Oxidative Stress Biomarkers as a Predictor of Stage Illness and Clinical Course of Schizophrenia

Oxidative and Excitatory Neurotoxic Stresses in CRISPR/Cas9-Induced Kynurenine Aminotransferase Knockout Mice: A Novel Model for Despair-Based Depression and Post-Traumatic Stress Disorder

BACKGROUNDS

Memory and emotion are especially vulnerable to psychiatric disorders such as post-traumatic stress disorder (PTSD), which is linked to disruptions in serotonin (5-HT) metabolism. Over 90% of the 5-HT precursor tryptophan (Trp) is metabolized via the Trp-kynurenine (KYN) metabolic pathway, which generates a variety of bioactive molecules. Dysregulation of KYN metabolism, particularly low levels of kynurenic acid (KYNA), appears to be linked to neuropsychiatric disorders. The majority of KYNA is produced by the aadat (kat2) gene-encoded mitochondrial kynurenine aminotransferase (KAT) isotype 2. Little is known about the consequences of deleting the KYN enzyme gene.

METHODS

In CRISPR/Cas9-induced aadat knockout (kat2-/-) mice, we examined the effects on emotion, memory, motor function, Trp and its metabolite levels, enzyme activities in the plasma and urine of 8-week-old males compared to wild-type mice.

RESULTS

Transgenic mice showed more depressive-like behaviors in the forced swim test, but not in the tail suspension, anxiety, or memory tests. They also had fewer center field and corner entries, shorter walking distances, and fewer jumping counts in the open field test. Plasma metabolite levels are generally consistent with those of urine: antioxidant KYNs, 5-hydroxyindoleacetic acid, and indole-3-acetic acid levels were lower; enzyme activities in KATs, kynureninase, and monoamine oxidase/aldehyde dehydrogenase were lower, but kynurenine 3-monooxygenase was higher; and oxidative stress and excitotoxicity indices were higher. Transgenic mice displayed depression-like behavior in a learned helplessness model, emotional indifference, and motor deficits, coupled with a decrease in KYNA, a shift of Trp metabolism toward the KYN-3-hydroxykynurenine pathway, and a partial decrease in the gut microbial Trp-indole pathway metabolite.

CONCLUSIONS

This is the first evidence that deleting the aadat gene induces depression-like behaviors uniquely linked to experiences of despair, which appear to be associated with excitatory neurotoxic and oxidative stresses. This may lead to the development of a double-hit preclinical model in despair-based depression, a better understanding of these complex conditions, and more effective therapeutic strategies by elucidating the relationship between Trp metabolism and PTSD pathogenesis.

Are Advanced Oxidation Protein Products (AOPPs) Levels Altered in Neuropsychiatric Disorders? An Integrative Review

Neuropsychiatric disorders such as major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ) are considered a public health problem since it interferes in personal relationships and at work. The pathophysiological mechanisms of these mental disorders are still not completely understood. The variety and heterogeneity of symptoms, as well as the absence of biomarkers, make the diagnosis, prognosis, and treatment of these disorders difficult. However, oxidative stress appears to play a role in the pathophysiology of these diseases. In this context, advanced oxidation protein products (AOPPs) are considered a biomarker of protein oxidative damage and have been associated with neuroinflammatory diseases. In patients with neuropsychiatric disorders, increased levels of AOPPs were associated with the severity of symptoms and decreased quality of life. Thus, the objective of this integrative review is to investigate and discuss the relationship between AOPPs levels and MDD, BD, and SZ. Different databases were consulted and approximately 112 scientific articles were found relating AOPPs and psychiatric disorders. In the majority of studies, the blood levels of AOPPs were increased in MDD, BD, and SZ and associated with the severity of the disorders. Although the association of this marker with the risk of developing one of these mental disorders is more uncertain, some studies have suggested this relationship. Of the twenty-four studies highlighted, only four did not find significant differences in AOPPs levels in patients with the disorders mentioned. In summary, it may be suggested that the assessment of AOPPs levels can be a useful tool in the evaluation of neuropsychiatric disorders, at least for prognostic evaluation. However, the role of this biomarker in the pathophysiology of mental disorders is still unclear, as well as whether reducing its levels represents a potential therapeutic strategy.

