Microvascular oxygenation, oxidative stress, NO suppression and superoxide dismutase during postischemic reperfusion

Plasma biomarkers of endothelial function, inflammation and oxidative stress in individuals with non-freezing cold injury

NEW FINDINGS

What is the central question of this study? Are biomarkers of endothelial function, oxidative stress and inflammation altered by non-freezing cold injury (NFCI)? What is the main finding and its importance? Baseline plasma [interleukin-10] and [syndecan-1] were elevated in individuals with NFCI and cold-exposed control participants. Increased [endothelin-1] following thermal challenges might explain, in part, the increased pain/discomfort experienced with NFCI. Mild to moderate chronic NFCI does not appear to be associated with either oxidative stress or a pro-inflammatory state. Baseline [interleukin-10] and [syndecan-1] and post-heating [endothelin-1] are the most promising candidates for diagnosis of NFCI.

ABSTRACT

Plasma biomarkers of inflammation, oxidative stress, endothelial function and damage were examined in 16 individuals with chronic NFCI (NFCI) and matched control participants with (COLD, n = 17) or without (CON, n = 14) previous cold exposure. Venous blood samples were collected at baseline to assess plasma biomarkers of endothelial function (nitrate, nitrite and endothelin-1), inflammation [interleukin-6 (IL-6), interleukin-10 (IL-10), tumour necrosis factor alpha and E-selectin], oxidative stress [protein carbonyl, 4-hydroxy-2-nonenal (4-HNE), superoxide dismutase and nitrotyrosine) and endothelial damage [von Willebrand factor, syndecan-1 and tissue type plasminogen activator (TTPA)]. Immediately after whole-body heating and separately, foot cooling, blood samples were taken for measurement of plasma [nitrate], [nitrite], [endothelin-1], [IL-6], [4-HNE] and [TTPA]. At baseline, [IL-10] and [syndecan-1] were increased in NFCI (P < 0.001 and P = 0.015, respectively) and COLD (P = 0.033 and P = 0.030, respectively) compared with CON participants. The [4-HNE] was elevated in CON compared with both NFCI (P = 0.002) and COLD (P < 0.001). [Endothelin-1] was elevated in NFCI compared with COLD (P < 0.001) post-heating. The [4-HNE] was lower in NFCI compared with CON post-heating (P = 0.032) and lower than both COLD (P = 0.02) and CON (P = 0.015) post-cooling. No between-group differences were seen for the other biomarkers. Mild to moderate chronic NFCI does not appear to be associated with a pro-inflammatory state or oxidative stress. Baseline [IL-10] and [syndecan-1] and post-heating [endothelin-1] are the most promising candidates for diagnosing NFCI, but it is likely that a combination of tests will be required.

Hypoxic preconditioning attenuates ischemia-reperfusion injury in young healthy adults

Ischemia-reperfusion injury induced by restoration of blood flow following occlusion impairs flow-mediated dilation, a marker of endothelium-dependent vasodilation. In young healthy adults, exposure to intermittent hypoxia, consisting of alternating short bouts of breathing hypoxic and normoxic air, before an ischemia-reperfusion injury significantly attenuated the reduction in flow-mediated dilation. Thus, hypoxic preconditioning represents a potential strategy to mitigate the effect of ischemia-reperfusion injury associated with ischemic events.

Nitrosative Stress and Its Association with Cardiometabolic Disorders

Reactive nitrogen species (RNS) are formed when there is an abnormal increase in the level of nitric oxide (NO) produced by the inducible nitric oxide synthase (iNOS) and/or by the uncoupled endothelial nitric oxide synthase (eNOS). The presence of high concentrations of superoxide anions (O₂⁻) is also necessary for their formation. RNS react three times faster than O₂⁻ with other molecules and have a longer mean half life. They cause irreversible damage to cell membranes, proteins, mitochondria, the endoplasmic reticulum, nucleic acids and enzymes, altering their activity and leading to necrosis and to cell death. Although nitrogen species are important in the redox imbalance, this review focuses on the alterations caused by the RNS in the cellular redox system that are associated with cardiometabolic diseases. Currently, nitrosative stress (NSS) is implied in the pathogenesis of many diseases. The mechanisms that produce damage remain poorly understood. In this paper, we summarize the current knowledge on the participation of NSS in the pathology of cardiometabolic diseases and their possible mechanisms of action. This information might be useful for the future proposal of anti-NSS therapies for cardiometabolic diseases.

Prolonged forearm ischemia attenuates endothelium-dependent vasodilatation and plasma nitric oxide metabolites in overweight middle-aged men

Purpose

Repeated cycles of endothelial ischemia–reperfusion injury and the resulting respiratory burst contribute to the irreversible pathophysiology of vascular diseases, and yet, the effects of ischemia reperfusion on vascular function, oxidative stress, and nitric oxide (NO) bioavailability have not been assessed simultaneously. Therefore, this study sought to examine the effects of prolonged forearm occlusion and subsequent reperfusion on NO-dependent brachial artery endothelial function.

Methods

Flow-mediated dilatation was measured at baseline and 15, 30, and 45 min after 20-min forearm occlusion in 14 healthy, but physically inactive middle-aged men (53.7 ± 1.2 years, BMI: 28.1 ± 0.1 kg m⁻²). Venous blood samples collected from the occluded arm were analyzed for NO metabolites and markers of oxidative stress.

Results

FMD was significantly depressed after the prolonged occlusion compared to baseline, with a significant reduction 15-min post-occlusion (6.6 ± 0.7 to 2.9 ± 0.4%, p < 0.001); FMD remained depressed after 30 min (4.1 ± 0.6%, p = 0.001), but was not significantly different to baseline after 45-min recovery (5.4 ± 0.7%, p = 0.079). Plasma nitrate (main time effect: p = 0.015) and nitrite (main time effect: p = 0.034) concentrations were significantly reduced after prolonged occlusion. Plasma catalase activity was significantly elevated at 4- (p = 0.016) and 45-min (p = 0.001) post-occlusion, but plasma peroxiredoxin 2 and protein carbonyl content did not change.

Conclusions

Prolonged forearm occlusion resulted in acute impairment of endothelium-dependent vasodilatation of the brachial artery for at least 30 min after reperfusion. We demonstrate that this vascular dysfunction is associated with oxidative stress and reduced NO bioavailability following reperfusion.

Effects of dietary nitrate supplementation on the response to extremity cooling and endothelial function in individuals with cold sensitivity. A double blind, placebo controlled, crossover, randomised control trial

Individuals with cold sensitivity have low peripheral skin blood flow and skin temperature possibly due to reduced nitric oxide (NO•) bioavailability. Beetroot has a high concentration of inorganic nitrate and may increase NO-mediated vasodilation. Using a placebo-controlled, double blind, randomised, crossover design, this study tested the hypotheses that acute beetroot supplementation would increase the rate of cutaneous rewarming following a local cold challenge and augment endothelium-dependent vasodilation in cold sensitive individuals. Thirteen cold sensitive participants completed foot and hand cooling (separately, in 15 °C water for 2 min) with spontaneous rewarming in 30 °C air whilst skin temperature and cutaneous vascular conductance (CVC) were measured (Baseline). On two further separate visits, participants consumed 140 ml of either concentrated beetroot juice (nitrate supplementation) or nitrate-depleted beetroot juice (Placebo) 90 min before resting seated blood pressure was measured. Endothelial function was assessed by measuring CVC at the forearm, finger and foot during iontophoresis of 1% w/v acetylcholine followed by foot and hand cooling as for Baseline. Plasma nitrite concentrations significantly increased in nitrate supplementation compared to Placebo and Baseline (502 ± 246 nmol L^-1; 73 ± 45 nmol L^-1; 74 ± 49 nmol L^-1 respectively; n = 11; P < 0.001). Resting blood pressure and the response to foot and hand cooling did not differ between conditions (all P > 0.05). Nitrate supplementation did not alter endothelial function in the forearm, finger or foot (all P > 0.05) compared to Placebo. Despite a physiologically meaningful rise in plasma nitrite concentrations, acute nitrate supplementation does not alter extremity rewarming, endothelial function or blood pressure in individuals with cold sensitivity.

