Measurement of myocardial free radical production during exercise using EPR spectroscopy

Sports activities and cardiovascular system change

Sports activity is generally considered to be beneficial to health. The World Health Organization (WHO) recommends physical activity as part of a healthy lifestyle. Sports activities significantly affect the cardiovascular system. A number of studies show that they significantly reduce the risk of cardiovascular disease as well as decrease cardiovascular mortality. This review discusses changes in various cardiovascular parameters in athletes - vagotonia/bradycardia, hypertrophy of heart, ECG changes, blood pressure, and variability of cardiovascular parameters. Because of its relationship to the cardiovascular system, VO2max, which is widely used as an indicator of cardiorespiratory fitness, is also discussed. The review concludes with a discussion of reactive oxygen species (ROS) and oxidative stress, particularly in relation to changes in the cardiovascular system in athletes. The review appropriately summarizes the above issues and points out some new implications.

Insulin signaling alters antioxidant capacity in the diabetic heart

Diabetic cardiomyopathy is associated with an increase in oxidative stress. However, antioxidant therapy has shown a limited capacity to mitigate disease pathology. The molecular mechanisms responsible for the modulation of reactive oxygen species (ROS) production and clearance must be better defined. The objective of this study was to determine how insulin affects superoxide radical (O₂^•–) levels. O₂^•– production was evaluated in adult cardiomyocytes isolated from control and Akita (type 1 diabetic) mice by spin-trapping electron paramagnetic resonance spectroscopy. We found that the basal rates of O₂^•– production were comparable in control and Akita cardiomyocytes. However, culturing cardiomyocytes without insulin resulted in a significant increase in O₂^•– production only in the Akita group. In contrast, O₂^•– production was unaffected by high glucose and/or fatty acid supplementation. The increase in O₂^•– was due in part to a decrease in superoxide dismutase (SOD) activity. The PI3K inhibitor, LY294002, decreased Akita SOD activity when insulin was present, indicating that the modulation of antioxidant activity is through insulin signaling. The effect of insulin on mitochondrial O₂^•– production was evaluated in Akita mice that underwent a 1-week treatment of insulin. Mitochondria isolated from insulin-treated Akita mice produced less O₂^•– than vehicle-treated diabetic mice. Quantitative proteomics was performed on whole heart homogenates to determine how insulin affects antioxidant protein expression. Of 29 antioxidant enzymes quantified, thioredoxin 1 was the only one that was significantly enhanced by insulin treatment. In vitro analysis of thioredoxin 1 revealed a previously undescribed capacity of the enzyme to directly scavenge O₂^•–. These findings demonstrate that insulin has a role in mitigating cardiac oxidative stress in diabetes via regulation of endogenous antioxidant activity.

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Insulin decreases ROS production in T1D Akita cardiomyocytes.

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Insulin signaling downstream of PI3K is required for this effect.

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Insulin increases the antioxidant capacity in the Akita heart.

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Trx1 is upregulated by insulin in the Akita heart in vivo.

Local Production of Soluble Urokinase Plasminogen Activator Receptor and Plasminogen Activator Inhibitor-1 in the Coronary Circulation Is Associated With Coronary Endothelial Dysfunction in Humans

