Judith Alferink

The CACNA1C gene encodes the α_1C subunit of voltage-gated Ca_V1.2 calcium channels, serving many pivotal functions throughout the body, including in the heart and brain. Clinical and genetic evidence implicates altered expression and/or function of CACNA1C/Ca_V1.2 in both cardiac and neuropsychiatric disease, including hypertension, cardiac arrhythmias, coronary artery disease, schizophrenia, bipolar disorder, depression, and autism. Gain-of-function mutations in CACNA1C cause Timothy syndrome, a potentially lethal multi-organ disorder with severe cardiac and neuropsychiatric defects. Conversely, the complete loss of Cacna1c is lethal in mice. The development of viable mouse and rat models with Cacna1c haploinsufficiency has allowed us to study the consequences of reduced expression and function of Cacna1c/Ca_V1.2 for heart and brain function from the molecular and cellular to the behavioral level. We review recent findings from these rodent models, revealing (i) alterations in behavior and (ii) in neuronal and non-neuronal function, as well as (iii) an impaired ability of the heart and its cardiomyocytes to adapt to (sympathetic) stress. Results lend further support to the notion that CACNA1C/Ca_V1.2 dysfunction represents a common link between cardiac and neuropsychiatric disorders and that appropriately targeting CACNA1C/Ca_V1.2 in selected patients may hold the promise of treating both conditions effectively with a single drug.

Introduction: Major depressive disorder (MDD) is a revalent and disabling condition increasingly associated with immune dysregulation. Dendritic cells (DCs) are key immune sentinels that shape inflammatory responses and T-cell polarization, including Th17 pathways implicated in depression-related mild inflammation. Given well-documented sex differences in immune responses and cytokine profiles in MDD, differential DC activation may represent a mechanistic link between sex-associated immune cell profiles in depression. However, DCs remain insufficiently characterized in MDD. Methods: We performed an exploratory study using flow cytometry-based immunophenotyping to assess circulating DC subsets, including CD1c ⁺ and CD141 ⁺ conventional DCs (cDCs), plasmacytoid DCs (pDCs), and their cytokine profiles in individuals with MDD ( n = 55) and healthy controls (HC, n = 32). Stratification by depression severity and sex, together with correlation and multivariate linear regression analyses, and cluster analysis, was used to examine associations between DC subsets and depressive symptom severity in females and males. Results: Stratification by HAM-D17 scores revealed reduced counts of pDCs and increased frequencies of CD11c ⁺ cDCs in the peripheral blood (PB) of severely depressed participants compared to HC or mildly depressed patients, respectively. Regarding cytokine-producing DCs, sex-stratified analyses showed that frequencies of IL-23 ⁺ cDCs were elevated and symptom-associated only in females with MDD compared to sex-matched controls, whereas frequencies of TNF ⁺ , IL-1β ⁺ , and IL-6 ⁺ cDCs were selectively increased in depressed males. Cluster analyses identified distinct female- and male-specific DC subset patterns distinguishing individuals with MDD from HC. Multivariate linear regression revealed a significant predictive contribution of cytokine-producing DCs, together with age and BMI, in females but not in males. Discussion: These findings demonstrate sex-specific alterations in cytokine-producing DCs in MDD and a strong association between IL-23 ⁺ cDCs and depressive symptom severity, suggesting a key role for these cells in immune dysregulation, particularly in females with depression.

The basic leucine zipper ATF-like transcription factor (BATF) plays a pivotal role in coordinating various aspects of lymphoid cell biology, yet essential functions in dendritic cells (DCs) have not been reported. Here we demonstrate that BATF deficiency leads to increased interferon (IFN) I production in Toll-like receptor 9 (TLR9)-activated plasmacytoid dendritic cells (pDCs), while BATF overexpression has an inhibitory effect. BATF-deficient mice exhibit elevated IFN I serum levels early in lymphocytic choriomeningitis virus (LCMV) infection. Through ATAC-Seq analysis, BATF emerges as a pioneer transcription factor, regulating approximately one third of the known transcription factors in pDCs. Integrated transcriptomics and ChIP-Seq approaches identified the transcriptional regulator DC-SCRIPT as a direct target of BATF that suppresses IFN I promoter activity by interacting with the interferon regulatory factor 7 (IRF7). Genome-wide association study (GWAS) analyses further implicate BATF in pDC-mediated human diseases. Our findings establish a novel negative feedback axis in IFN I regulation in pDCs during anti-viral immune responses orchestrated by BATF and DC-SCRIPT, with broader implications for pDC and IFN I-mediated autoimmunity.

Anorexia nervosa (AN) is a severe eating disorder characterized by excessive weight loss and lack of recognition of the seriousness of the current low body weight. Individuals with AN frequently exhibit an enhanced inflammatory state and altered blood levels of cytokines and chemokines. However, the expression of chemokine receptors in AN and the association with body composition parameters and treatment effects are still unknown. In this study, we examined the expression of CCR4, CCR6, CXCR3, and CXCR4 on peripheral blood T cells in female adolescents with AN before (T0, n = 24) and after 6 weeks of multimodal therapy (T1, n = 20). We also investigated their value to predict body mass index (BMI) and fat mass index (FMI) at baseline. Using multi-parameter flow cytometry, we found increased expression of CCR4, CXCR3, and CXCR4, but not CCR6, on CD4⁺ T cells in AN at T0 when compared to healthy controls (HC, n = 20). At T1, CXCR3 and CXCR4 expression decreased in AN. We found a close link between CCR4, CCR6 and CXCR4 expression and the adolescent mental health status in the study cohort as determined by the Strengths and Difficulties Questionnaire (SDQ). Specifically, CXCR4 expression correlated positively with emotional symptoms and peer relationship problems, as well as with the total sum score of the SDQ. In addition, CXCR4 expression on CD4⁺ T cells was a significant predictor of BMI and FMI in female adolescents. Our findings that CXCR4 expression on T cells is altered in adolescents with AN and predicts body composition parameters in adolescents suggest an impact of this chemokine receptor in the pathogenesis of AN.

