Increased number of monocytes and plasma levels of MCP-1 and YKL-40 in first-episode psychosis

Association of symptom severity and cerebrospinal fluid alterations in recent onset psychosis in schizophrenia-spectrum disorders - An individual patient data meta-analysis

Neuroinflammation and blood-cerebrospinal fluid barrier (BCB) disruption could be key elements in schizophrenia-spectrum disorderś(SSDs) etiology and symptom modulation. We present the largest two-stage individual patient data (IPD) meta-analysis, investigating the association of BCB disruption and cerebrospinal fluid (CSF) alterations with symptom severity in first-episode psychosis (FEP) and recent onset psychotic disorder (ROP) individuals, with a focus on sex-related differences. Data was collected from PubMed and EMBASE databases. FEP, ROP and high-risk syndromes for psychosis IPD were included if routine basic CSF-diagnostics were reported. Risk of bias of the included studies was evaluated. Random-effects meta-analyses and mixed-effects linear regression models were employed to assess the impact of BCB alterations on symptom severity. Published (6 studies) and unpublished IPD from n = 531 individuals was included in the analyses. CSF was altered in 38.8 % of individuals. No significant differences in symptom severity were found between individuals with and without CSF alterations (SMD = -0.17, 95 %CI -0.55-0.22, p = 0.341). However, males with elevated CSF/serum albumin ratios or any CSF alteration had significantly higher positive symptom scores than those without alterations (SMD = 0.34, 95 %CI 0.05-0.64, p = 0.037 and SMD = 0.29, 95 %CI 0.17-0.41p = 0.005, respectively). Mixed-effects and simple regression models showed no association (p > 0.1) between CSF parameters and symptomatic outcomes. No interaction between sex and CSF parameters was found (p > 0.1). BCB disruption appears highly prevalent in early psychosis and could be involved in positive symptomś severity in males, indicating potential difficult-to-treat states. This work highlights the need for considering BCB breakdownand sex-related differences in SSDs clinical trials and treatment strategies.

Significance of chitinase-3-like protein 1 in the pathogenesis of inflammatory diseases and cancer

Chitinase-3-like protein 1 (CHI3L1) is a secreted glycoprotein that mediates inflammation, macrophage polarization, apoptosis, and carcinogenesis. The expression of CHI3L1 is strongly upregulated by various inflammatory and immunological diseases, including several cancers, Alzheimer's disease, and atherosclerosis. Several studies have shown that CHI3L1 can be considered as a marker of disease diagnosis, prognosis, disease activity, and severity. In addition, the proinflammatory action of CHI3L1 may be mediated via responses to various proinflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-6, and interferon-γ. Therefore, CHI3L1 may contribute to a vast array of inflammatory diseases. However, its pathophysiological and pharmacological roles in the development of inflammatory diseases remain unclear. In this article, we review recent findings regarding the roles of CHI3L1 in the development of inflammatory diseases and suggest therapeutic approaches that target CHI3L1.

Systemic inflammatory biomarkers in Schizophrenia are changed by ECT administration and related to the treatment efficacy

Immune inflammation has long been implicated in the pathogenesis of schizophrenia. Despite as a rapid and effective physical therapy, the role of immune inflammation in electroconvulsive therapy (ECT) for schizophrenia remains elusive. The neutrophils to lymphocytes (NLR), platelets to monocytes (PLR) and monocytes to lymphocytes (MLR) are inexpensive and accessible biomarkers of systemic inflammation. In this study, 70 schizophrenia patients and 70 age- and sex-matched healthy controls were recruited. The systemic inflammatory biomarkers were measured before and after ECT. Our results indicated schizophrenia had significantly higher peripheral NLR, PLR and MLR compared to health controls at baseline, while lymphocytes did not differ. After 6 ECT, the psychiatric symptoms were significantly improved, as demonstrated by the Positive and Negative Syndrome Scale (PANSS). However, there was a decline in cognitive function scores, as indicated by the Mini-Mental State Examination (MMSE). Notably, the neutrophils and NLR were significantly reduced following ECT. Although lymphocytes remained unchanged following ECT, responders had significantly higher lymphocytes compared to non-responders. Moreover, the linear regression analyses revealed that higher lymphocytes served as a predictor of larger improvement in positive symptom following ECT. Overall, our findings further highlighted the presence of systemic inflammation in schizophrenia patients, and that ECT may exert a therapeutic effect in part by attenuating systemic inflammation. Further research may therefore lead to new treatment strategies for schizophrenia targeting the immune system.

