Modulation of leukocyte-endothelial interactions by reactive metabolites of oxygen and nitrogen: relevance to ischemic heart disease

Aedes aegypti saliva alters leukocyte recruitment and cytokine signaling by antigen-presenting cells during West Nile virus infection

West Nile virus (WNV) is transmitted during mosquito bloodfeeding. Consequently, the first vertebrate cells to contact WNV are cells in the skin, followed by those in the draining lymph node. Macrophages and dendritic cells are critical early responders in host defense against WNV infection, not just because of their role in orchestrating the immune response, but also because of their importance as sites of early peripheral viral replication. Antigen-presenting cell (APC) signals have a profound effect on host antiviral responses and disease severity. During transmission, WNV is intimately associated with mosquito saliva. Due to the ability of mosquito saliva to affect inflammation and immune responses, and the importance of understanding early events in WNV infection, we investigated whether mosquito saliva alters APC signaling during arbovirus infection, and if alterations in cell recruitment occur when WNV infection is initiated with mosquito saliva. Accordingly, experiments were performed with cultured dendritic cells and macrophages, flow cytometry was used to characterize infiltrating cell types in the skin and lymph nodes during early infection, and real-time RT-PCR was employed to evaluate virus and cytokine levels. Our in vitro results suggest that mosquito saliva significantly decreases the expression of interferon-beta and inducible nitric oxide synthase in macrophages (by as much as 50 and 70%, respectively), whilst transiently enhancing interleukin-10 (IL-10) expression. In vivo results indicate that the predominate effect of mosquito feeding is to significantly reduce the recruitment of T cells, leading the inoculation site of mice exposed to WNV alone to have up to 2.8 fold more t cells as mice infected in the presence of mosquito saliva. These shifts in cell population are associated with significantly elevated IL-10 and WNV (up to 4.0 and 10 fold, respectively) in the skin and draining lymph nodes. These results suggest that mosquito saliva dysregulates APC antiviral signaling, and reveal a possible mechanism for the observed enhancement of WNV disease mediated by mosquito saliva via a reduction of T lymphocyte and antiviral activity at the inoculation site, an elevated abundance of susceptible cell types, and a concomitant increase in immunoregulatory activity of IL-10.

Angiopoietin-2 in experimental colitis

BACKGROUND

The pathophysiology of inflammatory bowel disease (IBD) includes leukocyte infiltration, blood and lymphatic remodeling, weight loss and protein enteropathy. The roles of angiopoietin-2 (Ang-2) in initiating gut inflammation, leukocyte infiltration and angiogenesis are not well understood.

METHODS

Disease activity index, histopathological scoring, myeloperoxidase assay, immunohistochemistry and sodium dodecyl sulphate- polyacrylamide gel electrophoretic methods were employed in the present study to address the roles of Ang-2 in experimental colitis.

RESULTS

Several important differences were seen in the development of experimental IBD in Ang-2(-/-) mice. Although weight change and disease activity differ only slightly in WT and Ang-2(-/-) + DSS treated mice, leukocyte infiltration, inflammation and blood and lymphatic vessel density is significantly attenuated compared to WT + DSS mice. Gut capillary fragility and water export (stool blood and form) appear significantly earlier in Ang-2(-/-) + DSS mice vs. WT. Colon lengths were also significantly reduced in Ang-2(-/-) and gut histopathology was less severe in Ang-2(-/-) compared to WT + DSS. Lastly, the decrease in serum protein content in WT + DSS was less severe in Ang-2(-/-) + DSS, thus protein losing enteropathy (PLE) a feature of IBD is relieved by Ang-2(-/-).

CONCLUSION

These data demonstrate that in DSS colitis, Ang-2 mediates inflammatory hemangiogenesis, lymphangiogenesis and neutrophil infiltration to reduce some, but not all clinical features of IBD. The implications for Ang-2 manipulation in the development of IBD and other inflammatory diseases and treatments involving Ang-2 are discussed.

The effects of nitric oxide on the immune system during Trypanosoma cruzi infection

Trypanosoma cruzi infection triggers substantial production of nitric oxide (NO), which has been shown to have protective and toxic effects on the host's immune system. Sensing of trypomastigotes by phagocytes activates the inducible NO-synthase (NOS2) pathway, which produces NO and is largely responsible for macrophage-mediated killing of T. cruzi. NO is also responsible for modulating virtually all steps of innate and adaptive immunity. However, NO can also cause oxidative stress, which is especially damaging to the host due to increased tissue damage. The cytokines IFN-gamma and TNF-alpha, as well as chemokines, are strong inducers of NOS2 and are produced in large amounts during T. cruzi acute infection. Conversely, TGF-beta and IL-10 negatively regulate NO production. Here we discuss the recent evidence describing the mechanisms by which NO is able to exert its antimicrobial and immune regulatory effects, the mechanisms involved in the oxidative stress response during infection and the implications of NO for the development of therapeutic strategies against T. cruzi.

Human cardiac tissue in a microperfusion chamber simulating extracorporeal circulation--ischemia and apoptosis studies

BACKGROUND

After coronary artery bypass grafting ischemia/reperfusion injury inducing cardiomyocyte apoptosis may occur. This surgery-related inflammatory reaction appears to be of extreme complexity with regard to its molecular, cellular and tissue mechanisms and many studies have been performed on animal models. However, finding retrieved from animal studies were only partially confirmed in humans. To investigate this phenomenon and to evaluate possible therapies in vitro, adequate human cardiomyocyte models are required. We established a tissue model of human cardiomyocytes preserving the complex tissue environment. To our knowledge human cardiac tissue has not been investigated in an experimental setup mimicking extracorporeal circulation just in accordance to clinical routine, yet.

METHODS

Cardiac biopsies were retrieved from the right auricle of patients undergoing elective coronary artery bypass grafting before cardiopulmonary bypass. The extracorporeal circulation was simulated by submitting the biopsies to varied conditions simulating cardioplegia (cp) and reperfusion (rep) in a microperfusion chamber. Cp/rep time sets were 20/7, 40/13 and 60/20 min. For analyses of the calcium homoeostasis the fluorescent calcium ion indicator FURA-2 and for apoptosis detection PARP-1 cleavage immunostaining were employed. Further the anti-apoptotic effect of carvedilol [10 microM] was investigated by adding into the perfusate.

RESULTS

Viable cardiomyocytes presented an intact calcium homoeostasis under physiologic conditions. Following cardioplegia and reperfusion a time-dependent elevation of cytosolic calcium as a sign of disarrangement of the calcium homoeostasis occurred. PARP-1 cleavage also showed a time-dependence whereas reperfusion had the highest impact on apoptosis. Cardioplegia and carvedilol could reduce apoptosis significantly, lowering it between 60-70% (p < 0.05).

CONCLUSIONS

Our human cardiac preparation served as a reliable cellular model tool to study apoptosis in vitro. Decisively cardiac tissue from the right auricle can be easily obtained at nearly every cardiac operation avoiding biopsying of the myocardium or even experiments on animals.The apoptotic damage induced by the ischemia/reperfusion stimulus could be significantly reduced by the cold crystalloid cardioplegia. The additional treatment of cardiomyocytes with a non-selective beta-blocker, carvedilol had even a significantly higher reduction of apoptotis.

Toll-like receptors in ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injuries are implicated in a large array of pathological conditions such as myocardial infarction, cerebral stroke, and hepatic, renal, and intestinal ischemia, as well as following cardiovascular and transplant surgeries. The hallmark of these pathologies is excessive inflammation. Toll-like receptors (TLRs) are recognized as one of the main contributors to pathogen-induced inflammation and, more recently, injury-induced inflammation. Endogenous ligands such as low-molecular hyaluronic acid, fibronectin, heat shock protein 70, and heparin sulfate were all found to be cleaved in the inflamed tissue and to activate TLR2 and TLR4, initiating an inflammatory response even in the absence of pathogens and infiltrating immune cells. In this review, we discuss the contribution of TLR activation in hepatic, renal, cerebral, intestinal, and myocardial I/R injuries. A greater understanding of the role of TLRs in I/R injuries may aid in the development of specific TLR-targeted therapeutics to treat these conditions.