Affective disorders (AD) including major depressive disorder (MDD) and bipolar disorder (BD) are common mood disorders associated with increased disability and poor health outcomes. Altered immune responses characterized by increased serum levels of pro-inflammatory cytokines and neuroinflammation are common findings in patients with AD and in corresponding animal models. Dendritic cells (DCs) represent a heterogeneous population of myeloid cells that orchestrate innate and adaptive immune responses and self-tolerance. Upon sensing exogenous and endogenous danger signals, mature DCs secrete proinflammatory factors, acquire migratory and antigen presenting capacities and thus contribute to neuroinflammation in trauma, autoimmunity, and neurodegenerative diseases. However, little is known about the involvement of DCs in the pathogenesis of AD. In this review, we summarize the current knowledge on DCs in peripheral immune responses and neuroinflammation in MDD and BD. In addition, we consider the impact of DCs on neuroinflammation and behavior in animal models of AD. Finally, we will discuss therapeutic perspectives targeting DCs and their effector molecules in mood disorders.

Anorexia nervosa (AN) is a severe eating disorder and often associated with altered humoral immune responses. However, distinct B cell maturation stages in peripheral blood in adolescents with AN have not been characterized. Treatment effects and the relationship between clinical and B cell parameters are also not fully understood. Here we investigated the phenotype of circulating B cell subsets and the relationship with body composition in adolescents with AN before (T0, n = 24) and after 6 weeks (T1, n = 20) of treatment. Using multi-parameter flow cytometry, we found increased percentages of antigen-experienced B cells and plasmablasts in patients with AN compared to healthy controls (n = 20). In contrast, percentages of CD1d⁺CD5⁺ B cells and transitional B cells with immunoregulatory roles were reduced at T0 and T1. These B cell frequencies correlated positively with fat mass, fat mass index (FMI), free fat mass index, and body mass index standard deviation score. In addition, scavenger-like receptor CD5 expression levels were downregulated on transitional B cells and correlated with fat mass and FMI in AN. Our findings that regulatory B cell subgroups were reduced in AN and their strong relationship with body composition parameters point toward an impact of immunoregulatory B cells in the pathogenesis of AN.

Contact hypersensitivity (CHS) is an established animal model for allergic contact dermatitis. Dendritic cells (DCs) play an important role in the sensitization phase of CHS by initiating T cell responses to topically applied haptens. The cannabinoid receptors 1 (CB1) and 2 (CB2) modulate DC functions and inflammatory skin responses, but their influence on the capacity of haptenized DCs to induce CHS is still unknown. We found lower CHS responses to 2,4-dinitro-1-fluorobenzene (DNFB) in wild type (WT) mice after adoptive transfer of haptenized Cnr2^−/− and Cnr1^−/−/Cnr2^−/− bone marrow (BM) DCs as compared to transfer of WT DCs. In contrast, induction of CHS was not affected in WT recipients after transfer of Cnr1^−/− DCs. In vitro stimulated Cnr2^−/− DCs showed lower CCR7 and CXCR4 expression when compared to WT cells, while in vitro migration towards the chemokine ligands was not affected by CB2. Upregulation of MHC class II and co-stimulatory molecules was also reduced in Cnr2^−/− DCs. This study demonstrates that CB2 modulates the maturation phenotype of DCs but not their chemotactic capacities in vitro. These findings and the fact that CHS responses mediated by Cnr2^−/− DCs are reduced suggest that CB2 is a promising target for the treatment of inflammatory skin conditions.

Viral infections are associated with increased incidence of severe sepsis. Particularly during the early stages, type I interferons (IFNs) are known mediators of detrimental effects. However, the functional role of early interferon β (IFNβ) and its cellular source during sepsis in the context of preexisting viral infections has not been defined. Using the colon ascendens stent peritonitis (CASP) model, we demonstrate that IFNβ^−/− and type I IFN receptor (IFNAR1)^−/− mice were less susceptible to sepsis after pre-stimulation with the viral mimetic poly(I:C). Wild type (WT) mice treated with poly(I:C) exhibited altered expression patterns of TNF and IL-12p40 during CASP which were dependent on IFNβ or IFNAR1, suggesting a mechanism for the increased sepsis susceptibility of WT mice. Using a double cytokine reporter mouse model, we present novel data on the simultaneous expression of IFNβ and IL-12p40 on a single cell level during polymicrobial sepsis in vivo. Conventional dendritic cells (cDCs) were identified as primary source of IFNβ and the protective cytokine IL-12p40 after CASP surgery irrespective of poly(I:C) pre-stimulation. These data demonstrated that if polymicrobial sepsis is preceded by a viral infection, IFNβ and IL-12p40 are expressed by polyfunctional cDCs suggesting that these cells can play both detrimental and beneficial roles during sepsis development.