Dragoslav Nenezic

Mechanisms underlying the vasorelaxation of human internal mammary artery induced by (-)-epicatechin.

Evidences have suggested that flavanol compound (-)-epicatechin is associated with reduced risk of cardiovascular diseases. One of the mechanisms of its cardioprotective effect is vasodilation. However, the exact mechanisms by which (-)-epicatechin causes vasodilation are not yet clearly defined. The aims of the present study were to investigate relaxant effect of flavanol (-)-epicatechin on the isolated human internal mammary artery (HIMA) and to determine the mechanisms underlying its vasorelaxation. Our results showed that (-)-epicatechin induced a concentration-dependent relaxation of HIMA rings pre-contracted by phenylephrine. Among the K(+) channel blockers, 4-aminopyridine (4-AP) and margatoxin, blockers of voltage-gated K(+) (KV) channels, and glibenclamide, a selective ATP-sensitive K(+) (KATP) channels blocker, partly inhibited the (-)-epicatechin-induced relaxation of HIMA, while iberiotoxin, a most selective blocker of large conductance Ca(2+)-activated K(+) channels (BKCa), almost completely inhibited the relaxation. In rings pre-contracted by 80mM K(+), (-)-epicatechin induced partial relaxation of HIMA, whereas in Ca(2+)-free medium, (-)-epicatechin completely relaxed HIMA rings pre-contracted by phenylephrine and caffeine. Finally, thapsigargin, a sarcoplasmic reticulum Ca(2+)-ATPase inhibitor, slightly antagonized (-)-epicatechin-induced relaxation of HIMA pre-contracted by phenylephrine. These results suggest that (-)-epicatechin induces strong endothelium-independent relaxation of HIMA pre-contracted by phenylephrine whilst 4-AP- and margatoxin-sensitive KV channels, as well as BKCa and KATP channels, located in vascular smooth muscle, mediate this relaxation. In addition, it seems that (-)-epicatechin could inhibit influx of extracellular Ca(2+), interfere with intracellular Ca(2+) release and re-uptake by the sarcoplasmic reticulum.

Nicorandil directly and cyclic GMP-dependently opens K+ channels in human bypass grafts.

As we previously demonstrated the role of different K(+) channels in the action of nicorandil on human saphenous vein (HSV) and human internal mammary artery (HIMA), this study aimed to analyse the contribution of the cGMP pathway in nicorandil-induced vasorelaxation and to determine the involvement of cGMP in the K(+) channel-activating effect of nicorandil. An inhibitor of soluble guanylate cyclase (GC), ODQ, significantly inhibited nicorandil-induced relaxation, while ODQ plus glibenclamide, a selective ATP-sensitive K(+) (KATP) channel inhibitor, produced a further inhibition of both vessels. In HSV, ODQ in combination with 4-aminopyridine, a blocker of voltage-gated K(+) (KV) channels, did not modify the concentration-response to nicorandil compared with ODQ, whereas in HIMA, ODQ plus iberiotoxin, a selective blocker of large-conductance Ca(2+)-activated K(+) (BKCa) channels, produced greater inhibition than ODQ alone. We showed that the cGMP pathway plays a significant role in the vasorelaxant effect of nicorandil on HSV and HIMA. It seems that nicorandil directly opens KATP channels in both vessels and BKCa channels in HIMA, although it is possible that stimulation of GC contributes to KATP channels activation in HIMA. Contrary, the activation of KV channels in HSV is probably due to GC activation and increased levels of cGMP.

A rare case of large isolated internal iliac artery aneurysm with ureteral obstruction and hydronephrosis: Compression symptoms are limitation for endovascular procedures

Introduction In this report, we aim to present a rare case of isolated internal iliac artery aneurysm with associated left ureteric obstruction and consequent hydronephrosis. Case report A 66-year-old male patient was admitted for occasional pain in the lower back that appeared one month earlier. CT arteriography revealed isolated internal iliac artery (diameter 99 mm) with ureteral obstruction, hydroureter and left kidney hydronephrosis occurrence. Aneurysm was resected, after six months the patient was doing well. Bearing in mind that 77% of the patients with isolated internal iliac artery have symptoms caused by aneurysmal compression on adjacent organs, we wanted to highlight that despite the amazing expansion of endovascular procedures in the last decades, its therapeutic effect in isolated internal iliac artery’s treatment is to a great extent limited since compression symptoms cannot be solved. Conclusion Open surgery remains the gold standard for isolated internal iliac artery’s treatment considering significant limitations of endovascular procedures due to the inability to eliminate problems caused by compression.

