Major Depressive Disorder (MDD) is increasingly conceptualized as a neuroimmune-metabolic-oxidative stress (NIMETOX) condition, partly driven by environmental stressors. While new antidepressant strategies have emerged to target NIMETOX pathways, the mechanism by which chronic stress reshapes metabolic regulation-particularly in the absence of clinically overt metabolic disease-remain poorly understood. Using a 6-week chronic unpredictable mild stress (CUMS) paradigm in metabolically healthy male and female mice, we evaluated depressive-like behaviors alongside circulating glucose and metabolic hormones, including insulin, resistin, Glucose-dependent Insulinotropic Polypeptide (GIP), Glucagon-like Peptide-1 (GLP-1), glucagon, ghrelin, leptin, and Plasminogen Activator Inhibitor-1 (PAI-1). We further assessed whether simvastatin, curcumin, S-adenosyl methionine (SAMe), or pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor, normalize CUMS-induced metabolic and behavioral alterations, using fluoxetine as a reference antidepressant. CUMS induced a hypoinsulinemic state accompanied by enhanced basal insulin sensitivity and reduced insulin resistance, while central appetite regulation and adipose inflammatory profiles remained preserved. Indices of lower insulin resistance were strongly associated with sucrose preference and immobility time. Glucagon and PAI-1 showed positive associations with novel object recognition performance, whereas GIP and leptin were inversely related to open-field activity. Glucose levels correlated positively with rearing behavior. Despite significant improvements in depressive-like behaviors, none of the pharmacological interventions normalized the stress-induced metabolic hormone profile. Marked sex differences were observed, with females displaying a catabolic, immune-ready phenotype and males showing a relative anabolic bias. These findings indicate that CUMS induces a non-pathological, adaptive metabolic hormone reprogramming rather than metabolic dysfunction, supporting the interpretation of stress-related metabolic changes as resilient adaptations within the NIMETOX framework. ### Competing Interest Statement The authors have declared no competing interest. Sichuan Science and Technology Program, 2023YFG0130, 2025ZNSFSC1567

BACKGROUND:Major depressive disorder (MDD) involves dysregulated neuroimmune, metabolic, and inflammatory pathways. This study characterized metabolic hormone and adipokine profiles in Chinese MDD patients stratified for metabolic syndrome (MetS), and examined associations with depression severity (OSOD), suicidal ideation (SI), illness recurrence (ROI), and physiosomatic symptoms. METHODS:We enrolled 125 MDD inpatients (age 18-70 years) and 40 healthy controls (age 20-65 years). Fasting serum insulin, glucose, glucagon, GIP, GLP‑1, leptin, secretin, PAI‑1, resistin, ghrelin, and adiponectin were measured. The acute‑phase inflammatory (API) response was assessed using albumin, transferrin, and monomeric CRP. Group comparisons used ANOVA or general linear models (adjusted for age, BMI, MetS) with false discovery rate correction. Associations were tested with Pearson correlations, stepwise multiple regression, and binary logistic regression. Discriminatory performance was evaluated by ROC‑AUC. RESULTS:MDD showed significantly lower insulin, glucagon, and PAI‑1, along with a higher API index (all adjusted). A composite GAP index (ghrelin, adiponectin, PAI‑1) correlated negatively with OSOD, SI, ROI, physiosomatic symptoms, and adverse childhood experiences (ACEs). A model combining GAP index, API index, and ACEs discriminated MDD from controls with AUC = 0.864 and 80% accuracy. CONCLUSION:Severe MDD in this Chinese inpatient sample is characterized by suppressed anabolic hormones and lower adipokines coupled with mild chronic inflammation, independent of MetS. This hormonal‑immune‑metabolic signature is integral to MDD pathophysiology.

