Release Of Oxygen Free Radicals Research Articles

Ascorbic acid improves renal microcirculatory oxygenation in a rat model of renal I/R injury.

Background and objectivesAcute kidney injury (AKI) is a clinical condition associated with a degree of morbidity and mortality despite supportive care, and ischemia/reperfusion injury (I/R) is one of the main causes of AKI. The pathophysiology of I/R injury is a complex cascade of events including the release of free oxygen radicals followed by damage to proteins, lipids, mitochondria, and deranged tissue oxygenation. In this study, we investigated whether the antioxidant ascorbic acid would be able to largely prevent oxidative stress and consequently, reduce I/R-related injury to the kidneys in terms of oxygenation, inflammation, and renal failure.Materials and methodsRats were divided into three groups (n = 6/group): (1) a time control group; (2) a group subjected to renal ischemia for 60 min by high aortic occlusion followed by 2 h of reperfusion (I/R); and (3) a group subjected to I/R and treated with an i.v. 100 mg/kg bolus ascorbic acid 15 min before ischemia and continuous infusion of 50 mg/kg/hour for 2 h during reperfusion (I/R + AA). We measured renal tissue oxidative stress, microvascular oxygenation, renal oxygen delivery and consumption, and renal expression of inflammatory and injury markers.ResultsWe demonstrated that aortic clamping and release resulted in increased oxidative stress and inflammation that was associated with a significant fall in systemic and renal hemodynamics and oxygenation parameters. The treatment of ascorbic acid completely abrogated oxidative stress and inflammatory parameters. However, it only partly improved microcirculatory oxygenation and was without any effect on anuria.ConclusionThe ascorbic acid treatment partly improves microcirculatory oxygenation and prevents oxidative stress without restoring urine output in a severe I/R model of AKI.

Volatile anesthetics and ischemia-reperfusion injury.

Ischemia-reperfusion (IR) injury can occur under various clinical conditions in which the restoration of blood and oxygen to ischemic tissues results in a massive release of oxygen free radicals. For example, cardiac surgery, stroke, tourniquet application for orthopedic surgery, organ transplantation, and restoration of shock can cause IR injury. Reperfusion produces an increased free radical concentration with lipid peroxidation, microvascular injury, inflammatory cytokine release, and neutrophil activation. In addition, IR stress triggers necrotic or apoptotic cell death. Understanding the mechanisms of IR injury may provide therapeutic targets to decrease IR injury and improve outcomes in clinical settings (e.g., coronary or cerebral vascular disease). Some anesthetic agents, including volatile or intravenous anesthetics, are known to have a protective effect against IR injury. The guidelines of the American College of Cardiology and the American Heart Association recommend volatile anesthetic agents during non-cardiac surgery for the maintenance of general anesthesia in hemodynamically stable patients at risk for myocardial ischemia [1]. Several mechanisms have been proposed to explain the protective effect of volatile anesthetics against cardiac IR injury. IR can increase neutrophil adhesion to vascular endothelial cells, which contributes to reperfusion injury. Volatile anesthetics such as isoflurane and sevoflurane can reduce the reperfusion-induced adhesion of neutrophils at clinically relevant doses [2]. Volatile anesthetics are known to improve adenosine triphosphate (ATP) synthesis and decrease the production of reactive oxygen species, which are associated with reduced rates of respiration and phosphorylation in the electron transport chain and ATPase activity in mitochondria. The positive effects of volatile anesthetics are also associated with mitochondrial ATP-sensitive K+ channel opening, which leads to a decrease in postischemic intracellular Ca2+ concentrations [3]. Volatile anesthetics are known to diminish cerebral IR injury. Neuroprotective effects of volatile anesthetics have been shown in various in vitro and in vivo experimental models. In this issue of the Korean Journal of Anesthesiology, Kim et al. [4] report that isoflurane post-treatment provides neuroprotection against tissue plasminogen activator (tPA)-exaggerated brain IR injury. In this study, isoflurane improved neurobehavioral function and decreased the cerebral infarct volume and intracranial hemorrhage induced by tPA-exaggerated brain IR injury. Although tPA is an effective intervention for the treatment of acute ischemic stroke, it has various detrimental effects on brain IR injury, including hemorrhagic transformation, cytotoxicity, increased microvascular permeability, and neutrophil degranulation with the release of matrix metalloproteinase (MMP)-9, neutrophil elastase, and myeloperoxidase [5]. As discussed in this issue of the Korean Journal of Anesthesiology, the downregulation of MMP-9 is a plausible mechanism for the protective effect of isoflurane. Volatile anesthetics, including isoflurane and sevoflurane, are known to increase survival signaling such as PI3K/Akt signaling, which is involved in the protective effect of anesthetics against cerebral IR injury. Recent studies have shown that isoflurane post-conditioning decreased the infarct volume, number of apoptotic cells, and neurological deficits 4 weeks after middle cerebral artery occlusion-induced ischemic brain injury. Isoflurane reduced IR-induced nuclear transcription factor-κB activation, interleukin (IL)-1β, and IL-6 in the penumbral area [6]. These results suggest that the anti-inflammatory effect of isoflurane is also involved in the neuroprotective effect. Numerous studies have shown that various anesthetic agents can decrease cerebral IR injury. As described in this issue of the Korean Journal of Anesthesiology, isoflurane is a promising anesthetic agent in ischemic brain injury. IR injury is unavoidable in clinical situations, and anesthesia is necessary for surgical practice. Therefore, determining the optimal anesthetic modality is important to improve clinical outcomes.

