Anti-Inflammatory Metabolites in the Pathogenesis of Bacterial Infection

Exploring the impact of 2-hydroxyestradiol on heme oxygenase-1 to combat oxidative stress in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation driven by complex signaling pathways. Recent therapeutic approaches focus on small molecules targeting intracellular signaling to address specific physiological aspects of the disease. Previously we identified a small molecule, 2-hydroxyestradiol (2-OHE2), an inhibitor of TNF-α by an in-silico study. In the present study, our aim was to explore the efficacy of 2-OHE2 by studying the proteome profile of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) using SWATH-MS and validate its therapeutic potential in RA by in-vitro studies. Oxidative stress was assessed using various biochemical assays, and cellular bioenergetics were analyzed with the Seahorse XFe96 Analyzer. We identified 396 differential proteins by SWATH-MS, and 82 showed significant changes. PharmMapper analysis revealed the association of 2-OHE2 with HMOX1 (HO-1), confirmed by SWATH-MS data. Also, we revealed that 2-OHE2 enhanced the expression of HO-1 and lowered oxidative stress via activating the Nrf2/KEAP1/HO-1 pathway. Further, 2-OHE2 has been found to boost cellular respiration and ATP production. Our findings thus suggest that 2-OHE2 possesses therapeutic potential as an antioxidant for RA treatment, effective at low dosages.

Myeloid Cell-Specific Deletion of AMPKα1 Worsens Ocular Bacterial Infection by Skewing Macrophage Phenotypes

AMP-activated protein kinase (AMPK) plays a crucial role in governing essential cellular functions such as growth, proliferation, and survival. Previously, we observed increased vulnerability to bacterial (Staphylococcus aureus) endophthalmitis in global AMPKα1 knockout mice. In this study, we investigated the specific involvement of AMPKα1 in myeloid cells using LysMCre;AMPKα1fl mice. Our findings revealed that whereas endophthalmitis resolved in wild-type C57BL/6 mice, the severity of the disease progressively worsened in AMPKα1-deficient mice over time. Moreover, the intraocular bacterial load and inflammatory mediators (e.g., IL-1β, TNF-α, IL-6, and CXCL2) were markedly elevated in the LysMCre;AMPKα1fl mice. Mechanistically, the deletion of AMPKα1 in myeloid cells skewed macrophage polarization toward the inflammatory M1 phenotype and impaired the phagocytic clearance of S. aureus by macrophages. Notably, transferring AMPK-competent bone marrow from wild-type mice to AMPKα1 knockout mice preserved retinal function and mitigated the severity of endophthalmitis. Overall, our study underscores the role of myeloid-specific AMPKα1 in promoting the resolution of inflammation in the eye during bacterial infection. Hence, therapeutic strategies aimed at restoring or enhancing AMPKα1 activity could improve visual outcomes in endophthalmitis and other ocular infections.

Efficacy of Ambroxol Combined with Loquat Syrup on Bacterial Pneumonia in Mice

Purpose

Bacterial pneumonia is a prevalent respiratory disease and a primary cause of death among hospitalized patients. Ambroxol and loquat syrup are widely utilized pharmaceuticals for managing respiratory infections in China. This study investigates the potential application and efficacy of combining ambroxol with loquat syrup for treating bacterial pneumonia.

Methods

In this study, mice with P. aeruginosa-induced bacterial pneumonia were used to evaluate the therapeutic effects of ambroxol, loquat syrup, and their combination. A bacterial plate coating assay was performed to measure the P. aeruginosa content in saliva, lung tissue, and bronchoalveolar lavage fluid (BALF). A plate colony counting assay was conducted to assess the antibacterial activity of ambroxol and loquat syrup. Serum, BALF, and lung tissues were analyzed using qPCR, ELISA, immunohistochemistry, and hematoxylin-eosin staining to evaluate disease severity.

