Dopaminergic Regulation of Innate Immunity: a Review

Living in a Hostile World: Inflammation, New Drug Development, and Coronavirus

We present a brief history of the immune response and show that Metchnikoff's theory of inflammation and phagocytotic defense was largely ignored in the 20th century. For decades, the immune response was believed to be triggered centrally, until Lafferty and Cunningham proposed the initiating signal came from the tissues. This shift opened the way for Janeway's pattern recognition receptor theory, and Matzinger's danger model. All models failed to appreciate that without inflammation, there can be no immune response. The situation changed in the 1990s when cytokine biology was rapidly advancing, and the immune system's role expanded from host defense, to the maintenance of host health. An inflammatory environment, produced by immune cells themselves, was now recognized as mandatory for their attack, removal and repair functions after an infection or injury. We explore the cellular programs of the immune response, and the role played by cytokines and other mediators to tailor the right response, at the right time. Normally, the immune response is robust, self-limiting and restorative. However, when the antigen load or trauma exceeds the body's internal tolerances, as witnessed in some COVID-19 patients, excessive inflammation can lead to increased sympathetic outflows, cardiac dysfunction, coagulopathy, endothelial and metabolic dysfunction, multiple organ failure and death. Currently, there are few drug therapies to reduce excessive inflammation and immune dysfunction. We have been developing an intravenous (IV) fluid therapy comprising adenosine, lidocaine and Mg2+ (ALM) that confers a survival advantage by preventing excessive inflammation initiated by sepsis, endotoxemia and sterile trauma. The multi-pronged protection appears to be unique and may provide a tool to examine the intersection points in the immune response to infection or injury, and possible ways to prevent secondary tissue damage, such as that reported in patients with COVID-19.

Adipocytes and macrophages secretomes coregulate catecholamine-synthesizing enzymes

Obesity associates with macrophage accumulation in adipose tissue where these infiltrating cells interact with adipocytes and contribute to the systemic chronic metabolic inflammation present in immunometabolic diseases. Tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) are two of the main enzymes of catecholamines (CA) synthesis. Adipocytes and macrophages produce, secrete and respond to CA, but the regulation of their synthesis in the interplay between immune and metabolic systems remains unknown. A model of indirect cell coculture with conditioned medium (CM) from RAW 264.7 macrophages with or without LPS-activation and 3T3-L1 adipocytes and preadipocytes was established to study the effect of cellular secretomes on the expression of the above enzymes. During the adipocyte differentiation process, we found a decrease of TH and PNMT expression. The secretome from LPS-activated macrophages downregulated TH and PNMT expression in preadipocytes, but not in mature adipocytes. Mature adipocytes CM induced a decrease of PNMT levels in RAW 264.7 macrophages. Pre and mature adipocytes showed a similar pattern of TH, PNMT and peroxisome proliferator-activated receptor gamma expression after exposure to pro and anti-inflammatory cytokines. We evidenced macrophages and adipocytes coregulate the expression of CA synthesis enzymes through secretome, with non-inflammatory signaling networks possibly being involved. Mediators released by macrophages seem to equally affect CA production by adipocytes, while adipocytes secretome preferentially affect AD production by macrophages. CA synthesis seems to be more determinant in early stages of adipogenic differentiation. Our results suggest that CA are key signaling molecules in the regulation of immune-metabolic crosstalk within the adipose tissue.

Dopamine D1 Receptor in Cancer

Simple Summary

Circulating hormones and their specific receptors play a significant role in the development and progression of various cancers. This review aimed to summarize current knowledge about the dopamine D1 receptor’s biological role in different cancers, including breast cancer, central nervous system tumors, lymphoproliferative disorders, and other neoplasms. Treatment with dopamine D1 receptor agonists was proven to exert a major anti-cancer effect in many preclinical models. We highlight this receptor’s potential as a target for the adjunct therapy of tumors and discuss possibilities and necessities for further research in this area.

Abstract

Dopamine is a biologically active compound belonging to catecholamines. It plays its roles in the human body, acting both as a circulating hormone and neurotransmitter. It acts through G-protein-coupled receptors divided into two subgroups: D1-like receptors (D1R and D5R) and D2-like receptors (D2R, D3R, D4R). Physiologically, dopamine receptors are involved in central nervous system functions: motivation or cognition, and peripheral actions such as blood pressure and immune response modulation. Increasing evidence indicates that the dopamine D1 receptor may play a significant role in developing different human neoplasms. This receptor’s value was presented in the context of regulating various signaling pathways important in tumor development, including neoplastic cell proliferation, apoptosis, autophagy, migration, invasiveness, or the enrichment of cancer stem cells population. Recent studies proved that its activation by selective or non-selective agonists is associated with significant tumor growth suppression, metastases prevention, and tumor microvasculature maturation. It may also exert a synergistic anti-cancer effect when combined with tyrosine kinase inhibitors or temozolomide. This review provides a comprehensive insight into the heterogeneity of dopamine D1 receptor molecular roles and signaling pathways in human neoplasm development and discusses possible perspectives of its therapeutic targeting as an adjunct anti-cancer strategy of treatment. We highlight the priorities for further directions in this research area.

