Clinical application of pulmonary vascular resistance in patients with pulmonary arterial hypertension

Pulmonary arterial hypertension is a type of malignant pulmonary vascular disease, which is mainly caused by the increase of pulmonary vascular resistance due to the pathological changes of the pulmonary arteriole itself, which eventually leads to right heart failure and death. As one of the diagnostic indicators of hemodynamics, pulmonary vascular resistance plays an irreplaceable role in the pathophysiology, diagnosis and treatment of pulmonary arterial hypertension. It provides more references for the evaluation of pulmonary arterial hypertension patients. This article summarizes the clinical application of pulmonary vascular resistance in patients with pulmonary arterial hypertension.

EXPRESS: Clinical characteristics and prognosis analysis of idiopathic and hereditary pulmonary hypertension patients with ACVRL1 gene mutations

Pulmonary arterial hypertension (PAH) is a kind of heart and lung vascular disease with low incidence and poor prognosis. Genetic variants are the important factors of PAH. The mutations of activin receptor-like kinase-1 (ACVRL1) could cause pulmonary arteriole obstruction and occlusion in PAH patients. The ACVRL1 gene mutation and clinical characteristics of Chinese idiopathic or hereditary pulmonary hypertension (IPAH/HPAH) patients are still unclear. This study aimed to retrospective study the mutation characteristics of ACVRL1 gene in Chinese IPAH/HPAH patients and its effect on clinical prognosis. We analyzed the clinical, functional, hemodynamic and mutation characteristics of 12 IPAH/HPAH patients with ACVRL1 mutations, and compared with 94 IPAH/HPAH patients (27 patients carried bone morphogenetic protein receptor type 2 (BMPR2) mutations and 67 without mutations). All ACVRL1 mutations of 12 patients were single nucleotide missense mutations. The ratio of male to female in 12 patients was 1:1. The diagnosis age of ACVRL1 mutation patients was younger than that of BMPR2 mutation patients (13.6±11.3 years vs. 16.0±12.9 years), but higher than that of patients without mutations (13.6±11.3 years vs. 8.8±8.5years, P=0.006). IPAH/HPAH patients with ACVRL1 mutation have rapidly disease progresses, high overall mortality rate (approximately 50%) and no respond to the acute pulmonary vasodilation test. In conclusion, this is the first study to analyze the ACVRL1 gene mutation and clinical characteristics of Chinese IPAH/HPAH patients. It is beneficial to screen ACVRL1 gene mutation for IPAH/HPAH patients to facilitate genetic counseling and early prevention and treatment.

Bmi-1 alleviates adventitial fibroblast senescence by eliminating ROS in pulmonary hypertension

Objectives Pulmonary hypertension (PH) is a life-threatening progressive disease with high mortality in the elderly. However, the pathogenesis of PH has not been fully understood and there is no effective therapy to reverse the disease process. This study aims to determine whether cellular senescence is involved in the development of PH. Methods The rat PH model was established by intraperitoneal injection of monocrotaline and evaluated by pulmonary arteriole wall thickness and right ventricular hypertrophy index. Human lung fibroblasts (HLFs) were treated with CoCl2 or hypoxia to induce cellular senescence in vitro. SA-β-gal staining and the changes of senescent markers were used to examine cellular senescence. The molecular mechanism of cellular senescence was further explored by detecting reactive oxygen species (ROS) levels and culturing cells with a conditioned medium. Results We revealed the cellular senescence of pulmonary adventitial fibroblasts in vivo in the rat PH model. The expression of Bmi-1, an important regulator of senescence, was decreased in the lungs of PH rats and localized in adventitial fibroblasts. The in vitro experiments showed that p16 expression was increased while Bmi-1 expression was decreased after CoCl2 treatment in HLFs. Mechanistically, Bmi-1 could alleviate CoCl2-induced HLFs senescence by eliminating ROS which further promoted the proliferation of pulmonary artery smooth muscle cells by paracrine mode of action of HLFs. Conclusion Bmi-1 alleviates the cellular senescence of pulmonary fibroblasts in PH, which expands the pathogenesis of PH and provides a theoretical basis for targeting senescent cells in the treatment of PH.

