Pulmonary Capillary Endothelium Research Articles

Leukocyte kinetics and bacterial clearance during S. pneumoniae pneumonia and contributions of ICAM-1.

Streptococcus pneumoniae is a leading cause of community-acquired pneumonia. Intercellular adhesion molecule-1 (ICAM-1) is an adhesion molecule that is highly expressed on the pulmonary capillary endothelium, alveolar epithelium and other cell types within the lung. ICAM-1 plays important roles in leukocyte adhesion, migration, and motility. To determine the contributions of ICAM-1 to bacterial clearance and leukocyte kinetics during pneumonia, mice were inoculated with S. pneumoniae and evaluated 1, 4 and 7 days later. Our results show that Icam1-/-mice have a greater number of viable bacteria within the lung at each time point. The impaired clearance observed in Icam1-/- mice was not due to an impediment in leukocyte recruitment. In fact, Icam1-/- mice had a greater number of neutrophils and recruited inflammatory macrophages in the lung tissue and the alveoli/airways on day 7. In contrast, fewer alveolar macrophages were present in the BAL of Icam1-/-mice. The loss of body weight and the concentrations of inflammatory mediators in the BAL were also significantly greater in Icam1-/- mice. Mechanistic studies to understand the defect in clearance show that neutrophils and macrophage subpopulations had no defect in phagocytosis or acidification of phagosomes. RNA sequencing reveals many differences in gene expression, but no suggestion of a defect in phagocytosis or killing. Thus, that ICAM-1 is necessary for the clearance of S. pneumoniae and for the resolution of pneumonia, but is not required for the recruitment of neutrophils or inflammatory macrophages into the pneumonic lung parenchyma or the alveoli/airways during S. pneumoniae-induced pneumonia.

Ultrastructure of the Alveolar Cell Complex of Human Lung and its Functional Correlation: A Review

The human lung is a dynamic organ of constant biotransformation. Out of 40 different cell types of lungs, Type‑1 and Type‑2 pneumocytes, pulmonary capillary endothelium, and cells of lung interstitium play a vital role in functioning of the lung. Exploring the structure of these cells would shed light on the pathogenesis of various diseases affecting the lungs. A systematic literature search was conducted using three research databases – Medline, Google Scholar, and Cochrane. Out of ninety articles published between the year 1981 and 2020, 41 articles were included in the study based on the inclusion and exclusion criteria. Among the cellular components of the alveolar cell complex of the lung, the Type‑2 pneumocytes show versatility in its function in the form of surfactant synthesis, immune reaction, and regenerative capacity. The pathogenesis of the lung injury is due to the loss of functions of the Type‑2 pneumocytes and the intercellular junction functional discrepancy. Irrespective of the cause of lung disease, there is an increase in permeability in the alveolocapillary membrane leading to interstitial edema. This, in turn, leads to hyperventilation, low oxygen saturation, and a decrease in lung capacity. The pericytes present in the interstitium have a preventive role to play in lung injury and potential stem cell function. Keywords: alveolar epithelial cells, capillary endothelium, lung interstitium, type-1 pneumocytes, type-2 pneumocytes

Diffusion lung capacity for carbon monoxide correlates with HRCT findings in patients with diffuse parenchymal lung disease

Diffusion lung capacity for carbon monoxide correlates with HRCT findings in patients with diffuse parenchymal lung disease.BackgroundDiffuse parenchymal lung diseases (DPLDs) affect the alveolar epithelium, pulmonary capillary endothelium, basement membrane, and perivascular and perilymphatic tissues. High-resolution computed tomography (HRCT) of the chest is the gold standard modality for diagnosing DPLD. Pulmonary function tests usually show a restrictive defect in spirometry. Single breath diffusion lung capacity for carbon monoxide (DLCO-SB) technique is used to assess the diffuse parenchymal lung diseases, as there is thickening of the alveolar membrane and diminished total lung capacity due to interstitial processes with severe decline in the transfer factor. The aim of this work was to correlate between Warrick’s HRCT fibrosis score and DLCO-SB in DPLD and to assess the possibility of using DLCO as an only tool to follow up DPLD to avoid repeated radiation exposure of the patients in HRCT chest (decrease need for radiological follow-up) or vice versa.ResultsThis work recruited 89 patients over a period of 10 months duration, 74.2% of them were females. The Warrick’s score, ground-glass opacity, irregular pleural margin, subpleural cyst, honeycombing, and septal and subpleural lines were represented as 96.6%, 70.8%, 55.1%, 49.4%, and 48.3% respectively in HRCT of DPLD. Warrick’s score and its subscores (severity score, extent score, alveolitis score, and fibrosis score) were associated with a highly significant decrease in different pulmonary function indices (FVC, FEV1, TLC, and DLCO) with P value 0.001. A highly significant correlation between DLCO grades and total score grades was found with P value 0.001, and 86.8% of the patients with severe DLCO affection showed severe degree of total fibrosis score.ConclusionsBoth DLCO-SB and HRCT fibrosis scores were significantly correlated. Lifelong follow-up of function and structure of the lung in DPLD is needed by HRCT and DLCO. In an attempt to minimize repeated radiation exposure and reduce cost, we suggest DLCO to be used alone for longer follow-up periods rather than HRCT chest.

