Functional Impact of Human Genetic Variants of COL18A1/Endostatin on Pulmonary Endothelium.

Pulmonary arterial hypertension (PAH) is an incurable disease characterized by disordered and dysfunctional angiogenesis leading to small-vessel loss and an obliterative vasculopathy. The pathogenesis of PAH is not fully understood, but multiple studies have demonstrated links between elevated angiostatic factors, disease severity, and adverse clinical outcomes. ES (endostatin), one such circulating angiostatic peptide, is the cleavage product of the proteoglycan COL18A1 (collagen α1[XVIII] chain). Elevated serum ES is associated with increased mortality and disease severity in PAH. A nonsynonymous variant of ES (aspartic acid-to-asparagine substitution at amino acid 104; p.D104N) is associated with differences in PAH survival. Although COL18A1/ES expression is markedly increased in remodeled pulmonary vessels in PAH, the impact of ES on pulmonary endothelial cell (PEC) biology and molecular contributions to PAH severity remain undetermined. In the present study, we characterized the effects of exogenous ES on human PEC biology and signaling. We demonstrated that ES inhibits PEC migration, proliferation, and cell survival, with significant differences between human variants, indicating that they are functional genetic variants. ES promotes proteasome-mediated degradation of the transcriptional repressor ID1, increasing expression and release of TSP-1 (thrombospondin 1). ES inhibits PEC migration via an ID1/TSP-1/CD36-dependent pathway, in contrast to proliferation and apoptosis, which require both CD36 and CD47. Collectively, the data implicate ES as a novel negative regulator of ID1 and an upstream propagator of an angiostatic signal cascade converging on CD36 and CD47, providing insight into the cellular and molecular effects of a functional genetic variant linked to altered outcomes in PAH.

SU5416 does not attenuate early RV angiogenesis in the murine chronic hypoxia PH model.

BACKGROUND: Right ventricular (RV) angiogenesis has been associated with adaptive myocardial remodeling in pulmonary hypertension (PH), though molecular regulators are poorly defined. Endothelial cell VEGFR-2 is considered a "master regulator" of angiogenesis in other models, and the small molecule VEGF receptor tyrosine kinase inhibitor SU5416 is commonly used to generate PH in rodents. We hypothesized that SU5416, through direct effects on cardiac endothelial cell VEGFR-2, would attenuate RV angiogenesis in a murine model of PH. METHODS: C57 BL/6 mice were exposed to chronic hypoxia (CH-PH) to generate PH and stimulate RV angiogenesis. SU5416 (20 mg/kg) or vehicle were administered at the start of the CH exposure, and weekly thereafter. Angiogenesis was measured after one week of CH-PH using a combination of unbiased stereological measurements and flow cytometry-based quantification of myocardial endothelial cell proliferation. In complementary experiments, primary cardiac endothelial cells from C57 BL/6 mice were exposed to recombinant VEGF (50 ng/mL) or grown on Matrigel in the presence of SU5416 (5 µM) or vehicle. RESULT: SU5416 directly inhibited VEGF-mediated ERK phosphorylation, cell proliferation, and Kdr transcription, but not Matrigel tube formation in primary murine cardiac endothelial cells in vitro. SU5416 did not inhibit CH-PH induced RV angiogenesis, endothelial cell proliferation, or RV hypertrophy in vivo, despite significantly altering the expression profile of genes involved in angiogenesis. CONCLUSIONS: These findings demonstrate that SU5416 directly inhibited VEGF-induced proliferation of murine cardiac endothelial cells but does not attenuate CH-PH induced RV angiogenesis or myocardial remodeling in vivo.

Pulmonary arterial hypertension and atrial arrhythmias: incidence, risk factors, and clinical impact.

Atrial arrhythmia (AA) occurrence in pulmonary arterial hypertension (PAH) may determine clinical deterioration and affect prognosis. In this study we assessed AA incidence in idiopathic (IPAH) and systemic sclerosis related PAH (SSc-PAH) and evaluated risk factors, management, and impact on mortality. We collected baseline data from consecutive IPAH or SSc-PAH patients prospectively enrolled in the Johns Hopkins Pulmonary Hypertension Registry between January 2000 and July 2016. During follow-up AA onset, treatment, and outcome were recorded. Among 317 patients (201 SSc-PAH, 116 IPAH), 42 developed AA (19 atrial fibrillation, 10 flutter-fibrillation, 9 atrial flutter, and 4 atrial ectopic tachycardia) with a 13.2% cumulative incidence. Most events were associated with hospitalization (90.5%). Electrical or pharmacological cardioversion was attempted in most cases. Patients with AA had higher right atrial pressure, pulmonary wedge pressure ( P < 0.005), NT-proBNP ( P < 0.05), and thyroid disease prevalence ( P < 0.005). Higher mortality was observed in patients with AA, though not statistically significant (LogRank P = 0.323). Similar long-term mortality between IPAH with AA and SSc-PAH without AA was observed (LogRank P = 0.098). SSc-PAH with AA had the worst prognosis. In PAH patients AA occurrence is a matter of significant concern. Therapeutic strategies aimed at restoring sinus rhythm may represent an important goal.

The evolving landscape in the therapy of acute myeloid leukemia.

Acute myeloid leukemia (AML) is a heterogeneous clonal disorder of myeloid precursors arrested in their maturation, creating a diverse disease entity with a wide range of responses to historically standard treatment approaches. While significant progress has been made in characterizing and individualizing the disease at diagnosis to optimally inform those affected, progress in treatment to reduce relapse and induce remission has been limited thus far. In addition to a brief summary of the factors that shape prognostication at diagnosis, this review attempts to expand on the current therapies under investigation that have shown promise in treating AML, including hypomethylating agents, gemtuzumab ozogamicin, FLT3 tyrosine kinase inhibitors, antisense oligonucleotides, and other novel therapies, including aurora kinases, mTOR and PI3 kinase inhibitors, PIM kinase inhibitors, HDAC inhibitors, and IDH targeted therapies. With these, and undoubtedly many others in the future, it is the hope that by combining more accurate prognostication with more effective therapies, patients will begin to have a different, and more complete, outlook on their disease that allows for safer and more successful treatment strategies.