Integrin αIIbβ3 Regulates Platelet-Procoagulant Activity in the Lung

Pulmonary thrombosis is a major complication associated with high morbidity. Despite advances in diagnosis and treatment, the pathophysiology of pulmonary thrombosis remains incompletely understood. New clinical evidence suggests that in situ platelet activation resulting in enhanced procoagulant activity may promote pulmonary thrombosis. Improved understanding of the etiological mechanism would enable the development of new therapies for pulmonary thrombosis. Collagen and thromboplastin (TF) were administered intravascularly (IV) to C57BL/6 (WT) mice and the pulmonary microcirculation was visualized using quantitative fluorescence intravital fluorescence lung microscopy (qFILM). Fluorochrome-conjugated anti-mouse CD49b Ab and dextran was administered IV for in vivo staining of circulating platelets and visualization of blood vessels, respectively. Pulmonary thrombosis was defined as occlusion of blood vessels with platelet aggregates leading to pulmonary ischemia. Additionally, quantitative microfluidic fluorescence microscopy (qMFM) was used to study the effect of platelet αIIbβ3 inhibition on platelet procoagulant activity in human blood under vascular mimetic flow conditions. Collagen and TF triggered dose-dependent pulmonary thrombosis in mice in vivo, which involved development of platelet-rich thrombi in the pulmonary arteriolar bottlenecks (junction of pulmonary arteriole and capillaries), resulting in a transient ischemia in the arteriole and the down-stream capillary tree. The pulmonary arteriole thrombosis triggered by IV collagen or TF was protracted, lethal and completely abrogated following IV administration of αIIbβ3 receptor inhibitor (eptifibatide). Inhibition of platelet αIIbβ3 also significantly reduced platelet procoagulant activity, fibrin formation and thrombus formation in human blood flowing through microfluidic channels ex vivo. Our current findings suggest that αIIbβ3-dependent platelet procoagulant activity promotes pulmonary thrombosis. Both our models have potential application in investigating the molecular determinants of pulmonary thrombosis in diverse pulmonary disorders as well as evaluating efficacy of new antithrombotic drugs. Disclosures No relevant conflicts of interest to declare.

Serum biomarker analysis at the protein level on pulmonary hypertension secondary to old anterior myocardial infarction

Pulmonary hypertension (PH) related to old anterior myocardial infarction (OAMI) always accompanies a bad prognosis, and thus, we aimed to screen serum biomarkers related to PH in OAMI patients. According to right ventricular systolic pressure, we divided mice into sham, OAMI, and PH-OAMI groups and evaluated body, heart and lung weight, heart function, pulmonary blood flow velocity, cardiac fibrotic area, and pulmonary arteriole condition. Lung and serum were under the proteomic analysis. Levels of three identified proteins were measured. Compared with sham and OAMI mice, PH-OAMI mice showed heart dysfunction, low pulmonary blood flow, high right ventricular systolic pressure, heavy heart and lung weight, large cardiac fibrotic area, and pathological pulmonary arteriole remodeling ( P<0.05 or P<0.01). Haptoglobin, annexin A5, and Ig mu chain C region of lung and serum were changed significantly in PH-OAMI mice ( P<0.01). Then, we collected serum and clinical data, measured three serum protein levels, and performed multivariate regression and receiver operating characteristic curve in patients (normal, OAMI, and PH-OAMI groups). Compared with normal and OAMI patients, serum levels of three proteins in PH-OAMI patients were also altered notably ( P<0.01). These three proteins can predict PH in OAMI patients ( P<0.01). Receiver operating characteristic curve analysis revealed haptoglobin (cut-off value: 78.295, sensitivity: 62.8%, specificity: 94.4%), annexin A5 (cut-off value: 151.925, sensitivity: 41.9%, specificity: 82.4%), and Ig mu chain C region (cut-off value: 168.885, sensitivity: 86.0%, specificity: 79.6%) ( P<0.01). Three circulating serum proteins can be useful for the categorization of OAMI patients with and without PH.

