Decreased blood pressure response in mice deficient of the alpha1b-adrenergic receptor

To investigate the functional role of different alpha1-adrenergic receptor (alpha1-AR) subtypes in vivo, we have applied a gene targeting approach to create a mouse model lacking the alpha1b-AR (alpha1b-/-). Reverse transcription-PCR and ligand binding studies were combined to elucidate the expression of the alpha1-AR subtypes in various tissues of alpha1b +/+ and -/- mice. Total alpha1-AR sites were decreased by 98% in liver, 74% in heart, and 42% in cerebral cortex of the alpha1b -/- as compared with +/+ mice. Because of the large decrease of alpha1-AR in the heart and the loss of the alpha1b-AR mRNA in the aorta of the alpha1b-/- mice, the in vivo blood pressure and in vitro aorta contractile responses to alpha1-agonists were investigated in alpha1b +/+ and -/- mice. Our findings provide strong evidence that the alpha1b-AR is a mediator of the blood pressure and the aorta contractile responses induced by alpha1 agonists. This was demonstrated by the finding that the mean arterial blood pressure response to phenylephrine was decreased by 45% in alpha1b -/- as compared with +/+ mice. In addition, phenylephrine-induced contractions of aortic rings also were decreased by 25% in alpha1b-/- mice. The alpha1b-AR knockout mouse model provides a potentially useful tool to elucidate the functional specificity of different alpha1-AR subtypes, to better understand the effects of adrenergic drugs, and to investigate the multiple mechanisms involved in the control of blood pressure.

Leptin induces direct vasodilation through distinct endothelial mechanisms

In this study, we reveal that leptin evokes an acute hypotensive effect in 6-hydroxydopamine sympathectomized rats (response to maximal leptin dose, mean blood pressure: from 92 +/- 4 to 78 +/- 2 mmHg, P < 0.01). This hemodynamic effect is related to a direct action of the hormone on vascular tone, since in aortic and mesenteric rings increasing doses of leptin evoke a dose-dependent vasorelaxation (aorta: from 3 +/- 1 to 36 +/- 3, n = 15; mesenteric: from 6 +/- 1 to 30 +/- 5, n = 10), which is impaired by endothelial denudation. In particular, leptin-evoked vasorelaxation is impaired by nitric oxide synthase inhibition in aorta (delta% of maximal response: from 36 +/- 3 to 3 +/- 1, P < 0.01) and by endothelium-derived hyperpolarizing factor (EDHF) inhibition in mesenteric arteries (delta% of maximal response: from 30 +/- 5 to 7 +/- 2, P < 0.01), suggesting that vasorelaxation evoked by leptin is heterogeneous and related to the vascular bed. Finally, the inhibition of nitric oxide synthase by NG-nitro-L-arginine-methyl ester does not modify blood pressure response to leptin, suggesting a predominant role of the EDHF mechanism in the hypotensive effect of leptin.

A common variant of endothelial nitric oxide synthase (Glu298Asp) is an independent risk factor for carotid atherosclerosis

BACKGROUND AND PURPOSE

Endothelium-derived NO is formed from L-arginine by endothelial NO synthase (eNOS) encoded by the NOS 3 gene on chromosome 7. Because several studies have indicated that NO plays a key role in the development of the atherosclerotic process, we investigated whether common variants in the eNOS gene are associated with an increased risk of plaque on carotid arteries.

METHODS

We studied 375 subjects attending the hypertension center of our institution to be screened for arterial hypertension. The examined subjects were classified according to the presence of carotid plaques (intima-media thickness >/=1.5 mm), and 2 intronic (CA and 27-bp repeats) polymorphisms and 1 exonic (Glu298Asp) polymorphism of the eNOS gene were explored.

RESULTS

Only the Glu298Asp polymorphism of eNOS was associated with the presence of carotid plaques (P:<0.05). In particular, there was an excess of homozygotes for the Asp298 variant among subjects with carotid plaques, whereas the number of subjects who had the Glu298 allele in exon 7 of the eNOS gene was equally distributed in both study groups. Interestingly, the risk of having carotid plaques was increased approximately 3 times in subjects who were homozygotic for the Asp298 variant compared with subjects who were homozygotic for the Glu298 variant and was independent of the other common risk factors (age, blood pressure, and smoking).

CONCLUSIONS

Homozygosity for Asp298, a common variant of the eNOS gene, is an independent risk factor for carotid atherosclerosis in this study population.

