Interleukin-1 stimulates cytokines, prostaglandin E2 and matrix metalloproteinase-1 production via activation of MAPK/AP-1 and NF-kappaB in human gingival fibroblasts

Interleukin-1 (IL-1) plays a crucial role in the immunopathological responses involved with tissue destruction in chronic inflammatory diseases, such as periodontal disease, as it stimulates host cells including fibroblasts to produce various inflammatory mediators and catabolic factors. We comprehensively investigated the involvement of mitogen-activated protein kinases (MAPKs)/activator protein-1 (AP-1) and IkappaB kinases (IKKs)/IkappaBs/nuclear factor-kappaB (NF-kappaB) in IL-1beta-stimulated IL-6, IL-8, prostaglandin E(2) (PGE(2)) and matrix metalloproteinase-1 (MMP-1) production by human gingival fibroblasts (HGF). Three MAPKs, extracellular signal-regulated kinase (ERK), p38 MAPK and c-Jun N-terminal kinase (JNK), which were simultaneously activated by IL-1beta, mediated subsequent c-fos and c-jun mRNA expression and DNA binding of AP-1 at different magnitudes. IKKalpha/beta/IkappaB-alpha/NF-kappaB was also involved in the IL-1 signaling cascade. Further, IL-1beta stimulated HGF to produce IL-6, IL-8, PGE(2) and MMP-1 via activation of the 3 MAPKs and NF-kappaB, as inhibitors of each MAPK and NF-kappaB significantly suppressed the production of IL-1beta-stimulated factors, though these pathways might also play distinct roles in IL-1beta activities. Our results strongly suggest that the MAPKs/AP-1 and IKK/IkappaB/NF-kappaB cascades cooperatively mediate the IL-1beta-stimulated synthesis of IL-6, IL-8, PGE(2) and MMP-1 in HGF.     

Role of mitogen-activated protein kinases and tyrosine kinases on IL-1-Induced NF-kappaB activation and iNOS expression in bovine articular chondrocytes.

Nitric oxide (NO), produced by the inducible isoform of the NO synthase (iNOS), plays an important role in the pathophysiology of arthritic diseases. This work aimed at elucidating the role of the mitogen-activated protein kinases (MAPK), p38MAPK and p42/44MAPK, and of protein tyrosine kinases (PTK) on interleukin-1beta (IL-1)-induced iNOS expression in bovine articular chondrocytes. The specific inhibitor of the p38MAPK, SB 203580, effectively inhibited IL-1-induced iNOS mRNA and protein synthesis, as well as NO production, while the specific inhibitor of the p42/44MAPK, PD 98059, had no effect. These responses to IL-1 were also inhibited by treatment of the cells with the tyrosine kinase inhibitors, genistein and tyrphostin B42, which also prevented IL-1-induced NF-kappaB activation. The p38MAPK inhibitor, SB 203580, had no effect on IL-1-induced NF-kappaB activation. Finally, the p42/44MAPK inhibitor, PD 98059, prevented IL-1-induced AP-1 activation in a concentration that did not inhibit iNOS expression. In conclusion, this study shows that (1) PTK are part of the signaling pathway that leads to IL-1-induced NF-kappaB activation and iNOS expression; (2) the p38MAPK cascade is required for IL-1-induced iNOS expression; (3) the p42/44MAPK and AP-1 are not involved in IL-1-induced iNOS expression; and (4) NF-kappaB and the p38MAPK lie on two distinct pathways that seem to be independently required for IL-1-induced iNOS expression. Hence, inhibition of any of these two signaling cascades is sufficient to prevent iNOS expression and the subsequent production of NO in articular chondrocytes.     

