The dopaminergic system in autoimmune diseases

Dopamine induces in vitro migration of synovial fibroblast from patients with rheumatoid arthritis

Preventing synovial fibroblast (SF) migration into the adjacent cartilage is a desirable therapeutic target in rheumatoid arthritis (RA). As previous studies demonstrated that RASF and SF from osteoarthritis (OA) patients express dopamine receptors (DR), aim of the present study was to investigate the impact of dopamine on mobility of fibroblasts from patients with chronic arthritides. Synovial tissue and fibroblasts were obtained from RA and OA patients. Immunohistochemistry was performed for all DR-subtypes in the invasion zone. Migration- and motility-assays were performed under DR-stimulation. Cytokines were evaluated using ELISA. Expression of DRs was evaluated by flow cytometry, and DR activation was measured by xCELLigence real-time analysis. All DRs were expressed in RA invasion zone. Migration and motility of RASF and OASF were increased after DR stimulation in patients ≤ 75 years old. Synovial fibroblasts from older RA patients (> 75 years old) expressed lower levels of D1-, D2- and D4-DR than patients ≤ 75 years old. DR activation was not altered in older patients. Our results suggest a possible involvement of dopamine on migration of fibroblasts from arthritis patients. Therefore, the synovial dopaminergic pathway might represent a potential therapeutic target to interfere with progressive joint damage in RA patients.

Rojo A, Manda G, Boscá L, Cuadrado A. Inflammation in Parkinson's Disease: Mechanisms and Therapeutic Implications

Parkinson's disease (PD) is a common neurodegenerative disorder primarily characterized by the death of dopaminergic neurons that project from the substantia nigra pars compacta. Although the molecular bases for PD development are still little defined, extensive evidence from human samples and animal models support the involvement of inflammation in onset or progression. However, the exact trigger for this response remains unclear. Here, we provide a systematic review of the cellular mediators, i.e., microglia, astroglia and endothelial cells. We also discuss the genetic and transcriptional control of inflammation in PD and the immunomodulatory role of dopamine and reactive oxygen species. Finally, we summarize the preclinical and clinical approaches targeting neuroinflammation in PD.

Perphenazine Attenuates the Pro-Inflammatory Responses in Mouse Models of Th2-Type Allergic Dermatitis

Developing dermatitis therapeutics has been faced with challenges including adverse effects of topical steroid and high cost of new developing drugs. Here, we found the expression levels of dopamine receptor D2 is higher in skin biopsies of dermatitis patients and an oxazolone-induced animal model of dermatitis. We used perphenazine, an FDA-approved dopamine receptor antagonist to determine the therapeutic effect. Two different animal models including 12-o-tetradecanoylphorbol-13-acetate (TPA) and oxazolone (OXA)-induced dermatitis were employed. TPA and OXA-mediated ear swelling was attenuated by perphenazine. Moreover, perphenazine inhibited infiltrated mast cells into lesion area. We found levels of serum IgE, histamine and cytokines are decreased in mice cotreated with perphenazine and OXA compared to OXA-treated mice. Overall, this is a first study showing that the FDA-approved, anti-psychotic drug, perphenazine, alleviates animal models of dermatitis.

Microbiota Metabolites in Health and Disease

Metabolism is one of the strongest drivers of interkingdom interactions-including those between microorganisms and their multicellular hosts. Traditionally thought to fuel energy requirements and provide building blocks for biosynthetic pathways, metabolism is now appreciated for its role in providing metabolites, small-molecule intermediates generated from metabolic processes, to perform various regulatory functions to mediate symbiotic relationships between microbes and their hosts. Here, we review recent advances in our mechanistic understanding of how microbiota-derived metabolites orchestrate and support physiological responses in the host, including immunity, inflammation, defense against infections, and metabolism. Understanding how microbes metabolically communicate with their hosts will provide us an opportunity to better describe how a host interacts with all microbes-beneficial, pathogenic, and commensal-and an opportunity to discover new ways to treat microbial-driven diseases.

The Cross-Talk Between the Dopaminergic and the Immune System Involved in Schizophrenia

Dopamine is one of the neurotransmitters whose transmission is altered in a number of neural pathways in the brain of schizophrenic patients. Current evidence indicates that these alterations involve hyperactive dopaminergic transmission in mesolimbic areas, striatum, and hippocampus, whereas hypoactive dopaminergic transmission has been reported in the prefrontal cortex of schizophrenic patients. Consequently, schizophrenia is associated with several cognitive and behavioral alterations. Of note, the immune system has been found to collaborate with the central nervous system in a number of cognitive and behavioral functions, which are dysregulated in schizophrenia. Moreover, emerging evidence has associated schizophrenia and inflammation. Importantly, different lines of evidence have shown dopamine as a major regulator of inflammation. In this regard, dopamine might exert strong regulation in the activity, migration, differentiation, and proliferation of immune cells that have been shown to contribute to cognitive functions, including T-cells, microglial cells, and peripheral monocytes. Thereby, alterations in dopamine levels associated to schizophrenia might affect inflammatory response of immune cells and consequently some behavioral functions, including reference memory, learning, social behavior, and stress resilience. Altogether these findings support the involvement of an active cross-talk between the dopaminergic and immune systems in the physiopathology of schizophrenia. In this review we summarize, integrate, and discuss the current evidence indicating the involvement of an altered dopaminergic regulation of immunity in schizophrenia.

Integrative systems and functional analyses reveal a role of dopaminergic signaling in myelin pathogenesis

BACKGROUND

Myelin sheaths surrounding axons are critical for electrical signal transmission in the central nervous system (CNS). Diseases with myelin defects such as multiple sclerosis (MS) are devastating neurological conditions for which few effective treatments are available. Dysfunction of the dopaminergic system has been observed in multiple neurological disorders. Its role in myelin pathogenesis, however, is unclear.

METHODS

This work used a combination of literature curation, bioinformatics, pharmacological and genetic manipulation, as well as confocal imaging techniques. Literature search was used to establish a complete set of genes which is associated with MS in humans. Bioinformatics analyses include pathway enrichment and crosstalk analyses with human genetic association studies as well as gene set enrichment and causal relationship analyses with transcriptome data. Pharmacological and CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9) genetic manipulation were applied to inhibit the dopaminergic signaling in zebrafish. Imaging techniques were used to visualize myelin formation in vivo.

RESULTS

Systematic analysis of human genetic association studies revealed that the dopaminergic synapse signaling pathway is enriched in candidate gene sets. Transcriptome analysis confirmed that expression of multiple dopaminergic gene sets was significantly altered in patients with MS. Pathway crosstalk analysis and gene set causal relationship analysis reveal that the dopaminergic synapse signaling pathway interacts with or is associated with other critical pathways involved in MS. We also found that disruption of the dopaminergic system leads to myelin deficiency in zebrafish.

CONCLUSIONS

Dopaminergic signaling may be involved in myelin pathogenesis. This study may offer a novel molecular mechanism of demyelination in the nervous system.

