Quantification of the cAMP response element binding protein in ventricular nuclear protein from failing and nonfailing human hearts

Binding of FUN14 Domain Containing 1 With Inositol 1,4,5-Trisphosphate Receptor in Mitochondria-Associated Endoplasmic Reticulum Membranes Maintains Mitochondrial Dynamics and Function in Hearts in Vivo

BACKGROUND

FUN14 domain containing 1 (FUNDC1) is a highly conserved outer mitochondrial membrane protein. The aim of this study is to examine whether FUNDC1 modulates the mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs), mitochondrial morphology, and function in cardiomyocytes and intact hearts.

METHODS

The impacts of FUNDC1 on MAMs formation and cardiac functions were studied in mouse neonatal cardiomyocytes, in mice with cardiomyocyte-specific Fundc1 gene knockout (Fundc1^f/Y/Cre^αMyHC+/- ), and in the cardiac tissues of the patients with heart failure.

RESULTS

In mouse neonatal cardiomyocytes and intact hearts, FUNDC1 was localized in MAMs by binding to ER-resided inositol 1,4,5-trisphosphate type 2 receptor (IP₃R2). Fundc1 ablation disrupted MAMs and reduced the levels of IP₃R2 and Ca²⁺ in both mitochondria and cytosol, whereas overexpression of Fundc1 increased the levels of IP₃R2 and Ca²⁺ in both mitochondria and cytosol. Consistently, Fundc1 ablation increased Ca²⁺ levels in ER, whereas Fundc1 overexpression lowered ER Ca²⁺ levels. Further, Fundc1 ablation in cardiomyocytes elongated mitochondria and compromised mitochondrial functions. Mechanistically, we found that Fundc1 ablation-induced reduction of intracellular Ca²⁺ levels suppressed mitochondrial fission 1 protein (Fis1) expression and mitochondrial fission by reducing the binding of the cAMP response element binding protein (CREB) in the Fis1 promoter. Fundc1^f/Y/Cre^αMyHC+/- mice but not their littermate control mice (Fundc1^wt/Y/Cre^αMyHC+/- ) exhibited cardiac dysfunction. The ligation of the left ventricle artery of Fundc1^f/Y/Cre^αMyHC+/- mice caused more severe cardiac dysfunction than those in sham-treated Fundc1^f/Y/Cre^αMyHC+/- mice. Finally, we found that the FUNDC1/MAMs/CREB/Fis1 signaling axis was significantly suppressed in patients with heart failure.

CONCLUSIONS

We conclude that FUNDC1 binds to IP₃R2 to modulate ER Ca²⁺ release into mitochondria and cytosol. Further, a disruption of the FUNDC1 and IP₃R2 interaction lowers the levels of Ca²⁺ in mitochondria and cytosol, both of which instigate aberrant mitochondrial fission, mitochondrial dysfunction, cardiac dysfunction, and heart failure.

Effects of carvedilol treatment on cardiac cAMP response element binding protein expression and phosphorylation in acute coxsackievirus B3-induced myocarditis

Background

The role of β-adrenergic stimulation on viral myocarditis has been investigated in animal models of viral myocarditis. Excess stimulation of β-adrenergic receptors by catecholamines causes phosphorylation/activation of cAMP response element binding protein (CREB) by the cAMP signaling pathway. CREB as an important regulator of gene expression mediates the cardiovascular remodeling process and promotes anti-inflammatory immune responses. However, the CREB expression and phosphorylation have not been studied, and the effects of carvedilol (a nonselective β-adrenoceptor antagonist) on the CREB has not been investigated in the setting of acute viral myocarditis.

Methods

This study was therefore designed to examine the effects of carvedilol on the transcriptional factor CREB in a murine model of acute viral myocarditis. In a coxsackievirus B3 murine myocarditis model (Balb/c), effects of carvedilol on plasma noradrenaline, heart rate and blood pressure, myocardial histopathological changes and fibrosis, cardiomyocyte apoptosis, cardiac CREB and phosphorylated CREB, cytokine levels, and viral RNA were studied.

Results

The expression and phosphorylation of CREB were decreased with concomitant increase of IL-6 and TNF-α in murine coxsackievirus-induced acute viral myocarditis. The levels of IL-6 and TNF-α were correlated with the expression of CREB or phosphorylated CREB. Carvedilol increased the cardiac CREB expression and phosphorylation and decreased the plasma catecholamine levels and the production of IL-6 and TNF-α with amelioration of acute viral myocarditis.

