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

A neuroimmune pathway drives bacterial infection

Pathogen-induced septic death presents a substantial public health challenge, with its neuroimmune mechanisms largely unexplored. Our study investigates neurotransmitter modulation of ACOD1 expression, a regulator of immunometabolism activated by bacterial lipopolysaccharide (LPS). Screening neurotransmitters identifies dopamine as a potent inhibitor of LPS-induced ACOD1 expression in innate immune cells. Mechanistically, DRD2 forms a complex with TLR4, initiating MAPK3-dependent CREB1 phosphorylation and subsequent ACOD1 transcription. Conversely, dopamine disrupts TLR4-MYD88 interaction via DRD2 without affecting the formation of the LPS-induced TLR4-MD2-CD14 complex. Enhanced ACOD1 expression induces CD274/PD-L1 production independently of itaconate, precipitating inflammation-associated immunosuppression in sepsis. Delayed administration of pramipexole, a dopamine agonist, mitigates lethality in bacterial sepsis mouse models. Conversely, the dopamine antagonist aripiprazole exacerbates sepsis mortality. Dysregulation of the dopamine-ACOD1 axis correlates with sepsis severity in patients, indicating a potential therapeutic target for modulating this neuroimmune pathway.

Proteostasis regulation of GABAA receptors in neuronal function and disease

The γ-aminobutyric acid type A receptors (GABAARs) are ligand-gated anion channels that mediate fast inhibitory neurotransmission in the mammalian central nervous system. GABAARs form heteropentameric assemblies comprising two α1, two β2, and one γ2 subunits as the most common subtype in mammalian brains. Proteostasis regulation of GABAARs involves subunit folding within the endoplasmic reticulum, assembling into heteropentamers, receptor trafficking to the cell surface, and degradation of terminally misfolded subunits. As GABAARs are surface proteins, their trafficking to the plasma membrane is critical for proper receptor function. Thus, variants in the genes encoding GABAARs that disrupt proteostasis result in various neurodevelopmental disorders, ranging from intellectual disability to idiopathic generalized epilepsy. This review summarizes recent progress about how the proteostasis network regulates protein folding, assembly, degradation, trafficking, and synaptic clustering of GABAARs. Additionally, emerging pharmacological approaches that restore proteostasis of pathogenic GABAAR variants are presented, providing a promising strategy to treat related neurological diseases.

Metabolomic analysis of murine tissues infected with Brucella melitensis

Brucella is a gram negative, facultative intracellular bacterial pathogen that constitutes a substantial threat to human and animal health. Brucella can replicate in a variety of tissues and can induce immune responses that alter host metabolite availability. Here, mice were infected with B. melitensis and murine spleens, livers, and female reproductive tracts were analyzed by GC-MS to determine tissue-specific metabolic changes at one-, two- and four- weeks post infection. The most remarkable changes were observed at two-weeks post-infection when relative to uninfected tissues, 42 of 329 detected metabolites in reproductive tracts were significantly altered by Brucella infection, while in spleens and livers, 68/205 and 139/330 metabolites were significantly changed, respectively. Several of the altered metabolites in host tissues were linked to the GABA shunt and glutaminolysis. Treatment of macrophages with GABA did not alter control of B. melitensis infection, and deletion of the putative GABA transporter BMEI0265 did not alter B. melitensis virulence. While glutaminolysis inhibition did not affect control of B. melitensis in macrophages, glutaminolysis was required for macrophage IL-1β production in response to B. melitensis. In summary, these results indicate that Brucella infection alters host tissue metabolism and that these changes could have effects on inflammation and the outcome of infection.

The Perinatal Microbiota-Gut-Brain Axis: Implications for Postpartum Depression

BACKGROUND

Pregnancy and childbirth are accompanied by widespread maternal physiological adaptations and hormonal shifts that have been suggested to result in a period of vulnerability for the development of mood disorders such as postpartum depression (PPD). There is also evidence of peripartum changes in the composition of the gut microbiota, but the potential contribution of intestinal microbes to the adaptations, or subsequent vulnerabilities, during this period are unknown.

SUMMARY

Here, we outline key pathways involved in peripartum adaptations including GABAergic signaling, oxytocin, and immunomodulation that are also associated with susceptibility to mood disorders and present evidence that these pathways are modulated by gut microbes. We also discuss the therapeutic potential of the microbiota-gut-brain axis in PPD and identify future directions for research to help realize this potential.

KEY MESSAGES

Peripartum adaptations are associated with shifts in gut microbial composition. Disruption of GABAergic, oxytocin, and immunomodulatory pathways may contribute to vulnerability of mood disorders including PPD. These key adaptive pathways are modulated by intestinal microbes suggesting a role for the gut microbiota in determining susceptibility to PPD. More research is needed to confirm relationship between gut microbes and PPD and to gain the mechanistic understanding required to realize the therapeutic potential of microbiota-gut-brain axis in this mood disorder.

Legionella pneumophila subverts the antioxidant defenses of its amoeba host Acanthamoeba castellanii

Legionella pneumophila, the causative agent of Legionnaires' disease, interacts in the environment with free-living amoebae that serve as replicative niches for the bacteria. Among these amoebae, Acanthamoeba castellanii is a natural host in water networks and a model commonly used to study the interaction between L. pneumophila and its host. However, certain crucial aspects of this interaction remain unclear. One such aspect is the role of oxidative stress, with studies focusing on reactive oxygen species (ROS) production by the host and putting less emphasis on the involvement of the host's antioxidant defenses during the infectious process. In this study, we propose to examine the consequences of infection with L. pneumophila wild-type or with an isogenic ΔdotA mutant strain, which is unable to replicate intracellularly, on A. castellanii. For this purpose, we looked at the host ROS levels, host antioxidant defense transcripts, and metabolites linked to the amoeba's antioxidant defenses. It is known that L. pneumophila WT can block the activation of NADPH oxidase as soon as it enters the macrophage and suppress ROS production compared to ΔdotA mutant strain. In addition, it has been shown in macrophages that L. pneumophila WT decreases ROS at 24 h p.i.; here we confirm this result in amoebae and suggest that this decrease could be partly explained by L. pneumophila differentially regulated host antioxidant defense transcripts at 6 h p.i.. We also explored the metabolome of A. castellanii infected or not with L. pneumophila. Among the 617 metabolites identified, four with reduced abundances during infection may be involved in antioxidant responses. This study suggests that L. pneumophila could hijack the host's antioxidant defenses during its replication to maintain a reduced level of ROS.

Piezo1 Enhances Macrophage Phagocytosis and Pyrin Activation to Ameliorate Fungal Keratitis

Purpose

Fungal keratitis (FK) remains a treatment challenge, necessitating new therapeutic targets. Piezo1, a mechanosensitive ion channel, regulates calcium signaling and immune cell function. This study investigates its role in macrophage-mediated antifungal responses in FK.

Methods

Piezo1 and Pyrin expression in corneas and bone marrow-derived macrophages (BMDMs) were assessed by RNAseq, quantitative real-time PCR (qRT-PCR), Western blot, and immunofluorescence. Intracellular calcium ion concentration was detected by Fluo-4 AM fluorescent probe staining. Heterozygous Piezo1 deficiency (Piezo1+/-) mice and Yoda1 were performed to regulate the expression of Piezo1.

Results

Our investigation demonstrates elevated expression of Piezo1 in the corneas of patients with FK and infected mice. This upregulation of Piezo1 corresponded with the swift recruitment of macrophages via the limbus. Additionally, Piezo1+/- mice exacerbate the progression of FK in the infection model. Furthermore, Piezo1 knockdown in macrophages exhibit a notable reduction phagocytic capacity, accompanied by an increase in viable colony-forming units in an in vitro model of fungal infection. Moreover, using a pharmacologic activator of Piezo1 (Yoda1), a calcium ion (Ca2+) chelator of BAPTA or Piezo1+/- mice, we demonstrate that Piezo1 activation triggers the Pyrin inflammasome via augmented calcium ion influx, which is required for protection against FK in murine hosts.

Conclusions

Piezo1 is crucial for innate immunity in FK, enhancing macrophage recruitment, activation, and Pyrin inflammasome-mediated antifungal activity via calcium signaling. Using Piezo1+/- mice and Yoda1, we confirm Piezo1's role in fungal clearance. Targeting Piezo1 offers a novel strategy to improve FK outcomes by boosting macrophage function and immune response.

