NO reduces PMN adhesion to human vascular endothelial cells due to downregulation of ICAM-1 mRNA and surface expression

Chronic Effects of a High Sucrose Diet on Murine Gastrointestinal Nutrient Sensor Gene and Protein Expression Levels and Lipid Metabolism

The gastrointestinal tract (GIT) plays a key role in regulating nutrient metabolism and appetite responses. This study aimed to identify changes in the GIT that are important in the development of diet related obesity and diabetes. GIT samples were obtained from C57BL/6J male mice chronically fed a control diet or a high sucrose diet (HSD) and analysed for changes in gene, protein and metabolite levels. In HSD mice, GIT expression levels of fat oxidation genes were reduced, and increased de novo lipogenesis was evident in ileum. Gene expression levels of the putative sugar sensor, slc5a4a and slc5a4b, and fat sensor, cd36, were downregulated in the small intestines of HSD mice. In HSD mice, there was also evidence of bacterial overgrowth and a lipopolysaccharide activated inflammatory pathway involving inducible nitric oxide synthase (iNOS). In Caco-2 cells, sucrose significantly increased the expression levels of the nos2, iNOS and nitric oxide (NO) gas levels. In conclusion, sucrose fed induced obesity/diabetes is associated with changes in GI macronutrient sensing, appetite regulation and nutrient metabolism and intestinal microflora. These may be important drivers, and thus therapeutic targets, of diet-related metabolic disease.

Beyond Preconditioning: Postconditioning as an Alternative Technique in the Prevention of Liver Ischemia-Reperfusion Injury

Liver ischemia/reperfusion injury may significantly compromise hepatic postoperative function. Various hepatoprotective methods have been improvised, aiming at attenuating IR injury. With ischemic preconditioning (IPC), the liver is conditioned with a brief ischemic period followed by reperfusion, prior to sustained ischemia. Ischemic postconditioning (IPostC), consisting of intermittent sequential interruptions of blood flow in the early phase of reperfusion, seems to be a more feasible alternative than IPC, since the onset of reperfusion is more predictable. Regarding the potential mechanisms involved, it has been postulated that the slow intermittent oxygenation through controlled reperfusion decreases the burst production of oxygen free radicals, increases antioxidant activity, suppresses neutrophil accumulation, and modulates the apoptotic cascade. Additionally, favorable effects on mitochondrial ultrastructure and function, and upregulation of the cytoprotective properties of nitric oxide, leading to preservation of sinusoidal structure and maintenance of blood flow through the hepatic circulation could also underlie the protection afforded by postconditioning. Clinical studies are required to show whether biochemical and histological improvements afforded by the reperfusion/reocclusion cycles of postconditioning during early reperfusion can be translated to a substantial clinical benefit in liver resection and transplantation settings or to highlight more aspects of its molecular mechanisms.

Hydroxyurea with AKT2 inhibition decreases vaso-occlusive events in sickle cell disease mice

Heterotypic cell-cell adhesion and aggregation mediate vaso-occlusive events in patients with sickle cell disease (SCD). Although hydroxyurea (HU), an inducer of fetal hemoglobin, is the main therapy for treatment of SCD, it is unclear whether it has immediate benefits in acute vaso-occlusive events in SCD patients. Using real-time fluorescence intravital microscopy, we demonstrated that short-term coadministration of HU and Akti XII, an AKT2 inhibitor, efficiently reduced neutrophil adhesion and platelet-neutrophil aggregation in venules of Berkeley (SCD) mice challenged with tumor necrosis factor α (TNF-α) or hypoxia/reoxygenation. Importantly, compared with HU or Akti XII treatment alone, short-term treatment with both agents significantly improved survival in those mice. We found that the level of plasma nitric oxide species was elevated by HU but not Akti XII, AKT2 phosphorylation levels in activated neutrophils and platelets were reduced by Akti XII but not HU, and the expression of endothelial E-selectin and intercellular adhesion molecule 1 was decreased by either agent. Our results suggest that short-term coadministration of HU and Akti XII has immediate benefits for acute vaso-occlusive events and survival in SCD mice exceeding those seen for single therapy.

Adaptation of endothelial cells to physiologically-modeled, variable shear stress

Endothelial cell (EC) function is mediated by variable hemodynamic shear stress patterns at the vascular wall, where complex shear stress profiles directly correlate with blood flow conditions that vary temporally based on metabolic demand. The interactions of these more complex and variable shear fields with EC have not been represented in hemodynamic flow models. We hypothesized that EC exposed to pulsatile shear stress that changes in magnitude and duration, modeled directly from real-time physiological variations in heart rate, would elicit phenotypic changes as relevant to their critical roles in thrombosis, hemostasis, and inflammation. Here we designed a physiological flow (PF) model based on short-term temporal changes in blood flow observed in vivo and compared it to static culture and steady flow (SF) at a fixed pulse frequency of 1.3 Hz. Results show significant changes in gene regulation as a function of temporally variable flow, indicating a reduced wound phenotype more representative of quiescence. EC cultured under PF exhibited significantly higher endothelial nitric oxide synthase (eNOS) activity (PF: 176.0±11.9 nmol/10⁵ EC; SF: 115.0±12.5 nmol/10⁵ EC, p = 0.002) and lower TNF-a-induced HL-60 leukocyte adhesion (PF: 37±6 HL-60 cells/mm²; SF: 111±18 HL-60/mm², p = 0.003) than cells cultured under SF which is consistent with a more quiescent anti-inflammatory and anti-thrombotic phenotype. In vitro models have become increasingly adept at mimicking natural physiology and in doing so have clarified the importance of both chemical and physical cues that drive cell function. These data illustrate that the variability in metabolic demand and subsequent changes in perfusion resulting in constantly variable shear stress plays a key role in EC function that has not previously been described.

Ischemic postconditioning attenuates liver warm ischemia-reperfusion injury through Akt-eNOS-NO-HIF pathway

BACKGROUND

Ischemic postconditioning (IPO) has been demonstrated to attenuate ischemia/reperfusion (I/R) injury in the heart and brain, its roles to liver remain to be defined. The study was undertaken to determine if IPO would attenuate liver warm I/R injury and its protective mechanism.

