Abstract
We investigated the role of bacterial adherence and hemolysin production from Escherichia coli parent and genetically cloned strains as to their effects on histamine release from rat mast cells and leukotriene generation from human polymorphonuclear granulocytes. These mediators were involved in the induction of inflammatory disease processes and led, for example, to enhancement of vascular permeability, chemotaxis (leukotriene B4 [LTB4]), chemoaggregation, lysosomal enzyme release, and smooth muscle contraction, (LTC4, LTD4, and LTE4). Washed bacteria (E. coli K-12 MS+ Hly +/-; E. coli 536 MS+ MR +/-) as well as their culture supernatants were analyzed. Washed E. coli K-12 (Hly+), unlike Hly- strains, induced high amounts of histamine release from rat mast cells and chemotactic activity from human polymorphonuclear granulocytes. Significant leukotriene release was obtained with washed E. coli K-12 Hly+ strains and their bacterial culture supernatants. Leukotriene induction was dependent on the amount of hemolysin activity present in the supernatant. However, additional soluble factors should also be considered. The presence of hemolysin appeared to accelerate and enhance the rate of phagocytosis of bacteria by neutrophils. When E. coli 536 (MS+ MR +/- Hly +/-) strains were analyzed, the simultaneous presence of MR+ pili and hemolysin production led to an increase in histamine release as compared with MR- Hly+ strains. The genetically cloned MR+ Hly+ E. coli 536 strain induced higher amounts of leukotrienes as compared with the wild-type strain. Our data suggest a potent role for adhesins and hemolysin as virulence factors in inducing the release of inflammatory mediators.