Results

In this study, the experimental results demonstrate that, compared to treatment with ambroxol and/or loquat syrup alone, the combined administration of ambroxol and loquat syrup significantly increases the volume of saliva expectorated by mice infected with bacteria, concurrently augmenting bacterial presence in saliva while diminishing bacterial burden in the lungs, with significant differences observed (p<0.05). Furthermore, the combined therapy of ambroxol and loquat syrup achieved better therapeutic effects on P. aeruginosa pneumonia compared to ambroxol and/or loquat syrup alone (p<0.05), as evidenced by significantly reduced P. aeruginosa-induced lung injury, improved lung permeability, decreased inflammatory cell infiltration, and lower expression of inflammatory cytokines.

Conclusion

These findings suggest that the combination therapy of ambroxol and loquat syrup presents a safe and feasible new treatment strategy for bacterial pneumonia, offering promising benefits for ameliorating lung tissue damage and inflammation.

Elevated levels of butyric acid in the jejunum of an animal model of broiler chickens: from early onset of Clostridium perfringens infection to clinical disease of necrotic enteritis

BACKGROUND

Necrotic enteritis (NE) is an economically important disease of broiler chickens caused by Clostridium perfringens (CP). The pathogenesis, or disease process, of NE is still not clear. This study aimed to identify the alterations of metabolites and metabolic pathways associated with subclinical or clinical NE in CP infected birds and to investigate the possible variations in the metabolic profile of birds infected with different isolates of CP.

METHODOLOGY

Using a well-established NE model, the protein content of feed was changed abruptly before exposing birds to CP isolates with different toxin genes combinations (cpa, cpb2, netB, tpeL; cpa, cpb2, netB; or cpa, cpb2). Metabolomics analysis of jejunal contents was performed by a targeted, fully quantitative LC-MS/MS based assay.

RESULTS

This study detected statistically significant differential expression of 34 metabolites including organic acids, amino acids, fatty acids, and biogenic amines, including elevation of butyric acid at onset of NE in broiler chickens. Subsequent analysis of broilers infected with CP isolates with different toxin gene combinations confirmed an elevation of butyric acid consistently among 21 differentially expressed metabolites including organic acids, amino acids, and biogenic amines, underscoring its potential role during the development of NE. Furthermore, protein-metabolite network analysis revealed significant alterations in butyric acid and arginine-proline metabolisms.

CONCLUSION

This study indicates a significant metabolic difference between CP-infected and non-infected broiler chickens. Among all the metabolites, butyric acid increased significantly in CP-infected birds compared to non-infected healthy broilers. Logistic regression analysis revealed a positive association between butyric acid (coefficient: 1.23, P < 0.01) and CP infection, while showing a negative association with amino acid metabolism. These findings suggest that butyric acid could be a crucial metabolite linked to the occurrence of NE in broiler chickens and may serve as an early indicator of the disease at the farm level. Further metabolomic experiments using different NE animal models and field studies are needed to determine the specificity and to validate metabolites associated with NE, regardless of predisposing factors.

Staphylococcus aureus adapts to exploit collagen-derived proline during chronic infection

Staphylococcus aureus is a pulmonary pathogen associated with substantial human morbidity and mortality. As vaccines targeting virulence determinants have failed to be protective in humans, other factors are likely involved in pathogenesis. Here we analysed transcriptomic responses of human clinical isolates of S. aureus from initial and chronic infections. We observed upregulated collagenase and proline transporter gene expression in chronic infection isolates. Metabolomics of bronchiolar lavage fluid and fibroblast infection, growth assays and analysis of bacterial mutant strains showed that airway fibroblasts produce collagen during S. aureus infection. Host-adapted bacteria upregulate collagenase, which degrades collagen and releases proline. S. aureus then imports proline, which fuels oxidative metabolism via the tricarboxylic acid cycle. Proline metabolism provides host-adapted S. aureus with a metabolic benefit enabling out-competition of non-adapted strains. These data suggest that clinical settings characterized by airway repair processes and fibrosis provide a milieu that promotes S. aureus adaptation and supports infection.