Reduced retinol (vitamin A) and α-tocopherol (vitamin E) blood levels and increased myeloperoxidase (MPO) activity in children with high myopia

The study assessed selected parameters of redox status in the plasma of patients suffering from high myopia (HM). Thirty-five children with mean age 13.7 ± 2.7 years with HM and 40 healthy children were included. Plasma redox status parameters were determined using colorimetric kits. The levels of retinol, α-tocopherol and coenzyme Q10 were determined with a high-performance liquid chromatograph. Negative correlations were observed between the concentrations of retinol and the axial length of the eye (r = - 0.514 p < 0.001). Increased myeloperoxidase (MPO) activity (p < 0.018), and decreased concentrations of retinol (p < 0.001) and α-tocopherol (p < 0.023) in patients with HM and the axial length of the eye > 26 mm compared to controls were established. Significantly lower retinol and α-tocopherol concentrations were found in patients with the axial length of the eye > 26 mm compared to those with the axial length of the eye ≤ 26 mm (p < 0.001, p < 0.021, respectively). Increased MPO activity in advanced stages of HM may confirm an inflammatory process in HM patients. Reduced retinol and α-tocopherol concentrations and their link to disease progression indicate a need for monitoring their levels and supplementation in children with HM.

Pro/antioxidant status and selenium, zinc and arsenic concentration in patients with bipolar disorder treated with lithium and valproic acid

Disturbances in pro/antioxidant balance emerge as a crucial element in bipolar disorder (BD). Some studies suggest that treatment effects on trace element concentration in BD. This study aimed to identify (a) the changes related to oxidative stress in BD and their relationship with trace elements engaged in pro/antioxidant homeostasis; (b) BD biomarkers using machine learning algorithm classification and regression tree (C&RT) analysis. 62 individuals with BD and 40 healthy individuals (HC) were included in the study. The concentration of pro/antioxidant state and concentration of selenium, zinc, arsenic in blood were assessed. We found a higher concentration of total antioxidant capacity, catalase, advanced oxidation protein products and a lower concentration of 4-hydroxynonenal (4-HNE), glutathione, glutathione peroxidase (GPx) in BD compared to HC. All examined trace elements were lower in the BD group compared to HC. A combination of two variables, 4-HNE (cut-off: ≤ 0.004 uM/mg protein) and GPx (cut-off: ≤ 0.485 U/mg protein), was the most promising markers for separating the BD from the HC. The area under the receiver operating characteristic curve values for C&RT was 90.5%. Disturbances in the pro/antioxidant state and concentration of trace elements of patients with BD may be a target for new therapeutic or diagnostic opportunity of BD biomarkers.

The potential predictive value and relationship of blood-based inflammatory markers with the clinical symptoms of Han Chinese patients with first-episode adolescent-onset schizophrenia

Background

Inflammation is associated with the pathophysiology of schizophrenia. The blood markers for systemic inflammation include neutrophil-lymphocyte ratio (NLR), systemic immune-inflammation index (SII), lymphocyte-monocyte ratio (LMR), system inflammation response index (SIRI), and platelet-lymphocyte ratio (PLR). However, these inflammation markers and their relationships with clinical phenotypes among Han Chinese patients with first-episode adolescent-onset schizophrenia (AOS) is unclear. This investigation aimed to elucidate the impact of inflammation on Han Chinese AOS patients as well as the association of blood-based inflammation markers with clinical symptoms.

Methods

Altogether, 203 Han Chinese individuals participated in this study, 102 first-episode AOS patients and 101 healthy controls. The assessment of inflammatory indices was based on complete blood cell count. Furthermore, schizophrenia-related clinical symptoms were evaluated using the five-factor model of the Positive and Negative Syndrome Scale (PANSS).

Results

In Han Chinese first-episode AOS patients, levels of SIRI, PLR, SII, and NLR were significantly increased (p < 0.001), while LMR decreased (p < 0.001) compared to healthy controls. Furthermore, multivariate logistic regression showed that LMR, NLR, SII, and SIRI (all p < 0.05) were independently associated with AOS. Moreover, Receiver operating characteristics assessment indicated that NLR, SIRI, LMR, and SII could effectively distinguish AOS patients from healthy controls. Their areas under the curves were 0.734, 0.701, 0.715, and 0.730 (all p < 0.001). In addition, Correlation analysis revealed that LMR was negatively correlated with the PANSS total, negative, and cognitive factor scores (all p < 0.05); NLR was positively correlated with the cognitive factor score (p < 0.01); SII was negatively correlated with the positive factor score and positively with the negative and cognitive factor scores (all p < 0.05); SIRI was positively correlated with the PANSS total and cognitive factor scores (all p < 0.01).

Conclusions

This research established the involvement of peripheral blood inflammatory markers (LMR, NLR, SII, and SIRI) with the clinical manifestations and pathophysiology of schizophrenia, and these can serve as screening tools or potential indices of the inflammatory state and AOS symptoms severity.

