The mitogen-activated protein kinase p38 is necesssary for interleukin 1beta-induced monocyte chemoattractant protein 1 expression by human mesangial cells

Mitogen-activated protein (MAP) kinases have been suggested as potential mediators for interleukin 1beta (IL-1beta)-induced gene activation. This study investigated the role of the MAP kinases p38 and ERK2 in IL-1beta-mediated expression of the chemokine MCP-1 by human mesangial cells. Phosphorylation of p38 kinase, which is necessary for activation, increased significantly after IL-1beta treatment. p38 kinase immunoprecipitated from IL-1beta-treated cells phosphorylated target substrates to a greater extent than p38 kinase from controls. SB 203580, a selective p38 kinase inhibitor, was used to examine the role of p38 kinase in MCP-1 expression. SB 203580 decreased IL-1beta-induced MCP-1 mRNA and protein levels, but did not affect MCP-1 mRNA stability. Because NF-kappaB is necessary for MCP-1 gene expression, the effect of p38 kinase inhibition on IL-1beta induction of NF-kappaB was measured. SB 203580 (up to 25 microM) had no effect on IL-1beta-induced NF-kappaB nuclear translocation or DNA binding activity. Our previous work showed that IL-1beta also activates the MAP kinase ERK2 in human mesangial cells. PD 098059, a selective inhibitor of the ERK activating kinase MEK1, had no effect on IL-1beta-induced MCP-1 mRNA or protein levels, or on IL-1beta activation of NF-kappaB. These data indicate that p38 kinase is necessary for the induction of MCP-1 expression by IL-1beta, but is not involved at the level of cytoplasmic activation of NF-kappaB. In contrast, ERK2 does not mediate IL-1beta induced MCP-1 gene expression.     

Differential activation of mitogen-activated protein kinases in AGS gastric epithelial cells by cag+ and cag- Helicobacter pylori.

The aim of this study was to determine whether Helicobacter pylori activates mitogen-activated protein (MAP) kinases in gastric epithelial cells. Infection of AGS cells with an H. pylori cag+ strain rapidly (5 min) induced a dose-dependent activation of extracellular signal-regulated kinases (ERK), p38, and c-Jun N-terminal kinase (JNK) MAP kinases, as determined by Western blot analysis and in vitro kinase assay. Compared with cag+ strains, cag- clinical isolates were less potent in inducing MAP kinase, particularly JNK and p38, activation. Isogenic inactivation of the picB region of the cag pathogenicity island resulted in a similar loss of JNK and p38 MAP kinase activation. The specific MAP kinase inhibitors, PD98059 (25 microM; MAP kinase kinase (MEK-1) inhibitor) and SB203580 (10 microM; p38 inhibitor), reduced H. pylori-induced IL-8 production in AGS cells by 78 and 82%, respectively (p < 0.01 for each). Both inhibitors together completely blocked IL-8 production (p < 0.001). However, the MAP kinase inhibitors did not prevent H. pylori-induced IkappaBalpha degradation or NF-kappaB activation. Thus, H. pylori rapidly activates ERK, p38, and JNK MAP kinases in gastric epithelial cells; cag+ isolates are more potent than cag- strains in inducing MAP kinase phosphorylation and gene products of the cag pathogenicity island are required for maximal MAP kinase activation. p38 and MEK-1 activity are required for H. pylori-induced IL-8 production, but do not appear to be essential for H. pylori-induced NF-kappaB activation. Since MAP kinases regulate cell proliferation, differentiation, programmed death, stress, and inflammatory responses, activation of gastric epithelial cell MAP kinases by H. pylori cag+ strains may be instrumental in inducing gastroduodenal inflammation, ulceration, and neoplasia.     