PURPOSE:Fluoxetine, a selective serotonin reuptake inhibitor, is widely used for the treatment of depressive symptoms in cancer patients. However, there is conflicting evidence regarding its effects on immunity and cancer. The present study aimed to clarify the effect of fluoxetine administration before or after the initiation of B16F10 melanoma lung metastasis formation on cancer development. METHODS:In the present study, we used an experimental tumoral model of lung metastasis formation by melanoma B16F10 cells in C57BL/6J mice. Fluoxetine was administered 14 days before or 14 days after tumor cell injection. We assessed the mice's behavior in the forced swimming test, the formation of lung metastases, the proliferative and metabolic activity of splenocytes, and the activity of metalloproteinases. RESULTS:Results showed that repeated daily fluoxetine administration (10 mg/kg) after injection of tumor cells: 1) decreased the number of metastasis in the lungs; 2) decreased immobility time in forced swimming test; 3) increased proliferative and metabolic activity of splenocytes, 4) decreased ability of splenocytes to produce metalloproteinase 9 (MMP-9) whereas fluoxetine administration before injection of tumor cells induced opposite effect. CONCLUSION:Obtained data confirm the inhibitory effect of fluoxetine on melanoma growth, but only when this antidepressant is given to animals that already struggle with melanoma development. Fluoxetine administration before cancer development accelerates its progress and induces unbeneficial changes in immunity and metalloproteinase levels in comparison to saline-pretreated mice.

Interactions between the nervous and immune systems play a central role in depression, yet the mechanisms integrating neuroimmune signaling remain poorly understood. Here, we investigated the regulation of immune checkpoints in three mechanistically distinct models of depressive-like behavior: treatment-resistant Wistar Kyoto rats, Wistar rats exposed to chronic restraint stress, and Porphyromonas gingivalis-infected C57BL/6 mice. Using integrated molecular analyses that combine targeted gene and protein measurements with transcriptional profiling, we identified alterations in immune checkpoint signaling within the CD28 superfamily that were associated with the severity of depressive-like phenotypes across selected models. Across all models, immune signaling showed concurrent costimulatory activation (CD28, ICOS) alongside alterations in the PD-1/PD-L1 axis, including increased PD-1 levels in peripheral blood and changes in PD-L1 expression in the brain. Transcriptional alterations in CD28-superfamily regulators and related immune modulators further indicated the coexistence of immune activation and partial exhaustion signatures, consistent with chronic immune dysregulation rather than a uniform inflammatory response. Among the investigated immune checkpoints, reduced PD-L1 expression in the WKY model represented the most consistent finding across targeted and transcriptomic analyses. Despite model-specific transcriptional differences, the expression levels of selected immune checkpoint-related genes were associated with performance in the novel object recognition test. Together, these findings suggest that alterations in the CD28 immune checkpoint (PD-1/PD-L1, CD28/CD80, ICOS/ICOSL) network accompany depressive-like phenotypes and suggest that impaired immune checkpoint control may contribute to cognitive dysfunction in depressive disorders. Targeting immune checkpoint pathways may therefore represent a promising direction for future therapeutic strategies in treatment-resistant depression.

Significant associations exist between major depressive disorder (MDD), metabolic syndrome (MetS), and cardiovascular disease, potentially attributable to heightened atherogenicity. This study aimed to ascertain if MDD, depression severity, suicidal behaviors, and neuroticism associate with elevated pro-atherogenic indices and reduced anti-atherogenic indices, including a reverse cholesterol transport (RCT) index. This study comprised 34 healthy controls and 33 MDD patients without MetS, and 35 controls and 31 MDD patients with MetS. It assessed total cholesterol (TC) and free cholesterol (FC), high-density lipoprotein cholesterol (HDLc), low-density lipoprotein cholesterol (LDLc), triglycerides (TG), apolipoprotein (ApoA), ApoB, cholesterol esterification rate, and a RCT composite. No significant associations between MDD and lipids were seen in the total study group that combined individuals with and without MetS. In individuals devoid of MetS, MDD is significantly correlated with (a) elevated FC, TG, ApoB, Castelli risk index 1, and ApoB/ApoA, and (b) diminished HDLc, ApoA, and RCT index. In individuals without MetS, there are notable correlations between the severity of depression, suicidal tendencies, neuroticism, and ApoB/ApoA, Castelli risk, and RCT indices. The link between lipids and MDD features cannot be adequately estimated by combining participants with and without MetS. It should be examined in a study sample that excludes subjects with MetS. The depression phenome, suicidal behaviors, and neuroticism correlate with diminished RCT and heightened atherogenicity, which are likely implicated in the pathophysiology of MDD. Increased atherogenicity and lowered RCT may represent novel drug targets for the treatment and prevention of MDD, neuroticism, and suicidal behaviors.

