Prolactin Modulates Renal Ischemia Reperfusion Injury According to Sex and Cathepsin D Genotype

Renal ischemia reperfusion injury (IRI) is a major driver of acute kidney injury and a critical determinant of long term renal outcomes. Although sex differences in susceptibility to renal injury are well recognized, the hormonal mechanisms underlying these disparities remain incompletely understood. Prolactin (PRL), a pleiotropic hormone, has been implicated in both protective and deleterious renal effects, while Cathepsin D (CTD), a lysosomal protease, cleaves PRL into Vasoinhibins that possess antiangiogenic and immunomodulatory properties. The impact of CTD deficiency on PRL's role in renal IRI has not been defined. Here, we investigated whether CTD regulated prolactin signaling modulates renal responses to IRI in a sex dependent manner. Wild type (WT) and heterozygous CTD mice of both sexes were subjected to unilateral renal IRI. PRL overexpression was achieved via lentiviral vector, and renal function, inflammatory cytokines, and angiogenic factors were assessed. In vitro Prolactin cleavage assays confirmed the enzymatic role of CTD. Proteomic analysis of renal cortex tissue was performed using label free LC MS/MS and pathway enrichment tools. CTD cleaved PRL into Vasoinhibins at physiological pH, an effect blocked by Pepstatin A. PRL effects varied by sex and genotype. In WT females, PRL reduced renal dysfunction and increased IL-6 and TGF beta; expression following IRI. CTD+/- females exhibited protection from injury, with PRL treatment reversing IL-6 induction. In males, PRL alone had modest effects, but CTD deficiency led to pronounced creatinine elevation, which PRL treatment normalized. Proteomic data revealed differential regulation of cytoskeletal and inflammatory proteins. Cathepsin D heterozygosity modifies PRL's biological effects on the injured kidney. The CTD, PRL axis regulates key inflammatory and angiogenic responses after IRI, revealing new mechanistic insights and potential therapeutic targets in acute kidney injury.