Endothelium-dependent vasorelaxant effect of procyanidin B2 on human internal mammary artery

Abstract The aim of the present study was to investigate and characterize vasorelaxant effect of procyanidin B2 on human internal mammary artery (HIMA) as one of the mechanisms of its protective effect against vascular risk. Procyanidin B2 induced strong concentration‐dependent relaxation of HIMA rings pre‐contracted by phenylephrine. Pretreatment with L‐NAME, a NO synthase inhibitor, hydroxocobalamin, a NO scavenger, and ODQ, an inhibitor of soluble guanylate cyclase, significantly inhibited procyanidin B2‐induced relaxation of HIMA, while indomethacin, a cyclooxygenase inhibitor, considerably reduced effects of low concentrations. Among K+ channel blockers, iberiotoxin, a selective blocker of large conductance Ca2+‐activated K+ channels (BKCa), abolished procyanidin B2‐induced relaxation, glibenclamide, a selective ATP‐sensitive K+(KATP) channels blocker, induced partial inhibition, while 4‐aminopyridine, a blocker of voltage‐gated K+(KV) channels, and TRAM‐34, an inhibitor of intermediate‐conductance Ca2+‐activated K+(IKCa) channels, slightly reduced maximal relaxation of HIMA. Further, procyanidin B2 relaxed contraction induced by phenylephrine in Ca2+‐free Krebs solution, but had no effect on contraction induced by caffeine. Finally, thapsigargin, a sarcoplasmic reticulum Ca2+‐ATPase inhibitor, significantly reduced relaxation of HIMA produced by procyanidin B2. These results demonstrate that procyanidin B2 produces endothelium‐dependent relaxation of HIMA pre‐contracted by phenylephrine. This effect is primarily the result of an increased NO synthesis and secretion by endothelial cells and partially of prostacyclin, although it involves activation of BKCa and KATP, as well as KV and IKCa channels in high concentrations of procyanidin B2.

In situ revascularisation for femoropopliteal graft infection: ten years of experience with silver grafts:

Purpose The purpose of this study was to analyze clinical outcome of patients for femoropopliteal graft infection who were treated by in situ reconstruction with a silver-coated prosthesis. Basic methods From December 2001 to December 2011, 27 patients were treated for femoropopliteal graft infection. Twenty patients (74%) were male and seven (26%) were female. Mean age was 65 years. The primary endpoint was recurrence of infection. Secondary endpoints were early and late mortality and morbidity, primary graft patency, major amputation rates and patient survival. Principal findings Early reinfection occurred in 11% and late in 8% of patients. Perioperative mortality was 7% and late was 4%. Above-knee amputation was performed in 4% of patients during early postoperative course and in 12% of patients during follow-up. Early and late graft patency was 96% and 72%, respectively. Conclusions Results of in situ implantation of silver-coated grafts for femoropopliteal prosthesis infection are according to our opinion acceptable, but the risk of reinfection remains.

Different Potassium Channels are Involved in Relaxation of Rat Renal Artery Induced by P1075

