Neutrophil-mediated injury to endothelial cells. Enhancement by endotoxin and essential role of neutrophil elastase

Increased neutrophil chemotaxis in obstructive jaundice: an in vitro experiment in rats

BACKGROUND AND AIMS

Changes in neutrophil functions in obstructive jaundice have been poorly understood. An in vitro experimental study was performed to evaluate the effect of obstructive jaundice on the functions of macrophages (secretion of neutrophil chemoattractants) and neutrophils (chemotaxis and superoxide anion generation).

METHODS

Obstructive jaundice was produced in rats by 7 day bile duct ligation. Peripheral neutrophils and peritoneal macrophages were harvested from either normal, sham-ligated or bile duct-ligated rats and supernatants of the monolayers of the respective macrophages were prepared after stimulation with lipopolysaccharide. Neutrophil chemotaxis was evaluated with a modified Boyden method.

RESULTS

The supernatant of the bile duct-ligated rat macrophages showed a chemotactic effect on normal rat neutrophils with insignificant difference from the supernatant of the sham-ligated rat macrophages. Chemotaxis of the bile duct-ligated rat neutrophils towards the supernatant of the normal rat macrophages was significantly increased, compared with that of sham-ligated rat neutrophils. Similarly, neutrophils from bile duct-ligated rats showed significantly greater chemotaxis to formyl-methionyl-leucyl-phenylalanine than the sham-ligated rat neutrophils. Superoxide anion generation in response to formyl-methionyl-leucyl-phenylalanine or phorbol myristate acetate was significantly increased in the bile duct-ligated rats compared with the sham-ligated rats.

CONCLUSIONS

The results suggest that the neutrophil is primed in terms of chemotaxis and superoxide anion generation in obstructive jaundice. How these activated neutrophils play a role in the inflammatory response to obstructive jaundice should be evaluated.

Proteolysis of monocyte CD14 by human leukocyte elastase inhibits lipopolysaccharide-mediated cell activation

Human leukocyte elastase (HLE), a polymorphonuclear neutrophil (PMN) serine proteinase, is proteolytically active on some membrane receptors at the surface of immune cells. The present study focused on the effect of HLE on the expression of CD14, the main bacterial lipopolysaccharide (LPS) receptor at the surface of monocytes. HLE exhibited a time- and concentration-dependent downregulatory effect on CD14 surface expression. A 30-minute incubation of 3 microM HLE was required to display 95% disappearance of the receptor. This downregulation resulted from a direct proteolytic process, not from a shedding consecutive to monocyte activation as observed upon challenge with phorbol myristate acetate (PMA). To confirm that CD14 is a substrate for HLE, this enzyme was incubated with recombinant human CD14 (Mr approximately 57,000), and proteolysis was further analyzed by immunoblot analysis. Cleavage of the CD14 molecule was directly evidenced by the generation of short-lived fragments (Mr approximately 47,000 and 30,000). As a consequence of the CD14 proteolysis, a decrease in the responsiveness of monocytes to LPS was observed, as assessed by measuring tumor necrosis factor-alpha (TNF-alpha) formation. This inhibition was only observed with 1 ng/ml of LPS, i.e., when only the CD14-dependent pathway was involved. At a higher LPS concentration, such as 10 microgram/ml, when CD14-independent pathways were operative, this inhibition was overcome. The direct proteolysis by HLE of the membrane CD14 expressed on monocytes illustrates a potential anti-inflammatory effect of HLE through inhibition of LPS-mediated cell activation.

Inflammatory response to cardiopulmonary bypass using roller or centrifugal pumps

BACKGROUND

The inflammatory response in 29 patients undergoing coronary artery bypass grafting using either roller or centrifugal (CFP) pumps was evaluated in a prospective study.

METHODS

Patients were randomized in roller pump (n = 15) and CFP (n = 14) groups. Terminal complement complex activation (SC5b-9) and neutrophil activation (elastase) were assessed during the operation. Cytokine production (tumor necrosis factor-alpha, interleukin-6, interleukin-8) and circulating adhesion molecules (soluble endothelial-leukocyte adhesion molecule-1 and intercellular adhesion molecule-1) were assessed after the operation.

RESULTS

Release of SC5b-9 after stopping cardiopulmonary bypass and after protamine administration was higher in the CFP group (p = 0.01 and p = 0.004). Elastase level was higher after stopping cardiopulmonary bypass using CFP (p = 0.006). Multivariate analysis confirmed differences between roller pump and CFP groups in complement and neutrophil activation. After the operation, a significant production of cytokines was detected similarly in both groups, with peak values observed within the range of 4 to 6 hours after starting cardiopulmonary bypass. However, interleukin-8 levels were higher using CFP 2 hours after starting cardiopulmonary bypass (p = 0.02). Plasma levels of adhesion molecules were similar in both groups within the investigation period.

CONCLUSIONS

During the operation, CFP caused greater complement and neutrophil activation. After the operation, the inflammatory response was similar using either roller pump or CFP.

Plaunotol prevents indomethacin-induced gastric mucosal injury in rats by inhibiting neutrophil activation

BACKGROUND

Activated neutrophils play a critical role in indomethacin-induced gastric mucosal injury.

AIM

To investigate the effect of plaunotol, an anti-ulcer agent, on neutrophil activation in vitro and its effect on gastric mucosal injury and gastric accumulation of neutrophils in rats given indomethacin.

METHODS

Human monocytes and neutrophils were isolated from the peripheral blood of healthy volunteers. We examined the effect of plaunotol on neutrophil elastase release, production of O2-, intracellular calcium concentration and expression of adhesion molecules CD11b and CD18 in activated neutrophils in vitro. The effect of plaunotol on TNF-alpha production by monocytes stimulated with endotoxin also was investigated in vitro. The effect of plaunotol (100 mg/kg, p.o.) on gastric mucosal injury and neutrophil accumulation was investigated in male Wistar rats given indomethacin (30 mg/kg, p.o.).

RESULTS

Plaunotol inhibited the fMLP-induced release of neutrophil elastase from activated neutrophils, as well as the opsonized zymosan-induced production of O2- by neutrophils. Plaunotol significantly inhibited increased levels of intracellular calcium, a second messenger of neutrophil activation, in vitro. The fMLP-induced increases in CD11b and CD18 expression were also inhibited by plaunotol in vitro. Plaunotol inhibited monocytic production of TNF-alpha, a potent activator of neutrophils. Both gastric mucosal injury and gastric neutrophil infiltration in rats given indomethacin were significantly inhibited by the oral administration of plaunotol.

CONCLUSIONS

Plaunotol inhibits indomethacin-induced gastric mucosal injury, at least in part by inhibiting neutrophil activation.

Protective effects of ulinastatin against ischemia-reperfusion injury

We investigated the protective effect of urinary trypsin inhibitor (ulinastatin: UTI) in vitro, in relation to the neutrophil activity in hepatic ischemia/reperfusion (I/R) injury. The rat liver was removed and preserved in cold Ringer's lactate solution for 60 min, followed by 120 min of reperfusion with oxygenated perfusate. The rats were divided into four groups (n = 8 in each group). The livers were perfused with Krebs-Henseleit (K-H) solution containing no additives in group 1, 50,000 U/kg of UTI in group 2, 3.5 x 10(6) of neutrophils in group 3, and both neutrophils and UTI in group 4. In group 3, the AST and ALT levels were always higher than those in other three groups at any point evaluated (P < 0.01) and the LDH levels were observed to be significantly higher than those in other three groups at 0, 5, 10, 60, and 90 min after reperfusion (P < 0. 01). These increase were suppressed by additional pretreatment with UTI in group 4. The bile flow during reperfusion was significantly suppressed in group 3 compared to that of group 4, at both 30 (P < 0. 01) and 60 (P < 0.05) min after reperfusion. The MPO activity after reperfusion in group 3 also significantly increased compared to other three groups (P < 0.01). These data thus suggest that UTI ameliorated the ischemia/reperfusion injury in vitro by inhibiting of neutrophil accumulation in the postischemic liver.

