Comparison of endothelium-dependent vasoactivity of internal mammary arteries from hypertensive, hypercholesterolemic, and diabetic patients

Internal Mammary Arteries as a Model to Demonstrate Restoration of the Impaired Vasodilation in Hypertension, Using Liposomal Delivery of the CYP1B1 Inhibitor, 2,3',4,5'-Tetramethoxystilbene

A significant number of patients with severe cardiovascular disease, undergoing coronary artery bypass grafting (CABG), present with hypertension. While internal mammary arteries (IMAs) may be a better alternative to vein grafts, their impaired vasodilator function affects their patency. Our objectives were to (1) determine if inhibition of the cytochrome P450 enzyme CYP1B1, using liposome-encapsulated 2,3′,4,5′-tetramethoxystilbene (TMS), can potentiate vasodilation of IMAs from CABG patients, and (2) assess mechanisms involved using coronary arteries from normal rats, in an ex vivo model of hypertension. PEGylated liposomes were synthesized and loaded with TMS (mean diameter 141 ± 0.9 nm). Liposomal delivery of TMS improved its bioavailability Compared to TMS solution (0.129 ± 0.02 ng/mL vs. 0.086 ± 0.01 ng/mL at 4 h; p < 0.05). TMS-loaded liposomes alleviated attenuated endothelial-dependent acetylcholine (ACh)-induced dilation in diseased IMAs (@ACh 10−4 M: 56.9 ± 5.1%; n = 8 vs. 12.7 ± 7.8%; n = 6; p < 0.01) for TMS-loaded liposomes vs. blank liposomes, respectively. The alleviation in dilation may be due to the potent inhibition of CYP1B1 by TMS, and subsequent reduction in reactive oxygen species (ROS) moieties and stimulation of nitric oxide synthesis. In isolated rat coronary arteries exposed to a hypertensive environment, TMS-loaded liposomes potentiated nitric oxide and endothelium-derived hyperpolarization pathways via AMPK. Our findings are promising for the future development of TMS-loaded liposomes as a promising therapeutic strategy to enhance TMS bioavailability and potentiate vasodilator function in hypertension, with relevance for early and long-term treatment of CABG patients, via the sustained and localized TMS release within IMAs.

Exercise Training: The Holistic Approach in Cardiovascular Prevention

Nowadays, there are robust clinical and pathophysiological evidence supporting the beneficial effects of physical activity on cardiovascular (CV) system. Thus, the physical activity is considered a key strategy for CV prevention. In fact, exercise training exerts favourable effects on all risk factors for CV diseases (i.e. essential hypertension, type 2 diabetes mellitus, hypercholesterolemia, obesity, metabolic syndrome, etc…). In addition, all training modalities such as the aerobic (continuous walking, jogging, cycling, etc.) or resistance exercise (weights), as well as the leisure-time physical activity (recreational walking, gardening, etc) prevent the development of the major CV risk factors, or delay the progression of target organ damage improving cardio-metabolic risk. Exercise training is also the core component of all cardiac rehabilitation programs that have demonstrated to improve the quality of life and to reduce morbidity in patients with CV diseases, mostly in patients with coronary artery diseases. Finally, it is still debated whether or not exercise training can influence the occurrence of atrial and ventricular arrhythmias. In this regard, there is some evidence that exercise training is protective predominantly for atrial arrhythmias, reducing the incidence of atrial fibrillation. In conclusion, the salutary effects evoked by physical acitvity are useful in primary and secondary CV prevention.

Ultrastructural and histomorphologic properties of the internal thoracic artery: implications for coronary revascularization

Coronary artery disease represents a major health problem worldwide for which coronary artery bypass surgery remains a standard of care. Among the several grafts that are available, the internal thoracic artery (ITA) has long been considered the best as several advantages have been described compared with other vessels (e.g. saphenous vein or radial artery), namely, an absent to minor atherosclerotic development. In fact, several studies showed the presence of preatherosclerotic lesions, such as intimal and/or medial thickening, medial fibrosis, among others, in the presence of certain cardiovascular risk factors as well as established atherosclerotic lesions (i.e. type II or more lesions). This paper primarily aimed at reviewing the current knowledge on the histomorphological characteristics of ITA as well as the comparative histomorphology of ITA with other vessel grafts currently in use in coronary surgery. As some of the evidence is not clear or consensual, this paper also aimed at reviewing the main histopathological, histomorphometrical, and ultrastructural findings in ITAs from patients with known cardiovascular risk factors (e.g. aging, obesity, hypertension, diabetes, smoking, and others). As the presence of preatherosclerotic and/or atherosclerotic lesions may compromise the success of the myocardial revascularization and lead to graft failure, contributing toward the associated morbidity and/or mortality, it is essential to improve the scientific knowledge on the structural characterization of ITAs and its correlation with the cardiovascular risk profile.