Mechanisms of peroxynitrite-mediated nitration of tyrosine

The mechanisms of tyrosine nitration by peroxynitrous acid or nitrosoperoxycarbonate were investigated with the CBS-QB3 method. Either the protonation of peroxynitrite or a reaction with carbon dioxide gives a reactive peroxide intermediate. Peroxynitrous acid-mediated nitration of phenol occurs via unimolecular decomposition to give nitrogen dioxide and hydroxyl radicals. Nitrosoperoxycarbonate also undergoes unimolecular decomposition to give carbonate and nitrogen dioxide radicals. The reactions of tyrosine with the hydroxyl or carbonate radicals give a phenoxy radical intermediate. The reaction of the nitrogen dioxide with this radical intermediate followed by tautomerization gives nitrated tyrosine in both cases. According to CBS-QB3 calculations, the rate-limiting step for the nitration of phenol is the decomposition of peroxynitrous acid or nitrosoperoxycarbonate.

Effects of Antioxidant and Nitric Oxide on Chemokine Production in TNF-α-stimulated Human Dermal Microvascular Endothelial Cells

Chemokines have been implicated convincingly in the driving of leukocyte emigration in different inflammatory reactions. Multiple signaling mechanisms are reported to be involved in intracellular activation of chemokine expression in vascular endothelial cells by various stimuli. Nevertheless, redox-regulated mechanisms of chemokine expression in human dermal microvascular endothelial cells (HDMEC) remain unclear. This study examined the effects of pyrrolidine dithiocarbamate (PDTC, 0.1 mM) and spermine NONOate (Sper-NO, 1 mM) on the secretion and gene expression of chemokines, interleukin (IL)-8, monocyte chemotactic protein (MCP)-1, regulated upon activation normal T cell expressed and secreted (RANTES), and eotaxin. This study also addresses PDTC and Sper-NO effects on activation of nuclear factor kappa B (NF-kappaB) induced by TNF-alpha (10 ng/ml). Treatment with TNF-alpha for 8 h significantly increased secretion of IL-8, MCP-1, and RANTES, but not of eotaxin, in cultured HDMEC. Up-regulation of these chemokines was suppressed significantly by pretreatment with PDTC or Sper-NO for 1 h, but not by 1 mM 8-bromo-cyclic GMP. The mRNA accumulation of IL-8, MCP-1, RANTES, and eotaxin, and activation of NF-kappaB were induced by TNF-alpha for 2 h; all were suppressed significantly by the above two pretreatments. These findings indicate that both secretion and mRNA accumulation of IL-8, MCP-1, and RANTES in HDMEC induced by TNF-alpha are inhibited significantly by pretreatment with PDTC or Sper-NO, possibly via blocking redox-regulated NF-kappaB activation. These results suggest that restoration of the redox balance using antioxidant agents or nitric oxide pathway modulators may offer new opportunities for therapeutic interventions in inflammatory skin diseases.

Hepatocellular protection by nitric oxide or nitrite in ischemia and reperfusion injury

Ischemia and reperfusion (I/R)-induced liver injury occurs in several pathophysiological disorders including hemorrhagic shock and burn as well as resectional and transplantation surgery. One of the earliest events associated with reperfusion of ischemic liver is endothelial dysfunction characterized by the decreased production of endothelial cell-derived nitric oxide (NO). This rapid post-ischemic decrease in NO bioavailability appears to be due to decreased synthesis of NO, enhanced inactivation of NO by the overproduction of superoxide or both. This review presents the most current evidence supporting the concept that decreased bioavailability of NO concomitant with enhanced production of reactive oxygen species initiates hepatocellular injury and that endogenous NO or exogenous NO produced from nitrite play important roles in limiting post-ischemic tissue injury.

Vasculoprotective Effects of Apolipoprotein Mimetic Peptides: An Evolving Paradigm In Hdl Therapy (Vascular Disease Prevention, In Press.)

Anti-atherogenic effects of high density lipoprotein (HDL) and its major protein component apolipoprotein A-I (apoA-I) are principally thought to be due to their ability to mediate reverse cholesterol transport. These agents also possess anti-oxidant properties that prevent the oxidative modification of low density lipoprotein (LDL) and anti-inflammatory properties that include inhibition of endothelial cell adhesion molecule expression. Results of the Framingham study revealed that a reduction in HDL levels is an independent risk factor for coronary artery disease (CAD). Accordingly, there has been considerable interest in developing new therapies that specifically elevate HDL cholesterol. However, recent evidence suggests that increasing circulating HDL cholesterol levels alone is not sufficient as a mode of HDL therapy. Rather, therapeutic approaches that increase the functional properties of HDL may be superior to simply raising the levels of HDL per se. Our laboratory has pioneered the development of synthetic, apolipoprotein mimetic peptides which are structurally and functionally similar to apoA-I but possess unique structural homology to the lipid-associating domains of apoA-I. The apoA-I mimetic peptide 4F inhibits atherogenic lesion formation in murine models of atherosclerosis. This effect is related to the ability of 4F to induce the formation of pre-β HDL particles that are enriched in apoA-I and paraoxonase. 4F also possesses anti-inflammatory and anti-oxidant properties that are independent of its effect on HDL quality per se. Recent studies suggest that 4F stimulates the expression of the antioxidant enzymes heme oxygenase and superoxide dismutase and inhibits superoxide anion formation in blood vessels of diabetic, hypercholesterolemic and sickle cell disease mice. The goal of this review is to discuss HDL-dependent and -independent mechanisms by which apoA-I mimetic peptides reduce vascular injury in experimental animal models.

Neutralization of interleukin-18 ameliorates ischemia/reperfusion-induced myocardial injury

Ischemia/reperfusion (I/R) injury is characterized by the induction of oxidative stress and proinflammatory cytokine expression. Recently demonstrating that oxidative stress and TNF-alpha each stimulate interleukin (IL)-18 expression in cardiomyocytes, we hypothesized that I/R also induces IL-18 expression and thus exacerbates inflammation and tissue damage. Neutralization of IL-18 signaling should therefore diminish tissue injury following I/R. I/R studies were performed using a chronically instrumented closed chest mouse model. Male C57BL/6 mice underwent 30 min of ischemia by LAD coronary artery ligation followed by various periods of reperfusion. Sham-operated or ischemia-only mice served as controls. A subset of animals was treated with IL-18-neutralizing antibodies 1 h prior to LAD ligation. Ischemic LV tissue was used for analysis. Our results demonstrate that, compared with sham operation and ischemia alone, I/R significantly increased (i) oxidative stress (increased MDA/4-HNE levels), (ii) neutrophil infiltration (increased MPO activity), (iii) NF-kappaB DNA binding activity (p50, p65), and (iv) increased expression of IL-18Rbeta, but not IL-18Ralpha or IL-18BP transcripts. Administration of IL-18-neutralizing antibodies significantly reduced I/R injury measured by reduced infarct size (versus control IgG). In isolated adult mouse cardiomyocytes, simulated ischemia/reperfusion enhanced oxidative stress and biologically active IL-18 expression via IKK-dependent NF-kappaB activation. These results indicate that IL-18 plays a critical role in I/R injury and thus represents a promising therapeutic target.

Mouse model of liver ischemia and reperfusion injury: method for studying reactive oxygen and nitrogen metabolites in vivo

The mouse model of liver ischemia and reperfusion injury has proven to be valuable for our understanding of the role that reactive oxygen and nitrogen metabolites play in postischemic tissue injury. This methods paper provides a detailed protocol for inducing partial liver ischemia followed by reperfusion. Liver ischemia is induced in anesthetized mice by cross-clamping the hepatic artery and portal vein for varying lengths of time, resulting in deprivation of blood flow to approximately 70% of the liver. Restoration of blood flow to the ischemic lobes enhances superoxide production concomitant with a rapid and marked decrease in the bioavailability of nitric oxide, resulting in alterations in the redox state of the liver in favor of a more oxidative environment. This hepatocellular oxidative stress induces the activation of oxidant-sensitive transcription factors followed by the upregulation of proinflammatory cytokines and mediators that ultimately lead to liver injury. This model can be induced in any strain or sex of mouse and requires 1-2 months of practice to become proficient in the surgery and animal manipulation. The roles of various reactive metabolites of oxygen and nitrogen may be evaluated using genetically engineered mice as well as selective molecular, cellular, and/or pharmacological agents.