Mechanisms of acute inflammatory lung injury induced by abdominal sepsis

Sequestration of neutrophils and release of histotoxic mediators are considered important for the development of pathologic alterations of the lung defined as adult respiratory distress syndrome. Mechanisms of inflammatory lung injury caused by abdominal sepsis were investigated using the colon ascendens stent peritonitis (CASP) model that closely mimics the human disease. In the CASP model, a continuous leakage of intraluminal bacteria into the peritoneal cavity is induced by implantation of a stent in the ascending colon, generating a septic focus. In contrast to the cecal ligation and puncture model of peritonitis, survival of mice following CASP surgery is dependent on IFN-gamma, but independent of tumor necrosis factor (TNF). Here we show that the systemic inflammation induced by CASP surgery results in a rapid and profound increase of lung vascular permeability that was associated with the activation and recruitment of neutrophils to the lung. Activation of circulating granulocytes was characterized by increased production of serine proteinases and reactive oxygen metabolites, as well as elevated expression of cell surface Mac-1. Expression of MIP-2, KC, MIP-1alpha and E-selectin mRNA in lung was strongly increased within 3 h following CASP surgery, whereas up-regulation of IP-10, MCP-1 and P-selectin was delayed. In contrast, induction of RANTES, LIX, ICAM-1 and VCAM-1 mRNA was weak or not detectable after CASP surgery. Importantly, recruitment of leukocytes to the lung was normal in lipopolysaccharide-resistant mice, and was not affected by antibody neutralization of TNF or the chemokines MIP-2 and KC.

Antiinflammatory effects of soluble complement receptor type 1 promote rapid recovery of ischemia/reperfusion injury in rat small intestine

We examined the effect of soluble complement receptor type 1 (sCR1) on mucosal injury and inflammation in a rat model of ischemia/reperfusion. Groups of vehicle- and sCR1-treated rats underwent 30 min of mesenteric ischemia followed by 60 or 120 min of reperfusion. When compared to vehicle-treated rats, treatment with sCR1 (12 mg/kg) prior to 120 min of reperfusion significantly reduced mucosal injury, neutrophil infiltration, leukotriene B4 production, and restored villus height to control levels. The protective effect of sCR1 evident at 120 min of reperfusion was not observed at 60 min of reperfusion despite rapid inactivation of complement. These data suggest that complement inhibition minimized mucosal disruption by facilitating mucosal restitution or interrupting the inflammatory process. Delayed administration of sCR1 for 30 or 60 min into the reperfusion period progressively reduced the protection. sCR1-mediated rapid recovery of rat intestine after ischemia/reperfusion underscores the fundamental role of complement activation in neutrophil-mediated tissue injury.

Effect of azelastine on platelet-activating factor-induced microvascular leakage in rat airways

To determine the effect of the antiallergic drug azelastine on airway mucosal inflammation, we studied airway microvascular permeability in response to platelet-activating factor (PAF) in pathogen-free rats. Vascular permeability and neutrophil accumulation were assessed by the percent area occupied by Monastral blue-labeled blood vessels and by myeloperoxidase-containing granulocytes, respectively, in whole mounts of the trachea and main bronchus. Intravenous PAF caused dose-dependent increases in the area density of Monastral blue-labeled vessels and neutrophil influx, and the former effect was inhibited by depletion of circulating neutrophils by cyclophosphamide or treatment with the neutrophil elastase inhibitor ONO-5046. Pretreatment with azelastine inhibited PAF-induced vascular leakage without affecting neutrophil accumulation. This inhibitory effect of azelastine was not seen in neutropenic rats and ONO-5046-treated rats. PAF increased neutrophil elastase contents in bronchoalveolar lavage fluid, an effect that was inhibited by azelastine. Therefore, azelastine attenuates PAF-induced airway mucosal microvascular leakage, probably involving inhibition of the release of neutrophil elastase from activated neutrophils.

Monocyte adherence induced by lipopolysaccharide involves CD14, LFA-1, and cytohesin-1. Regulation by Rho and phosphatidylinositol 3-kinase

Mechanisms regulating lipopolysaccharide (LPS)-induced adherence to intercellular adhesion molecule (ICAM)-1 were examined using THP-1 cells transfected with CD14-cDNA (THP-1wt). THP-1wt adherence to ICAM-1 was LPS dose-related, time-dependent, and inhibited by antibodies to either CD14 or leukocyte function associated antigen (LFA)-1, but was independent of any change in the number of surface expressed LFA-1 molecules. A potential role for phosphatidylinositol (PI) 3-kinase (PI 3-kinase) in LPS-induced adherence was examined using the PI 3-kinase inhibitors LY294002 and Wortmannin. Both inhibitors selectively attenuated LPS-induced, but not phorbol 12-myristate 13-acetate-induced adherence. Inhibition by these agents was unrelated to any changes in either LPS binding to or LFA-1 expression by THP-1wt cells. LPS-induced adherence was also abrogated in U937 cells transfected with a dominant negative mutant of of PI 3-kinase. Toxin B from Clostridium difficile, an inhibitor of the Rho family of GTP-binding proteins, abrogated both PI-3 kinase activation and adherence induced by LPS. Cytohesin-1, a phosphatidylinositol 3,4,5-triphosphate-regulated adaptor molecule for LFA-1 activation, was found to be expressed in THP-1wt cells. In addition, treatment of THP-1wt with cytohesin-1 antisense attenuated LPS-induced adherence. These findings suggest a model in which LPS induces adherence through a process of "inside-out" signaling involving CD14, Rho, and PI 3-kinase. This converts low avidity LFA-1 into an active form capable of increased binding to ICAM-1. This change in LFA-1 appears to be cytohesin-1-dependent.

Role of liver NK cells and peritoneal macrophages in gamma interferon and interleukin-10 production in experimental bacterial peritonitis in mice

Gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and interleukin-10 (IL-10) production by liver, spleen, lung, peripheral blood mononuclear cells (MNC), and peritoneal exudate cells (PEC) in experimental bacterial peritonitis was examined by cecum ligation and puncture (CLP) (with an 18-gauge needle) of BALB/c mice. MNC of organs were cultured for 18 h, and cytokine levels in supernatants were examined. Cytokines contained in peritoneal lavage fluid were regarded as those produced by PEC. Only liver MNC and PEC produced substantial amounts of IFN-gamma, and PEC were the main source of IL-10, especially 12 h after CLP. As reflected by the cytokine production by liver MNC and PEC, serum IFN-gamma and IL-10 levels were elevated after CLP. C57BL/6 (B6) mice and BALB/c nude mice showed a similar pattern of cytokine production. TNF-alpha levels in culture supernatants, peritoneal lavage fluid, and sera were not significantly elevated compared to those of sham-operated mice. In vivo depletion of NK cells of B6 mice with anti-asialo GM1 or anti-NK1.1 antibody greatly decreased IFN-gamma levels in liver MNC culture supernatants and sera, suggesting that liver NK cells are IFN-gamma producers. On the other hand, plastic-adherent PEC macrophages are the major IL-10 producers. Mice subjected to a cecum ligation and cut procedure (which have a more severe peritonitis) showed much higher IFN-gamma and IL-10 levels than those subjected to CLP, while mice subjected to CLP with a smaller (22-gauge) needle showed low levels of these cytokines. These findings show that liver NK cells and PEC macrophages are important for the production of proinflammatory and anti-inflammatory cytokines in bacterial peritonitis.

Complement activation in relation to capillary leakage in children with septic shock and purpura

To assess the relationship between capillary leakage and inflammatory mediators during sepsis, blood samples were taken on hospital admission, as well as 24 and 72 h later, from 52 children (median age, 3.3 years) with severe meningococcal sepsis, of whom 38 survived and 14 died. Parameters related to cytokines (interleukin 6 [IL-6] IL-8, plasma phospholipase A2, and C-reactive protein [CRP]), to neutrophil degranulation (elastase and lactoferrin), to complement activation (C3a, C3b/c, C4b/c, and C3- and C4-CRP complexes), and to complement regulation (functional and inactivated C1 inhibitor and C4BP) were determined. The degree of capillary leakage was derived from the amount of plasma infused and the severity of disease by assessing the pediatric risk of mortality (PRISM) score. Levels of IL-6, IL-8, C3b/c, C3-CRP complexes, and C4BP on admission, adjusted for the duration of skin lesions, were significantly different in survivors and nonsurvivors (C3b/c levels were on average 2.2 times higher in nonsurvivors, and C3-CRP levels were 1.9 times higher in survivors). Mortality was independently related to the levels of C3b/c and C3-CRP complexes. In agreement with this, levels of complement activation products correlated well with the PRISM score or capillary leakage. Thus, these data show that complement activation in patients with severe meningococcal sepsis is associated with a poor outcome and a more severe disease course. Further studies should reveal whether complement activation may be a target for therapeutical intervention in this disease.

