Urinary tract infections are the second most common infectious disease in humans and are predominantly caused by uropathogenic E. coli (UPEC). A majority of UPEC isolates express the type 1 pilus adhesin, FimH, and cell culture and murine studies demonstrate that FimH is involved in invasion and apoptosis of urothelial cells. FimH initiates bladder pathology by binding to the uroplakin receptor complex, but the subsequent events mediating pathogenesis have not been fully characterized. We report a hitherto undiscovered signaling role for the UPIIIa protein, the only major uroplakin with a potential cytoplasmic signaling domain, in bacterial invasion and apoptosis. In response to FimH adhesin binding, the UPIIIa cytoplasmic tail undergoes phosphorylation on a specific threonine residue by casein kinase II, followed by an elevation of intracellular calcium. Pharmacological inhibition of these signaling events abrogates bacterial invasion and urothelial apoptosis in vitro and in vivo. Our studies suggest that bacteria-induced UPIIIa signaling is a critical mediator of bladder responses to insult by uropathogenic E. coli.

Uropathogenic Escherichia coli (UPEC), the most frequent cause of urinary tract infection (UTI), is associated with an inflammatory response which includes the induction of cytokine/chemokine secretion by urothelial cells and neutrophil recruitment to the bladder. Recent studies indicate, however, that UPEC can evade the early activation of urothelial innate immune response in vitro. In this study, we report that infection with the prototypic UPEC strain NU14 suppresses tumor necrosis factor alpha (TNF-␣)-mediated interleukin-8 (CXCL-8) and interleukin-6 (CXCL-6) secretion from urothelial cell cultures compared to infection with a type 1 piliated E. coli K-12 strain. Furthermore, examination of a panel of clinical E. coli isolates revealed that 15 of 17 strains also possessed the ability to suppress cytokine secretion. In a murine model of UTI, NU14 infection resulted in diminished levels of mRNAs encoding keratinocyte-derived chemokine, macrophage inflammatory peptide 2, and CXCL-6 in the bladder relative to infection with an E. coli K-12 strain. Furthermore, reduced stimulation of inflammatory chemokine production during NU14 infection correlated with decreased levels of bladder and urine myeloperoxidase and increased bacterial colonization. These data indicate that a broad phylogenetic range of clinical E. coli isolates, including UPEC, may evade the activation of innate immune response in the urinary tract, thereby providing a pathogenic advantage.Urinary tract infections (UTI) are most frequently caused by an ascending colonization of the bladder and/or kidneys by Escherichia coli (9, 33). Infection of the urinary tract results in an inflammatory response characterized by increased levels of urinary cytokines and neutrophil influx (1, 13-15). The innate immune response to infection by uropathogenic E. coli (UPEC) depends upon activation of host pattern recognition receptors of the Toll-like receptor pathway, including Toll-like receptor 4 (TLR4) (5,16,(37)(38)(39). Recognition of E. coli lipopolysaccharide (LPS) by urothelial cells that express TLR4 results in activation of the proinflammatory and prosurvival NF-B pathway and secretion of chemokines/cytokines, including CXCL-6 and CXCL-8 (2). The resulting accumulation of inflammatory chemokines in the bladder mucosa and urine during UTI induces the recruitment of neutrophils, which leads to the clearance of bacteria and resolution of infection. Infection of the urinary tract by UPEC also induces adaptive immune responses characterized by humoral and cell-mediated responses which protect against future infection (42).Many pathogenic bacterial species possess the ability to modulate the innate immune response to evade host defenses and promote colonization, including several that block the activation of the NF-B pathway (7,31,32,35,36). We previously reported that UPEC strain NU14 blocks activation of the NF-B pathway and thereby promotes apoptosis (26,27). Insertional mutation of the genes encoding the periplasmic chaperone SurA or the LPS biosynthetic oper...

Our study has identified a unique mechanism that describes how components of pathogens common in the urinary system may contribute to the malignant transformation of benign prostate epithelia.

The pyrimidine nucleotide biosynthesis (pyr) operon in Bacillus subtilis is regulated by transcriptional attenuation. The PyrR protein binds in a uridine nucleotide-dependent manner to three attenuation sites at the 5'-end of pyr mRNA. PyrR binds an RNA-binding loop, allowing a terminator hairpin to form and repressing the downstream genes. The binding of PyrR to defined RNA molecules was characterized by a gel mobility shift assay. Titration indicated that PyrR binds RNA in an equimolar ratio. PyrR bound more tightly to the binding loops from the second (BL2 RNA) and third (BL3 RNA) attenuation sites than to the binding loop from the first (BL1 RNA) attenuation site. PyrR bound BL2 RNA 4-5-fold tighter in the presence of saturating UMP or UDP and 150- fold tighter with saturating UTP, suggesting that UTP is the more important co-regulator. The minimal RNA that bound tightly to PyrR was 28 nt long. Thirty-one structural variants of BL2 RNA were tested for PyrR binding affinity. Two highly conserved regions of the RNA, the terminal loop and top of the upper stem and a purine-rich internal bulge and the base pairs below it, were crucial for tight binding. Conserved elements of RNA secondary structure were also required for tight binding. PyrR protected conserved areas of the binding loop in hydroxyl radical footprinting experiments. PyrR likely recognizes conserved RNA sequences, but only if they are properly positioned in the correct secondary structure.

Background Pelvic pain is a major component of the morbidity associated with urinary tract infection (UTI), yet the molecular mechanisms underlying UTI-induced pain remain unknown. UTI pain mechanisms likely contrast with the clinical condition of asymptomatic bacteriuria (ASB), where individuals have significant bacterial loads yet lack symptoms. Methods A murine UTI model was used to compare pelvic pain behavior elicited by infection with uropathogenic Escherichia coli strain NU14 and ASB strain 83972. Results NU14-infected mice developed pelvic pain, whereas mice infected with 83972 did not exhibit pain, similar to patients infected with 83972. NU14-induced pain was not dependent on mast cells, not correlated with bacterial colonization, nor correlated urinary neutrophils. UTI pain was not influenced by expression of type 1 pili, the bacterial adhesive appendage that induces urothelial apoptosis. However, purified NU14 lipopolysaccharide (LPS) induced TLR4-dependent pain, but 83972 LPS induced no pain. Indeed, 83972 LPS attenuated pain of NU14 infection, suggesting therapeutic potential. Conclusions These data suggest a novel mechanism of infection-associated pain that is dependent on TLR4 yet independent of inflammation. Clinically, these findings also provide the rational for probiotic therapies that would minimize the symptoms of infection without reliance on empiric therapies that contribute to antimicrobial resistance.