Hematopoietic stem cell transplantation alters susceptibility to pulmonary hypertension in Bmpr2-deficient mice.

Increasing evidence suggests that patients with pulmonary arterial hypertension (PAH) demonstrate abnormalities in the bone marrow (BM) and hematopoietic progenitor cells. In addition, PAH is associated with myeloproliferative diseases. We have previously demonstrated that low-dose lipopolysaccharide (LPS) is a potent stimulus for the development of PAH in the context of a genetic PAH mouse model of BMPR2 dysfunction. We hypothesized that the hematopoietic progenitor cells might be driving disease in this model. To test this hypothesis, we performed adoptive transfer of BM between wild-type (Ctrl) and heterozygous Bmpr2 null (Mut) mice. Sixteen weeks after BM reconstitution, mice were exposed to low-dose chronic LPS (0.5 mg/kg three times a week for six weeks). Mice underwent right heart catheterization and tissues were removed for histology. After chronic LPS dosing, Ctrl mice in receipt of Mut BM developed PAH, whereas Mut mice receiving Ctrl BM were protected from PAH. BM histology demonstrated an increase in megakaryocytes and there was an increase in circulating platelets in Ctrl mice receiving Mut BM. These findings demonstrate that the hematopoietic stem cell compartment is involved in the susceptibility to PAH in the Mut mouse. The results raise the possibility that hematopoietic stem cell transplantation might be a potential treatment strategy in genetic forms of PAH.

Levetiracetam-induced eosinophilic pneumonia.

Levetiracetam is widely regarded as a benign antiepileptic drug, compared to older antiepileptic medication. We report a case of eosinophilic pneumonia due to levetiracetam use in a non-smoking woman aged 59 years with no previous respiratory history. Our patient presented with exertional breathlessness and marked desaturation on exertion. She displayed 'reverse bat-wing' infiltrates on her chest radiograph and peripheral eosinophilia on a complete blood count. Her symptoms, radiology and peripheral eosinophilia resolved completely with cessation of levetiracetam and a course of prednisolone. This is the first report of isolated eosinophilic pneumonia due to levetiracetam. Other reports of levetiracetam-induced eosinophilia describe drug rash, eosinophilia and systemic symptoms (DRESS syndrome). Detection of pulmonary drug reactions requires a careful drug history and high index of suspicion. Identifying and reporting a causative agent is crucially important, as cessation of the drug is essential for resolution of the syndrome.

Impaired natural killer cell phenotype and function in idiopathic and heritable pulmonary arterial hypertension.

BACKGROUND: Beyond their role as innate immune effectors, natural killer (NK) cells are emerging as important regulators of angiogenesis and vascular remodeling. Pulmonary arterial hypertension (PAH) is characterized by severe pulmonary vascular remodeling and has long been associated with immune dysfunction. Despite this association, a role for NK cells in disease pathology has not yet been described. METHODS AND RESULTS: Analysis of whole blood lymphocytes and isolated NK cells from PAH patients revealed an expansion of the functionally defective CD56(-)/CD16(+) NK subset that was not observed in patients with chronic thromboembolic pulmonary hypertension. NK cells from PAH patients also displayed decreased levels of the activating receptor NKp46 and the killer immunoglobulin-like receptors 2DL1/S1 and 3DL1, reduced secretion of the cytokine macrophage inflammatory protein-1ß, and a significant impairment in cytolytic function associated with decreased killer immunoglobulin-like receptor 3DL1 expression. Genotyping patients (n=222) and controls (n=191) for killer immunoglobulin-like receptor gene polymorphisms did not explain these observations. Rather, we show that NK cells from PAH patients exhibit increased responsiveness to transforming growth factor-ß, which specifically downregulates disease-associated killer immunoglobulin-like receptors. NK cell number and cytotoxicity were similarly decreased in the monocrotaline rat and chronic hypoxia mouse models of PAH, accompanied by reduced production of interferon-γ in NK cells from hypoxic mice. NK cells from PAH patients also produced elevated quantities of matrix metalloproteinase 9, consistent with a capacity to influence vascular remodeling. CONCLUSIONS: Our work is the first to identify an impairment of NK cells in PAH and suggests a novel and substantive role for innate immunity in the pathobiology of this disease.

Praziquantel reverses pulmonary hypertension and vascular remodeling in murine schistosomiasis.

RATIONALE: Schistosomiasis is the most common worldwide cause of pulmonary arterial hypertension. The anti-schistosome drug praziquantel has been shown to reverse the liver fibrosis associated with Schistosoma mansoni in mice. OBJECTIVES: We sought to determine whether praziquantel reverses established pulmonary vascular remodeling and pulmonary hypertension in a mouse model of S. mansoni. METHODS: Mice were infected percutaneously with S. mansoni. At 17 weeks after infection mice were either killed or received two doses of praziquantel or vehicle by oral gavage. Treated mice were studied at 25 weeks after infection. MEASUREMENTS AND MAIN RESULTS: Vehicle-treated mice demonstrated significant increases in right ventricular systolic pressures (RVSP) and right ventricular hypertrophy (RVH) at 25 weeks, accompanied by pulmonary vascular remodeling. The degree of vascular remodeling correlated with proximity to granulomas. The elevation of RVSP and RVH at 25 weeks was dependent on the presence of eggs in the lung. Praziquantel eliminated the production of eggs in feces and led to clearance of eggs from the lung and to a lesser extent from liver. Praziquantel prevented the rise in RVSP and RVH seen in vehicle-treated mice and reversed established pulmonary vascular remodeling. Praziquantel significantly reduced lung mRNA expression of IL-13, IL-8, and IL-4, but did not reduce serum cytokine levels. CONCLUSIONS: The development of pulmonary hypertension associated with S. mansoni infection can be prevented by praziquantel, and established vascular remodeling can be reversed. The mechanism involves clearance of lung eggs and reduced local expression of lung cytokines.