Lipopolysaccharide enhances neurogenic plasma exudation in guinea-pig airways

1. Lipopolysaccharide (LPS) is implicated in many pulmonary and airway inflammatory diseases. Tachykinins released from nerve endings increase vascular permeability. In this study, we have assessed the enhancement by LPS of tachykinin-mediated plasma exudation in guinea-pig airways, and examined the role of oxidants as well as leukocyte adherence. 2. LPS (100 microg kg(-1), i.v.) was administered 0-3 h before bilateral electrical stimulation of the cervical vagus nerves in animals anaesthetized with urethane and ventilated. Vagal stimulation increased vascular permeability in the airways. LPS enhanced the vagally-mediated plasma exudation with the peak effect at 1 h after LPS administration. LPS alone induced no significant plasma exudation. LPS also enhanced exogenous substance P (10(-8) mol kg(-1), i.v.)-induced plasma exudation. 3. The NK-1 receptor antagonist L-732,138 abolished vagally-induced plasma exudation and significantly inhibited the enhancement by LPS. Pretreatment with superoxide dismutase (SOD, 5000 U kg(-1), i.p.) did not affect the vagally-induced plasma exudation, but inhibited the LPS-enhanced neurogenic plasma leakage. The LPS-enhanced vagally-induced plasma exudation was not completely inhibited by either L-732,138 or SOD pretreatment alone, but was blocked by the combination of both pretreatments. 4. Neutrophil depletion by cyclophosphamide alone did not influence vagally-induced plasma exudation, but significantly inhibited the LPS-enhanced response. 5. In conclusion, we have demonstrated LPS enhanced neurogenic plasma exudation by augmenting the response to tachykinins, partly through NK-1 receptors, to directly increase vascular permeability or to enhance leukocyte adhesion-mediated endothelial cell injury. Tachykinins released from nerve endings may contribute to endotoxin-related airway inflammatory responses.

The sepsis-coagulant axis: a review

Activation of coagulation is a normal component of the acute inflammatory response. Inflammatory cytokines initiate coagulation events locally at sites of inflammation by converting endothelium from an antithrombotic surface to a prothrombotic surface; by stimulating tissue factor production, which activates both the extrinsic and intrinsic coagulation systems; and by stimulating production of platelet-activating factors. The fibrinolytic system is initially activated but is subsequently inhibited. This results in a marked imbalance in coagulation and fibrinolysis resulting in a net procoagulant state. When thrombin generation and platelet activation exceed the body's capacity to inactivate or remove these factors, disseminated intravascular coagulation (DIC) results. DIC directly contributes to multiple organ failure and death associated with sepsis. Presently available treatments (i.e., heparin and aspirin) are relatively ineffective in treating DIC; however, newer, more potent drugs may soon be available for clinical use.

Pulmonary sequestration of polymorphonuclear leukocytes released from bone marrow in bacteremic infection

We examined the bone marrow response and the sequestration of polymorphonuclear leukocytes (PMNs) in lung using a bacteremic infection model in rabbits. PMNs were labeled with the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) in the bone marrow, and the bone marrow release and the sequestration of BrdU-labeled PMNs were measured using immunohistochemistry. A focal subcutaneous infection (S) was induced, and the bacteremia (B) was produced 4 h later with Streptococcus pneumoniae (S+B). This S+B group was compared with other groups with only subcutaneous infection or only bacteremia. The S+B group developed a profound leukopenia after the bacteremia that was associated with an increase in circulating BrdU-labeled PMNs. Morphometric studies showed more PMN sequestration in the lung of the S+B group compared with the others (P < 0.05). Compared with unlabeled PMNs, BrdU-labeled PMNs, which represent newly released PMNs, preferentially sequestered in lung (P < 0.05) and were slow to migrate into the infected tissues (P < 0.05). We conclude that bacteremic infection is associated with an accelerated release of PMNs from the bone marrow and that these newly released PMNs preferentially sequester in lung and are slow to migrate into infected tissues.

Neutrophil elastase promotes lung microvascular injury and proteolysis of endothelial cadherins

Intestinal ischemia-reperfusion (I-R) is associated with lung injury and the acute respiratory distress syndrome. The hypothesis of this study was that intestinal I-R activates circulating neutrophils to promote elastase-mediated lung injury. Isolated rat lungs were perfused with blood or plasma obtained after intestinal I-R, and lung neutrophil retention and injury and bronchoalveolar lavage (BAL) elastase were measured. Perfusion with I-R blood caused lung neutrophil accumulation and injury and increased BAL elastase. These effects were attenuated by the elastase inhibitor L-658758. Interference with neutrophil adherence before gut reperfusion blocked BAL elastase accumulation. The role of endothelial junction proteins (cadherins) in I-R-elicited lung damage was also evaluated. Activated human neutrophils proteolyzed cadherins in human umbilical vein endothelial cells. Furthermore, plasma of patients with acute respiratory distress syndrome contained soluble cadherin fragments. The results of this study suggest that the elastase released by systemically activated neutrophils contributes to lung neutrophil accumulation and pulmonary microvascular injury. Elastase-mediated proteolysis of endothelial cell cadherins may represent the mechanism through which lung microvascular integrity is disrupted after intestinal I-R.

Activation of polymorphonuclear leukocytes in oleic acid-induced lung injury

OBJECTIVE

Oleic acid (OA) can produce a lung injury similar to the adult respiratory distress syndrome (ARDS). Elastase and superoxides are thought to have an effect in ARDS. However, the effect that elastase and superoxide have in OA lung injury is unclear. To examine their involvement in OA lung injury, we tested the effects of methoxysuccinyl-alanyl-alanyl-prolyl-valyl chloromethyl ketone (MAAPVCK), an elastase inhibitor, and N-acetyl-L-cysteine (NAC), an active oxygen scavenger, on the increase in pulmonary vascular permeability caused by OA. We also examined whether OA stimulated elastase and/or superoxide release from polymorphonuclear leukocytes (PMNs).

DESIGN

Prospective trial.

SETTING

University laboratory.

INTERVENTIONS

(1) Guinea pigs were anesthetized. MAAPVCK (2.5 mg/ kg) or NAC (150 mg/kg) was infused over OA (15 microl/kg) injection. Evans blue was used to measure vascular permeability. (2) PMNs were isolated from the blood of guinea pigs and rats. Elastase release was measured with MeO-Suc-Ala-Ala-Pro-Val-7-amino-4-methylcoumarin. Superoxide production was measured by the ferricytochrome c reduction method.

MEASUREMENTS AND RESULTS

OA caused pulmonary hemorrhage and an increase in vascular permeability. MAAPVCK and NAC significantly attenuated the increase in vascular permeability in distal bronchus and trachea, respectively. OA induced superoxide production from PMNs in guinea pigs, but elastase release from PMNs was not detected.

CONCLUSIONS

These results suggest that elastase and superoxide are involved in OA lung injury.

Human endothelial cells regulate polymorphonuclear leukocyte degranulation

Neutrophil degranulation is an important event in inflammatory responses. We examined the regulation of neutrophil (PMN) degranulation by resting and activated human endothelial cells. Whereas PMNs adherent to endothelial cells that were stimulated to express P-selectin and platelet-activating factor did not release the specific granule marker lactoferrin or the primary granule enzyme, elastase, PMNs adherent to endothelial cells stimulated with interleukin-1 (IL-1) or tumor necrosis factor secreted both. PMN degranulation was dependent on the time of incubation of endothelial cells with the cytokine, its concentration, and the time of incubation of the PMNs with endothelial cells. Degranulation of PMNs and their adhesion to stimulated endothelial cells are correlated events, but they could be dissociated by blocking the tethering molecules used by the endothelial cells and neutrophils under these conditions. This suggested that paracrine signaling molecules that induce PMN degranulation are produced by cytokine-stimulated endothelial cells. We found that endothelial cells stimulated with IL-1 release newly synthesized degranulating factors that require transcription and translation. IL-8 was synthesized, released, and signaled granular secretion by PMNs. However, experiments with blocking antibodies indicated the presence of an additional degranulating factor not accounted for by IL-8. These experiments demonstrate that human endothelial cells regulate degranulation of neutrophils by generating signaling factors that are expressed differentially depending on the endothelial agonist and other features. Active modification of neutrophil granular secretion by endothelial cells can influence physiologic acute inflammatory responses but may also contribute to pathologic vascular and tissue damage.

Bacterial lipopolysaccharide induces endothelial cells to synthesize a degranulating factor for neutrophils

Enzymes and other factors secreted by degranulating neutrophils (polymorphonuclear leukocytes, PMNs) mediate endothelial injury, thrombosis, and vascular remodeling. In bacteremia and sepsis syndrome and their consequent complications (including acute respiratory distress syndrome and systemic ischemia-reperfusion resulting from septic shock), neutrophil degranulation is an important mechanism of injury. In related studies, we found that human endothelial cells regulate neutrophil degranulation and that inflammatory cytokines induce synthesis of degranulating factors by human endothelial cells. Here we show that lipopolysaccharides (LPS) from gram-negative bacteria were the most potent agonists for release of degranulating activity by endothelial cells when compared to several cytokines and stimulatory factors. LPS also induced the release of degranulating signals for PMNs from a human endothelial cell line, EA.hy 926. Interleukin 8 (IL-8) is synthesized by endothelial and EA.hy 926 cells in response to LPS and induces neutrophil degranulation. However, complementary strategies using receptor desensitization, translation of messenger RNA by Xenopus laevis oocytes, and purification and analysis of factors from conditioned supernatants demonstrated that degranulating factors distinct from IL8 are generated in response to LPS. The characteristics of a partially purified degranulating factor isolated from conditioned supernatants distinguished it from known chemokines and other factors that induce PMN degranulation and are generated by endothelial cells in response to LPS. Thus, cultured human endothelial cells and endothelial cell lines synthesize several unique signaling molecules that can trigger neutrophil granular secretion. If produced in vivo in response to LPS or other pathologic agonists, these degranulating signals may activate PMNs in combination or in sequence, initiating or propagating vascular damage.

