Dilinoleoyl-phosphatidylethanolamine from Hericium erinaceum protects against ER stress-dependent Neuro2a cell death via protein kinase C pathway.

In many types of neurodegeneration, neuronal cell death is induced by endoplasmic reticulum (ER) stress. Hence, natural products able to reduce ER stress are candidates for use in the attenuation of neuronal cell death and, hence, in the reduction of the damage, which occurs in neurodegenerative disease. In this study, we investigated ER stress-reducing natural products from an edible mushroom, Hericium erinaceum. As a result of screening by cell viability assay on the protein glycosylation inhibitor tunicamycin-induced (i.e., ER stress-dependent) cell death, we found that dilinoleoyl-phosphatidylethanolamine (DLPE) was one of the molecules effective at reducing ER stress-dependent cell death in the mouse neuroblastoma cell line Neuro2a cells. A purified DLPE, commercially available, also exhibited a reducing effect on this ER stress-dependent cell death. Therefore, we concluded that DLPE has potential as a protective molecule in ER stress-induced cell death. From the structure of DLPE, it was hypothesized that it might activate protein kinase C (PKC). The activity of PKC-epsilon, a novel-type PKC, was increased by adding DLPE, and PKC-gamma, a conventional-type PKC, was activated on the coaddition of diolein and DLPE, as shown by in vitro enzyme activity analysis. The protecting activity of DLPE was attenuated in the presence of a PKC inhibitor GF109203X but not completely diminished. Therefore, DLPE can protect neuronal cells from ER stress-induced cell death, at least in part by the PKC pathway.

Epigenetic disregulation induces cell growth retardation in primary cultured glial cells.

Some epigenetic mechanisms, including DNA methylation and histone deacetylation, act as transcriptional repression signals. In this study, we examined whether DNA methylation dependent transcriptional control regulates glial cell growth. Primary cultured mouse cortical glial cells were treated with the DNA methylation inhibitor 5-aza-deoxycytidine (5adC) or the histone deacetylase inhibitor sodium valproate (VPA), which inhibits DNA-methylation-dependent transcriptional repression. 5adC significantly reduced methylated C level determined by reversed-phase high-performance liquid chromatography (HPLC), while VPA did not. Treatments with these inhibitors significantly reduced cell number determined by MTT assay after 48 h. Both 5adC and VPA showed little cellular toxicity observed by live and dead cell staining. In contrast, both 5adC and VPA induced an abnormality in the cell cycle. Cells treated with the inhibitors represented a significantly higher ratio in the G2+M-phase and 5adC-treated cells showed a significantly lower ratio in the S-phase. Regarding the in vivo effect, prenatal treatment with VPA, which is an autistic model in rodents, significantly reduced the brain/body weight ratio in early postnatal days. Our data indicate that DNA-methylation- and histone-deacetylation-dependent transcriptional control is crucial for the regulation of glial cell growth. Our data suggest that abnormalities of epigenetic transcriptional regulatory mechanisms in glial cells cause an abnormal brain size, which may in turn cause mental diseases.