RESUMO
Semliki Forest virus (SFV) is an efficient vector for cardiac gene delivery. The relatively short transgene expression induced by SFV seems appropriate for angiogenic gene therapy. We tested the effects of SFV expressing vascular endothelial growth factor (VEGF) on cardiac angiogenesis and heart failure in the mRen2 transgenic rat.Six-week-old mRen2 rats received SFV-VEGF or control virus (n=7 each) administered intracoronarily. Twelve days after transfection, cardiac capillary density and function were assessed. Capillary density in cardiac regions where SFV expression was highest had decreased by 20% in the SFV-VEGF-treated group. The decrease in capillary density was accompanied by impaired systolic function as illustrated by increased endsystolic volumes and a 34% decrease in cardiac output.We conclude that the time frame of SFV expression is sufficient to induce structural alterations, but that VEGF in mRen2 transgenic rats did not elicit the expected angiogenic effect. Rather, capillary density was decreased and subsequently cardiac function was impaired. This paradoxical finding is possibly related to the pathophysiology associated with this model and warrants caution if one is to pursue VEGF-mediated, angiogenic therapy before proceeding to a clinical setting. (Neth Heart J 2007;15:335-41.).
RESUMO
BACKGROUND & AIMS: Biliary cholesterol secretion is coupled to that of phospholipids in a process controlled by mdr2 P-glycoprotein activity and bile salt secretion. Statins, the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, have been shown to affect hepatobiliary lipid secretion in rats. The aim of this study was to relate the effects of statins on bile formation to the expression of mdr2 and other hepatic adenosine triphosphate-dependent transport proteins involved in bile formation in rats. METHODS: Rats received simvastatin- or pravastatin-containing chow continuously for 5 days. In one group of rats, simvastatin treatment was withdrawn 9-12 hours before the end of the experiment to induce biliary cholesterol hypersecretion (rebound). Bile and liver tissue were collected for lipid analysis, and hepatic messenger RNA (mRNA) and protein levels were studied by reverse-transcription polymerase chain reaction, immunoblotting, and immunohistochemistry. RESULTS: Simvastatin feeding did not alter biliary bile salt secretion. Secretion of phospholipids and cholesterol was stimulated by 74% and 90%, respectively, in the simvastatin-continuous group and by 72% and 235%, respectively, in the rebound group compared with controls. mdr2 mRNA levels increased only in the continuous group. mdr2 protein levels increased in both simvastatin-fed groups. Induction was most pronounced in periportal hepatocytes. mdr1b mRNA levels were moderately increased in both simvastatin-fed groups. Levels of other hepatic transport proteins did not change. Similar results were obtained in pravastatin-fed rats. CONCLUSIONS: Statins increase expression of mdr2 and mdr1b in rats, revealing a novel effect of these commonly used drugs.
