Biology subjects

Sharp, W. W.

Publications and source records attributed to Sharp, W. W..

4 recordsLinked to original sources

bioRxiv2026

Fentanyl-Induced Diaphragmatic Discoordination during Overdose

Synthetic opioids like fentanyl are a leading cause of overdose mortality. Although the hallmark of fentanyl overdose is ventilatory depression, fentanyl also induces tonic activation of skeletal musculature, including the diaphragm, which may advance progression of overdose towards death. While tonicity may further restrict diaphragmatic contractility, phase-specific dysregulation may also reflect a larger state of discoordination in respiratory control. Using urethane-anesthetized mice exposed to fentanyl, we test the hypothesis that fentanyl-induced diaphragm tonicity results from a loss of coordinated motor activity. Fentanyl produced two distinct phases: an initial phase of maximal ventilatory depression with preserved phasic activity, and a later phase characterized by unstable ventilation that partially rebounds, tonic diaphragmatic activation with loss of inspiratory phase dominance in EMG activity, and diminished bilateral diaphragmatic coordination. Carotid body denervation eliminated tonic activity and expiratory-phase EMG elevation, but it did not prevent hemi-diaphragm discoordination or ventilatory instability. Rhythmic brainstem slice recordings showed that bilateral preBotzinger complex burst-amplitude coupling was disrupted by -opioid receptor (MOR) agonism. Furthermore, disordered diaphragm activity was reversed by administration of the MOR antagonist, naloxone. Our findings reframe fentanyl overdose as a temporally evolving syndrome that involves distinct mechanisms to disrupt respiratory motor coordination. SIGNIFICANCE STATEMENTRespiratory depression is the hallmark of fentanyl overdose. We demonstrate that fentanyl actively reorganizes motor control of breathing, resulting in aberrant diaphragmatic tonicity and a loss of bilateral coordination. These phenomena emerge in temporal sequence and are driven by distinct central and peripheral contributions, suggesting fentanyl overdose is a complex multistage process and may require unique intervention strategies at different stages.

physiology↗

bioRxiv2023

A Novel HIF-2α/ARNT Signaling Pathway Protects Against Microvascular Dysfunction and heart failure After Myocardial Infarction

Myocardial infarction (MI) significantly compromises the integrity of the cardiac microvascular endothelial barrier, leading to enhanced leakage and inflammation that contribute to the progression of heart failure. While HIF2 is highly expressed in cardiac endothelial cells (ECs) under hypoxic conditions, its role in regulating microvascular endothelial barrier function during MI is not well understood. In this study, we utilized mice with a cardiac-specific deletion of HIF2, generated through an inducible Cre (Cdh5Cre-ERT2) recombinase system. These mice exhibited no apparent phenotype under normal conditions. However, following left anterior descending (LAD) artery ligation-induced MI, they showed increased mortality associated with enhanced cardiac vascular leakage, inflammation, worsened cardiac function, and exacerbated heart remodeling. These outcomes suggest a protective role for endothelial HIF2 in response to cardiac ischemia. Parallel investigations in human cardiac microvascular endothelial cells (CMVECs) revealed that loss of ecHif2 led to diminished endothelial barrier function, characterized by reduced tight-junction protein levels and increased cell death, along with elevated expression of IL6 and other inflammatory markers. These effects were substantially reversed by overexpressing ARNT, a critical dimerization partner for HIF2 during hypoxia. Additionally, ARNT deletion also led to increased CMVEC permeability. Interestingly, ARNT, rather than HIF2 itself, directly binds to the IL6 promoter to suppress IL6 expression. Our findings demonstrate the critical role of endothelial HIF2 in response to MI and identify the HIF2/ARNT axis as a transcriptional repressor, offering novel insights for developing therapeutic strategies against heart failure following MI.

cell biology↗

bioRxiv2022

HIF-1α induces glycolytic reprogramming in tissue-resident alveolar macrophagesto promote survival during acute lung injury

Cellular metabolism is a critical regulator of macrophage effector function. Tissue-resident alveolar macrophages (TR-AMs) inhabit a unique niche marked by high oxygen and low glucose. We have recently shown that in contrast to bone marrow-derived macrophages (BMDMs), TR-AMs cannot utilize glycolysis and predominantly rely on mitochondrial function for their effector response. It is not known how changes in local oxygen concentration that occur during conditions such as acute respiratory distress syndrome (ARDS) might affect TR-AM metabolism and function; however, ARDS is associated with progressive loss of TR-AMs, which correlates with the severity of disease and mortality. Here, we demonstrate that hypoxia robustly stabilizes HIF-1 in TR-AMs to promote a glycolytic phenotype. Hypoxia altered TR-AM metabolite signatures, cytokine production, and decreased their sensitivity to the inhibition of mitochondrial function. By contrast, hypoxia had minimal effects on BMDM metabolism. The effects of hypoxia on TR-AMs were mimicked by FG-4592, a HIF-1 stabilizer. Treatment with FG-4592 decreased TR-AM death and attenuated acute lung injury in mice. These findings reveal the importance of microenvironment in determining macrophage metabolic phenotype, and highlight the therapeutic potential in targeting cellular metabolism to improve outcomes in diseases characterized by acute inflammation.

cell biology↗

bioRxiv2020

Assessment of Brain Glucose Metabolism Following Cardiac Arrest by FDG Positron Emission Tomography

BackgroundCardiac arrest (CA) patients who survived by cardiopulmonary resuscitation (CPR) can present different levels of neurological deficits ranging from minor cognitive impairments to persistent vegetative state and brain death. The pathophysiology of the resulting brain injury is poorly understood and whether changes in post-CA brain metabolism contribute to the injury are unknown. Here we utilized [18F]FDG-PET to study in vivo cerebral glucose metabolism 72 hours following CA in a murine cardiac arrest model. MethodsAnesthetized and ventilated adult C57BL/6 mice underwent 12-minute KCl-induced CA followed by CPR. Seventy-two hours following cardiac arrest, surviving mice were intraperitoneally injected with [18F]FDG (~186 Ci/200 L) and imaged on Molecubes preclinical micro PET/CT imaging systems after a 30-minute awake uptake period. Brain [18F]FDG uptake was determined by the VivoQuant software on fused PET/CT images with the 3D brain atlas. Upon completion of PET imaging, remaining [18F]FDG radioactivity in the brain, heart, and liver was determined using a gamma counter. ResultsGlobal increases in brain [18F]FDG uptake in post-CA mice were observed compared to shams and controls. The median standardized uptake value (SUV) of [18F]FDG for CA animals was 1.79 vs. sham 1.25 (p<0.05) and control animals 0.78 (p<0.01). This increased uptake was consistent throughout the 60-minute imaging period and across all brain regions reaching statistical significance in the midbrain, pons, and medulla. Biodistribution analyses of various key organs yielded similar observations that the median [18F]FDG uptake for brain were 7.04%ID/g tissue for CA mice vs 5.537%ID/g tissue for sham animals, p<0.05). ConclusionsThis study has successfully applied [18F]FDG-PET/CT to measure changes in brain metabolism in a murine model of asystolic CA. Our results demonstrate increased [18F]FDG uptake in the brain 72 hours following CA, suggesting increased metabolic demand in the case of severe neurological injury. Further study is warranted to determine the etiology of these changes.

neuroscience↗