Association and cosegregation of stroke with impaired endothelium-dependent vasorelaxation in stroke prone, spontaneously hypertensive rats

While hypertension is a major risk factor for stroke, it is not its sole determinant. Despite similar blood pressures, spontaneously hypertensive rats (SHR) do not share the predisposition to cerebrovascular disease typical of stroke-prone spontaneously hypertensive rats (SHRSP). We investigated vascular function in male SHR and SHRSP as well as in SHRSP/SHR-F2 hybrid animals. Animals were maintained on the appropriate dietary regimen necessary for the manifestation of stroke. Among the hybrid animals, a group of stroke-prone and a group of stroke-resistant rats were selected. Blood pressure was similar in all groups. Endothelium-independent vascular reactivity tested on isolated rings of thoracic aorta and basilar artery after death showed similar contractile and dilatory responses to serotonin and nitroglycerin, respectively, in all groups. In contrast, endothelium-dependent relaxation, in response to acetylcholine or substance P, was markedly reduced in SHRSP compared with SHR. Similarly, reduced vasodilatory responses were present in aortae of F2 rats that had suffered a stroke when compared with SHR or F2 rats resistant to stroke. The observed association and cosegregation of stroke with significant and specific impairment of endothelium-dependent vasorelaxation among SHRSP and stroke-prone F2 hybrids, respectively, suggest a potential causal role of altered endothelium-dependent vascular relaxation in the pathogenesis of stroke.

Insulin modulation of an endothelial nitric oxide component present in the alpha2- and beta-adrenergic responses in human forearm

We explored in 51 normal subjects, distributed in various series of experiments, whether endothelium nitric oxide may play a role in insulin modulation of alpha2- and beta-adrenergic- evoked vascular responses. In particular, we examined the forearm blood flow response (FBF, ml.min-1.dl-1) to intrabrachial infusion of BHT-933 (0.5, 1, and 2 microg.min-1.dl-1) or isoproterenol (1, 3, and 6 ng. min-1.dl-1) in control conditions, during intrabrachial infusion of insulin alone (0.05 mU.kg-1.min-1) and associated with l-N-monomethylarginine (L-NMMA) (0.05 microg.min-1.dl-1), a nitric oxide synthase inhibitor. In control conditions both BHT-933 and isoproterenol induced a dose-dependent vascular response. Local hyperinsulinemia (deep venous plasma insulin 68.5+/-4 microU/ml) did not change basal FBF whereas attenuated BHT-933 vasoconstriction and enhanced isoproterenol vasodilation. L-NMMA reduced basal FBF and abolished the insulin effect on BHT-933 and isoproterenol response. To clarify whether a nitric oxide component is included in alpha2- and beta-adrenergic response and may be responsible for insulin vascular effect, we further examined BHT-933 and isoproterenol responses during nitric oxide inhibition. Interestingly, L-NMMA potentiated the BHT-933 vasoconstriction and attenuated the isoproterenol vasodilation and, in these conditions, insulin was no more able to exhibit its vascular effects. Finally, to rule out the possibility that the conteracting effect of L-NMMA may not be specifically related to insulin action, dose-response curves to phenylephrine (0.5, 1, and 2 microg.min-1.dl-1) or sodium nitroprusside (1, 2, and 4 microg.min-1.dl-1) were also performed. Both insulin and L-NMMA were unable to alter the phenylephrine-induced vasoconstriction and the sodium nitroprusside vasodilation. In conclusion, our data demonstrate an endothelial nitric oxide component in the alpha2- and beta-adrenergic vascular responses which is the target of the insulin vascular action.

Impaired insulin-like growth factor I vasorelaxant effects in hypertension

Insulin-like growth factor I (IGF-I) can be considered a factor potentially involved in arterial hypertension not only for its growth-promoting features but also for its effects on vascular tone. Nevertheless, the actions of the hormone on vascular reactivity are still unexplored in hypertension. Therefore, the vasodilation induced by increasing doses of IGF-I and the modulation of norepinephrine vasoconstriction induced by low levels of the hormone were tested on aortic rings of spontaneously hypertensive and normotensive rats. The results indicate that the vasodilation evoked by IGF-I is impaired in hypertensive rats (Delta% of maximal vasorelaxation, 30+/-1 versus 41+/-1; P<0.01), and after the removal of endothelium or the inhibition of endothelial NO synthase, the vasodilation evoked by the hormone was blunted in both rat strains and became similar between hypertensive and normotensive rats (Delta% of maximal vasorelaxation, 21+/-1 versus 20+/-1; P=NS). Moreover, IGF-I does not show any effect on norepinephrine vasoconstriction in hypertensive rats, and this alteration may depend on the lack of sensitizing effect exerted by IGF-I on alpha(2)-adrenergic-evoked NO vasorelaxation. The defect in IGF-I vascular action is also present in young spontaneously hypertensive rats (age 5 weeks). In conclusion, our data demonstrate that IGF-I vasorelaxant properties are impaired in spontaneously hypertensive rats, suggesting that such defect may play a causative or permissive role in the development of hypertensive conditions.

A novel mechanism of action for statins against diabetes-induced oxidative stress

AIMS/HYPOTHESIS

Atorvastatin exerts beneficial vascular effects in diabetes, but the underlying mechanisms are yet to be elucidated. The aim of the present study was to determine whether Rac-1 is involved in the effect of atorvastatin on oxidative stress and vascular dysfunction.

MATERIALS AND METHODS

Using human aortic endothelial cells (HAECs) we evaluated the effect of high glucose levels on peroxide production by dihydrodichlorofluorescein and on Rac-1 activity using immunocytochemistry to detect Rac-1 translocation to the membrane. We evaluated vascular function, peroxide production by dihydroethidium and NADPH oxidase activity in vessels from atorvastatin-treated mice. Rac-1 activity was also assessed, both by immunoprecipitation of the Rac-p21-activated kinase complex and by analysis of Rac-1 translocation to the membrane. These experiments were also conducted in vessels infected with an adenoviral vector carrying a constitutively active mutant of Rac-1.

