semaxinib and macitentan

Pulmonary hypertension (PH) causes cardiac hypertrophy in the right ventricle (RV) and eventually leads to RV failure due to persistently elevated ventricular afterload. We hypothesized that the mechanical stress on the RV associated with increased afterload impairs vasodilator function of the right coronary artery (RCA) in PH. Coronary vascular response was assessed using microangiography with synchrotron radiation (SR) in two well-established PH rat models, monocrotaline injection or the combined exposure to chronic hypoxia and vascular endothelial growth factor receptor blockade with Su5416 (SuHx model). In the SuHx model, the effect of the treatment with the nonselective endothelin-1 receptor antagonist (ERA), macitentan, was also examined. Myocardial viability was determined in SuHx model rats, using

Topics: Animals; Antihypertensive Agents; Coronary Angiography; Coronary Vessels; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Hypertrophy, Right Ventricular; Hypoxia; Indoles; Monocrotaline; Predictive Value of Tests; Pulmonary Arterial Hypertension; Pyrimidines; Pyrroles; Rats, Sprague-Dawley; Severity of Illness Index; Sulfonamides; Synchrotrons; Vasodilation; Ventricular Dysfunction, Right; Ventricular Function, Right; Ventricular Remodeling

The efficacy of endothelin (ET) receptor antagonist bosentan in patients with severe pulmonary arterial hypertension (PAH) remains limited, partly because its higher doses for potential blockade of ET receptors have never been tested due to liver dysfunction. We hypothesized that rigorous blockade of ET receptors using the novel dual ET receptor antagonist macitentan would be effective in treating severe PAH without major side effects in a preclinical model appropriately representing the human disorder. In normal rats, 30 mg·kg·d of macitentan completely abolished big ET-1-induced increases in right ventricle (RV) systolic pressure. Adult male rats were injected with SU5416, a vascular endothelial growth factor blocker, and exposed to hypoxia for 3 weeks and then to normoxia for an additional 5 weeks (total 8 weeks). In intrapulmonary arterial rings isolated from rats with severe PAH, macitentan concentration dependently inhibited ET-1-induced contraction. Long-term treatment with macitentan (30 mg·kg·d, from week 3 to 8) reversed the high RV systolic pressure with preserved cardiac output. Development of RV hypertrophy, luminal occlusive lesions and medial wall thickening were also significantly improved without increasing serum levels of liver enzymes by macitentan. In conclusion, efficacious blockade of ET receptors with macitentan would reverse severe PAH without major adverse effects.

Topics: Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Indoles; Male; Pyrimidines; Pyrroles; Rats; Rats, Sprague-Dawley; Severity of Illness Index; Sulfonamides; Time Factors; Vascular Endothelial Growth Factor A