Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have favorable cardiovascular outcomes in patients with diabetes. However, whether SGLT2i can improve obesity-related cardiac dysfunction is ...unknown. Sestrin2 is a novel stress-inducible protein that regulates AMPK-mammalian target of rapamycin (mTOR) and suppresses oxidative damage. The aim of this study was to determine whether empagliflozin (EMPA) improves obesity-related cardiac dysfunction via regulating Sestrin2-mediated pathways in diet-induced obesity. C57BL/6J mice and
knockout mice were fed a high-fat diet (HFD) for 12 weeks and then treated with or without EMPA (10 mg/kg) for 8 weeks. Treating HFD-fed C57BL/6J mice with EMPA reduced body weight and whole-body fat and improved metabolic disorders. Furthermore, EMPA improved myocardial hypertrophy/fibrosis and cardiac function and reduced cardiac fat accumulation and mitochondrial injury. Additionally, EMPA significantly augmented Sestrin2 levels and increased AMPK and endothelial nitric oxide synthase phosphorylation, but inhibited Akt and mTOR phosphorylation. These beneficial effects were partially attenuated in HFD-fed
knockout mice. Intriguingly, EMPA treatment enhanced the Nrf2/HO-1-mediated oxidative stress response, suggesting antioxidant and anti-inflammatory activity. Thus, EMPA improved obesity-related cardiac dysfunction via regulating Sestrin2-mediated AMPK-mTOR signaling and maintaining redox homeostasis. These findings provide a novel mechanism for the cardiovascular protection of SGLT2i in obesity.
Activation of adrenergic receptors (AR) represents the primary mechanism to increase cardiac performance under stress. Activated βAR couple to Gs protein, leading to adenylyl cyclase-dependent ...increases in secondary-messenger cyclic adenosine monophosphate (cAMP) to activate protein kinase A. The increased protein kinase A activities promote phosphorylation of diversified substrates, ranging from the receptor and its associated partners to proteins involved in increases in contractility and heart rate. Recent progress with live-cell imaging has drastically advanced our understanding of the βAR-induced cAMP and protein kinase A activities that are precisely regulated in a spatiotemporal fashion in highly differentiated myocytes. Several features stand out: membrane location of βAR and its associated complexes dictates the cellular compartmentalization of signaling; βAR agonist dose-dependent equilibrium between cAMP production and cAMP degradation shapes persistent increases in cAMP signals for sustained cardiac contraction response; and arrestin acts as an agonist dose-dependent master switch to promote cAMP diffusion and propagation into intracellular compartments by sequestrating phosphodiesterase isoforms associated with the βAR signaling cascades. These features and the underlying molecular mechanisms of dynamic regulation of βAR complexes with adenylyl cyclase and phosphodiesterase enzymes and the implication in heart failure are discussed.
In this work, we performed a systematic study on the photoluminescence and scattering spectra of individual gold nanostructures that were lithographically defined. We identify the role of plasmons in ...photoluminescence as modulating the energy transfer between excited electrons and emitted photons. By comparing photoluminescence spectra with scattering spectra, we observed that the photoluminescence of individual gold nanostructures showed the same dependencies on shape, size, and plasmon coupling as the particle plasmon resonances. Our results provide conclusive evidence that the photoluminescence in gold nanostructures indeed occurs via radiative damping of plasmon resonances driven by excited electrons in the metal itself. Moreover, we provide new insight on the underlying mechanism based on our analysis of a reproducible blue shift of the photoluminescence peak (relative to the scattering peak) and observation of an incomplete depolarization of the photoluminescence.
Recent advances show that insulin may affect β adrenergic receptor (βAR) signaling in the heart to modulate cardiac function in clinically relevant states, such as diabetes mellitus (DM) and heart ...failure (HF). Conversely, activation of βAR regulates cardiac glucose uptake and promotes insulin resistance (IR) in HF. Here, we discuss the recent characterization of the interaction between the cardiac insulin receptor (InsR) and βAR in the myocardium, in which insulin stimulation crosstalks with cardiac βAR via InsR substrate (IRS)-dependent and G-protein receptor kinase 2 (GRK2)-mediated phosphorylation of β2 AR. The insulin-induced phosphorylation promotes β2 AR coupling to Gi and expression of phosphodiesterase 4D, which both inhibit cardiac adrenergic signaling and compromise cardiac contractile function. These recent developments could support new approaches for the effective prevention or treatment of obesity- or DM-related HF.
Phosphodiesterases (PDEs) are a superfamily of enzymes that hydrolyze cyclic nucleotides, including cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Both cyclic ...nucleotides are critical secondary messengers in the neurohormonal regulation in the cardiovascular system. PDEs precisely control spatiotemporal subcellular distribution of cyclic nucleotides in a cell- and tissue-specific manner, playing critical roles in physiological responses to hormone stimulation in the heart and vessels. Dysregulation of PDEs has been linked to the development of several cardiovascular diseases, such as hypertension, aneurysm, atherosclerosis, arrhythmia, and heart failure. Targeting these enzymes has been proven effective in treating cardiovascular diseases and is an attractive and promising strategy for the development of new drugs. In this review, we discuss the current understanding of the complex regulation of PDE isoforms in cardiovascular function, highlighting the divergent and even opposing roles of PDE isoforms in different pathogenesis.
