Role of Non-Transferrin-Bound Iron in the pathogenesis of cardiotoxicity in patients with ST-elevation myocardial infarction assessed by Cardiac Magnetic Resonance Imaging.

BACKGROUND: Hereditary hemochromatosis, thalassemia and myelodysplastic syndromes represent disease models with evidence of iron-related heart failure. Non-Transferrin Bound Iron (NTBI) induces cardiac toxicity through the production of reactive oxygen species and lipid peroxidation. In ST-elevation acute myocardial infarction (STEMI) with evidence of microvascular obstruction (MVO) and hemorrhage (HEM), HEM may be a source of iron-related cardiac toxicity through NTBI and pro-inflammatory mediators. AIM OF THE STUDY: The study aims to assess NTBI in patients with STEMI and its possible relationship with MVO and HEM. METHODS AND RESULTS: NTBI, LPO-Malondialdehyde (MDA) and interleukin-6 (IL-6) were assessed in 15 patients with STEMI immediately before primary percutaneous coronary intervention (PPCI) and at 3, 6, 9, 12, and 24h post-PPCI. Cardiac Magnetic Resonance (CMR) was performed at 5days and 6months after STEMI. Myocardial edema and HEM were assessed by T2 and T2* mapping. MVO and necrotic area were assessed by early and late gadolinium enhancement (LGE). NTBI was detected in 13/15 patients with the highest values in 4 patients with evidence of MVO and HEM. NTBI levels were significantly related to CK-MB and troponin T values. NTBI kinetics appeared to be different in patients with MVO and HEM (7/15 patients), with a peak value at 6h after PCI, in comparison with those with no evidence of MVO and HEM, in whom NTBI values were lower and remained indeterminable after the first 24h. CONCLUSIONS: The detection of elevated NTBI values in patients with STEMI, MVO and HEM suggests a possible role of iron cardiotoxicity in myocardial damage.

Cobalamin as a regulator of serum and cerebrospinal fluid levels of normal prions.

We have previously demonstrated that the concentration of normal prion proteins (PrP(C)) is increased in the serum and cerebrospinal fluid (CSF) of rats deficient in vitamin B(12) (cobalamin, Cbl). In this study, we investigated whether similar increases also occur in the serum and CSF of patients deficient in Cbl (Cbl-D), and whether the increase in serum levels can be corrected by Cbl therapy. The study involved two sample populations. The first consisted of 45 patients (13 patients with pernicious anemia [PA], 19 with other forms of anemia, and 13 healthy controls); and the second, 68 patients (five with subacute combined degeneration [SCD], 18 with amyotrophic lateral sclerosis, 22 with multiple sclerosis [MS], and 23 neurological controls). Serum PrP(C) levels were measured using an enzyme-linked-immunosorbent-assay before as well as after Cbl therapy. The mean serum PrP(C) levels in patients with PA were significantly higher than those of the controls (p=0.0017) but normalized after Cbl therapy; there was no significant change in the patients with other forms of anemia. Mean CSF PrP(C) levels in the patients with SCD were significantly higher than in the neurological controls (p<0.03). The serum and CSF PrP(C) levels of patients with PA and those with SCD were correlated significantly with serum (p=0.004) and CSF (p=0.0018) Cbl levels. In patients with MS, CSF PrP(C) concentrations were significantly lower than those of the controls regardless of their CSF Cbl levels. We found a correlation between Cbl and PrP(C) levels in the serum and CSF of Cbl-D patients, which suggests that Cbl may regulate the PrP(C) levels in the serum and CSF in humans.

Factors involved in sudden coagulation observed in patients with acute myocardial infarction.