Modern clinical retrospective on ventricular rhythm disturbances in acute myocardial infarction: Latest treatment mode according to the valid recommendations

Ventricular arrhythmias are the most common cause of mortality in patients with acute myocardial infarction. Arrhythmias in acute coronary syndrome occur because of unbalanced function of the autonomic nervous system, because of electrolyte status disturbances (hypokalemia, hypomagnesaemia, intracellular hypercalcemia) and because of slow conduction in ischemical myocardium zones. Arrhythmias contribute to acidosis and release of free oxygen radicals occurring during reperfusion of ischemic myocardium. Ventricular arrhythmias in acute myocardial infarction indicate the presence of extensive myocardial damage at a reduced left ventricular ejection fraction, and not infrequently in the formation of an aneurysm of the left ventricle. In patients with acute coronary syndrome, the most common ventricular arrhythmias are premature ventricular beats, ventricular tachycardia, ventricular flutter and fibrillation and accelerated idioventricular rhythm. Ventricular fibrillation, still the leading cause of sudden death in patients with acute coronary syndrome within the first four hours of myocardial infarction, occurs in 80 % of all ventricular fibrillations. The use of beta-blockers in the first 24 hours of acute myocardial infarction in patients with early ventricular fibrillation and tachycardia does not affect the degree of worsening heart failure and is directly associated with reduced rates of early mortality in these patients. Quick and adequate treatment of ventricular arrhythmias is a major advancement in the treatment of acute myocardial infarction.

Case Scenario: Compartment Syndrome of the Forearm in Patient with an Infraclavicular Catheter

Case Scenario: Compartment Syndrome of the Forearm in Patient with an Infraclavicular Catheter

Dexmedetomidine did not reduce the effects of tourniquet-induced ischemia-reperfusion injury during general anesthesia

