Expression of dopaminergic receptors on human CD4+ T lymphocytes: flow cytometric analysis of naive and memory subsets and relevance for the neuroimmunology of neurodegenerative disease

Single-cell peripheral immunoprofiling of lewy body and Parkinson's disease in a multi-site cohort

BACKGROUND

Multiple lines of evidence support peripheral organs in the initiation or progression of Lewy body disease (LBD), a spectrum of neurodegenerative diagnoses that include Parkinson's Disease (PD) without or with dementia (PDD) and dementia with Lewy bodies (DLB). However, the potential contribution of the peripheral immune response to LBD remains unclear. This study aims to characterize peripheral immune responses unique to participants with LBD at single-cell resolution to highlight potential biomarkers and increase mechanistic understanding of LBD pathogenesis in humans.

METHODS

In a case-control study, peripheral mononuclear cell (PBMC) samples from research participants were randomly sampled from multiple sites across the United States. The diagnosis groups comprise healthy controls (HC, n = 159), LBD (n = 110), Alzheimer's disease dementia (ADD, n = 97), other neurodegenerative disease controls (NDC, n = 19), and immune disease controls (IDC, n = 14). PBMCs were activated with three stimulants (LPS, IL-6, and IFNa) or remained at basal state, stained by 13 surface markers and 7 intracellular signal markers, and analyzed by flow cytometry, which generated 1,184 immune features after gating.

RESULTS

The model classified LBD from HC with an AUROC of 0.87 ± 0.06 and AUPRC of 0.80 ± 0.06. Without retraining, the same model was able to distinguish LBD from ADD, NDC, and IDC. Model predictions were driven by pPLCγ2, p38, and pSTAT5 signals from specific cell populations under specific activation. The immune responses characteristic for LBD were not associated with other common medical conditions related to the risk of LBD or dementia, such as sleep disorders, hypertension, or diabetes.

CONCLUSIONS AND RELEVANCE

Quantification of PBMC immune response from multisite research participants yielded a unique pattern for LBD compared to HC, multiple related neurodegenerative diseases, and autoimmune diseases thereby highlighting potential biomarkers and mechanisms of disease.

Peripheral immune profile in drug-naïve dementia with Lewy bodies

BACKGROUND

Accumulating evidence suggests that peripheral inflammation is associated with the pathogenesis of Parkinson's disease (PD). We examined peripheral immune profiles and their association with clinical characteristics in patients with DLB and compared these with values in patients with PD.

METHODS

We analyzed peripheral blood from 93 participants (drug-naïve DLB, 31; drug-naïve PD, 31; controls, 31). Absolute leukocyte counts, absolute counts of leukocyte subpopulations, and peripheral blood inflammatory indices such as neutrophil-to-lymphocyte ratio were examined. Associations with clinical characteristics, cardiac sympathetic denervation, and striatal 123I-2-carbomethoxy-3-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (123I-FP-CIT) binding were also examined.

RESULTS

Patients with DLB had lower absolute lymphocyte and basophil counts than did age-matched controls (both; p < 0.005). Higher basophil counts were marginally associated with higher global cognition (p = 0.054) and were significantly associated with milder motor severity (p = 0.020) and higher striatal 123I-FP-CIT binding (p = 0.038). By contrast, higher basophil counts were associated with more advanced PD characterized by decreased global cognition and severe cardiac sympathetic denervation. Although lower lymphocyte counts had relevance to more advanced PD, they had little relevance to clinical characteristics in patients with DLB. Higher peripheral blood inflammatory indices were associated with lower body mass index in both DLB and PD.

CONCLUSIONS

As in patients with PD, the peripheral immune profile is altered in patients with DLB. Some peripheral immune cell counts and inflammatory indices reflect the degree of disease progression. These findings may deepen our knowledge on the role of peripheral inflammation in the pathogenesis of DLB.

DRD1 suppresses cell proliferation and reduces EGFR activation and PD-L1 expression in NSCLC

Dopamine (DA) acts in various key neurological and physiological processes as both a neurotransmitter and circulating hormone. Over the past several decades, the DA signaling network has been shown to regulate the progression of several types of solid tumors, and considerable evidence has shown it is a druggable pathway in the cancer cell context. However, the specific activity and effect of these pathway components appears to be tissue-type and cell-context-dependent. In the present study, expression and methylation of dopamine receptor D1 (DRD1) were measured using RNA sequencing (RNAseq) and reverse transcription polymerase chain reaction (RT-PCR) in non-small cell lung cancer (NSCLC) samples, and validated using publicly available datasets, including The Cancer Genome Atlas (TCGA). In vitro and in vivo functional experiments were performed for cell proliferation and tumor growth, respectively. Mechanistic analyses of the transcriptome and kinome in DRD1-modulated cells informed further experiments, which characterized the effects on the epidermal growth factor receptor (EGFR) pathway and programmed cell death 1 ligand 1 (PD-L1) proteins. Through these experiments, we identified the DRD1 gene as a negative regulator of disease progression in NSCLC. We show that DRD1, as well as other DA pathway components, are expressed in normal human lung tissue, and that loss of DRD1 expression through promoter hypermethylation is a common feature in NSCLC patients and is associated with worse survival. At the cellular level, DRD1 affects proliferation by inhibiting the activation of EGFR and mitogen-activated protein kinase 1/2 (ERK1/2). Interestingly, we also found that DRD1 regulates the expression of PD-L1 in lung cancer cells. Taken together, these results suggest that DRD1 methylation may constitute a biomarker of poor prognosis in NSCLC patients while other components of this pathway could be targeted to improve response to EGFR- and PD-L1-targeted therapies.

The role of T-lymphocytes in central nervous system diseases

The central nervous system (CNS) has been considered an immunologically privileged site. In the past few decades, research on inflammation in CNS diseases has mostly focused on microglia, innate immune cells that respond rapidly to injury and infection to maintain CNS homeostasis. Discoveries of lymphatic vessels within the dura mater and peripheral immune cells in the meningeal layer indicate that the peripheral immune system can monitor and intervene in the CNS. This review summarizes recent advances in the involvement of T lymphocytes in multiple CNS diseases, including brain injury, neurodegenerative diseases, and psychiatric disorders. It emphasizes that a deep understanding of the pathogenesis of CNS diseases requires intimate knowledge of T lymphocytes. Aiming to promote a better understanding of the relationship between the immune system and CNS and facilitate the development of therapeutic strategies targeting T lymphocytes in neurological diseases.

Anti-Inflammatory Effects of Peripheral Dopamine

Dopamine is synthesized in the nervous system where it acts as a neurotransmitter. Dopamine is also synthesized in a number of peripheral organs as well as in several types of cells and has organ-specific functions and, as demonstrated more recently, is involved in the regulation of the immune response and inflammatory reaction. In particular, the renal dopaminergic system is very important in the regulation of sodium transport and blood pressure and is particularly sensitive to stimuli that cause oxidative stress and inflammation. This review is focused on how dopamine is synthesized in organs and tissues and the mechanisms by which dopamine and its receptors exert their effects on the inflammatory response.

Dopamine D2 receptor on CD4+ T cells is protective against inflammatory responses and signs in a mouse model of rheumatoid arthritis

BACKGROUND

Dopamine is a neurotransmitter and has been found to regulate lymphocytes by acting on dopamine receptors (DRs). CD4⁺ T cells express all the five subtypes of DRs, D1R to D5R. Although CD4⁺ T cells have been involved in pathogenesis of rheumatoid arthritis (RA), roles of DRs expressed on these cells in RA are poorly understood. This study determined whether D2R expressed on CD4⁺ T cells regulates inflammatory responses and signs in collagen type II (CII)-induced arthritis (CIA), a mouse model of RA.

METHODS

DBA/1 mice and C57BL/6 mice with global D1r or D2r deficiency (D1r^-/- or D2r^-/-) or CD4⁺ T cell-specific D2r deletion (D2r^fl/fl/CD4^Cre) were used to prepare CIA model by intradermal injection of CII. D2R agonist sumanirole was intraperitoneally administered in CIA mice. CD4⁺ T cells obtained from CIA mice were exposed to sumanirole or/and D2R antagonist L-741,626 in vitro. Arthritic symptoms were assessed by clinical arthritis scores. Flow cytometric assay measured frequencies of CD4⁺ T cell subsets (Th1, Th2, Th17 and Treg cells). Expression of specific transcription factors for the CD4⁺ T cell subsets was tested by Western blot. Cytokine production was estimated by quantitative PCR and ELISA.