METHODS

Mice were divided into sham, I/R, IPO+I/R (occlusing the porta hepatis for 60 min, then treated for three cycles of 10 sec brief reperfusion consecutively, followed by a persistent reperfusion); L-NAME+ sham (L-NAME, 16 mg/kg, i.v., 5 min before repefusion); L-NAME+I/R; and L-NAME+ IPO. Blood flow of caudate and left lobe of the liver was blocked. Functional and morphologic changes of livers were evaluated. Contents of nitric oxide, eNOS and iNOS in serum were assayed. Concentration of eNOS, iNOS, malondialdehyde (MDA) and activity of superoxide dismutase (SOD) in hepatic tissue were also measured. Expressions of Akt, p-Akt and HIF-1α protein were determined by western blot. Expressions of TNF-α and ICAM-1 were measured by immunohistochemistry and RT-PCR.

RESULTS

IPO attenuated the dramatically functional and morphological injuries. The levels of ALT was significantly reduced in IPO+I/R group (p < 0.05). Contents of nitric oxide and eNOS in serum were increased in the IPO+I/R group (p < 0.05). IPO also up-regulated the concentration of eNOS, activity of SOD in hepatic tissue (p < 0.05), while reduced the concentration of MDA (p < 0.05). Moreover, protein expressions of HIF-1α and p-Akt were markedly enhanced in IPO+I/R group. Protein and mRNA expression of TNF-α and ICAM-1 were markedly suppressed by IPO (p < 0.05). These protective effects of IPO could be abolished by L-NAME.

CONCLUSIONS

We found that IPO increased the content of NO and attenuated the overproduction of ROS and I/R-induced inflammation. Increased NO contents may contribute to increasing HIF-1α level, and HIF-1α and NO would simultaneously protect liver from I/R injury. These findings suggested IPO may have the therapeutic potential through Akt-eNOS-NO-HIF pathway for the better management of liver I/R injury.

Rb1 postconditioning attenuates liver warm ischemia-reperfusion injury through ROS-NO-HIF pathway

AIMS

Ginsenoside Rb1 could prevent ischemic neuronal death and focal cerebral ischemia, but its roles to liver warm I/R injury remain to be defined. We determined if Rb1 would attenuate warm I/R injury in mice.

MAIN METHODS

Mice were divided into sham, I/R, Rb1+I/R (Rb1 postconditioning, 20mg/kg, i.p. after ischemia), sham+L-NAME, I/R+L-NAME, and Rb1+I/R+L-NAME groups using 60min of the liver median and left lateral lobes ischemia. Serum levels of alanine aminotransferase (ALT) were measured and morphology changes of livers were evaluated. Contents of nitric oxide (NO) and nitric oxide synthase (NOS), malondialdehye (MDA) and activity of superoxide dismutase (SOD) were measured. Expressions of Akt, p-Akt, iNOS, HIF-1alpha, tumor necrosis factor-a (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) were also determined by western blot or immunohistochemistry.

KEY FINDINGS

Rb1 postconditioning attenuated the dramatically functional and morphological injuries. The levels of ALT were significantly reduced in Rb1 group (p<0.05). Rb1 upregulated the concentrations of NO, iNOS in serum, iNOS, and activity of SOD in hepatic tissues (p<0.05), while it dramatically reduced the concentration of MDA (p<0.05). Protein expressions of p-Akt, iNOS and HIF-1alpha were markedly enhanced in Rb1 group. Protein and mRNA expressions of TNF-α and ICAM-1 were markedly suppressed by Rb1 (p<0.05).

SIGNIFICANCE

We found that Rb1 postconditioning could protect liver from I/R injury by upregulating the content of NO and NOS, and also HIF-1alpha protein expression. These protective effects could be abolished by L-NAME. These findings suggested Rb1 may have the therapeutic potential through ROS-NO-HIF pathway for management of liver warm I/R injury.

Multiple antioxidants and L-arginine modulate inflammation and dyslipidemia in chronic renal failure rats

The kidney is an important source of L-arginine, the endogenous precursor of nitric oxide (NO). Surgical problems requiring extensive renal mass reduction (RMR) decrease renal NO production, leading to multiple hemodynamic and homeostatic disorders manifested by hypertension, oxidative stress, and increased inflammatory cytokines. Using the RMR model of chronic renal failure (CRF), we assessed the effects of twelve weeks' administration of L-arginine and/or a mixture of antioxidants (L-carnitine, catechin, vitamins E and C) on plasma cytokines, soluble intercellular adhesion molecule-1 (sICAM-1), nitrate and nitrites (NO(2)/NO(3)), lipid profile, blood pressure, and renal function. CRF rats showed increased plasma IL-1 alpha, IL1-beta, IL-6, TNF-alpha, and sICAM-1 levels and decreased anti-inflammatory cytokines IL-4 and 10 levels, hypertension, and dyslipidemia. L-arginine treatment improved kidney functions, decreased systolic blood pressure, and decreased inflammatory cytokines levels. Antioxidants administration decreased inflammatory cytokines and sICAM-1 levels and increased IL-4 levels. Combined use of both L-arginine and the antioxidant mixture were very effective in their tendency to recover normal values of kidney functions, plasma cytokines, sICAM-1, blood pressure, NO(2)/NO(3), cholesterol, and triglycerides concentrations. Indeed, the effects of L-arginine and the antioxidants on the reduction of proinflammatory cytokines may open new perspectives in the treatment of uremia.