Reference intervals for serum reactive oxygen metabolites, biological antioxidant potential, and oxidative stress index in adult rams

OBJECTIVE To establish reference intervals for serum reactive oxygen metabolites (ROMs), biological antioxidant potential (BAP), and oxidative stress index (OSi) in adult rams by use of controlled preanalytic and analytic procedures. ANIMALS 123 healthy 1- to 4-year-old rams of 2 Greek breeds (Chios [n = 62] and Florina [61]). PROCEDURES 4 hours after rams were fed, a blood sample was obtained from each ram, and serum was harvested. Concentrations of ROMs and BAP were measured colorimetrically on a spectrophotometric analyzer. The OSi was calculated as ROMs concentration divided by BAP concentration. Combined and breed-specific reference intervals were calculated by use of nonparametric and robust methods, respectively. Reference intervals were defined as the 2.5th to 97.5th percentiles. RESULTS Reference intervals for ROMs, BAP, and OSi for all rams combined were 65 to 109 Carratelli units, 2,364 to 4,491 μmol/L, and 18.2 to 43.0 Carratelli units/(mmol/L), respectively. Reference intervals of Chios rams for ROMs, BAP, and OSi were 56 to 113 Carratelli units, 2,234 to 4,290 μmol/L, and 12.9 to 38.4 Carratelli units/(mmol/L), respectively. Reference intervals of Florina rams for ROMs, BAP, and OSi were 68 to 111 Carratelli units, 2,337 to 4,363 μmol/L, and 14.1 to 38.1 Carratelli units/(mmol/L), respectively. CONCLUSIONS AND CLINICAL RELEVANCE Reference intervals calculated in this study can be used as a guide for the interpretation of ROMs, BAP, and OSi results in rams and, under appropriate conditions, can be adopted for use by veterinary laboratories.

Reperfusion Syndrome: Cellular Mechanisms of Microvascular Dysfunction and Potential Therapeutic Strategies

Reperfusion injury is the paradoxical and complex phenomenon of exacerbation of cellular dysfunction and increase in cell death after the restoration of blood flow to previously ischemic tissues. It involves biochemical and cellular changes causing oxidant production and complement activation, which culminates in an inflammatory response, mediated by neutrophil and platelet cell interactions with the endothelium and among the cells themselves. The mounted inflammatory response has both local and systemic manifestations. Despite improvements in imaging, interventional techniques, and pharmacological agents, morbidity from reperfusion remains high. Extensive research has furthered the understanding of the various pathophysiological mechanisms involved and the development of potential therapeutic strategies. Preconditioning has emerged as a powerful method of ameliorating ischemia reperfusion injury to the myocardium and in transplant surgery. More recently, postconditioning has been shown to provide a therapeutic counter to vasoocclusive emergencies. More research and well-designed trials are needed to bridge the gap between experimental evidence and clinical implementation.

Microcirculatory effects of L-arginine during acute anaerobic exercise in healthy men: A pilot study

Background/Objective

We hypothesized that L-arginine supplementation increases sublingual capillary perfusion during acute anaerobic exercise.

Methods

In a double-blind randomized study, 20 healthy men were randomly assigned to an L-arginine group or a placebo group. Both groups performed a standard 60-second duration BOSCO jumping test. Before the exercise, immediately after, and 30 minutes after exercise, systemic hemodynamic parameters were recorded. Sublingual evaluation of microcirculation using sidestream dark field (SDF) videomicroscopy was also carried out.

Results

There were no differences in mean arterial blood pressure and cardiac output between the placebo and L-arginine groups immediately after exercise and at 30 minutes after exercise. Both groups had no changes in the microvascular flow index and proportion of perfused vessels of small vessels over the testing period. We observed significantly higher functional capillary density [14.1 (12.5 - 16.0) vs. 11.7 (10.9 - 12.9) 1/mm, p = 0.021] and total vessel density of small vessels [27.8 (24.4 - 29.2) vs. 23.0 (21.6 - 24.2) mm/mm², p = 0.041] in the L-arginine group compared with the placebo group immediately after exercise, but after 30 minutes these differences had disappeared.

Conclusion

Our findings show that supplementation with L-arginine may cause additional effects on the acute anaerobic exercise-induced transient increase in capillary density in the sublingual mucosa of untrained men.

Oxidative stress predicts long-term resight probability and reproductive success in Scopoli's shearwater (Calonectris diomedea)

A major challenge in conservation physiology is to find out biomarkers that reliably reflect individual variation in wear and tear. Recent work has suggested that biomarkers of oxidative stress may provide an additional tool to assess the health state of individuals and to predict fitness perspectives. In this study, we assessed whether three biomarkers of plasma oxidative status predicted the following factors: (i) the resight probability as breeder in the next seasons; and (ii) the cumulative reproductive output over multiple years in Scopoli's shearwaters (Calonectris diomedea) using a 7 year individual-based data set. Our results show that shearwaters having higher levels of a marker of oxidative damage (reactive oxygen metabolites) in 2008 had a lower resight probability in the next years and a lower number of chicks raised from 2008 to 2014. In contrast, two biomarkers of antioxidant defences (non-enzymatic antioxidant capacity of plasma and thiols) did not have any predictive value. Increased concentrations of plasma reactive oxygen metabolites, together with the significant individual repeatability over time in this metric of oxidative stress found in numerous studies, suggest that this metric might serve as a blood-derived biomarker for health and fitness perspectives in birds and, possibly, also in other taxa.

Murine study of portal hypertension associated endothelin-1 hypo-response

AIM: To investigate endothelin-1 hypo-responsive associated with portal hypertension in order to improve patient treatment outcomes.

METHODS: Wild type, eNOS^-/- and iNOS^-/- mice received partial portal vein ligation surgery to induce portal hypertension or sham surgery. Development of portal hypertension was determined by measuring the splenic pulp pressure, abdominal aortic flow and portal systemic shunting. To measure splenic pulp pressure, a microtip pressure transducer was inserted into the spleen pulp. Abdominal aortic flow was measured by placing an ultrasonic Doppler flow probe around the abdominal aorta between the diaphragm and celiac artery. Portal systemic shunting was calculated by injection of fluorescent microspheres in to the splenic vein and determining the percentage accumulation of spheres in liver and pulmonary beds. Endothelin-1 hypo-response was evaluated by measuring the change in abdominal aortic flow in response to endothelin-1 intravenous administration. In addition, thoracic aorta endothelin-1 contraction was measured in 5 mm isolated thoracic aorta rings ex-vivo using an ADI small vessel myograph.