Microglia and Other Cellular Mediators of Immunological Dysfunction in Schizophrenia: A Narrative Synthesis of Clinical Findings

Schizophrenia is a complex psychiatric condition that may involve immune system dysregulation. Since most putative disease mechanisms in schizophrenia have been derived from genetic association studies and fluid-based molecular analyses, this review aims to summarize the emerging evidence on clinical correlates to immune system dysfunction in this psychiatric disorder. We conclude this review by attempting to develop a unifying hypothesis regarding the relative contributions of microglia and various immune cell populations to the development of schizophrenia. This may provide important translational insights that can become useful for addressing the multifaceted clinical presentation of schizophrenia.

Biomarkers in the cerebrospinal fluid of patients with psychotic disorders compared to healthy controls: a systematic review and meta-analysis

Psychotic disorders are severe mental disorders with poorly understood etiology. Biomarkers in the cerebrospinal fluid (CSF) could provide etiological clues and diagnostic tools for psychosis; however, an unbiased overview of CSF alterations in individuals with psychotic disorders is lacking. The objective of this study was to summarize all quantifiable findings in CSF from individuals with psychotic disorders compared to healthy controls (HC). Studies published before January 25th, 2023 were identified searching PubMed, EMBASE, Cochrane Library, Web of Science, ClinicalTrials.gov, and PsycINFO. Screening, full-text review, data extraction, and risk of bias assessments were performed by two independent reviewers following PRISMA guidelines. Findings in patients and healthy controls were compared and summarized using random-effects analyses and assessment of publication bias, subgroup and sensitivity analyses were performed. 145 studies, covering 197 biomarkers, were included, of which 163 biomarkers have not previously been investigated in meta-analyses. All studies showed some degree of bias. 55 biomarkers measured in CSF were associated with psychosis and of these were 15 biomarkers measured in ≥2 studies. Patients showed increased levels of noradrenaline (standardized mean difference/SMD, 0.53; 95% confidence interval/CI, 0.16 to 0.90) and its metabolite 3-methoxy-4-hydroxyphenylglycol (SMD, 0.30; 95% CI: 0.05 to 0.55), the serotonin metabolite 5-hydroxyindoleacetic acid (SMD, 0.11; 95% CI: 0.01 to 0.21), the pro-inflammatory neurotransmitter kynurenic acid (SMD, 1.58; 95% CI: 0.34 to 2.81), its precursor kynurenine (SMD,0.99; 95% CI: 0.60 to 1.38), the cytokines interleukin-6 (SMD, 0.58; 95% CI: 0.39 to 0.77) and interleukin-8 (SMD, 0.43; 95% CI: 0.24 to 0.62), the endocannabinoid anandamide (SMD, 0.78; 95% CI: 0.53 to 1.02), albumin ratio (SMD, 0.40; 95% CI: 0.08 to 0.72), total protein (SMD, 0.29; 95% CI: 0.16 to 0.43), immunoglobulin ratio (SMD, 0.45; 95% CI: 0.06 to 0.85) and glucose (SMD, 0.48; 95% CI: 0.01 to 0.94). Neurotensin (SMD, -0.67; 95% CI: -0.89 to -0.46) and γ-aminobutyric acid (SMD, -0.29; 95% CI: -0.50 to -0.09) were decreased. Most biomarkers showed no significant differences, including the dopamine metabolites homovanillic acid and 3,4-dihydroxyphenylacetic acid. These findings suggest that dysregulation of the immune and adrenergic system as well as blood-brain barrier dysfunction are implicated in the pathophysiology of psychotic disorders.

Evidence of innate immune dysfunction in first-episode psychosis patients with accompanying mood disorder

Background

Inflammation and increases in inflammatory cytokines are common findings in psychiatric disorders such as schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD). Meta-analyses of studies that measured circulating cytokines have provided evidence of innate inflammation across all three disorders, with some overlap of inflammatory cytokines such as IL-6 and TNF-α. However, differences across disorders were also identified, including increased IL-4 in BD that suggest different immune mechanisms may be involved depending on the type of disorder present.