Elevated plasma migration inhibitory factor in hypertension-hyperlipidemia patients correlates with impaired endothelial function

Migration inhibitory factor (MIF) has been shown to be critical in the pathology of early artherosclerosis; this article aim to investigate the plasma levels of MIF in hypertension plus hyperlipidemia patients.A total of 39 hypertension plus hyperlipidemia patients without any previous treatment were enrolled (HTN-HLP). Twenty-five healthy subjects were enrolled as the healthy control group (HEALTHY). Plasma MIF was measured by ELISA; laboratory and clinical characteristics were analyzed. HUVECs were treated with pooled plasma from HTN-HLP and HEALTHY groups, and the protein levels of adhesion molecules VCAM-1 and ICAM-1 were determined by ELISA. We found that plasma MIF was significantly elevated in the HTN-HLP group. Serum NO and eNOS levels were significantly lower; serum ET-1 (endothelin) levels were significantly higher in the HTN-HLP group. Furthermore, blood pressure, baPWV (brachial-ankle pulse wave velocity), and serum ET-1 level were significantly positively; serum NO and eNOS levels were negatively correlated with plasma MIF levels. Plasma from HTN-HLP significantly stimulated VCAM-1 and ICAM-1 protein expression on the surface of HUVECs.Plasma MIF was elevated in HTN-HLP patients and correlates with impaired endothelial function.

Comparative Effects of Preoperative Angiotensin-converting Enzyme In-hibitor, Statin and Beta-blocker Treatment on Human Internal Mammary Artery Reactivity in Patients with Coronary Artery Disease: A Pilot Study

PURPOSE

We investigated the effect of angiotensin-converting enzyme (ACE)- inhibitor, statin, and beta-blocker usage before coronary bypass surgery (CABG) on vascular reactivity of the internal mammary artery (IMA).

METHODS

Patients, who underwent elective CABG were evaluated. Samples of IMA obtained from 22 patients were divided into 4 groups in respect of drugs used by patients before bypass surgery (control group, ACE inhibitor + statin group, ACE inhibitor + statin + beta-blocker group, and ACE inhibitor + beta-blocker group). The discarded, distal end section of IMA was carefully removed, and the vasoreactivity of IMA rings was evaluated in vitro using an organ chamber. Smooth muscle contractile function was tested on artery segments exposed to 10-80 mM KCl and norepinephrine. The endothelial function of IMA rings was assessed with acetylcholine (ACh) and bradykinin, while endothelium-independent vasorelaxation was evaluated by sodium nitroprusside (SNP).

RESULTS

Both ACh and bradykinin caused concentration-dependent relaxation in endothelium-intact IMA rings. However, the maximal effect produced by endothelium-dependent agents in all treatment groups was more prominent when compared with the control group. There was no significant difference in the endothelium-dependent relaxation response of IMA between ACE inhibitor + statin, ACE inhibitor + beta-blocker and ACE inhibitor + statin + beta-blocker groups. The vasodilatory potency of SNP was similar in all groups. Similarly, contractile response to KCl or norepinephrine was not significantly different between groups.

CONCLUSION

Use of ACE inhibitors and statins before bypass surgery may influence IMA vasoreactivity by improving endothelial control of vascular tone.

How important is glycemic control during coronary artery bypass?

In summary, poor perioperative glycemic control in patients undergoing CABG is associated with increased morbidity and mortality. Maintaining serum glucose less than or equal to 180 mg/dL in patients with diabetes during CABG reduces morbidity and mortality, lowers the incidence of wound infections, reduces hospital length of stay, and enhances long-term survival. In nondiabetic patients undergoing CABG surgery, maintaining serum glucose less than 180 mg/dL has also resulted in improved perioperative outcomes. More aggressive glycemic control (80-120 mg/dL) provides no added improvement in CABG patients with less than or equal to 3 days of ICU care in the absence of ventilatory support or multiorgan failure. Although the precise value for achieving glycemic control in the perioperative period is the subject of much debate, the benefits of perioperative glycemic control with continuous insulin infusions in patients undergoing CABG is no longer debatable.

