Idiopathic arterial calcification in infancy

Three fatal cases of idiopathic arterial calcification in infancy are reported. The infants' ages ranged from 9 days to 3 months. Death was due to cardiac failure; in two cases caused by myocardial ischaemia, and in one by pulmonary hypertension. The histological findings are described and aetiology of the condition is discussed.     

Protective effects of N-acetylcysteine on myocardial injury induced by hindlimb ischaemia–reperfusion: a histological study in a rat model

This study evaluated the effects of N-acetylcysteine as a scavenger of radical oxygen species on myocardial injury as a remote organ after skeletal muscle ischaemia–reperfusion. Twenty male Wistar rats were allocated randomly into two experimental groups: ischaemia–reperfusion and ischaemia–reperfusion?+?N-acetylcysteine. All animals underwent 2 h of ischaemia by occlusion of the femoral artery followed by 24 h of reperfusion. Rats treated with N-acetylcysteine were given an intravenous dose of 150 mg/kg, immediately before reperfusion. After the reperfusion period, animals were euthanized and hearts harvested for histopathological analysis under light microscopy. In the ischaemia–reperfusion group, tissues showed histological changes with interstitial oedema, neutrophil infiltration and adhesion of neutrophils to the endothelium, haemorrhage and coagulative necrosis. Histopathologically, there was a significant difference (P?N-acetylcysteine significantly decreased myocardial injury induced by skeletal muscle ischaemia–reperfusion according to our histological findings.     

Cardiac accumulation of citrate during brief myocardial ischaemia and reperfusion in the pig in vivo

Citrate is a key intermediate in energy metabolism and an inhibitor of phosphofructokinase of the glycolytic pathway. During myocardial ischaemia glycolysis is the main source of cardiac ATP. The aim of the present study was to determine if myocardial ischaemia and reperfusion alter cardiac tissue levels of citrate. Open-chest, anaesthetized pigs were subjected to 10 min of regional myocardial ischaemia by occlusion of the left anterior descending coronary artery, with and without reperfusion, and to 10 min of global ischaemia by circulatory arrest. Citrate, amino acids, glucose and NH₃ were measured in biopsies. Ischaemia, whether regional or global, caused a 60–70% increase in tissue levels of citrate. During 1 min of reperfusion following regional ischaemia the level of citrate increased 460%, to ≈600 nmol g^?1 wet weight. The level of glutamate decreased by 20–33% (corresponding to 1300–2200 nmol g^?1 wet weight), indicating net consumption of this amino acid during ischaemia. The level of aspartate decreased 50% indicating conversion of aspartate to oxaloacetate for the synthesis of citrate. Theoretically, the accumulation of myocardial citrate during brief ischaemia and early reperfusion is large enough to significantly inhibit phosphofructokinase activity and could therefore affect the ability of the myocardium to increase the glycolytic rate in response to ischaemia. This could, however, be partly compensated by the metabolism of myocardial glutamate.     

Necropsy study of association between sudden death and cardiac enzymes.

AIMS: To determine if cardiac enzymes measured at necropsy could be used to predict early myocardial infarction. METHODS: Cardiac enzyme activities were measured in body fluids at necropsy. Coroners' necropsies were grouped by gross and microscopic findings into cases of definite myocardial infarction, cases with occlusive coronary artery atheroma but no identifiable myocardial infarction, and non-cardiac cases. Pericardial fluid, peripheral venous blood, and blood from the right atrium were collected. Total creatine phosphokinase, creatine phosphokinase isoenzymes, aspartate aminotransferase and hydroxybutarate dehydrogenase activities were measured and the results analysed by logistic regression. RESULTS: The values of creatine phosphokinase and its isoenzymes were raised in those who had died of cardiac disease and were most discriminatory. Cases of early myocardial infarction without evidence of infarction on routine histological examination could be identified from enzyme activities. CONCLUSIONS: Measurement of cardiac enzymes in blood and pericardial fluid at necropsy can provide valuable additional information in cases of sudden death as a result of myocardial ischaemia which have occurred before macroscopic or microscopic evidence of myocardial infarction.     

