L-NAME has opposite effects on the productions of S-adenosylhomocysteine and S-adenosylmethionine in V12-H-Ras and M-CR3B-Ras pheochromocytoma cells

Papaya epicarp extract protects against aluminum-induced neurotoxicity

In a previous study, we demonstrated the ability of papaya epicarp extract (PEE) to protect against oxidative stress-induced insult in human SH-SY5Y neuronal cells in a mechanism that appeared to be by means of PEE potent antioxidant properties. To further understand this relationship, we examined the effect of PEE intervention on aluminum (Al)-induced cytotoxicity in SH-SY5Y cells. The results indicated that PEE was effective in protecting against Al-induced cell death in a dose-dependent manner. PEE restored the Al-induced inhibition of folate-dependent methionine synthase activity and the antioxidant enzymes (catalase, glutathione peroxidases and superoxide dismutase). PEE ameliorated the Al-induced impairment of intracellular glutathione and total antioxidant capacity. Together, these findings indicate that PEE supplementation can play a neuroprotective role in ameliorating the changes in redox status of SH-SY5Y cells exposed to Al, a well-known environmental toxin that is involved in the pathogenesis of neurodegenerative diseases and neurodevelopmental disorders.

Oxidative stress modulates DNA methylation during melanocyte anchorage blockade associated with malignant transformation

Both oxidative/nitrosative stress and alterations in DNA methylation are observed during carcinogenesis of different tumor types, but no clear correlation between these events has been demonstrated until now. Melanoma cell lines were previously established after submitting the nontumorigenicmelanocyte lineage, melan-a, to cycles of anchorage blockade. In this work, increased intracellular oxidative species and nitric oxide levels, as well as alterations in the DNA methylation, were observed after melan-a detachment, which were also associated with a decrease in intracellular homocysteine (Hcy), an element in the methionine (universal methyl donor) cycle. This alteration was accompanied by increase in glutathione (GSH) levels and methylated DNA content. Furthermore, a significant increase in dnmt1 and 3b expression was identified along melan-a anchorage blockade. L(G)-Nitro-L-arginine methyl esther (L-NAME), known as a nitric oxide synthase (NOS) inhibitor, and N-acetyl-L-cysteine (NAC) prevented the increase in global DNA methylation, as well as the increase in dnmt1 and 3b expression, observed during melan-a detachment. Interestingly, both L-NAME and NAC did not inhibit nitric oxide (NO) production in these cells, but abrogated superoxide anion production during anchorage blockade. In conclusion, oxidative stress observed during melanocyte anchorage blockade seems to modulate DNA methylation levels and may directly contribute to the acquisition of an anoikis-resistant phenotype through an epigenetic mechanism.