Combined inorganic nitrate/nitrite supplementation blunts α-mediated vasoconstriction during exercise in patients with type 2 diabetes.

AIMS: Patients with type 2 diabetes mellitus (T2DM) have reduced vasodilatory responses during exercise partially attributable to low nitric oxide (NO) levels. Low NO contributes to greater α-adrenergic mediated vasoconstriction in contracting skeletal muscle. We hypothesized boosting NO bioavailability via 8wks of active beetroot juice (BRA, 4.03 mmol nitrate, 0.29 mmol nitrite, n = 19) improves hyperemia, via reduced α-mediated vasoconstriction, during handgrip exercise relative to nitrate/nitrite-depleted beetroot juice (BRP, n = 18) in patients with T2DM. METHODS: Forearm blood flow (FBF) and vascular conductance (FVC) were calculated at rest and during handgrip exercise (20%max, 20contractions·min-1). Phenylephrine (α1-agonist) and dexmedetomidine (α2-agonist) were infused intra-arterially during independent trials to determine the influence of α-mediated vasoconstriction on exercise hyperemia. Vasoconstriction was quantified as the percent-reduction in FVC during α-agonist infusion, relative to pre-infusion, as well as the absolute change in %FVC during exercise relative to the respective rest trial (magnitude of sympatholysis). RESULTS: ΔFBF (156 ± 69 to 175 ± 73 ml min-1) and ΔFVC (130 ± 54 to 156 ± 63 ml min-1·100 mmHg-1, both P < 0.05) during exercise were augmented following BRA, but not BRP (P = 0.96 and 0.51). Phenylephrine-induced vasoconstriction during exercise was blunted following BRA (-17.1 ± 5.9 to -12.6 ± 3.1%, P < 0.01), but not BRP (P = 0.58) supplementation; the magnitude of sympatholysis was unchanged by either (beverage-by-time P = 0.15). BRA supplementation reduced dexmedetomidine-induced vasoconstriction during exercise (-23.3 ± 6.7 to -19.7 ± 5.2%) and improved the corresponding magnitude of sympatholysis (25.3 ± 11.4 to 34.4 ± 15.5%, both P < 0.05). CONCLUSIONS: BRA supplementation improves the hyperemic and vasodilatory responses to exercise in patients with T2DM which appears to be attributable to reduced α-adrenergic mediated vasoconstriction in contracting skeletal muscle.

Reversal of cardiac, vascular, and renal dysfunction by non-quinazoline α1-adrenolytics in DOCA-salt hypertensive rats: a comparison with prazosin, a quinazoline-based α1-adrenoceptor antagonist.

We investigated the therapeutic effect of MH-76 and MH-79, which are non-quinazoline α1-adrenoceptor antagonists with an additional ability to stimulate the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/K + pathway, on deoxycorticosterone acetate (DOCA)-salt induced hypertension in rats. Prazosin was used as a reference compound, as quinazoline-based α1-adrenolytics may potentially exert unfavorable proapoptotic and necrotic effects. DOCA-salt hypertension was induced by DOCA (20 mg/kg s.c., twice weekly) administration plus 1% NaCl and 0.2% KCl solutions in drinking water for 12 weeks. The studied compounds MH-76, MH-79 (10 mg/kg i.p.) or prazosin (0.4 mg/kg i.p.) were administered to the DOCA-salt-treated rats, starting from the 6th week of DOCA-salt treatment and continuing for 6 weeks. This study showed that the administration of MH-79 and, to a lesser extent, MH-76 decreased elevated systolic blood pressure and heart rate, reduced heart and kidney hypertrophy, and reversed the histopathological alterations of the heart, kidney, and vessels in DOCA-salt hypertensive rats. MH-79 reversed endothelial dysfunction, which reduced inflammatory cell infiltration, arteriosclerotic alterations in renal and coronary arteries, and tubulointerstitial fibrosis. Prazosin showed a potent hemodynamic effect and reduced cardiac and renal fibrosis but exerted detrimental effects on blood vessels, potentiating fibroplasia of the media of the intrarenal artery and causing calcification of coronary arteries. Prazosin did not reverse endothelial dysfunction. Our results show the beneficial effect of non-quinazoline α1-adrenolytics on cardiac, vascular, and renal dysfunction in DOCA-salt hypertensive rats. Our findings also support the idea that targeting endothelial protection and endothelial integrity would yield beneficial effects against cardiac, blood vessel and renal injury related to hypertension.