HIGHER DONOR PAO2/FIO2 RATIO APPEARS TO BE ASSOCIATED WITH INCREASED INCIDENCE OF PRIMARY GRAFT DYSFUNCTION IN LUNG TRANSPLANT RECIPIENTS

SESSION TITLE: Transplantation Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Severe primary graft dysfunction (PGD) is the most common cause of early mortality in lung transplantation and is a significant risk factor for the development of chronic lung allograft dysfunction. Although numerous risk factors for PGD have been identified, little data exists on the impact of donor mechanical ventilation parameters on the incidence of PGD. Given the detrimental effects of hyperoxia on the pulmonary alveolar epithelium and capillary endothelium, we hypothesized that donor hyperoxia may increase the risk of PGD. METHODS: We reviewed 175 lung transplants performed at our institution from 2012 to 2019. The last reported arterial blood gas and ventilator parameters in the UNOS database were collected. Recipient PGD grade was calculated at 48-72 hours post-transplant. Other transplant variables were collected: intraoperative cardiopulmonary bypass use, donor smoking history, as well as recipient diagnosis and BMI. RESULTS: Mean donor P/F ratio was lower for recipients with PGD grades 0-2 (438±69) vs. PGD grade 3 (469±64.8);p=0.006. There was a significant difference in the mean donor P/F ratio between the extremes, PGD grade 0 (430±65.5) and the PGD grade 3 (469±64.8);p=0.005. Notably, the incidence of PGD grade 3 increased with an increase in the donor P/F ratio, with the highest incidence of PGD grade 3 observed when the P/F ratio was >500 (Fig. 1). Mean donor tidal volume (ml/kg of ideal body weight) was similar among all groups: 8.7, 8.8, 8.9, and 8.4 for PGD 0, 1, 2, or 3, respectively. CONCLUSIONS: Recipients with PGD grade 3 had significantly higher donor P/F ratios than those with PGD grade 0-2. Donor P/F ratio >500 was associated with an increased incidence of PGD grade 3. CLINICAL IMPLICATIONS: This preliminary data suggests that donor hyperoxia may lead to an increased risk for severe PGD. More research is needed to further delineate the effects of donor mechanical ventilation strategies and transplant recipient outcomes. DISCLOSURES: No relevant relationships by Kareem Ahmad, source=Web Response No relevant relationships by Shambhu Aryal, source=Web Response Speaker/Speaker's Bureau relationship with Genentech Please note: $5001 - $20000 Added 06/12/2020 by Anne Brown, source=Web Response, value=Honoraria Advisory Committee Member relationship with Vertex Please note: $1001 - $5000 Added 06/12/2020 by Anne Brown, source=Web Response, value=Honoraria Advisory Committee Member relationship with Promedior Please note: $5001 - $20000 Added 06/12/2020 by Anne Brown, source=Web Response, value=Consulting fee No relevant relationships by Vikramjit Khangoora, source=Web Response Advisory Committee Member relationship with Boehringer Ingelheim Please note: $5001 - $20000 Added 04/16/2020 by Christopher King, source=Web Response, value=Consulting fee Speaker/Speaker's Bureau relationship with Actelion Please note: $5001 - $20000 Added 04/16/2020 by Christopher King, source=Web Response, value=Honoraria Advisory Committee Member relationship with Actelion Please note: $1001 - $5000 Added 04/27/2020 by Christopher King, source=Web Response, value=Consulting fee Advisory Committee Member relationship with Boehringer Ingelheim pharmaceuticals Please note: $1001 - $5000 Added 04/27/2020 by Christopher King, source=Web Response, value=Consulting fee Speaker/Speaker's Bureau relationship with Actelion Please note: $1001 - $5000 Added 04/27/2020 by Christopher King, source=Web Response, value=Honoraria Speaker/Speaker's Bureau relationship with Boehringer Ingelheim Please note: $1001 - $5000 Added 04/27/2020 by Christopher King, source=Web Response, value=Honoraria Speaker/Speaker's Bureau relationship with Genentech Please note: $1001 - $5000 Added 04/27/2020 by Christopher King, source=Web Response, value=Honoraria Advisory Committee Member relationship with United therapeutics Please note: $1001 - $5000 Added 04/27/2020 by Christopher King, source=Web Response, value=Consulting fee Consultant relationship with Veracyte Please note: $1001 - $5000 Added 04/03/2020 by Steven Nathan, source=Web Response, value=Honoraria Consultant relationship with United Therapeutics Please note: $5001 - $20000 Added 05/27/2020 by Steven Nathan, source=Web Response, value=Consulting fee Consultant relationship with Bellerophon Please note: $5001 - $20000 Added 05/27/2020 by Steven Nathan, source=Web Response, value=Consulting fee Speaker/Speaker's Bureau relationship with Roche-Genentech Please note: $5001 - $20000 Added 05/27/2020 by Steven Nathan, source=Web Response, value=Honoraria Speaker/Speaker's Bureau relationship with Boerhinger-Ingelheim Please note: $20001 - $100000 Added 05/27/2020 by Steven Nathan, source=Web Response, value=Honoraria Scientific Medical Advisor relationship with Johnson & Johnson Please note: $1001 - $5000 Added 04/22/2020 by Oksana Shlobin, source=Web Response, value=Consulting fee Scientific Medical Advisor relationship with Bayer Please note: $1001 - $5000 Added 04/22/2020 by Oksana Shlobin, source=Web Response, value=Grant/Research Support Scientific Medical Advisor relationship with United Therapeutics Please note: $1001 - $5000 Added 04/22/2020 by Oksana Shlobin, source=Web Response, value=Consulting fee

