Dopamine receptors modulate cytotoxicity of natural killer cells via cAMP-PKA-CREB signaling pathway

Gamma-aminobutyric acid for delaying type 1 diabetes mellitus: an update

The current gold-standard management of hyperglycemia in individuals with type 1 diabetes mellitus (T1DM) is insulin therapy. However, this therapy is associated with a high incidence of complications, and delaying the onset of this disease produces a substantially positive impact on quality of life for individuals with a predisposition to T1DM, especially children. This review aimed to assess the use of gamma-aminobutyric acid (GABA) to delay the onset of T1DM in children. GABA produces protective and proliferative effects in 2 ways, β cell and immune cell modulation. Various in vitro and in vivo studies have shown that GABA induces proliferation of β cells, increases insulin levels, inhibits β-cell apoptosis, and suppresses T helper 1 cell activity against islet antigens. Oral GABA is safe as no serious adverse effects were reported in any of the studies included in this review. These findings demonstrate promising results for the use of GABA treatment to delay T1DM, specifically in genetically predisposed children, through immunoregulatory effects and the ability to induce β-cell proliferation.

Gm527 deficiency in dentate gyrus improves memory through upregulating dopamine D1 receptor pathway

AIMS

Dopamine D1 receptor (D1R) hypofunction is associated with negative and cognitive symptoms in schizophrenia; therefore, the mechanism of D1R function modulation needs further investigation. Gm527 is the rodent homologous of the schizophrenia-related gene C14orf28, encoding a predicated D1R-interacting protein. However, the role of Gm527-D1R interaction in schizophrenia needs to be clarified.

METHODS

Gm527-floxed mice were generated and crossed with D1-Cre mice (D1:Gm527-/-) to knockout Gm527 in D1R-positive neurons. Then behavioral tests were performed to explore the schizophrenia-related phenotypes. Immunofluorescence, fluorescence in situ hybridization, electrophysiological recording, quantitative real-time PCR, and western blotting were conducted to investigate the mechanisms.

RESULTS

Working memory, long-term memories, and adult neurogenesis in the DG were enhanced in D1:Gm527-/- mice. LTP was also increased in the DG in D1:Gm527-/- mice, resulting from the Gm527 knockout-induced D1R expression enhancement on the plasma membrane and subsequently cAMP signaling and NMDA receptor pathways activation. The requirement of Gm527 knockout in the DG was confirmed by reversing Gm527 expression or knockdown Gm527 in the DG D1R-positive neurons through AAV-CAG-FLEX-Gm527-GFP or AAV-CMV-FLEX-EGFP-Gm527-RNAi injection.

CONCLUSIONS

The DG Gm527 knockout induces D1R hyperfunction in improving schizophrenia cognitive symptoms.

Regulation Mechanism of Dopamine Receptor 1 in Low Temperature Response of Marsupenaeus japonicus

Dopamine receptors (DARs) are important transmembrane receptors responsible for receiving extracellular signals in the DAR-mediated signaling pathway, and are involved in a variety of physiological functions. Herein, the D1 DAR gene from Marsupenaeus japonicus (MjDAD1) was identified and characterized. The protein encoded by MjDAD1 has the typical structure and functional domains of the G-protein coupled receptor family. MjDAD1 expression was significantly upregulated in the gills and hepatopancreas after low temperature stress. Moreover, double-stranded RNA-mediated silencing of MjDAD1 significantly changed the levels of protein kinases (PKA and PKC), second messengers (cyclic AMP (cAMP), cyclic cGMP, calmodulin, and diacyl glycerol), and G-protein effectors (adenylate cyclase and phospholipase C). Furthermore, MjDAD1 silencing increased the apoptosis rate of gill and hepatopancreas cells. Thus, following binding to their specific receptors, G-protein effectors are activated by MjDAD1, leading to DAD1-cAMP/PKA pathway-mediated regulation of caspase-dependent mitochondrial apoptosis. We suggest that MjDAD1 is indispensable for the environmental adaptation of M. japonicus.

Dopaminergic regulation of inflammation and immunity in Parkinson's disease: friend or foe?

Parkinson's disease (PD) is a neurodegenerative disease affecting 7-10 million people worldwide. Currently, there is no treatment available to prevent or delay PD progression, partially due to the limited understanding of the pathological events which lead to the death of dopaminergic neurons in the substantia nigra in the brain, which is known to be the cause of PD symptoms. The current available treatments aim at compensating dopamine (DA) deficiency in the brain using its precursor levodopa, dopaminergic agonists and some indirect dopaminergic agents. The immune system is emerging as a critical player in PD. Therefore, immune-based approaches have recently been proposed to be used as potential antiparkinsonian agents. It has been well-known that dopaminergic pathways play a significant role in regulating immune responses in the brain. Although dopaminergic agents are the primary antiparkinsonian treatments, their immune regulatory effect has yet to be fully understood. The present review summarises the current available evidence of the immune regulatory effects of DA and its mimics and discusses dopaminergic agents as antiparkinsonian drugs. Based on the current understanding of their involvement in the regulation of neuroinflammation in PD, we propose that targeting immune pathways involved in PD pathology could offer a better treatment outcome for PD patients.

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.

Novel Anticancer Strategy by Targeting the Gut Microbial Neurotransmitter Signaling to Overcome Immunotherapy Resistance

Significance: Microbial neurotransmitters, as potential targets for cancer therapy, are expected to provide a new perspective on the interaction between the gut microbiome and cancer immunotherapy. Recent Advances: Mounting data reveal that most neurotransmitters can be derived from gut microbiota. Furthermore, modulation of neurotransmitter signaling can limit tumor growth and enhance antitumor immunity. Critical Issues: Here, we first present the relationships between microbial neurotransmitters and cancer cells mediated by immune cells. Then, we discuss the microbial neurotransmitters recently associated with cancer immunotherapy. Notably, the review emphasizes that neurotransmitter signaling plays a substantial role in cancer immunotherapy as an emerging cancer treatment target by regulating targeted receptors and interfering with the tumor microenvironment. Future Directions: Future studies are required to uncover the antitumor mechanisms of neurotransmitter signaling to develop novel treatment strategies to overcome cancer immunotherapy resistance. Antioxid. Redox Signal. 38, 298-315.