RESULTS

CIA mice manifested a bias of CD4⁺ T cells towards Th1 and Th17 cells. D2r^-/- CIA mice showed a stronger bias towards Th1 and Th17 phenotypes than CIA mice, while D1r^-/- CIA mice did not show the changes. CD4⁺ T cell-specific D2r deletion exacerbated both the polarization towards Th1 and Th17 cells and the symptoms of arthritis. Sumanirole administration in CIA mice ameliorated the bias of CD4⁺ T cells towards Th1 and Th17 phenotypes as well as arthritic symptoms. Sumanirole treatment of in vitro CD4⁺ T cells obtained from CIA mice promoted the shift to Treg cells, and the effect of sumanirole was blocked by L-741,626.

CONCLUSIONS

D2R expressed on CD4⁺ T cells is protective against imbalance between pro-inflammatory and anti-inflammatory T cells and arthritic symptoms in CIA.

Disease mechanisms as subtypes: Immune dysfunction in Parkinson's disease

In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.

The reciprocal interactions between microglia and T cells in Parkinson's disease: a double-edged sword

In Parkinson's disease (PD), neurotoxic microglia, Th1 cells, and Th17 cells are overactivated. Overactivation of these immune cells exacerbates the disease process and leads to the pathological development of pro-inflammatory cytokines, chemokines, and contact-killing compounds, causing the loss of dopaminergic neurons. So far, we have mainly focused on the role of the specific class of immune cells in PD while neglecting the impact of interactions among immune cells on the disease. Therefore, this review demonstrates the reciprocal interplays between microglia and T cells and the associated subpopulations through cytokine and chemokine production that impair and/or protect the pathological process of PD. Furthermore, potential targets and models of PD neuroinflammation are highlighted to provide the new ideas/directions for future research.

Dopamine, Immunity, and Disease

The neurotransmitter dopamine is a key factor in central nervous system (CNS) function, regulating many processes including reward, movement, and cognition. Dopamine also regulates critical functions in peripheral organs, such as blood pressure, renal activity, and intestinal motility. Beyond these functions, a growing body of evidence indicates that dopamine is an important immunoregulatory factor. Most types of immune cells express dopamine receptors and other dopaminergic proteins, and many immune cells take up, produce, store, and/or release dopamine, suggesting that dopaminergic immunomodulation is important for immune function. Targeting these pathways could be a promising avenue for the treatment of inflammation and disease, but despite increasing research in this area, data on the specific effects of dopamine on many immune cells and disease processes remain inconsistent and poorly understood. Therefore, this review integrates the current knowledge of the role of dopamine in immune cell function and inflammatory signaling across systems. We also discuss the current understanding of dopaminergic regulation of immune signaling in the CNS and peripheral tissues, highlighting the role of dopaminergic immunomodulation in diseases such as Parkinson's disease, several neuropsychiatric conditions, neurologic human immunodeficiency virus, inflammatory bowel disease, rheumatoid arthritis, and others. Careful consideration is given to the influence of experimental design on results, and we note a number of areas in need of further research. Overall, this review integrates our knowledge of dopaminergic immunology at the cellular, tissue, and disease level and prompts the development of therapeutics and strategies targeted toward ameliorating disease through dopaminergic regulation of immunity. SIGNIFICANCE STATEMENT: Canonically, dopamine is recognized as a neurotransmitter involved in the regulation of movement, cognition, and reward. However, dopamine also acts as an immune modulator in the central nervous system and periphery. This review comprehensively assesses the current knowledge of dopaminergic immunomodulation and the role of dopamine in disease pathogenesis at the cellular and tissue level. This will provide broad access to this information across fields, identify areas in need of further investigation, and drive the development of dopaminergic therapeutic strategies.

The Dopamine Gene Receptors (DRD1-5) Expression Alteration in Psoriasis Patients

BACKGROUND

Psoriasis is a chronic inflammatory autoimmune disease that is considered linked to genetic and environmental factors such as stress. Since the neurotransmitter dopamine has a close association with stress configuration, it can be a candidate for relieving psoriasis representation. In addition to the CNS, immune cells can play a decisive role in regulating immune functions through dopamine synthesis and the expression of its receptors. Altered response of immune cells to dopamine as well as a distorted expression of dopamine receptors (DRs) in immune cells have been reported in some chronic inflammatory conditions.

OBJECTIVE

This study aims the evaluation of dopamine receptor (DR1-DR5) gene expression in mononuclear blood cells of psoriatic patients in comparison with normal individuals.

METHODS

We isolated peripheral mononuclear cells (PBMCs) from blood samples followed by total RNA extraction, cDNA synthesis, and real-time PCR using specific primer pairs.

RESULTS

We found that all types of DRs are expressed in the PBMCs of normal and psoriatic individuals. We also concluded that compared to controls, DR2 and DR4 were overexpressed in psoriasis patients while DR3 was low-expressed.

CONCLUSION

Increased expression of DR2 and DR4 along with decreased expression of DR3 in PBMCs of psoriasis patients not only provide new insight into the pathogenesis of psoriasis but may also be effective in designing future therapeutic strategies attributable to psoriasis.

Effect of quetiapine on inflammation and immunity: a systematic review

INTRODUCTION

Knowledge about the neurobiology of psychiatric disorders is increasing in the last decades and evidence from literature suggests a central role for immuno-inflammatory mechanisms in these illnesses. The antipsychotic quetiapine acts on dopamine and serotonin signalling and well-established evidence demonstrates that these neurotransmitters can modulate immune functions in healthy and diseased conditions. Starting from this perspective, in the last few decades, a number of studies attempted to identify quetiapine effects on immune functions in order to highlight a possible additional effect of this drug in psychotic diseases, although no conclusive results were obtained.

METHODS

We critically reviewed preclinical and clinical studies evaluating quetiapine effects on immune systems, suggesting strategies for future work in this field.

RESULTS

Computerised search, in PubMed and Embase databases, was performed in March 2020: 120 studies were identified but only 29 relevant papers were selected for detailed review.

CONCLUSION

Despite some interesting preliminary findings about anti-inflammatory effects of quetiapine, mainly supported by preclinical studies, it is possible to conclude further studies are needed to investigate the immunomodulatory effects of this drug and achieve a better understanding of its relevance on clinical outcomes to finally identify new therapeutic approaches in psychiatric treatment.KeypointsMounting evidence points to a role for immuno-inflammatory mechanisms in psychiatric disorders.Quetiapine (QUE) acts on catecholamine (dopamine and norepinephrine) and serotonin signalling.The immunomodulatory effects of catecholamines are well established.Treatment with QUE in psychiatric disorders could leverage immunomodulatory effects.QUE unclear role in immune function modulation suggests future work.

Dopaminergic Inhibition of Human Neutrophils is Exerted Through D1-Like Receptors and Affected By Bacterial Infection

BACKGROUND

Dopamine (DA) affects immune functions in healthy subjects and during disease by acting on D1-like (D1 and D5) and D2-like (D2, D3 and D4) dopaminergic receptors (DR), however its effects on human polymorphonuclear leukocytes (PMN) are still poorly defined.

METHODS

We investigated DR expression in human PMN and the ability of DA to affect cell migration and reactive oxygen species (ROS) production. Experiments were performed on cells from healthy subjects (HS) and from patients (Pts) with bacterial infections as well, during the acute phase and after recovery. Some experiments were also performed in mice KO for the DRD5 gene.

RESULTS

PMN from HS express both D1-like and D2-like DR, and exposure to DA results in inhibition of activation-induced morphological changes, migration and ROS production which depend on the activation of D1-like DR. In agreement with these findings, DA inhibited migration of PMN obtained from wild-type mice, but not from DR D5 KO mice. In Pts with bacterial infections, during the febrile phase D1-like DR D5 on PMN were downregulated and DA failed to affect PMN migration. Both D1-like DR D5 expression and DA-induced inhibition of PMN migration were however restored after recovery.

CONCLUSION

Dopaminergic inhibition of human PMN is a novel mechanism which is likely to play a key role in the regulation of innate immunity. Evidence obtained in Pts with bacterial infections provides novel clues for the therapeutic modulation of PMN during infectious disease.

