Sepsis remains a common and serious condition with significant morbidity and mortality due to multiple organ dysfunction, especially acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Sepsis-induced ALI is characterized by injury and dysfunction of the pulmonary microvasculature and pulmonary microvascular endothelial cells (PMVEC), resulting in enhanced pulmonary microvascular sequestration and pulmonary infiltration of polymorphonuclear leukocytes (PMN) as well as disruption of the normal alveolo-capillary permeability barrier with leak of albumin-rich edema fluid into pulmonary interstitium and alveoli. The role of PMVEC death and specifically apoptosis in septic pulmonary microvascular dysfunction in vivo has not been established. In a murine cecal ligation/perforation (CLP) model of sepsis, we quantified and correlated time-dependent changes in pulmonary microvascular Evans blue (EB)-labeled albumin permeability with (1) PMVEC death (propidium iodide [PI]-staining) by both fluorescent intravital videomicroscopy (IVVM) and histology, and (2) PMVEC apoptosis using histologic fluorescent microscopic assessment of a panel of 3 markers: cell surface phosphatidylserine (detected by Annexin V binding), caspase activation (detected by FLIVO labeling), and DNA fragmentation (TUNEL labeling). Compared to sham mice, CLP-sepsis resulted in pulmonary microvascular barrier dysfunction, quantified by increased EB-albumin leak, and PMVEC death (PI+ staining) as early as 2 h and more marked by 4 h after CLP. Septic PMVEC also exhibited increased presence of all 3 markers of apoptosis (Annexin V+, FLIVO+, TUNEL+) as early as 30 mins – 1 h after CLP-sepsis, which all similarly increased markedly until 4 h. The time-dependent changes in septic pulmonary microvascular albumin-permeability barrier dysfunction were highly correlated with PMVEC death (PI+; r = 0.976, p < 0.01) and PMVEC apoptosis (FLIVO+; r = 0.991, p < 0.01). Treatment with the pan-caspase inhibitor Q-VD prior to CLP reduced PMVEC death/apoptosis and attenuated septic pulmonary microvascular dysfunction, including both albumin-permeability barrier dysfunction and pulmonary microvascular PMN sequestration (p < 0.05). Septic PMVEC apoptosis and pulmonary microvascular dysfunction were also abrogated following CLP-sepsis in mice deficient in iNOS (Nos2 −/− ) or NADPH oxidase (p47 phox−/− or gp91 phox−/− ) and in wild-type mice treated with the NADPH oxidase inhibitor, apocynin. Septic murine pulmonary microvascular dysfunction in vivo is due to PMVEC death, which is mediated through caspase-dependent apoptosis and iNOS/NADPH-oxidase dependent signaling.

Sepsis is a systemic inflammatory response that targets multiple components of the cardiovascular system including the microvasculature. Microvascular endothelial cells (MVEC) are central to normal microvascular function, including maintenance of the microvascular permeability barrier. Microvascular/MVEC dysfunction during sepsis is associated with barrier dysfunction, resulting in the leak of protein-rich edema fluid into organs, especially the lung. The specific role of MVEC apoptosis in septic microvascular/MVEC dysfunction in vivo remains to be determined. To examine pulmonary MVEC death in vivo under septic conditions, we used a murine cecal ligation/perforation (CLP) model of sepsis and identified non-viable pulmonary cells with propidium iodide (PI) by intravital videomicroscopy (IVVM), and confirmed this by histology. Septic pulmonary microvascular Evans blue (EB)-labeled albumin leak was associated with an increased number of PI-positive cells, which were confirmed to be predominantly MVEC based on specific labeling with three markers, anti-CD31 (PECAM), anti-CD34, and lectin binding. Furthermore, this septic death of pulmonary MVEC was markedly attenuated by cyclophosphamide-mediated depletion of neutrophils (PMN) or use of an anti-CD18 antibody developed for immunohistochemistry but shown to block CD18-dependent signaling. Additionally, septic pulmonary MVEC death was iNOS-dependent as mice lacking iNOS had markedly fewer PI-positive MVEC. Septic PI-positive pulmonary cell death was confirmed to be due to apoptosis by three independent markers: caspase activation by FLIVO, translocation of phosphatidylserine to the cell surface by Annexin V binding, and DNA fragmentation by TUNEL. Collectively, these findings indicate that septic pulmonary MVEC death, putatively apoptosis, is a result of leukocyte activation and iNOS-dependent signaling, and in turn, may contribute to pulmonary microvascular barrier dysfunction and albumin hyper-permeability during sepsis.