Background There are strong associations between major depressive disorder (MDD), metabolic syndrome (MetS) and cardiovascular disorder, which may be explained by increased atherogenicity and the microimmuneoxysome (Maes et al., 1994; 2011). The present study was conducted to determine if MDD, the severity of depression, suicidal behaviors, and neuroticism are associated with increased pro-atherogenic versus anti-atherogenic indices (PRO/ANTI-AI) and a reverse cholesterol transport (RCT) index. Methods This study included 34 healthy controls, 33 participants with MetS, and MDD patients with (n=31) and without (n=35) MetS, and measured total (TC) and free (FC) cholesterol, high (HDLc) and low (LDLc) density lipoprotein cholesterol, triglycerides (TG), apolipoprotein (ApoA), ApoB, cholesterol esterification rate (CER) and a composite (based on HDLc, ApoA and CER), reflecting RCT. Results In the combined MDD + MetS study group, no associations between MDD and lipids were detected. After the exclusion of all MetS participants, MDD is strongly associated with (a) increased FC, TG, ApoB, Castelli risk index 1, ApoB/ApoA, and (b) decreased HDLc, ApoA and the RCT index. In participants without MetS, there are significant associations between severity of depression, suicidal behaviors, and neuroticism and ApoB/ApoA, Castelli risk, and RCT indices. Conclusions Studies linking lipids to depressive subtypes can only be interpreted after MetS patients are excluded. The depression phenome, suicidal behaviors, and neuroticism are associated with a lowered RCT and increased atherogenicity, which are likely involved in the microimmuneoxidative pathophysiology of MDD. The RCT is a new drug target to treat and prevent MDD, neuroticism, and suicidal behaviors.

Due to the high prevalence of depression among cancer patients, antidepressant medications are frequently administered as adjuvant treatment. However, the safety of such medications in the development of metastasis is unclear. In this study, we investigated the effects of fluoxetine, desipramine, and mirtazapine on the liver metastasis of murine C26 colon carcinoma (cc). Balb/c male mice were administered these antidepressants intraperitoneally (i.p.) for 14 days following intrasplenic injections of C26 colon carcinoma cells. Desipramine and fluoxetine, but not mirtazapine, significantly increased the number of tumor foci and total volume of the tumor in liver tissue. This effect was associated with a decrease in the ability of splenocytes to produce interleukin (IL)-1β and interferon (IFN)-γ and an increase in their ability to produce interleukin (IL)-10. Similar changes were observed in plasma IL-1β, IFN-γ, and IL-10 levels. The current study demonstrates that the stimulatory effect of desipramine and fluoxetine, but not mirtazapine, on experimental colon cancer liver metastasis is associated with a suppression of immune defenses against the tumor.

There is evidence that chronic fatigue spectrum disorders (CFAS-Ds), including myalgic encephalomyelitis (ME), chronic fatigue syndrome (CFS), and chronic fatigue with physiosomatic symptoms including when due to comorbid medical disease, are characterized by neuroimmune and neuro-oxidative biomarkers. This study was performed to delineate the protein–protein interaction (PPI) network of CFAS-D and to discover the pathways, molecular patterns, and domains enriched in their PPI network. We performed network, enrichment, and annotation analyses using differentially expressed proteins and metabolics, which were established in patients with CFAS-D. The PPI network analysis revealed that the backbone of the highly connective CFAS-D network comprises NFKB1, CTNNB1, ALB, peroxides, NOS2, tumor necrosis factor (TNF), and interleukin-6 (IL-6) and that the network comprises interconnected immune-oxidative-nitrosative and Wnt/β-catenin subnetworks. Multiomics enrichment analysis shows that the CFAS-D network is highly significantly associated with cellular (antioxidant) detoxification, hydrogen peroxide metabolic process, peroxidase and oxidoreductase activity, interleukin-10 (IL-10) anti-inflammatory signaling and neurodegenerative canonical Wnt, the β-catenin complex, cadherin domains, cell–cell junctions and TLR2/4 pathways, and the transcription factors nuclear factor kappa B (NF-κB) and RELA. The top 10 DOID annotations of the CFAS-D network include four intestinal, three immune system disorders, cancer, and infectious disease. The custom Gene Ontology (GO) term annotation analysis revealed that the CFAS-D network is associated with a response to a toxic substance, lipopolysaccharides, bacterium, or virus. In conclusion, CFAS-D may be triggered by a variety of stimuli and their effects are mediated by aberrations in the cross-talks between redox, NF-κB, and Wnt/β-catenin signaling pathways leading to dysfunctions in multicellular organismal homeostatic processes.