Methods

We sought to identify if the presence or absence of an affective disorder in first-episode psychotic (FEP) patients was associated with variations in cytokine production after stimulation of peripheral blood mononuclear cells (PBMC). 98 participants were recruited and grouped into healthy controls (n = 45) and first-episode psychosis patients (n = 53). Psychosis patients were further grouped by presence (AFF; n = 22) or lack (NON; n = 31) of an affective disorder. We cultured isolated PBMC from all participants for 48 h at 37 °C under four separate conditions; (1) culture media alone for baseline, or the following three stimulatory conditions: (2) 25 ng/mL lipopolysaccharide (LPS), (3) 10 ng/mL phytohemagglutinin (PHA), and (4) 125 ng/ml α-CD3 plus 250 ng/ml α-CD28. Supernatants collected at 48 h were analyzed using multiplex Luminex assay to identify differences in cytokine and chemokine production. Results from these assays were then correlated to patient clinical assessments for positive and negative symptoms common to psychotic disorders.

Results

We found that PBMC from affective FEP patients produced higher concentrations of cytokines associated with both innate and adaptive immunity after stimulation than non-affective FEP patients and healthy controls. More specifically, the AFF PBMC produced increased tumor necrosis fctor (TNF)-α, interleukin (IL)-1β, IL-6, and others associated with innate inflammation. PBMC from AFF also produced increased IL-4, IL-17, interferon (IFN)γ, and other cytokines associated with adaptive immune activation, depending on stimulation. Additionally, inflammatory cytokines that differed at rest and after LPS stimulation correlated with Scale for the Assessment of Negative Symptoms (SANS) scores.

Conclusions

Our findings suggest that immune dysfunction in affective psychosis may differ from that of primary psychotic disorders, and inflammation may be associated with increased negative symptoms. These findings could be helpful in determining clinical diagnosis after first psychotic episode.

Cerebrospinal Fluid and Blood Biomarkers of Neuroinflammation and Blood-Brain Barrier in Psychotic Disorders and Individually Matched Healthy Controls

BACKGROUND AND HYPOTHESIS

Neuroinflammation and blood-brain barrier (BBB) dysfunction have been observed in patients with psychotic disorders. However, previous studies have mainly focused on selected patients and broad screenings of cerebrospinal fluid (CSF) of patients with recent onset psychosis compared to healthy controls are lacking.

STUDY DESIGN

We included 104 patients with recent onset psychotic disorder and 104 individually matched healthy controls. CSF and blood were analyzed for readily available markers assessing neuroinflammation and BBB dysfunction. Primary outcomes were CSF white blood cell count (WBC), total protein, IgG Index, and CSF/serum albumin ratio. Secondary outcomes included additional markers of inflammation and BBB, and analyses of association with clinical variables.

STUDY RESULTS

CSF/serum albumin ratio (Relative Mean Difference (MD): 1.11; 95%CI: 1.00-1.23; P = .044) and CSF/serum IgG ratio (MD: 1.17; 95%CI: 1.01-1.36; P = .036) was increased in patients compared to controls. A higher number of patients than controls had CSF WBC >3 cells/µl (seven vs. one, OR: 7.73, 95%CI: 1.33-146.49, P = .020), while WBC>5 cells/µl was found in two patients (1.9%) and no controls. Inpatients had higher serum WBC and neutrophil/lymphocyte ratio (all p-values for effect heterogeneity < .011). Mean CSF WBC (MD: 1.10; 95%CI: 0.97-1.26), protein (MD: 1.06; 95%CI: 0.98-1.15) and IgG index (MD: 1.05; 95%CI: 0.96-1.15) were not significantly elevated.

CONCLUSIONS

When comparing a broad group of patients with psychotic disorders with healthy controls, patients had increased BBB permeability, more patients had high CSF WBC levels, and inpatients had increased peripheral inflammation, consistent with the hypothesis of a subgroup of patients with increased activation of the immune system.

Lithium exposure and chronic inflammation with activated macrophages and monocytes associated with atherosclerosis in bipolar disorder

BACKGROUND

Atherosclerosis accounts for cardiovascular diseases (CVDs). This study aimed to explore the association between carotid intima-media thickness (CIMT), psycho-pharmacotherapy, and inflammatory markers along with other molecules related to atherosclerosis in bipolar disorder (BD).