Ischemia reperfusion injury causes the release of free oxygen radicals. Free oxygen radicals initiate the production of toxic metabolites, such as malondialdehyde (MDA), through the lipid peroxidation of cellular membranes. Following lipid peroxidation, the antioxidant enzyme system is activated against reactive oxygen species (ROS) and attempts to protect cells from oxidative damage. There is a balance between the scavenging capacity of antioxidant enzymes and ROS. Because of this balance, the total antioxidant capacity (TAC) measurement is a sensitive indicator of the overall protective effects of the antioxidants. Alpha2 receptor agonists are effective in preventing hemodynamic reactions during extremity surgeries by preventing the release of catecholamines secondary to tourniquet application. They have also been shown to possess preventive effects in various ischemia-reperfusion injury models. In our study, we examined the effects of dexmedetomidine on tourniquet-induced ischemia-reperfusion injury in lower extremity surgeries performed under general anesthesia. The effects of dexmedetomidine were measured with serum MDA and TAC levels. We studied 60 adult American Society of Anesthesiologists (ASA) physical status I or II patients undergoing one-sided lower extremity surgery with tourniquet. The patients were randomly divided into two groups. Group D was administered a dexmedetomidine infusion at a rate of 0.1μg/kg/minute−1 for 10 minutes prior to induction and then at 0.7μg/kg/hour−1 until 10 minutes before the end of the operation. The control group (Group C) received a saline infusion of the same amount and for the same period of time. General anesthesia was induced with thiopental, fentanyl, and rocuronium and maintained with nitrous oxide and sevoflurane in both groups. Venous blood samples were obtained before the administration of the study drugs (basal) at 1 minute before tourniquet release and at 5 and 20 minutes after tourniquet release (ATR). In both groups, MDA levels decreased at 5 and 20 minutes ATR when compared with the basal values (p<0.05). TAC levels decreased at 1 and 5 minutes ATR and then returned to basal values at 20 minutes ATR (p<0.05). In reference to the prevention of lipid peroxidation in tourniquet-induced ischemia-reperfusion injury, the results from the two groups in our study showed that dexmedetomidine did not have an additional protective role during routine general anesthesia.

Protection of penehyclidine hydrochloride on renal tissue injury induced by limb ischemia/reperfusion

To evaluate the protection of penehyclidine hydrochloric postconditioning on HIF-1α (hypoxia-inducible factor-1α) in renal tissue injury induced by lower limb ischemia/reperfusion (I/R). A total of 72 adult male Wistar rats weighing 230 - 250 g were randomly divided into 3 groups: control (group C), limb ischemia-reperfusion (group R/I) and penehyclidine hydrochloride postconditioning (group P). The animals were anesthetized by inhaling 2% isoflurane and blood flow of bilateral lower limbs was blocked with rubber bands for 3 h in groups P and R/I. In group P, penehyclidine hydrochloride 0.15 mg/kg was injected via caudal vein at 3 min pre-reperfusion. After sacrificing, their kidneys were removed at 3 h of ischemia and 1, 3, 6 h of reperfusion respectively. The blood urea nitrogen (BUN) and creatinine (Cr) were detected by colorimetric method, plasma tumor necrosis factor-α (TNF-α) by ELISA (enzyme-linked immunosorbent assay) and HIF-1α of renal tissue by immunohistochemistry. Renal pathological changes were observed under light microscope. Compared with group C, the serum levels of BUN and Cr increased while TNF-α and HIF-1α were up-regulated in groups I/R and P (P < 0.05). As compared with group I/R, the serum levels of BUN, Cr and MDA decreased while TNF-α and HIF-1α were down-regulated in group P. [at T2: (15.10 ± 1.88) mmol/L vs (19.46 ± 2.76) mmol/L, (113 ± 10) µmol/L vs (143 ± 11) µmol/L, (13.8 ± 1.7) nmol/g vs (15.5 ± 1.8) nmol/g, (53.1 ± 3.1) ng/L vs (53.9 ± 4.8) ng/L, 0.298 ± 0.015 vs 0.471 ± 0.032, all P < 0.05]. Penehyclidine hydrochloride can down-regulate the expression of HIF-1α and attenuate the renal injury induced by lower limb I/R. And the mechanisms may be through inhibiting the inflammatory reactions, reducing the release of oxygen free radicals and improving the conditions of hypoxia and ischemia.