DAT and TH expression marks human Parkinson's disease in peripheral immune cells

Parkinson's disease (PD) is marked by a loss of dopamine neurons, decreased dopamine transporter (DAT) and tyrosine hydroxylase (TH) expression. However, this validation approach cannot be used for diagnostic, drug effectiveness or investigational purposes in human patients because midbrain tissue is accessible postmortem. PD pathology affects both the central nervous and peripheral immune systems. Therefore, we immunophenotyped blood samples of PD patients for the presence of myeloid derived suppressor cells (MDSCs) and discovered that DAT+/TH+ monocytic MDSCs, but not granulocytic MDSCs are increased, suggesting a targeted immune response to PD. Because in peripheral immune cells DAT activity underlies an immune suppressive mechanism, we investigated whether expression levels of DAT and TH in the peripheral immune cells marks PD. We found drug naïve PD patients exhibit differential DAT+/TH+ expression in peripheral blood mononuclear cells (PBMCs) compared to aged/sex matched healthy subjects. While total PBMCs are not different between the groups, the percentage of DAT+/TH+ PBMCs was significantly higher in drug naïve PD patients compared to healthy controls irrespective of age, gender, disease duration, disease severity or treatment type. Importantly, treatment for PD negatively modulates DAT+/TH+ expressing PBMCs. Neither total nor the percentage of DAT+/TH+ PBMCs were altered in the Alzheimer's disease cohort. The mechanistic underpinning of this discovery in human PD was revealed when these findings were recapitulated in animal models of PD. The reverse translational experimental strategy revealed that alterations in dopaminergic markers in peripheral immune cells are due to the disease associated changes in the CNS. Our study demonstrates that the dopaminergic machinery on peripheral immune cells displays an association with human PD, with exciting implications in facilitating diagnosis and investigation of human PD pathophysiology.

Autoimmune Epilepsy - Novel Multidisciplinary Analysis, Discoveries and Insights

Epilepsy affects ~50 million people. In ~30% of patients the etiology is unknown, and ~30% are unresponsive to anti-epileptic drugs. Intractable epilepsy often leads to multiple seizures daily or weekly, lasting for years, and accompanied by cognitive, behavioral, and psychiatric problems. This multidisciplinary scientific (not clinical) 'Perspective' article discusses Autoimmune Epilepsy from immunological, neurological and basic-science angles. The article includes summaries and novel discoveries, ideas, insights and recommendations. We summarize the characteristic features of the respective antigens, and the pathological activity in vitro and in animal models of autoimmune antibodies to: Glutamate/AMPA-GluR3, Glutamate/NMDA-NR1, Glutamate/NMDA-NR2, GAD-65, GABA-R, GLY-R, VGKC, LGI1, CASPR2, and β2 GP1, found in subpopulations of epilepsy patients. Glutamate receptor antibodies: AMPA-GluR3B peptide antibodies, seem so far as the most exclusive and pathogenic autoimmune antibodies in Autoimmune Epilepsy. They kill neural cells by three mechanisms: excitotoxicity, Reactive-Oxygen-Species, and complement-fixation, and induce and/or facilitate brain damage, seizures, and behavioral impairments. In this article we raise and discuss many more topics and new insights related to Autoimmune Epilepsy. 1. Few autoimmune antibodies tilt the balance between excitatory Glutamate and inhibitory GABA, thereby promoting neuropathology and epilepsy; 2. Many autoantigens are synaptic, and have extracellular domains. These features increase the likelihood of autoimmunity against them, and the ease with which autoimmune antibodies can reach and harm these self-proteins. 3. Several autoantigens have 'frenetic character'- undergoing dynamic changes that can increase their antigenicity; 4. The mRNAs of the autoantigens are widely expressed in multiple organs outside the brain. If translated by default to proteins, broad spectrum detrimental autoimmunity is expected; 5. The autoimmunity can precede seizures, cause them, and be detrimental whether primary or epiphenomenon; 6. Some autoimmune antibodies induce, and associate with, cognitive, behavioral and psychiatric impairments; 7. There are evidences for epitope spreading in Autoimmune Epilepsy; 8. T cells have different 'faces' in the brain, and in Autoimmune Epilepsy: Normal T cells are needed for the healthy brain. Normal T cells are damaged by autoimmune antibodies to Glutamate/AMPA GluR3, which they express, and maybe by additional autoantibodies to: Dopamine-R, GABA-R, Ach-R, Serotonin-R, and Adrenergic-R, present in various neurological diseases (summarized herein), since T cells express all these Neurotransmitter receptors. However, autoimmune and/or cytotoxic T cells damage the brain; 9. The HLA molecules are important for normal brain function. The HLA haplotype can confer susceptibility or protection from Autoimmune Epilepsy; 10. There are several therapeutic strategies for Autoimmune Epilepsy.

Peripheral Immune Cell Numbers and C-Reactive Protein in Parkinson's Disease: Results from a Population-Based Study

BACKGROUND

The immune system is known to be involved in Parkinson's disease (PD) pathogenesis, but the temporal relationship between peripheral immune responses and PD remains unknown.

OBJECTIVE

We determined the association between peripheral immune cell numbers, C-reactive protein (CRP), and prevalent as well as incident PD.

METHODS

This study was embedded in the population-based setting of the Rotterdam Study. We repeatedly measured peripheral immune cell numbers (differential leukocyte count and platelet count, granulocyte-to-lymphocyte ratio [GLR], platelet-to-lymphocyte ratio [PLR], and adapted systemic immune-inflammation index [adapted SII]) and CRP between 1990 and 2016. Participants were continuously followed-up for PD until 2018. We estimated the association of the markers with prevalent and incident PD using logistic regression models and joint models, respectively. Models were adjusted for age, sex, smoking, body mass index, and medication use. Odds ratios (OR) and hazard ratios (HR) are shown per doubling of the marker.

RESULTS

A total of 12,642 participants were included in this study. The mean age (standard deviation) was 65.1 (9.8) years and 57.5%were women. Participants with a higher lymphocyte count were less likely to have prevalent PD (adjusted OR: 0.34, 95%CI 0.17-0.68). Participants with a higher GLR, PLR, and adapted SII were more likely to have prevalent PD, but these effects were explained by the lymphocyte count. The peripheral immune cell numbers and CRP were not significantly associated with the risk of incident PD.

CONCLUSION

We found participants with a higher lymphocyte count to be less likely to have prevalent PD, but we did not find an association between peripheral immune cell numbers nor CRP and the risk of incident PD.

Dopamine receptor D2 on CD4+ T cells is protective against neuroinflammation and neurodegeneration in a mouse model of Parkinson's disease

Parkinson's disease (PD) is a chronic neurodegenerative disease. Recently, neuroinflammation driven by CD4⁺ T cells has been involved in PD pathophysiology. Human and murine lymphocytes express all the five subtypes of dopamine receptors (DRs), DRD1 to DRD5. However, roles of DRs particularly DRD2 expressed on CD4⁺ T cells in PD remain elucidated. Global Drd1- or Drd2-knockout (Drd1^-/- or Drd2^-/-) mice or CD4⁺ T cell-specific Drd2-knockout (Drd2^fl/fl/CD4^Cre) mice were intraperitoneally injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to induce PD with the different mutants. On the 7th day following MPTP injection, mice were assessed for dopaminergic neurodegeneration, locomotor impairments, microglial activation, as well as CD4⁺ T-cell differentiation and function. Furthermore, in vitro CD4⁺ T cells were exposed to DRD2 agonist and antagonist and then differentiation and function of the cells were determined. MPTP induced dopaminergic neuronal loss in the nigrostriatal system, motor coordinative and behavioral impairments, microglial activation, and CD4⁺ T-cell polarization to pro-inflammatory T-helper (Th)1 and Th17 phenotypes. Importantly, either Drd2^-/- or Drd2^fl/fl/CD4^Cre mice manifested more severe dopaminergic neurodegeneration, motor deficits, microglial activation, and CD4⁺ T-cell bias towards Th1 and Th17 phenotypes in response to MPTP, but Drd1^-/- did not further alter MPTP intoxication. DRD2 agonist sumanirole inhibited shift of CD4⁺ T cells obtained from MPTP-intoxicated mice to Th1 and Th17 phenotypes and DRD2 antagonist L-741,626 reversed sumanirole effects. These findings suggest that DRD2 expressed on CD4⁺ T cells is protective against neuroinflammation and neurodegeneration in PD. Thus, developing a therapeutic strategy of stimulating DRD2 may be promising for mitigation of PD.