In silico analysis of proteins and microRNAs related to human African trypanosomiasis in tsetse fly

Human African trypanosomiasis (HAT), also known as sleeping sickness, causes millions of deaths worldwide. HAT is primarily transmitted by the vector tsetse fly (Glossina morsitans). Early diagnosis remains a key objective for treating this disease. MicroRNAs (miRNAs) are evolutionarily conserved small non-coding RNAs that play key roles in vector-borne diseases. To date, the roles of proteins and miRNAs in HAT disease have not been thoroughly elucidated. In this study, we have re-annotated the function of protein-coding genes and identified several miRNAs based on a series of bioinformatics tools. A batch of 81.1 % of tsetse fly proteins could be determined homology in mosquito genome, suggesting their probable similar mechanisms in vector-borne diseases. A set of 11 novel salivary proteins and 14 midgut proteins were observed in the tsetse fly, which could be applied to the development of vaccine candidates for the control of HAT disease. In addition, 35 novel miRNAs were identified, among which 10 miRNAs were found to be unique in tsetse fly. Pathway analysis of these 10 miRNAs indicated that targets of miR-15a-5p were significantly enriched in the HAT-related neurotrophin signaling pathway. Besides, topological analysis of the miRNA-gene network indicated that miR-619-5p and miR-2490-3p targeted several genes that respond to trypanosome infection, including thioester-containing protein Tep1 and heat shock protein Hsp60a. In conclusion, our work helps to elucidate the function of miRNAs in tsetse fly and establishes a foundation for further investigations into the molecular regulatory mechanisms of HAT disease.

Involvement of dopaminergic signaling in the cross talk between the renin-angiotensin system and inflammation

The renin-angiotensin system (RAS) is a fundamental regulator of blood pressure and has emerged as an important player in the control of inflammatory processes. Accordingly, imbalance on RAS components either systemically or locally might trigger the development of inflammatory disorders by affecting immune cells. At the same time, alterations in the dopaminergic system have been consistently involved in the physiopathology of inflammatory disorders. Accordingly, the interaction between the RAS and the dopaminergic system has been studied in the context of inflammation of the central nervous system (CNS), kidney, and intestine, where they exert antagonistic actions in the regulation of the immune system. In this review, we summarized, integrated, and discussed the cross talk of the dopaminergic system and the RAS in the regulation of inflammatory pathologies, including neurodegenerative disorders, such as Parkinson’s disease. We analyzed the molecular mechanisms underlying the interaction between both systems in the CNS and in systemic pathologies. Moreover, we also analyzed the impact of the commensal microbiota in the regulation of RAS and dopaminergic system and how it is involved in inflammatory disorders. Furthermore, we summarized the therapeutic approaches that have yielded positive results in preclinical or clinical studies regarding the use of drugs targeting the RAS and dopaminergic system for the treatment of inflammatory conditions. Further understanding of the molecular and cellular regulation of the RAS-dopaminergic cross talk should allow the formulation of new therapies consisting of novel drugs and/or repurposing already existing drugs, alone or in combination, for the treatment of inflammatory disorders.

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

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

Classification of Midbrain Dopamine Neurons Using Single-Cell Gene Expression Profiling Approaches

Dysfunctional dopamine (DA) signaling has been associated with a broad spectrum of neuropsychiatric disorders, prompting investigations into how midbrain DA neuron heterogeneity may underpin this variety of behavioral symptoms. Emerging literature indeed points to functional heterogeneity even within anatomically defined DA clusters. Recognizing the need for a systematic classification scheme, several groups have used single-cell profiling to catalog DA neurons based on their gene expression profiles. We aim here not only to synthesize points of congruence but also to highlight key differences between the molecular classification schemes derived from these studies. In doing so, we hope to provide a common framework that will facilitate investigations into the functions of DA neuron subtypes in the healthy and diseased brain.

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.

Beta-adrenergic receptor stimulation influences the function of monocytes/macrophages in ayu (Plecoglossus altivelis)

Adrenergic receptors (ARs) are members of the G-protein-coupled receptor superfamily that can be categorized into αARs and βARs. The specific function of ARs in teleost monocytes/macrophages (MO/MФ) remains unknown. We determined the cDNA sequence of ARs from ayu (Plecoglossus altivelis; PaαAR and PaβAR). Sequence comparisons showed that PaαAR was most closely related to the αAR of the Japanese flounder and Nile tilapia, while PaβAR was most closely related to the βAR of Atlantic salmon. The AR transcripts were mainly expressed in the spleen, and their expression was altered in various tissues upon infection with Vibrio anguillarum. PaαAR and PaβAR proteins were upregulated in MO/MФ after infection, and PaβAR knockdown resulted in a pro-inflammatory status in ayu MO/MФ upon V. anguillarum infection and lowered the phagocytic activity of MO/MФ. Our results indicate that PaβAR plays the role of an anti-inflammatory mediator in the immune response of ayu against bacterial infection.

