Jeremy P. T. Ward

Hypoxic pulmonary vasoconstriction (HPV) is a rapid and reversible constrictor response of the pulmonary vasculature, and especially its small muscular precapillary arteries, which is initiated by episodes of local alveolar hypoxia. Acting as a protective homeostatic vasomotor mechanism, HPV enables maximal gas exchange by diverting blood from poorly ventilated alveoli into those rich in oxygen, thereby optimizing oxygen uptake and the ventilation–perfusion (V/Q) ratio so as to maintain the arterial oxygen partial pressure (P_aO₂) within the physiological range. HPV is an intrinsic mechanism of pulmonary artery smooth muscle cells (PASMCs), and requires an O₂ sensor which acts through mediator(s) to trigger effector mechanisms within these cells to evoke constriction. Whereas HPV effector mechanisms are reasonably well defined, the nature of the O₂ sensor and mediators remains in dispute, and a number of proposals have been developed to account for these. Some (but not all) of these share a focus on the concept that hypoxia activates effector mechanisms by inducing a change in the PASMC cytoplasmic redox state. Of these, the Redox Theory, first proposed by Kenneth Weir and Stephen Archer in 1995, proposes that hypoxia inhibits mitochondrial production of reactive oxygen species (ROS), thereby causing the cytoplasm to become more reduced. This inhibits ongoing vasorelaxation maintained by the opening of voltage-gated K⁺ channels. In contrast, according to the Mitochondrial ROS hypothesis, introduced by Paul Schumacker and Naveen Chandel in 2001, hypoxia increases mitochondrial ROS production, causing an oxidizing shift in the cytoplasmic redox state that activates several vasoconstricting pathways. In a third redox-based scenario, developed by Michael Wolin and Sachin Gupte, hypoxia evokes contraction by causing a fall in H₂O₂ production by NADPH oxidase and by activating the pentose phosphate pathway. These effects inhibit basal vasorelaxation maintained by the guanylate cyclase and protein kinase G and also stimulate vasoconstricting mechanisms. In this comprehensive review, we first provide a detailed summary of the key studies contributing to the development of these proposals and then subject the evidence supporting them to a critical appraisal, based in part on how well they accord with the wider literature and recent developments in our understanding of how cells shape and deploy redox mechanisms in order to regulate cell function.

Hypoxic pulmonary vasoconstriction (HPV) is a rapid and reversible constrictor response of the pulmonary vasculature, and especially its small muscular precapillary arteries, which is initiated by episodes of local alveolar hypoxia. Acting as a protective homeostatic vasomotor mechanism, HPV enables maximal gas exchange by diverting blood from poorly ventilated alveoli in to those rich in oxygen, thereby optimizing oxygen uptake and the ventilation-perfusion (V/Q) ratio so as to maintain the arterial oxygen partial pressure (P_aO₂) within the physiological range. HPV is an intrinsic mechanism of pulmonary artery smooth muscle cells (PASMC), and requires an O₂ sensor which acts through mediator(s) to trigger effector mechanisms within these cells to evoke constriction. Whereas HPV effector mechanisms are reasonably well-defined, the nature of the O₂ sensor and mediators remain in dispute. The three most comprehensive models of O2 sensing in HPV share a focus on the concept that hypoxia activates effector mechanisms by inducing a change in the PASMC cytoplasmic redox state. According to the Redox Theory, first proposed by Kenneth Weir and Stephen Archer in 1995, hypoxia inhibits mitochondrial production of reactive oxygen species (ROS), thereby causing the cytoplasm to become more reduced. This inhibits ongoing vasorelaxation maintained by the opening of voltage-gated K+ channels. In contrast, according to the Mitochondrial ROS hypothesis, introduced by Paul Schumacker and Naveen Chandel in 2001, hypoxia increases mitochondrial ROS production, causing an oxidizing shift in the cytoplasmic redox poise which activate several vasoconstricting pathways. In a third scenario, developed by Michael Wolin and Sachin Gupte, hypoxia evokes contraction by causing a fall in H2O2 production by NADPH oxidase, and by activating the pentose phosphate pathway. These effects inhibit basal vasorelaxation maintained by the guanylate cyclase and protein kinase G and also stimulate vasoconstricting mechanisms. In this comprehensive review, we summarize the key studies contributing to the development of these proposals and then subject the evidence supporting them to critical appraisal, based in part on how well they accord with the wider literature and recent developments in our understanding of how cells shape and deploy redox mechanisms in order to regulate cell function.

