Phospholipid turnover in the inflamed intestinal mucosa: Arachidonic acid-rich phosphatidyl/plasmenyl-ethanolamine in the mucosa in inflammatory bowel disease

Cytosolic phospholipase A2 (PLase A2) is activated by low Ca2+ concentratio ns and translocates from thp cytosol tn the cell membrane releasing arachid onic acid: the arachidonic acid cascade then leads to the production of man y inflammatory mediators. The aim of this study, accordingly, was to invest igate the role of phospholipid metabolism in the intestinal mucosa in infla mmatory bowel disease (IBD). Surgically resected specimens from patients wi th Crohn's disease (CD), ulcerative colitis (UC), and colrectal cancer (non cancerous tissue; as a control) were submitted to phospholipid analysis and a PLase A2 assay, which measures the degradation of endogenous mucosal pho spholipids. A high percentage of plasmenylethanolamine (plas.E) was detecte d in the glycerophospholipid fraction of CD mucosa. The arachidonic acid co ntent of the phosphatidylethanolamine plus plas.E subfraction was higher in inflamed than in intact mucosa in CD. PLaseA2 activity, resulting in lysop hosphatidyl ethanolamine production, was detected only in inflamed mucosa f rom CD and UC patients, but not in normal mucosa from controls. PLaseA2 act ivity was highest in moderately inflamed mucosa adjacent to a severely ulce rated area. The PLasepA2 that reacts with endogenous phosphatidylcholine PL aseA2 (PC) to form lysoPC was found irrespective of the presence of inflamm ation. The PLaseA2 that reacts with ethanolamine-containing phospholipids i s more closely related to inflammation than other PLaseA2 isoenzymes in IBD mucosa.