Primed neutrophils require phosphatidic acid for maximal receptor-activated elastase release

BACKGROUND

Priming of neutrophils (PMNs) for protease release is believed to be central to the pathogenesis of PMN-mediated tissue injury observed in ARDS/MOF. Defining the intracellular signaling pathways involved with this excessive protease release may aid in establishing future therapies for ARDS. Phospholipase D (PLD) production of phosphatidic acid (PA) is thought to be pivotal in reactive oxygen species generation but its role in degranulation (i. e., protease release) remains unclear. Our hypothesis was that primed neutrophils require PLD production of PA for maximal activated release of elastase.

METHODS

Isolated human PMNs were incubated with a well described antagonist of PA production, ethanol (ETOH, 100-1000 mg/dL), and then primed (PAF, 200 nM) followed by activation (fMLP, 1 microM). To mimic fMLP receptor-dependent activation, PMNs were primed and then directly activated with exogenous dioctanoyl l-alpha-phosphatidic acid (PA8, 0.5-200 microM). To confirm the importance of PA in elastase release, PA8 was given to primed-activated PMNs after ethanol pretreatment in an attempt to recover the maximal response. Elastase release was measured by the cleavage of AAPV-pNA.

RESULTS

PA blockade with ETOH attenuated PAF-primed/fMLP-activated PMN elastase release in a dose-dependent manner. Exogenous PA8 reproduced maximally primed-activated PMN elastase release, and furthermore, PA8 was able to restore maximal elastase release following ethanol attenuation.

CONCLUSIONS

Elastase release from PAF-primed/ fMLP-activated neutrophils is dependent on PA production. Thus, PA production appears to be involved in both oxidant-dependent and independent mechanisms of neutrophil cytotoxicity and may be a potential therapeutic target in the treatment of hyperinflammatory diseases such as ARDS/MOF.

ICAM-1-CD18 interaction mediates neutrophil cytotoxicity through protease release

Interaction of the beta2-integrin complex on the polymorphonuclear neutrophil (PMN) with intercellular adhesion molecule-1 (ICAM-1) has been implicated in PMN-mediated cytotoxicity. This study examined interaction of the CD11a, CD11b, and CD18 subunits of the beta2-integrin with ICAM-1, transfected into Chinese hamster ovarian (CHO) cells to avoid effects of other adhesion molecules. Incubation of quiescent PMNs with wild-type and ICAM-1-transfected CHO cells produced nominal cell lysis. Similarly, when phorbol myristate acetate (PMA)-activated PMNs were incubated with wild-type CHO cells, minimal cytotoxicity was produced. However, when ICAM-1-transfected CHO cells were incubated with PMA-activated PMNs, 40% cell lysis occurred. Blockade with a monoclonal antibody (MAb) to ICAM-1 or MAbs to CD11a, CD11b, or CD18 reduced PMN-mediated cytotoxicity to baseline. To examine the role of adhesion in cytotoxicity, we studied beta2-integrin-mediated PMN adhesion to ICAM-1-transfected CHO cells and found that MAbs for CD11a, CD11b, and CD18 all abrogated PMN cytotoxicity despite disparate effects on adhesion. To assess the role of CD18, beta2-integrin subunits were cross-linked, and CD18 alone mediated protease release. Moreover, ICAM-1 was immunoprecipitated from transfected CHO cells and incubated with PMNs. This soluble ICAM-1 provoked elastase release, similar to PMA, which could be inhibited by MAbs to CD18 but not MAbs to other beta2-integrin subunits. In addition, coincubation with protease inhibitors eglin C and AAPVCK reduced PMN-mediated cytotoxicity to control levels. Finally, ICAM-1-transfected CHO cells were exposed to activated PMNs from a patient with chronic granulomatous disease that caused significant cell lysis, equivalent to that of PMNs from normal donors. Collectively, these data suggest that ICAM-1 provokes PMN-mediated cytotoxicity via CD18-mediated protease release.

Hypertonic saline activates lipid-primed human neutrophils for enhanced elastase release

BACKGROUND

Ongoing clinical trials have revived interest in hypertonic saline (HTS) for postinjury resuscitation; these studies have documented serum Na+ concentrations > or = 170 mmol/L. Recent animal studies have shown that HTS enhances T-cell and monocyte function, but effects on the polymorphonuclear neutrophil (PMN) remain unclear. The postinjury lipid mediators platelet-activating factor (PAF) and leukotriene B4 (LTB4) have been implicated in PMN priming for cytotoxicity, which is believed to be important in the pathogenesis of multiple organ failure. We hypothesized that HTS would stimulate PMN superoxide (O2-) and elastase release from PAF- and LTB4-primed PMNs.

METHODS

Isolated PMNs from five donors were primed for 5 minutes with 200 nmol/L PAF or 1 micromol/L LTB4 in Kreb's-Ringer's phosphate with dextrose at a Na+ concentration of 140 mmol/L (normal serum Na+ concentration), pelleted, and resuspended in Kreb's-Ringer's phosphate with dextrose for 10 minutes at a Na+ concentration of 130 to 170 mmol/L. O2- generation was measured by superoxide dismutase-inhibitable reduction of cytochrome c and elastase release by cleavage of N-methoxysuccinyl-Ala-Ala-Pro-Val p-nitroanilide.

RESULTS

HTS with Na+ concentration up to 170 mmol/L had no significant effect on O2- production or elastase release from quiescent cells. Na+ concentration of 160 and 170 mmol/L, however, activated PAF- and LTB4-primed PMNs for enhanced elastase release with no effect on O2- production.

CONCLUSION

In clinically relevant concentrations, elevated Na+ activates lipid-primed neutrophils for enhanced elastase degranulation. Consequently, the administration of HTS in the early postinjury resuscitation period, when PMNs are maximally primed, may activate PMN elastase release and thereby promote the development of multiple organ failure.

Relation between tumour necrosis factor alpha and interleukin 1beta producing capacity of peripheral monocytes and pulmonary complications following oesophagectomy

BACKGROUND

Adult respiratory distress syndrome and pneumonia remain a significant cause of morbidity and death following oesophagectomy. The aim of this study was to clarify the association between tumour necrosis factor (TNF) alpha and interleukin (IL) 1beta with these pulmonary complications.

METHODS

The in vitro TNF-alpha and IL-1beta producing capacity of peripheral monocytes with or without lipopolysaccaride (LPS) and serum level of IL-6 was measured in 19 patients with oesophageal cancer before and after surgery and in ten age-matched controls.

RESULTS

Six patients had raised TNF-alpha and IL-1beta producing capacity of monocytes without LPS both before operation and on the day after surgery. In these patients plasma elastase and serum IL-6 levels subsequently increased while the ratio of arterial partial pressure of oxygen to fraction inspired oxygen decreased, and they developed bilateral lung infiltration on chest radiography on days 3-7. Five of the six developed pneumonia compared with none of the remaining 13 patients (P < 0.05).

CONCLUSION

Pulmonary impairment and pneumonia following oesophageal surgery was associated with raised monocyte producing capacity of TNF-alpha and IL-1beta. These markers may be valuable in the preoperative assessment of patients awaiting oesophagectomy.

Bacteremic pneumococcal pneumonia: bone marrow release and pulmonary sequestration of neutrophils

OBJECTIVES

Neutrophils have been implicated in the pathogenesis of acute lung injury in bacteremic pneumococcal pneumonia. The characteristics of the population of neutrophils that injure the lung are still not known. This study was designed to compare the bone marrow release and lung sequestration of neutrophils during bacteremic pneumococcal pneumonia with nonbacteremic pneumonia and isolated bacteremia.

DESIGN

Prospective, controlled, experimental study.

SETTING

University research laboratory.

SUBJECTS

Female New Zealand white rabbits (n = 17; weight 2.3 to 2.7 kg).