Neuroendocrine Differentiation of Lung Cancer Cells Impairs the Activation of Antitumor Cytotoxic Responses in Mice

Lung cancer has the highest mortality among all types of cancer; during its development, cells can acquire neural and endocrine properties that affect tumor progression by releasing several factors, some acting as immunomodulators. Neuroendocrine phenotype correlates with invasiveness, metastasis, and low survival rates. This work evaluated the effect of neuroendocrine differentiation of adenocarcinoma on the mouse immune system. A549 cells were treated with FSK (forskolin) and IBMX (3-Isobutyl-1-methylxanthine) for 96 h to induce neuroendocrine differentiation (NED). Systemic effects were assessed by determining changes in circulating cytokines and immune cells of BALB/c mice immunized with PBS, undifferentiated A549 cells, or neuroendocrine A549_NED cells. A549 cells increased circulating monocytes, while CD4⁺CD8^- and CD4⁺CD8⁺ T cells increased in mice immunized with neuroendocrine cells. IL-2 and IL-10 increased in mice that received untreated A549 cells, suggesting that the immune system mounts a regulated response against adenocarcinoma, which did not occur with A549_NED cells. Cocultures demonstrated the cytotoxic capacity of PBMCs when confronted with A549 cells, while in the presence of neuroendocrine cells they not only were unable to show cytolytic activity, but also lost viability. Neuroendocrine differentiation seems to mount less of an immune response when injected in mice, which may contribute to the poor prognosis of cancer patients affected by this pathology.

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.

Dopaminergic Signalling Enhances IL-2 Production and Strengthens Anti-Tumour Response Exerted by Cytotoxic T Lymphocytes in a Melanoma Mouse Model

Dopamine has emerged as an important regulator of immunity. Recent evidence has shown that signalling through low-affinity dopamine receptors exerts anti-inflammatory effects, whilst stimulation of high-affinity dopamine receptors potentiates immunity in different models. However, the dopaminergic regulation of CD8⁺ T-cells in anti-tumour immunity remains poorly explored. Here, we studied the role of dopamine receptor D3 (DRD3), which displays the highest affinity for dopamine, in the function of CD8⁺ T-cells and its consequences in the anti-tumour immune response. We observed that the deficiency of Drd3 (the gene encoding DRD3) in CD8⁺ T-cells limits their in vivo expansion, leading to an impaired anti-tumour response in a mouse melanoma model. Mechanistic analyses suggest that DRD3 stimulation favours the production of interleukin 2 (IL-2) and the surface expression of CD25, the α-chain IL-2 receptor, which are required for expansion and effector differentiation of CD8⁺ T-cells. Thus, our results provide genetic and pharmacologic evidence indicating that DRD3 favours the production of IL-2 by CD8⁺ T-cells, which is associated with higher expansion and acquisition of effector function of these cells, promoting a more potent anti-tumour response in a melanoma mouse model. These findings contribute to understanding how dopaminergic signalling affects the cellular immune response and represent an opportunity to improve melanoma therapy.

Combining adoptive NK cell infusion with a dopamine-releasing peptide reduces senescent cells in aged mice

Aging inducing the development of senescent cells (SNCs) in various tissues is considered as the main cause of the age-related diseases. Senotherapy has become a promising anti-aging therapy. However, the effectivity and side-effect of senolytic agents are still concern. Here, we observed the downregulation of senescence-related genes by adoptive infusion of natural killer (NK) cells in 26 cases in peripheral blood CD3⁺ T cells. NK cell treatment also significantly decreased levels of senescence markers and senescence-associated secretory phenotypes (SASPs) in three senescent adipose tissues when culturing them together. Interestingly, cytotoxic activity of mouse NK cells against SNCs was significantly enhanced by dopamine in vitro through D1-like receptors. Acein, dopamine-releasing peptide, promoted the adoptive infusion of NK cells in effectively eliminating SNCs in a variety of tissues and reduced local and systemic SASPs in aging mice but Acein alone did not have the senolytic effect. These data demonstrated that adoptive infusion of NK cells is an effective means in removing SNCs, and peptide Acein combined with NK cells further enhances this effect in aging mice.

Tumor suppression and improvement in immune systems by specific activation of dopamine D1-receptor-expressing neurons in the nucleus accumbens

Recent research has suggested that the mesolimbic dopamine network that mainly terminates in the nucleus accumbens may positively control the peripheral immune system. The activation of dopamine receptors in neurons in the nucleus accumbens by the release of endogenous dopamine is thus expected to contribute to efferent immune regulation. As in the stimulation of Gs-coupled dopamine D1-receptors or Gi-coupled D2-receptors by endogenous dopamine, we investigated whether specific stimulation of dopamine D1-receptor-expressing neurons or inhibition of dopamine D2-receptor-expressing neurons in the nucleus accumbens could produce anti-tumor effects and improve the immune system in transgenic mice using pharmacogenetic techniques. Repeated stimulation of D1-receptor-expressing neurons in either the medial shell, lateral shell or core regions of the nucleus accumbens significantly decreased tumor volume under a state of tumor transplantation, whereas repeated suppression of D2-receptor-expressing neurons in these areas had no effect on this event. The number of splenic CD8⁺ T cells was significantly increased following repeated stimulation of D1-receptor-expressing neurons in the nucleus accumbens of mice with tumor transplantation. Furthermore, this stimulation produced a significant reduction in the population of splenic CD8⁺ T cells that expressed immune checkpoint-related inhibitory receptors, PD-1, TIM-3 and LAG-3. These findings suggest that repeated stimulation of D1-receptor-expressing neurons (probably D1-receptor-expressing medium spiny neurons) in the nucleus accumbens suppressed tumor progression and improved the immune system by suppressing the exhaustion of splenic CD8⁺ T cells.