Analysis and identification of ferroptosis-related diagnostic markers in rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune, inflammatory joint disease. There is growing evidence that ferroptosis is involved in the pathogenesis of RA. This study aimed to search for diagnostic markers of ferroptosis in RA and to analyse the potential mechanisms and clinical value.

MATERIALS AND METHODS

RA-associated datasets were used from the publicly available GEO database. Three methods of machine learning were applied to screen biomarkers. The diagnostic efficacy of the results was also verified by receiver operating characteristic (ROC) curve, external dataset, qRT-PCR and Western blot. Enrichment analysis was performed in this process, while protein-protein interaction (PPI) analysis and immune infiltration correlation analysis were performed using biomarkers, and competing endogenous RNA (ceRNA) networks were constructed to search for prospective therapeutic targets.

RESULTS

MMP13 and GABARAPL1 can be used as ferroptosis diagnostic genes in RA. The ROC curve and PPI result demonstrated that MMP13 and GABARAPL1 had an excellent diagnostic value. The results of signature genes in the external dataset, qRT-PCR and Western blot further confirm our findings. The enrichment analysis showed that p53, MAPK and NOD-like receptor signalling pathways may be involved in the process of ferroptosis in RA. In addition, two ferroptosis diagnostic genes in RA participate in the occurrence of ferroptosis in RA via oxidative stress, metabolism and immune response. Immune infiltration analysis showed that RA extensively infiltrated B cells, T cells, macrophages and other immune cells. Persistent immune activation may be an essential reason for the progression of ferroptosis in RA. We also obtained five potential therapeutic agents for RA and some long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) regulating ferroptosis diagnostic genes.

CONCLUSIONS

Our study suggests that MMP13 and GABARAPL1, which are closely linked with oxidative stress and immunological modulation, can be used as ferroptosis-related potential diagnostic markers in RA and provide new clues regarding the diagnostic and therapeutic targets of ferroptosis in RA.

Metabolomic Analysis of Murine Tissues Infected with Brucella melitensis

Brucella is a gram negative, facultative, intracellular bacterial pathogen that constitutes a substantial threat to human and animal health. Brucella can replicate in a variety of tissues and can induce immune responses that alter host metabolite availability. Here, mice were infected with B. melitensis and murine spleens, livers, and female reproductive tracts were analyzed by GC-MS to determine tissue-specific metabolic changes at one-, two- and four- weeks post infection. The most remarkable changes were observed at two-weeks post-infection when relative to uninfected tissues, 42 of 329 detected metabolites in reproductive tracts were significantly altered by Brucella infection, while in spleens and livers, 68/205 and 139/330 metabolites were significantly changed, respectively. Several of the altered metabolites in host tissues were linked to the GABA shunt and glutaminolysis. Treatment of macrophages with GABA did not alter control of B. melitensis infection, and deletion of the putative GABA transporter BMEI0265 did not alter B. melitensis virulence. While glutaminolysis inhibition did not affect control of B. melitensis in macrophages, glutaminolysis was required for macrophage IL-1β production in response to B. melitensis. In sum, these results indicate that Brucella infection alters host tissue metabolism and that these changes could have effects on inflammation and the outcome of infection.

Neuroscience in peripheral cancers: tumors hijacking nerves and neuroimmune crosstalk

Cancer neuroscience is an emerging field that investigates the intricate relationship between the nervous system and cancer, gaining increasing recognition for its importance. The central nervous system governs the development of the nervous system and directly affects brain tumors, and the peripheral nervous system (PNS) shapes the tumor microenvironment (TME) of peripheral tumors. Both systems are crucial in cancer initiation and progression, with recent studies revealing a more intricate role of the PNS within the TME. Tumors not only invade nerves but also persuade them through remodeling to further promote malignancy, creating a bidirectional interaction between nerves and cancers. Notably, immune cells also contribute to this communication, forming a triangular relationship that influences protumor inflammation and the effectiveness of immunotherapy. This review delves into the intricate mechanisms connecting the PNS and tumors, focusing on how various immune cell types influence nerve‒tumor interactions, emphasizing the clinical relevance of nerve‒tumor and nerve‒immune dynamics. By deepening our understanding of the interplay between nerves, cancer, and immune cells, this review has the potential to reshape tumor biology insights, inspire innovative therapies, and improve clinical outcomes for cancer patients.

Metabolic regulation of intestinal homeostasis: molecular and cellular mechanisms and diseases

Metabolism serves not only as the organism's energy source but also yields metabolites crucial for maintaining tissue homeostasis and overall health. Intestinal stem cells (ISCs) maintain intestinal homeostasis through continuous self-renewal and differentiation divisions. The intricate relationship between metabolic pathways and intestinal homeostasis underscores their crucial interplay. Metabolic pathways have been shown to directly regulate ISC self-renewal and influence ISC fate decisions under homeostatic conditions, but the cellular and molecular mechanisms remain incompletely understood. Understanding the intricate involvement of various pathways in maintaining intestinal homeostasis holds promise for devising innovative strategies to address intestinal diseases. Here, we provide a comprehensive review of recent advances in the regulation of intestinal homeostasis. We describe the regulation of intestinal homeostasis from multiple perspectives, including the regulation of intestinal epithelial cells, the regulation of the tissue microenvironment, and the key role of nutrient metabolism. We highlight the regulation of intestinal homeostasis and ISC by nutrient metabolism. This review provides a multifaceted perspective on how intestinal homeostasis is regulated and provides ideas for intestinal diseases and repair of intestinal damage.

Genome-wide screen of Mycobacterium tuberculosis-infected macrophages revealed GID/CTLH complex-mediated modulation of bacterial growth

The eukaryotic Glucose Induced Degradation/C-Terminal to LisH (GID/CTLH) complex is a highly conserved E3 ubiquitin ligase involved in a broad range of biological processes. However, a role of this complex in host anti-microbial defenses has not been described. We exploited Mycobacterium tuberculosis (Mtb) induced cytotoxicity in macrophages in a FACS based CRISPR genetic screen to identify host determinants of intracellular Mtb growth restriction. Our screen identified 5 (GID8, YPEL5, WDR26, UBE2H, MAEA) of the 12 predicted members of the GID/CTLH complex as determinants of intracellular growth of both Mtb and Salmonella serovar Typhimurium. We show that the anti-microbial properties of the GID/CTLH complex knockout macrophages are mediated by enhanced GABAergic signaling, activated AMPK, increased autophagic flux and resistance to Mtb induced necrotic cell death. Meanwhile, Mtb isolated from GID/CTLH knockout macrophages are nutritionally starved and oxidatively stressed. Our study identifies the GID/CTLH complex activity as broadly suppressive of host anti-microbial responses against intracellular bacterial infections.

Toxoplasma gondii macrophage migration inhibitory factor shows anti-Mycobacterium tuberculosis potential via AZIN1/STAT1 interaction

Mycobacterium tuberculosis (MTB) is a pathogenic bacterium, belonging to the family Mycobacteriaceae, that causes tuberculosis (TB). Toxoplasma gondii macrophage migration inhibitory factor (TgMIF), a protein homolog of macrophage migration inhibitory factor, has been explored for its potential to modulate immune responses during MTB infections. We observed that TgMIF that interacts with CD74, antizyme inhibitor 1 (AZIN1), and signal transducer and activator of transcription 1 (STAT1) modulates endocytosis, restoration of mitochondrial function, and macrophage polarization, respectively. These interactions promote therapeutic efficacy in mice infected with MTB, thereby presenting a potential route to host-directed therapy development. Furthermore, TgMIF, in combination with first-line TB drugs, significantly inhibited drug-resistant MTB strains, including multidrug-resistant TB. These results demonstrate that TgMIF is potentially a multifaceted therapeutic agent against TB, acting through immune modulation, enhancement of mitochondrial function, and dependent on STAT1 and AZIN1 pathways.