Background Soluble urokinase plasminogen activator receptor (su PAR ) is a proinflammatory biomarker associated with immune activation and fibrinolysis inhibition. Plasminogen activator inhibitor ( PAI -1) is associated with excessive fibrin accumulation, thrombus formation, and atherosclerosis. The relationship between cross-coronary su PAR and PAI -1 production and endothelial dysfunction remains unknown. Methods and Results Seventy-nine patients (age 53±10 years, 75% women) with angina and normal coronary arteries or mild coronary artery disease (<40% stenosis) on angiogram underwent acetylcholine assessment of epicardial endothelial dysfunction (mid-left anterior descending coronary artery diameter decrease >20% after acetylcholine) and mircovascular endothelial dysfunction (coronary blood flow change <50% after acetylcholine). Simultaneous left main and coronary sinus su PAR and PAI -1 levels were measured in each patient before acetylcholine administration, and cross-coronary su PAR and PAI -1 production rates were calculated. Patients' characteristics, except for age (51±10 versus 57±9, P=0.02), and resting coronary hemodynamics were not significantly different between patients with (26%) versus without (74%) epicardial endothelial dysfunction. Patients' characteristics and resting coronary hemodynamics were not significantly different between those with (62%) and those without (38%) mircovascular endothelial dysfunction. Patients with mircovascular endothelial dysfunction demonstrated local coronary su PAR production versus su PAR extraction in patients with normal microvascular function (median 25.8 [interquartile range 121.6, -23.7] versus -12.7 [52.0, -74.8] ng/min, P=0.03). Patients with epicardial endothelial dysfunction had higher median coronary PAI -1 production rates compared with those with normal epicardial endothelial function (1224.7 [12 940.7, -1915.4] versus -187.4 [4444.7, -4535.8] ng/min, P=0.03). Conclusions su PAR is released in coronary circulation of patients with mircovascular endothelial dysfunction and extracted in those with normal microvascular function. Cross-coronary PAI -1 release is higher in humans with epicardial endothelial dysfunction.

Electron Spin Resonance (ESR) for the study of Reactive Oxygen Species (ROS) on the isolated frog skin (Pelophylax bergeri): A non-invasive method for environmental monitoring

BACKGROUND

Reactive oxygen species (ROS) in biological tissues of elected biosentinels represent an optimal biomarker for eco-monitoring of polluted areas. Electron spin resonance (ESR) is the most definitive method for detecting, quantifying and possibly identifying radicals in complex systems.

OBJECTIVE

A non-invasive method for monitoring polluted areas by the quantitative determination of ROS in frog skin biopsy is presented.

METHODS

We assessed by ESR spectroscopy the ROS level in adult male of Pelophylax bergeri, specie not a risk of extinction, collected from the polluted Sarno River (SA, Italy) basin. The spin-trap ESR method was validated by immunohistochemical analysis of the well-assessed pollution biomarkers cytochrome P450 aromatase 1A (CYP1A) and glutathione S-transferase (GST), and by determining the poly(ADPribose) polymerase (PARP) and GST enzymatic activity.

RESULTS

ROS concentration in skin samples from frogs collected in the polluted area is significantly higher than that determined for the unpolluted reference area. Immunohistochemical analysis of CYP1A and GST supported the reliability of our approach, even in the absence of evident morphological and ultrastructural differences. PARP activity assay, connected to possible oxidative DNA damage, and the detoxification index by GST enzymatic assay give statistically significant evidence that higher levels of ROS are associated to alterations of the different biomarkers.

CONCLUSIONS

ROS concentration, measured by ESR on isolated frog skin, through the presented non-lethal method, is a reliable biomarker for toxicity screening and represents a useful basic datum for future modelling studies on environmental monitoring and biodiversity loss prevention.

Measurement of free radicals using electron paramagnetic resonance spectroscopy during open aorto-iliac arterial reconstruction

BACKGROUND

Aortic cross-clamping during abdominal aortic aneurysm (AAA) open repair leads to development of ischemia-reperfusion injury. Electron paramagnetic resonance spectroscopy (EPR) spin-trapping is a valuable method of direct measurement of free radicals. The objective of the study was to evaluate the results of EPR as a direct method of free radical measurement and degree of inflammatory response in open operative treatment of patients with AAA and aorto-iliac occlusive disease (AIOD).

MATERIAL/METHODS

The study was performed on a group of 32 patients with AAA and 25 patients with AIOD scheduled for open repair. Peripheral venous blood for EPR spectroscopy and for SOD, GPx, ox-LDL, Il-6, TNF-alfa, CRP, and HO-1 were harvested. Selected parameters were established accordingly to specified EPR and immunohistochemical methods and analyzed between groups by Mann-Whitney U test and Wilcoxon matched-pairs signed-ranks test with Bonferroni correction.