RESULTS: In wild type and iNOS^-/- mice splenic pulp pressure increased from 7.5 ± 1.1 mmHg and 7.2 ± 1 mmHg to 25.4 ± 3.1 mmHg and 22 ± 4 mmHg respectively. In eNOS^-/- mice splenic pulp pressure was increased after 1 d (P = NS), after which it decreased and by 7 d was not significantly elevated when compared to 7 d sham operated controls (6.9 ± 0.6 mmHg and 7.3 ± 0.8 mmHg respectively, P = 0.3). Abdominal aortic flow was increased by 80% and 73% in 7 d portal vein ligated wild type and iNOS when compared to shams, whereas there was no significant difference in 7 d portal vein ligated eNOS^-/- mice when compared to shams. Endothelin-1 induced a rapid reduction in abdominal aortic blood flow in wild type, eNOS^-/- and iNOS^-/- sham mice (50% ± 8%, 73% ± 9% and 47% ± 9% respectively). Following portal vein ligation endothelin-1 reduction in blood flow was significantly diminished in each mouse group. Abdominal aortic flow was reduced by 19% ± 9%, 32% ± 10% and 9% ± 9% in wild type, eNOS^-/- and iNOS^-/- mice respectively.

CONCLUSION: Aberrant endothelin-1 response in murine portal hypertension is NOS isoform independent. Moreover, portal hypertension in the portal vein ligation model is independent of ET-1 function.

The plant histaminase: a promising enzyme with antioxidant properties versus histamine release in isoprenaline-induced myocardial infarction in rats

The present study was designed to evaluate possible protective effects of purified histaminase from Lathyrus sativus L. seedling on the myocardial injuries upon isoprenaline-induced myocardial infarction in rats. In this regard, blood histamine concentration, creatine kinase-MB (CK-MB) activity, antioxidant status, and histopathological changes of the hearts were measured. A total of 40 adult male Sprague-Dawley rats were divided into five equal groups and treated in the following order: control (normal saline), isoprenaline (isoproterenol 110 mg/kg BW), Isopren.-H1 (isoprenaline plus histaminase 80 U/kg BW), Isopren.-H2 (isoprenaline plus histaminase 120 U/kg BW), and Isopren.-H3 (isoprenaline plus histaminase 160 U/kg BW). Myocardial infarction was manifested by a significant elevation in the level of CK-MB and histopathological findings in isoprenaline group when compared to controls. In contrast, histaminase pretreatment at dose of 160 U/kg prevented isoprenaline-induced histamine release and significantly decreased CK-MB activity as well as histopathological changes in Isopren.-H3 group. A significant increase in the catalase (CAT) and superoxide dismutase (SOD) activities was also observed by histaminase treatment in Isopren.-H2 and Isopren.-H3 groups. Although the activity of glutathione peroxidase (GPx) increased significantly to suppress oxidative stress in isoprenaline group, it was not able to prevent lipid peroxidation (as shown by TBARS concentration) in the heart of rats. In conclusion, the plant-originated histaminase presented as a promising enzyme with antioxidant properties against histamine release and myocardial infarction in rats, and it seems be a suitable therapeutic agent for future clinical trials in humans.

Glucagon effects on 3H-histamine uptake by the isolated guinea-pig heart during anaphylaxis

We estimated the influence of acute glucagon applications on ³H-histamine uptake by the isolated guinea-pig heart, during a single ³H-histamine passage through the coronary circulation, before and during anaphylaxis, and the influence of glucagon on level of histamine, NO, O₂⁻, and H₂O₂ in the venous effluent during anaphylaxis. Before anaphylaxis, glucagon pretreatment does not change ³H-histamine Umax and the level of endogenous histamine. At the same time, in the presence of glucagon, ³H-histamine Unet is increased and backflux is decreased when compared to the corresponding values in the absence of glucagon. During anaphylaxis, in the presence of glucagon, the values of ³H-histamine Umax and Unet are significantly higher and backflux is significantly lower in the presence of glucagon when compared to the corresponding values in the absence of glucagon. The level of endogenous histamine during anaphylaxis in the presence of glucagon (6.9–7.38 × 10⁻⁸  μM) is significantly lower than the histamine level in the absence of glucagon (10.35–10.45 × 10⁻⁸  μM). Glucagon pretreatment leads to a significant increase in NO release (5.69 nmol/mL) in comparison with the period before glucagon administration (2.49 nmol/mL). Then, in the presence of glucagon, O₂⁻ level fails to increase during anaphylaxis. Also, our results show no significant differences in H₂O₂ levels before, during, and after anaphylaxis in the presence of glucagon, but these values are significantly lower than the corresponding values in the absence of glucagon. In conclusion, our results show that glucagon increases NO release and prevents the increased release of free radicals during anaphylaxis, and decreases histamine level in the venous effluent during cardiac anaphylaxis, which may be a consequence of decreased histamine release and/or intensified histamine capturing by the heart during anaphylaxis.

Mesenchymal stem cell transplantation enhancement in myocardial infarction rat model under ultrasound combined with nitric oxide microbubbles

OBJECTIVE

This study evaluated the effects of ultrasound combined with the homemade nitric oxide (NO) micro-bubble destruction on the in vitro proliferation, apoptosis, and migration of mesenchymal stem cells (MSCs). Furthermore, we studied whether or not irradiation of the NO micro-bubble combined with bone-marrow derived MSC infusion had a better effect on treating myocardial infarction. The possible mechanism of MSC delivery into the infarcted myocardium was also investigated.

METHODS

The murine bone marrow-derived MSCs were isolated, cultured, irradiated, and combined with different concentrations of NO microbubbles. MTT proliferation assay, annexin V-FITC apoptosis detection, migration assay, and RT-PCR were performed 24 h after the irradiation. The NO micro-bubbles was a intravenously injected, followed by the infusion of MSCs, which were labeled by CM-Dil. Myocardium was harvested 48 h later and the distribution of MSCs was observed by laser scanning confocal microscope after frozen sectioning. Echocardiography, histological examination, RT-PCR, and western blotting were performed four weeks after the cell transplantation.

RESULTS

Ultrasound combined with 1:70 NO micro-bubbles had no significant impact on the proliferation or apoptosis of MSCs. Transwell chamber findings demonstrated that MSCs migrated more efficiently in group that underwent ultrasound combined with 1:70 NO micro-bubbles. The Real-time PCR results indicated that the expression of CXCR4 was much higher in the group undergoing ultrasound combined with 1:70 NO micro-bubbles. The normalized fluorescence intensity greatly increased in the group of US+NO micro-bubbles and the cardiac function was also markedly improved. Immunohistochemical staining showed that the capillary density was much greater in the group of US+NO micro-bubbles as compared to that of the other groups. RT-PCR and western blotting also revealed a higher SDF-1 and VEGF expression in the group of US+NO micro-bubbles.

CONCLUSIONS

NO micro-bubbles could be used in the cell transplantation, which efficiently promoted the MSC homing into the infarcted myocardium.

Glucagon-like peptide-1 preserves coronary microvascular endothelial function after cardiac arrest and resuscitation: potential antioxidant effects

Glucagon-like peptide-1 (GLP-1) has protective effects in the heart. We hypothesized that GLP-1 would mitigate coronary microvascular and left ventricular (LV) dysfunction if administered after cardiac arrest and resuscitation (CAR). Eighteen swine were subjected to ventricular fibrillation followed by resuscitation. Swine surviving to return of spontaneous circulation (ROSC) were randomized to receive an intravenous infusion of either human rGLP-1 (10 pmol·kg(-1)·min(-1); n = 8) or 0.9% saline (n = 8) for 4 h, beginning 1 min after ROSC. CAR caused a decline in coronary flow reserve (CFR) in control animals (pre-arrest, 1.86 ± 0.20; 1 h post-ROSC, 1.3 ± 0.05; 4 h post-ROSC, 1.25 ± 0.06; P < 0.05). GLP-1 preserved CFR for up to 4 h after ROSC (pre-arrest, 1.31 ± 0.17; 1 h post-ROSC, 1.5 ± 0.01; 4 h post-ROSC, 1.55 ± 0.22). Although there was a trend toward improvement in LV relaxation in the GLP-1-treated animals, overall LV function was not consistently different between groups. 8-iso-PGF(2α), a measure of reactive oxygen species load, was decreased in post-ROSC GLP-1-treated animals [placebo, control (NS): 38.1 ± 1.54 pg/ml; GLP-1: 26.59 ± 1.56 pg/ml; P < 0.05]. Infusion of GLP-1 after CAR preserved coronary microvascular and LV diastolic function. These effects may be mediated through a reduction in oxidative stress.

