Melatonin attenuates thiocyanate-induced vasoconstriction in aortic rings.

Cigarette smoking not only has a carcinogenic effect but also leads to an increase in arterial blood pressure. Besides its main components, i.e. nicotine, tar, and carbon monoxide, cigarette smoke also contains thiocyanate. Thiocyanate anions (SCN-) arise from the detoxification of hydrogen cyanide and its plasma concentrations were found to correlate significantly with cigarette consumption. There is also evidence that atherosclerotic disease progression is much more rapid when serum SCN- levels are increased. Melatonin, a non-toxic indolamine with various physiologic functions, is believed to protect against inflammatory processes and oxidative stress. It has been demonstrated that melatonin serves as free radical scavenger and represents a potent antioxidant. Therefore, it is believed that melatonin with its atheroprotective effects may be useful either as a sole therapy or in conjunction with others. The aim of this study was to quantify the thiocyanate-induced vasomotor response in aortic tissue and further to examine the potential of melatonin in affecting the generated vasoreactivity. Aortic rings of adult male normotensive Wistar rats were cut into 4-mm rings. Following the administration of thiocyanate in various concentrations, vasomotor response of aortic vessel segments was measured. To assess the effect of melatonin on vasomotor activity, organ bath concentrations were modulated from 60 to 360 pM, which corresponds to physiologic plasma up to the levels of patients with regular oral intake of 3 mg of melatonin as a supplement. Thirty-six rat aortic rings were studied. When exposed to thiocyanate, vessel segments revealed vasoconstriction in a concentration-dependent manner. In rings which were preincubated with melatonin at a concentration of 360 pM, a 56.5% reduction of effect size could be achieved (4.09 ± 1.22 mN versus 9.41 ± 1.74 mN, P < 0.0001). Additionally, administration of 360 pM melatonin at a norepinephrine concentration of 80 mM resulted in a relaxation of 10.9 ± 2.2%. The vasodilatatory effect of melatonin was significantly reduced to 1.3 ± 0.5% when concentration of norepinephrine was doubled (P < 0.002). This study indicates that vessel segments that were exposed to thiocyanate responded with a dose-dependent vasoconstriction. The effect could be markedly attenuated in segments preincubated in melatonin.

Coating of intravascular balloon with paclitaxel prevents constrictive remodeling of the dilated porcine femoral artery due to inhibition of intimal and media fibrosis.

Here we investigated how a coating of intravascular balloon with paclitaxel (drug-coated balloon; DCB, Freeway™) impacted porcine peripheral artery vascular function and remodeling. Domestic swine (n = 54) underwent percutaneous overstretch balloon dilation of femoral and iliac arteries, controlled by angiography and optical coherence tomography (OCT). Paclitaxel tissue uptake was measured at 1 h and 1, 3, and 9 days post-dilation. At these time-points and at 32 ± 2 days, vascular function of the dilated arteries was assessed using the organ chamber model. Neointimal growth and remodeling indices were determined using OCT and histology at 32 ± 2 days. Intima and media fibrosis were quantified by picrosirius red staining. Post-inflation femoral artery tissue drug levels were 460 ± 214, 136 ± 123, 14 ± 6, and 0.1 ± 0.1 ng/mg at 1 h and 1, 3, and 9 days, respectively. Compared to plain balloon, Freeway™ resulted in a significantly smaller neointimal area (P < 0.05), less tunica intima (8.0 ± 5.4 vs 14.2 ± 4.7 %) and media fibrosis (15.6 ± 7.7 vs 24.5 ± 5.4 %), and less femoral artery constrictive remodeling (remodeling index: 1.08 ± 0.08 vs 0.94 ± 0.08). The DCB was associated with significantly increased vasoconstrictor tone and endothelium-dependent vasodilation impairment shortly after post-overstretch injury. Overall, DCB dilation of peripheral arteries resulted in high drug uptake into arterial tissue. Compared with the plain balloon, the DCB was associated with decreased vessel wall fibrosis after balloon overstretch injury, and reduced degrees of constrictive remodeling and neointimal hyperplasia.

Low-level-laser irradiation induces photorelaxation in coronary arteries and overcomes vasospasm of internal thoracic arteries.