Correlation of morphological variables in the coronary atherosclerotic plaque with clinical patterns of ischemic heart disease

The frequency and severity of "morphological" variables (fibrosis, proteoglycan accumulation, atheroma, intimal vascularization, calcification, acute intimal hemorrhage, and both adventitial and intimal lymphoplasmacellular infiltrates) in atherosclerotic plaques were related to plaque type, percentage of lumen reduction, plaque length, and intimal and medial thickness in 3,640 coronary artery sections sampled at the site of maximal lumen reduction in 8 selected segments from 100 cases of acute myocardial infarct, 50 of chronic angina, 208 of unexpected sudden coronary death with or without prodromata, and from 97 normal subjects dying accidentally. Morphological variables were occasionally observed in 1,519 sections with no lumen reduction. They were found only in sections from ischemic patients. With increasing luminal stenosis and intimal thickness, progression of the coronary plaque seemed to start as a fibrous change followed by proteoglycan accumulation in the deeper portion of the fibrous intima. Proteoglycan deposits appeared as a recurrent phenomenon. In them, atheroma or calcification develop. Intimal hemorrhage was a less frequent variable. It was found mainly in a vessel supplying an infarcted area. Lymphoplasmacellular inflammation correlated mainly with proteoglycan accumulation and atheroma, both showing a parallel increase with increasing intimal thickness and lumen reduction. No correlation was found between plaque variables and sex, age, heart weight, and infarct size. Significant variations in the distribution of plaque variables were observed among hearts of patients in the ischemic groups and between them and controls. In particular, inflammatory reaction was significantly more frequent and severe in ischemic groups than in controls, independent of the degree of coronary stenosis. Coagulative myocytolysis (contraction band necrosis), found in the majority of ischemic patients, correlated with the inflammatory reaction in supplying vessels. A peculiar tropism of mononuclear cell infiltrates for adventitial nerve structures was found. As a result, we question whether this inflammation may trigger coronary spasm and/or coagulative myocytolysis ("active" plaque vs "inactive" plaque).     

Possible connection between milk and coronary heart disease: the calcium hypothesis

Excessive milk consumption may adversely affect the circulation on account of the high calcium content of milk and because lactose promotes the intestinal absorption of calcium. Excessive calcium intake may cause calcification and rigidification of the large elastic arteries, which could be an important factor in causing myocardial ischaemia.The calcium hypothesis can throw light on some puzzling peculiarities of arterial disease, for instance the changing ratio of male and female mortality rates in various age groups, the apparently beneficial effect of a warm environment and the entirely different worldwide distribution of coronary heart disease and strokes.     

A Chlamydia pneumoniae Component That Induces Macrophage Foam Cell Formation Is Chlamydial Lipopolysaccharide

Chlamydia pneumoniae infection is associated with atherosclerotic heart and vessel disease, but a causal relationship between this pathogen and the disease process has not been established. Recently, it was reported that C. pneumoniae induces human macrophage foam cell formation, a key event in early atheroma development, suggesting a role for the organism in atherogenesis. This study further examines C. pneumoniae-induced foam cell formation in the murine macrophage cell line RAW-264.7. Infected RAW cells accumulated cholesteryl esters when cultured in the presence of low-density lipoprotein in a manner similar to that described for human macrophages. Exposure of C. pneumoniae elementary bodies to periodate, but not elevated temperatures, inhibited cholesteryl ester accumulation, suggesting a role for chlamydial lipopolysaccharide (cLPS) in macrophage foam cell formation. Purified cLPS was found to be sufficient to induce cholesteryl ester accumulation and foam cell formation. Furthermore, the LPS antagonist lipid X inhibited C. pneumoniae and cLPS-induced lipid uptake. These data indicate that cLPS is a C. pneumoniae component that induces macrophage foam cell formation and suggest that infected macrophages chronically exposed to cLPS may accumulate excess cholesterol to contribute to atheroma development.     