INTERVENTIONS

The rabbits were pretreated with intravenous 5'-bromo-2-deoxyuridine (BrdU 100 mg/kg i.v.) to pulse label dividing neutrophils in the bone marrow. Twenty hours after the treatment with BrdU, the rabbits were anesthetized and pneumonia was induced by instilling Streptococcus pneumoniae (1.5 x 10(9) organisms) into the lower lobe of the lung. Four hours after pneumonia, bacteremia was induced by infusing S. pneumoniae (3.0 x 10(9) organisms) into the circulation (pneumonia + bacteremia: n = 6). These animals were compared with those with just pneumonia (n = 5) or bacteremia (n = 6).

MEASUREMENTS AND MAIN RESULTS

White blood cell, neutrophil, and differential count. BrdU-labeled neutrophils (neutrophilBrdU) were identified using immunohistochemistry. Cells in tissues were examined microscopically, using sequential level stereologic analysis. The pneumonia + bacteremia group developed a leukopenia (7.3 +/- 0.7 to 2.4 +/- 0.2 x 10(9)/L) following the bacteremia that was associated with an increase in circulating band cells and neutrophilBrdU (2.3 +/- 0.8% to 33.5 +/- 2.8%) which were both higher than those in the other groups (p < .005). Bone marrow smears showed accelerated maturation of neutrophils in the pneumonia + bacteremia group (neutrophilBrdU increased from 11.6 +/- 1.0 to 45.3 +/- 2.1%). Morphometric studies of the lung showed increased neutrophil sequestration in the untreated lung tissue of the pneumonia + bacteremia group (16 +/- 0.8 x 10(8)/mL tissue) compared with the pneumonia (6.6 +/- 0.3 x 10(8)/mL tissue) and bacteremia (12 +/- 0.6 x 10(8)/mL tissue) groups (p < .0001). NeutrophilBrdU preferentially sequester in the lungs of all groups but were slow to migrate into the alveolar air spaces (p < .05).

CONCLUSIONS

During bacteremic pneumococcal pneumonia there is an accelerated maturation of neutrophils in the bone marrow with an enhanced release of neutrophils into the circulation. These newly released neutrophils preferentially sequester in lung microvessels but are slow to migrate into the alveolar air space.

Plasma leukocyte elastase concentration and coronary artery disease

It has previously been shown that leukocyte elastase is involved in the pathogenesis of atherosclerosis. Few studies have addressed the relation between leukocyte elastase concentrations and coronary artery disease (CAD). The authors investigated (1) the clinical significance of leukocyte elastase determination in the diagnosis of CAD and (2) the relation between plasma leukocyte elastase concentration and lesion morphology. The study included 185 subjects (140 men, 45 women) who underwent coronary angiography during investigation of chest pain; 135 had coronary stenosis (Group I) and 50 had nonstenotic coronaries (Group II). Among Group I patients, those with simple atheromatous plaques were distinguished from those with complex plaques. Elastase concentrations in Group I were greater than in Group II (57.1 +/- 1.16 micrograms I[-1] vs 27.6 +/- 1.0 microgram, I[-1], P<0.001), and greater in complex plaque patients than in those with simple plaques (64.5 +/- 1.24 micrograms I[-1] vs 45.9 +/- 1.01 micrograms I[-1], P<0.001). Logistic regression analysis showed (1) that elastase concentration, age, and sex had independent value for prediction of CAD and (2) that among Group I patients, the risk of complex plaques was greatest for those with high elastase concentration. These results suggest that plasma leukocyte elastase concentration is a sensitive diagnostic marker of CAD and that high values of elastase may indicate the presence of complex atheromatous plaques.

Hydrogen peroxide modulation of the superoxide anion production by stimulated neutrophils

Hydrogen peroxide (H2O2) pretreatment of human neutrophils results in a suppression of the superoxide anion (O2) production in response to surface-acting stimulants such as lipopolysaccharide (LPS) and opsonized zymosan. This effect was not observed when phorbol myristate acetate (PMA), formyl-methionyl-leucyl-phenylalanine (fMLP) or tumor necrosis factor alpha (TNF alpha) were used as a stimuli. Since the response to PMA and other stimuli was unimpaired by preincubation with H2O2, we assume that the H2O2 modulated O2 production is probably due to alteration of the LPS receptor conformation rather than effecting directly NADPH-oxidase. The balance of reactive oxygen species (ROS) produced by neutrophils in the state of sepsis may thus be autoregulated by negative feedback phenomena of locally produced H202.

Effects of a neutrophil elastase inhibitor (ONO-5046) on acute pulmonary injury induced by tumor necrosis factor alpha (TNFalpha) and activated neutrophils in isolated perfused rabbit lungs

The aim of this study was to examine the effect of ONO-5046, a neutrophil elastase (NE) inhibitor, on a model of acute lung injury induced by tumor necrosis factor alpha (TNFalpha) and phorbol myristate acetate (PMA)-activated neutrophils in isolated perfused rabbit lungs. 120 min after TNFalpha (4,000 JRU/ml) was injected into the pulmonary artery (PA), 5 x 10(7) PMA-stimulated neutrophils were infused into the PA together with 1251-rabbit serum albumin (RSA). In the ONO-5046-treated group (ONO), ONO-5046 (20 mg/kg/h) was continuously infused during the experimental period from 30 min prior to neutrophil administration. Saline, the ONO-5046 vehicle, was infused instead of ONO-5046 in the positive control group (ALD) and nonactivated neutrophils were infused without TNFalpha in the negative control group (Cont). PA pressure was monitored over a 240 min period, and bronchoalveolar lavage (BAL) was performed at the end of the experiment. Lung tissues were examined immunohistochemically for the expression of thrombomodulin (TM). The levels of TM in the perfusate were also measured by ELISA and the radioactivities in the BAL fluid, lung tissue and perfusate were determined to calculate the permeability index (PI) as an indicator of alveolar septal or vascular endothelial damage. The rabbit lungs infused with ONO-5046 showed slower and less increases in PA pressure compared with ALD group. The PI was significantly higher in ALD group (PI[BAL] = 0.028 +/- 0.014, PI[LUNG] = 0.04 +/- 0.003) than Cont (PI[BAL] = 0.002 +/- 0.001, PI[LUNG] = 0.015 +/- 0.003) and ONO group (PI[BAL] = 0.004 +/- 0.003, PI[LUNG] = 0.028 +/- 0.003 (p < 0.05). ALD group had higher TM levels in the perfusate and showed decreased expression of TM on the vascular endothelium compared to Cont and ONO group, suggesting that there was shedding of TM on endothelium and ONO-5046 attenuated a shedding of TM. In conclusion, ONO-5046 attenuated acute lung injury by inhibiting the alveolar epithelial and vascular endothelial injury triggered by activated neutrophils. NE appears to play an important role in the neutrophil-induced increase of pulmonary epithelial and microvascular permeability observed in acute lung injury.

Enhanced endothelial cell injury by activated neutrophils in patients with obstructive jaundice

BACKGROUND/AIMS

A high incidence of complications has been documented in patients with obstructive jaundice after operations. Recent reports have revealed that neutrophils are involved in the mechanism causing postoperative complications. However, there are few reports investigating the interaction between neutrophils and endothelial cells in obstructive jaundice. The aim of this study was to evaluate neutrophil-mediated endothelial cell injury in patients with obstructive jaundice.

METHODS

Patients were divided into three groups: those with normal liver, obstructive jaundice, and relief of obstructive jaundice. Neutrophils were isolated from patients individually. Human umbilical vein endothelial cells and neutrophils were co-cultured after addition of phorbol myristate acetate. The release of lactate dehydrogenase and thrombomodulin was measured in the medium.

RESULTS

Lactate dehydrogenase and thrombomodulin were released in the co-culture medium, and Eglin C, which is an elastase inhibitor, reduced the release of lactate dehydrogenase and thrombomodulin in a dose-dependent manner. The release of lactate dehydrogenase and thrombomodulin in the group with relief of obstructive jaundice was significantly higher than in the group with normal liver. There was no significant difference between the group with obstructive jaundice and the group with normal liver. The elastase activity in neutrophil suspension was similarly higher in the group with relief of obstructive jaundice than in the group with normal liver.

CONCLUSIONS

This study suggests that neutrophils in patients with obstructive jaundice are not activated before its relief. After relief of obstructive jaundice, neutrophils are strongly primed and have the potential to cause endothelial cell injury. The neutrophil "priming" in patients with obstructive jaundice may be associated with the frequent occurrence of postoperative complications.

