GABA and GABA(A) receptor expression on immune cells in psoriasis: a pathophysiological role

Regulation of neutrophil migration in acute pulmonary inflammation by extraneuronal α1 gamma-aminobutyric acidA receptors

Acute pulmonary inflammation is a common disease on intensive care. Due to the lack of specific treatments, lethality is still very high. The ionotropic GABAA-receptors are known from the central nervous system (CNS) and have recently been detected in the lung. These receptors have been shown to influence inflammatory processes. Opposing data has been reported, where both, GABA site agonists and antagonists achieved anti-inflammatory effects. The distribution of the 19 known GABAA-receptor subunits (α1-6, β1-3, γ1-3, δ, ε, π, θ and ρ1-3) and their role in inflammation remain unclear. In murine models of LPS- and bacteria-induced inflammation, Muscimol (GABAA-receptor agonist) and Bicuculline (antagonist) were administered before the onset of inflammation. Transcription of GABAA-receptor subunits was evaluated by real-time polymerase chain reaction. Neutrophil counts and adhesion molecule expression in wild type and GABAα1 knock-in mice were determined by flow-cytometry. Myeloperoxidase, neutrophil extracellular traps and cytokines were determined. In a model of ventilator-induced lung injury, blood gas analysis was performed using arterial blood. A multiplex western blot was done to assess signaling proteins. Muscimol and Bicuculline inhibited neutrophil influx in the bronchoalveolar lavage but did not change neutrophil activation. Both altered surface expression of adhesion molecules on neutrophils and reduced release of interleukin-6 (IL-6). The increased α1 subunit expression on lung epithelium and endothelium after inflammation was abolished by Muscimol and Bicuculline. In GABAα1-knock-in mice the protective effects of both agents were no longer observed. Only Muscimol lowered protein extravasation, improved blood gas analysis and lung function. A multiplex assay ascribed these anti-inflammatory effects to the influence of the IL-6 and phosphoinositide 3-kinase signaling pathways. In conclusion, Muscimol and Bicuculline exert various protective effects in two murine models of acute pulmonary inflammation. The multiple effects of Muscimol were linked to the inhibition of the proinflammatory signaling pathways IL-6 and PI3K.

Tac1-expressing neurons in the central amygdala predominantly mediate histamine-induced itch by receiving inputs from parabrachial Tac1-expressing neurons

Itch is a distinct and bothersome sensation closely associated with a strong urge to scratch. Both the parabrachial nucleus (PBN) and the central amygdala (CeA) are responsive to itch stimuli and contain neurons that express tachykinin 1 (Tac1), which are known for their significant involvement in itch-induced scratching at both spinal and supraspinal levels. Significantly, the PBN neurons project their axons to form close connections with the CeA neurons. However, the role of the PBNTac1-CeATac1 pathway in modulating itch remains to be determined. We utilized immunohistochemistry, fiber photometry, chemogenetic, and behavioral techniques to investigate the role of the PBNTac1-CeATac1 pathway in itch. Our results indicate that neurons in the CeA can be more activated by acute itch than chronic itch. Notably, in response to acute itch stimuli, both CeATac1 and PBNTac1 neurons were specifically activated by histamine (His)-induced itch. Furthermore, the Tac1-positive terminals from the PBNTac1 neurons formed close connections with CeATac1 neurons. We also demonstrated that activating the PBNTac1-CeA pathway using a chemogenetic approach could increase scratching behaviors in His-induced itch, other than chloroquine (CQ)-induced itch. Conversely, inhibiting the PBNTac1-CeA pathway decreased scratching behaviors in mice with His-induced itch. Taken together, these results suggest that the PBNTac1-CeATac1 pathway may play a specific role in modulating His-induced acute itch.

Peripheral GABAA receptors - Physiological relevance and therapeutic implications

The role of γ- aminobutyric acid (GABA) and GABAA receptors is not only essential for neurotransmission in the central nervous system (CNS), but they are also involved in communication in various peripheral tissues such as the pancreas, liver, kidney, gastrointestinal tract, trachea, immune cells and blood vessels. GABAA receptors located outside the CNS ("peripheral GABAA receptors") enable both neuronal and non-neuronal GABA-ergic signaling in various physiological processes and are generally thought to have similar properties to the extrasynaptic receptors in the CNS. By activating these peripheral receptors, GABA and various GABAA receptor modulators, including drugs such as benzodiazepines and general anesthetics, may contribute to or otherwise affect the maintenance of general body homeostasis. However, the existing data in the literature on the role of non-neuronal GABA-ergic signaling in insulin secretion, glucose metabolism, renal function, intestinal motility, airway tone, immune response and blood pressure regulation are far from complete. In fact, they mainly focus on the identification of components for the local synthesis and utilization of GABA and on the expression repertoire of GABAA receptor subunits rather than on subunit composition, activation effects and (sub)cellular localization. A deeper understanding of how modulation of peripheral GABAA receptors can have significant therapeutic effects on a range of pathological conditions such as multiple sclerosis, diabetes, irritable bowel syndrome, asthma or hypertension could contribute to the development of more specific pharmacological strategies that would provide an alternative or complement to existing therapies. Selective GABAA receptor modulators with improved peripheral efficacy and reduced central side effects would therefore be highly desirable first-in-class drug candidates. This review updates recent advances unraveling the molecular components and cellular determinants of the GABA signaling machinery in peripheral organs, tissues and cells of both, humans and experimental animals.

Positive association between dehydroepiandrosterone (DHEA) and gene expression of the gamma-aminobutyric acid (GABA-A) receptor δ subunit

Gamma-aminobutyric acid A (GABA-A) receptors in the cells of the immune system enhance anti-inflammatory responses by regulating cytokine secretion, cytotoxic responses, and cell activation. In the CNS, the formation of GABA-A subunits into a pentameric structure has been extensively studied; however, no such study has been conducted in the immune system. The objective of the present study was to examine associations between the levels of steroid hormones and GABA-A receptor δ subunit expression in the immune system. We focused on this subunit because GABA-A receptors that contain it become significantly more sensitive to steroid hormones. We collected 80 blood samples from reproductive age women for the purpose of analyzing dehydroepiandrosterone (DHEA), 17β-estradiol, progesterone, and allopregnanolone using liquid chromatography-mass spectrometry (LC-MS). Furthermore, we extracted peripheral blood mononuclear cells (PBMCs) for determining mRNA expression levels of GABA-A receptor genes encoding the δ and ε subunits. We constructed linear mixed effect models for each GABA-A receptor subunit with all 4 steroid hormones, age, and age of menarche as predictors. Whereas DHEA was significantly associated with δ subunit expression (t-value = 2.981; p = 0.003), in line with our hypothesis, none of the steroid hormones were significantly associated with the expression of the ε subunit. Results of this study indicate that significant interactions between hormones from the steroid hormone biosynthesis pathway and GABAergic machinery from the immune cells may be utilized to expand models examining the molecular basis of inflammatory conditions.

Microbial perspective on the skin-gut axis and atopic dermatitis

Atopic dermatitis (AD) is a relapsing inflammatory skin condition that has become a global health issue with complex etiology and mounting prevalence. The association of AD with skin and gut microbiota has been revealed by virtue of the continuous development of sequencing technology and genomics analysis. Also, the gut-brain-skin axis and its mutual crosstalk mechanisms have been gradually verified. Accordingly, the microbiota-skin-gut axis also plays an important role in allergic skin inflammation. Herein, we reviewed the relationship between the microbiota-skin-gut axis and AD, explored the underlying signaling molecules and potential pathways, and focused on the potential mechanisms of probiotics, antimicrobial peptides (AMPs), coagulase-negative staphylococci transplantation, fecal microbiota transplantation, AMPs, and addition of essential fatty acids in alleviating AD, with the aim to provide a new perspective for targeting microbiota in the treatment of allergic skin inflammation.