Localisation of myocardial ischaemia from the magnetocardiogram using current density reconstruction method: computer simulation study

A computer simulation study is performed to investigate the method of current density reconstruction to localise myocardial ischaemia. A computer model of the entire human heart is used to simulate the excitation and repolarisation process in eight topographically different cases of myocardial ischaemia. The associated magnetocardiogram is calculated at 37 positions of the KRENIKON^* biomagnetic measurement equipment. The method of current density reconstruction is applied at the S-point (the last discemible deviation from the ST-segment at the end of the QRS-complex) of the MCG to find characteristics of the myocardial ischaemia simulated by the model. The results show that it is possible to determine the location of the ischaemia. The current density distribution may be interpreted physiologically in terms of the so-called ‘injury current’. This indicates that magnetocardiography might be a suitable method for noninvasive ischaemia diagnosis, and further investigations of the current density reconstruction method for the injury current should be performed on patients with ischaemic heart disease.     

Propofol improves recovery of the isolated working hypertrophic heart from ischaemia–reperfusion

The general anaesthetic propofol shows promise in protecting normal hearts against various cardiac insults, but little is known about its cardioprotective potential in hypertrophic hearts. This study tested the hypothesis that propofol at a clinically relevant dose would enhance functional recovery in hypertrophic hearts following ischaemia. Hypertrophic hearts from spontaneously hypertensive rats and hearts from their normotensive controls, Wistar Kyoto Rats, were equilibrated in the working mode prior to global normothermic ischaemia. Reperfusion commenced with 10?min in Langendorff mode, followed by 30-min working reperfusion. Functional performance was measured throughout the working mode, whilst reperfusion damage was assessed from myocardial troponin I release during Langendorff reperfusion. Where used, 4?μg/ml propofol was added 10?min before ischaemia and was washed out 10?min into working reperfusion. An additional protocol investigated recovery of hearts protected by normothermic hyperkalaemic cardioplegic arrest. Following 20-min ischaemia, reperfusion damage was significantly worse in hypertrophic hearts compared to normal hearts, whilst addition of propofol to hypertrophic hearts significantly improved the aortic flow (31 ± 5.8 vs. 11.6 ± 2.0?ml/min, n?=?6–7 ± SE, p?<?0.05). Propofol also conferred significant protection following 30-min ischaemia where the recovery of cardiac output and stroke volume was similar to that for cardioplegia alone. Incubation with propofol improved the NADH/NAD⁺ ratio in freshly isolated cardiomyocytes from hypertrophic hearts, suggesting possible improvements in metabolic flux. These findings suggest that propofol at the clinically relevant dose of 4?μg/ml is as effective as cardioplegic arrest in protecting hypertrophic hearts against ischaemia–reperfusion.     

Myocardial interstitial choline and glutamate levels during acute myocardial ischaemia and local ouabain administration

AIM: Noradrenaline (NA) uptake transporters are known to reverse their action during acute myocardial ischaemia and to contribute to ischaemia-induced myocardial interstitial NA release. By contrast, functional roles of choline and glutamate transporters during acute myocardial ischaemia remain to be investigated. Because both transporters are driven by the normal Na+ gradient across the plasma membrane in a similar manner to NA transporters, the loss of Na+ gradient would affect the transporter function, which would in turn alter myocardial interstitial choline and glutamate levels. The aim of the present study was to examine the effects of acute myocardial ischaemia and the inhibition of Na+,K+-ATPase on myocardial interstitial glutamate and choline levels. METHODS: In anaesthetized cats, we measured myocardial interstitial glutamate and choline levels while inducing acute myocardial ischaemia or inhibiting Na+,K+-ATPase by local administration of ouabain. RESULTS: The choline level was not changed significantly by ischaemia (from 0.93 +/- 0.06 to 0.82 +/- 0.13 microm, mean +/- SE, n = 6) and was decreased slightly by ouabain (from 1.30 +/- 0.06 to 1.05 +/- 0.07 microm, P < 0.05, n = 6). The glutamate level was significantly increased from 9.5 +/- 1.9 to 34.7 +/- 6.1 microm by ischaemia (P < 0.01, n = 6) and from 8.9 +/- 1.0 to 15.9 +/- 2.3 microm by ouabain (P < 0.05, n = 6). Inhibition of glutamate transport by trans-L-pyrrolidine-2,4-dicarboxylate (t-PDC) suppressed ischaemia- and ouabain-induced glutamate release. CONCLUSION: Myocardial interstitial choline level was not increased by acute myocardial ischaemia or by Na+,K+-ATPase inhibition. By contrast, myocardial interstitial glutamate level was increased by both interventions. The glutamate transporter contributed to glutamate release via retrograde transport.     