The autophagy-targeting compound V46 enhances antimicrobial responses to Mycobacteroides abscessus by activating transcription factor EB

Mycobacteroides abscessus (Mabc) is a rapidly growing nontuberculous mycobacterium that poses a considerable challenge as a multidrug-resistant pathogen causing chronic human infection. Effective therapeutics that enhance protective immune responses to Mabc are urgently needed. This study introduces trans-3,5,4'-trimethoxystilbene (V46), a novel resveratrol analogue with autophagy-activating properties and antimicrobial activity against Mabc infection, including multidrug-resistant strains. Among the resveratrol analogues tested, V46 significantly inhibited the growth of both rough and smooth Mabc strains, including multidrug-resistant strains, in macrophages and in the lungs of mice infected with Mabc. Additionally, V46 substantially reduced Mabc-induced levels of pro-inflammatory cytokines and chemokines in both macrophages and during in vivo infection. Mechanistic analysis showed that V46 suppressed the activation of the protein kinase B/Akt-mammalian target of rapamycin signaling pathway and enhanced adenosine monophosphate-activated protein kinase signaling in Mabc-infected cells. Notably, V46 activated autophagy and the nuclear translocation of transcription factor EB, which is crucial for antimicrobial host defenses against Mabc. Furthermore, V46 upregulated genes associated with autophagy and lysosomal biogenesis in Mabc-infected bone marrow-derived macrophages. The combination of V46 and rifabutin exerted a synergistic antimicrobial effect. These findings identify V46 as a candidate host-directed therapeutic for Mabc infection that activates autophagy and lysosomal function via transcription factor EB.

Evaluation of Gamma Aminobutyric Acid and Sodium Butyrate in Juvenile Red Seabream (Pagrus major) Diets Containing Graded Levels of Fish Meal and Soy Protein Concentrate

The experiment was conducted to evaluate the supplementary effects of gamma aminobutyric acid (GABA) and sodium butyrate (SB) when a graded level of fish meal (FM) was replaced with soy protein concentrate (SPC) in diets for juvenile red seabream (Pagrus major). A control diet was designed to contain 60% FM (F60). Two other diets were formulated by reducing FM levels to 40% and 20% with SPC (F40 and F20). Six more diets were formulated by adding 0.02% GABA or 0.2% SB to each F60, F40 and F20 diets (F60G, F60S, F40G, F40S, F20G and F20S). Each diet was randomly assigned to a triplicate group of fish (5.52 g/fish) and provided for eight weeks. Final body weight, weight gain and specific growth rate of fish fed F60G, F60S, F40G and F40S diets were comparable and significantly higher (p < 0.05) than other groups. The growth of fish fed SB-containing diets was significantly increased (p < 0.05) compared to fish fed the respective control diets. The feed efficiency and protein efficiency ratios were significantly higher (p < 0.05) in the fish fed all diets containing 60% and 40% FM compared to F20 and F20G groups. The F40S diet resulted in the highest feed utilization values. The F20S group exhibited significantly higher (p < 0.05) feed utilization than the F20 and F20G groups. Serum lysozyme activity was significantly higher (p < 0.05) in fish fed the GABA- and SB-containing diets compared to the F20 group. The F60S group exhibited the highest lysozyme activity which was significantly higher (p < 0.05) than in the F20 and F40 groups. Therefore, the growth performance, feed utilization and innate immunity of red seabream can be enhanced by dietary supplementation with GABA or SB in low-FM diets containing SPC. The FM level in the juvenile red seabream diet can be reduced to 40% with SPC and GABA or SB while maintaining performance better than a diet containing 60% FM.

Alleviating effect of vagus nerve cutting in Salmonella-induced gut infections and anxiety-like behavior via enhancing microbiota-derived GABA

The vagus nerve, a pivotal link within the gut-brain axis, plays a critical role in maintaining homeostasis and mediating communication between the gastrointestinal tract and the brain. It has been reported that gastrointestinal infection by Salmonella typhimurium (S. typhimurium) triggers gut inflammation and manifests as anxiety-like behaviors, yet the mechanistic involvement of the vagus nerve remains to be elucidated. In this study, we demonstrated that unilateral cervical vagotomy markedly attenuated anxiety-like behaviors induced by S. typhimurium SL1344 infection in C57BL/6 mice, as evidenced by the open field test and marble burying experiment. Furthermore, vagotomy significantly diminished neuronal activation within the nucleus of the solitary tract and amygdala, alongside mitigating aberrant glial cell activation in the hippocampus and amygdala. Additionally, vagotomy notably decreases serum endotoxin levels, counters the increase in splenic Salmonella concentration, and modulates the expression of inflammatory cytokines-including IL-6, IL-1β, and TNF-α-in both the gastrointestinal tract and brain, with a concurrent reduction in IL-22 and CXCL1 expression. This intervention also fostered the enrichment of beneficial gut microbiota, including Alistipes and Lactobacillus species, and augmented the production of gamma-aminobutyric acid (GABA) in the gut. Administration of GABA replicated the vagotomy's beneficial effects on reducing gut inflammation and anxiety-like behavior in infected mice. However, blockade of GABA receptors with picrotoxin abrogated the vagotomy's protective effects against gut inflammation, without influencing its impact on anxiety-like behaviors. Collectively, these findings suggest that vagotomy exerts a protective effect against infection by promoting GABA synthesis in the colon and alleviating anxiety-like behavior. This study underscores the critical role of the vagus nerve in relaying signals of gut infection to the brain and posits that targeting the gut-brain axis may offer a novel and efficacious approach to preventing gastrointestinal infections and associated behavioral abnormalities.

Allopregnanolone and its antagonist modulate neuroinflammation and neurological impairment

Neuroinflammation accompanies several brain disorders, either as a secondary consequence or as a primary cause and may contribute importantly to disease pathogenesis. Neurosteroids which act as Positive Steroid Allosteric GABA-A receptor Modulators (Steroid-PAM) appear to modulate neuroinflammation and their levels in the brain may vary because of increased or decreased local production or import from the systemic circulation. The increased synthesis of steroid-PAMs is possibly due to increased expression of the mitochondrial cholesterol transporting protein (TSPO) in neuroinflammatory tissue, and reduced production may be due to changes in the enzymatic activity. Microglia and astrocytes play an important role in neuroinflammation, and their production of inflammatory mediators can be both activated and inhibited by steroid-PAMs and GABA. What is surprising is the finding that both allopregnanolone, a steroid-PAM, and golexanolone, a novel GABA-A receptor modulating steroid antagonist (GAMSA), can inhibit microglia and astrocyte activation and normalize their function. This review focuses on the role of steroid-PAMs in neuroinflammation and their importance in new therapeutic approaches to CNS and liver disease.

Increased GABA signaling in liver macrophage promotes HBV replication in HBV-carrier mice

Gamma-aminobutyric acid (GABA) signals in various non-neuronal cells including hepatocytes and some immune cells. Studies, including ours, show that type A GABA receptors (GABAARs)-mediated signaling occurs in macrophages regulating tissue-specific functions. Our recent study reveals that activation of GABAARs in liver macrophages promotes their M2-like polarization and increases HBV replication in mice. This short article briefly summarizes the GABA signaling system in macrophages and discusses potential mechanisms by which GABA signaling promotes HBV replication.

Evaluation of Gamma-Aminobutyric Acid (GABA) as a Functional Feed Ingredient on Growth Performance, Immune Enhancement, and Disease Resistance in Olive Flounder (Paralichthys olivaceus) under High Stocking Density

Gamma-aminobutyric acid (GABA) is a non-protein amino acid that is found in the brain and central nervous system of animals as an inhibitory neurotransmitter. It has been shown to have a variety of physiological functions, including stress reduction and immune enhancement. This study investigated the effects of dietary supplementation with GABA on growth, serum biochemistry, innate immunity, and disease resistance in juvenile olive flounders (Paralichthys olivaceus) challenged with Edwardsiella tarda under high-stocking density. A control diet and three experimental diets were prepared, with 150 mg/kg (GABA150), 200 mg/kg (GABA200), and 250 mg/kg (GABA250) of GABA added to each diet, respectively. Each experimental diet was fed to olive flounders in triplicate with an initial weight of 12.75 g ± 0.3 g in 40 L tanks at two stocking densities: normal density (20 fish/tank) and high density (40 fish/tank). After 8 weeks of the feeding trial, growth, feed utilization, whole-body proximate compositions, blood analyses, and non-specific immune responses were measured, and challenge tests were performed. There were no significant differences in the weight gain (WG) and specific growth rate (SGR) among fish fed the GABA-supplemented diets at the two stocking densities. However, the normal-density groups showed significantly higher WG and SGR than the high-density groups (p < 0.05). There was no significant difference in feed efficiency and protein efficiency ratio among all groups. Moreover, there was no significant difference in the whole-body proximate composition analysis (p > 0.05). There were no significant differences in cortisol levels in fish fed the GABA at both densities, but the high-density group showed a significantly higher cortisol than the low-density group. Blood GABA significantly increased in a dose-dependent manner regardless of the density groups (p < 0.05). Superoxide dismutase activity showed significantly higher levels than the control group, but there was no significant effect of the stocking densities in fish fed the GABA diets (p < 0.05). Myeloperoxidase activities in fish fed the GABA200 and GABA250 diets showed significantly higher levels at both of the stocking densities (p < 0.05). Lysozyme activity was significantly higher in the GABA150 group than in the CON, GABA200, and GABA250 groups (p < 0.05). After 15 days of challenge tests with Edwardsiella tarda, the cumulative survival rates of the GABA150, GABA200, and GABA250 groups were significantly higher than that of the CON group (p < 0.05). The results suggested that the optimal dietary GABA level for juvenile olive flounder culture is 150 mg/kg, regardless of rearing density, to enhance growth, immunity, and disease resistance.

