Induction of ICAM-1 by TNF-alpha, IL-1 beta, and LPS in human endothelial cells after downregulation of PKC.
The intercellular adhesion molecule 1 (ICAM-1) is induced on endothelial cells by tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and lipopolysaccharide (LPS). We have reported the sensitivity of cytokine-induced ICAM-1 expression to protein kinase inhibitors, including inhibitors of protein kinase C (PKC) [C. L. Myers, S. N. Desai, J. Schembri-King, G. L. Letts, and R. W. Wallace. Am. J. Physiol. 262 (Cell Physiol. 31): C365-C373, 1992]. To directly investigate the role of PKC in ICAM-1 induction, we downregulated PKC by pretreatment of human umbilical vein endothelial cells with phorbol 12-myristate 13-acetate (PMA) and assessed ICAM-1 protein and mRNA induction elicited by subsequent exposure to inflammatory stimuli. PMA treatment results in ICAM-1 protein induction that declines to basal levels by 3 days. Western blots of endothelial cell lysates reveal a nearly complete loss of immunologically reactive PKC. Subsequent activation with cytokine or LPS leads to reinduction of ICAM-1 protein and mRNA; however, the cells no longer produced substantial amounts of ICAM-1 protein or mRNA in response to PMA stimulation. Cross desensitization is observed with phorbol dibutyrate, while 4 alpha-phorbol has no desensitizing effect. The data indicate that PKC activation, while capable of inducing ICAM-1 expression, is not essential for ICAM-1 induction by the inflammatory mediators TNF-alpha, IL-1 beta, or LPS.
Department of Biochemistry, Boehringer Ingelheim Pharmaceuticals, Ridgefield, Connecticut 06877.
C L
CL
Myers
S J
SJ
Wertheimer
J
J
Schembri-King
T
T
Parks
R W
RW
Wallace
D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D016207:Cytokines / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1; D007375:Interleukin-1 / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D015815:Cell Adhesion Molecules; D016207:Cytokines; D007375:Interleukin-1; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate