Increased Interleukin-17 and decreased BAFF serum levels in drug-free acute schizophrenia

B Cell-activating factor (BAFF): A promising trans-nosographic biomarker of inflammation and autoimmunity in bipolar disorder and schizophrenia

Immune dysregulation is an important aspect of schizophrenia (SZ) and bipolar disorders (BD) pathophysiology, including not only inflammatory but also autoimmune process reflective of abnormal humoral immune responses. Given that B cell-activating factor (BAFF) is an integral aspect of B lymphocyte regulation, the current study investigated BAFF in SZ and BD. 255 SZ patients, 407 BD patients and 185 healthy controls (HC) were investigated across three aspects of soluble BAFF (sBAFF) by (i) comparing sBAFF circulatory levels across SZ, BD and HC, (ii) determining potential correlations between the circulating levels of sBAFF and the genotype distribution of a functionally relevant polymorphism, namely the TNFSF13B 3'UTR insertion-deletion polymorphism (GCTGT>A), (iii) analyzing relationships between both sBAFF levels and 3'UTR insertion-deletion genotypes and disease risk, patients clinical characteristics and circulating levels of potent inflammatory molecules. In addition, in subsets of patients, we also searched for possible correlations between sBAFF levels and stigma of past infectious events as well as positivity for circulating systemic autoantibodies or those directed against central nervous system (CNS) structures. Studying blood derived serum and DNA, weobserved that circulating sBAFF levels were significantly higher in SZ and BD patients, versus HC (p = 5.3*10-10and p = 4.4*10-09). Patients experiencing acute episodes, versus stable patients, in between acute episodes, exhibited higher sBAFF levels (p = 0.017).In SZ patients, positive correlations were observed between elevated sBAFF levels and: (i) elevated positive psychotic symptoms (PANSS pos), (ii) history of childhood trauma (physical abuse), and (iii) low scores on global functioning (GAF) (p = 0.024, p = 0.024, and p = 0.041).We also found that the distribution of the BAFF Ins/Del genotypes was significantly correlated with circulating sBAFF levels in SZ and BD patients (p = 0.0004). Elevated sBAFF levels were also correlated with increased levels of pro-inflammatory markers in both SZ and BD cohorts (p < 0.001). Regarding infectious stigma, only patients seropositive, versus seronegative, for herpes simplex virus (HSV)1 immunoglobulin (Ig)G antibodies exhibited a significant association with high sBAFF levels (p = 0.013). In contrast, positivity for systemic or CNS autoantibodies was significantly associated with reduced sBAFF levels, compared to patients without autoantibodies (p = 0.0017). Overall, our findings indicate that BAFF may be a promising trans-nosographic biomarker of inflammation that is likely to offer predictive, diagnostic, and prognostic tools for the management of SZ and BD. The results therefore have practicable clinical utility given the availability of immunotherapeutic treatment options including targeted monoclonal antibodies against BAFF.

The Interrelationships between Cytokines and Schizophrenia: A Systematic Review

Schizophrenia (SCZ) imposes a significant burden on patients and their families because of its high prevalence rate and disabling nature. Given the lack of definitive conclusions regarding its pathogenesis, physicians heavily rely on patients' subjective symptom descriptions for diagnosis because reliable diagnostic biomarkers are currently unavailable. The role of the inflammatory response in the pathogenesis of SCZ has been supported by some studies. The findings of these studies showed abnormal changes in the levels of inflammatory factors, such as cytokines (CKs), in both peripheral blood and cerebrospinal fluid (CSF) among individuals affected by SCZ. The findings imply that inflammatory factors could potentially function as risk indicators for the onset of SCZ. Consequently, researchers have directed their attention towards investigating the potential utility of CKs as viable biomarkers for diagnosing SCZ. Extracellular vesicles (EVs) containing disease-specific components exhibit remarkable stability and abundance, making them promising candidates for biomarker discovery across various diseases. CKs encapsulated within EVs secreted by immune cells offer valuable insights into disease progression. This review presents a comprehensive analysis summarizing the relationship between CKs and SCZ and emphasizes the vital role of CKs encapsulated within EVs in the pathogenesis and development of SCZ.

Altered serum interleukin-17A and interleukin-23A levels may be associated with the pathophysiology and development of generalized anxiety disorder

In recent times, the pathogenesis of generalized anxiety disorder (GAD) and the influence of pro- and anti-inflammatory cytokines on it have garnered considerable interest. Cytokine research, especially Th-17 cytokine research on GAD patients, is limited. Here, we aim to assess the role of interleukin-17A (IL-17A) and interleukin-23A (IL-23A) in the pathophysiology and development of GAD. This investigation included 50 GAD patients and 38 age-sex-matched healthy controls (HCs). A psychiatrist diagnosed patients with GAD and assessed symptom severity using the DSM-5 and the GAD-7 scales. The serum concentrations of IL-17A and IL-23A were determined using commercially available ELISA kits. GAD patients exhibited elevated levels of IL-17A (77.14 ± 58.30 pg/ml) and IL-23A (644.90 ± 296.70 pg/ml) compared to HCs (43.50 ± 25.54 pg/ml and 334.40 ± 176.0 pg/ml). We observed a positive correlation between disease severity and cytokine changes (IL-23A: r = 0.359, p = 0.039; IL-17A: r = 0.397, p = 0.032). These findings indicate that IL-17A and IL-23A may be associated with the pathophysiology of GAD. ROC analysis revealed moderately higher AUC values (IL-23A: 0.824 and IL-17A: 0.710), demonstrating their potential to discriminate between patients and HCs. Also, the sensitivity values of both cytokines were relatively higher (IL-23A: 80.49% and IL-17A: 77.27%). According to the present findings, there may be an association between peripheral serum levels of IL-17A and IL-23A and the pathophysiology and development of GAD. These altered serum IL-17A and IL-23A levels may play a role in directing the early risk of developing GAD. We recommend further research to ascertain their exact role in the pathophysiology and their performance as risk assessment markers of GAD.

The associations of psychopathology and metabolic parameters with serum bilirubin levels in patients with acute-episode and drug-free schizophrenia: a 5-year retrospective study using an electronic medical record system

BACKGROUND

The oxidative system plays an important role in the pathogenesis of schizophrenia. Inconsistent associations were found between hyperbilirubinemia and psychopathology as well as glycolipid metabolism in patients with schizophrenia at different episodes. This current study aimed to examine these associations in patients with acute-episode and drug-free (AEDF) schizophrenia.

METHODS

This is a retrospective study using 5 years of data from May 2017 to May 2022 extracted from the electronic medical record system of Chaohu Hospital of Anhui Medical University. Healthy controls (HCs) from the local medical screening center during the same period were also included. Participants' data of the bilirubin levels [total bilirubin (TB), conjugated bilirubin (CB), unconjugated bilirubin (UCB)], glycolipid metabolic parameters and the score of the Brief Psychiatric Rating Scale (BPRS) were collected.

RESULTS

A total of 1468 case records were identified through the initial search. After screening, 89 AEDF patients and 100 HCs were included. Compared with HCs, patients had a higher CB level, and lower levels of glycolipid metabolic parameters excluding high density lipoprotein-cholesterol (HDL-C) (all P < 0.001). Binary logistic regression analyses revealed that high bilirubin levels in the patients were independently associated with higher total and resistance subscale scores of BPRS, a higher HDL-C level, and lower total cholesterol and triglyceride levels (all P < 0.05).

CONCLUSION

Bilirubin levels are elevated in patients with AEDF schizophrenia. Patients with high bilirubin levels have more severe psychopathology and relatively optimized glycolipid metabolism. In clinical practice, regular monitoring of bilirubin levels in this patient population should be carried out.

Association Between Maternal Mood Disorders and Schizophrenia and the Risk of Type 1 Diabetes in Offspring: A Nationwide Cohort Study

Objective

Our study aimed to determine whether mothers with bipolar disorder, major depressive disorder, schizophrenia, or schizoaffective disorder affected the risk of type 1 diabetes (T1D) in their offspring.

Methods

We conducted a nationwide cohort study by using data from Taiwan's National Health Insurance Research Database and the Maternal and Child Health Database from 2004 to 2018. A total of 2,556,640 mother-child pairs were identified. Cox proportional hazards models were used to compare the risk of T1D between children born to mothers with mood disorders and schizophrenia and those without.

Results

No significant difference in risk of T1D was observed between the offspring of mothers with major psychiatric disorders and those without (adjusted hazard ratio (aHR) of 0.86 with a 95% confidence interval (CI) of 0.58-1.24). In subgroup analysis, we found an aHR of 1.81 with a 95% CI of 0.83-3.82 in the maternal bipolar disorder on the risk of T1D in offspring and an aHR of 0.87 (95% CI: 0.59-1.25) in maternal major depressive disorder. In the schizophrenia/schizoaffective disorder group, aHR cannot be obtained due to lesser than three events in the analysis.

Conclusion

The risk of T1D in offspring of mothers with mood disorders and schizophrenia was not significant. However, children born to mothers with bipolar disorder may have a tendency to develop T1D. The relationship between maternal psychiatric disorders and the risk of T1D in offspring warrants further investigation in studies with longer follow-up periods.

Network analysis of inflammation and symptoms in recent onset schizophrenia and the influence of minocycline during a clinical trial

Attempts to delineate an immune subtype of schizophrenia have not yet led to the clear identification of potential treatment targets. An unbiased informatic approach at the level of individual immune cytokines and symptoms may reveal organisational structures underlying heterogeneity in schizophrenia, and potential for future therapies. The aim was to determine the network and relative influence of pro- and anti-inflammatory cytokines on depressive, positive, and negative symptoms. We further aimed to determine the effect of exposure to minocycline or placebo for 6 months on cytokine-symptom network connectivity and structure. Network analysis was applied to baseline and 6-month data from the large multi-center BeneMin trial of minocycline (N = 207) in schizophrenia. Pro-inflammatory cytokines IL-6, TNF-α, and IFN-γ had the greatest influence in the inflammatory network and were associated with depressive symptoms and suspiciousness at baseline. At 6 months, the placebo group network connectivity was 57% stronger than the minocycline group, due to significantly greater influence of TNF-α, early wakening, and pathological guilt. IL-6 and its downstream impact on TNF-α, and IFN-γ, could offer novel targets for treatment if offered at the relevant phenotypic profile including those with depression. Future targeted experimental studies of immune-based therapies are now needed.

Possible involvement of Interleukin-17A in the deterioration of prepulse inhibition on acoustic startle response in mice

AIM

Proinflammatory cytokines such as interleukin-6 (IL-6) and IL-17A have been implicated in the pathophysiology of schizophrenia which often shows sensorimotor gating abnormalities. This study aimed to examine whether a proinflammatory cytokine, IL-17A, induces impairment in sensorimotor gating in mice. We also examined whether IL-17A administration affects GSK3α/β protein level or phosphorylation in the striatum.

METHODS

Recombinant mouse IL-17A (low-dose: 0.5 ng/mL and high-dose: 50 ng/mL with 10 μL/g mouse body weight, respectively) or vehicle was intraperitoneally administered into C57BL/6 male mice 10 times in 3 weeks (sub-chronic administration). Prepulse inhibition test using acoustic startle stimulus was conducted 4 weeks after the final IL-17A administration. We evaluated the effect of IL-17A administration on protein level or phosphorylation of GSK3α/β in the striatum by using Western blot analysis.

RESULTS

Administration of IL-17A induced significant PPI deterioration. Low-dose of IL-17A administration significantly decreased both GSK3α (Ser21) and GSK3β (Ser9) phosphorylation in mouse striatum. There was no significant alteration of GSK3α/β protein levels except for GSK3α in low-dose IL-17A administration group.