The influence of the C1-inhibitor BERINERT and the protein-free haemodialysate ACTIHAEMYL20% on the evolution of the depth of scald burns in a porcine model

Standardized deep partial-thickness burns were inflicted on domestic pigs by scalding 30 per cent of the skin surface for 25 s with 75 degrees C hot water. The animals (n = 18; weight 25-35 kg) were divided into three groups: I, control group (n = 6), Ringer's lactate only; II, haemodialysate group (n = 6), Ringer's lactate and a protein-free haemodialysate of calf-blood (ACTIHAEMYL20%; AH) and III, C1-inhibitor group (n = 6), Ringer's lactate and C1-inhibitor (C1-INH; BERINERT). Skin biopsies were taken at defined time points (4, 28, 52 and 76 h) and investigated histologically. Depth of burn was determined morphometrically after coloration with a modified MTT-staining on frozen sections of the skin biopsies. Fluid therapy with C1-INH decelerated significantly the progression of the burn wound in the postburn-period compared to Ringer's lactate alone. In comparison with C1-INH, the treatment with AH demonstrated a less beneficial influence on the depth of scald burns. The favourable effects of C1-INH are explained by the protection of the dermal microcirculation during the acute phase of thermal injury.

Synergism between endotoxin priming and exotoxin challenge in provoking severe vascular leakage in rabbit lungs

Lipopolysaccharides (LPS) of gram-negative bacteria prime rabbit lungs for enhanced thromboxane-mediated vasoconstriction upon subsequent challenge with the exotoxin Escherichia coli hemolysin (HlyA) (Walmrath et al. J. Exp. Med. 1994;180:1437-1443). We investigated the impact of endotoxin priming and subsequent HlyA challenge on lung vascular permeability while maintaining constancy of capillary pressure. Rabbit lungs were perfused in a pressure-controlled mode in the presence of the thromboxane receptor antagonist BM 13.505, with continuous monitoring of flow. Perfusion for 180 min with 10 ng/ml LPS did not provoke vasoconstriction or alteration of capillary filtration coefficient (Kfc) values. HlyA (0.021 hemolytic units/ml) induced thromboxane release and a transient decrease in perfusion flow in the absence of significant changes in Kfc. Similar results were obtained when LPS and HlyA were coapplied simultaneously. However, when the HlyA challenge was undertaken after 180 min of LPS priming, a manifold increase in Kfc values was noted, with concomitant severe lung edema formation, although capillary pressure remained unchanged. Thus, endotoxin primes the lung vasculature to respond with a severe increase in vascular permeability to a subsequent low-dose application of HlyA. Such synergism between endotoxin priming and exotoxin challenge in provoking lung vascular leakage may contribute to the pathogenesis of respiratory failure in sepsis and severe lung infection.

Lipid mediators up-regulate CD11b and prime for concordant superoxide and elastase release in human neutrophils

BACKGROUND

The pathogenesis of multiple organ failure after injury is believed to involve priming and activation of the inflammatory cascade, and the polymorphonuclear neutrophil (PMN) appears to be an integral effector. Characterization of the primed PMN is evolving. Because much research has focused on the respiratory burst, the synergistic role of cytotoxic proteases, especially elastase, has been largely ignored. In addition, CD11b has been identified as pivotal in PMN-mediated tissue injury. Our hypothesis is that the well-recognized postinjury mediators platelet-activating factor (PAF) and leukotriene B4 (LTB4) prime PMNs for the concordant release of elastase and superoxide (O2-) as well as for CD11b up-regulation.

METHODS

Human PMNs were isolated and then incubated with PAF or LTB4 before N-formyl-methionyl-leucyl-phenylalanine activation. O2- generation was measured by reduction of cytochrome c. Elastase was measured by cleavage of Ala-Ala-Pro-Val p-nitroanilide. CD11b expression was quantified by incubation with R-phycoerythrin-labeled monoclonal antibodies followed by flow cytometry.

RESULTS

PAF and LTB4 primed PMNs maximally within 5 minutes for the production of O2-, elastase release, and simultaneous up-regulation of CD11b expression on the PMN surface.

CONCLUSION

PAF and LTB4 prime human PMNs for the concordant release of elastase, generation of O2-, and CD11b up-regulation. Understanding the physiologic characteristics of PMN priming may offer new therapeutic targets to avoid the development of multiple organ failure after injury.

Nitric oxide attenuates platelet-activating factor priming for elastase release in human neutrophils via a cyclic guanosine monophosphate-dependent pathway

BACKGROUND

Nitric oxide (NO) has proven benefits in treating adult respiratory distress syndrome (ARDS). The protective mechanism remains unclear, but cyclic guanosine monophosphate (cGMP)-dependent signal transduction pathways have been suggested. Our laboratory has implicated polymorphonuclear neutrophil (PMN) priming and subsequent activation in the pathogenesis of postinjury ARDS and has shown that NO inhibits superoxide anion production from activated PMNs. More recently, the pivotal role of elastase in PMN-mediated tissue injury has been emphasized. Consequently, our study hypothesis was that NO attenuates platelet-activating factor (PAF) priming for elastase release through a cGMP-dependent pathway in human PMNs.

METHODS

PMNs isolated from human volunteers were preincubated with the NO donor 3-morpholinosydnonimine hydrochloride (SIN-1; 10(-6) to 10(-2) mol/L), cGMP (10(-3) mol/L), or the cell-permeable cGMP analog dibutyryl-cGMP (10(-3) mol/L) for 10 minutes. The cells were then primed with platelet-activating factor (PAF) 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (200 nmol/L), which was followed by N-formyl-methionyl-leucyl-phenylalanine (fMLP) activation (1 mumol/L). Elastase release was measured by the cleavage of N-methoxysuccinyl-Ala-Ala-Pro-Val p-nitroanilide (AAPV-pNA).

RESULTS

NO (through SIN-1) significantly attenuated elastase release from PAF-primed PMNs in a dose-dependent manner. Cell-permeable dibutyryl-cGMP attenuated PMN elastase release similar to NO, but cGMP (not cell-permeable) had no effect.

CONCLUSIONS

NO attenuates elastase release from PAF-primed PMNs through an intracellular cGMP-dependent signal transduction pathway. These findings may partially explain the beneficial effects of NO in the treatment of postinjury ARDS and add to our knowledge of the complex intracellular pathways involved in NO/PMN interactions.

Beta-adrenergic stimulation down-regulates neutrophil priming for superoxide generation, but not elastase release

Platelet-activating factor (PAF) concordantly primes neutrophils (PMNs) for superoxide generation and elastase release. beta-Adrenergic stimulation of PMNs enhances cAMP-dependent protein kinase A (PKA) activity and has been shown to inhibit PAF-mediated NADPH-oxidase activity. PMN superoxide generation is thought to play a predominate microbicidal role, whereas elastase is known to mediate untoward PMN-endothelial interactions. We hypothesized that beta-adrenergic neutrophil stimulation has disparate effects on PAF-mediated PMN superoxide generation versus elastase release. Human PMNs were isolated using a standard Ficoll/Hypaque gradient. PMNs were then primed with PAF (200 nM) and activated with fMLP (1 microM). Subsets of PMNs were pretreated for 5 min with a beta agonist (10(-4) M isoprotereno) or an adenylate cyclase agonist (10(-5) M forskolin). Superoxide generation was determined by superoxide dismutase inhibitive cytochrome c reduction. Elastase activity was measured by the cleavage of n-methoxylsuccinyl-A-A-P-V-p-nitroanilide. Pretreatment with isoproterenol and forskolin yielded superoxide generation of 3.2 +/- 0.6 and 3.1 +/- 1.2 nmole/2.5 x 10(5) PMN/min compared to 9.0 +/- 0.6 nmole/2.5 x 10(5) PMN/min for PAF/fMLP alone, whereas isoproterenol and forskolin did not significantly affect PAF-mediated neutrophil elastase release, 22.4 +/- 5.3 and 24.0 +/- 3.6%, respectively, compared to 39.4 +/- 9.1% for PAF/fMLP alone. Disparate PMN signal transduction for superoxide generation versus elastase release may explain the SICU clinical paradox, in which patients are both susceptible to infection and vulnerable to PMN-mediated multiple organ failure.

Complement partially mediates acid aspiration-induced remote organ injury in the rat

BACKGROUND

Acid aspiration into one lung is known to cause both a local as well as remote organ injury characterized by neutrophil sequestration and subsequent edema. This study investigated investigated the role of the complement cascade in the development of acid aspiration-induced local lung and remote organ injuries using K-76 COONa (K76), an anticomplement agent that inhibits the complement pathway at the C5 step, and its usefulness as a treatment drug.

METHODS

Anesthetized rats underwent tracheostomy and insertion of a cannula. K76 was intraperitoneally administrated prior to or immediately after the instillation of 0.1 ml of HCl (0.1N) or phosphate buffer solution (PBS) into the left lung. Inflammatory responses were evaluated by tumor necrosis factor alpha (TNF alpha) in the plasma and the bronchoalveolar lavage fluid (BALF) (n = 4), tissue myeloperoxidase (MPO), wet-to-dry weight ratio (W/D ratio) (n = 6), and protein concentration in the BALF (n = 6).