Ischemia-reperfusion injury in rats affects hydraulic conductivity in two phases that are temporally and mechanistically separate

Ischemia-reperfusion (IR) injury is a major insult to postcapillary venules. We hypothesized that IR increases postcapillary venular hydraulic conductivity and that IR-mediated changes in hydraulic conductivity result from temporally and mechanistically separate processes. A microcannulation technique was used to determine hydraulic conductivity (Lp) in rat mesenteric postcapillary venules serially throughout ischemia (45 min) and reperfusion (5 h) induced by superior mesenteric artery occlusion and release. Mesenteric IR resulted in a biphasic increase in Lp. White blood cell (WBC) adhesion slowly increased with maximal adhesion corresponding to the second peak (P < 0.005). After IR, tissue was harvested for RT-PCR analysis of ICAM-1, E-selectin, and P-selectin mRNA. Intercellular adhesion molecule-1 (ICAM-1) mRNA in the gut showed the most significant upregulation. Quantitative real-time PCR revealed that ICAM-1 mRNA was upregulated 60-fold in the gut. An ICAM-1 antibody was therefore used to determine the effect of WBC adhesion on Lp during IR. ICAM-1 inhibition attenuated Lp during the first peak and completely blocked the second peak (P < 0.005). When rats were fed a tungsten diet to inhibit xanthine oxidase and then underwent IR, Lp was dramatically attenuated during the first peak and mildly decreased the second peak (P < 0.005). Inhibition of xanthine oxidase by oxypurinol decreased Lp during IR by over 60% (P < 0.002). Tempol, a superoxide dismutase mimetic, decreased Lp during IR by over 30% (P < 0.01). We conclude that IR induces a biphasic increase in postcapillary hydraulic conductivity. Reactive oxygen species impact both the first transient peak and the sustained second peak. However, the second peak is also dependent on WBC-endothelial cell adhesion. These serial measurements of postcapillary hydraulic conductivity may lead the way for optimal timing of pharmaceutical therapies in IR injury.

Modulatory effects of hypercapnia on in vitro and in vivo pulmonary endothelial-neutrophil adhesive responses during inflammation

Reducing tidal volume as a part of a protective ventilation strategy may result in hypercapnia. In this study, we focused on the influence of hypercapnia on endothelial-neutrophil responses in models of inflammatory-stimulated human pulmonary microvascular endothelial cells (HMVEC) and in an animal model of lipopolysaccharide (LPS)-induced acute lung injury. Neutrophil adhesion and adhesion molecules expression and nuclear factor-kappaB (NF-kappaB) were analyzed in TNF-alpha and LPS-treated HMVEC exposed to either eucapnia or hypercapnia. In the in vivo limb, bronchoalveolar lavage fluid cell counts and differentials, adhesion molecule and chemokine expression were assessed in LPS-treated rabbits ventilated with either low tidal volume ventilation and eucapnia or hypercapnia. In both the in vitro and in vivo models, hypercapnia significantly increased neutrophil adhesion and adhesion molecule expression compared to eucapnia. Activity of NF-kappaB was significantly enhanced by hypercapnia in the in vitro experiments. IL-8 expression was greatest both in vitro and in vivo under conditions of hypercapnia and concomitant inflammation. CD11a expression was greatest in isolated human neutrophils exposed to hypercapnia+LPS. Our results demonstrate that endothelial-neutrophil responses per measurement of fundamental molecules of adhesion are significantly increased during hypercapnia and that hypercapnia mimics conditions of eucapnia+inflammation.

Prevention of aortic fibrosis by N-acetyl-seryl-aspartyl-lysyl-proline in angiotensin II-induced hypertension

Fibrosis is an important component of large conduit artery disease in hypertension. The endogenous tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) has anti-inflammatory and antifibrotic effects in the heart and kidney. However, it is not known whether Ac-SDKP has an anti-inflammatory and antifibrotic effect on conduit arteries such as the aorta. We hypothesize that in ANG II-induced hypertension Ac-SDKP prevents aortic fibrosis and that this effect is associated with decreased protein kinase C (PKC) activation, leading to reduced oxidative stress and inflammation and a decrease in the profibrotic cytokine transforming growth factor-beta1 (TGF-beta1) and phosphorylation of its second messenger Smad2. To test this hypothesis we used rats with ANG II-induced hypertension and treated them with either vehicle or Ac-SDKP. In this hypertensive model we found an increased collagen deposition and collagen type I and III mRNA expression in the aorta. These changes were associated with increased PKC activation, oxidative stress, intercellular adhesion molecule (ICAM)-1 mRNA expression, and macrophage infiltration. TGF-beta1 expression and Smad2 phosphorylation also increased. Ac-SDKP prevented these effects without decreasing blood pressure or aortic hypertrophy. Ac-SDKP also enhanced expression of inhibitory Smad7. These data indicate that in ANG II-induced hypertension Ac-SDKP has an aortic antifibrotic effect. This effect may be due in part to inhibition of PKC activation, which in turn could reduce oxidative stress, ICAM-1 expression, and macrophage infiltration. Part of the effect of Ac-SDKP could also be due to reduced expression of the profibrotic cytokine TGF-beta1 and inhibition of Smad2 phosphorylation.

Involvement of NF-kappaB in the inhibitory actions of Platycarya strobilacea on the TNF-alpha-induced monocyte adhesion to colon epithelial cells and chemokine expression

Oxidative stress and the activation of nuclear factor (NF)-kappaB play crucial roles in the pathogenesis of inflammatory bowel disease (IBD). In the present study, we examined the effects of the ethanol extract of Platycarya strobilacea Sieb. stem (EPS) on TNF-alpha-induced monocyte adhesion to HT29 human colon epithelial cells, an initial step of colon inflammation. EPS contained high amount of polyphenols (0.241+/-0.017 mg of catechin equivalent/g of extract) and showed substantial DPPH radical scavenging activity. In addition, EPS significantly suppressed TNF-alpha-induced reactive oxygen species (ROS) increase. Moreover, TNF-alpha-induced monocyte adhesion to HT29 colon epithelial cells was significantly suppressed by EPS in a concentration-dependent manner. The reduced adhesion by EPS was correlated with suppressed expression of MCP-1 and IL-8, the major chemokines in IBD. EPS also prevented the TNF-alpha-induced nuclear translocation of NF-kappaB, one of the redox-sensitive transcription factors, in a concentration-dependent manner. Taken together, our results suggest that the anti-oxidant components of EPS prevent TNF-alpha-induced NF-kappaB activation, chemokine induction, and monocyte adhesion at the site of intestinal inflammation.

Inhibiting matrix metalloproteinase-2 reduces protein release into coronary effluent from isolated rat hearts during ischemia-reperfusion

BACKGROUND

Previous studies have shown that the disruption of the coronary endothelium and the increase in its permeability during ischemia-reperfusion (I/R), are linked to matrix metalloproteinase-2 (MMP-2) activity. Studies from our group have shown that during I/R, activity of MMP-2 in the coronary effluent increases and this increase is associated with cardiac dysfunction, which in turn, can be prevented by MMP inhibitors. Therefore, we hypothesize that inhibiting MMPs reduces the MMP-2 dependent disruption of the coronary endothelium and subsequent protein release during I/R.

METHODS

Isolated rat hearts were perfused in the Langendorff mode at a constant pressure and subjected to 15, 20 or 30 min no-flow ischemia followed by 30 min of reperfusion. The MMP inhibitors, o-phenanthroline (Phen, 100 microM) or doxycycline (Doxy, 30 microM) an inhibitors of MMPs, were added to the perfusion solution 10 min before ischemia and for the first 10 min of reperfusion. The coronary effluents were collected during perfusion for protein analysis. Creatine kinase was measured as an index of cellular damage. Endothelial integrity was assessed by measuring coronary flow and by measuring the levels of serotransferrin and interstitial albumin in the coronary effluent. Additionally, damage to the endothelium was assessed histologically by light microscopy analysis of the cellular structure of the myocardium. MMP-2 activity was measured by zymography in hearts subjected to 15, 20 and 30 min of ischemia without reperfusion.