The Mind Body Connection in Dermatologic Conditions: A Literature Review

Psychodermatology pertains to the relationship between the skin and brain. This review aims to summarize the evidence of the mind body connection in four psychophysiological conditions: rosacea, atopic dermatitis (AD), acne vulgaris (AV), and psoriasis. A literature search was conducted using several English language databases. All four conditions share similar psychiatric co-morbidities, including but not limited to anxiety, depression, and suicidality. In rosacea, the upregulation of transient receptor potential vanilloid type 1, Toll like receptor 2, and Th17 cells releases downstream products that are simultaneously implicated in mood disorders. Stress exacerbates AV through the hypothalamic-pituitary-adrenal (HPA) system, which alters functioning of sebocytes and Cutibacterium acnes. In AD and psoriasis, the HPA axis influences Th1, Th2, Th22, and Th1, Th17 immune mediated responses, respectively. This leads to the secretion of pro-inflammatory cytokines which are also involved in the pathogenesis of anxiety and depression. Neurotransmitters implicated in mental illness, such as gamma-aminobutyric acid and serotonin, may also play a role in the development of AD and psoriasis. The management of cutaneous disease may mitigate psychological distress, and future research may show the corollary to also be true.

Microbial-Derived γ-Aminobutyric Acid: Synthesis, Purification, Physiological Function, and Applications

γ-Aminobutyric acid (GABA) is an important nonprotein amino acid that extensively exists in nature. At present, GABA is mainly obtained through chemical synthesis, plant enrichment, and microbial production, among which microbial production has received widespread attention due to its safety and environmental benefits. After using microbial fermentation to obtain GABA, it is necessary to be isolated and purified to ensure its quality and suitability for various industries such as food, agriculture, livestock, pharmaceutics, and others. This article provides a comprehensive review of the different sources of GABA, including its presence in nature and the synthesis methods. The factors affecting the production of microbial-derived GABA and its isolation and purification methods are further elucidated. Moreover, the main physiological functions of GABA and its application in different fields are also reviewed. By advancing our understanding of GABA, we can unlock its full potential and further utilize it in various fields to improve human health and well-being.

From gut to skin: exploring the potential of natural products targeting microorganisms for atopic dermatitis treatment

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease. Recent studies have revealed that interactions between pathogenic microorganisms, which have a tendency to parasitize the skin of AD patients, play a significant role in the progression of the disease. Furthermore, specific species of commensal bacteria in the human intestinal tract can have a profound impact on the immune system by promoting inflammation and pruritogenesis in AD, while also regulating adaptive immunity. Natural products (NPs) have emerged as promising agents for the treatment of various diseases. Consequently, there is growing interest in utilizing natural products as a novel therapeutic approach for managing AD, with a focus on modulating both skin and gut microbiota. In this review, we discuss the mechanisms and interplay between the skin and gut microbiota in relation to AD. Additionally, we provide a comprehensive overview of recent clinical and fundamental research on NPs targeting the skin and gut microbiota for AD treatment. We anticipate that our work will contribute to the future development of NPs and facilitate research on microbial mechanisms, based on the efficacy of NPs in treating AD.

N-type calcium channel blockers: a new approach towards the treatment of chronic neuropathic pain

Neuropathic pain (NP) remains maltreated for a wide number of patients by the currently available treatments and little research has been done in finding new drugs for treating NP. Ziconotide (PrialtTM) had been developed as the new drug, which belongs to the class of ω-conotoxin MVIIA. It inhibits N-type calcium channels. Ziconotide is under the last phase of the clinical trial, a new non-narcotic drug for the management of NP. Synthetically it has shown the similarities with ω-conotoxin MVIIA, a constituent of poison found in fish hunting snails (Conus magus). Ziconotide acts by selectively blocking neural N-type voltage-sensitized Ca2+ channels (NVSCCs). Certain herbal drugs also have been studied but no clinical result is there and the study is only limited to preclinical data. This review emphasizes the N-type calcium channel inhibitors, and their mechanisms for blocking calcium channels with their remedial prospects for treating chronic NP.

Effects of Cyclosporine A and Adalimumab on the expression profiles histaminergic system-associated genes and microRNAs regulating these genes in HaCaT cells

Previous studies have not completely elucidated the role of the histaminergic system in the pathogenesis of psoriasis. This study aimed to evaluate the effects of adalimumab and cyclosporine A on the expression of histaminergic system-related genes and miRNAs regulating these genes in bacterial lipopolysaccharide A (LPS)-stimulated human keratinocyte (HaCaT) cells. HaCaT cells were treated with 1 µg/mL LPS for 8 h, followed by treatment with 8 µg/mL adalimumab or 100 ng/mL cyclosporine A for 2, 8, or 24 h. Untreated cells served as controls. The cells were subjected to ribonucleic acid (RNA) extraction and microarray, quantitative real-time polymerase chain reaction, and enzyme-linked immunosorbent assay analyses. Statistical analysis was performed using the Statistica 13.0 PL (StatSoft, Cracow, Poland) and the Transcriptome Analysis Console programs (Affymetrix, Santa Clara, CA, USA) (p < 0.05). The differential expression of the following two miRNAs was not affected in LPS-stimulated cells upon treatment with cyclosporine A or adalimumab: hsa-miR-583 (downregulated expression), involved in the regulation of histamine receptor 1 - HRH1 (overexpression); has-miR-1275 (downregulated expression), involved in the regulation of histamine receptor 1 - HRH3 (overexpression) and Solute carrier family 22 member 3 - SLC23A2 (downregulated expression)). Adalimumab and cyclosporine A modulated the histaminergic system in HaCaT cells in vitro. However, further studies are needed to elucidate the underlying mechanisms.Abbreviations: (-) - downregulated in comparison to the control, (+) - overexpression in comparison to the control, ACTB - β-actine, ADA - Adenosine deaminase, ADCYAP1 - Adenylate Cyclase Activating Polypeptide 1, BMP - bone morphogenetic protein, bp - base pair, cAMP - adenosine 3' 5'-cyclic monophosphate, CBX7 - Chromobox protein homolog 7, cDNA - double-stranded complementary DNA, CSA - cyclosporine A DAG - diacylglycerol, DIAPH - Diaphanous related formin 1, DNMT - DNA methyltransferases, DRD2 - Dopamine receptor D2, EDN1 - Endothelin 1, EDNRA - Endothelin receptor type A, ELISA - Enzyme-linked immunosorbent assay, EZH2 - Enhancer of zeste homolog 2, FC - fold change, GABRB1 - Gamma-aminobutyric acid (GABA) A receptor, alpha 1, GABRB2 - Gamma-aminobutyric acid (GABA) A receptor, alpha 2, GABRB3 - Gamma-aminobutyric acid (GABA) A receptor, alpha 3, HaCaT - Human adult, low-calcium, high-temperature keratinocytes, HIS - Human Histamine, HLAs - human leukocyte antigens, HNMT - Histamine N-methyltransferase, HNMT - Histamine N-Methyltransferase, HRH1 - histamine receptor 1, HRH2 - histamine receptor 2, HRH3 - histamine receptor 3, HRH4 - histamine receptor 4, HTR6 - 5-Hydroxytryptamine Receptor 6, IGF1 - Insulin-like growth factor 1, IL10 -interleukin 10, IL12 -interleukin 12, IL6 - interleukin 6, IP3 - inositol 1,4,5-triphosphate, LPS - bacterial lipopolysaccharide A, LYN - LYN Proto-Oncogene, Src Family Tyrosine Kinase, MAPKs -mitogen-activated protein kinases, miRNA - micro RNA, MMP2 - matrix metalloproteinase-2, NHDF - Normal Human Dermal Fibroblasts, NHEK - Normal Human Epidermal Keratinocytes, OCT3 - organic cation transporter 3, PANTHER - Protein ANalysis THrough Evolutionary Relationships Classification, PBS - phosphate-buffered saline, PI3K-AKT - phosphatidylinositol 3-kinase-protein kinase B, PIP2 - phosphatidylinositol 4,5 bisphosphate, PMSF - phenylmethylsulfonyl fluoride, PSORS1- psoriasis susceptibility gene 1, qRT-PCR - quantitative Reverse Transcription Polymerase Chain Reaction, RNA - ribonucleic acid, RNAi - RNA interference, RTqPCR - Real-Time Quantitative Reverse Transcription Reaction, SLC223A2 - Solute carrier family 22 member 3, SNX -Sorting nexin, SOX9 - SRY-Box Transcription Factor 9, TGF-α - transforming growth factor α, TGF-β - transforming growth factor beta, TNF-α - tumor necrosis factor alpha, TP53 - tumor protein 5 z, VAMP2 - Vesicle associated membrane protein 2.