Where Is Dopamine and how do Immune Cells See it?: Dopamine-Mediated Immune Cell Function in Health and Disease

Dopamine is well recognized as a neurotransmitter in the brain, and regulates critical functions in a variety of peripheral systems. Growing research has also shown that dopamine acts as an important regulator of immune function. Many immune cells express dopamine receptors and other dopamine related proteins, enabling them to actively respond to dopamine and suggesting that dopaminergic immunoregulation is an important part of proper immune function. A detailed understanding of the physiological concentrations of dopamine in specific regions of the human body, particularly in peripheral systems, is critical to the development of hypotheses and experiments examining the effects of physiologically relevant dopamine concentrations on immune cells. Unfortunately, the dopamine concentrations to which these immune cells would be exposed in different anatomical regions are not clear. To address this issue, this comprehensive review details the current information regarding concentrations of dopamine found in both the central nervous system and in many regions of the periphery. In addition, we discuss the immune cells present in each region, and how these could interact with dopamine in each compartment described. Finally, the review briefly addresses how changes in these dopamine concentrations could influence immune cell dysfunction in several disease states including Parkinson's disease, multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, as well as the collection of pathologies, cognitive and motor symptoms associated with HIV infection in the central nervous system, known as NeuroHIV. These data will improve our understanding of the interactions between the dopaminergic and immune systems during both homeostatic function and in disease, clarify the effects of existing dopaminergic drugs and promote the creation of new therapeutic strategies based on manipulating immune function through dopaminergic signaling. Graphical Abstract.

Chronic Infiltration of T Lymphocytes into the Brain in a Non-human Primate Model of Parkinson's Disease

Study of interactions between the nervous system and immunity offers insights into the pathogenesis of Parkinson's disease (PD) and potential therapeutic strategies for neurodegenerative diseases. Studies on rodents have revealed regulatory mechanisms of microglial activation and T lymphocyte recruitment in PD. However, the mechanisms underlying chronic T lymphocyte infiltration into the brain after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) injection into a non-human primate (NHP) model of PD remain unknown. This study aimed to investigate changes in serum RANTES (regulated on activation, normal T cell expression and secretion) and analyze the chronic infiltration of T lymphocytes into the brain and microglia activation in NHPs at 48 weeks post-MPTP administration. We found selective and local chronic infiltration of CD4+ and CD8+ T lymphocytes, loss of dopaminergic neurons, dopamine transporter expression, chronic normalization of RANTES in the peripheral blood, and altered microglial morphology at 48 weeks after MPTP injection. This study confirms the involvement of CD4+ and CD8+ T lymphocyte infiltration in MPTP-induced NHP models of PD. Additionally, we corroborated previous findings regarding the mechanisms of T lymphocyte-induced neurodegeneration. The findings of chronic infiltration of T lymphocytes in our NHP model of PD provide novel insights into PD pathogenesis and the development of preventive and therapeutic agents.

Instantaneous depolarization of T cells via dopamine receptors, and inhibition of activated T cells of Psoriasis patients and inflamed human skin, by D1-like receptor agonist: Fenoldopam

Activated T cells are pathological in various autoimmune and inflammatory diseases including Psoriasis, and also in graft rejection and graft-versus-host-disease. In these pathological conditions, selective silencing of activated T cells through physiological receptors they express remains a clinical challenge. In our previous studies we found that activation of dopamine receptors (DRs) in resting human T cells activates these cells, and induces by itself many beneficial T cell functions. In this study, we found that normal human T cells express all types of DRs, and that expression of D1R, D4R and D5R increases profoundly after T cell receptor (TCR) activation. Interestingly, DR agonists shift the membrane potential (V_m ) of both resting and activated human T cells, and induces instantaneous T cell depolarization within 15 seconds only. Thus, activation of DRs in T cells depolarize these immune cells, alike activation of DRs in neural cells. The skin of Psoriasis patients contains 20-fold more D1R⁺ T cells than healthy human skin. In line with that, 25-fold more D1R⁺ T cells are present in Psoriasis humanized mouse model. Highly selective D1-like receptor agonists, primarily Fenoldopam (Corlopam) - a D1-like receptor agonist and a drug used in hypertension, induced the following suppressive effects on activated T cells of Psoriasis patients: reduced chemotactic migration towards the chemokine SDF-1/CXCL12; reduced dramatically the secretion of eight cytokines: tumor necrosis factor-α, interferon-γ, interleukin-1β (IL-1β), IL-2, IL-4, IL-6, IL-8 and IL-10; and reduced three T cell activation proteins/markers: CD69, CD28 and IL-2. Next, we invented a novel topical/dermal Fenoldopam formulation, allowing it to be spread on, and providing prolonged and regulated release in, diseased skin. Our novel topical/dermal Fenoldopam: reduced secretion of the eight cytokines by activated human T cells; reduced IL-1β and IL-6 secretion by human lipopolysaccharide-inflamed skin; eliminated preferentially >90% of live and large/proliferating human T cells. Together, our findings show for the first time that both resting and activated T cells are depolarized instantaneously via DRs, and that targeting D1-like receptors in activated T cells and inflamed human skin by Fenoldopam, in Psoriasis, and potentially in other T cell-mediated diseases, could be therapeutic. Validation in vivo is required.

Metabolomic profile overlap in prototypical autoimmune humoral disease: a comparison of myasthenia gravis and rheumatoid arthritis

INTRODUCTION

Myasthenia gravis (MG) and rheumatoid arthritis (RA) are examples of antibody-mediated chronic, progressive autoimmune diseases. Phenotypically dissimilar, MG and RA share common immunological features. However, the immunometabolomic features common to humoral autoimmune diseases remain largely unexplored.

OBJECTIVES

The aim of this study was to reveal and illustrate the metabolomic profile overlap found between these two diseases and describe the immunometabolomic significance.

METHODS

Metabolic analyses using acid- and dansyl-labelled was performed on serum from adult patients with seropositive MG (n = 46), RA (n = 23) and healthy controls (n = 49) presenting to the University of Alberta Hospital specialty clinics. Chemical isotope labelling liquid chromatography mass spectrometry (CIL LC-MS) methods were utilized to assess the serum metabolome in patients; 12C/13C-dansyl chloride (DnsCl) was used to label amine/phenol metabolites and 12C/13C-p-dimethylaminophenacyl bromide (DmPA) was used for carboxylic acids. Metabolites matching our criteria for significance were selected if they were present in both groups. Multivariate statistical analysis [including principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA)] and biochemical pathway analysis was then conducted to gain understanding of the principal pathways involved in antibody-mediated pathogenesis.

RESULTS

We found 20 metabolites dysregulated in both MG and RA when compared to healthy controls. Most prominently, observed changes were related to pathways associated with phenylalanine metabolism, tyrosine metabolism, ubiquinone and other terpenoid-quinone biosynthesis, and pyruvate metabolism.

CONCLUSION

From these results it is evident that many metabolites are common to humoral disease and exhibit significant immunometabolomic properties. This observation may lead to an enhanced understanding of the metabolic underpinnings common to antibody-mediated autoimmune disease. Further, contextualizing these findings within a larger clinical and systems biology context could provide new insights into the pathogenesis and management of these diseases.

Dopamine: an immune transmitter

The dopaminergic system controls several vital central nervous system functions, including the control of movement, reward behaviors and cognition. Alterations of dopaminergic signaling are involved in the pathogenesis of neurodegenerative and psychiatric disorders, in particular Parkinson’s disease, which are associated with a subtle and chronic inflammatory response. A substantial body of evidence has demonstrated the non-neuronal expression of dopamine, its receptors and of the machinery that governs synthesis, secretion and storage of dopamine across several immune cell types. This review aims to summarize current knowledge on the role and expression of dopamine in immune cells. One of the goals is to decipher the complex mechanisms through which these cell types respond to dopamine, in order to address the impact this has on neurodegenerative and psychiatric pathologies such as Parkinson’s disease. A further aim is to illustrate the gaps in our understanding of the physiological roles of dopamine to encourage more targeted research focused on understanding the consequences of aberrant dopamine production on immune regulation. These highlights may prompt scientists in the field to consider alternative functions of this important neurotransmitter when targeting neuroinflammatory/neurodegenerative pathologies.

