GABAergic signalling in the immune system

GABA-mediated inhibition of human CD4+ T cell functions is enhanced by insulin but impaired by high glucose levels

BACKGROUND

γ-aminobutyric acid (GABA), known as the main inhibitory neurotransmitter in the brain, exerts immunomodulatory functions by interaction with immune cells, including T cells. Metabolic programs of T cells are closely linked to their effector functions including proliferation, differentiation, and cytokine production. The physiological molecules glucose and insulin may provide environmental cues and guidance, but whether they coordinate to regulate GABA-mediated T cell immunomodulation is still being examined.

METHODS

CD4+ T cells that were isolated from blood samples from healthy individuals and from patients with type 1 diabetes (T1D) were activated in vitro. We carried out metabolic assays, multiple proximity extension assay (PEA), ELISA, qPCR, immunoblotting, immunofluorescence staining, flow cytometry analysis, MS-based proteomics, as well as electrophysiology and live-cell Ca2+ imaging.

FINDINGS

We demonstrate that GABA-mediated reduction of metabolic activity and the release of inflammatory proteins, including IFNγ and IL-10, were abolished in human CD4+ T cells from healthy individuals and patients with T1D when the glucose concentration was elevated above levels typically observed in healthy people. Insulin increased GABAA receptor-subunit ρ2 expression, enhanced the GABAA receptors-mediated currents and Ca2+ influx. GABA decreased, whereas insulin sustained, hexokinase activity and glycolysis in a glucose concentration-dependent manner.

INTERPRETATION

These findings support that metabolic factors, such as glucose and insulin, influence the GABA-mediated immunomodulation of human primary T cells effector functions.

FUNDING

The Swedish Children's Diabetes Foundation, The Swedish Diabetes Foundation, The Swedish Research Council 2018-02952, EXODIAB, The Ernfors Foundation, The Thurings Foundation and the Science for Life Laboratory.

A genome-wide association study on hematopoietic stem cell transplantation reveals novel genomic loci associated with transplant outcomes

Introduction

Data on genomic susceptibility for adverse outcomes after hematopoietic stem cell transplantation (HSCT) for recipients are scarce.

Methods

We performed a genome wide association study (GWAS) to identify genes associated with survival/mortality, relapse, and severe graft-versus-host disease (sGvHD), fitting proportional hazard and subdistributional models to data of n=1,392 recipients of European ancestry from three centres.

Results

The single nucleotide polymorphism (SNP) rs17154454, intronic to the neuronal growth guidant semaphorin 3C gene (SEMA3C), was genome-wide significantly associated with event-free survival (p=7.0x10-8) and sGvHD (p=7.5x10-8). Further associations were detected for SNPs in the Paxillin gene (PXN) with death without prior relapse or sGvHD, as well as for SNPs of the Plasmacytoma Variant Translocation 1 gene (PVT1, a long non-coding RNA gene), the Melanocortin 5 Receptor (MC5R) gene and the WW Domain Containing Oxidoreductase gene (WWOX), all associated with the occurrence of sGvHD. Functional considerations support the observed associations.

Discussion

Thus, new genes were identified, potentially influencing the outcome of HSCT.

Fipronil disturbs the antigen-specific immune responses and GABAergic gene expression in the ovalbumin-immunized BALB/c mice

BACKGROUND

Fipronil (FPN) is a broad-spectrum pesticide and commonly known as low toxicity to vertebrates. However, increasing evidence suggests that exposure to FPN might induce unexpected adverse effects in the liver, reproductive, and nervous systems. Until now, the influence of FPN on immune responses, especially T-cell responses has not been well examined. Our study is designed to investigate the immunotoxicity of FPN in ovalbumin (OVA)-sensitized mice. The mice were administered with FPN by oral gavage and immunized with OVA. Primary splenocytes were prepared to examine the viability and functionality of antigen-specific T cells ex vivo. The expression of T cell cytokines, upstream transcription factors, and GABAergic signaling genes was detected by qPCR.

RESULTS

Intragastric administration of FPN (1-10 mg/kg) for 11 doses did not show any significant clinical symptoms. The viability of antigen-stimulated splenocytes, the production of IL-2, IL-4, and IFN-γ by OVA-specific T cells, and the serum levels of OVA-specific IgG1 and IgG2a were significantly increased in FPN-treated groups. The expression of the GABAergic signaling genes was notably altered by FPN. The GAD67 gene was significantly decreased, while the GABAR β2 and GABAR δ were increased.

CONCLUSION

FPN disturbed antigen-specific immune responses by affecting GABAergic genes in vivo. We propose that the immunotoxic effects of FPN may enhance antigen-specific immunity by dysregulation of the negative regulation of GABAergic signaling on T cell immunity.

Signal detection of adverse events associated with gabapentinoid use for chronic pain

INTRODUCTION

Gabapentinoids (GABA) prescribing as a potential and conceivably safer substitute for opioids has substantially increased. Understanding all potential adverse drug events (ADEs) associated with GABA will guide clinical decision-making for pain management.

METHODS

A 20% sample of Medicare enrollees with new chronic pain diagnoses in 2017-2018 was selected. GABA users were those with >=30 consecutive days prescription in a year without opioid prescription. Opioid users were similarly defined. The control group used neither of these drugs. Propensity score match across three groups based on demographics and comorbidity was performed. We used proportional reporting ratio (PRR), Gamma Poisson Shrinker, and tree-based scan statistic (TBSS) to detect ADEs within 3, 6, and 12 months of follow-up.

RESULTS

Immunity disorder was detected within 3 months of follow-up by PRR compared to opioid use (PRR:2.33), and by all three methods compared to controls. Complications of transplanted organs/tissues and schizophrenia spectrum/other psychotic disorders were consistently detected by PRR and TBSS within 3 months. Skin disorders were detected by TBSS; and stroke was detected by PRR within 3 months compared to opioid use (PRR:4.74). Some malignancies were detected by PRR within 12 months. Other signals detected in GABA users were neuropathy and nerve disorders.

CONCLUSIONS

Our study identified expected and unexpected ADE signals in GABA users. Neurological signals likely related to indications for GABA use. Signals for immunity, mental/behavior, and skin disorders were found in the FDA adverse event reporting system database. Unexpected signals of stroke and cancer require further confirmatory analyses to verify.

Physical activity interventions for cardiopulmonary fitness in obese children and adolescents: a systematic review and meta-analysis

PURPOSE

This study [PROSPERO CRD42023416272] systematically analysed the effects of a physical activity intervention on cardiorespiratory fitness in obese children and adolescents and elucidated the factors that influenced those effects.

METHODS

A systematic review of the literature on physical activity interventions for improving cardiopulmonary fitness in obese children and adolescents from January 1, 2011, to March 1, 2023, was conducted. The search was performed on the Web of Science and PubMed databases, and the selected literature was first screened and then assessed for quality. Finally, a systematic review was conducted.

RESULTS

Out of the initially identified 1424 search records, 28 studies were eventually included in the systematic review. These studies encompassed a total of 2724 participants aged 5 to 18 years, with the publication dates of the literature primarily ranging from 2011 to 2023. Physical activity was found to effectively improve the following parameters in obese children and adolescents: weight [mean difference (MD), -2.03 (95% confidence interval, -2.59 to -1.47), p < 0.00001], maximal oxygen consumption [MD, -1.95 (95% CI, -1.06 to -2.84), p < 0.0001], heart rate [MD, -2.77 (95% CI, -4.88 to -0.67), p = 0.010], systolic blood pressure [MD, -8.11 (95% CI, -11.41 to -4.81), p < 0.00001], and diastolic blood pressure [MD, -4.18 (95% CI, -5.32 to -3.03), p < 0.00001]. High-intensity exercise was found to yield greater improvements than low- to moderate-intensity exercise in maximal oxygen consumption [MD, 1.43 (95% CI, 0.04 to 2.82), p = 0.04] and diastolic blood pressure [MD, -6.94 (95% CI, -10.61 to -3.26), p = 0.0002] in obese children and adolescents.