Dopamine, a co-regulatory component, bridges the central nervous system and the immune system

Dopamine (DA) is a crucial neurotransmitter that plays an important role in maintaining physiological function in human body. In the past, most studies focused on the relationship between the dopaminergic system and neurological-related diseases. However, it has been found recently that DA is an immunomodulatory mediator and many immune cells express dopamine receptors (DRs). Some immune cells can synthesize and secrete DA and then participate in regulating immune function. DRs agonists or antagonists can improve the dysfunction of immune system through classical G protein signaling pathways or other non-receptor-dependent pathways. This article will discuss the relationship between the dopaminergic system and the immune system. It will also review the use of DRs agonists or antagonists to treat chronic and acute inflammatory diseases and corresponding immunomodulatory mechanisms.

Pharmacotherapy of schizophrenia: immunological aspects and potential role of immunotherapy

INTRODUCTION

Schizophrenia is a complex disorder owing to diversity in clinical phenotypes, overlapping symptoms, and heterogeneous clinical presentation. Even after decades of research, the exact causative mechanisms of schizophrenia are not completely known. Recent evidence indicates the role of immune dysfunction in schizophrenia pathogenesis as observed from alteration in immune cells, increased activity of complement cascade, and development of autoantibodies against neurotransmitter receptors. Immunotherapy involving immunosuppressants and cytokine-targeting drugs, have shown promising results in several clinical studies and it demands further research in this area.

AREAS COVERED

Here, the authors review the immunopathogenesis of schizophrenia, limitations of conventional, and atypical antipsychotic drugs and the potential role and limitations of immunotherapeutic drugs in schizophrenia management.

EXPERT OPINION

Schizophrenia is a complex disorder and poses a challenge to the currently available treatment approaches. Nearly 30% schizophrenia patients exhibit minimal response toward conventional and atypical antipsychotic drugs. Immune system dysfunction plays an important part of schizophrenia pathophysiology and existing monoclonal antibody (mAb) drugs targeting specific components of the immune system are being repositioned in schizophrenia. The authors call upon public and private funders to facilitate urgent and rigorous research efforts in exploring potential role of immunotherapy in schizophrenia.

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.

New insights into neuropeptides regulation of immune system and hemopoiesis: effects on hematologic malignancies

Several neurotransmitters and neuropeptides were reported to join to or to cooperate with different cells of the immune system, bone marrow, and peripheral cells and numerous data support that neuroactive molecules might control immune system activity and hemopoiesis operating on lymphoid organs, and the primary hematopoietic unit, the hematopoietic niche. Furthermore, many compounds seem to be able to take part to the leukemogenesis and lymphomagenesis process, and in the onset of multiple myeloma. In this review, we will assess the possibility that neurotransmitters and neuropeptides may have a role in the onset of haematological neoplasms, may affect the response to treatment or may represent a useful starting point for a new therapeutic approach. More in vivo investigations are needed to evaluate neuropeptide's role in haematological malignancies and the possible utilization as an antitumor therapeutic target. Comprehending the effect of the pharmacological administration of neuropeptide modulators on hematologic malignancies opens up new possibilities in curing clonal hematologic diseases to achieve more satisfactory outcomes.

Absence of Biomarker-Driven Treatment Options in Small Cell Lung Cancer, and Selected Preclinical Candidates for Next Generation Combination Therapies

Lung cancer is the second most common cancer in the United States, and small cell lung cancer (SCLC) accounts for about 15% of all lung cancers. In SCLC, more than other malignancies, the standard of care is based on clinical demonstration of efficacy, and less on a mechanistic understanding of why certain treatments work better than others. This is in large part due to the virulence of the disease, and lack of clinically or biologically relevant biomarkers beyond routine histopathology. While first line therapies work in the majority of patients with extensive stage disease, development of resistance is nearly universal. Although neuroendocrine features, Rb and p53 mutations are common, the current lack of actionable biomarkers has made it difficult to develop more effective treatments. Some progress has been made with the application of immune checkpoint inhibitors. There are new agents, such as lurbinectedin, that have completed late-phase clinical testing while other agents are still in the pre-clinical phase. ONC201/TIC10 is an imipridone with strong in vivo and in vitro antitumor properties and activity against neuroendocrine tumors in phase 1 clinical testing. ONC201 activates the cellular integrated stress response and induces the TRAIL pro-apoptotic pathway. Combination treatment of lurbinectedin with ONC201 are currently being investigated in preclinical studies that may facilitate translation into clinical trials for SCLC patients.

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.

ONC201 and imipridones: Anti-cancer compounds with clinical efficacy

ONC201 was originally discovered as TNF-Related Apoptosis Inducing Ligand (TRAIL)-inducing compound TIC10. ONC201 appears to act as a selective antagonist of the G protein coupled receptor (GPCR) dopamine receptor D2 (DRD2), and as an allosteric agonist of mitochondrial protease caseinolytic protease P (ClpP). Downstream of target engagement, ONC201 activates the ATF4/CHOP-mediated integrated stress response leading to TRAIL/Death Receptor 5 (DR5) activation, inhibits oxidative phosphorylation via c-myc, and inactivates Akt/ERK signaling in tumor cells. This typically results in DR5/TRAIL-mediated apoptosis of tumor cells; however, DR5/TRAIL-independent apoptosis, cell cycle arrest, or antiproliferative effects also occur. The effects of ONC201 extend beyond bulk tumor cells to include cancer stem cells, cancer associated fibroblasts and immune cells within the tumor microenvironment that can contribute to its efficacy. ONC201 is orally administered, crosses the intact blood brain barrier, and is under evaluation in clinical trials in patients with advanced solid tumors and hematological malignancies. ONC201 has single agent clinical activity in tumor types that are enriched for DRD2 and/or ClpP expression including specific subtypes of high-grade glioma, endometrial cancer, prostate cancer, mantle cell lymphoma, and adrenal tumors. Synergy with radiation, chemotherapy, targeted therapy and immune-checkpoint agents has been identified in preclinical models and is being evaluated in clinical trials. Structure-activity relationships based on the core pharmacophore of ONC201, termed the imipridone scaffold, revealed novel potent compounds that are being developed. Imipridones represent a novel approach to therapeutically target previously undruggable GPCRs, ClpP, and innate immune pathways in oncology.