Thiopental improves renal ischemia–reperfusion injury

Ischemia/reperfusion (I/R) occurs in a number of pathological conditions, including myocardial infarction, stroke, aortic surgery, cardiopulmonary bypass surgery, organ transplantation, resuscitation, and critical care. Massive and abrupt release of oxygen-free radicals after reperfusion triggers oxidative damage. Before critical operations or after resuscitation, it would be wise to find a suitable prophylactic treatment to avoid I/R damage. We aimed to determine whether several commonly used intravenous anesthetics protect against renal I/R injury. Methods: Animals were randomly divided into seven groups, each consisting of six animals: sham group, control group, thiopental group, propofol group, intralipid group, etomidate group, and ketamine group. At the end of the 60-min ischemic period, 60 min reperfusion was established and the materials administered 15 min before the reperfusion. At the end of the reperfusion period, the samples of blood and tissue were reaped for biochemical and serological evaluation. Results: I/R procedure significantly increased malondialdehyde (MDA) levels, decreased catalase (CAT) activities, and superoxide dismutase (SOD) levels. The lowest MDA mean level was in the thiopental group and the highest MDA mean level was in control group. The lowest CAT mean level was in the intralipid group and the highest CAT mean level was in the etomidate group. The lowest SOD mean level was in the control group and the highest SOD mean level was in the propofol group. Conclusion: Thiopental and propofol, especially thiopental, are more effective to protect renal I/R injury.

Role of inflammation in the pathogenesis of age-related macular degeneration

This article aims to review the role of inflammation in the pathogenesis of age-related macular degeneration. Besides environmental factors, a direct link to genetics in general and/or genetics of inflammatory pathways could be shown to contribute to both the initiation and propagation of the disease. The complement system with the Y402H variant of the complement factor H gene as one of the key factors plays a central role. A defect in the control mechanism leads to an activation in genetically predisposed individuals. The LOC387715/ARMS2 and HTRA1 genes, as well as certain chemokines and their receptors, especially the CX3CR1 chemokine receptor and the Toll-like receptors, are associated with the development of age-related macular degeneration. Among all inflammatory cells and mediators, macrophages deserve special attention. They have been shown to express both proinflammatory and angiogenic factors, such as VEGF and many others that have been identified in choroidal neovascularization membranes. However, there are controversial reports on the actual role of these inflammatory cells, as well as on the role of C-reactive protein. An additional mechanism that is directly related to inflammation is oxidative stress via the release of oxygen free radicals – a phenomenon that, to a certain extent, occurs in every mammalian organism – which may be increased in the aging body, thereby leading to oxidative tissue damage. This damage seems to be a crucial trigger for age-related macular degeneration via both direct damage of unsaturated fatty acids and activation of inflammatory pathways. Polyunsaturated fatty acids, major molecules of the photoreceptor outer segments, are highly susceptible to oxidation processes.

Interplay between signaling via the formyl peptide receptor (FPR) and chemokine receptor 3 (CCR3) in human eosinophils

Eosinophils express the chemoattractant receptors CCR3 and FPR. CCR3 binds several agonists such as eotaxin-1, -2, and -3 and RANTES, whereas the FPR binds the formylated tripeptide fMLP and a host of other ligands. The aim of this study was to investigate if there is interplay between these two receptors regarding the elicitation of migration and respiratory burst in human blood-derived eosinophils. Inhibition of the FPR with the antagonists CyH and boc-MLP abrogated the migration of eosinophils toward all of the CCR3 agonists. Similar results were seen when the FPR was desensitized with its cognate ligand, fMLP. In contrast, the respiratory burst triggered by eotaxin-1 was not inhibited by CyH. Thus, signals evoked via the FPR caused unidirectional down-regulation of CCR3-mediated chemotaxis but not respiratory burst in human eosinophils. The underlying mechanism was neither reduced ability of the CCR3 ligand eotaxin-1 to bind to CCR3 nor down-regulation of CCR3 from the cell surface. Finally, confocal microscopy and adFRET analysis ruled out homo- or heterodimer formation between FPR and/or CCR3 as an explanation for the reduction in chemotaxis via CCR3. Pharmacologic inhibition of signal transduction molecules showed that the release of free oxygen radicals in response to eotaxin-1 compared with fMLP is relatively more dependent on the p38 MAPK pathway.

