RESUMO
ß3-Adrenergic receptor (ß3AR) agonists have been shown to protect against ischemia-reperfusion injury (IRI). Since ß3ARs are present both in cardiomyocytes and in endothelial cells, the cellular compartment responsible for this protection has remained unknown. Using transgenic mice constitutively expressing the human ß3AR (hß3AR) in cardiomyocytes or in the endothelium on a genetic background of null endogenous ß3AR expression, we show that only cardiomyocyte expression protects against IRI (45 min ischemia followed by reperfusion over 24 h). Infarct size was also limited after ischemia-reperfusion in mice with cardiomyocyte hß3AR overexpression on top of endogenous ß3AR expression. hß3AR overexpression in these mice reduced IRI-induced cardiac fibrosis and improved long-term left ventricular systolic function. Cardiomyocyte-specific ß3AR overexpression resulted in a baseline remodeling of the mitochondrial network, characterized by upregulated mitochondrial biogenesis and a downregulation of mitochondrial quality control (mitophagy), resulting in elevated numbers of small mitochondria with a depressed capacity for the generation of reactive oxygen species but improved capacity for ATP generation. These processes precondition cardiomyocyte mitochondria to be more resistant to IRI. Upon reperfusion, hearts with hß3AR overexpression display a restoration in the mitochondrial quality control and a rapid activation of antioxidant responses. Strong protection against IRI was also observed in mice infected with an adeno-associated virus (AAV) encoding hß3AR under a cardiomyocyte-specific promoter. These results confirm the translational potential of increased cardiomyocyte ß3AR expression, achieved either naturally through exercise or artificially through gene therapy approaches, to precondition the cardiomyocyte mitochondrial network to withstand future insults.
RESUMO
Aortic stenosis (AS) is associated with left ventricular (LV) hypertrophy and heart failure (HF). There is a lack of therapies able to prevent/revert AS-induced HF. Beta3 adrenergic receptor (ß3AR) signaling is beneficial in several forms of HF. Here, we studied the potential beneficial effect of ß3AR overexpression on AS-induced HF. Selective ß3AR stimulation had a positive inotropic effect. Transgenic mice constitutively overexpressing human ß3AR in the heart (c-hß3tg) were protected from the development of HF in response to induced AS, and against cardiomyocyte mitochondrial dysfunction (fragmented mitochondria with remodeled cristae and metabolic reprogramming featuring altered substrate use). Similar beneficial effects were observed in wild-type mice inoculated with adeno-associated virus (AAV9) inducing cardiac-specific overexpression of human ß3AR before AS induction. Moreover, AAV9-hß3AR injection into wild-type mice at late disease stages, when cardiac hypertrophy and metabolic reprogramming are already advanced, reversed the HF phenotype and restored balanced mitochondrial dynamics, demonstrating the potential of gene-therapy-mediated ß3AR overexpression in AS. Mice with cardiac specific ablation of Yme1l (cYKO), characterized by fragmented mitochondria, showed an increased mortality upon AS challenge. AAV9-hß3AR injection in these mice before AS induction reverted the fragmented mitochondria phenotype and rescued them from death. In conclusion, our results step out that ß3AR overexpression might have translational potential as a therapeutic strategy in AS-induced HF.
Assuntos
Estenose da Valva Aórtica , Insuficiência Cardíaca , Humanos , Camundongos , Animais , Receptores Adrenérgicos beta 3 , Dinâmica Mitocondrial , Hipertrofia Ventricular Esquerda , Miócitos Cardíacos , Camundongos Transgênicos , MetaloendopeptidasesRESUMO
Background: Anthracycline-induced cardiotoxicity (AIC) debilitates quality of life in cancer survivors. Serial characterizations are lacking of the molecular processes occurring with AIC. Objectives: The aim of this study was to characterize AIC progression in a mouse model from early (subclinical) to advanced heart failure stages, with an emphasis on cardiac metabolism and mitochondrial structure and function. Methods: CD1 mice received 5 weekly intraperitoneal doxorubicin injections (5 mg/kg) and were followed by serial echocardiography for 15 weeks. At 1, 9, and 15 weeks after the doxorubicin injections, mice underwent fluorodeoxyglucose positron emission tomography, and hearts were extracted for microscopy and molecular analysis. Results: Cardiac atrophy was evident at 1 week post-doxorubicin (left ventricular [LV] mass 117 ± 26 mg vs 97 ± 25 mg at baseline and 1 week, respectively; P < 0.001). Cardiac mass nadir was observed at week 3 post-doxorubicin (79 ± 16 mg; P = 0.002 vs baseline), remaining unchanged thereafter. Histology confirmed significantly reduced cardiomyocyte area (167 ± 19 µm2 in doxorubicin-treated mice vs 211 ± 26 µm2 in controls; P = 0.004). LV ejection fraction declined from week 6 post-doxorubicin (49% ± 9% vs 61% ± 9% at baseline; P < 0.001) until the end of follow-up at 15 weeks (43% ± 8%; P < 0.001 vs baseline). At 1 week post-doxorubicin, when LV ejection fraction remained normal, reduced cardiac metabolism was evident from down-regulated markers of fatty acid oxidation and glycolysis. Metabolic impairment continued to the end of follow-up in parallel with reduced mitochondrial adenosine triphosphate production. A transient early up-regulation of nutrient-sensing and mitophagy markers were observed, which was associated with mitochondrial enlargement. Later stages, when mitophagy was exhausted, were characterized by overt mitochondrial fragmentation. Conclusions: Cardiac atrophy, global hypometabolism, early transient-enhanced mitophagy, biogenesis, and nutrient sensing constitute candidate targets for AIC prevention.