BACKGROUND AND OBJECTIVE: As low-level laser irradiation (LLLI) seems to induce vasodilation besides many other known biological effects, LLLI has been increasingly used in therapy of medical conditions with various irradiation parameters. The aim of this study was to investigate the effect of LLLI on photorelaxation of human coronary and internal thoracic arteries (ITA). MATERIALS AND METHODS: Thirty vessel segments of ITA used for routine coronary artery bypass grafting as well as left anterior descending coronary arteries (LAD) of patients undergoing cardiac transplantation were cut into 4-mm rings stored in a modified Krebs-Henseleit solution and evaluated in a myograph. Both types of vessel segments were irradiated by a semiconductor non-thermal GaAs diode laser operating at a wavelength of 680 nm. After precontraction with thromboxane agonist U44619, respective relaxation responses were evaluated and compared to pharmacological dilatation induced by substance P. RESULTS: Mean pharmacological vasodilation by substance P was 22.6 ± 3.3%, 12.8 ± 1.4%, and 20.4 ± 3.2% in macroscopic healthy LAD, LAD with atheromatous plaque, and ITA, respectively. Average photorelaxation induced by LLLI was 16.5 ± 2.0%, 1.9 ± 1.7%, and 6.8 ± 4.7%, accordingly. Vasodilatatory responses induced either by substance P or administration of LLLI were significantly decreased in LAD with atheromatous plaque (P < 0.0001). Vasospasms of ITA segments occurring during experiments could be abandoned when LLLI was administered. CONCLUSION: Macroscopic healthy LAD exposed to LLLI revealed significant photorelaxation. With the administration of LLLI, 73% of the maximal obtainable effect by an endothelium-dependent vasodilator could be reached. Furthermore, LLLI has the potential to overcome vasospasms of ITA.

Redox-sensitive impairment of porcine coronary artery vasodilation by hypochlorite-modified LDL.

Atherosclerotic vascular disease is associated with abnormal vasomotor function and oxidized low density lipoproteins (OxLDL) are believed to play a keyrole therein. Several compounds emerging from LDL lipid peroxidation have been shown to be able to alter vasomotion but the role of oxidized apoB in this process is not fully understood. Myeloperoxidase has been identified in atherosclerotic lesions and hypochlorite produced by this enzyme represents a strong oxidant. LDL oxidation by hypochlorite differs from most other forms of LDL oxidation in that hypochlorite-mediated oxidation shows a predilection for the protein moiety of LDL and does not result in lipid peroxidation. In this work, we use porcine coronary artery segments and show that hypochlorite-oxidized LDL (hyp-OxLDL) are able to impair dilatation induced by substance P in a dose- and modification-dependent way. Treatment of hyp-OxLDL with methionine resulted in quantitative elimination of reactive chloramines in LDL and complete recovery of relaxation. As application of the scavenger receptor antagonist maleylated albumin strongly interferes with the effects of hyp-OxLDL on vasomotion, we conclude that specific binding of hypochlorite-modified apoB is likely to be involved in mediating the observed effects.

Light-induced vasodilation of coronary arteries and its possible clinical implication.

BACKGROUND: Low-level laser therapy and light-emitting diodes (LED) are increasingly used in phototherapy. Their therapeutic effects are at least partly mediated by light-induced vasodilation. The aim of this study was to determine the effect of different light sources on coronary arteries. METHODS: Porcine left coronary arteries were cut into 4-mm rings that were irradiated either by a semiconductor nonthermal gallium-arsenide diode laser or a noncoherent athermic red light source both with the same energy density up to 16 J/cm(2). After precontraction with 9, 11-dideoxy-11α, 9α-epoxymethano-prostaglandin F(2)α, respective relaxation responses were evaluated. The role of endothelium as well as intracellular pathways was investigated. RESULTS: Maximum vasodilation after exposure to laser was observed at 10 J/cm(2) (56.8% ± 1.2%) and decreased to 43.9% ± 2.8% at 16 J/cm(2) (p < 0.003). After adjusting exposure time to achieve equivalent energy densities in the LED group, vessel segments revealed photorelaxation of 52.9% ± 6.5% and 47.5% ± 0.6%, respectively. Vasodilations achieved by either light source were comparable at 10 J/cm(2) (p < 0.574) and 16 J/cm(2) (p < 0.322). Furthermore, vasodilation could be inhibited by administration of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (nitric oxide scavenger) and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (guanocyclase inhibitor) but not with L-nitro-arginine methyl ester or deendothelialization. CONCLUSIONS: Vessels exposed to either light source showed a remarkable as well as comparable photorelaxation at definite energy densities. This effect is mediated by an intracellular nitric oxide-dependent mechanism. As LED sources are of small size, simple, and inexpensive build-up, they may be used during routine coronary artery bypass surgery to ease suturing of anastomosis by target vessel vasodilation.

Time course of endothelium-dependent and -independent coronary vasomotor response to coronary balloons and stents. Comparison of plain and drug-eluting balloons and stents.

