Abstract-This study examines the effects of an increase in passive stretch in endothelium-removed bovine coronary artery on oxidant-induced changes in force generation. Increasing passive stretch on the arterial segments from 5 to 20 g for 20 minutes caused a subsequent increase (PϽ0.05) in force generation to 30 mmol/L KCl or 0.1 mol/L serotonin compared with the prestretch control response. Also associated with the passive stretch were increases in superoxide detection by lucigenin and a selective increase in extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase phosphorylation measured by Western analysis. The stretch-induced increase in force generation was eliminated by inhibition of the ERK pathway by the MEK inhibitor PD98059 but not by inhibitors of the p38 MAP kinase pathway (SB202190) or c-Jun N-terminal protein kinase pathway (SP200169). Additionally, stretch-induced increases in both ERK phosphorylation and force generation were attenuated by inhibition of tyrosine kinases (genistein), src (PP2), and specific sites on the epidermal growth factor receptor (EGFR) (AG1478). Probes for oxidant signaling, including NAD(P)H oxidase inhibitors (diphenyliodonium and apocynin) or enhancement of peroxide consumption (ebselen) but not inhibition of xanthine oxidase (allopurinol), attenuated the effects of stretch on both ERK phosphorylation and force generation. Furthermore, stretch caused an increase in EGFR phosphorylation and cytosolic to membrane translocation of the p47phox NAD(P)H oxidase subunit. Hydrogen peroxide also elicited contraction through EGFR phosphorylation and ERK. In summary, stretch seems to enhance force generation via ERK signaling through an EGFR/src-dependent mechanism activated by peroxide derived from a stretch-mediated activation of the NAD(P)H oxidase, a response that may contribute to hypertensive alterations in vascular reactivity. Key Words: stretch Ⅲ mitogen-activated protein kinases Ⅲ NAD(P)H oxidase Ⅲ hydrogen peroxide Ⅲ oxidant signaling T here is recent evidence that mechanical stretch can increase reactive oxygen species (ROS) production 1 and that ROS may be involved with the myogenic response of the microcirculation. 2 In addition, extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal protein kinase (JNK), subsets of the mitogen-activated protein (MAP) kinases, have been shown to be activated by mechanical 3,4 and pulsatile 5-7 stretch as well as oxidants such as peroxide. 8 Recent studies on the mechanisms of myogenic responses have detected evidence that both the p38 and ERK MAP kinase pathways mediate this response. 9 However, myogenic responses are not observed in conduit arteries, and evidence for oxidant-induced activation of the MAP kinases has generally been derived from studies in cultured cells, and their subsequent involvement in stretch-induced contractile responses has not yet been established.Preliminary observations from our laboratory have demonstrated that brief stretching of the coronary vessels increases luc...

Key pointsr The gastrointestinal epithelial enterochromaffin (EC) cell synthesizes the vast majority of the body's serotonin. As a specialized mechanosensor, the EC cell releases this serotonin in response to mechanical forces. However, the molecular mechanism of EC cell mechanotransduction is unknown.r In the present study, we show, for the first time, that the mechanosensitive ion channel Piezo2 is specifically expressed by the human and mouse EC cells. r The results of the present study suggest that the mechanosensitive ion channel Piezo2 is specifically expressed by the EC cells of the human and mouse small bowel and that it is important for EC cell mechanotransduction.Abstract The enterochromaffin (EC) cell in the gastrointestinal (GI) epithelium is the source of nearly all systemic serotonin (5-hydroxytryptamine; 5-HT), which is an important neurotransmitter and endocrine, autocrine and paracrine hormone. The EC cell is a specialized mechanosensor, and it is well known that it releases 5-HT in response to mechanical forces. However, the EC cell mechanotransduction mechanism is unknown. The present study aimed to determine whether Piezo2 is involved in EC cell mechanosensation. Piezo2 mRNA was expressed in human jejunum and mouse mucosa from all segments of the small bowel. Piezo2 immunoreactivity localized specifically within EC cells of human and mouse small bowel epithelium. The EC cell model released 5-HT in response to stretch, and had Piezo2 mRNA and protein, as well as a mechanically-sensitive inward non-selective cation current characteristic of Piezo2. Both inward currents and 5-HT release were inhibited by Piezo2 small interfering RNA and antagonists (Gd 3+ and D-GsMTx4). Jejunum mucosal pressure increased 5-HT release and short-circuit current via submucosal 5-HT3 and 5-HT4 receptors. Pressure-induced secretion was inhibited by the mechanosensitive ion channel antagonists gadolinium, ruthenium red and D-GsMTx4. We conclude that the EC cells in the human and mouse small bowel GI epithelium selectively express the mechanosensitive ion channel Piezo2, and also that activation of Piezo2 by force leads to inward currents, 5-HT release and an increase in mucosal secretion. Therefore, Piezo2 is critical to EC cell mechanosensitivity and downstream physiological effects.

