by They revealed a very high content of COX-2 mRNA at 4 hr, which was higher in KO mice (relative RNA expression: 1743) than in WT mice (1046). during Mouse monoclonal to ERBB3 late peritonitis. Application of selective COX inhibitors revealed enhanced COX-1-dependent PGE2production and impaired COX-2-dependent PGD2synthesis in MMP-9/mice. Most importantly, inhibition of COX-1 abolished prolonged neutrophil accumulation in the peritoneal cavity of MMP-9/mice and increased apoptosis of inflammatory leucocytes. Similarly, weaker apoptosis of MMP-9/bone marrow neutrophils treatedin vitrowith zymosan was reversed by COX-1 inhibition. In conclusion, enhanced COX-1 expression is responsible for persistent neutrophil presence in TPOP146 the peritoneum of MMP-9/mice because of increased synthesis of anti-apoptotic PGE2. In non-transgenic mice, however, inflammatory leucocytes die apoptotically in the late stages of peritonitis as a result of COX-2-dependent PGD2activity. Overall, we show a dependence of COX expression on the presence of MMP-9. Keywords:apoptosis, cyclooxygenase, matrix metalloproteinase-9, peritoneal inflammation, prostaglandin D2, prostaglandin E2 == Introduction == Gelatinase B, also known as matrix metalloproteinase-9 (MMP-9), is a Zn2+-dependent endopeptidase with a major role in the remodelling of extracellular matrix components. Along with gelatinase A (MMP-2) it belongs to a subfamily of MMPs possessing similar substrate specificities.1MMP-9 functions in inflammation, bone resorption, wound healing, thrombosis, atherosclerosis and the invasion of tumours.1,2The substrates of MMP-9 include components of basement membranes and extracellular matrix (e.g. denatured collagen types IV and V, fibronectin and elastin) suggesting that at least one of its functions concerns vascular remodelling and assistance in the migration of cells.3In fact the roles of MMP-9 in inflammatory cell diapedesis and chemotaxis and in tumour cell invasion TPOP146 have been extensively investigated.46Studies of acute inflammation in animal models, including studies with knockout mice, showed that MMP-9 facilitates neutrophil accumulation at the inflammatory focus.4,5,710However, our studies on MMP-9/mice showed that although initially the neutrophil influx is decreased in those animals, subsequently the cells persist at the inflammatory site for several hours in contrast to what occurs in wild-type controls.9Moreover, other investigations unexpectedly revealed increased cyclooxygenase 1 (COX-1) messenger RNA (mRNA) expression in MMP-9/mice in comparison with the phenotype in wild-type controls.11We aimed to verify whether the phenomenon of MMP-9/COX-1-linked expression concerns also the later stages of peritoneal inflammation, and if a similar dependency exists between MMP-9 and COX-2 expression; and therefore if altered COX-1 or COX-2 expression might explain the prolonged accumulation of inflammatory neutrophils in MMP-9/mice during late peritonitis. Prostaglandin H synthase (PGHS), known commonly as cyclooxygenase, exhibits two catalytic activities as it catalyses arachidonic acid conversion by COX activity to prostaglandin G2(PGG2) and also has peroxidase activity, which reduces PGG2to PGH2.12,13At least two COX isoforms (COX-1, COX-2) exist. They are products of different genes, which differ in regulation of their expression and tissue distribution. 14Cyclooxygenase-1 is expressed constitutively in most tissues, whereas COX-2 is normally induced by a variety of stimuli, including inflammation and cancer.12However, constitutive expression of COX-2 has been reported in some tissues, e.g. brain and kidney.15,16Moreover, it has been recognized that COX-1 also plays an important role in inflammation.17,18The function of COX products has been investigated in the course of zymosan-induced peritonitis. In particular, it has been shown that PGE2and PGI2of COX-1 origin co-drive the early vascular TPOP146 permeability changes in this model19,20and that the inhibition of COX by indomethacin decreases neutrophil accumulation within the first hours of zymosan-induced peritoneal inflammation.20,21 Cyclooxygenase activity is responsible for prostanoid synthesis as it diverges arachidonic acid into prostaglandins and thromboxanes.22The former group plays important roles at all stages of inflammation and functionally can be divided into proinflammatory (e.g. PGE2, PGI2) and anti-inflammatory (e.g. PGD2and PGJ2) prostaglandins.23,24Furthermore, prostaglandins from the two subgroups can either prevent or induce the apoptotic death of inflammatory leucocytes at the inflammatory focus, respectively. This is because the PGE2-related prostaglandins activate nuclear factor-B (NF-B) (and so activate the synthesis of proinflammatory mediators) while PGD2and its metabolites induce apoptosis by inhibiting NF-B activation.2527 Some observations on an association between MMP-9 and COX-2 have been reported. In particular, the increased coexpression of MMP-9 and COX-2 is frequently described during inflammation and cancer.2833This was explained by the expression of both genes being NF-B-dependent.30However, it was also reported that production of MMP-9 by human monocytes occurs through the PGE2/cAMP-dependent pathway.31Therefore, it has been postulated that COX-2 metabolites (including PGE2) stimulate/activate other factors, such as MMP-9 because they are not themselves sufficient to induce the migration of leucocytes or.