Conclusion

These results show that CREB may be involved in the pathophysiology of viral myocarditis and carvedilol exerts some of its beneficial effects by increasing the CREB expression and phosphorylation.

Differential involvement of 3′, 5′-cyclic adenosine monophosphate-dependent protein kinase in regulation of Fos and tyrosine hydroxylase expression in the heart after naloxone induced morphine withdrawal

We previously demonstrated that morphine withdrawal induced hyperactivity of the heart by the activation of noradrenergic pathways innervating the left and right ventricle, as evaluated by noradrenaline (NA) turnover and Fos expression. We investigated whether cAMP-dependent protein kinase (PKA) plays a role in this process by estimating changes in PKA immunoreactivity and the influence of inhibitor of PKA on Fos protein expression, tyrosine hydroxylase (TH) immunoreactivity levels and NA turnover in the left and right ventricle. Dependence on morphine was induced by a 7-day s.c. implantation of morphine pellets. Morphine withdrawal was precipitated on day 8 by an injection of naloxone (5 mg/kg). When opioid withdrawal was precipitated, an increase in PKA immunoreactivity and phospho-CREB (cyclic AMP response element protein) levels were observed in the heart. Moreover, morphine withdrawal induces Fos expression, an enhancement of NA turnover and an increase in the total TH levels. When the selective PKA inhibitor HA-1004 was infused, concomitantly with morphine pellets, it diminished the increase in NA turnover and the total TH levels observed in morphine-withdrawn rats. However, this inhibitor neither modifies the morphine withdrawal induced Fos expression nor the increase of nonphosphorylated TH levels. The present findings indicate that an up-regulated PKA-dependent transduction pathway might contribute to the activation of the cardiac catecholaminergic neurons in response to morphine withdrawal and suggest that Fos is not a target of PKA at heart levels.

IGF-1 protects cardiac myocytes from hyperosmotic stress-induced apoptosis via CREB

Hyperosmotic stress stimulates a rapid and pronounced apoptosis in cardiac myocytes which is attenuated by insulin-like growth factor-1 (IGF-1). Because in these cells IGF-1 induces intracellular Ca(2+) increase, we assessed whether the cyclic AMP response element-binding protein (CREB) is activated by IGF-1 through Ca(2+)-dependent signalling pathways. In cultured cardiac myocytes, IGF-1 induced phosphorylation (6.5 +/- 1.0-fold at 5 min), nuclear translocation (30 min post-stimulus) and DNA binding activity of CREB. IGF-1-induced CREB phosphorylation was mediated by MEK1/ERK, PI3-K, p38-MAPK, as well as Ca(2+)/calmodulin kinase and calcineurin. Exposure of cardiac myocytes to hyperosmotic stress (sorbitol 600 mOsm) decreased IGF-1-induced CREB activation Moreover, overexpression of a dominant negative CREB abolished the anti-apoptotic effects of IGF-1. Our results suggest that IGF-1 activates CREB through a complex signalling pathway, and this transcription factor plays an important role in the anti-apoptotic action of IGF-1 in cultured cardiac myocytes.

Perinatal cocaine exposure stimulates the expression and activation of CREB in the neonatal rat heart

cAMP response binding protein (CREB) is a transcriptional factor known to regulate gene expression. Phosphorylation of CREB at serine 133 is necessary for CREB activation, and quantification of phospho-CREB (p-CREB) expression is an index of CREB activation. Because CREB expression and activation in specific brain regions are modified after chronic cocaine administration, we sought to determine whether chronic perinatal cocaine exposure affects the expression of CREB and p-CREB in the postnatal rat heart. Pregnant rats were treated daily with saline (control) or cocaine at 20 mg/kg (C20) or 60 mg/kg (C60) by intragastric administration throughout gestation. The expression of total CREB and p-CREB was quantified in nuclear extracts isolated from 1- and 7-d-old neonatal rat hearts. Cardiac nuclear p-CREB was increased in the C20 and C60 groups on d 1 and 7 of age compared with their respective age-matched control groups. The increase in p-CREB expression corresponded to an increase in cAMP response element binding activity. We also assayed nuclear protein kinase A activity, which was up-regulated in d 1 animals with prenatal cocaine exposure, but was comparable in all groups at d 7. Our results suggest that perinatal cocaine exposure stimulates CREB activation in the neonatal heart, and it may be mediated by different mechanisms at d 1 and d 7. The changes in myocardial CREB activation induced by perinatal cocaine exposure are likely to result in modified gene expression in the neonatal heart that may account for the cardiac dysfunction reported in human neonates born to cocaine-abusing mothers.