Anti-dopamine D2 receptor antibodies in chronic tic disorders

AIM

To investigate the association between circulating anti-dopamine D2 receptor (D2R) autoantibodies and the exacerbation of tics in children with chronic tic disorders (CTDs).

METHOD

One hundred and thirty-seven children with CTDs (108 males, 29 females; mean age [SD] 10y 0mo [2y 7mo], range 4-16y) were recruited over 18 months. Patients were assessed at baseline, at tic exacerbation, and at 2 months after exacerbation. Serum anti-D2R antibodies were evaluated using a cell-based assay and blinded immunofluorescence microscopy scoring was performed by two raters. The association between visit type and presence of anti-D2R antibodies was measured with McNemar's test and repeated-measure logistic regression models, adjusting for potential demographic and clinical confounders.

RESULTS

At exacerbation, 11 (8%) participants became anti-D2R-positive ('early peri-exacerbation seroconverters'), and nine (6.6%) became anti-D2R-positive at post-exacerbation ('late peri-exacerbation seroconverters'). The anti-D2R antibodies were significantly associated with exacerbations when compared to baseline (McNemar's odds ratio=11, p=0.003) and conditional logistic regression confirmed this association (Z=3.49, p<0.001) after adjustment for demographic and clinical data and use of psychotropic drugs.

INTERPRETATION

There is a potential association between immune mechanisms and the severity course of tics in adolescents with CTDs.

Regulation of natural killer cell activity by glucocorticoids, serotonin, dopamine, and epinephrine

The immune system and the nervous system are highly complex organs composed of various different cells that must interact with each other for proper function of the system. This communication can be mediated by soluble factors. The factors released by the nervous system (neurotransmitters) differ from those released by the immune system (cytokines). Nevertheless, the nervous and immune systems can influence each other’s activity because immune cells express neurotransmitter receptors, and neurons express cytokine receptors. Moreover, immune cells can synthesize and release neurotransmitters themselves, thus using neurotransmitter-mediated pathways via autocrine and paracrine mechanisms. Natural killer (NK) cells are innate lymphocytes that are important for early and effective immune reactions against infections and cancer. Many studies have shown the strong influence of stress and the nervous system on NK cell activity. This phenomenon may be one reason why chronic stress leads to a higher incidence of infections and cancer. Here, we review the effects of neuroendocrine factors on the different activities of NK cells. Understanding the effects of neuroendocrine factors on NK cell activities during physiological and pathophysiological conditions may result in novel therapeutic strategies to enhance NK cell functions against tumors.

The Neuroprotective Effect of L-Stepholidine on Methamphetamine-Induced Memory Deficits in Mice

Repeated methamphetamine (METH) exposure can cause severe neurotoxicity to the central nervous system, and lead to memory deficits. L-Stepholidine (L-SPD) is a structurally identified alkaloid extract of the Chinese herb Stephania intermedia, which elicits dopamine (DA) D1-type receptors partial agonistic activity and D2-type receptors antagonistic activity. In this study, we investigated the effect of L-SPD on METH-induced memory deficits in mice and its underlying mechanisms. We found that repeated exposure to METH (10 mg/kg, i.p., once per day for 7 consecutive days) impaired memory functions in the novel object recognition experiment. Pretreatment of L-SPD (10 mg/kg, i.p.) significantly improved METH-induced memory deficits in mice. Meanwhile, the protein expression of dopaminergic D2 receptors in hippocampus area was significantly increased by repeated METH exposure, while the protein expression of dopamine transporter (DAT) was significantly reduced. Additionally, the protein expression of phospho-protein kinase A (p-PKA) was significantly increased by repeated METH exposure. The hyperpolarization-activated cyclic-nucleotide-gated non-selective cation 1 (HCN1) channel, which was a key regulator of memory functions and could be regulated by p-PKA, was also significantly increased by repeated METH exposure. These changes caused by METH could be prevented by L-SPD pretreatment. Therefore, our data firstly showed that pretreatment of L-SPD exhibited the protective effect against METH-induced memory deficits, possibly through reducing METH-induced upregulation of dopaminergic pathway and HCN1 channels.

Safety and enhanced immunostimulatory activity of the DRD2 antagonist ONC201 in advanced solid tumor patients with weekly oral administration

Background

ONC201 is a small molecule antagonist of DRD2, a G protein-coupled receptor overexpressed in several malignancies, that has prolonged antitumor efficacy and immunomodulatory properties in preclinical models. The first-in-human trial of ONC201 previously established a recommended phase II dose (RP2D) of 625 mg once every three weeks. Here, we report the results of a phase I study that evaluated the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of weekly ONC201.

Methods

Patients ≥ 18 years old with an advanced solid tumor refractory to standard treatment were enrolled. Dose escalation proceeded with a 3 + 3 design from 375 mg to 625 mg of ONC201. One cycle, also the dose-limiting toxicity (DLT) window, was 21 days. The primary endpoint was to determine the RP2D of weekly ONC201, which was confirmed in an 11-patient dose expansion cohort.

Results

Twenty patients were enrolled: three at 375 mg and 17 at 625 mg of ONC201. The RP2D was defined as 625 mg with no DLT, treatment discontinuation, or dose modifications due to drug-related toxicity. PK profiles were consistent with every-three-week dosing and similar between the first and fourth dose. Serum prolactin and caspase-cleaved cytokeratin-18 induction were detected, along with intratumoral integrated stress response activation and infiltration of granzyme B+ Natural Killer cells. Induction of immune cytokines and effectors was higher in patients who received ONC201 once weekly versus once every three weeks. Stable disease of > 6 months was observed in several prostate and endometrial cancer patients.

