MON-223 CHANGES IN MERCAPTURATES OF CYSTEINE-DISULFIDES ASSOCIATE TO ACUTE KIDNEY INJURY INDUCED BY CISPLATIN AND GENTAMICIN

Abstract

Disulfide stress is a mechanism of redox signalling associated with increased formation of cysteine-disulfides (CysSSX) in inflammatory/oxidative conditions. The kidney is a primordial organ for CysSSX accumulation due to its high metabolic rate and dependence on oxidative phosphorylation to produce energy. CysSSX undergo filtration and their increased urinary levels have been associated with a decreased tubular reabsorption. They are also secreted through glutathione turnover. In addition, they are eliminated in urine in the form of mercapturates (uNAC) that are generated upon CysSSX acetylation in proximal tubular cells through the mercapturate pathway. We investigated the tubular detoxification of CysSSX in animal models of nephrotoxic-mediated acute kidney injury (AKI). Female Wistar rats weighing 200–250 g were allocated under controlled environmental conditions in individual metabolic cages, for 24-h urine samples collection. Rats were randomly divided into three groups: (1) control group (CTL), receiving daily vehicle intraperitoneal for 6 days; (2) gentamicin group (G), receiving gentamicin intraperitoneal (150 mg/kg) for 6 days; and (3) cisplatin group (CISP), receiving a single intraperitoneal dose of cisplatin (5 mg/kg). At the end of the experiment, kidneys were perfused by the aorta with saline and immediately dissected and processed. Blood and urine samples were obtained at different time points. The levels of urinary total cysteine (uCys) (CysSSX filtration+secretion) and total cysteine-glycine (uCys-Gly) (measure of glutathione turnover) and uNAC (measure of mercapturate formation) were also quantified. Hematoxylin–eosin-stained kidney sections revealed a clear tubular necrosis in both gentamicin and cisplatin-treated rats. Plasma creatinine levels increased at day 4 after cisplatin initiation (2.55±0.56 mg/dL) and at day 5 after gentamicin (3.3±0.4 mg/dL) in comparison with CTL group (0.55±0.05 mg/dL) (p<0.001). The levels of uNAC decreased 2 days after initiation of CISP (64±10 µM) worsening at day 4 (47±3 µM) in comparison with the basal state group (163±6 µM) (p<0.001). The same tendency was observed for G, despite with lower levels of uNAC excretion (basal state 97±14 µM) and only reaching significance at day 5 (37±7 µM) (p=0.044). Changes in uCys levels were coincident with serum creatinine increases and more evident for CISP (319±58 µM) than for G (53±11 µM), comparing to basal state (27±3 µM and 56±3 µM for CISP and G) (p<0.001 and p=0.039 for CISP and G). A decrease of uCysGly was observed for the CISP group at day 2 (18±2 µM) and day 4 (9±2 µM) in relation to basal state (33±3 µM) (p<0.001). No changes were observed for the G group. uNAC might represent an early biomarker of drug induced-AKI, particularly for drugs undergoing the mercapturate pathway, such as cisplatin. Moreover, CysSSX acetylation might represent the primary mechanism of detoxification of the large burden of CysSSX formed in kidney tubule upon injury, particularly when there is an impairment of CysSSX secretion (eg.CISP).