β-Adrenoceptors differentially regulate vascular tone and angiogenesis of rat aorta via ERK1/2 and p38

O6-methylguanine-DNA methyltransferase inhibition leads to cellular senescence and vascular smooth muscle dysfunction

Inhibiting O6-methylguanine-DNA methyltransferase (MGMT) is crucial for overcoming chemoresistance to alkylating agents, though its use is limited by myelosuppression. Beyond bone marrow, other adverse effects were not studied. Given chemotherapy-induced senescence in healthy tissues, e.g., cardiovascular damage, we investigated the impact of the MGMT inhibitor O6-benzylguanine (BG) on aortic vascular smooth muscle cells (VSMCs) and aorta. Starting on day 3 of BG incubation, VSMCs exhibited altered morphology, reduced growth, increased SAβGal activity and elevated senescence markers p27 or γH2A.X. BG activated senescence-related pathways, including Erk1/2, p38α, Akt and mTORC1; induced BCl2, MnSOD and CDK1; and decreased αSMA and skp2 levels. These changes suggest BG-induced γH2A.X, p38 and Akt activation, resulting in G2/M cell cycle arrest via pCDK1. Functionally, BG impaired the vascular reactivity of aortic rings to phenylephrine, isoprenaline and sodium nitrite. In rats, systemic BG administration similarly reduced the response to sodium nitrite but left phenylephrine and isoprenaline responses unchanged. Our findings highlight BG's potential adverse effects on vascular smooth muscle, marked by senescence activation and reduced vascular reactivity. These results emphasise the need for caution in the clinical use of MGMT inhibitors. Furthermore, we present the model of senescence in primary VSMCs characterised by the expression of several senescence markers and G2/M checkpoint arrest.

The place of beta-adrenergic receptor blockers in the treatment of arterial hypertension: From bench-to-bedside

Arterial hypertension is a multifaceted condition influenced by numerous pathophysiological factors. The key contributors to its pathogenesis encompass an unhealthy lifestyle, dysregulation of the sympathetic nervous system, alterations in the activity of adrenergic receptors, disruptions in sodium metabolism, structural and functional abnormalities in the vascular bed, as well as endothelial dysfunction, low-grade inflammation, oxidative stress etc. Despite extensive research into the mechanisms of arterial hypertension development over the centuries, its pathogenesis remains incompletely understood, and the selection of an effective treatment strategy continues to pose a significant challenge. Arterial hypertension is characterized by a diminished sensitivity of the β-adrenergic system, leading to the utilization of β-adrenergic blockers and other antihypertensive drugs in its treatment. This review delves into the mechanisms of action of beta-adrenergic receptor blockers in the treatment of hypertension and their respective effects.

The Endothelial Dysfunction Could Be a Cause of Heart Failure with Preserved Ejection Fraction Development in a Rat Model

50% of patients with heart failure have a preserved ejection fraction (HFpEF). Numerous studies have investigated the pathophysiological mechanisms of HFpEF and have shown that endothelial dysfunction plays an important role in HFpEF. Yet no studies answered whether endothelial dysfunction could be the cause or is the consequence of HFpEF. Recently, we have shown that the endothelial overexpression of human β3-adrenoreceptor (Tgβ3) in rats leads to the slow development of diastolic dysfunction over ageing. The aim of the study is to decipher the involvement of endothelial dysfunction in the HFpEF development. For that, we investigated endothelial and cardiac function in 15-, 30-, and 45-week-old wild-type (WT) and Tgβ3 rats. The aortic expression of •NO synthase (NOS) isoforms was evaluated by Western blot. Finally, electron paramagnetic resonance measurements were performed on aortas to evaluate •NO and O2•- production. Vascular reactivity was altered as early as 15 weeks of age in response to isoproterenol in Tgβ3 aortas and mesenteric arteries. NOS1 (neuronal NOS) expression was higher in the Tgβ3 aorta at 30 and 45 weeks of age (30 weeks: WT: $1.00\pm 0.21$ ; Tgβ3: $6.08\pm 2.30$ ; 45 weeks: WT: $1.00\pm 0.12$ ; Tgβ3: $1.55\pm 0.17$ ; $p<0.05$ ). Interestingly, the endothelial NOS (NOS3) monomer form is increased in Tgβ3 rats at 45 weeks of age (ratio NOS3 dimer/NOS3 monomer; WT: $1.00\pm 0.37$ ; Tgβ3: $0.13\pm 0.05$ ; $p<0.05$ ). Aortic •NO production was increased by NOS2 (inducible NOS) at 15 weeks of age in Tgβ3 rats (+52% vs. WT). Aortic O2•- production was increased in Tgβ3 rats at 30 and 45 weeks of age (+75% and+76%, respectively, vs. WT, $p<0.05$ ). We have shown that endothelial dysfunction and oxidative stress are present as early as 15 weeks of age and therefore conclude that endothelial dysfunction could be a cause of HFpEF development.