Insulin inhibits leukocyte-endothelium adherence via an Akt-NO-dependent mechanism in myocardial ischemia/reperfusion

Clinical evidence indicates that intensive insulin therapy during critical illness protects the endothelium and contributes to prevention of organ failure and death but the mechanisms involved remain unclear. This study was designed to test the hypothesis that insulin inhibits adherence of polymorphonuclear leukocytes (PMNs) to endothelial cells in myocardial ischemia/reperfusion (MI/R) and to investigate the underlying mechanisms. Anesthetized rabbits were subjected to MI/R (45 min/4 h) and randomly received saline, glucose-insulin-potassium (GIK) or GK respectively (2 mL/kg/h, i.v.). In vitro study was performed on cultured endothelial cells subjected to simulated ischemia/reperfusion. In vivo treatment with GIK but not GK attenuated myocardial injury as evidenced by reduced plasma creatine kinase activity, myocardial apoptosis and infarct size in MI/R rabbits compared with the saline group. Interestingly, GIK but not GK significantly decreased coronary endothelial expression of P-selectin and intercellular adhesion molecule-1 (ICAM-1), inhibited adherence of PMNs to coronary endothelium (107.7+/-7.4 vs. 155.0+/-9.2 PMNs/mm(2) in saline group, n=8, P<0.01), and therefore decreased myocardial PMNs accumulation. In cultured endothelial cells subjected to simulated ischemia/reperfusion, insulin (10(-)(7) M) increased Akt activity and eNOS phosphorylation with subsequent NO production, and concurrently exerted an anti-adhesive effect as manifested by reduced endothelial P-selectin and ICAM-1 surface expression and PMNs adherence (13.7+/-1.3% vs. 22.2+/-1.9% in vehicle, n=9, P<0.01), all of which are abolished by the specific Akt inhibitor. Furthermore, inhibition of insulin-stimulated NO production using either the selective eNOS inhibitor cavtratin or the NOS inhibitor L-NAME blocked the anti-adhesive effect of insulin. These results demonstrate that insulin reduces endothelial P-selectin and ICAM-1 expression, and thus inhibits leukocyte-endothelium adherence in MI/R rabbit hearts. The anti-adhesive property by insulin may be mediated by the Akt-mediated and NO-dependent pathway.

Effects of hydrocortisone on microcirculatory alterations in patients with septic shock

OBJECTIVE

To evaluate the effects of hydrocortisone on microcirculatory blood flow alterations in patients with septic shock.

DESIGN

Prospective, open-label study.

SETTING

A 31-bed, medico-surgical intensive care unit of a university hospital.

PATIENTS

Twenty patients with septic shock.

INTERVENTIONS

Intravenous hydrocortisone (50 mg/6 hr).

MEASUREMENTS AND MAIN RESULTS

An orthogonal polarization spectral device (Cytoscan ARII, Cytometrics; Philadelphia, PA) was used to investigate the sublingual microcirculation in 20 patients who received so-called "stress doses" of hydrocortisone as part of their management for septic shock. Hemodynamic measurements and orthogonal polarization spectral images were obtained before administration of the first dose (50 mg) of hydrocortisone and 1, 2, 4, and 24 hours later. Measurements were also made before an adrenocorticotropic hormone (ACTH) test, whenever performed. Global hemodynamic variables were similar at all study time points. Microcirculatory variables improved slightly already at 1 hour after the start of hydrocortisone administration. In particular, perfused vessel density increased from 5.7 (4.8-6.4) to 7.2 (6.5-9.0)n/mm, p < 0.01, which was due to combined increases in small vessel density from 5.2 (4.6-6.2) to 6.0 (5.1-7.5)n/mm, p < 0.01, and in the proportion of perfused vessels from 82.1 (68.7-88.0) to 89.2 (83.4-92.6)%, p < 0.01. There were no differences in microcirculatory variables during hydrocortisone administration between ACTH test responders and nonresponders.

CONCLUSIONS

The administration of moderate doses of hydrocortisone in septic shock results in a modest but consistent improvement in capillary perfusion, independent of the response to the ACTH test. The mechanisms underlying this effect need to be elucidated.

Production of nitric oxide by peripheral blood mononuclear cells from the Florida manatee, Trichechus manatus latirostris

Florida manatees (Trichechus manatus latirostris) are exposed to many conditions in their habitat that may adversely impact health and impair immune function in this endangered species. In an effort to increase the current knowledge base regarding the manatee immune system, the production of an important reactive nitrogen intermediate, nitric oxide (NO), by manatee peripheral blood mononuclear cells (PBMC) was investigated. PBMC from healthy captive manatees were stimulated with LPS, IFN-gamma, or TNF-alpha, either alone or in various combinations, with NO production assessed after 24, 48, 72, and 96 h of culture. NO production in response to LPS stimulation was significantly greater after 48, 72, or 96 h of culture compared to NO production after 24h of culture. A specific inhibitor of inducible nitric oxide synthase (iNOS), L-NIL (L-N(6)-(1-iminoethyl)lysine), significantly decreased NO production by LPS-stimulated manatee PBMC. Manatee specific oligonucleotide primers for iNOS were designed to measure expression of relative amounts of mRNA in LPS-stimulated manatee PBMC from captive manatees. NO production by PBMC from manatees exposed to red tide toxins was analyzed, with significantly greater NO production by both unstimulated and LPS stimulated PBMC from red tide exposed compared with healthy captive or cold-stress manatees. Free-ranging manatees produced significantly lower amounts of nitric oxide compared to either captive or red tide rescued manatees. Results presented in this paper contribute to the current understanding of manatee immune function and represent the first report of nitric oxide production in the immune system of a marine mammal.

Platelets, inflammation and atherosclerosis

An expanding body of evidence continues to build on the role of platelets as initial actors in the development of atherosclerotic lesions. Platelets bind to leukocytes and endothelial cells, and initiate monocyte transformation into macrophages. Platelets internalize oxidized phospholipids and promote foam cell formation. Platelets also recruit progenitor cells to the scene that are able to differentiate into foam cells or endothelial cells depending on conditions. Platelets tip the scales in the initiation, development and total extent of atherosclerotic lesions.

Inhaled nitric oxide does not prevent postpneumonectomy pulmonary edema in pigs

OBJECTIVE

Increase in lung permeability is an inevitable consequence of pneumonectomy in relation to inflammatory injury and increased perfusion flow. We tested whether inhaled nitric oxide, a potent vasodilatator and anti-inflammatory agent, prevents postpneumonectomy edema in the first 24 hours after pneumonectomy in pigs.

METHODS

We assessed hemodynamics, gas exchange, extravascular lung water estimated with the double-indicator dilution method, and lung neutrophil sequestration measured on the basis of lung myeloperoxidase activity at 1 and 24 hours after left pneumonectomy in 14 pigs randomly assigned to inhaled nitric oxide (10 ppm) or control groups.

RESULTS

Extravascular lung water content markedly increased at 1 and 24 hours after pneumonectomy, with no difference between the 2 groups. Hemodynamics did not differ between the 2 groups. Myeloperoxidase activity was higher and PaO2 values were lower in the nitric oxide group compared with in the control group.

