Toll-like receptor 9-mediated cytosolic phospholipase A2 activation regulates expression of inducible nitric oxide synthase.
Although CpG containing DNA is an important regulator of innate immune responses via toll-like receptor 9 (TLR9), excessive activation of this receptor is detrimental to the host. Here, we show that cytosolic phospholipase A(2) (cPLA(2)) activation is important for TLR9-mediated inducible nitric oxide synthase (iNOS) expression. Activation of TLR9 signaling by CpG induces iNOS expression and NO production. Inhibition of TLR9 blocked the iNOS expression and NO production. The CpG also stimulates cPLA(2)-hydrolyzed arachidonic acid (AA) release. Inhibition of cPLA(2) activity by inhibitor attenuated the iNOS expression by CpG response. Additionally, knockdown of cPLA(2) protein by miRNA also suppressed the CpG-induced iNOS expression. Furthermore, the CpG rapidly phosphorylates three MAPKs and Akt. A potent inhibitor for p38 MAPK or Akt blocked the CpG-induced AA release and iNOS expression. These results suggest that TLR9 activation stimulates cPLA(2) activity via p38 or Akt pathways and mediates iNOS expression.
Lee
Sun-Hye
SH
Aging-associated Vascular Disease Research Center, Department of Biochemistry & Molecular Biology, College of Medicine, Yeungnam University, 317-1 Daemyung-5 Dong, Daegu 705-717, South Korea.
Lee
Jin-Gu
JG
Kim
Jae-Ryong
JR
Baek
Suk-Hwan
SH
D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D051217:Toll-Like Receptor 9; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D054513:Group IV Phospholipases A2