Pulmonary hypertension in chronic hemolytic anemias: Pathophysiology and treatment

Targeting lung heme iron by aerosol hemopexin adminstration in sickle cell disease pulmonary hypertension

Lung tissue from human patients and murine models of sickle cell disease pulmonary hypertension (SCD-PH) show perivascular regions with excessive iron accumulation. The iron accumulation arises from chronic hemolysis and extravasation of hemoglobin (Hb) into the lung adventitial spaces, where it is linked to nitric oxide depletion, oxidative stress, inflammation, and tissue hypoxia, which collectively drive SCD-PH. Here, we tested the hypothesis that intrapulmonary delivery of hemopexin (Hpx) to the deep lung is effective at scavenging heme-iron and attenuating the progression of SCD-PH. Herein, we evaluated in a murine model of hemolysis driven SCD-PH, if intrapulmonary Hpx administration bi-weekly for 10 weeks improves lung iron deposition, exercise tolerance, cardiovascular function, and multi-omic indices associated with SCD-PH. Data shows Hpx delivered with a micro-sprayer deposits Hpx in the alveolar regions. Hpx extravasates into the perivascular compartments but does not diffuse into the circulation. Histological examination shows Hpx therapy decreased lung iron deposition, 4-HNE, and HO-1 expression. This was associated with improved exercise tolerance, cardiopulmonary function, and multi-omic profile of whole lung and RV tissue. Our data provides proof of concept that treating lung heme-iron by direct administration of Hpx to the lung attenuates the progression of PH associated with SCD.

White blood cell-to-haemoglobin ratio as a predictor of 30-day mortality in ICU patients with pulmonary hypertension: a MIMIC-IV database study

BACKGROUND AND OBJECTIVE

The white blood cell-to-haemoglobin ratio (WHR) is a comprehensive indicator of inflammation and anaemia status. However, the relationship between the WHR and the risk of 30-day mortality among intensive care unit (ICU) patients with pulmonary hypertension (PH) remains unclear. The purpose of this study was to investigate the association between the WHR and 30-day mortality in critically ill patients with PH.

METHODS

Clinical data of patients with PH were extracted from the MIMIC-IV (2.2) database. Restricted cubic splines and logistic regression analysis were used to investigate the relationship between the WHR and 30-day mortality. Subgroup analysis was used to assess the robustness of the results.

RESULTS

A total of 451 patients with PH were enrolled, with 78 (17.3%) dying within 30 days. Restricted cubic spline analysis revealed a linear relationship between the WHR and 30-day mortality. Logistic regression analysis revealed the WHR was an independent predictor for 30-day mortality in critically ill patients with PH (OR, 1.58; 95% CI, 1.05-2.37; P = 0.028). The AUC of the WHR was 0.646 (95% CI: 0.60-0.69).

CONCLUSIONS

A higher WHR was an independent predictor for 30-day mortality in critically ill patients with PH.

CLINICAL TRIAL NUMBER

Not applicable.

Complement Immune System in Pulmonary Hypertension-Cooperating Roles of Circadian Rhythmicity in Complement-Mediated Vascular Pathology

Originally discovered in the 1890s, the complement system has traditionally been viewed as a "compliment" to the body's innate and adaptive immune response. However, emerging data have shown that the complement system is a much more complex mechanism within the body involved in regulating inflammation, gene transcription, attraction of macrophages, and many more processes. Sustained complement activation contributes to autoimmunity and chronic inflammation. Pulmonary hypertension is a disease with a poor prognosis and an average life expectancy of 2-3 years that leads to vascular remodeling of the pulmonary arteries; the pulmonary arteries are essential to host homeostasis, as they divert deoxygenated blood from the right ventricle of the heart to the lungs for gas exchange. This review focuses on direct links between the complement system's involvement in pulmonary hypertension, along with autoimmune conditions, and the reliance on the complement system for vascular remodeling processes of the pulmonary artery. Furthermore, circadian rhythmicity is highlighted as the disrupted homeostatic mechanism in the inflammatory consequences in the vascular remodeling within the pulmonary arteries, which could potentially open new therapeutic cues. The current treatment options for pulmonary hypertension are discussed with clinical trials using complement inhibitors and potential therapeutic targets that impact immune cell functions and complement activation, which could alleviate symptoms and block the progression of the disease. Further research on complement's involvement in interstitial lung diseases and pulmonary hypertension could prove beneficial for our understanding of these various diseases and potential treatment options to prevent vascular remodeling of the pulmonary arteries.