CONCLUSION

Physical activity can effectively improve the body weight, maximal oxygen consumption, heart rate, systolic blood pressure, and diastolic blood pressure of obese children and adolescents. The type of physical activity directly influences the participation interest of obese children and adolescents, with moderate- to high-intensity physical activity showing the most significant impact on intervention outcomes. High-frequency, long-term interventions yield better results than short-term interventions.

Establishment and identification of a skin cell line from Chinese tongue sole (Cynoglossus semilaevis) and analysis of the changes in its transcriptome upon LPS stimulation

The Chinese tongue sole (Cynoglossus semilaevis) holds significant economic importance within the fishing industry along the eastern coasts of China. In recent years, the frequent outbreaks of bacterial diseases have become a common concern as the aquaculture scale expands. The majority of the diseased fish exhibit symptoms such as skin congestion, damage and skin ulceration. As the skin serves as the first line of defense against bacterial infections, establishing a skin cell line for immunological research on Chinese tongue sole's response to bacterial infection is of utmost importance. In this study, a cell line named CSS (derived from the skin of the Chinese tongue sole) was successfully established. The cells have demonstrated stability during passages and exhibit a multipolar fibroblast-like morphology. They were cultured in L-15 medium with 20% serum and have been successfully passed through 60 passages over a period of 20 months. The identification of the mitochondrial CO1 gene confirmed that the cell originated from Chinese tongue sole. The karyotype detection revealed that the cell had a chromosome number of 2n = 42. After being stored in liquid nitrogen for 15 months, the cells can maintain more than 75% viability upon recovery. After transfecting with cy3-labeled scramble siRNA and pEGFP-N3 plasmid, clear fluorescence was observed in the transfected cells. We observed that lipopolysaccharide (LPS) from Escherichia coli significantly upregulate the gene expression of various immune-related pathways at 2 h in the CSS cell line. Additionally, the differentially expressed genes showed a higher enrichment in immune-related pathways at 2 and 6 h after stimulation compared to the 24 h point. Moreover, we identified 347 genes that exhibited a gradual increase in expression during the 0-24 h stimulation period. These genes were primarily enriched in pathways related to Autophagy, GABAergic synapse, Apelin signaling and Ferroptosis. In general, the CSS cell line established in this study exhibits stable growth and can serve as a valuable tool for in vitro studies of immunology and other basic biologies of Chinese tongue sole.

Anti-proliferative and anti-inflammatory effects of the application of baclofen cream, a GABAB receptor agonist, on skin inflammation in mice

Previous studies have demonstrated the role of γ-aminobutyric acid type B (GABAB) receptors in skin-related conditions and pain. However, most studies have focused on the main effects of GABAB on the central nervous system. Therefore, this study has aimed to determine the potential topical anti-inflammatory and anti-proliferative effects of baclofen cream in an inflammatory skin disease model. The effects of the baclofen cream were evaluated using acute and chronic models of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin inflammation in mouse ears. Histological and immunohistochemical evaluations were performed using an ear oedema assay. The effect of baclofen on keratinocyte proliferation was assessed in PAM212, the murine keratinocyte cell line. The results demonstrate that a single topical application of 5% baclofen, 7.5% baclofen, and 1% dexamethasone each inhibited acute TPA-induced ear oedema (58.94 ± 6.14%, 47.73 ± 11.26%, and 87.33 ± 4.59%, respectively). These results were confirmed by histological analysis. In the chronic model, baclofen (5%) and dexamethasone (1%) each inhibited ear oedema and the maximum inhibitory effect was reached at the end of the experiment (9th day of TPA application) with a percentage inhibition of 54.60 ± 6.15% for baclofen and 71.68 ± 3.45% for dexamethasone, when compared to the vehicle. These results were confirmed by histological analysis. Baclofen and dexamethasone also reduced proliferating cell nuclear antigen expression by 62.01 ± 6.65% and 70.42 ± 6.11%, respectively. However, baclofen did not inhibit keratinocyte proliferation in PAM212 cells. In conclusion, these results demonstrate that baclofen exhibits notable topical antiproliferative and anti-inflammatory properties and could be a potential therapeutic alternative for treating inflammatory and proliferative skin diseases.

The hepatic GABAergic system promotes liver macrophage M2 polarization and mediates HBV replication in mice

Macrophages display functional phenotypic plasticity. Hepatitis B virus (HBV) infection induces polarizations of liver macrophages either to M1-like pro-inflammatory phenotype or to M2-like anti-inflammatory phenotype. Gamma-aminobutyric acid (GABA) signaling exists in various non-neuronal cells including hepatocytes and some immune cells. Here we report that macrophages express functional GABAergic signaling components and activation of type A GABA receptors (GABAARs) promotes M2-polarization thus advancing HBV replication. Notably, intraperitoneal injection of GABA or the GABAAR agonist muscimol increased HBV replication in HBV-carrier mice that were generated by hydrodynamical injection of adeno-associated virus/HBV1.2 plasmids (pAAV/HBV1.2). The GABA-augmented HBV replication in HBV-carrier mice was significantly reduced by the GABAAR inhibitor picrotoxin although picrotoxin had no significant effect on serum HBsAg levels in control HBV-carrier mice. Depletion of liver macrophages by liposomal clodronate treatment also significantly reduced the GABA-augmented HBV replication. Yet adoptive transfer of liver macrophages isolated from GABA-treated donor HBV-carrier mice into the liposomal clodronate-pretreated recipient HBV-carrier mice restored HBV replication. Moreover, GABA or muscimol treatment increased the expression of "M2" cytokines in macrophages, but had no direct effect on HBV replication in the HepG2.2.15 cells, HBV1.3-transfected Huh7, HepG2, or HepaRG cells, or HBV-infected Huh7-NTCP cells. Taken together, these results suggest that increasing GABA signaling in the liver promotes HBV replication in HBV-carrier mice by suppressing the immunity of liver macrophages, but not by increasing the susceptibility of hepatocytes to HBV infection. Our study shows that a previously unknown GABAergic system in liver macrophage has an essential role in HBV replication.

Inhibitory Synaptic Influences on Developmental Motor Disorders

During development, GABA and glycine play major trophic and synaptic roles in the establishment of the neuromotor system. In this review, we summarise the formation, function and maturation of GABAergic and glycinergic synapses within neuromotor circuits during development. We take special care to discuss the differences in limb and respiratory neuromotor control. We then investigate the influences that GABAergic and glycinergic neurotransmission has on two major developmental neuromotor disorders: Rett syndrome and spastic cerebral palsy. We present these two syndromes in order to contrast the approaches to disease mechanism and therapy. While both conditions have motor dysfunctions at their core, one condition Rett syndrome, despite having myriad symptoms, has scientists focused on the breathing abnormalities and their alleviation-to great clinical advances. By contrast, cerebral palsy remains a scientific quagmire or poor definitions, no widely adopted model and a lack of therapeutic focus. We conclude that the sheer abundance of diversity of inhibitory neurotransmitter targets should provide hope for intractable conditions, particularly those that exhibit broad spectra of dysfunction-such as spastic cerebral palsy and Rett syndrome.

GABAergic signaling as a potential therapeutic target in cancers

GABA is the most common inhibitory neurotransmitter in the vertebrate central nervous system. Synthesized by glutamic acid decarboxylase, GABA could specifically bind with two GABA receptors to transmit inhibition signal stimuli into cells: GABAA receptor and GABAB receptor. In recent years, emerging studies revealed that GABAergic signaling not only participated in traditional neurotransmission but was involved in tumorigenesis as well as regulating tumor immunity. In this review, we summarize the existing knowledge of the GABAergic signaling pathway in tumor proliferation, metastasis, progression, stemness, and tumor microenvironment as well as the underlying molecular mechanism. We also discussed the therapeutical advances in targeting GABA receptors to provide the theoretical basis for pharmacological intervention of GABAergic signaling in cancer treatment especially immunotherapy.

