Zoltán Galajda

Red Cells, Hemoglobin, Heme, Iron, and Atherogenesis

Objective—We investigated whether red cell infiltration of atheromatous lesions promotes the later stages of atherosclerosis. Methods and Results—We find that oxidation of ferro (FeII) hemoglobin in ruptured advanced lesions occurs generating ferri (FeIII) hemoglobin and via more extensive oxidation ferrylhemoglobin (FeIII/FeIV=O). The protein oxidation marker dityrosine accumulates in complicated lesions, accompanied by the formation of cross-linked hemoglobin, a hallmark of ferrylhemoglobin. Exposure of normal red cells to lipids derived from atheromatous lesions causes hemolysis and oxidation of liberated hemoglobin. In the interactions between hemoglobin and atheroma lipids, hemoglobin and heme promote further lipid oxidation and subsequently endothelial reactions such as upregulation of heme oxygenase-1 and cytotoxicity to endothelium. Oxidative scission of heme leads to release of iron and a feed-forward process of iron-driven plaque lipid oxidation. The inhibition of heme release from globin by haptoglobin and sequestration of heme by hemopexin suppress hemoglobin-mediated oxidation of lipids of atheromatous lesions and attenuate endothelial cytotoxicity. Conclusion—The interior of advanced atheromatous lesions is a prooxidant environment in which erythrocytes lyse, hemoglobin is oxidized to ferri- and ferrylhemoglobin, and released heme and iron promote further oxidation of lipids. These events amplify the endothelial cell cytotoxicity of plaque components.

The diagnosis, morphological particularities, and surgical technique in a case of intravascular leiomyoma extended to the right heart chambers

Intravenous leiomyoma is a benign smooth muscle cell tumor of uterine origin that may grow into the pelvic veins and the inferior vena cava. It usually affects premenopausal women and the majority (90%) are parous. Because cardiac involvement is present in up to 10% of cases, it may be misdiagnosed as a primary cardiac tumor or a venous thrombus-in-transit. We describe a case of intravascular leiomyomatosis with cardiac extension and the morphological particularities of the removed tumor.

Minimally invasive harvesting of the radial artery as a coronary artery bypass graft.

We harvested radial arteries for coronary artery bypass procedures with a minimally invasive technique for 40 patients through two transverse 2-cm incisions in the forearm. With the help of instruments developed by us, the operation can be performed either with the use of an endoscope or with the naked eye. There were no complications in the forearm or the hand. The condition of the intima of the arterial grafts was checked by transmission and scanning electron microscopic methods and was found to be intact.

Various clinical scenarios leading to development of the string sign of the internal thoracic artery after coronary bypass surgery: the role of competitive flow, a case series.

BackgroundThe left internal mammary artery (LIMA) is the choice for grafting of the left anterior descending coronary artery (LAD). One possible mechanism of the rare graft failure involve the presence of competitive flow.Method105 patients who had undergone coronary bypass grafting between 1998 and 2000 were included in this observational study. The recatheterizations were performed 28 months after the operations. The rate of patency the LIMA grafts was determined, and the cases with graft failure were analyzed.ResultsThe LIMA graft was patent in 99 patients (94%). Six patients (6%) exhibited diffuse involution of the graft (string sign). The string sign was always associated with competitive flow as the basis of the LIMA graft involution. In one case quantitative re-evaluation of the preoperative coronary angiography revealed merely less than 50% diameter stenosis on the LAD with a nonligated side-branch of the LIMA. At recatheterization in two patients the pressure wire measurements demonstrated only a non-significant decrease of the fractional flow reserve (0.83 and 0.89), despite the 53% and 57% diameter stenosis in the angiogram. Another patient displayeda significant regression of the LAD lesion between the pre- and postoperative coronary angiography (from 76% to 44%) as the cause of the development of the competitive flow. In one instance, a radial artery graft on the LAD during a redo bypass operation resulted in competitive flow in the radial graft due to the greater diameter than that of the LIMA. In a further patient, competitive flow developed from a short sequential part of the LIMA graft between the nonsignificantly stenosed diagonal branch and the LAD, with involution of the main part of the graft to the diagonal branch.ConclusionsThe most common cause of the development of the string sign of a LIMA graft due to competitive flow is overassessment of the lesion of the LAD. Regression of a previous lesion or some other neighboring graft can also cause the phenomenon.