RESULTS

Free radicals level was correlated with the time of the aortic cross-clamping after the reperfusion of he first and second leg in AAA (r=0.7; r=0.47). ox-LDL in AAA decreased 5 min after reperfusion of the first leg (32.99 U/L, range: 14.09-77.12) and 5 min after reperfusion of the second leg (26.75 U/L, range: 11.56-82.12) and 24 h after the operation (25.85 U/L, range: 14.29-49.70). HO-1 concentration increased to above the level before intervention 24 h after surgery. The activities of GPx and SOD decreased 5 min after the first-leg reperfusion in AAA. Twenty-four hours after surgery, inflammatory markers increased in AAA to CRP was 14.76 ml/l (0.23-38.55), IL-6 was 141.22 pg/ml (84.3-591.03), TNF-alfa was 6.82 pg/ml (1.76-80.01) and AIOD: CRP was 18.44 mg/l (2.56-33.14), IL-6: 184.1 pg/ml (128.46-448.03), TNF-alfa was 7.74 pg/ml (1.74-74.74).

CONCLUSIONS

EPR spin-trapping demonstrates temporarily elevated level of free radicals in early phase of reperfusion, leading to decrease antioxidants in AAA. Elevated free radical levels decreased 24 h after surgery due to various endogenous antioxidants and therapies.

Reactive oxygen species are not a required trigger for exercise-induced late preconditioning in the rat heart

Reactive oxygen species (ROS) have been reported to play a primary role in triggering the cardioprotective adaptations by some preconditioning procedures, but whether they are required for exercise-induced preconditioning is unclear. Thus in this study we used the free radical scavenger N-(2-mercaptopropionyl)glycine (MPG) to test the hypothesis that ROS is the trigger for exercise-induced preconditioning of the heart against ischemia-reperfusion injury. Male F344 rats were assigned to four groups: sedentary (SED, n = 7), SED/MPG (100 mg/kg ip daily for 2 days, n = 12), exercised on a treadmill for 2 days at 20 m/min, 6° grade, for 60 min (RUN, n = 7), and RUN/MPG with 100 mg/kg MPG injected 15 min before exercise (n = 10). Preliminary experiments verified that MPG administration maintained myocardial redox status during the exercise bout. Twenty-four hours postexercise or MPG treatment isolated perfused working hearts were subjected to global ischemia for 22.5 min followed by reperfusion for 30 min. Recovery of myocardial external work (percentage of preischemic systolic pressure times cardiac output) for SED (50.4 ± 4.5) and SED/RUN (54.7 ± 6.6) was similar and improved in both exercise groups (P < 0.05) to 77.9 ± 3.0 in RUN and 76.7 ± 4.5 in RUN/MPG. A 2 × 2 ANOVA also revealed that exercise decreased lactate dehydrogenase release from the heart during reperfusion (marker of cell damage) without MPG effects or interactions. Expression of the cytoprotective protein inducible heat shock protein 70 increased by similar amounts in the left ventricles of RUN and RUN/MPG compared with sedentary groups (P < 0.05). We conclude that ROS are not a necessary trigger for exercise-induced preconditioning in rats.

Coronary endothelial dysfunction in humans is associated with coronary retention of osteogenic endothelial progenitor cells

AIMS

Endothelial progenitor cells (EPC) may participate in the repair of injured coronary endothelium. We have recently identified EPC co-expressing the osteoblastic marker osteocalcin [OCN (+) EPC] and found that their numbers are increased in patients with early and late coronary atherosclerosis. The current study was designed to test the hypothesis that early coronary atherosclerosis is associated with the retention of osteogenic EPC within the coronary circulation.

