Lipopolysaccharide activates Akt in vascular smooth muscle cells resulting in induction of inducible nitric oxide synthase through nuclear factor-kappa B activation.
Bacterial lipopolysaccharide and other immunostimulants induce gene expression of an isoform of nitric oxide synthase (iNOS) in vascular smooth muscle cells. This process is dependent on nuclear factor-kappa B (NF-kappa B) activation. The aim of this study was to investigate whether the NF-kappa B and Akt signaling pathways converge to induce iNOS in lipopolysaccharide-stimulated vascular smooth muscle cells. Treatment of vascular smooth muscle cells with lipopolysaccharide plus interferon-gamma (LPS/IFN) caused activation of Akt and NF-kappa B. LPS/IFN caused activation of the iNOS promoter and transcription of iNOS mRNA/protein, resulting in NO production. A pharmacological inhibitor of the phosphoinositide 3-kinase (PI3K)-Akt pathway, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002), inhibited phosphorylation of Akt and suppressed activation of NF-kappa B by attenuating the phosphorylation and degradation of I kappa B. LY294002 thereby inhibited LPS/IFN-induced iNOS expression and NO production. Another inhibitor of the PI3K-Akt pathway, wortmannin, also inhibited NO production in VSMC. LY294002 similarly inhibited interleukin-1 beta- or tumor necrosis factor-alpha-induced NO production. The data indicate that lipopolysaccharide or cytokine stimulation of vascular smooth muscle cells leads to activation of the PI3K-Akt pathway, which then activates the NF-kappa B pathway. Thus, the PI3K-Akt pathway controls the expression of iNOS in lipopolysaccharide- and cytokine-stimulated vascular smooth muscle cells.
Hattori
Yoshiyuki
Y
Department of Endocrinology and Metabolism, Dokkyo University School of Medicine, Mibu, Tochigi 321-0293, Japan. yhattori@dokkyomed.ac.jp
Hattori
Sachiko
S
Kasai
Kikuo
K
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation / Q000502:physiology; D004790:Enzyme Induction / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology*; D016328:NF-kappa B / Q000378:metabolism* / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017208:Rats, Wistar
D008070:Lipopolysaccharides; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt