Defective lipopolysaccharide-dependent ERK 1/2 activation in endotoxin tolerant murine macrophages is reversed by direct protein kinase C stimulation.
Lipopolysaccharide (LPSp) pretreatment inhibits TNF secretion in endotoxin-tolerant macrophages via alterations in signal transduction pathways of LPS activation (LPSa). Protein kinase C inhibitors prevent TNF release in response to LPSa and direct protein kinase C activation with phorbol myristate acetate (PMA) restores TNF secretion after LPSp. In the current experiments the effect of protein kinase C modulation on LPSa-stimulated ERK 1/2 activation was investigated. Murine macrophage TNF production was determined after stimulation with 100 ng/mL of LPSa, +/- 24 h pretreatment with 10 ng/mL of LPSp. Direct protein kinase C activators (PMA or indolactam) or inhibitors (H7 or bisindolylmaleimide) were added 1 h before LPSa. Diphosphorylated ERK 1/2 was assayed after LPSa stimulation by Western blot. LPS tolerance after LPSp was characterized by inhibition of LPSa-stimulated TNF and accompanied by impaired ERK 1/2 activation by LPSa. Protein kinase C activation with PMA or indolactam restored ERK 1/2 activation and TNF secretion. Inhibition of protein kinase C with H7 or bisindolylmaleimide prevented TNF secretion and ERK 1/2 activation by LPSa. These findings suggest that both ERK 1/2 and protein kinase C are required for TNF production in nontolerant macrophages and that LPS tolerance may be associated with an inability to phosphorylate ERK 1/2.
West
M A
MA
Department of Surgery, Hennepin County Medical Center, University of Minnesota, Minneapolis 55415, USA.
Clair
L
L
Bellingham
J
J
Wahlstrom
K
K
Rodriguez
J L
JL
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000818:Animals; D004361:Drug Tolerance; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D007211:Indoles / Q000494:pharmacology; D007769:Lactams / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics
D004791:Enzyme Inhibitors; D005419:Flavonoids; D007211:Indoles; D007769:Lactams; D008070:Lipopolysaccharides; D008301:Maleimides; D014409:Tumor Necrosis Factor-alpha; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; C043969:indolactam V; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C088060:bisindolylmaleimide; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one