Adaptive physiological and metabolic alterations in Staphylococcus aureus evolution under vancomycin exposure

Staphylococcus aureus can develop antibiotic resistance and evade immune responses, causing infections in different body sites. However, the metabolic changes underlying this process are poorly understood. A variant strain, C1V, was derived from the parental strain C1 by exposing it to increasing concentrations of vancomycin in vitro. C1V exhibited a vancomycin-intermediate phenotype and physiological changes compared to C1. It showed higher survival rates than C1 when phagocytosed by Raw264.7 cells. Metabolomics analysis identified significant metabolic differences pre- and post-induction (C1 + SC1 vs. C1V + SC1V: 201 metabolites) as well as pre- and post-phagocytosis (C1 vs. SC1: 50 metabolites; C1V vs. SC1V: 95 metabolites). The variant strain had distinct morphological characteristics, decreased adhesion ability, impaired virulence, and enhanced resistance to phagocytosis compared to the parental strain. Differential metabolites may contribute to S. aureus ' resistance to antibiotics and phagocytosis, offering insights into potential strategies for altering vancomycin nonsusceptibility and enhancing phagocyte killing by manipulating bacterial metabolism.

Type I interferon governs immunometabolic checkpoints that coordinate inflammation during Staphylococcal infection

Macrophage metabolic plasticity is central to inflammatory programming, yet mechanisms of coordinating metabolic and inflammatory programs during infection are poorly defined. Here, we show that type I interferon (IFN) temporally guides metabolic control of inflammation during methicillin-resistant Staphylococcus aureus (MRSA) infection. We find that staggered Toll-like receptor and type I IFN signaling in macrophages permit a transient energetic state of combined oxidative phosphorylation (OXPHOS) and aerobic glycolysis followed by inducible nitric oxide synthase (iNOS)-mediated OXPHOS disruption. This disruption promotes type I IFN, suppressing other pro-inflammatory cytokines, notably interleukin-1β. Upon infection, iNOS expression peaks at 24 h, followed by lactate-driven Nos2 repression via histone lactylation. Type I IFN pre-conditioning prolongs infection-induced iNOS expression, amplifying type I IFN. Cutaneous MRSA infection in mice constitutively expressing epidermal type I IFN results in elevated iNOS levels, impaired wound healing, vasculopathy, and lung infection. Thus, kinetically regulated type I IFN signaling coordinates immunometabolic checkpoints that control infection-induced inflammation.

L-arginine attenuates Streptococcus uberis-induced inflammation by decreasing miR155 level

L-arginine, as an essential substance of the immune system, plays a vital role in innate immunity. MiR155, a multi-functional microRNA, has gained importance as a regulator of homeostasis in immune cells. However, the immunoregulatory mechanism between L-arginine and miR155 in bacterial infections is unknown. Here, we investigated the potential role of miR155 in inflammation and the molecular regulatory mechanisms of L-arginine in Streptococcus uberis (S. uberis) infections. And we observed that miR155 was up-regulated after infection, accompanying the depletion of L-arginine, leading to metabolic disorders of amino acids and severe tissue damage. Mechanically, the upregulated miR155 mediated by the p65 protein played a pro-inflammatory role by suppressing the suppressor of cytokine signaling 6 (SOCS6)-mediated p65 ubiquitination and degradation. This culminated in a violently inflammatory response and tissue damage. Interestingly, a significant anti-inflammatory effect was revealed in L-arginine supplementation by reducing miR155 production via inhibiting p65. This work firstly uncovers the pro-inflammatory role of miR155 and an anti-inflammatory mechanism of L-arginine in S.uberis infection with a mouse mastitis model. Collectively, we provide new insights and strategies for the prevention and control of this important pathogen, which is of great significance for ensuring human food health and safety.

