Inflammation and anti-inflammation: gating of cell/cell adhesion at the level of mitogen-activated protein kinases

Matrix metalloproteinase secretion by gastric epithelial cells is regulated by E prostaglandins and MAPKs

Because matrix metalloproteinases (MMPs) play roles in inflammatory tissue injury, we asked whether MMP secretion by gastric epithelial cells may contribute to gastric injury in response to signals involved in Helicobacter pylori-induced inflammation and/or cyclooxygenase inhibition. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and epidermal growth factor (EGF) stimulated gastric cell MMP-1 secretion, indicating that MMP-1 secretion occurs in inflammatory as well as non-inflammatory situations. MMP-1 secretion required activation of the MAPK Erk and subsequent protein synthesis but was down-regulated by the alternate MAPK, p38. In contrast, secretion of MMP-13 was stimulated by TNF-alpha/IL-1beta but not EGF and was Erk-independent and mediated by p38. MMP-13 secretion was more rapid (peak, 6 h) than MMP-1 (peak > or =30 h) and only partly depended on protein synthesis, suggesting initial release of a pre-existing MMP-13 pool. Therefore, MMP-1 and MMP-13 secretion are differentially regulated by MAPKs. MMP-1 secretion was regulated by E prostaglandins (PGEs) in an Erk-dependent manner. PGEs enhanced Erk activation and MMP-1 secretion in response to EGF but inhibited Erk and MMP-1 when TNF-alpha and IL-1beta were the stimuli, indicating that the effects of PGEs on gastric cell responses are context-dependent. These data show that secretion of MMPs is differentially regulated by MAPKs and suggest mechanisms through which H. pylori infection and/or cyclooxygenase inhibition may induce epithelial cell signaling to contribute to gastric ulcerogenesis.

Cyclooxygenase-2-derived E prostaglandins down-regulate matrix metalloproteinase-1 expression in fibroblast-like synoviocytes via inhibition of extracellular signal-regulated kinase activation

We examined the regulation of matrix metalloproteinase (MMP) production by mitogen-activated protein kinases and cyclooxygenases (COXs) in fibroblast-like synoviocytes (FLSCs). IL-1beta and TNF-alpha stimulated FLSC extracellular signal-regulated kinase (ERK) activation as well as MMP-1 and -13 release. Pharmacologic inhibitors of ERK inhibited MMP-1, but not MMP-13 expression. Whereas millimolar salicylates inhibited both ERK and MMP-1, nonsalicylate COX and selective COX-2 inhibitors enhanced stimulated MMP-1 release. Addition of exogenous PGE(1) or PGE(2) inhibited MMP-1, reversed the effects of COX inhibitors, and inhibited ERK activation, suggesting that COX-2 activity tonically inhibits MMP-1 production via ERK inhibition by E PGs. Exposure of FLSCs to nonselective COX and selective COX-2 inhibitors in the absence of stimulation resulted in up-regulation of MMP-1 expression in an ERK-dependent manner. Moreover, COX inhibition sufficient to reduce PGE levels increased ERK activity. Our data indicate that: 1) ERK activation mediates MMP-1 but not MMP-13 release from FLSCs, 2) COX-2-derived E PGs inhibit MMP-1 release from FLSCs via inhibition of ERK, and 3) COX inhibitors, by attenuating PGE inhibition of ERK, enhance the release of MMP-1 by FLSC.

Human macrophage adhesion on fibronectin: the role of substratum and intracellular signalling kinases

Fibronectin and Arg-Gly-Asp (RGD)- and/or Pro-His-Ser-Arg-Asn (PHSRN)-containing oligopeptides were immobilized onto physicochemically distinct substrata: polyethyleneglycol-based networks or tissue culture polystyrene (TCPS). The role of selected signalling kinases in the adhesion of human primary blood-derived macrophages on these modified substrata was investigated. We demonstrated that the protein tyrosine kinase (PTK) or protein serine/threonine kinase (PSK) dependency and the PTK-PSK cross-talk compensation for macrophage adhesion varied dynamically with the substratum modification and the culture time. The inhibition of MAPK kinase (MAPKK) decreased macrophage adhesion on TCPS, whereas the inhibition of phosphoinositide-3 kinase (PI3 kinase) decreased macrophage adhesion on networks at 24 h. The PI3 kinase-protein kinase C (PKC)-MAPK cascade was involved in macrophage adhesion on fibronectin-preadsorbed TCPS or networks but not on fibronectin-grafted networks. This fibronectin-mediated adhesion signalling involved both RGD and PHSRN sequences in a form of G(3)RGDG(6)PHSRNG on TCPS but not on networks. Furthermore, G(3)RGDG(6)PHSRNG grafted onto networks evoked unique signalling in macrophage adhesion from that preadsorbed onto networks. Thus, macrophage adhesion and the role of selected signalling kinases were modulated by the substratum and the ligand conjugation method.