Annexin A2-Mediated Plasminogen Activation in Endothelial Cells Contributes to the Proangiogenic Effect of Adenosine A2A Receptors

Adenosine A_2A receptor mediates the promotion of wound healing and revascularization of injured tissue, in healthy and animals with impaired wound healing, through a mechanism depending upon tissue plasminogen activator (tPA), a component of the fibrinolytic system. In order to evaluate the contribution of plasmin generation in the proangiogenic effect of adenosine A_2A receptor activation, we determined the expression and secretion of t-PA, urokinase plasminogen activator (uPA), plasminogen activator inhibitor-1 (PAI-1) and annexin A2 by human dermal microvascular endothelial cells stimulated by the selective agonist CGS-21680. The plasmin generation was assayed through an enzymatic assay and the proangiogenic effect was studied using an endothelial tube formation assay in Matrigel. Adenosine A_2A receptor activation in endothelial cells diminished the release of PAI-1 and promoted the production of annexin A2, which acts as a cell membrane co-receptor for plasminogen and its activator tPA. Annexin A2 mediated the increased cell membrane-associated plasmin generation in adenosine A_2A receptor agonist treated human dermal microvascular endothelial cells and is required for tube formation in an in vitro model of angiogenesis. These results suggest a novel mechanism by which adenosine A_2A receptor activation promotes angiogenesis: increased endothelial expression of annexin A2, which, in turn, promotes fibrinolysis by binding tPA and plasminogen to the cell surface.

β-Adrenoreceptors do not oppose sympathetic vasoconstriction in resting and contracting skeletal muscle of male rats

Sympathetic nervous system (SNS) vasoconstriction is primarily achieved through the binding of norepinephrine (NE) to α-adrenoreceptors. However, NE may also bind to β-adrenoreceptors and cause vasodilation that may oppose/blunt SNS-mediated vasoconstriction. Therefore, this study investigated the hypothesis that β-adrenoreceptor–mediated vasodilation opposes evoked vasoconstriction in resting and contracting skeletal muscle. Male (n = 9) Sprague–Dawley rats were anesthetized and surgically instrumented for stimulation of the lumbar sympathetic chain and measurement of arterial blood pressure and femoral artery blood flow. The percentage change of femoral vascular conductance in response to sympathetic chain stimulation delivered at 2 and 5 Hz was determined at rest and during triceps surae skeletal muscle contraction before (control) and after β-adrenoreceptor blockade (propranolol; 0.075 mg·kg−1, intravenously). β-Adrenoreceptor blockade did not alter (P > 0.05) baseline hemodynamics or the hyperemic response to exercise. At the 2 Hz stimulation frequency, sympathetic vasoconstriction was similar (P > 0.05) in control and β-blockade conditions in resting (control, −34% ± 6%; β-blockade, −33% ± 8%) and contracting (control, −16% ± 6%; β-blockade, −14% ± 7%) muscle. At the 5 Hz stimulation frequency, sympathetic vasoconstrictor responsiveness was reduced (main effect of drug, P < 0.05) following β-blockade (rest: control, −52% ± 7%; β-blockade, −51% ± 9%; contraction: control, −32% ± 11%; β-blockade, −29% ± 13%).

Novelty These data indicate that β-adrenoreceptor blockade did not augment sympathetic vasoconstriction at rest or during exercise. The study demonstrates that β-adrenoreceptors do not oppose evoked sympathetic vasoconstriction in resting or contracting skeletal muscle or contribute to functional sympatholysis.