Acute Renal Failure and Mechanical Ventilation: Reality or Myth?

Acute Renal Failure and Mechanical Ventilation: Reality or Myth?

Lecithinized Superoxide Dismutase Suppresses Free Radical Substrates During the Early Phase of Burn Care in Rats

Severe hypovolemia is caused by an increase in blood vessel permeability in the early phase after an extensive burn; massive fluid volume replacement has been used for the treatment of this condition. The release of oxygen free radicals and chemical mediators, especially from skin tissue, induces the increase in blood vessel permeability. Free radical burst is associated with ischemia-related skin tissue injury. Although various antioxidant therapies have been used to inhibit the consequences of hypovolemia, an effective method has not been established. To elucidate the protective effects of lecithinized superoxide dismutase (PC-SOD) as an antioxidant agent. Each rat sustained a 30% total body surface area burn (n = 20) on the back by the Walker and Mason method were allocated into three groups: (1) no treatment group (n = 6), (2) a low dose of PC-SOD (0.67 mg/kg) group (n = 7), and (3) a high dose of PC-SOD (1.33 mg/kg) group (n = 7). The concentrations of malondialdehyde and SOD in the serum, skin tissue, and lung tissue were measured in each group 1 hour after burning. Both low and high doses of PC-SOD prevented malondialdehyde concentration associated with free radical burst after burning compared with the no treatment group (P < .05); serum (27.7 +/- 6.8, 10.8 +/- 2.7, and 12.1 +/- 2.8 nmol/L), skin tissue (2251.3 +/- 560.5, 802.7 +/- 228.8, and 790.1 +/- 188.3 nmol/wet.g), and lung (157.3 +/- 19.5, 109.1 +/- 23.9, and 81.9 +/- 20.3 nmol/wet.g). These data suggest that PC-SOD may be a protective agent against free radical-induced vasodilatation caused by severe, extensive burns.

Reciprocal Activation Between CD4+ T Cells and Kupffer Cells During Hepatic Ischemia-Reperfusion

Mechanisms mediating CD4+ T-cell recruitment during alloantigen-independent hepatic ischemia-reperfusion (I/R) remain not fully understood. We hypothesized that Kupffer cells activate CD4+ T-cells in the postischemic liver, by the release of free oxygen radicals and cytokines. Recruitment of freshly isolated and fluorescence-labeled CD4+ T-cell was analyzed after hepatic I/R (90/30-120 min) using intravital microscopy in sham-operated mice, in mice after hepatic I/R and in postischemic groups after Kupffer cell depletion, after treatment with antioxidant glutathione, in interleukin (IL)-6-/- mice; and in wild-type mice after infusion of tumor necrosis factor (TNF) receptor-1-/-CD4+ T-cells. Using flow cytometry and immunohistochemistry, we assessed whether Kupffer cell-derived mediators activate CD4+ T-cells and sinusoidal endothelial cells. The clearance kinetics of fluorescence-labeled latex beads was determined as a marker of Kupffer cell activity in vivo. I/R-induced accumulation of CD4+ T-cells in hepatic sinusoids was significantly attenuated on Kupffer cell depletion, after scavenging of free radicals and after interruption of the IL-6- and TNF-alpha-dependent pathways. These mediators directly activate CD4+ T-cells and up-regulated the expression of T cell-relevant adhesion molecules on sinusoidal endothelial cells. Postischemic activity of Kupffer cells was significantly impaired in wild-type mice, and was even more depressed in CD4-/- animals. Kupffer cells trigger recruitment of CD4+ T-cells in the postischemic liver by the release of reactive oxygen species, IL-6, and TNF-alpha. These mediators are capable of activating CD4+ T-cells and sinusoidal endothelial cells. CD4+ T-cells, in turn, influence the activation of Kupffer cells.