Adrenergic receptor agonists induce the differentiation of pluripotent stem cell-derived hepatoblasts into hepatocyte-like cells.

Current induction methods of hepatocytes from human induced pluripotent stem cells (hiPSCs) are neither low cost nor stable. By screening a chemical library of 1,120 bioactive compounds and known drugs, we identified the α1-adrenergic receptor agonist methoxamine hydrochloride as a small molecule that promotes the differentiation of hiPSC-derived hepatoblasts into ALBUMIN+ hepatocyte-like cells. Other α1-adrenergic receptor agonists also induced the differentiation of hepatocyte-like cells, and an α1-receptor antagonist blocked the hepatic-inducing activity of methoxamine hydrochloride and that of the combination of hepatocyte growth factor (HGF) and Oncostatin M (OsM), two growth factors often used for the induction of hepatoblasts into hepatocyte-like cells. We also confirmed that treatment with methoxamine hydrochloride activates the signal transducer and activator of transcription 3 (STAT3) pathway downstream of IL-6 family cytokines including OsM. These findings allowed us to establish hepatic differentiation protocols for both mouse embryonic stem cells (mESCs) and hiPSCs using small molecules at the step from hepatoblasts into hepatocyte-like cells. The results of the present study suggest that α1-adrenergic agonists induce hepatocyte-like cells by working downstream of HGF and OsM to activate STAT3.

Pilomotor function is impaired in patients with Parkinson's disease: A study of the adrenergic axon-reflex response and autonomic functions.

INTRODUCTION: Autonomic nervous system disturbances including sweating abnormalities and cardiovascular symptoms are frequent in Parkinson's disease (PD) and often precede motor involvement. Cholinergic vasomotor and sudomotor skin nerves are impaired in patients with PD even at early disease stages. We hypothesized that adrenergic pilomotor nerve function is similarly impaired in early PD and might constitute a novel diagnostic target. METHODS: We conducted a study in 12 PD patients (Hoehn&Yahr 1-2) and 12 healthy control subjects. Pilomotor function was evaluated after iontophoresis of phenylephrine on the dorsal forearm to elicit axon-reflex mediated pilomotor erection (goose bumps). Silicone impressions were obtained, scanned and quantified for pilomotor muscle impressions by number, area and axon-reflex spread. Vasomotor function was evaluated using laser Doppler flowmetry and sudomotor function via sympathetic skin response. Cardiac autonomic function was assessed via heart rate variability. Severity of autonomic symptoms was evaluated using the Scales for Outcomes in Parkinson's disease-Autonomic questionnaire. RESULTS: Pilomotor response was reduced in PD patients compared to control subjects (impression number: 12.2 ± 8.2 vs. 16.5 ± 5.9, p < 0.05; impression area: 10.8 ± 2.2 mm2 vs. 24.8 ± 3.1 mm2, p < 0.01; axon-reflex spread: 89.0 ± 10.6 mm2 vs. 185.9 ± 10.8 mm2, p < 0.01) and correlated negatively with severity of autonomic symptoms (p < 0.01). Similarly, sudomotor (p < 0.01) and vasomotor (p < 0.05) but not cardiac autonomic (p = n.s.) function were reduced in PD patients versus control subjects. CONCLUSION: Pilomotor function is impaired in early stages of PD. Pilomotor axon-reflex assessment might be useful in the investigation of disease related pathology and supplement other clinical markers of autonomic neuropathy in PD.

Effects of catecholamines on volemic replacement with saline solution and the impact on heart rate variability in rabbits subjected to hemorrhage. A study by spectral analysis.