The association of SOD and HsCRP with the efficacy of sulforaphane in schizophrenia patients with residual negative symptoms

OBJECTIVES

Emerging evidence indicates a connection between oxidative stress, immune-inflammatory processes, and the negative symptoms of schizophrenia. In addition to possessing potent antioxidant and anti-inflammatory properties, sulforaphane (SFN) has shown promise in enhancing cognitive function among individuals with schizophrenia. This study aims to investigate the efficacy of combined treatment with SFN in patients with schizophrenia who experience negative symptoms and its effect on the levels of superoxide dismutase (SOD) and the inflammatory marker, high-sensitivity C-reactive protein (HsCRP).

DESIGN

Forty-five patients with schizophrenia were recruited, who mainly experienced negative symptoms during a stable period. In addition to the original treatments, the patients received SFN tablets at a daily dose of 90 mg for 24 weeks. At baseline, 12 weeks, and 24 weeks, the participants were interviewed and evaluated. The reduction rate of the Positive and Negative Syndrome Scale (PANSS) was used to assess each participant. The side effects scale of Treatment Emergent Symptom Scale (TESS) was applied to assess the adverse reactions. Additionally, the levels of the SOD, HsCRP, and other indicators were examined.

RESULTS

The study findings revealed a significant decrease in PANSS negative subscale scores (P < 0.001). Furthermore, there was a significant increase in SOD activity and HsCRP levels (P < 0.001 and P < 0.05). Notably, the group of participants who exhibited a reduction in PANSS negative subscale scores demonstrated a significant improvement in HsCRP levels (P < 0.05).

CONCLUSIONS

Our study suggests that SFN may potentially serve as a safe adjunctive intervention to improve the negative symptoms of schizophrenia. The potential mechanism by which SFN improves negative symptoms in schizophrenia patients may involve its anti-inflammatory properties, specifically its ability to reduce HsCRP levels. Trial registration ClinicalTrial.gov (ID: NCT03451734).

The usefulness of a complete blood count in the prediction of the first episode of schizophrenia diagnosis and its relationship with oxidative stress

A complete blood count (CBC) is a routinely performed blood examination. Only a few studies assess the relationship between CBC and oxidative stress (OS) in schizophrenia (SZ). The aim of the study was to assess the utility of CBC in the prediction of SZ diagnosis, and the relationship between CBC and OS. The study included: 47 individuals with the first episode of psychosis (26 drug-naive: FEP-nt; 21 patients under antipsychotic treatment: FEP-t) and 30 healthy persons (control group, HC). CBC and oxidative stress-related parameters were assessed in blood samples. The FEP group had higher levels of WBC, MCHC, NEU, MONO, EOZ, BASO, and %EOZ compared to HC (p<0.05). Various relationships between OS and CBC were found, and this connection was significantly different between healthy individuals and patients. The most promising C&RT model for discriminating FEP from HC was combining monocytes, eosinophils, and neutrophils (accuracy: 77%, 95%CI = 0.67-0.87). The analysis singled out WBC and HT (accuracy: 74%, 95%CI = 0.64-0.90) as the most promising to distinguish FEP-nt from HC; WBC and %Neu to allocate to FEP-t or HC group (accuracy: 87%, 95%CI = 0.64-0.90); RDW-SD and LYMPH (accuracy: 86%, 95% CI = 0.75-97) for distinguishing FEP-nt from FEP-t. CBC could be a promising, cheap tool to determine abnormalities related to schizophrenia. However, more studies with larger sample sizes are required.

Differential Impacts of Endogenous Antioxidants on Clinical Symptoms and Cognitive Function in Acute and Chronic Schizophrenia Patients

BACKGROUND

Impaired antioxidant defense is implicated in the pathophysiology of schizophrenia, and superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) are 3 first-line endogenous antioxidants. Various cognitive functions decline differently during the schizophrenia course. The characteristic roles of the 3 antioxidants in clinical and cognitive profiles in acute and chronic phases of schizophrenia require study.

METHODS

We recruited 311 patients with schizophrenia, including 92 acutely exacerbated patients who had been off antipsychotics for at least 2 weeks and 219 chronic patients who had been stable on medication for at least 2 months. Blood SOD, CAT, and GSH levels; clinical symptoms; and 9 cognitive test scores were measured.

RESULTS

Blood CAT levels were higher in the acute patients than in the chronic patients, whereas SOD and GSH levels were similar to one another. Higher CAT levels were correlated with less positive symptoms, better working memory and problem solving in the acute phase, and less negative symptoms, less general psychopathology, better global assessment of function, and better cognitive function (in speed of processing, attention, problem solving) in the chronic period. Higher SOD levels were correlated with better global assessment of function in the acute phase and better speed of processing, working memory, and verbal learning and memory in the chronic period. GSH influenced neither clinical nor cognitive manifestations.

