Under Pressure to Clarify Pulmonary Hypertension Clinical Risk

[Role of myelin and lymphocyte protein in regulating pulmonary artery smooth muscle cell proliferation and apoptosis in pulmonary hypertension]

OBJECTIVE

To investigate the role of myelin and lymphocyte protein (MAL) in pulmonary hypertension (PAH).

METHODS

Blood samples were collected from 50 patients with PAH (PAH group) and 50 healthy individuals for detection of plasma MAL expression using ELISA.According to the echocardiographic findings, the patients were divided into moderate/severe group (n=18) and mild group (n=32), and the correlation between MAL protein level and the severity of PAH was analyzed.In a pulmonary artery smooth muscle cell model of PAH with hypoxia-induced abnormal proliferation, the effects of mal gene knockdown and overexpression on cell growth, proliferation and starvation-induced apoptosis were observed; the changes in NK-κB signaling pathway in the transfected cells were detected to explore the molecular mechanism by which MAL regulates PAMSC proliferation and apoptosis.

RESULTS

The plasma level of MAL was significantly higher in patients with PAH than in healthy individuals (P < 0.05), and the patients with moderate/severe PAH had significantly higher MAL level than those with mild PAH (P < 0.001).In PAMSCs, exposure to hypoxia significantly increased the mRNA and protein expression levels of MAL (P < 0.05), and MAL knockdown obviously inhibited hypoxia-induced proliferation and promoted starvation-induced apoptosis of the PAMSCs (P < 0.05).Knocking down mal significantly inhibited the activation of NK-κB signaling pathway that participated in regulation of PAMSC proliferation (P < 0.05).

CONCLUSION

The plasma level of MAL is elevated in PAH patients in positive correlation with the disease severity.MAL knockdown inhibits abnormal proliferation and promotes apoptosis of PAMSCs by targeted inhibition of the NF-κB signaling pathway to improve vascular remodeling in PAH.

Sexual Dimorphism of Dexamethasone as a Prophylactic Treatment in Pathologies Associated With Acute Hypobaric Hypoxia Exposure

Dexamethasone can be taken prophylactically to prevent hypobaric hypoxia-associated disorders of high-altitude. While dexamethasone-mediated protection against high-altitude disorders has been clinically evaluated, detailed sex-based mechanistic insights have not been explored. As part of our India-Leh-Dexamethasone-expedition-2020 (INDEX 2020) programme, we examined the phenotype of control (n = 14) and dexamethasone (n = 13) groups, which were airlifted from Delhi (∼225 m elevation) to Leh, Ladakh (∼3,500 m), India, for 3 days. Dexamethasone 4 mg twice daily significantly attenuated the rise in blood pressure, heart rate, pulmonary pressure, and drop in SaO₂ resulting from high-altitude exposure compared to control-treated subjects. Of note, the effect of dexamethasone was substantially greater in women than in men, in whom the drug had relatively little effect. Thus, for the first time, this study shows a sex-biased regulation by dexamethasone of physiologic parameters resulting from the hypoxic environment of high-altitude, which impacts the development of high-altitude pulmonary hypertension and acute mountain sickness. Future studies of cellular contributions toward sex-specific regulation may provide further insights and preventive measures in managing sex-specific, high-altitude–related disorders.

The different facets of sickle cell disease-related pulmonary hypertension

PURPOSE OF REVIEW

Sickle cell disease (SCD), one of the most common genetic diseases in the world, is characterized by repeated episodes of hemolysis and vaso-occlusion. Hemolytic anemia is a risk factor for the development of pulmonary hypertension, and currently SCD-related pulmonary hypertension is classified as World Health Organization group 5 pulmonary hypertension. Patients with SCD-related pulmonary hypertension have unique hemodynamics, multiple comorbidities, and distinct phenotypes that may contribute to the development of pulmonary hypertension.

RECENT FINDINGS

SCD-related pulmonary hypertension is defined as a mean pulmonary artery pressure >20 mmHg, a pulmonary artery occlusion pressure ≤15 mmHg and relatively low pulmonary vascular resistance (>2 Wood units) rather than the traditional definition of ≥3 Wood units, an important distinction due to a baseline high-cardiac output state in the setting of chronic anemia and low vascular resistance. Diastolic dysfunction is frequently identified in this patient population and right heart catheterization is essential to determine if combined pre- and postcapillary pulmonary hypertension is present. Thromboembolism is common among patients with SCD, and screening for chronic thromboembolic pulmonary hypertension is essential. Data regarding advanced therapies are limited. Primary treatment options include targeting correction of their primary hemoglobinopathy as well as aggressive management of underlying comorbid conditions.

SUMMARY

SCD-related pulmonary hypertension is common among patients with SCD and is associated with increased mortality. A high index of suspicion is warranted during evaluation to identify all potential factors that may be contributing to disease.

Association of persistent tachycardia with early myocardial dysfunction in children undergoing allogeneic hematopoietic cell transplantation

Cancer survivors who have undergone hematopoietic cell transplantation (HCT) are at risk for myocardial dysfunction. Children who receive allogenic HCT encounter systemic inflammation resulting in tachycardia and hypertension. The effect of these abnormalities on myocardial function is not known. The aim of this study was to determine whether cardiac dysfunction early after HCT can be predicted by tachycardia or hypertension, within a retrospective single-center sample of pediatric HCT recipients. Early tachycardia or hypertension was defined as a majority of values taken from infusion date to 90 days post-infusion being abnormal. Ejection fraction <53% determined systolic dysfunction. A composite score of accepted pediatric diastolic abnormalities determined diastolic dysfunction. Among 80 subjects (median age 8 years), early tachycardia, systolic dysfunction, and diastolic dysfunction were present in 64%, 25%, and 48% of the sample, respectively. In multivariable models, early tachycardia was an independent predictor of early systolic dysfunction (OR = 12.6 [1.4-112.8], p = 0.024) and diastolic dysfunction (OR = 3.9 [1.3-11.5], p = 0.013). Tachycardia and cardiac dysfunction are common and associated with one another in the early period after pediatric HCT. Future studies may elucidate the role of tachycardia and myocardial dysfunction early after HCT as important predictors of future cardiovascular dysfunction.

