 was increased by preincubation of PC12 with IL-6 for 20 hr before serum deprivation. The inhibition of protein synthesis by cycloheximide had no effect on the protective effect of IL-6 on the serum deprivation-induced cell death. IL-6 also inhibited the death of PC12 cells induced by addition of the calcium ionophore A23 187 to the culture medium. Specific in situ labeling of DNA cleavage was observed in PC12 cells subjected to both serum deprivation and A23187 for 24 hr. IL-6 inhibited DNA fragmentation in PC12 cells following serum deprivation. These results suggest that the death of PC12 cells induced by serum deprivation or by the addition of calcium ionophore is apoptosis, and that IL-6 blocks apoptosis of PC12 cells.