2-(5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazol-3-yl)-N-(2-hydroxyethyl)-2-oxoacetamide (CDMPO) has anti-inflammatory properties in microglial cells and prevents neuronal and behavioral deficits in MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is characterized by the selective loss of nigrostriatal dopamine neurons associated with microglial activation. Inhibition of the inflammatory response elicited by activated microglia could be an effective strategy to alleviate the progression of PD. Here, we synthesized 2-(5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazol-3-yl)-N-(2-hydroxyethyl)-2-oxoacetamide (CDMPO) and studied its protective anti-inflammatory mechanisms following lipopolysaccharide (LPS)-induced neuroinflammation in vitro and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in vivo. CDMPO and its parent compound, rimonabant, significantly attenuated nitric oxide (NO) production in LPS-stimulated primary microglia and BV2 cells. Furthermore, CDMPO significantly inhibited the release of proinflammatory cytokines and prostaglandin E2 (PGE₂) by activated BV2 cells, also suppressed expression of inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). Mechanistically, CDMPO attenuated LPS-induced activation of nuclear factor-kappa B (NF-κB), inhibitor of kappa B alpha (IκBα), and p38 phosphorylation in BV2 cells. MPTP intoxication of mice results in glial activation, tyrosine hydroxylase (TH) depletion, and significant behavioral deficits. Prophylactic treatment with CDMPO decreased proinflammatory molecules via NF-κB and p38 mitogen-activated protein kinase signaling, resulting in protection of dopaminergic neurons and improved behavioral impairments. These results suggest that CDMPO is a promising neuroprotective agent for the prevention and treatment of microglia-mediated neuroinflammatory conditions and may be useful for behavioral improvement in PD phenotype.

Dopamine receptor D3 signalling in astrocytes promotes neuroinflammation

BACKGROUND

Neuroinflammation constitutes a pathogenic process leading to neurodegeneration in several disorders, including Alzheimer's disease, Parkinson's disease (PD) and sepsis. Despite microglial cells being the central players in neuroinflammation, astrocytes play a key regulatory role in this process. Our previous results indicated that pharmacologic-antagonism or genetic deficiency of dopamine receptor D3 (DRD3) attenuated neuroinflammation and neurodegeneration in two mouse models of PD. Here, we studied how DRD3-signalling affects the dynamic of activation of microglia and astrocyte in the context of systemic inflammation.

METHODS

Neuroinflammation was induced by intraperitoneal administration of LPS. The effect of genetic DRD3-deficiency or pharmacologic DRD3-antagonism in the functional phenotype of astrocytes and microglia was determined by immunohistochemistry and flow cytometry at different time-points.

RESULTS

Our results show that DRD3 was expressed in astrocytes, but not in microglial cells. DRD3 deficiency resulted in unresponsiveness of astrocytes and in attenuated microglial activation upon systemic inflammation. Furthermore, similar alterations in the functional phenotypes of glial cells were observed by DRD3 antagonism and genetic deficiency of DRD3 upon LPS challenge. Mechanistic analyses show that DRD3 deficiency resulted in exacerbated expression of the anti-inflammatory protein Fizz1 in glial cells both in vitro and in vivo.

CONCLUSIONS

These results suggest that DRD3 signalling regulates the dynamic of the acquisition of pro-inflammatory and anti-inflammatory features by astrocytes and microglia, finally favouring microglial activation and promoting neuroinflammation.

Altered Amplitude of Low-Frequency Fluctuations in Inactive Patients with Nonneuropsychiatric Systemic Lupus Erythematosus

Objective

This study is aimed at investigating the characteristics of the spontaneous brain activity in inactive patients with nonneuropsychiatric systemic lupus erythematosus (non-NPSLE).

Methods

Thirty-one female inactive patients with non-NPSLE and twenty healthy controls were examined by resting-state functional magnetic resonance imaging (RS-fMRI). Three amplitude methods including amplitude of low-frequency fluctuations (ALFF), fractional amplitude of low-frequency fluctuations (fALFF), and percent amplitude of fluctuation (PerAF) (with and without standardization) were applied to evaluate the spontaneous brain activity. The correlation was performed between low-frequency oscillations and clinical and neuropsychological factors in inactive patients with non-NPSLE.

Results

Compared to healthy controls, patients with non-NPSLE showed increased standardized ALFF (mALFF) in the left inferior temporal gyrus and left putamen, decreased PerAF in the right postcentral gyrus and bilateral precentral gyrus, and increased standardized PerAF (mPerAF) in the left putamen and decreased mPerAF in the right postcentral gyrus and bilateral precentral gyrus. By standardized fALFF (mfALFF), no significant brain regions were found between the two groups. Correlation analysis revealed significantly positive correlations between glucocorticoid dose and PerAF in the right precentral gyrus and mPerAF in the left putamen, and Complement 3 (C3) and mPerAF in the right postcentral gyrus. There was a significant negative correlation between C3 and mALFF in the left putamen.

Conclusion

Abnormal low-frequency oscillations in multiple brain regions were found in inactive patients with non-NPSLE, indicating that the alteration of mALFF, PerAF, and mPerAF in specific brain regions might be an imaging biomarker of brain dysfunction in inactive patients with non-NPSLE.

Dopamine-mediated immunomodulation affects choroid plexus function

Immune system alterations have been implicated in various dopamine-related disorders, such as schizophrenia, bipolar disorder, and attention-deficit/hyperactivity disorder (ADHD). How immunity might be influenced by dopaminergic dysfunction and impact on clinically-relevant behaviors is still uncertain. We performed a peripheral and cerebral immunophenotyping in mice bearing dopaminergic alteration produced by genetic liability (hypofunction of the dopamine transporter DAT) and psychostimulant (amphetamine) administration. We found that DAT hypofunction influences immune tolerance by increasing functional Tregs and adrenomedullin levels in the thymus and spleen, while reducing microglia activation and infiltration of brain monocyte-derived macrophages (mo-MΦ). Remarkably, both DAT hypofunction and amphetamine treatment are associated with a weaker activation of the choroid plexus (CP) gateway. Conversely, amphetamine reactivated the CP in the setting of DAT hypofunction, paralleling its paradoxical ADHD-relevant behavioral effects. These findings add new knowledge on dopaminergic immunopharmacology and support the immunomodulation of CP functionality as a promising therapeutic strategy for neurodevelopmental and psychiatric disorders.

Progressive dopaminergic defect in a patient with primary progressive multiple sclerosis

Dopamine has a modulatory role in a number of autoimmune diseases, but there are no published cases of longitudinal dopaminergic imaging in multiple sclerosis (MS). Here we report a patient with primary progressive multiple sclerosis (PPMS) who was scanned twice with brain dopamine transporter single photon emission computed tomography (SPECT) with an interval of four years. The results showed a loss of tracer binding that corresponded to a 4-7 fold steeper decline than in normal ageing. The finding points to a relevant role of nigrostriatal dopaminergic degeneration in the pathological process of PPMS.