Adiponectin stimulates proliferation and cytokine secretion in colonic epithelial cells

Adiponectin is a recently described mediator secreted by adipose tissue. Here we report the growth promoting and pro-inflammatory actions of adiponectin on colonic epithelial cancer cells. Full-length and globular adiponectin produced an identical stimulation of HT-29 cell growth that was blocked by inhibition of adenylate cyclase and protein kinase A and partially inhibited by a pan-specific protein kinase C inhibitor, but was unaffected by specific inhibition of extracellular signal-related kinase (ERK) or p38 MAP kinase. Globular adiponectin but not full-length adiponectin significantly increased the secretion and mRNA levels of IL-8, GM-CSF and MCP-1. Globular adiponectin doubled IL-1beta-stimulated IL-8 and GM-CSF secretion. Adiponectin-stimulated cytokine secretion was blocked by pharmacological inhibitors of NF-kappaB, ERK and p38 MAP kinase. Globular adiponectin increased phosphorylation of both ERK and p38 MAP kinase and increased the nuclear translocation of active NF-kappaB. Adiponectin has pro-proliferative and pro-inflammatory actions on colonic epithelial cells; these appear to be differentially activated by the adiponectin isoforms. Adiponectin may have a role in the regulation of gastrointestinal mucosal function, inflammation and colon carcinogenesis.     

IL-1beta stimulates IL-6 production in cultured skeletal muscle cells through activation of MAP kinase signaling pathway and NF-kappa B

Recent studies suggest that the skeletal muscle may be a significant site of IL-6 production in various conditions, including exercise, inflammation, hypoperfusion, denervation, and local muscle injury. The mediators and molecular mechanisms regulating muscle IL-6 production are poorly understood. We tested the hypothesis that IL-6 production in muscle cells is regulated by IL-1beta and that mitogen-activated protein (MAP) kinase signaling and NF-kappaB activation are involved in IL-1beta-induced IL-6 production. Cultured C2C12 cells, a mouse skeletal muscle cell line, were treated with different concentrations (0.1-2 ng/ml) of IL-1beta in the absence or presence of the p38 MAP kinase inhibitor SB-208350 or the p42/44 inhibitor PD-98059. Protein and gene expression of IL-6 were determined by ELISA and real-time PCR, respectively. NF-kappaB DNA binding activity was determined by electrophoretic mobility shift assay and by transfecting myocytes with a luciferase reporter plasmid containing a promoter construct with multiple repeats of NF-kappaB binding site. Treatment of myotubes with IL-1beta resulted in a dose- and time-dependent increase of IL-6 production accompanied by an approximately 25-fold increase in IL-6 mRNA levels. IL-1beta stimulated NF-kappaB DNA binding activity and gene activation. SB-208350 and PD-98059 inhibited the increase in IL-6 production induced by IL-1beta. The present results support the concept that skeletal muscle is an important site of IL-6 production. In addition, the results suggest the IL-1beta regulates muscle IL-6 production at least in part by activating the MAP kinase pathway and NF-kappaB.     

Regulation of IL-11 expression in intestinal myofibroblasts: role of c-Jun AP-1- and MAPK-dependent pathways

IL-11 inhibits the activation of NF-kappaB and induces the Th2 polarization of CD4+ T cells. The clinical utility of IL-11 is being investigated in Crohn's disease. However, physiological secretion of IL-11 in the intestine remains unclear. In this study, we investigated IL-11 secretion in human intestinal subepithelial myofibroblasts (SEMFs). Intestinal SEMFs were isolated from the human colonic mucosa. IL-11 secretion and mRNA expression were determined by ELISA and Northern blot analysis. The activating protein (AP)-1-DNA binding activity was evaluated by EMSA. IL-11 secretion was induced by IL-1beta and transforming growth factor (TGF)-beta1. These were also observed at the mRNA level. The EMSAs demonstrated that both IL-1beta and TGF-beta1 induced AP-1 activation within 2 h after stimulation, and a blockade of AP-1 activation by the recombinant adenovirus containing a dominant negative c-Jun markedly reduced the IL-1beta- and TGF-beta1-induced IL-11 mRNA expression. IL-1beta and TGF-beta1 induced an activation of ERK p42/44 and p38 MAP kinases, and the MAP kinase inhibitors (SB-202190, PD-98059, and U-0216) significantly reduced the IL-1beta- and TGF-beta1-induced IL-11 secretion. The upregulation of IL-11 mRNA by IL-1beta- and TGF-beta1 was also mediated by a p38 MAP kinase-mediated mRNA stabilization. The combination of IL-1beta and TGF-beta1 additively enhanced IL-11 secretion. Intestinal SEMFs secreted IL-11 in response to IL-1beta- and TGF-beta1. Mucosal IL-11 secretion might be important as an anti-inflammatory response in the pathogenesis of intestinal inflammation.