Do eicosanoids cause colonic dysfunction in experimental E coli 0157:H7 (EHEC) infection?

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Abstract
BACKGROUND The pathophysiology of enterohaemorrhagicEscherichia coli (EHEC) infection remains unclear. Eicosanoids have been implicated as pathophysiological mediators in other colitides. AIMS To determine if prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) contribute to mucosal inflammation and dysfunction in EHEC colitis. METHODS Ten day old rabbits were infected with EHEC. For five days after infection, mucosal synthesis of PGE2 and LTB4 was measured in distal colonic tissue from control and infected animals and51Cr-EDTA permeability was assessed in vivo. Myeloperoxidase activity was measured and histological inflammation and damage were assessed at five days in control and infected animals and after treatment of infected animals with the LTB4 synthesis inhibitor MK-886. In separate experiments, ion transport was measured in Ussing chambers, before and after in vitro addition of the cyclooxygenase inhibitor indomethacin. RESULTS LTB4synthesis was increased from day 2 after infection onwards and PGE2 synthesis was increased on day 3. Mucosal permeability did not increase until day 5 after infection. MK-886 inhibited colonic LTB4 production but did not reduce diarrhoea, inflammation, or mucosal damage. Electrolyte transport was not significantly altered on day 3 after infection. However, both Cl secretion and reduced Na absorption found on day 5 were partially reversed by indomethacin. CONCLUSIONS Tissue synthesis of PGE2 and LTB4 did not correlate temporally with EHEC induced inflammation or changes in mucosal permeability and ion transport. Cyclooxygenase inhibition partially reversed ion transport abnormalities but lipoxygenase inhibition did not affect mucosal inflammation or histological damage. We conclude that the contribution of eicosanoids to mucosal injury and dysfunction is more complex than previously suggested.