Dopaminergic Therapeutics in Multiple Sclerosis: Focus on Th17-Cell Functions

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS) with an autoimmune mechanism of development. Currently, one of the most promising directions in the study of MS pathogenesis are the neuroimmune interactions. Dopamine is one of the key neurotransmitters in CNS. Furthermore, dopamine is a direct mediator of interactions between the immune and nervous systems and can influence MS pathogenesis by modulating immune cells activity and cytokine production. Recent studies have shown that dopamine can enhance or inhibit the functions of innate and adaptive immune system, depending on the activation of different dopaminergic receptors, and can therefore influence the course of experimental autoimmune encephalomyelitis (EAE) and MS. In this review, we discuss putative dopaminergic therapeutics in EAE and MS with focus on Th17-cells, which are thought to play crucial role in MS pathogenesis. We suggest that targeting dopaminergic receptors could be explored as a new kind of disease-modifying treatment of MS. Graphical Abstract.

Interaction of neurotransmitters and neurochemicals with lymphocytes

Neurotransmitters and neurochemicals can act on lymphocytes by binding to receptors expressed by lymphocytes. This review describes lymphocyte expression of receptors for a selection of neurotransmitters and neurochemicals, the anatomical locations where lymphocytes can interact with neurotransmitters, and the effects of the neurotransmitters on lymphocyte function. Implications for health and disease are also discussed.

A Sentinel in the Crosstalk Between the Nervous and Immune System: The (Immuno)-Proteasome

The wealth of recent evidence about a bi-directional communication between nerve- and immune- cells revolutionized the traditional concept about the brain as an “immune-privileged” organ while opening novel avenues in the pathophysiology of CNS disorders. In fact, altered communication between the immune and nervous system is emerging as a common hallmark in neuro-developmental, neurodegenerative, and neuro-immunological diseases. At molecular level, the ubiquitin proteasome machinery operates as a sentinel at the crossroad between the immune system and brain. In fact, the standard proteasome and its alternative/inducible counterpart, the immunoproteasome, operate dynamically and coordinately in both nerve- and immune- cells to modulate neurotransmission, oxidative/inflammatory stress response, and immunity. When dysregulations of the proteasome system occur, altered amounts of standard- vs. immune-proteasome subtypes translate into altered communication between neurons, glia, and immune cells. This contributes to neuro-inflammatory pathology in a variety of neurological disorders encompassing Parkinson's, Alzheimer's, and Huntingtin's diseases, brain trauma, epilepsy, and Multiple Sclerosis. In the present review, we analyze those proteasome-dependent molecular interactions which sustain communication between neurons, glia, and brain circulating T-lymphocytes both in baseline and pathological conditions. The evidence here discussed converges in that upregulation of immunoproteasome to the detriment of the standard proteasome, is commonly implicated in the inflammatory- and immune- biology of neurodegeneration. These concepts may foster additional studies investigating the role of immunoproteasome as a potential target in neurodegenerative and neuro-immunological disorders.

T-Cell-Driven Inflammation as a Mediator of the Gut-Brain Axis Involved in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder affecting mainly the dopaminergic neurons of the nigrostriatal pathway, a neuronal circuit involved in the control of movements, thereby the main manifestations correspond to motor impairments. The major molecular hallmark of this disease corresponds to the presence of pathological protein inclusions called Lewy bodies in the midbrain of patients, which have been extensively associated with neurotoxic effects. Importantly, different research groups have demonstrated that CD4⁺ T-cells infiltrate into the substantia nigra of PD patients and animal models. Moreover, several studies have consistently demonstrated that T-cell deficiency results in a strong attenuation of dopaminergic neurodegeneration in animal models of PD, thus indicating a key role of adaptive immunity in the neurodegenerative process. Recent evidence has shown that CD4⁺ T-cell response involved in PD patients is directed to oxidised forms of α-synuclein, one of the main constituents of Lewy bodies. On the other hand, most PD patients present a number of non-motor manifestations. Among non-motor manifestations, gastrointestinal dysfunctions result especially important as potential early biomarkers of PD, since they are ubiquitously found among confirmed patients and occur much earlier than motor symptoms. These gastrointestinal dysfunctions include constipation and inflammation of the gut mucosa and the most distinctive pathologic features associated are the loss of neurons of the enteric nervous system and the generation of Lewy bodies in the gut. Moreover, emerging evidence has recently shown a pivotal role of gut microbiota in triggering the development of PD in genetically predisposed individuals. Of note, PD has been positively correlated with inflammatory bowel diseases, a group of disorders involving a T-cell driven inflammation of gut mucosa, which is strongly dependent in the composition of gut microbiota. Here we raised the hypothesis that T-cell driven inflammation, which mediates dopaminergic neurodegeneration in PD, is triggered in the gut mucosa. Accordingly, we discuss how structural components of commensal bacteria or how different mediators produced by gut-microbiota, including short-chain fatty acids and dopamine, may affect the behaviour of T-cells, triggering the development of T-cell responses against Lewy bodies, initially confined to the gut mucosa but later extended to the brain.

Targeting the Dopaminergic System in Autoimmunity

Dopamine has emerged as a fundamental regulator of inflammation. In this regard, it has been shown that dopaminergic signalling pathways are key players promoting homeostasis between the central nervous system and the immune system. Dysregulation in the dopaminergic system affects both innate and adaptive immunity, contributing to the development of numerous autoimmune and inflammatory pathologies. This makes dopamine receptors interesting therapeutic targets for either the development of new treatments or repurposing of already available pharmacological drugs. Dopamine receptors are broadly expressed on different immune cells with multifunctional effects depending on the dopamine concentration available and the pattern of expression of five dopamine receptors displaying different affinities for dopamine. Thus, impaired dopaminergic signalling through different dopamine receptors may result in altered behaviour of immunity, contributing to the development and progression of autoimmune pathologies. In this review we discuss the current evidence involving the dopaminergic system in inflammatory bowel disease, multiple sclerosis and Parkinson's disease. In addition, we summarise and analyse the therapeutic approaches designed to attenuate disease development and progression by targeting the dopaminergic system. Graphical Abstract Targetting the dopaminergic system in autoimmunity. Effector T-cells (Teff) orchestrate inflamamtion involved in autoimmunity, whilst regulatory T-cells (Tregs) suppress Teff activity promoting tolerance to self-constituents. Dopamine has emerged as a key regulator of Teff and Tregs function, thereby dopamine receptors have becoming important therapeutic targets in autoimmune disorders, especially in those affecting the brain and the gut, where dopamine levels strongly change with inflammation.

Dopamine promotes colonic mucus secretion through dopamine D5 receptor in rats

Dopamine regulates gastrointestinal mucosal barrier. Mucus plays important roles in the protection of intestinal mucosa. Here, the regulatory effect of dopamine on rat colonic mucus secretion was investigated. RT-PCR, immunofluorescence, Periodic Acid-Schiff reagent assay, Alcian blue-Periodic Acid-Schiff staining, and enzyme-linked immunosorbent assay were used to observe the expression of dopamine receptor and the direct effect of dopamine on the colonic mucus. Mice injected intraperitoneally with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) destroying enteric dopamine (DA) neurons, rats microinjected with 6-hydroxydopamine (6-OHDA) into the bilateral substantia nigra damaging central dopaminergic neurons, and dopamine D₅ receptor-downregulated transgenic mice were used to detect the effect of endogenous enteric dopamine or dopamine receptors on distal colonic mucus. Our results indicated that D₅ immunoreactivity was widely distributed on the colonic goblet cells. Dopamine dose-dependently increased rat distal colonic mucus secretion in vitro. D₁-like receptor antagonist SCH23390 inhibited dopamine (1 μΜ)-induced distal colonic mucus secretion. D1-like receptor agonist SKF38393 promoted mucin 2 (MUC2) secretion and increased the intracellular cAMP level of colonic mucosa. D₅ receptor-downregulated transgenic mice showed a decreased colonic MUC2 content. MPTP-treated mice exhibited lower colonic dopamine content and decreased colonic mucus content. 6-OHDA rats had an increase in the dopamine content in colonic mucosa but decreases in the protein levels of D₁ and D₅ receptors and MUC2 content in the colonic mucosa. These findings reveal that dopamine is able to promote distal colonic mucus secretion through the D₅ receptor, which provides important evidence to better understand the possible role of dopamine in the colonic mucosal barrier.