Facilitation of ischaemia-induced ventricular fibrillation by catecholamines is mediated by β1 and β2 agonism in the rat heart in vitro

BACKGROUND AND PURPOSE

Antiarrhythmic β-blockers are used in patients at risk of myocardial ischaemia, but the survival benefit and mechanisms are unclear. We hypothesized that β-blockers do not prevent ventricular fibrillation (VF) but instead inhibit the ability of catecholamines to facilitate ischaemia-induced VF, limiting the scope of their usefulness.

EXPERIMENTAL APPROACH

ECGs were analysed from ischaemic Langendorff-perfused rat hearts perfused with adrenoceptor antagonists and/or exogenous catecholamines (CATs: 313 nM noradrenaline + 75 nM adrenaline) in a blinded and randomized study. Ischaemic zone (IZ) size was deliberately made small or large.

KEY RESULTS

In rat hearts with large IZs, ischaemia-induced VF incidence was high in controls. Atenolol, butoxamine and trimazosin did not affect VF at concentrations with β1 -, β2 - or α1 - adrenoceptor specificity and selectivity (confirmed in separate rat aortae myography experiments). In hearts with small IZs and low baseline incidence of ischaemia-induced VF, CATs, delivered to the uninvolved zone (UZ), increased ischaemia-induced VF incidence. This effect was not mimicked by atrial pacing, hence, not due to sinus tachycardia. However, the CATs-facilitated increase in ischaemia-induced VF was inhibited by atenolol and butoxamine (but not trimazosin), indicative of β1 - and β2 - but not α1 -adrenoceptor involvement (confirmed by immunoblot analysis of downstream phosphoproteins). CATs did not facilitate VF in low-flow globally ischaemic hearts, which have no UZ.

CONCLUSIONS AND IMPLICATIONS

Catecholamines facilitated ischaemia-induced VF when risk was low, acting via β1 - and β2 - adrenoceptors located in the UZ. There was no scope for facilitation when VF risk was high (large IZ), which may explain why β-blockers have equivocal effectiveness in humans.

A novel mechanism of angiotensin II-regulated placental vascular tone in the development of hypertension in preeclampsia

The present study tested the hypothesis that angiotensin II plays a role in the regulation of placental vascular tone, which contributes to hypertension in preeclampsia. Functional and molecular assays were performed in large and micro placental and non-placental vessels from humans and animals. In human placental vessels, angiotensin II induced vasoconstrictions in 78.7% vessels in 155 tests, as referenced to KCl-induced contractions. In contrast, phenylephrine only produced contractions in 3.0% of 133 tests. In non-placental vessels, phenylephrine induced contractions in 76.0% of 67 tests, whereas angiotensin II failed to produce contractions in 75 tests. Similar results were obtained in animal placental and non-placental vessels. Compared with non-placental vessels, angiotensin II receptors and β -adrenoceptors were significantly increased in placental vessels. Compared to the vessels from normal pregnancy, angiotensin II-induced vasoconstrictions were significantly reduced in preeclamptic placentas, which was associated with a decrease in angiotensin II receptors. In addition, angiotensin II and angiotensin converting enzyme in the maternal-placenta circulation in preeclampsia were increased, whereas angiotensin I and angiotensin1-7 concentrations were unchanged. The study demonstrates a selective effect of angiotensin II in maintaining placental vessel tension, which may play an important role in development of hypertension in preeclampsia.

Methodological Approach to Use Fresh and Cryopreserved Vessels as Tools to Analyze Pharmacological Modulation of the Angiogenic Growth

The sprouting of new vessels is greatly influenced by the procedure chosen. We sought to optimize the experimental conditions of the angiogenic growth of fresh and cryopreserved vessels cultured in Matrigel with the aim to use this system to analyze the pharmacological modulation of the process. Segments of second-order branches of rat mesenteric resistance arteries, thoracic aorta of rat or mouse, and cryopreserved rat aorta and human femoral arteries were cultured in Matrigel for 7-21 days in different mediums, as well as in the absence of endothelial or adventitia layer. Quantification of the angiogenic growth was performed by either direct measurement of the mean length of the neovessels or by calcein AM staining and determination of fluorescence intensity and area. Fresh and cryopreserved arterial rings incubated in Matrigel exhibited a spontaneous angiogenic response that was strongly accelerated by fetal calf serum. Addition of vascular endothelial growth factor, fibroblast growth factor, endothelial growth factor, or recombinant insulin-like growth factor failed to increase aortic sprouting, unless all were added together. Removal of adventitia, but not the endothelial layer, abrogated the angiogenic response of aortic rings. Determination of the mean neovessel length is an easy and accurate method to quantify the angiogenic growth devoid of confounding factors, such as inclusion of other cellular types surrounding the neovessels. Activity of a α1-adrenoceptor agonist (phenylephrine) and its inhibition by a selective antagonist (prazosin) were analyzed to prove the usefulness of the Matrigel system to evaluate the pharmacological modulation of the angiogenic growth.