Conclusions

Weekly, oral ONC201 is well-tolerated and results in enhanced immunostimulatory activity that warrants further investigation.

Trial registration

NCT02250781 (Oral ONC201 in Treating Patients With Advanced Solid Tumors), NCT02324621 (Continuation of Oral ONC201 in Treating Patients With Advanced Solid Tumors).

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0599-8) contains supplementary material, which is available to authorized users.

Dopamine Alters Lipopolysaccharide-Induced Nitric Oxide Production in Microglial Cells via Activation of D1-Like Receptors

Dopamine (DA) is important in the maintenance of normal nervous system function. DA is the target of multiple drugs, and it induces critical alterations in immune cells. However, these impacts are controversial, and the mechanism remains unclear. In the present study, we treated BV-2 microglial cells and primary microglia with DA and measured the changes in cytokines. We also identified the expression of DA receptors (DRs) using confocal and immunofluorescent microscopy. Specific agonists and antagonists of D1-like DRs (D1DR and D5DR) were used to observe alterations in cytokines. Western blot and siRNA interference were performed to investigate the involvement of the downstream signaling molecules of DRs. We also measured changes in mitogen-activated protein kinases (MAPKs) and the nuclear factor-kappa B (NF-κB) signaling pathway and assessed their involvement using inhibitors. We found that DA alone produced no effects on IL-6, TNF-α or nitric oxide (NO) production, and it inhibited lipopolysaccharide (LPS)-induced NO in microglial cells. Microglia expressed a high abundance of D1-like DRs (D1DR and D5DR). The agonists inhibited NO production, and antagonists reversed the DA-induced suppression of NO. Adenylatec cyclase (AC), cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) mediated DA function, and cAMP-response element binding protein (CREB) was not involved. ERK1/2 and NF-κB, but not p-38 or JNK, played roles in DA-suppressed NO generation via altering inducible nitric oxide synthase (iNOS) transcription. These data illustrate that DA modulates LPS-induced NO production via the AC/cAMP-PKA-ERK1/2-NF-κB-iNOS axis in mouse microglia, and D1-like DRs are involved. The present study provides functional evidence for an essential role of DA in immunoregulation.

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.

Effect of A549 neuroendocrine differentiation on cytotoxic immune response

The present study was designed to determine the effects of factors secreted by the lung adenocarcinoma cell line with the neuroendocrine phenotype, A549_NED, on cytotoxic T lymphocytes (CTLs) activity in vitro A perspective that integrates the nervous, endocrine and immune system in cancer research is essential to understand the complexity of dynamic interactions in tumours. Extensive clinical research suggests that neuroendocrine differentiation (NED) is correlated with worse patient outcomes; however, little is known regarding the effects of neuroendocrine factors on the communication between the immune system and neoplastic cells. The human lung cancer cell line A549 was induced to NED (A549_NED) using cAMP-elevating agents. The A549_NED cells showed changes in cell morphology, an inhibition of proliferation, an overexpression of chromogranin and a differential pattern of biogenic amine production (decreased dopamine and increased serotonin [5-HT] levels). Using co-cultures to determine the cytolytic CTLs activity on target cells, we showed that the acquisition of NED inhibits the decrease in the viability of the target cells and release of fluorescence. Additionally, the conditioned medium of A549_NED and 5-HT considerably decreased the viability and proliferation of the Jurkat cells after 24 h. Thus, our study successfully generated a neuroendocrine phenotype from the A549 cell line. In co-cultures with CTLs, the pattern of secretion by A549_NED impaired the proliferation and cytotoxic activity of CTLs, which might be partly explained by the increased release of 5-HT.

Norepinephrine inhibits the cytotoxicity of NK92‑MI cells via the β2‑adrenoceptor/cAMP/PKA/p‑CREB signaling pathway

Norepinephrine (NE) can regulate natural killer (NK) cell activity, but the mechanism remains unclear. In the present study the roles of adrenergic receptors (ARs) in inhibiting NK92‑MI cells‑mediated cytotoxicity by NE were investigated. To examine the effect of NE on NK92‑MI cytotoxicity, a lactate dehydrogenase‑release cytotoxicity assay was used to determine the cytotoxicity of NK92‑MI cells against K562 cells. To evaluate the possible function of the α, β1 and β2 AR in mediating NE‑induced effects, NK92‑MI cells were pre‑incubated with phenol‑amine, CGP20712A and ICI118551 prior to stimulation by NE. To evaluate the role of cyclic adenosine monophosphate (cAMP)‑protein kinase A (PKA) signaling pathway in the inhibitory effect on cytotoxicity of NK92‑MI cell by NE, NK92‑MI cells were pre‑incubated with PKA inhibitor Rp‑8‑Br‑cAMP prior to stimulation by NE. It was demonstrated that NE decreased cytotoxicity and downregulated the expression of perforin, granzyme B and interferon (IFN)‑γ of NK92‑MI cells in a dose‑dependent manner. Blocking NE functional receptors by ARs antagonists, particularly of β2 AR antagonist, suppressed the inhibitory effect of NE on cytotoxicity and expression of perforin, granzyme B, IFN‑γ of NK92‑MI cells significantly. Blockade of β2 AR in NE treated NK92‑MI cells resulted in a reduction of the expression of phosphorylated (p)‑cAMP‑responsive element‑binding protein (CREB) and intracellular cAMP concentration. Inhibiting the activity of PKA by Rp‑8‑Br‑cAMP in NE treated NK92‑MI cells resulted in increased cytotoxicity. The results of the present study suggest that NE can inhibit cytotoxicity and expression of perforin, granzyme B, IFN‑γ of NK92‑MI cell mainly via the β2‑AR/cAMP/PKA/p‑CREB signaling pathway.

