Expression of PKCeta in NIH-3T3 cells promotes production of the pro-inflammatory cytokine interleukin-6.
Protein kinase C encodes a family of enzymes implicated in cellular differentiation, growth control and tumor promotion. The generation and characterization of NIH-3T3 cells which stably overexpress the PKCeta isoform has been previously described by us. In these cells, overexpression of PKCeta altered the expression of specific cell cycle regulators and promoted differentiation [20]. Since PKC has been implicated in the regulation of gene expression, including that of various cytokines, we examined the production of several cytokines in these cells. We report here that out of the major pro-inflammatory cytokines examined, IL-1alpha, IL-1beta, TNF-alpha and IL-6, only IL-6 was generated and secreted in PKCeta -expressing cells without any additional inducer in serum-supplemented cultures (10% FCS). IL-6 was not detected in the control cell line, transfected with the same vector, but lacking the cDNA coding for PKCeta. Moreover, the production of IL-6 on serum stimulation correlated with the levels of PKCeta expressed in these cells. This implies that factors in the serum activate PKCeta and induce IL-6 production. We have examined several growth factors and cytokines for their ability to induce IL-6 production in our PKCeta-expressing cells. Among the growth factors tested (EGF, PDGF, FGF, insulin, IGF-1 and IL-1), PDGF and FGF were the most potent IL-6 inducers. The effects of FGF and PDGF on IL-6 production were blocked in the presence of PKC inhibitors. We also examined the signaling pathways that mediate production of IL-6 in PKCeta-expressing cells. Using specific inhibitors of the MAPK pathway, we have shown a role for ERK and p38 MAPK in FGF- and serum-stimulated IL-6 production, but only for p38 MAPK in PDGF-stimulated IL-6 production. Our studies provide evidence that PDGF and FGF can serve as upstream regulators of PKCeta and that PKCeta is involved in the expression of IL-6. This suggests that inhibition of PKC may provide a basis for the development of drugs for the treatment of disorders in which IL-6 is pathologically involved.
Fima
E
E
Department of Microbiology and Immunology, Faculty of Health Sciences, Ben Gurion University, Beer Sheva 84105, Israel.
Shahaf
G
G
Hershko
T
T
Apte
R N
RN
Livneh
E
E
D016475:3T3 Cells; D000818:Animals; D017077:Culture Media, Conditioned / Q000737:chemistry; D016207:Cytokines / Q000032:analysis; D004789:Enzyme Activation / Q000187:drug effects; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D015870:Gene Expression; D006133:Growth Substances / Q000494:pharmacology; D015850:Interleukin-6 / Q000032:analysis / Q000096:biosynthesis*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048369:MAP Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
D017077:Culture Media, Conditioned; D016207:Cytokines; D006133:Growth Substances; D015850:Interleukin-6; D007527:Isoenzymes; D010982:Platelet-Derived Growth Factor; D005346:Fibroblast Growth Factors; C081975:protein kinase C eta; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases