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 pheochromocytom a 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 PC 12 cells by serum deprivation. The protective effect of IL-6 was incre ased by preincubation of PC12 with IL-6 for 20 hr before serum depriva tion. The inhibition of protein synthesis by cycloheximide had no effe ct on the protective effect of IL-6 on the serum deprivation-induced c ell death. IL-6 also inhibited the death of PC12 cells induced by addi tion of the calcium ionophore A23187 to the culture medium. Specific i n situ labeling of DNA cleavage was observed in PC12 cells subjected t o both serum deprivation and A23187 for 24 hr. IL-6 inhibited DNA frag mentation in PC12 cells following serum deprivation. These results sug gest that the death of PC12 cells induced by serum deprivation or by t he addition of calcium ionophore is apoptosis, and that IL-6 blocks ap optosis of PC12 cells.