Comparative Toxicity of Nanomaterials to Air-blood Barrier Permeability Using an In Vitro Model

ObjectiveTo comparatively study the toxicity of four metal-containing nanoparticles (MNPs) and their chemical counterparts to the air-blood barrier (ABB) permeability using an in vitro model. MethodsABB model, which was developed via the co-culturing of A549 and pulmonary capillary endothelium, was exposed to spherical CuO-NPs (divided into CuO-40, CuO-80, and CuO-100 based on particle size), nano-Al2O3 (sheet and short-rod-shaped), nano-ZnO, nano-PbS, CuSO4, Al2(SO4)3, Zn(CH3COO)2, and Pb(NO3)2 for 60 min. Every 10 min following exposure, the cumulative cleared volume (ΔTCL) of Lucifer yellow by the model was calculated. A clearance curve was established using linear regression analysis of ΔTCL versus time. Permeability coefficient (P) was calculated based on the slope of the curve to represent the degree of change in the ABB permeability. ResultsThe results found the increased P values of CuO-40, CuO-80, sheet, and short-rod-shaped nano-Al2O3, Al2(SO4)3, and Pb(NO3)2. Among them, small CuO-40 and CuO-80 were stronger than CuO-100 and CuSO4; no difference was observed between Al2(SO4)3 and sheet and short-rod-shaped nano-Al2O3; and nano-PbS was slightly weaker than Pb(NO3)2. So clearly the MNPs possess diverse toxicity. ConclusionABB permeability abnormality means pulmonary toxicity potential. More studies are warranted to understand MNPs toxicity and ultimately control the health hazards.

РОЛЬ ЛЕГКИХ В ПОДДЕРЖАНИИ БАЛАНСА СИСТЕМЫ ГЕМОСТАЗА НА ФОНЕ ХРОНИЧЕСКОГО ВОЗДЕЙСТВИЯ ВОЗДУШНЫХ ПОЛЛЮТАНТОВ

The aim of the study is to determine the nature of the consequences of non-respiratory lung function disorders and their influence on the hemostatic system in chronic inhalation of industrial hydrogen sulfide gas (HS). There were studied the parameters of hemostasis system (the number and function of platelet, total clotting time, level of soluble fibrin-monomer complex and D-dimer, speed of XIIa-dependent euglobulin lysis, the activity of Willebrand factor and factors VIII, protein C and inhibitor of tissue plasminogen activator-1 (TPA-1), the content of antithrombin III and plasminogen) in 146 white laboratory male rats taking into account the artery-venous difference. Blood collection was carried out from the abdominal aorta (pars abdominalis aortae) ("after the lungs") and from the posterior vena cava (vena cava caudalis) ("to the lungs", that excludes the influence of the liver). The rats were divided into 9 groups: four groups were experimental, which were exposed to HS for one month (20 animals), two months (20 animals), three months (19 animals) and four months (19 animals). HS was fed into chambers at a concentration of 70±2.34 mg/m3 by static method (once). Inhalation of rats with gas lasted for 4 hours a day, 5 days a week. The control groups were rats placed in cells with a normal air composition in a similar mode for a period of one, two, three and four months (12 individuals each). The reference parameters of the hemostatic system were determined before the experiment in a group of 20 rats. It was found that the artery-venous difference in the indicators of soluble fibrin-monomer complex (p<0.05), the content of antithrombin III (p<0.05), the activity of protein C (p<0.01) is more pronounced in the groups of the 1st month of exposure to HS. Increased activity of platelets (p<0.05), of Willebrand factor (p<0.05) and TPA-1 (p<0.001), as well as slowing of fibrinolysis (p<0.05) indicates the damage to the endothelium of pulmonary capillaries by the 4th month of HS inhalation and the decrease of ability of the lungs to regulate hemostasiological balance.

