G-protein-coupled receptor (GPCR) kinases, GRKs, are known as serine/threonine kinases that regulate GPCR signaling, but recent findings propose functions for these kinases besides receptor desensitization. Indeed, GRK5 can translocate to the nucleus by means of a nuclear localization sequence, suggesting that this kinase regulates transcription events in the nucleus. To evaluate the effect of GRK5-IB␣ interaction on NFB signaling, we induced the overexpression and the knockdown of GRK5 in cell cultures. GRK5 overexpression causes nuclear accumulation of IB␣, leading to the inhibition of NFB transcriptional activity. Opposite results are achieved by GRK5 knockdown through siRNA. A physical interaction between GRK5 and IB␣, rather than phosphorylative events, appears as the underlying mechanism. We identify the regulator of gene protein signaling homology domain of GRK5 (RH) and the N-terminal domain of IB␣ as the regions involved in such interaction. To confirm the biological relevance of this mechanism of regulation for NFB, we evaluated the effects of GRK5-RH on NFB-dependent phenotypes. In particular, GRK5-RH overexpression impairs apoptosis protection and cytokine production in vitro and inflammation and tissue regeneration in vivo. Our results reveal an unexpected role for GRK5 in the regulation of NFB transcription activity. Placing these findings in perspective, this mechanism may represent a therapeutic target for all those conditions involving excessive NFB activity.angiogenesis ͉ gene transcription ͉ inflammation ͉ signal transduction G -protein-coupled receptor (GPCR) kinases, GRKs, constitute a large family of serine/threonine protein kinases that regulate GPCR signaling (1-3), consisting of 7 isoforms that share structural and functional similarities (4). A central catalytic domain is flanked by an N-terminal domain that includes a region of homology to regulators of G-protein signaling (RH) and a C-terminal domain of variable length (5, 6). The catalytic domain of GRKs is relatively well-conserved among the members of different subfamilies (Ϸ45% sequence identity), whereas N-terminal RH domains display weak homology (Ϸ27%) and C termini have little or no sequence homology. GRKs have different tissue distribution, subcellular localization, and kinase activity regulation (7,8). GRKs mostly localize at the plasma membrane (2), but recently Johnson et al. (7) demonstrated that GRK4-6 (but not other GRKs) can shuttle between cytosol and nucleus through functional nuclear localization sequence (NLS) and nuclear exporting sequence (NES), thus suggesting a nuclear effect for the GRK4-6 subfamily.NFB is an ubiquitously expressed and highly regulated dimeric transcription factor (3) regulating the expression of genes responsible for innate and adaptive immunity, tissue regeneration, stress responses, apoptosis, cell proliferation, and differentiation (9-14). Within the canonical view of the regulation of the NFB activity, the inactive NFB/IB␣ complex localizes in the cytosol until an extracellular stimulus, ...

Our data indicate that exercise favourably affects angiogenesis and improves LV remodelling and contractility reserve in a rat model of severe chronic HF.

The main regulator of neovascularization is Vascular Endothelial Growth Factor (VEGF). We recently demonstrated that QK, a de novo engineered VEGF mimicking peptide, shares in vitro the same biological properties of VEGF, inducing capillary formation and organization. On these grounds, the aim of this study is to evaluate in vivo the effects of this small peptide. Therefore, on Wistar Kyoto rats, we evaluated vasomotor responses to VEGF and QK in common carotid rings. Also, we assessed the effects of QK in three different models of angiogenesis: ischemic hindlimb, wound healing and Matrigel plugs. QK and VEGF present similar endothelium-dependent vasodilatation. Moreover, the ability of QK to induce neovascularization was confirmed us by digital angiographies, dyed beads dilution and histological analysis in the ischemic hindlimb as well as by histology in wounds and Matrigel plugs. Our findings show the proangiogenic properties of QK, suggesting that also in vivo this peptide resembles the full VEGF protein. These data open to new fields of investigation on the mechanisms of activation of VEGF receptors, offering clinical implications for treatment of pathophysiological conditions such as chronic ischemia.