Dopamine: an immune transmitter

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

Effects of dopamine on immune signaling pathway factors, phagocytosis and exocytosis in hemocytes of Litopenaeus vannamei

Dopamine (DA) is an important neuroendocrine factor, which can act as neurotransmitter and neurohormone. In this study, we explored the immune defense mechanism in Litopenaeus vannamei with injection of dopamine at 10^-7 and 10^-6 mol shrimp^-1, respectively. The genes expressions of dopamine receptor (DAR), G proteins (Gs, Gi, Gq), phagocytosis and exocytosis-related proteins, as well as intracellular signaling pathway factors, and immune defense parameters were measured. Results showed that mRNA expression levels of dopamine receptor D4 (D4), Gi, nuclear transcription factors and exocytosis-related proteins decreased significantly and reached the minimum at 3 h, while the genes expressions of Gs, Gq and phagocytosis-related proteins reached the highest and lowest levels at 3 h and 6 h, respectively. The second messenger synthetases increased significantly in treatment groups within 3 h. Simultaneously, the second messengers and protein kinases shared a similar trend, which were significantly elevated and reached the peak value at 3 h. Ultimately lead to the total hemocyte count (THC), proPO activity and phagocytic activity decreased significantly, reaching minimum values at 3 h, 3 h and 6 h, respectively. While PO activity showed obvious peak changes, which maximum value reached at 3 h. These results suggested that DA receptor could couple with G protein after DA injection and might regulate immunity through cAMP-PKA, DAG-PKC or CaM pathway.

Dopamine activates NF-κB and primes the NLRP3 inflammasome in primary human macrophages

Induction of innate immune genes in the brain is thought to be a major factor in the development of addiction to substances of abuse. As the major component of the innate immune system in the brain, aberrant activation of myeloid cells such as macrophages and microglia due to substance use may mediate neuroinflammation and contribute to the development of addiction. All addictive drugs modulate the dopaminergic system and our previous studies have identified dopamine as a pro-inflammatory modulator of macrophage function. However, the mechanism that mediates this effect is currently unknown. Inflammatory activation of macrophages and induction of cytokine production is often mediated by the transcription factor NF-κB, and prior studies have shown that dopamine can modulate NF-κB activity in T-cells and other non-immune cell lines. Here we demonstrated that dopamine can activate NF-κB in primary human macrophages, resulting in the induction of its downstream targets including the NLRP3 inflammasome and the inflammatory cytokine IL-1β. These data also indicate that dopamine primes but does not activate the NLRP3 inflammasome in human macrophages. Activation of NF-κB was required for dopamine-mediated increases in IL-1β, as an inhibitor of NF-κB was able to abrogate the effects of dopamine on production of these cytokines. Connecting an increase in extracellular dopamine to NF-κB activation and inflammation suggests specific intracellular targets that could be used to ameliorate the inflammatory impact of dopamine in neuroinflammatory conditions associated with myeloid cell activation such as addiction.

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Dopamine exposure primes, but does not activate the NLRP3 inflammasome.

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Inflammasome priming can be mediated, at least partially, by a dopamine-induced increase in the activation and nuclear translocation of NF-κB in primary human macrophages.

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Dopamine additively increases the impact of cytomegalovirus on NF-κB activation in macrophages.

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Dopamine priming increases IL-1β release in response to inflammasome activation.

G Protein-Coupled Receptors (GPCRs)-Mediated Calcium Signaling in Ovarian Cancer: Focus on GPCRs activated by Neurotransmitters and Inflammation-Associated Molecules

G-coupled protein receptors (GCPR) involve several signaling pathways, some of them being coupled with intracellular calcium (Ca²⁺) mobilization. GPCRs were involved in migration, invasion and metastasis of different types of cancers, including ovarian cancer. Many studies have discussed the essential contribution of GPCRs activated by steroid hormones in ovarian cancer. However, ovarian cancer is also associated with altered signals coming from the nervous system, the immune system or the inflammatory environment, in which GPCRs are ‘sensing’ these molecular signals. Many studies have been oriented so far on ovarian cell lines (most of them being of human cell lines), and only few studies based on animal models or clinical studies have been devoted to the expression changes or functional role of GPCRs in ovarian cancer. In this paper, we review the alterations of GPCRs activated by neurotransmitters (muscarinic receptors, serotonin receptors, dopamine receptors, adrenoceptors) or inflammation-associated molecules (bradykinin receptors, histamine receptors, chemokine receptors) in ovarian cancer and we discuss their potential as histological biomarkers.

A novel approach to study markers of dopamine signaling in peripheral immune cells

Human monocytes express known markers of dopamine synthesis, storage and clearance, including dopamine transporter (DAT), tyrosine hydroxylase (TH), all subtypes of dopamine receptors and vesicular monoamine transporter 2 (VMAT2). Immunohistochemical and immunofluorescent methodologies have traditionally been employed to determine DAT and TH expression in the CNS, their detection in the blood and specifically in the peripheral monocytes has not been studied by flow cytometry. Flow cytometry assays are widely used in medicine and in basic, preclinical or clinical research to quantify physical and chemical characteristics of target cell populations. Here, we have established a highly sensitive and reproducible flow cytometry panel to detect and quantify DAT and TH expression in freshly isolated or cryopreserved human peripheral monocytes. In healthy humans (n = 41 biological replicates), we show baseline DAT and TH expressing monocytes constitute ~12% of the peripheral blood mononuclear cell (PBMC) fraction when examined in fresh isolation from whole blood. Using an identical flow cytometry panel, we found that cryopreservation of PBMCs using multiple techniques resulted in altered PBMC populations as compared to fresh isolation and relative to one another. Among these, we identified an optimum cryopreservation method for detecting TH and DAT in cryopreserved PBMCs. Our data provide a sensitive and reproducible approach to examine dopamine signaling in peripheral human immune cells. This approach can be applied to study peripheral dopamine signaling under healthy and potentially under disease conditions. The use of dopamine signaling could also be explored as a technique to monitor therapeutic interventions particularly those targeting DAT and TH in the periphery.

