s-adenosylhomocysteine and Nerve-Degeneration

Previously, we reported that isoflavones exert a protective effect against the endoplasmic reticulum (ER) stress-mediated neuronal degeneration, and ER stress-mediated homocysteine toxicity may play an important role in the pathogenesis of neurodegeneration. Therefore, in this study we investigated the effects of isoflavones (genistein and daidzein) against homocysteine-mediated neurotoxicity in SH-SY5Y human neuroblastoma cells. The treatment of cells with either 17beta-estradiol or isoflavones significantly protected the cells against homocysteine-mediated apoptosis. Isoflavones repressed homocysteine-mediated ER stress, reflected in the reduced expression of the immunoglobin heavy chain-binding protein mRNA, spliced X-box-protein-1 mRNA and the phosphorylated form of eukaryotic translation initiation factor 2alpha protein. Homocysteine caused significant increases in intracellular S-adenosylhomocysteine (SAH) and DNA damage. Isoflavones significantly alleviated DNA damage, but did not change SAH levels. Furthermore, the treatment of cells with isoflavones significantly reduced the microtubule-associated protein tau hyperphosphorylation by inactivating glycogen synthase kinase-3beta and activating serine/threonine-protein phosphatase 2A. These results clearly demonstrate that isoflavones alleviate the ER stress- and DNA damage-mediated neurodegeneration caused by homocysteine.

Topics: Alzheimer Disease; Apoptosis; Cell Line, Tumor; Endoplasmic Reticulum; Homocysteine; Humans; Isoflavones; Nerve Degeneration; Neurons; Protective Agents; S-Adenosylhomocysteine

Increased concentrations of plasma total homocysteine (tHcy) have been associated with age-related diseases, including dementia, stroke, and Parkinson disease (PD). Methylation status might link Hcy metabolism to neurodegenerative proteins in patients with PD.. We tested blood samples from 87 patients with PD (median age 68 years; 35 men) for tHcy, methylmalonic acid (MMA), vitamin B(12), vitamin B(6), folate, S-adenosyl methionine (SAM), S-adenosyl homocysteine (SAH), and amyloid-beta(1-42). We collected citrate blood from a subset of 45 patients to prepare platelet-rich plasma, and we used washed platelets to prepare cell extracts for amyloid precursor protein (APP) and alpha-synuclein assays. We used brain parenchyma sonography to estimate the substantia nigra echogenic area in a subset of 59 patients.. Serum concentrations of tHcy were increased in PD patients (median 14.8 micromol/L). tHcy (beta coefficient = -0.276) and serum creatinine (beta = -0.422) were significant predictors of the ratio of SAM/SAH in plasma (P < 0.01). The plasma SAM/SAH ratio was a significant determinant for DemTect scores (beta = 0.612, P = 0.004). Significant negative correlations were found between concentrations of SAH in plasma and platelet APP and between SAM and platelet alpha-synuclein. A larger echogenic area of the substantia nigra was related to higher serum concentrations of MMA (P = 0.016).. Markers of neurodegeneration (APP, alpha-synuclein) are related to markers of methylation (SAM, SAH) in patients with PD. Better cognitive function was related to higher methylation potential (SAM/SAH ratio).

Topics: Aged; alpha-Synuclein; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Biomarkers; Blood Platelets; Cognition Disorders; Female; Folic Acid; Homocysteine; Humans; Male; Methylation; Middle Aged; Nerve Degeneration; Parkinson Disease; Peptide Fragments; S-Adenosylhomocysteine; S-Adenosylmethionine; Substantia Nigra; Ultrasonography; Vitamin B 6

We investigated the effect of S-adenosyl-L-methionine (SAMe) on the prevention of the delayed neuronal death in rats subjected to transient and brief forebrain ischemia. As the results, SAMe dose-dependently protected the hippocampal CA1 neurons from degeneration and necrosis, whose effect was suppressed by simultaneous administration of S-adenosyl-L-homocysteine, a potent inhibitor in transmethylation. No protective effect was observed in CDP-choline, phosphatidylcholine and L-methionine. Therefore, it is necessary for the prevention of the delayed neuronal death to enhance cerebral SAMe level and to activate transmethylation using SAMe as a methyl donor in postischemic brain.

Topics: Animals; Cell Membrane; Cell Survival; Cytidine Diphosphate Choline; Hippocampus; Ischemic Attack, Transient; Male; Methionine; Methylation; Necrosis; Nerve Degeneration; Neurons; Phosphatidylcholines; Rats; Rats, Inbred Strains; S-Adenosylhomocysteine; S-Adenosylmethionine