Prevention of diabetic vascular calcification by nifedipine, a dihydropyridine-based calcium channel blocker

Vascular calcification is a common feature in advanced atherosclerosis and also a predictor of future cardiovascular events such as unstable angina and myocardial infarction, especially in diabetes. There is a growing body of evidence that advanced glycation end products (AGEs), senescent macroprotein derivatives formed at an accelerated rate in diabetes, exist within atherosclerotic lesions, thereby being implicated in the pathogenesis of accelerated atherosclerosis in diabetes. Indeed, we have previously shown that AGE - their receptor (RAGE) interaction could induce angiogenesis through autocrine production of vascular endothelial growth factor, suggesting its role for plaque formation and enlargement in diabetes. Furthermore, we have found that AGEs have the ability to induce the osteoblatic differentiation of pericytes, thus contributing to the development of vascular calcification as well. These observations suggest that the inhibition of AGE formation or blockade of the downstream signaling of RAGE may be a novel therapeutic target for the inhibition of vascular calcification in diabetic atherosclerosis. Since we, along with others, have shown that nifedipine inhibits glycation of low-density lipoprotein in vitro and blocks the AGE-induced RAGE expression in endothelial cells through its anti-oxidative properties, nifedipine could inhibit vascular calcification by blocking the AGE formation or the downstream signaling in diabetes. In this paper, we would like to propose the possible ways of testing our hypothesis. Does nifedipine treatment slow down the progression of coronary calcification in diabetic patients? If the answer is yes, is this beneficial effect of nifedipine superior to that of other DHPs with equihypotensive properties? Does nifedipine treatment decrease expression levels of AGEs and RAGE in diabetic atherosclerosis? Is the unique effect of nifedipine on vascular calcification correlated with its AGE or RAGE-suppressing properties? These prospective studies will provide further valuable information whether nifedipine could prevent vascular calcification in diabetic atherosclerosis by blockade the AGE-RAGE signaling in vascular wall cells.     

Cholinergic agonists may produce preservation of myocardial ischaemia/reperfusion injury

The best treatment for myocardial infarction is to restore blood flow in the ischaemic region, though it will bring new myocardial damage known as myocardial ischaemia/reperfusion (I/R) injury. Both the ischaemia preconditioning and the ischaemia postcondioning have been shown to reduce the myocardial I/R injury, but their deficits restrict wide clinical availability. It has been demonstrated that inflammation plays a critical role in the I/R injury process. Also plasma levels of cytokines and inflammation response can be regulated by specifically augmenting cholinergic signaling via the efferent vagus nerve and α7 subunit-containing nicotinic acetylcholine receptor (α7nAChR). Because cholinergic modalities, acting through vagus nerve- and/or α7nAChR-mediated mechanism, have been confirmed to suppress excessive inflammation during the I/R injury in kidney, liver, lung and intestine, therefore, we hypothesize that cholinergic agonists may also provide a protection for the myocardial I/R injury.     

Expression of angiotensin-converting enzyme 2 and its end product angiotensin 1-7 is increased in diabetic atheroma: implications for inflammation and neovascularization

AimsThe angiotensin-converting enzyme 2 (ACE2) and its end product angiotensin 1-7 (Ang1-7) are key counterregulatory proteins to offset the deleterious effects of angiotensin II. ACE2 is decreased in diabetic kidney disease but overexpressed in metabolically active atheroma. We tested the hypothesis that ACE2 is increased in diabetic peripheral atheroma, concomitantly with Ang1-7, angiotensin II receptor 1 (AT1R), proinflammatory cytokines, macrophage infiltration, and plaque neovascularization.Methods and ResultsPeripheral atherectomy plaques collected from 12 diabetic (DM) and 12 non-DM patients were immunostained for ACE2, Ang1-7, AT1R, and proinflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Macrophage infiltration and neovascularization were counted using double-label immunochemistry with CD68/CD3 and CD34, respectively. Quantification was performed blindly by randomly counting positively stained cells in 20 high-power fields using previously validated methods. Tissue content of ACE2, Ang1-7, and AT1R was increased in DM when compared to non-DM (P<.0001). IL-6 and TNF-α were also increased in DM when compared to non-DM (P<.0001), as well as macrophage infiltration score and neovessel counting (P<.0001).ConclusionExpression of ACE2 and its end product Ang1-7 is increased in DM atheroma, along with overexpression of AT1R, IL6, TNF-α, macrophage infiltration, and neovascularization. These results suggest that the renin–angiotensin system counterregulatory pathway may be preserved in metabolically active atheroma, offering potential targets for future therapies in diabetic atherosclerosis.     

