sirolimus and Hypertrophy--Right-Ventricular

To investigate the effects of rapamycin (RAP) on pulmonary hypertension (PH) in rats, and to provide new insights into medication selection for the clinical treatment of PH.. Fifty male Sprague-Dawley rats were randomly divided into blank control, PH model, solvent control, RAP 1, and RAP 2 groups. A rat model of PH was induced by left pneumonectomy (PE) and monocrotaline (MCT). At 5 days after PH model establishment, the solvent control group and the RAP 1 group received an intramuscular injection of solvent and RAP, respectively. At 35 days after PH model establishment, the RAP 2 group received an intramuscular injection of RAP. The mean pulmonary artery pressure (mPAP) and the right ventricle/left ventricle plus septum weight ratio (RV/LV+S) were measured in each group. Histopathological changes in the right lung were evaluated by hematoxylin-eosin (HE) staining. The relative expression of alpha-smooth muscle actin (α-SMA) and smooth muscle protein 22-alpha (SM22α) in each group was determined using real-time PCR.. At 35 days after surgery, the PH model and the solvent control groups had significantly higher mPAP and RV/LV+S than the blank control group, while the RAP 1 and the RAP 2 groups had significantly lower mPAP than the solvent control group (P<0.05). The RV/LV+S in the RAP 1 group was significantly lower than that in the solvent control group (P<0.05); however, there was no significant difference in RV/LV+S between the RAP 2 and the solvent control groups (P>0.05). HE staining in the right lung showed the substantially thickened pulmonary artery wall and narrowed arterial lumen in the PH model and the solvent control groups compared with the blank control group. Different degrees of reversal of the pulmonary artery wall thickening were observed after RAP administration. The results of real-time PCR revealed that the relative expression of α-SMA and SM22α in the PH model and the solvent control groups was significantly lower than in the blank control group, while the relative expression of α-SMA and SM22α in the RAP 1 and the RAP 2 groups was significantly higher than in the solvent control group (P<0.05).. RAP can reverse the increase in pulmonary artery pressure and the right ventricular hypertrophy probably by regulation of the phenotypic conversion of vascular smooth muscle cells.

Topics: Actins; Animals; Hemodynamics; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Microfilament Proteins; Muscle Proteins; Pulmonary Artery; Rats; Rats, Sprague-Dawley; RNA, Messenger; Sirolimus

The present study was conducted to determine the magnitude and duration of ribosomal protein translation in response to pressure overload and determine if additional, paracrine events associated with mechanical transduction, such as integrin activation using a bioactive peptide ligand, RGD or endothelin stimulation lead to ribosomal protein translation. Polysome analysis of ventricular tissue samples obtained from an in vivo model of right-ventricular pressure overload (RVPO) showed a significant shift in the proportion of a 5'-terminal oligopyrimidine (5'-TOP) mRNA, rpL32, associated with the polysomal fraction when compared with non-5'-TOP mRNAs, beta-actin and beta-myosin heavy chain (beta-MHC), in the early stages of the hypertrophic response (24-48 h). Furthermore, this increase in polysome-bound rpL32 mRNA was accompanied by the phosphorylation of mammalian target of rapamycin (mTOR), p70 S6 kinase (S6K1), and S6 ribosomal protein. In our in vitro studies, treatment of primary cultures of adult feline cardiomyocytes (cardiocytes) with 100 nM endothelin, 9 mM RGD, 100 nM insulin, or 100 nM TPA activated mTOR via distinct signaling pathways and resulted in an increased proportion of polysome-bound rpL32 mRNA. Pre-treatment of cardiocytes with the mTOR inhibitor rapamycin blocked the agonist-induced rpL32 mRNA mobilization to polysomes. These results show that mechanisms that regulate ribosomal biogenesis in the myocardium are dynamically sensitive to pressure overload. Furthermore, our in vitro studies indicate that distinct pathways are operational during the early course of hypertrophic growth and converge to activate mTOR resulting in the translational activation of 5'-TOP mRNA.

Topics: Actins; Analysis of Variance; Animals; Blotting, Western; Cats; Cells, Cultured; Disease Models, Animal; Endothelins; Hypertrophy, Right Ventricular; Insulin; Myocytes, Cardiac; Myosin Heavy Chains; Nonmuscle Myosin Type IIB; Oligopeptides; Phosphorylation; Polyribosomes; Protein Biosynthesis; Protein Kinases; Reverse Transcriptase Polymerase Chain Reaction; Ribosomal Protein S6; Ribosomal Protein S6 Kinases; RNA 5' Terminal Oligopyrimidine Sequence; RNA, Messenger; Signal Transduction; Sirolimus; Tetradecanoylphorbol Acetate; TOR Serine-Threonine Kinases

Chronic hypoxia induces pulmonary arterial hypertension (PAH). Smooth muscle cell (SMC) proliferation and hypertrophy are important contributors to the remodeling that occurs in chronic hypoxic pulmonary vasculature. We hypothesized that rapamycin (RAPA), a potent cell cycle inhibitor, prevents pulmonary hypertension in chronic hypoxic mice.. Mice were held either at normoxia (N; 21% O2) or at hypobaric hypoxia (H; 0.5 atm; ~10% O2). RAPA-treated animals (3 mg/kg*d, i.p.) were compared to animals injected with vehicle alone. Proliferative activity within the pulmonary arteries was quantified by staining for Ki67 (positive nuclei/vessel) and media area was quantified by computer-aided planimetry after immune-labeling for alpha-smooth muscle actin (pixel/vessel). The ratio of right ventricle to left ventricle plus septum (RV/[LV+S]) was used to determine right ventricular hypertrophy.. Proliferative activity increased by 34% at day 4 in mice held under H (median: 0.38) compared to N (median: 0.28, p = 0.028) which was completely blocked by RAPA (median HO+RAPA: 0.23, p = 0.003). H-induced proliferation had leveled off within 3 weeks. At this time point media area had, however, increased by 53% from 91 (N) to 139 (H, p < 0.001) which was prevented by RAPA (H+RAPA: 102; p < 0.001). RV/[LV+S] ratio which had risen from 0.17 (N) to 0.26 (H, p < 0.001) was attenuated in the H+RAPA group (0.22, p = 0.041). For a therapeutic approach animals were exposed to H for 21 days followed by 21 days in H +/- RAPA. Forty two days of H resulted in a media area of 129 (N: 83) which was significantly attenuated in RAPA-treated mice (H+RAPA: 92). RV/[LV+S] ratios supported prevention of PH (N 0.13; H 0.27; H+RAPA 0.17). RAPA treatment of N mice did not influence any parameter examined.. Therapy with rapamycin may represent a new strategy for the treatment of pulmonary hypertension.

Topics: Animals; Disease Models, Animal; Female; Hypertrophy, Right Ventricular; Hypoxia; Lung; Male; Mice; Sirolimus