CONCLUSIONS

Over the 24 hours after pneumonectomy, intraoperative inhaled nitric oxide levels neither improved gas exchange nor attenuated accumulation of lung water. On the contrary, they were associated with an increase in lung neutrophil sequestration and deterioration of arterial oxygenation, suggesting the occurrence of an early and toxic effect of nitric oxide.

Caffeic acid phenethyl ester reduces neurovascular inflammation and protects rat brain following transient focal cerebral ischemia

Ischemic stroke is a neurovascular disease treatable by thrombolytic therapy, but the therapy has to be initiated within 3 h of the incident. This therapeutic limitation stems from the secondary injury which results mainly from oxidative stress and inflammation. A potent antioxidant/anti-inflammatory agent, caffeic acid phenethyl ester (CAPE) has potential to mitigate stroke's secondary injury, and thereby widening the therapeutic window. We observed that CAPE protected the brain in a dose-dependent manner (1-10 mg/kg body weight) and showed a wide therapeutic window (about 18 h) in a rat model of transient focal cerebral ischemia and reperfusion. The treatment also increased nitric oxide and glutathione levels, decreased lipid peroxidation and nitrotyrosine levels, and enhanced cerebral blood flow. CAPE down-regulated inflammation by blocking nuclear factor kappa B activity. The affected mediators included adhesion molecules (intercellular adhesion molecule-1 and E-selectin), cytokines (tumor necrosis factor-alpha and interleukin-1beta) and inducible nitric oxide synthase. Anti-inflammatory action of CAPE was further documented through reduction of ED1 (marker of activated macrophage/microglia) expression. The treatment inhibited apoptotic cell death by down-regulating caspase 3 and up-regulating anti-apoptotic protein Bcl-xL. Conclusively, CAPE is a promising drug candidate for ischemic stroke treatment due to its inhibition of oxidative stress and inflammation, and its clinically relevant wide therapeutic window.

Cerebrovascular protection by various nitric oxide donors in rats after experimental stroke

The efficacy of nitric oxide (NO) treatment in ischemic stroke, though well recognized, is yet to be tested in clinic. NO donors used to treat ischemic injury are structurally diverse compounds. We have shown that treatment of S-nitrosoglutathione (GSNO) protects the brain against injury and inflammation in rats after experimental stroke [M. Khan, B. Sekhon, S. Giri, M. Jatana, A. G. Gilg, K. Ayasolla, C. Elango, A. K. Singh, I. Singh, S-Nitrosoglutathione reduces inflammation and protects brain against focal cerebral ischemia in a rat model of experimental stroke, J. Cereb. Blood Flow Metab. 25 (2005) 177-192.]. In this study, we tested structurally different NO donors including GSNO, S-nitroso-N-acetyl-penicillamine (SNAP), sodium nitroprusside (SNP), methylamine hexamethylene methylamine NONOate (MAHMA), propylamine propylamine NONOate (PAPA), 3-morpholinosydnonimine (SIN-1) and compared their neuroprotective efficacy and antioxidant property in rats after ischemia/reperfusion (I/R). GSNO, in addition to neuroprotection, decreased nitrotyrosine formation and lipid peroxidation in blood and increased the ratio of reduced versus oxidized glutathione (GSH/GSSG) in brain as compared to untreated animals. GSNO also prevented the I/R-induced increase in mRNA expression of ICAM-1 and E-Selectin. SNAP and SNP extended limited neuroprotection, reduced nitrotyrosine formation in blood and blocked increase in mRNA expression of ICAM-1 and E-Selectin in brain tissue. PAPA, MAHMA, and SIN-1 neither protected the brain nor reduced oxidative stress. We conclude that neuroprotective action of NO donors in experimental stroke depends on their ability to reduce oxidative stress both in brain and blood.

The influence of propofol on P-selectin expression and nitric oxide production in re-oxygenated human umbilical vein endothelial cells

BACKGROUND

Reperfusion injury is characterized by free radical production and endothelial inflammation. Neutrophils mediate much of the end-organ injury that occurs, requiring P-selectin-mediated neutrophil-endothelial adhesion, and this is associated with decreased endothelial nitric oxide production. Propofol has antioxidant properties in vitro which might abrogate this inflammation.

METHODS

Cultured human umbilical vein endothelial cells were exposed to 20 h of hypoxia and then returned to normoxic conditions. Cells were treated with saline, Diprivan 5 microg/l or propofol 5 microg/l for 4 h after re-oxygenation and were then examined for P-selectin expression and supernatant nitric oxide concentrations for 24 h. P-selectin was determined by flow cytometry, and culture supernatant nitric oxide was measured as nitrite.

RESULTS

In saline-treated cells, a biphasic increase in P-selectin expression was demonstrated at 30 min (P = 0.01) and 4 h (P = 0.023) after re-oxygenation. Propofol and Diprivan prevented these increases in P-selectin expression (P < 0.05). Four hours after re-oxygenation, propofol decreased endothelial nitric oxide production (P = 0.035).

CONCLUSION

This is the first study to demonstrate an effect of propofol upon endothelial P-selectin expression. Such an effect may be important in situations of reperfusion injury such as cardiac transplantation and coronary artery bypass surgery. We conclude that propofol attenuates re-oxygenation-induced endothelial inflammation in vitro.

Nitric Oxide Mediates the Effect of Fluvastatin on Intercellular Adhesion Molecule-1 and Platelet Endothelial Cell Adhesion Molecule-1 Expression on Human Endothelial Cells