RESULTS

In HAECs exposed to high glucose levels, atorvastatin prevented oxidative stress, and this protection was associated with impaired Rac-1 activation. This effect was also observed in a murine model of diabetes mellitus. More importantly, the addition of geranylgeranyl pyrophosphate (GGPP) blocked the effects of atorvastatin in both glucose-exposed HAECs and diabetic vessels. Atorvastatin failed to afford protection against vascular abnormalities in the presence of a constitutively active mutant of Rac-1.

CONCLUSIONS/INTERPRETATION

The results of this study demonstrate that the vascular antioxidant effect of atorvastatin in diabetes is mediated through inhibition of Rac-1 via a reduction in GGPP. Thus, selective Rac-1 inhibition should be considered in the design of novel pharmacological strategies to reduce the impact of diabetes mellitus on vascular function.

Insulin modulation of vascular reactivity is already impaired in prehypertensive spontaneously hypertensive rats

Hyperinsulinemia reduces the vasoconstrictive response to norepinephrine in Wistar-Kyoto rats (WKY) but not in spontaneously hypertensive rats (SHR). It has been hypothesized that this difference in the vascular effect of insulin could be a hallmark of the hypertensive state. To test this hypothesis we studied SHR before (5 weeks old, n = 10) and after (15 weeks old, n = 10) the establishment of hypertension as well as two groups of age- and sex-matched WKY (5 weeks old, n = 14; 15 weeks old, n = 13). Blood pressure was significantly higher in SHR compared with WKY (181 +/- 5 versus 118 +/- 6 mm Hg, respectively, P < .001) in the 15-week-old rats but not in the 5-week-old rats (121 +/- 5 versus 117 +/- 3 mm Hg, P < NS). We tested vascular reactivity using increasing amounts of norepinephrine (from 10(-10) to 10(-5) mmol/L) on isolated aortic rings in control conditions and after 30 minutes of exposure to 715 pmol/L insulin. In WKY insulin reduced the vascular response to norepinephrine in both the 5-week-old (repeated-measures ANOVA with grouping factor: F = 2.443, P < .05) and 15-week-old (F = 9.667, P < .01) groups. In SHR at both ages insulin failed to modify the vascular response to norepinephrine (5 weeks: F = 0.107, P < NS; 15 weeks: F = 0.075, P < NS). Sodium nitroprusside was able to attenuate the vascular response to norepinephrine in WKY and SHR at 5 and 15 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin enhances endothelial alpha2-adrenergic vasorelaxation by a pertussis toxin mechanism

To investigate whether insulin effect on endothelium is related to a specific signal transduction pathway or reflects a more generalized action of the hormone, we studied in aortic rings of Wistar-Kyoto (WKY) rats the effects of the hormone on endothelium-dependent relaxations generated by acetylcholine, adenosine diphosphate, the selective alpha2-adrenergic agonist UK 14,304, and the calcium ionophore ionomycin. The responses were evaluated both in control conditions and after 30 minutes of exposure to three different levels of insulin (30, 100, and 500 microU/mL). Insulin failed to modify the phenylephrine aortic contractions and the relaxations induced by acetylcholine, adenosine diphosphate, and ionomycin. In contrast, both 100 and 500 microU/mL insulin were able to potentiate the UK 14,304-induced vasorelaxation (+96+/-19% and +91+/-12%, respectively). Pertussis toxin, which causes alpha2-adrenergic receptor Gi uncoupling, reduced the alpha2-adrenergic vasorelaxation and prevented the insulin potentiation of the response to UK 14,304. Furthermore, in primary cultured aortic endothelial cells from WKY, we evaluated the conversion of [3H]arginine to [3H]citrulline in response to acetylcholine, ionomycin, and UK 14,304, both in control conditions and during insulin exposure. Again, insulin did not affect basal citrulline production or the increase induced by acetylcholine and ionomycin, whereas it potentiated the response to UK 14,304. Finally, in aortic rings of spontaneously hypertensive rats, insulin treatment (100 and 500 microU/mL) was unable to enhance the alpha2-adrenergic vasodilator response; in vascular endothelial cells from spontaneously hypertensive rats, insulin did not potentiate the increase in citrulline production evoked by UK 14,304. In conclusion, insulin selectively enhances alpha2-adrenergic endothelial vasorelaxation through a pertussis toxin-sensitive mechanism, by potentiating endothelial nitric oxide production. This vasorelaxant mechanism is altered in spontaneously hypertensive rats.

Noradrenergic vascular hyper-responsiveness in human hypertension is dependent on oxygen free radical impairment of nitric oxide activity

BACKGROUND

Noradrenergic vascular hyper-responsiveness is a hallmark of essential hypertension. To evaluate whether nitric oxide plays a role in the enhanced vascular response to norepinephrine in hypertension, we examined 32 hypertensives and 28 normotensives who were distributed in 3 experimental series.