Clinicoradiological and demographic pattern in diffuse parenchymal lung diseases: An observational study

Introduction: Diffuse parenchymal disease is a group of lung disease affecting alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissue. It includes many diseases like IPF, Sarcoidosis, BOOP, COP, LAM etc. it is still under diagnosed entirety. Many patients die due to lack of awareness and investigating modalities. Aims and objective: This study is to see Demographic pattern of DPLD, its clinical pattern and radiological findings in different type of ILDs. Study Type: It is a Prospective Observational Study done over a period of 1 year. Material & Method: Patients studied over20 years of age and having respiratory symptoms. We excluded patients of other diseases like COPD, Tuberculosis etc. Total 75 patients were diagnosed as a case of DPLD by clinical findings, and investigations like X ray chest, HRCT thorax, Bronchoscopy. Results: Most common ILD (Interstitial lung Disease) is IPF 40.0% followed by Sarcoidosis etc. Most common clinical symptom was breathlessness (100.00%) in IPF, Fever & Chest Pain are common in Granulomatous type. Conclusion: DPLD (Diffuse Paranchymal lung Disease) is a chronic lung disease characterized by progressive decline in lung function. IPF is most common in DPLD and leads to fast deterioration of lung function. HRCT (High Resolution computed tomography) is very important to assess type of disease. Spirometry, Broncoscopy are important for diagnosis of ILD and lung function.

Ultrastructural Alteration of Pulmonary Capillary Endothelial Glycocalyx During Endotoxemia

The most recent diagnostic criteria for sepsis include organ failure. Microvascular endothelial injury is believed to lead to the multiple organ failure seen in sepsis, although the precise mechanism is still controversial. ARDS is the primary complication during the sequential development of multiple organ dysfunction in sepsis, and endothelial injury is deeply involved. Sugar-protein glycocalyx coats all healthy vascular endothelium, and its disruption is one factor believed to contribute to microvascular endothelial dysfunction during sepsis. The goal of this study was to observe the three-dimensional ultrastructural alterations in the pulmonary capillary endothelium, including the glycocalyx, during sepsis-induced pulmonary vasculitis. This study investigated the three-dimensional ultrastructure of pulmonary vascular endothelial glycocalyx in a mouse lipopolysaccharide-induced endotoxemia model. Lungs were fixed with lanthanum-containing alkaline fixative to preserve the glycocalyx. On both scanning and transmission electron microscopic imaging, the capillary endothelial glycocalyx appeared as a moss-like structure entirely covering the endothelial cell surface in normal mice. In the septic lung following liposaccharide injection, however, this structure was severely disrupted; it appeared to be peeling away and coagulated. In addition, syndecan-1 levels were significantly reduced in the septic lung, and numerous spherical structures containing glycocalyx were observed on the endothelial surface. It appears that endothelial glycocalyx in the lung is markedly disrupted under experimental endotoxemia conditions. This finding supports the notion that disruption of the glycocalyx is causally related to the microvascular endothelial dysfunction that is characteristic of sepsis-induced ARDS.

Nanomedicine for the Treatment of Acute Respiratory Distress Syndrome. The 2016 ATS Bear Cage Award-winning Proposal.

After dozens of clinical trials, there are still no Food and Drug Administration-approved drugs that improve mortality in acute respiratory distress syndrome (ARDS). These poor results may be caused in part by three unique pharmacological challenges presented by ARDS: (1) Patients with ARDS are fragile because of concomitant multiple organ dysfunction, so they do not tolerate off-target side effects of drugs; (2) inhaled drug delivery is impeded by the column of proteinaceous fluid covering the injured alveoli; and (3) ARDS is heterogeneous in its underlying pathophysiology, so targeting one pathway is unlikely to improve most patients. To address these three pharmacological problems, I present the development of pulmonary endothelium-targeted liposomes (PELs). PELs are approximately 100-nm drug carriers coated with antibodies that bind to the pulmonary capillary endothelium. In model organisms, intravenously injected PELs strongly concentrate drugs in alveoli, even in animal models displaying severe, spatially heterogeneous pathology similar to severe ARDS. By concentrating drugs in inflamed alveoli, PELs solve pharmacological challenge (1) above. By being obligate intravenous medications, they solve challenge (2). Finally, because PELs can be loaded with at least three drugs, they can solve challenge (3) with combination drug therapy. My colleagues and I are currently testing PELs loaded with numerous candidate drugs in mouse models of ARDS, and we are testing drug distribution in live pigs and ex vivo human lungs. We aim to use such preclinical validation to move PELs into a partnership with industry, and then to patients.

