Identification of biomarkers associated with M1 macrophages in the ST-segment elevation myocardial infarction through bioinformatics and machine learning approaches

ST-segment elevation myocardial infarction (STEMI) is considered a critical cardiac condition with a poor prognosis. Shortly after STEMI occurs, the increased number of circulating leukocytes including macrophages can lead to the accumulation of more cells in the myocardium, affecting the cardiac immune microenvironment. Identifying serum biomarkers associated with immune infiltration after STEMI is important for diagnosing and treating STEMI. In this work, we aimed to use integrated bioinformatics and machine learning methods to identify new biomarkers. First, candidate genes closely associated with M1 macrophage immune infiltration and STEMI were obtained using the limma package, the CIBERSORTx package, weighted gene coexpression network analysis (WGCNA), and protein‒protein interaction (PPI) networks from the GSE59867 dataset, which comprises peripheral blood mononuclear cell (PBMC) samples. The STEMI patients were subsequently stratified into subtypes using the ConsensusClusterPlus package. Furthermore, using machine learning methods, we identified AKT3, GJC2, HMGCL and RBM17 as the genes with the greatest potential to be associated with STEMI subtypes and with M1 macrophage infiltration during the acute phase of STEMI. Finally, the expression profile and diagnostic value of the four feature genes were validated in the GSE59867 and GSE62646 datasets and in 24 patients using real-time PCR. This study revealed logically and comprehensively that AKT3, GJC2, HMGCL and RBM17, which are derived from PBMCs, could enhance the accuracy of STEMI diagnosis and might provide effective treatment options for STEMI patients.

Preclinical efficacy of TZG in myofascial pain syndrome by impairing PI3K-RAC2 signaling-mediated neutrophil extracellular traps

Tianhe Zhuifeng Gao (TZG) shows a satisfying therapeutic efficacy in treating arthromyodynia, which shares similar etiology to myofascial pain syndrome (MPS). We herein aim to explore whether TZG could be a potential prescription for MPS therapy. An MPS rat model was successfully established presenting with reduced pain thresholds, abnormal local switch responses, etc., which was effectively reversed by TZG treatment externally. A transcriptome sequencing based on the active MTrPs samples of rats, combined with network analysis revealed that TZG might ameliorate the progression of MPS by impairing neutrophil extracellular traps (NETs) release through inhibiting PI3K-RAC2 signaling to reduce NADPH oxidase-originated ROS. Experimentally, the expression levels of inducers, biomarkers of NETs formation and vessel injury, and p-PI3K, p-P47, and RAC2 proteins were all significantly up-regulated in affected tissues, which were markedly reversed by TZG. Our results not only shed light into broadening the clinical indications of TZG, but benefit MPS therapy.

Innate immune cell-intrinsic ketogenesis is dispensable for organismal metabolism and age-related inflammation

Aging is accompanied by chronic low-grade inflammation, but the mechanisms that allow this to persist are not well understood. Ketone bodies are alternative fuels produced when glucose is limited and improve indicators of healthspan in aging mouse models. Moreover, the most abundant ketone body, β-hydroxybutyrate, inhibits the NLRP3 inflammasome in myeloid cells, a key potentiator of age-related inflammation. Given that myeloid cells express ketogenic machinery, we hypothesized this pathway may serve as a metabolic checkpoint of inflammation. To test this hypothesis, we conditionally ablated ketogenesis by disrupting expression of the terminal enzyme required for ketogenesis, 3-Hydroxy-3-Methylglutaryl-CoA Lyase (HMGCL). By deleting HMGCL in the liver, we validated the functional targeting and establish that the liver is the only organ that can produce the life-sustaining quantities of ketone bodies required for survival during fasting or ketogenic diet feeding. Conditional ablation of HMGCL in neutrophils and macrophages had modest effects on body weight and glucose tolerance in aging but worsened glucose homeostasis in myeloid cell-specific Hmgcl-deficient mice fed a high-fat diet. Our results suggest that during aging, liver-derived circulating ketone bodies might be more important for deactivating the NLRP3 inflammasome and controlling organismal metabolism.

