Aleksandar Kibel

Impact of glucocorticoids and chronic stress on progression of Parkinson's disease.

Parkinsons disease, a chronic progressive neurodegenerative disorder, has a mainly unknown multifactorial etiology. It is characterized by progressive degeneration of dopaminergic neurons. Chronic stress, a condition mediated by elevated concentrations of glucocorticoids over an extended period of time, has been shown to be unfavourable for neurons and to cause damage and neuronal loss in certain brain areas. Glucocorticoids are most probably not toxic in a direct manner, but can make neuronal damage through several potential indirect mechanisms in combination with other destructive factors. We postulate that chronic stress will have a harmful effect on patients with Parkinsons disease, facilitating neuronal degeneration and accelerating progression of clinical manifestations. The damaging impact on neurons will not be because of direct cytotoxicity, but by putting them into an energetically unfavourable condition, in which they will be more sensitive to destructive factors caused by the primary process. Possible mechanisms include elevation of excitatory amino acid concentration, which are excitotoxic, disruption of calcium homeostasis, metabolic disturbance or impairment of neurogenesis. This could have significant implications for patients with Parkinsons disease and chronic stress, or patients with glucocorticoid treatment for various immunopathological diseases, as well as patients with abnormal secretion of glucocorticoids such as in Cushings syndrome. If confirmed, this hypothesis would represent a valuable advancement in care of patients with Parkinsons disease.

Hyperbaric oxygenation modulates vascular reactivity to angiotensin-(1-7) in diabetic rats: potential role of epoxyeicosatrienoic acids.

Previously, a facilitating effect of hyperbaric oxygenation (HBO2) on aortic ring responses to angiotensin-(1-7) in healthy rats was reported, with epoxyeicosatrienoic acids (EETs) possibly playing an important role. The aim of this study was to assess whether HBO2 exerts similar effects in diabetic rats and to further explore the role of specific cytochrome P450 (CYP) enzymes in changes induced by HBO2. Aortic relaxation to angiotensin-(1-7) was significantly higher in HBO2 diabetic rats compared to control diabetic rats, while HBO2 had no effect on angiotensin II contraction. N-methylsulphonyl-6-(2-propargyloxyphenyl/hexanamide inhibited the facilitation of angiotensin-(1-7) responses in HBO2 rats, suggesting an important role of EETs in this modulation. mRNA expression of CYP2J3 and protein expression of CYP2C11 were significantly upregulated in HBO2 diabetic rats, whereas CYP4A1, CYP4A2 and CYP4A3 mRNA and CYP2J3 protein expression was similar between groups. Mean arterial pressure, ferric reducing ability of plasma and Thiobarbituric Acid Reactive Substances levels and serum angiotensin-(1-7) concentrations were not significantly changed.

Obesity Related Coronary Microvascular Dysfunction: From Basic to Clinical Practice

Obesity related coronary microvascular disease is a medical entity which is not yet fully elucidated. The pathophysiological basis of coronary microcirculatory dysfunction consists of a heterogeneous group of disorders with individual morphologic/functional/clinical presentation and prognosis. Coronary microcirculatory changes include mechanisms connected with vascular dysfunction, as well as extravascular and vasostructural changes in responses to neural, mechanical, and metabolic factors. Cardiometabolic changes that include obesity, dyslipidemia, diabetes mellitus type II, and hypertension are associated with atherosclerosis of epicardial coronary arteries and/or microvascular coronary dysfunction, with incompletely understood underlying mechanisms. In obesity, microvascular disease is mediated via adipokines/cytokines causing chronic, subclinical inflammation with (a) reduced NO-mediated dilatation, (b) changed endothelial- and smooth muscle-dependent vasoregulating mechanisms, (c) altered vasomotor control with increased sympathetic activity, and (d) obesity related hypertension with cardiomyocytes hypertrophy and impaired cardiac vascular adaptation to metabolic needs. From a clinical point of view it can present itself in acute or chronic form with different prognosis, as a practice problem for real-life diagnosis and treatment.

Restoring Vascular Function with Hyperbaric Oxygen Treatment: Recovery Mechanisms

Treatment with hyperbaric oxygen can be a beneficial adjuvant therapy in various disorders characterized by compromised tissue oxygenation and perfusion. However, the effects of hyperbaric oxygenation cannot be simply explained as a compensation of the oxygen deficit. Hyperbaric oxigenation has a much broader influence and has the ability to alter protein expression, modulate signaling pathways and affect vascular structure and function. We discuss some of the most important uses of hyperbaric oxigenation for clinical conditions that involve abnormal vascular function. We present recent studies and insights into the mechanisms and effects of hyperbaric oxygen in the vasculature.