METHODS AND RESULTS

Blood samples were taken simultaneously from the proximal aorta and the coronary sinus from 31 patients undergoing invasive coronary endothelial function testing. Using flow cytometry, peripheral blood mononuclear cells were analysed for EPC markers (CD133, CD34, KDR) and OCN. The net gradient of EPC was calculated by multiplying the coronary blood flow by the arteriovenous EPC gradient (a negative net gradient indicating retention of EPC). Similarly, serum samples were analysed for stromal cell-derived factor-1 alpha (SDF-1 alpha) and interleukin-8 (IL-8) and their net production calculated. Compared with controls (n = 17) patients with endothelial dysfunction (ED, n = 14) had a significant net retention of CD34+/CD133-/KDR+/OCN+ EPC [118.38 (0.00, 267.04) vs. -112.03 (838.36, 0.00), P = 0.004]. The retention of OCN (+) EPC correlated with the degree of ED. Patients with ED also showed a net retention of CD34+/CD133-/KDR+ EPC (P = 0.010). Net production of IL-8 was positive in ED [1540.80 (-300.40, 21744.10)pg/mL] but negative in controls [-3428.50 (-11225.00, 647.48), P = 0.025].

CONCLUSION

Our study demonstrates that patients with early coronary atherosclerosis are characterized by retention of OCN (+) EPC within the coronary circulation, potentially leading to progressive coronary calcification rather than normal repair.

Molecular distinction between physiological and pathological cardiac hypertrophy: experimental findings and therapeutic strategies

Cardiac hypertrophy can be defined as an increase in heart mass. Pathological cardiac hypertrophy (heart growth that occurs in settings of disease, e.g. hypertension) is a key risk factor for heart failure. Pathological hypertrophy is associated with increased interstitial fibrosis, cell death and cardiac dysfunction. In contrast, physiological cardiac hypertrophy (heart growth that occurs in response to chronic exercise training, i.e. the 'athlete's heart') is reversible and is characterized by normal cardiac morphology (i.e. no fibrosis or apoptosis) and normal or enhanced cardiac function. Given that there are clear functional, structural, metabolic and molecular differences between pathological and physiological hypertrophy, a key question in cardiovascular medicine is whether mechanisms responsible for enhancing function of the athlete's heart can be exploited to benefit patients with pathological hypertrophy and heart failure. This review summarizes key experimental findings that have contributed to our understanding of pathological and physiological heart growth. In particular, we focus on signaling pathways that play a causal role in the development of pathological and physiological hypertrophy. We discuss molecular mechanisms associated with features of cardiac hypertrophy, including protein synthesis, sarcomeric organization, fibrosis, cell death and energy metabolism and provide a summary of profiling studies that have examined genes, microRNAs and proteins that are differentially expressed in models of pathological and physiological hypertrophy. How gender and sex hormones affect cardiac hypertrophy is also discussed. Finally, we explore how knowledge of molecular mechanisms underlying pathological and physiological hypertrophy may influence therapeutic strategies for the treatment of cardiovascular disease and heart failure.

Local Production of Lipoprotein-Associated Phospholipase A 2 and Lysophosphatidylcholine in the Coronary Circulation

Background— Lipoprotein-associated phospholipase A 2 (Lp-PLA 2 ) is a novel marker and participant in vascular inflammation. Inflammation also is associated with coronary atherosclerosis. We tested the hypothesis that local coronary production of Lp-PLA 2 is enhanced in patients with early coronary atherosclerosis and associated with local endothelial function.

Methods and Results— Coronary angiography, blood flow, flow reserve, endothelial function assessment, and intravascular ultrasound with volumetric analysis were performed in 15 patients with mild coronary atherosclerosis and in 15 control subjects. Plasma samples were collected simultaneously from the left main coronary artery and coronary sinus for measurement of Lp-PLA 2 , lysophosphatidylcholine (a product of Lp-PLA 2 ), and C-reactive protein. Hemodynamic parameters and cholesterol were similar in both groups. Arterial Lp-PLA 2 levels were similar in patients and control subjects: 225 ng/mL (interquartile range [IQR], 196 to 273 ng/mL) versus 221 ng/mL (IQR, 177 to 294 ng/mL). Lp-PLA 2 net production in the coronary circulation was higher in patients compared with control subjects: 519 ng/min (IQR, 198 to 1276 ng/min) versus −529 ng/min (IQR, −872 to −79 ng/min; P =0.001) and correlated with percent atheroma volume ( r s =0.37, P =0.04). Net production of lysophosphatidylcholine was higher in patients compared with control subjects: 199 ng/min (IQR, −592 to 470 ng/min) versus −505 ng/min (IQR, −1119 to 0 ng/min; P =0.03) and correlated with coronary endothelial dysfunction ( r s =0.5, P =0.005). C-reactive protein was not significantly different between the groups.

