Effect of single dose N-acetylcysteine administration on resting state functional connectivity in schizophrenia

Nutrition and schizophrenia: associations worthy of continued revaluation

BACKGROUND

Accumulating evidence have shown that diet and nutrition play significant roles in mental illness, such as depression, anxiety and bipolar disorder. However, comprehensive evaluation of the relationship between nutrition and schizophrenia is lacking.

OBJECTIVE

The present review aims to synthetic elaborate the associations between nutrition and schizophrenia. Relevant studies on dietary patterns, macronutrients, micronutrients were performed through a literature search to synthesize the extracted data.

SUMMARY

Dietary interventions may help prevent the occurrence of schizophrenia, or delay symptoms: Healthy diets like nutritious plant-based foods and high-quality protein, have been linked to reducing the risk or symptoms of schizophrenia. Moreover, diet high in saturated fat and sugar is linked to more serious outcomes of schizophrenia. Additionally, when N-acetylcysteine acts as an adjuvant therapy, the overall symptoms of schizophrenia are significantly reduced. Also nascent evidence showed mental disorders may be related to intestinal microbiota dysfunction. Our study offered important insights into the dietary habits of patients with schizophrenia and the potential impact of nutritional factors on the disease. We also emphasized the need for further research, particularly in the form of large randomized double-blind controlled trials, to better understand the effects of nutrients on schizophrenia symptoms in different populations and disease types.

Caught in vicious circles: a perspective on dynamic feed-forward loops driving oxidative stress in schizophrenia

A growing body of evidence has emerged demonstrating a pathological link between oxidative stress and schizophrenia. This evidence identifies oxidative stress as a convergence point or "central hub" for schizophrenia genetic and environmental risk factors. Here we review the existing experimental and translational research pinpointing the complex dynamics of oxidative stress mechanisms and their modulation in relation to schizophrenia pathophysiology. We focus on evidence supporting the crucial role of either redox dysregulation, N-methyl-D-aspartate receptor hypofunction, neuroinflammation or mitochondria bioenergetics dysfunction, initiating "vicious circles" centered on oxidative stress during neurodevelopment. These processes would amplify one another in positive feed-forward loops, leading to persistent impairments of the maturation and function of local parvalbumin-GABAergic neurons microcircuits and myelinated fibers of long-range macrocircuitry. This is at the basis of neural circuit synchronization impairments and cognitive, emotional, social and sensory deficits characteristic of schizophrenia. Potential therapeutic approaches that aim at breaking these different vicious circles represent promising strategies for timely and safe interventions. In order to improve early detection and increase the signal-to-noise ratio for adjunctive trials of antioxidant, anti-inflammatory and NMDAR modulator drugs, a reverse translation of validated circuitry approach is needed. The above presented processes allow to identify mechanism based biomarkers guiding stratification of homogenous patients groups and target engagement required for successful clinical trials, paving the way towards precision medicine in psychiatry.

Recent Reports on Redox Stress-Induced Mitochondrial DNA Variations, Neuroglial Interactions, and NMDA Receptor System in Pathophysiology of Schizophrenia

Schizophrenia (SZ) is a chronic psychiatric disorder affecting several people worldwide. Mitochondrial DNA (mtDNA) variations could invoke changes in the OXPHOS system, calcium buffering, and ROS production, which have significant implications for glial cell survival during SZ. Oxidative stress has been implicated in glial cells-mediated pathogenesis of SZ; the brain comparatively more prone to oxidative damage through NMDAR. A confluence of scientific evidence points to mtDNA alterations, Nrf2 signaling, dynamic alterations in dorsolateral prefrontal cortex (DLPFC), and provocation of oxidative stress that enhance pathophysiology of SZ. Furthermore, the alterations in excitatory signaling related to NMDAR signaling were particularly reported for SZ pathophysiology. Current review reported the recent evidence for the role of mtDNA variations and oxidative stress in relation to pathophysiology of SZ, NMDAR hypofunction, and glutathione deficiency. NMDAR system is influenced by redox dysregulation in oxidative stress, inflammation, and antioxidant mediators. Several studies have demonstrated the relationship of these variables on severity of pathophysiology in SZ. An extensive literature search was conducted using Medline, PubMed, PsycINFO, CINAHL PLUS, BIOSIS Preview, Google scholar, and Cochrane databases. We summarize consistent evidence pointing out a plausible model that may elucidate the crosstalk between mtDNA alterations in glial cells and redox dysregulation during oxidative stress and the perturbation of NMDA neurotransmitter system during current therapeutic modalities for the SZ treatment. This review can be beneficial for the development of promising novel diagnostics, and therapeutic modalities by ascertaining the mtDNA variations, redox state, and efficacy of pharmacological agents to mitigate redox dysregulation and augment NMDAR function to treat cognitive and behavioral symptoms in SZ.