Exploring the Role of Neurotransmitters in Multiple Sclerosis: An Expanded Review

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system (CNS). Although emerging evidence has shown that changes in neurotransmitter levels in the synaptic gap may contribute to the pathophysiology of MS, their specific role has not been elucidated yet. In this review, we aim to analyze preclinical and clinical evidence on the structural and functional changes in neurotransmitters in MS and critically discuss their potential role in MS pathophysiology. Preclinical studies have demonstrated that alterations in glutamate metabolism may contribute to MS pathophysiology, by causing excitotoxic neuronal damage. Dysregulated interaction between glutamate and GABA results in synaptic loss. The GABAergic system also plays an important role, by regulating the activity and plasticity of neural networks. Targeting GABAergic/glutamatergic transmission may be effective in fatigue and cognitive impairment in MS. Acetylcholine (ACh) and dopamine can also affect the T-mediated inflammatory responses, thereby being implicated in MS-related neuroinflammation. Also, melatonin might affect the frequency of relapses in MS, by regulating the sleep-wake cycle. Increased levels of nitric oxide in inflammatory lesions of MS patients may be also associated with axonal neuronal degeneration. Therefore, neurotransmitter imbalance may be critically implicated in MS pathophysiology, and future studies are needed for our deeper understanding of their role in MS.

The role of the gut microbiota and fecal microbiota transplantation in neuroimmune diseases

The gut microbiota plays a key role in the function of the host immune system and neuroimmune diseases. Alterations in the composition of the gut microbiota can lead to pathology and altered formation of microbiota-derived components and metabolites. A series of neuroimmune diseases, such as myasthenia gravis (MG), multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSDs), Guillain-Barré syndrome (GBS), and autoimmune encephalitis (AIE), are associated with changes in the gut microbiota. Microecological therapy by improving the gut microbiota is expected to be an effective measure for treating and preventing some neuroimmune diseases. This article reviews the research progress related to the roles of gut microbiota and fecal microbiota transplantation (FMT) in neuroimmune diseases.

Gamma-Aminobutyric Acid Promotes Beige Adipocyte Reconstruction by Modulating the Gut Microbiota in Obese Mice

Given the increasing prevalence of obesity, the white-to-beige adipocyte conversion has attracted interest as a target for obesity treatment. Gamma-aminobutyric acid (GABA) treatment can reduce obesity, but the underlying mechanism remains unclear. Here, we aimed to investigate the mechanism by which GABA triggers weight loss by improving the beiging of inguinal white adipose tissue (iWAT) and the role of gut microbiota in this process. The results showed that GABA reduced body weight and adipose inflammation and promoted the expression of thermogenic genes in the iWAT. The 16S rRNA sequence analysis of gut microbiota showed that GABA treatment increased the relative abundance of Bacteroidetes, Akkermansia, and Romboutsia and reduced that of Firmicutes and Erysipelatoclostridium in obese mice. Additionally, serum metabolomic analysis revealed that GABA treatment increased 3-hydroxybutyrate and reduced oxidized lipid levels in obese mice. Spearman's correlation analysis showed that Akkermansia and Romboutsia were negatively associated with the levels of oxidized lipids. Fecal microbiota transplantation analysis confirmed that the gut microbiota was involved in the white-to-beige adipocyte reconstruction by GABA. Overall, our findings suggest that GABA treatment may promote iWAT beiging through the gut microbiota in obese mice. GABA may be utilized to protect obese people against metabolic abnormalities brought on by obesity and gut dysbiosis.

Beyond the γ-aminobutyric acid hypothesis of schizophrenia

Abnormalities in the γ-aminobutyric acid (GABA) system have been reported in the postmortem brains of individuals with schizophrenia. In particular, the reduction of one of the GABA-synthesizing enzymes, the 67-kDa isoform of glutamate decarboxylase (GAD67), has garnered interest among researchers because of its role in the formation of γ-oscillations and its potential involvement in the cognitive dysfunction observed in schizophrenia. Although several animal models have been generated to simulate the alterations observed in postmortem brain studies, they exhibit inconsistent behavioral phenotypes, leading to conflicting views regarding their contributions to the pathogenesis and manifestation of schizophrenia symptoms. For instance, GAD67 knockout rats (also known as Gad1 knockout rats) exhibit marked impairments in spatial working memory, but other model animals do not. In this review, we summarize the phenotypic attributes of these animal models and contemplate the potential for secondary modifications that may arise from the disruption of the GABAergic nervous system.

Angiotensin-converting enzyme 2 improves hepatic insulin resistance by regulating GABAergic signaling in the liver

The angiotensin-converting enzyme 2 (ACE2)/angiotensin 1-7/MAS axis and the gamma-aminobutyric acid (GABA)ergic signaling system have both been shown to have the dual potential to improve insulin resistance (IR) and hepatic steatosis associated with obesity in the liver. Recent studies have demonstrated that ACE2 can regulate the GABA signal in various tissues. Notwithstanding this evidence, the functional relationship between ACE2 and GABA signal in the liver under IR remains elusive. Here, we used high-fat diet-induced models of IR in C57BL/6 mice as well as ACE2KO and adeno-associated virus-mediated ACE2 overexpression mouse models to address this knowledge gap. Our analysis showed that glutamate decarboxylase (GAD)67/GABA signaling was weakened in the liver during IR, whereas the expression of GAD67 and GABA decreased significantly in ACE2KO mice. Furthermore, exogenous administration of angiotensin 1-7 and adeno-associated virus- or lentivirus-mediated overexpression of ACE2 significantly increased hepatic GABA signaling in models of IR both in vivo and in vitro. We found that this treatment prevented lipid accumulation and promoted fatty acid β oxidation in hepatocytes as well as inhibited the expression of gluconeogenesis- and inflammation-related genes, which could be reversed by allylglycine, a specific GAD67 inhibitor. Collectively, our findings show that signaling via the ACE2/A1-7/MAS axis can improve hepatic IR by regulating hepatic GABA signaling. We propose that this research might indicate a potential strategy for the management of diabetes.

The role of GABA in islet function

Gamma aminobutyric acid (GABA) is a non-proteinogenic amino acid and neurotransmitter that is produced in the islet at levels as high as in the brain. GABA is synthesized by the enzyme glutamic acid decarboxylase (GAD), of which the 65 kDa isoform (GAD65) is a major autoantigen in type 1 diabetes. Originally described to be released via synaptic-like microvesicles or from insulin secretory vesicles, beta cells are now understood to release substantial quantities of GABA directly from the cytosol via volume-regulated anion channels (VRAC). Once released, GABA influences the activity of multiple islet cell types through ionotropic GABAA receptors and metabotropic GABAB receptors. GABA also interfaces with cellular metabolism and ATP production via the GABA shunt pathway. Beta cells become depleted of GABA in type 1 diabetes (in remaining beta cells) and type 2 diabetes, suggesting that loss or reduction of islet GABA correlates with diabetes pathogenesis and may contribute to dysfunction of alpha, beta, and delta cells in diabetic individuals. While the function of GABA in the nervous system is well-understood, the description of the islet GABA system is clouded by differing reports describing multiple secretion pathways and effector functions. This review will discuss and attempt to unify the major experimental results from over 40 years of literature characterizing the role of GABA in the islet.

The influence of a tomato food matrix on the bioavailability and plasma kinetics of oral gamma-aminobutyric acid (GABA) and its precursor glutamate in healthy men

Gamma-aminobutyric acid (GABA) and its precursor glutamate play signaling roles in a range of tissues. Both function as neurotransmitters in the central nervous system, but they also modulate pancreatic and immune functioning, for example. Besides endogenous production, both compounds are found in food products, reaching relatively high levels in tomatoes. Recent studies in rodents suggest beneficial effects of oral GABA on glucose homeostasis and blood pressure. However, the bioavailability from food remains unknown. We studied the bioavailability of GABA and glutamate from tomatoes relative to a solution in water. After a fasting blood sample was taken, eleven healthy men randomly received 1 liter of 4 different drinks in a cross-over design with a one-week interval. The drinks were a solution of 888 mg L^-1 GABA, a solution of 3673 mg L^-1 glutamate, pureed fresh tomatoes and plain water as the control. Following intake, 18 blood samples were taken at intervals for 24 hours. Plasma GABA and glutamate concentrations were determined by ultra-pressure liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). Fasting plasma GABA and glutamate concentrations were found to be 16.71 (SD 2.18) ng mL^-1 and 4626 (SD 1666) ng mL^-1, respectively. Fasting GABA levels were constant (5.8 CV%) between individuals, while fasting glutamate levels varied considerably (23.5 CV%). GABA from pureed tomatoes showed similar bioavailability to that of a solution in water. For glutamate, the absorption from pureed tomatoes occurred more slowly as seen from a longer t_max (0.98 ± 0.14 h vs. 0.41 ± 0.04 h, P = 0.003) and lower C_max (7815 ± 627 ng mL^-1vs. 16 420 ± 2778 ng mL^-1, P = 0.006). These data suggest that GABA is bioavailable from tomatoes, and that food products containing GABA could potentially induce health effects similar to those claimed for GABA supplements. The results merit further studies on the bioavailability of GABA from other food products and the health effects of GABA-rich diets. The clinical trial registry number is NCT04086108 (https://clinicaltrials.gov/ct2/show/NCT04303468).

