Toll-Like Receptor 4 Promoter Polymorphisms: Common TLR4 Variants May Protect against Severe Urinary Tract Infection

10.1371/journal.pone.0010734PLoS ONE55

Interleukin 8 Receptor Deficiency Confers Susceptibility to Acute Experimental Pyelonephritis and May Have a Human Counterpart

Neutrophils migrate to infected mucosal sites that they protect against invading pathogens. Their interaction with the epithelial barrier is controlled by CXC chemokines and by their receptors. This study examined the change in susceptibility to urinary tract infection (UTI) after deletion of the murine interleukin 8 receptor homologue (mIL-8Rh). Experimental UTIs in control mice stimulated an epithelial chemokine response and increased chemokine receptor expression. Neutrophils migrated through the tissues to the epithelial barrier that they crossed into the lumen, and the mice developed pyuria. In mIL-8Rh knockout (KO) mice, the chemokine response was intact, but the epithelial cells failed to express IL-8R, and neutrophils accumulated in the tissues. The KO mice were unable to clear bacteria from kidneys and bladders and developed bacteremia and symptoms of systemic disease, but control mice were fully resistant to infection. The experimental UTI model demonstrated that IL-8R–dependent mechanisms control the urinary tract defense, and that neutrophils are essential host effector cells. Patients prone to acute pyelonephritis also showed low CXC chemokine receptor 1 expression compared with age-matched controls, suggesting that chemokine receptor expression may also influence the susceptibility to UTIs in humans. The results provide a first molecular clue to disease susceptibility of patients prone to acute pyelonephritis

A Genetic Basis of Susceptibility to Acute Pyelonephritis

For unknown reasons, urinary tract infections (UTIs) are clustered in certain individuals. Here we propose a novel, genetically determined cause of susceptibility to acute pyelonephritis, which is the most severe form of UTI. The IL-8 receptor, CXCR1, was identified as a candidate gene when mIL-8Rh mutant mice developed acute pyelonephritis (APN) with severe tissue damage.We have obtained CXCR1 sequences from two, highly selected APN prone patient groups, and detected three unique mutations and two known polymorphisms with a genotype frequency of 23% and 25% compared to 7% in controls (p<0.001 and p<0.0001, respectively). When reflux was excluded, 54% of the patients had CXCR1 sequence variants. The UTI prone children expressed less CXCR1 protein than the pediatric controls (p<0.0001) and two sequence variants were shown to impair transcription.The results identify a genetic innate immune deficiency, with a strong link to APN and renal scarring

Low CXCR1 Expression and Susceptibility to Acute Pyelonephritis

Urinary tract infections (UTIs) are clustered in certain individuals but the molecular basis of disease susceptibility is not known. A single gene was shown to control the susceptibility to acute pyelonephritis and renal scarring in mice. The IL-8 receptor homologue (mIL-8Rh) controls neutrophil function during acute infection and the mIL-8Rh deletion causes tissue damage through neutrophil entrapment in the kidneys. To investigate if analogous defects might explain the susceptibility to urinary tract infection (UTI) in man, we examined the CXCR1 expression, mRNA levels and DNA sequences between children with acute pyelonephritis (APN) and pediatric controls. APN-prone children expressed less CXCR1 protein and mRNA than the pediatric controls (p<0.0001). DNA sequencing revealed two heterozygous CXCR1 polymorphisms (SNPs) and three mutations (variant 3-5) in the patients (38%) but only one pediatric control had an SNP (4%). The increased SNP frequency was confirmed in APN-prone adults (24% for SNP1, p<0.02 and 26% for SNP2, p<0.006). The polymorphic sequences were located in highly conserved regions of CXCR1, which potentially influenced gene expression through changes in transcription factor specificity or transcript processing. SNP1 was shown to reduce the affinity for the transcription factor RUNX1 and variant 5 close to the 3´polyadenylation site decreased the amount of large CXCR1 transcript. The CXCR1 variants may thus render individuals APN-prone by lowering CXCR1 expression, neutrophil function and the innate host defense against APN. By using a family study approach, we found that APN was more common among relatives of the APN-prone children (20/130, 15%) than controls (3/101, 3%, p < 0·002). In addition, the CXCR1 expression was low in 80 % of the APN-prone relatives, compared to adult controls (p < 0·005). The results show that genetic factors influence the susceptibility to APN and suggest that low CXCR1 expression might predispose to disease

Inherited susceptibility to acute pyelonephritis: a family study of urinary tract infection.

Background. Urinary tract infections (UTIs) are important causes of morbidity and death. The present study investigated whether genetic factors influence susceptibility to acute pyelonephritis (APN). CXCR1 expression was investigated as a factor predisposing to APN, because low CXCR1 expression has been associated with disease susceptibility in mice and disease-prone children. Methods. The families of APN-prone children (n=130) and of age-matched control subjects without UTI (n=101) were studied. Three- generation pedigrees of UTI-associated morbidity were established by means of structured interviews of the families. CXCR1 expression was quantified by flow cytometric analysis of peripheral blood neutrophils obtained from family members and control subjects. Results. APN was significantly more common in the family members of the APN-prone children (20 [15%] of 130 family members) than in the relatives of the control subjects (3 [3%] of 101 family members) (P <.002). Acute cystitis, in contrast, occurred with equal frequency in both groups (19%; P=1.0). Some families included many affected individuals, consistent with a dominant pattern of inheritance, whereas other families showed a recessive pattern of disease susceptibility. CXCR1 expression was significantly lower in the APN-prone children and in their relatives than in pediatric and adult control subjects (P < .0001). Conclusions. Our results suggest that susceptibility to APN is inherited and that low CXCR1 expression might predispose to disease

Neutrophil recruitment, chemokine receptors, and resistance to mucosal infection

Abstract: Neutrophil migration to infected muco-sal sites involves a series of complex interactions with molecules in the lamina propria and at the epithelial barrier. Much attention has focussed on the vascular compartment and endothelial cells, but less is known about the molecular determinants of neutrophil behavior in the periphery. We have studied urinary tract infections (UTIs) to deter-mine the events that initiate neutrophil recruitment and interactions of the recruited neutrophils with the mucosal barrier. Bacteria activate a chemo-kine response in uroepithelial cells, and the che-mokine repertoire depends on the bacterial viru-lence factors and on the specific signaling pathways that they activate. In addition, epithelial chemo-kine receptor expression is enhanced. Interleukin (IL)-8 and CXCR1 direct neutrophil migration across the epithelial barrier into the lumen. In-deed, mIL-8Rh knockout mice showed impaired transepithelial neutrophil migration, with tissue ac-cumulation of neutrophils, and these mice devel-oped renal scarring. They had a defective antibac-terial defense and developed acute pyelonephritis with bacteremia. Low CXCR1 expression was also detected in children with acute pyelonephritis. These results demonstrate that chemokines and chemokine receptors are essential to orchestrate a functional antimicrobial defense of the urinary tract mucosa. Mutational inactivation of the IL-8R caused both acute disease and chronic tissue damage. J. Leukoc. Biol. 69: 899–906; 2001. Key Words: urinary tract infection z bacterial virulence factors z neutrophil migration z innate immunity z chemokine