Local oxidative and nitrosative stress increases in the microcirculation during leukocytes-endothelial cell interactions

Leukocyte-endothelial cell interactions and leukocyte activation are important factors for vascular diseases including nephropathy, retinopathy and angiopathy. In addition, endothelial cell dysfunction is reported in vascular disease condition. Endothelial dysfunction is characterized by increased superoxide (O₂^•−) production from endothelium and reduction in NO bioavailability. Experimental studies have suggested a possible role for leukocyte-endothelial cell interaction in the vessel NO and peroxynitrite levels and their role in vascular disorders in the arterial side of microcirculation. However, anti-adhesion therapies for preventing leukocyte-endothelial cell interaction related vascular disorders showed limited success. The endothelial dysfunction related changes in vessel NO and peroxynitrite levels, leukocyte-endothelial cell interaction and leukocyte activation are not completely understood in vascular disorders. The objective of this study was to investigate the role of endothelial dysfunction extent, leukocyte-endothelial interaction, leukocyte activation and superoxide dismutase therapy on the transport and interactions of NO, O₂^•− and peroxynitrite in the microcirculation. We developed a biotransport model of NO, O₂^•− and peroxynitrite in the arteriolar microcirculation and incorporated leukocytes-endothelial cell interactions. The concentration profiles of NO, O₂^•− and peroxynitrite within blood vessel and leukocytes are presented at multiple levels of endothelial oxidative stress with leukocyte activation and increased superoxide dismutase accounted for in certain cases. The results showed that the maximum concentrations of NO decreased ∼0.6 fold, O₂^•− increased ∼27 fold and peroxynitrite increased ∼30 fold in the endothelial and smooth muscle region in severe oxidative stress condition as compared to that of normal physiologic conditions. The results show that the onset of endothelial oxidative stress can cause an increase in O₂^•− and peroxynitrite concentration in the lumen. The increased O₂^•− and peroxynitrite can cause leukocytes priming through peroxynitrite and leukocytes activation through secondary stimuli of O₂^•− in bloodstream without endothelial interaction. This finding supports that leukocyte rolling/adhesion and activation are independent events.

Tackling endothelial dysfunction by modulating NOS uncoupling: new insights into its pathogenesis and therapeutic possibilities

Endothelial nitric oxide synthase (eNOS) serves as a critical enzyme in maintaining vascular pressure by producing nitric oxide (NO); hence, it has a crucial role in the regulation of endothelial function. The bioavailability of eNOS-derived NO is crucial for this function and might be affected at multiple levels. Uncoupling of eNOS, with subsequently less NO and more superoxide generation, is one of the major underlying causes of endothelial dysfunction found in atherosclerosis, diabetes, hypertension, cigarette smoking, hyperhomocysteinemia, and ischemia/reperfusion injury. Therefore, modulating eNOS uncoupling by stabilizing eNOS activity, enhancing its substrate, cofactors, and transcription, and reversing uncoupled eNOS are attractive therapeutic approaches to improve endothelial function. This review provides an extensive overview of the important role of eNOS uncoupling in the pathogenesis of endothelial dysfunction and the potential therapeutic interventions to modulate eNOS for tackling endothelial dysfunction.

Homocysteine induces cardiomyocyte dysfunction and apoptosis through p38 MAPK-mediated increase in oxidant stress

Elevated plasma homocysteine (Hcy) is a risk factor for cardiovascular disease. While Hcy has been shown to promote endothelial dysfunction by decreasing the bioavailability of nitric oxide and increasing oxidative stress in the vasculature, the effects of Hcy on cardiomyocytes remain less understood. In this study we explored the effects of hyperhomocysteinemia (HHcy) on myocardial function ex vivo and examined the direct effects of Hcy on cardiomyocyte function and survival in vitro. Studies with isolated hearts from wild type and HHcy mice (heterozygous cystathionine-beta synthase deficient mice) demonstrated that HHcy mouse hearts had more severely impaired cardiac relaxation and contractile function and increased cell death following ischemia reperfusion (I/R). In isolated cultured adult rat ventricular myocytes, exposure to Hcy for 24 h impaired cardiomyocyte contractility in a concentration-dependent manner, and promoted apoptosis as revealed by terminal dUTP nick-end labeling and cleaved caspase-3 immunoblotting. These effects were associated with activation of p38 MAPK, decreased expression of thioredoxin (TRX) protein, and increased production of reactive oxygen species (ROS). Inhibition of p38 MAPK by the selective inhibitor SB203580 (5 μM) prevented all of these Hcy-induced changes. Furthermore, adenovirus-mediated overexpression of TRX in cardiomyocytes significantly attenuated Hcy-induced ROS generation, apoptosis, and impairment of myocyte contractility. Thus, Hcy may increase the risk for CVD not only by causing endothelial dysfunction, but also by directly exerting detrimental effects on cardiomyocytes.

Hepatic oxidative stress in an animal model of sleep apnoea: effects of different duration of exposure

BACKGROUND

Repeated apnoea events cause intermittent hypoxia (IH), which alters the function of various systems and produces free radicals and oxidative stress.

METHODS

We investigated hepatic oxidative stress in adult mice subjected to intermittent hypoxia, simulating sleep apnoea. Three groups were submitted to 21 days of IH (IH-21), 35 days of IH (IH-35), or 35 days of sham IH. We assessed the oxidative damage to lipids by TBARS and to DNA by comet assay; hepatic tissue inflammation was assessed in HE-stained slides. Antioxidants were gauged by catalase, superoxide dismutase, glutathione peroxidase activity and by total glutathione.

RESULTS

After IH-21, no significant change was observed in hepatic oxidative stress. After IH-35, significant oxidative stress, lipid peroxidation, DNA damage and reduction of endogenous antioxidants were detected.

CONCLUSIONS

In an animal model of sleep apnoea, intermittent hypoxia causes liver damage due to oxidative stress after 35 days, but not after 21 days.

Histamine blood concentration in ischemic heart disease patients

The aim of this study was to investigate histamine blood concentration in subjects suffering from different types of ischemic heart diseases during the period of eight days. Our results showed that the histamine blood level was associated with different types of ischemic heart diseases. The blood histamine level in all investigated patients was significantly higher when compared to control subjects (44.87 ± 1.09 ng mL⁻¹), indicating the increase of histamine release in patients suffering from coronary diseases. In patients suffering from ACS-UA and ACS-STEMI, the second day peak of histamine level occurs (90.85 ± 6.34 ng mL⁻¹ and 121.7 ± 6.34 ng mL⁻¹, resp.) probably as the reperfusion event. Furthermore, our data suggest that histamine can be additional parameter of myocardial ischemia along with cardiac specific enzymes and may prove to be an excellent single prognostic marker for multitude of ischemic heart diseases.

