Expression and function of angiotensin converting enzyme, chymase, and angiotensin II in the human radial artery and internal thoracic artery

Effect of perivascular low dose ethanol on rat femoral vessels: Preliminary study

Vasospasm is one of the important causes of morbidity in free flap and replantation surgery. In secondary Raynaud's phenomenon, nearly half of the patients experience digital ulceration, pain and loss of function at least once in their lifetime. The aim of this study is to investigate the vasodilation effect of ethanol-mediated chemical denervation on peripheral vessels by topical administration. In this study, 27 Wistar albino male rats weighing 250-300 grams were used. The rats were randomly divided into three groups: saline (group S, n = 8), lidocaine (group L, n = 9) and 96% ethanol (group E, n = 9). According to group, 0.1 mL saline, 0.1 mL lidocaine and 0.1 mL ethanol were applied around the rat femoral neurovascular bundle. After the application, on the 0th day and 3th weeks, femoral artery and vein diameters were measured. After 3. weeks, histopathological samples from femoral artery, vein and nerve were evaluated. On the 0th day, the mean diameter of the femoral artery and vein was similar in group E and L and higher than group S. After three weeks, the vasodilatation effect of ethanol was increased in group E. In Group L and S, the vasodilatation effect was lost. Histopathological examination showed that ethanol significantly caused perivascular inflammation and nerve degeneration compared to other agents and did not cause endothelial damage. Vasodilatation obtained by ethanol is a rapid onset and long-lasting effect. It is also inexpensive and effective for peripheral vasodilatation.

Pharmacokinetics, Safety, and Tolerability of the Novel Chymase Inhibitor BAY 1142524 in Healthy Male Volunteers

The orally available chymase inhibitor BAY 1142524 is currently being developed as a first-in-class treatment for left-ventricular dysfunction after myocardial infarction. Results from 3 randomized, single-center, phase 1 studies in healthy male volunteers examining the safety, tolerability, and pharmacokinetics of BAY 1142524 are summarized. In this first-in-human study, single oral doses of 1-200 mg were administered in fasted state as liquid service formulation or immediate release (IR) tablets. The relative bioavailability and the effect of a high-fat/high-calorie meal were investigated at the 5-mg dose. In a multiple-dose escalation study, doses of 5-50 mg twice daily and 100 mg once daily were given for 5 consecutive days. BAY 1142524 was safe and well tolerated and had no effects on heart rate or blood pressure compared with placebo. BAY 1142524 was absorbed with peak concentration 1-3 hours after administration for IR tablets; it was eliminated from plasma with a terminal half-life of 6.84-12.0 hours after administration of liquid service formulation or IR tablets. Plasma exposures appeared to be dose-linear, with a negligible food effect. There was only low accumulation of BAY 1142524 after multiple dosing. BAY 1142524 exhibited a pharmacokinetic profile allowing for once-daily dosing. The absence of blood pressure effects after administration of BAY 1142524 supports the combination of this novel anti-remodeling drug with existing standard of care in patients with left-ventricular dysfunction after acute myocardial infarction.

Results of endoscopic radial artery harvesting in 1577 patients

OBJECTIVE

We reviewed 1577 consecutive patients undergoing coronary artery bypass grafting (CABG) using endoscopic harvesting of the radial artery (RA) to define our current results.

METHODS

Since 2000, we have performed endoscopic RA harvest on 1577 consecutive patients; 1476 patients had isolated CABG, and 101 patients had CABG and other procedures. The mean ± SD age was 59.4 ± 9.0 years; 80.2% were men and 40% had diabetes mellitus. All data were prospectively collected. All-cause mortality was determined using the Social Security Death Index.

RESULTS

There were nine in-hospital or 30-day deaths, for an operative mortality of 0.57%: mortality was 0.34% in isolated CABG and 3.85% in CABG/combined procedures. The overall estimated Kaplan-Meier survival at 1, 5, and 10 years was 99%, 95%, and 88%. In 37 patients, the RAs were not harvested or were not used for grafting because of a positive Allen test, extensive calcification or dissection, intramural hematoma, and scarring from previous arterial lines or catheterization. During postoperative follow-up, five patients (0.32%) were treated for incisional infection, and there were no ischemic hand complications. Three patients had a perioperative myocardial infarction in the RA graft distribution, and 15 patients had a coronary artery reintervention in the RA graft distribution. Two other patients had a percutaneous coronary intervention of their RAs. The overall RA patency at 10 years was 82%.

CONCLUSIONS

Endoscopic harvest of the RA is an excellent minimally invasive conduit harvesting technique with minimal morbidity.