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.

The Case for Clinical Trials with Novel GABAergic Drugs in Diabetes Mellitus and Obesity

Obesity and diabetes mellitus have become the surprising menaces of relative economic well-being worldwide. Gamma amino butyric acid (GABA) has a prominent role in the control of blood glucose, energy homeostasis as well as food intake at several levels of regulation. The effects of GABA in the body are exerted through ionotropic GABAA and metabotropic GABAB receptors. This treatise will focus on the pharmacologic targeting of GABAA receptors to reap beneficial therapeutic effects in diabetes mellitus and obesity. A new crop of drugs selectively targeting GABAA receptors has been under investigation for efficacy in stroke recovery and cognitive deficits associated with schizophrenia. Although these trials have produced mixed outcomes the compounds are safe to use in humans. Preclinical evidence is summarized here to support the rationale of testing some of these compounds in diabetic patients receiving insulin in order to achieve better control of blood glucose levels and to combat the decline of cognitive performance. Potential therapeutic benefits could be achieved (i) By resetting the hypoglycemic counter-regulatory response; (ii) Through trophic actions on pancreatic islets, (iii) By the mobilization of antioxidant defence mechanisms in the brain. Furthermore, preclinical proof-of-concept work, as well as clinical trials that apply the novel GABAA compounds in eating disorders, e.g., olanzapine-induced weight-gain, also appear warranted.

Gastrointestinal Microbiome and Neurologic Injury

Communication between the enteric nervous system (ENS) of the gastrointestinal (GI) tract and the central nervous system (CNS) is vital for maintaining systemic homeostasis. Intrinsic and extrinsic neurological inputs of the gut regulate blood flow, peristalsis, hormone release, and immunological function. The health of the gut microbiome plays a vital role in regulating the overall function and well-being of the individual. Microbes release short-chain fatty acids (SCFAs) that regulate G-protein-coupled receptors to mediate hormone release, neurotransmitter release (i.e., serotonin, dopamine, noradrenaline, γ-aminobutyric acid (GABA), acetylcholine, and histamine), and regulate inflammation and mood. Further gaseous factors (i.e., nitric oxide) are important in regulating inflammation and have a response in injury. Neurologic injuries such as ischemic stroke, spinal cord injury, traumatic brain injury, and hemorrhagic cerebrovascular lesions can all lead to gut dysbiosis. Additionally, unfavorable alterations in the composition of the microbiota may be associated with increased risk for these neurologic injuries due to increased proinflammatory molecules and clotting factors. Interventions such as probiotics, fecal microbiota transplantation, and oral SCFAs have been shown to stabilize and improve the composition of the microbiome. However, the effect this has on neurologic injury prevention and recovery has not been studied extensively. The purpose of this review is to elaborate on the complex relationship between the nervous system and the microbiome and to report how neurologic injury modulates the status of the microbiome. Finally, we will propose various interventions that may be beneficial in the recovery from neurologic injury.

Activation of the α1β2γ2L GABAA Receptor by Physiological Agonists

The Cl⁻ permeable GABA_A receptor is a major contributor to cellular inhibition in the brain. The receptor is normally activated by synaptically-released or ambient GABA but is sensitive to a number of physiological compounds such as β-alanine, taurine, and neurosteroids that, to various degrees, activate the receptor and modulate responses either to the transmitter or to each other. Here, we describe α1β2γ2L GABA_A receptor activation and modulation by combinations of orthosteric and allosteric activators. The overall goal was to gain insight into how changes in the levels of endogenous agonists modulate receptor activity and influence cellular inhibition. Experimental observations and simulations are described in the framework of a cyclic concerted transition model. We also provide general analytical solutions for the analysis of electrophysiological data collected in the presence of combinations of active compounds.

Metabolomics Analysis of the Effect of GAT-2 Deficiency on Th1 Cells in Mice

The classic neurotransmitter γ-aminobutyric acid (GABA) has been shown to shape the activation and function of immune cells. There are four high-affinity GABA transporters (GATs, including GAT-1, GAT-2, GAT-3, and GAT-4) responsible for the transmembrane transport of GABA in mice. To explore the effect of GAT-2 on type 1 helper T (Th1) cells, naïve CD4⁺ T cells were isolated from splenocytes of GAT-2 knockout (KO) and wild-type (WT) mice and cultured for Th1 cell differentiation, and then, metabolomics analysis of Th1 cells was performed via gas chromatography coupled to time-of-flight mass spectrometry added with multivariate analyses. Based on the variable importance projection value > 1 and P < 0.05, a total of nine differentially expressed metabolites (DEMs) were identified between WT and KO. Then, DEMs were mapped to the KEGG database, and five metabolic pathways were significantly enriched, including the cysteine and methionine metabolism, the riboflavin metabolism, the purine metabolism, the glycerolipid metabolism, and the glycerophospholipid metabolism. Collectively, our metabolomics analysis revealed that deficiency of GAT-2 influenced the metabolomics profile of Th1 cells, which will provide insights into T cell response to GAT-2 deficiency in mice. Data are available via MetaboLights with identifier MTBLS3358.

Emerging Roles of γ Aminobutyric Acid (GABA) Gated Channels in Plant Stress Tolerance

The signaling role for γ-Aminobutyric acid (GABA) has been documented in animals for over seven decades. However, a signaling role for GABA in plants is just beginning to emerge with the discovery of putative GABA binding site/s and GABA regulation of anion channels. In this review, we explore the role of GABA in plant growth and development under abiotic stress, its interactions with other signaling molecules and the probability that there are other anion channels with important roles in stress tolerance that are gated by GABA.

GABAergic signaling in human and murine NK cells upon challenge with Toxoplasma gondii

Protective cytotoxic and proinflammatory cytokine responses by NK cells impact the outcome of infections by Toxoplasma gondii, a common parasite in humans and other vertebrates. However, T. gondii can also sequester within NK cells and downmodulate their effector functions. Recently, the implication of GABA signaling in infection and inflammation-related responses of mononuclear phagocytes and T cells has become evident. Yet, the role of GABAergic signaling in NK cells has remained unknown. Here, we report that human and murine NK cells synthesize and secrete GABA in response to infection challenge. Parasitized NK cells secreted GABA, whereas activation stimuli, such as IL-12/IL-18 or parasite lysates, failed to induce GABA secretion. GABA secretion by NK cells was associated to a transcriptional up-regulation of GABA synthesis enzymes (glutamate decarboxylases [GAD65/67]) and was abrogated by GAD inhibition. Further, NK cells expressed GABA-A receptor subunits and GABA signaling regulators, with transcriptional modulations taking place upon challenge with T. gondii. Exogenous GABA and GABA-containing supernatants from parasitized dendritic cells (DCs) impacted NK cell function by reducing the degranulation and cytotoxicity of NK cells. Conversely, GABA-containing supernatants from NK cells enhanced the migratory responses of parasitized DCs. This enhanced DC migration was abolished by GABA-A receptor antagonism or GAD inhibition and was reconstituted by exogenous GABA. Jointly, the data show that NK cells are GABAergic cells and that GABA hampers NK cell cytotoxicity in vitro. We hypothesize that GABA secreted by parasitized immune cells modulates the immune responses to T. gondii infection.