Methamphetamine modulates the production of interleukin-6 and tumor necrosis factor-alpha via the cAMP/PKA/CREB signaling pathway in lipopolysaccharide-activated microglia

Methamphetamine (METH) elicits neuroinflammatory effects that may implicate its regulatory role on the microglial immune response. However, the mechanism underlying this remains unclear. In the present study, the effects of METH on lipopolysaccharide (LPS)-induced interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) productions were tested in BV-2 cells and primary microglial cells. Additionally, western blot analysis was used to examine the phosphorylation of mitogenactivated protein kinases (MAPKs). Next, we detected the alterations in cAMP content and the phosphorylation levels of CREB in microglial cells to determine the involvement of the cAMP/CREB signaling pathway. We also used an adenylyl cyclase (AC) agonist (forskolin) and antagonist (MDL-12330A) and a PKA antagonist (H89) to confirm their participation. We observed that METH alone did not affect the production of IL-6 or TNF-α. In contrast, METH augmented the IL-6 production and inhibited the TNF-α production induced by LPS. A similar effect of forskolin was also observed in BV-2 cells. While MAPK activation was not influenced by METH alone, the LPS-induced phosphorylation of p38, JNK and ERK1/2 were all reduced by METH. Both the concentration of cAMP and the phosphorylation of CREB were increased by METH in LPS-activated microglial cells. The effects of METH were altered by MDL-12330A and H89. Moreover, the inhibition of the phosphorylation of ERK1/2 by METH was also reversed. These results suggest that the differential regulation of IL-6 and TNF-α by METH in LPS-activated microglial cells may be attributable to the cAMP/PKA/CREB signaling pathway.

Histamine receptor 2 modifies iNKT cell activity within the inflamed lung

BACKGROUND

Histamine is a key immunoregulatory mediator and can dampen proinflammatory responses via activation of histamine receptor 2 (H₂ R). The aim of this study was to determine the role of H₂ R in modulating lung inflammatory responses.

METHODS

H₂ R was blocked using famotidine or activated using dimaprit in both the ovalbumin (OVA) and house dust mite extract (HDM) murine models of respiratory inflammation. H₂ R-deficient animals and CD1d/H₂ R-deficient animals were utilized to examine the CD1d presentation of lipid antigens (αGalCer or OCH) to invariant natural killer T (iNKT) cells.

RESULTS

Famotidine treatment resulted in more severe airway disease in the OVA model, while dimaprit treatment significantly reduced disease severity. Both OVA and HDM-induced airway diseases were more severe in H₂ R-deficient animals. Flow cytometric analysis of lung tissue from H₂ R-deficient animals revealed increased numbers of CD1d⁺ dendritic cells and increased numbers of iNKT cells. In vitro, αGalCer-stimulated iNKT cells from H₂ R-deficient mice secreted higher levels of IL-4, IL-5, and GM-CSF. In vivo, αGalCer or OCH administration to the lung resulted in enhanced mucus secretion, inflammatory cell recruitment, and cytokine production in H₂ R-deficient or famotidine-treated animals, while dimaprit dampened the lung iNKT cell response to αGalCer. Removal of iNKT cells in H₂ R-deficient (CD1d^-/- H₂ R^-/- ) animals normalized the lung response to HDM.

CONCLUSION

The deliberate activation of H₂ R, or its downstream signaling molecules, may represent a novel therapeutic target for chronic lung inflammatory diseases, especially when CD1d-mediated presentation of lipid antigens to iNKT cells is contributing to the pathology.

Modulation of cyclic nucleotide-mediated cellular signaling and gene expression using photoactivated adenylyl cyclase as an optogenetic tool

Cyclic nucleotide signaling pathway plays a significant role in various biological processes such as cell growth, transcription, inflammation, in microbial pathogenesis, etc. Modulation of cyclic nucleotide levels by optogenetic tools has overcome certain limitations of studying transduction cascade by pharmacological agents and has allowed several ways to modulate biological processes in a spatiotemporal manner. Here, we have shown the optogenetic modulation of the cyclooxygenase 2 (Cox-2) gene expression and their downstream effector molecule (PGE₂) in HEK-293T cells and the development process of Dictyostelium discoideum via modulating the cyclic nucleotide (cAMP) signaling pathway utilizing photoactivated adenylyl cyclases (PACs) as an optogenetic tool. Light-induced activation of PACs in HEK-293T cells increases the cAMP level that leads to activation of cAMP response element-binding protein (CREB) transcription factor and further upregulates downstream Cox-2 gene expression and their downstream effector molecule prostaglandin E2. In D. discoideum, the light-regulated increase in cAMP level affects the starvation-induced developmental process. These PACs could modulate the cAMP levels in a light-dependent manner and have a potential to control gene expression and their downstream effector molecules with varying magnitude. It would enable one to utilize PAC as a tool to decipher cyclic nucleotide mediated signaling pathway regulations and their mechanism.

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.

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.

Dopamine modulates astroglial and microglial activity via glial renin-angiotensin system in cultures

Dopamine is an immunomodulatory molecule that acts on immune effector cells both in the CNS and peripheral tissues. However, the role of changes in dopamine levels in the neuroinflammatory response is controversial. The local/paracrine renin-angiotensin system (RAS) plays a major role in inflammatory processes in peripheral tissues and brain. In the present study, we investigated the possible role of the brain RAS in the effects of dopamine on the glial inflammatory responses. Astrocytes are the major source of the precursor protein angiotensinogen and angiotensin II (AII) in the brain. Neurotoxins such as MPP⁺ (1-methyl-4-phenylpyridinium) can act directly on astrocytes to increase levels of angiotensinogen and AII. Conversely, dopamine, via type-2 (D2) receptors, inhibited production of angiotensinogen, decreased expression of angiotensin type-1 (AT1) receptors and increased expression of AT2 receptors. In microglia, dopamine and dopamine agonists also regulated RAS activity. First, indirectly, via downregulation of the astrocyte-derived AII. Second, via dopamine-induced regulation of microglial angiotensin receptors. Dopamine decreased the microglial AT1/AT2 ratio leading to inhibition of the pro-inflammatory AT1/NADPH-oxidase/superoxide axis. D2 receptors were particularly responsible for microglial RAS inhibition in basal culture conditions. However, both D1 and D2 agonists inhibited the AT1/NADPH-oxidase axis in lipopolysaccharide-treated (LPS; i.e. activated) microglia. The results indicate that the decrease in dopamine levels observed in early stages of Parkinson's disease and aging may promote neuroinflammation and disease progression via glial RAS exacerbation.