Protein kinase C contributes to the maintenance of contractile force in human ventricular cardiomyocytes

Prolonged Ca2+ stimulations often result in a decrease in contractile force of isolated, demembranated human ventricular cardiomyocytes, whereas intact cells are likely to be protected from this deterioration. We hypothesized that cytosolic protein kinase C (PKC) contributes to this protection. Prolonged contracture (10 min) of demembranated human cardiomyocytes at half-maximal Ca2+ resulted in a 37 ± 5% reduction of active force (p < 0.01), whereas no decrease (2 ± 3% increase) was observed in the presence of the cytosol (reconstituted myocytes). The PKC inhibitors GF 109203X and Gö 6976 (10μmol/liter) partially antagonized the cytosol-mediated protection (15 ± 5 and 9 ± 2% decrease in active force, p < 0.05). Quantitation of PKC isoform expression revealed the dominance of the Ca2+-dependent PKCα over PKCδ and PKCϵ (189 ± 31, 7 ± 3, and 7 ± 2 ng/mg protein, respectively). Ca2+ stimulations of reconstituted human cardiomyocytes resulted in the translocation of endogenous PKCα, but not PKCβ1, δ, and ϵ from the cytosol to the contractile system (PKCα association: control, 5 ± 3 arbitrary units; +Ca2+, 39 ± 8 arbitrary units; p < 0.01, EC50,Ca = 645 nmol/liter). One of the PKCα-binding proteins were identified as the thin filament regulatory protein cardiac troponin I (TnI). Finally, the Ca2+-dependent interaction between PKCα and TnI was confirmed using purified recombinant proteins (binding without Ca2+ was only 28 ± 18% of that with Ca2+). Our data suggest that PKCα translocates to the contractile system and anchors to TnI in a Ca2+-dependent manner in the human heart, contributing to the maintenance of contractile force.

Radial artery grafts: surgical anatomy and harvesting techniques

At present more and more surgeons are using the radial artery as a graft for coronary bypass. The statistics until now show that the patency of radial grafts exceeds that of the venous grafts used up to the present. In our department we used radial artery for coronary bypass in 515 patients between January 1990 and December 2000. The radial artery harvesting with minimally invasive technique developed by us was applied in 50 of these patients while the rest were performed with the traditional method. No ischemic complications occurred in forearm or hand following either of the methods. One year after the operation we carried out control examinations on 197 consecutive patients. Our surveys showed that following the traditional technique of radial artery harvesting neurological complications (temporary dysaesthesia) occurred in 16.5% of the patients. After the minimally invasive procedure, temporary dysaesthesia occurred in one case (2%). These complaints ceased within 1-12 months (an average of 3.8 months). Definitive neurological complications did not occur in any of the patients. In summation, we experienced that both operating techniques can be safely applied. The proportion of temporary neurological complications is higher following the traditional procedure, therefore, further development and application of the minimally invasive procedure should be considered.

Histamine and H1 -histamine receptors faster venous circulation.

The study has analysed the action of histamine in the rabbit venous system and evaluated its potential role in contraction during increased venous pressure. We have found that a great variety exists in histamine sensitivity and H1‐histamine receptor expression in various types of rabbit veins. Veins of the extremities (saphenous vein, femoral vein, axillary vein) and abdomen (common iliac vein, inferior vena cava) responded to histamine by a prominent, concentration‐dependent force generation, whereas great thoracic veins (subclavian vein, superior vena cavas, intrathoracic part of inferior vena cava) and a pelvic vein (external iliac vein) exhibited slight sensitivity to exogenous histamine. The lack of reactivity to histamine was not due to increased activity of nitric oxide synthase (NOS) or heme oxygenase‐1. H1‐histamine receptor expression of veins correlated well with the histamine‐induced contractions. Voltage‐dependent calcium channels mediated mainly the histamine‐induced force generation of saphenous vein, whereas it did not act in the inferior vena cava. In contrast, the receptor‐operated channels were not involved in this response in either vein. Tyrosine phosphorylation occurred markedly in response to histamine in the saphenous vein, but not in the inferior vena cava. Histamine induced a prominent ρ kinase activation in both vessels. Protein kinase C and mitogen‐activated protein kinase (MAPK) were not implicated in the histamine‐induced intracellular calcium sensitization. Importantly, transient clamping of the femoral vein in animals caused a short‐term constriction, which was inhibited by H1‐histamine receptor antagonist in vivo. Furthermore, a significantly greater histamine immunopositivity was detected in veins after stretching compared to the resting state. We conclude that histamine receptor density adapts to the actual requirements of the circulation, and histamine liberated by the venous wall during increased venous pressure contributes to the contraction of vessels, providing a force for the venous return.

