AIMS:Incretin agonists are used to treat obesity and metabolic dysfunction. Instead of systemically delivering high levels of hormone receptor agonists that can lead to adverse effects, we tested and optimized oral microbead formulations that activate endogenous enteroendocrine signalling systems via distal nutrient-sensing cells. MATERIALS AND METHODS:We report two randomized Phase 1 studies (NCT05713773 and NCT05737927) measuring acute pharmacokinetic/pharmacodynamic responses following consumption of microbeads that deliver glucose to the distal small intestine: these studies compared coating variations and glucose dosing. The primary endpoint was plasma glucagon-like peptide 1 (GLP-1) levels; we also measured GLP-2, PYY, glicentin, oxyntomodulin, glucose-dependent insulinotropic peptide, C-peptide, and insulin as exploratory endpoints. In a subsequent randomized Phase 2a trial (NCT05803772), prediabetic subjects consumed a lead formulation or placebo once daily for 6 weeks each in a two-period, two-sequence crossover design. Oral glucose tolerance was measured at baseline and following treatment in each sequence, with the primary endpoint being the change in the area under the curve. RESULTS:Our microbead formulation successfully targeted the distal small intestine and elicited a robust plurihormonal enteroendocrine response; our Phase 2a data show that the lead formulation improved glucose tolerance in pre-diabetic patients, comparable to results using GLP-1 mimetics. Adverse events were infrequent and modest. CONCLUSIONS:Targeted glucose release activates endogenous enteroendocrine signalling networks, improves a clinically relevant metabolic endpoint, and has minimal adverse effects. The approach to target native enteroendocrine signalling has disruptive potential for the treatment of metabolic disorders, including obesity.

IntroductionHypertension and impaired tissue perfusion are frequent comorbidities in obesity. Since resistance arteries are the primary regulators of peripheral resistance and hence, systemic blood pressure and local blood flow control, we hypothesized that resistance arteries isolated from obese mice would display augmented myogenic reactivity and altered vasomotor responses, compared to non-obese controls. MethodsEight-week-old C57BL/6J mice were fed either a high-fat diet (60% calories from fat; HFD) or a matched control diet for 16 weeks. Body weight, fasting blood glucose, oral glucose tolerance and insulin tolerance were measured. In parallel studies, we measured mean arterial pressure, conducted echocardiographic measurements of cardiac morphology and function and assessed skeletal muscle, mesenteric and cerebral resistance artery reactivity ex vivo with pressure myography. ResultsHFD mice exhibited substantial weight gain and metabolic dysfunction compared to controls. Left ventricular wall thickness and mass were increased in HFD mice, but no other morphological or functional cardiac parameters were different from controls. Blood pressure was modestly increased in HFD mice (from 81 to 87 mmHg; measured under anesthesia); however, contrary to our hypothesis, resistance arteries from HFD mice showed no overt microvascular phenotype in any microvascular bed tested (i.e., no differences in passive diameter, myogenic reactivity or vasomotor responses to phenylephrine or acetylcholine). ConclusionWe conclude that resistance artery function is unaltered in this diet-induced model of obesity with metabolic dysfunction.

Lumacaftor is an active ingredient in the US Food and Drug Administration-approved combination medication Orkambi®, which is used for treating cystic fibrosis. Experimental evidence suggests that lumacaftor can be used as a monotherapy to improve brain perfusion and memory in heart failure. To clinically assess this therapeutic intervention, a formulation with demonstrated bioequivalence to the currently approved combination product is required. This comparative bioavailability and food-effect study compared lumacaftor pharmacokinetics in healthy patients following: (i) oral administration of lumacaftor (400 mg; Test Product) or Orkambi® (lumacaftor 400 mg/ivacaftor 250 mg; Reference Product) in the fed state and (ii) oral administration of lumacaftor (400 mg; Test Product) in the fasted to fed state. Plasma lumacaftor concentrations were measured with a standard liquid chromatography with tandem mass spectrometry approach. The “Test-to-Reference ratio” of the geometric least-square means for maximum plasma concentration and area under the curve met the Food and Drug Administration-defined criteria for bioequivalence; median times to maximum plasma concentration values were not statistically different. The “Fed to Fasted ratio” of the geometric least-square means for maximum plasma concentration and area under the curve indicated a clear food effect on bioavailability. Lumacaftor exposure was approximately two times higher when administered with fatty foods than when taken in a fasting state. The monosubstance formulation was well tolerated. We conclude that the lumacaftor monosubstance formulation delivers lumacaftor exposure that is not meaningfully different than the currently approved combination product. ClinicalTrials.gov identifier: NCT05968612.