Genome-wide screen of Mycobacterium tuberculosis- infected macrophages identified the GID/CTLH complex as a determinant of intracellular bacterial growth

The eukaryotic GID/CTLH complex is a highly conserved E3 ubiquitin ligase involved in a broad range of biological processes. However, a role of this complex in host antimicrobial defenses has not been described. We exploited Mycobacterium tuberculosis ( Mtb ) induced cytotoxicity in macrophages in a FACS based CRISPR genetic screen to identify host determinants of intracellular Mtb growth restriction. Our screen identified 5 ( GID8 , YPEL5 , WDR26 , UBE2H , MAEA ) of the 10 predicted members of the GID/CTLH complex as determinants of intracellular growth of both Mtb and Salmonella serovar Typhimurium. We show that the antimicrobial properties of the GID/CTLH complex knockdown macrophages are mediated by enhanced GABAergic signaling, activated AMPK, increased autophagic flux and resistance to cell death. Meanwhile, Mtb isolated from GID/CTLH knockdown macrophages are nutritionally starved and oxidatively stressed. Our study identifies the GID/CTLH complex activity as broadly suppressive of host antimicrobial responses against intracellular bacterial infections.

Graphical abstract

Unraveling the Mechanism of Xiaochaihu Granules in Alleviating Yeast-Induced Fever Based on Network Analysis and Experimental Validation

Xiaochaihu granules (XCHG) are extensively used to treat fever. Nevertheless, the underlying mechanism remains elusive. This study aimed to explore the potential of XCHG in mitigating yeast-induced fever and the underlying metabolic pathways. The chemical composition of XCHG was ascertained using ultra-fast liquid chromatography/quadrupole-time-of-flight tandem mass spectrometry (UFLC-Q-TOF-MS/MS), followed by integrated network analysis to predict potential targets. We then conducted experimental validation using pharmacological assays and metabolomics analysis in a yeast-induced mouse fever model. The study identified 133 compounds in XCHG, resulting in the development of a comprehensive network of herb-compound-biological functional modules. Subsequently, molecular dynamic (MD) simulations confirmed the stability of the complexes, including γ-aminobutyric acid B receptor 2 (GABBR2)-saikosaponin C, prostaglandin endoperoxide synthases (PTGS2)-lobetyolin, and NF-κB inhibitor IκBα (NFKBIA)-glycyrrhizic acid. Animal experiments demonstrated that XCHG reduced yeast-induced elevation in NFKBIA's downstream regulators [interleukin (IL)-1β and IL-8], inhibited PTGS2 activity, and consequently decreased prostaglandin E2 (PGE2) levels. XCHG also downregulated the levels of 5-hydroxytryptamine (5-HT), γ-aminobutyric acid (GABA), corticotropin releasing hormone (CRH), and adrenocorticotrophin (ACTH). These corroborated the network analysis results indicating XCHG's effectiveness against fever in targeting NFKBIA, PTGS2, and GABBR2. The hypothalamus metabolomics analysis identified 14 distinct metabolites as potential antipyretic biomarkers of XCHG. In conclusion, our findings suggest that XCHG alleviates yeast-induced fever by regulating inflammation/immune responses, neuromodulation, and metabolism modules, providing a scientific basis for the anti-inflammatory and antipyretic properties of XCHG.

Postantibiotic leukocyte enhancement-mediated reduction of intracellular bacteria by macrophages

INTRODUCTION

Potentiation of the bactericidal activities of leukocytes, including macrophages, upon antibacterial agent administration has been observed for several decades and is summarized as the postantibiotic leukocyte enhancement (PALE) theory. Antibiotics-induced bacterial sensitization to leukocytes is commonly recognized as the mechanism of PALE. However, the degree of sensitization drastically varies with antibiotic classes, and little is known about whether and how the potentiation of leukocytes contributes to PALE.

OBJECTIVES

In this study, we aim to develop a mechanistic understanding of PALE by investigating the immunoregulation of traditional antibiotics on macrophages.

METHODS

Interaction models between bacteria and macrophages were constructed to identify the effects of different antibiotics on the bactericidal activities of macrophages. Oxygen consumption rate, expression of oxidases, and antioxidants were then measured to evaluate the effects of fluoroquinolones (FQs) on the oxidative stress of macrophages. Furthermore, the modulation in endoplasmic reticulum stress and inflammation upon antibiotic treatment was detected to analyze the mechanisms. At last, the peritoneal infection model was utilized to verify the PALE in vivo.

RESULTS

Enrofloxacin significantly reduced the intracellular burden of diverse bacterial pathogens through promoting the accumulation of reactive oxygen species (ROS). The upregulated oxidative response accordingly reprograms the electron transport chain with decreased production of antioxidant enzymes to reduce internalized pathogens. Additionally, enrofloxacin modulated the expression and spatiotemporal localization of myeloperoxidase (MPO) to facilitate ROS accumulation to target invaded bacteria and downregulated inflammatory response to alleviate cellular injury.

CONCLUSION

Our findings demonstrate the crucial role of leukocytes in PALE, shedding light on the development of new host-directed antibacterial therapies and the design of rational dosage regimens.

Heat-killed Prevotella intermedia promotes the progression of oral squamous cell carcinoma by inhibiting the expression of tumor suppressors and affecting the tumor microenvironment

BACKGROUND

Oral microbial dysbiosis contributes to the development of oral squamous cell carcinoma (OSCC). Our previous study showed that Prevotella intermedia (P. intermedia) were enriched in the oral mucosal surface, plaque, and saliva of patients with OSCC. Intratumoral microbiome could reshape the immune system and influence the development of various tumors. However, the invasion status of human OSCC tissues by P. intermedia and the pathway through which intratumoral P. intermedia potentiates tumor progression remain unexplored.

METHODS

P. intermedia in human OSCC or normal tissues was detected by FISH. A mouse OSCC cell line SCC7 was adopted to investigate the effects of heat-killed P. intermedia treatment on cell proliferation, invasion, and cytokine release by using CCK-8 assay, transwell invasion assay and ELISA. Moreover, we established a mouse transplanted tumor model by using SCC7 cells, injected heat-killed P. intermedia into tumor tissues, and investigated the effects of heat-killed P. intermedia on tumor growth, invasion, cytokine levels, immune cell infiltrations, and expression levels by using gross observation, H&E staining, ELISA, immunohistochemistry, mRNA sequencing, and transcriptomic analysis.

RESULTS

Our results indicated that P. intermedia were abundant in OSCC and surrounding muscle tissues. Heat-killed P. intermedia promoted SCC7 cell proliferation, invasion and proinflammatory cytokine secretions, accelerated transplanted tumor growth in mice, exacerbate muscle and perineural invasion of OSCC, elevated the serum levels of IL-17A, IL-6, TNF-α, IFN-γ, and PD-L1, induced Treg cells M2 type macrophages in mouse transplanted tumors. The data of transcriptomic analysis revealed that heat-killed P. intermedia increased the expression levels of inflammatory cytokines and chemokines while reduced the expression levels of some tumor suppressor genes in mouse transplanted tumors. Additionally, IL-17 signaling pathway was upregulated whereas GABAergic system was downregulated by heat-killed P. intermedia treatment.

CONCLUSIONS

Taken together, our results suggest that P. intermedia could inhibit the expression of tumor suppressors, alter the tumor microenvironment, and promote the progression of OSCC.