METHODS AND RESULTS

In the first series, we measured the forearm blood flow (FBF) response to a norepinephrine infusion under control conditions and during the infusion of L-N-monomethylarginine (L-NMMA). Norepinephrine evoked dose-dependent vasoconstriction that was greater in hypertensives than in normotensives (maximum FBF, -61+/-1 versus -51+/-1%; P<0.01). During L-NMMA infusion, norepinephrine vasoconstriction was not modified in hypertensives; however, it was potentiated in normotensives (maximum FBF, -64+/-2%; P<0.01). In the second series, we tested whether norepinephrine vasoconstriction could be affected by an antioxidant such as ascorbic acid. Norepinephrine vasoconstriction was blunted by ascorbic acid administration only in hypertensives (maximum FBF, -49+/-3 versus -63+/-2%; P<0.01); the vasoconstriction became similar to that observed in normotensives. During ascorbic acid plus L-NMMA administration, the vascular response to norepinephrine increased to a similar extent in both study groups. To rule out the possibility that the effect of ascorbic acid on norepinephrine vasoconstriction could depend on adrenergic receptor-induced nitric oxide release, in the last series we inhibited endogenous nitric oxide and replaced it with an exogenous nitric oxide donor (sodium nitroprusside). Even in these conditions, ascorbic acid attenuated norepinephrine vasoconstriction only in hypertensives (maximum FBF, -50+/-2 versus -62+/-1%; P<0.01).

CONCLUSIONS

Our data demonstrate that noradrenergic vascular hyper-responsiveness in hypertension is dependent on an impairment of nitric oxide activity that is realized through norepinephrine-induced oxygen free radical production.

Haemodynamic and metabolic effects of rilmenidine in hypertensive patients with metabolic syndrome X. A double-blind parallel study versus amlodipine

OBJECTIVE

To compare the effects of rilmenidine with those of amlodipine on blood pressure, glucose metabolism, plasma lipid concentration and fibrinolysis parameters.

DESIGN

A four-month randomized double-blind, parallel group study.

PATIENTS AND METHODS

Obese hypertensive patients with hypertriglyceridaemia (> or = 2.3 mmol/l) and impaired glucose tolerance (OMS-ADA) were included (n = 52). A placebo run-in period of 2 weeks was followed by 4 months of double-blind treatment with either rilmenidine or amlodipine. Blood pressure was recorded using a mercury sphygmomanometer. Glucose metabolism was evaluated by an oral glucose tolerance test

RESULTS

Of the 52 patients recruited, 47 (21 rilmenidine and 26 amlodipine) completed the 4-month treatment period. The intention-to-treat analysis showed a comparable reduction in systolic and diastolic blood pressure (SBP, DBP) with the two anti-hypertensive treatments (rilmenidine -13.9/-13.5 mmHg; amlodipine - 17.6/-15.0 mmHg). Insulin concentrations under basal conditions and 2 h after a standard oral glucose load did not change significantly after treatment in both groups. Plasma glucose under basal conditions and 2 h after a standard oral glucose load as well as the area under the plasma glucose concentration curve tended to decrease in the rilmenidine group and to increase in the amlodipine group so that the changes in these parameters were significantly different between the two study groups (P= 0.041, P = 0.042 and P = 0.015, respectively). Plasminogen activator inhibitor type 1 (PAI-1) antigen and PAI-1 activity were only decreased in the rilmenidine group (not statistically significant).

CONCLUSION

Our results demonstrate that rilmenidine and amlodipine have a comparable anti-hypertensive effect but only rilmenidine is able to improve glucose metabolism.

Insulin modulation of beta-adrenergic vasodilator pathway in human forearm

BACKGROUND

Insulin modulates sympathetic vasoconstriction, but the mechanisms underlying this effect are not completely elucidated. We have recently investigated the insulin effect on the alpha 1- and alpha 2-adrenergic vasoconstriction pathway, where it is still conflicting with the possible insulin influence on the beta-adrenergic vasodilator pathway. The aim of the present study was to investigate this issue.

METHODS AND RESULTS

The study was performed on the forearm of healthy humans, and all test substances were infused into the brachial artery at systemically ineffective rates. In five subjects, we evaluated isoproterenol-induced vasodilation (1, 3, 6, and 9 ng. kg-1. min-1) both under control conditions and during insulin infusion (0.05 mU. kg-1. min-1). In another group of five subjects, we tested whether the vasorelaxant effect of sodium nitroprusside (1, 2, 4, and 8 ng . kg-1 . min-1) was modified by insulin. Moreover, to explore whether the interaction between insulin and forearm beta-adrenergic pathway participates in insulin modulation of sympathetic-evoked vasoconstriction, we measured in six normal subjects the forearm vascular response to lower-body negative pressure under control conditions and during intrabrachial infusion of insulin alone and in combination with a selective beta-adrenergic blocking agent (propranolol 10 micrograms/100 mL per minute). Finally, to verify whether insulin interaction with the beta-adrenergic pathway may also account for insulin modulation of alpha 2-adrenergic vasoconstriction, we assessed the vascular response to a selective alpha 2-adrenergic agonist before and after propranolol administration. Insulin exposure potentiated the vascular responsiveness to isoproterenol but did not affect the vasodilator response to sodium nitroprusside. Furthermore, the insulin-induced attenuation of sympathetic vasoconstriction was partially corrected by propranolol. In contrast, the insulin modulation of alpha 2-adrenergic vasoconstriction was not influenced by beta-adrenergic blockade.