The ATP‐sensitive K+ channels opener (KATPCO), P1075 [N‐cyano‐N′‐(1,1‐dimethylpropyl)‐N″‐3‐pyridylguanidine], has been shown to cause relaxation of various isolated animal and human blood vessels by opening of vascular smooth muscle ATP‐sensitive K+ (KATP) channels. In addition to the well‐known effect on the opening of KATP channels, it has been reported that vasorelaxation induced by some of the KATPCOs includes some other K+ channel subtypes. Given that there is still no information on other types of K+ channels possibly involved in the mechanism of relaxation induced by P1075, this study was designed to examine the effects of P1075 on the rat renal artery with endothelium and with denuded endothelium and to define the contribution of different K+ channel subtypes in the P1075 action on this blood vessel. Our results show that P1075 induced a concentration‐dependent relaxation of rat renal artery rings pre‐contracted by phenylephrine. Glibenclamide, a selective KATP channels inhibitor, partly antagonized the relaxation of rat renal artery induced by P1075. Tetraethylammonium (TEA), a non‐selective inhibitor of Ca2+‐activated K+ channels, as well as iberiotoxin, a most selective blocker of large‐conductance Ca2+‐activated K+ (BKCa) channels, did not abolish the effect of P1075 on rat renal artery. In contrast, a non‐selective blocker of voltage‐gated K+ (KV) channels, 4‐aminopyridine (4‐AP), as well as margatoxin, a potent inhibitor of KV1.3 channels, caused partial inhibition of the P1075‐induced relaxation of rat renal artery. In addition, in this study, P1075 relaxed contractions induced by 20 mM K+, but had no effect on contractions induced by 80 mM K+. Our results showed that P1075 induced strong endothelium‐independent relaxation of rat renal artery. It seems that KATP, 4‐AP‐ and margatoxin‐sensitive K+ channels located in vascular smooth muscle mediated the relaxation of rat renal artery induced by P1075.

Images in vascular medicine: Giant aneurysm of the aberrant right subclavian artery (arteria lusoria)

A 68-year-old man presented with a history of progressively worsening dysphagia, excessive weight loss of more than 30 kg during the preceding 6 months, and retrosternal discomfort. During the previous 2 weeks, any attempt at food or liquid intake provoked vomiting. After gastroenterological evaluation and endoscopy identified pulsating extraluminal compression on the esophagus, he was referred to a vascular surgeon for further evaluation. The patient was hypertensive without any history of ischemic heart disease. A contrast-enhanced CT scan of the mediastinum (Panel A) revealed a giant fusiform aneurysm measuring approximately 10 cm in diameter which contained extensive mural thrombus. The aneurysm compressed the trachea (Panel B; arrow 1), and almost completely obliterated the esophagus (Panel B; arrow 2). CT angiography (Panel C) revealed the aneurysm of an Panel A

(−)-Epicatechin-induced relaxation of isolated human saphenous vein: Roles of K+ and Ca2+ channels

In this study, we aimed to investigate relaxant effect of flavanol (−)‐epicatechin on the isolated human saphenous vein (HSV), as a part of its cardioprotective action, and to define the mechanisms underlying this vasorelaxation. (−)‐Epicatechin induced a concentration‐dependent relaxation of HSV pre‐contracted by phenylephrine. Among K+ channel blockers, 4‐aminopyridine, margatoxin, and iberiotoxin significantly inhibited relaxation of HSV, while glibenclamide considerably reduced effects of the high concentrations of (−)‐epicatechin. Additionally, (−)‐epicatechin relaxed contraction induced by 80 mM K+, whereas in the presence of nifedipine produced partial relaxation of HSV rings pre‐contracted by phenylephrine. In Ca2+‐free solution, (−)‐epicatechin relaxed contraction induced by phenylephrine, but had no effect on contraction induced by caffeine. A sarcoplasmic reticulum Ca2+‐ATPase inhibitor, thapsigargin, significantly reduced relaxation of HSV produced by (−)‐epicatechin. These results demonstrate that (−)‐epicatechin produces endothelium‐independent relaxation of isolated HSV rings. Vasorelaxation to (−)‐epicatechin probably involves activation of 4‐aminopyridine‐ and margatoxin‐sensitive KV channels, BKCa channels, and at least partly, KATP channels. In addition, not only the inhibition of extracellular Ca2+ influx, but regulation of the intracellular Ca2+ release, via inositol‐trisphosphate receptors and reuptake into sarcoplasmic reticulum, via stimulation of Ca2+‐ATPase, as well, most likely participate in (−)‐epicatechin‐induced relaxation of HSV.