Tenets in Microbial Endocrinology: A New Vista in Teleost Reproduction

Climate vulnerability and induced changes in physico-chemical properties of aquatic environment can bring impairment in metabolism, physiology and reproduction in teleost. Variation in environmental stimuli mainly acts on reproduction by interfering with steroidogenesis, gametogenesis and embryogenesis. The control on reproductive function in captivity is essential for the sustainability of aquaculture production. There are more than 3,000 teleost species across the globe having commercial importance; however, adequate quality and quantity of seed production have been the biggest bottleneck. Probiotics are widely used in aquaculture as a growth promoter, stress tolerance, pathogen inhibition, nutrient digestibility and metabolism, reproductive performance and gamete quality. As the gut microbiota exerts various effects on the intestinal milieu which influences distant organs and pathways, therefore it is considered to be a full-fledged endocrine organ. Researches on Gut-Brain-Gonad axis (GBG axis) and its importance on physiology and reproduction have already been highlighted for higher mammals; however, the study on fish physiology and reproduction is limited. While looking into the paucity of information, we have attempted to review the present status of microbiome and its interaction between the brain and gut. This review will address a process of the microbiome physiological mechanism involved in fish reproduction. The gut microbiota influences the BPG axis through a wide variety of compounds, including neuropeptides, neurotransmitter homologs and transmitters. Currently, research is being conducted to determine the precise process by which gut microbial composition influences brain function in fish. The gut-brain bidirectional interaction can influence brain biochemistry such as GABA, serotonin and tryptophan metabolites which play significant roles in CNS regulation. This review summarizes the fact, how microbes from gut, skin and other parts of the body influence fish reproduction through the Gut-Brain-Gonad axis.

Dietary gamma-aminobutyric acid (GABA) improves non-specific immunity and alleviates lipopolysaccharide (LPS)-induced immune overresponse in juvenile Chinese mitten crab (Eriocheir sinensis)

Inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is an immunomodulator to inhibit immune-mediated pro-inflammatory response and has been used to treat various immune-related diseases in mammals. However, the immunoregulatory effect of GABA in crustaceans has not been reported. This study evaluates the regulatory effect of dietary GABA supplementation on the innate immune status and immunoregulatory potential in lipopolysaccharide (LPS)-induced immune response in juvenile Eriocheir sinensis. Juvenile crabs were fed with six diets supplemented with graded GABA levels (0, 40, 80, 160, 320 and 640 mg/kg dry matter) for 8 weeks and then 24 h LPS challenge test was carried out. The results showed that dietary GABA supplementation significantly decreased mortality at 4 and 8 weeks. Moreover, the hemocyanin content, acid phosphatase, and alkaline phosphatase activities significantly increased in the crabs fed GABA supplementation compared with the control. On the contrary, the alanine aminotransferase and alanine aminotransferase activities in serum decreased significantly in the GABA supplementation groups compared with the control. Similarly, superoxide dismutase activity, glutathione content, and the transcriptional expression of the antioxidant-related genes and immune-related genes were significantly higher in the GABA supplementation groups than in the control. In addition, the mRNA expressions of anti-lipopolysaccharide factors (ALF 1, ALF 2, ALF 3) and inflammatory signaling pathways related genes (TLR, Myd88, Relish, LITAF, P38-MAPK, ADAM17) were significantly up-regulated in LPS stimulation groups compared with PBS treatment. Meanwhile, pro-apoptosis-related genes' mRNA expressions were significantly up-regulated, and anti-apoptosis-related genes were significantly down-regulated under LPS stimulation compared with PBS treatment. However, GABA pretreatment effectively alleviated LPS-induced immune overresponse and apoptosis. Therefore, this study demonstrates that dietary GABA supplementation could be used as an immunomodulator to improve the non-specific immunity and antioxidant capacity and alleviate the immune-mediated immune overresponse of juvenile E. sinensis.

DNA Methylation Patterns in CD8+ T Cells Discern Psoriasis From Psoriatic Arthritis and Correlate With Cutaneous Disease Activity

Background: Psoriasis is a T cell-mediated chronic autoimmune/inflammatory disease. While some patients experience disease limited to the skin (skin psoriasis), others develop joint involvement (psoriatic arthritis; PsA). In the absence of disease- and/or outcome-specific biomarkers, and as arthritis can precede skin manifestations, diagnostic and therapeutic delays are common and contribute to disease burden and damage accrual.

Objective: Altered epigenetic marks, including DNA methylation, contribute to effector T cell phenotypes and altered cytokine expression in autoimmune/inflammatory diseases. This project aimed at the identification of disease-/outcome-specific DNA methylation signatures in CD8⁺ T cells from patients with psoriasis and PsA as compared to healthy controls.

Method: Peripheral blood CD8⁺ T cells from nine healthy controls, 10 psoriasis, and seven PsA patients were collected to analyze DNA methylation marks using Illumina Human Methylation EPIC BeadChips (>850,000 CpGs per sample). Bioinformatic analysis was performed using R (minfi, limma, ChAMP, and DMRcate packages).

Results: DNA methylation profiles in CD8⁺ T cells differentiate healthy controls from psoriasis patients [397 Differentially Methylated Positions (DMPs); 9 Differentially Methylated Regions (DMRs) when ≥CpGs per DMR were considered; 2 DMRs for ≥10 CpGs]. Furthermore, patients with skin psoriasis can be discriminated from PsA patients [1,861 DMPs, 20 DMRs (≥5 CpGs per region), 4 DMRs (≥10 CpGs per region)]. Gene ontology (GO) analyses considering genes with ≥1 DMP in their promoter delivered methylation defects in skin psoriasis and PsA primarily affecting the BMP signaling pathway and endopeptidase regulator activity, respectively. GO analysis of genes associated with DMRs between skin psoriasis and PsA demonstrated an enrichment of GABAergic neuron and cortex neuron development pathways. Treatment with cytokine blockers associated with DNA methylation changes [2,372 DMPs; 1,907 DMPs within promoters, 7 DMRs (≥5 CpG per regions)] affecting transforming growth factor beta receptor and transmembrane receptor protein serine/threonine kinase signaling pathways. Lastly, a methylation score including TNF and IL-17 pathway associated DMPs inverse correlates with skin disease activity scores (PASI).

Conclusion: Patients with skin psoriasis exhibit DNA methylation patterns in CD8⁺ T cells that allow differentiation from PsA patients and healthy individuals, and reflect clinical activity of skin disease. Thus, DNA methylation profiling promises potential as diagnostic and prognostic tool to be used for molecular patient stratification toward individualized treatment.

GABAergic signaling by cells of the immune system: more the rule than the exception

Gamma-aminobutyric acid (GABA) is best known as an essential neurotransmitter in the evolved central nervous system (CNS) of vertebrates. However, GABA antedates the development of the CNS as a bioactive molecule in metabolism and stress-coupled responses of prokaryotes, invertebrates and plants. Here, we focus on the emerging findings of GABA signaling in the mammalian immune system. Recent reports show that mononuclear phagocytes and lymphocytes, for instance dendritic cells, microglia, T cells and NK cells, express a GABAergic signaling machinery. Mounting evidence shows that GABA receptor signaling impacts central immune functions, such as cell migration, cytokine secretion, immune cell activation and cytotoxic responses. Furthermore, the GABAergic signaling machinery of leukocytes is implicated in responses to microbial infection and is co-opted by protozoan parasites for colonization of the host. Peripheral GABA signaling is also implicated in inflammatory conditions and diseases, such as type 1 diabetes, rheumatoid arthritis and cancer cell metastasis. Adding to its role in neurotransmission, growing evidence shows that the non-proteinogenic amino acid GABA acts as an intercellular signaling molecule in the immune system and, as an interspecies signaling molecule in host–microbe interactions. Altogether, the data raise the assumption of conserved GABA signaling in a broad range of mammalian cells and diversification of function in the immune system.