Novel targeted fluorescent biosensors provide key insights into very local nanodomains of cAMP and PKA activity, and how they respond differently to β-adrenergic activation in cardiac myocytes. This ...unique spatiotemporal detail in living cells is not available with biochemical measurements of total cellular cAMP and PKA, and provides unique physiological insights.
This protocol describes a single-molecule pull-down (SiMPull) assay for analyzing physiological protein complexes. The assay combines the conventional pull-down assay with single-molecule total ...internal reflection fluorescence (TIRF) microscopy and allows the probing of single macromolecular complexes directly from cell or tissue extracts. In this method, antibodies against the protein of interest are immobilized on a passivated microscope slide. When cell extracts are applied, the surface-tethered antibody captures the protein together with its physiological interaction partners. After washing away the unbound components, single-molecule fluorescence microscopy is used to probe the pulled-down proteins. Captured proteins are visualized through genetically encoded fluorescent protein tags or through antibody labeling. Compared with western blot analysis, this ultrasensitive assay requires considerably less time and reagents and provides quantitative data. Furthermore, SiMPull can distinguish between multiple association states of the same protein. SiMPull is generally applicable to proteins from a variety of cellular contexts and to endogenous proteins. Starting with the cell extracts and passivated slides, the assay requires 1.5-2.5 h for data acquisition and analysis.
Tetracycline (TC), a popularly found drug pollutant, can be contaminated in food and aquatic regions and causes a severe impact on human health. In this research, a visible light active p-stannic ...oxide/n-copper manganate (p-SnO2/n-CuMnO2) heterojunction was synthesized and has been applied for a signal on photoelectrochemical sensing of antibiotic TC. Firstly, the n-SnO2 microrods were synthesized via a simple and efficient homogeneous precipitation method and the p-CuMnO2 nanoparticles were synthesized by a facile ultrasound-assisted hydrothermal method. The SnO2/CuMnO2 microrods p-n heterojunction was prepared through a simple impregnation method and physicochemical properties of the microrods are characterized by using X-ray diffraction (XRD), Raman, Brunauer-Emmett-Teller (BET), Fourier-transform infrared (FTIR), UV–Vis diffuse reflectance spectroscopy (UVDRS), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Mott-Schottky analyses. The photoelectrochemical sensing performance of SnO2/CuMnO2 microrods was 2.7 times higher than that of as-synthesized pure SnO2 microrods is due to the more visible light absorption ability and p-n heterojunction (synergy). The designed SnO2/CuMnO2/ITO sensor gives photocurrent signals for the detection of TC in the range of 0.01–1000 μM with the detection limit (LOD) of 5.6 nM. The practical applicability of the sensor was monitored in cow milk and the Taipei River water sample.
•A novel of SnO2 microrods was synthesized via a facile homogeneous precipitation method.•A visible light active n-SnO2/p-CuMnO2 p-n heterojunction was prepared.•A SnO2/CuMnO2 based Photoelectrohemical sensor of tetracycline was fabricated.•A high sensitivity in TC sensing was achieved with low LOD.
β-adrenergic signaling pathways mediate key aspects of cardiac function. Its dysregulation is associated with a range of cardiac diseases, including dilated cardiomyopathy (DCM). Previously, we ...established an iPSC model of familial DCM from patients with a mutation in TNNT2, a sarcomeric protein. Here, we found that the β-adrenergic agonist isoproterenol induced mature β-adrenergic signaling in iPSC-derived cardiomyocytes (iPSC-CMs) but that this pathway was blunted in DCM iPSC-CMs. Although expression levels of several β-adrenergic signaling components were unaltered between control and DCM iPSC-CMs, we found that phosphodiesterases (PDEs) 2A and PDE3A were upregulated in DCM iPSC-CMs and that PDE2A was also upregulated in DCM patient tissue. We further discovered increased nuclear localization of mutant TNNT2 and epigenetic modifications of PDE genes in both DCM iPSC-CMs and patient tissue. Notably, pharmacologic inhibition of PDE2A and PDE3A restored cAMP levels and ameliorated the impaired β-adrenergic signaling of DCM iPSC-CMs, suggesting therapeutic potential.
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•β-AR signaling switch from β-2 AR to β-1/2 AR mode during human iPSC-CM maturation•Upregulation of PDE2/3 leads to compromised β-adrenergic regulation in DCM iPSC-CMs•Epigenetic activation of PDE2/3 is a key molecular event during pathogenesis of DCM•Nuclear localization of mutated TNNT2 contributes to epigenetic modification in DCM
In this paper, Wu et al. profiled the β-adrenergic signaling properties in human iPSC-CMs and demonstrated novel epigenetic mechanisms that underlie the compromised β-adrenergic signaling in DCM, a common cause of heart failure and cardiac transplantation. These results enhance our understanding of DCM pathogenesis and may uncover new therapeutic targets.
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