Adverse childhood experiences (ACEs) enhance pro-inflammatory and pro-oxidant responses. In affective disorders, recent precision nomothetic psychiatry studies disclosed new pathway phenotypes, including an ROI—reoccurrence of illness (ROI)—oxidative stress latent construct. The aim of the present study is to delineate a) whether ACEs sensitize the M1 macrophage, the T helper cells (Th)1, Th2, and Th17, the IRS (immune-inflammatory-responses system), the CIRS (compensatory immunoregulatory system), and the neuroimmunotoxic and growth factor (GF) profiles and whether they are associated with ROI and the phenome of affective disorders and b) the molecular pathways underpinning the effects of the ACEs. We collected supernatants of stimulated (5 μg/mL of PHA and 25 μg/mL of LPS) and unstimulated diluted whole blood in 20 healthy controls and 30 depressed patients and measured a panel of 27 cytokines/GF using a Luminex method. ACEs (comprising mental and physical trauma, mental neglect, domestic violence, family history of mental disease, and parent loss) are accompanied by the increased stimulated, but not unstimulated, production of M1, Th1, Th2, Th17, IRS, neuroimmunotoxic, and GF profiles and are strongly correlated with ROI and the phenome. A latent vector extracted from the ROI features (recurrent episodes and suicidal behaviors) and the IRS/neuroimmunotoxic/GF profiles explains 66.8% of the variance in the phenome and completely mediates the effects of ACEs on the phenome. Enrichment analysis showed that the ACE-associated sensitization of immune/GF profiles involves JAK-STAT, nuclear factor-κB, tumor necrosis factor-α, G-protein coupled receptor, PI3K/Akt/RAS/MAPK, and hypoxia signaling. In summary, the ACE-induced sensitization of immune pathways and secondary immune hits predicts the phenome of affective disorders.

The physio-affective phenome of Long COVID-19 is predicted by (a) immune-inflammatory biomarkers of the acute infectious phase, including peak body temperature (PBT) and oxygen saturation (SpO2), and (b) the subsequent activation of immune and oxidative stress pathways during Long COVID. The purpose of this study was to delineate the effects of PBT and SpO2 during acute infection, as well as the increased neurotoxicity on the physical, psychological, social and environmental domains of health-related quality of life (HR-QoL) in people with Long COVID. We recruited 86 participants with Long COVID and 39 normal controls, assessed the WHO-QoL-BREF (World Health Organization Quality of Life Instrument-Abridged Version, Geneva, Switzerland) and the physio-affective phenome of Long COVID (comprising depression, anxiety and fibromyalgia-fatigue rating scales) and measured PBT and SpO2 during acute infection, and neurotoxicity (NT, comprising serum interleukin (IL)-1β, IL-18 and caspase-1, advanced oxidation protein products and myeloperoxidase, calcium and insulin resistance) in Long COVID. We found that 70.3% of the variance in HR-QoL was explained by the regression on the physio-affective phenome, lowered calcium and increased NT, whilst 61.5% of the variance in the physio-affective phenome was explained by calcium, NT, increased PBT, lowered SpO2, female sex and vaccination with AstraZeneca and Pfizer. The effects of PBT and SpO2 on lowered HR-QoL were mediated by increased NT and lowered calcium yielding increased severity of the physio-affective phenome which largely affects HR-QoL. In conclusion, lowered HR-Qol in Long COVID is largely predicted by the severity of neuro-immune and neuro-oxidative pathways during acute and Long COVID.