Functionalized BaTiO3 enhances piezoelectric effect towards cell response of bone scaffold

Piezoelectric effect of polyvinylidene fluoride (PVDF) plays a crucial role in restoring the endogenous electrical microenvironment of bone tissue, whereas more β phase in PVDF leads to higher piezoelectric performance. Nanoparticles can induce the nucleation of the β phase. However, they are prone to aggregate in PVDF matrix, resulting in weakened nucleation ability of β phase. In this work, the hydroxylated BaTiO₃ nanoparticles were functionalized with polydopamine to promote their dispersion in PVDF scaffolds fabricated via selective laser sintering. On one hand, the catechol groups of polydopamine could form hydrogen bonding with the hydroxyl groups of the BaTiO₃. On the other hand, the amino groups of polydopamine were able to bond with CF group of PVDF. As a result, the functionalized BaTiO₃ nanoparticles homogeneously distributed in PVDF matrix, which significantly increased the β phase fraction from 46% to 59% with an enhanced output voltage by 356%. Cell testing confirmed the enhanced surface electric cues significantly promoted cell adhesion, proliferation and differentiation. Furthermore, the scaffolds exhibited enhanced tensile strength and modulus, which was ascribed to the rigid particle strengthening effect and the improved interfacial adhesion. This study suggested that the piezoelectric scaffolds shown a potential application in bone repair.

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.

Dopamine-mediated immunomodulation affects choroid plexus function

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

Neurotransmitters: emerging targets in cancer

Neurotransmitters are conventionally viewed as nerve-secreted substances that mediate the stimulatory or inhibitory neuronal functions through binding to their respective receptors. In the past decades, many novel discoveries come to light elucidating the regulatory roles of neurotransmitters in the physiological and pathological functions of tissues and organs. Notably, emerging data suggest that cancer cells take advantage of the neurotransmitters-initiated signaling pathway to activate uncontrolled proliferation and dissemination. In addition, neurotransmitters can affect immune cells and endothelial cells in the tumor microenvironment to promote tumor progression. Therefore, a better understanding of the mechanisms underlying neurotransmitter function in tumorigenesis, angiogenesis, and inflammation is expected to enable the development of the next generation of antitumor therapies. Here, we summarize the recent important studies on the different neurotransmitters, their respective receptors, target cells, as well as pro/antitumor activity of specific neurotransmitter/receptor axis in cancers and provide perspectives and insights regarding the rationales and strategies of targeting neurotransmitter system to cancer treatment.

Roles of HSV-1 infection-induced microglial immune responses in CNS diseases: friends or foes?

Microglia, as brain-resident macrophages, are the first line of defense against brain invading pathogens. Further, their dysfunction has been recognized to be closely associated with mounting CNS diseases. Of note, chronic HSV-1 infection leads to the persistent activation of microglia, which elicit a comprehensive response by generating certain factors with neurotoxic and neuroprotective effects. CNS infection with HSV-1 results in herpes simplex encephalitis and herpes simplex keratitis. Microglial immune response plays a crucial role in the development of these diseases. Moreover, HSV-1 infection is strongly associated with several CNS diseases, especially Alzheimer's disease and schizophrenia. These CNS diseases can be effectively ameliorated by eliciting an appropriate immune response, such as inhibition of microglial proliferation and activation. Therefore, it is crucial to reassess the positive and negative roles of microglia in HSV-1 CNS infection for a more comprehensive and detailed understanding of the relationship between microglia and CNS diseases. Hence, the present review focuses on the dual roles of microglia in mediating HSV-1 CNS infection, as well as on the strategy of targeting microglia to ameliorate CNS diseases. Further research in this field can help comprehensively elucidate the dual role of the microglial immune response in HSV-1 CNS infection, providing a theoretical basis for identifying therapeutic targets against overactive microglia in CNS diseases and HSV-1 infection.

