N-acetylcysteine (NAC), a plant antioxidant naturally found in onion, is a precursor to glutathione. It has been used as a drug since the 1960s and is listed on the World Health Organization (WHO) Model List of Essential Medicines as an antidote in poisonings. There are numerous other uses or proposed uses in medicine that are still in preclinical and clinical investigations. NAC is also used in food supplements and cosmetics. Despite its abundant use, there are projections that the NAC global market will grow in the next five years; therefore, the purpose of this work is to provide a balanced view of further uses of NAC as a dietary supplement. Although NAC is considered a safe substance, the results among clinical trials are sometimes controversial or incomplete, like for many other antioxidants. More clinical trials are underway that will improve our understanding of NAC applicability.

Antipsychotics used to treat schizophrenia can cause drug-induced liver injury (DILI), according to the Roussel Uclaf Causality Assessment Method. The role of oxidative stress in triggering injury in these DILI cases is unknown. We repeatedly administrated two second-generation antipsychotics, aripiprazole and olanzapine, at laboratory alert levels to study underlying mechanisms in stress prevention upon acute oxidative stress. The drugs were administered continuously for up to 8 weeks. For this, hepatoma Fao cells, which are suitable for metabolic studies, were used, as the primary hepatocytes survive in the culture only for about 1 week. Four stress responses—the oxidative stress response, the DNA damage response and the unfolded protein responses in the endoplasmic reticulum and mitochondria—were examined in H₂O₂-treated cells by antioxidant enzyme activity measurements, gene expression and protein quantification. Oxidant conditions increased the activity of antioxidant enzymes and upregulated genes and proteins associated with oxidative stress response in aripiprazole-treated cells. While the genes associated with DNA damage response, Gadd45 and p21, were upregulated in both aripiprazole- and olanzapine-treated cells, only aripiprazole treatment was associated with upregulation in response to even more H₂O₂, which also coincided with better survival. Endoplasmic reticulum stress-induced Chop was also upregulated; however, neither endoplasmic reticulum nor mitochondrial unfolded protein response was activated. We conclude that only aripiprazole, but not olanzapine, protects liver cells against oxidative stress. This finding could be relevant for schizophrenia patients with high-oxidative-stress-risk lifestyles and needs to be validated in vivo.

Aripiprazole has fewer metabolic side effects than other antipsychotics; however, there are some severe ones in the liver, leading to drug-induced liver injury. Repeated treatment with aripiprazole affects cell division. Since this process requires a lot of energy, we decided to investigate the impact of aripiprazole on rat liver cells and mitochondria as the main source of cellular energy production by measuring the mitochondrial membrane potential, respiration, adenosine triphosphate (ATP) production, oxidative stress, antioxidative response, and human blood haemolysis. Here, we report that mitochondrial hyperpolarisation from aripiprazole treatment is accompanied by higher reactive oxygen species (ROS) production and increased antioxidative response. Lower mitochondrial and increased glycolytic ATP synthesis demand more glucose through glycolysis for equal ATP production and may change the partition between the glycolysis and pentose phosphate pathway in the liver. The uniform low amounts of the haemolysis of erythrocytes in the presence of aripiprazole in 25 individuals indicate lower quantities of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH+H⁺), which is in accordance with a decreased activity of glucose 6-phosphate dehydrogenase and the lower dehydrogenase activity upon aripiprazole treatment. The lower activity of glucose 6-phosphate dehydrogenase supports a shift to glycolysis, thus rescuing the decreased mitochondrial ATP synthesis. The putative reduction in NADPH+H⁺ did not seem to affect the oxidised-to-reduced glutathione ratio, as it remained equal to that in the untreated cells. The effect of aripiprazole on glutathione reduction is likely through direct binding, thus reducing its total amount. As a consequence, the low haemolysis of human erythrocytes was observed. Aripiprazole causes moderate perturbations in metabolism, possibly with one defect rescuing the other. The result of the increased antioxidant enzyme activity upon treatment with aripiprazole is increased resilience to oxidative stress, which makes it an effective drug for schizophrenia in which oxidative stress is constantly present because of disease and treatment.

Chronic administration of atypical antipsychotics (AAPs) is commonly associated with in-creased cardiovascular disease load. Although the increase in weight gain and related dis-ease risk is generally considered the main contributing factor, direct interference with mi-tochondrial bioenergetics, particularly in the liver, where these drugs are catabolized, is emerging as an additional relevant contributor to metabolic disease risk that needs to be considered. In this study, we compared the effects of two AAPs with disparate metabolic profiles, olanzapine (OLA), which is obesogenic, and aripiprazole (ARI), which is not, on the response of Fao cells to oxidative stress. We found that Fao cells treated with ARI sur-vive better a challenge with H2O2 while OLA treatment has the opposite effect. This en-hanced survival is not related to a reduction in the apoptosis rate. In fact, ARI treated cells display higher apoptotic rates than control cells exposed to H2O2. Gene expression analysis of pro and anti-apoptotic factors revealed that the changes induced by H2O2 were generally dampened in ARI treated cells, but not in OLA treated cells, suggesting a reduced respon-siveness to stimuli, a notion that was consistent with a reduced activation of MAPK and STAT3 phosphorylation in response to H2O2, while OLA enhanced their activation in re-sponse to H2O2. Loss of stress response in ARI treated cells is consistent with the elevation of mitochondrial production of O2•-, a known desensitizing factor. The physiological rele-vance of the increased production of O2•- in ARI treated cells is further supported by the observed elevation of the mitophagy flux in ARI treated cells, likely related to mitochon-drial damage. An additional relevant finding was that OLA treatment protected the pro-teasome activity in Fao cells exposed to H2O2, an effect possibly related to the better preservation of stress signaling and mitochondrial function in OLA treated cells. In sum, this study highlights the underlying alterations in cell physiology derived from the inter-ference of ARI with mitochondrial function, that de-sensitize cells to stress signaling, while OLA has the opposite effect.