Kidney Week

Abstract: PO1100

Dietary Ammonium Exacerbates Pyelonephritis in Mice Prone to Vesicoureteral Reflux

Session Information

• Fluid, Electrolyte, and Acid-Base Disorders: Basic
  November 04, 2021 | Location: On-Demand, Virtual Only
  Abstract Time: 10:00 AM - 12:00 PM

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

Jeffrey M. Purkerson, PhD

• Schwartz, George J., University of Rochester Medical Center, Rochester, New York, United States

George J. Schwartz,

Background

In a mouse model of urinary tract infection with Uropathogenic E. Coli (UPEC-UTI) dietary NH₄Cl (AC) induces metabolic acidosis and increases UPEC burden in reflux prone C3H-HeN, but not Tlr4 deficient, C3H-HeJ mice². We have confirmed and extended these studies by comparing the inflammatory response in C3H-HeN mice fed AC-diet vs. standard chow (SC), and by examining the effect of HCl-acidosis.

Methods

Female C3H-HeN mice were fed: standard chow (SC), NH₄Cl (2% w/w; AC), or 1g/ml 0.4 N HCl supplemented chow (HCl-A). 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; 10⁷-10⁸ cfu/50 µl) was induced via transurethral inoculation. UPEC burden (cfu/g) was determined by culture of tissue homogenates. NOS2 mRNA in bladder and kidney cells was quantitated by qRT-PCR. Ly6G+ kidney neutrophil infiltrates, phagocytosis of UPEC-GFP (GFP mean fluorescent intensity, MFI, in Ly6G+ neutrophils) and oxidative burst (DHR123 fluorescence, MFI) were quantitated by flow cytometry. Statistics: Two-tailed T-test or Mann-Whitney U-Test p<0.05.

Results

Consistent with higher UPEC burden in bladder and kidney and increased chemokine/cytokine production², Ly6G+ neutrophil infiltrates were 4.5±0.6 fold higher in kidneys from AC vs. SC-infected mice (N=3; p<0.01)², and NOS2 (iNOS) mRNA was increased 8.7±1.8 vs. SC-infected bladder and 10.5±2.5 fold vs uninfected kidney (N=10; p<0.002). The % double (GFP⁺Ly6G⁺) neutrophils (Mean±SE: SC= 66.6±3.6%, N=5; AC= 69.1±7.5%, N=4), UPEC-GFP MFI in Ly6G+ neutrophils (SC=4.6E3±756, N=5; AC = 6.3E3±2.8E3, N=4), and DHR123 fluorescence of Ly6G+ cells (DHR123 MFI: SC =5E3±712; AC=8.1E3±107) were not significantly different between groups (p>0.5) indicating that neutrophil phagocytosis and oxidative burst were unaffected by dietary ammonium. HCl-acidosis (s[HCO3-]: HCl-A=16.3±0.1 vs. SC=23.2±0.6, N=4; p<0.01) did not increase UPEC burden (Kidney cfu/g: SC: 4E3±2E3 vs. HCL-A: 2E3±8E2, p>0.05) indicating that acidosis per se does not impair UPEC-UTI clearance.
²Purkerson et al. (2020) Physiolog.Rep. 8(19)e14525.

Conclusion

Dietary ammonium chloride impairs clearance of UPEC-UTI and exacerbates pyelonephritis. The effect of dietary ammonium is unrelated to acidosis and neutrophil function.

Funding

• Private Foundation Support