Coronary artery diseases (CAD) evolving into acute myocardial infarction (AMI) is associated with coagulation and thrombotic occlusion of coronary vessels in the presence of unstable atheroma. The atheromatous plaque becomes unstable when it is infiltrated by monocytes, macrophages and neutrophils capable of secreting proteases that induce plaque erosion, rupture and initialize the coagulation process. The aim of this study was (a) to analyse the plasma of patients with AMI for the presence of proteases that may activate rapid coagulation, (b) to evaluate coagulation markers as prothrombin fragment (F1+2) and antithrombin III and (c) to find an interrelation between proteases and coagulation markers. The examined plasma showed high values of prothrombin fragment (F1+2) and low levels of antithrombin III. These markers showed a highly significant negative-correlation. The plasma also exhibited increased levels of matrix metalloproteinase-9 (MMP-9) which were positively-correlated with the prothrombin fragment (F1+2). MMP-9 seems to cause the coagulation activity by increasing the level of prothrombin fragment (F1+2) and the consumption of antithrombin III. The examined plasma also exhibited high levels of neutrophil gelatinase-associated lipocalin (NGAL), which is known to modulate MMP-9 activity. The high plasma levels of MMP-9 and NGAL can be attributed to plaque instability and appear to activate sudden coagulation. MMP-9 and NGAL, in the presence of altered values of prothrombin fragment (F1+2) and antithrombin III in AMI patients, seem to be suitable markers to be studied in unstable plaque patients, for the prediction and prevention of acute coronary syndrome.

Pretreatment with tetrandrine has protective effects against isoproterenol-induced myocardial infarction in rabbits.

Tetrandrine, the active principle of Stephania tetrandra radix extracts, has broad pharmacological activity, including effects on the cardiovascular system: it has been shown to reduce the size of acute myocardial infarction in rats undergoing coronary vessel ligation and to improve heart lesions in the constriction/reperfusion model by means of mechanisms involving peroxidation, calcium antagonism and coagulation. The aim of this study was to investigate whether tetrandrine has anti-infarction, antioxidant and anticoagulant effects in rabbits treated with isoproterenol, a drug capable of causing peroxide generation, calcium overload and coagulation alterations, and inducing myocardial infarction. The results showed that pretreatment with tetrandrine protects against the myocardial injuries caused by isoproterenol. It counteracted the appearance of myocardial necrotic lesions and ischemic electrocardiographic modifications, such as ST segment alterations, prevented the appearance of the plasma cardiac necrosis markers c-troponin I and myoglobin, lowered malondialdehyde levels, and prolonged partial thromboplastin time. The protective effects of tetrandrine can be attributed to its antioxidant action in lowering peroxide levels and its ability to counteract coagulating activity. Tetrandrine seems to offer full protection against myocardial infarction experimentally induced by the non-invasive treatment of rabbits with isoprotenerol.

Plasma cardiac necrosis markers C-troponin I and creatine kinase, associated with increased malondialdehyde levels, induced in rabbits by means of 5-aminolevulinic acid injection.

A number of papers have described high levels of 5-aminolevulinic acid in cases of heart damage due to acute myocardial infarction, acute intermittent porphyria or chronic kidney failure, but it is not known whether the heart damage is directly associated with 5-aminolevulinic acid. The aim of this study was to verify whether such an association exists by injecting rabbits with 5-aminolevulinic acid and searching for the appearance of cardiac necrosis markers and histological heart alterations, and investigate whether the cardiotoxic activity of 5-aminolevulinic acid may involve peroxidation by seeking the presence of the peroxide marker malondialdehyde. The administration of 5-aminolevulinic acid led to the appearance of c-troponin I and creatine kinase, induced histological heart alterations and increased the malondialdehyde levels. The plasma levels of malondialdehyde and cardiac necrosis markers were also measured after the injection of 5-aminolevulinic acid in combination with the daunorubicin agent inducing peroxidation. The combined administration very significantly increased the plasma levels of 5-aminolevulinic acid, malondialdehyde, and the cardiac necrosis markers c-troponin I and creatine kinase. It therefore seems that there is a close relationship between altered 5-aminolevulinic acid levels, malondialdehyde and cardiac necrosis markers, which is attributable to the capacity of 5-aminolevulinic acid to generate toxic oxygen species that damage the heart. High plasma 5-aminolevulinic acid levels should be considered a factor contributing to cardiotoxicity and to the appearance of cardiac necrosis markers.

