Hajime Sano

Several studies indicate that nonsteroidal anti-inflammatory drugs including indomethacin, aspirin, sulindac, and piroxicam reduce the risk of colon cancer. Furthermore, nonsteroidal anti-inflammatory drugs that inhibit the cyclooxygenase (COX) enzyme were shown to inhibit the development of colon cancer in animal models of carcinogenesis. Non-steroidal anti-inflammatory drugs inhibit the enzymatic activity of both the constitutive (COX-1) and inducible (COX-2) isoforms of COX enzyme. We have investigated the expression of COX-1 and COX-2 polypeptides in human colon cancer tissues using immunohistochemistry. Enhanced COX-2 expression was observed in colon cancer tissues from 15 subjects with clinically diagnosed colorectal cancer. Marked COX-2 expression was observed in cancer cells, inflammatory cells, vascular endothelium, and fibroblasts of the lesional tissues compared with the nonlesional and normal colon tissues. The extent and intensity of the immunoreactive COX-2 in cancer cells was much greater than that of the other cell types. In contrast, the expression of COX-1 polypeptide was weak in both normal and cancerous specimens. These data suggest that the enhanced expression of the COX-2 gene in colon cancer tissues may contribute to the enhanced synthesis of prostaglandin E2 by the colon cancer tissues. Enhanced expression of COX-2 may play a role in the pathogenesis of colon cancer. Furthermore, selective inhibition of COX-2 may prove to be more efficacious in the retardation of colon cancer development.

High levels of immunoreactive cyclooxygenase (Cox; prostaglandin H synthase) are present in synovia from patients with rheumatoid arthritis (RA). We now show that the recently identified inducible isoform of Cox, Cox-2, is expressed in synovia from patients with RA. To further explore modulation of the Cox isoforms in RA synovial tissues, we examined the expression and modulation of Cox-1 and -2 in rheumatoid synovial explant cultures and cultured rheumatoid synovial fibroblast-like cells (synoviocytes). Immunoprecipitation of in vitro labeled proteins and Western blot analysis demonstrated the presence of both Cox-1 and -2 under basal conditions in freshly explanted rheumatoid synovial tissues. De novo synthesis of Cox-2 polypeptide was enhanced by IL-1 beta or PMA, and dramatically suppressed by dexamethasone (dex). Cox-1 expression, under the same conditions, showed only minor variation. Since mRNA for Cox-2 is highly unstable, we examined the regulation of Cox-2 transcripts in cultured rheumatoid synoviocytes. Under basal conditions both Cox-1 and -2 mRNAs were present at low levels, but Cox-2 mRNA was markedly increased by treatment with IL-1 beta or PMA. dex markedly suppressed the induction of Cox-2 mRNA. In sharp contrast, Cox-1 transcripts were not modulated by IL-1 beta or dex. These data suggest that modulation of Cox-2 expression by IL-1 beta and corticosteroids may be an important component of the inflammatory process in synovial tissues from patients with RA.

Corticotropin-releasing hormone (CRH) functions as a regulator of the hypothalamic-pituitary-adrenal axis and coordinator of the stress response. CRH receptors exist in peripheral sites of the immune system, and CRH promotes several immune functions in vitro. The effect of systemic immunoneutralization of CRH was tested in an experimental model of chemically induced aseptic inflammation in rats. Intraperitoneal administration of rabbit antiserum to CRH caused suppression of both inflammatory exudate volume and cell concentration by approximately 50 to 60 percent. CRH was detected in the inflamed area but not in the systemic circulation. Immunoreactive CRH is therefore produced in peripheral inflammatory sites where, in contrast to its systemic indirect immunosuppressive effects, it acts as an autocrine or paracrine inflammatory cytokine.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily and have a dominant regulatory role in adipocyte and monocyte differentiation. PPAR-gamma agonists are also negative regulators of macrophage activation and have modulatory effects on tumorigenesis. In this study we demonstrate that synovial tissue localized expression of PPAR-gamma in patients with rheumatoid arthritis (RA). We detected markedly enhanced expression of PPAR-gamma in macrophages, as well as modestly enhanced expression in the synovial lining layer, fibroblasts, and endothelial cells. Activation of the PPAR-gamma by 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) and the synthetic PPAR-gamma ligand (troglitazone) induced RA synoviocyte apoptosis in vitro. Moreover, intraperitoneal administration of these PPAR-gamma ligands ameliorated adjuvant-induced arthritis with suppression of pannus formation and mononuclear cell infiltration in female Lewis rats. Anti-inflammatory effects of 15d-PGJ(2) were more potent than troglitazone. These findings suggest that PPAR-gamma may be an important immunoinflammatory mediator and its ligands, especially 15d-PGJ(2), may be useful in the treatment of RA.

Cyclooxygenase (COX), or prostaglandin (PG) H synthase, plays a role in inflammatory diseases, but very limited data exist on the regulation of COX in vivo. We, therefore, studied the in vivo expression of COX in synovia from patients with rheumatoid arthritis (RA) and osteoarthritis (OA), as well as joints of rats with streptococcal cell wall (SCW) and adjuvant arthritis. Extensive and intense intracellular COX immuno- staining, which correlated with the extent and intensity ofmono- nuclear cell infiltration, was observed in cells throughout RA synovia. Significantly less or equivocal staining was noted in OA and normal human synovia. Similarly, COX immunostain- ing was equivocal in the joints of normal and arthritis-resistant F344/N rats. In contrast, high level expression developed rap- idly in euthymic female Lewis (LEW/N) rats throughout the hindlimb joints and overlying tissues including skin, preceding or paralleling clinically apparent experimental arthritis. COX was expressed in the joints of athymic LEW.rnu/rnu rats 24 d after injection ofSCW or adjuvant but was not sustained. Physiological doses of antiinflammatory glucocorticoids, but not pro- gesterone, suppressed both arthritis and COX expression in LEW/N rats. These observations suggest that, in vivo, (a) COX expression is upregulated in inflammatory joint diseases, (b) the level of expression is genetically controlled and is a biochemical correlate of disease severity, (c) sustained high level up-regulation is T cell dependent, and (d) expression is down-regulated by antiinflammatory glucocorticoids. (J. Clin. Invest.