Leukocyte and platelet adhesion to endothelial cells, an early step in the pathogenesis of atherosclerosis, is mediated through adhesion molecules. It has been shown that statins decrease adhesion molecule expression. We examined the hypothesis that fluvastatin decreased intercellular adhesion molecule-1 (ICAM-1) and platelet endothelial cell adhesion molecule-1 (PECAM-1) expression through a nitric oxide-mediated pathway. Human iliac artery endothelial cells were exposed to fluvastatin in the presence or absence of 2 mM N-monomethyl-L-arginine (L-NMMA). Flow cytometry analysis was used to measure ICAM-1 and PECAM-1 expression. In a separate experiment, confluent cell cultures were exposed in a serum-free medium to fluvastatin 20 microM, and the supernatant was collected for nitrate/nitrite determination after 6 and 48 hr of incubation. Protein was isolated and processed for immunoblotting with monoclonal antibodies specific for endothelial nitric oxide synthase (eNOS), Ser(1177)-phosphorylated eNOS, and AMP kinase. Relative band intensity was assessed with densitometry. Results are presented as the mean +/- standard deviation (SD), and p < 0.05 was considered significant. ICAM-1 and PECAM-1 were expressed constitutively. Human iliac artery endothelial cells (HIAECS) treated with 5 microM fluvastatin did not exhibit reduced expression of PECAM-1 or ICAM-1. Incubation with 10 microM fluvastatin reduced basal expression of both ICAM-1 and PECAM-1. Fluorescence intensity (FI) for these substance was as follows: 3638 +/- 1671, p = 0.01 and PECAM-1 vs. control FI 276 +/- 52 vs. 522 +/- 78, p = 0.02. In the presence of 2 mM L-NMMA, fluvastatin failed to decrease the expression of ICAM-1 (fluvastatin 10 microM + L-NMMA: FI was 3042 +/- 1378 vs. 3638 +/- 1671 for the control p = 0.01) or PECAM-1 (fluvastatin 10 microM + L-NMMA: FI was 415 +/- 188 vs. 522 +/- 78 for the control, p = 0.1). Incubation with 20 microM fluvastatin similarly reduced ICAM-1 expression (FI was 2014 +/- 1595 vs. 3638 +/- 1671 for the control, p = 0.02) and PECAM-1 expression (FI was 196 +/- 109 vs. 522 +/- 78 for the control, p = 0.02). This reduction was prevented in the presence of 2 mM L-NMMA. L-NMMA in a concentration of 2 mM had no significant effect on adhesion molecule expression (p > 0.05 for all comparisons of the control FI versus 2 mM L-NMMA mean FI). After a 48 hr incubation with 20 microM fluvastatin there was a 219 +/- 35% increase in the cell eNOS protein content (p = 0.01) and a 170 +/- 26% increase in the cell AMPK protein content (p = 0.02). Ser(1177)-phosphorylated eNOS protein levels were increased by 41 +/- 8% (p = 0.03). The nitric oxide concentration in the medium of the HIAEC treated with 20 microM fluvastatin for 48 hr was significantly higher than that in the control (p = 0.0004), pointing to increased production during the incubation period. Fluvastatin thus decreases basal expression of ICAM-1 and PECAM-1. Competitive inhibition of eNOS with L-NMMA abolishes the effect of fluvastatin on ICAM-1 and PECAM-1 expression. The statin up-regulates eNOS and AMP kinase, one of the enzymes that activates eNOS via phosphorylation at Ser(1177). We have shown that after a 48-hr exposure to fluvastatin there is an increased amount of the phosphorylated enzyme in the endothelial cells.

Dengue virus infection of human microvascular endothelial cells from different vascular beds promotes both common and specific functional changes

Dengue shock syndrome (DSS), the major life threatening outcome of severe dengue disease, which occurs in some patients in the course of dengue infection, is the consequence of plasma leakage in the microvascular territories. Data from clinical and in vitro studies suggest that an inadequate immunological response is partly responsible for the pathophysiology of DSS, but few is known concerning the consequences of direct infection of endothelial cells by dengue virus per se. In this study, an attempt was made to study the response of two microvascular human cell lines originating, respectively, from liver and dermis to infection by a dengue type 2 virus, by analyzing the virus-induced modulation of functional markers. It is shown that the two microvascular cell lines exhibit both common and specific behaviors upon infection. In particular, LSEC and HMEC-1 replicate efficiently the low-passage virus and respond to infection by over-producing inflammatory mediators involved in the cross talk with circulating immune cells. However, direct infection modulates differently the cell surface expression of molecules critically involved in the interactions between endothelial and inflammatory cells. ICAM-1 and HLA-I are up regulated as a consequence of infection in LSEC whereas direct infection results in downregulation of ICAM-1 in HMEC-1. The present results show that infection of human microvascular cells by unadapted dengue virus results in both common and specific activation patterns depending likely on the tissue origin of the cells, thus suggesting that endothelia from different territories may contribute differently to the pathophysiological events in the course of dengue infection.

Nitric oxide regulates interactions of PMN with human brain microvessel endothelial cells

The hypothesis that the NO/cGMP pathway modulates PMN adhesion to human brain microvessel endothelial cells (HBMEC) was examined. Human PMN were incubated with resting or TNF-alpha-treated endothelial monolayers, and adhesion was quantified by light microscopy. TNF-alpha upregulated PMN adhesion in a time-dependent manner. Treatment of HBMEC with the NO donors SNP and DETA NONOate for 4 or 24 h decreased PMN adhesion. This was completely reversed by the guanylyl cyclase inhibitor ODQ, while addition of a cGMP agonist (8-Br-cGMP) decreased PMN adhesion. NO donors did not affect the levels of E-selectin or ICAM-1 in HBMEC. However, pre-treatment of PMN with NO donors or 8-Br-cGMP decreased their adhesion to recombinant E-selectin and ICAM-1, suggesting an effect of NO on PMN. These findings indicate that NO modulates PMN-HBMEC interactions through cGMP and decreases the binding of PMN to the adhesion molecules E-selectin and ICAM-1.

Propofol Improves Skin Flap Survival in a Rat Model

Accumulation of neutrophils in a random pattern skin flap has been demonstrated to contribute to the necrosis of distal flap tissue. This study proposes that administration of propofol anesthesia can effectively reduce neutrophil activity and enhance skin flap survival. The study was a randomized controlled trial using male Sprague-Dawley rats as subjects. For flap survival studies, a 3- by 12-cm, dorsal, cranial-based, random pattern skin flap was elevated and reapproximated. Flaps were examined for viability 10 days postsurgery. To assess neutrophil activity, flap biopsies were taken 12, 24, or 48 hours postsurgery from distal, middle, and proximal flap regions, and myeloperoxidase enzyme content was analyzed. Animals were randomly assigned to 1 of 4 groups: group 1, ketamine anesthesia (controls); group 2, propofol anesthesia; group 3, ketamine anesthesia plus 10% lipid emulsion (propofol vehicle); group 4, ketamine anesthesia without flap elevation (nonoperated controls for myeloperoxidase study). Flap survival was significantly improved in the propofol group compared with both the ketamine and vehicle control groups (P <0.01). Increased flap viability was correlated with a reduction in myeloperoxidase content in the propofol group compared with control operated animals, with minor variations observed in the different flap regions and time points tested. This study indicates that the use of propofol can potentially improve skin flap survival. The beneficial effects may be attributed to a reduction in neutrophil activity within the flap.