Sleep disorders cause Parkinson's disease or the reverse is true: Good GABA good night

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative brain disease due to degeneration of dopaminergic neurons (DNs) presented with motor and non-motor symptoms. PD symptoms are developed in response to the disturbance of diverse neurotransmitters including γ-aminobutyric acid (GABA). GABA has a neuroprotective effect against PD neuropathology by protecting DNs in the substantia nigra pars compacta (SNpc). It has been shown that the degeneration of GABAergic neurons is linked with the degeneration of DNs and the progression of motor and non-motor PD symptoms. GABA neurotransmission is a necessary pathway for normal sleep patterns, thus deregulation of GABAergic neurotransmission in PD could be the potential cause of sleep disorders in PD.

AIM

Sleep disorders affect GABA neurotransmission leading to memory and cognitive dysfunction in PD. For example, insomnia and short sleep duration are associated with a reduction of brain GABA levels. Moreover, PD-related disorders including rigidity and nocturia influence sleep patterns leading to fragmented sleep which may also affect PD neuropathology. However, the mechanistic role of GABA in PD neuropathology regarding motor and non-motor symptoms is not fully elucidated. Therefore, this narrative review aims to clarify the mechanistic role of GABA in PD neuropathology mainly in sleep disorders, and how good GABA improves PD. In addition, this review of published articles tries to elucidate how sleep disorders such as insomnia and REM sleep behavior disorder (RBD) affect PD neuropathology and severity. The present review has many limitations including the paucity of prospective studies and most findings are taken from observational and preclinical studies. GABA involvement in the pathogenesis of PD has been recently discussed by recent studies. Therefore, future prospective studies regarding the use of GABA agonists in the management of PD are suggested to observe their distinct effects on motor and non-motor symptoms.

CONCLUSION

There is a bidirectional relationship between the pathogenesis of PD and sleep disorders which might be due to GABA deregulation.

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.

Tumor-derived GABA promotes lung cancer progression by influencing TAMs polarization and neovascularization

BACKGROUND

Gamma-aminobutyric acid (GABA), a common neurotransmitter, has been found in various cancers but its origin and its role in the tumor immune microenvironment remains unclear.

METHODS

Here, we reported the expression of glutamate decarboxylase 1 (GAD1, converting glutamate into GABA) in lung cancer tissues based on the publicly available database, and explored the effects and underlying mechanism of GABA on lung cancer progression.

RESULTS

Compared with normal tissues, GAD1 was aberrantly overexpressed in lung adenocarcinoma (LUAD) based on TCGA database. Furthermore, the LUAD patients' overall survival was negatively correlated with the GAD1 expression levels. Our work found that a GABAa receptor inhibitor had a therapeutic effect on mouse tumors and significantly reduced tumor size and weight. Further experiments showed that GABA derived from tumor cells promoted tumor progression not by directly affecting cancer cells but by affecting macrophages polarization in the tumor microenvironment. We found that GABA inhibited the NF-κB pathway and STAT3 pathway to prevent macrophages from polarizing towards M1 type, while promoting macrophage M2 polarization by activating the STAT6 pathway. GABA was also found to promote tumor neovascularization by increasing the expression of FGF2 in macrophages.

CONCLUSIONS

These results suggest that GABA affects tumor progression by regulating macrophage polarization, and targeting GABA and its signaling pathway may represent a potential therapy for lung cancer.

Saponins of Panax japonicus ameliorates cardiac aging phenotype in aging rats by enhancing basal autophagy through AMPK/mTOR/ULK1 pathway

Heart disease is a significant health concern for elderly individuals, with heart aging being the primary cause. Recent studies have shown that autophagy can play a protective role in preventing cardiac aging. Our previous research confirmed that Chikusetsu saponin IVa, a fundamental component of Saponins of Panax japonics (SPJ), can enhance basic autophagy levels in cardiomyocyte of isoproterenol induced cardiac fibrosis mice. However, it remains unclear whether SPJ possesses a protective effect on cardiac dysfunction during the natural aging process. Rats were randomly divided into four groups: adult control group (6 months old), aging group (24 months old), aging group treated with 10 mg/kg SPJ, and aging group treated with 30 mg/kg SPJ. The heart function, blood pressure, and heart mass index (HMI) were measured. Hematoxylin and eosin staining (H&E) and Wheat Germ Agglutinin (WGA) staining were used to observe the changes in morphology, while Masson staining was used to examine collagen deposition in the rat hearts and CD45 immunohistochemistry was conducted to examine the macrophage infiltration in heart tissues. TUNEL kit was used to detect apoptosis level of cardiomyocyte, and western blot was used to evaluate autophagy-related proteins as well as AMPK/mTOR/ULK1 pathway-related markers. SPJ treatment improved the cardiac function, reduced HMI, attenuated myocardial fiber disorder, inhibited inflammatory cell infiltration, and decreased collagen deposition and cardiomyocyte apoptosis in aging rats. Additionally, SPJ treatment decreased the expression of aging-related proteins and restored the expression of autophagy-related markers. SPJ activated autophagy through the activation of AMPK, which in turn increased the phosphorylation of ULK1(Ser555), while inhibited the phosphorylation of mTOR and ULK1(Ser757). Our study demonstrates that SPJ improves the cardiac function of aging rats by enhancing basal autophagy through the AMPK/mTOR/ULK1 pathway. These results offer a theoretical foundation and empirical evidence to support the clinical advancement of SPJ in enhancing age-related cardiac dysfunction.

Mycobacterium tuberculosis: Pathogenesis and therapeutic targets

Tuberculosis (TB) remains a significant public health concern in the 21st century, especially due to drug resistance, coinfection with diseases like immunodeficiency syndrome (AIDS) and coronavirus disease 2019, and the lengthy and costly treatment protocols. In this review, we summarize the pathogenesis of TB infection, therapeutic targets, and corresponding modulators, including first-line medications, current clinical trial drugs and molecules in preclinical assessment. Understanding the mechanisms of Mycobacterium tuberculosis (Mtb) infection and important biological targets can lead to innovative treatments. While most antitubercular agents target pathogen-related processes, host-directed therapy (HDT) modalities addressing immune defense, survival mechanisms, and immunopathology also hold promise. Mtb's adaptation to the human host involves manipulating host cellular mechanisms, and HDT aims to disrupt this manipulation to enhance treatment effectiveness. Our review provides valuable insights for future anti-TB drug development efforts.

Activation of GABA receptor attenuates intestinal inflammation by modulating enteric glial cells function through inhibiting NF-κB pathway

AIMS

Emerging research indicates that γ-aminobutyric acid (GABA) provides substantial benefits during enteritis. Nevertheless, GABA signaling roles on enteric glial cells (EGCs) remain unknown. The study's objective was to evaluate the underlying mechanisms of GABA signaling on EGCs in vitro and in vivo.

MAIN METHODS

We established LPS-induced mouse models and stimulated EGCs with LPS to mimic intestinal inflammation, and combined GABA, GABAA receptor (GABAAR) or GABAB receptor (GABABR) agonists to explore the exact mechanisms of GABA signaling.

KEY FINDINGS

EGCs were immunopositive for GAD65, GAD67, GAT1, GABAARα1, GABAARα3, and GABABR1, indicating GABAergic and GABAceptive properties. GABA receptor activation significantly inhibited the high secretions of proinflammatory factors in EGCs upon LPS stimulation. Interestingly, we found that EGCs express immune-related molecules such as CD16, CD32, CD80, CD86, MHC II, iNOS, Arg1, and CD206, thus establishing their characterization of E1 and E2 phenotype. EGCs exposed to LPS mainly acted as E1 phenotype, whereas GABABR activation strongly promoted EGCs polarization into E2 phenotype. Transcriptome analysis of EGCs indicated that GABA, GABAAR or GABABR agonists treatment participated in various biological processes, however all of these treatments exhibit inhibitory effects on NF-κB pathway. Notably, in LPS-induced mice, activation of GABABR mitigated intestinal damage through modulating inflammatory factors expressions, strengthening sIgA and IgG levels, inhibiting NF-κB pathway and facilitating EGCs to transform into E2 phenotype.

SIGNIFICANCE

These data demonstrate that the anti-inflammatory actions of GABA signaling system offer in enteritis via regulating EGCs-polarized function through impeding NF-κB pathway, thus providing potential targets for intestinal inflammatory 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.

