Neuroprotective influence of sitagliptin against cisplatin-induced neurotoxicity, biochemical and behavioral alterations in Wistar rats.

Cisplatin has been extensively used as a chemotherapeutic agent since around 40 years, though its usage is limited due to severe adverse effects like neurotoxicity that might be because of oxidative stress. Hence, the present study was planned to investigate the possible protective role of sitagliptin against cisplatin-associated neurotoxic, biochemical, and behavioral alterations in male Wistar rats. Sitagliptin is a dipeptidyl peptidase-4 inhibitor that shows dual effects by improving the control on metabolism as well as decreasing the debility in cognitive function that is associated with increased insulin sensitivity and antioxidant property. For the in vitro assay, cultured rat pheochromocytoma (PC12) cells were exposed to different concentrations (10, 20, and 50 mM) of sitagliptin for 24 h. Cisplatin at 5 mM concentrations was added and cell viability was assessed using MTT assay. For in vivo study, animals were divided into four groups. Group I (Vehicle control): animals were administered 0.9% (w/v) of normal saline (1 mL/100 g; p.o.). Group II (Cisplatin): animals were treated with cisplatin (2 mg/kg; i.p.). Group III (Cisplatin + sitagliptin): animals were administered cisplatin along with sitagliptin. Group IV (Sitagliptin): animals were given sitagliptin (10 mg/kg; p.o.). All the treatments were administered for 8 weeks. On last day of treatment, behavioral evaluations including locomotor and rotarod studies were performed. In addition, several antioxidant enzymes were also estimated from cerebellum tissues; such as levels of thiobarbituric acid reactive substance (TBARS) were determined as a marker of lipid peroxidation, reduced glutathione (GSH) and catalase (CAT) were also estimated. Histological study of cerebellum tissue was also performed after performing the behavioral study. Exposure to cisplatin decreased cell viability in PC12 cells which were significantly increased by co-treatment with sitagliptin. In in vivo study, cisplatin significantly elevated the level of TBARS and reduced the level of antioxidant enzymes such as GSH and CAT which were significantly restored in sitagliptin + cisplatin group of rats. In addition, cisplatin impaired performance on the locomotor and rotarod activities, whereas sitagliptin significantly improved the performance of both activities. These results suggested the neuroprotective influence of sitagliptin by protecting cerebellum part of brain against cisplatin-induced toxicity.