ACOD1 deficiency offers protection in a mouse model of diet-induced obesity by maintaining a healthy gut microbiota

Aconitate decarboxylase 1 (ACOD1) is the enzyme synthesizing itaconate, an immuno-regulatory metabolite tuning host-pathogen interactions. Such functions are achieved by affecting metabolic pathways regulating inflammation and microbe survival. However, at the whole-body level, metabolic roles of itaconate remain largely unresolved. By using multiomics-integrated approaches, here we show that ACOD1 responds to high-fat diet consumption in mice by promoting gut microbiota alterations supporting metabolic disease. Genetic disruption of itaconate biosynthesis protects mice against obesity, alterations in glucose homeostasis and liver metabolic dysfunctions by decreasing meta-inflammatory responses to dietary lipid overload. Mechanistically, fecal metagenomics and microbiota transplantation experiments demonstrate such effects are dependent on an amelioration of the intestinal ecosystem composition, skewed by high-fat diet feeding towards obesogenic phenotype. In particular, unbiased fecal microbiota profiling and axenic culture experiments point towards a primary role for itaconate in inhibiting growth of Bacteroidaceae and Bacteroides, family and genus of Bacteroidetes phylum, the major gut microbial taxon associated with metabolic health. Specularly to the effects imposed by Acod1 deficiency on fecal microbiota, oral itaconate consumption enhances diet-induced gut dysbiosis and associated obesogenic responses in mice. Unveiling an unrecognized role of itaconate, either endogenously produced or exogenously administered, in supporting microbiota alterations underlying diet-induced obesity in mice, our study points ACOD1 as a target against inflammatory consequences of overnutrition.

Staphylococcus aureus suppresses the pentose phosphate pathway in human neutrophils via the adenosine receptor A2aR to enhance intracellular survival

IMPORTANCE

Staphylococcus aureus is one of the leading causes of antimicrobial-resistant infections whose success as a pathogen is facilitated by its massive array of immune evasion tactics, including intracellular survival within critical immune cells such as neutrophils, the immune system's first line of defense. In this study, we describe a novel pathway by which intracellular S. aureus can suppress the antimicrobial capabilities of human neutrophils by using the anti-inflammatory adenosine receptor, adora2a (A2aR). We show that signaling through A2aR suppresses the pentose phosphate pathway, a metabolic pathway used to fuel the antimicrobial NADPH oxidase complex that generates reactive oxygen species (ROS). As such, neutrophils show enhanced ROS production and reduced intracellular S. aureus when treated with an A2aR inhibitor. Taken together, we identify A2aR as a potential therapeutic target for combatting intracellular S. aureus infection.

Gallium Liquid Metal: Nanotoolbox for Antimicrobial Applications

The proliferation of drug resistance in microbial pathogens poses a significant threat to human health. Hence, treatment measures are essential to surmount this growing problem. In this context, liquid metal nanoparticles are promising. Gallium, a post-transition metal notable for being a liquid at physiological temperature, has drawn attention for its distinctive properties, high antimicrobial efficacy, and low toxicity. Moreover, gallium nanoparticles demonstrate anti-inflammatory properties in immune cells. Gallium can alloy with other metals and be prepared in various composites to modify and tailor its characteristics and functionality. More importantly, the bactericidal mechanism of gallium liquid metal could sidestep the threat of emerging drug resistance mechanisms. Building on this rationale, gallium-based liquid metal nanoparticles can enable impactful and innovative strategic pathways in the battle against antimicrobial resistance. This review outlines the characteristics of gallium-based liquid metals at the nanoscale and their corresponding antimicrobial mechanisms to provide a comprehensive yet succinct overview of their current antimicrobial applications. In addition, challenges and opportunities that require further research efforts have been identified and discussed.