Multiple Targets for Oxysterols in Their Regulation of the Immune System

Oxysterols, or cholesterol oxidation products, are naturally occurring lipids which regulate the physiology of cells, including those of the immune system. In contrast to effects that are mediated through nuclear receptors or by epigenetic mechanism, which take tens of minutes to occur, changes in the activities of cell-surface receptors caused by oxysterols can be extremely rapid, often taking place within subsecond timescales. Such cell-surface receptor effects of oxysterols allow for the regulation of fast cellular processes, such as motility, secretion and endocytosis. These cellular processes play critical roles in both the innate and adaptive immune systems. This review will survey the two broad classes of cell-surface receptors for oxysterols (G-protein coupled receptors (GPCRs) and ion channels), the mechanisms by which cholesterol oxidation products act on them, and their presence and functions in the different cell types of the immune system. Overall, this review will highlight the potential of oxysterols, synthetic derivatives and their receptors for physiological and therapeutic modulation of the immune system.

Plants have neither synapses nor a nervous system

The alleged existence of so-called synapses or equivalent structures in plants provided the basis for the concept of Plant Neurobiology (Baluska et al., 2005; Brenner et al., 2006). More recently, supporters of this controversial theory have even speculated that the phloem acts as a kind of nerve system serving long distance electrical signaling (Mediano et al., 2021; Baluska and Mancuso, 2021). In this review we have critically examined the literature cited by these authors and arrive at a completely different conclusion. Plants do not have any structures resembling animal synapses (neither chemical nor electrical). While they certainly do have complex cell contacts and signaling mechanisms, none of these structures provides a basis for neuronal-like synaptic transmission. Likewise, the phloem is undoubtedly a conduit for the propagation of electrical signaling, but the characteristics of this process are in no way comparable to the events underlying information processing in neuronal networks. This has obvious implications in regard to far-going speculations into the realms of cognition, sentience and consciousness.

Biobehavioral organization shapes the immune epigenome in infant rhesus Macaques (Macaca mulatta)

How individuals respond to and cope with stress is linked with their health and well-being. It is presumed that early stress responsiveness helps shape the health of the developing organism, but the relationship between stress responsiveness and early immune function during development is not well-known. We hypothesized that stress responsiveness may shape epigenetic regulation of immune genes in infancy. We investigated whether aspects of behavioral responsiveness and hypothalamic-pituitary adrenal stress-response were associated with epigenome-wide immune cell DNA methylation patterns in 154 infant rhesus monkeys (3-4 months old). Infants' behavioral and physiological responses were collected during a standardized biobehavioral assessment, which included temporary relocation and separation from their mother and social group. Genome-wide DNA methylation was quantified using restricted representation bisulfite sequencing (RRBS) from blood DNA collected 2-hours post-separation. Epigenome-wide analyses were conducted using simple regression, multiple regression controlling for immune cell counts, and permutation regression, all corrected for false discovery rate. Across the variables analyzed, there were 20,368 unique sites (in 9,040 genes) at which methylation was significantly associated with at least one behavioral responsiveness or cortisol measure across the three analyses. There were significant associations in 442 genes in the Immune System Process ontology category, and 94 genes in the Inflammation mediated by chemokine and cytokine signaling gene pathway. Out of 35 candidate genes that were selected for further investigation, there were 13 genes with at least one site at which methylation was significantly associated with behavioral responsiveness or cortisol, including two intron sites in the glucocorticoid receptor gene, at which methylation was negatively correlated with emotional behavior the day following the social separation (Day 2 Emotionality; β = -0.39, q < 0.001) and cortisol response following a relocation stressor (Sample 1; β = -0.33, q < 0.001). We conclude that biobehavioral stress responsiveness may correlate with the developing epigenome, and that DNA methylation of immune cells may be a mechanism by which patterns of stress response affect health and immune functioning.

Cardiorespiratory fitness in children with overweight/obesity: Insights into the molecular mechanisms

OBJECTIVES

High cardiorespiratory fitness (CRF) levels reduce the risk of developing cardiovascular disease (CVD) during adulthood. However, little is known about the molecular mechanisms underlying the health benefits of high CRF levels at the early stage of life. This study aimed to analyze the whole-blood transcriptome profile of fit children with overweight/obesity (OW/OB) compared to unfit children with OW/OB.

DESIGN

27 children with OW/OB (10.14 ± 1.3 years, 59% boys) from the ActiveBrains project were evaluated. VO₂ peak was assessed using a gas analyzer, and participants were categorized into fit or unfit according to the CVD risk-related cut-points. Whole-blood transcriptome profile (RNA sequencing) was analyzed. Differential gene expression analysis was performed using the limma R/Bioconductor software package (analyses adjusted by sex and maturational status), and pathways' enrichment analysis was performed with DAVID. In addition, in silico validation data mining was performed using the PHENOPEDIA database.

RESULTS

256 genes were differentially expressed in fit children with OW/OB compared to unfit children with OW/OB after adjusting by sex and maturational status (FDR < 0.05). Enriched pathway analysis identified gene pathways related to inflammation (eg, dopaminergic and GABAergic synapse pathways). Interestingly, in silico validation data mining detected a set of the differentially expressed genes to be related to CVD, metabolic syndrome, hypertension, inflammation, and asthma.

CONCLUSION

The distinct pattern of whole-blood gene expression in fit children with OW/OB reveals genes and gene pathways that might play a role in reducing CVD risk factors later in life.

Diazepam Impairs Innate and Adaptive Immune Responses and Ameliorates Experimental Autoimmune Encephalomyelitis

Currently there is increasing attention on the modulatory effects of benzodiazepines on the immune system. Here, we evaluate how Diazepam (DZ) affects both innate and adaptive immunity. We observed that treatment with DZ and Lipopolysaccharide (LPS) on macrophages or dendritic cells (DCs) induced a defective secretion of IL-12, TNF-α, IL-6 and a lesser expression of classical activation markers as NO production and CD40 in comparison with LPS condition. More importantly, mice pre-treated with DZ and then challenged to LPS induced-septic shock showed reduced death. The DZ treatment shifted the LPS-induced pro-inflammatory cytokine production of peritoneal cells (PCs) to an anti-inflammatory profile commanded by IL-10. In agreement with this, DZ treatment prevented LPS-induced DC ability to initiate allogeneic Th1 and Th17 responses in vitro when compared with LPS-matured DC. Since these inflammatory responses are the key in the development of the experimental autoimmune encephalomyelitis (EAE), we treated EAE mice preventively with DZ. Mice that received DZ showed amelioration of clinical signs and immunological parameters of the disease. Additionally, DZ reduced the release of IFN-γ and IL-17 by splenocytes from untreated sick mice in vitro. For this reason, we decided to treat diseased mice therapeutically with DZ when they reached the clinical score of 1. Most importantly, this treatment ameliorated clinical signs, reduced the MOG-specific inflammatory cytokine production and prevented axonal damage. Altogether, these results indicate that DZ is a potent immunomodulator capable of controlling undesired innate and adaptive immune responses, both at the beginning of these responses and also once they have started.

The Role of the GABAergic System in Diseases of the Central Nervous System

It is well known that the central nervous system (CNS) is a complex neuronal network and its function depends on the balance between excitatory and inhibitory neurons. Disruption of the excitatory/inhibitory (E/I) balance is the main cause for the majority of the CNS diseases. In this review, we will discuss roles of the inhibitory system in the CNS diseases. The GABAergic system as the main inhibitory system, is essential for the appropriate functioning of the CNS, especially as it is engaged in the formation of learning and memory. Many researchers have reported that the GABAergic system is involved in regulating synaptic plasticity, cognition and long-term potentiation. Some clinical manifestations (such as cognitive dysfunctions, attention deficits, etc.) have also been shown to emerge after abnormalities in the GABAergic system accompanied with concomitant diseases, that include Alzheimer's disease (AD), Parkinson's disease (PD), Autism spectrum disorder (ASD), Schizophrenia, etc. The GABAergic system consists of GABA, GABA transporters, GABAergic receptors and GABAergic neurons. Changes in any of these components may contribute to the dysfunctions of the CNS. In this review, we will synthesize studies which demonstrate how the GABAergic system participates in the pathogenesis of the CNS disorders, which may provide a new idea that might be used to treat the CNS diseases.

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.