RESULTS

MMP-2 activity was increased in heart tissue at the end of ischemia and was correlated with duration of ischemia. The post-ischemia decrease in coronary flow, and the increase in the release of serotransferrin and albumin were attenuated by Phen. Edema (another indirect marker of endothelial damage) was observed in I/R heart and the edema was abolished in I/R heart treated with MMP inhibitors.

CONCLUSION

MMP inhibition not only reduces cardiac mechanical dysfunction but also reduces endothelial damage resulting from cardiac I/R injury.

Differential mechanisms of hepatic vascular dysregulation with mild vs. moderate ischemia-reperfusion

Endotoxemia produces hepatic vascular dysregulation resulting from inhibition of endothelin (ET)-stimulated NO production. Mechanisms include overexpression of caveolin-1 (Cav-1) and altered phosphorylation of endothelial nitric oxide (NO) synthase (NOS; eNOS) in sinusoidal endothelial cells. Since ischemia-reperfusion (I/R) also causes vascular dysregulation, we tested whether the mechanisms are the same. Rats were exposed to either mild (30 min) or moderate (60 min) hepatic ischemia in vivo followed by reperfusion (6 h). Livers were harvested and prepared into precision-cut liver slices for in vitro analysis of NOS activity and regulation. Both I/R injuries significantly abrogated both the ET-1 (1 microM) and the ET(B) receptor agonist (IRL-1620, 0.5 microM)-mediated stimulation of NOS activity. 30 min I/R resulted in overexpression of Cav-1 and loss of ET-stimulated phosphorylation of Ser1177 on eNOS, consistent with an inflammatory response. Sixty-minute I/R also resulted in loss of ET-stimulated Ser1177 phosphorylation, but Cav-1 expression was not altered. Moreover, expression of ET(B) receptors was significantly decreased. This suggests that the failure of ET to activate eNOS following 60-min I/R is associated with decreased protein expression consistent with ischemic injury. Thus hepatic vascular dysregulation following I/R is mediated by inflammatory mechanisms with mild I/R whereas ischemic mechanisms dominate following more severe I/R stress.

Inhibitory effect of simvastatin on the TNF-alpha- and angiotensin II-induced monocyte adhesion to endothelial cells is mediated through the suppression of geranylgeranyl isoprenoid-dependent ROS generation

Vascular endothelial cell activation by cytokines and other pro-inflammatory mediators is an initial event in atherosclerosis and in other vascular diseases. Simvastatin, a HMG-CoA reductase inhibitor, suppressed both tumor necrosis factor (TNF)-alpha- and angiotensin (Ang) II-induced monocyte adhesion to endothelial cells (an initial step in vascular inflammation) and reactive oxygen species (ROS) production. Diphenyleneiodonium and apocynin, both NADPH oxidase inhibitors, also suppressed TNF-alpha-induced ROS and monocyte-endothelial cell adhesion, demonstrating that TNF-alpha-induced monocyte adhesion is mediated through ROS produced by NADPH oxidase activation. Furthermore, exogenously applied mevalonate or geranylgeranylpyrophosphate in combination with simvastatin completely prevented the inhibitory effects of simvastatin on ROS generation and monocyte-endothelial cell adhesion by TNFalpha and Ang II. These results suggest that monocyte adhesion to endothelial cells induced by TNF-alpha or Ang II is mediated via the geranylgeranyl isoprenoid-dependent generation of ROS, and that this is inhibited by simvastatin.

Nasal continuous positive airway pressure treatment reduces systemic oxidative stress in patients with severe obstructive sleep apnea syndrome

OBJECTIVE

To evaluate whether nasal continuous positive airway pressure (nCPAP) reduces oxidative stress in patients with severe obstructive sleep apnea (OSA) syndrome.

MATERIALS AND METHODS

Forty-six patients with severe OSA (AHI> or =30) requiring nasal CPAP treatment and 46 controls (subjects without OSA and with mild OSA as defined by an AHI<15) were enrolled. Oxidative stress was evaluated in blood samples with a commercially available automated spectrophotometric assay (D-ROMs test, Diacron, Grosseto, Italy). Blood samples were collected the evening before (10:00 p.m.) and the morning after (07:00 a.m.) a diagnostic polysomnography. Patients with severe OSA syndrome were subsequently submitted to a second polysomnography with nasal CPAP titration the following night. Using the same schedule we collected blood samples from the patients the morning after the nCPAP titration and after two months of nCPAP treatment.

RESULTS

Patients with severe OSA presented higher levels of oxidative stress than patients with AHI<15 in the evening and in the morning (357.57+/-13.07 UCarr vs. 319.28+/-12.66 UCarr, p=0.038, and 371.83+/-12.83 UCarr vs. 328.09+/-11.76 UCarr, p=0.014, respectively). Patients with severe OSA presented a significant reduction the levels of oxidative stress the morning after the nCPAP titration study (371.83+/-12.83 UCarr vs. 298.21+/-9.62 UCarr, p=0.001) and this reduction was further preserved after a period of two months of nCPAP treatment (293.72+/-6.55 UCarr, p=0.001 vs. baseline). Statistically significant correlations were observed between levels of oxidative stress and nocturnal polysomnography (NPSG) markers as oxygen desaturation index (ODI), arousal index (AI), lowest oxygen saturation of hemoglobin, and mean oxygen saturation of hemoglobin.

CONCLUSIONS

Patients with severe OSA syndrome presented increased systemic oxidative stress. A single night of nCPAP treatment significantly reduced the levels of oxidative stress in patients with severe OSA syndrome, and this reduction was maintained at least after two months of nCPAP treatment.

New insights into the causes and therapy of cerebral vasospasm following subarachnoid hemorrhage

Cerebral vasospasm lingers as the leading preventable cause of death and disability in patients who experience aneurysmal subarachnoid hemorrhage. Despite the potentially devastating consequences of cerebral vasospasm, the mechanisms behind it are incompletely understood. Nitric oxide, endothelin-1, bilirubin oxidation products and inflammation appear to figure prominently in its pathogenesis. Therapies directed at many of these mechanisms are currently under investigation and hold significant promise for an ultimate solution to this substantial problem.

In vivo observation of leukocyte-endothelium interaction in ischemia reperfusion injury with the dorsal window chamber and the effects of pentoxifylline on reperfusion injury

OBJECTIVE

Ischemia reperfusion injury can cause failure in microsurgical operations. Interaction between leukocytes and endothelium is recognized as an integral step in ischemia reperfusion injury. Pentoxifylline is a methylxanthine derivative that has pharmacological properties that can be beneficial in ischemia reperfusion injury. The aim of this study was to investigate the in vivo effect of pentoxifylline on leukocyte-endothelium interaction in ischemia reperfusion injury.

METHODS

Intravital fluorescent microscopy was used to observe leukocyte-endothelium interaction in a "dorsal window chamber" model. Twenty-eight postcapillary veins were analyzed in group 1, and twenty-two in group 2. Group 1 received 25 mg/kg pentoxifylline 20 min before reperfusion. Group 2 received an equivalent volume of 0.9% saline at the same time. The period of ischemia was 4 h.

RESULTS

Quantification of leukocyte 'sticking' and 'rolling' was done before ischemia and at 30, 60, and 120 min after reperfusion. Offline video analysis was used for evaluating the results. Statistical evaluation showed that pentoxifylline significantly attenuated leukocyte 'sticking' and 'rolling' in postcapillary venules. It was also effective in preventing 'no-reflow' when compared with the control group.

CONCLUSION

These results indicate pentoxifylline diminishes leukocyte-endothelium interaction, and may have a therapeutic role in preventing ischemia reperfusion injury in microsurgical operations.