OBJECTIVES: This study sought to determine the time dependency of the endothelium-dependent and -independent vascular responses after percutaneous coronary intervention (PCI) with drug-eluting (DEB) or plain balloons, bare-metal (BMS), and drug-eluting (DES) stents, or controls. BACKGROUND: Long-term endothelial dysfunction after DES implantation is associated with delayed healing and late thrombosis. METHODS: Domestic pigs underwent PCI using DEB or plain balloon, BMS, or DES. The dilated and stented segments, and the proximal reference segments of stents and control arteries were explanted at 5-h, 24-h, 1-week, and 1-month follow-up (FUP). Endothelin-induced vasoconstriction and endothelium-dependent and -independent vasodilation of the arterial segments were determined in vitro and were related to histological results. RESULTS: DES- and BMS-treated arteries showed proneness to vasoconstriction 5 h post-PCI. The endothelium-dependent vasodilation was profoundly (p < 0.05) impaired early after PCI (9.8 ± 3.7%, 13.4 ± 9.2%, 5.7 ± 5.3%, and 7.6 ± 4.7% using plain balloon, DEB, BMS, and DES, respectively), as compared with controls (49.6 ± 9.5%), with slow recovery. In contrast to DES, the endothelium-related vasodilation of vessels treated with plain balloon, DEB, and BMS was increased at 1 month, suggesting enhanced endogenous nitric oxide production of the neointima. The endothelium-independent (vascular smooth muscle-related) vasodilation decreased significantly at 1 day, with slow normalization during FUP. All PCI-treated vessels exhibited imbalance between vasoconstriction-vasodilation, which was more pronounced in DES- and BMS-treated vessels. No correlation between histological parameters and vasomotor function was found, indicating complex interactions between the healing neoendothelium and smooth muscle post-PCI. CONCLUSIONS: Coronary arteries treated with plain balloon, DEB, BMS, and DES showed time-dependent loss of endothelial-dependent and -independent vasomotor function, with imbalanced contraction/dilation capacity.

Drug-eluting introducer sheath prevents local peripheral complications: pre-clinical evaluation of nitric oxide-coated sheath.

OBJECTIVES: This study evaluated the protective effect of nitric oxide-coating of introducer sheath on the local complications in juvenile porcine femoral arteries with similar size to human radial arteries. BACKGROUND: Insertion of an introducer sheath induces vasospasm and transient or permanent vessel occlusion of radial arteries. METHODS: Nitric oxide-coated or control introducer sheaths with or without spasmolytic cocktail (control + C-sheath) were inserted into porcine femoral arteries, followed by percutaneous coronary intervention (PCI). The diameter of the femoral artery at the puncture site, distally and proximally, was measured by quantitative angiography. Histopathological and histomorphometric parameters of the femoral arteries were analyzed 1 h or 1 week after PCI. RESULTS: Insertion of femoral sheath led to mild or severe spasms, with significantly higher vessel diameter at the access site (2.69 ± 0.81 mm vs. 1.77 ± 0.77 mm and 1.85 ± 0.66 mm, p < 0.001), and proximal and distal to it, during PCI in the nitric oxide-sheath group versus the control-sheath and control + C-sheath groups, respectively. Immediately following PCI, significantly less luminal thrombosis (12% vs. 33% and 31% of all analyzed segments, p < 0.001) was observed in the nitric oxide-sheath arteries. At 1 week, lower intimal inflammation score (0.43 ± 11 vs. 1.03 ± 0.35 and 1.04 ± 0.32, p < 0.05), less luminal thrombosis (8% vs. 21% and 30% p < 0.05), and smaller intimal hyperplasia (0.31 ± 0.31 mm(2) vs. 0.47 ± 1.00 mm(2) and 0.86 ± 0.82 mm(2), p < 0.05) were observed in NO-sheath arteries at the injury site. CONCLUSIONS: Nitric oxide coating on the introducer sheath prevents local complications during PCI and results in less vascular thrombosis and inflammation at the access site, contributing to patency of the access vessel with similar size to the radial artery.

Delayed recovery of myocardial blood flow after intracoronary stem cell administration.