The role of dopamine receptors in lymphocytes and their changes in schizophrenia

Dopamine and its 5 receptors, which are grouped into two families (D1-like and D2-like), modulate functions at a systemic level in both the central nervous system and periphery. The central nervous system and the immune system are the main adaptive systems, which participate in a continuous and functional crosstalk to guarantee homeostasis. On binding to its 5 dopamine receptors, dopamine acts as a co-regulator of the immune system, contributing to the interaction of the central nervous system and inflammatory events and as a source of communication between the different immune cells. Dopaminergic perturbations in the central nervous system are observed in several neurological and psychiatric disorders. Schizophrenia is one of the most common mental disorders with a poorly understood pathoaetiology that includes genetic and environmental components that promote alterations in the dopaminergic system. Interestingly, abnormalities in dopamine receptors expression in lymphocytes of schizophrenia patients have been reported, often significantly correlating with the severity of the psychotic illness. Here, we review the current literature regarding the dopaminergic system in human lymphocytes and its alterations in schizophrenia.

1.

The existence of DA in the bloodstream suggests the presence of dopaminergic components that modulate functions at a systemic level; therefore, its effects are not limited to the CNS and the signalling in the neuronal dopaminergic system should be independent from that of the peripheral systems.

2.

The effects by DA-mediated activation of different DRs on immune cells show different sensitivities to DA, but binding profiles of DA on T cells are similar to those in neuronal membranes, suggesting receptors act similarly to those found in neurons.

3.

All DRs are expressed on the LYM membrane. However, more detailed information is required on the expression patterns of DR in immune cells in healthy conditions and in pathologies.

4.

DA has been observed to influence LYM functions acting in a variety of important processes, like cytokine secretion, cell adhesion, chemotaxis, and cytotoxicity.

5.

In human LYM, DA on D1-like receptors decreases oxidative metabolism and apoptosis, activates the selective secretion of IL-10 and TNFα, and facilitates NK cells. In contrast, most of the immunostimulatory DA effects on LYM depend on stimulation of D2-like receptors including activation, proliferation, differentiation, and suppression of NK cells.

6.

To date, an altered expression or signalling of neurotransmitter receptors is observed in immune cells during psychiatric disorders and, consequently, these cells also markedly respond to antipsychotics.

7.

Numerous technologies have been used in search of biomarkers for SCZ. However, after a century of studying SCZ their application in psychiatry remains rare and there are currently no validated biomarkers for the diagnosis and prognosis of patients with SCZ or the prediction of treatment efficacy.

Neurotransmitters and Neuropeptides decrease PD-1 in T cells of healthy subjects and patients with hepatocellular carcinoma (HCC), and increase their proliferation and eradication of HCC cells

T cells of aged people, and of patients with either cancer or severe infections (including COVID-19), are often exhausted, senescent and dysfunctional, leading to increased susceptibilities, complications and mortality. Neurotransmitters and Neuropeptides bind their receptors in T cells, and induce multiple beneficial T cell functions. Yet, T cells of different people vary in the expression levels of Neurotransmitter and Neuropeptide receptors, and in the magnitude of the corresponding effects. Therefore, we performed an individual-based study on T cells of 3 healthy subjects, and 3 Hepatocellular Carcinoma (HCC) patients. HCC usually develops due to chronic inflammation. The inflamed liver induces reduction and inhibition of CD4⁺ T cells and Natural Killer (NK) cells. Immune-based therapies for HCC are urgently needed. We tested if selected Neurotransmitters and Neuropeptides decrease the key checkpoint protein PD-1 in human T cells, and increase proliferation and killing of HCC cells. First, we confirmed human T cells express all dopamine receptors (DRs), and glutamate receptors (GluRs): AMPA-GluR3, NMDA-R and mGluR. Second, we discovered that either Dopamine, Glutamate, GnRH-II, Neuropeptide Y and/or CGRP (10nM), as well as DR and GluR agonists, induced the following effects: 1. Decreased significantly both %PD-1⁺ T cells and PD-1 expression level per cell (up to 60% decrease, within 1 h only); 2. Increased significantly the number of T cells that proliferated in the presence of HCC cells (up to 7 fold increase), 3. Increased significantly T cell killing of HCC cells (up to 2 fold increase). 4. Few non-conventional combinations of Neurotransmitters and Neuropeptides had surprising synergistic beneficial effects. We conclude that Dopamine, Glutamate, GnRH-II, Neuropeptide Y and CGRP, alone or in combinations, can decrease % PD-1⁺ T cells and PD-1 expression per cell, in T cells of both healthy subjects and HCC patients, and increase their proliferation in response to HCC cells and killing of HCC cells. Yet, testing T cells of many more cancer patients is absolutely needed. Based on these findings and previous ones, we designed a novel "Personalized Adoptive Neuro-Immunotherapy", calling for validation of safety and efficacy in clinical trials.

Peripheral Immune Profile and Neutrophil-to-Lymphocyte Ratio in Parkinson's Disease

BACKGROUND

The neutrophil-to-lymphocyte ratio (NLR) in peripheral blood is a well-established inflammatory marker, but its role in Parkinson's disease (PD) remains unclear.

OBJECTIVES

To determine whether a different peripheral immune profile and NLR were present in PD patients.

METHODS

We conducted a case-control study that included 377 PD patients and 355 healthy controls (HCs). Leukocytes, subpopulations, and the NLR were measured. Multivariate linear regression analyses were applied to determine the differences between groups and the association between NLR and clinical characteristics in PD. A meta-analysis was performed to clarify the association between NLR and PD.

RESULTS

In our case-control study, the NLR was significantly higher in PD patients compared with HCs (2.47 ± 1.1 vs. 1.98 ± 0.91, P < 0.001). No association between NLR and age at onset, disease severity, or disease duration was found. The meta-analysis showed that the NLR was likely to be higher in PD patients.

CONCLUSIONS

PD patients had an altered peripheral immune profile and a higher NLR compared with HCs. © 2021 International Parkinson and Movement Disorder Society.

Cellular and molecular pathophysiology in the progression of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder etiologically linked to the loss of substantia nigra (SN) dopaminergic neurons in the mid-brain. The etiopathology of sporadic PD is still unclear; however, the interaction of extrinsic and intrinsic factors may play a critical role in the onset and progression of the disease. Studies in animal models and human post-mortem tissue have identified distinct cellular and molecular changes in the diseased brain, suggesting complex interactions between different glial cell types and various molecular pathways. Small changes in the expression of specific genes in a single pathway or cell type possibly influence others at the cellular and system levels. These molecular and cellular signatures like neuroinflammation, oxidative stress, and autophagy have been observed in PD patients' brain tissue. While the etiopathology of PD is still poorly understood, the interplay between glial cells and molecular events may play a crucial role in disease onset and progression.

T Cells Plead for Rejuvenation and Amplification; With the Brain's Neurotransmitters and Neuropeptides We Can Make It Happen

T cells are essential for eradicating microorganisms and cancer and for tissue repair, have a pro-cognitive role in the brain, and limit Central Nervous System (CNS) inflammation and damage upon injury and infection. However, in aging, chronic infections, acute SARS-CoV-2 infection, cancer, chronic stress, depression and major injury/trauma, T cells are often scarce, exhausted, senescent, impaired/biased and dysfunctional. People with impaired/dysfunctional T cells are at high risk of infections, cancer, other diseases, and eventually mortality, and become multi-level burden on other people, organizations and societies. It is suggested that “Nerve-Driven Immunity” and “Personalized Adoptive Neuro-Immunotherapy” may overcome this problem. Natural Neurotransmitters and Neuropeptides: Glutamate, Dopamine, GnRH-II, CGRP, Neuropeptide Y, Somatostatin and others, bind their well-characterized receptors expressed on the cell surface of naïve/resting T cells and induce multiple direct, beneficial, and therapeutically relevant effects. These Neurotransmitters and Neuropeptides can induce/increase: gene expression, cytokine secretion, integrin-mediated adhesion, chemotactic migration, extravasation, proliferation, and killing of cancer. Moreover, we recently found that some of these Neurotransmitters and Neuropeptides also induce rapid and profound decrease of PD-1 in human T cells. By inducing these beneficial effects in naïve/resting T cells at different times after binding their receptors (i.e. NOT by single effect/mechanism/pathway), these Neurotransmitters and Neuropeptides by themselves can activate, rejuvenate, and improve T cells. “Personalized Adaptive Neuro-Immunotherapy” is a novel method for rejuvenating and improving T cells safely and potently by Neurotransmitters and Neuropeptides, consisting of personalized diagnostic and therapeutic protocols. The patient’s scarce and/or dysfunctional T cells are activated ex vivo once by pre-selected Neurotransmitters and/or Neuropeptides, tested, and re-inoculated to the patient’s body. Neuro-Immunotherapy can be actionable and repeated whenever needed, and allows other treatments. This adoptive Neuro-Immunotherapy calls for testing its safety and efficacy in clinical trials.