Elevated plasma chymotrypsin-like protease (chymase) activity in women with preeclampsia

OBJECTIVE

Chymase, a chymotrypsin-like protease, is a non-ACE angiotensin II (Ang II) generating enzyme. We determined if maternal chymotrypsin-like protease/chymase activity was increased in women with preeclampsia (PE).

METHODS

Maternal plasma was extracted from venous blood of healthy nonpregnant women, women with normal and preeclamptic pregnancies. Chymotrypsin-like protease/chymase activity was measured by a colorimetric assay. Maternal vessel chymotrypsin-like protease/chymase expression was examined by immunohistochemistry.

RESULTS

Maternal plasma chymotrypsin-like protease/chymase activity was significantly higher in women with PE than in nonpregnant and normal pregnant women: 0.181 +/- 0.011 vs. 0.097 +/- 0.05 (p < 0.01) and 0.132 +/- 0.013 (p < 0.05) microkat/mL. Chymotrypsin-like protease/chymase activity was markedly reduced 24 hours postpartum in women with PE, p < 0.05. Enhanced chymotrypsin-like protease/chymase expression was observed in vascular endothelium in women with PE compared with those in normal pregnancies.

CONCLUSIONS

Elevated maternal chymotrypsin-like protease/chymase activity and enhanced protease immunostaining in the maternal vessel endothelium may constitute the exacerbated inflammatory state and account for the increased vascular Ang II sensitivity in PE.

Antioxidant Properties of the Internal Thoracic Artery and the Radial Artery

BACKGROUND

The antioxidant properties of blood vessels contribute to their performance and patency of that vessel when used as a bypass conduit. Despite increased use of the radial artery (RA) in recent years, very little is known about its antioxidant properties. We compared the ability of the RA to generate superoxide and assessed its antioxidant protective capacity with that of the internal thoracic artery (ITA).

METHODS

Vascular segments of the ITA and the RA were obtained from patients undergoing coronary artery bypass grafting (CABG) incubated in culture media for 2, 24, 48 and 72 hours. The amount of superoxide generated by each artery, and the deterioration of the endothelial function were assessed by using chemiluminescence (CL) and organ bath techniques. We also assessed the expression, localisation and the activity of superoxide dismutase (SOD) in both arteries; using reverse transcription-polymerase chain reaction (RT-PCR), immunolocalisation techniques and standard biochemical assessment of SOD activity.

RESULTS

Under stress, the RA generated more superoxide (133.6+/-54.7 at 72h vs. 16.8+/-6.4 at 2h; P<0.01) and its endothelial function deteriorated faster (56.3+/-7.3 at 72h vs. 20.2+/-1.5 at 2h; P<0.0001) than that of ITA. Cu/Zn-SOD was found to be prevalent in the endothelium, while Ec-SOD was distributed evenly in the endothelium and media of both arteries. The activity of SOD was less in the RA compared with that of the ITA (510.2+/-219.8 vs. 808.6+/-343.7, respectively; P=0.03).

CONCLUSIONS

Our study shows that the RA is less equipped with an antioxidant protective mechanism compared with the ITA. These findings could partially explain the differential clinical performance of these conduits in CABG.

Diadenosine polyphosphates are selective vasoconstrictors in human coronary artery bypass grafts

Diadenosine polyphosphates (Ap(n)A) are released by degranulating platelets and high, local concentrations may form at sites of platelet activation. Radial artery grafts, now often used alongside the internal mammary artery in coronary artery bypass surgery, are particularly reactive to several vasoconstrictors but the response to Ap(n)A has not been investigated. This study compared the vasoconstrictor activity of Ap(n)A in human radial artery with other vessels commonly used as bypass grafts. Radial artery demonstrated robust concentration-dependent vasoconstriction to Ap(n)A (n=4-6) at concentrations in the micromolar range. In contrast, average responses in internal mammary artery were negligible. Cross-desensitization revealed that Ap(n)A-mediated vasoconstriction occurred via an alphabetamethyleneATP-sensitive receptor. Responses to both Ap(5)A and alphabetamethyleneATP were inhibited by suramin but were insensitive to the P2X(1) receptor antagonist 8,8'-[Carbonylbis(imino-4,1-phenylenecarbonylimino-4,1-phenylenecarbonylimino)]bis-1,3,5-naphthalenetrisulfonic acid (NF279). Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) enhanced responses to Ap(5)A. Similar responses were obtained in saphenous vein. In conclusion, diadenosine polyphosphates contract radial artery and saphenous vein by an as yet uncharacterized P2X receptor but have only limited activity in internal mammary artery. The selective activity of diadenosine polyphosphates in radial artery would implicate them as potential mediators of post-operative contraction in this graft.