METHODS

The euthymic patients with bipolar I disorder (BD-I) aged over 20 years were recruited to measure CIMT through ultrasound and the blood levels of lipid profiles, soluble tumor necrosis factor receptor-1 (sTNF-R1), soluble interleukin-6 receptor (sIL-6R), monocyte chemoattractant protein-1, chitinase 3-like 1, endothelial adhesive proteins, and thrombin-antithrombin complex.

RESULTS

Participants were 103 BD-I patients with mean 44.3 years old. The ratio of lithium exposure in relation to illness chronicity and the current daily dosage of lithium therapy exhibited an inverse relationship with CIMT in the entire sample. After controlling for age and BMI, multivariate regression indicated that a higher lithium level was significantly associated with decreased CIMT in the entire sample, high-risk (those with CVDs or endocrine diseases, N = 48), middle-risk (those without CVDs and endocrine diseases, N = 55), and low-risk (those aged <45 years in the middle-risk subgroup, N = 43) subgroups. Furthermore, higher levels of sTNF-R1 in the entire sample and high-risk subgroup and sIL-6R in the middle- and low-risk subgroups were statistically associated with greater CIMT.

LIMITATION

The age range was too wide to control for the effect of age on CIMT and medication.

CONCLUSIONS

Lithium exposure may be a protective factor for atherosclerosis progression in BD-I. The chronic inflammation in BD-I with activated macrophages and monocytes may link with the atherosclerosis development over time.

Peripheral inflammatory markers associated with brain volume reduction in patients with bipolar I disorder

BACKGROUND

Neuroinflammation and brain structural abnormalities are found in bipolar disorder (BD). Elevated levels of cytokines and chemokines have been detected in the serum and cerebrospinal fluid of patients with BD. This study investigated the association between peripheral inflammatory markers and brain subregion volumes in BD patients.

METHODS

Euthymic patients with bipolar I disorder (BD-I) aged 20-45 years underwent whole-brain magnetic resonance imaging. Plasma levels of monocyte chemoattractant protein-1 (MCP-1), chitinase-3-like protein 1 (also known as YKL-40), fractalkine (FKN), soluble tumour necrosis factor receptor-1 (sTNF-R1), interleukin-1β, and transforming growth factor-β1 were measured on the day of neuroimaging. Clinical data were obtained from medical records and interviewing patients and reliable others.

RESULTS

We recruited 31 patients with a mean age of 29.5 years. In multivariate regression analysis, plasma level YKL-40, a chemokine, was the most common inflammatory marker among these measurements displaying significantly negative association with the volume of various brain subareas across the frontal, temporal, and parietal lobes. Higher YKL-40 and sTNF-R1 levels were both significantly associated with lower volumes of the left anterior cingulum, left frontal lobe, right superior temporal gyrus, and supramarginal gyrus. A greater number of total lifetime mood episodes were also associated with smaller volumes of the right caudate nucleus and bilateral frontal lobes.

CONCLUSIONS

The volume of brain regions known to be relevant to BD-I may be diminished in relation to higher plasma level of YKL-40, sTNF-R1, and more lifetime mood episodes. Macrophage and macrophage-like cells may be involved in brain volume reduction among BD-I patients.

The role of the immune system in postpartum psychosis

Postpartum psychosis is the most severe psychiatric disorder associated with childbirth. The risk is particularly high for women with a history of bipolar disorder or schizoaffective disorder, or those who have suffered a previous episode of postpartum psychosis. However, the aetiology of the illness remains unclear. Pregnancy and the early postpartum are times of significant immunological change. Furthermore, alterations to the immune system have been implicated in the onset and course of various psychopathologies, both related and unrelated to childbirth. Emerging evidence, from studies on immune related disorders, immune cells and inflammatory markers, suggests that the immune system might also be involved in the pathophysiology of postpartum psychosis. Furthermore, recent research has also begun to explore the potential mechanisms underlying immune dysfunction in postpartum psychosis (e.g., disturbances in the Treg-CCN3 protein-(re)myelination axis). Nevertheless, more research is required to understand whether immune dysfunction is a cause or consequence of postpartum psychosis and to clarify the exact mechanisms involved. The aim of this short review is to present the current findings on immune system dysregulation in postpartum psychosis, discuss possible mechanisms underlying the association, highlight potential challenges and confounders and provide suggestions for future research.