CONCLUSION

We demonstrated for the first time that sub-chronic IL-17A administration induced PPI disruption and that IL-17A administration resulted in decreased phosphorylation of GSKα/β at the striatum. These results suggest that IL-17A could be a target molecule in the prevention and treatment of sensorimotor gating abnormalities observed in schizophrenia.

Genetic polymorphism of IL-17F rs763780 contributes to the susceptibility to bipolar disorder but not to schizophrenia in the Turkish population

This study aims to investigate the genetic polymorphism in the interleukin-17F (IL-17F) (rs763780, 7488 A/G) gene in bipolar disorder (BD) and schizophrenia (SCZ) patients by comparing it with healthy controls considering clinical parameters. A sample of 107 patients with BD, 129 patients with SCZ, and 100 healthy volunteers were included. SCID-I was used to confirm the diagnosis according to DSM-IV-TR criteria. The Young Mania Rating Scale (YMRS) and the Hamilton Depression Rating Scale (HAM-D) were administered to BD patients. The Positive and Negative Symptoms Scale (PANSS) was applied to the patients with SCZ. PCR-RFLP was used to determine IL-17F gene polymorphism. Our results demonstrated that the distributions of the IL-17F genotype and the allele frequencies of BD patients were statistically significantly different from the control group. The AA genotype (OR: 0.283; 95% Cl: 0.140-0.573; p<.001) and A allele (OR: 0.333; 95% Cl: 0.171-0.646; p=.001) frequencies were significantly higher in the control group than in the BD group. The IL-17F genotype and the allele frequency distributions of SCZ patients were not statistically significantly different from the control group. When comparing scale scores due to the IL-17F genotype distributions in patients with BD or SCZ, there was no statistically significant difference between the groups of IL-17F genotypes. In summary, whereas the IL-17F polymorphism may be associated with BD, this polymorphism was not related to SCZ.

The interleukin-6/interleukin-23/T helper 17-axis as a driver of neuro-immune toxicity in the major neurocognitive psychosis or deficit schizophrenia: A precision nomothetic psychiatry analysis

BACKGROUND

Schizophrenia and especially deficit schizophrenia (DSCZ) are characterized by increased activity of neuroimmunotoxic pathways and a generalized cognitive decline (G-CoDe). There is no data on whether the interleukin (IL)-6/IL-23/T helper 17 (IL-6/IL-23/Th17)-axis is more associated with DSCZ than with non-deficit schizophrenia (NDSCZ) and whether changes in this axis are associated with the G-CoDe and the phenome (a factor extracted from all symptom domains) of schizophrenia.

METHODS

This study included 45 DSCZ and 45 NDSCZ patients and 40 controls and delineated whether the IL-6/IL-23/Th17 axis, trace elements (copper, zinc) and ions (magnesium, calcium) are associated with DSCZ, the G-CoDe and the schizophrenia phenome.

RESULTS

Increased plasma IL-23 and IL-6 levels were associated with Th17 upregulation, assessed as a latent vector (LV) extracted from IL-17, IL-21, IL-22, and TNF-α. The IL-6/IL-23/Th17-axis score, as assessed by an LV extracted from IL-23, IL-6, and the Th17 LV, was significantly higher in DSCZ than in NDSCZ and controls. We discovered that 70.7% of the variance in the phenome was explained by the IL-6/IL-23/Th17-axis (positively) and the G-CoDe and IL-10 (both inversely); and that 54.6% of the variance in the G-CoDe was explained by the IL-6/IL-23/Th17 scores (inversely) and magnesium, copper, calcium, and zinc (all positively).

CONCLUSION

The pathogenic IL-6/IL-23/Th17-axis contributes to the generalized neurocognitive deficit and the phenome of schizophrenia, especially that of DSCZ, due to its key role in peripheral inflammation and neuroinflammation and its consequent immunotoxic effects on neuronal circuits. These clinical impairments are more prominent in subjects with lowered IL-10, magnesium, calcium, and zinc.

Variants of Th17 pathway-related genes influence brain morphometric changes and the risk of schizophrenia through epistatic interactions

OBJECTIVE

T helper 17 (Th17) pathway has been reported to be abnormal in schizophrenia; however, it is not known whether variation within genes of this pathway has any impact on schizophrenia. Herein, the impact of genetic variations and gene-gene interactions of Th17 pathway-related genes on the risk, psychopathology, and brain volume was examined in schizophrenia patients.

METHODS

Functional polymorphisms within interleukin 6 ( IL6 )(rs1800795 and rs1800797), IL10 (rs1800872 and rs1800896), IL17A (rs2275913 and rs8193036), IL22 (rs2227484 and rs2227485), IL23R (rs1884444), and IL27 (rs153109 and rs181206) genes were studied in 224 schizophrenia patients and 226 healthy controls. These variants were correlated with the brain morphometry, analyzed using MRI in a subset of patients ( n = 117) and controls ( n = 137).

RESULTS

Patients carrying CC genotype of rs2227484 of IL22 gene had significantly higher apathy total score [ F (1,183) = 5.60; P = 0.019; partial ɳ 2 = 0.030]. Significant epistatic interactions between IL6 (rs1800797) and IL17A (rs2275913) genes were observed in schizophrenia patients. GG genotype of rs2275913 of IL17A gene was associated with reduced right middle occipital gyrus volume in schizophrenia patients ( T = 4.56; P < 0.001).

CONCLUSION

Interactions between genes of Th17 pathway impact the risk for schizophrenia. The variants of Th17 pathway-related genes seem to have a determining effect on psychopathology and brain morphometric changes in schizophrenia.