The aim of the present study was to investigate the changes in absolute myocardial blood flow (AMF) after intracoronary injections of mesenchymal SC (MSC) and compared to controls in closed-chest reperfused acute myocardial infarction (AMI) in pigs. Male MSCs, transiently transfected with Luciferase (Luc-MSC) were delivered (9.7 ± 1.2 x 10(6)) intracoronary in the open infarct-related artery one-week post-AMI in female pigs (group MSC), while saline was injected with the same injection rate in controls (group C). The AMF was measured immediately after, and 3, 12 and 24 h post-intracoronary Luc-MSC or saline injections. In vitro bioluminescence images and quantitative real-time TaqMan PCR measurements were performed to quantify the sex-mismatched MSCs. No difference between the groups was observed regarding the weight, heart rate, blood pressure and global ejection fraction 1-week post-AMI. The baseline AMF were similar in the groups (61.3 ± 15. vs 61.1 ± 12.0 ml/min). AMF was decreased significantly immediately after intracoronary MSC delivery (42.0 ± 12.4 vs 57.7 ± 15.7 ml/min p = 0.013), and remained low at 3 h (40.9 ± 13.4 vs 55.8 ± 4.9 ml/min, p = 0.004), 12 h (43.0 ± 3.7 vs 57.8 ± 5.4 ml/min, p = 0.001) with incomplete recovery at 24 h (47.2 ± 5.5 vs 62.1 ± 14.1 ml/min, p = 0.038) as compared to controls, respectively. In vitro bioluminescence displayed transfected Luc-MSCs along the proximal and mid part of the LAD, with limited number (295 ± 101 sry copied/million cardiac cells) of Y-chromosome-MSCs in the infarcted area. Intracoronary injection of SCs results in immediate decrease of AMF, with delayed recovery. The delivery of the SC into the injured myocardium might be hindered by the altered coronary pressure and flow conditions.

Effect of blower-mister devices on vasoreactivity of coronary artery bypass grafts.

OBJECTIVE: Potential disadvantages, such as lower graft patency rates, that could lead to the need for more subsequent revascularization after off-pump coronary artery bypass grafting are discussed. One mechanism may involve endothelial damage originating from tools to facilitate a bloodless surgical field during anastomosis. We investigated the effect of the use of a blower-mister device on in vitro endothelial and contractile functions of human internal thoracic arteries and greater saphenous veins. METHODS: The distal ends of both bypass graft types were exposed to the air and water stream of the device for 10 minutes, representing the usual time needed for completion of an anastomosis using the off-pump technique. Vessel segments of both groups were cut into 4-mm rings and stored in a modified Krebs-Henseleit solution. Contraction responses to U44619 and relaxation responses to acetylcholine, substance P, papaverine, and nitroprusside were evaluated. RESULTS: Forty-eight artery ring segments from 8 patients were studied. Absolute maximum contraction to U44619 was significantly less in rings subjected to the blower-mister device than in controls (internal thoracic artery: 17.17 ± 2.57 mN vs 8.67 ± 4.54 mN, P < .048; greater saphenous vein: 28.33 ± 9.71 mN vs 11.42 ± 7.97 mN, P < .026). Control rings had significantly greater endothelium-dependent relaxation response to acetylcholine (mean difference 29.2% ± 3.4%, P < .001), whereas those subjected to the blower-mister device had reduced responses. Endothelium-independent relaxation to nitroprusside was not significantly different among the groups. CONCLUSIONS: Vessels exposed to the air and water stream of a blower-mister device showed a reduced vasoreactivity. This effect should be studied further, especially if it contributes to lower graft patency rates in off-pump surgery.

Pinacidil-primed ATP-sensitive potassium channels mediate feedback control of mechanical power output in isolated myocardium of rats and guinea pigs.

We tested the hypothesis, that ATP-sensitive potassium (K(ATP)) channels limit cardiac energy demand by a feedback control of mean power output at increased cardiac rates. We analysed the interrelationships between rising energy demand of adult rat and guinea pig left ventricular papillary muscle and down-regulatory electromechanical effects mediated by K(ATP) channels. Using the K(ATP)-opener pinacidil the stimulation frequency was increased stepwise and the mechanical parameters and action potentials were recorded. Power output was derived from force-length area or force-time integral calculations, respectively. Simultaneously oxygen availability in the preparations was estimated by flavoprotein fluorescence measurements. ADP/ATP ratios were determined by HPLC. We found highly linear relationships between isotonic power output and the effects of pinacidil on isotonic shortening in both rat (r(2)=0.993) and guinea pig muscles (r(2)=0.997). These effects were solely observed for the descending limb of shortening-frequency relationships. In addition, a highly linear correlation between total force-time integral-derived power and pinacidil effects on action potential duration (APD(50), r(2)=0.92) was revealed. Power output became constant and frequency-independent in the presence of pinacidil at higher frequencies. In contrast, the K(ATP)-blocker glibenclamide produced a lengthening of APD(50) and increased force transiently at higher power levels. Pinacidil prevented core hypoxia and a change in ADP/ATP ratio during high frequency stimulation. We conclude, that pinacidil-primed cardiac K(ATP) channels homeostatically control power output during periods of high energy demand. This effect is associated with a reduced development of hypoxic areas inside the heart muscle by adapting cardiac function to a limited energy supply.