PURPOSE: To verify the effects of different catecholamines on volemic expansion and on the autonomic nervous system in rabbits that were subjected to hemorrhage. METHODS: Twenty four rabbits subjected to hemorrhage (with a 25% loss of blood volume) and were randomly divided into four experimental groups: 1) HEMO Group underwent replacement with their own blood in an equal volume; 2) SS Group underwent replacement with saline solution (SS) in a volume that corresponded to three times the removed blood volume; 3) ISP Group underwent replacement with SS and isoprenaline; 4) FNL Group underwent replacement with SS and phenylephrine. Spectral Analysis of the heart rate and heart rate variability were performed from the recorded data. Hematocrit was measured throughout the experiment. RESULTS: Replacement with SS and an α- or ß-agonist did not produce differences in the intravascular retention compared to replacement with SS alone. An analysis of HRV showed that the FNL group maintained the LF/HF ratio better than ISP and SS. CONCLUSIONS: No difference in vascular retention when α- or ß- agonists were added to SS during post-hemorrhagic recovery. The animals in the FNL group maintained the integrity of the autonomic response within normal physiological standards during hemorrhagic stress.

Effects of catecholamines on volemic replacement with saline solution and the impact on heart rate variability in rabbits subjected to hemorrhage. A study by spectral analysis

PURPOSE: To verify the effects of different catecholamines on volemic expansion and on the autonomic nervous system in rabbits that were subjected to hemorrhage. METHODS: Twenty four rabbits subjected to hemorrhage (with a 25% loss of blood volume) and were randomly divided into four experimental groups: 1) HEMO Group underwent replacement with their own blood in an equal volume; 2) SS Group underwent replacement with saline solution (SS) in a volume that corresponded to three times the removed blood volume; 3) ISP Group underwent replacement with SS and isoprenaline; 4) FNL Group underwent replacement with SS and phenylephrine. Spectral Analysis of the heart rate and heart rate variability were performed from the recorded data. Hematocrit was measured throughout the experiment. RESULTS: Replacement with SS and an α- or β-agonist did not produce differences in the intravascular retention compared to replacement with SS alone. An analysis of HRV showed that the FNL group maintained the LF/HF ratio better than ISP and SS. CONCLUSIONS: No difference in vascular retention when α- or β- agonists were added to SS during post-hemorrhagic recovery. The animals in the FNL group maintained the integrity of the autonomic response within normal physiological standards during hemorrhagic stress. .

Attenuation of alpha-adrenergic-induced vasoconstriction by dietary wild blueberries (Vaccinium angustifolium) is mediated by the NO-cGMP pathway in spontaneously hypertensive rats (SHRs).

The role of wild blueberries (WB) on key signaling steps of nitric oxide (NO) and cyclooxygenase (COX) pathways was examined in spontaneously hypertensive rats (SHRs) after eight weeks on a control (C) or an 8% w/w WB diet. Aortic rings from SHRs were stimulated with phenylephrine (Phe) in the absence or presence of inhibitors of: soluble guanylyl cyclase (sGC), phosphodiesterase-5 (PDE(5)), prostaglandin I(2) (PGI(2)) synthase and thromboxane A(2) (TXA(2)) synthase. Additionally, enzymatic activities in these pathways were determined by the concentration of NO, cyclic guanosine monophosphate (cGMP), PGI(2) and TXA(2). In the WB-fed SHR, attenuation of Phe-induced vasoconstriction was mediated by an increased synthesis or preservation of cGMP. Despite an increased release of PGI(2) in the WB group, neither inhibition of PGI(2) or TXA(2) synthase resulted in a different response to Phe between the control and the WB rings. Hence, in the SHR, WB decrease Phe-mediated vasoconstriction under basal conditions by enhancing NO-cGMP signaling without a significant involvement of the COX pathway.

Wake-promoting actions of noradrenergic α1 - and ß-receptors within the lateral hypothalamic area.

