PKC mediates LPS- and phorbol-induced cardiac cell nitric oxide synthase activity and hypocontractility.
Lipopolysaccharide (LPS) treatment impairs cardiac myocyte contractility in a nitric oxide synthase (NOS)-dependent manner. The objective of this study was to assess whether protein kinase C (PKC) transduces the LPS signal into an enhanced NOS activity in rat cardiac myocytes. LPS (100 ng/ml) stimulated myocyte PKC activity, inducible NOS (iNOS) expression, and NOS activity in a time- and protein synthesis-dependent fashion. Directly activating PKC with beta-phorbol 12,13-dibutyrate (beta-PDB) also induced myocyte iNOS synthesis and NOS activity and reduced electrically stimulated contractility, while the inactive alpha-PDB was ineffectual. Contractility could be restored to beta-PDB-incubated cells by superfusion with the NOS inhibitor N omega-nitro-L-arginine methyl ester. PKC blockade with sphingosine, chelerythrine, or calphostin-C precluded LPS- and beta-PDB-induced increases in NOS activity and protected contractility. Depletion of PKC by 18 h of incubation with beta-PDB in the presence of chelerythrine also blocked acquisition of enhanced NOS activity and contractile dysfunction when the myocytes were subsequently exposed to LPS. These findings suggest that PKC is a significant intracellular mediator for the effects of LPS on cardiac cell NOS activity and contractile function.
McKenna
T M
TM
Septic Shock Research Program, Naval Medical Research Institute, Bethesda, Maryland 20889, USA.
Li
S
S
Tao
S
S
D000818:Animals; D002478:Cells, Cultured; D004558:Electric Stimulation; D004790:Enzyme Induction; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D011493:Protein Kinase C / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D008070:Lipopolysaccharides; D015240:Phorbol 12,13-Dibutyrate; D019001:Nitric Oxide Synthase; D011493:Protein Kinase C