Polymer–drug conjugates for novel molecular targets

Polymer therapeutics can be already considered as a promising field in the human healthcare context. The discovery of the enhanced permeability and retention effect by Maeda, together with the modular model for the polymer–drug conjugate proposed by Ringsdorf, directed the early steps of polymer therapeutics towards cancer therapy. Orthodox anticancer drugs were preferentially chosen in the development of the first conjugates. The fast evolution of polymer chemistry and bioconjugation techniques, and a deeper understanding of cell biology has opened up exciting new challenges and opportunities. Four main directions have to be considered to develop this ‘platform technology’ further: the control of the synthetic process, the exhaustive characterization of the conjugate architectures, the conquest of combination therapy and the disclosure of new therapeutic targets. We illustrate in this article the exciting approaches offered by polymer–drug conjugates beyond classical cancer therapy, focusing on new, more effective and selective targets in cancer and in their use as treatments for other major human diseases.

Glucagon effects on ischemic vasodilatation in the isolated rat heart

The myocardial reperfusion following ischemia leads to the ischemic vasodilation by affecting the release of various vasoactive substances, such as free radicals, NO, and histamine. In addition, some evidences suggest that glucagon itself may alter the release of those substances. In this study, we investigated the ischemic vasodilation of the isolated rat heart, as well as the concentrations of NO, TBARS, and histamine in the coronary venous effluent either in the presence or in the absence of glucagon. Our results showed that in the presence of glucagon, there was a faster restoration of coronary perfusion pressure during ischemic vasodilation compared to the absence of glucagon (124 +/- 5.6 versus 81 +/- 5.2 s) with no apparent changes in TBARS concentration. The glucagon's administration leads to the decreased release of histamine by approximately 35%. Biphasic release of NO in the presence of glucagon initially showed augmentation by 60%, followed by the significant attenuation of 45%.

Melatonin reduces microvascular damage and insulin resistance in hamsters due to chronic intermittent hypoxia

Obstructive sleep apnea (OSA) causes intermittent hypoxia (IH) associated with hypertension, insulin resistance and a systemic inflammatory response. We evaluated the effects of melatonin on vasodilation, capillary perfusion in hamster cheek pouch and insulin resistance, hypertension, and reactive oxygen species (ROS) and nitrate/nitrite levels after IH for 4 wk. Syrian hamsters were divided into four groups: control group (CON), IH group, and melatonin (10 mg/kg) intraperitoneally administered daily for 4 wk/30 min before intermittent air (MEL) or IH (IH + MEL) exposure. IH alone caused elevated blood pressure, increased hematocrit, fasting hyperglycemia, elevated ROS and nitrite/nitrate levels, and vasoconstriction and reduced microvascular perfusion. Melatonin treatment of IH-exposed animals decreased blood pressure, blood glucose, and ROS and nitrite/nitrate levels, and increased vasodilation and capillary perfusion. An oral glucose tolerance test was performed after 4 wk of IH. During the last 30 min of the hyperinsulinemic euglycemic clamp, blood glucose, and insulin levels were identically matched between groups, but the glucose infusion rate was significantly reduced in IH (29.9 +/- 1.9 mg/kg/min) versus IH + MEL group (45.4 +/- 1.5 mg/kg/min, P < 0.05) demonstrating a decrease in insulin sensitivity. These results suggest that ROS and nitrite/nitrate levels play important roles in the microvascular dysfunction in IH and that this process is attenuated by melatonin. In conclusion, protection induced by melatonin against functional and metabolic impairment in IH is related to the regulation of ROS and nitrite/nitrate levels in the microcirculation. These observations may have importance to OSA pathological changes.

Mechanisms of flavonoid protection against myocardial ischemia-reperfusion injury

Flavonoids have long been acknowledged for their unique antioxidant properties, and possess other activities that may be relevant to heart ischemia-reperfusion. They may prevent production of oxidants (e.g. by inhibition of xanthine oxidase and chelation of transition metals), inhibit oxidants from attacking cellular targets (e.g. by electron donation and scavenging activities), block propagation of oxidative reactions (by chain-breaking antioxidant activity), and reinforce cellular antioxidant capacity (through sparing effects on other antioxidants and inducing expression of endogenous antioxidants). Flavonoids also possess anti-inflammatory and anti-platelet aggregation effects through inhibiting relevant enzymes and signaling pathways, resulting ultimately in lower oxidant production and better re-establishment of blood in the ischemic zone. Finally, flavonoids are vasodilatory through a variety of mechanisms, one of which is likely interaction with ion channels. These multifaceted activities of flavonoids raise their utility as possible therapeutic interventions to ameliorate ischemia-reperfusion injury.

Derivatives of reactive oxygen metabolites correlates with high-sensitivity C-reactive protein

AIM

High-sensitivity C-reactive protein (hsCRP) is a predictor of cardiovascular events. Although oxidative stress may also be related to cardiovascular disease, there are few studies comparing the two. We therefore examined the association of hsCRP, serum lipids, and derivatives of reactive oxygen metabolites (D-ROMs) in coronary artery disease.

METHODS

We measured the levels of serum lipids, hsCRP, plasma brain natriuretic peptides (BNP) and D-ROMs in 131 consecutive patients undergoing cardiac catheterization. We divided these subjects into three groups according to their levels of hsCRP.

RESULTS

In group C (hsCRP>3.0 mg/L), mean levels of serum D-ROMs were significantly higher than in groups A (hsCRP<1.0 mg/L) and B (hsCRP 1.0 to 3.0 mg/L). Serum levels of D-ROMs and log (hsCRP) correlated in the total population (r=0.479, p<0.0001), and D-ROMs, HDL-C, LDL-C and log-transformed plasma BNP were independent predictors of hsCRP (p<0.0001).

CONCLUSION

We concluded that oxidative stress increases in patients at high risk for cardiovascular events based on their hsCRP.

Novel soluble guanylyl cyclase stimulator BAY 41-2272 attenuates ischemia-reperfusion-induced lung injury

The protective effects of nitric oxide (NO), a physiological activator of soluble guanylyl cyclase (sGC), have been reported in ischemia-reperfusion (I/R) syndrome of the lung. Therefore, we studied the effects of BAY 41-2272, a novel sGC stimulator, on I/R injury of the lung in an isolated intact organ model. Lung injury was assessed by measuring weight gain and microvascular permeability (capillary filtration coefficient, K(fc)). Release of reactive oxygen species (ROS) into the perfusate was measured during early reperfusion by electron spin resonance (ESR) spectroscopy. Rabbit lungs were treated with BAY 41-2272, N(G)-monomethyl-L-arginine (L-NMMA), or NO to evaluate the effects on I/R-induced lung injury. In untreated lungs, a dramatic rise in K(fc) values and weight gain during reperfusion were observed, and these results were associated with increased ROS production. Both, BAY 41-2272 and L-NMMA significantly attenuated vascular leakage and suppressed ROS release. Additional experiments showed that BAY 41-2272 diminished PMA-induced ROS production by NADPH oxidase. A pharmacological inhibition of the enzyme with consequent reduction in ROS levels decreased I/R injury. NO had only marginal effect on I/R injury. Thus BAY 41-2272 protects against I/R-induced lung injury by interfering with the activation of NADPH oxidases.

Intra-arterial vitamin C prevents endothelial dysfunction caused by ischemia-reperfusion

OBJECTIVE

Ischemia-reperfusion (IR) injury causes tissue injury and endothelial dysfunction. There is evidence that oxidative stress plays an important role.

