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Background & Aims: The endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG) inhibit cancer cell proliferation by acting at cannabinoid receptors (CBRs). We studied (1) the levels of endocannabinoids, cannabinoid CB"1 and CB"2 receptors, and fatty acid amide hydrolase (FAAH, which catalyzes endocannabinoid hydrolysis) in colorectal carcinomas (CRC), adenomatous polyps, and neighboring healthy mucosa; and (2) the effects of endocannabinoids, and of inhibitors of their inactivation, on human CRC cell proliferation. Methods: Tissues were obtained from 21 patients by biopsy during colonoscopy. Endocannabinoids were measured by liquid chromatography-mass spectrometry (LC-MS). CB"1, CB"2, and FAAH expression were analyzed by RT-PCR and Western immunoblotting. CRC cell lines (CaCo-2 and DLD-1) were used to test antiproliferative effects. Results: All tissues and cells analyzed contain anandamide, 2-AG, CBRs, and FAAH. The levels of the endocannabinoids are 3- and 2-fold higher in adenomas and CRCs than normal mucosa. Anandamide, 2-AG, and the CBR agonist HU-210 potently inhibit CaCo-2 cell proliferation. This effect is blocked by the CB"1 antagonist SR141716A, but not by the CB"2 antagonist SR144528, and is mimicked by CB"1-selective, but not CB"2-selective, agonists. In DLD-1 cells, both CB"1 and CB"2 receptors mediate inhibition of proliferation. Inhibitors of endocannabinoid inactivation enhance CaCo-2 cell endocannabinoid levels and block cell proliferation, this effect being antagonized by SR141716A. CaCo-2 cell differentiation into noninvasive cells results in increased FAAH expression, lower endocannabinoid levels, and no responsiveness to cannabinoids. Conclusions: Endocannabinoid levels are enhanced in transformed colon mucosa cells possibly to counteract proliferation via CBRs. Inhibitors of endocannabinoid inactivation may prove useful anticancer agents.

Factor XIIIa, a circulating form of transglutaminase, plays a key role in intestinal mucosal repair. We found that transglutaminase levels are decreased in serum of patients with inflammatory bowel diseases and demonstrated in a rat model of chronic colitis that serum transglutaminase is closely related to the severity of intestinal damage. We aimed, therefore, to correlate serum transglutaminase levels with standard endoscopic and histopathologic grading systems in patients affected by ulcerative colitis (UC). In 249 patients with UC, we assayed serum transglutaminase activity by a radioenzymatic method and measured clinical activity index (CAI) according to modified Rachmilewitz's criteria. In a subset of 82 patients undergoing colonoscopy, endoscopic and histologic indices were studied. Biopsy specimens were also taken from 28 patients to measure myeloperoxidase (MPO) as a marker of mucosa inflammation. Serum transglutaminase levels significantly correlated with the CAI scoring (r = −0.63; P < 0.01); likewise serum transglutaminase showed the best correlation with endoscopic (r = −0.71; P < 0.001) and histologic (r = −0.79; P < 0.001) scores. Myeloperoxidase activity was significantly higher in patients with active UC than those in remission (P < 0.01), showing a significant correlation with serum transglutaminase levels (r = −0.68; P < 0.01). Immunohistochemistry showed factor XIIIa localization in the extracellular matrix of damaged mucosa. In conclusion, these results suggest that transglutaminase assay can be useful in managing UC as a serological, noninvasive indicator of intestinal mucosal status.

Simple rat models of acute and chronic colonic inflammation were used to study the behaviour in serum and mucosa of transglutaminase (TG), an enzyme recently found to be reduced in serum of patients with inflammatory bowel disease (IBD) and related to the activity index of the disease. In the first model the intraluminal administration of 400 mM lactic acid in the colon caused an acute inflammation resembling that of florid ulcerative colitis in humans. In the second, intraluminal administration of the hapten 2,4,6-trinitrobenzenesulphonic acid (TNB) (10 or 30 mg) in 0.25 ml of ethanol as a 'barrier breaker' produced a chronic inflammatory disease. The results showed a reduced TG activity in colon of rats in both acute and chronic induced colitis (447 pm75 versus 1344 pm59 mU/g protein (p < 0.001) and 484 pm59 versus 1204 pm75 mU/g protein (p < 0.001)). This decreased activity was related to the severity of mucosal damage, which was dose-dependent. Moreover, in severe colitis the immunohistochemistry showed a TG location in repairing tissue. Serum TG activity was decreased after TNB administration (1.36 pm0.05 versus 3.44 pm0.20 mU/ml (p < 0.001)) but not after lactic acid treatment (3.97 pm0.11 versus 3.78 pm0.16 mU/ml). In summary, the reduction of TG activity in both tissue and serum when the damage is stabilized reflects the altered morphofunctional integrity of the colon and suggests that serum assay of this enzyme could be a simple marker of intestinal mucosal status in IBD.

We evaluated the serum transglutaminase activity in patients with inflammatory bowel diseases (IBD) to correlate its level with clinical status. There were 49 patients with Crohn's disease (CD), 50 with ulcerative colitis (UC), 35 with diseases other than IBD as control group and 42 healthy subjects matched for sex and age. Enzyme activity was significantly lower in both IBD groups than in controls and in normal subjects (p < 0.001); we found a significant negative correlation between serum transglutaminase (TG) activity and clinical severity of the disease in both IBD patient groups (r =−0.54 in CD, and r= −0.69 in UC). Moreover, in UC and CD patients, a serum TG value lower than 0.80 mU/ml retrospectively proved to predict the need for major surgery and/or total parenteral nutrition. These results suggest that serum TG may prove useful in the management of inflammatory intestinal diseases in predicting clinical outcome.