Melissa officinalis Acidic Fraction Protects Cultured Cerebellar Granule Neurons Against Beta Amyloid-Induced Apoptosis and Oxidative Stress.

Abstract

Extracellular deposition of the beta-amyloid (Aβ) peptide, which is the main finding in the pathophysiology of Alzheimer's disease (AD), leads to oxidative damage and apoptosis in neurons. Melissa officinalis (M. officinalis) is a medicinal plant from the Lamiaceae family that has neuroprotective activity. In the present study we have investigated the protective effect of the acidic fraction of M. officinalis on Aβ-induced oxidative stress and apoptosis in cultured cerebellar granule neurons (CGN). Additionally, we investigated a possible role of the nicotinic receptor. This study was an in vitro experimental study performed on mice cultured CGNs. CGNs were pre-incubated with different concentrations of the acidic fraction of M. officinalis for 24 hours, followed by incubation with Aβ for an additional 48 hours. CGNs were also pre-incubated with the acidic fraction of M. officinalis and mecamylamin, followed by incubation with Aβ. We used the 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay to measure cell viability. Acetylcholinesterase (AChE) activity, reactive oxygen species (ROS) production, lipidperoxidation, and caspase-3 activity were measured after incubation. Hochst/annexin Vfluorescein isothiocyanate (FITC)/propidium iodide (PI) staining was performed to detect apoptotic cells. The acidic fraction could protect CGNs from Aβ-induced cytotoxicity. Mecamylamine did not abolish the protective effect of the acidic fraction. AChE activity, ROS production, lipid peroxidation, and caspase-3 activity increased after Aβ incubation. Preincubation with the acidic fraction of M. officinalis ameliorated these factors and decreased the number of apoptotic cells. Our results indicated that the protective effect of the acidic fraction of M. officinalis was not mediated through nicotinic receptors. This fraction could protect CGNs through antioxidant and anti-apoptotic activities.