BackgroundIn male mice, a circadian rhythm in myogenic reactivity influences the extent of brain injury following subarachnoid haemorrhage (SAH). We hypothesized that female mice have a different cerebrovascular phenotype and consequently, a distinct SAH-induced injury phenotype.MethodsSAH was modelled by pre-chiasmatic blood injection. Olfactory cerebral resistance arteries were functionally assessed by pressure myography; these functional assessments were related to brain histology and neurobehavioral assessments. Cystic fibrosis transmembrane conductance regulator (CFTR) expression was assessed by PCR and Western blot. We compared non-ovariectomized and ovariectomized mice.FindingsCerebrovascular myogenic reactivity is not rhythmic in females and no diurnal differences in SAH-induced injury are observed; ovariectomy does not unmask a rhythmic phenotype for any endpoint. CFTR expression is rhythmic, with similar expression levels compared to male mice. CFTR inhibition studies, however, indicate that CFTR activity is lower in female arteries. Pharmacologically increasing CFTR expression in vivo (3 mg/kg lumacaftor for 2 days) reduces myogenic tone at Zeitgeber time 11, but not Zeitgeber time 23. Myogenic tone is not markedly augmented following SAH in female mice and lumacaftor loses its ability to reduce myogenic tone; nevertheless, lumacaftor confers at least some injury benefit in females with SAH.InterpretationFemale mice possess a distinct cerebrovascular phenotype compared to males, putatively due to functional differences in CFTR regulation. This sex difference eliminates the CFTR-dependent cerebrovascular effects of SAH and may alter the therapeutic efficacy of lumacaftor compared to males.FundingBrain Aneurysm Foundation, Heart and Stroke Foundation and Ted Rogers Centre for Heart Research.

Elevated total peripheral resistance (TPR) is a hallmark of many cardiovascular diseases and furthers disease progression. We previously demonstrated that myogenic tone, regulated by membrane-bound tumour necrosis factor (mTNF) reverse signalling, is a primary modulator of TPR. Thus, inhibiting mTNF reverse signalling should reduce TPR with the potential to improve disease outcome. However, since mTNF is a ubiquitous protein with critical biological functions, its indiscriminate inhibition can cause widespread side effects. Therefore, therapeutics aiming to reduce myogenic tone and TPR must target other elements of mTNF reverse signalling. To identify these unknown participants of mTNF reverse signalling, we used proximity-dependent biotinylation coupled to mass spectrometry (BioID). Our search identified 42 high confidence hits that interact with and/or are proximal to mTNF’s cytoplasmic domain. Gene ontology (GO) analysis revealed that molecularly, these proteins are structural constituents of the cytoskeleton involved in actin and cell adhesion molecule binding. This aligns with our underlying hypothesis that mTNF functions as a mechanosensor that tethers to its receptors and initiates myogenic vasoconstriction in response to changes in transmural pressure. GO also identified proteins involved in MAPK and RhoA signalling, which are critically involved in myogenic vasoconstriction. Our most abundant hit (fold change = 12.6, p-value = 0.0023) is a cytoskeletal protein that plays a role in maintaining the structural integrity of cells. This protein also interacts with proteins involved in various signalling cascades, namely, RhoA and calcium-dependent signalling pathways. Thus, we hypothesize that this protein is essential for formation of signalling complexes with mTNF and interacts with other proteins to mediate reverse signalling . We will employ a bioluminescence-based approach to quantify the strength of all interactions detected by BioID and identify small molecule inhibitors that can disrupt these interactions. These newly discovered inhibitors could potentially be used as novel therapeutics targeting myogenic tone and hence, elevated TPR to improve disease management and clinical outcome of cardiovascular diseases.

