Tumor necrosis factor-alpha induces interleukin-6 mRNA and protein in human granulosa luteinizing cells via protein tyrosine kinase without involving ceramide.

This study examines how interleukin-6 (IL-6) expression by human luteinizing granulosa cells is regulated. IL-6 was assayed in culture supernatants, mRNA in cells by in situ hybridization and by a competitive reverse-transcriptase polymerase chain reaction (RT-PCR). TNF alpha (100 pg-1 ng/ml) induced IL-6 mRNA and protein. Phorbol 12-myristate 13-acetate (PMA) (50 nM) mimicked this effect. DibutyrylcAMP (1 mM) and 10 microM forskolin. C2-, C6- and C8-ceramide (15 microM), all had no effect. The inhibitor of protein tyrosine kinase (PTK), genistein (100 micrograms/ml) reduced tumor necrosis factor (TNF) effects. The inhibitors of protein kinase C (PKC) (staurosporine, 10 nM), of phospholipase C (U73122, 2 microM), of phospholipase A2 (PLA2), (indomethacin 30 microM, mepacrin 50 microM, nordihydroguaiaretic acid 10 microM, ONO-RS-082 3,5 microM), none prevented it. Hence, IL-6 is induced by TNF alpha via activation of PTK. Protein kinase A, phosphoinositide and conventional PKC, sphingomyelin and PLA2 pathways are not implicated.