CONCLUSIONS

Taken together, our results suggest that insulin modulation of sympathetic-induced vasoconstriction is carried out through an interaction of the hormone with the pathways of both alpha 2-and beta -adrenergic receptors.

Systemic hypertension and coronary artery disease: the link

A direct, continuous, and independent association between blood pressure values and incidence of coronary artery disease has been well documented. However, the evidence that the reduction of blood pressure alone is not able to completely reverse the increase in the risk of coronary artery disease associated with essential hypertension suggests that the link between hypertension and coronary artery disease is a complex process including other factors beside the increase in blood pressure values. In this regard, the main determinant of coronary artery disease in hypertensive patients seems to be the development of left ventricular hypertrophy (LVH). In fact, hypertensive patients who died from sudden cardiac death showed a lesser degree of coronary atherosclerosis compared with normotensives, but a higher incidence of LVH. Several mechanisms can account for the increased coronary risk with LVH, including (1) an increase in left ventricular (LV) mass, which by itself requires more oxygen for tissue perfusion; (2) impairment of coronary flow reserve; (3) perivascular fibrosis, which then impairs oxygen supply to the myocardium; and (4) deterioration of LV diastolic function, which hampers myocardial perfusion. Recently, a study reported an impairment of endothelial function and abnormal control of the sympathetic tone in hypertensive patients, which may contribute to the risk of coronary artery disease. In particular, the impaired endothelial function resulting in a prevalence of vasoconstrictive, thrombogenic, and proliferative factors may account for the enhanced ischemic susceptibility of these patients. Furthermore, the cardiac adrenergic system plays an important role in regulating myocardial blood flow. On one hand, hypertensive patients show an exaggerated sympathetic response to physiologic stimuli, whereas on the other hand, the beta-adrenergic receptor-mediated vasodilating component of the sympathetic response is blunted in hypertension. Finally, excess body weight, dyslipidemia, glucose intolerance, and hyperinsulinemia, which are frequently interrelated, represent independent predictors of both coronary artery disease and hypertension.

Lipid nano-vesicles for thyroid hormone encapsulation: A comparison between different fabrication technologies, drug loading, and an in vitro delivery to human tendon stem/progenitor cells in 2D and 3D culture

Phosphatidylcholine (PC) vesicles loaded with Triiodothyronine (T3) were fabricated using different manufacturing methods: thin layer hydration plus sonication (TF-UF), supercritical liposome formation (SC), and microfluidic technology (MF). Vesicles obtained by MF had the lowest mean diameter (88.61 ± 44.48 nm) with a Zeta Potential of -20.1 ± 5.90 mV and loading of 10 mg/g (encapsulation efficiency: 57%). In contrast, SC vesicles showed extremely low encapsulation efficiency (<10%) probably due to T3 solubility in ethanol/carbon dioxide mixture; despite TF-UF vesicles exhibiting good size (167.7 ± 90 nm; Zp -8.50 ± 0.60 mV) and loading (10 mg/g), poor mass recovery was obtained (50% loss). MF vesicles had low cytotoxicity, and they were well enough internalized by both HeLa and human tendon stem/progenitor cells (hTSPCs). Their biological activity was also monitored in both 2D and 3D cultures of hTSPCs supplemented with therapeutical concentrations of PC/T3 nano-liposomes. 2D culture showed almost similar constitutive gene expression compared to control culture supplemented with free-T3. On the contrary, when hTPSCs 3D culture was assembled, it showed a more evident homogeneous distribution of FITC labeled vesicles within the high-density structure and a significant upregulation of cell constitutive genes, such as type I Collagen (4.8-fold; p < 0.0001) at day 7, compared to the control, suggesting that T3/PC formulation has increased T3 cytosolic concentration, thus improving cells metabolic activity. The study supported MF technology for nano-carriers fabrication and opens perspectives on the activity of PC/T3 nano-vesicles as innovative formulations for TPSCs stimulation in ECM secretion.

Impaired vasorelaxant responses to natriuretic peptides in the stroke-prone phenotype of spontaneously hypertensive rats

BACKGROUND

We have previously shown that a locus on rat chromosome 5, termed STR 2, co-localizes with the genes encoding atrial natriuretic and brain natriuretic peptides, and is closely linked to the development of strokes in rats of a F2 hybrid cohort obtained by crossing stroke-prone spontaneously hypertensive rats and spontaneously hypertensive rats. We also demonstrated that there are significant differences in vascular functioning that are co-segregated with stroke latency of stroke-prone spontaneously hypertensive rats.

OBJECTIVE

To investigate the vascular responses to natriuretic peptides in the stroke-prone phenotype of spontaneously hypertensive rats.