MicroRNA-210 Plays a Critical Role in the Angiogenic Effect of Isoprenaline on Human Umbilical Vein Endothelial Cells via Regulation of Noncoding RNAs

Background:

β-adrenoceptors play a crucial regulatory role in blood vessel endothelial cells. Isoprenaline (ISO, a β-adrenergic agonist) has been reported to promote angiogenesis through upregulation of vascular endothelial growth factor (VEGF) expression; however, the underlying mechanism remains to be investigated. It is widely accepted that certain noncoding RNAs, including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), can regulate endothelial cell behavior, including their involvement in angiogenesis. Therefore, we aimed to investigate whether noncoding RNAs participate in ISO-mediated angiogenesis using human umbilical vein endothelial cells (HUVECs).

Methods:

We evaluated VEGF-A messenger RNA (mRNA) and protein levels in ISO-treated HUVECs by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. To establish whether noncoding RNAs are associated with ISO-mediated angiogenesis, we measured expression of the miRNAs miR-210, miR-21, and miR-1, as well as that of the lncRNAs growth arrest-specific transcript 5 (GAS5), maternally expressed 3 (MEG3), and metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in HUVECs exposed to ISO. Furthermore, to ascertain its importance in ISO-mediated angiogenesis, we constructed the HUVECs with overexpressing miR-210 and detected the subsequent expression of VEGF-A and noncoding RNAs. All statistical analyses were performed using SPSS 16.0 software. Intergroup comparisons were carried out by one-way analysis of variance.

Results:

VEGF-A mRNA levels were elevated in the ISO group (1.57 ± 0.09) compared to those in the control group (P < 0.01). Moreover, concentrations of VEGF-A in culture supernatants significantly differed between the control (113.00 ± 19.21 pg/ml) and ISO groups (287.00 ± 20.27 pg/ml; P < 0.01). Expression of miR-1, miR-21, and miR-210 was higher (3.89 ± 0.44, 2.87 ± 087, and 3.33 ± 1.31, respectively) in ISO-treated cells than that in controls (P < 0.01), whereas that of GAS5 and MEG3 (0.22 ± 0.10 and 0.58 ± 0.16, respectively) was lower as a result of ISO administration (P < 0.05). There was no significant difference in the expression of MALAT1 between the groups. Interestingly, miR-210 overexpression heightened the levels of VEGF-A and miR-21 (5.87 ± 1.24 and 2.74 ± 1.15, respectively; P < 0.01) and reduced those of GAS5 and MEG3 (0.19 ± 0.01 and 0.09 ± 0.05, respectively; P < 0.01).

Conclusions:

ISO-mediated angiogenesis was associated with altered expression of miR-210, miR-21, and the lncRNAs GAS5 and MEG3. The effects of miR-210 on the expression of VEGF-A and noncoding RNAs were similar to those of ISO, indicating that it might play an important role in ISO-mediated angiogenesis.

Overview of Antagonists Used for Determining the Mechanisms of Action Employed by Potential Vasodilators with Their Suggested Signaling Pathways

This paper is a review on the types of antagonists and the signaling mechanism pathways that have been used to determine the mechanisms of action employed for vasodilation by test compounds. Thus, we exhaustively reviewed and analyzed reports related to this topic published in PubMed between the years of 2010 till 2015. The aim of this paperis to suggest the most appropriate type of antagonists that correspond to receptors that would be involved during the mechanistic studies, as well as the latest signaling pathways trends that are being studied in order to determine the route(s) that atest compound employs for inducing vasodilation. The methods to perform the mechanism studies were included. Fundamentally, the affinity, specificity and selectivity of the antagonists to their receptors or enzymes were clearly elaborated as well as the solubility and reversibility. All the signaling pathways on the mechanisms of action involved in the vascular tone regulation have been well described in previous review articles. However, the most appropriate antagonists that should be utilized have never been suggested and elaborated before, hence the reason for this review.