Superoxide-Dependent Cathepsin Activation Is Associated with Hypertensive Myocardial Remodeling and Represents a Target for Angiotensin II Type 1 Receptor Blocker Treatment

The elastolytic activity of cathepsins in the myocardium is implicated in hypertensive heart failure (HF). Given that reactive oxygen species are also implicated in protease activation associated with cardiac remodeling, we examined the role of the reactive oxygen species-induced cathepsin activation system in cardiac remodeling during the development of hypertensive HF. Dahl salt-sensitive hypertensive rats maintained on a high-salt diet were treated with vehicle, the cathepsin inhibitor E64d, or the angiotensin receptor blocker olmesartan from 12 to 19 weeks of age. Cathepsin expression and activity were increased in the left ventricle of HF rats; olmesartan inhibited these effects, restored the balance between elastin and collagen in the left ventricle, and suppressed degradation of the elastic lamina of coronary arteries of HF rats. Furthermore, olmesartan inhibited up-regulation of NADPH oxidase subunits and activity as well as superoxide generation. These effects of olmesartan were mimicked by E64d and were accompanied by amelioration of cardiac fibrosis. Finally, olmesartan and apocynin reduced angiotensin II-induced increases in cathepsin mRNA and protein levels in cultured rat neonatal cardiac myocytes. These data suggest that cathepsins likely trigger and promote cardiac remodeling and that blocking the angiotensin II type 1 receptor attenuates cathepsin expression and activity by inhibiting the production of superoxide by NADPH oxidase, thereby attenuating cardiac remodeling and dysfunction.

Effect of sevoflurane postconditioning on spinal cord ischemia reperfusion injury via the release of oxygen free radicals in rabbits

To investigate whether postconditioning with sevoflurane could alleviate spinal cord ischemia reperfusion injury in rabbits, and whether the beneficial effect is dependent on oxygen free radicals. In Experiment 1, 48 male New Zealand white rabbits were randomly assigned to six groups (n=8 each). Animals in the sham group only underwent sham-operation. Animals in the control group underwent spinal cord ischemia for 20 min without postconditioning. Animals in 02 postconditioning group (Group O2) inhaled 100% O2 from 5 min before reperfusion and lasted 13 min. Animals in sevoflurane postconditioning groups (Group Sevo0.5, Sevo1.0 and Sevo1.5) inhaled 0.5, 1.0, 1.5 minimum alveolar concentration (MAC) sevoflurane in 100% O2 from 5 min before reperfusion and lasted 10 min, then inhaled 100% O2 for 3 min to wash out the remaining sevoflurane. In Experiment 2, 36 male New Zealand White rabbits were randomly assigned to four groups (n=9 each). Animals in O2 and Sevo groups received normal saline (5 ml/kg intravenously) 1 h before postconditioning with 100% O2 and 1.0 MAC sevoflurane, respectively. In the DMTU + Sevo and DMTU + O2 groups, 5 ml/kg of 10% dimethylthiourea (DMTU, a potent oxygen free radical scavenger, dissolved in saline) was administered intravenously at the same time. Spinal cord ischemia was induced by an infrarenal aorta clamping for 20 min. Forty-eight hours after reperfusion, hind-limb motor function and histopathology of the spinal cord were examined in a blinded fashion. (1) The neurologic and histopathologic outcomes in the sevoflurane postconditioning groups were better than those in the control group (P < 0.05), the histopathologic outcomes in Sevo1.0 group were better than that in Sevo0.5 and Sevo1.5 groups (P < 0.05). (2) The neurologic and histopathologic outcomes in Sevo, DMTU + Sevo and DMTU + O2 groups were better than those in the O2 group (P < 0.05), the histopathologic outcomes in Sevo group were better than that in the DMTU + Sevo and DMTU + O2 groups (P < 0.05). Our study demonstrates that sevoflurane postconditioning against spinal cord ischemia injury via the release of oxygen free radicals in rabbits.

