Transcriptional Profiles in Ischemia/Reperfusion-Injured Murine Kidneys Synergistically Protected by Erythropoietin Derived Peptide CHBP and Caspase-3 siRNA

Abstract Background: Target-specific treatment is not available for acute kidney injury (AKI). A novel erythropoietin-derived cyclic helix B surface peptide (CHBP) protects kidneys against AKI subjected to different causes. Herein, we investigated the transcriptional profile of renoprotection induced by CHBP and its potential synergistic effects with caspase-3 siRNA (CASP3siRNA) on ischemia/reperfusion (IR) injury associated AKI. Methods: A mouse renal IR model was established by clamping bilateral pedicles for 30 min and reperfusion for 48 h. 0.03 mg/kg of CASP3siRNA/negative control (NCsiRNA) was injected via tail vein 2 h pre-surgery, with/without 24 nmol/kg of CHBP administered to peritoneal cavity at 15 min post reperfusion. The transcriptomic profile in kidneys was assessed by affymetrix gene chips, along with renal function, histology, active caspase-3 and HMGB1.Results: CHBP or CASP3siRNA significantly improved renal function and structure, with decreased caspase-3 and HMGB1 in IR kidneys. Combined treatment of CHBP and CASP3siRNA further preserved kidney structure, and reduced active caspase-3 and HMGB1. Furthermore, fold change > 1.414 and P < 0.05 were used to identify differentially expressed genes (DEGs). In IR kidneys, 281 DEGs induced by CHBP were mainly involved in promoting cell division and improving cellular function and metabolism (up-regulated STAT5B and SLC22A7). The additional administration of CASP3siRNA caused 504 and 418 DEGs in IR + CHBP kidneys with or without NCsiRNA, with 37 genes in common. These DEGs were associated with modulated apoptosis and inflammation (up-regulated BCL6，SLPI and SERPINA3M), and immunity, injury and microvascular homeostasis (up-regulated CFH and GREM1, and down-regulated ANGPTL2). Conclusions: This proof-of-effect study indicated that the synergistic renoprotection of CHBP and CASP3siRNA at the early stage of IR-induced AKI. Underlying genes, BCL6, SLPI, SERPINA3M, GREM1 and ANGPTL2, might be potential new biomarkers for clinical applications.