Synergistic Neuroprotective Effect of Endogenously-Produced Hydroxytyrosol and Synaptic Vesicle Proteins on Pheochromocytoma Cell Line against Salsolinol

Abstract

Oxidative stress triggers a lethal cascade, leading to Parkinson’s disease by causing degeneration of dopaminergic neurons. In this study, eight antioxidants were screened for their neuroprotective effect on PC12 cells (pheochromocytoma cell line) under oxidative stress induced by salsolinol (OSibS). Hydroxytyrosol was found to be the strongest neuroprotective agent; it improved viability of PC12 cells by up to 81.69% under OSibS. Afterward, two synaptic vesicle proteins, synapsin-1 and septin-5, were screened for their neuroprotective role; the overexpression of synapsin-1 and the downregulation of septin-5 separately improved the viability of PC12 cells by up to 71.17% and 67.00%, respectively, compared to PC12 cells only treated with salsolinol (PoTwS) under OSibS. Subsequently, the PC12+syn++sep− cell line was constructed and pretreated with 100 µM hydroxytyrosol, which improved its cell viability by up to 99.03% and led to 14.71- and 6.37-fold reductions in the levels of MDA and H2O2, respectively, and 6.8-, 12.97-, 10.57-, and 7.57-fold increases in the activity of catalase, glutathione reductase, superoxide dismutase, and glutathione peroxidase, respectively, compared to PoTwS under OSibS. Finally, alcohol dehydrogenase-6 from Saccharomyces cerevisiae was expressed in PC12+syn++sep− cells to convert 3,4-dihydroxyphenylacetaldehyde (an endogenous neurotoxin) into hydroxytyrosol. The PC12+syn++sep−+ADH6+ cell line also led to 22.38- and 12.33-fold decreases in the production of MDA and H2O2, respectively, and 7.15-, 13.93-, 12.08-, and 8.11-fold improvements in the activity of catalase, glutathione reductase, superoxide dismutase, and glutathione peroxidase, respectively, compared to PoTwS under OSibS. Herein, we report the endogenous production of a powerful antioxidant, hydroxytyrosol, from 3,4-dihydroxyphenylacetaldehyde, and evaluate its synergistic neuroprotective effect, along with synapsin-1 and septin-5, on PC12 cells under OSibS.

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Role of Hydroxytyrosol and Oleuropein in the Prevention of Aging and Related Disorders: Focus on Neurodegeneration, Skeletal Muscle Dysfunction and Gut Microbiota

“…Similarly, a two-fold increase of cell viability occurred in PC12 cells overexpressing synapsin1 and with downregulation of septin-5 (synaptic vesicle proteins), treated with 100 μM HTyr, under oxidative stress triggered by salsolinol, a dopaminergic neurotoxin. This effect was accompanied by an increase of catalase (CAT), glutathione reductase (GR) and peroxidase (GPX), and SOD [ 249 ]. All these enzymes are antioxidant, since the GPX function is to reduce lipid hydroperoxides to alcohols and H 2 O 2 to water, CAT as well reduces H 2 O 2 to H 2 O, while GR catalyzes the formation of antioxidant GSH from GSSG, and SOD degrades superoxide molecules (O−2).…”

“…The figure depicts the activation by HTyr of Nrf2, which regulates several anti-oxidizing systems, and can thus be representative of the main antioxidant activity of HTyr. In red are the molecules demonstrated to be up- or down-regulated (NOX2) by HTyr [ 143 , 144 , 248 , 249 , 263 , 264 ].…”