Changes of immune-related factors in the blood of schizophrenia and bipolar disorder patients receiving monotherapy

Schizophrenia (SCZ) and bipolar disorder (BPD) are associated with abnormal expression of immune-related factors (IRFs), which have been proposed as biomarkers of either disease diagnosis (trait markers) or treatment (state markers). However, the state markers have been found to be less reproducible than the trait markers in previous studies. In the current study, we focused on the changes of IRFs in blood of SCZ and BPD patients receiving monotherapy. SCZ (N = 49) and BPD (N = 49) Chinese patients were recruited at acute episode and followed for 9 to 51 days until remission. Blood samples were collected at two state-points, acute state before treatment and remission state after treatment. A total of 41 IRFs in plasma were quantified by the Luminex assay. After adjusting covariates, we found four cytokines or cytokine receptors were significantly increased at remission when compared to acute episode in all the patients, including CD30, BAFF, CCL20, and CXCL10 (Bonferroni corrected p < 0.05). CD30 and BAFF were consistently increased in both SCZ and BPD while the increase of CCL20 was only observed in BPD but not SCZ when analyzing the two disorders separately. CXCL10 change was not significant in either SCZ or BPD alone. The changes of these four factors were correlated with each other, but not with clinical features. CD30 concentration in the BPD acute state was correlated with sleep quality (Spearman's rs = 0.365, Bonferroni corrected p < 0.05). Overall, we found that four factors (CD30, BAFF, CCL20, and CXCL10) might be associated with treatment of psychosis.

Plasma Levels of the Cytokines B Cell-Activating Factor (BAFF) and A Proliferation-Inducing Ligand (APRIL) in Schizophrenia, Bipolar, and Major Depressive Disorder: A Cross Sectional, Multisite Study

BACKGROUND

Immune dysfunction has been implicated in the pathogenesis of schizophrenia and other nonaffective psychosis (SCZ), bipolar spectrum disorder (BIP) and major depressive disorder (MDD). The cytokines B cell-activating factor (BAFF) and A proliferation-inducing ligand (APRIL) belong to the tumor necrosis factor (TNF) super family and are essential in orchestrating immune responses. Abnormal levels of BAFF and APRIL have been found in autoimmune diseases with CNS affection.

METHODS

We investigated if plasma levels of BAFF and APRIL differed between patients with SCZ, BIP, and MDD with psychotic symptoms (n = 2009) and healthy control subjects (HC, n = 1212), and tested for associations with psychotic symptom load, controlling for sociodemographic status, antipsychotic and other psychotropic medication, smoking, body-mass-index, and high sensitivity CRP.

RESULTS

Plasma APRIL level was significantly lower across all patient groups compared to HC (P < .001; Cohen's d = 0.33), and in SCZ compared to HC (P < .001; d = 0.28) and in BIP compared to HC (P < .001; d = 0.37). Lower plasma APRIL was associated with higher psychotic symptom load with nominal significance (P = .017), but not with any other clinical characteristics. Plasma BAFF was not significantly different across patient groups vs HC, but significantly higher in BIP compared to HC (P = .040; d = 0.12) and SCZ (P = .027; d = 0.10).

CONCLUSIONS

These results show aberrant levels of BAFF and APRIL and association with psychotic symptoms in patients with SCZ and BIP. This suggest that dysregulation of the TNF system, mediated by BAFF and APRIL, is involved in the pathophysiology of psychotic disorders.

Schizophrenia Plays a Negative Role in the Pathological Development of Myocardial Infarction at Multiple Biological Levels

It has shown that schizophrenia (SCZ) is associated with a higher chance of myocardial infarction (MI) and increased mortality. However, the underlying mechanism is largely unknown. Here, we first constructed a literature-based genetic pathway linking SCZ and MI, and then we tested the expression levels of the genes involved in the pathway by a meta-analysis using nine gene expression datasets of MI. In addition, a literature-based data mining process was conducted to explore the connection between SCZ at different levels: small molecules, complex molecules, and functional classes. The genetic pathway revealed nine genes connecting SCZ and MI. Specifically, SCZ activates two promoters of MI (IL6 and CRP) and deactivates seven inhibitors of MI (ADIPOQ, SOD2, TXN, NGF, ADORA1, NOS1, and CTNNB1), suggesting that no protective role of SCZ in MI was detected. Meta-analysis showed that one promoter of MI (CRP) presented no significant increase, and six out of seven genetic inhibitors of MI demonstrated minor to moderately increased expression. Therefore, the elevation of CRP and inhibition of the six inhibitors of MI by SCZ could be critical pathways to promote MI. Nine other regulators of MI were influenced by SCZ, including two gene families (inflammatory cytokine and IL1 family), five small molecules (lipid peroxide, superoxide, ATP, ascorbic acid, melatonin, arachidonic acid), and two complexes (CaM kinase 2 and IL23). Our results suggested that SCZ promotes the development and progression of MI at different levels, including genes, small molecules, complex molecules, and functional classes.

Effect of risperidone treatment on insulin-like growth factor-1 and interleukin-17 in drug naïve first-episode schizophrenia

Increasing evidence suggests that the inflammatory system is activated in schizophrenia and antipsychotics may affect cytokines levels. we conducted a cross-sectional and prospective study.One hundred and thirteen patients and 58 normal subjects matched by gender, age were enrolled in the study. All the patients had risperidonemonotherapy and undertook a 10-week follow-up. Serum levels of IL-17 and IGF-1 were examined using the enzyme-linked immunosorbent assay and the Positive and Negative Symptoms Scale (PANSS) was applied to estimate the clinical symptoms in patients with schizophrenia. All procedures were repeated at the 10 weeks for patients group.The serum levels of IL-17 and IGF-1 in patients were significantly higher than in normal people. After treatment, IGF-1 levels in patients decreased significantly, whereas the IL-17 serum levels had no significant change compared to their baseline concentration. IGF-1 levels at the baseline were negatively associated with the reduction in negative symptoms score after controlling for age, gender distribution, education, smoking status, and WHR. Additionally, the magnitude of IGF-1 change was negatively correlated with negative symptoms score change after controlling for potential confounding variables. Results suggested that the inflammatory system is activated and serum IGF-1 may contribute to the pathophysiology of the negative symptoms of schizophrenia.