Immune response of zebrafish ( Danio rerio) against a newly isolated bacterial pathogen Aeromonas hydrophila

A strain of Aeromonas hydrophila associated with unusual mortalities in zebrafish ( Danio rerio) culture facilities was isolated, identified and characterized. In challenge experiments, adult zebrafish were susceptible to infection by intraperitoneal (i.p.) injection with viable bacteria and its extracellular products (ECPs) reaching very high mortalities in a few hours. The infection, by the viable bacteria or the ECPs, caused cell death in kidney, due to the cytotoxic and haemolytic activities of the bacterial ECPs. Moreover, the infection affected the release of oxygen (ROS) and nitrogen (NO) reactive free radicals. To determine if this A. hydrophila infection induces an inflammatory response, mRNA expression levels of tumour necrosis factor-α (TNFα), interleukin-1β (IL-1β), interferon-γ (IFNγ) and inducible nitric oxide (iNOS) were assessed by real time PCR. The expression levels of TNFα, IL-1β and IFNγ were upregulated in the kidneys of infected zebrafish with viable bacteria, heat-killed bacteria and ECPs. Expression levels of iNOS were upregulated by ECPs. Mortality rate (LD 50) and histopathology were also determined.

Protective effects of glucagon‐like peptide 2 on intestinal ischemia‐reperfusion rats

Our objective was to evaluate the protective effects of glucagon-like peptide 2 (GLP-2) on intestinal ischemia/reperfusion (I/R) rats. Thirty-two rats were randomly assigned to four experimental groups, each of 8: Group A, sham rats underwent laparotomy only, without superior mesenteric artery (SMA) occlusion; Group B, I/R animals underwent laparotomy and occlusion of the SMA for 60 minutes followed by 120 minutes of reperfusion; Group C, I/R animals underwent intestinal I/R, and received pretreatment with GLP-2 for 3 days preoperatively; and Group D, I/R animals underwent intestinal I/R, received pretreatment with GLP-2 as above, and during the reperfusion phase were injected intravenously with GLP-2. After the reperfusion of intestinal ischemia, samples of intestinal mucosa, mesenteric lymph nodes (MLN) and blood were prepared for determination. In the pretreatment rats with GLP-2 (group C), Chiu's scores, bacterial colony counts, serum D-lactate, intestinal mucosal MDA and ET-1, and serum endotoxin, TNF-alpha and IL-6 were significantly reduced compared with intestinal I/R rats (group B). Administration of GLP-2 during the reperfusion phase following pretreatment (group D) showed further protective effects in comparison with the pretreatment rats (group C). We conclude that treatment with GLP-2 attenuates intestinal I/R injury, reduces bacterial translocation, inhibits the release of oxygen free radicals and ET-1, and may well inhibit the production of proinflammatory cytokines.

The mechanism of nitrate-induced preconditioning

Nitroglycerin (GTN) has been shown, in both human and animal studies, to induce a protective phenotype that limits tissue damage after ischemia and reperfusion. This phenomenon is similar to ischemic preconditioning, and several reports suggest that also the molecular pathways involved in this protective effect of nitrates are the same that determine ischemic preconditioning. Our group conducted a series of studies aimed at investigating, using a human model of endothelial IR injury, the mechanism of nitrate-induced preconditioning and particularly the role of reactive oxygen species formation and of the opening of mitochondrial permeability transition pores. Our data demonstrate that GTN protects the endothelium against postischemic endothelial dysfunction in a mechanism that is mediated by oxygen free radical release and opening of mitochondrial permeability transition pores. In contrast, the protective effect of pentaerithrityl tetranitrate appears to be independent of these mechanisms, and it seems to be mediated by induction of antioxidant genes. Finally, isosorbide mononitrate seems to be devoid of a significant protective effect. These data are summarized and discussed in the present paper.

