—Transgenic mouse models have been developed to manipulate β-adrenergic receptor (βAR) signal transduction. Although several of these models have altered βAR subtypes, the specific functional sequelae of βAR stimulation in murine heart, particularly those of β₂-adrenergic receptor (β₂AR) stimulation, have not been characterized. In the present study, we investigated effects of β₂AR stimulation on contraction, [Ca²⁺]_itransient, and L-type Ca²⁺currents (I_Ca) in single ventricular myocytes isolated from transgenic mice overexpressing human β₂AR (TG4 mice) and wild-type (WT) littermates. Baseline contractility of TG4 heart cells was increased by 3-fold relative to WT controls as a result of the presence of spontaneous β₂AR activation. In contrast, β₂AR stimulation by zinterol or isoproterenol plus a selective β₁-adrenergic receptor (β₁AR) antagonist CGP 20712A failed to enhance the contractility in TG4 myocytes, and more surprisingly, β₂AR stimulation was also ineffective in increasing contractility in WT myocytes. Pertussis toxin (PTX) treatment fully rescued theI_Ca, [Ca²⁺]_i, and contractile responses to β₂AR agonists in both WT and TG4 cells. The PTX-rescued murine cardiac β₂AR response is mediated by cAMP-dependent mechanisms, because it was totally blocked by the inhibitory cAMP analog Rp-cAMPS. These results suggest that PTX-sensitive G proteins are responsible for the unresponsiveness of mouse heart to agonist-induced β₂AR stimulation. This was further corroborated by an increased incorporation of the photoreactive GTP analog [γ-³²P]GTP azidoanilide into α subunits of G_i2and G_i3after β₂AR stimulation by zinterol or isoproterenol plus the β₁AR blocker CGP 20712A. This effect to activate G_iproteins was abolished by a selective β₂AR blocker ICI 118,551 or by PTX treatment. Thus, we conclude that (1) β₂ARs in murine cardiac myocytes couple to concurrent G_sand G_isignaling, resulting in null inotropic response, unless the G_isignaling is inhibited; (2) as a special case, the lack of cardiac contractile response to β₂AR agonists in TG4 mice is not due to a saturation of cell contractility or of the cAMP signaling cascade but rather to an activation of β₂AR-coupled G_iproteins; and (3) spontaneous β₂AR activation may differ from agonist-stimulated β₂AR signaling.

Endothelium is a community of endothelial cells (ECs), which line the blood and lymphatic vessels, thus forming an interface between the tissues and the blood or lympha. This strategic position of endothelium infers its indispensable functional role in controlling vasoregulation, haemostasis, and inflammation. The state of endothelium is simultaneously the cause and effect of many diseases, and this is coupled with modifications of endothelial phenotype represented by markers and with biochemical profile of blood represented by biomarkers. In this paper, we briefly review data on the functional role of endothelium, give definitions of endothelial markers and biomarkers, touch on the methodological approaches for revealing biomarkers, present an implicit role of endothelium in some toxicological mechanistic studies, and survey the role of reactive oxygen species (ROS) in modulation of endothelial status.

Background— Myocardial contractile response to β ₁ - and β ₂ -adrenergic receptor (AR) stimulation is severely impaired in chronic heart failure, in which G _i signaling and the ratio of β ₂ /β ₁ are often increased. Because β ₂ -AR but not β ₁ -AR couples to G _s and G _i with the G _i coupling negating the G _s -mediated contractile response, we determined whether the heart failure–associated augmentation of G _i signaling contributes differentially to the defects of these β-AR subtypes and, if so, whether inhibition of G _i or selective activation of β ₂ -AR/G _s by ligands restores β ₂ -AR contractile response in the failing heart. Methods and Results— Cardiomyocytes were isolated from 18- to 24-month-old failing spontaneously hypertensive (SHR) or age-matched Wistar-Kyoto (WKY) rat hearts. In SHR cardiomyocytes, either β-AR subtype–mediated inotropic effect was markedly diminished, whereas G _i proteins and the β ₂ /β ₁ ratio were increased. Disruption of G _i signaling by pertussis toxin (PTX) enabled β ₂ - but not β ₁ -AR to induce a full positive inotropic response in SHR myocytes. Furthermore, screening of a panel of β ₂ -AR ligands revealed that the contractile response mediated by most β ₂ -AR agonists, including zinterol, salbutamol, and procaterol, was potentiated by PTX, indicating concurrent G _s and G _i activation. In contrast, fenoterol, another β ₂ -AR agonist, induced a full positive inotropic effect in SHR myocytes even in the absence of PTX. Conclusions— We conclude that enhanced G _i signaling is selectively involved in the dysfunction of β ₂ - but not β ₁ -AR in failing SHR hearts and that disruption of G _i signaling by PTX or selective activation of β ₂ -AR/G _s signaling by fenoterol restores the blunted β ₂ -AR contractile response in the failing heart.

The albumin molecule, in contrast to many other plasma proteins, is not covered with a carbohydrate moiety and can bind and transport various molecules of endogenous and exogenous origin. The enzymatic activity of albumin, the existence of which many scientists perceive skeptically, is much less studied. In toxicology, understanding the mechanistic interactions of organophosphates with albumin is a special problem, and its solution could help in the development of new types of antidotes. In the present work, the history of the issue is briefly examined, then our in silico data on the interaction of human serum albumin with soman, as well as comparative in silico data of human and bovine serum albumin activities in relation to paraoxon, are presented. Information is given on the substrate specificity of albumin and we consider the possibility of its affiliation to certain classes in the nomenclature of enzymes.

The volume of publications on the role of reactive oxygen species (ROS) in biological processes has been increasing exponentially over the last decades. ROS in large amounts clearly have detrimental effects on cell physiology, whereas low concentrations of ROS are permanently produced in cells and play a role as signaling molecules. An imbalance in ROS production and defense mechanisms can lead to pathological vascular remodeling, atherosclerosis being among them. The aim of this review is to examine different sources of ROS from the point of view of their participation in pathogenesis of atherosclerosis and related cardiovascular risk. Among the possible sources of ROS discussed here are mitochondria, NADPH-oxidases, xanthine oxidase, peroxidases, NO-synthases, cytochrome P450, cyclooxygenases, lipoxygenases, and hemoglobin of red blood cells. A great challenge for future research is to establish interrelations, feedback and feed-forward regulation mechanisms of various sources of ROS in development of atherosclerosis and other vascular pathologies.