Peripheral Mechanisms of Neuropathic Pain-the Role of Neuronal and Non-Neuronal Interactions and Their Implications for Topical Treatment of Neuropathic Pain

Neuropathic pain in humans arises as a consequence of injury or disease of somatosensory nervous system at peripheral or central level. Peripheral neuropathic pain is more common than central neuropathic pain, and is supposed to result from peripheral mechanisms, following nerve injury. The animal models of neuropathic pain show extensive functional and structural changes occurring in neuronal and non-neuronal cells in response to peripheral nerve injury. These pathological changes following damage lead to peripheral sensitization development, and subsequently to central sensitization initiation with spinal and supraspinal mechanism involved. The aim of this narrative review paper is to discuss the mechanisms engaged in peripheral neuropathic pain generation and maintenance, with special focus on the role of glial, immune, and epithelial cells in peripheral nociception. Based on the preclinical and clinical studies, interactions between neuronal and non-neuronal cells have been described, pointing out at the molecular/cellular underlying mechanisms of neuropathic pain, which might be potentially targeted by topical treatments in clinical practice. The modulation of the complex neuro-immuno-cutaneous interactions in the periphery represents a strategy for the development of new topical analgesics and their utilization in clinical settings.

Amino acids: key sources for immunometabolites and immunotransmitters

Immune-cell activation and functional plasticity are closely linked to metabolic reprogramming that is required to supply the energy and substrates for such dynamic transformations. During such processes, immune cells metabolize many kinds of molecules including nucleic acids, sugars and lipids, which is called immunometabolism. This review will mainly focus on amino acids and their derivatives among such metabolites and describe the functions of these molecules in the immune system. Although amino acids are essential for, and well known as, substrates for protein synthesis, they are also metabolized as energy sources and as substrates for functional catabolites. For example, glutamine is metabolized to produce energy through glutaminolysis and tryptophan is consumed to supply nicotinamide adenine dinucleotide, whereas arginine is metabolized to produce nitric acid and polyamine by nitric oxide synthase and arginase, respectively. In addition, serine is catabolized to produce nucleotides and to induce methylation reactions. Furthermore, in addition to their intracellular functions, amino acids and their derivatives are secreted and have extracellular functions as immunotransmitters. Many amino acids and their derivatives have been classified as neurotransmitters and their functions are clear as transmitters between nerve cells, or between nerve cells and immune cells, functioning as immunotransmitters. Thus, this review will describe the intracellular and external functions of amino acid from the perspective of immunometabolism and immunotransmission.

Gut-Brain-Skin Axis in Psoriasis: A Review

Introduction

Psoriasis is a common skin disease, with chronic inflammation and a complex etiology. It has long been recognized that chronic skin conditions and mental health disorders are often co-morbid. Thus, the concept of the gut–brain–skin axis emphasized in mental health disorders may also regulate the health of skin.

Results

The gut microbiota has been found to be the bridge between the immune system and nervous system. By leveraging clinical cases and animal models of psoriasis, an important communication pathway has been identified along the gut–brain–skin axis that is associated with the modulation of neurotransmitters from the microbiota. Furthermore, mammalian neurotransmitters, including dopamine, serotonin, or γ-aminobutyric acid (GABA), can be produced and/or consumed by several types of bacteria. Other studies suggest that manipulating these neurotransmitters by bacteria may have an effect on host physiology, and the levels of neurotransmitter can be altered by microbiota-based interventions.

Conclusions

Nonetheless, it is unknown whether or not the manipulation of neurotransmitter levels by bacteria can affect the occurrence and development of psoriasis. Notably, preliminary experiments found that oral consumption of probiotics improves the clinical symptoms in patients with psoriasis, perhaps correlated with the gut microbiome-mediated crosstalk between the immune system and the nervous system by secreting neurotransmitters in psoriasis. In this review, the communication along the gut–brain–skin axis is discussed.

Sub-basal increases of GABA enhance the synthesis of TNF-α, TGF-β, and IL-1β in the immune system organs of the Nile tilapia

The cells of the immune and neuronal systems share different receptors for cytokines or neurotransmitters, producing feedback responses between both systems. Cytokines such as IL-1β and TNF-α can induce inflammation; however, the secretion of these molecules can be modulated by anti-inflammatory cytokines, as is the case for TGF-β, as well as by different hormones or neurotransmitters such as the γ-aminobutyric acid (GABA). In this study, we evaluated the secretion of IL-1β, TNF-α, and TGF-β under basal conditions, in the head of the kidney, spleen, thymus, and serum of the Nile tilapia, as well as their release induced by different sub-basal increases of GABA. We found that at the higher dose of GABA these cytokines were synthesised at a higher concentration compared to the control group. These results may suggest that there is feedback between both systems and that GABA plays a role in the modulation of the immune response.

Molecular and Cellular Mechanisms of Itch in Psoriasis

Itch (or pruritus) was not previously recognized as a serious symptom of psoriasis. However, approximately 60-90% of psoriatic patients with pruritus have stated that it deteriorates their quality of life. Since conventional antipruritic therapies, such as antihistamines, only exert limited effects, the establishment of a treatment option for itch in psoriasis is urgently needed. Although a definitive drug is not currently available, various itch mediators are known to be involved in pruritus in psoriasis. In this review, we describe the clinical features of pruritus in psoriasis, classify a wide range of itch mediators into categories, such as the nervous, immune, endocrine, and vascular systems, and discuss the mechanisms by which these mediators induce or aggravate itch in the pathophysiology of psoriasis.

Exploring Beneficial Properties of the Bacteriocinogenic Enterococcus faecium ST10Bz Strain Isolated from Boza, a Bulgarian Cereal-Based Beverage

The bacteriocin-producing strain Enterococcus faecium ST10Bz, isolated from boza, a Bulgarian cereal-based beverage, exhibited strong activity against Listeria strains, vancomycin-resistant and other Enterococcus strains, but not against most of the other lactic acid bacteria (LAB) strains included in the test panel. Bacteriocin ST10Bz was proven as a stable antimicrobial, even after exposure to various environmental conditions, including varying pH values, temperatures, and commonly used chemicals in industry and laboratory practice. Bacteriocin activity against L. monocytogenes ATCC^®15313™ was recorded at 25,600 AU/mL when the producer strain was cultured in MRS broth at 25 °C and 30 °C, and 19,200 AU/mL, when cultured at 37 °C. Additionally, bacteriocin ST10Bz exhibited bactericidal mode of action when added to actively growing cultures of L. monocytogenes ATCC^®15313™ and Enterococcus faecalis 200A. E. faecium ST10Bz was susceptible to the antibiotics kanamycin, gentamycin, ampicillin, streptomycin, tylosin, chloramphenicol, clindamycin, tetracycline, and vancomycin; with no evidence for vanA, B, C, D, E, or G genes. PCR analysis of DNA from strain ST10Bz generated positive results for presence of some bacterial adhesion genes, including map, mub and ef-tu, as well as the gamma aminobutyric acid (GABA) production-related gene, gad. Under simulated gastrointestinal conditions in single and co-culture with L. monocytogenes ATCC^®15313™ and E. faecalis 200A, E. faecium ST10Bz showed a high survival rate and the ability to reduce the viable numbers of the two test strains.

