Document Type

Conference Proceeding

Publication Date

2024

Keywords

Esculetin; Coumarin; Neuroprotective; Parkinson’s disease.

Abstract

Parkinson’s disease (PD) is a prevalent and complex neurological disorder that affects about 0.1-0.2% of the population, with the elderly population being the most commonly affected. It is considered the second most prevalent neurodegenerative disorder among the elderly. As the disease progresses, the motor symptoms become more severe, significantly lowering the patient's self-care ability and quality of life. Since there is no definitive diagnosis in the early stages of PD and no effective treatment to slow down the neurodegenerative processes, developing an effective measure to prevent the development and progression of the disease may reduce the social and economic burden imposed by PD. Esculetin (a natural coumarin) was found to protect PC12 cells from cell death induced by 6-OHDA in a concentration dependent manner. To explore the cellular mechanisms underlying the neuroprotective effects of esculetin, we investigated the ERK signaling pathway. We introduced PD98059, a specific inhibitor of MEK, into PC12 cells before exposing them to 6-OHDA (600 μM). PD98059 (10, 30, and 50 μM) slightly but significantly increased cell viability compared to 6-OHDA alone. However, western blot assays showed no significant difference in the protein expression of p-ERK between the 6-OHDA treated alone and esculetin pretreated groups. To determine whether the GSK3β pathway was involved in 6-OHDA-induced apoptosis in PC12 cells, cells were pretreated with SB415286, the specific inhibitor of GSK3β, for 2 hours before being exposed to 6-OHDA. SB415286 effectively prevented 6-OHDA-induced cell death. It was found that 6-OHDA triggered a significant decrease in the protein expression of phospho-Ser473-Akt. Pre-treating cells with LY294002, the specific inhibitor of PI3-K, prior to the incubation of esculetin and 6-OHDA, significantly abolished the increased protein level of phospho-Ser473-Akt induced by esculetin. Additionally, 6-OHDA decreased the protein expression of phospho-Ser9-GSK3β and LY294002 significantly abolished the increased protein level of phospho-Ser9-GSK3β provided by esculetin. The results indicated that the beneficial effects of esculetin against 6-OHDA-induced PD symptoms may be attributed to the PI3K/Akt/GSK3β pathway. Our results also clearly demonstrated that esculetin effectively protects zebrafish from 6-OHDA-induced neurotoxicity via the activation of the PI3-K/Akt/GSK3β pathway. To understand the involvement of apoptotic genes in the current zebrafish model, we investigated the expression of apoptotic genes in response to 100 μM esculetin exposure for 5 days. The qRT-PCR results indicated that esculetin significantly altered the expression of apoptotic genes, with the pro-apoptotic gene caspase 3 being reduced by ~36% and the anti-apoptotic gene bcl-2 being increased by ~100%. It has been reported that the oxidative response involved in apoptosis is related to the PD process. Therefore, these findings suggest that esculetin may affect the expression of genes involved in apoptosis, providing further insights into its neuroprotective effects in PD.

Source Publication

International Conference on BIOMED-2024 Biomedical Engineering and Biotechnology, Aug 2024, Webinar

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