The use of angiotensin II in distributive shock.

The interest in the use of non-catecholamine vasopressors for the treatment of hypotension and shock has increased in recent years. The use of vasopressin as an adjunctive vasopressor in shock was reinvigorated by Landry and colleagues [1] and then carefully assessed in the Vasopressin versus Norepinephrine Infusion in Patients with Septic Shock (VASST) trial [2]. In a large, international, multi-center trial, vasopressin demonstrated a satisfactory safety profile, but did not show an improvement in survival compared to norepinephrine [2]. In addition to vasopressin, angiotensin II (ATII) has been proposed as a useful vasopressor for the management of shock [3, 4]. The original studies that assessed ATII for the management of shock were conducted decades ago [3, 5]. In those trials, ATII was assessed primarily in head-to-head studies compared to catecholamine vasopressors, and was shown to have comparable vasopressor effect to norepinephrine [5]. Multiple case reports demonstrated the ability of ATII to work effectively as a vasopressor and also showed that ATII could be used in combination with catecholamines. However, ATII has not been subjected to a randomized controlled trial (RCT) and ATII has not been available at the bedside for at least 15 years. ATII has been used extensively in physiology, hypertension, cancer, and pregnancy studies in humans and has a good safety profile. Recently, we published in Critical Care the first RCT of ATII in patients with distributive shock, and showed that a dose of ATII of 5–40 ng/kg/min was associated with improved blood pressure that resulted in significant catecholamine sparing [6]. In that modest-sized study, we noted that 2 of the 10 patients treated with ATII were exquisitely sensitive to ATII. In these two cases, the subjects receiving physiologic doses of ATII were hypertensive despite the discontinuation of their norepinephrine. When ATII was stopped in these two patients, re-initiation of a high dose of norepinephrine (i.e., 0.3 μg/kg/min) was immediately required in order to maintain mean arterial pressure goals. We speculated that the reason for this sensitivity was likely due to premorbid exposure to angiotensin-converting enzyme (ACE) inhibitors prior to the development of shock. Our theory was that if the subjects were previously treated with ACE inhibitors, their ATII Type I receptors would be upregulated, thus making the patient more sensitive to exogenous ATII infusion. However, after a thorough chart review and re-review, we could not document an ACE inhibitor exposure. While it is possible that the ACE inhibitor exposure was present and not documented, there is an alternative explanation which is related to the nature and distribution of ACE. Angiotensin I (ATI) is converted efficiently to ATII almost exclusively in the lung [7]. ACE is an ectoenzyme which is distributed primarily on the pulmonary capillary endothelium [8, 9]. As a consequence, diseases that affect the pulmonary capillary endothelium can disrupt ACE functionality. Acute respiratory distress syndrome (ARDS) is often associated with significant pulmonary endothelial injury [10]. Patients with more severe ARDS have less capacity to convert angiotensin ATI to ATII, and this disturbance is inversely correlated to the severity of ARDS [11]. Upon re-review, we found that the two patients in our study who were exquisitely ATII sensitive had severe ARDS. Our revised hypothesis is that patients with severe ARDS may have significant pulmonary endothelial injury, which results in either an absolute or relative insufficiency of ATII due to loss of pulmonary ACE. Pre-clinical and human case reports demonstrate that when ATII production is inhibited by ACE inhibition, patients become catecholamine resistant [12]. Thus, patients with ARDS may be at particular risk for ATII insufficiency, which would likely exacerbate existing hypotension. In addition, ATII insufficiency can lead to acute kidney injury due to decreased intra-glomerular pressure. We hypothesize that some patients with shock and ARDS may be at particular risk for a deleterious cascade of events related to ATII insufficiency (Fig. 1). Fig. 1 Proposed cascade of events leading to angiotensin II insufficiency. The figure outlines a cascade of events that could occur amongst patients with inflammation and/or lung injury. When acute lung injury is significantly complicated by pulmonary endothelial ... We would anticipate that, for those patients with ATII insufficiency, increased levels of ATI and reduced ATII may be indicative of this pathophysiology, and that ATI and ATII levels, as well as the ratio of ATI/ATII, may be useful as biomarkers of early ARDS or ARDS severity prior to the development of severe hypoxemia. Moreover, we would anticipate these patients to be ATII-sensitive. We believe that further research to test this hypothesis is warranted. Currently, ATII is being studied in a multi-center international RCT (NCT02338843) wherein some of these parameters will be assessed and may shed further light on this proposed hypothesis.

Transfusion Related Acute Lung Injury (TRALI): A Single Institution Experience of 15Years.

