ZYMOSAN-INDUCED BACTERIAL TRANSLOCATION - A STUDY OF MECHANISMS

Background and Methods: At nonlethal doses, zymosan induces a systemic inflammatory state and promotes bacterial translocation. This study was performed to investigate the mechanisms by which zymosan causes intestinal mucosal injury and bacterial translocation. Bacterial translocation to the mesenteric lymph node was measured 24 hrs after intraperitoneal challenge with saline or zymosan (0.1 mg) in normal (CD-1), congenitally macrophage-hyporesponsive (C3H/HeJ), complement-deficient (DBA/2), or mast cell-deficient (W/W(v)) mice. Since zymosan-induced bacterial translocation may be mediated by xanthine oxidase-generated oxidants, bacterial translocation was measured in mice pretreated with the xanthine oxidase inhibitor, allopurinol. To further investigate the role of oxidants in zymosan-induced bacterial translocation, ileal and hepatic levels of xanthine oxidase, myeloperoxidase, conjugated dienes, malondialdehyde, and the antioxidants-superoxide dismutase, catalase, and glutathione peroxidase, were measured. Results: Zymosan-induced mucosal injury and bacterial translocation occurred to a similar extent (p < .05) in all four genetic strains of mice, but were reduced in the mice pretreated with allopurinol. Zymosan increased (p < .03) ileal and hepatic xanthine oxidase activity, while reducing (p < .01) antioxidant (catalase) activity. There was also evidence of hepatic, but not ileal, lipid peroxidation (conjugated diene) (p < .05) and neutrophil sequestration (myeloperoxidase) (p < .01). Conclusions: Zymosan-induced intestinal mucosal injury and bacterial translocation do not require complement activation, or the release of macrophage or mast cell products. They appear to be mediated by xanthine oxidase-generated products and associated with disruption of the normal ileal and hepatic oxidant-antioxidant balance.