Role of the End-Point Mediators of Sympathoadrenal and Sympathoneural Stress Axes in the Pathogenesis of Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

The role of stress effector systems in the initiation and progression of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), the most commonly used experimental model of MS, has strongly been suggested. To corroborate this notion, alterations in activity of the sympathoadrenal and sympathoneural axes of sympathoadrenal system (a major communication pathway between the central nervous system and the immune system), mirrored in altered release of their end-point mediators (adrenaline and noradrenaline, respectively), are shown to precede (in MS) and/or occur during development of MS and EAE in response to immune cell activation (in early phase of disease) and disease-related damage of sympathoadrenal system neurons and their projections (in late phase of disease). To add to the complexity, innate immunity cells and T-lymphocytes synthesize noradrenaline that may be implicated in a local autocrine/paracrine self-amplifying feed-forward loop to enhance myeloid-cell synthesis of proinflammatory cytokines and inflammatory injury. Furthermore, experimental manipulations targeting noradrenaline/adrenaline action are shown to influence clinical outcome of EAE, in a disease phase-specific manner. This is partly related to the fact that virtually all types of cells involved in the instigation and progression of autoimmune inflammation and target tissue damage in EAE/MS express functional adrenoceptors. Although catecholamines exert majority of immunomodulatory effects through β₂-adrenoceptor, a role for α-adrenoceptors in EAE pathogenesis has also been indicated. In this review, we summarize all aforementioned aspects of immunopathogenetic action of catecholamines in EAE/MS as possibly important for designing new strategies targeting their action to prevent/mitigate autoimmune neuroinflammation and tissue damage.

Neuroimmunological Implications of Subclinical Lipopolysaccharide from Salmonella Enteritidis

Mounting evidence has indicated that lipopolysaccharide (LPS) is implicated in neuroimmunological responses, but the body’s response to subclinical doses of bacterial endotoxin remains poorly understood. The influence of a low single dose of LPS from Salmonella Enteritidis, which does not result in any clinical symptoms of intoxication (subclinical lipopolysaccharide), on selected cells and signal molecules of the neuroimmune system was tested. Five juvenile crossbred female pigs were intravenously injected with LPS from S. Enteritidis (5 μg/kg body weight (b.w.)), while five pigs from the control group received sodium chloride in the same way. Our data demonstrated that subclinical LPS from S. Enteritidis increased levels of dopamine in the brain and neuropeptides such as substance P (SP), galanin (GAL), neuropeptide Y (NPY), and active intestinal peptide (VIP) in the cervical lymph nodes with serum hyperhaptoglobinaemia and reduction of plasma CD4 and CD8 T-lymphocytes seven days after lipopolysaccharide administration. CD4 and CD8 T-lymphocytes from the cervical lymph node and serum interleukin-6 and tumour necrosis factor α showed no significant differences between the control and lipopolysaccharide groups. Subclinical lipopolysaccharide from S. Enteritidis can affect cells and signal molecules of the neuroimmune system. The presence of subclinical lipopolysaccharide from S. Enteritidis is associated with unknown prolonged consequences and may require eradication and a deeper search into the asymptomatic carrier state of Salmonella spp.

Peripheral Dopamine Controlled by Gut Microbes Inhibits Invariant Natural Killer T Cell-Mediated Hepatitis

Neurotransmitters have been shown to regulate immune responses, and thereby are critically related to autoimmune diseases. Here we showed that depletion of dopaminergic neurons significantly promoted activation of hepatic iNKT cells and augmented concanavalin A (Con A)-induced liver injury. The suppressive effect of dopamine on iNKT cells was mediated by D1-like receptor-PKA pathway. Clearance of gut microbiota by antibiotic cocktail reduced synthesis of dopamine in intestines and exacerbated liver damage, and that could be restored by recovery of gut microbiota or replenishment of D1-like receptor agonist. Our results demonstrate that peripheral dopamine controlled by gut microbes inhibits IL4 and IFNγ production in iNKT cells and suppresses iNKT cell-mediated hepatitis. Together, we propose a gut microbe-nervous system-immune system regulatory axis in modulating autoimmune hepatitis.

Dopamine Receptor D5 Signaling Plays a Dual Role in Experimental Autoimmune Encephalomyelitis Potentiating Th17-Mediated Immunity and Favoring Suppressive Activity of Regulatory T-Cells

A number of studies have shown pharmacologic evidence indicating that stimulation of type I dopamine receptor (DR), favors T-helper-17 (Th17)-mediated immunity involved in experimental autoimmune encephalomyelitis (EAE) and in some other inflammatory disorders. Nevertheless, the lack of drugs that might discriminate between DRD1 and DRD5 has made the pharmacological distinction between the two receptors difficult. We have previously shown genetic evidence demonstrating a relevant role of DRD5-signaling in dendritic cells (DCs) favoring the CD4⁺ T-cell-driven inflammation in EAE. However, the role of DRD5-signaling confined to CD4⁺ T-cells in the development of EAE is still unknown. Here, we analyzed the functional role of DRD5-signaling in CD4⁺ T-cell-mediated responses and its relevance in EAE by using a genetic approach. Our results show that DRD5-signaling confined to naive CD4⁺ T-cells exerts a pro-inflammatory effect promoting the development of EAE with a stronger disease severity. This pro-inflammatory effect observed for DRD5-signaling in naive CD4⁺ T-cells was related with an exacerbated proliferation in response to T-cell activation and to an increased ability to differentiate toward the Th17 inflammatory phenotype. On the other hand, quite unexpected, our results show that DRD5-signaling confined to Tregs strengthens their suppressive activity, thereby dampening the development of EAE manifestation. This anti-inflammatory effect of DRD5-signaling in Tregs was associated with a selective increase in the expression of glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR), which has been described to play a critical role in the expansion of Tregs. Our findings here indicate a complex role for DRD5-signaling in CD4⁺ T-cells-driven responses potentiating early inflammation mediated by effector T-cells in EAE, but exacerbating suppressive activity in Tregs and thereby dampening disease manifestation in late EAE stages.