Progressive dopaminergic defect in a patient with primary progressive multiple sclerosis

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

Dopaminergic impact of cART and anti-depressants on HIV neuropathogenesis in older adults

The success of combination antiretroviral therapy (cART) has transformed HIV infection into a chronic condition, resulting in an increase in the number of older, cART-treated adults living with HIV. This has increased the incidence of age-related, non-AIDS comorbidities in this population. One of the most common comorbidities is depression, which is also associated with cognitive impairment and a number of neuropathologies. In older people living with HIV, treating these overlapping disorders is complex, often creating pill burden or adverse drug-drug interactions that can exacerbate these neurologic disorders. Depression, NeuroHIV and many of the neuropsychiatric therapeutics used to treat them impact the dopaminergic system, suggesting that dopaminergic dysfunction may be a common factor in the development of these disorders. Further, changes in dopamine can influence the development of inflammation and the regulation of immune function, which are also implicated in the progression of NeuroHIV and depression. Little is known about the optimal clinical management of drug-drug interactions between cART drugs and antidepressants, particularly in regard to dopamine in older people living with HIV. This review will discuss those interactions, first examining the etiology of NeuroHIV and depression in older adults, then discussing the interrelated effects of dopamine and inflammation on these disorders, and finally reviewing the activity and interactions of cART drugs and antidepressants on each of these factors. Developing better strategies to manage these comorbidities is critical to the health of the aging, HIV-infected population, as the older population may be particularly vulnerable to drug-drug interactions affecting dopamine.

Microglia-mediated neuroinflammation in neurodegenerative diseases

Microglia, being the resident immune cells of the central nervous system, play an important role in maintaining tissue homeostasis and contributes towards brain development under normal conditions. However, when there is a neuronal injury or other insult, depending on the type and magnitude of stimuli, microglia will be activated to secrete either proinflammatory factors that enhance cytotoxicity or anti-inflammatory neuroprotective factors that assist in wound healing and tissue repair. Excessive microglial activation damages the surrounding healthy neural tissue, and the factors secreted by the dead or dying neurons in turn exacerbate the chronic activation of microglia, causing progressive loss of neurons. It is the case observed in many neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. This review gives a detailed account of the microglia-mediated neuroinflammation in various neurodegenerative diseases. Hence, resolving chronic inflammation mediated by microglia bears great promise as a novel treatment strategy to reduce neuronal damage and to foster a permissive environment for further regeneration effort.

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

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

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.

Do Th17 Lymphocytes and IL-17 Contribute to Parkinson's Disease? A Systematic Review of Available Evidence

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive loss of dopaminergic neurons, appearance of Lewy bodies and presence of neuroinflammation. No treatments currently exist to prevent PD or delay its progression, and dopaminergic substitution treatments just relieve the consequences of dopaminergic neuron loss. Increasing evidence points to peripheral T lymphocytes as key players in PD, and recently there has been growing interest into the specific role of T helper (Th) 17 lymphocytes. Th17 are a proinflammatory CD4+ T cell lineage named after interleukin (IL)-17, the main cytokine produced by these cells. Th17 are involved in immune-related disease such as psoriasis, rheumatoid arthritis and inflammatory bowel disease, and drugs targeting Th17/IL-17 are currently approved for clinical use in such disease. In the present paper, we first summarized current knowledge about contribution of the peripheral immune system in PD, as well as about the physiopharmacology of Th17 and IL-17 together with its therapeutic relevance. Thereafter, we systematically retrieved and evaluated published evidence about Th17 and IL-17 in PD, to help assessing Th17/IL-17-targeting drugs as potentially novel antiparkinson agents. Critical appraisal of the evidence did not allow to reach definite conclusions: both animal as well as clinical studies are limited, just a few provide mechanistic evidence and none of them investigates the eventual relationship between Th17/IL-17 and clinically relevant endpoints such as disease progression, disability scores, intensity of dopaminergic substitution treatment. Careful assessment of Th17 in PD is anyway a priority, as Th17/IL-17-targeting therapeutics might represent a straightforward opportunity for the unmet needs of PD patients.

Targeting the Dopaminergic System in Autoimmunity

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

Bacterial Metabolites Mirror Altered Gut Microbiota Composition in Patients with Parkinson's Disease

Increasing evidence is supporting the hypothesis of α-synuclein pathology spreading from the gut to the brain although the exact etiology of Parkinson's disease (PD) is unknown. Furthermore, it has been proposed that inflammation, via the gastrointestinal tract, potentially through infections, may contribute to α-synuclein pathogenesis, and thus to the risk of developing PD. Recently, many studies have shown that PD patients have an altered microbiota composition compared to healthy controls. Inflammation in the gut might drive microbiota alterations or vice versa. Many studies focused on the detection of biomarkers of the etiology, onset, or progression of PD however also report metabolites from bacterial origin. These metabolites might reflect the bacterial composition and as well play an important role in immune homeostasis, ultimately affecting the progression of PD. Besides the bacterial metabolites, pharmacological treatment of PD might play a crucial role during the progression and thus treatment of the disease on the immune system. This review aims to establish a link between the microbial composition with the observed alterations of bacterial metabolites and their impact on the immune system, which could have influential effect in onset, progression and etiology of PD.