DESIGN AND METHODS

In view of the important vasoactive properties of natriuretic peptides, we tested the vascular responses to 10(-11)-10(-9) mol/l atrial natriuretic peptide and to 10(-11)-10(-7) mol/l brain natriuretic peptide in isolated rings of aortas and internal carotid arteries obtained from stroke-prone and stroke-resistant spontaneously hypertensive rats. The 6-week-old rats were exposed for 4 weeks either to their regular diet (n = 15 of both strains) or to the stroke-permissive Japanese-style diet (n = 14 of both strains). A group of 14 normotensive, age-matched and sex-matched Wistar-Kyoto rats was also studied.

RESULTS

Systolic blood pressures in stroke-prone and stroke-resistant spontaneously hypertensive rats were similar, and were significantly higher than those in Wistar-Kyoto rats. Vascular responses to nitroglycerin, atrial natriuretic peptide, and brain natriuretic peptide in rats of the two hypertensive strains and in Wistar-Kyoto rats fed their regular diet were comparable. In contrast, the vasorelaxant responses to atrial natriuretic peptide in stroke-prone spontaneously hypertensive rats fed Japanese diet were lower both in aortas and in internal carotid arteries than were those in spontaneously hypertensive rats (both P < 0.05 by analysis of variance) and in Wistar-Kyoto rats (both P < 0.05). Similarly, vasorelaxant responses to brain natriuretic peptide were lower both in aortas and in internal carotid arteries of stroke-prone spontaneously hypertensive rats than they were in spontaneously hypertensive rats (both P < 0.05) and in Wistar-Kyoto rats (P < 0.05). The responses to nitroglycerin in the stroke-prone spontaneously hypertensive rats and spontaneously hypertensive rats fed Japanese-style diet were also similar.

CONCLUSION

The vasorelaxant effects of natriuretic peptides are impaired in stroke-prone spontaneously hypertensive rats. This abnormality could play a role in the pathogenesis of stroke incidence in this hypertensive model.

Dietary sodium restriction impairs endothelial effect of insulin

Hyperinsulinemia and high salt intake represent two independent cardiovascular risk factors. However, it is still unknown whether the change in dietary salt intake may affect the ability of insulin to stimulate whole-body glucose uptake and to modulate endothelial function. Regarding this latter issue, we have recently demonstrated that insulin enhances endothelial-mediated alpha2-adrenergic vasorelaxation. In overnight-fasted, freely moving Wistar-Kyoto rats (10 to 12 weeks old), we assessed whole-body glucose uptake (in milligrams per kilogram per minute) during a euglycemic-hyperinsulinemic clamp (insulin infusion rate, 3 mU x kg(-1) x min(-1)) after 3 weeks of normal (NSD, 2% NaCl), high (HSD, 6% NaCl), and low (LSD, 0.6% NaCl) sodium diet. Three days after the clamp study, rats were killed to assess alpha2-adrenergic vasorelaxation evoked by UK 14,304 (10(-9) to 10(-6) mol/L) in aortic rings in control conditions and after insulin exposure (100 microU/mL). Different sodium intakes did not modify the mean blood pressure or the insulin-stimulated whole-body glucose uptake (NSD: 14+/-1.2, n=16; HSD: 15.4+/-1.7, n=14; LSD: 14.8+/-0.8, n=14; NS). In contrast, we confirmed the ability of insulin to enhance alpha2-adrenergic vasorelaxation during NSD and HSD (delta% of maximal relaxation, NSD: from 32+/-3% to 58+/-3.4%, n=9, P<0.01; HSD: from 33+/-3.8% to 59+/-3.5%, n=8, P<0.01), but this effect was impaired during LSD (delta% maximal relaxation, from 36+/-1.5% to 36+/-3.4%, n=8, NS). In conclusion, our data demonstrate that in Wistar-Kyoto rats, changes in dietary salt intake do not modify the insulin-stimulated whole-body glucose uptake. In contrast, LSD impairs the insulin potentiation of alpha2-adrenergic vasorelaxation, thus suggesting that dietary salt restriction provokes an impairment of insulin effect on endothelial function.

Sortilin evokes endothelial dysfunction and arterial hypertension through the dysregulation of sphingolipid metabolism and oxidative stress

Background

Sortilin, a member of vacuolar protein sorting domain family Vps10, has been positively correlated with vascular and metabolic disorders in humans. Previous study has shown that, in response to Fas receptor stimulation, sortilin together with acid sphingomyelinase (ASMase) promote the clustering of lipid rafts and subsequent activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in coronary endothelial cells. However, whether sortilin plays a role in endothelial cells function is currently unknown.

Purpose

To assess whether sortilin per se was able to influence vascular function, thereby contributing to the pathogenesis of cardiovascular diseases.