Emerging role of dopamine in neovascularization of pheochromocytoma and paraganglioma

Dopamine is a catecholamine that acts both as a neurotransmitter and as a hormone, exerting its functions via dopamine (DA) receptors that are present in a broad variety of organs and cells throughout the body. In the circulation, DA is primarily stored in and transported by blood platelets. Recently, the important contribution of DA in the regulation of angiogenesis has been recognized. In vitro and in vivo studies have shown that DA inhibits angiogenesis through activation of the DA receptor type 2. Overproduction of catecholamines is the biochemical hallmark of pheochromocytoma (PCC) and paraganglioma (PGL). The increased production of DA has been shown to be an independent predictor of malignancy in these tumors. The precise relationship underlying the association between DA production and PCC and PGL behavior needs further clarification. Herein, we review the biochemical and physiologic aspects of DA with a focus on its relations with VEGF and hypoxia inducible factor related angiogenesis pathways, with special emphasis on DA producing PCC and PGL.-Osinga, T. E., Links, T. P., Dullaart, R. P. F., Pacak, K., van der Horst-Schrivers, A. N. A., Kerstens, M. N., Kema, I. P. Emerging role of dopamine in neovascularization of pheochromocytoma and paraganglioma.

MPTP Impairs Dopamine D1 Receptor-Mediated Survival of Newborn Neurons in Ventral Hippocampus to Cause Depressive-Like Behaviors in Adult Mice

Parkinson’s disease (PD) is characterized by motor symptoms with depression. We evaluated the influence of dopaminergic depletion on hippocampal neurogenesis process to explore mechanisms of depression production. Five consecutive days of 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) injection in mice (MPTP-mice) reduced dopaminergic fibers in hippocampal dentate gyrus (DG). MPTP-mice exhibited depressive-like behaviors later for 2–3 weeks. BrdU was injected 4 h after last-injection of MPTP. BrdU-positive (BrdU⁺) cells in dorsal (d-DG) and ventral (v-DG) DG were examined on day 1 (D1), 7 (D7), 14 (D14) and 21 (D21) after BrdU injection. Fewer D7-, D14- and D21-BrdU⁺ cells or BrdU⁺/NeuN⁺ cells, but not D1-BrdU⁺ cells, were found in v-DG of MPTP-mice than in controls. However, the number of BrdU⁺ cells in d-DG did not differ between the both. Loss of doublecortin-positive (DCX⁺) cells was observed in v-DG of MPTP-mice. Protein kinase A (PKA) and Ca²⁺/cAMP-response element binding protein (CREB) phosphorylation were reduced in v-DG of MPTP-mice, which were reversed by D1-like receptor (D1R) agonist SKF38393, but not D2R agonist quinpirole. The treatment of MPTP-mice with SKF38393 on days 2–7 after BrdU-injection reduced the loss of D7- and D21-BrdU⁺ cells in v-DG and improved the depressive-like behaviors; these changes were sensitive to PKA inhibitor H89. Moreover, the v-DG injection of SKF38393 in MPTP-mice could reduce the loss of D21-BrdU⁺ cells and relieve the depressive-like behaviors. In control mice, the blockade of D1R by SCH23390 caused the reduction of D21-BrdU⁺ cells in v-DG and the depressive-like behaviors. Our results indicate that MPTP-reduced dopaminergic depletion impairs the D1R-mediated early survival of newborn neurons in v-DG, producing depressive-like behaviors.

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.

Reduced number of peripheral natural killer cells in schizophrenia but not in bipolar disorder

Overwhelming evidence indicates that subthreshold inflammatory state might be implicated in the pathophysiology of schizophrenia (SCZ) and bipolar disorder (BPD). It has been reported that both groups of patients might be characterized by abnormal lymphocyte counts. However, little is known about alterations in lymphocyte proportions that may differentiate SCZ and BPD patients. Therefore, in this study we investigated blood cell proportions quantified by means of microarray expression deconvolution using publicly available data from SCZ and BPD patients. We found significantly lower counts of natural killer (NK) cells in drug-naïve and medicated SCZ patients compared to healthy controls across all datasets. In one dataset from SCZ patients, there were no significant differences in the number of NK cells between acutely relapsed and remitted SCZ patients. No significant difference in the number of NK cells between BPD patients and healthy controls was observed in all datasets. Our results indicate that SCZ patients, but not BPD patients, might be characterized by reduced counts of NK cells. Future studies looking at lymphocyte counts in SCZ should combine the analysis of data obtained using computational deconvolution and flow cytometry techniques.

The cAMP Pathway as Therapeutic Target in Autoimmune and Inflammatory Diseases

Nucleotide signaling molecules contribute to the regulation of cellular pathways. In the immune system, cyclic adenosine monophosphate (cAMP) is well established as a potent regulator of innate and adaptive immune cell functions. Therapeutic strategies to interrupt or enhance cAMP generation or effects have immunoregulatory potential in autoimmune and inflammatory disorders. Here, we provide an overview of the cyclic AMP axis and its role as a regulator of immune functions and discuss the clinical and translational relevance of interventions with these processes.

