BACKGROUND AND PURPOSE: Despite recent advances in understanding its pathophysiology, treatment of acute kidney injury (AKI) remains a major unmet medical need, and novel therapeutic strategies are needed. Cathelicidin-related antimicrobial peptide (CRAMP) with immunomodulatory properties has an emerging role in various disease contexts. Here, we aimed to investigate the role of CRAMP and its underlying mechanisms in AKI.
EXPERIMENTAL APPROACH: The human homologue LL-37 and CRAMP were measured in blood samples of AKI patients and in experimental AKI mice respectively. Experimental AKI was induced in wild-type and CRAMP-deficient (Cnlp) mice by ischaemia/reperfusion (I/R). Therapeutic evaluation of CRAMP was performed with exogenous CRAMP (5 mg·kg, i.p.) treatment.
KEY RESULTS: Cathelicidin expression was inversely related to clinical signs in patients and down-regulated in renal I/R-induced injury in mice. Cnlpmice exhibited exacerbated I/R-induced renal dysfunction, aggravated inflammatory responses and apoptosis. Moreover, over-activation of the NLRP3 inflammasome in Cnlpmice was associated with I/R-induced renal injury. Exogenous CRAMP treatment markedly attenuated I/R-induced renal dysfunction, inflammatory response and apoptosis, correlated with modulation of immune cell infiltration and phenotype. Consistent with Cnlpmouse data, CRAMP administration suppressed renal I/R-induced NLRP3 inflammasome activation, and its renal protective effects were mimicked by a specific NLRP3 inhibitor CY-09. The reno-protective and NLRP3 inhibitory effects of CRAMP required the EGF receptor.
CONCLUSION AND IMPLICATIONS: Our results suggest that CRAMP acts as a novel immunomodulatory mediator of AKI and modulation of CRAMP may represent a potential therapeutic strategy.