Preconditioning protects endothelium by preventing ET-1-induced activation of NADPH oxidase and xanthine oxidase in post-ischemic heart

The hypothesis was tested that endothelin-1 (ET-1)-induced superoxide (O(2)(-)) generation mediates post-ischemic coronary endothelial injury, that ischemic preconditioning (IPC) affords endothelial protection by preventing post-ischemic ET-1, and thus O(2)(-), generation, and that opening of the mitochondrial ATP-dependent potassium channel (mK(ATP)) triggers the mechanism of IPC. Furthermore, the study was aimed at identifying the source of O(2)(-) mediating the endothelial injury. Langendorff-perfused guinea-pig hearts were subjected either to 30 min ischemia/35 min reperfusion (IR) or were preconditioned prior to IR with three cycles of either 5 min ischemia/5 min reperfusion or 5 min infusion/5 min washout of mK(ATP) opener diazoxide (0.5 mM). Coronary flow responses to acetylcholine (ACh) served as a measure of endothelium-dependent vascular function. Myocardial outflow of ET-1 and O(2)(-) and functional recoveries were followed during reperfusion. NADPH oxidase and xanthine oxidase (XO) activities were measured in cardiac homogenates. IR augmented ET-1 and O(2)(-) outflow and impaired ACh response. All these effects were attenuated or prevented by IPC and diazoxide, and 5-hydroxydecanoate (a selective mK(ATP) blocker) abolished the effects of IPC and diazoxide. Superoxide dismutase and tezosentan (a mixed ET-1-receptor antagonist) mimicked the effects of IPC, although they had no effect on the ET-1 generation. IR augmented also the activity of NADPH oxidase and XO. Apocynin treatment, that resulted in NADPH oxidase inhibition, prevented XO activation and O(2)(-) generation in IR hearts. The inhibition of XO, either by allopurinol or feeding the animals with tungsten-enriched chow, prevented post-ischemic O(2)(-) generation, although these interventions had no effect on the NADPH activity. In addition, the post-ischemic activation of NADPH oxidase and XO, and O(2)(-) generation were prevented by IPC, tezosentan, thenoyltrifluoroacetone (mitochondrial complex II inhibitor), and tempol (cell-membrane permeable O(2)(-) scavenger). In guinea-pig heart: (i) ET-1-induced O(2)(-) generation mediates post-ischemic endothelial dysfunction; (ii) IPC and diazoxide afford endothelial protection by attenuating the ET-1, and thus O(2)(-) generation, and the mK(ATP) opening triggers the protection; (iii) the NADPH oxidase maintains the activity of XO, and the XO-derived O(2)(-) mediates the endothelial injury, and (iv) ET-1 and O(2)(-) (probably of mitochondrial origin) are upstream activators of the NADPH oxidase-XO cascade, and IPC prevents the cascade activation and the endothelial dysfunction by preventing the ET-1 generation.

Concentration decrease of nitric oxide in the postischemic muscle is not only caused by the generation of O2−

Reperfusion of ischemic skeletal muscle is associated with an alteration of the concentrations of O(2) (-) and NO. In this study, the influence of epigallocatechin-3-gallate (EGCG), a known radical scavenger, on the balance of O(2) (-) and NO has been measured online in the skeletal muscle of Wistar rats. The hind limb of 14 male rats had been exposed to ischemic stress for 2 h. Seven rats received an infusion of 1.5 micromol EGCG/kg 5 min before reperfusion. O(2) (-), NO, and temperature were measured during reperfusion. The concentration of O(2) (-) declined under the influence of EGCG from 156.5 to 72.2 nmol/l (P = 0.01). The level of NO was found to decrease; this decrease was not significantly changed by EGCG (-175 nmol/l vs. - 227 nmol/l; P = 0.33). Thus the different superoxide concentrations did not correspond to different levels of NO, and the interaction of both radicals is not the only reason for the concentration decrease of NO in the reperfusion period. We conclude that EGCG protects skeletal muscle from I/R-injury without influencing the NO concentration profile to a large extent.

The effects of oxidative stress on the liver and ileum in rats caused by one-lung ventilation

BACKGROUND AND AIM

Reactive oxygen radicals that cause remote organ injury are increased after the one-lung ventilation frequently used in thoracic surgery. The aim of this study was to examine the effects of one-lung ventilation on the liver and ileum.

MATERIALS AND METHODS

Thirty rats were divided into five groups: a sham group; 3- and 4-h mechanical ventilation groups; and 1- and 2-h left lung collapse/2-h re-expansion groups (n = 6 for each group). In the collapse groups, the left lung was collapsed by bronchial occlusion for 1 and 2 h and then re-expanded and ventilated for an additional 2 h. At the end of the study, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were determined to assess liver functions. Myeloperoxidase (MPO) and malondialdehyde (MDA) activity were determined in the liver and ileum tissues. The tissues were also examined by light and electron microscope. Apoptosis was assessed using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) assay.

RESULTS

Plasma ALT and AST, tissue MDA, and MPO activities in both tissues were significantly higher in the 2-h collapse/2-h re-expansion group than in the 4-h mechanical ventilation group (P < 0.05). Moreover, the levels were significantly higher in the 2-h collapse group compared to the 1-h collapse group (P < 0.016). Tissue damage and apoptotic index were most prominent in the 2-h collapse/2-h re-expansion group.

CONCLUSION

Our findings showed that one-lung ventilation causes tissue damage in the liver and ileum and that this damage increases as occlusion duration rises.

Tumor necrosis factor-alpha down-regulates human Cu/Zn superoxide dismutase 1 promoter via JNK/AP-1 signaling pathway

Overexpression of Cu/Zn superoxide dismutase 1 (SOD1) in monocytes blocks reactive oxygen species-induced inhibition of cell growth and apoptosis and renders cells resistant to the toxic effect of tumor necrosis factor (TNF)-alpha, suggesting that TNF-alpha represses the SOD1 gene in these cells. We herein show that TNF-alpha decreases SOD1 mRNA, protein, and promoter activity in U937 cells. Electrophoretic mobility-shift assays (EMSA) show that TNF-alpha decreased binding of three different complexes. Ectopic Sp1 overexpression markedly increased SOD1-basal promoter activity and partially antagonized the TNF-alpha inhibitory effect. In contrast, ectopic c-Jun overexpression mimics TNF-alpha inhibitory effects and antagonizes Sp1 stimulatory effects. In agreement with these findings, EMSA shows a TNF-alpha-induced increase in AP-1 and a decrease in Sp1 DNA binding. Disruption of the C/EBP site decreases, whereas mutation in the Sp1/Egr-1 site completely abolishes DNA-binding and promoter activity. A JNK inhibitor antagonized the negative effects of TNF-alpha on SOD1 promoter activity, suggesting that JNK signaling through c-Jun protein activation is critical for the TNF-alpha-dependent SOD1 repression. A greater understanding of the mechanisms of TNF-alpha-induced SOD1 repression could facilitate the design and development of novel therapeutic drugs for inflammatory conditions.

A zebrafish assay for identifying neuroprotectants in vivo

In this study, we developed an in vivo method to determine drug effects on oxidation-induced apoptosis in the zebrafish brain caused by treatment with L-hydroxyglutaric acid (LGA). We confirmed that LGA-induced apoptosis was caused by oxidation by examining the presence of an oxidative product, nitrotyrosine. Next, we examined the effects of 14 characterized neuroprotectants on LGA-treated zebrafish, including: D-methionine (D-Met), Indole-3-carbinol, deferoxamine (DFO), dihydroxybenzoate (DHB), deprenyl, L-NAME (N(G)-nitro-L-arginine methyl ester), n-acetyl L-cysteine (L-NAC), 2-oxothiazolidine-4-carboxylate (OTC), lipoic acid, minocycline, isatin, cortisone, ascorbic acid and alpha-tocopherol. Eleven of 14 neuroprotectants and 7 of 7 synthetic anti-oxidants exhibit significant protection in zebrafish. Buthionine sulfoximine (BSO), used as a negative control, exhibited no significant protective effects. In addition, three blood-brain barrier (BBB) impermeable compounds exhibited no significant effects. Our results in zebrafish were similar to results reported in mammals supporting the utility of this in vivo method for identifying potential neuroprotective anti-oxidants.

