Bicyclol improves cognition deficits and inhibits oxidative stress-induced neuronal cell apoptosis in alzheimer's disease via Nrf2/HO-1 pathway.

Alzheimer's disease (AD) is identified as the prevalent neurodegenerative condition globally, ultimately resulting in dementia. Currently, the mechanisms that contribute to AD are not well comprehended, and there are few therapeutic alternatives available. Bicyclol, a substance extracted from the Chinese herb Schisandra Chinensis, has shown remarkable antioxidant, anti-inflammatory, anti-apoptotic, and neuroprotective characteristics. However, there is a shortage of research focusing on the therapeutic effects of bicyclol on AD as well as the molecular pathways that may be involved. This study sought to evaluate the effects of bicyclol on cognitive impairments in a mouse model of AD, explore its neuroprotective benefits associated with antioxidant functions and apoptosis suppression, and reveal the mechanisms involved. In this study, APP/PS1 mice underwent a 2-month treatment with bicyclol administered via gavage, after which their cognitive abilities were evaluated through behavioral assessments. The apoptosis of cortical neurons was evaluated using TUNEL staining and immunofluorescence techniques. N2A cells, which were exposed to Aβ1-42 oligomers, received a pretreatment with bicyclol, and their viability was subsequently measured. The expression levels of proteins such as nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), NAD(P) H-quinine oxidoreductase-1 (NQO1), BCL2 associated X Protein (Bax), B-cell lymphoma-2 (Bcl-2), and Cleaved caspase-3 were quantified in vitro and in vivo using western blotting and qPCR methods. Moreover, N2A cells lacking Nrf2 were utilized to investigate the underlying mechanisms through which bicyclol exerts its effects in Alzheimer's disease. Bicyclol has been shown to enhance cognitive function while simultaneously reducing the levels of cortical Aβ1-40 and Aβ1-42, and it also protects against neuronal degeneration in the APP/PS1 mouse model. Moreover, it increases the activity of cortical SOD and GSH-Px, concurrently decreasing levels of ROS and MDA in vivo. Additionally, bicyclol significantly lessened oxidative stress and apoptosis induced by Aβ1-42 in N2A cells. It further elevated the expression of proteins such as Nrf2, HO-1, and NQO1, along with mRNA levels in both in vitro and in vivo experiments. Furthermore, the silencing of Nrf2 via siRNA transfection counteracted the regulatory effects of bicyclol on apoptotic markers including Bax, Bcl-2, and Cleaved caspase-3 in vitro. Our study provides compelling evidence that bicyclol effectively alleviates cognitive impairments observed in APP/PS1 mice. Furthermore, our findings indicate that bicyclol plays a significant role in reducing oxidative stress-induced injury and neuronal apoptosis. This protective effect is associated with the activation of the Nrf2/HO-1 signaling pathway. These results suggest that bicyclol has the potential to be developed as a therapeutic agent for the treatment of Alzheimer's disease, highlighting its promise in addressing the cognitive decline associated with this debilitating condition.