Biology subjects

Poynter, M. E.

Publications and source records attributed to Poynter, M. E..

5 recordsLinked to original sources

bioRxiv2025

Acidosis Licenses the NLRP3 Inflammasome-Inhibiting Effects of Beta-Hydroxybutyrate and Short-Chain Carboxylic Acids

NLRP3 inflammasome activation induces the cleavage and secretion of IL-1{beta} and IL-18, and causes pyroptosis. Generated during times of energetic crisis (e.g., caloric insufficiency), the ketone body {beta}-hydroxybutyrate (BHB) has been reported to inhibit NLRP3 inflammasome activation. However, the conditions under which BHB exerts this activity and whether other short-chain carboxylic acids (SCCAs) share this effect are unexplored. Since BHB is often produced in high abundance endogenously accompanied by metabolic acidosis, we aimed to examine the pH-dependence for the ability of BHB and similar molecules to inhibit NLRP3 inflammasome activation and to test receptors conferring these effects. Whereas {beta}-hydroxybutyric acid (BHBA) enantiomers function equivalently to dose-dependently inhibit NLRP3 inflammasome-induced IL-1{beta} secretion, sodium-{beta}-hydroxybutyrate (NaBHB) and NaOH-neutralized BHBA do not inhibit NLRP3 inflammasome activation. Acidifying the pH of the NaBHB stock solution or the media in which cells are exposed to NaBHB, or allowing the cells to endogenously acidify their media, enables NaBHB to inhibit NLRP3 inflammasome activation. Several other SCCAs also inhibit NLRP3 inflammasome activation in a pH-dependent manner and prevent pyroptotic cell death. Finally, Free Fatty Acid Receptor 3 (GPR41/FFAR3) activation phenocopies and augments the NLRP3 inflammasome-inhibiting effects of BHBA. In conclusion, acidification licenses the ability of BHB and related SCCAs to inhibit NLRP3 inflammasome activation, in part through GPR41/FFAR3, thereby expanding the repertoire of metabolites capable of modulating this important pro-inflammatory pathway during times of energetic crisis and optimizing conditions for the potential use of ketone bodies as anti-inflammatories. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=189 SRC="FIGDIR/small/650510v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@f3b90corg.highwire.dtl.DTLVardef@f9fab5org.highwire.dtl.DTLVardef@1babd12org.highwire.dtl.DTLVardef@d30d88_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

Beta-Hydroxybutyrate Inhibits Bronchial Smooth Muscle Contraction

Asthma is a chronic respiratory condition characterized by airway inflammation, remodeling, and hyperresponsiveness to triggers causing airway constriction. Bronchial smooth muscle plays a critical role by narrowing airways, leading to obstruction and breathing difficulties, often exacerbated by mast cell infiltration and histamine release. Whereas current treatments, including bronchodilators, corticosteroids, and biologics provide effective management for most patients, alternative therapies are needed for difficult-to-treat asthma. Recent research highlights the potential of therapeutic ketosis, achieved through dietary interventions or supplementation with exogenous ketones, to reduce airway hyperresponsiveness and inflammation. Ketone bodies, known for providing energy during carbohydrate scarcity, also influence asthma by activating cell-surface receptors and transporters. In vivo, interventions like weight loss and caloric restriction increase ketone body levels, correlating with improved asthma symptoms, reduced oxidative stress, and inflammation. These effects suggest ketone bodies, particularly {beta}-hydroxybutyrate, may play a therapeutic role in mitigating bronchoconstriction and smooth muscle contraction in asthma. We utilize human bronchial smooth muscle cells (in vitro) and mouse precision-cut lung slices (PCLS) (ex vivo) to assess the effects of BHB on histamine-induced bronchoconstriction. Brightfield microscopy showed that BHB reduces contraction in human bronchial smooth muscle cells, an effect involving free fatty acid receptor 3 (FFAR3) activation. Light microscopy of PCLS revealed that BHB inhibits airway narrowing and cellular extrusion, demonstrating its ability to mitigate bronchoconstriction by suppressing smooth muscle contraction. These results implicate bronchial smooth muscle as a cellular target of therapeutic ketosis, an important contributor to the beneficial effects of BHB in preclinical models of asthma. Graphical AbstractIn accordance with journal requirements, a graphical abstract will be submitted if we are invited to revise this manuscript.

cell biology↗

bioRxiv2025

Beta-Hydroxybutyrate Attenuates Bronchial Smooth Muscle Pro-Inflammatory Cytokine Production

Asthma is a common airway condition causing breathing difficulties due to reversible airflow obstruction. It often affects obese individuals, with symptoms triggered by environmental factors that induce immune responses, leading to inflammation and bronchoconstriction. Bronchial smooth muscle (BSM) plays a central role in airway narrowing, driven by type 2 immune responses involving cytokines like IL-4, IL-5, and IL-13, along with leukocytes including eosinophils and type 2 T-helper cells. These responses cause structural changes such as fibrosis and airway thickening, while BSM cells worsen asthma by releasing pro-inflammatory cytokines in response to allergens, microbial signals, or inflammatory cytokines from other cells. While current treatments manage asthma in most patients, alternative therapies are needed for difficult-to-treat cases, particularly prevalent in obese, allergic individuals. Emerging research suggests that therapeutic ketosis, induced by dietary changes or ketone supplementation, may reduce airway hyperresponsiveness and inflammation. The primary ketone body, {beta}-hydroxybutyrate (BHB), produced during carbohydrate scarcity, acts via cell-surface receptors and transporters, potentially mitigating asthma symptoms. Weight loss and caloric restriction increase ketone levels, correlating with reduced inflammation and improved asthma outcomes. We hypothesized that {beta}-hydroxybutyrate (BHB) reduces bronchoconstriction and inflammation in asthma by targeting bronchial smooth muscle. Using human bronchial smooth muscle cells (HBSMC) in vitro, we demonstrate herein that BHB suppresses IL-1{beta}-induced pro-inflammatory cytokine production through Free Fatty Acid Receptor 3 (FFAR3) activation. These findings suggest that bronchial smooth muscle is a key target of therapeutic ketosis, supporting BHBs potential benefits in preclinical asthma models.

cell biology↗

bioRxiv2024

Novel preclinical model of human lung cancer cachexia

Cancer cachexia (CC), a syndrome of skeletal muscle and adipose wasting, reduces responsiveness to therapies and increases mortality. There are no approved treatments for CC, which may relate to discordance between pre-clinical models and human CC. To address the need for clinically relevant models of lung CC, we generated inducible, lung epithelial cell specific KrasG12D/+ (G12D) mice. G12D mice develop CC over a protracted time course and phenocopy tissue and tumor, cellular, mutational, transcriptomic, and metabolic characteristics of human lung CC. G12D mice demonstrate early loss of adipose, a phenotype that was apparent across numerous models of CC and translates to patients with lung cancer. Tumor-released factors promote adipocyte lipolysis, a driver of adipose wasting in CC, and adipose wasting was inversely related to tumor burden. Thus, G12D mice model key features of human lung CC and highlight a role for early tumor metabolic reprogramming of adipose tissue in CC. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=199 SRC="FIGDIR/small/615385v3_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@66d87dorg.highwire.dtl.DTLVardef@f1cb4org.highwire.dtl.DTLVardef@2580f1org.highwire.dtl.DTLVardef@3463d5_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2021

The polyanionic drug suramin neutralizes histones and prevents endotheliopathy

Drugs are needed to protect against the neutrophil-derived histones responsible for endothelial injury in acute inflammatory conditions such as trauma and sepsis. Heparin and other polyanions can neutralize histones but may cause secondary, deleterious effects such as excessive bleeding. Here, we demonstrate that suramin--a widely available polyanionic drug--completely neutralizes the toxic effects of histones. The sulfate groups on suramin form stable electrostatic interactions with hydrogen bonds in the histone octamer with a dissociation constant of 250 nM. In cultured endothelial cells (Ea.Hy926), histone-induced thrombin generation was significantly decreased by suramin. In isolated murine blood vessels, suramin abolished aberrant endothelial cell calcium signals and rescued impaired endothelial-dependent vasodilation caused by histones. Suramin significantly decreased pulmonary endothelial cell ICAM-1 expression and neutrophil recruitment caused by infusion of sub-lethal doses of histones in vivo. Suramin also prevented lung edema, intra-alveolar hemorrhage and mortality in mice receiving a lethal dose of histones. Protection of vascular endothelial function from histone-induced damage is a novel mechanism of action for suramin with therapeutic implications for conditions characterized by elevated histone levels. Significance StatementPathologic levels of circulating histones cause acute endotheliopathy, characterized by widespread disruption of critical endothelial functions and thromboinflammation. We discovered that suramin binds histones and prevents histone-induced endothelial dysfunction, thrombin generation, lung injury, and death. Histone binding is a novel mechanism of action for suramin, considered among the safest and most effective drugs by the World Health Organization. These results support the use of suramin for protection of blood vessels in conditions exacerbated by circulating histones including trauma and sepsis.

immunology↗