Dialog between skin and its microbiota: Emergence of "Cutaneous Bacterial Endocrinology"

Microbial endocrinology is studying the response of microorganisms to hormones and neurohormones and the microbiota production of hormones-like molecules. Until now, it was mainly applied to the gut and revealed that the intestinal microbiota should be considered as a real organ in constant and bilateral interactions with the whole human body. The skin harbours the second most abundant microbiome and contains an abundance of nerve terminals and capillaries, which in addition to keratinocytes, fibroblasts, melanocytes, dendritic cells and endothelial cells, release a huge diversity of hormones and neurohormones. In the present review, we will examine recent experimental data showing that, in skin, molecules such as substance P, calcitonin gene-related peptide, natriuretic peptides and catecholamines can directly affect the physiology and virulence of common skin-associated bacteria. Conversely, bacteria are able to synthesize and release compounds including histamine, glutamate and γ-aminobutyric acid or peptides showing partial homology with neurohormones such as α-melanocyte-stimulating hormone (αMSH). The more surprising is that some viruses can also encode neurohormones mimicking proteins. Taken together, these elements demonstrate that there is also a cutaneous microbial endocrinology and this emerging concept will certainly have important consequences in dermatology.

Characteristics of Pruritus according to Morphological Phenotype of Psoriasis and Association with Neuropeptides and Interleukin-31

Background

Pruritus is a common symptom in psoriasis. However, few studies have assessed the characteristics of pruritus according to morphological phenotypes of psoriasis.

Objective

To investigate the characteristics of pruritus according to morphological phenotypes of psoriasis and to assess the association with inflammatory mediators related to pruritus.

Methods

Psoriasis patients were divided into 2 groups according to clinical phenotype: eruptive inflammatory (EI) and chronic stable (CS). Clinical data of pruritus were assessed by an itch questionnaire. Serum neuropeptides and cytokines including substance P, histamine, vasoactive intestinal peptide, neuropeptide Y, calcitonin gene-related peptide and interleukin-31 (IL-31) were quantitatively measured.

Results

In total, 50 patients with psoriasis (30 male, 20 female; mean age, 45.7 years) were studied (EI, n=15 and CS, n=35). Pruritus was reported by 80% of EI and CS patients. There were no significant differences in prevalence of pruritus, pruritus intensity, severity of psoriasis, serum neuropeptides, or IL-31 between the 2 groups.

Conclusion

The morphological phenotype does not seem to be an important factor affecting the prevalence and characteristics of pruritus in psoriasis.

Psoriasis and alcohol

Psoriasis is a chronic inflammatory skin disease that may be triggered or worsened by several factors, including alcohol. A higher than average alcohol consumption is common among individuals with psoriasis. Neurobiological signaling affected by alcohol intake includes a range of neurotransmitters, such as the dopaminergic, serotonergic, and tachykinergic systems, involved in reward and drug-seeking. These neurotransmitters may also have an impact on the inflammatory processes per se in psoriasis. Future therapy may, therefore, be targeted at neurotransmitter networks involved with both alcohol intake and the inflammatory processes.

Evaluation of Brain Nuclear Medicine Imaging Tracers in a Murine Model of Sepsis-Associated Encephalopathy

Purpose

The purpose of this study was to evaluate a set of widely used nuclear medicine imaging agents as possible methods to study the early effects of systemic inflammation on the living brain in a mouse model of sepsis-associated encephalopathy (SAE). The lipopolysaccharide (LPS)-induced murine systemic inflammation model was selected as a model of SAE.

Procedures

C57BL/6 mice were used. A multimodal imaging protocol was carried out on each animal 4 h following the intravenous administration of LPS using the following tracers: [^99mTc][2,2-dimethyl-3-[(3E)-3-oxidoiminobutan-2-yl]azanidylpropyl]-[(3E)-3-hydroxyiminobutan-2-yl]azanide ([^99mTc]HMPAO) and ethyl-7-[¹²⁵I]iodo-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxylate ([¹²⁵I]iomazenil) to measure brain perfusion and neuronal damage, respectively; 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG) to measure cerebral glucose uptake. We assessed microglia activity on another group of mice using 2-[6-chloro-2-(4-[¹²⁵I]iodophenyl)-imidazo[1,2-a]pyridin-3-yl]-N-ethyl-N-methyl-acetamide ([¹²⁵I]CLINME). Radiotracer uptakes were measured in different brain regions and correlated. Microglia activity was also assessed using immunohistochemistry. Brain glutathione levels were measured to investigate oxidative stress.

Results

Significantly reduced perfusion values and significantly enhanced [¹⁸F]FDG and [¹²⁵I]CLINME uptake was measured in the LPS-treated group. Following perfusion compensation, enhanced [¹²⁵I]iomazenil uptake was measured in the LPS-treated group’s hippocampus and cerebellum. In this group, both [¹⁸F]FDG and [¹²⁵I]iomazenil uptake showed highly negative correlation to perfusion measured with ([^99mTc]HMPAO uptake in all brain regions. No significant differences were detected in brain glutathione levels between the groups. The CD45 and P2Y12 double-labeling immunohistochemistry showed widespread microglia activation in the LPS-treated group.

Conclusions

Our results suggest that [¹²⁵I]CLINME and [^99mTc]HMPAO SPECT can be used to detect microglia activation and brain hypoperfusion, respectively, in the early phase (4 h post injection) of systemic inflammation. We suspect that the enhancement of [¹⁸F]FDG and [¹²⁵I]iomazenil uptake in the LPS-treated group does not necessarily reflect neural hypermetabolism and the lack of neuronal damage. They are most likely caused by processes emerging during neuroinflammation, e.g., microglia activation and/or immune cell infiltration.

Electronic supplementary material

The online version of this article (10.1007/s11307-018-1201-3) contains supplementary material, which is available to authorized users.

Itch: an under-recognized problem in psoriasis

Psoriasis has historically been considered a nonpruritic dermatosis, in contrast with atopic dermatitis. Thus, itch has often been underappreciated and overlooked in psoriasis. However, increasing evidence over the past decade has shown that itch can be one of the most prevalent and burdensome symptoms associated with psoriasis, affecting almost every patient to some degree. Itch can involve the entire body, although it predominantly affects the legs, hands, back, body and especially the scalp. Uncontrolled itch can significantly impact all aspects of the well-being and quality of life of the patient. While there has been some progress in trying to better understand the pathophysiology of itch in psoriasis, more research effort and interest are needed. This under-recognition of itch in psoriasis is clearly reflected in the dearth of treatment options targeting itch despite significant advancement in treating the lesions themselves. Recently, however, clinical studies have begun to include itch as a study outcome. The resulting data have demonstrated concomitant antipruritic benefits and improved Psoriasis Area and Severity Index (PASI) scores with mainstay treatments for psoriasis, such as topical corticosteroids and vitamin D analogs, phototherapies, and various systemics and biologics. This article takes a closer look at this debilitating symptom, reviewing the available epidemiology data for psoriatic itch, presenting the current understanding of psoriatic itch pathophysiology and highlighting important clinical data for various treatment options for itch. Practical considerations for increasing the recognition of itch as well as improving its management in psoriasis are also provided.

GABA-Producing Natural Dairy Isolate From Artisanal Zlatar Cheese Attenuates Gut Inflammation and Strengthens Gut Epithelial Barrier in vitro

Probiotic bacteria are recognized for their health-promoting properties, including maintenance of gut epithelial integrity and host immune system homeostasis. Taking into account the beneficial health-promoting effects of GABA, the presence of the gadB gene, encoding glutamate decarboxylase that converts L-glutamate to GABA, was analyzed in Lactic Acid Bacteria (LAB) natural isolates from Zlatar cheese. The results revealed that 52% of tested Lactobacillus spp. and 8% of Lactococcus spp. isolates harbor the gadB gene. Qualitative and quantitative analysis of GABA production performed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) revealed the highest GABA production by Lactobacillus brevis BGZLS10-17. Since high GABA-producing LAB natural isolates are the most valuable source of naturally produced GABA, the probiotic properties of BGZLS10-17 were characterized. This study demonstrated high adhesion of BGZLS10-17 strain to Caco-2 cells and the ability to decrease the adhesion of Escherichia coli ATCC25922 and Salmonella enterica C29039. Treatment of differentiated Caco-2 cells monolayer with BGZLS10-17 supernatant containing GABA alleviated inflammation (production of IL-8) caused by IL-1β and significantly stimulated the expression of tight junction proteins (zonulin, occludin, and claudin 4), as well as the expression of TGF-β cytokine leading to the conclusion that immunosuppression and strengthening the tight junctions can have significant role in the maintenance of intestinal epithelial barrier integrity. Taken together the results obtained in this study support the idea that using of GABA producing BGZLS10-17 probiotic strain could be a good strategy to modulate immunological response in various inflammatory diseases, and at the same time, it could be a good candidate for adjunct starter culture for production of GABA-enriched dairy foods and beverages offering new perspectives in designing the novel functional foods.

