Background-The therapeutic effects of nonspecific ␤-blockers are limited by vasoconstriction, thus justifying the interest in molecules with ancillary vasodilating properties. Nebivolol is a selective ␤ 1 -adrenoreceptor antagonist that releases nitric oxide (NO) through incompletely characterized mechanisms. We identified endothelial ␤ 3 -adrenoreceptors in human coronary microarteries that mediate endothelium-and NO-dependent relaxation and hypothesized that nebivolol activates these ␤ 3 -adrenoreceptors. Methods and Results-Nebivolol dose-dependently relaxed rodent coronary resistance microarteries studied by videomicroscopy (10 mol/L, Ϫ86Ϯ6% of prostaglandin F2␣ contraction); this was sensitive to NO synthase (NOS) inhibition, unaffected by the ␤ 1-2 -blocker nadolol, and prevented by the ␤ 1-2-3 -blocker bupranolol (PϽ0.05; nϭ3 to 8). Importantly, nebivolol failed to relax microarteries from ␤ 3 -adrenoreceptor-deficient mice. Nebivolol (10 mol/L) also relaxed human coronary microvessels (Ϫ71Ϯ5% of KCl contraction); this was dependent on a functional endothelium and NO synthase but insensitive to ␤ 1-2 -blockade (all PϽ0.05). In a mouse aortic ring assay of neoangiogenesis, nebivolol induced neocapillary tube formation in rings from wild-type but not ␤ 3 -adrenoreceptor-or endothelial NOS-deficient mice. In cultured endothelial cells, 10 mol/L nebivolol increased NO release by 200% as measured by electron paramagnetic spin trapping, which was also reversed by NOS inhibition. In parallel, endothelial NOS was dephosphorylated on threonine 495 , and fura-2 calcium fluorescence increased by 91.8Ϯ23.7%; this effect was unaffected by ␤ 1-2 -blockade but abrogated by ␤ 1-2-3 -blockade (all PϽ0.05). Conclusions-Nebivolol dilates human and rodent coronary resistance microarteries through an agonist effect on endothelial ␤ 3 -adrenoreceptors to release NO and promote neoangiogenesis. These properties may prove particularly beneficial for the treatment of ischemic and cardiac failure diseases through preservation of coronary reserve.

451H emodynamic overload and ischemic or oxidative stress promote adverse cardiac remodeling, a leading cause of worsening heart failure.1,2 Most of these pathophysiologic conditions are associated with (and to a certain extent, mediated by) adrenergic stimulation and catecholamines release, resulting in adrenoceptor (AR) activation on different cell types within the myocardium. Among these, cardiac myocyte β1-ARs are classically considered to mediate short-term positive effects on all aspects of myocardial contractility; however, long-term stimulation produces adverse effects on myocardial remodeling, in part through activation of calciumdependent prohypertrophic effects, ultimately associated with cardiomyocyte loss. 3,4 Such maladaptive remodeling is usually accompanied by left ventricle (LV) geometry disruption Background-β1-2-adrenergic receptors (AR) are key regulators of cardiac contractility and remodeling in response to catecholamines. β3-AR expression is enhanced in diseased human myocardium, but its impact on remodeling is unknown. Methods and Results-Mice with cardiac myocyte-specific expression of human β3-AR (β3-TG) and wild-type (WT) littermates were used to compare myocardial remodeling in response to isoproterenol (Iso) or Angiotensin II (Ang II). β3-TG and WT had similar morphometric and hemodynamic parameters at baseline. β3-AR colocalized with caveolin-3, endothelial nitric oxide synthase (NOS) and neuronal NOS in adult transgenic myocytes, which constitutively produced more cyclic GMP, detected with a new transgenic FRET sensor. Iso and Ang II produced hypertrophy and fibrosis in WT mice, but not in β3-TG mice, which also had less re-expression of fetal genes and transforming growth factor β1.Protection from Iso-induced hypertrophy was reversed by nonspecific NOS inhibition at low dose Iso, and by preferential neuronal NOS inhibition at high-dose Iso. Adenoviral overexpression of β3-AR in isolated cardiac myocytes also increased NO production and attenuated hypertrophy to Iso and phenylephrine. Hypertrophy was restored on NOS or protein kinase G inhibition. Mechanistically, β3-AR overexpression inhibited phenylephrine-induced nuclear factor of activated T-cell activation. Conclusions-Cardiac-specific overexpression of β3-AR does not affect cardiac morphology at baseline but inhibits the hypertrophic response to neurohormonal stimulation in vivo and in vitro, through a NOS-mediated mechanism. Activation of the cardiac β3-AR pathway may provide future therapeutic avenues for the modulation of hypertrophic remodeling. and interstitial and replacement fibrosis leading to progressive diastolic and systolic heart failure. Deciphering the underlying signaling pathways may lead to new therapeutic strategies that favorably modulate remodeling. The use of β1-AR blockers provided a major advance in this direction, albeit far from totally efficient. 5 The third isotype of β-AR (β3-AR) has classically been considered as a metabolic regulator (eg, by mediating lipolysis in the adipose tissue).6 β3-ARs ...

Persistent strains of Theiler's virus, a murine picornavirus, produce a life-long infection of the central nervous system of the mouse and induce a chronic demyelinating disease. Strain DA1, a molecular clone of such a persistent strain, produces a prominent cytopathic effect in BHK-21 cells but is less efficient at infecting L929 cells. We cloned the cDNA of a derivative of virus DA1, adapted to promote a rapid cytopathic effect in L929 cells. Adaptation of the new variant (named KJ6) to L929 cells correlated with an enhanced viral entry rather than with an increased replication rate of the genome. Mutations responsible for L929 cells adaptation occurred in amino acids exposed at the surface of the capsid, in the CD loop of VP1 (100-102) and in the EF loop of VP2 (162-171-173), suggesting that these residues could be involved in receptor recognition. These two clusters of amino acids are precisely known to be part of neutralization epitopes. They also differentiate persistent from neurovirulent strains of Theiler's virus. Adaptation of the virus to L929 cells was accompanied by attenuation of its virulence for the mouse. Taken together, these data suggest a close relationship between receptor binding, virus neutralization, and virus phenotype.

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