Endoplasmic reticulum stress is involved in cardiac damage and vascular endothelial dysfunction in hypertensive mice

OBJECTIVE

Cardiac damage and vascular dysfunction are major causes of morbidity and mortality in hypertension. In the present study, we explored the beneficial therapeutic effect of endoplasmic reticulum (ER) stress inhibition on cardiac damage and vascular dysfunction in hypertension.

METHODS AND RESULTS

Mice were infused with angiotensin II (400 ng/kg per minute) with or without ER stress inhibitors (taurine-conjugated ursodeoxycholic acid and 4-phenylbutyric acid) for 2 weeks. Mice infused with angiotensin II displayed an increase in blood pressure, cardiac hypertrophy and fibrosis associated with enhanced collagen I content, transforming growth factor-β1 (TGF-β1) activity, and ER stress markers, which were blunted after ER stress inhibition. Hypertension induced ER stress in aorta and mesenteric resistance arteries (MRA), enhanced TGF-β1 activity in aorta but not in MRA, and reduced endothelial NO synthase phosphorylation and endothelium-dependent relaxation (EDR) in aorta and MRA. The inhibition of ER stress significantly reduced TGF-β1 activity, enhanced endothelial NO synthase phosphorylation, and improved EDR. The inhibition of TGF-β1 pathway improved EDR in aorta but not in MRA, whereas the reduction in reactive oxygen species levels ameliorated EDR in MRA only. Infusion of tunicamycin in control mice induced ER stress in aorta and MRA, and reduced EDR by a TGF-β1-dependent mechanism in aorta and reactive oxygen species-dependent mechanism in MRA.

CONCLUSIONS

ER stress inhibition reduces cardiac damage and improves vascular function in hypertension. Therefore, ER stress could be a potential target for cardiovascular diseases.

Expression of inducible nitric oxide synthase in conduits used in patients with diabetes mellitus undergoing coronary revascularization

BACKGROUND

Expression of inducible nitric oxide synthase (iNOS) is a marker of vascular inflammation which can result in thrombosis and atherosclerosis. This study was undertaken to examine the difference in iNOS expression in the internal mammary artery (IMA) and saphenous veins (SVs) of patients with diabetes mellitus undergoing coronary artery bypass graft (CABG) surgery using both qualitative and quantitative methodology.

METHODS

Segments of IMA and SV harvested in 100 diabetic patients with diabetes mellitus undergoing CABG surgery were fixed in formalin and immunostained to detect the presence of iNOS. Sections were graded using a qualitative score (0 = absence of iNOS expression to 3 = extensive expression of iNOS) and a quantitative computer-aided image analysis (area of staining/area of endothelium). Linear regression analyses were performed to assess the association of the degree of iNOS expression in both the IMA and SV with the type of diabetes control (insulin, oral, diet), and the serum levels of HbAlc, glucose, free fatty acids (ffa), C-reactive protein (CRP), and low-density liproprotein (LDL) at the time of conduit harvest.

RESULTS

The degree of iNOS expression was significantly lower in the IMA compared to the SV by both qualitative (0.88 +/- 0.74 SD IMA vs. 1.38 +/- 0.68 SV; p < 0.0001) and quantitative (11.76 +/- 3.34% IMA vs. 17.10 +/- 2.54% SV; p = 0.01) methods. The Spearman rank correlation analysis showed a highly statistically significant association between the two methodologies (p < 0.0001). There was no correlation between iNOS expression in either the IMA or SV and the type of diabetes control, or levels of HA1c, glucose, ffa, and CRP. However, there was a significant (p = 0.04) correlation between LDL and iNOS expression in the SV graft, but not the IMA.

CONCLUSIONS

iNOS expression is significantly decreased in the IMA compared to the SV in patients with diabetes mellitus undergoing CABG surgery. The degree of iNOS expression is unrelated to the level of glycemic control at the time of conduit harvest, but is associated with serum LDL levels in the SV, but not in the IMA grafts.

Internal Mammary Artery Grafts Reactivity in Hypertensive Patients: Role of Stretching in Extraendothelial Nitric Oxide

BACKGROUND

The internal mammary artery (IMA) used in bypass coronary surgery remains efficient for a longer time than other grafts, such as saphenous veins; however, its biological characteristics are incompletely defined.

OBJECTIVE

To compare in IMA grafts from hypertensive (HT) and normotensive (NT) patients the presence of endothelium and their functionability, the response to passive stretching and basal tone, the reactivity to exogenous vasoconstrictors, the role of stretching in NO release, and the possible extraendothelial NO source.