CONCLUSIONS

This study showed that blood CAT affected different clinical and cognitive domains between acute and chronic stages of schizophrenia, SOD influenced cognitive functions in chronic state, but GSH affected none. Further studies are needed to explore the underlying mechanisms.

Paraoxonase/Arylesterase Activity of Serum Paraoxonase-1 and Schizophrenia: A Systematic Review and Meta-Analysis

The presence of a pro-oxidant state in patients with schizophrenia may account for the increased risk of atherosclerosis and cardiovascular disease in this group and supports the potential utility of circulating biomarkers of oxidative stress for risk stratification and management. We investigated this issue by conducting a systematic review and meta-analysis of the association between the circulating concentrations of paraoxonase-1, an antioxidant calcium-dependent high-density lipoprotein (HDL)-associated esterase, with paraoxonase and arylesterase activity in schizophrenia. We searched electronic databases from inception to 31 May 2023 for studies investigating paraoxonase-1 in patients with schizophrenia and healthy controls and assessed the risk of bias and the certainty of evidence (PROSPERO registration number: CRD42023435442). Thirteen studies were identified for analysis. There were no significant between-group differences in paraoxonase (standard mean difference, SMD = 0.12, 95% CI -0.23 to 0.48, p = 0.50; extremely low certainty of evidence) or arylesterase activity (SMD = -0.08, 95% CI -0.39 to 0.23, p = 0.61; very low certainty of evidence). However, in meta-regression and subgroup analysis we observed significant associations between the SMD of paraoxonase and age (p = 0.003), HDL-cholesterol (p = 0.029), and study country (p = 0.04), and the SMD of arylesterase and age (p = 0.007), body mass index (p = 0.012), HDL-cholesterol (p = 0.002), and pharmacological treatment for schizophrenia (p < 0.001). In the absence of overall between-group differences, our systematic review and meta-analysis suggests that alterations in paraoxonase-1 may reflect a pro-oxidant state in specific subgroups of patients with schizophrenia that require further assessment in appropriately designed studies.

Oxidative Stress Biomarkers among Schizophrenia Inpatients

Background. Finding the associations between schizophrenia symptoms and the biomarkers of inflammation, oxidative stress and the kynurenine pathway may lead to the individualization of treatment and increase its effectiveness. Methods. The study group included 82 schizophrenia inpatients. The Positive and Negative Symptoms Scale (PANSS), the Brief Assessment of Cognition in Schizophrenia (BACS) and the Calgary Depression in Schizophrenia Scale were used for symptom evaluation. Biochemical analyses included oxidative stress parameters and brain-derived neurotrophic factor (BDNF). Results. Linear models revealed the following: (1) malondiadehyde (MDA), N-formylkynurenine (N-formKYN), advanced oxidation protein products (AOPP), advanced glycation end-products of proteins (AGE) and total oxidative status (TOS) levels are related to the PANSS-total score; (2) MDA, reduced glutathione (GSH) and BDNF levels are related to the PANSS-negative score; (3) TOS and kynurenine (KYN) levels are related to the PANSS-positive score; (4) levels of total antioxidant status (TAS) and AOPP along with the CDSS score are related to the BACS-total score; (5) TAS and N-formKYN levels are related to the BACS-working memory score. Conclusions. Oxidative stress biomarkers may be associated with the severity of schizophrenia symptoms in positive, negative and cognitive dimensions. The identification of biochemical markers associated with the specific symptom clusters may increase the understanding of biochemical profiles in schizophrenia patients.

Comparative Analysis of the Pre- and Post-Medication Effects of Antipsychotic Agents on the Blood-Based Oxidative Stress Biomarkers in Patients with Schizophrenia: A Meta-Analysis

OBJECTIVE

Studies have shown that oxidative stress (OS) is related to the pathophysiology of schizophrenia (SCZ), but whether antipsychotics can induce OS has not been investigated well. Moreover, antipsychotics have differential effects on the OS level modulation, i.e., different types of antipsychotics have different effects on the cellular antioxidants or pro-oxidants.

METHODS

We followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines and investigated the OS indicators including both enzymatic and nonenzymatic markers, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), malondialdehyde (MDA), glutathione (GSH), vitamin C, etc., of SCZ patients at baseline and follow-up of mono-medication.