Background Cognitive impairment is a serious comorbidity in heart failure patients, but effective therapies are lacking. We investigated the mechanisms that alter hippocampal neurons following myocardial infarction (MI). Methods MI was induced in male C57Bl/6 mice by left anterior descending coronary artery ligation. We utilised standard procedures to measure cystic fibrosis transmembrane regulator (CFTR) protein levels, inflammatory mediator expression, neuronal structure, and hippocampal memory. Using in vitro and in vivo approaches, we assessed the role of neuroinflammation in hippocampal neuron degradation and the therapeutic potential of CFTR correction as an intervention. Findings Hippocampal dendrite length and spine density are reduced after MI, effects that associate with decreased neuronal CFTR expression and concomitant microglia activation and inflammatory cytokine expression. Conditioned medium from lipopolysaccharide-stimulated microglia (LCM) reduces neuronal cell CFTR protein expression and the mRNA expression of the synaptic regulator post-synaptic density protein 95 (PSD-95) in vitro. Blocking CFTR activity also down-regulates PSD-95 in neurons, indicating a relationship between CFTR expression and neuronal health. Pharmacologically correcting CFTR expression in vitro rescues the LCM-mediated down-regulation of PSD-95. In vivo, pharmacologically increasing hippocampal neuron CFTR expression improves MI-associated alterations in neuronal arborisation, spine density, and memory function, with a wide therapeutic time window. Interpretation Our results indicate that CFTR therapeutics improve inflammation-induced alterations in hippocampal neuronal structure and attenuate memory dysfunction following MI. Copyright (C) 2022 The Author(s). Published by Elsevier B.V

The Earth's rotation generates environmental oscillations (e.g., in light and temperature) that have imposed unique evolutionary pressures over millions of years. Consequently, the circadian clock, a ubiquitously expressed molecular system that aligns cellular function to these environmental cues, has become an integral component of our physiology. The resulting functional rhythms optimize and economize physiological performance: perturbing these rhythms, therefore, is frequently deleterious. This perspective article focuses on circadian rhythms in resistance artery myogenic reactivity, a key mechanism governing tissue perfusion, total peripheral resistance and systemic blood pressure. Emerging evidence suggests that myogenic reactivity rhythms are locally generated in a microvascular bed-specific manner at the level of smooth muscle cells. This implies that there is a distinct interface between the molecular clock and the signalling pathways underlying myogenic reactivity in the microvascular beds of different organs. By understanding the precise nature of these molecular links, it may become possible to therapeutically manipulate microvascular tone in an organ-specific manner. This raises the prospect that interventions for vascular pathologies that are challenging to treat, such as hypertension and brain malperfusion, can be significantly improved.

AIMS:Circadian rhythms orchestrate important functions in the cardiovascular system: the contribution of microvascular rhythms to cardiovascular disease progression/severity is unknown. This study hypothesized that (i) myogenic reactivity in skeletal muscle resistance arteries is rhythmic and (ii) disrupting this rhythmicity would alter cardiac injury post-myocardial infarction (MI).METHODS AND RESULTS:Cremaster skeletal muscle resistance arteries were isolated and assessed using standard pressure myography. Circadian rhythmicity was globally disrupted with the ClockΔ19/Δ19 mutation or discretely through smooth muscle cell-specific Bmal1 deletion (Sm-Bmal1 KO). Cardiac structure and function were determined by echocardiographic, hemodynamic and histological assessments. Myogenic reactivity in cremaster muscle resistance arteries is rhythmic. This rhythm is putatively mediated by the circadian modulation of a mechanosensitive signalosome incorporating tumour necrosis factor and casein kinase 1. Following left anterior descending coronary artery ligation, myogenic responsiveness is locked at the circadian maximum, although circadian molecular clock gene expression cycles normally. Disrupting the molecular clock abolishes myogenic rhythmicity: myogenic tone is suspended at the circadian minimum and is no longer augmented by MI. The reduced myogenic tone in ClockΔ19/Δ19 mice and Sm-Bmal1 KO mice associates with reduced total peripheral resistance (TPR), improved cardiac function and reduced infarct expansion post-MI.CONCLUSIONS:Augmented microvascular constriction aggravates cardiac injury post-MI. Following MI, skeletal muscle resistance artery myogenic reactivity increases specifically within the rest phase, when TPR would normally decline. Disrupting the circadian clock interrupts the MI-induced augmentation in myogenic reactivity: therapeutics targeting the molecular clock, therefore, may be useful for improving MI outcomes.