Effect of preinfarction angina pectoris on myocardial blush grade after reperfusion in first anterior wall acute myocardial infarction

BACKGROUND

The aim of the present study was to clarify the effect of preinfarction angina pectoris (PIA) on myocardial blush grade (MBG), a simple marker of myocardial tissue-level reperfusion, in acute myocardial infarction (AMI).

METHODS AND RESULTS

One hundred forty-two patients with first anterior wall AMI who were admitted within 6 h after onset of symptoms were examined. PIA was defined as typical chest pain within 48 h before onset of symptoms. MBG was evaluated by coronary angiography after reperfusion. Patients with MBG 2 or 3 (n=103) had a higher frequency of PIA and a lower frequency of diabetes mellitus than those with MBG 0 or 1 (n=39) (57% vs 28%, p=0.004, and 23% vs 44%, p=0.03, respectively). The former had a lower peak creatine kinase level and a greater left ventricular ejection fraction at predischarge than the latter (3,652+/-2,440 vs 5,507+/-3,058 IU/L, p=0.0002, and 57+/-12% vs 45+/-11%, p<0.0001, respectively). Multivariate logistic regression analysis showed that PIA (p=0.004) and diabetes mellitus (p=0.03) were independently associated with MBG 2 or 3 after reperfusion.

CONCLUSIONS

PIA has beneficial effects on myocardial tissue-level reperfusion evaluated by MBG in first anterior wall AMI.

Chunghyuldan activates NOS mRNA expression and suppresses VCAM-1 mRNA expression in human endothelial cells

Chunghyuldan (CHD), a combinatorial drug that has antihyperlipidemic and anti-inflammatory activities, has been shown to improve arterial stiffness and inhibit stroke recurrence in clinical study. To understand the molecular basis of CHD's clinical effects, we explored its effect on cell proliferation and expression of nitric oxide synthase (NOS) and vascular cell adhesion molecule (VCAM-1) in human umbilical vein endothelial cells (HUVECs). Cell number counting and [3H]thymidine incorporation assay demonstrated that nontoxic doses of CHD have an inhibitory effect on DNA synthesis and suppress cell cycle progression of HUVECs. CHD treatment led to a marked induction of NO production through up-regulation of NOS mRNA expression in a dose- and time-dependent manner, whereas it suppressed VCAM-1 expression. CHD inhibition of VCAM-1 expression was totally blocked by pretreatment with the NO synthesis inhibitor L-NMMA, whereas pretreatment with the NO donor DETA-NO further decreased VCAM-1 level in CHD-treated HUVECs, indicating that VCAM-1 regulation by CHD is mediated through increased NO synthesis by CHD. In addition, TNF-alpha-mediated VCAM-1 activation was substantially impeded by CHD treatment. Collectively, our data suggest that anti-inflammatory or anti-hyperlipidemic effects of CHD might be associated with its ability to activate NO production and suppress VCAM-1 expression in human endothelial cells.

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.

Inhibition of sickle red cell adhesion and vasoocclusion in the microcirculation by antioxidants

In sickle cell anemia (SCA), inflammatory (i.e., intravascular sickling and transient vasoocclusive) events result in chronic endothelial activation. In addition to sickling behavior, sickle (SS) red blood cells exhibit abnormal interaction with the vascular endothelium, which is considered to have an important role in initiation of vasoocclusion. Upregulation of endothelial adhesion molecules caused by oxidants (and cytokines) may lead to increased SS red cell adhesion. We hypothesize that endothelial activation is indispensable in SS red cell adhesion to the endothelium and that antioxidants will have an inhibitory effect on this interaction. We examined the effect of selected antioxidants in ex vivo mesocecum vasculature, a well-established model that allows measurement of hemodynamic parameters and, by intravital microscopy, can allow quantification of adhesion. We tested antioxidant enzymes (SOD and catalase) and an intravascular SOD mimetic, polynitroxyl albumin (PNA), in the presence of platelet-activating factor (PAF); the latter causes endothelial oxidant generation and endothelial activation, which characterize SCA. In ex vivo preparations, PAF not only induced marked endothelial oxidant generation, it also enhanced SS red cell adhesion, resulting in frequent blockage of small-diameter venules. The adhesion, inversely related to venular diameter, and vasoocclusion were markedly inhibited by antioxidants, resulting in improved hemodynamics. PNA, the most effective antioxidant, also abolished SS red cell adhesion in non-PAF-activated preparations. Thus SS red cell adhesion and related vasoocclusion may be ameliorated by antioxidant therapy with a stable and long-acting molecule (e.g., PNA).

Purification and characterization of NEIL1 and NEIL2, members of a distinct family of mammalian DNA glycosylases for repair of oxidized bases

NEIL1 and NEIL2 were newly discovered as mammalian orthologs of Escherichia coli Nei and Fpg, oxidized base-specific DNA glycosylases. These are distinct from previously characterized OGG1 and NTH1, the other two glycosylases for repairing oxidatively damaged bases in mammalian cells, in regards to reaction mechanism. Recombinant human NEIL1 and NEIL2 were purified from E. coli and biochemically characterized. Some damaged bases are common substrates for both groups of enzymes. However, in contrast to the lack of activity of NTH1 and OGG1 for substrate lesions in single-stranded DNA, the NEILs have unique preference for bubble or single-stranded DNA substrates, suggesting their preferential involvement in repairing transcribed or replicating DNA sequences.

Platelets, Inflammation, and Atherothrombotic Neurovascular Disease: The Role of Endothelial Dysfunction

The vascular endothelium is an indispensable organ in the regulation of tonicity and vascular homeostasis. Endothelial dysfunction is a marker of atherosclerosis and contributes to the atherogenic process and the development of atherothrombotic complications. Endothelial dysfunction is the common meeting point among factors for vascular risk and launches complex cellular and biochemical interactions that are characterized by oxidative stress and an intense inflammatory response. The strategic importance of the concept of endothelial dysfunction arises from the following facts: its diagnosis is simple, it allows the identification of asymptomatic arteriosclerotic subjects with a high risk of developing atherothrombotic complications, it is reversible, and it responds to various therapeutic strategies.

Rac1 inhibition protects against hypoxia/reoxygenation-induced lipid peroxidation in human vascular endothelial cells

Both in vivo models of ischemia/reperfusion and in vitro models of hypoxia (H)/reoxygenation (R) have demonstrated the crucial role of the Rac1-regulated NADPH oxidase in the production of injurious reactive oxygen species (ROS) by vascular endothelial cells (ECs). Since membrane lipid peroxidation has been established as one of the mechanisms leading to cell death, we examined lipid peroxidation in H/R-exposed cultured human umbilical vein ECs (HUVECs) and the role of Rac1 in this process. H (24 h at 1% O2)/R (5 min) caused an increase in intracellular ROS production compared to a normoxic control, as measured by dichlorofluorescin fluorescence. Nutrient deprivation (ND; 24 h), a component of H, was sufficient to induce a similar increase in ROS under normoxia. Either H(24 h)/R (2 h) or ND (24 h) induced increases in lipid peroxidation of similar magnitude as measured by flow cytometry of diphenyl-1-pyrenylphosphine-loaded HUVECs and Western blotting analysis of 4-hydroxy-2-nonenal-modified proteins in cell lysates. In cells infected with a control adenovirus, H (24 h)/R (2 h) and ND (24 h) resulted in increases in NADPH-dependent superoxide production by 5- and 9-fold, respectively, as measured by lucigenin chemiluminescence. Infection of HUVECs with an adenovirus that encodes the dominant-negative allele of Rac1 (Rac1N17) abolished these increases. Rac1N17 expression also suppressed the H/R- and ND-induced increases in lipid peroxidation. In conclusion, ROS generated via the Rac1-dependent pathway are major contributors to the H/R-induced lipid peroxidation in HUVECs, and ND is able to induce Rac1-dependent ROS production and lipid peroxidation of at least the same magnitude as H/R.

