title: Nitric oxide post-transcriptionally up-regulates LPS-induced IL-8 expression through p38 MAPK activation.
abstract: Nitric oxide (NO(.-)) contributes to vascular collapse in septic shock and regulates inflammation. Here, we demonstrate in lipopolysaccharide (LPS)-stimulated human THP-1 cells and monocytes that NO(.-) regulates interleukin (IL)-8 and tumor necrosis factor alpha (TNF-alpha) by distinct mechanisms. Dibutyryl-cyclic guanosine 5'-monophosphate (cGMP) failed to simulate NO(.-)-induced increases in TNF-alpha or IL-8 production. In contrast, dibutyryl-cyclic adenosine monophosphate blocked NO(.-)-induced production of TNF-alpha (P=0.009) but not IL-8. NO(.-) increased IL-8 (5.7-fold at 4 h; P=0.04) and TNF-alpha mRNA levels (2.2-fold at 4 h; P=0.037). However, nuclear run-on assays demonstrated that IL-8 transcription was slightly decreased by NO(.-) (P=0.08), and TNF-alpha was increased (P=0.012). Likewise, NO(.-) had no effect on IL-8 promoter activity (P=0.84) as measured by reporter gene assay. In THP-1 cells and human primary monocytes treated with actinomycin D, NO(.-) had no effect on TNF-alpha mRNA stability (P>0.3 for both cell types) but significantly stabilized IL-8 mRNA (P=0.001 for both cell types). Because of its role in mRNA stabilization, the p38 mitogen-activated protein kinase (MAPK) pathway was examined and found to be activated by NO(.-) in LPS-treated THP-1 cells and human monocytes. Further, SB202190, a p38 MAPK inhibitor, was shown to block NO(.-)-induced stabilization of IL-8 mRNA (P<0.02 for both cell types). Thus, NO(.-) regulates IL-8 but not TNF-alpha post-transcriptionally. IL-8 mRNA stabilization by NO(.-) is independent of cGMP and at least partially dependent on p38 MAPK activation.
authors.affiliation: Bldg. 10, Rm. 7D43, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Penglin
authors.initials: P
authors.lastname: Ma
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Cui
authors.forename: Shuibang
authors.initials: S
authors.lastname: Wang
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
authors.forename: Ervant V
authors.initials: EV
authors.lastname: Nishanian
authors.forename: Weihan
authors.initials: W
authors.lastname: Wang
authors.forename: Robert A
authors.initials: RA
authors.lastname: Wesley
authors.forename: Robert L
authors.initials: RL
authors.lastname: Danner
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis*; D007963:Leukocytes, Mononuclear / Q000187:drug effects* / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009569:Nitric Oxide / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational; D020871:RNA Stability; D012333:RNA, Messenger / Q000032:analysis; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000187:drug effects; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D004791:Enzyme Inhibitors; D016209:Interleukin-8; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D000242:Cyclic AMP; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D006152:Cyclic GMP