Mechanism of Pulmonary Thrombosis in Hemolytic Disorders

Hemolysis is a hallmark of various inherited or acquired blood disorders including sickle cell disease, thalassemia, paroxysmal nocturnal hemoglobinuria, thrombotic thrombocytopenic purpura and hemolytic-uremic syndrome. Epidemiological evidence suggests that in situ pulmonary thrombosis is a major pathological event contributing to cardiopulmonary morbidities affecting patients with hemolytic disorders. Intravascular hemolysis promotes the release of erythrocyte-derived damage associated molecular patterns (eDAMPs) molecules such as cell free hemoglobin (Hb), heme and adenosine diphosphate (ADP). Although these eDAMPS may activate platelets, promote endothelial dysfunction and drive sterile thrombo-inflammation, the pathogenesis of pulmonary thrombosis in hemolytic disorders and the role of platelets in this process remains unclear. Intravascular hemolysis in C57BL/6 (WT) mice was induced by intravenous (IV) administration of deionized water (H2O). Alternatively, eDAMPs or tissue derived DAMPs relevant to hemolysis or endothelial injury were administered IV to WT mice. The pulmonary microcirculation was visualized using quantitative intravital fluorescence lung microscopy (qFILM). Fluorochrome-conjugated anti-mouse CD49b Ab and dextran were administered IV for in vivo staining of circulating platelets and visualization of blood vessels, respectively. Time series of qFILM images were collected at baseline and post IV administration of agonists to assess pulmonary thrombosis. IV administration of H2O led to arrival of platelet-rich thrombi in the pulmonary arterioles that occluded the arteriolar bottle-necks located at the junction of pulmonary arterioles and capillaries leading to their transient obstruction. DAMPs such as ADP, collagen, thrombin and tissue factor also triggered dose-dependent PT in mice. Identical to IV H2O, DAMPs triggered pulmonary thrombosis also involved entrapment of platelet-rich thrombi in the arteriolar bottle-necks, which led to ischemia in the pulmonary arteriole and the down-stream capillaries. Interestingly, pretreatment with IV heparin (300 U/kg) prevented TF-induced but not ADP-triggered pulmonary thrombosis in mice. In contrast, IV administration of αIIbβ3 receptor inhibitor eptifibatide (10 mg/kg) completely abrogated TF-, collagen and ADP-dependent PT. Our current findings provide the first real-time in vivo visual evidence establishing that intravascular hemolysis directly induces pulmonary thrombosis, which involves entrapment of platelet-rich thrombi in the pre-capillary pulmonary arterioles. Our results are the first to identify that platelet activation and procoagulant activity contribute to pathogenesis of hemolysis induced pulmonary thrombosis. Disclosures Ragni: OPKO: Research Funding; Bioverativ/Sanofi: Other: Advisory Board, Research Funding; Shire/Takeda: Other: Advisory Board, Research Funding; Sangamo: Research Funding; Spark Therapeutics: Other: Advisory Board, Research Funding; Alnylam/Sanofi: Other: Advisory Board, Research Funding; BioMarin: Other: Advisory Board, Research Funding. Neal:Janssen Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees. Gladwin:Bayer Pharmaceuticals: Other: Co-investigator; United Therapeutics: Patents & Royalties: Co-inventor on an NIH government patent for the use of nitrite salts in cardiovascular diseases ; Globin Solutions, Inc: Patents & Royalties: Provisional patents for the use of recombinant neuroglobin and heme-based molecules as antidotes for CO poisoning.

Lung Vaso-Occlusion in Sickle Cell Disease Mediated By Arteriolar Neutrophil-Platelet Micro-Emboli

Background: Vaso-occlusive crisis (VOC) is the primary reason for emergency medical care by sickle cell disease (SCD) patients. SCD patients hospitalized with VOC often develop acute chest syndrome (ACS), a form of acute lung injury, suggesting a role for pulmonary vaso-occlusion in the onset of ACS. However, the cellular, molecular and biophysical mechanism of pulmonary vaso-occlusion is unknown. Methods: SCD transgenic or non-sickle control mice were intravenously (IV) challenged with 2 to 3 ng of bacterial lipopolysaccharide (LPS). Fluorescent anti-mouse Ly-6G and CD49b mAbs were administered IV for in vivo staining of circulating neutrophils and platelets, respectively. Multiphoton excitation enabled quantitative fluorescence intravital lung microscopy (qFILM) was used to determine the molecular mechanism of pulmonary vaso-occlusion in live mice. Function-blocking anti-mouse P-selectin mAb (Fab fragments) was administered IV to assess the role of platelet P-selectin in promoting pulmonary vaso-occlusion. Results: A nanogram dose of IV LPS selectively triggered pulmonary vaso-occlusion in SCD but not control mice. Remarkably, pulmonary vaso-occlusion involved occlusion of the pre-capillary pulmonary arteriole bottle-necks (junction of an arteriole and capillaries) by large neutrophil-platelet embolic aggregates. IV administration of Fab fragments of function blocking anti-P-selectin mAb led to the resolution of pulmonary vaso-occlusion, which was primarily mediated by the attenuation of large neutrophil-platelet aggregates into smaller aggregates that are not stopped by the arteriolar bottle-necks. Conclusion: These results establish the relevance of neutrophil-platelet aggregation in pulmonary arterioles in promoting pulmonary vaso-occlusion in SCD and also highlight the therapeutic potential of inhibiting platelet P-selectin to prevent ACS in SCD patients hospitalized with VOC. Acknowledgments: This study was supported by 1R01HL128297-01 (P.S.), AHA 11SDG7340005 (P.S.), VMI startup funds (P.S.). M.F.B. was supported by NIH-NHLBI training grant T32HL110849 and NIH-NHLBI F32 NRSA 1F32HL131216-01. Disclosures No relevant conflicts of interest to declare.