Identification of Hub Genes and Typing of Tuberculosis Infections Based on Autophagy-Related Genes

Tuberculosis (TB) caused by Mycobacterium tuberculosis is one of the leading causes of morbidity and death in humans worldwide. Some autophagy genes associated with TB and some miRNAs regulating TB have been found, but the identification of autophagy-related genes in M. tuberculosis remains to be explored. Forty-seven autophagy-related genes differentially expressed in TB were identified in this study by analysis of TB-related datasets in the Gene Expression Omnibus (GEO) and autophagy-related genes in the Human Autophagy Database. The potential crucial genes affecting TB were found through the protein-protein interaction (PPI) network, and the possible pathways affected by these genes were verified. Analysis of the PPI network of miRNAs associated with M. tuberculosis infection and their target genes revealed that hsa-let-7, hsa-mir-155, hsa-mir-206, hsa-mir-26a, hsa-mir-30a, and hsa-mir-32 may regulate the expression of multiple autophagy-related genes (MAPK8, UVRAG, UKL2, and GABARAPL1) alone or in combination. Subsequently, Cytoscape was utilized to screen the differentially expressed genes related to autophagy. The hub genes (GABARAPL1 and ULK2) affecting TB were identified. Combined with Gene Set Enrichment Analysis (GSEA), the signaling pathways affected by the hub genes were verified. Finally, we divided TB patients into two subgroups based on autophagy-related genes, and the immune microenvironment of patients in different subgroups was significantly different. Our study found two autophagy-related hub genes that could affect TB and divide TB samples into two subgroups. This finding is of great significance for TB treatment and provides new ideas for exploring the pathogenesis of M. tuberculosis.

Peripheral modulation of antidepressant targets MAO-B and GABAAR by harmol induces mitohormesis and delays aging in preclinical models

Reversible and sub-lethal stresses to the mitochondria elicit a program of compensatory responses that ultimately improve mitochondrial function, a conserved anti-aging mechanism termed mitohormesis. Here, we show that harmol, a member of the beta-carbolines family with anti-depressant properties, improves mitochondrial function and metabolic parameters, and extends healthspan. Treatment with harmol induces a transient mitochondrial depolarization, a strong mitophagy response, and the AMPK compensatory pathway both in cultured C2C12 myotubes and in male mouse liver, brown adipose tissue and muscle, even though harmol crosses poorly the blood-brain barrier. Mechanistically, simultaneous modulation of the targets of harmol monoamine-oxidase B and GABA-A receptor reproduces harmol-induced mitochondrial improvements. Diet-induced pre-diabetic male mice improve their glucose tolerance, liver steatosis and insulin sensitivity after treatment with harmol. Harmol or a combination of monoamine oxidase B and GABA-A receptor modulators extend the lifespan of hermaphrodite Caenorhabditis elegans or female Drosophila melanogaster. Finally, two-year-old male and female mice treated with harmol exhibit delayed frailty onset with improved glycemia, exercise performance and strength. Our results reveal that peripheral targeting of monoamine oxidase B and GABA-A receptor, common antidepressant targets, extends healthspan through mitohormesis.

GABAergic signaling beyond synapses: an emerging target for cancer therapy

Traditionally, γ-aminobutyric acid (GABA) is best known for its role as a primary inhibitory neurotransmitter reducing neuronal excitability in the mammalian central nervous system (CNS), thereby producing calming effects. However, an emerging body of data now supports a function for GABA beyond neurotransmission as a potent factor regulating cancer cell growth and metastasis, as well as the antitumor immune response, by shaping the tumor microenvironment (TME). Here, we review the current knowledge on GABA's effects on the function of tumor cells, tumor-immune interactions, and the underlying molecular mechanisms. Since altered GABAergic signaling is now recognized as a feature of certain types of solid tumors, we also discuss the potential of repurposing existing GABAergic agents as a new class of anticancer therapy.

γ-Aminobutyric acid promotes the inhibition of hair growth induced by chronic restraint stress

Stress plays a critical role in hair loss, although the underlying mechanisms are largely unknown. γ-aminobutyric acid (GABA) has been reported to be associated with stress; however, whether it affects stress-induced hair growth inhibition is unclear. This study aimed to investigate the potential roles and mechanisms of action of GABA in chronic restraint stress (CRS)-induced hair growth inhibition. We performed RNA-seq analysis and found that differentially expressed genes (DEGs) associated with neuroactive ligand-receptor interaction, including genes related to GABA receptors, significantly changed after mice were treated with CRS. Targeted metabolomics analysis and enzyme-linked immunosorbent assay (ELISA) also showed that GABA levels in back skin tissues and serum significantly elevated in the CRS group. Notably, CRS-induced hair growth inhibition got aggravated by GABA and alleviated through GABA_A antagonists, such as picrotoxin and ginkgolide A. RNA sequencing analysis revealed that DEGs related to the cell cycle, DNA replication, purine metabolism, and pyrimidine metabolism pathways were significantly downregulated in dermal papilla (DP) cells after GABA treatment. Moreover, ginkgolide A, a GABA_A antagonist extracted from the leaves of Ginkgo biloba, promoted the cell cycle of DP cells. Therefore, the present study demonstrated that the increase in GABA could promote CRS-induced hair growth inhibition by downregulating the cell cycle of DP cells and suggested that ginkgolide A may be a promising therapeutic drug for hair loss.

Dimethyl itaconate is effective in host-directed antimicrobial responses against mycobacterial infections through multifaceted innate immune pathways

BACKGROUND

Itaconate, a crucial immunometabolite, plays a critical role in linking immune and metabolic functions to influence host defense and inflammation. Due to its polar structure, the esterified cell-permeable derivatives of itaconate are being developed to provide therapeutic opportunities in infectious and inflammatory diseases. Yet, it remains largely uncharacterized whether itaconate derivatives have potentials in promoting host-directed therapeutics (HDT) against mycobacterial infections. Here, we report dimethyl itaconate (DMI) as the promising candidate for HDT against both Mycobacterium tuberculosis (Mtb) and nontuberculous mycobacteria by orchestrating multiple innate immune programs.

RESULTS

DMI per se has low bactericidal activity against Mtb, M. bovis Bacillus Calmette-Guérin (BCG), and M. avium (Mav). However, DMI robustly activated intracellular elimination of multiple mycobacterial strains (Mtb, BCG, Mav, and even to multidrug-resistant Mtb) in macrophages and in vivo. DMI significantly suppressed the production of interleukin-6 and -10, whereas it enhanced autophagy and phagosomal maturation, during Mtb infection. DMI-mediated autophagy partly contributed to antimicrobial host defenses in macrophages. Moreover, DMI significantly downregulated the activation of signal transducer and activator of transcription 3 signaling during infection with Mtb, BCG, and Mav.

CONCLUSION

Together, DMI has potent anti-mycobacterial activities in macrophages and in vivo through promoting multifaceted ways for innate host defenses. DMI may bring light to new candidate for HDT against Mtb and nontuberculous mycobacteria, both of which infections are often intractable with antibiotic resistance.

Bioinformatic identification and validation of autophagy-related genes in rheumatoid arthritis

OBJECTIVES

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disorder characterized by progressive synovial inflammation and joint destruction, with a largely unknown etiology. Studies have suggested that autophagy and its expression may be involved in the pathogenesis of RA; however, autophagy-related genes in RA are still largely unidentified. Therefore, in this study, we aimed to identify and validate autophagy-related genes in RA.

METHODS

We identified differentially expressed autophagy-related genes between patients with RA and healthy individuals using gene expression profiles in the GSE55235 dataset and R software. Subsequently, correlation analysis, protein-protein interaction, gene ontology enrichment, and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were carried out using these differentially expressed autophagy-related genes. Finally, our results were validated by examining the expression of differentially expressed autophagy-related hub genes in clinical samples using qRT-PCR.

RESULTS

We identified 52 potential autophagy-related genes in RA based on bioinformatic analyses. Ten hub genes, CASP8, CTSB, TNFSF10, FADD, BAX, MYC, FOS, CDKN1A, GABARAPL1, and BNIP3, were validated to be differentially expressed and may serve as valuable prognostic markers and new potential therapeutic targets for RA via the regulation of autophagy.

CONCLUSIONS

Our results may help improve the understanding of RA pathogenesis. Autophagy-related genes in RA could be valuable biomarkers for diagnosis and prognosis and they might be exploited clinically as therapeutic targets in the future.