The ultrastructural effects of global ischaemia on Purkinje fibres compared with working myocardium: A qualitative and morphometric investigation on the canine heart

Summary During open heart surgery, reperfusion-induced arrhythmias arising after short periods of ischaemia may originate from subendocardial Purkinje fibres. We investigated the ultrastructure of these fibres during 30 min of global ischaemia at 25° C. The effects both with myocardial protection (HTK cardioplegia) and without it (pure ischaemia) were compared qualitatively and morphometrically. After 30 min pure ischaemia overcontraction of sarcomeres, hypercontraction and contraction bands, together with considerable changes in organelles, predominate over cellular oedema. In Purkinje fibres, both cellular and mitochondrial swelling were significantly increased within this 30-min time period from the onset of pure ischaemia. In contrast, following HTK cardioplegia and 30 min ischaemia, cellular and mitochondrial swelling remain moderate and over-contractions are almost entirely lacking. This means that despite remarkable differences between pure ischaemia and HTK cardioplegia in the degree of protection attained it is clear that, compared with the working myocardium, subendocardial Purkinje fibres do not display a higher resistance to early global ischaemia. Further investigations of this sensitivity of Purkinje fibres to global ischaemia and certain drugs may bring about new insights into myocardial protection and pharmacotherapy of arrhythmias.     

REDUCTION OF RAT MYOCARDIAL ISCHAEMIA/REPERFUSION INJURY BY A SYNTHETIC SELECTIN OLIGOPEPTIDE

Neutrophils infiltrate into myocardial tissue subjected to ischaemia followed by reperfusion and play a major role in myocardial reperfusion injury. The infiltration of neutrophils begins within 2 h after reperfusion, indicating the engagement of rapidly inducible adhesion molecules, such as P-selectin, on vascular endothelial cells of myocardial tissue. To investigate the essential role of P-selectin in myocardial reperfusion injury, this study examined the expression of P-selectin in rat hearts subjected to 30 min of ischaemia followed by reperfusion. The induction of P-selectin was also evaluated on the surface of cultured rat vascular endothelial cells subjected to 60 min of hypoxia, followed by reoxygenation in vitro . Finally, the effects of in vitro administration of a synthetic selectin oligopeptide on myocardial necrosis were analysed. Reperfusion of ischaemic myocardial tissue resulted in enhanced expression of P-selectin on the luminal surface of vascular endothelium and surface expression of P-selectin was induced on cultured vascular endothelial cells by hypoxia/reoxygenation in vitro . The in vitro administration of a synthetic selectin oligopeptide significantly reduced the area of myocardial infarction produced by 30 min of ischaemia, followed by 48 h of reperfusion. These data offer therapeutic possibilities for acute myocardial infarction.     

INDUCTION OF SIALYL LEWISX ON THE SURFACE OF CULTURED RAT VASCULAR ENDOTHELIAL CELLS AND CARDIAC MYOCYTES BY HYPOXIA/REOXYGENATION IN VITRO