Transfusion related acute Lung injury (TRALI) though a serious blood transfusion reaction with a fatality rate of 5-25% presents with acute respiratory distress with hypoxaemia and noncardiac pulmonary oedema within 6h of transfusion. In non fatal cases, it may resolve within 72h or earlier. Although reported with an incidence of 1:5000, its true occurrence is rather unknown. Pathogenesis is believed to be related to sequestration and adhesion of neutrophils to the pulmonary capillary endothelium and its activation leading to its destruction and leaks. The patient's underlying condition, anti-neutrophil antibody in the transfused donor plasma and certain lipids that accumulate in routinely stores blood and components are important in its aetiopathogenesis. Patient's predisposing conditions include haematological malignancy, major surgery (especially cardiac), trauma and infections. The more commonly incriminated products include fresh frozen plasma (FFP), platelets (whole blood derived and apheresis), whole blood and Packed RBC. Occasional cases involving cryoprecipitate and Intravenous immunoglobulin (IVig) have also been reported. We present a 15year single institution experience of TRALI, during which we observed 9 cases among 170,871 transfusions, giving an incidence of 1:19,000. We did not encounter cases of haematological malignancy or cardiac surgery in our TRALI patients. Among the blood products, that could be related to TRALI in our patients included solitary cases receiving cryoprecipitate, IVIg, and recombinant Factor VII apart from platelets and FFP. All patients were treated with oxygen support. Six patients required mechanical ventilation. Off label hydrocortisone was given to all patients. There were no cases of fatality among our patients.

Morphometric characteristics of cells in the alveolar region of mammalian lungs.

Morphometric procedures have been used to study the characteristics of cells in the alveolar region of the lungs of rats, dogs, baboons, and humans. Compared with the other species, human lungs were found to contain greater numbers of macrophages and to have larger alveolar type II, endothelial, and interstitial cells. The thickness of the interstitium and the pulmonary capillary endothelium were also significantly greater in the human lungs. These differences in human lung anatomy may be due to increased exposure to airborne pollutants and to tobacco smoke. Despite the above differences and the fact that there are large variations in size and functional characteristics of the lungs of these mammals, an overall striking similarity in characteristics of individual lung cells was found. The distribution of cells in alveolar tissue was remarkably constant between species as was the average volume and surface area of most cell types. Computer-aided three-dimensional reconstruction techniques were used to determine the spatial relationship of organelles in individual alveolar type II cells from rats. A three-dimensional reconstruction of cells permits quantification of number, size, surface area, and volume of subcellular organelles and correlations of their three-dimensional spatial relationships.

The rise and fall of β-agonists in the treatment of ARDS

The acute respiratory distress syndrome (ARDS) is a severe inflammatory condition of the lung, which can be triggered by a number of different pulmonary and extra-pulmonary insults [1]. The characteristic pathological changes of ARDS include an exudative phase, with the accumulation of fluid within the lung, the release of pro-inflammatory cytokines and infiltration of inflammatory cells, especially neutrophils, into the lung parenchyma. Damage to the alveolar epithelium and pulmonary capillary endothelium occur and patients develop the characteristic histological appearance of diffuse alveolar damage [1]. This manifests clinically as non-cardiogenic pulmonary edema, which reduces lung compliance and impairs gas exchange.

Circulating endothelial microparticles as a measure of early lung destruction in cigarette smokers.

There is increasing evidence that emphysema is associated with primary loss of pulmonary capillary endothelium. Plasma levels of endothelial microparticles (EMPs), small vesicles released from activated or apoptotic endothelial cells, are elevated in vascular-related disorders. To evaluate whether plasma EMP levels are elevated in smokers with early lung destruction as assessed by normal spirometry but reduced diffusing capacity of the lung for carbon monoxide (Dl(co)). Lung health was assessed by pulmonary function tests (PFTs: spirometry, total lung capacity, Dl(co)) and chest X-ray; smoking status was assessed by urine nicotine and cotinine. EMP levels (CD42b(-)CD31(+) microparticles) were quantified as activated or apoptotic. The initial cohort (n = 92) included healthy nonsmokers (normal PFTs), healthy smokers (normal PFTs), and smokers with early evidence of lung destruction (normal spirometry, low Dl(co)). Two prospective cohorts were then tested: a group similar to the initial cohort and an HIV1(+) cohort. Healthy smokers had mildly increased levels of EMPs. Strikingly, 95% of smokers with normal spirometry, low Dl(co) had increased EMPs, with reduced CD62(+)/CD31(+) ratios (P < 10(-4)) and elevated CD42b(-)CD31(+) annexin V(+) EMPs (P < 10(-4)), suggesting derivation from endothelial apoptosis. Most elevated EMPs were angiotensin-converting enzyme positive, suggesting derivation from pulmonary capillaries. Both prospective cohorts confirmed the initial cohort data. Plasma EMPs with apoptotic characteristics are elevated in smokers with normal spirometry but reduced Dl(co), consistent with the concept that emphysema is associated, in part, with capillary endothelium apoptosis, suggesting that the early development of emphysema might be monitored with plasma EMP levels.