Coronary microvascular dysfunction in diabetes mellitus

The significance, mechanisms and consequences of coronary microvascular dysfunction associated with diabetes mellitus are topics into which we have insufficient insight at this time. It is widely recognized that endothelial dysfunction that is caused by diabetes in various vascular beds contributes to a wide range of complications and exerts unfavorable effects on microcirculatory regulation. The coronary microcirculation is precisely regulated through a number of interconnected physiological processes with the purpose of matching local blood flow to myocardial metabolic demands. Dysregulation of this network might contribute to varying degrees of pathological consequences. This review discusses the most important findings regarding coronary microvascular dysfunction in diabetes from pre-clinical and clinical perspectives.

The Metabolites of Arachidonic Acid in Microvascular Function

Arachidonic acid (AA) metabolites have an important role in mediating vascular reactivity to various stimuli, affecting tissue perfusion and tissue supply. In addition, they exert proinflammatory or anti‐inflammatory effects on vessels. AA is metabolized by cyclooxygenases (COX) 1 and 2 to prostaglandins (PGs) and thromboxane (TX), by lipooxygenase to leukotrienes; by cytochrome P450 (CYP450)‐hydroxylase to 20‐ hydroxyeicosatetraenoic acid (20‐HETE) and by CYP450‐epoxygenase to epoxyeicosa‐ trienoic acids (EETs). Increased vascular oxidative stress may induce non‐enzymatic production of isoprostanes from AA, which, together with vasoconstrictor metabolites of AA underlie endothelial damage and impaired vascular function. The balance among vasodilator and vasoconstrictor metabolites of AA may be disturbed in cardiometabolic diseases. (e.g. hypertension,obesity,diabetes) Dietary habits significantly affect the metabolism of AA, particularly excessive kitchen salt (NaCl) intake. Control of environmental risks factors, good maintenance of the occurring diseases and balanced nutrition with restricted salt intake can significantly improve the metabolism of AA and alleviate microvascular dysfunction and subsequent organ damage. Current research on pharmacological manipulation of certain components of the AA pathways (such as 20‐HETE production inhibition or prolongation of the life of epoxyeicoatrienoic acids(EETs) by inhibitors of soluble epoxide hydrolaze (sEH)promises effective therapy of cardiovascular and cerebrovascular diseases in the future.

Coronary Microcirculatory Dysfunction in Human Cardiomyopathies: A Pathologic and Pathophysiologic Review.

Cardiomyopathies are a heterogeneous group of diseases of the myocardium. The term cardiomyopathy involves a wide range of pathogenic mechanisms that affect the structural and functional states of cardiomyocytes, extravascular tissues, and coronary vasculature, including both epicardial coronary arteries and the microcirculation. In the developed phase, cardiomyopathies present with various clinical symptoms: dyspnea, chest pain, palpitations, swelling of the extremities, arrhythmias, and sudden cardiac death. Due to the heterogeneity of cardiomyopathic patterns and symptoms, their diagnosis and therapies are great challenges. Despite extensive research, the relation between the structural and functional abnormalities of the myocardium and the coronary circulation are still not well understood in the various forms of cardiomyopathy. The main pathological characteristics of cardiomyopathies and the coronary microcirculation develop in a progressive manner due to (1) genetic-immunologic-systemic factors; (2) comorbidities with endothelial, myogenic, metabolic, and inflammatory changes; (3) aging-induced arteriosclerosis; and (4) myocardial fibrosis. The aim of this review is to summarize the most important common pathological features and/or adaptations of the coronary microcirculation in various types of cardiomyopathies and to integrate the present understanding of the underlying pathophysiological mechanisms responsible for the development of various types of cardiomyopathies. Although microvascular dysfunction is present and contributes to cardiac dysfunction and the potential outcome of disease, the current therapeutic approaches are not specific for the given types of cardiomyopathy.

Could angiotensin-(1-7) be connected with improvement of microvascular function in diabetic patients? Angiotensin-(1-7) iontophoresis may provide the answer.