A New Perspective of Acupuncture: The Interaction among Three Networks Leads to Neutralization

Acupuncture has been used to treat multiple medical conditions, but whether the diverse effects of acupuncture are intrinsically linked and how they might be connected have yet to be determined. More and more researches have shown that acupuncture is a kind of nociceptive stimulus, which can cause inflammatory reaction in the sites of acupuncture and then further activate the nerve-endocrine-immune systems to cause the cascade amplification of the acupuncture effect. This review seeks to provide a comprehensive summary of the existing literature concerning the role of "acupoint-meridian-disease network" in various effects of acupuncture and suggest a novel notion that acupuncture may restore homeostasis under different pathological conditions by regulating this network, resulting in the activation of different reaction cascades in response to pathological injury. We think that acupuncture acts on acupoints, first activating the small network of acupoints (Acupoint Network). The information of acupuncture is amplified by cascade, and the nerve endocrine immune system (NEI) is activated through the large network of meridians (Meridian Network) of the body itself. The nerve-endocrine-immune system (NEI) further outputs the effect information to the target organ through multilevel and multisystems and finally acts on the disease network (Disease Network) to produce acupuncture effect.

Mast cell-neural interactions contribute to pain and itch

Mast cells are best recognized for their role in allergy and anaphylaxis, but increasing evidence supports their role in neurogenic inflammation leading to pain and itch. Mast cells act as a "power house" by releasing algogenic and pruritogenic mediators, which initiate a reciprocal communication with specific nociceptors on sensory nerve fibers. Consequently, nerve fibers release inflammatory and vasoactive neuropeptides, which in turn activate mast cells in a feedback mechanism, thus promoting a vicious cycle of mast cell and nociceptor activation leading to neurogenic inflammation and pain/pruritus. Mechanisms underlying mast cell differentiation, activation, and intercellular interactions with inflammatory, vascular, and neural systems are deeply influenced by their microenvironment, imparting enormous heterogeneity and complexity in understanding their contribution to pain and pruritus. Neurogenic inflammation is central to both pain and pruritus, but specific mediators released by mast cells to promote this process may vary depending upon their location, stimuli, underlying pathology, gender, and species. Therefore, in this review, we present the contribution of mast cells in pathological conditions, including distressing pruritus exacerbated by psychologic stress and experienced by the majority of patients with psoriasis and atopic dermatitis and in different pain syndromes due to mastocytosis, sickle cell disease, and cancer.

GABAergic signaling linked to autophagy enhances host protection against intracellular bacterial infections

Gamma-aminobutyric acid (GABA) is the principal inhibitory neurotransmitter in the brain; however, the roles of GABA in antimicrobial host defenses are largely unknown. Here we demonstrate that GABAergic activation enhances antimicrobial responses against intracellular bacterial infection. Intracellular bacterial infection decreases GABA levels in vitro in macrophages and in vivo in sera. Treatment of macrophages with GABA or GABAergic drugs promotes autophagy activation, enhances phagosomal maturation and antimicrobial responses against mycobacterial infection. In macrophages, the GABAergic defense is mediated via macrophage type A GABA receptor (GABA_AR), intracellular calcium release, and the GABA type A receptor-associated protein-like 1 (GABARAPL1; an Atg8 homolog). Finally, GABAergic inhibition increases bacterial loads in mice and zebrafish in vivo, suggesting that the GABAergic defense plays an essential function in metazoan host defenses. Our study identified a previously unappreciated role for GABAergic signaling in linking antibacterial autophagy to enhance host innate defense against intracellular bacterial infection.

Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter in neuronal systems, but the potential role for such neurotransmitters on the immune system are emerging. Here the authors show GABA signaling is linked to autophagy, enhancing the host response against intracellular bacteria.

Dysregulation of GABAergic Signalling Contributes in the Pathogenesis of Diarrhea-predominant Irritable Bowel Syndrome

Background/Aims

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a prevalent functional bowel disorder. Abdominal pain, discomfort and altered intestinal habits are the salient features of IBS-D. Low grade inflammation and altered neurotransmitters are the 2 recently identified factors contributing to the pathogenesis of IBS-D, but their role and interactions has not been elucidated in detail. Here we investigate the potential role of γ-aminobutyric acid (GABA) in regulating gut inflammation during IBS-D.

Methods

Blood samples and colonic mucosal biopsies from clinically diagnosed IBS-D patients and controls were collected. Levels of GABA were measured in serum samples through enzyme-linked immunosorbent assay (ELISA). Expression of GABAergic system and proinflammatory cytokines were analyzed in biopsy samples by reverse transcriptase polymerase chain reaction (RT-PCR). Effect of GABA and its antagonist on the expression of proinflammatory cytokines in lipopolysaccharide (LPS)-stimulated HT-29 cells was examined through RT-PCR.

Results

ELISA data revealed diminished level of GABA in IBS-D patients as compared to controls. RT-PCR analysis showed altered GABAergic signal system in IBS-D patients as compared to controls. GABA reduced the expression of proinflammatory cytokines in LPS stimulated HT-29 cells, whereas bicuculline methiodide (GABA antagonist) upregulated the expression of same cytokines in LPS stimulated HT-29 cells.

Conclusions

Our sets of data indicate that diminished level of GABA and altered GABAergic signal system contributes to pathogenesis of IBS-D by regulating inflammatory processes. These results provide novel evidence for anti-inflammatory role of GABA in IBS-D patients by altering the expression of pro-inflammatory cytokines.

Activation of GABAA Receptors in Colon Epithelium Exacerbates Acute Colitis

Emerging evidence indicates that gamma-aminobutyric acid (GABA) has many beneficial effects such as ameliorating immune and inflammatory response. But, here we reported that activation of GABA_A receptors (GABA_A Rs) aggravated dextran sulfate sodium (DSS)-induced colitis, although the expression of pro-inflammatory cytokines was inhibited. By contrast, blocking of GABA_A Rs markedly alleviated DSS-induced colitis. Notably, GABA_A Rs and glutamic acid decarboxylase 65/67 were significantly increased in colon mucosa of ulcerative colitis patients and the mouse model of colitis. Further studies showed that GABA treatment resulted in an increment of serum FITC-dextran following its oral administration, a decrement of transepithelial electrical resistance, and an increment of bacterial invasion, effects which were blocked by bicuculline. In addition, GABA inhibited the expression of tight junction proteins and mucin secretion in colitis colon. GABA also decreased the expression of ki-67 and increased cleaved-caspase 3 expression in intestinal epithelia. Our data indicate that the GABA_A Rs activation within colon mucosa disrupts the intestinal barrier and increases the intestinal permeability which facilitates inflammatory reaction in colon. Meanwhile, the suppression effect of GABA on pro-inflammatory cytokines leads to insufficient bacteria elimination and further aggravated the bacteria invasion and inflammatory damage.

Attenuated GABAergic Signaling in Intestinal Epithelium Contributes to Pathogenesis of Ulcerative Colitis

BACKGROUND

Neuromediators produced by enteric nervous system regulate inflammatory processes via interacting with enteric immune system. Role of γ-aminobutyric acid (GABA), which is also a neuromediator, has been implicated in autoimmune diseases like multiple sclerosis, type 1 diabetes, and rheumatoid arthritis, where they modulate the immune responses. However, its role in ulcerative colitis (UC) has not been defined.