Itaconate family-based host-directed therapeutics for infections

Itaconate is a crucial anti-infective and anti-inflammatory immunometabolite that accumulates upon disruption of the Krebs cycle in effector macrophages undergoing inflammatory stress. Esterified derivatives of itaconate (4-octyl itaconate and dimethyl itaconate) and its isomers (mesaconate and citraconate) are promising candidate drugs for inflammation and infection. Several itaconate family members participate in host defense, immune and metabolic modulation, and amelioration of infection, although opposite effects have also been reported. However, the precise mechanisms by which itaconate and its family members exert its effects are not fully understood. In addition, contradictory results in different experimental settings and a lack of clinical data make it difficult to draw definitive conclusions about the therapeutic potential of itaconate. Here we review how the immune response gene 1-itaconate pathway is activated during infection and its role in host defense and pathogenesis in a context-dependent manner. Certain pathogens can use itaconate to establish infections. Finally, we briefly discuss the major mechanisms by which itaconate family members exert antimicrobial effects. To thoroughly comprehend how itaconate exerts its anti-inflammatory and antimicrobial effects, additional research on the actual mechanism of action is necessary. This review examines the current state of itaconate research in infection and identifies the key challenges and opportunities for future research in this field.

Metabolite interactions between host and microbiota during health and disease: Which feeds the other?

Metabolites produced by the host and microbiota play a crucial role in how human bodies develop and remain healthy. Most of these metabolites are produced by microbiota and hosts in the digestive tract. Metabolites in the gut have important roles in energy metabolism, cellular communication, and host immunity, among other physiological activities. Although numerous host metabolites, such as free fatty acids, amino acids, and vitamins, are found in the intestine, metabolites generated by gut microbiota are equally vital for intestinal homeostasis. Furthermore, microbiota in the gut is the sole source of some metabolites, including short-chain fatty acids (SCFAs). Metabolites produced by microbiota, such as neurotransmitters and hormones, may modulate and significantly affect host metabolism. The gut microbiota is becoming recognized as a second endocrine system. A variety of chronic inflammatory disorders have been linked to aberrant host-microbiota interplays, but the precise mechanisms underpinning these disturbances and how they might lead to diseases remain to be fully elucidated. Microbiome-modulated metabolites are promising targets for new drug discovery due to their endocrine function in various complex disorders. In humans, metabolotherapy for the prevention or treatment of various disorders will be possible if we better understand the metabolic preferences of bacteria and the host in specific tissues and organs. Better disease treatments may be possible with the help of novel complementary therapies that target host or bacterial metabolism. The metabolites, their physiological consequences, and functional mechanisms of the host-microbiota interplays will be highlighted, summarized, and discussed in this overview.

Paracrine Factors of Stressed Peripheral Blood Mononuclear Cells Activate Proangiogenic and Anti-Proteolytic Processes in Whole Blood Cells and Protect the Endothelial Barrier

Tissue-regenerative properties have been attributed to secreted paracrine factors derived from stem cells and other cell types. In particular, the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCsec) has been shown to possess high tissue-regenerative and proangiogenic capacities in a variety of preclinical studies. In light of future therapeutic intravenous applications of PBMCsec, we investigated the possible effects of PBMCsec on white blood cells and endothelial cells lining the vasculature. To identify changes in the transcriptional profile, whole blood was drawn from healthy individuals and stimulated with PBMCsec for 8 h ex vivo before further processing for single-cell RNA sequencing. PBMCsec significantly altered the gene signature of granulocytes (17 genes), T-cells (45 genes), B-cells (72 genes), and, most prominently, monocytes (322 genes). We detected a strong upregulation of several tissue-regenerative and proangiogenic cyto- and chemokines in monocytes, including VEGFA, CXCL1, and CXCL5. Intriguingly, inhibitors of endopeptidase activity, such as SERPINB2, were also strongly induced. Measurement of the trans-endothelial electrical resistance of primary human microvascular endothelial cells revealed a strong barrier-protective effect of PBMCsec after barrier disruption. Together, we show that PBMCsec induces angiogenic and proteolytic processes in the blood and is able to attenuate endothelial barrier damage. These regenerative properties suggest that systemic application of PBMCsec might be a promising novel strategy to restore damaged organs.