Therapeutic potential of the novel compound N-acetylcysteine ethyl ester (NACET) in modulate plasma thiols and homocysteine levels

Hyperhomocysteinemia (HH) is a condition characterized by a high plasma concentration of homocysteine (HCys), a cysteine metabolite (Cys), which has proven to be a risk factor for a wide range of cardiovascular, neurological, and metabolic diseases. Among the variants of HH, the mild form (mHH) represents an important subgroup that, although less severe, can still significantly contribute to the risk of cardiovascular and neurodegenerative diseases. One of the mechanisms by which HH can exert its harmful effects is the reduction of glutathione levels (GSH), an important endogenous antioxidant mechanism involved in protecting cells from oxidative damage. The use of therapeutic strategies based on the administration of B vitamins to reduce circulating levels of HCys has produced conflicting results on their real effectiveness. Therefore, the attention of the scientific community has focused on new more decisive alternatives. In this current work, our initial aim was to assess plasma levels of HCys in a meticulously chosen cohort, while diligently mitigating potential confounding variables. Specifically, we restricted sample collection to a three-month timeframe (April-June) to minimize seasonal variations in fruit and vegetable availability that could influence outcomes. Additionally, we limited the age range of participants to 20 years, recognizing the well-established impact of age on HCys levels, and implemented selection criteria based on dietary habits, alcohol consumption, and other pertinent factors. Stemming from the observation that an increase in plasmatic low molecular weight thiol is associated with a decrease in circulating homocysteine, we posited the hypothesis that homocysteine itself may not be inherently detrimental to the cardiovascular system, but rather serves as a biomarker indicating underlying physiological irregularities. Our results showed an inverse correlation between circulating LMW-SH and HCys levels. Through other in vitro studies, a series of experiments have been carried out to highlight cellular and/or tissue participation in GSH efflux. Therefore, we have carried out comparative studies with several pro-Cys drugs to evaluate and analyze their effectiveness in increasing intracellular synthesis and GSH efflux. In this context, the administration of N-acetylcysteine ethyl ester (NACET), a pro-Cys drug, emerges as a promising strategy to modulate GSH levels and reduce the novel effects of HH lowering the plasmatic HCys levels. This paper aims to examine the role of NACET in modulating GSH levels through a series of experiments aimed at identifying the parameters that are used to describe a human’s thiolome, this part was performed on blood samples from a group of healthy subjects. Our attention then focused on an in vitro study in which blood samples were subjected to oxidative stimuli to analyze other biomarkers of oxidative stress (malondialdehyde and protein carbonyls). Finally, studies have been carried out on how NACET can influence the synthesis and release of GSH and modulate the levels of circulating plasma HCys through in vitro experiments on cell cultures or blood samples comparing its effectiveness with other thiol compounds.