Methods

Pressure myography was used to study vascular reactivity of mesenteric arteries. To investigate the involvement of acid sphingomyelinase (ASM), we performed gene silencing approach and fluorometric activity assay. NADPH oxidase lucigenin assay was used to evaluate oxidative stress in endothelial cells and resistance vessels. The effects of circulating sortilin on cardiovascular system was evaluated by systemic delivery of recombinant sortilin protein to wild-type (WT), sphingosine-1-phosphate receptor 3 (S1P3) and NADPH oxidase 2 (gp91phox/NOX2) deficient mice. Systolic arterial blood pressure (SBP) was noninvasively registered in conscious mice by tail-cuff blood monitoring. Finally, to explore the translational relevance of sortilin, we measured sortilin and NOX2 soluble derived peptide levels using ELISA and quantified sphingosine-1-phosphate (S1P) by liquid chromatography–tandem mass spectrometry (LC-MS/MS) in plasma of hypertensive patients.

Results

Here we demonstrated that sortilin evoked endothelial dysfunction in mesenteric arteries due to increased NADPH oxidase-derived oxidative stress. Knockdown of ASM successfully prevented impairment of endothelial function. Using the inhibitor of sphingosine kinase type 1 (SphK1), sortilin failed to evoke endothelial impairment as well as NADPH oxidase activation. In endothelial cells, sortilin induced S1P-dependent activation of Rac1/NOX2 signaling axis, which was prevented by TY-52156, an antagonist of lysosphingolipid receptor S1P3. In vivo sortilin administration induced arterial hypertension in WT mice. In contrast, genetic deletion of S1P3 and gp91phox/NOX2 resulted in preservation of endothelial function and SBP unchanged levels after 14 days of systemic sortilin administration. Finally, to translate these research findings into a clinical setting, we found that hypertensive patients have higher plasma levels of sortilin, ASMase, S1P and soluble NOX2 derived peptide than normotensive subjects.

Conclusions

These results demonstrate the pathologic role of sortilin in the modulation of endothelial function and arterial blood pressure, suggesting that sortilin and its mediators might represent novel therapeutic targets in vascular diseases and hypertension.

Funding Acknowledgement

Type of funding source: None

P97 VALIDATION OF THE ACADEMIC RESEARCH CONSORTIUM HIGH BLEEDING RISK CRITERIA IN PATIENTS UNDERGOING PERCUTANEOUS CORONARY INTERVENTION: A SYSTEMATIC REVIEW AND METANALYSIS OF 10 STUDIES AND 67,862 PATIENTS

Background

The Academic Research Consortium for High Bleeding Risk (ARC–HBR) has recently proposed, by consensus, twenty clinical criteria for the assessment of the bleeding risk after percutaneous coronary intervention (PCI). A major criterion was defined as any individual clinical condition conferring in isolation a risk for major bleeding ≥4% up to 1 year after PCI; instead, a minor criterion was considered to confer a bleeding risk of &lt; 4%. The aim of this meta–analysis was to assess the performance of the ARC–HBR criteria in stratifying the risk of bleeding and ischemic events after PCI.

Methods

MEDLINE, COCHRANE, Web of Sciences, and SCOPUS were searched for studies aimed at validating the ARC–HBR criteria in patients treated with PCI. The primary outcome measure of this meta–analysis was major bleeding.

Results

The analysis included 10 studies encompassing 67,862 patients undergoing PCI; the HBR definition was fulfilled in 44.7% of the cases. The risk of major bleeding was significantly higher in HBR vs. Non–HBR group (RR, 2.56, 95% CI 2.28–2.89). The average C–statistic was 0.64 (95% CI 0.60–0.68), indicating modest discrimination. The risk of intracranial hemorrhage, gastrointestinal bleeding, fatal bleeding, ischaemic stroke, cardiac death and all–cause death was higher in HBR vs. Non–HBR group. Despite a higher incidence of myocardial infarction and stent thrombosis in patients deemed at HBR, the rate of target lesion revascularization was comparable between groups (RR, 1.01, 95% CI 0.88–1.16). When assessed in isolation, the mean cumulative incidence of major bleeding at 1 year exceeded the cut–off value of 4% for all the major criteria and for two out of six minor criteria, including age ≥75 years and moderate chronic kidney disease (CKD) (Figure).

Conclusion

The ARC–HBR definition identifies patients at higher risk of major bleeding and other adverse cardiovascular events after PCI. Almost all major criteria, but also two of the minor criteria, were individually associated with rates of major bleeding above 4% thus fulfilling the definition of major HBR criteria. These findings corroborate the ability of ARC–HBR major criteria in identifying PCI patients who are more likely to develop adverse events, but also suggest caution in the decision making of patients with isolated minor criteria, including age≥75 years and moderate CKD.

Clinical profile and in-hospital course of patients with primary and secondary takotsubo syndrome: single center experience

Background

Takotsubo syndrome (TTS) is an acute cardiac disease increasingly recognized in a variety of clinical scenarios. Heart Failure Association of the ESC classified TTS in primary (occurring in the setting of psychological or emotional trigger or without clear identifiable stressors) and secondary (triggered by physical stressors or other critical illnesses). However, the clinical profile and outcome of these different subtypes is still controversial.

Aim of the study

To compare baseline features, clinical presentation and in-hospital outcomes in patients with primary or secondary TTS in a single referral center.

