Cytotoxic necrotizing factor 1 and hemolysin from uropathogenic Escherichia coli elicit different host responses in the murine bladder

Abstract

Cytotoxic necrotizing factor 1 (CNF1) and hemolysin (HlyA1) are toxins produced by uropathogenic Escherichia coli(UPEC). We previously showed that these toxins contribute to the inflammation and tissue damage seen in a mouse modelof ascending urinary tract infection. CNF1 constitutively activates small Rho GTPases by deamidation of a conserved glutamineresidue, and HlyA1 forms pores in eukaryotic cell membranes. In this study, we used cDNA microarrays of bladdertissue isolated from mice infected intraurethrally with wild-type CP9, CP9cnf1, or CP9ΔhlyA to further evaluate the rolethat each toxin plays in the host response to UPEC. Regardless of the strain used, we found that UPEC itself elicited a significantchange in host gene expression 24 h after inoculation. The largest numbers of upregulated genes were in the cytokineand chemokine signaling and Toll-like receptor signaling pathways. CNF1 exerted a strong positive influence on expressionof genes involved in innate immunity and signal transduction and a negative impact on metabolism- andtransport-associated genes. HlyA1 evoked an increase in expression of genes that encode innate immunity factors and adecrease in expression of genes involved in cytoskeletal and metabolic processes. Multiplex cytokine and myeloperoxidaseassays corroborated our finding that a strong proinflammatory response was elicited by all strains tested. Bladders challengedintraurethrally with purified CNF1 displayed pathology similar to but significantly less intense than the pathologythat we observed in CP9-challenged mice. Our data demonstrate substantial roles for CNF1 and HlyA1 in initiation of astrong proinflammatory response to UPEC in the bladder. © 2013, American Society for Microbiology.