The approach towards myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) remains in a permanent state of crisis with fierce competition between the psychosocial school, which attributes ME/CFS to the perception of effort, and the medical approach (Maes and Twisk, BMC Med, 2010, 8, 35). The aim of this paper is to review how to construct a nomothetic model of ME/CFS using Partial Least Squares (PLS) path analysis and ensembling causome (bacterial translocation as assessed with IgM/IgA responses to LPS), protectome (lowered coenzyme Q10), adverse outcome pathways (AOP) including increased lysozyme, CD38+ T cell activation, cell-mediated immune activation (CMI), and IgM responses to oxidative specific epitopes and NO-adducts (IgM OSENO).Using PLS, we trained, tested and validated this knowledge- and data-driven causal ME/CFS model, which showed adequate convergence, construct and replicability validity.This bottom- up explicit data model of ME/CFS objectivates the descriptive narratives of the ME/CFS phenome, using causome-protectome-AOP data, whereby the abstract concept ME/CFS is translated into pathways, thereby securing the reification of the ME/CFS phenome. We found that 31.6% of the variance in the physiosomatic symptom dimension of ME/CFS was explained by the cumulative effects of CMI and CD38+ activation, IgM OSENO, IgA LPS, lysozyme (all positive) and coenzyme Q10 (inversely). Cluster analysis performed on the PLS-generated latent vector scores of all feature sets exposed three distinct immune groups of ME/CFS, namely one with increased lysozyme, one with increased CMI + CD38 activation + depressive symptoms, and another with increased bacterial translocation + autoimmune responses to OSENO.

Allergic contact dermatitis (ACD) is a T cell-mediated type of skin inflammation resulting from contact hypersensitivity (CHS) to antigens. There is strong comorbidity between ACD and major depression. Keratinocytes release immunomodulatory mediators including pro-inflammatory cytokines and chemokines, which modulate skin inflammation and are crucial cell type for the development of CHS. Our previous studies showed that fluoxetine and desipramine were effective in suppressing CHS in different mouse strains. However, the immune and molecular mechanisms underlying this effect remain to be explored. The aim of the current study was to determine the immune and molecular mechanisms of action of antidepressant drugs engaged in the inhibition of CHS response in the stimulated keratinocyte HaCaT cell line. The results show that LPS, TNF-α/IFN-γ, and DNFB stimulate HaCaT cells to produce large amounts of pro-inflammatory factors including IL-1β, IL-6, CCL2, and CXCL8. HaCaT stimulation was associated with increased expression of ICAM-1, a cell adhesion molecule, and decreased expression of E-cadherin. Imipramine, desipramine, and fluoxetine suppress the production of IL-1β, CCL2, as well as the expression of ICAM-1. LPS and TNF-α/IFN-γ activate p-38 kinase, but antidepressants do not regulate this pathway. LPS decreases E-cadherin protein expression and fluoxetine normalizes these effects. In summary, the antidepressant drugs examined in this study attenuate the stimulated secretion of pro-inflammatory cytokines, chemokines, and modulate adhesion molecule expression by the HaCaT cell line. Therefore, antidepressants may have some clinical efficacy in patients with ACD and patients with comorbid depression and contact allergy.

Nowoczesny styl życia, zanieczyszczenia środowiska i postępująca industrializacja przyczyniają się do wzrostu zachorowań na alergiczne kontaktowe zapalenie skóry, które jest reakcją odpornościową na niskocząsteczkowe substancje ? hapteny. Klinicznie manifestuje się na skórze obrzękiem, pęcherzami i pęknięciami, którym dodatkowo towarzyszy ból i świąd. Zapalny charakter choroby oraz widoczne na skórze zmiany, przyczyniają się do pogorszenia jakości życia chorych oraz zwiększają prawdopodobieństwo wystąpienia zaburzeń depresyjnych. Niewątpliwie objawy z kręgu zaburzeń lękowych i depresyjnych (przebiegających z bezsennością) mogą dotyczyć nawet 60% pacjentów dermatologicznych. Ponadto, jakość snu oraz stan skóry są ze sobą ściśle skorelowane i wzajemnie na siebie oddziałują. Niezwykle obiecujące są wyniki badań ostatnich lat, które wskazują, że leki przeciwdepresyjne, w praktyce klinicznej stosowane w leczeniu bezsenności, hamują również reakcję nadwrażliwości kontaktowej. Dlatego niniejsza praca jest poświęcona problemowi współwystępowania chorób skóry, depresji i bezsenności, roli układu odpornościowego w etiologii tych chorób oraz immunomodulacyjnych właściwości leków przeciwdepresyjnych, mogących wywierać terapeutyczne efekty w chorobach z zakresu psychodermatologii.