Clinical challenges in the treatment of a patient with decompensated heart failure and glucose-6-phosphate dehydrogenase deficiency (G6PDd)

We present a case of a man in his 60s, known with glucose-6-phosphate dehydrogenase deficiency (G6PDd) and cor pulmonale, admitted to the department of cardiology due to cardiac decompensation and anaemia. The main complaint was dyspnoea. Echocardiography confirmed severe cor pulmonale with compression of the left ventricle. G6PDd has been linked with pulmonary hypertension which could contribute to aforementioned echocardiographic findings. Diuretics are the first line of treatment when it comes to cardiac decompensation, but sulfonamide diuretics can induce or exacerbate haemolysis in patients with G6PDd. Due to the respiratory distress of the patient, a treatment plan including sulfonamide diuretics was initiated in collaboration with the haematologists. Unfortunately, the patient died 2 days after admission. This case emphasises that not all cardiac patients can tolerate standard treatment with sulfonamide diuretics; despite this, they remain essential in the acute setting, and they are associated with foreseeable but only partly manageable complications in susceptible patients.

Prevalence and Clinical Features of Portopulmonary Hypertension in Patients With Hepatic Cirrhosis: An Echocardiographic Study

Objective The present study was conducted to delineate the prevalence and clinical features of portopulmonary hypertension in patients with hepatic cirrhosis. Possible associations between echocardiographic variables and portopulmonary hypertension were also explored. Methods A prospective, observational study was conducted between September 2017 and August 2018. Differences in demographics, clinical presentation, laboratory findings, and echocardiographic findings in cirrhosis patients with and without portopulmonary hypertension were compared. Results The prevalence of portopulmonary hypertension in patients with hepatic cirrhosis was found to be 9.3%. Hemoglobin was significantly lower among patients with portopulmonary hypertension compared to those without portopulmonary hypertension (5.50±0.68 g/dl vs. 7.26±1.43 g/dl, p=0.001). All patients with portopulmonary hypertension displayed right atrial (major: p=0.0001 and minor: p=0.001) and right ventricular (basal, p=0.0001; longitudinal, p=0.0001) dilation. Several variables such as right ventricular systolic pressure (p=0.0001), pulmonary artery diameter (major: p=0.0001; right: p=0.0001; and left: p=0.007), pulmonary vascular resistance (p=0.0001), tricuspid regurgitation (p=0.0001), pulmonary regurgitation peak pressure gradient (p=0.0001), pulmonary regurgitation end diastolic gradient (p=0.0001), left atrial dimension (major axis: p=0.002), left atrial volume (p=0.04), left ventricular outflow tract (p=0.001), inferior vena cava diameter (p=0.001), and inferior vena cava collapsibility (p=0.001) were higher in patients with portopulmonary hypertension compared to patients without portopulmonary hypertension. Conclusions The present study revealed a 9.3% prevalence of portopulmonary hypertension among patients with hepatic cirrhosis. Patients with portopulmonary hypertension displayed significantly lower haemoglobin levels, right and left ventricular dilation, and higher values of several echocardiographic variables as compared to those without portopulmonary hypertension.

Efficacy and safety of inhaled nitrite in addition to sildenafil in thalassemia patients with pulmonary hypertension: A 12-week randomized, double-blind placebo-controlled clinical trial

Pulmonary hypertension is a significant complication in thalassemia patients. Recent studies showed that inhaled nebulized nitrite could rapidly decrease pulmonary artery pressure. We conducted a multicenter, randomized, double-blind, placebo-controlled trial in thalassemia patients with symptomatic pulmonary hypertension diagnosed by right heart catheterization. Eleven patients were recruited; five were assigned to the nitrite group and six to the placebo group. Patients were treated with the optimal doses of sildenafil for pulmonary hypertension and randomly assigned into the placebo or nitrite groups. Patients in the nitrite group were given inhaled nebulized 30 mg sodium nitrite twice a day for 12 weeks. The clinical outcomes measured at week 12 were the changes in 6-min walk distance (6MWD), mean pulmonary artery pressure (MPAP), and N-terminal pro B-type natriuretic peptide. The MPAP estimated by echocardiography was significantly reduced from 33.6 ± 7.5 mmHg to 25.8 ± 6.0 mmHg (mean difference = 7.76 ± 3.69 mmHg, p = 0.009 by paired t-test). Furthermore, 6MWD was slightly increased from 382.0 ± 54.0 m to 432 ± 53.9 m (mean difference = 50.0 ± 42.8 m, p = 0.059 by paired t-test) in the nitrite group. At week 12, the nitrite group had lower MPAP than the placebo group (25.8 ± 6.0 vs. 45.7 ± 18.5 mmHg, p = 0.048 by unpaired t-test). No significant difference in 6MWD and N-terminal pro B-type natriuretic peptide between the two groups was observed at week 12. There was no hypotension or other significant adverse effects in the nitrite group.