Immune Signatures of Treatment-Resistant Schizophrenia: A FondaMental Academic Centers of Expertise for Schizophrenia (FACE-SZ) Study

Treatment-resistant schizophrenia (TRS) affects around 30% of patients with schizophrenia (SZ) resulting in poor functioning, relapses, and reduced quality of life. Convergent findings show that inflammation could contribute to resistance. We thus search for immune signatures of patients with TRS/ultra TRS (UTRS) in a sample of community-dwelling outpatients with SZ. In total, 195 stabilized SZ patients (mean age = 31.2 years, 73% male gender) were consecutively included in the network of the FondaMental Expert Centers for Schizophrenia in France and received a thorough clinical assessment. At inclusion, psychotic symptomatology was evaluated by the Positive and Negative Syndrome Scale (PANSS) for schizophrenia. Circulating serum/plasma levels of a large panel of markers reflecting the main inflammatory pathways were evaluated. TRS was defined by current treatment by clozapine (CLZ) and UTRS by current CLZ treatment + PANSS total score ≥ 70. The frequency of TRS and UTRS patients was, respectively, 20% and 7.7% and was defined using multivariable analysis elevated by high levels of interleukin (IL)-12/IL-23p40, IL-17A, IL-10, and beta 2 microglobulin (B2M) and IL-12/IL-23p40, IL-17A, IL-6, IL-10, IFNγ, and B2M, respectively. These observations suggest that resistance and ultra resistance to CLZ treatment are underpinned by pro-inflammatory molecules mainly belonging to the T helper 17 pathway, a finding making sense given the interplay between inflammation and antipsychotic treatment responses. If confirmed, our findings may allow us to consider IL-23/IL-17 pathway as a therapeutic target for patients with resistance to antipsychotics.

Cytokine Imbalance in Schizophrenia. From Research to Clinic: Potential Implications for Treatment

Cytokines are one of the most important components of the immune system. They orchestrate the brain's response to infectious and other exogenous insults and are crucial mediators of the cross-talk between the nervous and immune systems. Epidemiological studies have demonstrated that severe infections and autoimmune disorders, in addition to genetic predisposition, are risk factors for schizophrenia. Furthermore, maternal infection during pregnancy appears to increase the risk of schizophrenia, and proinflammatory cytokines may be negatively involved in the neurodevelopmental process. A cytokine imbalance has been described in the blood and cerebrospinal fluid of schizophrenia patients, particularly in the T helper type 1 [Th1] and type 2 [Th2] cytokines, albeit the results of such studies appear to be contradictory. Chronic stress, likewise, appears to contribute to a lasting proinflammatory state and likely also promotes the disorder. The aim of this mini-review is to investigate the roles of different cytokines in the pathophysiology of schizophrenia and define how cytokines may represent key molecular targets to regulate for the prevention and treatment of schizophrenia. How current antipsychotic drugs impact cytokine networks is also evaluated. In this context, we propose to change the focus of schizophrenia from a traditionally defined brain disorder, to one that is substantially impacted by the periphery and immune system.

Type 17 Immune Response Facilitates Progression of Inflammation and Correlates with Cognition in Stable Schizophrenia

Dysregulation of the type 17 immune pathway has already been considered in schizophrenia and we previously measured decreased sera values of interleukin (IL)-17 in early stages. We further explored the possible correlation of IL-17 systemic levels with proinflammatory cytokines and cognitive scores and additionally analyzed the percentage of IL-17 producing lymphocytes in peripheral blood of patients with stable schizophrenia. We included 27 patients diagnosed with schizophrenia (F20), after a three-month stable depot antipsychotic therapy (risperidone or paliperidone) and 18 healthy control subjects. Positive and Negative Syndrome Scale of Schizophrenia and the Montreal-Cognitive Assessment (MoCA) were conducted. Sera concentrations of IL-17, IL-6, tumor necrosis factor alpha (TNF-α) and soluble ST2 receptor (sST2) were measured. Flow cytometry and Natural Killer (NK) and T cell analyses were done in 10 patients and 10 healthy controls. Moderate positive correlation was established between IL-17 and TNF-α (r = 0.640; p = 0.001), IL-17 and IL-6 (r = 0.514; p = 0.006), IL-17 and sST2 (r = 0.394; p = 0.042). Furthermore, a positive correlation between the serum levels of IL-17 and MoCA scores was observed, especially with visuospatial and executive functioning, as well as language functioning and delayed recall (p < 0.05). Significantly higher percentage of IL-17 producing CD56⁺ NK cells was measured in peripheral blood of patients with schizophrenia in remission vs. healthy individuals (p = 0.001). The percentage of CD4⁺ T cells and CD4⁺ T cells that produce IL-17 was significantly increased in patients (p = 0.001). This study revealed the involvement of innate type 17 immune response in the progression of inflammation and this could be related to cognitive functioning in stable schizophrenia.

Interleukin-17 and Interleukin-10 Association with Disease Progression in Schizophrenia

BACKGROUND

Alteration in cytokine levels are known to be involved in the pathogenesis of schizophrenia.

OBJECTIVES

To estimate the serum levels of interleukin-17 (IL-17) and interleukin-10 (IL-10) and their association with disease progression in schizophrenia.

METHODS

A total of 67 schizophrenia cases were enrolled in the present study. IL-17 and IL-10 were estimated by enzyme-linked immunosorbent assay. Positive and Negative Syndrome Scale (PANSS) was used to evaluate disease severity.

