915 IMPAIRED NEUTROPHIL RECRUITMENT DRIVEN BY DECREASED AND INTERRUPTED EXPRESSION LEVEL OF MACROPHAGE INFLAMMATORY PROTEIN-2 (MIP-2α) AND MONOCYTE CHEMOTACTIC PROTEIN-1 (MCP-1) PROLONGS UTI IN DIABETES

Abstract

putative urothelial receptor for UPEC binding but the molecular bases underlying invasion remain poorly understood. Rab27b belongs to a family of membrane-associated GTPases that coordinate host cell signal transduction, cytoskeletal organization, and vesicular traffic. Rab27b is highly expressed in the urothelium and Bishop and colleagues recently showed that UPECs exist in urothelial cytoplasmic vesicles positive for Rab27b and UPIa. However, in vivo evidence is still lacking as to what exact roles Rab27b plays in the invasion of UPEC into the urothelial cell. METHODS: Ascending UTI experiments were performed using Rab 27b knockout (KO) mice, lacking urothelial Rab27b expression, and wild-type (WT) control mice. 6-9 wk old females were inoculated, transurethrally, with a UPEC cystitis strain UTI89. Mice (5/genotype/ time point) were sacrificed at 1, 12, 32 h post-infection and subject to antibody staining and Western blotting to identify and quantify UPEC, uroplakins and extent of apoptosis. RESULTS: Rab27b KO mice had significantly fewer UPECs attached to the urothelial surface at 1 h post-inoculation when compared to WT mice. At 12 h post-inoculation, the superficial urothelial cells of WT mice harbored a large number of IBCs whereas Rab27b KO urothelial cells were almost devoid of IBCs. This trend held at 32 h post-inoculation, as there were considerably fewer QIRs in Rab27b KO versus WT mice. Additionally, urothelial cells of the Rab27b KO mice expressed significantly lower level of UPIa and sustained less apoptosis in response to UPEC. CONCLUSIONS: Our data provide the first in vivo evidence implicating Rab27b as an important player in UTI pathogenesis. Rab27b affects the expression of urothelial receptors for UPECs and potentially alters UPEC invasion into and/or exit from the urothelium. Because intracellular vesicular trafficking mediated by molecules like Rab27b is affected in various human genetic diseases, it will be of interest to determine if patients with these conditions are more prone or resistant to UTI.