Study On The Effect Of Vanillic Acid On Alleviating The Damage Of Prion-infected SMB-S15 Cells

Prion diseases are types of neurodegenerative diseases that affect the central nervous system of human and many animals,with long incubation period and 100%fatality rate.Studies have shown that prion infection is accompanied by oxidative stress,endoplasmic reticulum stress,autophagy and mitochondrial dysfunction.Up to now,efficacious therapeutic drugs or prophylactic vaccines are not available.Vanillic acid is a kind of phenolic acid compound isolated and purified from Inonotus obliquus.Studies revealed that vanillic acid has antioxidant,anti-inflammatory,antibacterial and anticancer pharmacological activities,and is a potential treatment for Alzheimer’s disease.However,it has not been reported whether vanillic acid has similar neuroprotective effect in prion diseases.To investigate the inhibitory effect of vanillic acid with strong antioxidant activity and neuroprotection on prion deposition and to relieve nerve cell injury,multiple methods were utilized.Using cell counting kit-8 and lactate dehydrogenase assay methods to determine the maximum concentration of vanillic acid-treated cells as 10μM.SMB-S15 cells were treated with vanillic acid,western blots showed that the PrP^Sc level in SMB-S15 cells was reduced significantly after incubation with vanillic acid（10μM）for 14 days.Meanwhile,levels of reactive oxygen species and hydrogen peroxide were reduced in a dose-dependent manner,whereas levels of some antioxidant factors,such as heme oxygenase-1（HO-1）,glutamate-cysteine ligase catalytic subunit（GCLC）and glutamate-cysteine ligase modifier subunit（GCLM）,were increased significantly.Furthermore,the activities of total glutathione and superoxide dismutase were increased.Vanillic acid-treated SMB-S15 cells showed up-regulation of expression of unfolded protein response（UPR）-related proteins,including protein kinase R（PKR）-like endoplasmic reticulum kinase（PERK）,inositol-requiring enzyme1α（IRE1α）,activating transcription factor 6（ATF6）,glucose-regulated protein 78（GRP78）,and activation of the autophagy system.The abnormalities in sirtuin-3 expression caused by prion infection were relieved by vanillic acid treatment.Nevertheless,under the same experimental conditions,the normal control cell SMB-PS cells were treated with vanillic acid,and the above-mentioned obvious changes were not found.This study shows that vanillic acid can reduce the level of PrP^Sc in prion-infected cells,activate UPR and autophagy system,and alleviate intracellular oxidative stress,endoplasmic reticulum stress and mitochondrial dysfunction by increasing the level of various antioxidant factors,which has a protective effect on cells.Our study may provide new research targets and treatment ways for prion diseases.