The Potential of N-Acetyl-L-Cysteine (NAC) in the Treatment of Psychiatric Disorders

N-acetyl-L-cysteine (NAC) is a compound of increasing interest in the treatment of psychiatric disorders. Primarily through its antioxidant, anti-inflammatory, and glutamate modulation activity, NAC has been investigated in the treatment of neurodevelopmental disorders, schizophrenia spectrum disorders, bipolar-related disorders, depressive disorders, anxiety disorders, obsessive compulsive-related disorders, substance-use disorders, neurocognitive disorders, and chronic pain. Whilst there is ample preclinical evidence and theoretical justification for the use of NAC in the treatment of multiple psychiatric disorders, clinical trials in most disorders have yielded mixed results. However, most studies have been underpowered and perhaps too brief, with some evidence of benefit only after months of treatment with NAC. Currently NAC has the most evidence of having a beneficial effect as an adjuvant agent in the negative symptoms of schizophrenia, severe autism, depression, and obsessive compulsive and related disorders. Future research with well-powered studies that are of sufficient length will be critical to better understand the utility of NAC in the treatment of psychiatric disorders.

Drugs Based on NMDAR Hypofunction Hypothesis in Schizophrenia

Treatments for negative symptoms and cognitive dysfunction in schizophrenia remain issues that psychiatrists around the world are trying to solve. Their mechanisms may be associated with N-methyl-D-aspartate receptors (NMDARs). The NMDAR hypofunction hypothesis for schizophrenia was brought to the fore mainly based on the clinical effects of NMDAR antagonists and anti-NMDAR encephalitis pathology. Drugs targeted at augmenting NMDAR function in the brain seem to be promising in improving negative symptoms and cognitive dysfunction in patients with schizophrenia. In this review, we list NMDAR-targeted drugs and report on related clinical studies. We then summarize their effects on negative symptoms and cognitive dysfunction and analyze the unsatisfactory outcomes of these clinical studies according to the improved glutamate hypothesis that has been revealed in animal models. We aimed to provide perspectives for scientists who sought therapeutic strategies for negative symptoms and cognitive dysfunction in schizophrenia based on the NMDAR hypofunction hypothesis.

Oxidative Stress-Related Mechanisms in Schizophrenia Pathogenesis and New Treatment Perspectives

Schizophrenia is recognized to be a highly heterogeneous disease at various levels, from genetics to clinical manifestations and treatment sensitivity. This heterogeneity is also reflected in the variety of oxidative stress-related mechanisms contributing to the phenotypic realization and manifestation of schizophrenia. At the molecular level, these mechanisms are supposed to include genetic causes that increase the susceptibility of individuals to oxidative stress and lead to gene expression dysregulation caused by abnormal regulation of redox-sensitive transcriptional factors, noncoding RNAs, and epigenetic mechanisms favored by environmental insults. These changes form the basis of the prooxidant state and lead to altered redox signaling related to glutathione deficiency and impaired expression and function of redox-sensitive transcriptional factors (Nrf2, NF-κB, FoxO, etc.). At the cellular level, these changes lead to mitochondrial dysfunction and metabolic abnormalities that contribute to aberrant neuronal development, abnormal myelination, neurotransmitter anomalies, and dysfunction of parvalbumin-positive interneurons. Immune dysfunction also contributes to redox imbalance. At the whole-organism level, all these mechanisms ultimately contribute to the manifestation and development of schizophrenia. In this review, we consider oxidative stress-related mechanisms and new treatment perspectives associated with the correction of redox imbalance in schizophrenia. We suggest that not only antioxidants but also redox-regulated transcription factor-targeting drugs (including Nrf2 and FoxO activators or NF-κB inhibitors) have great promise in schizophrenia. But it is necessary to develop the stratification criteria of schizophrenia patients based on oxidative stress-related markers for the administration of redox-correcting treatment.

Interaction of N-acetyl-l-cysteine with Na+, Ca2+, Mg2+ and Zn2+. Thermodynamic aspects, chemical speciation and sequestering ability in natural fluids

The estimation of thermodynamic parameters of N-Acetyl-L-cysteine (NAC) protonation were determined in NaCl(aq), (CH3)4NCl(aq), (C2H5)4NI(aq), employing various temperature and ionic strengths conditions, by potentiometric measurements. The interaction of NAC with some essential metal cations (e.g., Ca2+, Mg2+ and Zn2+) was investigated as well at 298.15 K in NaCl(aq) in the ionic strength range 0.1 ≤ I/mol dm-3 ≤ 1.0. The values of protonation constants at infinite dilution and at T = 298.15 K are: log K 1 H = 9.962 ± 0.005 (S-H) and log K 2 H = 3.347 ± 0.008 (COO-H). In the presence of a background electrolyte, both log K 1 H and log K 2 H values followed the trend (C2H5)4NI ≥ (CH3)4NCl ≥ NaCl. The differences in the values of protonation constants among the three ionic media were interpreted in terms of variation of activity coefficients and formation of weak complexes. Accordingly, the determination of the stability of 4 species, namely: NaL-, NaHL0 (aq), (CH3)4NL-, (CH3)4NHL0 (aq) was assessed. In addition, as regards the interactions of Mg2+, Ca2+ and Zn2+ with NAC, the main species where the ML0 (aq), ML(OH)-, and ML2 2-, that were found to be important in the chemical speciation of NAC in real multicomponent solutions. The whole set of the data collected may be crucial for the development of NAC-based materials for natural fluids selective decontamination from heavy metals.