Central norepinephrine exerts potent wake-promoting effects, in part through the actions of noradrenergic α1 - and ß-receptors located in the medial septal and medial preoptic areas. The lateral hypothalamic area (LHA), including the lateral hypothalamus, perifornical area and adjacent dorsomedial hypothalamus, is implicated in the regulation of arousal and receives a substantial noradrenergic innervation. To date the functional significance of this innervation is unknown. The current studies examined the degree to which noradrenergic α1 - and ß-receptor stimulation within the rat LHA modulates arousal. Specifically, these studies examined the wake-promoting effects of intra-tissue infusions (250 nL) of the α1 -receptor agonist phenylephrine (10, 20 and 40 nmol) and the ß-receptor agonist isoproterenol (3, 10 and 30 nmol) in rats. Results show that stimulation of LHA α1 -receptors elicits robust and dose-dependent increases in waking. In contrast, ß-receptor stimulation within the LHA had relatively modest arousal-promoting actions. Nonetheless, combined α1 - and ß-receptor stimulation elicited additive wake-promoting effects. Arousal-promoting hypocretin/orexin (HCRT)-synthesising neurons are located within the LHA. Therefore, additional immunohistochemical studies examined whether α1 -receptor-dependent waking is associated with an activation of HCRT neurons as measured by Fos, the protein product of the immediate-early gene c-fos. Analyses indicate that although intra-LHA α1 -receptor agonist infusion elicited a robust increase in Fos immunoreactivity (ir) in this region, this treatment did not activate HCRT neurons as measured by Fos-ir. Collectively, these observations indicate that noradrenergic α1 -receptors within the LHA promote arousal via actions that are independent of HCRT neuronal activation.

Vascular dysfunction induced in offspring by maternal dietary fat involves altered arterial polyunsaturated fatty acid biosynthesis.

Nutrition during development affects risk of future cardiovascular disease. Relatively little is known about whether the amount and type of fat in the maternal diet affect vascular function in the offspring. To investigate this, pregnant and lactating rats were fed either 7%(w/w) or 21%(w/w) fat enriched in either 18:2n-6, trans fatty acids, saturated fatty acids, or fish oil. Their offspring were fed 4%(w/w) soybean oil from weaning until day 77. Type and amount of maternal dietary fat altered acetylcholine (ACh)-mediated vaso-relaxation in offspring aortae and mesenteric arteries, contingent on sex. Amount, but not type, of maternal dietary fat altered phenylephrine (Pe)-induced vasoconstriction in these arteries. Maternal 21% fat diet decreased 20:4n-6 concentration in offspring aortae. We investigated the role of Δ6 and Δ5 desaturases, showing that their inhibition in aortae and mesenteric arteries reduced vasoconstriction, but not vaso-relaxation, and the synthesis of specific pro-constriction eicosanoids. Removal of the aortic endothelium did not alter the effect of inhibition of Δ6 and Δ5 desaturases on Pe-mediated vasoconstriction. Thus arterial smooth muscle 20:4n-6 biosynthesis de novo appears to be important for Pe-mediated vasoconstriction. Next we studied genes encoding these desaturases, finding that maternal 21% fat reduced Fads2 mRNA expression and increased Fads1 in offspring aortae, indicating dysregulation of 20:4n-6 biosynthesis. Methylation at CpG -394 bp 5' to the Fads2 transcription start site predicted its expression. This locus was hypermethylated in offspring of dams fed 21% fat. Pe treatment of aortae for 10 minutes increased Fads2, but not Fads1, mRNA expression (76%; P<0.05). This suggests that Fads2 may be an immediate early gene in the response of aortae to Pe. Thus both amount and type of maternal dietary fat induce altered regulation of vascular tone in offspring though differential effects on vaso-relaxation, and persistent changes in vasoconstriction via epigenetic processes controlling arterial polyunsaturated fatty acid biosynthesis.

Myocardial and systemic iron depletion in heart failure implications for anemia accompanying heart failure.

OBJECTIVES: This study sought to determine the potential pathophysiological link between anemia and disease severity, and adverse outcome in heart failure (HF). BACKGROUND: Anemia frequently accompanies advanced HF; however, the pathophysiological mechanism responsible for the association between anemia and more severe HF remains uncertain. We hypothesized that a depletion of myocardial iron content may provide the biological link. METHODS: Complementary clinical and basic studies were performed. Hemodynamic, biochemical, and echocardiographic investigations were performed in 9 healthy controls and 25 patients with advanced HF (left ventricular ejection fraction: 23 ± 10%). Tissue iron content and type 1 transferrin receptor (Tfr1) expression were assessed in human myocardial tissue, and the regulation of Tfr1 expression was studied in isolated cardiomyocytes. RESULTS: HF patients displayed evidence of iron deficiency as measured by lower serum iron (p < 0.05) and transferrin saturation (TFS) (p < 0.05). When subclassified according to the presence of anemia, TFS was lower in anemic compared with nonanemic HF patients, whereas TFS in nonanemic HF patients was intermediate. In association, myocardial iron content was reduced in HF versus non-HF samples (0.49 ± 0.07 µg/g vs. 0.58 ± 0.09 µg/g, p < 0.05), and there was a significant reduction (p < 0.05) in the myocardial mRNA expression of Tfr1, which plays a key role in cellular iron transport. In the context of HF, catecholamines and aldosterone both down-regulated Tfr1 expression in isolated cardiomyocytes. CONCLUSIONS: This study suggests the presence of iron depletion in the failing human heart, providing a potential link for the association between anemia and adverse prognosis in HF.