Myocardial infarction non-invasively induced in rabbits by administering isoproterenol and vasopressin: protective effects exerted by verapamil.

Myocardial infarction is usually induced in small animals by means of invasive procedures: the aim of this study was to cause heart necrosis lesions by non-invasive means. We injected rabbits with isoproterenol (3 mg/kg, i.p.) and vasopressin (0.3 mg/kg/5 min, i.v.) alone and in combination, and studied their effects on myocardial histology, electrocardiographic profiles, the appearance of the plasma cardiac necrosis marker c-troponin I (c-TPN I), hemodynamic parameters (blood pressure, heart rate), the coagulative process partial throboplastine time (PTT), and plasma nitric oxide (NO) levels. In the rabbits treated with vasopressin alone, the ischemic damage was associated with a decrease in NO values, and the appearance of electrocardiographic T-wave inversion and low plasma c-TPN I levels, whereas the animals treated with isoproterenol alone had necrotic bands in the myocardium, plasma c-TPN I, and electrocardiographic modifications (ST-segment changes and T-wave inversion). Combined treatment increased myocardial alterations such as contraction band necrosis, induced the appearance of specific hypoxic lesions such as areas of coagulative necrosis and leukocyte infiltration, and led to higher plasma c-TPN I levels and altered ECG profiles. Both drugs favored a decrease in plasma NO values and further alterations in hemodynamic parameters, such as higher blood pressure and greater procoagulant activity. The myocardial necrosis and modified cardiovascular parameters were attributed to calcium activated processes and the decrease in NO levels. As this model of myocardial damage involves the use of drugs that facilitate the opening of L-calcium channels, we also investigated their effects on cardiovascular parameters and heart histology after pretreatment with the calcium antagonist verapamil; this drug protected against the appearance of histological myocardial lesions, electrocardiographic alterations and high plasma c-TPN I levels, and prevented the hemodynamic and procoagulation changes, but did not affect the decrease in plasma NO values. The protective effects were attributed to the drug's calcium antagonist activity. In conclusion, the injection of isoproterenol and vasopressin induces a myocardial infarction non-invasively and seems to be suitable for studying early myocardial ischemic lesions and the effects of drugs interfering with myocardial damage and its related phenomena.

Isoproterenol-induced myocardial infarction in rabbits. Protection by propranolol or labetalol: a proposed non-invasive procedure.

Myocardial infarction is usually induced in small animals by means of invasive techniques based on mechanical coronary obstruction. As it has been reported that isoproterenol can cause ischemic myocardial alterations, lipid peroxide generation and procoagulant activity, we administered it to rabbits in order to induce a non-invasive myocardial infarction associated with above mentioned cardiovascular risk factors. Considerable ischemic alterations were observed in the animals treated with isoproterenol, including areas of myocardial necrosis, contraction band necrosis, increased plasma levels of cardiac necrosis markers (c-troponin I and myoglobin), and electrocardiographic modifications (ST segment changes and T wave inversion). The myocardial infarction was attributed to the inotropic activity of isoproterenol leading to intracellular calcium overload. The cardiac necrosis phenomena appear to be associated with isoproterenol-induced lipid peroxide generation (as shown by the decrease in plasma Vitamin E levels) and increased procoagulant activity (a shortened PTT). As this model of myocardial damage is based on the use of beta-stimulatory isoproterenol, the beta-blockers propranolol and labetalol were administered to isoproterenol-treated animals. Pretreatment with propranolol or labetalol counteracted the appearance of the myocardial histological alterations and the associated ECG and biochemical lesions. This protective activity was attributed to the beta-blockade. The results of this study demonstrate that myocardial infarction can be induced chemically and non-invasively in small laboratory animals. The procedure is proposed for the study of early ischemic myocardial lesions and the screening of drugs (such as beta-blockers) that can prevent myocardial necrosis damage and the associated risk factors.