N6-methyladenosine modification in mRNA: machinery, function and implications for health and diseases

N6-methyladenosine (m(6) A) modification in mRNA is extremely widespread, and functionally modulates the eukaryotic transcriptome to influence mRNA splicing, export, localization, translation, and stability. Methylated adenines are present in a large subset of mRNAs and long noncoding RNAs (lncRNAs). Methylation is reversible, and this is accomplished by the orchestrated action of highly conserved methyltransferase (m(6) A writer) and demethylase (m(6) A eraser) enzymes to shape the cellular 'epitranscriptome'. The engraved 'methyl code' is subsequently decoded and executed by a group of m(6) A reader/effector components, which, in turn, govern the fate of the modified transcripts, thereby dictating their potential for translation. Reversible mRNA methylation thus adds another layer of regulation at the post-transcriptional level in the gene expression programme of eukaryotes that finely sculpts a highly dynamic proteome in order to respond to diverse cues during cellular differentiation, immune tolerance, and neuronal signalling.

Dopamine receptor DR2 expression in B cells is negatively correlated with disease activity in rheumatoid arthritis patients

OBJECTIVE

Dopamine receptor (DR) signaling is involved in the pathogenesis of autoimmune diseases. We aimed to measure the expression levels of DR1-5 on B cells from patients with rheumatoid arthritis (RA) and to analyze the relationship between DRs and clinical manifestations, inflammatory biomarkers, functional status and disease activity.

METHODS

A total of 29 patients with RA, 12 healthy donors and 12 patients with osteoarthritis (OA) were recruited in this study. Flow cytometry was used to measure the levels of DR1-5 expressed on B cells. The relationships between B cell DR expressions and clinical features in RA patients were analyzed using the Spearman correlation test.

RESULTS

The expression levels of B cell DR1-5 in both the RA and OA groups were lower than those in healthy controls. After 3 months of medication, all five receptors were elevated in RA patients, with DR2 and DR3 being significantly increased from the baseline. DR2 expression on B cells was negatively correlated with inflammatory biomarkers and disease activity.

CONCLUSION

RA patients had lower expression level of DR2 on B cells compared to the healthy controls, and the level of DR2 negatively correlated with the disease activity. DR2 and DR3 might be novel predictors of patient responses to disease modifying antirheumatic drug therapy.

Dopamine inhibits the effector functions of activated NK cells via the upregulation of the D5 receptor

Several lines of evidence indicate that dopamine (DA) plays a key role in the cross-talk between the nervous and immune systems. In this study, we disclose a novel immune-regulatory role for DA: inhibition of effector functions of activated NK lymphocytes via the selective upregulation of the D5 dopaminergic receptor in response to prolonged cell stimulation with rIL-2. Indeed, engagement of this D1-like inhibitory receptor following binding with DA suppresses NK cell proliferation and synthesis of IFN-γ. The inhibition of IFN-γ production occurs through blocking the repressor activity of the p50/c-REL dimer of the NF-κB complex. Indeed, the stimulation of the D5 receptor on rIL-2-activated NK cells inhibits the binding of p50 to the microRNA 29a promoter, thus inducing a de novo synthesis of this miRNA. In turn, the increased levels of microRNA 29a were inversely correlated with the ability of NK cells to produce IFN-γ. Taken together, our findings demonstrated that DA switches off activated NK cells, thus representing a checkpoint exerted by the nervous system to control the reactivity of these innate immune effectors in response to activation stimuli and to avoid the establishment of chronic and pathologic inflammatory processes.

The higher prevalence of non-right handers among patients with restless leg syndrome

Restless leg syndrome (RLS) is a common disorder described as an urge to move the legs. Dopamine, the main neuro-transmitter in the pathophysiology of RLS, is likely related to the development of brain laterality and human handedness. We aimed to compare the prevalence of RLS in right and non-right handers. A checklist including Edinburgh questioner for handedness, questions for RLS diagnosis and basic characteristics was filled out by a sample of population. The exclusion criteria included prolonged use of dopaminergic or psychologic drugs and having diseases with similar symptoms to RLS. The frequency of non-right handers in RLS patients was compared with the controls by Chi square test. P value less than 0.05 was considered significant. 164 persons were divided into RLS patients (69) and non-RLS controls (95). There was no significant difference between demographic characteristics. The prevalence of non-right handers in RLS patients was significantly more than non-RLS controls (P: 0.03). Our finding regarding the higher prevalence of non-right handers in RLS patients needs more justifications based on neuroscientists' guides. RLS as a disease in which dopaminergic system involves is highly assumed to be linked with handedness. This is just a hypothesis that impaired modulation of immune system in left handers may be accompanied with lower dopamine levels in RLS.

Low-dose levodopa protects nerve cells from oxidative stress and up-regulates expression of pCREB and CD39

Objective

This study aimed to investigate the influence of low-dose levodopa (L-DOPA) on neuronal cell death under oxidative stress.

Methods

PC12 cells were treated with L-DOPA at different concentrations. We detected the L-DOPA induced reactive oxygen species (ROS). Meanwhile, MTT and LDH assay were performed to determine the proliferation and growth of PC12 cells with or without ROS scavenger. In addition, after pretreatment with L-DOPA at different concentrations alone or in combination with CD39 inhibitor, PC12 cells were incubated with hydrogen peroxide (H₂O₂) and the cell viability was evaluated by MTT and LDH assay. In addition, the expression of pCREB and CD39 was detected by immunofluorescence staining and Western blot assay in both cells and rat’s brain after L-DOPA treatment.

Results

After treatment with L-DOPA for 3 days, the cell proliferation and growth were promoted when the L-DOPA concentration was <30 µM, while cell proliferation was comparable to that in control group when the L-DOPA concentration was >30 µM. Low dose L-DOPA could protect the PC12 cells from H₂O₂ induced oxidative stress, which was compromised by CD39 inhibitor. In addition, the expression of CD39 and pCREB increased in both PC12 cells and rats’ brain after L-DOPA treatment.

Conclusions

L-DOPA at different concentrations has distinct influence on proliferation and growth of PC12 cells, and low dose (<30 µM) L-DOPA protects PC12 cells against oxidative stress which might be related to the up-regulation of CD39 and pCREB expression.