Ca(2+)-dependent contraction by the saponoside escin in rat vena cava: implications in venotonic treatment of varicose veins.

BACKGROUND: Saponosides (horse chestnut seed extract, escin) and flavonoids (diosmin, Daflon 500, Servier, France) exhibit venotonic properties that have been utilized in treatment of varicose veins. However, the cellular mechanisms underlying the venotonic properties of escin and diosmin are unclear. Because Ca(2+) is a major regulator of venous smooth muscle (VSM) function, we tested the hypothesis that escin and diosmin promote Ca(2+)-dependent venous contraction. METHODS: Rings of inferior vena cava (IVC) from male rats were suspended in a tissue bath for measurement of isometric contraction. Following control contraction to 96 mM KCl, the effects of escin and diosmin (10(-10) to 10(-4) M) on vein contraction were measured. To test the role of intracellular Ca(2+) release, the vein response to escin and diosmin was measured in Ca(2+)-free (2mM EGTA) Krebs. To test for Ca(2+)-dependent effects, IVC segments were pretreated with escin or diosmin (10(-4) M) in 0 Ca(2+) Krebs, then extracellular CaCl(2) (0.1, 0.3, 0.6, 1, 2.5 mM) was added and the [Ca(2+)](e)-contraction relationship was constructed. To test for synergistic effects of diosmin, IVC segments were pretreated with diosmin (10(-4) M), then stimulated with KCl (16-96 mM) or escin (10(-10) to 10(-4) M) and vein contraction was measured. Contraction data were presented as mg/mg tissue (means ± SEM). RESULTS: In IVC segments incubated in normal Krebs (2.5 mM Ca(2+)), escin caused concentration-dependent contraction (max 104.3 ± 19.6 at 10(-4) M). Escin-induced contraction was not a rigor state, because after washing with Krebs, the veins returned to a relaxed state. In Ca(2+)-free Krebs, there was essentially no contraction to escin. In escin-treated veins incubated in 0 Ca(2+) Krebs, stepwise addition of extracellular CaCl(2) caused corresponding increases in contraction (max 80.0 ± 11.1 at 2.5 mM). In the absence of escin, the α-adrenergic agonist phenylephrine (PHE, 10(-5) M), angiotensin II (AngII, 10(-6) M), and membrane depolarization by KCl (96 mM) caused significant contraction (122.5 ± 45.1, 114.2 ± 12.2 and 221.7 ± 35.4, respectively). In IVC segments pretreated with escin (10(-4) M), the contractile response to PHE (9.7 ± 2.6), AngII (36.0 ± 9.1), and KCl (82.3 ± 10.2) was significantly reduced. Diosmin (10(-4) M) caused small contractions in normal Krebs (11.7 ± 1.9) and Ca(2+)-free Krebs (4.2 ± 2.2). In diosmin-treated veins incubated in 0 Ca(2+) Krebs, addition of extracellular CaCl(2) caused minimal contraction. Diosmin did not enhance the IVC contraction to PHE, AngII, or escin, but enhanced the contractile response to KCl (24-51 mM). CONCLUSION: In rat IVC, escin induces extracellular Ca(2+)-dependent contraction, but disrupts α-adrenergic and AT(1)R receptor-mediated pathways and depolarization-induced contraction. The initial venotonic benefits of escin may be offset by disruption of vein response to endogenous venoconstrictors, limiting its long-term therapeutic benefits in varicose veins. Diosmin does not cause venous contraction or potentiate the venotonic effects of endogenous venoconstrictors or escin ex vivo, and its use as venotonic may need to be further evaluated.