Eosinophils Contribute to Intestinal Inflammation via Chemoattractant Receptor-homologous Molecule Expressed on Th2 Cells, CRTH2, in Experimental Crohn's Disease.

BACKGROUND AND AIMS: Prostaglandin [PG] D2 activates two receptors, DP and CRTH2. Antagonism of CRTH2 has been shown to promote anti-allergic and anti-inflammatory effects. We investigated whether CRTH2 may play a role in Crohn's disease [CD], focusing on eosinophils which are widely present in the inflamed mucosa of CD patients and express both receptors. METHODS: Using the 2,4,6-trinitrobenzenesulfonic acid [TNBS]-induced colitis model, involvement of CRTH2 in colitis was investigated by pharmacological antagonism, immunohistochemistry, Western blotting, immunoassay, and leukocyte recruitment. Chemotactic assays were performed with isolated human eosinophils. Biopsies and serum samples of CD patients were examined for presence of CRTH2 and ligands, respectively. RESULTS: High amounts of CRTH2-positive cells, including eosinophils, are present in the colonic mucosa of mice with TNBS colitis and in human CD. The CRTH2 antagonist OC-459, but not the DP antagonist MK0524, reduced inflammation scores and decreased TNF-α, IL-1ß, and IL-6 as compared with control mice. OC-459 inhibited recruitment of eosinophils into the colon and also inhibited CRTH2-induced chemotaxis of human eosinophils in vitro. Eosinophil-depleted ΔdblGATA knockout mice were less sensitive to TNBS-induced colitis, whereas IL-5 transgenic mice with lifelong eosinophilia were more severely affected than wild types. In addition, we show that serum levels of PGD2 and Δ(12)-PGJ2 were increased in CD patients as compared with control individuals. CONCLUSIONS: CRTH2 plays a pro-inflammatory role in TNBS-induced colitis. Eosinophils contribute to the severity of the inflammation, which is improved by a selective CRTH2 antagonist. CRTH2 may, therefore, represent an important target in the pharmacotherapy of CD.

Opposing roles of prostaglandin D2 receptors in ulcerative colitis.

Proresolution functions were reported for PGD2 in colitis, but the role of its two receptors, D-type prostanoid (DP) and, in particular, chemoattractant receptor homologous molecule expressed on Th2 cells (CRTH2), is less well defined. We investigated DP and CRTH2 expression and function during human and murine ulcerative colitis (UC). Expression of receptors was measured by flow cytometry on peripheral blood leukocytes and by immunohistochemistry and immunoblotting in colon biopsies of patients with active UC and healthy individuals. Receptor involvement in UC was evaluated in a mouse model of dextran sulfate sodium colitis. DP and CRTH2 expression changed in leukocytes of patients with active UC in a differential manner. In UC patients, DP showed higher expression in neutrophils but lower in monocytes as compared with control subjects. In contrast, CRTH2 was decreased in eosinophils, NK, and CD3(+) T cells but not in monocytes and CD3(+)/CD4(+) T cells. The decrease of CRTH2 on blood eosinophils clearly correlated with disease activity. DP correlated positively with disease activity in eosinophils but inversely in neutrophils. CRTH2 internalized upon treatment with PGD2 and 11-dehydro TXB2 in eosinophils of controls. Biopsies of UC patients revealed an increase of CRTH2-positive cells in the colonic mucosa and high CRTH2 protein content. The CRTH2 antagonist CAY10595 improved, whereas the DP antagonist MK0524 worsened inflammation in murine colitis. DP and CRTH2 play differential roles in UC. Although expression of CRTH2 on blood leukocytes is downregulated in UC, CRTH2 is present in colon tissue, where it may contribute to inflammation, whereas DP most likely promotes anti-inflammatory actions.

O-1602, an atypical cannabinoid, inhibits tumor growth in colitis-associated colon cancer through multiple mechanisms.

Cannabinoids have antiinflammatory and antitumorigenic properties. Some cannabinoids, such as O-1602, have no or only little affinity to classical cannabinoid receptors but exert cannabinoid-like antiinflammatory effects during experimental colitis. Here, we investigated whether O-1602 shows antitumorigenic effects in colon cancer cells and whether it could reduce tumorigenesis in the colon in vivo. The colon cancer cell lines HT-29 and SW480 were used to study the effect of O-1602 on viability and apoptosis. The effect of O-1602 on tumor growth in vivo was studied in a colitis-associated colon cancer mouse model. O-1602 decreased viability and induced apoptosis in colon cancer cells in a concentration-dependent manner (0.1-10 µM). In the mouse model, treatment with O-1602 (3 mg/kg, i.p., 12×) reduced tumor area by 50 % and tumor incidence by 30 %. Histological scoring revealed a significant decrease in tumor load. In tumor tissue, O-1602 decreased levels of proliferating cell nuclear antigen (PCNA), activation of oncogenic transcription factors STAT3 and NFκB p65, and expression of TNF-α while levels for proapoptotic markers, such as p53 and BAX, increased. The in vivo effects of O-1602 on PCNA, BAX, and p53 were also observed in colon cancer cells. The data provide a novel insight into antitumorigenic mechanisms of atypical cannabinoids. O-1602 exerts antitumorigenic effects by targeting colon cancer cells as well as proinflammatory pathways known to promote colitis-associated tumorigenesis. Due to its lack of central sedation, O-1602 could be an interesting compound for the treatment of colon and possibly other cancers.

The bioactive potential of red raspberry (Rubus idaeus L.) leaves in exhibiting cytotoxic and cytoprotective activity on human laryngeal carcinoma and colon adenocarcinoma.

In this article, the bioactive potential of red raspberry leaves, a by-product of this widely spread plant, mostly valued for its antioxidant-rich fruits, was determined. The polyphenolic profile and antioxidative properties of red raspberry leaf extract were determined and examined for potential biological activity. Cytotoxic effect, antioxidative/prooxidative effect, and effect on total glutathione concentration were determined in human laryngeal carcinoma (HEp2) and colon adenocarcinoma (SW 480) cell lines. SW 480 cells are more susceptible to raspberry leaf extract in comparison with HEp2 cells. The antioxidative nature of raspberry leaf extract was detected in HEp2 cells treated with hydrogen peroxide, as opposed to SW 480 cells, where raspberry leaf extract induced reactive oxygen species formation. Raspberry leaf extract increased total glutathione level in HEp2 cells. This effect was reinforced after 24 hours of recovery, indicating that induction was caused by products formed during cellular metabolism of compounds present in the extract. Comparison of the results obtained on these two cell lines indicates that cellular response to raspberry extract will depend on the type of the cells that are exposed to it. The results obtained confirmed the biological activity of red raspberry leaf polyphenols and showed that this traditional plant can supplement the daily intake of valuable natural antioxidants, which exhibit beneficial health effects.