Transcriptomic Analysis of the Effect of GAT-2 Deficiency on Differentiation of Mice Naïve T Cells Into Th1 Cells In Vitro

The neurotransmitter γ-aminobutyric acid (GABA) is known to affect the activation and function of immune cells. This study investigated the role of GABA transporter (GAT)-2 in the differentiation of type 1 helper T (Th1) cells. Naïve CD4+ T cells isolated from splenocytes of GAT-2 knockout (KO) and wild-type (WT) mice were cultured; Th1 cell differentiation was induced and transcriptome and bioinformatics analyses were carried out. We found that GAT-2 deficiency promoted the differentiation of naïve T cells into Th1 cells. RNA sequencing revealed 2984 differentially expressed genes including 1616 that were up-regulated and 1368 that were down-regulated in GAT-2 KO cells compared to WT cells, which were associated with 950 enriched Gene Ontology terms and 33 enriched Kyoto Encyclopedia of Genes and Genomes pathways. Notably, 4 signal transduction pathways (hypoxia-inducible factor [HIF]-1, Hippo, phospholipase D, and Janus kinase [JAK]/signal transducer and activator of transcription [STAT]) and one metabolic pathway (glycolysis/gluconeogenesis) were significantly enriched by GAT-2 deficiency, suggesting that these pathways mediate the effect of GABA on T cell differentiation. Our results provide evidence for the immunomodulatory function of GABA signaling in T cell-mediated immunity and can guide future studies on the etiology and management of autoimmune diseases.

Contribution of Gut Microbiota to Immunological Changes in Alzheimer's Disease

Emerging evidence suggests that both central and peripheral immunological processes play an important role in the pathogenesis of Alzheimer's disease (AD), but regulatory mechanisms remain unknown. The gut microbiota and its key metabolites are known to affect neuroinflammation by modulating the activity of peripheral and brain-resident immune cells, yet an overview on how the gut microbiota contribute to immunological alterations in AD is lacking. In this review, we discuss current literature on microbiota composition in AD patients and relevant animal models. Next, we highlight how microbiota and their metabolites may contribute to peripheral and central immunological changes in AD. Finally, we offer a future perspective on the translation of these findings into clinical practice by targeting gut microbiota to modulate inflammation in AD. Since we find that gut microbiota alterations in AD can induce peripheral and central immunological changes via the release of microbial metabolites, we propose that modulating their composition may alter ongoing inflammation and could therefore be a promising future strategy to fight progression of AD.

An investigation of the anti-inflammatory effects of gabapentin on acetic acid-induced colitis in rats

Inflammatory bowel disease (IBD) is considered a chronic inflammatory gastrointestinal disease with treatment options which exhibit low efficacies and lead to considerable side effects. Hence, the challenge to alleviate IBD complications is remained to be resolved. The purpose of this study is evaluating anti-inflammatory impacts of gabapentin on acetic acid-induced colitis in rats. Colitis was induced by the instillation of 2 mL of 3% acetic acid solution into rat's colons. Rats were randomly allocated into six groups including normal group, colitis control group, gabapentin-treated groups (25, 50, and 100 mg/kg; i.p.), and dexamethasone-treated group (1 mg/kg; i.p.). Based on the macroscopic assessment besides histological and biochemical findings [myeloperoxidase (MPO), pro-inflammatory cytokines], the efficacy of gabapentin was investigated. Gabapentin (50 and 100 mg/kg), and dexamethasone considerably reduced macroscopic and microscopic colonic lesions induced by acetic acid in rats in comparison with colitis control group. These results were confirmed by reduced levels of MPO activity and colonic concentrations of interleukin-6, interleukin-1 beta, and tumor necrosis factor-alpha, in inflamed colon tissue. Our data demonstrated that gabapentin exerts profitable impacts in experimental colitis that might be ascribed to its anti-inflammatory features and thus can be a potential therapeutic agent for IBD treatment.

Positivity of oligoclonal bands in the cerebrospinal fluid predisposed to metabolic changes and rearrangement of inhibitory/excitatory neurotransmitters in subcortical brain structures in multiple sclerosis

BACKGROUND

The latest diagnostic criteria for multiple sclerosis (MS) have revitalized the role of oligoclonal bands synthesis in the cerebrospinal fluid (CSF-OCB). This study identifies predictors of CSF-OCB-positivity among in vivo metabolic markers in the subcortical gray/white matter in MS patients after their first episode (CIS) and in patients with relapsing-remitting course (RRMS).

METHODS

The study enrolled 13 CIS and 23 RRMS patients. Metabolism was evaluated using Mescher-Garwood-edited proton-magnetic resonance spectroscopy on a 3T MR scanner. In addition to N-acetyl-aspartate (tNAA), myoinositol (mIns), and choline- and creatine compounds (tCho, tCr) were also evaluated γ-aminobutyric acid (GABA) and glutamate-glutamine (Glx) ratios.

RESULTS

CSF-OCB-positivity was found in 76.9% of CIS and 78.2% of RRMS patients. GABA and Glx ratios in putamen and corpus callosum strongly determined CSF-OCB-positive CIS patients. Other essential predictors of CSF-OCB-positive CIS were mIns and Glx ratios in the putamen, and tCho/tNAA in the corpus callosum. In RRMS, GABA ratios in the right thalamus and Glx ratios in the left hippocampus strongly predicted CSF-OCB-positive patients. tCho/tNAA and tNAA/tCr in the left hippocampus were also identified as essential predictors of CSF-OCB-positive RRMS patients.

CONCLUSION

This is the first in vivo evidence of GABA-Glx rearrangement in CSF-OCB-positive patients since its early stages of MS.

Expression profiles and potential functions of long noncoding RNAs and mRNAs in autoimmune pulmonary alveolar proteinosis patients

Autoimmune pulmonary alveolar proteinosis (APAP) is a rare lung disease that may be associated with surfactant overaccumulation. To assess the function of long noncoding RNAs (lncRNAs) in APAP, we performed microarray analyses to identify differentially expressed (DE) lncRNAs and mRNAs between peripheral blood samples from five APAP patients and five healthy volunteers. In total, 12459 DE lncRNAs and 9331 DE mRNAs were identified in APAP patient samples. A qRT-PCR validation of 20 DE lncRNAs and 20 mRNAs indicated that 12 DE lncRNAs may be involved in the pathogenesis of APAP. Coding and noncoding co-expression (CNC) and competing endogenous RNA (ceRNA) regulatory networks were constructed with these 12 DE lncRNAs. Gene Ontology analysis of the downregulated mRNAs and the CNC network revealed that “ubiquitin-like protein transferase activity” was suppressed in APAP patient samples. Kyoto Encyclopedia of Genes and Genomes analysis demonstrated that the “MAPK signaling pathway” was enriched in the ceRNA network. Gene Ontology analysis also indicated that mRNAs involved in many transmembrane ion transport processes were upregulated in APAP patients. The DE lncRNAs and mRNAs discovered in this study have elucidated the pathogenesis of APAP, and the CNC and ceRNA networks have provided novel insights for future functional research.

GABA transporter sustains IL-1β production in macrophages

Accumulating evidence shows that nervous system governs host immune responses; however, how γ-aminobutyric acid (GABA)ergic system shapes the function of innate immune cells is poorly defined. Here, we demonstrate that GABA transporter (GAT2) modulates the macrophage function. GAT2 deficiency lowers the production of interleukin-1β (IL-1β) in proinflammatory macrophages. Mechanistically, GAT2 deficiency boosts the betaine/S-adenosylmethionine (SAM)/hypoxanthine metabolic pathway to inhibit transcription factor KID3 expression through the increased DNA methylation in its promoter region. KID3 regulates oxidative phosphorylation (OXPHOS) via targeting the expression of OXPHOS-related genes and is also critical for NLRP3-ASC-caspase-1 complex formation. Likewise, GAT2 deficiency attenuates macrophage-mediated inflammatory responses in vivo, including lipopolysaccharide-induced sepsis, infection-induced pneumonia, and high-fat diet-induced obesity. Together, we propose that targeting GABAergic system (e.g., GABA transporter) could provide previously unidentified therapeutic opportunities for the macrophage-associated diseases.

