Erinacine A Prevents Lipopolysaccharide-Mediated Glial Cell Activation to Protect Dopaminergic Neurons against Inflammatory Factor-Induced Cell Death In Vitro and In Vivo

Hericium erinaceus (HE) is a common edible mushroom consumed in several Asian countries and considered to be a medicinal mushroom with neuroprotective effects. Erinacine A (EA) is a bioactive compound in Hericium erinaceus mycelium (HEM) that has been shown to have a neuroprotective effect against neurodegenerative diseases, e.g., Parkinson’s disease (PD). Although the etiology of PD is still unclear, neuroinflammation may play an important role in causing dopaminergic neuron loss, which is a pathological hallmark of PD. However, glial cell activation has a close relationship with neuroinflammation. Thus, this study aimed to investigate the anti-neuroinflammatory and neuroprotective effects of EA on lipopolysaccharide (LPS)-induced glial cell activation and neural damage in vitro and in vivo. For the in vitro experiments, glial cells, BV-2 microglial cells and CTX TNA2 astrocytes were pretreated with EA and then stimulated with LPS and/or IFN-γ. The expression of proinflammatory factors in the cells and culture medium was analyzed. In addition, differentiated neuro-2a (N2a) cells were pretreated with EA or HEM and then stimulated with LPS-treated BV-2 conditioned medium (CM). The cell viability and the amount of tyrosine hydroxylase (TH) and mitogen-activated protein kinases (MAPKs) were analyzed. In vivo, rats were given EA or HEM by oral gavage prior to injection of LPS into the substantia nigra (SN). Motor coordination of the rats and the expression of proinflammatory mediators in the midbrain were analyzed. EA pretreatment prevented LPS-induced iNOS expression and NO production in BV-2 cells and TNF-α expression in CTX TNA2 cells. In addition, both EA and HEM pretreatment significantly increased cell viability and TH expression and suppressed the phosphorylation of JNK and NF- κB in differentiated N2a cells treated with CM. In vivo, both EA and HEM significantly improved motor dysfunction in the rotarod test and the amphetamine-induced rotation test and reduced the expression of TNF-α, IL-1β and iNOS in the midbrain of rats intranigrally injected with LPS. The results demonstrate that EA ameliorates LPS-induced neuroinflammation and has neuroprotective properties.

Erinacine A-Enriched Hericium erinaceus Mycelium Delays Progression of Age-Related Cognitive Decline in Senescence Accelerated Mouse Prone 8 (SAMP8) Mice

There have been many reports on the neuroprotective effects of Hericium erinaceus mycelium, in which the most well-known active compounds found are diterpenoids, such as erinacine A. Previously, erinacine A-enriched Hericeum erinaceus mycelium (EAHEM) was shown to decrease amyloid plaque aggregation and improve cognitive disability in Alzheimer’s disease model APP/PS1 mice. However, its effects on brain aging have not yet been touched upon. Here, we used senescence accelerated mouse prone 8 (SAMP8) mice as a model to elucidate the mechanism by which EAHEM delays the aging of the brain. Three-month-old SAMP8 mice were divided into three EAHEM dosage groups, administered at 108, 215 and 431 mg/kg/BW/day, respectively. During the 12th week of EAHEM feeding, learning and memory of the mice were evaluated by single-trial passive avoidance and active avoidance test. After sacrifice, the amyloid plaques, induced nitric oxidase synthase (iNOS) activity, thiobarbituric acid-reactive substances (TBARS) and 8-OHdG levels were analyzed. We found that the lowest dose of 108 mg/kg/BW EAHEM was sufficient to significantly improve learning and memory in the passive and active avoidance tests. In all three EAHEM dose groups, iNOS, TBARS and 8-OHdG levels all decreased significantly and showed a dose-dependent response. The results indicate that EAHEM improved learning and memory and delayed degenerative aging in mice brains.

Enhanced Erinacine A Production by Hericium erinaceus Using Solid-State Cultivation

Hericium erinaceus (HE) is a large edible medicinal fungus. Erinacine A (ErA) is a secondary metabolite presented in the mycelia of HE, with pharmacological effects as a nerve growth factor on the central nervous system. In this study, solid-state cultivation of HE was carried out in Petri dishes and glass jars for the production of mycelial biomass and ErA. The potato dextrose agar (PDA) had the highest mycelial biomass at an optimal temperature of 25 °C, but no ErA was found in the agar media. In glass jar cultivation, the mycelial biomass and specific yield of ErA in different substrates, particle sizes, substrate weights, nitrogen sources, and inorganic salts were investigated. The ErA was purified by a self-pack silica gel column and a semi-preparative HPLC and was identified by liquid chromatography-tandem mass spectrometer. The best conditions for solid-state cultivation of HE when using corn kernel as substrate, particle size less than 2.38 mm, and addition of 10mM ZnSO4, 7H2O, mycelial biomass of 50.24 mg cell dry weight/g substrate was obtained, in addition, the specific yield of ErA could reach 165.36 mg/g cell dry weight.