A comparative study of complete blood count inflammatory markers in substance-free acute psychotic disorder and substance-induced psychosis

AIM

Recent studies showed a compare complete blood count (CBC) with its related measurements, including neutrophil to lymphocyte ratio (NLR), monocyte to lymphocyte ratio (MLR), and platelet to lymphocyte ratio, are a simple and affordable test for inflammatory markers. The aim of this controlled study is to compare CBC inflammatory markers in substance-induced psychosis (SIP) and substance-free acute psychotic disorder (SF-APD) and to evaluate whether these CBC inflammation values can be used in diagnosis.

METHODS

This retrospective study was conducted with the data of 76 SF-APD patients (including 60 cases of first-episode psychosis [FEP]), 98 SIP patients (including 48 cases of FEP), and 32 controls.

RESULTS

Patients with SF-APD and SIP had higher white blood cell counts, neutrophil and monocyte counts, and MLR than controls. An increased NLR was more distinct in SF-APD, while an increased MLR was observed in APD (both SF and SI) and FEP groups more than in the controls. A receiver operating characteristic analysis showed that the NLR could contribute to the identification of SF-APD (52.6% sensitivity and 12.5% specificity, area under curve [AUC] = 0.704, 2.47 cutoff value) while an MLR could contribute to the identification of APD (70.1% sensitivity and 12.5% specificity, AUC = 0.842) as well as FEP (71.3% sensitivity and 12.5% specificity AUC = 0.831) with 0.26 cutoff value.

CONCLUSIONS

An NLR and MLR might be of interest for inflammatory processes involved in acute and first-episode psychotic events, regardless of substance involvement.

Chemokine MCP1 is associated with cognitive flexibility in schizophrenia: A preliminary analysis

BACKGROUND

Peripheral levels of pro-inflammatory biomarkers have been shown to be altered in schizophrenia (SZ) and associated with cognitive impairments, but their relevance to specific cognitive domains remains unclear.

METHODS

Plasma levels of cytokines, chemokines, and vascular biomarkers were quantified and compared between SZ and healthy comparison (HC) groups. Cognition was assessed using the Delis-Kaplan Executive Function System Trail Making (TM) and Color Word Interference (CWI) tests. Linear regression analyses examined differential relationships of inflammatory biomarkers with executive function between groups.

RESULTS

Plasma levels of TNFα, ICAM1, and MCP1 were higher in individuals with SZ compared to HCs. Higher level of MCP1 was associated with increased CWI Inhibition Switching Errors in SZ but not HCs.

CONCLUSION

Like other studies, we found evidence for increased peripheral inflammation in SZ. We also showed that SZ with particularly high MCP1 levels had poor cognitive flexibility. Interventions to reduce chemokine elevations might prove beneficial for cognitive performance.

Therapeutic Drug Monitoring of Second- and Third-Generation Antipsychotic Drugs-Influence of Smoking Behavior and Inflammation on Pharmacokinetics

Both inflammation and smoking can influence a drug’s pharmacokinetic properties, i.e., its liberation, absorption, distribution, metabolism, and elimination. Depending on, e.g., pharmacogenetics, these changes may alter treatment response or cause serious adverse drug reactions and are thus of clinical relevance. Antipsychotic drugs, used in the treatment of psychosis and schizophrenia, should be closely monitored due to multiple factors (e.g., the narrow therapeutic window of certain psychotropic drugs, the chronicity of most mental illnesses, and the common occurrence of polypharmacotherapy in psychiatry). Therapeutic drug monitoring (TDM) aids with drug titration by enabling the quantification of patients’ drug levels. Recommendations on the use of TDM during treatment with psychotropic drugs are presented in the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology; however, data on antipsychotic drug levels during inflammation or after changes in smoking behavior—both clinically relevant in psychiatry—that can aid clinical decision making are sparse. The following narrative review provides an overview of relevant literature regarding TDM in psychiatry, particularly in the context of second- and third-generation antipsychotic drugs, inflammation, and smoking behavior. It aims to spread awareness regarding TDM (most pronouncedly of clozapine and olanzapine) as a tool to optimize drug safety and provide patient-tailored treatment.