RESULTS

Acid instillation caused an increase in the plasma TNF alpha, which was significantly attenuated by the administration of K76 prior to or after the acid instillation. Acid instillation to the left lung resulted in an increase of MPO and W/D ratios of the left lung, the right lung, and the small intestine. The administration of K76 inhibited the increase of MPO in these organs. K76 inhibited the increase of W/D ratios of the right non-instillated lung and the small intestine. Acid instillation led to increased protein concentration in the BALF of the left lung, which was not inhibited by K76. K76 administrated after the acid instillation had the same effects. TNF alpha in the BALF was not detected in all groups.

CONCLUSION

These results suggest that localized acid aspiration induces, through the C5a step of the complement system-dependent mechanisms, TNF alpha formation and neutrophil sequestration, which caused the increase of endothelial permeability of the systemic organs. K76 is effective as a treatment drug in modulating some of the injuries caused by the acid instillation, but further investigations is warranted as to its potential as a therapeutic agent.

Plasma factors augment neutrophil and endothelial cell activation during aortic surgery

Lung injury following reperfusion results from endothelial damage caused by release of cytotoxic products by activated neutrophils (PMN) in the pulmonary microvasculature. This process is facilitated by the release of pro-inflammatory cytokines and arachidonic metabolites following the outset of reperfusion. This study aimed to evaluate the effect of plasma obtained before and after revascularisation on neutrophil and endothelial cell activation. Plasma (IR-plasma) was obtained from venous blood samples taken before and during aortic cross-clamping, and 5, 40 and 60 min following clamp removal in seven patients undergoing elective infrarenal aortic aneurysm resection. PMN from healthy volunteers (n = 5) were incubated with these plasma samples or with fMLP (N-formylmethionyl-leucyl-phenylalanine) as positive control for 30 min and assessed flow-cytometrically for CD11b expression. Human endothelial cells (ECV-304) were incubated with IR plasma for 2, 4 and 6 h or with tumour necrosis factor (TNF) (20 ng/ml) as positive control and assessed for ICAM-1 expression. Incubation with IR plasma resulted in a significant increase from pre-clamp in PMN CD11b expression. A similar trend was seen in endothelial cell ICAM-1 expression following 2 h incubation. These results indicate that reperfusion-induced endothelial dysfunction may be mediated by plasma factors released upon revascularisation which facilitate neutrophil-endothelial interaction through up-regulation of adhesion receptor expression.

Effects of heparin coating on the expression of CD11b, CD11c and CD62L by leucocytes in extracorporeal circulation in vitro

Leucocyte adhesion molecules are involved in the leucocyte-endothelial interaction and in the activation of coagulation and binding of complement and endotoxin. Thus, they are important in inflammation, systemic acute phase reaction, ischaemia reperfusion injury and resistance against infections. The expression of the adhesion molecules CD11b, CD11c and CD62L on leucocytes and changes in plasma products of neutrophil activation (myeloperoxidase, lactoferrin) and complement activation (C3bc, SC5b-9 (TCC)) were examined in an extracorporeal circulation (ECC) model and the effects of Carmeda bioactive surface (CBAS) heparin coating (n = 7) of the circuits were compared to uncoated control circuits (n = 5). In this model, new 'unactivated' cells mobilized from the bone marrow could not interfere with descriptive measures of cell activation as seen in in vivo studies. In the control group, CD11b and CD11c were upregulated on monocytes and granulocytes during ECC, whereas CD62L was downregulated. Heparin coating reduced the increase in CD11b and CD11c on granulocytes (p < 0.02 at 2 h), but the delayed increase in CD11c on monocytes and the delayed downregulation of CD62L on granulocytes and monocytes did not reach statistical significance. Further, heparin coating also reduced the initial decrease in the absolute cell counts of monocytes and granulocytes (p = 0.01 at 2 h), reflecting reduced adhesion to the oxygenator/tubing. The increases in plasma myeloperoxidase, lactoferrin, C3bc and TCC were lower in the heparin-coated group compared to the control group. The increases in plasma myeloperoxidase and lactoferrin correlated significantly to the increase in CD11b (r = 0.71, p = 0.02 and r = 0.64, p = 0.05, respectively) and CD11c (r = 0.72, p = 0.008 and r = 0.72, p = 0.008, respectively) on granulocytes, suggesting interacting regulatory pathways in the process of neutrophil adhesion, activation and degranulation. Thus, in this in vitro ECC model, heparin coating of oxygenator/tubing sets reduced leucocyte activation and leucocyte adhesion-related phenomena.

Effect of the 21-aminosteroid tirilazad mesylate on leukocyte adhesion and macromolecular leakage during endotoxemia

BACKGROUND

Interstitial accumulation of leukocytes has been related to the development of multiple organ failure after sepsis. Oxygen radicals are involved in the process of leukocyte adherence to the microvascular wall. This study investigates the effects of the oxygen radical scavenger tirilazad mesylate on leukocyte-endothelial interactions, macromolecular leakage, and microhemodynamics in mesenteric venules during endotoxemia.

METHODS

Male Wistar rats were randomly allocated to receive tirilazad mesylate (group A, n = 10), its vehicle (group B, n = 10), or saline 0.9% (group C, n = 10) before a 120-minute infusion of endotoxin (2 mg/kg/hr). Furthermore, a control group without receiving endotoxin (group D, n = 10) was investigated. Leukocyte adherence, emigration of leukocytes, and macromolecular leakage were determined in postcapillary venules of the mesentery by using intravital videomicroscopy.

RESULTS

During the administration of endotoxin the number of adherent leukocytes per square millimeter of vessel surface progressively increased in group B (baseline, 431 +/- 35 cells/mm2; 120 minutes, 1121 +/- 71 cells/mm2) and group C (baseline, 398 +/- 44 cells/mm2; 120 minutes, 1290 +/- 116 cells/mm2). In group A no increase in leukocyte adherence was observed after 120 minutes (baseline, 415 +/- 81 cells/mm2; 120 minutes, 638 +/- 87 cells/mm2). In control animals the leukocyte adherence remained unchanged (baseline, 347 +/- 41 cells/mm2; 120 minutes, 507 +/- 75 cells/mm2). After 120 minutes, tirilazad mesylate prevented the increase in leukocyte emigration observed in group B and C. Increased macromolecular leakage during endotoxemia (groups B and C) was not influenced by pretreatment with tirilazad. Tirilazad did not affect the decrease in red cell velocity, volumetric blood flow, and venular shear rate observed during endotoxemia.

CONCLUSIONS

This study demonstrates inhibitory effects of tirilazad on endotoxin-induced leukocyte adherence and emigration, suggesting a potential therapeutic role for this substance in the prevention of sepsis-induced multiple organ failure.

Rebamipide attenuates indomethacin-induced gastric mucosal lesion formation by inhibiting activation of leukocytes in rats

Granulocyte elastase released from activated leukocytes plays an important role in leukocyte infiltration. Since activated leukocytes have been shown to be involved in the pathogenesis of gastric mucosal lesion formation induced by nonsteroidal antiinflammatory drugs, inhibition of granulocyte elastase release from activated leukocytes may be useful in the prevention of these lesions. Rebamipide, a novel antiulcer agent, inhibited granulocyte elastase release from activated neutrophils in vitro. Rebamipide and ONO-5046, a granulocyte elastase inhibitor, markedly inhibited gastric mucosal lesion formation in rats. Gastric myeloperoxidase activity was significantly increased 3 hr after indomethacin administration. This increase was significantly inhibited by rebamipide and ONO-5046. Cimetidine did not inhibit granulocyte elastase release from activated neutrophils. Although cimetidine markedly prevented the indomethacin-induced gastric mucosal lesion formation, it did not reduce the gastric myeloperoxidase activity. Therefore, unlike cimetidine, rebamipide may prevent indomethacin-induced gastric mucosal lesion formation by inhibiting neutrophil activation.

Endothelial cell injury in cardiovascular surgery: ischemia-reperfusion

Myocardial ischemia and reperfusion is a common occurrence in cardiovascular surgery patients. Acute ischemia results in a spectrum of derangements, which range from transient reversible stunning of the myocardium to severe irreversible abnormalities such as infarction. Many of these abnormalities are accentuated upon reperfusion with oxygenated blood. Recently, the endothelium has been shown to play a key role in the injury suffered after ischemia and reperfusion. When rendered hypoxic and then reoxygenated, endothelial cells become activated to express proinflammatory properties that include the induction of leukocyte-adhesion molecules, procoagulant factors and vasoconstrictive agents that increase vasomotor tone. These changes may contribute to the no-reflow phenomenon by promoting endothelial edema, neutrophil and platelet plugging, microthrombosis, and enhanced vasomotor tone. An increased understanding of the role that hypoxic endothelial cell activation plays in myocardial dysfunction after ischemia/reperfusion may allow therapies to be designed to further attenuate this response.