AIMS

This study was carried out to investigate the role of GABA and its signaling components in pathogenesis of UC.

METHODS

Peripheral blood, colon mucosal biopsy, and fecal specimens were collected from UC and control groups. Quantification of GABA was done using ELISA. Expression of GABAergic signal system components was analyzed through RT-PCR analysis. Enumeration of GABA-producing bacteria was done by qPCR analysis. Activity of p38 MAPK and expression of proinflammatory cytokines were determined by immunohistochemistry and RT-PCR analysis, respectively.

RESULTS

GABA levels were significantly reduced in patients with UC as compared to control group when measured in serum and colon biopsy. Altered expression of GABAergic signal system was observed in UC patients. Reduced abundance of selected GABA-producing bacteria was detected in stool samples of UC patients as compared to control. p38 MAPK activity and expression of its downstream effector cytokines were found to be increased in UC patients as compared to control.

CONCLUSIONS

Reduced levels of GABA were observed in patients with UC, and this leads to hyperactivation of p38 MAPK and overexpression of downstream effector cytokines suggesting a role of GABA in pathogenesis of UC.

A glutamic acid decarboxylase (CgGAD) highly expressed in hemocytes of Pacific oyster Crassostrea gigas

Glutamic acid decarboxylase (GAD), a rate-limiting enzyme to catalyze the reaction converting the excitatory neurotransmitter glutamate to inhibitory neurotransmitter γ-aminobutyric acid (GABA), not only functions in nervous system, but also plays important roles in immunomodulation in vertebrates. However, GAD has rarely been reported in invertebrates, and never in molluscs. In the present study, one GAD homologue (designed as CgGAD) was identified from Pacific oyster Crassostrea gigas. The full length cDNA of CgGAD was 1689 bp encoding a polypeptide of 562 amino acids containing a conserved pyridoxal-dependent decarboxylase domain. CgGAD mRNA and protein could be detected in ganglion and hemocytes of oysters, and their abundance in hemocytes was unexpectedly much higher than those in ganglion. More importantly, CgGAD was mostly located in those granulocytes without phagocytic capacity in oysters, and could dynamically respond to LPS stimulation. Further, after being transfected into HEK293 cells, CgGAD could promote the production of GABA. Collectively, these findings suggested that CgGAD, as a GABA synthase and molecular marker of GABAergic system, was mainly distributed in hemocytes and ganglion and involved in neuroendocrine-immune regulation network in oysters, which also provided a novel insight to the co-evolution between nervous system and immune system.

[Pruritus in psoriasis : Profile and therapy]

Psoriasis is a common chronic inflammatory disease with an incidence of about 0.5-3 %. Previously psoriasis was not primarily regarded to be associated with pruritus; however, this perception has changed in recent years. Meanwhile data conclusively show that between 64 and 97 % of patients report about pruritus that can be severe in a number of cases. Apart from suffering from psoriasis, the presence of pruritus causes additional stress and leads to a significant impairment of health-related quality of life. Neurogenic inflammation at least in part contributes to the development of pruritus in psoriasis skin lesions. A number of neuropeptides including substance P and calcitonin gene related peptide can act as pro-inflammatory mediators. There is evidence for a dysbalance between κ‑ and µ‑opioid receptors in lesional skin favoring inflammation and pruritus. After clearing of psoriasis lesions, pruritus is relieved as well. Therefore, specific treatment of pruritus is not necessary in general. In cases where severe pruritus is a prominent symptom, targeted therapy with mirtazapin or doxepin or neuroleptic compounds such as pregabalin or gabapentin or drugs affecting the κ‑ und µ‑opioid receptor balance can be administered. Today the importance of pruritus as a prominent symptom of psoriasis lesions has been widely accepted. In recent and running clinical trials with new drugs, pruritus at baseline and the effect of these drugs on pruritus is always assessed. This awareness also fuels basic research about pruritus in psoriasis.

Development of GABAA Receptor Subtype-Selective Imidazobenzodiazepines as Novel Asthma Treatments

Recent studies have demonstrated that subtype-selective GABAA receptor modulators are able to relax precontracted human airway smooth muscle ex vivo and reduce airway hyper-responsiveness in mice upon aerosol administration. Our goal in this study was to investigate systemic administration of subtype-selective GABAA receptor modulators to alleviate bronchoconstriction in a mouse model of asthma. Expression of GABAA receptor subunits was identified in mouse lungs, and the effects of α4-subunit-selective GABAAR modulators, XHE-III-74EE and its metabolite XHE-III-74A, were investigated in a murine model of asthma (ovalbumin sensitized and challenged BALB/c mice). We observed that chronic treatment with XHE-III-74EE significantly reduced airway hyper-responsiveness. In addition, acute treatment with XHE-III-74A but not XHE-III-74EE decreased airway eosinophilia. Immune suppressive activity was also shown in activated human T-cells with a reduction in IL-2 expression and intracellular calcium concentrations [Ca(2+)]i in the presence of GABA or XHE-III-74A, whereas XHE-III-74EE showed only partial reduction of [Ca(2+)]i and no inhibition of IL-2 secretion. However, both compounds significantly relaxed precontracted tracheal rings ex vivo. Overall, we conclude that the systemic delivery of a α4-subunit-selective GABAAR modulator shows good potential for a novel asthma therapy; however, the pharmacokinetic properties of this class of drug candidates have to be improved to enable better beneficial systemic pharmacodynamic effects.

The inhibitory role of γ-aminobutyric acid (GABA) on immunomodulation of Pacific oyster Crassostrea gigas

γ-aminobutyric acid (GABA) is an inhibitory neurotransmitter to suppress the immune-mediated pro-inflammatory reactions, and it has been used in the treatment of many inflammation-related diseases in vertebrates, while its immunomodulatory role in invertebrates has never been reported. In the present study, GABA was found to exist in the hemolymph of Pacific oyster Crassostrea gigas, and its concentration decreased slightly from 8.00 ± 0.37 μmol L(-1) at normal condition to 7.73 ± 0.15 μmol L(-1) at 6 h after LPS stimulation, and then increased to 9.34 ± 0.15 μmol L(-1), 8.86 ± 0.68 μmol L(-1) at 12 h and 48 h, respectively. After LPS stimulation, the mRNA expressions of pro-inflammatory cytokines (CgIL-17 and CgTNF) and immune effectors (CgSOD and CgBPI), and the protein expression of NOS increased significantly, and these increased trends were remarkably inhibited by GABA stimulation. At the same time, the phagocytosis rate and apoptosis rate of immunocytes also increased obviously after LPS stimulation, whereas the increase was repressed with the addition of GABA. The results collectively demonstrated that GABA was an indispensable inhibitory agent for both humoral and cellular immune response, which mainly functioned at the late phase of immune response to avoid the excess immune reactions and maintain the immune homeostasis.

Understanding autoimmunity: The ion channel perspective

Ion channels are integral membrane proteins that orchestrate the passage of ions across the cell membrane and thus regulate various key physiological processes of the living system. The stringently regulated expression and function of these channels hold a pivotal role in the development and execution of various cellular functions. Malfunction of these channels results in debilitating diseases collectively termed channelopathies. In this review, we highlight the role of these proteins in the immune system with special emphasis on the development of autoimmunity. The role of ion channels in various autoimmune diseases is also listed out. This comprehensive review summarizes the ion channels that could be used as molecular targets in the development of new therapeutics against autoimmune disorders.