Real-Time Detection of Melatonin Using Fast-Scan Cyclic Voltammetry

Melatonin is an important hormone whose functions span from regulating circadian rhythm in the brain to providing anti-inflammatory properties in the immune system. Melatonin secretion from the pineal gland is known; however, the mechanism of melatonin signaling in the immune system is not well understood. The lymph node is the hub of the immune system, and melatonin secretion from lymphocytes was proposed to be an important source specifically for regulating cytokine secretion. Methods exist to quantify the concentration of melatonin within biological samples; however, they often suffer from either a lack of selectivity for melatonin over common biological interferences or temporal resolution, which is not amenable to measuring real-time signaling dynamics. Here, we have characterized an electrochemical method for optimal melatonin detection with subsecond resolution using fast-scan cyclic voltammetry at carbon-fiber microelectrodes. The oxidation peaks detected for melatonin were at 1.0, 1.1, and 0.6 V. Evidence for electrode fouling of the tertiary peak was present; therefore, an optimized waveform was developed scanning from 0.2 to 1.3 V at 600 V/s. The optimized waveform eliminated the detection of fouling products on the electrode with a 24 ± 10 nM limit of detection. Melatonin was distinguished between biological interferences, and codetection with the major synthetic precursor, serotonin, was possible. This method was used to detect melatonin in live lymph node slices and provides the first real-time measurements within the lymph node using FSCV. Real-time detection of melatonin dynamics could provide useful information on the mechanism of immunomodulation during inflammatory disease.

Trace Amine-Associated Receptors as Novel Therapeutic Targets for Immunomodulatory Disorders

Trace amines and their receptors (trace amine-associated receptors; TAARs) are an emerging pharmacological target for the treatment of human disorders. While most studies have focused on their therapeutic potential for neurologic and psychiatric disorders, TAARs are also expressed throughout the periphery, including prominent expression in human leukocytes. Furthermore, recent independent, unbiased metabolomic studies have consistently identified one or more TAAR ligands as potential etiologic factors in inflammatory bowel disease (IBD). The putative role of TAARs in diseases such as IBD that are associated with hyperactive immune responses has not, however, previously been systematically addressed. Here, we review the current state of the knowledge of the effects of TAARs on leukocyte function, in particular in the context of mucosal epithelial cells that interface with the environment; developing a model whereby TAARs may be considered as a novel therapeutic target for disorders associated with dysregulated immune responses to environmental factors. In this model, we hypothesize that altered trace amine homeostasis results in hyperactivity of the immune system. Such loss of homeostasis can occur through many different mechanisms including TAAR polymorphisms and altered trace amine load due to changes in host synthesis and/or degradative enzymes, diet, or microbial dysbiosis. The resulting alterations in TAAR functioning can then lead to a loss of homeostasis of leukocyte chemotaxis, differentiation, and activation, as well as an altered ability of members of the microbiota to adhere to and penetrate the epithelial cell layers. Such changes would generate a pro-inflammatory state at mucosal epithelial barrier layers that can manifest as clinical symptomatology such as that seen in IBD. These alterations may also have the potential to induce systemic effects, which could possibly contribute to immunomodulatory disorders in other systems, including neurological diseases.

Associations between D3R expression in synovial mast cells and disease activity and oxidant status in patients with rheumatoid arthritis

Dopamine D3 receptor (D3R) on immune cells is involved in the pathogenesis of rheumatoid arthritis (RA). Mast cells (MCs) are currently identified as important effector cells in synovial inflammation of RA, but little is known about the role of D3R on synovial MCs in the pathogenesis of RA. Several inflammatory cells in the synovium induce reactive oxygen species (ROS) formation which are involved in the progression of RA. However, it is unclear whether D3R on synovial MCs is related to the levels of ROS in RA patients. In this study, a total of 73 patients with RA were divided into three groups according to disease activity DAS28 scores. The number of cases in group 1, group 2, and group 3 was 19, 26, and 28, respectively. We examined D3R-positive MC numbers in the synovial fluid and ROS levels in each group of RA patients, and we also analyzed the association of D3R-positive MC numbers with RA disease activity and ROS levels. MDA and protein carbonylation in the serum and synovial fluid were measured to reflect the level of lipid peroxidation and protein oxidation, respectively. Additionally, superoxide dismutase (SOD) and catalase (CAT) in the serum and synovial fluid were used to be markers of antioxidant levels. Our results showed that D3R-positive MCs in the synovial fluid showed a declining trend with the increased disease activity DAS28 score in RA patients. There was negative correlation between D3R-positive MC numbers in the synovial fluid and disease severity DAS28 score of RA patients. Moreover, D3R-positive MC numbers in the synovial fluid were negatively correlated with the level of MDA and protein carbonylation while were positively correlated with antioxidant levels such as SOD and CAT in RA patients. Our results suggested that D3R on MCs may be involved in ROS-mediated pathogenesis of RA.

Dopaminergic Stimulation of Myeloid Antigen-Presenting Cells Attenuates Signal Transducer and Activator of Transcription 3-Activation Favouring the Development of Experimental Autoimmune Encephalomyelitis

The dual potential to promote tolerance or inflammation to self-antigens makes dendritic cells (DCs) fundamental players in autoimmunity. Previous results have shown that stimulation of dopamine receptor D5 (DRD5) in DCs potentiates their inflammatory behaviour, favouring the development of experimental autoimmune encephalomyelitis (EAE). Here, we aimed to decipher the underlying mechanism and to test its relevance in multiple sclerosis (MS) patients. Our data shows that DRD5-deficiency confined to DCs in EAE mice resulted in reduced frequencies of CD4⁺ T-cell subsets with inflammatory potential in the central nervous system, including not only Th1 and Th17 cells but also granulocyte-macrophage colony-stimulating factor producers. Importantly, ex vivo depletion of dopamine from DCs resulted in a dramatic reduction of EAE severity, highlighting the relevance of an autocrine loop promoting inflammation in vivo. Mechanistic analyses indicated that DRD5-signalling in both mouse DCs and human monocytes involves the attenuation of signal transducer and activator of transcription 3-activation, a transcription factor that limits the production of the inflammatory cytokines interleukin (IL)-12 and IL-23. Furthermore, we found an exacerbated expression of all dopamine receptors in peripheral blood pro-inflammatory monocytes obtained from MS patients. These findings illustrate a novel mechanism by which myeloid antigen-presenting cells may trigger the onset of their inflammatory behaviour promoting the development of autoimmunity.

CD4 T cells react to local increase of α-synuclein in a pathology-associated variant-dependent manner and modify brain microglia in absence of brain pathology

We have previously shown that immunological processes in the brain during α-synuclein-induced neurodegeneration vary depending on the presence or absence of cell death. This suggests that the immune system is able to react differently to the different stages of α-synuclein pathology. However, it was unclear whether these immune changes were governed by brain processes or by a direct immune response to α-synuclein modifications. We have herein locally increased the peripheral concentration of α-synuclein or its pathology-associated variants, nitrated or fibrillar, to characterize the modulation of the CD4 T cell pool by α-synuclein and brain microglia in the absence of any α-synuclein brain pathology. We observed that α-synuclein changed the CD4:CD8 ratio by contracting the CD3+CD4+ T cell pool and reducing the pool of memory Regulatory T cells (Treg). Nitrated α-synuclein induced the expansion of both the CD3+CD4+ and CD3+CD4- T cells, while fibrils increased the percentage of Foxp3+ Treg cells and induced anti-α-synuclein antibodies. Furthermore, the activation pattern of CD3+CD4+ T cells was modulated in a variant-dependent manner; while nitrated and fibrillar α-synuclein expanded the fraction of activated Treg, all three α-synuclein variants reduced the expression levels of STAT3, CD25 and CD127 on CD3+CD4+ T cells. Additionally, while monomeric α-synuclein increased CD103 expression, the fibrils decreased it, and CCR6 expression was decreased by nitrated and fibrillar α-synuclein, indicating that α-synuclein variants affect the homing and tolerance capacities of CD3+CD4+ T cells. Indeed, this correlated with changes in brain microglia phenotype, as determined by FACS analysis, in an α-synuclein variant-specific manner and coincided in time with CD4+ T cell infiltration into brain parenchyma. We have shown that the peripheral immune system is able to sense and react specifically to changes in the local concentration and structure of α-synuclein, which results in variant-specific T cell migration into the brain. This may have a specific repercussion for brain microglia.