Distribution of Capillary Transit Times in Isolated Lungs of Oxygen-Tolerant Rats

Rats pre-exposed to 85% O₂ for 5-7 days tolerate the otherwise lethal effects of 100% O₂. The objective was to evaluate the effect of rat exposure to 85% O₂ for 7 days on lung capillary mean transit time t(c) and distribution of capillary transit times (h(c)(t)). This information is important for subsequent evaluation of the effect of this hyperoxia model on the redox metabolic functions of the pulmonary capillary endothelium. The venous concentration vs. time outflow curves of fluorescein isothiocyanate labeled dextran (FITC-dex), an intravascular indicator, and coenzyme Q₁ hydroquinone (CoQ₁H₂), a compound which rapidly equilibrates between blood and tissue on passage through the pulmonary circulation, were measured following their bolus injection into the pulmonary artery of isolated perfused lungs from rats exposed to room air (normoxic) or 85% O₂ for 7 days (hyperoxic). The moments (mean transit time and variance) of the measured FITC-dex and CoQ₁H₂ outflow curves were determined for each lung, and were then used in a mathematical model [Audi et al. J. Appl. Physiol. 77: 332-351, 1994] to estimate t(c) and the relative dispersion (RD(c)) of h (c)(t). Data analysis reveals that exposure to hyperoxia decreases lung t(c) by 42% and increases RD(c), a measure h(c)(t) heterogeneity, by 40%.

α1GT-type calcium channel selectively regulates P-selectin surface expression in pulmonary capillary endothelium

Regulated P-selectin surface expression provides a rapid measure for endothelial transition to a proinflammatory phenotype. In general, P-selectin surface expression results from Weibel-Palade body (WPb) exocytosis. Yet, it is unclear whether pulmonary capillary endothelium possesses WPbs or regulated P-selectin surface expression and, if so, how inflammatory stimuli initiate exocytosis. We used immunohistochemistry, immunofluorescence labeling, ultrastructural assessment, and an isolated perfused lung model to demonstrate that capillary endothelium lacks WPbs but possesses P-selectin. Thrombin stimulated P-selectin surface expression in both extra-alveolar vessel and alveolar capillary endothelium. Only in capillaries was the thrombin-stimulated P-selectin surface expression considerably mitigated by pharmacologic blockade of the T-type channel or genetic knockout of the T-type channel alpha(1G)-subunit. Depolarization of endothelial plasma membrane via high K(+) perfusion capable of eliciting cytosolic Ca(2+) transients also provoked P-selectin surface expression in alveolar capillaries that was abolished by T-type channel blockade or alpha(1G) knockout. Our findings reveal an intracellular WPb-independent P-selectin pool in pulmonary capillary endothelium, where the regulated P-selectin surface expression is triggered by Ca(2+) transients evoked through activation of the alpha(1G) T-type channel.

New Developments in Lung Endothelial Heterogeneity: von Willebrand Factor, P-Selectin, and the Weibel-Palade Body

Quiescent pulmonary endothelium establishes an antithrombotic, anti-inflammatory surface that promotes blood flow. However, the endothelium rapidly responds to injury and inflammation by promoting thrombosis and enabling the directed transmigration of inflammatory cells, such as neutrophils, into the alveolar airspace. Although the endothelial cell signals responsible for establishing a prothrombotic surface are distinct from those responsible for recognizing circulating neutrophils, these processes are highly interrelated. Von Willebrand factor (VWF)-stimulated secretion plays an important role in thrombus formation, and P-selectin surface expression plays a key role in neutrophil binding necessary for transmigration. Both VWF and P-selectin are located within Weibel-Palade bodies in pulmonary arteries and arterioles, yet Weibel-Palade bodies are absent in capillaries. Despite the absence of the Weibel-Palade bodies, pulmonary capillaries express both VWF and P-selectin. The physiological and pathophysiological significance of these observations is unclear. In this review, we address some anatomical and physiological features that distinguish pulmonary artery, capillary, and vein endothelium. In addition, we review our current understanding regarding the stimulated secretion of VWF and P-selectin in pulmonary artery and capillary endothelium. This information is considered in the context of vasculitis and pneumonia, two pathophysiological processes to which the stimulated secretion of VWF and P-selectin contribute.

