Biomedical subjects
Gianluigi Condorelli
Publications and source records attributed to Gianluigi Condorelli.
Akt induces enhanced myocardial contractility and cell size in vivo in transgenic mice.
The serine-threonine kinase Akt seems to be central in mediating stimuli from different classes of receptors. In fact, both IGF-1 and IL6-like cytokines induce hypertrophic and antiapoptotic signals in cardiomyocytes through PI3K-dependent Akt activation. More recently, it was shown that Akt is involved also in the hypertrophic and antiapoptotic effects of beta-adrenergic stimulation. Thus, to determine the effects of Akt on cardiac function in vivo, we generated a model of cardiac-specific Akt overexpression in mice. Transgenic mice were generated by using the E40K, constitutively active mutant of Akt linked to the rat alpha-myosin heavy chain promoter. The effects of cardiac-selective Akt overexpression were studied by echocardiography, cardiac catheterization, histological and biochemical techniques. We found that Akt overexpression produced cardiac hypertrophy at the molecular and histological levels, with a significant increase in cardiomyocyte cell size and concentric LV hypertrophy. Akt-transgenic mice also showed a remarkable increase in cardiac contractility compared with wild-type controls as demonstrated by the analysis of left ventricular (dP/dt(max)) in an invasive hemodynamic study, although with graded dobutamine infusion, the maximum response was not different from that in controls. Diastolic function, evaluated by left ventricular dP/dt(min), was not affected at rest but was impaired during graded dobutamine infusion. Isoproterenol-induced cAMP levels, beta-adrenergic receptor (beta-AR) density, and beta-AR affinity were not altered compared with control mice. Moreover, studies on signaling pathway activation from myocardial extracts demonstrated that glycogen synthase kinase3-beta is phosphorylated, whereas p42/44 mitogen-activated protein kinases is not, indicating that Akt induces hypertrophy in vivo by activating the glycogen synthase kinase3-beta/GATA 4 pathway. In summary, our results not only demonstrate that Akt regulates cardiomyocyte cell size in vivo, but, importantly, show that Akt modulates cardiac contractility in vivo without directly affecting beta-AR signaling capacity.
Efficacy and age-related effects of nitric oxide-releasing aspirin on experimental restenosis.
Restenosis after percutaneous transluminal coronary angioplasty is caused by neointimal hyperplasia, which involves impairment of nitric oxide (NO)-dependent pathways, and may be further exacerbated by a concomitant aging process. We compared the effects of NO-releasing-aspirin (NCX-4016) and aspirin (ASA) on experimental restenosis in both adult and elderly rats. Moreover, to ascertain the efficacy of NCX-4016 during vascular aging, we fully characterized the release of bioactive NO by the drug. Sprague-Dawley rats aged 6 and 24 months were treated with NO releasing-aspirin (55 mg/kg) or ASA (30 mg/kg) for 7 days before and 21 days after standard carotid balloon injury. Histological examination and immunohistochemical double-staining were used to evaluate restenosis. Plasma nitrite and nitrate and S-nitrosothiols were determined by a chemiluminescence-based assay. Electron spin resonance was used for determining nitrosylhemoglobin. Treatment of aged rats with NCX-4016 was associated with increased bioactive NO, compared with ASA. NO aspirin, but not ASA, reduced experimental restenosis in old rats, an effect associated with reduced vascular smooth muscle cell proliferation. NCX-4016, but not ASA, was well tolerated and virtually devoid of gastric damage in either adult or old rats. Thus, impairment of NO-dependent mechanisms may be involved in the development of restenosis in old rats. We suggest that an NCX-4016 derivative could be an effective drug in reducing restenosis, especially in the presence of aging and/or gastrointestinal damage.
ErbB2 is essential in the prevention of dilated cardiomyopathy.
Amplification of the gene encoding the ErbB2 (Her2/neu) receptor tyrosine kinase is critical for the progression of several forms of breast cancer. In a large-scale clinical trial, treatment with Herceptin (trastuzumab), a humanized blocking antibody against ErbB2, led to marked improvement in survival. However, cardiomyopathy was uncovered as a mitigating side effect, thereby suggesting an important role for ErbB2 signaling as a modifier of human heart failure. To investigate the physiological role of ErbB2 signaling in the adult heart, we generated mice with a ventricular-restricted deletion of Erbb2. These ErbB2-deficient conditional mutant mice were viable and displayed no overt phenotype. However, physiological analysis revealed the onset of multiple independent parameters of dilated cardiomyopathy, including chamber dilation, wall thinning and decreased contractility. Additionally, cardiomyocytes isolated from these conditional mutants were more susceptible to anthracycline toxicity. ErbB2 signaling in cardiomyocytes is therefore essential for the prevention of dilated cardiomyopathy.
TNF-alpha signal transduction in rat neonatal cardiac myocytes: definition of pathways generating from the TNF-alpha receptor.
Cardiomyocyte hypertrophy and apoptosis have been implicated in the loss of contractile function during heart failure (HF). Moreover, patients with HF have been shown to exhibit increased levels of tumor necrosis factor alpha (TNF-alpha) in the myocardium. However, the multiple signal transduction pathways generating from the TNF-alpha receptor in cardiomyocytes and leading preferentially to apoptosis or hypertrophy are still unknown. Here we demonstrate in neonatal rat cardiomyocytes that 1) TNF-alpha induces phosphorylation of AKT, activation of NF-kappaB, and the phosphorylation of JUN kinase; 2) blocking AKT activity prevents NF-kappaB activation, suggesting a role for AKT in regulating NF-kappaB function; 3) AKT and JUN are both critical for the hypertrophic effects of TNF-alpha, since dominant-negative mutants of these genes are capable of inhibiting TNF-alpha-induced ANF-promoter up-regulation and increase in cardiomyocyte cell size, and 4) blocking NF-kappaB, AKT, or JUN alone or in combination does not sensitize cardiomyocytes to the proapoptotic effects of TNF-alpha, in contrast to other cell types, suggesting a cardiac-specific pathway regulating the anti-apoptotic events induced by TNF-alpha. Altogether, the data presented evidence the role of AKT and JUN in TNF-alpha-induced cardiomyocyte hypertrophy and apoptosis.
c-Myc oncoprotein: cell cycle-related events and new therapeutic challenges in cancer and cardiovascular diseases.
Advanced stages of both cancer and atherosclerosis are characterized by a local increase in tissue mass that may be hard to control. This increase in tissue mass can be attributed to oxidation-sensitive modification of cell cycle-related events, including cellular proliferation, differentiation, and apoptosis, which could be secondary to alteration in the activity of tumor suppressor gene and oncogene products. The oncogene c-Myc has classically been considered to be involved in carcinogenesis and has more recently been implicated in both endothelial dysfunction and atherogenesis as well. Consequently, inhibition of c-Myc-dependent signaling has become a novel therapeutic opportunity and challenge in atherosclerosis and other cardiovascular diseases. Antioxidant strategies, RNA synthesis inhibitors such as mithramycin, and gene therapeutic approaches with antisense oligonucleotides against c-Myc are some of the promising strategies. In general, the increased biologic understanding of the participation of cell cycle events and targeting these events may enable to attenuate or prevent some of the complications of vascular and neoplastic diseases.