BACKGROUND AND PURPOSE:Circadian rhythms influence the extent of brain injury following subarachnoid hemorrhage (SAH), but the mechanism is unknown. We hypothesized that cerebrovascular myogenic reactivity is rhythmic and explains the circadian variation in SAH-induced injury. METHODS:SAH was modeled in mice with prechiasmatic blood injection. Inducible, smooth muscle cell-specific Bmal1 (brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1) gene deletion (smooth muscle-specific Bmal1 1 knockout [sm-Bmal1 KO]) disrupted circadian rhythms within the cerebral microcirculation. Olfactory cerebral resistance arteries were functionally assessed by pressure myography in vitro; these functional assessments were related to polymerase chain reaction/Western blot data, brain histology (Fluoro-Jade/activated caspase-3), and neurobehavioral assessments (modified Garcia scores). RESULTS:Cerebrovascular myogenic vasoconstriction is rhythmic, with a peak and trough at Zeitgeber times 23 and 11 (ZT23 and ZT11), respectively. Histological and neurobehavioral assessments demonstrate that higher injury levels occur when SAH is induced at ZT23, compared with ZT11. In sm-Bmal1 KO mice, myogenic reactivity is not rhythmic. Interestingly, myogenic tone is higher at ZT11 versus ZT23 in sm-Bmal1 KO mice; accordingly, SAH-induced injury in sm-Bmal1 KO mice is more severe when SAH is induced at ZT11 compared to ZT23. We examined several myogenic signaling components and found that CFTR (cystic fibrosis transmembrane conductance regulator) expression is rhythmic in cerebral arteries. Pharmacologically stabilizing CFTR expression in vivo (3 mg/kg lumacaftor for 2 days) eliminates the rhythmicity in myogenic reactivity and abolishes the circadian variation in SAH-induced neurological injury. CONCLUSIONS:Cerebrovascular myogenic reactivity is rhythmic. The level of myogenic tone at the time of SAH ictus is a key factor influencing the extent of injury. Circadian oscillations in cerebrovascular CFTR expression appear to underlie the cerebrovascular myogenic reactivity rhythm.

Subarachnoid hemorrhage (SAH) is a devastating stroke subtype with a high rate of mortality and morbidity. The poor clinical outcome can be attributed to the biphasic course of the disease: even if the patient survives the initial bleeding emergency, delayed cerebral ischemia (DCI) frequently follows within 2 weeks time and levies additional serious brain injury. Current therapeutic interventions do not specifically target the microvascular dysfunction underlying the ischemic event and as a consequence, provide only modest improvement in clinical outcome. SAH perturbs an extensive number of microvascular processes, including the “automated” control of cerebral perfusion, termed “cerebral autoregulation.” Recent evidence suggests that disrupted cerebral autoregulation is an important aspect of SAH-induced brain injury. This review presents the key clinical aspects of cerebral autoregulation and its disruption in SAH: it provides a mechanistic overview of cerebral autoregulation, describes current clinical methods for measuring autoregulation in SAH patients and reviews current and emerging therapeutic options for SAH patients. Recent advancements should fuel optimism that microvascular dysfunction and cerebral autoregulation can be rectified in SAH patients.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its clinical manifestation (COVID-19; coronavirus disease 2019) have caused a worldwide health crisis. Disruption of epithelial and endothelial barriers is a key clinical turning point that differentiates patients who are likely to develop severe COVID-19 outcomes: it marks a significant escalation in respiratory symptoms, loss of viral containment and a progression toward multi-organ dysfunction. These barrier mechanisms are independently compromised by known COVID-19 risk factors, including diabetes, obesity and aging: thus, a synergism between these underlying conditions and SARS-CoV-2 mechanisms may explain why these risk factors correlate with more severe outcomes. This review examines the key cellular mechanisms that SARS-CoV-2 and its underlying risk factors utilize to disrupt barrier function. As an outlook, we propose that glucagon-like peptide 1 (GLP-1) may be a therapeutic intervention that can slow COVID-19 progression and improve clinical outcome following SARS-CoV-2 infection. GLP-1 signaling activates barrier-promoting processes that directly oppose the pro-inflammatory mechanisms commandeered by SARS-CoV-2 and its underlying risk factors.