Wstęp

Interleukina (IL)-6 charakteryzuje się szerokim, plejotropowym działaniem nie tylko na komórki układu odpornościowego, ale na szereg innych komórek, w tym komórki ośrodkowego układu nerwowego. Cytokina ta oddziałuje na komórki poprzez 2 rodzaje receptorów: mIL-6R?, transbłonowy receptor (droga klasyczna), oraz jego rozpuszczalną formę sIL-6R? (transsygnalizacja). Wywoływana przez IL-6 transsygnalizacja jest odpowiedzialna za neurodegenerację, podczas gdy klasyczna sygnalizacja pełni rolę regeneracyjną i protekcyjną w tkance nerwowej. Komórki mikrogleju przejawiają działanie prozapalne prawie wyłącznie w wyniku transsygnalizacji. IL-6 zwiększa popęd snu zgodnie z rytmem dobowym i sprawuje kontrolę nad wzorcem snu. Bardzo poważne zaburzenia snu dotykają większości osób chorych na chorobę Alzheimera (AD) sprzyjając odkładaniu ? amyloidu (A?). Badania in vitro wskazują na szkodliwą rolę transsygnalizacji IL-6-sIL-6R w AD opartą o zwiększanie A? i hiperfosforylację białka tau, a badania in vivo przeciwnie, wskazują, że IL-6 umożliwia komórkom mikrogleju degradację fibrylarnego A?.

In depression, excessive glucocorticoid action may cause maladaptive brain changes, including in the pathways controlling energy metabolism. Insulin and glucagon-like peptide-1 (GLP-1), besides regulation of glucose homeostasis, also possess neurotrophic properties. Current study was aimed at investigating the influence of prenatal stress (PS) on insulin, GLP-1 and their receptor (IR and GLP-1R) levels in the hypothalamus. GLP-1 and GLP-1R were assayed also in the hippocampus and frontal cortex — brain regions mainly affected in depression. The second objective was to determine the influence of exendin-4 and insulin on CRH promoter gene activity in in vitro conditions. Adult male PS rats were subjected to acute stress and/or received orally glucose. Levels of hormones and their receptors were assayed with ELISA method. In vitro studies were performed on mHypoA-2/12 hypothalamic cell line, stably transfected with CRH promoter coupled with luciferase. PS has reduced GLP-1 and GLP-1R levels, attenuated glucose-induced increase in insulin concentration and increased the amount of phosphorylated IR in the hypothalamus of animals subjected to additional stress stimuli, and also decreased the GLP-1R level in the hippocampus. In vitro studies demonstrated that insulin is capable of increasing CRH promoter activity in the condition of stimulation of the cAMP/PKA pathway in the applied cellular model. Prenatal stress may act as a preconditioning factor, affecting the concentrations of hormones such as insulin and GLP-1 in the hypothalamus in response to adverse stimuli. The decreased GLP-1R level in the hippocampus could be linked with the disturbances in neuronal plasticity.

Several lines of evidence indicate that aberrations in immune-inflammatory pathways may contribute to the pathophysiology of schizophrenia spectrum disorders. Here, we propose a novel theoretical framework that was previously developed for major depression and bipolar disorder, namely, the compensatory immune-regulatory reflex system (CIRS), as applied to the neuro-immune pathophysiology of schizophrenia and its phenotypes, including first-episode psychosis (FEP), acute relapses, chronic and treatment-resistant schizophrenia (TRS), comorbid depression, and deficit schizophrenia. These schizophrenia phenotypes and manifestations are accompanied by increased production of positive acute-phase proteins, including haptoglobin and α2-macroglobulin, complement factors, and macrophagic M1 (IL-1β, IL-6, and TNF-α), T helper (Th)-1 (interferon-γ and IL-2R), Th-2 (IL-4, IL-5), Th-17 (IL-17), and T regulatory (Treg; IL-10 and transforming growth factor (TGF)-β1) cytokines, cytokine-induced activation of the tryptophan catabolite (TRYCAT) pathway, and chemokines, including CCL-11 (eotaxin), CCL-2, CCL-3, and CXCL-8. While the immune profiles in the different schizophrenia phenotypes indicate the activation of the immune-inflammatory response system (IRS), there are simultaneous signs of CIRS activation, including increased levels of the IL-1 receptor antagonist (sIL-1RA), sIL-2R and tumor necrosis factor-α receptors, Th-2 and Treg phenotypes with increased IL-4 and IL-10 production, and increased levels of TRYCATs and haptoglobin, α2-macroglobulin, and other acute-phase reactants, which have immune-regulatory and anti-inflammatory effects. Signs of activated IRS and CIRS pathways are also detected in TRS, chronic, and deficit schizophrenia, indicating that these conditions are accompanied by a new homeostatic setpoint between upregulated IRS and CIRS components. In FEP, increased baseline CIRS activity is a protective factor that may predict favorable clinical outcomes. Moreover, impairments in the CIRS are associated with deficit schizophrenia and greater impairments in semantic and episodic memory. It is concluded that CIRS plays a key role in the pathophysiology of schizophrenia by negatively regulating the primary IRS and contributing to recovery from the acute phase of illness. Therefore, components of the CIRS may offer promising therapeutic targets for schizophrenia.