Drugs modifying nitric oxide metabolism affect plasma cholesterol levels, coagulation parameters, blood pressure values and the appearance of plasma myocardial necrosis markers in rabbits: opposite effects of L-NAME and nitroglycerine.

UNLABELLED: Various experiments have shown that decreased nitric oxide values alter plasma lipid levels or coagulation parameters or blood pressure values or cause myocardial necrosis phenomena, but it is not clear whether these alterations are reciprocally connected, or whether nitric oxide changes are involved in the appearance of some coronary disease risk factors (lipid, coagulation, blood pressure alterations) and myocardial necrosis. AIMS: We modified nitric oxide levels in rabbits using L-NAME (a NO synthase blocker) or nitroglycerine (a NO donor), and simultaneously evaluated variations in total and HDL cholesterol levels, some coagulation parameters, mean blood pressure values and myocardial necrosis patterns. RESULTS: L-NAME lowered plasma nitric oxide values, increased plasma total cholesterol and decreased HDL cholesterol levels, enhanced the amount of plasma fibrinogen, shortened prothrombin times, elevated the mean blood pressure values and caused the appearance of cardiac necrosis markers (c-troponin I, creatine kinase) in plasma and coagulative necrosis lesions in the myocardium. The administration of nitroglycerine to rabbits treated with L-NAME increased plasma nitric oxide levels and reversed the biochemical lesions caused by L-NAME. CONCLUSIONS: Our data show that the studied alterations in cholesterol values, coagulation parameters, increased mean blood pressure values and myocardial necrosis markers are strictly related to modified plasma nitric oxide levels, and that the regulation of nitric oxide metabolism affects the presence or absence of some coronary disease risk factors (lipid, coagulation and blood pressure alterations) and plasma indicators of myocardial necrosis.

Cardiac necrosis markers associated with low nitric oxide levels in the plasma of rabbits after treatment with vasopressin: protective effects of nitroglycerin administration.

It has been reported that the administration of vasopressin induces myocardial ischaemia in rats, which causes electrocardiographic ST segment alterations according to many authors. But rat electrocardiogram (ECG) lacks ST segment. Consequently it appears important to study the effects of vasopressin in rabbits, which show ST segment present in the ECG. Since cardiac necrosis markers are released in the plasma of humans with myocardial infarction, as well as in a variety of experimental models of myocardial necrosis, it is possible that the same may occur in rabbits with myocardial ischaemia induced by vasopressin. The main aim of this study was to investigate whether the administration of vasopressin causes the appearance of specific myocardial necrosis markers, such as cardiac troponin I, myoglobin or creatine kinase MB (CK MB) in rabbits in the presence or absence of modified ECG profile, and to also verify whether these markers are associated with the alterations in some coagulation parameters, that are known to be induced by vasopressin. As the effects of vasopressin are counteracted by nitric oxide (NO), another aim was to verify whether vasopressin also affects plasma NO levels and whether the administration of a NO donor can reverse these effects. Vasopressin was administered to rabbits and caused ischaemic alterations such as electrocardiographic changes, and significantly increased the levels of plasma cardiac necrosis markers (c-troponin I, myoglobin and CK MB). It also elevated diastolic blood pressure (BP), lowered heart rate (HR), increased procoagulation activity, and lowered plasma NO levels. The appearance of heart necrosis, demonstrated by plasma cardiac necrosis markers in the animals receiving vasopressin, was attributed to a drug-induced increase in vasoconstriction and coagulation activity. The intense vasoconstriction and thrombosis may lead to endothelium necrosis and a consequent drop in NO production. The administration of the NO donor nitroglycerin (NG) in the vasopressin treated animals restored NO values, and was capable of preventing the appearance of the plasma cardiac necrosis markers and altered coagulation values. The protective activity of NG was attributed to NO release, which lowers BP values and counteracts coagulation activity in vasopressin-treated animals. The described procedure may also be proposed for the study of early ischaemic myocardial lesions and the screening of NO donors preventing myocardial damage.