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

Athinan Prommahom,1 Tatcha Balit,2 Sunisa Somkana,1 Satjapot Manprasong,1 Chonlakorn Panyasuppakun,1 Atipha Kijkraikul,1 Preawanit Thawornrungroaj,1 Pitchaya Thawornrungroaj,1 Permphan Dharmasaroja,1 Thanasup Gonmanee,1 Phisit Khemawoot,1 Kawinthra Khwanraj1 1Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Samut Prakan, Thailand; 2Department of Medical Science, School of Medicine, Walailak University, Nakhon Si Thammarat, ThailandCorrespondence: Kawinthra Khwanraj, Email [email protected]: 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 (ΔΨm), 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 ΔΨm 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. Keywords: asiatic acid, dopaminergic neuron-like cells, autophagy, mitochondria, mitophagy