Sitagliptin and liraglutide reversed nigrostriatal degeneration of rodent brain in rotenone-induced Parkinson’s disease

The present study investigated the possible relationship between pro-inflammatory cytokines and programmed nigral neuronal death in rotenone model of Parkinson’s disease (PD). Sitagliptin and liraglutide efficacy to inhibit the inflammatory-apoptotic degenerative process were investigated, too. The experimental PD were induced in male albino rats by ten subcutaneously injections of rotenone (3 mg/kg/day, s.c). All treatment drugs were administered for 16 days after induction of Parkinson rat’s model. Sitagliptin and liraglutide were administered in three different dose levels (10–20–30 mg/kg, p.o), (25–50–100 μg/kg, s.c), respectively. Cylindrical and catalepsy tests were used to detect the optimum dose response of each drug. Sitagliptin (30 mg/kg/day, p.o) and liraglutide (50 μg/kg, s.c.) showed statistically significant ( p ≤ 0.05) effect on behavioral activity. Where both doses improved the motor performance significantly in comparison with other doses in both cylindrical and catalepsy tests. Furthermore, they reversed rotenone-induced nigral neuronal loss, associated with marked decrease of pro-inflammatory cytokines: interleukin (IL)-1β, IL-6, transforming growth factor (TGF)-β1, together with a significant increase of striatal dopamine, nigral glial cell line-derived neurotrophic factor (GDNF), and tyrosine hydroxylase positive (TH+) cells. Moreover, the pro-apoptotic environment in nigrostriatal tissues was abrogated significantly, as the pro-apoptotic protein Bax decreased along with the anti-apoptotic protein Bcl-2 increased. In conclusion, sitagliptin and liraglutide represent a promising strategy to mitigate the progression of PD by their anti-inflammatory, anti-apoptotic neurotrophic and neurogenic mechanistic activities.