Subarachnoid hemorrhage (SAH) is a devastating cerebral event caused by an aneurysmal rupture. In addition to neurological injury, SAH has significant effects on cardiac function and the peripheral microcirculation. Since these peripheral complications may exacerbate brain injury, the prevention and management of these peripheral effects are important for improving the overall clinical outcome after SAH. In this investigation, we examined the effects of SAH on cardiac function and vascular reactivity in a well-characterized blood injection model of SAH. Standard echocardiographic and blood pressure measurement procedures were utilized to assess cardiac function and hemodynamic parameters in vivo; we utilized a pressure myography approach to assess vascular reactivity in cremaster skeletal muscle resistance arteries ex vivo. We observed that elevated catecholamine levels in SAH stun the myocardium, reduce cardiac output and augment myogenic vasoconstriction in isolated cremaster arteries. These cardiac and vascular effects are driven by beta- and alpha-adrenergic receptor signaling, respectively. Clinically utilized adrenergic receptor antagonists can prevent cardiac injury and normalize vascular function. We found that tumor necrosis factor (TNF) gene deletion prevents the augmentation of myogenic reactivity in SAH: since membrane-bound TNF serves as a mechanosensor in the arteries assessed, alpha-adrenergic signaling putatively augments myogenic vasoconstriction by enhancing mechanosensor activity.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its clinical manifestation (COVID-19; coronavirus disease 2019) have caused a worldwide health crisis. Disruption of epithelial and endothelial barriers is a key clinical turning point that differentiates patients who are likely to develop severe COVID-19 outcomes: it marks a significant escalation in respiratory symptoms, loss of viral containment and a progression toward multi-organ dysfunction. These barrier mechanisms are independently compromised by known COVID-19 risk factors, including diabetes, obesity and aging: thus, a synergism between these underlying conditions and SARS-CoV-2 mechanisms may explain why these risk factors correlate with more severe outcomes. This review examines the key cellular mechanisms that SARS-CoV-2 and its underlying risk factors utilize to disrupt barrier function. As an outlook, we propose that glucagon-like peptide 1 (GLP-1) may be a therapeutic intervention that can slow COVID-19 progression and improve clinical outcome following SARS-CoV-2 infection. GLP-1 signaling activates barrier-promoting processes that directly oppose the pro-inflammatory mechanisms commandeered by SARS-CoV-2 and its underlying risk factors.

Several pathological manifestations in coronavirus disease 2019 (COVID-19), including thick mucus, poor mucociliary clearance, and bronchial wall thickening, overlap with cystic fibrosis disease patterns and may be indicative of "acquired" cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction. Indeed, tumor necrosis factor (TNF), a key cytokine driving COVID-19 pathogenesis, downregulates lung CFTR protein expression, providing a strong rationale that acquired CFTR dysfunction arises in the context of COVID-19 infection. In this perspective, we propose that CFTR therapeutics, which are safe and generally well-tolerated, may provide benefit to COVID-19 patients. Although CFTR therapeutics are currently only approved for treating cystic fibrosis, there are efforts to repurpose them for conditions with "acquired" CFTR dysfunction, for example, chronic obstructive pulmonary disease. In addition to targeting the primary lung pathology, CFTR therapeutics may possess value-added effects: their anti-inflammatory properties may dampen exaggerated immune cell responses and promote cerebrovascular dilation; the latter aspect may offer some protection against COVID-19 related stroke.

Heart failure (HF) and subarachnoid hemorrhage (SAH) chronically reduce cerebral perfusion, which negatively affects clinical outcome. This work demonstrates a strong relationship between cerebral artery cystic fibrosis transmembrane conductance regulator (CFTR) expression and altered cerebrovascular reactivity in HF and SAH. In HF and SAH, CFTR corrector compounds (C18 or lumacaftor) normalize pathological alterations in cerebral artery CFTR expression, vascular reactivity, and cerebral perfusion, without affecting systemic hemodynamic parameters. This normalization correlates with reduced neuronal injury. Therefore, CFTR therapeutics have emerged as valuable clinical tools to manage cerebrovascular dysfunction, impaired cerebral perfusion, and neuronal injury.