Unexplained iron deficiency in idiopathic and heritable pulmonary arterial hypertension.

BACKGROUND: Anaemia is common in left heart failure and is associated with a poorer outcome. Many patients with pulmonary arterial hypertension (PAH) are anaemic or iron-deficient. This study was performed to investigate the prevalence of iron deficiency in PAH and to identify possible causes. METHODS: All patients with idiopathic or heritable PAH diagnosed in 1995-2008 were identified. Controls were selected from patients with chronic thromboembolic pulmonary hypertension (CTEPH). Full blood counts were examined and any abnormality was investigated. Patients were excluded if they had a cause for iron deficiency. The prevalence study was based on 85 patients with idiopathic PAH and 120 with CTEPH. A separate group of 20 patients with idiopathic PAH and 24 with CTEPH with matching haemodynamics were prospectively investigated for serum factors affecting iron metabolism. RESULTS: The prevalence study identified a point prevalence of unexplained iron deficiency of 50% in premenopausal women with idiopathic PAH compared with 8% in premenopausal women with CTEPH (p=0.002); 14% in postmenopausal women with idiopathic PAH compared with 6% in postmenopausal women with CTEPH (p=0.16); 28% in men with idiopathic PAH men compared with 2% in men with CTEPH (p=0.002); and 60% in patients with heritable PAH. The serum study showed that patients with idiopathic PAH had lower serum iron and transferrin saturations than those with CTEPH. Interleukin-6 levels correlated with iron levels (r=-0.6, p=0.006) and transferrin saturations (r=-0.68, p=0.001) in idiopathic PAH but not in CTEPH. CONCLUSIONS: The prevalence of unexplained iron deficiency is significantly higher in idiopathic PAH than in CTEPH. This may be linked to interleukin-6.

(18)FDG PET imaging can quantify increased cellular metabolism in pulmonary arterial hypertension: A proof-of-principle study.

The past decade has seen increased application of 18-flurodeoxyglucose positron emission tomography ((18)FDG-PET) imaging to help diagnose and monitor disease, particularly in oncology, vasculitis and atherosclerosis. Disordered glycolytic metabolism and infiltration of plexiform lesions by inflammatory cells has been described in idiopathic pulmonary arterial hypertension (IPAH). We hypothesized that increased (18)FDG uptake may be present in the lungs, large pulmonary arteries and right ventricle of patients with pulmonary hypertension, and that this uptake would be related to markers of immune activation. We imaged the thorax of 14 patients with pulmonary hypertension (idiopathic and chronic thromboembolic) and six controls by (18)FDG-PET/computed tomography (CT) and measured uptake in the lung parenchyma, large pulmonary arteries and right ventricle. (18)FDG uptake in the lungs and pulmonary arteries was normalized for venous blood activity to give a target-to-background ratio (TBR). Blood was contemporaneously drawn for high-sensitivity CRP - C-reactive protein (CRP) (hsCRP), N-Terminal Probrain natriuteric peptide (NT-ProBNP) and other inflammatory cytokines. IPAH patients had significantly higher lung parenchymal TBR (P=0.034) and right ventricle FDG uptake (P=0.007) than controls. Uptake in the main pulmonary arteries was similar in chronic thromboembolic pulmonary hypertension, IPAH and controls. There were no correlations between (18)FDG uptake and hsCRP or inflammatory cytokine levels. NT-ProBNP correlated with RV uptake in those with pulmonary hypertension (r=0.55, P=0.04). In this pilot study, we found increased (18)FDG uptake in the lung parenchyma and right ventricle of subjects with IPAH. The lung uptake might be useful as a surrogate marker of increased cellular metabolism and immune activation as underlying mechanisms in this disease. Further evaluation of the impact of targeted therapies in treatment-naïve patients and the significance of right ventricular uptake is suggested.

Elevated levels of inflammatory cytokines predict survival in idiopathic and familial pulmonary arterial hypertension.

BACKGROUND: Inflammation is a feature of pulmonary arterial hypertension (PAH), and increased circulating levels of cytokines are reported in patients with PAH. However, to date, no information exists on the significance of elevated cytokines or their potential as biomarkers. We sought to determine the levels of a range of cytokines in PAH and to examine their impact on survival and relationship to hemodynamic indexes. METHODS AND RESULTS: We measured levels of serum cytokines (tumor necrosis factor-alpha, interferon-gamma and interleukin-1beta, -2, -4, -5, -6, -8, -10, -12p70, and -13) using ELISAs in idiopathic and heritable PAH patients (n=60). Concurrent clinical data included hemodynamics, 6-minute walk distance, and survival time from sampling to death or transplantation. Healthy volunteers served as control subjects (n=21). PAH patients had significantly higher levels of interleukin-1beta, -2, -4, -6, -8, -10, and -12p70 and tumor necrosis factor-alpha compared with healthy control subjects. Kaplan-Meier analysis showed that levels of interleukin-6, 8, 10, and 12p70 predicted survival in patients. For example, 5-year survival with interleukin-6 levels of >9 pg/mL was 30% compared with 63% for patients with levels < or = 9 pg/mL (P=0.008). In this PAH cohort, cytokine levels were superior to traditional markers of prognosis such as 6-minute walk distance and hemodynamics. CONCLUSIONS: This study illustrates dysregulation of a broad range of inflammatory mediators in idiopathic and familial PAH and demonstrates that cytokine levels have a previously unrecognized impact on patient survival. They may prove to be useful biomarkers and provide insight into the contribution of inflammation in PAH.