The Functional Significance of Endocrine-immune Interactions in Health and Disease

Hormones are known to influence various body systems that include skeletal, cardiac, digestive, excretory, and immune systems. Emerging investigations suggest the key role played by secretions of endocrine glands in immune cell differentiation, proliferation, activation, and memory attributes of the immune system. The link between steroid hormones such as glucocorticoids and inflammation is widely known. However, the role of peptide hormones and amino acid derivatives such as growth and thyroid hormones, prolactin, dopamine, and thymopoietin in regulating the functioning of the immune system remains unclear. Here, we reviewed the findings pertinent to the functional role of hormone-immune interactions in health and disease and proposed perspective directions for translational research in the field.

Control of T-Cell Activation and Signaling by Amino-Acid Catabolizing Enzymes

Amino acids are essential for protein synthesis, epigenetic modification through the methylation of histones, and the maintenance of a controlled balance of oxidoreduction via the production of glutathione and are precursors of certain neurotransmitters. T lymphocytes are particularly sensitive to fluctuations in amino acid levels. During evolution, the production of amino-acid catabolizing enzymes by mainly antigen-presenting cells has become a physiological mechanism to control T-cell activation and polarization. The action of these enzymes interferes with TCR and co-stimulation signaling, allowing tuning of the T-cell response. These capacities can be altered in certain pathological conditions, with relevant consequences for the development of disease.

Pro-inflammatory dopamine-2 receptor-specific T cells in paediatric movement and psychiatric disorders

Objectives

A dysregulated inflammatory response against the dopamine‐2 receptor (D2R) has been implicated in movement and psychiatric disorders. D2R antibodies were previously reported in a subset of these patients; however, the role of T cells in these disorders remains unknown. Our objective was to identify and characterise pro‐inflammatory D2R‐specific T cells in movement and psychiatric disorders.

Methods

Blood from paediatric patients with movement and psychiatric disorders of suspected autoimmune and neurodevelopmental aetiology (n = 24) and controls (n = 16) was cultured in vitro with a human D2R peptide library, and D2R‐specific T cells were identified by flow cytometric quantification of CD4⁺CD25⁺CD134⁺ T cells. Cytokine secretion was analysed using a cytometric bead array and ELISA. HLA genotypes were examined in D2R‐specific T‐cell‐positive patients. D2R antibody seropositivity was determined using a flow cytometry live cell‐based assay.

Results

Three immunodominant regions of D2R, amino acid (aa)121–131, aa171–181 and aa396–416, specifically activated CD4⁺ T cells in 8/24 patients. Peptides corresponding to these regions were predicted to bind with high affinity to the HLA of the eight positive patients and had also elicited the secretion of pro‐inflammatory cytokines IL‐2, IFN‐ γ, TNF, IL‐6, IL‐17A and IL‐17F. All eight patients were seronegative for D2R antibodies.

Conclusion

Autoreactive D2R‐specific T cells and a pro‐inflammatory Th1 and Th17 cytokine profile characterise a subset of paediatric patients with movement and psychiatric disorders, further underpinning the theory of immune dysregulation in these disorders. These findings offer new perspectives into the neuroinflammatory mechanisms of movement and psychiatric disorders and can influence patient diagnosis and treatment.

Dopaminergic and Adrenergic Pathways as Targets for Drug Repurposing in the Neuroimmune Network

Dopamine, noradrenaline and adrenaline are catecholamines, and are all produced along the same metabolic pathway. Their discovery dates back to the early 1900s, and they were appreciated until the second half of the century mainly for their role in the brain and in the regulation of autonomic functions. Nonetheless, in the 1970s characterization of the key role of sympathoadrenergic nerve fibers in the cross-talk between the brain and the immune system paved the way to the raise of modern neuroimmunology, and understanding the immune effects of dopamine occurred in the subsequent decades. Both adrenergic and dopaminergic transmission offer a possibly unparalleled wealth of therapeutic targets, and most of them have been already successfully exploited for cardiovascular, respiratory, neurologic and even psychiatric diseases, however so far the therapeutic potential of adrenergic and dopaminergic agents in the neuroimmune network remains relatively unexploited. This special issue provides a unique collection of expert contributions from some of the most prominent researchers currently studying dopaminergic and adrenergic agents in major diseases like cancer, autoimmunity, neurodegeneration, and even in emerging areas like hematology and metabolism. It is strongly hoped that these reviews will be not only helpful for researchers already working on topics related to the neuroimmune pharmacology of catecholamines, but will also attract novel researchers as much work is still needed to fully exploit the therapeutic potential of dopaminergic and adrenergic drugs for the benefit of patients.

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.

Age-Related Dopaminergic Innervation Augments T Helper 2-Type Allergic Inflammation in the Postnatal Lung

Young children are more susceptible to developing allergic asthma than adults. As neural innervation of the peripheral tissue continues to develop after birth, neurons may modulate tissue inflammation in an age-related manner. Here we showed that sympathetic nerves underwent a dopaminergic-to-adrenergic transition during post-natal development of the lung in mice and humans. Dopamine signaled through a specific dopamine receptor (DRD4) to promote T helper 2 (Th2) cell differentiation. The dopamine-DRD4 pathway acted synergistically with the cytokine IL-4 by upregulating IL-2-STAT5 signaling and reducing inhibitory histone trimethylation at Th2 gene loci. In murine models of allergen exposure, the dopamine-DRD4 pathway augmented Th2 inflammation in the lungs of young mice. However, this pathway operated marginally after sympathetic nerves became adrenergic in the adult lung. Taken together, the communication between dopaminergic nerves and CD4⁺ T cells provides an age-related mechanism underlying the susceptibility to allergic inflammation in the early lung.

Peripheral Immunity, Immunoaging and Neuroinflammation in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder among elderly population, characterized by the progressive degeneration of dopaminergic neurons in the midbrain. To date, exact cause remains unknown and the mechanism of neurons death uncertain. It is typically considered as a disease of central nervous system (CNS). Nevertheless, numerous evidence has been accumulated in several past years testifying undoubtedly about the principal role of neuroinflammation in progression of PD. Neuroinflammation is mainly associated with presence of activated microglia in brain and elevated levels of cytokine levels in CNS. Nevertheless, active participation of immune system as well has been noted, such as, elevated levels of cytokine levels in blood, the presence of auto antibodies, and the infiltration of T cell in CNS. Moreover, infiltration and reactivation of those T cells could exacerbate neuroinflammation to greater neurotoxic levels. Hence, peripheral inflammation is able to prime microglia into pro-inflammatory phenotype, which can trigger stronger response in CNS further perpetuating the on-going neurodegenerative process. In the present review, the interplay between neuroinflammation and the peripheral immune response in the pathobiology of PD will be discussed. First of all, an overview of regulation of microglial activation and neuroinflammation is summarized and discussed. Afterwards, we try to collectively analyze changes that occurs in peripheral immune system of PD patients, suggesting that these peripheral immune challenges can exacerbate the process of neuroinflammation and hence the symptoms of the disease. In the end, we summarize some of proposed immunotherapies for treatment of PD.

The modulatory role of dopamine receptors in brain neuroinflammation

Neuroinflammation is a general pathological feature of central nervous system (CNS) diseases, primarily caused by activation of astrocytes and microglia, as well as the infiltration of peripheral immune cells. Inhibition of neuroinflammation is an important strategy in the treatment of brain disorders. Dopamine (DA) receptor, a significant G protein-coupled receptor (GPCR), is classified into two families: D1-like (D1 and D5) and D2-like (D2, D3 and D4) receptor families, according to their downstream signaling pathways. Traditionally, DA receptor forms a wide variety of psychological activities and motor functions, such as voluntary movement, working memory and learning. Recently, the role of DA receptor in neuroinflammation has been investigated widely, mainly focusing on nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome, renin-angiotensin system, αB-crystallin, as well as invading peripheral immune cells, including T cells, dendritic cells, macrophages and monocytes. This review briefly outlined the functions and signaling pathways of DA receptor subtypes as well as its role in inflammation-related glial cells, and subsequently summarized the mechanisms of DA receptors affecting neuroinflammation. Meaningfully, this article provided a theoretical basis for drug development targeting DA receptors in inflammation-related brain diseases.