Role of Macrophage Dopamine Receptors in Mediating Cytokine Production: Implications for Neuroinflammation in the Context of HIV-Associated Neurocognitive Disorders

Despite the success of combination anti-retroviral therapy (cART), around 50% of HIV-infected individuals still display a variety of neuropathological and neurocognitive sequelae known as NeuroHIV. Current research suggests these effects are mediated by long-term changes in CNS function in response to chronic infection and inflammation, and not solely due to active viral replication. In the post-cART era, drug abuse is a major risk-factor for the development of NeuroHIV, and increases extracellular dopamine in the CNS. Our lab has previously shown that dopamine can increase HIV infection of primary human macrophages and increase the production of inflammatory cytokines, suggesting that elevated dopamine could enhance the development of HIV-associated neuropathology. However, the precise mechanism(s) by which elevated dopamine could exacerbate NeuroHIV, particularly in chronically-infected, virally suppressed individuals remain unclear. To determine the connection between dopaminergic alterations and HIV-associated neuroinflammation, we have examined the impact of dopamine exposure on macrophages from healthy and virally suppressed, chronically infected HIV patients. Our data show that dopamine treatment of human macrophages isolated from healthy and cART-treated donors promotes production of inflammatory mediators including IL-1β, IL-6, IL-18, CCL2, CXCL8, CXCL9, and CXCL10. Furthermore, in healthy individuals, dopamine-mediated modulation of specific cytokines is correlated with macrophage expression of dopamine-receptor transcripts, particularly DRD5, the most highly-expressed dopamine-receptor subtype. Overall, these data will provide more understanding of the role of dopamine in the development of NeuroHIV, and may suggest new molecules or pathways that can be useful as therapeutic targets during HIV infection.

Differential effect of the DRD3 genotype on inflammatory cytokine responses during abstinence in amphetamine-dependent women

Amphetamine exposure impacts on innate and adaptive immunity and DRD3 may modulate the effect of amphetamine on the immune response. We assessed the immune-cytokine markers in 72 female patients with amphetamine dependence (AD) at baseline and after 4-week drug abstinence and in 51 healthy women. Multiplex magnetic bead assay was used to measure the plasma cytokine expression level simultaneously in all participants and DRD3 rs6280 polymorphism was genotyped in patients. We demonstrated an increase of the T helper 1 (Th1) cytokines (IL-2), Th2 cytokines (IL-4, IL-5, IL-6 and IL-10) and other cytokines (IL-1β) in the entire AD cohort. A similar cytokine pattern, along with a significantly decreased IL-8 and IL-10 levels was observed after 4-week abstinence. Among AD patients with DRD3 rs6280 TT genotype, the cytokine expression profile was consistent with total AD cohort at baseline and revealed a significant down-regulated plasma level of the Th1, Th2, and other cytokines except for IL-6 after 4-week abstinence. In AD group with DRD3 rs6280 C allele carrier, we found IL-2 level was significantly higher than healthy controls at baseline and remained higher, accompanied with a borderline increase in IL-4, IL-6 and IL-1β levels after 4-week abstinence. Our results suggest that chronic use of amphetamine increased both pro- and anti-inflammatory cytokines in AD patients, indicating the immune imbalance that may persist for 4 weeks or more. Besides, DRD3 rs6280 TT genotype may be associated with favorable recovery in general inflammatory cytokines during period of abstinence.

Modulation of the Immune System for the Treatment of Glaucoma

Background:

At present intraocular pressure (IOP) lowering therapies are the only approach to treat glaucoma. Neuroprotective strategies to protect the retinal ganglion cells (RGC) from apoptosis are lacking to date. Substantial amount of research concerning the role of the immune system in glaucoma has been performed in the recent years. This review aims to analyse changes found in the peripheral immune system, as well as selected local changes of retina immune cells in the glaucomatous retina.

Methods:

By dividing the immune system into the innate and the adaptive immune system, a systematic literature research was performed to find recent approaches concerning the modulation of the immune system in the context of glaucoma. Also ClinicalTrials.gov was assessed to identify studies with a translational context.

Results:

We found that some aspects of the immune system, such as changes in antibody levels, changes in toll like receptor signalling, T cells and retinal microglial cells, experience more research activity than other areas such as changes in dendritic cells or macrophages. Briefly, results from clinical studies revealed altered immunoreactivities against retinal and optic nerve antigens in sera and aqueous humor of glaucoma patients and point toward an autoimmune involvement in glaucomatous neurodegeneration and RGC death. IgG accumulations along with plasma cells were found localised in human glaucomatous retinae in a pro-inflammatory environment possibly maintained by microglia. Animal studies show that antibodies (e.g. anti- heat shock protein 60 and anti-myelin basic protein) elevated in glaucoma patients provoke autoaggressive RGC loss and are associated with IgG depositions and increased microglial cells. Also, studies addressing changes in T lymphocytes, macrophages but also local immune responses in the retina have been performed and also hold promising results.

Conclusions:

This recapitulation of recent literature demonstrates that the immune system definitely plays a role in the pathogenesis of glaucoma. Multiple changes in the peripheral innate as well as adaptive immune system have been detected and give room for further research concerning valuable therapeutic targets. We conclude that there still is a great need to bring together the results derived from basic research analysing different aspects of the immune system in glaucoma to understand the immune context of the disease. Furthermore local immune changes in the retina of glaucoma patients still leave room for further therapeutic targets

Differential Regulation of Adhesion and Phagocytosis of Resting and Activated Microglia by Dopamine