Abstract-␤ 2 -Adrenergic receptors (␤ 2 ARs) are widely expressed, although their physiological relevance in many tissuesis not yet fully understood. In vascular endothelial cells, they regulate NO release and vessel tone. Here we provide novel evidence that ␤ 2 ARs can regulate neoangiogenesis in response to chronic ischemia. We used in vivo adenoviral-mediated gene transfer of the human ␤ 2 AR to the endothelium of the rat femoral artery and increased ␤ 2 AR signaling resulting in ameliorated angiographic blood flow and hindlimb perfusion after chronic ischemia. Histological analysis confirmed that ␤ 2 AR overexpression also produced benefits on capillary density. The same maneuver partially rescued impaired angiogenesis in spontaneously hypertensive rats (SHR), whereas gene delivery of the G-proteincoupling defective mutant Ile164 ␤ 2 AR failed to provide ameliorations. Stimulation of endogenous and overexpressed ␤ 2 AR on endothelial cells in vitro was found to regulate cell number by inducing proliferation and [ 3 H]-thymidine incorporation through means of extracellular receptor-activated kinase and vascular endothelial growth factor. The ␤ 2 AR also has novel effects on endothelial cell number through stimulation of proapoptosis and antiapoptosis pathways involving p38 mitogen-activated protein kinase and PI3-kinase/Akt activation. Therefore, ␤ 2 ARs play a critical role in endothelial cell proliferation and function including revascularization, suggesting a novel and physiologically relevant role in neoangiogenesis in response to ischemia. Key Words: angiogenesis Ⅲ rats Ⅲ polymorphism Ⅲ hypertension Ⅲ in vivo digital angiography T he endothelium controls several vascular functions, including vascular tone and permeability, thrombosis, hemostasis, and angiogenesis. 1 It is noteworthy that all these functions can be regulated by activation of receptors, and often, the same receptor can activate multiple endothelial functions.Adult angiogenesis only occurs in particular conditions such as wound healing, tumorogenesis, hypoxia, and chronic ischemia. 2 It is a phenomenon intimately associated with endothelial cell (EC) proliferation, which appears to be under control of the extracellular receptor-activated kinase (ERK)/ mitogen-activated protein kinase (MAPK)-mediated signaling cascades. 2 The most important system regulating angiogenesis is the cytokine vascular endothelial growth factor (VEGF), although a number of other cytokines and hormones acting through various tyrosine kinase and G-protein-coupled receptors are also implicated in this process.The adrenergic system is the major regulator of cardiac and vascular function, and evidence is mounting for the relevance of this system in the control of endothelial vasodilation through means of ␣ 2-and ␤-adrenergic receptors (␤ARs). In particular, ␤ 2 ARs, the most abundant ␤ARs in the vasculature, 3,4 modulate the release of NO, causing endotheliumdependent vasodilation. 5 ␤ 2 ARs are G-protein-coupled receptors activated by adrenergic catecholamines and prom...

BackgroundUncoupling protein 3 (ucp3) is a member of the mitochondrial anion carrier superfamily of proteins uncoupling mitochondrial respiration. In this study, we investigated the effects of ucp3 genetic deletion on mitochondrial function and cell survival under low oxygen conditions in vitro and in vivo.Methods and ResultsTo test the effects of ucp3 deletion in vitro, murine embryonic fibroblasts and adult cardiomyocytes were isolated from wild‐type (WT, n=67) and ucp3 knockout mice (ucp3−/−, n=70). To test the effects of ucp3 genetic deletion in vivo, myocardial infarction (MI) was induced by permanent coronary artery ligation in WT and ucp3−/− mice. Compared with WT, ucp3−/− murine embryonic fibroblasts and cardiomyocytes exhibited mitochondrial dysfunction and increased mitochondrial reactive oxygen species generation and apoptotic cell death under hypoxic conditions in vitro (terminal deoxynucleotidyl transferase‐dUTP nick end labeling–positive nuclei: WT hypoxia, 70.3±1.2%; ucp3−/− hypoxia, 85.3±0.9%; P<0.05). After MI, despite similar areas at risk in the 2 groups, ucp3−/− hearts demonstrated a significantly larger infarct size compared with WT (infarct area/area at risk: WT, 48.2±3.7%; ucp3−/−, 65.0±2.9%; P<0.05). Eight weeks after MI, cardiac function was significantly decreased in ucp3−/− mice compared with WT (fractional shortening: WT MI, 42.7±3.1%; ucp3−/− MI, 24.4±2.9; P<0.05), and this was associated with heightened apoptotic cell death (terminal deoxynucleotidyl transferase‐dUTP nick end labeling–positive nuclei: WT MI, 0.7±0.04%; ucp3−/− MI, 1.1±0.09%, P<0.05).ConclusionsOur data indicate that ucp3 levels regulate reactive oxygen species levels and cell survival during hypoxia, modulating infarct size in the ischemic heart.