Diabetes mellitus, a metabolic disorder with significant global health care burden, causes chronic microvascular and macrovascular complications that still comprise a therapeutic challenge. Angiotensin-(1-7), a heptapeptide with vasodilatory properties, has been found to restore vascular reactivity and endothelial cell function, mostly in experiments on larger isolated animal vessels and in cell cultures. The presented hypothesis suggests that angiotensin-(1-7) might have beneficial effects on microvascular function that is damaged in diabetic patients, alleviating endothelial dysfunction and increasing microvascular reactivity to various vasoactive agents in diabetes. It is further proposed that iontophoresis with angiotensin-(1-7) might be used to explore this potential beneficial effect, as well as provide a possible future therapeutic delivery method for angiotensin-(1-7). Since other peptides and proteins have been previously tested and used in iontophoretic transdermal delivery, it is plausible that angiotensin-(1-7) would be a suitable candidate for transdermal iontophoretic application for research (and potentially therapeutic) purposes. If confirmed, the delineated hypothesis would have immense implications for more effective care of diabetic patients, as well as for better understanding of microcirculatory pathophysiological mechanisms in diabetes.

Pojavnost intramiokardijalnih masnih stanica u stijenci desne pretklijetke i desne klijetke – postmortalna humana analiza

SUMMARY – Histologic and radiologic studies describe intramyocardial fat tissue as a normal finding or as part of cardiac pathology. The role of fat cells within the myocardium is not fully understood. The aim of this study was to assess fat tissue distribution in the myocardium of right atrium (RA) and right ventricle (RV) and age differences in subjects free from cardiac disease. The study included 10 males without cardiac disease divided into two groups according to age (below/above 50 years). Three cross sections were performed (RV free wall and apex and RA free wall) with histomorphological analysis on digital photographs. The shares of total myocardial fat (TMF), perivascular fat (PVF) and non-perivascular (nPVF) fat were calculated. Samples from the older group had larger amounts of fat in the epicardium and myocardium, without statistically significant difference (TMF p=0.847, PVF p=0.4 and nPVF p=0.4). The largest quantities of fat tissue were found in the RV apex samples (14.9%), followed by RV free wall (7.5%) and RA (4.5%), where total apical RV fat share was significantly larger than in RA sample (p=0.044). Intramyocardial fat cells were present within the non-diseased RA and RV in all samples, mostly in the apex. Further investigations on age difference, effect of visceral obesity and sex differences are needed.

PS 10-09 HYPERBARIC OXYGEN TREATMENT INCREASES SERUM ANGIOTENSIN-CONVERTING ENZYME ACTIVITY LEVELS IN HEALTHY BUT NOT IN DIABETIC RATS

Objective: Hyperbaric oxygen (HBO2) treatment, used for a number of pathologic conditions, has incompletely elucidated mechanisms of action in vasculature. Previously, repetitive treatment with HBO2 was found to potentially affect components of the renin-angiotensin system, with HBO2 increasing aortic vascular reactivity to angiotensin-(1–7) in healthy and diabetic rats, while not changing angiotensin-(1–7) serum concentrations. The aim of this study was to investigate whether HBO2 has an effect on serum angiotensin-converting enzyme (ACE) activity. Design and Method: Healthy male Sprague-Dawley rats and rats with streptozocin-induced diabetes mellitus were divided into control and HBO2 groups. The latter were treated with 100% oxygen at a pressure of 2 bars in a hyperbaric chamber for 2 hours a day (with additional 15 minutes for each compression and decompression) for 4 consecutive days. On the fifth day, the animals were anesthetized (2.5 mg/kg midazolam + 75 mg/kg ketamine intraperitoneally) and decapitated. Serum samples were stored at -80°C and quantitative determination of ACE was performed spectrophotometrically using Thermo Scientific Infinity ACE Liquid Stable Reagent. Students t-test (the samples showed normal distribution) was used for comparison between control and HBO2 ACE levels. Results: Mean ACE serum activity in healthy control rats (n = 10) was 107.660 ± 6.931 U/L, whereas the HBO2 treated healthy group (n = 10) had a mean serum ACE activity of 125.385 ± 18.348 U/L, the difference was statistically significant (t-test, P = 0.010). Mean ACE serum activity levels were 142.150 ± 22.555 U/L in diabetic control (untreated) rats (n = 10) and 136.670 ± 24.024 U/L in diabetic HBO2 rats (n = 10), with no significant difference between these two groups (t-test, P = 0.605). Conclusions: The results suggest that intermittent exposure to HBO2 leads to an increase in serum ACE activity in healthy rats. Such an effect was not observed in diabetic rats treated with HBO2. This data might significantly contribute to better understanding of circulatory HBO2 mechanisms of action in different conditions.