Premium
Endotoxin Stimulates Cytokine and Nitric Oxide Production in Rat Hepatic Stellate Cells (HSCs) via p38 MAPK and Reactive Oxygen Species
Author(s) -
Thirunavukkarasu Chinnasamy,
Gandhi Chandrashekhar R
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a203-d
Subject(s) - pyrrolidine dithiocarbamate , p38 mitogen activated protein kinases , nitric oxide , cytokine , reactive oxygen species , mapk/erk pathway , hepatic stellate cell , chemistry , microbiology and biotechnology , signal transduction , nitric oxide synthase , nf κb , kinase , tumor necrosis factor alpha , biology , endocrinology , immunology , organic chemistry
Endotoxin‐stimulated HSCs may contribute to liver failure by hepatocyte growth inhibition and apoptosis. Two major effects of endotoxin on HSCs are increased synthesis of nitric oxide (NO) and potent inflammatory cytokines TNF‐á and IL‐6. These effects of endotoxin are novel as they do not require LBP, CD14/TLR‐4. Since the intracellular signaling mechanisms of these effects are not known, we investigated if they are mediated by oxidative stress and signaling via NF‐êB and mitogen‐activated protein kinases (MAPKs) in rat HSCs. HSCs isolated from rat liver were activated in culture for 8‐10 days and challenged with endotoxin. Activation of MAPKs and NF‐êB, production of reactive oxygen species, and expression of iNOS, IL‐6 and TNF‐á were determined. Endotoxin induced time‐ and dose‐dependent increases in the mRNA and protein expression of iNOS, NO synthesis as well as mRNA expression and release of IL‐6 and TNF‐á. Endotoxin also stimulated activation NF‐êB, ERK1/2, p38 and JNK, and generation of H 2 O 2 . Exogenous H 2 O 2 stimulated IL‐6 and TNF‐á but not NO synthesis, and did not activate NF‐êB or MAPKs. Inhibition of p38 MAPK by SB203580 and that of NF‐êB activation by pyrrolidine dithiocarbamate blocked endotoxin‐induced H 2 O 2 , NO and cytokine synthesis. Inhibition of ERK1/2 and JNK phosphorylation did not alter the effects of endotoxin on NO or cytokine synthesis. While SB203580 inhibited LPS‐induced NF‐êB activation, PDTC did not affect p38 phosphorylation in LPS‐stimulated cells. The results indicate that endotoxin‐induced NO and cytokine synthesis in HSCs is initiated by p38 MAPK and mediated by NF‐êB, with involvement of H 2 O 2 in the cytokine production. Supported by a grant (RO1‐DK 54411) from the NIH.