Hypercoagulability in Pulmonary Hypertension

Pulmonary hypertension (PH) is divided into varied pathophysiological and etiologic groupings, as classified by the World Health Organization (WHO). Pulmonary arterial hypertension (PAH), which falls under WHO group 1 PH, is a progressive and potentially fatal disease characterized by a vasoconstrictive, proliferative, and thrombotic phenotype, which leads to increased pulmonary artery pressure, right heart failure, and death. Pathologically, in situ thromboses are found in the small distal pulmonary arteries. Dysregulation of coagulation, platelet function, and endothelial cells may contribute to a prothrombotic state. There is mixed evidence for the use of anticoagulation or antiplatelet therapy in PAH patients.

Haemodynamic definitions and updated clinical classification of pulmonary hypertension

Since the 1st World Symposium on Pulmonary Hypertension (WSPH) in 1973, pulmonary hypertension (PH) has been arbitrarily defined as mean pulmonary arterial pressure (mPAP) ≥25 mmHg at rest, measured by right heart catheterisation. Recent data from normal subjects has shown that normal mPAP was 14.0±3.3 mmHg. Two standard deviations above this mean value would suggest mPAP >20 mmHg as above the upper limit of normal (above the 97.5th percentile). This definition is no longer arbitrary, but based on a scientific approach. However, this abnormal elevation of mPAP is not sufficient to define pulmonary vascular disease as it can be due to an increase in cardiac output or pulmonary arterial wedge pressure. Thus, this 6th WSPH Task Force proposes to include pulmonary vascular resistance ≥3 Wood Units in the definition of all forms of pre-capillary PH associated with mPAP >20 mmHg. Prospective trials are required to determine whether this PH population might benefit from specific management.

Regarding clinical classification, the main Task Force changes were the inclusion in group 1 of a subgroup “pulmonary arterial hypertension (PAH) long-term responders to calcium channel blockers”, due to the specific prognostic and management of these patients, and a subgroup “PAH with overt features of venous/capillaries (pulmonary veno-occlusive disease/pulmonary capillary haemangiomatosis) involvement”, due to evidence suggesting a continuum between arterial, capillary and vein involvement in PAH.

State of the art and research perspectives of haemodynamic definitions and clinical classification of pulmonary hypertensionhttp://ow.ly/TJeR30mgWKj

Haemodynamic definitions and updated clinical classification of pulmonary hypertension

Since the 1st World Symposium on Pulmonary Hypertension (WSPH) in 1973, pulmonary hypertension (PH) has been arbitrarily defined as mean pulmonary arterial pressure (mPAP) ≥25 mmHg at rest, measured by right heart catheterisation. Recent data from normal subjects has shown that normal mPAP was 14.0±3.3 mmHg. Two standard deviations above this mean value would suggest mPAP >20 mmHg as above the upper limit of normal (above the 97.5th percentile). This definition is no longer arbitrary, but based on a scientific approach. However, this abnormal elevation of mPAP is not sufficient to define pulmonary vascular disease as it can be due to an increase in cardiac output or pulmonary arterial wedge pressure. Thus, this 6th WSPH Task Force proposes to include pulmonary vascular resistance ≥3 Wood Units in the definition of all forms of pre-capillary PH associated with mPAP >20 mmHg. Prospective trials are required to determine whether this PH population might benefit from specific management.Regarding clinical classification, the main Task Force changes were the inclusion in group 1 of a subgroup "pulmonary arterial hypertension (PAH) long-term responders to calcium channel blockers", due to the specific prognostic and management of these patients, and a subgroup "PAH with overt features of venous/capillaries (pulmonary veno-occlusive disease/pulmonary capillary haemangiomatosis) involvement", due to evidence suggesting a continuum between arterial, capillary and vein involvement in PAH.

Pathophysiology of Sickle Cell Disease

Since the discovery of sickle cell disease (SCD) in 1910, enormous strides have been made in the elucidation of the pathogenesis of its protean complications, which has inspired recent advances in targeted molecular therapies. In SCD, a single amino acid substitution in the β-globin chain leads to polymerization of mutant hemoglobin S, impairing erythrocyte rheology and survival. Clinically, erythrocyte abnormalities in SCD manifest in hemolytic anemia and cycles of microvascular vaso-occlusion leading to end-organ ischemia-reperfusion injury and infarction. Vaso-occlusive events and intravascular hemolysis promote inflammation and redox instability that lead to progressive small- and large-vessel vasculopathy. Based on current evidence, the pathobiology of SCD is considered to be a vicious cycle of four major processes, all the subject of active study and novel therapeutic targeting: ( a) hemoglobin S polymerization, ( b) impaired biorheology and increased adhesion-mediated vaso-occlusion, ( c) hemolysis-mediated endothelial dysfunction, and ( d) concerted activation of sterile inflammation (Toll-like receptor 4- and inflammasome-dependent innate immune pathways). These molecular, cellular, and biophysical processes synergize to promote acute and chronic pain and end-organ injury and failure in SCD. This review provides an exhaustive overview of the current understanding of the molecular pathophysiology of SCD, how this pathophysiology contributes to complications of the central nervous and cardiopulmonary systems, and how this knowledge is being harnessed to develop current and potential therapies.