Idiopathic pulmonary fibrosis (IPF) is a disease with a poor prognosis and no curative therapies. Fibroblast activation by transforming growth factor β1 (TGFβ1) and disrupted metabolic pathways, including the arginine–polyamine pathway, play crucial roles in IPF development. Polyamines are agonists of the calcium/cation-sensing receptor (CaSR), activation of which is detrimental for asthma and pulmonary hypertension, but its role in IPF is unknown. To address this question, we evaluated polyamine abundance using metabolomic analysis of IPF patient saliva. Furthermore, we examined CaSR functional expression in human lung fibroblasts (HLFs), assessed the anti-fibrotic effects of a CaSR antagonist, NPS2143, in TGFβ1-activated normal and IPF HLFs by RNA sequencing and immunofluorescence imaging, respectively; and NPS2143 effects on polyamine synthesis in HLFs by immunoassays. Our results demonstrate that polyamine metabolites are increased in IPF patient saliva. Polyamines activate fibroblast CaSR in vitro, elevating intracellular calcium concentration. CaSR inhibition reduced TGFβ1-induced polyamine and pro-fibrotic factor expression in normal and IPF HLFs. TGFβ1 directly stimulated polyamine release by HLFs, an effect that was blocked by NPS2143. This suggests that TGFβ1 promotes CaSR activation through increased polyamine expression, driving a pro-fibrotic response. By halting some polyamine-induced pro-fibrotic changes, CaSR antagonists exhibit disease-modifying potential in IPF onset and development.

In our department patients with oesophago-gastric junctional adenocarcinomas with signet ring differentiation undergo a second endoscopy for gastric mapping biopsies to investigate the extent of tumour extension into the proximal stomach. This is due to the perceived aggressive morphology and to avoid a R1 (microscopic positive) resection at the distal margin. Our aim was to elucidate whether gastric mapping endoscopic biopsies are necessary prior to resection in signet ring adenocarcinomas of the oesophago-gastric junction (OGJ). Patients with operable OGJ adenocarcinomas with signet ring morphology were retrospectively analysed from 2011–2021 from our databank of completed oesophagectomies at our upper gastrointestinal cancer surgical department. From 2014–2021, OGJ adenocarcinomas identified with signet ring differentiation were subjected to a second invasive endoscopy with gastric mapping biopsies to determine the distal ex-tent of microscopic invasion into the cardia and beyond. These were analysed to determine the histopathological yield from gastric mapping biopsies and the number of cases with a positive (R1) distal resection margin. From 2014, 322 oesophagectomy cases were completed and these were analysed further. Of these, 21.7% (n = 70) were found pre-operatively to have signet ring differentiation and thus underwent a second gastric mapping endoscopy. Within the signet ring morphology cohort, only one patient (1.4%) was found to involve a R1 resection margin which necessitated a second operation involving gastric resection and colonic interposition. Our results suggest that patients with signet ring adenocarcinoma of the OGJ do not need gastric mapping biopsies to determine the distal margin prior to resection. Although considered a more aggressive subtype of adenocarcinoma, radial infiltration from the tumour does not seem to affect conventional surgical oncological margins.

Oesophageal cancer is clinically staged using the TNM classification by modalities such as CT, PET-CT and endoscopic ultrasound. This is used to assess and guide oncological treatment in the form of neoadjuvant chemotherapy, radiotherapy and surgery. Following neoadjuvant therapy and/or surgery the resected specimen is analysed and given a final histological stage. The purpose of this study was to evaluate the accuracy and variation in pre-operative (radiological) stage from the final histopathological stage. This retrospective study was conducted using an electronic database containing pre- and post-operative TNM staging information on all patients undergoing elective oesophagectomies from April 2009 to December 2021 at a single tertiary upper gastrointestinal cancer centre. 568 patients underwent Ivor Lewis oesophagectomies. The median age was 63 years old (45–82) with M:F 1.78:1. The median length of stay (LOS) was 13 (3–148) days. Results on table attached. Based on our data, there is an observed significant down-staging amongst tumours with higher T and N stages from their predicted pre-operative stage to the final TNM stage allocated after histopathology review. This reflects the continued value of neoadjuvant chemo(radio)therapy. Early T1N0 tumours still appear challenging to accurately stage pre-operatively, hence adjuncts such as endoscopic ultrasound remain crucial in guiding management.