METHODS

We tested if IR-induced endothelial dysfunction could be prevented by administration of the antioxidant vitamin C. Twenty-six healthy male subjects and eight male patients with peripheral arterial disease (PAD) were enrolled in this randomised placebo-controlled study. Forearm blood flow (FBF) measurements in response to the vasodilators acetylcholine (ACh; endothelium-dependent agonist) or nitroglycerin (NTG; endothelium-independent) were performed before and after forearm ischemia for 20 min. FBF responses were reassessed during reperfusion with intra-arterial co-administration of 24 mg/min vitamin C or placebo. In six volunteers responses to the NO-synthase inhibitor N-monomethyl-L-arginine (L-NMMA) were also assessed before and after ischemia with and without vitamin C.

RESULTS

ACh-induced vasodilation was blunted in subjects receiving placebo after reperfusion (p<0.05 versus baseline). Administration of vitamin C completely prevented impaired responsiveness. NTG-induced vasodilation was not affected by reperfusion or vitamin C. This finding was consistent in patients with PAD and impaired endothelial function, where local vitamin C infusion restored FBF reactivity to ACh before and after IR injury (p<0.05 versus baseline). Again, NTG-induced vasodilation was not affected. Blunted L-NMMA responses seen during reperfusion could be completely reversed by vitamin C.

CONCLUSIONS

Our data indicate that IR-induced vascular injury can be prevented by administration of antioxidants.

Intermittent hypoxia modulates nitric oxide-dependent vasodilation and capillary perfusion during ischemia-reperfusion-induced damage

The microvascular function of nitric oxide (NO) during ischemia-reperfusion (I/R) in intermittent hypoxia (IH)-pretreated hamsters was analyzed using 20 mg/kg of the nonselective NO inhibitor N(omega)-nitro-l-arginine methyl ester (l-NAME) and 5 mg/kg of the preferential inducible NO inhibitor S-methylisothiourea sulphate (SMT) injected before I/R. Studies were made in the hamster cheek pouch microcirculation (intravital fluorescence microscopy). IH consisted of 6 min of 8% O(2) breathing followed by 6 min of 21% O(2) for every 8 h for 21 days. Normoxia controls (NCs) were exposed to room air for the same period. The effects were characterized in terms of systemic hemodynamics, diameter, flow, wall shear stress in arterioles, capillary perfusion, and the concentrations of thiobarbituric acid-reactive substances (TBARS) and plasma NO, assessed as nitrite/nitrate (NOx) levels. IH did not change arterial blood pressure and increased hematocrit and shear stress. IH increased NOx and TBARS levels and reduced arterial diameter, blood flow, and capillary perfusion versus the NC. Conversely, TBARS and NOx were lower during I/R in IH-pretreated hamsters, resulting in vasodilation and the increase of capillary perfusion and shear stress. After IH, capillary perfusion was reduced by 24% (2.3%) and enhanced by 115% (1.7%) after I/R (P < 0.05). Both modalities of NO blockade decreased NOx generation and increased TBARS versus IH. l-NAME and SMT induced a significant decrease in arteriolar diameter, blood flow, and capillary perfusion (P < 0.05). l-NAME enhanced TBARS more than SMT and aggravated I/R damage. In conclusion, we demonstrated that preconditioning with IH greatly reduces oxidative stress and stimulates NO-induced vasodilation during I/R injury, thus maintaining capillary perfusion.

The use of diagnostic frequency continuous ultrasound to improve microcirculatory function after ischemia-reperfusion injury

OBJECTIVE

Damage to the circulatory system resulting from ischemia-reperfusion injury (I/R injury) occurs during heart attacks and hemorrhagic shock. The authors report a method for mitigating microcirculatory injury, using diagnostic frequency continuous-mode ultrasound and how effects are influenced by nitric oxide production impairment.

METHODS

Five groups of hamsters were studied using the dorsal skin fold window chamber: (1) I/R; (2) I/R + ultrasound during ischemia; (3) I/R + ultrasound after ischemia; (4) I/R + N(omega)-nitro-L-arginine methyl ester (L-NAME); and (5) I/R + L-NAME + ultrasound. Functional capillary density (FCD) and microvascular diameter, flow velocity, and flow were monitored. During the exposures 2.49 MHz continuous ultrasound was used.

RESULTS

Significant improvements in animals exposed to ultrasound after ischemia were found at 24 h of reperfusion in FCD, arteriolar diameter, and arteriolar and venular flow velocity and flow. Animals exposed to ultrasound during ischemia showed significantly improved FCD. L-NAME treatment reduced the improvement of microvascular function, compared to animals exposed after ischemia.

CONCLUSIONS

The use of continuous-mode diagnostic frequency ultrasound is beneficial in preventing long-term ischemia-reperfusion effects in the microcirculation as shown by the return of microvascular parameters to baseline values, an effect not attained in the absence of ultrasound treatment. The effects may be in part due to the production of nitric oxide consequent to locally induced shear stress effects by ultrasound exposure.

In vivo reactive oxygen species production induced by ischemia in muscle arterioles of mice: involvement of xanthine oxidase and mitochondria

Reactive oxygen species (ROS) participate in tissue injury after ischemia-reperfusion. Their implication in leukocyte adherence and increase in permeability at the venular side of the microcirculation have been reported, but very little is known about ROS production in arterioles. The objective of this work was to evaluate, in the arteriole wall in vivo, the temporal changes in superoxide anion production during ischemia and reperfusion and to identify the source of this production. Mouse cremaster muscle was exposed to 1 h of ischemia followed by 30 min of reperfusion, and superoxide anion production was assessed by a fluorescent probe, i.e., intracellular dihydroethidium oxidation. During ischemia, we found a significant increase in dihydroethidium oxidation; however, we observed no additional increase in fluorescence during the subsequent reperfusion. This phenomenon was significantly inhibited by pretreatment with superoxide dismutase. Allopurinol (xanthine oxidase inhibitor) or stigmatellin [Q(o)-site (oriented toward the intermembrane space) inhibitor of mitochondrial complex III] or simultaneous administration of these two inhibitors significantly reduced superoxide production during ischemia to 80%, 88%, and 72%, respectively, of that measured in the untreated ischemia-reperfusion group. By contrast, no significant inhibition was found when NADPH oxidase was inhibited by apocynin or when mitochondrial complex I or complex II was inhibited by rotenone or thenoyltrifluoroacetone. A significant increase in ROS was found with antimycin A [Q(i)-site (located in the inner membrane and facing the mitochondrial matrix) inhibitor of mitochondrial complex III]. We conclude that a significant increase in ROS production occurs during ischemia in the arteriolar wall. This increased production involves both a cytoplasmic source (i.e., xanthine oxidase) and the mitochondrial complex III at the Q(o) site.

Oxidative stress-mediated arterial dysfunction in patients with metabolic syndrome: Effect of ascorbic acid

Arterial dysfunction is a hallmark of early atherosclerosis; however, its behavior in patients with metabolic syndrome (MS) is still unclear. We investigated the role of oxidative stress on ischemia-induced flow-mediated dilatation (FMD) in patients with MS. FMD and oxidative stress, as assessed by serum levels of 8-hydroxy-2-deoxy-2-deoxyguanosine (8-OHdG), were studied in 18 MS and 30 control subjects. Thereafter, in the 18 MS patients, FMD was assessed after iv infusion of 1 g vitamin C or placebo in a randomized, double-blind, crossover design; serial blood samples were taken in peripheral circulation before and after FMD to analyze 8-OHdG. Compared to controls, MS patients had higher 8-OHdG (p<0.001) and lower FMD (p<0.001); 8-OHdG and FMD were inversely correlated (R=-0.74; p<0.01). In MS patients, placebo administration did not change FMD, whereas vitamin C significantly enhanced it (p<0.001). After placebo, ischemia-induced FMD was associated with a significant increase in 8-OHdG (p<0.001), an effect that was counteracted by vitamin C. Vitamin C infusion was associated with an inverse correlation between the changes in FMD and oxidative stress (R=-0.67; p<0.01). The present study shows that arterial dilatation is impaired and that enhanced oxidative stress may play a key role in patients with MS.