Potential for diagnosis versus therapy monitoring of attention deficit hyperactivity disorder: a new epigenetic biomarker interacting with both genotype and auto-immunity

In view of the need for easily accessible biomarkers, we evaluated in ADHD children the epigenetic status of the 5'-untranslated region (UTR) in the SLC6A3 gene, coding for human dopamine transporter (DAT). We analysed buccal swabs and sera from 30 children who met DSM-IV-TR criteria for ADHD, assigned to treatment according to severity. Methylation levels at six-selected CpG sites (among which, a CGGCGGCGG and a CGCG motif), alone or in combination with serum titers in auto-antibodies against dopamine transporter (DAT aAbs), were analysed for correlation with CGAS scores (by clinicians) and Conners' scales (by parents), collected at recruitment and after 6 weeks. In addition, we characterized the DAT genotype, i.e., the variable number tandem repeat (VNTR) polymorphisms at the 3'-UTR of the gene. DAT methylation levels were greatly reduced in ADHD patients compared to control, healthy children. Within patients carrying at least one DAT 9 allele (DAT 9/x), methylation at positions CpG2 and/or CpG6 correlated with recovery, as evident from delta-CGAS scores as well as delta Conners' scales ('inattentive' and 'hyperactive' subscales). Moreover, hypermethylation at CpG1 position denoted severity, specifically for those patients carrying a DAT 10/10 genotype. Intriguingly, high serum DAT-aAbs titers appeared to corroborate indications from high CpG1 versus high CpG2/CpG6 levels, likewise denoting severity versus recovery in DAT 10/10 versus 9/x patients, respectively. These profiles suggest that DAT 5'UTR epigenetics plus serum aAbs can serve as suitable biomarkers, to confirm ADHD diagnosis and/or to predict the efficacy of treatment.

Dual-Tasking in Multiple Sclerosis - Implications for a Cognitive Screening Instrument

The monitoring of cognitive functions is central to the assessment and consecutive management of multiple sclerosis (MS). Though, especially cognitive processes that are central to everyday behavior like dual-tasking are often neglected. We examined dual-task performance using a psychological-refractory period (PRP) task in N = 21 patients and healthy controls and conducted standard neuropsychological tests. In dual-tasking, MS patients committed more erroneous responses when dual-tasking was difficult. In easier conditions, performance of MS patients did not differ to controls. Interestingly, the response times were generally not affected by the difficulty of the dual task, showing that the deficits observed do not reflect simple motor deficits or deficits in information processing speed but point out deficits in executive control functions and response selection in particular. Effect sizes were considerably large with d∼0.80 in mild affected patients and the achieved power was above 99%. There are cognitive control and dual tasking deficits in MS that are not attributable to simple motor speed deficits. Scaling of the difficulty of dual-tasking makes the test applied suitable for a wide variety of MS-patients and may complement neuropsychological assessments in clinical care and research setting.

Adipose-derived stromal cell in regenerative medicine: A review

The application of appropriate cell origin for utilizing in regenerative medicine is the major issue. Various kinds of stem cells have been used for the tissue engineering and regenerative medicine. Such as, several stromal cells have been employed as treat option for regenerative medicine. For example, human bone marrow-derived stromal cells and adipose-derived stromal cells (ADSCs) are used in cell-based therapy. Data relating to the stem cell therapy and processes associated with ADSC has developed remarkably in the past 10 years. As medical options, both the stromal vascular and ADSC suggests good opportunity as marvelous cell-based therapeutics. The some biological features are the main factors that impact the regenerative activity of ADSCs, including the modulation of the cellular immune system properties and secretion of bioactive proteins such as cytokines, chemokines and growth factors, as well as their intrinsic anti-ulcer and anti-inflammatory potential. A variety of diseases have been treated by ADSCs, and it is not surprising that there has been great interest in the possibility that ADSCs might be used as therapeutic strategy to improve a wider range of diseases. This is especially important when it is remembered that routine therapeutic methods are not completely effective in treat of diseases. Here, it was discuss about applications of ADSC to colitis, liver failure, diabetes mellitus, multiple sclerosis, orthopaedic disorders, hair loss, fertility problems, and salivary gland damage.

Potential Roles of Peripheral Dopamine in Tumor Immunity

Recent years, immunotherapy has turned out to be a promising strategy against tumors. Peripheral dopamine (DA) has important roles in immune system among tumor patients. Accumulated reports demonstrate variable expression and distribution of DA receptors (DRs) in diverse immune cells. Interestingly, peripheral DA also involves in tumor progression and it exerts anticancer effects on immunomodulation, which includes inflammasomes in cancer, function of immune effector cells, such as T lymphocytes, myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs) and natural killer (NK) cells. Given the specific immunologic status, DA medication may be a valuable candidate in pancreatic cancer treatment. The major purpose of this review is to discuss the novel potential interactions between peripheral dopamine and tumor immunity.

The role of enteric neurons in the development and progression of colorectal cancer

The enteric nervous system (ENS) is the intrinsic neural network of the gastrointestinal tract, which is essential for regulating gut functions and intestinal homeostasis. The importance of the ENS is underscored by the existence of severe gastrointestinal diseases, such as Hirschsprung's disease and intestinal pseudo-obstruction, which arise when the ENS fails to develop normally or becomes dysregulated. Moreover, it is known that enteric neurons are involved in intestinal inflammation. However, the role of the ENS in colorectal cancer (CRC) carcinogenesis remains poorly understood, even though processes like perineural invasion and neoneurogenesis are important factors in CRC. Here we summarize how enteric neurons are affected during CRC and discuss the influence of enteric neurons, either direct or indirect, on the development and/or progression of CRC. Finally, we illustrate how the ENS could be targeted as a potential anti-cancer therapy, establishing the ENS as an integral part of the tumor microenvironment.

Toxoplasma gondii: Entry, association, and physiological influence on the central nervous system

Toxoplasma gondii is one of the world’s most successful parasites, in part because of its ability to infect and persist in most warm-blooded animals. A unique characteristic of T. gondii is its ability to persist in the central nervous system (CNS) of a variety of hosts, including humans and rodents. How, what, and why T. gondii encysts in the CNS has been the topic of study for decades. In this review, we will discuss recent work on how T. gondii is able to traverse the unique barrier surrounding the CNS, what cells of the CNS play host to T. gondii, and finally, how T. gondii infection may influence global and cellular physiology of the CNS.

Dopaminergic Regulation of Innate Immunity: a Review

Dopamine (DA) is a neurotransmitter in the central nervous system as well as in peripheral tissues. Emerging evidence however points to DA also as a key transmitter between the nervous system and the immune system as well as a mediator produced and released by immune cells themselves. Dopaminergic pathways have received so far extensive attention in the adaptive branch of the immune system, where they play a role in health and disease such as multiple sclerosis, rheumatoid arthritis, cancer, and Parkinson's disease. Comparatively little is known about DA and the innate immune response, although DA may affect innate immune system cells such as dendritic cells, macrophages, microglia, and neutrophils. The present review aims at providing a complete and exhaustive summary of currently available evidence about DA and innate immunity, and to become a reference for anyone potentially interested in the fields of immunology, neurosciences and pharmacology. A wide array of dopaminergic drugs is used in therapeutics for non-immune indications, such as Parkinson's disease, hyperprolactinemia, shock, hypertension, with a usually favorable therapeutic index, and they might be relatively easily repurposed for immune-mediated disease, thus leading to innovative treatments at low price, with benefit for patients as well as for the healthcare systems.