METHODS AND RESULTS

IMA rings contractility, presence of endothelium, and nitrite release were studied. An endothelial dysfunction associated with hypertension was found. IMA rings from HT had an impaired response to passive stretching, resulting in a decreased relaxation. All IMA grafts had an increased basal tone demonstrated by relaxation to SNP; however, a lesser response was found in HT. Interestingly, it was demonstrated that NO release was present in IMA grafts, despite an endothelial dysfunction and that stretching increased NO release. This effect was inhibited by Ca2+ -free media, L-NAME and a specific neuronal NO synthase (nNOS) inhibitor. Furthermore, the demonstration of the presence of nNOS in smooth muscle cells by immunohistochemistry supports a role of extraendothelial NO.

CONCLUSION

We demonstrate the impact of hypertension in IMA grafts producing increased endothelial dysfunction, reduced response to passive stretching, increased basal tone, and impaired responsiveness to exogenous vasoconstrictors and NO release. A specific role of stretching in extraendothelial NO release was demonstrated, which may have an important role in the outcome of IMA grafts due to the protective actions of NO, even in the absence of the endothelium.

C-Type Natriuretic Peptide Relaxes Human Coronary Artery Bypass Grafts Preconstricted by Endothelin-1

BACKGROUND

Endothelin is implicated in graft spasm after coronary artery bypass grafting. We assessed reversal by the endothelium-derived vasodilator C-type natriuretic peptide of prior contraction of radial artery and other vessels commonly used for coronary artery bypass surgery.

METHODS

Segments of human radial artery, saphenous vein, and internal mammary artery were mounted in organ baths after removal from patients undergoing cardiac surgery (n = 34; 64 +/- 2 years). Effects of increasing concentrations of C-type natriuretic peptide (with or without aprotinin, 1,000 U/mL) on endothelin-induced contraction were compared with acetylcholine, sodium nitroprusside, and papaverine.

RESULTS

C-type natriuretic peptide relaxed endothelin precontraction in all vessels (F = 17.8, 36.3, and 48.4, respectively; p < 0.001), with maximum relaxations of 44%, 54%, and 66% in saphenous vein, internal mammary artery, and radial artery, respectively. Aprotinin did not affect relaxation to C-type natriuretic peptide. Acetylcholine relaxed the saphenous vein weakly, with maximal relaxation of 9% at 10(-6) M. However, the radial artery and internal mammary artery relaxed strongly to acetylcholine. The highest concentration of papaverine completely relaxed all vessels, but responses were less sensitive than to sodium nitroprusside or acetylcholine.

CONCLUSIONS

C-type natriuretic peptide reverses endothelin-induced constriction in arterial and venous conduits used for coronary artery bypass, particularly the radial artery. Proteolytic breakdown of C-type natriuretic peptide by local vascular enzymes appears of little importance in vitro. This signals the therapeutic potential of using C-type natriuretic peptide as an antagonist of graft vasospasm after coronary artery bypass surgery.

Compromised arterial function in human type 2 diabetic patients

Diabetes is associated with a perturbation of signaling pathways in vascular tissue, which causes vasomotor dysfunction such as hypertension and accelerated atherosclerosis. In the present study, the mechanisms of vasomotor dysfunction, Akt (Thr308 and Ser473) phosphorylation and expression of endothelial NO (nitric oxide) synthase, and inducible NO synthase were investigated in human diabetic internal mammary arteries. The phospho-Akt (Thr308) level in arteries from diabetic patients was reduced to about one-half of the level in nondiabetic patients, suggesting impaired insulin signaling in human diabetic vascular tissue. Augmented vasoconstriction was observed in diabetic arteries, due in part to deficiency of basal and stimulated NO production. This correlated with decreased endothelial NO synthase expression and activity in diabetic vessels. The sensitivity of diabetic vessels to the NO donor, sodium nitroprusside, was reduced as well, suggesting that NO breakdown and/or decreased sensitivity of smooth muscle to NO are also responsible for abnormal vasoconstriction. In addition, the abnormal vasoconstriction in diabetic vessels was not completely abolished in the presence of Nomega-nitro-L-arginine methyl ester, revealing that NO-independent mechanisms also contribute to vasomotor dysfunction in diabetes. In conclusion, diabetes downregulates the Akt-signaling pathway and compromises human arterial function through a decrease in NO availability as well as through NO-independent mechanisms.