Influence of β-glucans on the immune responses of carpet shell clam ( Ruditapes decussatus) and Mediterranean mussel ( Mytilus galloprovincialis)

The effects of β-glucans on several immune functions of carpet shell clam ( Ruditapes decussatus) and Mediterranean mussel ( Mytilus galloprovincialis) hemocytes were determined. Nitric oxide (NO) production increased significantly in β-glucan treated mussels and clams. In mussels, β-glucans increased by themselves the release of free oxygen radicals and also were able to enhance the phorbol 12-myristate 13-acetate (PMA) mediated effect on this hemocyte activity. However, high doses of β-glucans when combined with zymosan decreased this respiratory burst. In clams, hemolymph treated with several doses of β-glucans limited the growth of the three bacteria, Vibrio algynolyticus (strain TA15), Vibrio splendidus (strain TA2) and Escherichia coli (strain ATCC 13706). This modulation on the antibacterial activity, however, was not observed when mussel hemolymph was incubated with β-glucans. These results suggest that the immune responses of these animals can be up and down modulated by external stimuli and, although clams and mussels are both relatively closely related species, their behaviour concerning immune responses can be different.

Relationship Between Biofeedback and Oxidative Stress in Patients With Chronic Migraine

Chronic migraine (1.5.1) is burdened with headache-related disability. During noxious stimulation, changes of cerebral blood flow enhance the release of oxygen free radicals that react with nitric oxide (NO). We investigated the role of biofeedback in limiting migraine disability by influencing oxidative stress. Peroxides, NO and superoxide dismutase (SOD) were analysed in 20 female subjects with chronic migraine and in 20 female healthy controls before and after biofeedback sessions. NO(x) levels (23.7 +/- 4.2 vs. 34.9 +/- 4.6 microm; P < 0.05) and SOD activity (6.5 +/- 1.0 vs. 8.0 +/- 0.7 U/ml; P < 0.05) were lower in migraine sufferers before treatment than in healthy controls, whereas peroxide levels (145.8 +/- 40.3 vs. 78.0 +/- 20.0 microm; P < 0.05) were higher in migraine sufferers before treatment than in healthy controls. In migraine sufferers NO(x) levels (23.7 +/- 4.2 vs. 31.3 +/- 7.1 microm; P < 0.05) and SOD activity (6.5 +/- 1.0 vs. 7.9 +/- 0.9 U/ml; P < 0.05) were lower before than after treatment, whereas peroxide levels (145.8 +/- 40.3 vs. 82.4 +/- 21.1 microm; P < 0.05) were higher before than after treatment. SOD serum activity correlated positively with NO(x) serum levels and negatively with peroxide serum levels in healthy controls and in chronic migraine sufferers before and after biofeedback. The mean Migraine Disability Assessment Score before biofeedback sessions was higher than after treatment (36.9 +/- 13.9 vs. 18.8 +/- 10.4; P < 0.001). The effectiveness of biofeedback in limiting chronic migraine may be related to muscular relaxation associated with decreased oxidative stress accompanied by psychological well-being.

Elastin in blood vessels.

Elastin fibres give blood vessels important rheological properties, such as the postsystolic elastic recoil. The age-dependent increase of Ca2+ and lipid content, and elastolytic degradation of the fibres progressively impairs their function and produces circulating elastin peptides. Their interaction with the elastin receptor on smooth muscle cells induces not only increased cell-elastin fibre adhesion and endothelium-dependent vasorelaxation but also the release of lytic enzymes and oxygen free radicals from monocytes penetrating the vascular wall during atherogenesis. The age-dependent 'uncoupling' of the receptor has been shown to be involved in the loss of Ca2+ homeostatic mechanisms and the progressive calcification of the vessel wall.