RESULTS

IL-17 was positively correlated with positive symptom score (r = 0.256, p = .036), general psychopathology score (r = 0.255, p = .038) and total score (r = 0.273, p = .025) in schizophrenia. IL-17 and IL-10 were significantly increased in schizophrenia cases with PANSS more than 85 compared to those with 71-85.

CONCLUSION

IL-17 and IL-10 are associated with disease severity in schizophrenia but are not good markers for predicting the disease progression.

Inflammation and Oxidative Stress in Deficit Schizophrenia

Introduction

Differences in parameters related to inflammatory and oxidative stress in deficit (DS) and nondeficit schizophrenia (non-DS) may support the DS/non-DS categorization of schizophrenia. For DS patients, non-DS patients, and for healthy controls, this study aims to evaluate the serum levels of: proinflammatory cytokines of interleukin (IL) 1β, tumor necrosis factor (TNF) α, Interferon (IFN) γ, IL-12, and IL-17; anti-inflammatory cytokines of IL-10, IFN-α, and transforming growth factor (TGF) β; and antioxidant biomarkers of paraoxonase1 (PON1) and Total Antioxidant Capacity (TAOC).

Method

Serum IL-1β, TNF-α, IFN-γ, IL-12, IL-17, IL-10, IFN-α, TGF-β, PON1 and TAOC levels were measured and performed in DS (n=26), non-DS (n=28), and healthy control (n=28) groups.

Results

Patients in the DS group had higher IL-17 levels than the non-DS group did. TGF-β values for both patient groups were significantly higher than those of the controls. PON1 and TAOC values for both patient groups were significantly lower than those of the controls.

Conclusion

Our findings may be evidence for the consideration that DS reflects a coherent entity within schizophrenia. Increased levels of IL-17 from pro-inflammatory cytokines may be related with DS.

Inflammation and Negative Symptoms of Schizophrenia: Implications for Reward Processing and Motivational Deficits

Negative symptoms of schizophrenia are debilitating and chronic in nature, are difficult to treat, and contribute to poor functional outcomes. Motivational deficits are a core negative symptom and may involve alterations in reward processing, which involve subcortical regions such as the basal ganglia. More specifically, dopamine-rich regions like the ventral striatum, have been implicated in these reward-processing deficits. Inflammation is one mechanism that may underlie negative symptoms, and specifically motivational deficits, via the effects of inflammatory cytokines on the basal ganglia. Previous work has demonstrated that inflammatory stimuli decrease neural activity in the ventral striatum and decrease connectivity in reward-relevant neural circuitry. The immune system has been shown to be involved in the pathophysiology of schizophrenia, and inflammatory cytokines have been shown to be altered in patients with the disorder. This paper reviews the literature on associations between inflammatory markers and negative symptoms of schizophrenia as well as the role of anti-inflammatory drugs to target negative symptoms. We also review the literature on the role of inflammation and reward processing deficits in both healthy controls and individuals with depression. We use the literature on inflammation and depression as a basis for a model that explores potential mechanisms responsible for inflammation modulating certain aspects of negative symptoms in patients with schizophrenia. This approach may offer novel targets to treat these symptoms of the disorder that are significant barriers to functional recovery and do not respond well to available antipsychotic medications.

B-cells and schizophrenia: A promising link or a finding lost in translation?

Recent genetic studies have suggested a potential role for B-cells in the pathogenesis of schizophrenia. Greater insight in the functioning of B-cells in patients with schizophrenia is therefore of importance. In this narrative review we aim to give an overview of the current literature on B-cells and schizophrenia. We found no evidence for altered numbers of these cells in blood. We did find support for increased levels of B-cell related cytokines and certain autoantibodies. Studies on B-cell development and function, or their numbers in cerebrospinal fluid or brain tissue are very limited. Based on the available data we appraise whether various B-cell mediated pathological mechanisms are likely to play a role in schizophrenia and provide directions for future research.

A Meta-analysis of Immune Parameters, Variability, and Assessment of Modal Distribution in Psychosis and Test of the Immune Subgroup Hypothesis

Immune parameters are elevated in psychosis, but it is unclear whether alterations are homogenous across patients or heterogeneity exists, consistent with the hypothesis that immune alterations are specific to a subgroup of patients. To address this, we examine whether antipsychotic-naïve first-episode psychosis patients exhibit greater variability in blood cytokines, C-reactive protein, and white cell counts compared with controls, and if group mean differences persist after adjusting for skewed data and potential confounds. Databases were searched for studies reporting levels of peripheral immune parameters. Means and variances were extracted and analyzed using multivariate meta-analysis of mean and variability of differences. Outcomes were (1) variability in patients relative to controls, indexed by variability ratio (VR) and coefficient of variation ratio (CVR); (2) mean differences indexed by Hedges g; (3) Modal distribution of raw immune parameter data using Hartigan's unimodality dip test. Thirty-five studies reporting on 1263 patients and 1470 controls were included. Variability of interleukin-6 (IL6) (VR = 0.19), tumor necrosis factor-α (TNFα) (VR = 0.36), interleukin-1β (VR = 0.35), interleukin-4 (VR = 0.55), and interleukin-8 (VR = 0.28) was reduced in patients. Results persisted for IL6 and IL8 after mean-scaling. Ninety-four percent and one hundred percent of raw data were unimodally distributed in psychosis and controls, respectively. Mean levels of IL6 (g = 0.62), TNFα (g = 0.56), interferon-γ (IFNγ) (g = 0.32), transforming growth factor-β (g = 0.53), and interleukin-17 (IL17) (g = 0.48) were elevated in psychosis. Sensitivity analyses indicated this is unlikely explained by confounders for IL6, IFNγ, and IL17. These findings show elevated cytokines in psychosis after accounting for confounds, and that the hypothesis of an immune subgroup is not supported by the variability or modal distribution.