Nitric oxide, inflammation and acute burn injury

Nitric oxide (NOz.rad;) is a diatomic mediator liberated on oxidation of L-arginine by the nitric oxide synthase (NOS) family of enzymes. It has complex and wide ranging functions in vivo and has been implicated in the development of the profound inflammatory response that occurs as a result of cutaneous burn injury. In addition, dysregulation of NOS activity has been associated with multiple organ failure in human burn patients and may therefore represent a novel therapeutic target in such circumstances. This review focuses on the role of NOz.rad; in inflammation, with particular emphasis on the acute post-burn inflammatory response. Specific areas of discussion include the maintenance of microvascular haemostasis, leukocyte recruitment and remote organ dysfunction following thermal injury.

Mice lacking inducible nitric oxide synthase demonstrate impaired killing of Porphyromonas gingivalis

Porphyromonas gingivalis is a primary etiological agent of generalized severe periodontitis, and emerging data suggest the importance of reactive oxygen and nitrogen species in periodontal tissue damage, as well as in microbial killing. Since nitric oxide (NO) released from inducible NO synthase (iNOS) has been shown to possess immunomodulatory, cytotoxic, and antibacterial effects in experimental models, we challenged iNOS-deficient (iNOS(-/-)) mice with P. gingivalis by using a subcutaneous chamber model to study the specific contribution of NO to host defense during P. gingivalis infection. iNOS(-/-) mice inoculated with P. gingivalis developed skin lesions and chamber rejection with higher frequency and to a greater degree than similarly challenged C57BL/6 wild-type (WT) mice. Chamber fluid from iNOS(-/-) mice possessed significantly more P. gingivalis than that of WT mice. The immunoglobulin G responses to P. gingivalis in serum was similar in WT and iNOS(-/-) mice, and the inductions of tumor necrosis factor alpha, interleukin-1 beta and interleukin-6, and prostaglandin E(2) were comparable between the two mouse strains. Although no differences in total leukocyte counts in chamber fluids were observed between iNOS(-/-) and WT mice, the percentage of dead polymorphonuclear leukocytes (PMNs) was significantly greater in iNOS(-/-) mouse chamber fluids than that of WT samples. Interestingly, casein-elicited PMNs from iNOS(-/-) mice released more superoxide than did WT PMNs when stimulated with P. gingivalis. These results indicate that modulation of superoxide levels is a mechanism by which NO influences PMN function and that NO is an important element of the host defense against P. gingivalis.

A randomized trial of inhaled nitric oxide to prevent ischemia-reperfusion injury after lung transplantation

Inhalation of nitric oxide (NO) has been advocated as a method to prevent ischemia-reperfusion injury after lung transplantation. We enrolled 84 patients into a concealed, randomized, placebo-controlled trial to evaluate the effect of inhaled NO (20 ppm NO or nitrogen) initiated 10 minutes after reperfusion on outcomes after lung transplantation. The groups (n = 42) were balanced with respect to age, sex, lung disease, procedure, and total ischemic times. PaO2/FIO2 ratios were similar on admission to the intensive care unit (ICU) (NO 361 +/- 134; control patients 357 +/- 132), and over the duration of the study. There were no differences in hemodynamics between the two groups. Severe reperfusion injury (PaO2/FIO2 < 150) was present at the time of admission to the ICU in 14.6% NO patients versus 9.5% of control patients (p = 0.48). The groups had similar median times to first successful trial of unassisted breathing (25 vs. 27 hours; p = 0.76), successful extubation (32 vs. 34 hours; p = 0.65), ICU discharge (3.0 days for both groups), and hospital discharge (27 vs. 29 days; p = 0.563). Five NO versus six control patients died during their hospital stay. Adjusting for age, sex, lung disease etiology, presence of pulmonary hypertension, and total ischemic time did not alter these results. In conclusion, we did not detect a significant effect of inhaled NO administered 10 minutes after reperfusion on physiologic variables or outcomes in lung transplant patients.

Effect of endogenous nitric oxide on hyperoxia and tumor necrosis factor-alpha-induced leukosequestration and proinflammatory cytokine release in rat airways

OBJECTIVE

To investigate the effects of endogenous nitric oxide on hyperoxia and tumor necrosis factor-alpha-induced leukosequestration and proinflammatory cytokine release in rat airways.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Experimental laboratory.

SUBJECTS

Male Sprague-Dawley rats weighing 350-500 g.

INTERVENTIONS

The rats were pretreated with N(G)-nitro-L-arginine methyl ester (L-NAME; 10 mg/kg) or saline intravenously 4-6 mins before intratracheal administration of tumor necrosis factor-alpha, 95% oxygen, or both, when the vasopressor effect of L-NAME had reached a plateau.

MEASUREMENTS AND MAIN RESULTS

Bronchoalveolar lavage fluid was recovered from the airway of rats after exposure to 95% oxygen and tumor necrosis factor-alpha for 6 hrs under ventilator support. Neutrophils in lavage fluid were isolated and examined for the inducible nitric oxide synthase expression by flow-cytometric assay. Tumor necrosis factor-alpha and interleukin-1 beta in lavage fluid were measured by enzyme-linked immunosorbent assay. The percentage of neutrophils in bronchoalveolar fluid was significantly higher in rats exposed to hyperoxia + tumor necrosis factor-alpha (29.7 +/- 12.5%) compared with rats with hyperoxia (16.3 +/- 1.2%), tumor necrosis factor-alpha (4.2 +/- 1.1%), or room air (5.0 +/- 1.8%) alone (p <.05). Rats exposed to hyperoxia + tumor necrosis factor-alpha had significantly higher concentrations of inducible nitric oxide synthase of neutrophils (350.1 +/- 75.7 mean fluorescence intensity), compared with rats with hyperoxia (64.9 +/- 1.6 mean fluorescence intensity), tumor necrosis factor-alpha (102.6 +/- 15.3 mean fluorescence intensity), or room air (111.2 +/- 25.8 mean fluorescence intensity) alone (p <.05). Rats exposed to hyperoxia + tumor necrosis factor-alpha significantly produced higher concentrations of tumor necrosis factor-alpha and interleukin-1 beta, compared with rats with tumor necrosis factor-alpha, hyperoxia, or room air alone. Hyperoxia + tumor necrosis factor-alpha also significantly increased growth-related oncogene/cytokine-induced neutrophil chemoattractant (GRO/CINC)-1 in bronchoalveolar fluid, compared with those receiving tumor necrosis factor-alpha alone, hyperoxia alone, or room air alone. L-NAME significantly enhanced the percentage of neutrophil recovery and the production of tumor necrosis factor-alpha, interleukin-1 beta, and GRO/CINC-1 in airways compared with the corresponding hyperoxia + tumor necrosis factor-alpha treatment alone.