Reduction of Staphylococcus epidermidis in the mammary tumor microbiota induces antitumor immunity and decreases breast cancer aggressiveness

The mammary gland hosts a microbiota, which differs between malignant versus normal tissue. We found that aerosolized antibiotics decrease murine mammary tumor growth and strongly limit lung metastasis. Oral absorbable antibiotics also reduced mammary tumors. In ampicillin-treated nodules, the immune microenvironment consisted of an M1 profile and improved T cell/macrophage infiltration. In these tumors, we noted an under-representation of microbial recognition and complement pathways, supported by TLR2/TLR7 protein and C3-fragment deposition reduction. By 16S rRNA gene profiling, we observed increased Staphylococcus levels in untreated tumors, among which we isolated Staphylococcus epidermidis, which had potent inflammatory activity and increased Tregs. Conversely, oral ampicillin lowered Staphylococcus epidermidis in mammary tumors and expanded bacteria promoting an M1 phenotype and reducing MDSCs and tumor growth. Ampicillin/paclitaxel combination improved the chemotherapeutic efficacy. Notably, an Amp-like signature, based on genes differentially expressed in murine tumors, identified breast cancer patients with better prognosis and high immune infiltration that correlated with a bacteria response signature. This study highlights the significant influence of mammary tumor microbiota on local immune status and the relevance of its treatment with antibiotics, in combination with breast cancer therapies.

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.

Chromosome-scale genomes reveal genomic consequences of inbreeding in the South China tiger: A comparative study with the Amur tiger

The South China tiger (Panthera tigris amoyensis, SCT) is the most critically endangered subspecies of tiger due to functional extinction in the wild. Inbreeding depression is observed among the captive population descended from six wild ancestors, resulting in high juvenile mortality and low reproduction. We assembled and characterized the first SCT genome and an improved Amur tiger (P. t. altaica, AT) genome named AmyTig1.0 and PanTig2.0. The two genomes are the most continuous and comprehensive among any tiger genomes yet reported at the chromosomal level. By using the two genomes and resequencing data of 15 SCT and 13 AT individuals, we investigated the genomic signature of inbreeding depression of the SCT. The results indicated that the effective population size of SCT experienced three phases of decline, ~5.0-1.0 thousand years ago, 100 years ago, and since captive breeding in 1963. We found 43 long runs of homozygosity fragments that were shared by all individuals in the SCT population and covered a total length of 20.63% in the SCT genome. We also detected a large proportion of identical-by-descent segments across the genome in the SCT population, especially on ChrB4. Deleterious nonsynonymous single nucleotide polymorphic sites and loss-of-function mutations were found across genomes with extensive potential influences, despite a proportion of these loads having been purged by inbreeding depression. Our research provides an invaluable resource for the formulation of genetic management policies for the South China tiger such as developing genome-based breeding and genetic rescue strategy.

Visible Light Induced High Resolution and Swift 3D Printing System by Halogen Atom Transfer

3D printing technology offers solutions for numerous needs in industry and the daily life of individuals. In recent years, most research efforts have focused on this technology as the market share has grown and requirements have become specified in their related fields. In this work, a novel visible light induced 3D printing system with high resolution and short printing time using dimanganese decacarbonyl (Mn₂ (CO)₁₀ ) in combination with organic halides is reported. The radicals formed through halogen abstraction by photochemically generated manganese pentacarbonyl from organic halides with high quantum efficiency initiate the polymerization of acrylic resins. The kinetics of the process using various halide-containing molecules in the photoinitiaiting system are investigated with real-time fourrier transform infrared spectroscopy and photo-differential scanning calorimetry analyses, and the characteristics of 3D printouts are presented and compared with that of the commercial photoinitiator, 2,4,6-trimethylbenzoyl)phosphine oxide without Mn₂ (CO)₁₀ . The results obtained confirm that the combination of Mn₂ (CO)₁₀ and structurally diverse organic halides is a class of promising 3D system for various applications.

Elevated GABRP expression is correlated to the excessive autophagy in intrahepatic cholestasis of pregnancy

In intrahepatic cholestasis of pregnancy (ICP) patients, high concentrations of bile acids altered the normal maternal-fetal-unit physiological condition and could bring negative influence on placenta functionality. GABRP is the pi subunit of the gamma-aminobutyric acid type A receptor (GABA_A) and plays pivotal role in regulating GABA_A receptor's physiological function. Here we presented evidence that increased expression of GABRP in parallel with autophagic biomarkers, LC3 and ATG14, in patients with ICP.

METHODS

A total of 27 participants, including 18 ICP patients and 9 healthy pregnancies were recruited according to strict inclusion criteria. Placentas of ICP patients and controls were collected immediately after cesarean section before labor onset. GABRP and autophagic markers expression in placenta were investigated by immunohistochemistry (IHC), RT-qPCR, and Western blot.

RESULTS

The neonatal birthweight and gestational weeks were significantly lower in severe ICP group, while the hepatic enzymes were elevated in ICP group. Semiquantitative analysis of IHC revealed the AOD of GABRP in severe ICP patients was higher than that in mild ICP patients and control pregnancies. Western blot and RT-qPCR analysis both indicated that the expression of GABRP and ATG14 were significantly elevated in severe ICP patients. Moreover, GABRP was correlated with TBA (r = 0.64, p < 0.05), ATG14 (r = 0.87, p < 0.05), direct bilirubin (r = 0.54, p < 0.05), ALT (r = 0.72, p < 0.05), and AST (r = 0.67, p < 0.05).

CONCLUSION

There were elevated expression of GABRP, ATG14 and LC3 in ICP placentas compared with uncomplicated pregnancies. The expression of GABRP was associated with autophagy and was correlated with the TBA levels.

The GABA and GABA-Receptor System in Inflammation, Anti-Tumor Immune Responses, and COVID-19

GABA and GABA_A-receptors (GABA_A-Rs) play major roles in neurodevelopment and neurotransmission in the central nervous system (CNS). There has been a growing appreciation that GABA_A-Rs are also present on most immune cells. Studies in the fields of autoimmune disease, cancer, parasitology, and virology have observed that GABA-R ligands have anti-inflammatory actions on T cells and antigen-presenting cells (APCs), while also enhancing regulatory T cell (Treg) responses and shifting APCs toward anti-inflammatory phenotypes. These actions have enabled GABA_A-R ligands to ameliorate autoimmune diseases, such as type 1 diabetes (T1D), multiple sclerosis (MS), and rheumatoid arthritis, as well as type 2 diabetes (T2D)-associated inflammation in preclinical models. Conversely, antagonism of GABA_A-R activity promotes the pro-inflammatory responses of T cells and APCs, enhancing anti-tumor responses and reducing tumor burden in models of solid tumors. Lung epithelial cells also express GABA-Rs, whose activation helps maintain fluid homeostasis and promote recovery from injury. The ability of GABA_A-R agonists to limit both excessive immune responses and lung epithelial cell injury may underlie recent findings that GABA_A-R agonists reduce the severity of disease in mice infected with highly lethal coronaviruses (SARS-CoV-2 and MHV-1). These observations suggest that GABA_A-R agonists may provide off-the-shelf therapies for COVID-19 caused by new SARS-CoV-2 variants, as well as novel beta-coronaviruses, which evade vaccine-induced immune responses and antiviral medications. We review these findings and further advance the notions that (1) immune cells possess GABA_A-Rs to limit inflammation in the CNS, and (2) this natural "braking system" on inflammatory responses may be pharmacologically engaged to slow the progression of autoimmune diseases, reduce the severity of COVID-19, and perhaps limit neuroinflammation associated with long COVID.

GABAergic Neuromuscular Junction Suppresses Intestinal Defense of Caenorhabditis elegans by Attenuating Muscular Oxidative Phosphorylation

Innate immunity is an ancient and evolutionarily conserved system that constitutes the first line of host defense against invading microbes. We previously determined that the GABAergic neuromuscular junction (NMJ) suppresses intestinal innate immunity via muscular insulin signaling. Here, we found that a muscular mitochondrial oxidative phosphorylation pathway of Caenorhabditis elegans is involved in GABAergic NMJs-mediated intestinal defense. Deficiency in GABAergic neurotransmission increases reactive oxygen species (ROS) abundance and inhibits the nuclear translocation of SKN-1, whereas exogenous GABA administration represses it. SKN-1 is an important transcription factor involved in oxidative stress and the innate immune response. Moreover, deficiency in GABAergic postsynaptic UNC-49/GABAAR robustly promotes the mitochondrial function of GABAergic postsynaptic muscle cells, which may contribute to the muscular ROS decrease and intestinal SKN-1 suppression, ultimately inhibiting the intestinal defense of C. elegans. Our findings reveal a potential role of muscle mitochondrial ROS in intestinal defense in vivo and expand our understanding of mechanisms of intestinal innate immunity.