Methods

Overall study population included 210 patients (mean age 66.1±12.2 years, 14 male); 165 and 45 with primary and secondary TTS, respectively; consecutively enrolled from 2012 to 2019 in our center. Clinical, instrumental and laboratory data and in-hospital events were also recorded in both groups.

Results

Compared to patients with primary TTS, patients with secondary form were older (70.6±14.6 vs 64.9±11.2 years; p=0.006) and more frequently man (13.3% vs 4.8%; p=0.043). Several comorbidities such as diabetes (23.8% vs 8.9%; p=0.008); pulmonary (45.2% vs 12.9%; p&lt;0.001); neurologic (23.8% vs 9.7%; p=0.015); nephro-urologic (31% vs 13.5%; p=0.008); psychiatric (42.9% vs 26.5%; p=0.039) and orthopedic (28.6% vs 13.5%; p=0.020) diseases were prevalent in secondary TTS patients. Atypical presentation with higher incidence of dyspnea was significantly prevalent (42.2% vs 19.4%; p=0.002) in secondary group. The number of patients with ST-T elevation on admission was similar (80% vs 77%; p=0.5) in both groups. Prolonged QT interval in a majority of secondary TTS patients (46.3% vs 28.4%; p=0.029) was detected. Peak levels of troponin, creatine-kinase and myoglobin did not differ between the two groups. Echocardiography revealed larger left ventricular end-diastolic and end-systolic volumes (62.7±25.3 vs 50.6±14.3 ml/mq; p=0.024 and 35.1±14.5 vs 28.7±9 ml/mq; p=0.048) at presentation in secondary TTS, however no differences in baseline left ventricular ejection fraction were detected. Furthermore, the prevalence of apical ballooning was similar between the two groups. Of note, secondary TTS patients experienced more frequently acute heart failure (40.5% vs 23.1%; p=0.024), hyperkinetic arrhythmia (9.1% vs 1.9%; p=0.022), cardiogenic shock (15.9% vs 3.2%; p=0.002), and mechanical ventilation use (9.3% vs 1.3%; p=0.006) during the acute phase. In-hospital stay (10.8±6.9 vs 7.4±6.2 days, p=0.004) was longer in this cohort.

Conclusion

Our results demonstrate that to classify TTS patients in primary or secondary form is clinically relevant. Secondary form generally is associated to higher rate of comorbidities and to atypical presentation. Owing to the worse in-hospital outcome of the secondary TTS patients a tailored and more intensive treatment should be adopted in this cohort.

Funding Acknowledgement

Type of funding source: None

P192 LONG TERM PROGNOSTIC EFFECT OF LIPROTEIN(A) IN PATIENTS WITH AND WITHOUT DIABETES MELLITUS AFTER MYOCARDIAL INFARCTION

Aims

To describe the baseline clinical, laboratory and angiographic characteristics of patients with acute myocardial infarction (MI) according to the presence or not of diabetes mellitus (DM), and to evaluate if DM may influence the effect of lipoprotein(a) [Lp(a)] serum level on long–term outcome in this very high–risk population.

Methods

This was a retrospective, single–center, study including consecutive patients admitted with MI diagnosis between January 1, 2017, and December 31, 2020. The availability of data on baseline Lp(a) serum level was considered as an inclusion criterion. The study population was divided into two groups according to the presence or not of DM. The Lp(a) value of 50 mg/dL was used to test the hypothesis of a different effect of Lp(a) on the clinical outcome of patients with or without DM. The primary study outcome was all–cause death at 3–year follow–up.

Results

The study population included 997 patients (mean age 63.7±13.5 years; 75.7% were males). Diabetes was reported in 280 (28.1%) patients. DM patients were older than those without DM (67.8±12.1 vs. 62.0±13.7 years, p &lt; 0.001) and showed a significantly higher prevalence of dyslipidemia, hypertension, obesity, prior MI and prior coronary revascularization (p &lt; 0.001). DM patients showed higher SYNTAX score value (19.8 vs. 15.1, p &lt; 0.001) and a higher prevalence of left main involvement (6.3 vs. 3.1, p = 0.023). At Kaplan–Meier analysis, in the group without DM, patients with Lp(a)≥50 mg/dL showed a significantly lower long–term survival compared with those with Lp(a)&lt;50 mg/dL (Log–Rank=0.004). In DM patients DM, conversely, no survival difference was found between patients with Lp(a)≥50 mg/dL vs. those with Lp(a)&lt;50 mg/dL. At multivariable Cox regression analysis, in patients without DM, Lp(a) serum level (HR: 2.68, 95% CI 1.23–5.83; p = 0.013) and age (HR: 1.06, 95% CI 1.04–1.09; p &lt; 0.001) were independent predictors of mortality at 3–year follow–up. Among DM patients, only age was independently associated with 3–year mortality (HR: 1.07, 95% CI 1.03–1.10; p &lt; 0.001) (Table).

Conclusion

In this MI population, Lp(a) was independently associated with long–term mortality in patients without DM, but not in patients with DM. Whether DM can modify the effect of Lp(a) on clinical outcome after MI requires confirmation by larger prospective studies.