Hand perfusion with 99mTc-HSA in patients expecting to undergo coronary bypass surgery: Elaboration of a new complex diagnostic protocol for the safe removal of a radial artery graft

BackgroundThe Allen test is used worldwide for radial artery graft removal. The postoperative examination of our patients’ hand function and circulation proved that beside the transient neurological complications chronic hand circulatory disorders may arise. AimTo develop a non-invasive method suitable for an objective evaluation of the hands circulation to make it possible to use radial arteries safely for the revascularization of coronary arteries. MethodsWe examined 35 patients. After selective compression of the radial and ulnar arteries of both hands, we injected 400 MBq 99mTc-HSA intravenously and acquired 240 images, each of 1 s. After 30 s we released the ulnar artery first, and after 120 s the radial artery, too. Then computer analysis was performed. ResultsThe patients could be divided into two groups. In the majority of them, releasing only the ulnar artery resulted in a good circulation of the fingers. It meant that the time–activity curve rapidly reached its maximum, and the activity did not change even after releasing the radial artery. In a smaller proportion of the patients the activity of the fingers increased only slowly, and did not reach a plateau even after 30 s. Following the release of the radial artery a further increase in the activity could be observed. We assume that the latter patient group is at risk of consequent circulatory disorder of the fingers after the removal of the radial artery, whereas in the former group the artery could be removed safely. ConclusionsHand perfusion with 99mTc-HSA is useful in patients selected for coronary bypass operations, so we recommend the introduction of this method as a routine examination before the removal of the radial artery in patients with an abnormal Allen test.

Approximation of A1 adenosine receptor reserve appertaining to the direct negative inotropic effect of adenosine in hyperthyroid guinea pig left atria

Hyperthyroidism elevates cardiovascular mortality by several mechanisms, including increased risk of ischemic heart disease. Therefore, therapeutic strategies, which enhance tolerance of heart to ischemia-reperfusion injury, may be particularly useful for hyperthyroid patients. One promising cardioprotective approach is use of agents that cause (directly or indirectly) A1 adenosine receptor (A1 receptor) activation, since A1 adenosinergic pathways initiate protective mechanisms such as ischemic preconditioning. However, previously we found great A1 receptor reserve for the direct negative inotropic effect of adenosine in isolated guinea pig atria. This phenomenon suggests that weakening of atria is a possible side effect of A1 adenosinergic stimulant agents. Thus, the goal of the present investigation was to explore this receptor reserve in hyperthyroidism. Our recently developed method was used that prevents the rapid intracellular elimination of adenosine, allowing sufficient time for exogenous adenosine administered for the generation of concentration-response curves to exert its effect. Our method also allowed correction for the bias caused by the consequent endogenous adenosine accumulation. Our results demonstrate that thyroxine treatment does not substantially affect the A1 receptor reserve for the direct negative inotropic effect of adenosine. Consequently, if an agent causing A1 receptor activation is administered for any indication, the most probable adverse effect affecting the heart may be a decrease of atrial contractility in both eu- and hyperthyroid conditions.

The peroxynitrite evoked contractile depression can be partially reversed by antioxidants in human cardiomyocytes

In this study, we aimed to determine the contribution of peroxynitrite‐dependent sulfhydryl group (SH) oxidation to the contractile dysfunction in permeabilized left ventricular human cardiomyocytes using a comparative approach with the SH‐oxidant 2,2′‐dithiodipyridine (DTDP). Additionally, different antioxidants: dithiothreitol (DTT), reduced glutathione (GSH) or N‐acetyl‐L‐cysteine (NAC) were employed to test reversibility. Maximal isometric active force production (Fo) and the maximal turnover rate of the cross‐bridge cycle (ktr,max) illustrated cardiomyocyte mechanics. SH oxidation was monitored by a semi‐quantitative Ellman’s assay and by SH‐specific protein biotinylation. Both peroxynitrite and DTDP diminished Fo in a concentration‐dependent manner (EC50,peroxynitrite= 49 μM; EC50,DTDP= 2.75 mM). However, ktr,max was decreased only by 2.5‐mM DTDP, but not by 50 μM peroxynitrite. The diminution of Fo to zero by DTDP was paralleled by the complete elimination of the free SH groups, while the peroxynitrite‐induced maximal reduction in free SH groups was only to 58 ± 6% of the control (100%). The diminutions in Fo and free SH groups evoked by 2.5‐mM DTDP were completely reverted by DTT. In contrast, DTT induced only a partial restoration in Fo (ΔFo,:∼13%; P < 0.05) despite full reversion in protein SH content after 50 μM peroxynitrite. Although, NAC or DTT were equally effective on Fo after peroxynitrite exposures, NAC or GSH did not restore Fo or ktr,max after DTDP treatments. Our results revealed that the peroxynitrite‐evoked cardiomyocyte dysfunction has a small, but significant component resulting from reversible SH oxidation, and thereby illustrated the potential benefit of antioxidants during cardiac pathologies with excess peroxynitrite production.