Scoring system to predict early carotid restenosis after eversion endarterectomy by analysis of inflammatory markers

Background: Inflammation is one of the mechanisms that leads to carotid restenosis (CR). The aim of this study was to examine the influence of increased values of inflammation markers (high‐sensitivity C‐reactive protein [hs‐CRP], C3 complement, and fibrinogen) on CR development after eversion carotid endarterectomy (CEA). Methods: A consecutive 300 patients were included in the study, in which eversion CEA was performed between March 1 and August 1, 2010. Demographic data, atherosclerosis risk factors, comorbidities, and ultrasound plaque characteristics were listed in relation to potential risk factors for CR. Serum concentrations of hs‐CRP, fibrinogen, and C3 complement were taken just before surgery (6 hours); 48 hours after CEA; and during regular checkups at 1 month, 6 months, 1 year, and 2 years. An “inflammatory score” was also created, which consisted of six predictive values of inflammatory markers (hs‐CRP just before and just after CEA, fibrinogen just before and just after CEA, and C3 complement just before and just after CEA) with a maximum score of 6 and a minimum score of 0. At every follow‐up visit to the outpatient clinic, ultrasound assessment of the carotid artery for restenosis was done. Results: Our results showed an increased risk of early CR within 1 year in patients with increased hs‐CRP before CEA (6 hours) and increased fibrinogen 48 hours after surgery and in patients not taking aspirin after CEA. Sex was determined to be an independent predictor of CR, with female patients having a higher risk (P = .002). Male patients taking aspirin with an inflammatory score >2 had an increased risk for restenosis compared with male patients with inflammatory score <2. Not taking aspirin after CEA and fibrinogen (48 hours) were the strongest predictors, and the Fisher equation incorporating these predictors was used to predict CR. A computer program was created to calculate whether the patient was at high or low risk for CR by selecting whether the patient was taking aspirin (yes or no) and whether fibrinogen was increased 48 hours after CEA (yes or no) and to display the recommended therapeutic algorithm consisting of aspirin, clopidogrel, cilostazol, and statins. Conclusions: Increased hs‐CRP before CEA, increased fibrinogen 48 hours after CEA, and not taking aspirin were the main predictors of early CR. With the clinical implementation of the Fisher equation, it is possible to identify patients at high risk for early CR and to apply an aggressive therapeutic algorithm, finally leading to a decreased CR rate.

NEW DRUGS FOR THE TREATMENT OF DYSLIPIDEMIA

Dyslipidemia is the leading risk factor for the development of atherosclerosis and associated consequences, such as coronary heart disease, ischemic cerebrovascular and peripheral vascular disease. These diseases are the major cause of mortality in the world and in Europe as well, where they are responsible for around 45% of all deaths. Treatment of dyslipidemia includes the use of statins, ezetimibe, fibrates, niacin, bile acids sequestrants and omega-3 fatty acids. Although statins play the major role in dyslipidemia treatment by reducing the risk of cardiovascular (CV) events by 30%, there is a need for additional new drugs that reduce the residual risk even more. PCSK9 inhibitors, apolipoprotein B (apoB) synthesis inhibitors, MTP inhibitors and CETP inhibitors are already approved for the specific indications, or are in the advanced stages of clinical investigation. Two PCSK9 inhibitors, alirocumab and evolocumab are approved for use in combination with statins for the treatment of heterozygous familial hypercholesterolemia (FH), but also in patients with clinical atherosclerotic CV diseases who require additional low-density lipoprotein cholesterol (LDL-C) level reduction. In addition, evolocumab is approved for use in patients with homozygous FH. Mipomersen, apoB synthesis inhibitor, lomitapide, and oral MTP inhibitor are currently approved in the treatment of patients with homozygous FH as an adjunct to the maximum tolerated doses of statins and other lipidlowering drugs. Although the new lipid-lowering agents produce significant LDL-C level reduction, more clinical studies are necessary to confirm their efficacy and safety in dyslipidemia treatment. Acta Medica Medianae 2018;57(1):54-63.