The kynurenine pathway (KP), a major route of tryptophan catabolism, may be associated with the pathophysiology of depressive disorders. KP is responsible for ca. 99% of brain tryptophan metabolism via its degradation to kynurenine (KYN) catalyzed by indoleamine 2,3-dioxygenase (IDO). Some cytokines, such as interferon-γ (IFN-γ) and interleukin (IL)-6 are potent inducers of IDO. KYN is further converted by kynurenine aminotransferase (KAT) to the more neuroprotective kynurenic acid or by kynurenine 3-monooxygenase (KMO) to neurotoxic 3-hydroxykynurenine. The aim of the present study was to delineate whether the administration of imipramine (IMI) to rats subjected to chronic mild stress (CMS) may reverse behavioral changes induced by CMS in association with changes in immune-inflammatory markers and KP. We confirmed that the CMS procedure modeled one of the main symptoms of depression, i.e. anhedonia, and administration of IMI for 5 weeks resulted in a significant reduction in anhedonia in a majority of animals (CMS IMI-R animals), whereas 20% of animals did not respond to IMI treatment (CMS IMI-NR animals). We established that CMS procedure increased IFN-γ and IDO mRNA and decreased KAT II mRNA expression in the rat cortex. In the cortex and hippocampus, IMI treatment and non-responsiveness to IMI (in CMS IMI-NR animals) were associated with increased IL-6 mRNA expression. In the spleen, CMS increased production of IFN-γ and IL-6 proteins, while these cytokines were decreased by IMI in CMS IMI-R animals. Chronic IMI administration to CMS rats decreased IDO and KMO mRNA and protein expression and increased KAT II/KMO mRNA and protein ratio in IMI responders (CMS IMI-R) in comparison to CMS rats. In CMS IMI-NR rats, a significant increase in IDO mRNA expression and protein level in comparison with IMI responders was observed. Our findings indicate that resistance to therapeutic action of IMI could be explained by a deficiency of the inhibitory properties of IMI on IDO, KMO and KYN synthesis in the cortex. We conclude that the antidepressant activity of IMI may, at least in part, be explained by modulatory activities on the KAT II/KMO ratio in brain areas.

Major depressive disorder (MDD) is accompanied by higher serum IgM/IgA responses to LPS of Gram-negative bacteria, suggesting increased bacterial translocation and gut dysbiosis while the latter may occur in bipolar disorder (BD). There are differences between MDD and BD type 1 (BP1) and 2 (BP2) in nitro-oxidative stress biomarkers associated with leaky gut. This study examines serum IgM/IgA responses directed to LPS of 6 Gram-negative bacteria as well as IgG responses to oxidized LDL (oxLDL) in 29 BP1, 37 BP2, 44 MDD, and 30 healthy individuals. Increased IgM/IgA responses to Pseudomonas aeruginosa significantly discriminated patients with affective disorders (MDD plus BD) from controls. BP1 patients showed higher IgM responses to Morganella morganii as compared with MDD and BP2 patients. Patients with melancholia showed higher IgA responses to Citrobacter koseri as compared to controls and non-melancholic depression. The total score on the Hamilton Depression Rating Scale was significantly associated with IgA responses to C. koseri. IgG to oxLDL was significantly associated with increased bacterial translocation. In conclusion, MDD, BP1, and BP2 are accompanied by an immune response due to the increased load of LPS while these aberrations in the gut-brain axis are most pronounced in BP1 and melancholia. Activated oxidative stress pathways and autoimmune responses to oxidative specific epitopes in mood disorders may be driven by a breakdown in gut paracellular, transcellular, and/or vascular pathways. If replicated, drugs that protect the integrity of the gut barrier may offer novel therapeutic opportunities for BP1 and MDD.