GABA regulates IL-1β production in macrophages

Neurotransmitters have been well documented to determine immune cell fates; however, whether and how γ-amino butyric acid (GABA) shapes the function of innate immune cells is still obscure. Here, we demonstrate that GABA orchestrates macrophage maturation and inflammation. GABA treatment during macrophage maturation inhibits interleukin (IL)-1β production from inflammatory macrophages. Mechanistically, GABA enhances succinate-flavin adenine dinucleotide (FAD)-lysine specific demethylase1 (LSD1) signaling to regulate histone demethylation of Bcl2l11 and Dusp2, reducing formation of the NLRP3-ASC-Caspase-1 complex. The GABA-succinate axis reduces succinylation of mitochondrial proteins to promote oxidative phosphorylation (OXPHOS). We also find that GABA alleviates lipopolysaccharides (LPS)-induced sepsis as well as high-fat-diet-induced obesity in mice. Our study shows that GABA regulates pro-inflammatory macrophage responses associated with metabolic reprogramming and protein succinylation, suggesting a strategy for treating macrophage-related inflammatory diseases.

Inhibition of GABAA receptors in intestinal stem cells prevents chemoradiotherapy-induced intestinal toxicity

Lethal intestinal tissue toxicity is a common side effect and a dose-limiting factor in chemoradiotherapy. Chemoradiotherapy can trigger DNA damage and induce P53-dependent apoptosis in LGR5+ intestinal stem cells (ISCs). Gamma-aminobutyric acid (GABA) and its A receptors (GABAAR) are present in the gastrointestinal tract. However, the functioning of the GABAergic system in ISCs is poorly defined. We found that GABAAR α1 (GABRA1) levels increased in the murine intestine after chemoradiotherapy. GABRA1 depletion in LGR5+ ISCs protected the intestine from chemoradiotherapy-induced P53-dependent apoptosis and prolonged animal survival. The administration of bicuculline, a GABAAR antagonist, prevented chemoradiotherapy-induced ISC loss and intestinal damage without reducing the chemoradiosensitivity of tumors. Mechanistically, it was associated with the reduction of reactive oxygen species-induced DNA damage via the L-type voltage-dependent Ca2+ channels. Notably, flumazenil, a GABAAR antagonist approved by the U.S. Food and Drug Administration, rescued human colonic organoids from chemoradiotherapy-induced toxicity. Therefore, flumazenil may be a promising drug for reducing the gastrointestinal side effects of chemoradiotherapy.

Secreted immune metabolites that mediate immune cell communication and function

Metabolites are emerging as essential factors for the immune system that are involved in both metabolic circuits and signaling cascades. Accumulated evidence suggests that altered metabolic programs initiated by the activation and maturation of immune cell types are accompanied by the delivery of various metabolites into the local environment. We propose that, in addition to protein/peptide ligands, secreted immune metabolites (SIMets) are essential components of immune communication networks that fine-tune immune responses under homeostatic and pathological conditions. We summarize recent advances in our understanding of SIMets and discuss the potential mechanisms by which some metabolites engage in immunological responses through receptor-, transporter-, and post-translational-mediated regulation. These insights may contribute to understanding physiology and developing effective therapeutics for inflammatory and immune-mediated diseases.

A GABA-receptor agonist reduces pneumonitis severity, viral load, and death rate in SARS-CoV-2-infected mice

Gamma-aminobutyric acid (GABA) and GABA-receptors (GABA-Rs) form a major neurotransmitter system in the brain. GABA-Rs are also expressed by 1) cells of the innate and adaptive immune system and act to inhibit their inflammatory activities, and 2) lung epithelial cells and GABA-R agonists/potentiators have been observed to limit acute lung injuries. These biological properties suggest that GABA-R agonists may have potential for treating COVID-19. We previously reported that GABA-R agonist treatments protected mice from severe disease induced by infection with a lethal mouse coronavirus (MHV-1). Because MHV-1 targets different cellular receptors and is biologically distinct from SARS-CoV-2, we sought to test GABA therapy in K18-hACE2 mice which develop severe pneumonitis with high lethality following SARS-CoV-2 infection. We observed that GABA treatment initiated immediately after SARS-CoV-2 infection, or 2 days later near the peak of lung viral load, reduced pneumonitis severity and death rates in K18-hACE2 mice. GABA-treated mice had reduced lung viral loads and displayed shifts in their serum cytokine/chemokine levels that are associated with better outcomes in COVID-19 patients. Thus, GABA-R activation had multiple effects that are also desirable for the treatment of COVID-19. The protective effects of GABA against two very different beta coronaviruses (SARS-CoV-2 and MHV-1) suggest that it may provide a generalizable off-the-shelf therapy to help treat diseases induced by new SARS-CoV-2 variants and novel coronaviruses that evade immune responses and antiviral medications. GABA is inexpensive, safe for human use, and stable at room temperature, making it an attractive candidate for testing in clinical trials. We also discuss the potential of GABA-R agonists for limiting COVID-19-associated neuroinflammation.

The contribution of ion channels to shaping macrophage behaviour

The expanding roles of macrophages in physiological and pathophysiological mechanisms now include normal tissue homeostasis, tissue repair and regeneration, including neuronal tissue; initiation, progression, and resolution of the inflammatory response and a diverse array of anti-microbial activities. Two hallmarks of macrophage activity which appear to be fundamental to their diverse cellular functionalities are cellular plasticity and phenotypic heterogeneity. Macrophage plasticity allows these cells to take on a broad spectrum of differing cellular phenotypes in response to local and possibly previous encountered environmental signals. Cellular plasticity also contributes to tissue- and stimulus-dependent macrophage heterogeneity, which manifests itself as different macrophage phenotypes being found at different tissue locations and/or after different cell stimuli. Together, plasticity and heterogeneity align macrophage phenotypes to their required local cellular functions and prevent inappropriate activation of the cell, which could lead to pathology. To execute the appropriate function, which must be regulated at the qualitative, quantitative, spatial and temporal levels, macrophages constantly monitor intracellular and extracellular parameters to initiate and control the appropriate cell signaling cascades. The sensors and signaling mechanisms which control macrophages are the focus of a considerable amount of research. Ion channels regulate the flow of ions between cellular membranes and are critical to cell signaling mechanisms in a variety of cellular functions. It is therefore surprising that the role of ion channels in the macrophage biology has been relatively overlooked. In this review we provide a summary of ion channel research in macrophages. We begin by giving a narrative-based explanation of the membrane potential and its importance in cell biology. We then report on research implicating different ion channel families in macrophage functions. Finally, we highlight some areas of ion channel research in macrophages which need to be addressed, future possible developments in this field and therapeutic potential.

Advances in Translational 3D Printing for Cartilage, Bone, and Osteochondral Tissue Engineering

The regeneration of 3D tissue constructs with clinically relevant sizes, structures, and hierarchical organizations for translational tissue engineering remains challenging. 3D printing, an additive manufacturing technique, has revolutionized the field of tissue engineering by fabricating biomimetic tissue constructs with precisely controlled composition, spatial distribution, and architecture that can replicate both biological and functional native tissues. Therefore, 3D printing is gaining increasing attention as a viable option to advance personalized therapy for various diseases by regenerating the desired tissues. This review outlines the recently developed 3D printing techniques for clinical translation and specifically summarizes the applications of these approaches for the regeneration of cartilage, bone, and osteochondral tissues. The current challenges and future perspectives of 3D printing technology are also discussed.

Effects of propofol on macrophage activation and function in diseases

Macrophages work with monocytes and dendritic cells to form a monocyte immune system, which constitutes a powerful cornerstone of the immune system with their powerful antigen presentation and phagocytosis. Macrophages play an essential role in infection, inflammation, tumors and other pathological conditions, but these cells also have non-immune functions, such as regulating lipid metabolism and maintaining homeostasis. Propofol is a commonly used intravenous anesthetic in the clinic. Propofol has sedative, hypnotic, anti-inflammatory and anti-oxidation effects, and it participates in the body’s immunity. The regulation of propofol on immune cells, especially macrophages, has a profound effect on the occurrence and development of human diseases. We summarized the effects of propofol on macrophage migration, recruitment, differentiation, polarization, and pyroptosis, and the regulation of these propofol-regulated macrophage functions in inflammation, infection, tumor, and organ reperfusion injury. The influence of propofol on pathology and prognosis via macrophage regulation is also discussed. A better understanding of the effects of propofol on macrophage activation and function in human diseases will provide a new strategy for the application of clinical narcotic drugs and the treatment of diseases.