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Abstract: PO1417

Metabolic Acidosis Exacerbates Pyelonephritis in Mice Prone to Vesicoureteral Reflux

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 901 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

  • Purkerson, Jeffrey M., University of Rochester Medical Center, Rochester, New York, United States
  • Corley, Janine L., University of Rochester Medical Center, Rochester, New York, United States
  • Schwartz, George J., University of Rochester Medical Center, Rochester, New York, United States
Background

Acute pyelonephritis is a serious bacterial infection in children. The prevalence of acute pyelonephritis is due at least in part to vesicoureteral reflux (VUR). Although an association between pyelonephritis and abnormalities in acid-base balance is common in young children, the impact of metabolic acidosis (MA) on progression of acute pyelonephritis is not fully understood. In the current study the effect of metabolic acidosis on pyelonephritis was studied in C3H mouse strains prone to VUR.

Methods

MA was induced in female C3H mice via NH4Cl (2% w/w) supplementation of food. Acid-base state was assessed by blood /gas analysis using an iSTAT® G3+ and urine pH. UPEC-UTI: Urinary Tract Infection of mice (6-8 wks) with Uropathogenic E. Coli (UPEC strain CFT073) 0.5-1X107 cfu/50 µl was performed via the transurethral inoculation. Bacteria burden (cfu/g) in bladder and kidney was determined by culture of tissue homogenates. Collecting duct (CD) fragments and neutrophils were enriched from collagenase-digested kidney by magnetic-sorting utilizing DBA-lectin and monoclonal anti-Ly6G (1A8). Cytokine (IL-1β, TNFα, IL-6) and chemokine (CXCL1, CXCL2, CXCL5) RNA in CD cells was quantitated by qRT-PCR. Ly6G+ cells were enumerated by imaging utilizing a Cellometer K2 Image Cytometer. Statistics: T-test or two-tailed Mann-Whitney U-Test p<0.05 or P ≤ 0.02 for Bonferroni correction.

Results

NH4Cl fed-mice were acidotic (s[HCO3-]: 17±0.6*, Ur pH: 5.8±0.02*) compared to normal (s[HCO3-]: 22.2±0.68; Ur pH: 6.8±0.01, N≥4; *p<0.05). MA concurrent with UPEC-UTI markedly increased kidney UPEC burden in innate immune competent HeN mice (HeN = 4E2±2E2 versus MA HeN= 1E6±1E6; p<0.02 MW U-TEST), but not Tlr4-deficient HeJ mice (HeJ = 2E6 ±1E6 versus MA HeJ = 5E5±1E5). MA markedly increased CD inflammation in infected HeN mice characterized by an 18-124 fold increase in chemokine/cytokine mRNA abundance and a 4.5±0.6 fold increase in Ly6G+ neutrophil infiltrates over normal-infected mice, N=3; p<0.01 versus normal, TTEST.

Conclusion

Concurrent metabolic acidosis exacerbates pyelonephritis in innate immune competent mice that is characterized by an elevated cytokine and chemokine expression and kidney neutrophil infiltrates.