RESULTS

Twenty studies met the inclusion criteria, with a total of 1162 patients enrolled at baseline, and 1105 patients completed the follow-up. OS markers were changed after a period of antipsychotic treatment in SCZ patients. The GPx activity and MDA level decreased in the whole blood (P<0.05), also the serum MDA level decreased (P<0.05). For the first-episode SCZ patients, the activity of GPx and the level of MDA decreased, while the level of vitamin C increased (all P<0.05). The levels of MDA in patients receiving atypical antipsychotics decreased (P<0.05), while the level of GSH in patients with typical antipsychotics decreased (P=0.05).

CONCLUSION

Antipsychotic medication may cause changes in the levels of OS markers in different blood samples of SCZ patients. However, the available studies might not be sufficient to reveal the underlying facts accurately due to the poor quality of experimental designs in the published literature.

Oxidative Stress and Emergence of Psychosis

Treatment and prevention strategies for schizophrenia require knowledge about the mechanisms involved in the psychotic transition. Increasing evidence suggests a redox imbalance in schizophrenia patients. This narrative review presents an overview of the scientific literature regarding blood oxidative stress markers’ evolution in the early stages of psychosis and chronic patients. Studies investigating peripheral levels of oxidative stress in schizophrenia patients, first episode of psychosis or UHR individuals were considered. A total of 76 peer-reviewed articles published from 1991 to 2022 on PubMed and EMBASE were included. Schizophrenia patients present with increased levels of oxidative damage to lipids in the blood, and decreased levels of non-enzymatic antioxidants. Genetic studies provide evidence for altered antioxidant functions in patients. Antioxidant blood levels are decreased before psychosis onset and blood levels of oxidative stress correlate with symptoms severity in patients. Finally, adjunct treatment of antipsychotics with the antioxidant N-acetyl cysteine appears to be effective in schizophrenia patients. Further studies are required to assess its efficacy as a prevention strategy. Redox imbalance might contribute to the pathophysiology of emerging psychosis and could serve as a therapeutic target for preventive or adjunctive therapies, as well as biomarkers of disease progression.

α-Lipoic Acid Strengthens the Antioxidant Barrier and Reduces Oxidative, Nitrosative, and Glycative Damage, as well as Inhibits Inflammation and Apoptosis in the Hypothalamus but Not in the Cerebral Cortex of Insulin-Resistant Rats

The research determined the role of α-lipoic acid (ALA) in reducing the brain manifestations of insulin resistance. The mechanism of ALA action is mainly based on its ability to “scavenge” oxygen free radicals and stimulate biosynthesis of reduced glutathione (GSH), considered the most critical brain antioxidant. Although the protective effect of ALA is widely documented in various diseases, there are still no studies assessing the influence of ALA on brain metabolism in the context of insulin resistance and type 2 diabetes. The experiment was conducted on male Wistar rats fed a high-fat diet for ten weeks with intragastric administration of ALA for four weeks. We are the first to demonstrate that ALA improves the function of enzymatic and nonenzymatic brain antioxidant systems, but the protective effects of ALA were mainly observed in the hypothalamus of insulin-resistant rats. Indeed, ALA caused a significant increase in superoxide dismutase, catalase, peroxidase, and glutathione reductase activities, as well as GSH concentration and redox potential ([GSH]²/[GSSG]) in the hypothalamus of HFD-fed rats. A consequence of antioxidant barrier enhancement by ALA is the reduction of oxidation, glycation, and nitration of brain proteins, lipids, and DNA. The protective effects of ALA result from hypothalamic activation of the transcription factor Nrf2 and inhibition of NF-κB. In the hypothalamus of insulin-resistant rats, we demonstrated reduced levels of oxidation (AOPP) and glycation (AGE) protein products, 4-hydroxynoneal, 8-isoprostanes, and 3-nitrotyrosine and, in the cerebral cortex, lower levels of 8-hydroxydeoxyguanosine and peroxynitrite. In addition, we demonstrated that ALA decreases levels of proinflammatory TNF-α but also increases the synthesis of anti-inflammatory IL-10 in the hypothalamus of insulin-resistant rats. ALA also prevents neuronal apoptosis, confirming its multidirectional effects within the brain. Interestingly, we have shown no correlation between brain and serum/plasma oxidative stress biomarkers, indicating the different nature of redox imbalance at the central and systemic levels. To summarize, ALA improves antioxidant balance and diminishes oxidative/glycative stress, protein nitrosative damage, inflammation, and apoptosis, mainly in the hypothalamus of insulin-resistant rats. Further studies are needed to determine the molecular mechanism of ALA action within the brain.