Microglia, the immune competent cells of the central nervous system (CNS), normally exist in a resting state characterized by a ramified morphology with many processes, and become activated to amoeboid morphology in response to brain injury, infection, and a variety of neuroinflammatory stimuli. Many studies focused on how neurotransmitters affect microglia activation in pathophysiological circumstances. In this study, we tried to gain mechanistic insights on how dopamine (DA) released from neurons modulates cellular functions of resting and activated microglia. DA induced the reduction of the number of cellular processes, the increase of cell adhesion/spreading, and the increase of vimentin filaments in resting primary and BV₂ microglia. In contrast to resting cells, DA downregulated the cell spreading and phagocytosis of microglia activated by LPS. DA also significantly downregulated ERK1/2 phosphorylation in activated microglia, but not in resting microglia. Downregulation of ERK1/2 by DA in activated microglia required receptor signaling. In contrast, we found a significant increase of p38MAPK activity by DA treatment in resting, but not in activated microglia. These latter effects required the uptake of DA through the high-affinity transporter but did not require receptor signaling. Activation of p38MAPK resulted in the increase of focal adhesion number via phosphorylation of paxillin at Ser⁸³. These results indicate that DA might have a differential, depending upon the activation stage of microglia, impact on cellular functions such as adhesion and phagocytosis.

Effects of chronic antipsychotic drug exposure on the expression of Translocator Protein and inflammatory markers in rat adipose tissue

The precise effect of antipsychotic drugs on either central or peripheral inflammation remains unclear. An important issue in this debate is to what extent the known peripheral metabolic effects of antipsychotics, including increased adiposity, may contribute to increased inflammation. Adipose tissue is known to contribute to the development of systemic inflammation, which can eventually lead to insulin resistance and metabolic dysregulation. As a first step to address this question, we evaluated whether chronic exposure to clinically comparable doses of haloperidol or olanzapine resulted in the immune activation of rat adipose tissue. Samples of visceral adipose tissue were sampled from male Sprague-Dawley rats exposed to, haloperidol, olanzapine or vehicle (all n = 8), for 8 weeks. From these we measured a cytokine profile, protein expression of F4/80 (a phenotypic macrophage marker) and translocator protein (TSPO), a target for radiotracers putatively indicating microgliosis in clinical neuroimaging studies. Chronic olanzapine exposure resulted in significantly higher adipose IL-6 levels compared with vehicle-controls (ANOVA p = 0.008, Bonferroni post-hoc test p = 0.006); in parallel, animals exposed to olanzapine had significantly higher F4/80 expression when compared with vehicle-controls (Mann Whitney Test, p = 0.014), whereas there was no difference between haloperidol and vehicle groups (Mann Whitney test, p = 0.1). There were no significant effects of either drug on adipose TSPO protein levels. Nevertheless, we found a positive correlation between F4/80 and TSPO adipose protein levels in the olanzapine-exposed rats (Spearman's rho = 0.76, p = 0.037). Our data suggest that chronic exposure to olanzapine, but not haloperidol, increases production of the pro-inflammatory cytokine IL-6 in adipose tissue and increased macrophages expression (F4/80), in the absence of measurable changes in TSPO with respect to vehicle. This may have potentially important consequences in terms of metabolic dysregulation associated with long-term antipsychotic treatment.

Dopamine alleviated acute liver injury induced by lipopolysaccharide/d-galactosamine in mice

Dopamine (DA), a crucial neurotransmitter, not only functions in the central nervous system but also plays important roles in the modulation of inflammation. Several studies suggest that DA might suppress the inflammatory response both in vitro and in vivo. In the present study, the potential effects of DA in a mouse model with lipopolysaccharide (LPS)/d-galactosamine (D-Gal)-induced acute liver injury were investigated. The results show that DA-treated LPS/D-Gal-exposed mice had reduced incidence of histologic lesions, lower plasma aminotransferases and improved the survival rates compared to LPS/D-Gal-exposed mice. Treatment with DA also suppressed LPS/D-Gal-induced production of TNF-α, phosphorylation of c-jun-N-terminal kinase (JNK), cleavage of caspase-3, up-regulation of hepatic caspase-3, caspase-8, and caspase-9 activities and reduced the count of TUNEL-positive hepatocytes. These data indicate that DA attenuated LPS/D-Gal-induced fulminant liver injury in mice, which implies that DA might have value for the prevention of inflammatory liver disease.

The dopamine transporter: An unrecognized nexus for dysfunctional peripheral immunity and signaling in Parkinson's Disease

The second-most common neurodegenerative disease, Parkinson's Disease (PD) has three hallmarks: dysfunctional dopamine transmission due, at least in part, to dopamine neuron degeneration; intracellular inclusions of α-synuclein aggregates; and neuroinflammation. The origin and interplay of these features remains a puzzle, as does the underlying mechanism of PD pathogenesis and progression. When viewed in the context of neuroimmunology, dopamine also plays a role in regulating peripheral immune cells. Intriguingly, plasma dopamine levels are altered in PD, suggesting collateral dysregulation of peripheral dopamine transmission. The dopamine transporter (DAT), the main regulator of dopaminergic tone in the CNS, is known to exist in lymphocytes and monocytes/macrophages, but little is known about peripheral DAT biology or how DAT regulates the dopaminergic tone, much less how peripheral DAT alters immune function. Our review is guided by the hypothesis that dysfunctional peripheral dopamine signaling might be linked to the dysfunctional immune responses in PD and thereby suggests a potential bidirectional communication between central and peripheral dopamine systems. This review seeks to foster new perspectives concerning PD pathogenesis and progression.