CD40 Ligand Influences Platelet Release of Reactive Oxygen Intermediates

OBJECTIVE

Soluble CD40 ligand (sCD40L) has been recently implicated in the pathogenesis of atherosclerosis. Elevated levels of sCD40L in acute coronary syndrome patients suggests enhanced platelet function; however, the exact mechanism by which this occurs is unknown. In this study, we examined the effect of sCD40L on platelet function and reactive oxygen and nitrogen species (RONS) generation.

METHODS AND RESULTS

Platelet stimulation in the presence of recombinant sCD40L (rsCD40L) led to enhanced generation of RONS as measured by DCFHDA oxidation and confocal microscopy. Incubation with rsCD40L led to enhanced platelet P-selectin expression, aggregation, and platelet-leukocyte conjugation. Platelets isolated from CD40L-deficient mice had decreased agonist-induced NO release as compared with wild-type mice. Incubation of platelets with rsCD40L enhanced stimulation-induced p38 MAP kinase and Akt phosphorylation.

CONCLUSIONS

Soluble CD40L enhances platelet activation, aggregation, and platelet-leukocyte conjugation, as well as increases stimulation-induced platelet release of RONS through activation of Akt and p38 MAP kinase signaling pathways. These data suggest that sCD40L regulates platelet-dependent inflammatory and thrombotic responses that contribute to the pathogenesis of atherothrombosis.

Inhibitory effects of eutigosides isolated fromEurya emarginata on the inflammatory mediators in RAW264.7 cells

The anti-inflammatory activity of Eurya emarginata (Thumb) Makino, of which leaves have been traditionally used to treat ulcers or diuretic in Jeju Island, has been investigated in the present study. Through the phytochemical study from the methanol extract of E. emaginiata, eutigosides B and C were isolated as the active components. Sseveral inflammatory markers including TNF-alpha, IL-1beta, IL-6, NO, iNOS, and COX-2 were examined. Eutigosides B and C potentially inhibited production of pro-inflammatory cytokines (IL-6 and TNF-alpha) in a dose-dependent manner. Additionally, the intracellular contents of iNOS protein were markedly decreased after treatment with eutigosides B and C. The inhibition of iNOS activity was correlated with the decrease in nitrite levels. These results suggest that eutigoside B and C from E. emarginata may have anti-inflammatory activity through the inhibition of pro-inflammatory cytokines (TNF-alpha and IL-6), iNOS and COX-2.

Epigallocatechin, a green tea polyphenol, attenuates myocardial ischemia reperfusion injury in rats

Epigallocatechin-3-gallate (EGCG) is the most prominent catechin in green tea. EGCG has been shown to modulate numerous molecular targets in the setting of inflammation and cancer. These molecular targets have also been demonstrated to be important participants in reperfusion injury, hence this study examines the effects of EGCG in myocardial reperfusion injury. Male Wistar rats were subjected to myocardial ischemia (30 min) and reperfusion (up to 2 h). Rats were treated with EGCG (10 mg/kg intravenously) or with vehicle at the end of the ischemia period followed by a continuous infusion (EGCG 10 mg/kg/h) during the reperfusion period. In vehicle-treated rats, extensive myocardial injury was associated with tissue neutrophil infiltration as evaluated by myeloperoxidase activity, and elevated levels of plasma creatine phosphokinase. Vehicle-treated rats also demonstrated increased plasma levels of interleukin-6. These events were associated with cytosol degradation of inhibitor kappaB-alpha, activation of IkappaB kinase, phosphorylation of c-Jun, and subsequent activation of nuclear factor-kappaB and activator protein-1 in the infarcted heart. In vivo treatment with EGCG reduced myocardial damage and myeloperoxidase activity. Plasma IL-6 and creatine phosphokinase levels were decreased after EGCG administration. This beneficial effect of EGCG was associated with reduction of nuclear factor-kB and activator protein-1 DNA binding. The results of this study suggest that EGCG is beneficial for the treatment of reperfusion-induced myocardial damage by inhibition of the NF-kappaB and AP-1 pathway.

Endothelial oxidative stress induced by serum from patients with severe trauma hemorrhage

OBJECTIVE

Shock induces oxidative stress by ischemia-reperfusion phenomenon. Endothelial cells are involved in the inflammatory response and oxidative stress responsible for microcirculation impairment and organ failure. We examined the potential of serum from patients to induce in vitro reactive oxygen species production by cultured human umbilical vein endothelial cells (HUVECs).

PATIENTS

Three groups were compared: hemorrhagic shock trauma patients, isolated brain injured patients, and healthy volunteers.

METHODS

In the hemorrhagic shock group we sought a correlation between reactive oxygen species production and severity of shock. Serum was separated and perfused in an in vitro model of perfused HUVECs. Ex vivo reactive oxygen species production was assessed by fluorescence microscopy using dichlorodihydrofluorescein, an intracellular dye oxidized by H2O2. Results are expressed in proportional change from baseline and normalized by protidemia to control for variation related to hemodilution.

RESULTS

Reactive oxygen species production by endothelial cells exposed to serum from hemorrhagic shock patients (46.2+/-24.9%) was significantly greater than in those with brain injury (3.9+/-35.1%) and in healthy volunteers (-6.8+/-5.8%). In the hemorrhagic shock group dichlorodihydrofluorescein fluorescence was strongly correlated positively to Simplified Acute Physiology Score II and lactatemia and negatively to [HCO3-].

CONCLUSIONS

Serum from trauma patients with hemorrhagic shock induces reactive oxygen species formation in naive endothelial cells which is correlated to shock severity.

Do preservation solutions protect rat cremaster microcirculation during ischemia and reperfusion?

BACKGROUND

Our aim was to investigate the potential of the preservation solution Celsior to protect rat cremaster muscle microcirculation during ischemia and reperfusion, and to compare its effects with those of HTK (histidine-tryptophan-ketoglutarate-Bretschneider solution). Because of its anti-oxidant contents, we expected Celsior to be more protective than HTK.

MATERIALS AND METHODS

Capillary perfusion and leukocyte-endothelium interactions were examined in rat cremaster muscle using intravital microscopy. After perfusion with Celsior or HTK (4 degrees C), the cremaster was subjected to 4 or 6 h of warm (33-34 degrees C) ischemia and 2 h of reperfusion. Measurements were performed prior to perfusion and/or ischemia, and 0, 1, and 2 h after restoration of flow.

RESULTS

Without Celsior or HTK, capillary perfusion transiently decreased to 50% of baseline after 4 h of ischemia; it remained low (45%) after 6 h of ischemia. Whereas HTK had no significant influence, Celsior deteriorated capillary perfusion: it remained low after 4 h of ischemia (39-48%) and decreased even further after 6 h of ischemia (18-8%). Both preservation solutions similarly reduced the increase in leukocyte-endothelium interactions after ischemia.

CONCLUSIONS

Preischemic tissue perfusion with Celsior had an adverse effect on capillary perfusion in rat cremaster muscle after 4 and 6 h of ischemia, whereas HTK did not significantly influence this parameter. Both preservation solutions similarly prevented the increase in leukocyte-endothelium interactions after ischemia. These data suggest that HTK is more suited as a preservation solution for muscular tissue than Celsior, especially when the known protective effects of HTK on muscle function are taken into account.

Endothelial nitric oxide synthase protects the post-ischemic liver: potential interactions with superoxide

Hepatic ischemia and reperfusion (I/R) continues to represent a significant cause of post-transplant liver failure. The roles that certain free radicals including nitric oxide (NO) and superoxide (O(2)(-)) play in this process are not well understood. The present study was designed to assess the role of endothelial cell nitric oxide synthase (eNOS) in I/R-induced liver injury in a murine model of hepatic I/R. Forty five minutes of partial (70%) hepatic ischemia followed by 3 and 6 h of reperfusion resulted in a significant increase in liver injury which occurred in the absence of neutrophil infiltration. eNOS-deficient mice displayed enhanced liver injury when compared to their wild type controls again in the absence of neutrophil infiltration. Interestingly, basal liver blood flow was significantly decreased in these mice when compared to controls though their blood flow during reperfusion was not significantly reduced from their wild type controls. Treatment of eNOS(-/-) mice with gadolinium chloride, a potent inhibitor of Kupffer cell function, but not superoxide dismutase, significantly reduced post-ischemic hepatocellular injury while either treatment protected the wild type mouse livers. Taken together, these data suggest that NO derived from eNOS may act to protect the post-ischemic liver possibly by suppression of Kupffer cell function and not by modulation of tissue perfusion. Further the data presented here would indicate that the protective effects conferred by SOD are related to its ability to increase the bioavailability of NO rather than by attenuating superoxide-dependent reactions. Data generated from these studies may prove useful in developing new drug therapies to treat the post-ischemic liver.