Analysis of Vasoreactivity of Isolated Human Radial Artery

Radial artery (RA) is increasingly used as graft for coronary artery bypass grafting due to its good long-term patency. However, the mechanism of peri- and post-operative spasm is still unclear. Because of that, the aim of our study is to analyze the contractility of RA and to determine whether the presence of functional endothelium alters its contractile properties. Contractions of isolated RA rings were provoked by exogenously applied vasoconstrictors or by electrical field stimulation (EFS, 20 Hz). The order of vasoconstrictors potency based on their EC50 values was as follows: angiotensin II > phenylephrine > 5-hydroxytriptamine. Presence of endothelium increased both EC50 and maximal contraction to phenylephrine and angiotensin II, but inhibited reactivity of RA to 5-hydroxytriptamine. Spontaneous rhythmic contractions (SRC, <4 mHz) and EFS-induced contractions of RA are endothelium-independent and weaker than contractions induced by exogenously applied vasoconstrictors. Our study concludes that RA shows marked sensitivity and reactivity to angiotensin II, phenylephrine, and 5-hydroxytriptamine. Further investigations are necessary to answer why angiotensin II and phenylepehrine induce stronger contractions in the presence of endothelium. In addition, SRC as well as contractions of neurogenic origin may take part in developing vascular spasm of RA.

Radial Artery Graft for Coronary Artery Bypass Surgery: Biological Characteristics and Clinical Outcome

The radial artery (RA) is gaining popularity as a bypass conduit for coronary artery bypass grafting, and its impact on clinical practice has been extensively explored. In the present article, we provide a review of postoperative hand circulation, vascular biological characteristics of the RA graft, the efficacy of vasodilator therapies, and mid-term clinical results of use of the RA graft. Fundamental studies revealed excellent vascular biological characteristics of the RA graft as a living arterial conduit, making it almost equivalent to the internal thoracic artery (ITA) graft. Clinical studies have yielded encouraging mid-term results. Most studies reported in favor of the RA graft over the saphenous vein graft with regard to patency rate, freedom from cardiac events, and survival. However, superiority of either the RA or right ITA graft has not been conclusively determined. The long-term results of RA grafts remain unknown, but at present, supplementary use of an RA graft with a left ITA graft appears feasible for CABG.

Expression, localisation and function of ACE and chymase in normal and atherosclerotic human coronary arteries

The expression, localisation and function of enzymes responsible for the local formation of angiotensin II in atherosclerotic and non-atherosclerotic human coronary arteries were studied. Human epicardial coronary arteries expressed mRNA for both ACE and chymase. Immunohistochemical studies revealed that ACE was localised to the vascular endothelium, and to a lesser extent the medial smooth muscle cells, in both large and small arteries. Chymase was detected in both types of vessel but was shown to be associated with mast cells. The contractions to angiotensin I in large arteries were inhibited only by a combination of quinaprilat and soyabean trypsin inhibitor. In the intramyocardial arteries the response to angiotensin I was markedly inhibited in the presence of chymostatin. These findings demonstrate that a dual pathway for the synthesis of angiotensin II is active in diseased and non-diseased coronary arteries.

Effects of cerivastatin on vascular function of human radial and left internal thoracic arteries

BACKGROUND

Statins may enhance vascular function independently of effects on cholesterol. This study investigated the ability of statins to modulate the vascular recovery of arteries used as coronary bypass grafts.

METHODS

Specimens of radial artery and left internal thoracic artery were obtained during coronary artery bypass grafting. The specimens were divided into vascular rings, which were incubated in the absence or presence of cerivastatin (10(-6) mol/L) for either 2 or 24 hours. Using an organ bath technique, endothelial function was examined using acetylcholine (10(-9) to 10(-5) mol/L) after contraction by 3x10(-8) mol/L of endothelin-1.

RESULTS

Time-related endothelial dysfunction was shown in the control group of radial artery but not in the cerivastatin group: maximal endothelium-dependent vasodilation in the control and cerivastatin groups were 56.8% +/- 10.2% and 65.9% +/- 10.1% at 2 hours and 39.4% +/- 4.7% and 68.4% +/- 5.0% (p < 0.01, vs control) at 24 hours, respectively. On the other hand, in the left internal thoracic artery, those in the control and cerivastatin groups were 38.3% +/- 8.2% and 45.0% +/- 5.5% at 2 hours and 38.1% +/- 8.2% and 56.5% +/- 8.8% at 24 hours, respectively (NS).

CONCLUSIONS

In radial artery, cerivastatin significantly preserved endothelium-dependent vasodilation, which diminished with time in the control group. This could have very important implications in the clinical practice of coronary artery bypass grafting.