Oxidant production and regulation is becoming increasingly important in the study of vascular signaling mechanisms, and recent reviews have characterized some of the possible roles for known downstream products of superoxide formation. In this review, we will examine current research in the field, with a special emphasis on the role of the superoxide molecule itself and its place amongst the slightly better understood roles of peroxide and peroxynitrite. The regulatory roles of oxidant species are wide-ranging, and their involvement in processes ranging from intracellular and receptor signaling mechanisms that regulate endothelial mediator release and vascular contractile function to processes that control cellular growth and apoptosis has been implied. Cellular sources of superoxide production and metabolism and the chemical interaction of oxidant species with specific components of cellular signaling mechanisms are considered important factors which determine physiological responses that control vascular function.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a continuum of injury that may arise from a number of primary insults.Localised injury may progress due to trauma from mechanical ventilation, a finding that has led to intense debate in the clinical and experimental literature over optimal ventilator management. The implementation of low tidal volume strategies has led to an improvement in outcomes; however, mortality remains unacceptably high.In the current review, ventilator-associated lung injury is examined, as it relates to the pathophysiological changes beyond direct airway trauma in ALI and ARDS, and an attempt is made to provide a historical perspective to outline potential current and future pitfalls in the use of surrogate end-points and the discovery of potential biomarkers. The systemic responses that lead to multi-organ dysfunction, the leading causes of morbidity and mortality in ALI and ARDS, are caused by pro-inflammatory signalling cascades and the activation of such diverse mediators as reactive oxygen species, immune response elements, apoptotic constituents and coagulation proteins.These areas are examined, including key mediators, and possible future areas of interest are discussed, including the potential of an ''acute lung injury chip'' to integrate measured surrogate biomarkers with real-time clinical information to improve patient outcomes.

BackgroundCoronavirus disease 2019 (COVID-19) is a disease caused by severe acute respiratory syndrome-coronavirus-2. Consensus suggestions can standardise care, thereby improving outcomes and facilitating future research.MethodsAn International Task Force was composed and agreement regarding courses of action was measured using the Convergence of Opinion on Recommendations and Evidence (CORE) process. 70% agreement was necessary to make a consensus suggestion.ResultsThe Task Force made consensus suggestions to treat patients with acute COVID-19 pneumonia with remdesivir and dexamethasone but suggested against hydroxychloroquine except in the context of a clinical trial; these are revisions of prior suggestions resulting from the interim publication of several randomised trials. It also suggested that COVID-19 patients with a venous thromboembolic event be treated with therapeutic anticoagulant therapy for 3 months. The Task Force was unable to reach sufficient agreement to yield consensus suggestions for the post-hospital care of COVID-19 survivors. The Task Force fell one vote shy of suggesting routine screening for depression, anxiety and post-traumatic stress disorder.ConclusionsThe Task Force addressed questions related to pharmacotherapy in patients with COVID-19 and the post-hospital care of survivors, yielding several consensus suggestions. Management options for which there is insufficient agreement to formulate a suggestion represent research priorities.