Therapeutic Drug Monitoring of Second- and Third-Generation Antipsychotic Drugs—Influence of Smoking Behavior and Inflammation on Pharmacokinetics

Both inflammation and smoking can influence a drug’s pharmacokinetic properties, i.e., its liberation, absorption, distribution, metabolism, and elimination. Depending on, e.g., pharmacogenetics, these changes may alter treatment response or cause serious adverse drug reactions and are thus of clinical relevance. Antipsychotic drugs, used in the treatment of psychosis and schizophrenia, should be closely monitored due to multiple factors (e.g., the narrow therapeutic window of certain psychotropic drugs, the chronicity of most mental illnesses, and the common occurrence of polypharmacotherapy in psychiatry). Therapeutic drug monitoring (TDM) aids with drug titration by enabling the quantification of patients’ drug levels. Recommendations on the use of TDM during treatment with psychotropic drugs are presented in the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology; however, data on antipsychotic drug levels during inflammation or after changes in smoking behavior—both clinically relevant in psychiatry—that can aid clinical decision making are sparse. The following narrative review provides an overview of relevant literature regarding TDM in psychiatry, particularly in the context of second- and third-generation antipsychotic drugs, inflammation, and smoking behavior. It aims to spread awareness regarding TDM (most pronouncedly of clozapine and olanzapine) as a tool to optimize drug safety and provide patient-tailored treatment.

Therapeutic Drug Monitoring of Second- and Third-Generation Antipsychotic Drugs-Influence of Smoking Behavior and Inflammation on Pharmacokinetics

Both inflammation and smoking can influence a drug's pharmacokinetic properties, i.e., its liberation, absorption, distribution, metabolism, and elimination. Depending on, e.g., pharmacogenetics, these changes may alter treatment response or cause serious adverse drug reactions and are thus of clinical relevance. Antipsychotic drugs, used in the treatment of psychosis and schizophrenia, should be closely monitored due to multiple factors (e.g., the narrow therapeutic window of certain psychotropic drugs, the chronicity of most mental illnesses, and the common occurrence of polypharmacotherapy in psychiatry). Therapeutic drug monitoring (TDM) aids with drug titration by enabling the quantification of patients' drug levels. Recommendations on the use of TDM during treatment with psychotropic drugs are presented in the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology; however, data on antipsychotic drug levels during inflammation or after changes in smoking behavior-both clinically relevant in psychiatry-that can aid clinical decision making are sparse. The following narrative review provides an overview of relevant literature regarding TDM in psychiatry, particularly in the context of second- and third-generation antipsychotic drugs, inflammation, and smoking behavior. It aims to spread awareness regarding TDM (most pronouncedly of clozapine and olanzapine) as a tool to optimize drug safety and provide patient-tailored treatment.

Monocyte count in schizophrenia and related disorders: a systematic review and meta-analysis

OBJECTIVE

Increasing evidence suggests that immunological and inflammatory dysfunctions may play an important role in predisposition, onset, and progression of schizophrenia and related psychosis. The activation of cells of the mononuclear phagocyte system, especially microglia and monocytes, has been reported in schizophrenia. We carried out this systematic review and meta-analysis to investigate if there are significant differences in monocyte count comparing healthy controls with people suffering from schizophrenia and related disorders.

METHODS

We searched main electronic databases; nine records met all our criteria and were included in the meta-analysis. Meta-analyses based on random effects models have been carried out generating pooled standardised mean differences (SMDs) of monocyte count in peripheral blood between schizophrenia and related psychosis and healthy controls. Heterogeneity was estimated. Relevant sensitivity and subgroup analyses were conducted.

RESULTS

Patients showed higher monocyte count as compared with healthy control (SMD = 0.393; p = 0.001). Heterogeneity across studies was from moderate to high (I2 = 65.952%); sensitivity analysis leaving out two studies responsible for most of the heterogeneity showed a slightly higher SMD. Subgroup analyses confirmed this result, showing no significant differences in the effect size across different study characteristics.

CONCLUSIONS

Monocyte count can be considered an indirect marker of microglia activation in the central nervous system. Thus, the observed higher monocyte count in patients could be considered as a possible peripheral marker of microglia's activation in schizophrenia disorder.