Shift work is a risk factor for many diseases, including cardiovascular disease. Although the biological pathways are still unclear, it is hypothesized that cortisol disruption during night work is an intermediate. The objective of this study is to determine whether total cortisol production and cortisol pattern mediate the relationship between current shift work and cardiometabolic risk (CMR) among female hospital employees.A cross-sectional study was conducted among 326 female employees (166 rotating shift workers, 160 day workers), recruited from a hospital in Southeastern Ontario, Canada, during 2011 to 2014. Participants completed a baseline interview, questionnaire, and clinical exam. Urine samples were collected over two 24-hour periods and used to analyze creatinine-adjusted cortisol, which was then used to calculate total cortisol production (AUCG), and pattern (AUCI). Mediation analysis was performed to test the mediating effect of cortisol in the relationship between shift work and a continuous CMR score.Current shift work is associated with a 0.52 higher CMR score (95% CI: 0.15, 0.89), a lower cortisol output (AUCG), and a flatter pattern (AUCI) over a 2-day period. AUCG is a partial mediator in the relationship between shift work and CMR, whereas AUCI is not. AUCG is also associated with CMR while controlling for shift work, suggesting that lower total cortisol production is also linked to CMR in non-shift workers.Total cortisol production is a partial mediator in the relationship between rotating shift work and CMR among female hospital employees, whereas cortisol pattern is not a mediator.Le travail par roulement est un facteur de risque de nombreuses maladies, y compris les maladies cardiovasculaires. Bien que les mécanismes biologiques en cause ne soient pas encore élucidés, une hypothèse voudrait que la perturbation du métabolisme du cortisol pendant le travail de nuit soit un mécanisme intermédiaire. L’objectif de cette étude est de déterminer si la production de cortisol total et le profil du cortisol assurent la médiation du lien entre le travail par roulement en cours et le risque cardiométabolique (RCM) chez des femmes travaillant dans un hôpital.Une étude transversale a été menée auprès de 326 employées (166 employées ayant un travail en rotation et 160 employées de jour) recrutées dans un hôpital du sud-est de l’Ontario (Canada) entre 2011 et 2014. Les participantes ont passé une entrevue initiale, elles ont répondu à un questionnaire et passé un examen clinique. Des échantillons d’urine ont été recueillis pendant deux périodes de 24 heures aux fins d’analyse des taux de cortisol corrigés selon la créatinine; ces taux ont ensuite servi à calculer la production de cortisol total (ASCG) et le profil du cortisol (ASCI). Une analyse a été réalisée pour tester l’effet médiateur du cortisol dans le contexte du lien existant entre le travail par roulement et un score de RCM continu.Le travail par roulement en cours est associé à un score de RCM plus élevé de 0,52 (intervalle de confiance [IC] à 95 %: 0,15 à 0,89), à une élimination inférieure du cortisol (ASCG) et à un profil plus plat (ASCI) du cortisol sur une période de deux jours. L’ASCG est un médiateur partiel du lien entre le travail par roulement et le RCM, ce qui n’est pas le cas de l’ASCI. L’ASCG est également associée au RCM lorsqu’une correction est apportée en fonction du travail par roulement, ce qui indique que la production inférieure de cortisol total est également liée au RCM chez les personnes n’ayant pas un travail par roulement.Contrairement au cycle du cortisol, la production de cortisol total est un médiateur partiel du lien existant entre le travail en rotation et le RCM chez les employées de l’hôpital de l’étude.

Aneurysmal subarachnoid hemorrhage (SAH) is a devastating cerebral event that kills or debilitates the majority of those afflicted. The blood that spills into the subarachnoid space stimulates profound cerebral artery vasoconstriction and consequently, cerebral ischemia. Thus, once the initial bleeding in SAH is appropriately managed, the clinical focus shifts to maintaining/improving cerebral perfusion. However, current therapeutic interventions largely fail to improve clinical outcome, because they do not effectively restore normal cerebral artery function. This review discusses emerging evidence that perturbed cerebrovascular “myogenic reactivity,” a crucial microvascular process that potently dictates cerebral perfusion, is the critical element underlying cerebral ischemia in SAH. In fact, the myogenic mechanism could be the reason why many therapeutic interventions, including “Triple H” therapy, fail to deliver benefit to patients. Understanding the molecular basis for myogenic reactivity changes in SAH holds the key to develop more effective therapeutic interventions; indeed, promising recent advancements fuel optimism that vascular dysfunction in SAH can be corrected to improve outcome.

Tumour necrosis factor (TNF) is a ubiquitously expressed cytokine with functions beyond the immune system. In several diseases, the induction of TNF expression in resistance artery smooth muscle cells enhances microvascular myogenic vasoconstriction and perturbs blood flow. This pathological role prompted our hypothesis that constitutively expressed TNF regulates myogenic signalling and systemic haemodynamics under non-pathological settings. Here we show that acutely deleting the TNF gene in smooth muscle cells or pharmacologically scavenging TNF with etanercept (ETN) reduces blood pressure and resistance artery myogenic responsiveness; the latter effect is conserved across five species, including humans. Changes in transmural pressure are transduced into intracellular signals by membrane-bound TNF (mTNF) that connect to a canonical myogenic signalling pathway. Our data positions mTNF ‘reverse signalling’ as an integral element of a microvascular mechanosensor; pathologic or therapeutic perturbations of TNF signalling, therefore, necessarily affect microvascular tone and systemic haemodynamics.