Cardiac and Vascular Atrogin-1 mRNA Expression is Not Associated with Dexamethasone Efficacy in the Monocrotaline Model of Pulmonary Hypertension

• Published in: Cardiovascular toxicology Vol. 12; no. 3; pp. 226 - 234
• Main Authors: Paffett, Michael L., Channell, Meghan M., Naik, Jay S., Lucas, Selita N., Campen, Matthew J.
• Format: Journal Article
• Language: English
• Published: New York Humana Press Inc 01.09.2012; Springer; Springer Nature B.V
• Subjects: Analysis; Animals; Biomedical and Life Sciences; Biomedicine; Blood pressure; Blood Pressure - drug effects; Blood Pressure - physiology; Body weight; Cardiac muscle; Cardiology; Catheters; Central nervous system depressants; Dexamethasone; Dexamethasone - pharmacology; Disease Models, Animal; Drug Antagonism; Gene Expression; Glucocorticoids; Glucocorticoids - pharmacology; Heart; Heart diseases; Heart Ventricles - drug effects; Heart Ventricles - pathology; Heart Ventricles - physiopathology; Hemodynamics; Histopathology; Hypertension; Hypertension, Pulmonary - drug therapy; Hypertension, Pulmonary - metabolism; Hypertension, Pulmonary - physiopathology; Hypertrophy; Hypertrophy, Right Ventricular - chemically induced; Hypertrophy, Right Ventricular - pathology; Hypertrophy, Right Ventricular - physiopathology; Ligases; Lung; Male; Messenger RNA; Monocrotaline; Monocrotaline - toxicity; Muscle Proteins - genetics; Muscle Proteins - metabolism; Muscles; Musculoskeletal system; Myocardium; myostatin; Myostatin - metabolism; Ostomy; Pathology; Pharmacology/Toxicology; proteasomes; Pulmonary arteries; Pulmonary artery; Pulmonary Artery - drug effects; Pulmonary Artery - metabolism; Pulmonary Artery - pathology; Pulmonary hypertension; Rats; Rats, Sprague-Dawley; RNA, Messenger - metabolism; Skeletal muscle; SKP Cullin F-Box Protein Ligases - genetics; SKP Cullin F-Box Protein Ligases - metabolism; Smooth muscle; Transcription; Ubiquitin; Ubiquitin-protein ligase; Veins & arteries; Ventricle; New Mexico; United States > US; Vascular smooth muscle; Atrogin; Glucocorticoid; Ubiquitin proteasome system; Pulmonary hypertension
• ISSN: 1530-7905; 1559-0259
• DOI: 10.1007/s12012-012-9158-y

Atrophic signaling elements of the ubiquitin–proteasome system (UPS) are involved in skeletal muscle wasting as well as pressure overload models of heart failure. In our prior experiments, we demonstrated a transcriptional downregulation of atrophy-inducing vascular E3 ubiquitin ligases in a toxic model of pulmonary hypertension where pulmonary artery and right ventricle (RV) hypertrophy are evident. Given the numerous reports of glucocorticoid activation of the UPS and the negative regulator of muscle mass, myostatin, we investigated the efficacy of dexamethasone to reverse monocrotaline (MCT)-induced pulmonary hypertension and augment atrogin-1 expression in both pulmonary arteries and myocardium. Dexamethasone caused significant reductions in body weight in combination with MCT. As predicted, MCT-induced pulmonary hypertension was evident by increases in RV systolic pressure, right ventricle to left ventricle plus septal weight ratios (RV/LVS) and arterial remodeling. MCT treatment significantly reduced both RV and PA atrogin-1 expression. Dexamethasone treatment reversed the MCT-induced pathological indices and restored RV atrogin-1 expression, but did not impact atrogin-1 expression in pulmonary arteries. Myostatin was poorly expressed in pulmonary arteries compared to the RV, and dexamethasone treatment increase RV myostatin in controls but not MCT-treated rats. These findings suggest that mechanisms independent of myostatin/atrogin-1 are responsible for glucocorticoid efficacy in this model of pulmonary hypertension.