Delayed gastric emptying (DGE) is a known complication following oesophagectomy with gastric conduit reconstruction. Pyloroplasty is often performed to mitigate the consequences of DGE. It remains contentious whether performing a pyloroplasty has a significant role in reducing DGE. We discuss our twelve-year experience at a single centre routinely performing Heineke-Mikulicz pyloroplasty for all oesophagectomies. This retrospective study employed an electronic database containing information on all patients who underwent elective Ivor Lewis oesophagectomies from April 2009 to December 2021 in a tertiary upper gastrointestinal cancer centre. Across six surgeons in the centre, a standardised pyloroplasty technique was performed. DGE was defined as patients who had high nasogastric output (> 1.5 litres per day) after ten post-operative days or required endoscopic pyloric balloon dilatation within one year following oesophagectomy. 578 patients underwent Ivor Lewis oesophagectomy during the study period. The mean age was sixty years and the male to female ratio was 1.8:1. The median length of stay was 13 days (3–148). DGE was seen in 9.9% (n = 57) patients. Of these patients, 39.7% (n = 29) cases required oesophageal dilatation within 12 months after their oesophagectomy. 50.8% (n = 21) required in-patient endoscopic dilatation, 14.0% (n = 8) required out-patient endoscopic dilatation. From those who developed DGE, the 30- and 90-day mortality was nil. There were 1.2% (n = 7) leaks specifically from the pyloroplasty which were all managed conservatively. The rate of delayed gastric emptying is reported to be approximately 15% (Zhang & Zhang, 2018). Our study demonstrates that performing a pyloroplasty reduces this risk to 9.9% and is worthwhile as the complication rate from pyloroplasty is low. Although there are various methods employed in overcoming pyloric sphincter denervation following oesophagectomy (pyloroplasty, pyloromyotomy, digital or instrumental pyloric stretching or intra-operative balloon dilatation), the most effective method of reducing DGE warrants a randomised control trial.

In this review article we present the evidence to date supporting the role of the calcium-sensing receptor (CaSR) as a key, pluripotential molecular trigger for asthma and speculate on the likely benefits of topical therapy of asthma with negative allosteric modulators of the CaSR: calcilytics.

Background: Idiopathic pulmonary fibrosis (IPF) is a disease with very poor prognosis and no curative therapies. The G protein-coupled, calcium/cation-sensing receptor (CaSR) is activated by environmental pollutants and by arginine-derived polyamines, which are thought to play a role in IPF. Whether the CaSR is involved in the pathogenesis of pulmonary fibrosis is unknown. Objective: To investigate the CaSR as a novel drug target for the treatment of pulmonary fibrosis (PF). Methods and results: CaSR protein expression is found in the airway epithelium in the neuroepithelial bodies of the healthy and IPF human lung. Expression of arginine pathway-linked polyamines is increased in PF patient saliva samples compared to non-PF patients. Arginine pathway metabolites, ornithine and spermine, activate the CaSR in primary normal human lung fibroblasts (NHLF), effects prevented by CaSR antagonism using the calcilytic NPS2143. In NHLF calcilytic also reversed the pro-fibrotic effects of exogenous TGFβ1 administration on Rho kinase and αSMA expression, proliferation, collagen production and IL-8 secretion. Targeted CaSR ablation from fibroblasts and smooth muscle cells protects mice from spontaneously occurring, age-related lung fibrosis. Conclusions: Sustained CaSR activation in the lung drives pro-fibrotic processes, which can be reversed by calcilytic. Pharmacological and genetic CaSR blockade reduce both TGFβ1-induced and naturally occurring pro-fibrotic changes. This work provides the scientific rationale for developing inhaled calcilytics as novel therapeutics for IPF. KEY MESSAGES: Key question: How does the calcium/cation-sensing receptor (CaSR) promote pulmonary fibrosis? Bottom line: The CaSR is expressed in human IPF and experimental models of PF where receptor inhibition prevents pro-fibrotic changes and pulmonary remodeling. Why read on: CaSR blockers, calcilytics, represent a novel treatment for IPF.

Chronic mucus hypersecretion (CMH) contributes to the morbidity and mortality of asthma, and remains uncontrolled by current therapies in the subset of patients with severe, steroid-resistant disease. Altered cross-talk between airway epithelium and airway smooth muscle cells (ASMCs), driven by pro-inflammatory cytokines such as interleukin (IL)-1β, provides a potential mechanism that influences CMH. This study investigated mechanisms underlying CMH by comparing IL-1β-induced gene expression profiles between asthma and control-derived ASMCs and the subsequent paracrine influence on airway epithelial mucus productionin vitro.IL-1β-treated ASMCs from asthmatic patients and healthy donors were profiled using microarray analysis and ELISA. Air–liquid interface (ALI)-cultured CALU-3 and primary airway epithelial cells were treated with identified candidates and mucus production assessed.The IL-1β-inducedCCL20expression and protein release was increased in ASMCs from moderate compared with mild asthmatic patients and healthy controls.IL-1β induced lowerMIR146Aexpression in asthma-derived ASMCs compared with controls. DecreasedMIR146Aexpression was validatedin vivoin bronchial biopsies from 16 asthmatic patientsversus39 healthy donors. miR-146a-5p overexpression abrogated CCL20 release in ASMCs. CCL20 treatment of ALI-cultured CALU-3 and primary airway epithelial cells induced mucus production, while CCL20 levels in sputum were associated with increased levels of CMH in asthmatic patients.Elevated CCL20 production by ASMCs, possibly resulting from dysregulated expression of the anti-inflammatory miR-146a-5p, may contribute to enhanced mucus production in asthma.