Neuroprotective Effects of Asiatic Acid on Autophagy and Mitochondrial Integrity in a Parkinson's Disease Cellular Model.

Abstract

Background: Parkinson's disease (PD) is a progressive neurodegenerative disorder. PD patients mostly exhibit mitochondrial dysfunction and autophagic impairment. Asiatic acid (AA) is a triterpenoid with the highest antioxidant activity used to treat oxidative stress. It has been found to have a neuroprotective effect against mitochondrial dysfunction in cellular models of PD; however, its effect on autophagy has not been investigated.

Purpose: This study aimed to investigate whether AA affects autophagy in a cellular model of PD.

Methods: SH-SY5Y cells were differentiated into dopaminergic neuron-like cells via retinoic acid administration. Differentiated cells were treated with AA for 24 h and then exposed to 1-methyl-4-phenylpyridinium (MPP⁺). Cell viability was assessed using a 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay. The expression of microtubule-associated protein 1 light chain 3 (LC3)-II/I, Beclin-1, sequestosome-1/ubiquitin-binding protein p62 (SQSTM1/p62), and tyrosine hydroxylase (TH) was analyzed via Western blot. Caspase-3/7 and LC3 expression was measured using immunofluorescence, as was the colocalization of LC3 and mitochondria. MitoTracker and JC-10 were used to assess the mitochondrial morphology and mitochondrial membrane potential (ΔΨ_m), respectively.

Results: Pretreating cells with AA before MPP⁺ exposure resulted in significantly higher expression of LC3-II/I and Beclin-1, while the expression of SQSTM1/p62 was slightly lower compared to that in cells not pretreated with AA. Cells pretreated with AA exhibited significantly higher viability and TH expression, but significantly lower caspase-3/7 expression and numbers of apoptotic nuclei compared to cells treated with MPP⁺ alone. Notably, pretreatment with AA resulted in tubular mitochondria with considerably higher ΔΨ_m values. The colocalization of LC3 and mitochondria was also significantly higher in the cells pretreated with AA.

Conclusion: AA protected dopaminergic neuron-like cells against MPP⁺-induced apoptosis via the induction of autophagy and the enhancement of mitochondrial function, suggesting that it could be developed as a therapeutic agent for PD.