Conclusions— Early coronary atherosclerosis in humans is characterized by local production of Lp-PLA 2 . Local coronary production of lysophosphatidylcholine, the active product of Lp-PLA 2 , is associated with endothelial dysfunction. These results support the role for Lp-PLA 2 in the mechanism of regional vascular inflammation and atherosclerosis in humans.

Proteomic analysis of age dependent nitration of rat cardiac proteins by solution isoelectric focusing coupled to nanoHPLC tandem mass spectrometry

Protein nitration occurs as a result of oxidative stress induced by reactive oxygen (ROS) and reactive nitrogen species (RNS). Therefore, protein nitration serves as a hallmark for protein oxidation in vivo. We have previously reported on age dependent protein nitration in cardiac tissue of Fisher 344 BN-F1 rats analyzed by two-dimensional gel electrophoresis; however, only one specific nitration site was identified [Kanski, J., Behring, A., Pelling, J., Schöneich, C., 2005a. Proteomic identification of 3-nitrotyrosine-containing rat cardiac proteins: effects of biological aging. Am. J. Physiol. Heart Circ. Physiol. 288, H371-381]. In the present report, we used solution phase isoelectric focusing (IEF) followed by nanoHPLC-ESI-MS/MS that allowed us to obtain good MS/MS data to identify specific sites of protein nitration in cardiac tissue. As expected, more nitrated proteins were detected in cardiac tissue of old rats, including myosin heavy chain, neurofibromin, tropomyosin and nebulin-related anchoring protein. The post-translational modification of these cytoskeletal proteins may provide some rationale for the age-dependent functional decline of the heart.

Hydrogen Peroxide

OBJECTIVE

We tested the hypothesis that hydrogen peroxide (H2O2), the dismutated product of superoxide (O2*-), couples myocardial oxygen consumption to coronary blood flow. Accordingly, we measured O2*- and H2O2 production by isolated cardiac myocytes, determined the role of mitochondrial electron transport in the production of these species, and determined the vasoactive properties of the produced H2O2.

METHODS AND RESULTS

The production of O2*- is coupled to oxidative metabolism because inhibition of complex I (rotenone) or III (antimycin) enhanced the production of O2*- during pacing by about 50% and 400%, respectively; whereas uncoupling oxidative phosphorylation by decreasing the protonmotive force with carbonylcyanide-p-trifluoromethoxyphenyl-hydrazone (FCCP) decreased pacing-induced O2*- production. The inhibitor of cytosolic NAD(P)H oxidase assembly, apocynin, did not affect O2*- production by pacing. Aliquots of buffer from paced myocytes produced vasodilation of isolated arterioles (peak response 67+/-8% percent of maximal dilation) that was significantly reduced by catalase (5+/-0.5%, P<0.05) or the antagonist of Kv channels, 4-aminopyridine (18+/-4%, P<0.05). In intact animals, tissue concentrations of H2O2 are proportionate to myocardial oxygen consumption and directly correlated to coronary blood flow. Intracoronary infusion of catalase reduced tissue levels of H2O2 by 30%, and reduced coronary flow by 26%. Intracoronary administration of 4-aminopyridine also shifted the relationship between myocardial oxygen consumption and coronary blood flow or coronary sinus pO2.

CONCLUSIONS

Taken together, our results demonstrate that O2*- is produced in proportion to cardiac metabolism, which leads to the production of the vasoactive reactive oxygen species, H2O2. Our results further suggest that the production of H2O2 in proportion to metabolism couples coronary blood flow to myocardial oxygen consumption.