Endotoxin-induced shedding of viable uroepithelial cells is and antimicrobial defense mechanism

ICR mice were infected intravesically with a virulent (7343) or a nonvirulent (U⁺) Escherichia coli strain. The U⁺ strain induced considerably more shedding of uroepithelial cells than did the 7343 strain. The stimulus for this shedding was shown to be associated with lipopolysaccharide and was abrogated by pretreatment with aprotinin. Desquamation commenced within 1 h postinjection, and the cells that were shed proved to be viable. Comparison of C3H/HeJ and C3H mice revealed that only the latter responded to shedding inducers. However, C3H/HeJ mice succumbed to a systemic infection on injection of 10⁶ U⁺ cells intravesically, whereas other mouse strains required a 100-fold dose of bacteria for this effect. Since the first stage of a bacterial infection entails adherence of the microbes to epithelial cells, inducible shedding is an antimicrobial defense mechanism.