Alpha synuclein in hematopoiesis and immunity

Parkinson's disease (PD) is the second most common neurodegenerative condition and intracellular deposition of Lewy bodies in the substantia nigra (SN), which can cause dopaminergic neuronal death, is the hallmark of this syndrome. α-synuclein (syn) is a small protein expressed mainly in neurons but can also be found in a number of tissues. It can be present as a soluble monomer under normal physiological conditions, but can be toxic in its oligomeric or fibrillary forms. Most of the available literature has focused on the effects of α-syn pathology in the mechanisms leading to PD. However, the normal functions of α-syn still remain to be fully elucidated. Notably, α-syn in the hematopoietic system seems to mediate important functions as indicated by anemia and incomplete cell maturation when this protein is absent. This review will summarize basic genetic and structural findings, and critical information that suggests an essential role of α-syn in the development and activation of the hematopoietic system and immunity.

Dopamine inhibits human CD8+ Treg function through D1-like dopaminergic receptors

CD8+ T regulatory/suppressor cells (Treg) affect peripheral tolerance and may be involved in autoimmune diseases as well as in cancer. In view of our previous data showing the ability of DA to affect adaptive immune responses, we investigated the dopaminergic phenotype of human CD8+ Treg as well as the ability of DA to affect their generation and activity. Results show that CD8+ T cells express both D₁-like and D₂-like dopaminergic receptors (DR), tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of DA, and vesicular monoamine transporter (VMAT) 2 and contain high levels of intracellular DA. Preferential upregulation of DR mRNA levels in the CD8+CD28- T cell compartment occurs during generation of CD8+ Treg, which is reduced by DA and by the D₁-like DR agonist SKF-38393. DA and SKF-38393 also reduce the suppressive activity of CD8+ Treg on human peripheral blood mononuclear cells. Treg are crucial for tumor escape from the host immune system, thus the ability of DA to inhibits Treg function supports dopaminergic pathways as a druggable targets to develop original and innovative antitumor strategies.

The Prospective Value of Dopamine Receptors on Bio-Behavior of Tumor

Dopamine receptors are belong to the family of G protein-coupled receptor. There are five types of dopamine receptor (DR), including DRD1, DRD2, DRD3, DRD4, and DRD5, which are divided into two major groups: the D1-like receptors (DRD1 and DRD5), and the D2-like receptors (DRD2, DRD3, and DRD4). Dopamine receptors are involved in all of the physiological functions of dopamine, including the autonomic movement, emotion, hormonal regulation, dopamine-induced immune effects, and tumor behavior, and so on. Increasing evidence shows that dopamine receptors are associated with the regulation of tumor behavior, such as tumor cell death, proliferation, invasion, and migration. Recently, some studies showed that dopamine receptors could regulate several ways of death of the tumor cell, including apoptosis, autophagy-induced death, and ferroptosis, which cannot only directly affect tumor behavior, but also limit tumor progress via activating tumor immunity. In this review, we focus mainly on the function of the dopamine receptor on Bio-behavior of tumor as a potential therapeutic target.

Expression of Dopamine Receptors in Immune Regulatory Cells

OBJECTIVE

Parkinson's disease (PD) patients are usually treated with L-dopa and/or dopaminergic agonists, which act by binding five types of dopaminergic receptors (DRD1-DRD5). Peripheral immune cells are known to express dopamine receptors on their membrane surface, and therefore they could be directly affected by the treatment. Regulatory cells are the main modulators of inflammation, but it is not clear whether dopaminergic treatment could affect their functions. While only regulatory T cells (Tregs) have been proved to express dopamine receptors, it is not known whether other regulatory cells such as CD8regs, regulatory B cells (Bregs), tolerogenic dendritic cells, and intermediate monocytes also express them.

METHODS

The expression of dopamine receptors in Tregs, CD8regs, Bregs, tolerogenic dendritic cells, and intermediate monocytes was herein evaluated. cDNA from 11 PD patients and 9 control subjects was obtained and analyzed.

RESULTS

All regulatory cell populations expressed the genes coding for dopamine receptors, and this expression was further corroborated by flow cytometry. These findings may allow us to propose regulatory populations as possible targets for PD treatment.

CONCLUSIONS

This study opens new paths to deepen our understanding on the effect of PD treatment on the cells of the regulatory immune response.

Upgraded Methodology for the Development of Early Diagnosis of Parkinson's Disease Based on Searching Blood Markers in Patients and Experimental Models

Numerous attempts to develop an early diagnosis of Parkinson's disease (PD) by searching biomarkers in biological fluids were unsuccessful. The drawback of this methodology is searching markers in patients at the clinical stage without guarantee that they are also characteristic of either preclinical stage or prodromal stage (preclinical-prodromal stage). We attempted to upgrade this methodology by selecting only markers that are found both in patients and in PD animal models. HPLC and RT-PCR were used to estimate the concentration of amino acids, catecholamines/metabolites in plasma and gene expression in lymphocytes in 36 untreated early-stage PD patients and 52 controls, and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice at modeling the clinical ("symptomatic") stage and preclinical-prodromal ("presymptomatic") stage of PD. It was shown that among 13 blood markers found in patients, 7 markers are characteristic of parkinsonian symptomatic mice and 3 markers of both symptomatic and presymptomatic mice. According to our suggestion, the detection of the same marker in patients and symptomatic animals indicates adequate reproduction of pathogenesis along the corresponding metabolic pathway, whereas the detection of the same marker in presymptomatic animals indicates its specificity for preclinical-prodromal stage. This means that the minority of markers found in patients-decreased concentration of L-3,4-dihydroxyphenylalanine (L-DOPA) and dihydroxyphenylacetic acid (DOPAC) and increased dopamine D3 receptor gene expression-are specific for preclinical-prodromal stage and are suitable for early diagnosis of PD. Thus, we upgraded a current methodology for development of early diagnosis of PD by searching blood markers not only in patients but also in parkinsonian animals.

The role of dopaminergic immune cell signalling in poststroke inflammation

Upon ischaemic stroke, brain-resident and peripheral immune cells accumulate in the central nervous system (CNS). Interestingly, these cells express pattern specific to neurotransmitter receptors and, therefore, seem to be susceptible to neurotransmitter stimulation, potentially modulating their properties and functions. One of the principal neurotransmitters in the CNS, dopamine, is involved in the regulation of processes of brain development, motor control and higher brain functions. It is constantly released in the brain and there is experimental and clinical evidence that dopaminergic signalling is involved in recovery of lost neurological function after stroke. Independent studies have revealed specific but different patterns of dopamine receptor subtypes on different populations of immune cells. Those patterns are dependent on the activation status of cells. Generally, exposure to dopamine or dopamine receptor agonists decreases detrimental actions of immune cells. In contrast, a reduction of dopaminergic inputs perpetuates a pro-inflammatory state associated with increased release of pro-inflammatory molecules. In addition, subsets of immune cells have been identified to synthesize and release dopamine, suggesting autoregulatory mechanisms. Evidence supports that inflammatory processes activated following ischaemic stroke are modulated by dopaminergic signalling.

[The effect of antipsychotic drug on monoamine receptors in peripheral blood mononuclear cells: affinity linked mechanism]

Schizophrenia is one of the most serious and common mental disorders, which is characterized by high levels of pathogenic heterogeneity as well as neuroimmune abnormalities, which require treatment with antipsychotic drugs. Monoamines are one of the key neurotransmitters which play an important role in neuroimmune interactions of the human organism. We suggest that the quantity of the monoamine receptors on mononuclear cells of the peripheral blood (PBMCs) can be associated with the cytokine profile of patients. With this quantity being a key component of the mental status correction mechanism in antipsychotic therapy. In this study we measured cytokine levels (IL-6, IL-1b and TGF-b) in blood serum, the protein expression status of the serotonin receptor 5HTR2A and the dopamine receptors D1 (DRD1), DRD2, DRD3 in PBMCs of drug-naive, first episode schizophrenia patients before and after the treatment with olanzapine and haloperidol. This study has shown for the first time that the antipsychotic therapy leads to a decrease in protein levels of monoamine receptors in PBMCs associated with the affinity of the drug used. Blood cytokine levels were significantly higher in serum from studied patients as compared with the reference values. The antipsychotic-linked change of the TGF-b production caused by the therapy is probably associated with the reduction of various monoamine receptors. The relationship between the psychopathological status and the protein level of 5THR2A suggests that the amount of 5HTR2A may serve as a potential biomarker for the personalized appointment of the antipsychotic therapy.