Effect of AQP1 knock out on mouse exercise tolerance

The water channel Aquaporin 1 (AQP1) is widely expressed throughout the body. Our lab demonstrated that AQP1 also can act as a CO2 channel when heterologously expressed in oocytes or when studied in the intact proximal tubule. We hypothesized that AQP1 plays a physiologically important role in O2 transport. Because AQP1 is present at high levels in erythrocytes and the pulmonary capillary endothelium, we compared voluntary wheel running over a 24‐h period in AQP1‐null vs wild‐type mice under conditions of hypoxia (ambient [O2] = 16%), normoxia (21%), and hyperoxia (40%). For wild‐type mice, the distances run were 16%: 9.2 ± 0.5 km (n = 28), 21%: 10.7 ± 0.5 km (n = 37), and 40%: 12.1 ± 0.6 km (n = 21). For AQP1‐null mice, the distances were 16%: 4.7 ± 0.5 km (n = 8), 21%: 6.2 ± 0.6 km (n = 13), and 40%: 6.9 ± 0.6 km (n = 12). We performed a linear‐regression analysis of distance run as a function of AQP1 status and [O2], treating [O2] categorically in reference to 21% O2. The AQP1 knockout reduced the distance run by 4.7 ± 0.5 km (p &lt; 0.001), adjusting for [O2]. Compared to 21% O2, reducing [O2] to 16% reduced the distance run by 1.6 ± 0.6 km (p = 0.01), whereas increasing [O2] to 40% increased the distance run by 1.2 ± 0.6 km (p = 0.04), adjusting for AQP1 status. Thus, AQP1‐null mice have a major defect in voluntary exercise tolerance, consistent with the hypothesis that AQP1 plays an important physiological role in O2 transport across plasma membranes.

Ca2+ entry via α1G and TRPV4 channels differentially regulates surface expression of P-selectin and barrier integrity in pulmonary capillary endothelium

Pulmonary vascular endothelial cells express a variety of ion channels that mediate Ca(2+) influx in response to diverse environmental stimuli. However, it is not clear whether Ca(2+) influx from discrete ion channels is functionally coupled to specific outcomes. Thus we conducted a systematic study in mouse lung to address whether the alpha(1G) T-type Ca(2+) channel and the transient receptor potential channel TRPV4 have discrete functional roles in pulmonary capillary endothelium. We used real-time fluorescence imaging for endothelial cytosolic Ca(2+), immunohistochemistry to probe for surface expression of P-selectin, and the filtration coefficient to specifically measure lung endothelial permeability. We demonstrate that membrane depolarization via exposure of pulmonary vascular endothelium to a high-K(+) perfusate induces Ca(2+) entry into alveolar septal endothelial cells and exclusively leads to the surface expression of P-selectin. In contrast, Ca(2+) entry in septal endothelium evoked by the selective TRPV4 activator 4alpha-phorbol-12,13-didecanoate (4alpha-PDD) specifically increases lung endothelial permeability without effect on P-selectin expression. Pharmacological blockade or knockout of alpha(1G) abolishes depolarization-induced Ca(2+) entry and surface expression of P-selectin but does not prevent 4alpha-PDD-activated Ca(2+) entry and the resultant increase in permeability. Conversely, blockade or knockout of TRPV4 specifically abolishes 4alpha-PDD-activated Ca(2+) entry and the increase in permeability, while not impacting depolarization-induced Ca(2+) entry and surface expression of P-selectin. We conclude that in alveolar septal capillaries Ca(2+) entry through alpha(1G) and TRPV4 channels differentially and specifically regulates the transition of endothelial procoagulant phenotype and barrier integrity, respectively.

A distinct subcellular pool and an α1G T‐type Ca2+ channel regulated surface expression of P‐selectin in pulmonary capillary endothelium

Regulated P‐selectin surface expression provides a rapid measure of endothelial transition to a pro‐inflammatory phenotype. In general, P‐selectin surface expression results from Weibel‐Palade body (WPB) exocytosis. Yet, it is unclear whether pulmonary capillary endothelium possesses WPBs or regulated P‐selectin surface expression. We used immunohistochemistry, immunofluorescence, ultrastructural assessment, and an isolated perfused lung model to demonstrate that capillary endothelium lacks WPBs, but possesses P‐selectin. Thrombin stimulated P‐selectin surface expression in both extra‐alveolar vessel and capillary endothelium. Only in capillaries was the thrombin‐stimulated P‐selectin surface expression markedly reduced by pharmacological inhibition of T‐type Ca2+ channels, or by genetically eliminating T‐type channel α1G‐subunits. T‐type channel‐mediated cytosolic Ca2+ transients were detected by real‐time imaging of fura‐2‐loaded capillary endothelium following plasma membrane depolarization via high K+ perfusion. Depolarization also induced P‐selectin surface expression in capillary endothelium, which was abolished by T‐type channel blockade or eliminating α1G‐subunits. Collectively, these findings indicate that, in capillary endothelium, subcellular P‐selectin is WPB‐independent, and its regulated surface expression is driven by mechanism(s) distinct from WPB exocytosis; namely, Ca2+ entry through the α1G T‐type channel controls the regulated P‐selectin surface expression in capillary endothelium.