Effect of dietary docosahexaenoic acid on the endothelium-dependent vasorelaxation in diabetic rats

1. The aim of the present study was to investigate the responses to acetylcholine (ACh; 3 nmol/L-30 micromol/L) and sodium nitroprusside (SNP; 3 nmol/L-30 micromol/L) of precontracted aortic rings from diabetic rats supplemented with docosahexaenoic acid (DHA). 2. Diabetes was induced by streptozotocin (STZ; 55 mg/kg). Diabetic and sham rats were fed, over a period of 8 weeks, either control diet or a DHA-supplemented diet. Aortic endothelial fatty acid composition was analysed by gas chromatography. The involvement of endothelial-derived nitric oxide (NO) and cyclo-oxygenase (COX) metabolites in response to ACh was assessed using the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (100 micromol/L) and the COX inhibitor indomethacin (1 micromol/L), respectively. 3. The DHA-supplemented diet induced a small increase in n-3 polyunsaturated fatty acids (PUFA; P < 0.001) owing to the incorporation of DHA in the endothelial cells of sham animals (1.6 +/- 0.2% in the DHA group compared with traces in the control group; P < 0.001) and diabetic animals (1.3 +/- 0.2% in the DHA group compared with traces in control group; P < 0.001), without a decrease in n-6 PUFA, despite a small decrease in arachidonic acid content (P < 0.05). Diabetes did not modify the incorporation of DHA in endothelial cells, but did significantly increase the arachidonic acid content (0.6 +/- 0.0 vs 0.4 +/- 0.1% in control group in the STZ and sham groups, respectively; P < 0.001). Acetylcholine-induced relaxation was significantly reduced in STZ groups compared with the sham groups (P < 0.001) and the DHA-supplemented diet did not modify these effects. In contrast, neither the DHA-supplemented diet nor diabetes affected the aortic relaxation induced by SNP. N(G)-Nitro-L-arginine methyl ester strongly inhibited the relaxant effects of ACh in the sham groups (P < 0.001) and abolished ACh-induced relaxation in the STZ groups (P < 0.001). The diet did not modify these effects. In the presence of indomethacin, the relaxation induced by ACh was decreased in the sham groups (P < 0.01), but not in the STZ groups. The DHA-supplemented diet did not have any effect on these responses. 4. In conclusion, these results suggest that, in the present study, the endothelial dysfunction occurring in the rat model of STZ-induced diabetes is associated with modifications of both the synthesis of COX derivatives and NO metabolism and is not affected by dietary supplementation with DHA.

Regular physical activity improves endothelial function in patients with coronary artery disease by increasing phosphorylation of endothelial nitric oxide synthase

BACKGROUND

In stable coronary artery disease (CAD), exercise training has well-documented positive effects on arterial endothelial function. NO derived from endothelial NO synthase (eNOS) is regarded as a protective factor against atherosclerosis. The aim of the present study was to investigate the effects of exercise training on the endothelial function in relation to the expression of eNOS and Akt-dependent eNOS phosphorylation in the left internal mammary artery (LIMA) of patients with stable CAD.

METHODS AND RESULTS

In 17 training patients (T) and 18 control patients (C), endothelium-dependent vasodilation and average peak flow velocity (APV) in response to acetylcholine were measured invasively at study beginning and after 4 weeks in the LIMA. In LIMA tissue sampled during bypass surgery, eNOS expression and content of pospho-eNOS-Ser1177, Akt, and phospho-Akt were determined by Western blot and quantitative reverse transcriptase-polymerase chain reaction. After exercise training, LIMA APV in response to acetylcholine was increased by 56+/-8% (from +48+/-8% at beginning to +104+/-11% after 4 weeks, P<0.001). Patients in T had a 2-fold higher eNOS protein expression (T 1.0+/-0.7 versus C 0.5+/-0.3 arbitrary units, P<0.05) and 4-fold higher eNOS Ser1177-phosphorylation levels in LIMA-endothelium (1.2+/-0.9 versus 0.3+/-0.2 arbitrary units, P<0.01). A linear correlation was confirmed between Akt phosphorylation and phospho-eNOS levels (R=0.80, P<0.05) and between phospho-eNOS and Delta APV (R=0.59, P<0.05).

CONCLUSIONS

Exercise training in stable CAD leads to an improved agonist-mediated endothelium-dependent vasodilatory capacity. The change in acetylcholine-induced vasodilatation was closely related to a shear stress-induced/Akt-dependent phosphorylation of eNOS on Ser1177.