Involvement of integrins, MAPK, and NF-kappaB in regulation of the shear stress-induced MMP-9 expression in endothelial cells

Variations in the matrix metalloproteinase (MMP)-9 gene are related to the presence and severity of atherosclerosis. The aim of this study was to determine the signaling pathways of MMP-9 in endothelial cells subjected to low fluid shear stress. We found that low fluid shear stress significantly increased MMP-9 expression, IkappaBalpha degradation, NF-kappaB DNA-binding activity and phosphorylation of MAPK in cultured human umbilical vein endothelial cells (HUVECs). Inhibition of NF-kappaB resulted in remarkable downregulation of stress-induced MMP-9 expression. Pretreatment of HUVECs with inhibitors of p38 mitogen-activating protein kinase (MAPK) and extracellular signal-regulated kinase1/2 (ERK1/2) also led to significant suppression of stress-induced MMP-9 expression and NF-kappaB DNA-binding activity. Similarly, addition of integrins inhibitor to HUVECs suppressed the stress-induced MMP-9 expression, IkappaBalpha degradation, NF-kappaB DNA-binding activity and the phosphorylation of p38 MAPK, ERK1/2. Our findings demonstrated that the shear stress-induced MMP-9 expression involved integrins-p38 MAPK or ERK1/2-NF-kappaB signaling pathways.     

Constitutive collagenase-1 synthesis through MAPK pathways is mediated, in part, by endogenous IL-1alpha during fibrotic repair in corneal stroma

Collagenase-1 is a protease expressed by active fibroblasts that is involved in remodeling of the extracellular matrix (ECM). In this study, we characterize the intracellular signaling mechanism of collagenase-1 production by IL-1alpha in subcultured normal fibroblasts (NF) from uninjured normal corneas, compared to that in repair wound fibroblasts (WF). In NF, collagenase-1 was induced specifically after the exogenous addition of IL-1alpha via activation of ERK and p38MAPK. Collagenase-1 expression was strongly suppressed upon treatment with either a MEK or p38MAPK inhibitor. In contrast, repair WF constitutively synthesized both IL-1alpha and collagenase-1. Combined treatment with both mitogen-activated protein kinase (MAPK) inhibitors dramatically reduced collagenase-1 synthesis, while individual MEK1 or p38 inhibitors weakly modulated the collagenase-1 level. The results indicate that both pathways are crucial in the regulation of collagenase-1 synthesis. Furthermore, an IL-1alpha receptor antagonist (IL-1ra) could not abolish constitutive collagenase-1 synthesis, even at high doses, suggesting that other cytokines/factors are additionally involved in this process. We propose that induction of collagenase-1 by IL-1alpha in both WF and NF depends on a unique combination of cell type-specific signaling pathways.     

Lymphotoxin beta receptor induces interleukin 8 gene expression via NF-kappaB and AP-1 activation

The human lymphotoxin beta receptor (LTbetaR), a member of the tumor necrosis factor (TNF) receptor superfamily, is essential for not only the development and organization of secondary lymphoid tissues, but also for chemokine release. Even though LTbetaR was shown to recruit TNF-receptor-associated factor (TRAF) 2, 3, and 5, and to induce cell apoptosis or NF-kappaB activation, however, the downstream signaling leading to chemokine expression is not illustrated yet. In this study, we find that overexpression of LTbetaR in HEK293 cells increases IL-8 promoter activity and leads to IL-8 release. LTbetaR-induced IL-8 gene expression requires NF-kappaB (-80 to -71) and AP-1 (-126 to -12) binding sites located in IL-8 promoter, and NF-kappaB is more crucial than AP-1 for IL-8 gene expression. Reporter assay with dominant-negative mutants of TRAFs reveals that TRAF2, 3, and 5, as well as the downstream signal molecules NIK, IKKalpha, and IKKbeta, are involved in IL-8 gene expression. LTbetaR-mediated IL-8 response was inhibited by the dominant-negative mutants of ASK1, MKK4, MKK7, and JNK, but not by those of MEKK1, TAK1, MEK, ERK, and p38 MAPK. This suggests that IL-8 induction by LTbetaR is via TRAFs-elicited signaling pathways, including NIK/IKK-dependent NF-kappaB activation and ASK/MKK/JNK-dependent AP-1 activation.