Meta-analysis of total and differential white blood cell counts in schizophrenia

OBJECTIVE

Schizophrenia is associated with alterations in blood inflammatory markers, including cytokines. Total white blood cell (WBC) count is a marker of low-grade inflammation. We conducted a meta-analysis of total and differential WBC counts in patients with schizophrenia.

METHOD

Articles were identified through a systematic search of PsycINFO, Pub Med, Web of Science, and the associated references. Data were analyzed using a random effects approach.

RESULTS

Twenty-four studies met the inclusion criteria. Blood total WBC, monocytes, and neutrophils were significantly higher in schizophrenia vs. controls with small-to-medium effect sizes (standardized mean difference [SMD] = 0.39-0.53, P < 0.01 for each). In first-episode psychosis compared with controls, neutrophils and monocytes were significantly increased with similar effect sizes (SMD = 0.40-0.41, P ≤ 0.01 for each), and there was a trend for higher total WBC (SMD = 0.46, P = 0.05).

CONCLUSIONS

Consistent with studies of other inflammatory markers, we found evidence for increased total and differential WBC counts in schizophrenia. Our results complement other studies of WBC counts in schizophrenia. These findings are relevant to the pathophysiology and potentially the treatment of schizophrenia.

Overlapping evidence of innate immune dysfunction in psychotic and affective disorders

Disturbances of the immune system and immune responses after activation are a common finding in neuropsychiatric disorders. Psychotic and affective disorders such as major depressive disorder (MDD), schizophrenia (SCZ) and bipolar disorder (BD) also share high rates of comorbidity with inflammatory and metabolic disorders. Evidence of elevated circulating inflammatory cytokines, altered numbers and function of immune cells, and evidence of neuroinflammation including activation of microglia in the brain have been found in patients with SCZ, BD and MDD. Often these findings correlate to psychological state at the time of measurement. However, significant variation exists across these studies in many aspects, creating challenges in identifying a specific signature of immune dysfunction in these disorders. Innate immune dysfunction, and alterations in monocytes, the critical sentinel cells of the innate immune system, have been seen repeatedly in all three of these disorders, with frequent overlap in findings. In this review, dysfunction specific to the innate arm of the immune system is compared for overlapping evidence across three major psychotic and affective disorders.

Twin study shows association between monocyte chemoattractant protein-1 and kynurenic acid in cerebrospinal fluid

Preclinical studies indicate a link between the kynurenine pathway and monocyte chemoattractant protein-1 (MCP-1), but there is a lack of clinical studies examining this further. We here perform a secondary analysis of kynurenine metabolites and MCP-1 in cerebrospinal fluid of 23 twins affected from schizophrenia, bipolar disorder or unaffected. We show an association between MCP-1 and kynurenic acid (KYNA), driven by unique environmental influences and a less pronounced association between MCP-1 and tryptophan. No association was detected between MCP-1 and quinolinic acid. Further studies on the mechanism behind the putative relationship between KYNA and MCP-1 are needed.

Protective Effect of the MCP-1 Gene Haplotype against Schizophrenia

While cytokines and their genetic variants have been intensively studied in schizophrenia, little attention has been focused on chemokines in the last years. The monocyte chemoattractant protein 1 (MCP-1) is known to attract peripheral monocytes to the brain during an inflammatory reaction and to affect the T helper (Th) cell development by stimulating Th2 polarization. Owing to the neuroinflammation in schizophrenia and the variable level of MCP-1 in these patients' sera, we proposed to analyze the impact of functional genetic variants of the MCP-1 gene (MCP-1-2518A/G (rs1024611), MCP-1-362G/C (rs2857656), and MCP-1 int1del554-567 (rs3917887)) in schizophrenic patients. We conducted a case-control study on a Tunisian population composed of 200 patients and 200 controls using RFLP-PCR. Our results indicated that the minor alleles (-2518G and Del554-567) were significantly more prevalent in controls than in patients (P=0.001/adjusted OR = 0.42, P=0.04/adjusted OR = 0.64), whereas, for -362C minor allele, increased risk of schizophrenia was revealed (P=0.001, adjusted OR = 2.38). In conclusion, we have identified the haplotype combination -2581G/-362G/int1del554-567 that could mediate protection against schizophrenia (P=0.0038, OR = 0.19) and the effect could result more strongly from the MCP-1 -2582G with -362G variants, whereas the effect of int1del554-567 may in part be explained by its LD with -362.