Neutrophils adhere to and roll on vascular endothelial cells (VECs) through interaction of selectins and their carbohydrate ligands in the early stages of inflammation; this adhesion is then later strengthened through interaction of integrins on neutrophils with intercellular adhesion molecule-1 (ICAM-1) on endothelial cells. Recent, as yet unpublished studies showed that myocardial ischaemia/reperfusion caused rapid expression of sialyl Lewis^X (SLe^X), one of the carbohydrate ligands of selectins, on VECs and cardiac myocytes and that an anti-SLe^X monoclonal antibody (MAb) significantly reduced myocardial reperfusion injury in vivo . In the present study, to investigate whether or not ischaemia/reperfusion itself can induce the expression of SLe^X on VECs and cardiac myocytes, the expression of SLe^X on cultured rat VECs and cardiac myocytes was examined by treatment with hypoxia/reoxygenation in vitro , because ischaemia/reperfusion stimuli may partly be due to hypoxia/reoxygenation. The expression of SLe^X was induced rapidly and temporarily on the surface of cultured rat cardiac myocytes and VECs by hypoxia/reoxygenation in vitro . This strongly suggests that the expression of SLe^X on the surface of myocardial cells is induced initially and directly by ischaemia/reperfusion, which results in the rolling attachment of neutrophils in the early stages of myocardial reperfusion injury.     

Fibroblast growth factor (FGF)‐23 and fetuin‐A in calcified carotid atheroma

Voigt M, Fischer D‐C, Rimpau M, Schareck W & Haffner D
(2010) Histopathology 56 , 775–788
Fibroblast growth factor (FGF)‐23 and fetuin‐A in calcified carotid atheroma Aims: Human atheroma calcification occurs secondary to repetitive injury/remodelling of the vessel wall and might be initiated by adherence of mineral‐loaded fetuin‐A whether or not professional matrix mineralizing cells are present. The aim was to investigate the contribution of fibroblast growth factor (FGF)‐23 to ectopic mineralization. Methods and results: Serial sections of formalin‐fixed paraffin‐embedded human carotid atheroma (n = 54) were investigated with respect to (i) size and distribution of calcific deposits, (ii) indicators of chondrogenic/osteogenic transformation, and (iii) expression of fetuin‐A and FGF‐23. All specimens were calcified and SOX‐9, collagen type II, cathepsin‐K, fetuin‐A and FGF‐23 expression was seen in 46, 53, 53, 54 and 48 specimens, respectively. The intracellular detection of FGF‐23 (45/48) indicates local synthesis. Whereas fetuin‐A expression was seen also within areas of vascular smooth muscle actin‐positive cells adjacent to calcific deposits, FGF‐23 expression was apparently restricted to the mineralization‐prone areas. Both local expression and FGF‐23 serum concentrations were significantly associated with the degree of atheroma calcification. Conclusions: Besides the induction of bone islets and subsequent mineral deposition, severe remodelling of the vessel wall is sufficient to create a mineralizable fetuin‐A‐attracting microenvironment. FGF‐23 might contribute to the formation of proper mineral, i.e. control local phosphate concentration.     

Remote vs. local ischaemic preconditioning in the rat heart: infarct limitation,suppression of ischaemic arrhythmia and the role of reactive oxygen species

The unmet clinical need for myocardial salvage during ischaemia–reperfusion injury requires the development of new techniques for myocardial protection. In this study the protective effect of different local ischaemic preconditioning (LIPC) and remote ischaemic preconditioning (RIPC) protocols was compared in the rat model of myocardial ischaemia–reperfusion, using infarct size and ischaemic tachyarrhythmias as end‐points. In addition, the hypothesis that there is involvement of reactive oxygen species (ROS) in the protective signalling by RIPC was tested, again in comparison with LIPC. The animals were subjected to 30‐min coronary occlusion and 90‐min reperfusion. RIPC protocol included either transient infrarenal aortic occlusion (for 5, 15 and 30 min followed by 15‐min reperfusion) or 15‐min mesenteric artery occlusion with 15‐min reperfusion. Ventricular tachyarrhythmias during test ischaemia were quantified according to Lambeth Conventions. It was found that the infarct‐limiting effect of RIPC critically depends on the duration of a single episode of remote ischaemia, which fails to protect the heart from infarction when it is too short or, instead, too prolonged. It was also shown that RIPC is ineffective in reducing the incidence and severity of ischaemia‐induced ventricular tachyarrhythmias. According to our data, the infarct‐limiting effect of LIPC could be partially eliminated by the administration of ROS scavenger N‐2‐mercaptopropionylglycine (90 mg/kg), whereas the same effect of RIPC seems to be independent of ROS signalling.