Background: Neonatal sepsis triggers an inflammatory response that contributes to high mortality and acute kidney injury (AKI). AKI occurs in ~25% term and ~75% preterm septic neonates and contributes to mortality and long-term renal dysfunction. Pentoxifylline (PTX), a phosphodiesterase inhibitor with anti-inflammatory and rheological properties that is under study as adjunctive sepsis therapeutic, has demonstrated renal protection from ischemia and inflammation. We hypothesized that adjunctive PTX to antibiotics may decrease biomarkers of kidney injury as surrogate for AKI in a murine neonatal sepsis model.
Objective: To determine the effects of PTX in addition to gentamicin (GENT) on markers of renal tissue injury and inflammation in murine neonatal E. coli sepsis.
Design/Methods: Newborn C57BL/6J mice (<24 hours (h) old) were intravenously injected with bioluminescent E. coli K1 at 105 colony forming units (CFUs)/g body weight, and adequacy of intravenous injections was confirmed using in vivo imaging and Evans blue dye as previously described. A total of 98 pups (mean weight 1.5 g) were randomly assigned to intraperitoneal GENT, PTX, (GENT+PTX) or saline (SAL) at 1.5 h after sepsis initiation, and euthanized after an additional 4 h. CFUs and kidney injury biomarkers were measured from homogenized renal tissue with multiplex assays. Group comparisons employed one-way ANOVA or Kruskal-Wallis tests corrected by false discovery rate.
Results: Renal tissue CFUs were lower (median 193 CFUs/mg tissue, IQR 64-895) compared to CFUs in blood from untreated E. coli septic pups (Speer et al., Front Immunol 2020), and were mostly undetectable in pups treated with antibiotics, whereby the addition of PTX did not enhance bacterial growth. (GENT+PTX) but not GENT alone decreased renal tissue concentrations of neutrophil gelatinase-associated lipocalin, tissue inhibitor of metalloproteinases and vascular endothelial growth factor to 57%, 77% and 92% of control values, respectively, p<0.05. Whereas GENT or PTX alone led to only mild inhibition of renal interferon-inducible protein 10 (IP-10), (GENT+PTX) markedly (~62% of control values) suppressed IP-10 in septic mice, p<0.001, suggesting at least an additive renal protective effect from inflammation and cellular infiltration. Renin and the proximal tubular injury marker kidney injury molecule 1 were not modified by these treatments. Despite its known nephrotoxic effects, GENT alone did not increase any of the renal injury biomarkers, which might be due to the short treatment period or counteracting protective antimicrobial and anti-inflammatory actions.
Conclusions: Addition of PTX to GENT in newborn mice with E. coli sepsis suppresses the expression of several kidney injury biomarkers, suggesting potential protection from sepsis-induced AKI.