CONCLUSIONS

Endogenous nitric oxide may be an important endogenous inhibitor of hyperoxia + tumor necrosis factor-alpha-induced leukocyte recruitment and subsequently tumor necrosis factor-alpha, interleukin-1 beta, and GRO/CINC-1 release.

Soluble intercellular adhesion molecule-1 is related to endothelial vasodilatory function in healthy individuals

OBJECTIVE

To investigate the associations between markers of systemic and vascular inflammation, and indicators of vascular morphology and function.

METHODS

In 59 apparently healthy individuals, we measured serum levels of highly sensitive C-reactive protein (hsCRP), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin. Endothelium-dependent (EDV) and -independent (EIDV) vasodilatation was evaluated in the forearm by venous occlusion plethysmography and local infusions of methacholine and sodium nitroprussid. Endothelial function index (EFI) was expressed as the EDV/EIDV ratio. The intima-media thickness (IMT) of the common carotid artery was investigated with ultrasound (far wall).

RESULTS

EFI was inversely related only to ICAM-1 (r=-0.31, P<0.02) by univariate analysis. This association remained significant after adjustment for age, sex, blood pressure, smoking and serum cholesterol. EFI did not relate to hsCRP, VCAM-1 or E-selectin. Neither hsCRP, nor the adhesion molecules were significantly related to carotid artery IMT.

CONCLUSION

ICAM-1 was related to endothelial vasodilatory function, but not to IMT, suggesting that endothelial inflammatory activation is related to an impaired vascular relaxation in apparently healthy individuals.

Oxidative stress and neutrophil activation—the two keystones of ischemia/reperfusion injury

The widespread introduction of fibrinolytics and recently also PTCA in the treatment of myocardial infarction has changed the picture of modern cardiology. But this therapy also raises new problems and challenges. One of them is the occurrence of extensive tissue injury caused by reperfusion. Reinstitution of oxygen to the ischemic tissues initiates various processes leading to generation of reactive oxygen species (ROSs). Acting on the plasma membrane ROS damage its organization and release various proinflammatory agents. Different proteins, including receptors, ionic channels, transporters or components of transduction pathways are substrates of oxidation by ROSs. Their changed structure results in altered functioning and disruption of vital cellular processes. Another key factor of reperfusion injury is activation and infiltration of infarcted area by polymorphonuclear leukocytes (PMNs). Multiple studies identified consecutive stages of PMN activation and substances being involved in it. Main interest lies in cellular adhesion molecules, particularly selectins and beta2 integrins, as their antagonists were repeatedly found to diminish neutrophil activation and infarct size. Nevertheless new publications strike at the foundations of the established order and confront the relation between neutrophil infiltration and infarct size. PMNs are linked by close ties to other cells involved in inflammatory response. Seemingly also in cardiac ischemia-reperfusion injury, the activity of neutrophils is modulated by lymphocytes and macrophages. The article describes mutual interactions between different factors involved in the reperfusion injury that may enable preparing new treatments, hopefully as effective and successful as reperfusion therapy.

The effects of the nitric oxide donor SIN-1 on ischemia-reperfused cutaneous and myocutaneous flaps

Ischemia-reperfusion injury causes tissue damage that leads to a decrease in bioavailability of nitric oxide. The authors hypothesized that an exogenous supply of nitric oxide will have beneficial effects on survival of skin and skeletal muscle subjected to ischemia-reperfusion injury. By using the nitric oxide donor SIN-1 (3-morpholino-sydnonimine) the effects of direct intraarterial infusion of an exogenous source of nitric oxide in reperfused flaps was studied. Bilateral island buttock skin flaps and latissimus dorsi myocutaneous flaps were elevated in eight pigs, for a total of 32 flaps. Flaps were subjected to 6 hours of ischemia followed by 18 hours of reperfusion. Flaps on one side of each animal were randomized to be treated with the nitric oxide donor (treatment group). The contralateral side was treated with an equivalent volume of saline vehicle (infusion control) SIN-1, or saline was administered as a continuous direct intraarterial infusion at the onset of reperfusion and continued during the observation period. Outcomes measured were tissue neutrophil accumulation by using myeloperoxidase assay and tissue survival (intravenous fluorescein and nitroblue tetrazolium for skin and muscle, respectively). In both skin and myocutaneous flaps, SIN-1 treatment caused a significant improvement in survival and a decrease in neutrophil accumulation. Nitric oxide may play an important role in the pathophysiologic process of ischemia-induced reperfusion injury in skin and skeletal muscle. Nitric oxide donors may be a promising family of therapeutic agents for the prevention of ischemia-induced reperfusion injury in cutaneous and myocutaneous flaps.