Inhibition of dopamine receptor D3 signaling in dendritic cells increases antigen cross-presentation to CD8+ T-cells favoring anti-tumor immunity

Dendritic cells (DCs) display the unique ability for cross-presenting antigens to CD8⁺ T-cells, promoting their differentiation into cytotoxic T-lymphocytes (CTLs), which play a pivotal role in anti-tumor immunity. Emerging evidence points to dopamine receptor D3 (D3R) as a key regulator of immunity. Accordingly, we studied how D3R regulates DCs function in anti-tumor immunity. The results show that D3R-deficiency in DCs enhanced expansion of CTLs in vivo and induced stronger anti-tumor immunity. Co-culture experiments indicated that D3R-inhibition in DCs potentiated antigen cross-presentation and CTLs activation. Our findings suggest that D3R in DCs constitutes a new therapeutic target to strengthen anti-tumor immunity.

Cognition and fatigue in patients with relapsing multiple sclerosis treated by subcutaneous interferon β-1a: an observational study SKORE

BACKGROUND

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system, which often causes progressive neurological disability. In addition to motor and sensory dysfunction, cognitive decline and fatigue are frequent manifestations of the disease. Fatigue is probably the most common symptom, with up to 90% of MS individuals reporting fatigue at some point. Cognitive impairment affects about 50% of patients and may be present at all MS stages. The aim of this observational study was to evaluate changes in cognition, fatigue, and disability status in 300 relapsing-remitting MS (RRMS) patients, treated with subcutaneous (sc) interferon (IFN) β-1a over 2 years.

METHODS

The study was designed as an observational, multicentre, prospective, single-arm, phase IV study carried out in 13 MS centres in the Czech Republic. Cognition status was assessed using the Paced Auditory Serial Addition Task (PASAT), fatigue using the Fatigue Descriptive Scale (FDS), and disability using the Expanded Disability Status Scale (EDSS), at baseline, and after 6, 12 and 24 months. The percentage of patients with changed versus stable cognition, fatigue status and disability was calculated at each time point and the changes in these scores were evaluated.

RESULTS

The proportion of patients with cognitive improvement was higher compared with those with a stable or decreased PASAT scores at all time points, and the average cognitive performance improved during the follow-up period. Also the proportion of patients with stable or improved fatigue and EDSS scores was higher compared with those in which FDS or EDSS scores declined, this was found at all time points of the analysed sample. However, the direct effect of IFN β-1a on cognition and fatigue cannot be concluded from this study.

CONCLUSIONS

The results of this observational study have demonstrated a stable or improved cognitive performance, fatigue status, and disability level in the majority of RRMS patients treated with sc IFN β-1a over a two-year follow-up period, in a real life setting, in the Czech Republic.

Inflammation Effects on Motivation and Motor Activity: Role of Dopamine

Motivational and motor deficits are common in patients with depression and other psychiatric disorders, and are related to symptoms of anhedonia and motor retardation. These deficits in motivation and motor function are associated with alterations in corticostriatal neurocircuitry, which may reflect abnormalities in mesolimbic and mesostriatal dopamine (DA). One pathophysiologic pathway that may drive changes in DAergic corticostriatal circuitry is inflammation. Biomarkers of inflammation such as inflammatory cytokines and acute-phase proteins are reliably elevated in a significant proportion of psychiatric patients. A variety of inflammatory stimuli have been found to preferentially target basal ganglia function to lead to impaired motivation and motor activity. Findings have included inflammation-associated reductions in ventral striatal neural responses to reward anticipation, decreased DA and DA metabolites in cerebrospinal fluid, and decreased availability, and release of striatal DA, all of which correlated with symptoms of reduced motivation and/or motor retardation. Importantly, inflammation-associated symptoms are often difficult to treat, and evidence suggests that inflammation may decrease DA synthesis and availability, thus circumventing the efficacy of standard pharmacotherapies. This review will highlight the impact of administration of inflammatory stimuli on the brain in relation to motivation and motor function. Recent data demonstrating similar relationships between increased inflammation and altered DAergic corticostriatal circuitry and behavior in patients with major depressive disorder will also be presented. Finally, we will discuss the mechanisms by which inflammation affects DA neurotransmission and relevance to novel therapeutic strategies to treat reduced motivation and motor symptoms in patients with high inflammation.

Down-regulation of serotonin and dopamine transporter genes in individual rats expressing a gambling-prone profile: A possible role for epigenetic mechanisms

Gambling Disorder (GD) is characterized by excessive gambling despite adverse consequences on individual functioning. In spite of some positive findings, it is difficult to draw any conclusion on the genetics of GD. Indeed, beyond DNA sequence variation, other regulatory mechanisms (like those that engage epigenetics) may explain gene alterations in this addictive disease. Wistar male rats underwent an operant task for the evaluation of individual propensity to gamble. Few rats, after having learnt to prefer nose-poking for a large over a small food reward, were sacrificed to obtain a baseline profile of gene expression at both central and peripheral levels. In the remaining rats, probability of occurrence of large-reward delivery decreased progressively to very low levels. Thus, rats were faced with temptation to "gamble", i.e. to nose-poke for a binge reward, whose delivery was omitted the majority of times. After 3weeks of testing, rats showing a clear-cut profile of either gambling proneness or aversion were selected and sacrificed after the last session. A selective down-regulation of i) serotonin transporter in prefrontal cortex, ii) tyrosine hydroxylase in ventral striatum, iii) dopamine transporter in lymphocytes was evidenced in "gambler" vs "non-gambler" rats. The exposure to such operant task (compared to home-cage alone) modulated ventrostriatal but not prefrontal genes. A consistent increase of DNA methylation, in one specific CpG site at serotonin transporter gene, was evident in prefrontal cortex of "gambler" rats. Elucidation of epigenetic changes occurring during GD progression may pave the way to the development of new therapeutic strategies through specific modulation of epigenetic factors.

Immunomodulatory Effects Mediated by Dopamine

Dopamine (DA), a neurotransmitter in the central nervous system (CNS), has modulatory functions at the systemic level. The peripheral and central nervous systems have independent dopaminergic system (DAS) that share mechanisms and molecular machinery. In the past century, experimental evidence has accumulated on the proteins knowledge that is involved in the synthesis, reuptake, and transportation of DA in leukocytes and the differential expression of the D1-like (D1R and D5R) and D2-like receptors (D2R, D3R, and D4R). The expression of these components depends on the state of cellular activation and the concentration and time of exposure to DA. Receptors that are expressed in leukocytes are linked to signaling pathways that are mediated by changes in cAMP concentration, which in turn triggers changes in phenotype and cellular function. According to the leukocyte lineage, the effects of DA are associated with such processes as respiratory burst, cytokine and antibody secretion, chemotaxis, apoptosis, and cytotoxicity. In clinical conditions such as schizophrenia, Parkinson disease, Tourette syndrome, and multiple sclerosis (MS), there are evident alterations during immune responses in leukocytes, in which changes in DA receptor density have been observed. Several groups have proposed that these findings are useful in establishing clinical status and clinical markers.