Objective:To investigate the level of endogenous hydrogen sulfide (H 2S) in contrast-induced acute kidney injury (CIAKI), as well as the potential role of H 2S against CIAKI by down-regulating NLRP3 inflammasome. Methods:Twenty-four healthy male Sprague-Dawley rats, weighing 180-220 g, were randomly divided into three groups according to the random number table method: control group, CIAKI group (iopromide 2.9 g/kg) and CIAKI+NaHS group (NaHS 4 mg/kg for three days before 2.9 g/kg iopromide injection). Kidneys were collected for whole-genome sequencing and bioinformatic analysis. HE and PAS staining were used for kidney histological examination. TUNEL assays were applied to detect renal tubular epithelial injury. Expressions of NLRP3 inflammasome (NLRP3, ASC and caspase-1) were evaluated by immunofluorescence staining. The role of H 2S in contrast (iopromide 200 mgI/kg)-induced injury on human renal tubular epithelium (HK-2 cells) was investigated, and CCK-8 assay was used to detect cellular viability. Results:Compared with the control group, the expression of endogenous H 2S synthetases-related genes [cystathionine β-synthase ( CBS), cystathionine-γ-lyase ( CSE) and 3-mercaptopyruvate sulfurtransferase ( 3- MST)] was lower in CIAKI group (all P<0.05). The gene expression levels of CBS, CSE and 3- MST were negatively correlated with renal function biomarkers serum creatinine, blood urea nitrogen and cystatin-C (all P<0.05). Compared with the CIAKI group, CIAKI+NaHS group showed alleviated creatinine, blood urea nitrogen and cystatin-C, improved histological changes, reduced apoptosis. Moreover, the expression levels of NLRP3, ASC and caspase-1 in CIAKI+NaHS group were lower than those in CIAKI group (all P<0.05). In HK-2 cells, compared with the contrast group, the cellular viability was higher in the contrast+NaHS group; reducing endogenous H 2S by CBS inhibitor could enhance contrast-induced cell viability ( P<0.05). Conclusions:Injury of endogenous H 2S system is pivotal to CIAKI pathogenesis. Up-regulation of H 2S ameliorates renal injury of CIAKI rats, which may be related to regulation of NLRP3 inflammasome.