Heme stimulates platelet mitochondrial oxidant production to induce targeted granule secretion

Hemolysis, a pathological component of many diseases, is associated with thrombosis and vascular dysfunction. Hemolytic products, including cell-free hemoglobin and free heme directly activate platelets. However, the effect of hemolysis on platelet degranulation, a central process in not only thrombosis, but also inflammatory and mitogenic signaling, remains less clear. Our group showed that hemoglobin-induced platelet activation involved the production of mitochondrial reactive oxygen species (mtROS). However, the molecular mechanism by which extracellular hemolysis induces platelet mtROS production, and whether these mtROS regulate platelet degranulation remains unknown. Here, we demonstrate using isolated human platelets that cell free heme is a more potent agonist for platelet activation than hemoglobin, and stimulates the release of a specific set of molecules, including the glycoprotein thrombospondin-1 (TSP-1), from the α-granule of platelets. We uncover the mechanism of heme-mediated platelet mtROS production which is dependent on the activation of platelet toll-like receptor 4 (TLR4) signaling and leads to the downstream phosphorylation and inhibition of complex-V by the serine kinase Akt. Notably, inhibition of platelet TLR4 or Akt, or scavenging of mtROS prevents heme-induced granule release in vitro. Further, heme-dependent granule release is significantly attenuated in vivo in mice lacking TLR4 or those treated with the mtROS scavenger MitoTEMPO. These data elucidate a novel mechanism of TLR4-mediated mitochondrial regulation, establish the mechanistic link between hemolysis and platelet degranulation, and begin to define the heme and mtROS-dependent platelet secretome. These data have implications for hemolysis-induced thrombo-inflammatory signaling and for the consideration of platelet mitochondria as a therapeutic target in hemolytic disorders.

Evaluation of the Relationship Among Pulmonary Artery Pressure with Serum Ferritin Level and CMR T2* in Thalassemia Major

Background: Pulmonary hypertension is one of the most common cardiac complications among patients with β-thalassemia major (β-TM). The aim of this study is to investigate the correlation of pulmonary artery pressure (PAP), serum ferritin level, and cardiac T2* MRI in patients with β-TM. Method: This cross-sectional study was performed on 50 patients older than 7 years old. Echocardiography, electrocardiography, and cardiac T2* MRI were performed on all patients and their serum ferritin levels were measured. Based on the echocardiographic the patients were divided into two groups of PAP>30 and <30 mmHg. Results: 40% had PAP higher than 30 mmHg, 32% had abnormal T2* MRI, and 36% had serum ferritin levels higher than 1500ng/dl. there were significant negative correlations between CMRI *T2 and PAP (-0.36) and the P-pulmonary (-0.29). the serum ferritin level was positively correlated with PAP (0.44) and the P pulmonary in ECG (0.30). in the patients with PAP>30, the means of age, serum ferritin level, and P-pulmonary were significantly higher than patients with PAP<30 (P=0.001). In the patients with PAP>30mmHg, CMRI *T2 had higher accuracy (80%), sensitivity (65%), and specificity (90%) compared to the measurement of serum ferritin levels. Conclusion: The PAP was positively correlated with serum ferritin levels and negatively with T2MRI. The accuracy of 80% for T2MRI as a method to diagnose or even anticipate PH among patients with TM suggested that this method is a useful and accurate method of PH diagnosis and can be used as an alternative among clinicians.

Nutritional immunity: the impact of metals on lung immune cells and the airway microbiome during chronic respiratory disease

Nutritional immunity is the sequestration of bioavailable trace metals such as iron, zinc and copper by the host to limit pathogenicity by invading microorganisms. As one of the most conserved activities of the innate immune system, limiting the availability of free trace metals by cells of the immune system serves not only to conceal these vital nutrients from invading bacteria but also operates to tightly regulate host immune cell responses and function. In the setting of chronic lung disease, the regulation of trace metals by the host is often disrupted, leading to the altered availability of these nutrients to commensal and invading opportunistic pathogenic microbes. Similarly, alterations in the uptake, secretion, turnover and redox activity of these vitally important metals has significant repercussions for immune cell function including the response to and resolution of infection. This review will discuss the intricate role of nutritional immunity in host immune cells of the lung and how changes in this fundamental process as a result of chronic lung disease may alter the airway microbiome, disease progression and the response to infection.

