Protective role of apigenin on rotenone induced rat model of Parkinson's disease: Suppression of neuroinflammation and oxidative stress mediated apoptosis.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra which is associated with oxidative stress, neuroinflammation and apoptosis. Apigenin (AGN), a non-mutagenic flavone found in fruits and vegetables, exhibits a variety of biological effects including anti-apoptotic, anti-inflammatory, and free radical scavenging activities. The current study was aimed to investigate the neuroprotective effects and molecular mechanisms of AGN in a rat model of PD induced by rotenone (ROT). Unilateral stereotaxic intranigral infusion of ROT caused the loss of tyrosine hydroxylase (TH) immunoreactivity in striatum and substantia nigra. AGN treatment (10 and 20 mg/kg, i.p.) showed a significant improvement in behavioral, biochemical and mitochondrial enzyme activities as compared to ROT exposed rats. The mRNA expression of inflammatory markers and neurotrophic factors was quantified by reverse transcriptase polymerase chain reaction (RT-PCR). Administration of AGN significantly attenuated the upregulation of NF-κB gene expression in ROT induced group and prevented the neuroinflammation in substantia nigra pars compacta (SNpc). Further, AGN inhibited the release of pro-inflammatory cytokines TNF- α, IL-6 and pro-inflammatory enzyme iNOS-1 induced by ROT. Additionally, AGN prevents the reduction of neurotrophic factors BDNF and GDNF mRNA expression in ROT lesioned rats. Immunoblot results illustrated that AGN treatment downregulated α-synuclein aggregation and upregulated the TH protein expression as well as dopamine D2 receptor (D2R) expression in ROT lesioned rats. Thus, the present findings collectively suggest that AGN exerts its neuroprotection in ROT model of PD and may act as an effective agent for treatment of PD.