Neuroprotective Effects of Extracts from Tiger Milk Mushroom Lignosus rhinocerus Against Glutamate-Induced Toxicity in HT22 Hippocampal Neuronal Cells and Neurodegenerative Diseases in Caenorhabditis elegans

Abstract

Despite the Tiger Milk Mushroom Lignosus rhinocerus (LR) having been used as a traditional medicine, little is known about the neuroprotective effects of LR extracts. This study aims to investigate the neuroprotective effect of three extracts of LR against glutamate-induced oxidative stress in mouse hippocampal (HT22) cells as well as to determine their effect in Caenorhabditis elegans. In vitro, we assessed the toxicity of three LR extracts (ethanol extract (LRE), cold-water extract (LRC) and hot-water extract (LRH)) and their protective activity by MTT assay, Annexin V-FITC/propidium iodide staining, Mitochondrial Membrane Potential (MMP) and intracellular ROS accumulation. Furthermore, we determined the expression of antioxidant genes (catalase (CAT), superoxide dismutase (SOD1 and SOD2) and glutathione peroxidase (GPx)) by qRT-PCR. In vivo, we investigated the neuroprotective effect of LRE, not only against an Aβ-induced deficit in chemotaxis behavior (Alzheimer model) but also against PolyQ40 formation (model for Morbus Huntington) in transgenic C. elegans. Only LRE significantly reduced both apoptosis and intracellular ROS levels and significantly increased the expression of antioxidant genes after glutamate-induced oxidative stress in HT22 cells. In addition, LRE significantly improved the Chemotaxis Index (CI) in C. elegans and significantly decreased PolyQ40 aggregation. Altogether, the LRE exhibited neuroprotective properties both in vitro and in vivo.

Extracts of the Tiger Milk Mushroom (Lignosus rhinocerus) Enhance Stress Resistance and Extend Lifespan in Caenorhabditis elegans via the DAF-16/FoxO Signaling Pathway

“…Our study confirms a previous report showing that an ethanol extract of LR (LRE) exerted the highest antioxidant activity in vitro via DPPH and ABTS free radical scavenging capacity [15,42]. The bioactive compounds of LRE identified by GLC-MS, including phenol, oleic acid, linoleic acid, and ethyl ester, as shown in Table 2, have been reported to have antioxidant properties [27,43,44]. These phytochemical constituents are similar to the LC-MS results from our research group [16] and the GLC-MS data from other findings [12,13,45].…”

Neuroprotective Effects against Glutamate-Induced HT-22 Hippocampal Cell Damage and Caenorhabditis elegans Lifespan/Healthspan Enhancing Activity of Auricularia polytricha Mushroom Extracts

“…Although glutamate plays an essential role in neurotransmitters, a high glutamate level in the brain shows a risk of NDDs [16,28]. Several edible mushroom-derived products have been reported to attenuate glutamate-induced neurotoxicity [29][30][31]. Our study found that APE and APH could decrease the toxicity of glutamate on HT-22 cells.…”

“…Herein, we demonstrated that exposure to high-concentration of glutamate could exert antioxidant mechanisms by decreasing antioxidant enzymes and increasing oxidative stress, leading to neuronal damage [31,38]. In contrast, the treatment of NAC could attenuate the effects of glutamate.…”

“…Previous studies have shown that the ethanolic extracts of Streblus asper, Aquilariae lignum, and Vitis vinifera decreased intracellular ROS accumulation and protected against neuronal death in glutamate-induced HT-22 cells [18,32,33]. Ethanolic extract of tiger milk mushroom (Lignosus rhinocerus) presented high potential in neuroprotection against glutamate-induced cell damage, while cold and hot water extracts from this mushroom provided the unnoticeable neuroprotective effect [31].…”

“…It has been reported that natural compounds isolated from plants and mushrooms, such as Camellia sinensis, Anacardium occidentale L., Lignosus rhinocerus, and Glochidion zeylanicum, could upregulate the mRNA expressions of antioxidant enzymes. In addition, these extracts could provide the cells with neuroprotection from glutamate-induced neuronal damage [31,36,41,42].…”