High-fat diet induces protein kinase A and G-protein receptor kinase phosphorylation of β2 -adrenergic receptor and impairs cardiac adrenergic reserve in animal hearts.

Key pointsPatients with diabetes show a blunted cardiac inotropic response to β-adrenergic stimulation despite normal cardiac contractile reserve. Acute insulin stimulation impairs β-adrenergically induced contractile function in isolated cardiomyocytes and Langendorff-perfused hearts. In this study, we aimed to examine the potential effects of hyperinsulinaemia associated with high-fat diet (HFD) feeding on the cardiac β2 -adrenergic receptor signalling and the impacts on cardiac contractile function. We showed that 8 weeks of HFD feeding leads to reductions in cardiac functional reserve in response to β-adrenergic stimulation without significant alteration of cardiac structure and function, which is associated with significant changes in β2 -adrenergic receptor phosphorylation at protein kinase A and G-protein receptor kinase sites in the myocardium. The results suggest that clinical intervention might be applied to subjects in early diabetes without cardiac symptoms to prevent further cardiac complications.AbstractPatients with diabetes display reduced exercise capability and impaired cardiac contractile reserve in response to adrenergic stimulation. We have recently uncovered an insulin receptor and adrenergic receptor signal network in the heart. The aim of this study was to understand the impacts of high-fat diet (HFD) on the insulin-adrenergic receptor signal network in hearts. After 8 weeks of HFD feeding, mice exhibited diabetes, with elevated insulin and glucose concentrations associated with body weight gain. Mice fed an HFD had normal cardiac structure and function. However, the HFD-fed mice displayed a significant elevation of phosphorylation of the β2 -adrenergic receptor (β2 AR) at both the protein kinase A site serine 261/262 and the G-protein-coupled receptor kinase site serine 355/356 and impaired adrenergic reserve when compared with mice fed on normal chow. Isolated myocytes from HFD-fed mice also displayed a reduced contractile response to adrenergic stimulation when compared with those of control mice fed normal chow. Genetic deletion of the β2 AR led to a normalized adrenergic response and preserved cardiac contractile reserve in HFD-fed mice. Together, these data indicate that HFD promotes phosphorylation of the β2 AR, contributing to impairment of cardiac contractile reserve before cardiac structural and functional remodelling, suggesting that early intervention in the insulin-adrenergic signalling network might be effective in prevention of cardiac complications in diabetes

Beta-Adrenergic Receptor Blockade By Propranolol Enhances Retention In A Multitrial Passive-Avoidance Procedure

The effect of beta -adrenergic receptor blockade on retention in a mildly aversive passive-avoidance procedure was investigated. Rats were given passive-avoidance training-1 trial per day for 4 days-and were administered saline, the centrally and peripherally acting beta -adrenergic blocker propranolol (4 or 10 mg/kg ip), or the peripherally acting P-adrenergic blocker sotalol (4 or 10 mg/kg ip) immediately or 2 hr after the Ist trial. Enhanced retention occurred only with the higher dose (10 mg/kg) of propranolol and only when it was administered immediately after training. The enhanced retention produced by propranolol is discussed in terms of opposing, regionally specific actions of beta -adrenergic receptor-mediated neural circuits on modulation of memory

β2-adrenergic agonists modulate TNF-α induced astrocytic inflammatory gene expression and brain inflammatory cell populations

Background: The NF-kappa B signaling pathway orchestrates many of the intricate aspects of neuroinflammation. Astrocytic beta(2)-adrenergic receptors have emerged as potential regulators in central nervous system inflammation and are potential targets for pharmacological modulation. The aim of this study was to elucidate the crosstalk between astrocytic beta(2)-adrenergic receptors and the TNF-alpha induced inflammatory gene program. Methods: Proinflammatory conditions were generated by the administration of TNF-alpha. Genes that are susceptible to astrocytic crosstalk between beta(2)-adrenergic receptors (stimulated by clenbuterol) and TNF-alpha were identified by qPCR-macroarray-based gene expression analysis in a human 1321 N1 astrocytoma cell line. Transcriptional patterns of the identified genes in vitro were validated by RT-PCR on the 1321 N1 cell line as well as on primary rat astrocytes. In vivo expression patterns were examined by intracerebroventricular administration of clenbuterol and/or TNF-alpha in rats. To examine the impact on the inflammatory cell content of the brain we performed extensive FACS analysis of rat brain immune cells after intracerebroventricular clenbuterol and/or TNF-alpha administration. Results: Parallel transcriptional patterns in vivo and in vitro confirmed the relevance of astrocytic beta(2)-adrenergic receptors as modulators of brain inflammatory responses. Importantly, we observed pronounced effects of beta(2)-adrenergic receptor agonists and TNF-alpha on IL-6, CXCL2, CXCL3, VCAM1, and ICAM1 expression, suggesting a role in inflammatory brain cell homeostasis. Extensive FACS-analysis of inflammatory cell content in the brain demonstrated that clenbuterol/TNF-alpha co-administration skewed the T cell population towards a double negative phenotype and induced a shift in the myeloid brain cell population towards a neutrophilic predominance. Conclusions: Our results show that astrocytic beta(2)-adrenergic receptors are potent regulators of astrocytic TNF-alpha-activated genes in vitro and in vivo, and ultimately modulate the molecular network involved in the homeostasis of inflammatory cells in the central nervous system. Astrocytic beta(2)-adrenergic receptors and their downstream signaling pathway may serve as potential targets to modulate neuroinflammatory responses