Hydroxycarboxylic acid receptor 2 (HCA2) agonists induce NET formation and MMP-9 release from bovine polymorphonuclear leukocytes

Periparturient cows are commonly fed diets supplemented with Niacin (nicotinic acid, NA) because of its anti-lipolytic properties. NA confers its anti-lipolytic effects by activating the hydroxycarboxylic acid 2 receptor (HCA2). HCA2 is also activated by the ketone body beta-hydroxybutyrate (BHB) and circulating BHB levels are elevated in postpartum dairy cows. The HCA2 receptor is highly expressed in bovine polymorphonuclear leukocytes (PMN) and could link metabolic and innate immune responses in cattle. We investigated how HCA2 agonists affected bovine PMN function in vitro. We studied different PMN responses, such as granule release, surface expression of CD11b and CD47, generation of neutrophil extracellular traps (NETs), and apoptosis. NA, BHB, and 4,4aR,5,5aR-tetrahydro-1H-cyclopropa [4,5] cyclopenta [1,2-c] pyrazole-3-carboxylic acid (MK-1903) treatment triggered the release of matrix metalloproteinase 9 (MMP-9), a component of the tertiary granule, from neutrophils. Additionally, all HCA2 agonists induced NETs formation but did not affect surface expression of CD11b and CD47. Finally, none of the HCA2 agonists triggered apoptosis in bovine PMN. This information will give new insights into the potential role of the HCA2 receptor in the bovine innate immune response.

Ketone body augmentation decreases methacholine hyperresponsiveness in mouse models of allergic asthma

Background

Individuals with allergic asthma exhibit lung inflammation and remodeling accompanied by methacholine hyperresponsiveness manifesting in proximal airway narrowing and distal lung tissue collapsibility, and they can present with a range of mild-to-severe disease amenable or resistant to therapeutic intervention, respectively. There remains a need for alternatives or complements to existing treatments that could control the physiologic manifestations of allergic asthma.

Objectives

Our aim was to examine the hypothesis that because ketone bodies elicit anti-inflammatory activity and are effective in mitigating the methacholine hyperresponsiveness associated with obese asthma, increasing systemic concentrations of ketone bodies would diminish pathologic outcomes in asthma-relevant cell types and in mouse models of allergic asthma.

Methods

We explored the effects of ketone bodies on allergic asthma-relevant cell types (macrophages, airway epithelial cells, CD4 T cells, and bronchial smooth muscle cells) in vitro as well as in vivo by using preclinical models representative of several endotypes of allergic asthma to determine whether promotion of ketosis through feeding a ketogenic diet or providing a ketone precursor or a ketone ester dietary supplement could affect immune and inflammatory parameters as well as methacholine hyperresponsiveness.

Results

In a dose-dependent manner, the ketone bodies acetoacetate and β-hydroxybutyrate (BHB) decreased proinflammatory cytokine secretion from mouse macrophages and airway epithelial cells, decreased house dust mite (HDM) extract-induced IL-8 secretion from human airway epithelial cells, and decreased cytokine production from polyclonally and HDM-activated T cells. Feeding a ketogenic diet, providing a ketone body precursor, or supplementing the diet with a ketone ester increased serum BHB concentrations and decreased methacholine hyperresponsiveness in several acute HDM sensitization and challenge models of allergic asthma. A ketogenic diet or ketone ester supplementation decreased methacholine hyperresponsiveness in an HDM rechallenge model of chronic allergic asthma. Ketone ester supplementation synergized with corticosteroid treatment to decrease methacholine hyperresponsiveness in an HDM-driven model of mixed-granulocytic severe asthma. HDM-induced morphologic changes in bronchial smooth muscle cells were inhibited in a dose-dependent manner by BHB, as was HDM protease activity.

Conclusions

Increasing systemic BHB concentrations through dietary interventions could provide symptom relief for several endotypes of allergic asthmatic individuals through effects on multiple asthma-relevant cells.