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Background:Resolvin D1 (RvD1) is a newly found anti-inflammatory bioactive compound derived from polyunsaturated fatty acids.The current study aimed to explore the protective effect of RvD1 on lipopolysaccharide (LPS)-induced acute kidney injury (AKI) and its possible mechanism.Methods:Both in vivo and in vitro studies were conducted.Male BALB/c mice were randomly divided into control group (saline),LPS group (LPS 5 mg/kg),RvD1 group (RvD1 5 μg/kg + LPS 5 mg/kg),and blockage group (Boc-MLP 5 μ g/kg + RvD1 5μg/kg + LPS 5 mg/kg).Boc-MLP is a RvD1 receptor blocker.The mice were intraperitoneally injected with these drugs and recorded for general condition for 48 h,while the blood and kidneys were harvested at 2,6,12,24,and 48 h time points,respectively (n =6 in each group at each time point).Human proximal tubule epithelial cells (HK-2) were randomly divided into control group (medium only),LPS group (LPS 5 μg/ml),RvD1 group (RvD1 10 ng/ml + LPS 5 μg/ml),and blockage group (Boc-MLP 10 ng/ml + RvD1 10 ng/ml + LPS 5 μg/ml).The cells were harvested for RNA at 2,4,6,12,and 24 h time points,respectively (n =6 in each group at each time point).Blood creatinine was tested by using an Abbott i-STAT portable blood gas analyzer.Tumor necrosis factor-α (TNF-α) level was detected by ELISA.Kidney pathology was observed under hematoxylin and eosin (HE) staining and transmission electron microscope (TEM).We hired immune-histological staining,West blotting,and fluorescence quantitative polymerase chain reaction to detect the expression ofRvD l receptor ALX,nuclear factor-kappa B (NF-κB) signaling pathway as well as caspase-3.Kidney apoptosis was evaluated by TUNEL staining.Results:RvD1 receptor ALX was detected on renal tubular epithelials.Kaplan-Meier analysis indicated that RvD1 improved 48 h animal survival (80%) compared with LPS group (40%) and RvD1 blockage group (60%),while RvD1 also ameliorated kidney pathological injury in HE staining and TEM scan.After LPS stimulation,the mRNA expression of toll-like receptor 4,myeloid differentiation factor 88,and TNF-α in both mice kidneys and HK-2 cells were all up-regulated,while RvD1 substantially inhibited the up-regulation of these genes.West blotting showed that the phosphorylated-IκB/IκB ratio in LPS group was significantly higher than that in the control group,which was inhibited in the RvD1 group.RvD1 could inhibit the up-regulation of cleaved-caspase-3 protein stimulated by LPS,which was prohibited in RvD1 blockage group.RvD1 group also had a lower proportion of apoptotic nuclei in mice kidney by TUNEL staining compared with LPS group.Conclusion:In LPS-induced AKI,RvD1 could decrease TNF-α level,ameliorate kidney pathological injury,protect kidney function,and improve animal survival by down-regulating NF-κB inflammatory signal as well as inhibiting renal cell apoptosis.