Tumor necrosis factor alpha (TNF) increases granulosa cell proliferation: dependence on c-Jun and TNF receptor type 1

TNF alpha has significant in vitro effects on steroidogenesis and folliculogenesis and reproductive alterations occur in TNF receptor type 1 (TNFR1) knockout mice. The present study investigated the effect of in vitro TNF on granulosa cell proliferation from immature mice at 28 d of age, with emphasis on intracellular signaling that regulates granulosa cell proliferation. TNF dose dependently increased granulosa cell proliferation and the proto-oncogene c-Jun protein. However, other Jun family members such as JunD was expressed constitutively and JunB was not expressed. In vitro TNF did not increase c-Jun and proliferation in granulosa cells from TNFR1 knockout mice. The time course of TNF-induced c-Jun revealed biphasic patterns of short-term (3 h) and long-term (24 h) induction. The time courses of Ser63- and Ser73-phospho c-Jun coincided with changes in total c-Jun. Among MAPK cascades, stress-activated protein kinase/c-Jun-NH(2)-teminal kinase signaling was increased transiently in TNF-treated cells, whereas p38MAPK and ERK1 and 2 were not changed. In addition, overexpression of nuclear factor-kappa B and addition of ceramide and 8-bromo-cAMP did not increase c-Jun or proliferation. Antisense oligonucleotides for c-Jun blocked cell proliferation induced by TNF. In conclusion, the above results demonstrate that TNF increased c-Jun by activating stress-activated protein kinase/c-Jun-NH(2)-teminal kinase signaling via TNFR1 in mouse granulosa cells, and the induced c-Jun resulted in increased cell proliferation.