Alteration of Mevalonate Pathway in Rat Splenic Lymphocytes: Possible Role in Cytokines Secretion Regulated by L-Theanine

L-Theanine is a nonprotein amino acid in tea, and its immunomodulatory function has been confirmed. This study aimed to investigate the effect of L-theanine addition on cytokines secretion in rat splenic lymphocytes and explore its potential immunomodulatory effects on the mevalonate biosynthetic pathway. Our results showed that L-theanine treatment did not influence the proliferation and division indexes of the splenic lymphocytes subsets. Interestingly, L-theanine treatment had regulated the contents of IFN-γ, IL-2, IL-4, IL-10, IL-12, and TNF-α  (P < 0.001) except IL-6 and upregulated the mRNA and protein expression of Ras-related protein Rap-1A (Rap1A), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), and farnesyl diphosphate synthase (FDPs) (P < 0.001). Additionally, there was a positive correlation between Rap1A and HMGCR proteins expression and IFN-γ, IL-4, and IL-6 levels. In conclusion, L-theanine regulated the secretion of cytokines probably by activating expression of Rap1A and HMGCR proteins involved in the mevalonate biosynthetic pathway in rat splenic lymphocytes. Therefore, L-theanine might be a promising potential drug candidate as immunopotentiator.

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.

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.

Complex Changes in the Innate and Adaptive Immunity Accompany Progressive Degeneration of the Nigrostriatal Pathway Induced by Intrastriatal Injection of 6-Hydroxydopamine in the Rat

We investigated changes in innate and adaptive immunity paralleling the progressive nigrostriatal damage occurring in a neurotoxic model of Parkinson's disease (PD) based on unilateral infusion of 6-hydroxydopamine (6-OHDA) into the rat striatum. A time-course analysis was conducted to assess changes in morphology (activation) and cell density of microglia and astrocytes, microglia polarization (M1 vs. M2 phenotype), lymphocyte infiltration in the lesioned substantia nigra pars compacta (SNc), and modifications of CD8+ and subsets of CD4+ T cell in peripheral blood accompanying nigrostriatal degeneration. Confirming previous results, we observed slightly different profiles of activation for astrocytes and microglia paralleling nigral neuronal loss. For astrocytes, morphological changes and cell density increases were mostly evident at the latest time points (14 and 28 days post-surgery), while moderate microglia activation was present since the earliest time point. For the first time, in this model, we described the time-dependent profile of microglia polarization. Activated microglia clearly expressed the M2 phenotype in the earlier phase of the experiment, before cell death became manifest, gradually shifting to the M1 phenotype as SNc cell death started. In parallel, a reduction in the percentage of circulating CD4+ T regulatory (Treg) cells, starting as early as day 3 post-6-OHDA injection, was detected in 6-OHDA-injected rats. Our data show that nigrostriatal degeneration is associated with complex changes in central and peripheral immunity. Microglia activation and polarization, Treg cells, and the factors involved in their cross-talk should be further investigated as targets for the development of therapeutic strategies for disease modification in PD.

Pleiotrophin overexpression regulates amphetamine-induced reward and striatal dopaminergic denervation without changing the expression of dopamine D1 and D2 receptors: Implications for neuroinflammation

It was previously shown that mice with genetic deletion of the neurotrophic factor pleiotrophin (PTN-/-) show enhanced amphetamine neurotoxicity and impair extinction of amphetamine conditioned place preference (CPP), suggesting a modulatory role of PTN in amphetamine neurotoxicity and reward. We have now studied the effects of amphetamine (10mg/kg, 4 times, every 2h) in the striatum of mice with transgenic PTN overexpression (PTN-Tg) in the brain and in wild type (WT) mice. Amphetamine caused an enhanced loss of striatal dopaminergic terminals, together with a highly significant aggravation of amphetamine-induced increase in the number of GFAP-positive astrocytes, in the striatum of PTN-Tg mice compared to WT mice. Given the known contribution of D1 and D2 dopamine receptors to the neurotoxic effects of amphetamine, we also performed quantitative receptor autoradiography of both receptors in the brains of PTN-Tg and WT mice. D1 and D2 receptors binding in the striatum and other regions of interest was not altered by genotype or treatment. Finally, we found that amphetamine CPP was significantly reduced in PTN-Tg mice. The data demonstrate that PTN overexpression in the brain blocks the conditioning effects of amphetamine and enhances the characteristic striatal dopaminergic denervation caused by this drug. These results indicate for the first time deleterious effects of PTN in vivo by mechanisms that are probably independent of changes in the expression of D1 and D2 dopamine receptors. The data also suggest that PTN-induced neuroinflammation could be involved in the enhanced neurotoxic effects of amphetamine in the striatum of PTN-Tg mice.

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.

Diabetic ketoacidosis in patients exposed to antipsychotics: a systematic literature review and analysis of Danish adverse drug event reports

RATIONALE

Patients exposed to second-generation antipsychotics (SGAs) have approximately 10 times increased risk of diabetic ketoacidosis (DKA) compared with the general population. However, as DKA is a rare complication of type 2 diabetes mellitus, and susceptible patients exposed to antipsychotics may rapidly develop DKA independently of treatment duration and weight gain, this is rather suggestive of type 1 diabetes mellitus (T1DM) or latent autoimmune diabetes in adults.

OBJECTIVES

We performed a systematic review of current studies regarding antipsychotic-associated DKA with type 1 etiology and analyzed Danish adverse drug event (ADE) reports (previously unpublished cases).

METHODS

PubMed, Embase, and the Cochrane Library were searched for all relevant studies, and the Danish Medicines Agency retrieved ADE reports using the Danish ADE database (up to date as of June 28, 2016). Diagnosis of antipsychotic-associated DKA with type 1 etiology was either considered confirmed or possible depending on authors' conclusions in the studies and/or clinical aspects. In addition, clinico-demographic risk factors were extracted.

RESULTS

A total of 655 records and 11 ADE reports were identified, and after screening for eligibility, we included 21 case reports/series and two ADE reports (n = 24). No relevant clinical studies were included. Although fatal cases were identified, these were excluded because of diagnostic uncertainties (n = 15). DKA occurred in 15 males (62.5 %) and nine females (37.5 %), with a mean age ± standard deviation of 34.8 ± 12.4 years. Median time to DKA was 5 months (interquartile range: 1.4-11 months). Associated antipsychotics were olanzapine (n = 9, 36 %), aripiprazole (n = 6, 24 %), risperidone (n = 6, 24 %), clozapine (n = 3, 12 %), and quetiapine (n = 1, 4 %). Nine patients (37.5 %) were confirmedly diagnosed with T1DM following DKA resolution, whereas 15 patients (62.5 %) had possible T1DM. In 22 patients (91.7 %), ongoing insulin treatment was required for glycemic control.

CONCLUSIONS

Increased awareness of the potential risk of antipsychotic-associated DKA and subsequent T1DM diagnosis, with insulin requirements for glycemic control, is warranted. The underlying mechanisms are poorly understood but most probably multifactorial. Certainly, further studies are warranted. Clinicians must utilize appropriate monitoring in susceptible patients and consider the possibility of continuing antipsychotic treatment with appropriate diabetic care.