Ischemia/reperfusion injury: a review in relation to free tissue transfers

Events during ischemia/reperfusion (I/R) injury include: neutrophil-mediated endothelial cytotoxicity and activation, generation of free radicals, triggering of cytokines and chemokines, and activation of adhesion molecules and complement system. This article briefly reviews events occurring during tissue ischemia and reperfusion in relation to free tissue transfers. The consequences of tissue damage at the microcirculatory level are presented. Preventive measures of I/R injury are outlined.

Addition of nitric oxide donor S-nitroso-N-acetylcysteine to selective iNOS inhibitor 1400W further improves contractile function in reperfused skeletal muscle

This study examines the effects of combination therapy with the nitric oxide (NO) donor S-nitroso-N-acetylcysteine (SNAC) and the iNOS inhibitor N-(3-(aminomethyl)benzyl) acetamidine (1400W) on contractile function in reperfused rat skeletal muscle. The right extensor digitorum longus (EDL) muscles of 104 rats were subjected to 3 h of ischemia followed by reperfusion times of 3 h, 24 h, and 7 days. For each time period, rats were further divided into sham operation, control, 1400W only, and 1400W plus SNAC groups. In vitro muscle contractile functional testing was performed in an organ chamber with electrical stimulation. The results showed that twitch and isometric tetanic forces were significantly improved in the 1400W-alone group compared to controls for 24 h and 7 days, but not 3 h of reperfusion. However, all three time periods of reperfusion showed that combination treatment of 1400W + SNAC significantly improved muscle contractile force compared to both control and 1400W-only groups. This corresponded to the decreased tissue necrosis and inflammation seen with combination therapy histologically. Our results demonstrate that combination treatment of 1400W + SNAC promotes functional recovery in reperfused skeletal muscle, supporting that manipulation of NO levels with a NO donor and an iNOS inhibitor is more beneficial than either treatment in isolation.

Effects of antioxidants and NO on TNF-alpha-induced adhesion molecule expression in human pulmonary microvascular endothelial cells

Pro-inflammatory cytokines initiate the vascular inflammatory response via upregulation of adhesion molecules on the endothelium. Recent observations suggest that reactive oxygen intermediates may play a pivotal role in TNF-alpha signaling and upregulate gene expression. We therefore evaluated the effects of pyrrolidine dithiocarbamate (PDTC; 0.1 mM) and spermine NONOate (Sper-NO; 1 mM) on adhesion molecule expression and nuclear factor kappa B (NF-kappaB) activation induced by TNF-alpha (10 ng/ml) in cultured human pulmonary microvascular endothelial cells (PMVEC). Treatment of cells with TNF-alpha for 4 h significantly induced the surface expression of E-selectin and ICAM-1. Treatment with TNF-alpha for 8 h significantly induced the surface expression of E-selectin, ICAM-1 and VCAM-1. The upregulation of these adhesion molecules was suppressed significantly by pretreatment with PDTC or Sper-NO for 1 h. 8-Bromo-cyclic GMP (1 mM) had no such effect, suggesting that the NO donor's effect was non-cGMP-dependent. The mRNA expression of E-selectin, ICAM-1 and VCAM-1, and activation of NF-kappaB induced by TNF-alpha for 2 h were decreased significantly by the above two pretreatments. N-acetylcysteine (10 mM) and S-nitroso-N-acetylpenicillamine (1 mM) had little inhibitory effects on the cell surface and mRNA expression of these adhesion molecules stimulated by TNF-alpha. Treatment with TNF-alpha for 4 h enhanced HL-60 leukocyte adhesion to human PMVEC, the effect of which was inhibited significantly by pretreatment with PDTC or Sper-NO. These findings indicate that both cell surface and mRNA expression of adhesion molecules in human PMVEC induced by TNF-alpha are inhibited significantly by pretreatment with PDTC or Sper-NO, possibly in part through blocking the activation of NF-kappaB. Although our in vitro results cannot be directly extrapolated to the in vivo situation, they suggest a potential therapeutic approach for intervention in cytokine-mediated inflammatory processes in the human lung.

Oleuropein prevents oxidative myocardial injury induced by ischemia and reperfusion

The potential protective effects of oleuropein, a dietary antioxidant of olive oil, has been investigated in the isolated rat heart. The organs were subjected to 30 minutes of no-flow global ischemia and then reperfused. At different time intervals, the coronary effluent was collected and assayed for creatine kinase activity as well as for reduced and oxidized glutathione. In addition, the extent of lipid peroxidation was evaluated by measuring thiobarbituric acid reactive substance concentration in cardiac muscle. Pretreatment with 20 microg/g oleuropein before ischemia resulted in a significant decrease in creatine kinase and reduced glutathione release in the perfusate. The protective effect of oleuropein against the post-ischemic oxidative burst was investigated by measuring the release, in the coronary effluent, of oxidized glutathione, a sensitive marker of heart's exposure to oxidative stress. Reflow in ischemic hearts was accompanied by a prompt release of oxidized glutathione; in ischemic hearts pretreated with oleuropein, this release was significantly reduced. Membrane lipid peroxidation was also prevented by oleuropein. The reported data provide the first experimental evidence of a direct cardioprotective effect of oleuropein in the acute events that follow coronary occlusion, likely because of its antioxidant properties. This finding strengthens the hypothesis that the nutritional benefit of olive oil in the prevention of coronary heart disease can be also related to the high content of oleuropein and its derivatives. Moreover, our data, together with the well documented antithrombotic and antiatherogenic activity of olive oil polyphenols, indicate these antioxidants as possible therapeutic tools for the pharmacological treatment of coronary heart disease as well as in the case of cardiac surgery, including transplantation.

Effects of antioxidants and nitric oxide on TNF-α-induced adhesion molecule expression and NF-κB activation in human dermal microvascular endothelial cells

Cell adhesion molecules expressed on endothelial cells in inflamed skin appear to be controlled by the actions of cytokines and reactive oxygen species. However, molecular mechanisms of the expression of adhesion molecules during skin inflammation are currently not well understood. To evaluate the role of antioxidants and nitric oxide in modulating inflammatory processes in the skin, we examined the effects of pyrrolidine dithiocarbamate (PDTC, 0.1 mM) and spermine NONOate (Sper-NO, 1 mM) on adhesion molecule expression and nuclear factor kappa B (NF-kappaB) activation induced by TNF-alpha (10 ng/ml) in cultured human dermal microvascular endothelial cells (HDMEC). Treatment of cells with TNF-alpha for 4 h significantly induced the surface expression of E-selectin and intercellular adhesion molecule-1 (ICAM-1). Treatment with TNF-alpha for 8 h significantly induced the surface expression of E-selectin, ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1). The up-regulation of these adhesion molecules was suppressed significantly by pretreatment with PDTC or Sper-NO for 1 h. The mRNA expression of E-selectin, ICAM-1 and VCAM-1, and activation of NF-kappaB induced by TNF-alpha for 2 h were significantly decreased by the above two pretreatments. N-acetylcysteine (10 mM) and S-nitroso-N-acetylpenicillamine (1 mM) had no significant inhibitory effects on the cell surface and mRNA expression of these adhesion molecules stimulated by TNF-alpha. These findings indicate that both cell surface and mRNA expression of adhesion molecules in HDMEC induced by TNF-alpha are inhibited significantly by pretreatment with PDTC or Sper-NO, possibly in part through blocking the activation of NF-kappaB. These results suggest a potential therapeutic approach using antioxidant agents or nitric oxide pathway modulators in the treatment of inflammatory skin diseases.