Pulmonary arterial hypertension (PAH) leads to reduced health-related quality of life (HRQoL). The objectives of this analysis were to evaluate the effect of macitentan on HRQoL in patients with PAH in the Study with an Endothelin Receptor Antagonist in Pulmonary Arterial Hypertension to Improve Clinical Outcome (SERAPHIN) study. The association between baseline HRQoL and long-term outcomes was also investigated. Patients were randomized to placebo, macitentan 3 mg, or macitentan 10 mg once daily. Patients aged 14 years or older completed the 36-Item Short Form Survey (SF-36) at baseline, at month 6 and month 12, and at the end of treatment (EOT). The absolute change from baseline to month 6 in SF-36 scores was calculated. The time to a clinically meaningful deterioration in the SF-36 physical component summary and mental component summary (PCS and MCS) scores and associations between baseline PCS/MCS scores and time to morbidity/mortality events were also assessed. At month 6, macitentan 10 mg significantly improved seven of eight SF-36 domains and the PCS and MCS scores vs placebo. Macitentan 10 mg significantly reduced the risk of a three-point or greater deterioration in PCS (hazard ratio [HR], 0.60; 95% CI, 0.47-0.76; P < .0001) and MCS scores (HR, 0.76; 95% CI, 0.61-0.95; P = .0173) until EOT vs placebo. Patients with a baseline PCS score greater than the median baseline value had a significantly reduced risk of morbidity/mortality compared with patients with a PCS score less than the median; a similar result was observed for the MCS score. Macitentan significantly improved HRQoL in patients with PAH compared with placebo and significantly reduced the risk of a clinically meaningful HRQoL deterioration. An association between better baseline HRQoL and improved long-term outcomes was shown. ClinicalTrials.gov; No.: NCT00660179; URL: clinicaltrials.gov.

Nitric oxide produced by inducible nitric oxide synthase (iNOS) contributes importantly to acute lung injury (ALI), but the specific contribution of neutrophil iNOS has not been defined. Thus, we defined the role of neutrophils and specifically neutrophil iNOS in a murine model of septic ALI. Four hours after cecal ligation/perforation, ALI was characterized by increases in pulmonary neutrophil infiltration (tissue myeloperoxidase activity, bronchoalveolar lavage neutrophils), microvascular leak of Evans blue (EB) dye–labeled albumin, and oxidant stress (8-isoprostane levels). Septic ALI was neutrophil dependent, as pretreatment with anti-CD18 before cecal ligation/perforation significantly (P < 0.05) attenuated septic increases in pulmonary myeloperoxidase (39 ± 11 vs. 85 ±14 mU/mg protein), bronchoalveolar lavage neutrophils (0.5% ± 0.2% vs. 2.1% ± 0.6%), microvascular EB-albumin leak (1.3 ± 0.3 vs. 2.6 ± 0.7 μg EB/g per minute), and 8-isoprostane content (74 ± 15 vs. 115 ± 16 pg/mg protein). The role of neutrophil iNOS was assessed by creation of neutrophil-iNOS chimeric mice: iNOS^+/+ versus iNOS^−/− mice were bone marrow depleted by irradiation and selectively reconstituted with iNOS^+/+ versus iNOS^−/− neutrophils. Cecal ligation/perforation resulted in significant septic ALI in + to − neutrophil-iNOS chimeric mice (iNOS^+/+ neutrophils in iNOS^−/− mice), but not in − to + neutrophil depleted-reconstituted mice (iNOS^−/− neutrophils in iNOS^+/+ mice). There were no significant differences between iNOS^+/+ and iNOS^−/− neutrophils in phagocytosis, respiratory burst, or CD11a/b/CD18 surface expression, although septic shedding of CD62L was blunted in iNOS^−/− neutrophils. Neutrophil iNOS contributes importantly to murine septic ALI in vivo, but not simply through a change in neutrophil phenotype. We speculate that neutrophil iNOS may modulate neutrophil-endothelial interactions in complex fashion, including regulation of transendothelial neutrophil migration and pulmonary neutrophil infiltration.

Chronic obstructive pulmonary disease-associated pulmonary hypertension (COPD-PH) is an increasingly recognised condition which contributes to worsening dyspnea and poor survival in COPD. It is uncertain whether specific treatment of COPD-PH, including use of medications approved for pulmonary arterial hypertension (PAH), improves clinical outcomes. This systematic review and meta-analysis assesses potential benefits and risks of therapeutic options COPD-PH. We searched Medline and Embase for relevant publications until Sep 2020. Articles were screened for studies on treatment of COPD-PH for at least 4 weeks in 10 or more patients. Screening, data extraction, and risk of bias assessment were performed independently in duplicate. When possible, relevant results were pooled using the random effects model. Supplemental long-term O₂ therapy (LTOT) mildly reduced mean pulmonary artery pressure (PAP), slowed progression of PH, and reduced mortality, but other clinical or functional benefits were not assessed. Phosphodiesterase type-5 inhibitors significantly improved systolic PAP (pooled treatment effect −5.9 mmHg; 95%CI −10.3, −1.6), but had inconsistent clinical benefits. Calcium-channel blockers and endothelin receptor antagonists had limited hemodynamic, clinical, or survival benefits. Statins had limited clinical benefits despite significantly lowering systolic PAP (pooled treatment effect −4.6 mmHg; 95% CI: −6.3, −2.9). This review supports guideline recommendations for LTOT in hypoxemic COPD-PH patients as well as recommendations against treatment with PAH-targeted medications, Effective treatment of COPD-PH depends upon research into the pathobiology, and future high-quality studies comprehensively assessing clinically relevant outcomes are needed.