Dopaminergic Receptors on CD4+ T Naive and Memory Lymphocytes Correlate with Motor Impairment in Patients with Parkinson's Disease

Parkinson’s disease (PD) is characterized by loss of dopaminergic neurons in substantia nigra pars compacta, α-synuclein (α-syn)-rich intraneuronal inclusions (Lewy bodies), and microglial activation. Emerging evidence suggests that CD4+ T lymphocytes contribute to neuroinflammation in PD. Since the mainstay of PD treatment is dopaminergic substitution therapy and dopamine is an established transmitter connecting nervous and immune systems, we examined CD4+ T naive and memory lymphocytes in PD patients and in healthy subjects (HS), with specific regard to dopaminergic receptor (DR) expression. In addition, the in vitro effects of α-syn were assessed on CD4+ T naive and memory cells. Results showed extensive association between DR expression in T lymphocytes and motor dysfunction, as assessed by UPDRS Part III score. In total and CD4+ T naive cells expression of D₁-like DR decrease, while in T memory cells D₂-like DR increase with increasing score. In vitro, α-syn increased CD4+ T memory cells, possibly to a different extent in PD patients and in HS, and affected DR expression with cell subset-specific patterns. The present results support the involvement of peripheral adaptive immunity in PD, and may contribute to develop novel immunotherapies for PD, as well as to better use of current dopaminergic antiparkinson drugs.

Possible biomarkers modulating haloperidol efficacy and/or tolerability

Haloperidol (HP) is widely used in the treatment of several forms of psychosis. Despite of its efficacy, HP use is a cause of concern for the elevated risk of adverse drug reactions. adverse drug reactions risk and HP efficacy greatly vary across subjects, indicating the involvement of several factors in HP mechanism of action. The use of biomarkers that could monitor or even predict HP treatment impact would be of extreme importance. We reviewed the elements that could potentially be used as peripheral biomarkers of HP effectiveness. Although a validated biomarker still does not exist, we underlined the several potential findings (e.g., about cytokines, HP metabolites and genotypic biomarkers) which could pave the way for future research on HP biomarkers.

In vivo effects of methamphetamine on HIV-1 replication: A population-based study

BACKGROUND

Although a number of in vitro studies have shown that methamphetamine (METH) can increase HIV-1 replication in human immune cells, a direct link between METH use and HIV-1 pathogenesis remains to be determined among HIV-1 patients.

METHODS

According to the status of METH use and HIV-1 infection, we enrolled participants and divided them into four groups: METH+HIV+, METH-HIV+, METH+HIV-, and METH-HIV-. HIV viral loads and HIV-1-related cellular factors were measured and compared among different groups.

RESULTS

A total of 60 participants were enrolled into this study, 15 within each group. HIV viral loads in METH+HIV+ group were significantly higher than those in METH-HIV+ group, while CD4+ T cell counts had an inverse trend between the two groups (p<0.05). METH users or HIV-1 infected patients had lower CCR5+, CXCR4+ percentages in CD4+ T cells than METH-HIV- subjects (p<0.01). However, METH use had little effect on CD3 expression in PBMCs and the levels of MIP-1α, MIP-1β and IL-6 in PBMCs or plasma, which were increased by HIV-1 infection with or without METH. TLR-9 and IFN-α levels in PBMCs of METH users with or without HIV infection were higher than non-METH users (p<0.05).

CONCLUSIONS

METH use is associated with higher viral loads and lower CD4+ T cell counts in HIV-infected individuals. This finding may be mediated by activation of innate immunity (TLR-9, IFN-α) by METH use.

Pramipexole, a Dopamine D2/D3 Receptor-Preferring Agonist, Prevents Experimental Autoimmune Encephalomyelitis Development in Mice

Experimental autoimmune encephalomyelitis (EAE) is the most used animal model of multiple sclerosis (MS) for the development of new therapies. Dopamine receptors can modulate EAE and MS development, thus highlighting the potential use of dopaminergic agonists in the treatment of MS, which has been poorly explored. Herein, we hypothesized that pramipexole (PPX), a dopamine D2/D3 receptor-preferring agonist commonly used to treat Parkinson's disease (PD), would be a suitable therapeutic drug for EAE. Thus, we report the effects and the underlying mechanisms of action of PPX in the prevention of EAE. PPX (0.1 and 1 mg/kg) was administered intraperitoneally (i.p.) from day 0 to 40 post-immunization (p.i.). Our results showed that PPX 1 mg/kg prevented EAE development, abolishing EAE signs by blocking neuroinflammatory response, demyelination, and astroglial activation in spinal cord. Moreover, PPX inhibited the production of inflammatory cytokines, such as IL-17, IL-1β, and TNF-α in peripheral lymphoid tissue. PPX was also able to restore basal levels of a number of EAE-induced effects in spinal cord and striatum, such as reactive oxygen species, glutathione peroxidase, parkin, and α-synuclein (α-syn). Thus, our findings highlight the usefulness of PPX in preventing EAE-induced motor symptoms, possibly by modulating immune cell responses, such as those found in MS and other T helper cell-mediated inflammatory diseases.

Dopamine and T cells: dopamine receptors and potent effects on T cells, dopamine production in T cells, and abnormalities in the dopaminergic system in T cells in autoimmune, neurological and psychiatric diseases

Dopamine, a principal neurotransmitter, deserves upgrading to 'NeuroImmunotransmitter' thanks to its multiple, direct and powerful effects on most/all immune cells. Dopamine by itself is a potent activator of resting effector T cells (Teffs), via two independent ways: direct Teffs activation, and indirect Teffs activation by suppression of regulatory T cells (Tregs). The review covers the following findings: (i) T cells express functional dopamine receptors (DRs) D1R-D5R, but their level and function are dynamic and context-sensitive, (ii) DR membranal protein levels do not necessarily correlate with DR mRNA levels, (iii) different T cell types/subtypes have different DR levels and composition and different responses to dopamine, (iv) autoimmune and pro-inflammatory T cells and T cell leukaemia/lymphoma also express functional DRs, (v) dopamine (~10(-8) M) activates resting/naive Teffs (CD8(+) >>>CD4(+) ), (vi) dopamine affects Th1/Th2/Th17 differentiation, (vii) dopamine inhibits already activated Teffs (i.e. T cells that have been already activated by either antigen, mitogen, anti-CD3 antibodies cytokines or other molecules), (viii) dopamine inhibits activated Tregs in an autocrine/paracrine manner. Thus, dopamine 'suppresses the suppressors' and releases the inhibition they exert on Teffs, (ix) dopamine affects intracellular signalling molecules and cascades in T cells (e.g. ERK, Lck, Fyn, NF-κB, KLF2), (x) T cells produce dopamine (Tregs>>>Teffs), can release dopamine, mainly after activation (by antigen, mitogen, anti-CD3 antibodies, PKC activators or other), uptake extracellular dopamine, and most probably need dopamine, (xi) dopamine is important for antigen-specific interactions between T cells and dendritic cells, (xii) in few autoimmune diseases (e.g. multiple sclerosis/SLE/rheumatoid arthritis), and neurological/psychiatric diseases (e.g. Parkinson disease, Alzheimer's disease, Schizophrenia and Tourette), patient's T cells seem to have abnormal DRs expression and/or responses to dopamine or production of dopamine, (xiii) drugs that affect the dopaminergic system have potent effects on T cells (e.g. dopamine=Intropin, L-dopa, bromocriptine, haloperidol, quinpirole, reserpine, pergolide, ecopipam, pimozide, amantadine, tetrabenazine, nomifensine, butaclamol). Dopamine-induced activation of resting Teffs and suppression of Tregs seem beneficial for health and may also be used for immunotherapy of cancer and infectious diseases. Independently, suppression of DRs in autoimmune and pro-inflammatory T cells, and also in cancerous T cells, may be advantageous. The review is relevant to Immunologists, Neurologists, Neuroimmunologists, Hematologists, Psychiatrists, Psychologists and Pharmacologists.

The Second Insubria Autumn School on Neuroimmune Pharmacology: Repurposing Established Drugs for Novel Indications

The Second Insubria Autumn School on Neuroimmune Pharmacology was held at the University of Insubria in Varese (Italy) in November 16th-20th 2015, under the auspices of the Society on NeuroImmune Pharmacology, the Italian Society of Pharmacology, and the Italian Association for Neuroimmunology. The School was dedicated to the repurposing of established drugs for novel indications, considering the enormous opportunities for drug repositioning provided by the prominent innovative and interdisciplinary approaches peculiar to neuroimmune pharmacology. More than 40 graduate students and postdoctoral fellows from 12 european universities, research institutes and hospitals attended the School, and lectures were given by 20 internationally acknowledged experts in the fields of basic and clinical neurosciences, immunology, and pharmacology. A poster session provided young researchers the opportunity to present their results, and the best poster was given the Journal of Neuroimmune Pharmacology Young Investigator Award.