Gravin orchestrates protein kinase A and 2-adrenergic receptor signaling critical for synaptic plasticity and memory

A kinase-anchoring proteins (AKAPs) organize compartmentalized pools of protein kinase A (PKA) to enable localized signaling events within neurons. However, it is unclear which of the many expressed AKAPs in neurons target PKA to signaling complexes important for long-lasting forms of synaptic plasticity and memory storage. In the forebrain, the anchoring protein gravin recruits a signaling complex containing PKA, PKC, calmodulin, and PDE4D (phosphodiesterase 4D) to the β2-adrenergic receptor. Here, we show that mice lacking the α-isoform of gravin have deficits in PKA-dependent long-lasting forms of hippocampal synaptic plasticity including β2-adrenergic receptor-mediated plasticity, and selective impairments of long-term memory storage. Furthermore, both hippocampal β2-adrenergic receptor phosphorylation by PKA, and learning-induced activation of ERK in the CA1 region of the hippocampus are attenuated in mice lacking gravin-α. We conclude that gravin compartmentalizes a significant pool of PKA that regulates learning-induced β2-adrenergic receptor signaling and ERK activation in the hippocampus in vivo, thereby organizing molecular interactions between glutamatergic and noradrenergic signaling pathways for long-lasting synaptic plasticity, and memory storage

Inflammation produces catecholamine resistance in obesity via activation of PDE3B by the protein kinases IKKε and TBK1.

Obesity produces a chronic inflammatory state involving the NFκB pathway, resulting in persistent elevation of the noncanonical IκB kinases IKKε and TBK1. In this study, we report that these kinases attenuate β-adrenergic signaling in white adipose tissue. Treatment of 3T3-L1 adipocytes with specific inhibitors of these kinases restored β-adrenergic signaling and lipolysis attenuated by TNFα and Poly (I:C). Conversely, overexpression of the kinases reduced induction of Ucp1, lipolysis, cAMP levels, and phosphorylation of hormone sensitive lipase in response to isoproterenol or forskolin. Noncanonical IKKs reduce catecholamine sensitivity by phosphorylating and activating the major adipocyte phosphodiesterase PDE3B. In vivo inhibition of these kinases by treatment of obese mice with the drug amlexanox reversed obesity-induced catecholamine resistance, and restored PKA signaling in response to injection of a β-3 adrenergic agonist. These studies suggest that by reducing production of cAMP in adipocytes, IKKε and TBK1 may contribute to the repression of energy expenditure during obesity. DOI: http://dx.doi.org/10.7554/eLife.01119.001

A Sarcoplasmic Reticulum Localized Protein Phosphatase Regulates Phospholamban Phosphorylation and Promotes Ischemia Reperfusion Injury in the Heart.

Phospholamban (PLN) is a key regulator of sarcolemma calcium uptake in cardiomyocyte, its inhibitory activity to SERCA is regulated by phosphorylation. PLN hypophosphorylation is a common molecular feature in failing heart. The current study provided evidence at molecular, cellular and whole heart levels to implicate a sarcolemma membrane targeted protein phosphatase, PP2Ce, as a specific and potent PLN phosphatase. PP2Ce expression was elevated in failing human heart and induced acutely at protein level by β -adrenergic stimulation or oxidative stress in cardiomyocytes. PP2Ce expression in mouse heart blunted β-adrenergic response and exacerbated ischemia/reperfusion injury. Therefore, PP2Ce is a new regulator for cardiac function and pathogenesis

The effects of ganglionic and adrenergic blockade on the circulation of the young chimpanzee Final technical report, 1 Oct. 1963 - 30 Apr. 1965

Ganglionic and adrenergic blockade effects on circulatory system studied on young chimpanze

Targeting protein–protein interactions within the cyclic AMP signaling system as a therapeutic strategy for cardiovascular disease

The cAMP signaling system can trigger precise physiological cellular responses that depend on the fidelity of many protein–protein interactions, which act to bring together signaling intermediates at defined locations within cells. In the heart, cAMP participates in the fine control of excitation–contraction coupling, hence, any disregulation of this signaling cascade can lead to cardiac disease. Due to the ubiquitous nature of the cAMP pathway, general inhibitors of cAMP signaling proteins such as PKA, EPAC and PDEs would act non-specifically and universally, increasing the likelihood of serious ‘off target’ effects. Recent advances in the discovery of peptides and small molecules that disrupt the protein–protein interactions that underpin cellular targeting of cAMP signaling proteins are described and discussed