Association of baseline inflammatory markers and the development of negative symptoms in individuals at clinical high risk for psychosis

Negative symptoms are common in individuals at clinical high-risk (CHR) for psychosis and are associated with worse functional outcomes. Inflammation may be one mechanism underlying negative symptoms. Inflammatory markers are altered in individuals at CHR and are associated with negative symptoms in patients with schizophrenia. We thus hypothesized that baseline inflammatory markers would predict the development of negative symptoms in individuals at CHR for psychosis. Thirty seven individuals from the North American Prodromal Longitudinal Study who met CHR criteria were included in the study. Inflammatory cytokines, including interferon (IFN)-λ, Interleukin (IL)-1β, IL-1 receptor antagonist (IL-1RA), IL-4, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF) were measured at baseline. Negative symptoms as measured by the Scale of Prodromal Symptoms, were measured at baseline and six and twelve months. Associations between inflammatory markers and the trajectory of negative symptoms (slope) over the first year of follow-up, were assessed using linear regression models controlling for age, sex, race and depressive symptom severity (as assessed by the Calgary Depression Scale for Schizophrenia). Baseline TNF (beta = 0.361, p = 0.007) and IL-6 (beta = -0.306, p = 0.026) predicted negative symptoms slopes, along with depressive symptom severity at baseline (beta = -0.596, p = 0.000). These findings demonstrate that inflammatory cytokines may underlie the development of negative symptoms in some individuals at CHR for psychosis. TNF predicted the development of negative symptoms independent of baseline depression. Given the heterogeneity of the CHR population, the comorbidity of negative symptoms and depression in this population, and the particular challenges in treating negative symptoms, immune markers could represent potential biomarkers that underlie the development of negative symptoms, representing a potential treatment target.

Role of IL-6/RORC/IL-22 axis in driving Th17 pathway mediated immunopathogenesis of schizophrenia

The immuno-inflammatory origin of schizophrenia in a subset of patients is viewed as a key element of an overarching etiological construct. Despite substantial research, the immune components exerting major effect are yet to be fully clarified. Disrupted T cell networks have consistently been linked to the pathogenesis of schizophrenia. Amongst the Th cell subsets, the Th17 cells have emerged as a paradigmatic lineage with significant functional implications in a vast number of immune mediated diseases including brain disorders such as schizophrenia. The present study was aimed at examining the functional role of the Th17 pathway in schizophrenia. To address this, genotyping of IL17A (rs2275913; G197A) Single Nucleotide Polymorphism was carried out by the PCR-RFLP method in 221 schizophrenia patients and 223 healthy control subjects. Gene expression of two transcription factors STAT3 and RORC was quantified in a subset of drug naïve schizophrenia patients (n = 56) and healthy controls (n = 52) by TaqMan assay. The plasma levels of fifteen cytokines belonging to Th17 pathway were estimated in a subset of drug naïve schizophrenia patients (n = 61) and healthy controls (n = 50) by using Bio-Plex Pro Human Th17 cytokine assays. The AA genotype was associated with higher total score of bizarre behaviour and apathy in female schizophrenia patients. A high gene expression level of RORC was observed in drug naïve schizophrenia patients. In addition, significantly elevated plasma levels of IL-6 and IL-22, and reduced levels of IL-1β and IL-17F were noted in schizophrenia patients. Taken together, these findings indicate a dysregulated Th17 pathway in schizophrenia patients.

TNF-α and IL-6 are associated with the deficit syndrome and negative symptoms in patients with chronic schizophrenia

INTRODUCTION

Increased inflammatory markers have been found in patients with chronic schizophrenia, and have been associated with negative symptoms. The deficit syndrome is a distinct subtype of schizophrenia, characterized by primary and enduring negative symptoms.

METHOD

We measured inflammatory markers in patients with and without deficit schizophrenia and controls.

RESULTS

Using multivariate analyses, tumor necrosis factor (TNF)-α and interleukin-6 were associated with the deficit syndrome, and TNF-α predicted blunted affect, alogia, and total negative symptoms.

CONCLUSIONS

Findings suggest that deficit schizophrenia subtype is associated with increased inflammation and immunotherapies may be a novel target for negative symptoms.

Elevated interleukin-17 and reduced testosterone in bipolar disorder. Relation with suicidal behaviour

Hormonal imbalance and inflammation are associated with bipolar disorder and suicidal behavior. The present study was designed to assess the levels of testosterone and interleukin-17 and their association with suicidal behavior in patients with bipolar disorder in remission. 41 bipolar disorder cases in remission and 41 age matched controls were enrolled in the study. Testosterone and interleukin-17 levels were assessed in both the groups. Interleukin-17 was significantly increased and testosterone was significantly reduced in bipolar disorder when compared with controls. IL-17 was negatively correlated with testosterone (r = -0.368, p = 0.018) and positively correlated with duration of disease (r = 0.382, p = 0.014) in bipolar disorder patients. Both didn't show any association with suicidal behavior. We conclude that testosterone is increased and interleukin-17 is reduced in bipolar disorder in remission and these were not associated with suicidal behavior in these patients.

Immune and metabolic alterations in first episode psychosis (FEP) patients

The molecular underpinnings associated to first episode psychosis (FEP) remains to be elucidated, but compelling evidence supported an association of FEP with blood alterations in biomarkers related to immune system, growth factors and metabolism regulators. Many of these studies have not been already confirmed in larger samples or have not considered the FEP diagnostic subgroups. In order to identify biochemical signatures of FEP, the serum levels of the growth factors BDNF and VEGF, the immune regulators IL-1RA, IL-6, IL-10 and IL-17, RANTES/CCL5, MIP-1b/CCL4, IL-8 and the metabolic regulators C-peptide, ghrelin, GIP, GLP-1, glucagon, insulin, leptin, PAI-1, resistin and visfatin were analysed in 260 subjects collected in the GET UP project. The results indicated an increase of MIP-1b/CCL4, VEGF, IL-6 and PAI-1, while IL-17, ghrelin, glucagon and GLP-1 were decreased in the whole sample of FEP patients (p < 0.01 for all markers except for PAI-1 p < 0.05). No differences were evidenced for these markers among the diagnostic groups that constitute the FEP sample, whereas IL-8 is increased only in patients with a diagnosis of affective psychosis. The principal component analysis (PCA) and variable importance analysis (VIA) indicated that MIP-1b/CCL4, ghrelin, glucagon, VEGF and GLP-1 were the variables mostly altered in FEP patients. On the contrary, none of the analysed markers nor a combination of them can discriminate between FEP diagnostic subgroups. These data evidence a profile of immune and metabolic alterations in FEP patients, providing new information on the molecular mechanism associated to the psychosis onset for the development of preventive strategies and innovative treatment targets.