Mechanisms by which low-intensity ultrasound improve tolerance to ischemia-reperfusion injury

Recent studies show that low-intensity ultrasound (US) increases endothelial nitric oxide (NO) levels in different models both in vitro and in vivo. Ischemia-reperfusion (I/R) injury is characterized by endothelial cell dysfunction, mainly as a result of altered shear stress responses associated with vasoconstriction, reduced capillary perfusion and excessive oxidative stress. This review provides an overview of the microvascular effects of low-intensity US and suggests that US exposure can be a method to provide tolerance to I/R damage. The hamster cheek pouch, extensively used in studies of I/R-induced injury, has been characterized in terms of changes of arteriolar diameter, flow and shear stress. The low-intensity US exposure reduces vasoconstriction and leukocyte adhesion and increases capillary perfusion during postischemic reperfusion. These effects may be the result of enhanced fluctuations in shear stress exerted by the flowing blood on the vessel wall. The fluctuations in turn are due to mechanical perturbations arising from the difference in acoustical impedance between the endothelial cells and the vessel content. We believe that periodic pulses of US may also cause a sustained reduction of oxidative stress and an enhanced endothelial NO level by increasing oscillatory shear stress during postischemic reperfusion. Low-intensity US exposure may represent a safe and novel important therapeutic target for patients with acute coronary syndromes and for treatment of chronic myocardial ischemia.

Melatonin reduces ventricular arrhythmias and preserves capillary perfusion during ischemia-reperfusion events in cardiomyopathic hamsters

Earlier studies showed that melatonin has powerful antioxidative effects on ischemia-reperfusion (I/R) injury in healthy hamsters. In the present study, the possible protective effects of melatonin in 10-month-old cardiomyopathic (CM) hamsters were evaluated in a model of I/R in the cheek pouches observed by intravital microscopy. In CM (BIO 14.6) hamsters diameter, red blood cell (RBC) velocity and flow in arterioles as well as lipid peroxide and nitrite/nitrate concentrations in the systemic blood, perfused capillary length, vascular permeability, and leukocyte adhesion were measured after melatonin injection (6 mg/kg intraperitoneally daily for 3 weeks), and after I/R. The influence of melatonin on the incidence of postischemic-reperfusion-induced ventricular tachycardia (VT) and ventricular fibrillation (VF) were also measured. Changes in the arteriolar response to NG-monomethyl-L-arginine (L-NMMA), a nitric oxide inhibitor, norepinephrine (NE), and angiotensin II (ANG II) were studied before and after melatonin injection (10 mg/kg intravenously). In CM hamsters, melatonin restored normal arteriolar responses to L-NMMA, NE, and ANG II. I/R elevated lipid peroxide and nitrate/nitrite levels, and vascular permeability while arteriolar diameter, RBC velocity, flow and capillary perfusion were reduced. These effects were more marked in CM versus healthy hamsters. During I/R melatonin reduced oxidative and nitrosative stress, vasoconstriction, leukocyte adhesion, and vascular permeability and increased capillary perfusion. Melatonin reduced the incidence of VT while VF during reperfusion disappeared totally. In conclusion, melatonin prevents both microvascular injury and ventricular arrhythmias during postischemic reperfusion by modulating the lipid peroxide overproduction and nitrative stress which are involved in the development of cardiomyopathy.

Reactive oxygen species and erectile dysfunction: possible role of NADPH oxidase

Erectile dysfunction (ED) is a widespread condition, the incidence of which is increasing globally. ED is also indicative of underlying vasculopathy and represents a predictor of more serious cardiovascular disorders. Understanding the aetiology of ED may therefore provide invaluable pointers to the pathobiology of other cardiovascular diseases (CVDs) and syndromes. It follows, too, that therapeutic interventions that are successful in treating ED may, ipso facto, be effective in treating the early stages of conditions that include atherosclerosis, angina, plaque rupture and diabetic angiopathy. One common pathological denominator in both CVD and ED is oxidative stress, that is, the overproduction of reactive oxygen species (ROS), in particular, superoxide (O(2)(*-)) and hydrogen peroxide (H(2)O(2)). In this review, therefore, we consider the aetiology and pathobiology of O(2)(*-) in promoting ED and focus on NADPH oxidase as an inducible source of O(2)(*-) and H(2)O(2). Therapeutic strategies aimed at reducing oxidative stress to improve erectile function are also discussed.

Melatonin reduces ischemia/reperfusion-induced superoxide generation in arterial wall and cell death in skeletal muscle

The purpose of this study was to determine the effect of melatonin on superoxide generation in arterial wall at an early phase of reperfusion and on endothelial dysfunction of microvasculature and cell viability of cremaster muscle at late phase of reperfusion (24 hr) after prolonged ischemia. Bilateral vascular pedicles which supply blood flow to the cremaster muscle were exposed. After surgical preparation, microvascular clamps were applied on the right iliac, femoral and spermatic arteries to create 4 hr of ischemia in both feeding vessels and the unexposed cremaster muscle. The vascular clamping was omitted on the left iliac, femoral and spermatic arteries and served as an internal control. Melatonin or Vehicle was via by intravenous injection at 10 min prior to reperfusion and 10 min after reperfusion. In the first experiment, the vascular pedicle was harvested after reperfusion to measure superoxide generation in real time by lucigenin-derived chemiluminescence. In the second experiment, endothelial-dependent and -independent vasodilatation was examined in the terminal arteriole of cremaster muscle which was then harvested to examine cell viability by WST-1 assay on day 2. Superoxide generation in arterial wall peaked at first 5-min of reperfusion and declined to near baseline after 60 min of reperfusion. Melatonin treatment significantly reduced superoxide generation in arterial walls and improved cell viability in cremaster muscles. Melatonin treatment also significantly reduced microvascular endothelial dysfunction which was still observable in the microcirculation of cremaster muscle after 24 hr of reperfusion. Melatonin reduces superoxide generation in the early phase of reperfusion resulting in attenuating endothelial dysfunction and muscle cell death in the late phase of reperfusion.

Polyethylene glycol and a novel developed polyethylene glycol-nitric oxide normalize arteriolar response and oxidative stress in ischemia-reperfusion

Polyethylene glycol (PEG) has been shown to repair cell membranes and, thus, inhibit free radical production in in vitro and in vivo models. We hypothesized that PEG and newly developed organic nitrate forms of PEG (PEG-NO) could repair endothelial dysfunction in ischemia-reperfusion (I/R) injury in the hamster cheek pouch visualized by intravital fluorescent microscopy. After treatments, we evaluated diameter and RBC velocity and flow in arterioles, as well as lipid peroxides in the systemic blood, perfused capillary length, vascular permeability, leukocyte adhesion, and amount of von Willebrand factor (vWF) in the blood after I/R injury. A control group was treated with 5,000- or 10,000-Da PEG, and three groups were treated with PG1 (1 NO molecule covalently bound to PEG, 5,170 Da), PG8 (8 NO molecules covalently bound to PEG, 11,860 Da), and PG16 (16 NO molecules covalently bound to PEG, 14,060 Da). All animals received 0.5 mg/0.5 ml. Lipid peroxides increased at 5 and 15 min of reperfusion, whereas diameter, RBC velocity, and blood flow decreased in arterioles after I/R injury. Vascular permeability, leukocyte adhesion, and vWF increased significantly. PEG and PG1 attenuated lipid peroxides and vasoconstriction during reperfusion and decreased leukocyte adhesion and vascular permeability. PG8 maintained lipid peroxides at normal levels, increased arteriolar diameter, flow, and perfused capillary length, and decreased vWF level and leukocyte adhesion (P < 0.05). PG16 was less effective than PG1 and PG8. In conclusion, PEG-NO shows promise as a compound that protects microvascular perfusion by normalizing the balance between NO level and excessive production of free radicals in endothelial cells during I/R injury.