Suppression of diabetic retinopathy with angiopoietin-1

Diabetic retinopathy remains a leading cause of irreversible blindness. A critical early pathology in the disease is the adhesion of leukocytes to the retinal vasculature, a process that occurs, in part, via intercellular adhesion molecule-1. Once leukocyte adhesion occurs, endothelial cell injury ensues, as does blood-retinal barrier breakdown. Here we show that angiopoietin-1 can prevent and reverse these diabetic retinal vascular changes in both new and established diabetes. Angiopoietin-1, when given intravitreally to newly diabetic rats, normalized retinal vascular endothelial growth factor (VEGF) and intercellular adhesion molecule-1 mRNA and protein levels, leading to reductions in leukocyte adhesion, endothelial cell injury, and blood-retinal barrier breakdown. When an adenovirus coding for angiopoietin-1 was given systemically to mice with established diabetes, it similarly inhibited leukocyte adhesion and endothelial cell injury and blood-retinal barrier breakdown. These changes coincided with reductions in retinal eNOS, nitric oxide, Akt (protein kinase B), and MAP kinase activity, known mediators of VEGF bioactivity and leukocyte adhesion. When endogenous VEGF bioactivity was inhibited with a soluble Flt-1/Fc chimera, retinal Akt kinase activity was significantly reduced in vivo. Taken together, these data document new vascular and anti-inflammatory bioactivities for angiopoietin-1 and identify it as the first naturally occurring protein that directly protects the retinal vasculature in diabetes.

Cytotoxicity of IFN-gamma and TNF-alpha for vascular endothelial cell is mediated by nitric oxide

Endothelial cell injury is a critical event in tissue damage accompanying inflammation, in which both inflammatory cytokines and reactive oxygen species may play pivotal roles, although the exact mechanism has not yet been clarified. We found that combined stimulation with interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) induced both cytotoxicity to murine vascular endothelial cell line F-2 and an increase in nitric oxide (NO). Therefore, in the present study, the implication of NO in cytotoxicity was examined. A potent iNOS-specific inhibitor ONO-1714 completely blocked both cytokine-induced cytotoxicity and NO production. NO scavengers such as carboxy-PTIO and hemoglobin blocked cytotoxicity. Moreover, exogenous NO from NOC 18 also caused cytotoxicity. These results together demonstrated that cytotoxicity of IFN-gamma and TNF-alpha for endothelial cell F-2 was mediated by NO, suggesting a pathogenic role of cytokine-induced NO production in endothelial damage under inflammatory conditions.

Retinal vascular endothelial growth factor induces intercellular adhesion molecule-1 and endothelial nitric oxide synthase expression and initiates early diabetic retinal leukocyte adhesion in vivo

Leukocyte adhesion to the diabetic retinal vasculature results in early blood-retinal barrier breakdown, capillary nonperfusion, and endothelial cell injury and death. Previous work has shown that intercellular adhesion molecule-1 (ICAM-1) and CD18 are required for these processes. However the relevant in vivo stimuli for ICAM-1 and CD18 expression in diabetes remain unknown. The current study investigated the causal role of endogenous vascular endothelial growth factor (VEGF) and nitric oxide in initiating these events. Diabetes was induced in Long-Evans rats with streptozotocin, resulting in a two- to threefold increase in retinal leukocyte adhesion. Confirmed diabetic animals were treated with a highly specific VEGF-neutralizing Flt-Fc construct (VEGF TrapA(40)). Retinal ICAM-1 mRNA levels in VEGF TrapA(40)-treated diabetic animals were reduced by 83.5% compared to diabetic controls (n = 5, P < 0.0001). VEGF TrapA(40) also potently suppressed diabetic leukocyte adhesion in retinal arterioles (47%, n = 11, P < 0.0001), venules (36%, n = 11, P < 0.0005), and capillaries (36%, n = 11, P < 0.001). The expression of endothelial nitric oxide synthase (eNOS), a downstream mediator of VEGF activity, was increased in diabetic retina, and was potently suppressed with VEGF TrapA(40) treatment (n = 8, P < 0.005). Further, VEGF TrapA(40) reduced the diabetes-related nitric oxide increases in the retinae of diabetic animals. The inhibition of eNOS with N-omega-nitro-L-arginine methyl ester also potently reduced retinal leukocyte adhesion. Although neutrophil CD11a, CD11b, and CD18 levels were increased in 1-week diabetic animals, VEGF TrapA(40) did not alter the expression of these integrin adhesion molecules. Taken together, these data demonstrate that VEGF induces retinal ICAM-1 and eNOS expression and initiates early diabetic retinal leukocyte adhesion in vivo. The inhibition of VEGF bioactivity may prove useful in the treatment of the early diabetic retinopathy.

Activated platelets mediate inflammatory signaling by regulated interleukin 1beta synthesis

Platelets release preformed mediators and generate eicosanoids that regulate acute hemostasis and inflammation, but these anucleate cytoplasts are not thought to synthesize proteins or cytokines, or to influence inflammatory responses over time. Interrogation of an arrayed cDNA library demonstrated that quiescent platelets contain many messenger RNAs, one of which codes for interleukin 1beta precursor (pro-IL-1beta). Unexpectedly, the mRNA for IL-1beta and many other transcripts are constitutively present in polysomes, providing a mechanism for rapid synthesis. Platelet activation induces rapid and sustained synthesis of pro-IL-1beta protein, a response that is abolished by translational inhibitors. A portion of the IL-1beta is shed in its mature form in membrane microvesicles, and induces adhesiveness of human endothelial cells for neutrophils. Signal-dependent synthesis of an active cytokine over several hours indicates that platelets may have previously unrecognized roles in inflammation and vascular injury. Inhibition of beta3 integrin engagement markedly attenuated the synthesis of IL-1beta, identifying a new link between the coagulation and inflammatory cascades, and suggesting that antithrombotic therapies may also have novel antiinflammatory effects.

Profile of eicosanoids produced by human saphenous vein endothelial cells and the effect of dietary fatty acids

Human saphenous vein endothelial cells (HSVECs) derived from primary cultures of adult human veins constitute an excellent in vitro model for studying human endothelial metabolism. In this study we report the (14)C-labelled prostanoid profile of HSVECs under resting and stimulated conditions and the effect of the n-3 polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid on them. Results indicate that HSVECs while under resting conditions produce mainly prostaglandin F(2alpha)(PGF(2alpha)). After stimulation with calcium ionophore A23187, the cells were found to synthesise PGI(2), PGE(2)and PGF(2alpha) as major products and thromboxane B(2)and PGD(2)as minor products. Production of (14)C-labelled hydroxyeicosatetraenoic acids was not detected. Eicosapentaenoic acid was found to inhibit basal and stimulated prostanoid production whereas docosahexaenoic acid inhibited basal but strongly increased stimulated prostanoid production. These results may offer the basis for further studies aiming to investigate targets for pharmacological intervention in inflammatory conditions.