The role of catecholamines in HIV neuropathogenesis

The success of anti-retroviral therapy has improved the quality of life and lifespan of HIV + individuals, transforming HIV infection into a chronic condition. These improvements have come with a cost, as chronic HIV infection and long-term therapy have resulted in the emergence of a number of new pathologies. This includes a variety of the neuropathological and neurocognitive effects collectively known as HIVassociated neurocognitive disorders (HAND) or NeuroHIV. These effects persist even in the absence of viral replication, suggesting that they are mediated the long-term changes in the CNS induced by HIV infection rather than by active replication. Among these effects are significant changes in catecholaminergic neurotransmission, especially in dopaminergic brain regions. In HIV-infected individuals not treated with ARV show prominent neuropathology is common in dopamine-rich brain regions and altered autonomic nervous system activity. Even infected individuals on therapy, there is significant dopaminergic neuropathology, and elevated stress and norepinephrine levels correlate with a decreased effectiveness of antiretroviral drugs. As catecholamines function as immunomodulatory factors, the resultant dysregulation of catecholaminergic tone could substantially alter the development of HIVassociated neuroinflammation and neuropathology. In this review, we discuss the role of catecholamines in the etiology of HIV neuropathogenesis. Providing a comprehensive examination of what is known about these molecules in the context of HIV-associated disease demonstrates the importance of further studies in this area, and may open the door to new therapeutic strategies that specifically ameliorate the effects of catecholaminergic dysregulation on NeuroHIV.

cAMP levels in lymphocytes and CD4+ regulatory T-cell functions are affected by dopamine receptor gene polymorphisms

The neurotransmitter dopamine (DA) has prominent effects in the immune system and between the immune cells, CD4⁺ regulatory T (Treg) lymphocytes, a specialized T-cell subset crucial for the control of immune homeostasis, are especially sensitive to DA. Dopaminergic receptors (DR) are grouped into two families according to their pharmacological profile and main second messenger coupling: the D₁ -like (D₁ and D₅ ), which activate adenylate cyclase, and the D₂ -like (D₂ , D₃ and D₄ ), which inhibit adenylate cyclase and exist in several variants that have been associated to clinical conditions such as schizophrenia, bipolar disorder, substance abuse and addiction. We aimed to examine, in venous blood samples from healthy volunteers, the relationship between the arbitrary DR score and DR functional responses in human lymphocytes. All the samples were genotyped for selected DR gene variants (DRD1: rs4532 and rs686; DRD2: rs1800497 and rs6277; DRD3: rs6280; DRD4: rs747302 and seven 48-base pair variable number tandem repeat (VNTR)) and a DR score was attributed to each participant. We have also tested whether DR gene polymorphisms might affect Treg cell ability to suppress effector T-cell function. To our knowledge, this is the first study showing a correlation between DR gene variants and human T lymphocyte function. The main results are that both D₁ -like and D₂ -like DR are functionally active in human lymphocytes, although the D₁ -like DR stimulation results in stronger effects in comparison to the D₂ -like DR stimulation. In addition, it seems that the DR genetic profile may affect the ability of lymphocytes to respond to dopaminergic agents. More investigations are needed about the possible clinical relevance of such findings.

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.

Differential Response of Dopamine Mediated by β-Adrenergic Receptors in Human Keratinocytes and Macrophages: Potential Implication in Wound Healing

OBJECTIVE

Dopamine is an immunomodulatory neurotransmitter. In the skin, keratinocytes and macrophages produce proinflammatory cytokines and metalloproteinases (MMPs) which participate in wound healing. These cells have a catecholaminergic system that modulates skin pathophysiologic processes. We have demonstrated that dopamine modulates cytokine production in keratinocytes via dopaminergic and adrenergic receptors (ARs). The aim of this study was to evaluate the effect of dopamine and its interaction with β-ARs in human HaCaT keratinocytes and THP-1 macrophages. We evaluated the production of inflammatory mediators implicated in wound healing.

METHODS

Cells were stimulated with dopamine in the absence or presence of the β-adrenergic antagonist propranolol. Wound closure, MMP activity, and the production of IL-8, IL-1β, and IκB/NFκB pathway activation were determined in stimulated cells.

RESULTS

Dopamine did not affect the wound closure in human keratinocytes, but diminished the propranolol stimulatory effect, thus delaying cell migration. Similarly, dopamine significantly decreased MMP-9 activity and the propranolol-induced MMP activity. Dopamine significantly increased the p65-NFκB subunit levels in the nuclear extracts, which were reduced in the presence of propranolol in keratinocytes. On the other hand, dopamine significantly increased MMP-9 activity in THP-1 macrophages, but did not modify the propranolol-increased enzymatic activity. Dopamine significantly increased IL-8 production in human macrophages, an effect that was partially reduced by propranolol. Dopamine did not modify the p65-NFκB levels in the nuclear extracts in THP-1 macrophages.

CONCLUSION

We suggest that the effect of dopamine via β-ARs depends on the physiological condition and the cell type involved, thus contributing to either improve or interfere with the healing process.