Emphysema Is-at the Most-Only a Mild Phenotype in the Sugen/Hypoxia Rat Model of Pulmonary Arterial Hypertension.

Translational research is essential to develop strategies for the treatment of pulmonary arterial hypertension (PAH) using animal models which reproduce the severity, the progressive nature and resistance to treatment of human PAH, including severe arterial remodeling and progressive right ventricular (RV) failure. We read with interest the letter by Kojonazariov et al. who propose to have found “severe emphysema in the SU5416/Hypoxia (SuHx) rat model of pulmonary hypertension”. The authors report that Wistar-Kyoto rats exposed to the combination of VEGFR2 inhibition by SU5416 and chronic hypoxia had moderately increased RVSP and RV mass compared to normoxic untreated animals. They applied in vivo micro-computed tomography (CT) to demonstrate an increase in lung volume and decreased lung density, an unaltered amount of lung tissue, but an increased air-to-tissue ratio, and claim these findings were confirmed by histological analysis, including mean linear intercept as surrogate of emphysema. Indeed, SU5416 has been previously shown to induce emphysema in normoxia, but this required repetitive SU5416 dosing (3 times weekly over 3 weeks) and occurred more predominantly in rats younger than 4 weeks of age (Norbert Voelkel, personal communication). In addition, emphysema could be negated, at the cost of the development of severe angioproliferative hypertension, by concomitant exposure to hypoxia

The Adult Sprague-Dawley Sugen-Hypoxia Rat Is Still "the One:" A Model of Group 1 Pulmonary Hypertension: Reply to Le Cras and Abman.

To the editor: Kojonazarov et al. recently reported severe emphysema in the SU5416/Hypoxia (SuHx) rat model of pulmonary hypertension (1). The authors found that adult male Wistar Kyoto (WKY) rats had increased air-to-tissue ratio as judged by non-gated in vivo micro-computed tomography (CT), and an increased mean linear intercept (MLI) as surrogate of emphysema (1, 2). Le Cras and Abman now responded to the Kojonazarov report by underlining the “important role of the developmental timing of disrupted VEGF signaling” (3). They cite earlier studies conducted on the ovine fetus showing that VEGF inhibition caused vascular remodeling, reduction in vascular/airway growth, and neonatal pulmonary hypertension at birth (4). Although SU5416 is known to induce emphysema in rats housed in room air at Denver altitude (1609m altitude) (5, 6), we contended in our response letter (11) that, at least in male Sprague Dawley (SD) rats, the combination of VEGFR inhibition and hypoxia does not lead to any biologically relevant emphysema or other significant parenchymal lung disease (7) but to pulmonary arterial hypertension (PAH) due to severe angioproliferative remodeling (7, 8)

Overexpression of CYP2J2 provides protection against doxorubicin-induced cardiotoxicity

Human cytochrome P-450 (CYP)2J2 is abundant in heart and active in biosynthesis of epoxyeicosatrienoic acids (EETs). Recently, we demonstrated that these eicosanoid products protect myocardium from ischemia-reperfusion injury. The present study utilized transgenic (Tr) mice with cardiomyocyte-specific overexpression of human CYP2J2 to investigate protection toward toxicity resulting from acute (0, 5, or 15 mg/kg daily for 3 days, followed by 24-h recovery) or chronic (0, 1.5, or 3.0 mg/kg biweekly for 5 wk, followed by 2-wk recovery) doxorubicin (Dox) administration. Acute treatment resulted in marked elevations of serum lactate dehydrogenase and creatine kinase levels that were significantly greater in wild-type (WT) than CYP2J2 Tr mice. Acute treatment also resulted in less activation of stress response enzymes in CYP2J2 Tr mice (catalase 750% vs. 300% of baseline, caspase-3 235% vs. 165% of baseline in WT vs. CYP2J2 Tr mice). Moreover, CYP2J2 Tr hearts exhibited less Dox-induced cardiomyocytes apoptosis (measured by TUNEL) compared with WT hearts. After chronic treatment, comparable decreases in body weight were observed in WT and CYP2J2 Tr mice. However, cardiac function, assessed by measurement of fractional shortening with M-mode transthoracic echocardiography, was significantly higher in CYP2J2 Tr than WT hearts after chronic Dox treatment (WT 37 ± 2%, CYP2J2 Tr 47 ± 1%). WT mice also had larger increases in β-myosin heavy chain and cardiac ankryin repeat protein compared with CYP2J2 Tr mice. CYP2J2 Tr hearts had a significantly higher rate of Dox metabolism than WT hearts (2.2 ± 0.25 vs. 1.6 ± 0.50 ng·min−1·100 μg protein−1). In vitro data from H9c2 cells demonstrated that EETs attenuated Dox-induced mitochondrial damage. Together, these data suggest that cardiac-specific overexpression of CYP2J2 limited Dox-induced toxicity