Chorioamnionitis, IL-17A, and fetal origins of neurologic disease

The Centers for Disease Control and Prevention estimate that 1 in 323 infants have cerebral palsy. Highly correlated to intrauterine infection and inflammation, the incidence of cerebral palsy has remained constant over the last few decades despite significant advances in neonatal intensive care including improved ventilator techniques, surfactant therapy, maternal steroid administration, and use of intrapartum empiric antimicrobials. Recent advances in our understanding of immune responses to infection and inflammation have identified the cytokine IL-17A as a crucial component of early proinflammatory mediators that cause brain injury associated with neurologic impairment. Remarkably, maternal inflammatory responses to in utero inflammation and infection can also lead to potentially debilitating neurologic conditions in the offspring, which often become clinically apparent during childhood and/or early adulthood. This review details the role of IL-17A in fetal and maternal proinflammatory responses that lead to fetal brain injury and neurologic sequelae, including cerebral palsy. Recent findings regarding the role of maternal inflammatory responses in the development of childhood and adult neurologic conditions, such as autism, schizophrenia, and multiple sclerosis, will also be highlighted.

Interleukin-17 Alteration in First-Episode Psychosis: A Meta-Analysis

Schizophrenia is accompanied with central nervous system and peripheral immune system imbalances. Interleukin-17 (IL-17) is implicated in various immune and inflammatory processes. Aberrant levels of IL-17 have been reported in patients with schizophrenia, whereas the results are not consistent. To clarify the relationship between IL-17 and schizophrenia, we performed a meta-analysis in this study. We carried out a structured literature search in PubMed and Embase database up to April 16, 2017, and retrieved all eligible case-control studies according to the inclusion criteria. Finally, a total of 313 patients with drug-naïve first-episode psychosis and 238 healthy control subjects from 5 studies were included in our meta-analysis. There were no significant differences between first-episode psychosis patients and healthy controls with respect to the levels of IL-17 (p = 0.21), even when we removed 2 studies which were not European samples (p = 0.12). Our findings suggested that IL-17 may not be involved in the pathological mechanism of schizophrenia.

A meta-analysis of blood cytokine network alterations in psychiatric patients: comparisons between schizophrenia, bipolar disorder and depression

Schizophrenia, bipolar disorder and major depressive disorder (MDD) have all been associated with aberrant blood cytokine levels; however, neither the pattern of cytokine alterations nor the impact of clinical status have been compared across disorders. We performed a meta-analysis of blood cytokines in acutely and chronically ill patients with these major psychiatric disorders. Articles were identified by searching the PubMed, PsycInfo and Web of Science, and the reference lists of these studies. Sixty-eight studies met the inclusion criteria (40 schizophrenia, 10 bipolar disorder and 18 MDD) for acutely ill patients. Forty-six studies met the inclusion criteria (18 schizophrenia, 16 bipolar disorder and 12 MDD) for chronically ill patients. Levels of two cytokines (interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α)), one soluble cytokine receptor (sIL-2R), and one cytokine receptor antagonist (IL-1RA) were significantly increased in acutely ill patients with schizophrenia, bipolar mania and MDD compared with controls (P<0.01). Following treatment of the acute illness, IL-6 levels significantly decreased in both schizophrenia and MDD (P<0.01); sIL-2R levels increased in schizophrenia; and IL-1RA levels in bipolar mania decreased. In chronically ill patients, the levels of IL-6 were significantly increased in schizophrenia, euthymic (but not depressed) bipolar disorder and MDD compared with controls (P<0.01). The levels of IL-1β and sIL-2R were significantly increased in both chronic schizophrenia and euthymic bipolar disorder. Overall, there were similarities in the pattern of cytokine alterations in schizophrenia, bipolar disorder and MDD during acute and chronic phases of illness, raising the possibility of common underlying pathways for immune dysfunction. Effects of treatment on cytokines were more robust for schizophrenia and MDD, but were more frequently studied than for acute mania. These findings have important implications for our understanding of the pathophysiology and treatment of major psychiatric disorders.

Functional Implications of the IL-23/IL-17 Immune Axis in Schizophrenia

The aetiology of schizophrenia seems to stem from complex interactions amongst environmental, genetic, metabolic, immunologic and oxidative components. Chronic low-grade inflammation has been persistently linked to schizophrenia, and this has primarily been based on the findings derived from Th1/Th2 cytokine balance. While the IL-23/IL-17 axis plays crucial role in the pathogenesis of several immune-mediated disorders, it has remained relatively unexplored in neuropsychiatric disorders. Altered levels of cytokines related to IL-23/IL-17 axis have been observed in schizophrenia patients in a few studies. In addition, other indirect factors known to confer schizophrenia risk like complement activation and altered gut microbiota are shown to modulate the IL-23/IL-17 axis. These preliminary observations provide crucial clues about the functional implications of IL-23/IL-17 axis in schizophrenia. In this review, an attempt has been made to highlight the biology of IL-23/IL-17 axis and its relevance to schizophrenia risk and pathogenesis. Given the pathogenic potential of the IL-23/IL-17 axis, therapeutic targeting of this axis may be a promising approach to benefit patients suffering from this devastating disorder.