Preclinical Bioavailability, Tissue Distribution, and Protein Binding Studies of Erinacine A, a Bioactive Compound from Hericium erinaceus Mycelia Using Validated LC-MS/MS Method

Erinacine A, derived from the mycelia of Hericium erinaceus, has attracted much attention due to its neuroprotective properties. However, very few studies have been conducted on the bioavailability, tissue distribution, and protein binding of erinacine A. This study aimed to investigate the bioavailability, tissue distribution, and protein binding of erinacine A in Sprague-Dawley rats. After oral administration (po) and intravenous administration (iv) of 2.381 g/kg BW of the H. erinaceus mycelia extract (equivalent to 50 mg/kg BW of erinacine A) and 5 mg/kg BW of erinacine A, respectively, the absolute bioavailability of erinacine A was estimated as 24.39%. Erinacine A was detected in brain at 1 h after oral dosing and reached the peak at 8 h. Protein binding assay showed unbound erinacine A fractions in brain to blood ratio is close to unity, supporting passive diffusion as the dominating transport. Feces was the major route for the elimination of erinacine A. This study is the first to show that erinacine A can penetrate the blood-brain barrier of rats by the means of passive diffusion and thus support the development of H. erinaceus mycelia for the improvement of neurohealth.

Neuroprotective Metabolites of Hericium erinaceus Promote Neuro-Healthy Aging

Frailty is a geriatric syndrome associated with both locomotor and cognitive decline, typically linked to chronic systemic inflammation, i.e., inflammaging. In the current study, we investigated the effect of a two-month oral supplementation with standardized extracts of H. erinaceus, containing a known amount of Erinacine A, Hericenone C, Hericenone D, and L-ergothioneine, on locomotor frailty and cerebellum of aged mice. Locomotor performances were monitored comparing healthy aging and frail mice. Cerebellar volume and cytoarchitecture, together with inflammatory and oxidative stress pathways, were assessed focusing on senescent frail animals. H. erinaceus partially recovered the aged-related decline of locomotor performances. Histopathological analyses paralleled by immunocytochemical evaluation of specific molecules strengthened the neuroprotective role of H. erinaceus able to ameliorate cerebellar alterations, i.e., milder volume reduction, slighter molecular layer thickness decrease and minor percentage of shrunken Purkinje neurons, also diminishing inflammation and oxidative stress in frail mice while increasing a key longevity regulator and a neuroprotective molecule. Thus, our present findings demonstrated the efficacy of a non-pharmacological approach, based on the dietary supplementation using H. erinaceus extract, which represent a promising adjuvant therapy to be associated with conventional geriatric treatments.

Retraction Note to: Hericium erinaceus mycelium and its isolated erinacine A protection from MPTP-induced neurotoxicity through the ER stress, triggering an apoptosis cascade

This article has been retracted. Please see the Retraction Notice for more detail: https://doi.org/10.1186/s12967-016-0831-y.

Chemical studies on bioactive compounds related to higher fungi

Hericium erinaceus (Yamabushitake in Japan) is a well-known edible and medicinal mushroom. We discovered antidementia compounds, hericenones C to H, from the fruiting bodies and erinacine A to I from the cultured mycelia of the fungus. Based on the data of the compounds, several clinical experiments were performed using the fungus. “Fairy rings” is a phenomenon that turfgrass grows more prolific or inhibited than the surrounding area as a ring and then occasionally mushrooms develop on the ring. We found fairy-ring causing principles “fairy chemicals” and the biosynthetic routes of the compounds on the purine metabolic pathway in plants and mushrooms.

Optimization of Ultrasonic Extraction to Obtain Erinacine A and Polyphenols with Antioxidant Activity from the Fungal Biomass of Hericium erinaceus

Hericium erinaceus is a medicinal fungal species that produces the active biological metabolite erinacine A with strong antioxidant activity. The classical extraction techniques used to date to obtain metabolites from this fungal species require high consumption of resources and energy and, in the end, prove to be expensive and inefficient, especially on a biomedical scale. The aim of this research is based on the development of an ultrasonic extraction (UE) method for the identification and extraction of biological compounds with high antioxidant activity from the mycelia of H. erinaceus biomass developed through a solid cultivation process. The extraction process was optimized by varying parameters to determine the best extraction yield of metabolites involved in such antioxidant activity, using the response surface methodology (RSM). The physicochemical analyses were oriented towards the investigation of polyphenols, flavonoids, and the diterpenoid erinacine A. It is highlighted that there is a very good mutual connection between the concentration of polyphenols and flavonoids in the extracts studied and the diterpenoid erinacine A. Also, this study describes an efficient and qualitative extraction method for extracting natural antioxidants from the H. erinaceus mushroom, since toxic solvents were not used in the developed extraction procedure. This biomass can be used both as a food source and as a possible phytotherapeutic tool in the prevention or treatment of various neurodegenerative disorders that require drugs with strong antioxidant activity.