Tiagabine Protects Dopaminergic Neurons against Neurotoxins by Inhibiting Microglial Activation

Microglial activation and inflammation are associated with progressive neuronal apoptosis in neurodegenerative disorders such as Parkinson's disease (PD). γ-Aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system, has recently been shown to play an inhibitory role in the immune system. Tiagabine, a piperidine derivative, enhances GABAergic transmission by inhibiting GABA transporter 1 (GAT 1). In the present study, we found that tiagabine pretreatment attenuated microglial activation, provided partial protection to the nigrostriatal axis and improved motor deficits in a methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. The protective function of tiagabine was abolished in GAT 1 knockout mice that were challenged with MPTP. In an alternative PD model, induced by intranigral infusion of lipopolysaccharide (LPS), microglial suppression and subsequent neuroprotective effects of tiagabine were demonstrated. Furthermore, the LPS-induced inflammatory activation of BV-2 microglial cells and the toxicity of conditioned medium toward SH-SY5Y cells were inhibited by pretreatment with GABAergic drugs. The attenuation of the nuclear translocation of nuclear factor κB (NF-κB) and the inhibition of the generation of inflammatory mediators were the underlying mechanisms. Our results suggest that tiagabine acts as a brake for nigrostriatal microglial activation and that it might be a novel therapeutic approach for PD.

Pruritus in psoriasis: An update

BACKGROUND AND OBJECTIVE

Psoriasis is one of the most common chronic inflammatory skin diseases, found in about 1-3% of the general population. Pruritus affects about 60-90% of patients with psoriasis. The aim of this review was to summarize current knowledge about the pathogenesis and treatment of this symptom in psoriasis patients.

RESULTS

Majority of psoriatic patients consider pruritus as the most bothersome symptom. The pathogenesis of pruritus is still unknown but the major concept of its origin is focused on neurogenic inflammation. Possible itch mediators include neuropeptides released from dermal nerve endings upon various stimuli, which were found to be abnormally expressed in itchy psoriatic plaques. Another important phenomenon supporting the idea of neurogenic inflammation as a key player in pruritus accompanying psoriasis is abnormal innervations of psoriatic skin. Possibly increased innervation density in psoriasis may decrease the threshold for pruritic stimuli. It is also suggested that pruritus in psoriasis might be related to abnormal functioning of the peripheral opioid system. Despite the high frequency of pruritus in psoriasis, to date there is no single antipruritic therapy dedicated specifically to treat itch in this disease.

CONCLUSIONS

Neurogenic inflammation seems to be important for itchiness in psoriasis. Treatment of pruritus in patients with psoriasis should be directed towards the resolution of skin lesions, as disease remission usually is linked with pruritus relief.

Propofol Increases Host Susceptibility to Microbial Infection by Reducing Subpopulations of Mature Immune Effector Cells at Sites of Infection

Anesthetics are known to modulate host immune responses, but separating the variables of surgery from anesthesia when analyzing hospital acquired infections is often difficult. Here, the bacterial pathogen Listeria monocytogenes (Lm) was used to assess the impact of the common anesthetic propofol on host susceptibility to infection. Brief sedation of mice with physiologically relevant concentrations of propofol increased bacterial burdens in target organs by more than 10,000-fold relative to infected control animals. The adverse effects of propofol sedation on immune clearance of Lm persisted after recovery from sedation, as animals given the drug remained susceptible to infection for days following anesthesia. In contrast to propofol, sedation with alternative anesthetics such as ketamine/xylazine or pentobarbital did not increase susceptibility to systemic Lm infection. Propofol altered systemic cytokine and chemokine expression during infection, and prevented effective bacterial clearance by inhibiting the recruitment and/or activity of immune effector cells at sites of infection. Propofol exposure induced a marked reduction in marginal zone macrophages in the spleens of Lm infected mice, resulting in bacterial dissemination into deep tissue. Propofol also significantly increased mouse kidney abscess formation following infection with the common nosocomial pathogen Staphylococcus aureus. Taken together, these data indicate that even brief exposure to propofol severely compromises host resistance to microbial infection for days after recovery from sedation.

The anti-spasticity drug baclofen alleviates collagen-induced arthritis and regulates dendritic cells

Baclofen is used clinically as a drug that treats spasticity, which is a syndrome characterized by excessive contraction of the muscles and hyperflexia in the central nervous system (CNS), by activating GABA(B) receptors (GABA(B)Rs). Baclofen was recently reported to desensitize chemokine receptors and to suppress inflammation through the activation of GABA(B)Rs. GABA(B)Rs are expressed in various immune cells, but the functions of these receptors in autoimmune diseases remain largely unknown. In this study, we investigated the effects of baclofen in murine collagen-induced arthritis (CIA). Oral administration of baclofen alleviated the clinical development of CIA, with a reduced number of IL-17-producing T helper 17 (T(H)17) cells. In addition, baclofen treatment suppressed dendritic cell (DC)-primed T(H)17 cell differentiation by reducing the production of IL-6 by DCs in vitro. Furthermore, the pharmacological and genetic blockade of GABA(B)Rs in DCs weakened the effects of baclofen, indicating that GABA(B)Rs are the molecular targets of baclofen on DCs. Thus, our findings revealed a potential role for baclofen in the treatment of CIA, as well as a previously unknown signaling pathway that regulates DC function.

GABA transport and neuroinflammation are coupled in multiple sclerosis: regulation of the GABA transporter-2 by ganaxolone

Interactions between neurotransmitters and the immune system represent new prospects for understanding neuroinflammation and associated neurological disease. GABA is the chief inhibitory neurotransmitter but its actions on immune pathways in the brain are unclear. In the present study, we investigated GABAergic transport in conjunction with neuroinflammation in models of multiple sclerosis (MS). Protein and mRNA levels of γ-amino butyric acid transporter 2 (GAT-2) were examined in cerebral white matter from MS and control (Non-MS) patients, in cultured human macrophages, microglia and astrocytes, and in spinal cords from mice with and without experimental autoimmune encephalomyelitis (EAE) using western blotting, immunocytochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). GABA levels were measured by HPLC. The GAT-2's expression was increased in MS patients' (n=6) white matter, particularly in macrophage lineage cells, compared to Non-MS patients (n=6) (p<0.05). Interferon-γ (IFN-γ) stimulation of human macrophage lineage cells induced GAT-2 expression and reduced extracellular GABA levels (p<0.05) but soluble GABA treatment suppressed HLA-DRα, GAT-2 and XBP-1/s expression in stimulated macrophage lineage cells (p<0.05). Similarly, the synthetic allopregnanolone analog, ganaxolone (GNX), repressed GAT-2, JAK-1 and STAT-1 expression in activated macrophage lineage cells (p<0.05). In vivo GNX treatment reduced Gat-2, Cd3ε, MhcII, and Xbp-1/s expression in spinal cords following EAE induction (p<0.05), which was correlated with improved neurobehavioral outcomes and reduced neuroinflammation, demyelination and axonal injury. These findings highlight altered GABAergic transport through GAT-2 induction during neuroinflammation. GABA transport and neuroinflammation are closely coupled but regulated by GNX, pointing to GABAergic pathways as therapeutic targets in neuroinflammatory diseases.

Intrahepatic cholestasis of pregnancy: new insights into its pathogenesis

AIM

To search a specific gene expression profile in women with intrahepatic cholestasis of pregnancy (ICP) and to evaluate the maternal and foetal outcome.

METHODS

We consecutively enrolled 12 women with ICP and 12 healthy pregnant controls. The gene expression profile was assayed with the microarray technique including a panel of 5541 human genes. Microarray data were validated by real-time PCR technique.

RESULTS

Caesarean delivery was performed in eight patients with ICP versus three controls (p = 0.05). ICP women delivered at earlier gestational age than control (p < 0.001). Foetal distress was recorded in two babies, but we failed to find any correlation between bile salt concentration and foetal distress. Twenty genes potentially correlated with ICP were found differentially expressed (p < 0.05). Among these, three belong to genetic classes involved in pathogenic mechanisms of ICP: (1) pathophysiology of pruritus (GABRA2, cases versus controls = 2, upregulated gene); (2) lipid metabolism and bile composition (HLPT, cases versus controls = 0.6, down-regulated gene) and (3) protein trafficking and cytoskeleton arrangement (KIFC3, cases versus controls = 0.5, down-regulated gene).

CONCLUSIONS

Different gene expression may contribute to the complex pathogenesis of ICP. An upregulation of GABRA2 receptor may indicate that GABA may play a role in the pathogenesis of pruritus in this condition.