Relationship between oxidative stress in muscle tissue and weight-lifting-induced muscle damage

We examined whether oxidative stress-induced muscle damage occurs during weight-lifting exercise using the rat model. Male Wistar rats were subjected to a single exhaustive session of weight-lifting exercise, and dynamics of blood volume and hemoglobin levels in the exercising muscle were monitored by near-infrared spectroscopy. Total muscle damage was evaluated by the efflux of serum creatine kinase (CK) and uptake of [(3)H]thymidine. The production of reactive oxygen species (ROS) in the muscle was estimated by serial changes in total superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) activities (established indirect markers). Immunohistochemical detection of GPX was also performed. A relatively anoxic state occurred repeatedly after every exercise set in exercising muscle following rapid blood reperfusion and was similar to an ischemia-reperfusion state. Serum CK and mitotic activity in the muscle consistently increased, and damaged muscle fibers that reacted positively to anti-GPX antibody were also observed after exercise. Serial changes in total SOD, GPX, and CAT activities were biphasic and exhibited peaks immediately and 24-72 h after exercise. The first increase was caused by a repeated ischemia-reperfusion-like state following weight-lifting exercise, and the second was dependent on the accumulation of infiltrated phagocytic cells at the damaged portions. These results suggest that ROS-induced muscle fiber damage occurred as a consequence of weight-lifting exercise.

Nitric oxide-cGMP-protein kinase G signaling pathway induces anoxic preconditioning through activation of ATP-sensitive K+ channels in rat hearts

Nitric oxide (NO) plays an important role in anoxic preconditioning to protect the heart against ischemia-reperfusion injuries. The present work was performed to study better the NO-cGMP-protein kinase G (PKG) signaling pathway in the activation of both sarcolemmal and mitochondrial ATP-sensitive K+ (KATP) channels during anoxic preconditioning (APC) and final influence on reducing anoxia-reperfusion (A/R)-induced cardiac damage in rat hearts. The upstream regulating elements controlling NO-cGMP-PKG signal-induced KATP channel opening that leads to cardioprotection were investigated. The involvement of both inducible and endothelial NO synthases (iNOS and eNOS) in the progression of this signaling pathway was followed. Final cellular outcomes of ischemia-induced injury after different preconditioning in the form of lactate dehydrogenase release, DNA strand breaks, and malondialdehyde formation as indexes of cell injury and lipid peroxidation, respectively, were investigated. The lactate dehydrogenase and malondialdehyde values decreased in the groups that underwent preconditioning periods with specific mitochondrial KATP channels opener diazoxide (100 microM), nonspecific mitochondrial KATP channels opener pinacidil (50 microM), S-nitroso-N-acetylpenicillamine (SNAP, 300 microM), or beta-phenyl-1,N2-etheno-8-bromoguanosine-3',5'-cyclicmonophosphorothioate, Sp-isomer (10 microM) before the A/R period. Preconditioning with SNAP significantly reduced the DNA damage. The effect was blocked by glibenclamide (50 microM), 5-hydroxydecanoate (100 microM), NG-nitro-L-arginine methyl ester (200 microM), and beta-phenyl-1,N2-etheno-8-bromoguanosine-3',5'-cyclic monophosphorothioate, Rp-isomer (1 microM). The results suggest iNOS, rather than eNOS, as the major contributing NO synthase during APC treatment. Moreover, the PKG shows priority over NO as the upstream regulator of NO-cGMP-PKG signal-induced KATP channel opening that leads to cardioprotection during APC treatment.

Role of nitric oxide in capillary perfusion and oxygen delivery regulation during systemic hypoxia

The role of nitric oxide (NO) and reactive oxygen species (ROS) in regulating capillary perfusion was studied in the hamster cheek pouch model during normoxia and after 20 min of exposure to 10% O2-90% N2. We measured PO2 by using phosphorescence quenching microscopy and ROS production in systemic blood. Identical experiments were performed after treatment with the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) and after the reinfusion of the NO donor 2,2'-(hydroxynitrosohydrazono)bis-etanamine (DETA/NO) after treatment with L-NMMA. Hypoxia caused a significant decrease in the systemic PO2. During normoxia, arteriolar intravascular PO2 decreased progressively from 47.0 +/- 3.5 mmHg in the larger arterioles to 28.0 +/- 2.5 mmHg in the terminal arterioles; conversely, intravascular PO2 was 7-14 mmHg and approximately uniform in all arterioles. Tissue PO2 was 85% of baseline. Hypoxia significantly dilated arterioles, reduced blood flow, and increased capillary perfusion (15%) and ROS (72%) relative to baseline. Administration of L-NMMA during hypoxia further reduced capillary perfusion to 47% of baseline and increased ROS to 34% of baseline, both changes being significant. Tissue PO2 was reduced by 33% versus the hypoxic group. Administration of DETA/NO after L-NMMA caused vasodilation, normalized ROS, and increased capillary perfusion and tissue PO2. These results indicate that during normoxia, oxygen is supplied to the tissue mostly by the arterioles, whereas in hypoxia, oxygen is supplied to tissue by capillaries by a NO concentration-dependent mechanism that controls capillary perfusion and tissue PO2, involving capillary endothelial cell responses to the decrease in lipid peroxide formation controlled by NO availability during low PO2 conditions.

Antioxidant activity of nitro derivative of aspirin against ischemia-reperfusion in hamster cheek pouch microcirculation

Aspirin that has been chemically combined with a nitric oxide (NO) donor (NCX-4016) has been shown to inhibit cyclooxygenase and prostaglandin generation while maintaining the inhibitory effects of aspirin. The possible role of reactive oxygen species (ROS) in the action of NCX-4016 in ischemia-reperfusion (I/R) has not been studied. Furthermore, we were interested in comparing the effects of a conventional NO donor [2,2'-hydroxynitrosohydrazino-bis-etanamine (DETA/NO)] and NCX-4016 at the microvascular level in the hamster cheek pouch visualized by using an intravital fluorescent microscopy technique. Microvascular injury was assessed by measuring diameter change, the perfused capillary length (PCL), and leukocyte adhesion. Animals were treated with NCX-4016 (100 mg/kg or 30 mg.kg(-1).day(-1) for 5 days po) or DETA-NO (0.5 mg/kg). Mean arterial blood pressure increased slightly but significantly after NCX-4016 treatment. During 5- and 15-min reperfusion, lipid peroxides in the systemic blood increased by 72 and 89% vs. baseline, respectively, and were still higher than in basal conditions after 30-min reperfusion in the I/R group. Pretreatment with NCX-4016 maintained ROS at normal levels; increased arteriolar diameter, blood flow, and PCL; and decreased leukocyte adhesion (P < 0.05). DETA-NO decreased ROS during 30-min reperfusion; however, later there was a significant increase during reperfusion. DETA-NO decreased leukocyte adhesion (P < 0.05) but microvascular permeability increased after 30 min of reperfusion. In conclusion, NCX-4016 attenuates oxidative stress and prevents arteriolar constriction during I/R, whereas DETA-NO increases lipid peroxides in the systemic blood and permeability after reperfusion.