Hyaluronic acid coated bilirubin nanoparticles attenuate ischemia reperfusion-induced acute kidney injury

Acute kidney injury (AKI) is a common pathological process that is globally associated with a high morbidity and mortality rate. The underlying AKI mechanisms include over-produced reactive oxygen species (ROS), inflammatory cell infiltration, and high levels of inflammatory mediators. Bilirubin is an endogenous compound with antioxidant, anti-inflammatory and anti-apoptotic properties, and could, therefore, be a promising therapeutic candidate. Nanotechnology-mediated therapy has emerged as a novel drug delivery strategy for AKI treatment. In this study, we report a hyaluronic acid (HA) coated ε-polylysine-bilirubin conjugate (PLBR) nanoparticle (nHA/PLBR) that can selectively accumulate in injured kidneys and alleviate the oxidative/inflammatory-induced damage. The in vitro study revealed that nHA/PLBR has good stability, biocompatibility, and exhibited higher antioxidant as well as anti-apoptotic effects when compared to nPLBR or bilirubin. The in vivo study showed that nHA/PLBR could target and accumulate in the injured kidney, effectively relieve oxidative stress and inflammatory reactions, protect the structure and function of the mitochondria, and more importantly, inhibit the apoptosis of tubular cells in an ischemia/reperfusion-induced AKI rat model. Therefore, nHA/PLBR has the capacity to enhance specific biodistribution and delivery efficiency of bilirubin, thereby providing better treatment for AKI in the future.