Infectious
peritonitis is a common complication in patients undergoing chronic
peritoneal dialysis (PD), limiting the duration of PD as a modality for
renal replacement therapy and increasing patient morbidity and mortality.
Antimicrobial peptides (AMPs) serve critical roles in mucosal defense, but their expression and activity during
peritonitis are poorly understood. We hypothesized that AMPs belonging to the
Ribonuclease (
RNase) A Superfamily are present in peritoneal fluid and increase during
peritonitis in patients undergoing chronic PD. In the absence of
peritonitis, we detected
RNase 3,
RNase 6, and
RNase 7 in cell-free supernatants and viable cells obtained from peritoneal fluid of chronic PD patients. The cellular sources of these RNases were eosinophils (
RNase 3), macrophages (
RNase 6), and mesothelial cells (
RNase 7). During
peritonitis,
RNase 3 increased 55-fold and
RNase 7 levels increased 3-fold on average, whereas
RNase 6 levels were unchanged. The areas under the receiver-operating characteristic curves for
RNase 3 and
RNase 7 were 0.99 (95% confidence interval (CI): 0.96-1.0) and 0.79 (95% CI: 0.64-0.93), respectively, indicating their potential as
biomarkers of
peritonitis. Discrete omental reservoirs of these RNases were evident in patients with
end stage kidney disease prior to PD initiation, and omental
RNase 3 reactive cells increased in patients undergoing PD with a history of
peritonitis. We propose that constitutive and inducible pools of antimicrobial RNases form a network to shield the peritoneal cavity from microbial invasion in patients undergoing chronic PD.