Development and validation of a UPLC-MS/MS method for the simultaneous determination of gamma-aminobutyric acid and glutamic acid in human plasma

Gamma-aminobutyric acid (GABA) and its precursor glutamic acid are important neurotransmitters. Both are also present in peripheral tissues and the circulation, where abnormal plasma concentrations have been linked to specific mental disorders. In addition to endogenous synthesis, GABA and glutamic acid can be obtained from dietary sources. An increasing number of studies suggest beneficial cardio-metabolic effects of GABA intake, and therefore GABA is being marketed as a food supplement. The need for further research into their health effects merits accurate and sensitive methods to analyze GABA and glutamic acid in plasma. To this end, an ultra-pressure liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the quantification of GABA and glutamic acid in human plasma. Samples were prepared by a protein precipitation step and subsequent solid phase extraction using acetonitrile. Chromatographic separation was achieved on an Acquity UPLC HSS reversed phase C18 column using gradient elution. Analytes were detected using electrospray ionization and selective reaction monitoring. Standard curve concentrations for GABA ranged from 3.4 to 2500 ng/mL and for glutamic acid from 30.9 ng/mL to 22,500 ng/mL. Within- and between-day accuracy and precision were <10% in quality control samples at low, medium and high concentrations for both GABA and glutamic acid. GABA and glutamic acid were found to be stable in plasma after freeze-thaw cycles and up to 12 months of storage. The validated method was applied to human plasma from 17 volunteers. The observed concentrations ranged between 11.5 and 20.0 ng/ml and 2269 and 7625 ng/ml for respectively GABA and glutamic acid. The reported method is well suited for the measurement of plasma GABA and glutamic acid in pre-clinical or clinical studies.

Retrospective Observational Study of Daytime Add-On Administration of Zopiclone to Difficult-to-Treat Psychiatric Inpatients With Unpredictable Aggressive Behavior, With or Without EEG Dysrhythmia

Managing violent behavior is a particularly challenging aspect of hospital psychiatric care. Available pharmacological interventions are often unsatisfactory. Aim: To assess the effectiveness and safety of daytime zopiclone add-on administration in violent and difficult-to-treat psychiatric inpatients. Methods: Chart review of inpatients treated with daytime zopiclone, between 2014 and 2018, with up to 12 weeks follow-up. Effectiveness was retrospectively assessed with the Clinical Global Impression rating scale (CGI) and the frequency and severity of aggressive incidents recorded with the Staff Observation Aggression Scale-Revised (SOAS-R). Results: Forty-five (30 male, 15 female) cases, 18-69 years age range, average (SD) baseline CGI-S score of 5.4 (1.0), and a variety of diagnoses. Sixty-nine percent showed CGI-S improvement of any degree. For patients with at least one aggressive incident within 7 days prior to initiation of zopiclone (N = 22), average (SD) SOAS-R-Severity LOCF to baseline change was -3.5 (2.7) P < 0.0001. Most patients reported no side effects; 24% reported one or more side effects, and 11% discontinued zopiclone due to sedation (4), insomnia (1) or slurred speech (1). No SAEs were recorded. Zopiclone maximum daily dose correlated with CGI-S baseline-to-LOCF change (rho = -0.5, P = 0.0003). The ROC AUC of zopiclone maximum daily dose and improvement on CGI-S was 0.84 (95% CI 0.70-0.93, P < 0.0001). The ROC AUC of zopiclone maximum daily dose and SOAS-R-N improvement was 0.80 (95% CI 0.58-0.92; P = 0.0008) and maximum Youden's index value was achieved at a dose of >30 mg. Conclusions: Zopiclone doses >30 mg daily achieved the best anti-aggressive effect.

A Benzodiazepine Ligand with Improved GABAA Receptor α5-Subunit Selectivity Driven by Interactions with Loop C

The family of GABA_A receptors is an important drug target group in the treatment of sleep disorders, anxiety, epileptic seizures, and many others. The most frequent GABA_A receptor subtype is composed of two α-, two β-, and one γ2-subunit, whereas the nature of the α-subunit critically determines the properties of the benzodiazepine binding site of those receptors. Nearly all of the clinically relevant drugs target all GABA_A receptor subtypes equally. In the past years, however, drug development research has focused on studying α5-containing GABA_A receptors. Beyond the central nervous system, α5-containing GABA_A receptors in airway smooth muscles are considered as an emerging target for bronchial asthma. Here, we investigated a novel compound derived from the previously described imidazobenzodiazepine SH-053-2'F-R-CH3 (SH53d-ester). Although SH53d-ester is only moderately selective for α5-subunit-containing GABA_A receptors, the derivative SH53d-acid shows superior (>40-fold) affinity selectivity and is a positive modulator. Using two-electrode voltage clamp electrophysiology in Xenopus laevis oocytes and radioligand displacement assays with human embryonic kidney 293 cells, we demonstrated that an acid group as substituent on the imidazobenzodiazepine scaffold leads to large improvements of functional and binding selectivity for α5β3γ2 over other αxβ3γ2 GABA_A receptors. Atom level structural studies provide hypotheses for the improved affinity to this receptor subtype. Mutational analysis confirmed the hypotheses, indicating that loop C of the GABA_A receptor α-subunit is the dominant molecular determinant of drug selectivity. Thus, we characterize a promising novel α5-subunit-selective drug candidate. SIGNIFICANCE STATEMENT: In the current study we present the detailed pharmacological characterization of a novel compound derived from the previously described imidazobenzodiazepine SH-053-2'F-R-CH3. We describe its superior (>40-fold) affinity selectivity for α5-containing GABA_A receptors and show atom-level structure predictions to provide hypotheses for the improved affinity to this receptor subtype. Mutational analysis confirmed the hypotheses, indicating that loop C of the GABA_A receptor α-subunit is the dominant molecular determinant of drug selectivity.

A Targeted Bioinformatics Assessment of Adrenocortical Carcinoma Reveals Prognostic Implications of GABA System Gene Expression

Adrenocortical carcinoma (ACC) is a rare but deadly cancer for which few treatments exist. Here, we have undertaken a targeted bioinformatics study of The Cancer Genome Atlas (TCGA) ACC dataset focusing on the 30 genes encoding the γ-aminobutyric acid (GABA) system—an under-studied, evolutionarily-conserved system that is an emerging potential player in cancer progression. Our analysis identified a subset of ACC patients whose tumors expressed a distinct GABA system transcriptome. Transcript levels of ABAT (encoding a key GABA shunt enzyme), were upregulated in over 40% of tumors, and this correlated with several favorable clinical outcomes including patient survival; while enrichment and ontology analysis implicated two cancer-related biological pathways involved in metastasis and immune response. The phenotype associated with ABAT upregulation revealed a potential metabolic heterogeneity among ACC tumors associated with enhanced mitochondrial metabolism. Furthermore, many GABA_A receptor subunit-encoding transcripts were expressed, including two (GABRB2 and GABRD) prognostic for patient survival. Transcripts encoding GABA_B receptor subunits and GABA transporters were also ubiquitously expressed. The GABA system transcriptome of ACC tumors is largely mirrored in the ACC NCI-H295R cell line, suggesting that this cell line may be appropriate for future functional studies investigating the role of the GABA system in ACC cell growth phenotypes and metabolism.

Discovery of a new class of orthosteric antagonists with nanomolar potency at extrasynaptic GABAA receptors

Brain GABA_Α receptors are ionotropic receptors belonging to the class of Cys-loop receptors and are important drug targets for the treatment of anxiety and sleep disorders. By screening a compound library (2,112 compounds) at recombinant human α₄β₁δ GABA_Α receptors heterologously expressed in a HEK cell line, we identified a scaffold of spirocyclic compounds with nanomolar antagonist activity at GABA_Α receptors. The initial screening hit 2027 (IC₅₀ of 1.03 μM) was used for analogue search resulting in 018 (IC₅₀ of 0.088 μM). 018 was most potent at α_3,4,5-subunit containing receptors, thus showing preference for forebrain-expressed extrasynaptic receptors. Schild analysis of 018 at recombinant human α₄β₁δ receptors and displacement of [³H]muscimol binding in rat cortical homogenate independently confirmed a competitive profile. The antagonist profile of 018 was further validated by whole-cell patch-clamp electrophysiology, where kinetic studies revealed a slow dissociation rate and a shallow hill slope was observed. Membrane permeability studies showed that 2027 and 018 do not cross membranes, thus making the compounds less attractive for studying central GABA_Α receptors effects, but conversely more attractive as tool compounds in relation to emerging peripheral GABA_Α receptor-mediated effects of GABA e.g. in the immune system.