Prevalence of pulmonary hypertension in myelofibrosis

Pulmonary hypertension (PH) has been described in myelofibrosis (MF), but it is rare and typically found in advanced disease. Although the etiology of PH in MF is unclear, early predictors may be detected by echocardiogram. The goals of our study were to evaluate the prevalence of PH as determined by echocardiography in a cohort of MF patients and to identify clinical risk factors for PH. We performed a retrospective review of MF patients from October 2015 to May 2017 at MD Anderson Cancer Center in the ambulatory clinic, and those with echocardiogram were included. Clinical, echocardiographic, and laboratory data were reviewed. Patients with and without PH were compared using a chi-square or Fisher's exact test, and logistic regression was performed with an outcome variable of PH. There were 143 patients with MF who underwent echocardiogram, and 20 (14%) had echocardiographic findings consistent with PH. Older age, male gender, hypertension, hyperlipidemia, coronary artery disease, dyspnea, hematocrit, brain natriuretic peptide (BNP), and N-terminal prohormone BNP (NT-proBNP) were significantly different between those without PH and those with PH (p < 0.05). Female gender was protective (OR 0.21, 95% CI 0.049-0.90, p = 0.035), and NT-proBNP was a significant clinical predictor of PH (OR 1.07, CI 1.02 = 1.12, p = 0.006). PH in MF is lower than previously reported in our MF cohort, but many patients had cardiac comorbidities. PH due to left-sided heart disease may be underestimated in MF. Evaluation of respiratory symptoms and elevated NT-proBNP should prompt a baseline echocardiogram. Early detection of PH with a multidisciplinary approach may allow treatment of reversible etiologies.

Splenectomy is not associated with a higher tricuspid regurgitant jet velocity in people with sickle cell anemia

BACKGROUND

Vascular complications such as pulmonary hypertension (PH) occur at an increased rate following splenectomy in patients with various hemolytic blood disorders including thalassemia. The goal of this retrospective cross-sectional analysis was to assess the independent association of splenectomy with an elevated tricuspid regurgitation velocity (TRV) in people with homozygous sickle cell disease (HbSS). TRV is a noninvasive screening test for PH and a surrogate marker of prognosis in sickle cell disease (SCD).

PROCEDURE

Data were obtained from the multicenter Walk-PHaSST (treatment of pulmonary hypertension and sickle cell disease with sildenafil therapy) study of PH (NCT00492531). We compared TRV in the cohort of patients with HbSS who were surgically splenectomized with patients who were not surgically splenectomized.

RESULTS

We found no significant differences in TRV between the two groups.

CONCLUSIONS

The lack of difference in TRV between the two groups is most likely because members of the comparator nonsurgical group in many cases experienced autoinfarction of the spleen in childhood. Splenectomy does not seem to confer additional risk for the development of a higher TRV in HbSS, unlike in patients with thalassemia or other hemolytic anemias. This could be an important consideration when weighing the risks and benefits of splenectomy in patients with HbSS.

An Hb-mediated circulating macrophage contributing to pulmonary vascular remodeling in sickle cell disease

Circulating macrophages recruited to the lung contribute to pulmonary vascular remodeling in various forms of pulmonary hypertension (PH). In this study we investigated a macrophage phenotype characterized by intracellular iron accumulation and expression of antioxidant (HO-1), vasoactive (ET-1), and proinflammatory (IL-6) mediators observed in the lung tissue of deceased sickle cell disease (SCD) patients with diagnosed PH. To this end, we evaluated an established rat model of group 5 PH that is simultaneously exposed to free hemoglobin (Hb) and hypobaric hypoxia (HX). Here, we tested the hypothesis that pulmonary vascular remodeling observed in human SCD with concomitant PH could be replicated and mechanistically driven in our rat model by a similar macrophage phenotype with iron accumulation and expression of a similar mixture of antioxidant (HO-1), vasoactive (ET-1), and inflammatory (IL-6) proteins. Our data suggest phenotypic similarities between pulmonary perivascular macrophages in our rat model and human SCD with PH, indicating a potentially novel maladaptive immune response to concomitant bouts of Hb and HX exposure. Moreover, by knocking out circulating macrophages with gadolinium trichloride (GdCl3), the response to combined Hb and hypobaric HX was significantly attenuated in rats, suggesting a critical role for macrophages in the exacerbation of SCD PH.