RESUMO
Volume overload frequently caused in dogs by chronic degenerative valvular disease (CDVD), eventually leads to cardiac failure. Experimental and clinical evidences demonstrate that increased interleukin-1beta serum level in patients with heart insufficiency correlates with the severity of failure irrespective of its etiology. Very little is known about the IL-1beta expression in failing vs. non-failing myocardium. IL-1beta transcript level was determined in the CDVD dogs (n=17) and control animals (n=9) without cardiac insufficiency by real-time PCR. IL-1beta transcript level in failing hearts was higher than in the control. In both groups the highest IL-1beta level was detected in the left ventricles. Although IL-1beta is a major pro-inflammatory cytokine most of the CDVD dogs displayed no inflammatory infiltrates into the myocardium. Massive fibrosis was observed in the control group, unlike the failing hearts, in which cardiomyocyte hypertrophy and atrophy dominated. The alternative IL-1beta transcript identified here (IL-1betasv1) was significantly elevated in the failing myocardium compared with the control group. Increased IL-1beta expression seems to be associated with mechanical heart overload. Its endogenous origin, and certain histopathological findings attributed to IL-1beta indicate its importance in cardiac hypertrophy and failure. The lack of some typical IL-1beta actions, i.e. inflammatory, pyrogenic and fibrotic, may suggest a different role of this cytokine in myocardium. It appears that the canine IL-1beta gene can be transcribed in two ways in heart tissue, with the IL-1betasv1 form present mainly in failing hearts.
Assuntos
Processamento Alternativo/genética , Regulação da Expressão Gênica/genética , Doenças das Valvas Cardíacas/metabolismo , Interleucina-1beta/metabolismo , Sequência de Aminoácidos , Animais , Autopsia , Temperatura Corporal , Cães , Feminino , Doenças das Valvas Cardíacas/genética , Doenças das Valvas Cardíacas/patologia , Proteína Antagonista do Receptor de Interleucina 1/metabolismo , Interleucina-1beta/química , Interleucina-1beta/genética , Masculino , Dados de Sequência Molecular , RNA Mensageiro/genética , Transcrição Gênica/genéticaRESUMO
BACKGROUND: There are few experimental models of heart failure (HF) in large animals, despite structural and functional similarities to human myocardium. We have developed a porcine model of chronic tachycardia-induced cardiomyopathy. METHODS: Homogenous siblings of White Large breed swine (n=6) underwent continuous right ventricular (RV) pacing at 170 bpm; 2 subjects served as controls. In the course of RV pacing, animals developed a clinical picture of HF and were presented for euthanasia at subsequent stages: mild, moderate and end-stage HF. Left ventricle (LV) sections were analyzed histologically and relative ANP, BNP, phospholamban and sarcoplasmic reticulum calcium ATPase 2a transcript levels in LV were quantified by real time RT-PCR. RESULTS: In the course of RV pacing, animals demonstrated reduced exercise capacity (time of running until being dyspnoeic: 6.6 ± 0.5 vs. 2.4 ± 1.4 min), LV dilatation (LVEDD: 4.9 ± 0.4 vs. 6.7 ± 0.4 cm), impaired LV systolic function (LVEF: 69 ± 8 vs. 32 ± 7 %), (all baseline vs. before euthanasia, all p<0.001). LV tissues from animals with moderate and end-stage HF demonstrated local foci of interstitial fibrosis, congestion, cardiomyocyte hypertrophy and atrophy, which was not detected in controls and mild HF animals. The up-regulation of ANP and BNP and a reduction in a ratio of sarcoplasmic reticulum calcium ATPase 2a and phospholamban in failing myocardium were observed as compared to controls. CONCLUSIONS: In pigs, chronic RV pacing at relatively low rate can be used as an experimental model of HF, as it results in a gradual deterioration of exercise tolerance accompanied by myocardial remodeling confirmed at subcellular level.