The unicellular eukaryotic parasite Toxoplasma gondii hijacks the migration machinery of mononuclear phagocytes to promote its dissemination

Toxoplasma gondii is an obligate intracellular protozoan with the ability to infect virtually any type of nucleated cell in warm-blooded vertebrates including humans. Toxoplasma gondii invades immune cells, which the parasite employs as shuttles for dissemination by a Trojan horse mechanism. Recent findings are starting to unveil how this parasite orchestrates the subversion of the migratory functions of parasitised mononuclear phagocytes, especially dendritic cells (DCs) and monocytes. Here, we focus on how T. gondii impacts host cell signalling that regulates leukocyte motility and systemic migration in tissues. Shortly after active parasite invasion, DCs undergo mesenchymal-to-amoeboid transition and adopt a high-speed amoeboid mode of motility. To trigger migratory activation - termed hypermigratory phenotype - T. gondii induces GABAergic signalling, which results in calcium fluxes mediated by voltage-gated calcium channels in parasitised DCs and brain microglia. Additionally, a TIMP-1-CD63-ITGB1-FAK signalling axis and signalling via the receptor tyrosine kinase MET promotes sustained hypermigration of parasitised DCs. Recent reports show that the activated signalling pathways converge on the small GTPase Ras to activate the MAPK Erk signalling cascade, a central regulator of cell motility. To date, three T. gondii-derived putative effector molecules have been linked to hypermigration: Tg14-3-3, TgWIP and ROP17. Here, we discuss their impact on the hypermigratory phenotype of phagocytes. Altogether, the emerging concept suggests that T. gondii induces metastasis-like migratory properties in parasitised mononuclear phagocytes to promote infection-related dissemination.

γ-Aminobutyric acid and related amino acids in plant immune responses: Emerging mechanisms of action

The entanglement between primary metabolism regulation and stress responses is a puzzling and fascinating theme in plant sciences. Among the major metabolites found in plants, γ-aminobutyric acid (GABA) fulfils important roles in connecting C and N metabolic fluxes through the GABA shunt. Activation of GABA metabolism is known since long to occur in plant tissues following biotic stresses, where GABA appears to have substantially different modes of action towards different categories of pathogens and pests. While it can harm insects thanks to its inhibitory effect on the neuronal transmission, its capacity to modulate the hypersensitive response in attacked host cells was proven to be crucial for host defences in several pathosystems. In this review, we discuss how plants can employ GABA's versatility to effectively deal with all the major biotic stressors, and how GABA can shape plant immune responses against pathogens by modulating reactive oxygen species balance in invaded plant tissues. Finally, we discuss the connections between GABA and other stress-related amino acids such as BABA (β-aminobutyric acid), glutamate and proline.

Critical Neurotransmitters in the Neuroimmune Network

Immune cells rely on cell-cell communication to specify and fine-tune their responses. They express an extensive network of cell communication modes, including a vast repertoire of cell surface and transmembrane receptors and ligands, membrane vesicles, junctions, ligand and voltage-gated ion channels, and transporters. During a crosstalk between the nervous system and the immune system these modes of cellular communication and the downstream signal transduction events are influenced by neurotransmitters present in the local tissue environments in an autocrine or paracrine fashion. Neurotransmitters thus influence innate and adaptive immune responses. In addition, immune cells send signals to the brain through cytokines, and are present in the brain to influence neural responses. Altered communication between the nervous and immune systems is emerging as a common feature in neurodegenerative and immunopathological diseases. Here, we present the mechanistic frameworks of immunostimulatory and immunosuppressive effects critical neurotransmitters - dopamine (3,4-dihydroxyphenethylamine), serotonin (5-hydroxytryptamine), substance P (trifluoroacetate salt powder), and L-glutamate - exert on lymphocytes and non-lymphoid immune cells. Furthermore, we discuss the possible roles neurotransmitter-driven neuroimmune networks play in the pathogenesis of neurodegenerative disorders, autoimmune diseases, cancer, and outline potential clinical implications of balancing neuroimmune crosstalk by therapeutic modulation.

The effect of repetitive exposure to intravenous anesthetic agents on the immunity in mice

Introduction: This study was designed to assess the effect of repetitive exposure to intravenous anesthetic agents on the immunity in mice. Materials and Methods: The mice were divided into six groups: three intravenous anesthetic agents groups (dexmedetomidine, midazolam and propofol groups), and three corresponding control groups (C_D, C_M, and C_P groups). The intravenous injections were administered once per day for 5 days. The immunity of mice was checked after the last intravenous injection. Histopathology and immunochemistry of liver and kidneys were evaluated. Cytokine levels in the blood was also checked. vs. evaluated with cytokine levels in the blood. Results: Cluster of differentiation (CD)4⁺ T cells were significantly less expressed in dexmedetomidine and propofol groups, compared with the corresponding control groups [34.08 ± 5.63% in the dexmedetomidine group vs. 59.74 ± 8.64% in the C_D group, p < 0.05; 25.28 ± 7.28% in the propofol group vs. 61.12 ± 2.70% in the C_p group, p < 0.05]. Apoptosis of CD4⁺ T cells was increased significantly in dexmedetomidine and propofol groups, compared with the corresponding control groups. Histopathological findings of liver and kidneys did not show any specific differences of any of three intravenous anesthetic agents groups with their corresponding control groups, although immunohistochemical examination indicated significantly lower expression of Toll-like receptor-4 from liver and kidneys in dexmedetomidine and propofol groups. The cytokine levels were not different between the groups. Conclusion: Repetitive exposure to dexmedetomidine and propofol reduced the expression of CD4⁺ T cells but did not induce any significant liver or kidney injuries.

Depression, GABA, and Age Correlate with Plasma Levels of Inflammatory Markers

Immunomodulation is increasingly being recognised as a part of mental diseases. Here, we examined whether levels of immunological protein markers changed with depression, age, or the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). An analysis of plasma samples from patients with a major depressive episode and control blood donors (CBD) revealed the expression of 67 inflammatory markers. Thirteen of these markers displayed augmented levels in patients compared to CBD. Twenty-one markers correlated with the age of the patients, whereas 10 markers correlated with the age of CBD. Interestingly, CST5 and CDCP1 showed the strongest correlation with age in the patients and CBD, respectively. IL-18 was the only marker that correlated with the MADRS-S scores of the patients. Neuronal growth factors (NGFs) were significantly enhanced in plasma from the patients, as was the average plasma GABA concentration. GABA modulated the release of seven cytokines in anti-CD3-stimulated peripheral blood mononuclear cells (PBMCs) from the patients. The study reveals significant changes in the plasma composition of small molecules during depression and identifies potential peripheral biomarkers of the disease.

Mechanism and effects of pulsatile GABA secretion from cytosolic pools in the human beta cell

Pancreatic beta cells synthesize and secrete the neurotransmitter γ-aminobutyric acid (GABA) as a paracrine and autocrine signal to help regulate hormone secretion and islet homeostasis. Islet GABA release has classically been described as a secretory vesicle-mediated event. Yet, a limitation of the hypothesized vesicular GABA release from islets is the lack of expression of a vesicular GABA transporter in beta cells. Consequentially, GABA accumulates in the cytosol. Here we provide evidence that the human beta cell effluxes GABA from a cytosolic pool in a pulsatile manner, imposing a synchronizing rhythm on pulsatile insulin secretion. The volume regulatory anion channel (VRAC), functionally encoded by LRRC8A or Swell1, is critical for pulsatile GABA secretion. GABA content in beta cells is depleted and secretion is disrupted in islets from type 1 and type 2 diabetic patients, suggesting that loss of GABA as a synchronizing signal for hormone output may correlate with diabetes pathogenesis.