Neutrophils obtained from obliterative atherosclerotic patients exhibit enhanced resting respiratory burst and increased degranulation in response to various stimuli

Tissue destruction in atherosclerosis is partly due to uncontrolled protease and oxygen radical release. In this study we investigated the release of elastase and myeloperoxidase, as well as the production of reactive oxygen species by polymorphonuclear leukocytes (PMNLs) obtained from patients with obliterative atherosclerotic of the lower legs. In addition we measured the plasma concentration of xanthine oxidase. PMNLs of atherosclerotic patients have a greater ability to increase elastase and myeloperoxidase release after their stimulation with formyl-methionin-leucyl-phenylalanin (fMLP) and calcium ionophore, A23187, independently of their age, than PMNLs of healthy middle-aged subjects. Similarly to healthy elderly subjects there was an increased superoxide anion (O2-) production under basal condition in both atherosclerotic patient age-groups. The activation of PMNLs with fMLP and A23187 enhanced O2- formation both in healthy subjects and in patients with atherosclerotic disease of the lower legs, however the increase was significantly less in the latter group. No biochemical parameters showed significant correlation with patient's risk factors, however myeloperoxidase production was significantly higher in less severe stage of the disease (P < 0.05). We found that patients with atherosclerotic disease of the lower legs have higher plasma xanthine oxidase level than control subjects. This study indicates an other piece of evidence suggesting the activation and involvement of neutrophils in the pathogenesis of atherosclerosis of the lower legs. The similar tendencies in the reactivity of neutrophils during aging and in atherosclerosis suggest that atherosclerosis may be an early aging process.

Superoxide and hydrogen peroxide induce CD18-mediated adhesion in the postischemic heart

A burst of endothelial derived oxidants including hydrogen peroxide (H2O2) and superoxide (.O2-) occurs on reperfusion of ischemic tissues that directly causes injury; however, it is not known if this also triggers further injury due to subsequent leukocyte adhesion and adhesion molecule expression. Therefore, studies were performed in an isolated heart model developed to enable study of the role of isolated cellular and humoral factors in the mechanism of postischemic injury. Isolated rat hearts were subjected to 20 min of 37 degrees C-global ischemia followed by reperfusion with polymorphonuclear leukocytes (PMNs) and plasma in the presence or absence of superoxide dismutase (SOD), 200 U/ml, or catalase, 500 U/ml. Measurements of contractile function, coronary flow, high-energy phosphates, free radical generation, and PMN accumulation were performed. Adhesion molecule expression was measured on the surface of effluent PMNs by fluorescence flow cytometry and within the tissue using immunohistochemistry. SOD or catalase treatment resulted in 2- to 3-fold higher recoveries of contractile function, coronary flow, and high energy phosphates. EPR spin trapping measurements demonstrated that SOD totally quenched the free radical generation observed upon reperfusion while catalase prevented the formation of hydroxyl and alkyl radicals derived from superoxide. SOD or catalase treatment decreased PMN accumulation in the reperfused heart and prevented the marked upregulation of CD18 expression seen after reperfusion. These experiments demonstrate that in addition to their direct antioxidative actions, SOD and catalase each decrease PMN adhesion and CD18 expression resulting in marked suppression of PMN-mediated injury in the postischemic heart. Thus, endothelial derived H2O2 and .O2- further amplify postischemic injury by triggering CD18 expression on the surface of PMNs leading to increased PMN adhesion within the heart.

Soluble intercellular adhesion molecule-1 provokes polymorphonuclear leukocyte elastase release by CD18

BACKGROUND

Elevated levels of soluble intercellular adhesion molecule-1 (sICAM-1) correlate with the development of postinjury multiple organ failure. Soluble ICAM-1 secretion is known to be induced in endothelial cells and monocytes by diverse inflammatory stimuli. We have found that incubation of quiescent polymorphonuclear leukocytes (PMNs) with sICAM-1 elicits elastase release and, more recently, that cross-linking CD18 receptors on PMNs also produces elastase release. Consequently, our study hypothesis was that sICAM-1 provokes PMN elastase release through its interaction with CD18.

METHODS

To obtain sICAM-1, Chinese hamster ovarian cells transfected with human ICAM-1 were lysed and centrifuged at 150,000 g for 1 hour; the supernatant was passed over an ICAM-1 affinity column, eluted with 0.1 mmol/L glycine HCl, and concentrated with dialysis filter. Human PMNs (2.5 x 10(5)) were saturated with specific monoclonal antibodies for the beta 2 subunits (CD11a, CD11b, CD18) or nonspecific monoclonal antibodies for 30 minutes on ice before a 1-hour incubation with sICAM-1 (75 ng/ml) at 37 degrees C. Elastase activity was measured by the cleavage of n-methoxysuccinyl-A-A-P-V-p-nitroanilide.

RESULTS

Neutrophil incubation with sICAM-1 resulted in 19.2% +/- 2.8% of total PMN elastase, compared with 2.4% +/- 0.5% in the controls. Blockade of CD18 abrogated sICAM-1 provoked elastase release with monoclonal antibodies to CD18 (TS1/18, 31H8) resulting in 4.3% +/- 1.0% and 5.5% +/- 1.4% elastase release, respectively. Blockade of CD11a, CD11b, and nonspecific antibody controls had no effect on sICAM-1 induced elastase release.

CONCLUSIONS

In vitro, sICAM-1 provokes PMN elastase release through CD18. This may represent a mechanism by which elevated levels of circulating sICAM-1, released from local injury sites, provoke distal organ dysfunction.

Pulmonary damage by Vibrio vulnificus cytolysin

Vibrio vulnificus is an estuarine bacterium that causes septicemia and serious wound infection. Cytolysin produced by V. vulnificus has been incriminated as one of the important virulence determinants of bacterial infection. Cytolysin (8 hemolytic units) given intravenously to mice via their tail veins caused severe hemoconcentration and lethality. Cytolysin treatment greatly increased pulmonary wet weight and vascular permeability as measured by (125)I-labeled albumin leakage without affecting those factors of other organs significantly. Blood neutrophils were markedly decreased in number after cytolysin injection, with a concomitant increase in the level of pulmonary myeloperoxidase activity, indicating that cytolysin-induced neutropenia might be due to pulmonary sequestration of neutrophils. By microscopic examination, severe perivascular edema and neutrophil infiltration were evident in lung tissues. These results suggest that increased vascular permeability and neutrophil sequestration in the lungs are important factors in lethal activity by cytolysin.

Effects of recombinant bactericidal/permeability-increasing protein (rBPI23) on neutrophil activity in burned rats

Bactericidal/permeability-increasing protein (BPI) is a neutrophil granule protein with potent bactericidal and lipopolysaccharide (LPS)-neutralizing activities. The purpose of this study was to determine if a human recombinant BPI product, rBPI23, would influence neutrophil (PMN) sequestration into various tissues in a rat burn injury model. Leukosequestration may produce local tissue injury from proteases and high-energy oxygen species released from PMNs. Rats received tracheostomy and venous cannulation, then received 17 to 20% total body surface area full-thickness contact burns and resuscitation with 20 ml, of intraperitoneal saline. Ten mg/kg body weight rBPI23 in saline was given by intravenous injection immediately after burn injury, followed by intravenous doses of 2 mg/kg at 2 and 4 hours. Control animals received intravenous saline only. PMN retention in lung, liver, spleen, gut, skin, muscle, kidney, and brain tissues was determined by removing (before burn injury) and differentially radiolabeling PMNs (111In) and erythrocytes (51Cr), reinfusing cells 4.5 hours after burn injury, and measuring tissue radioactivity 30 minutes later. Edema was estimated by measuring extravasated 125I-labeled albumin in the various tissues, 30 minutes after injection. Peripheral blood PMNS were analyzed for intracellular H2O2 content by flow cytometry using a fluorescent dye that reacts with H2O2. Radioisotope studies demonstrated significant (p < 0.05) leukosequestration into lung, liver, gut, kidney, and skin tissues at 5 hours after burn injury. Tissue edema, manifested by radiolabeled albumin retention, was not observed in any tissues. Postburn PMN deposition in lungs and skin was decreased (p < 0.05) by the immediate administration of rBPI23 after burn injury. Flow cytometry showed increased intracellular H2O2 content in peripheral blood PMNs 5 hours after burn injury (p < 0.05), which was unaffected by administration of rBPI23. Since sequestration of metabolically active PMNs may induce tissue injury, therapies that block leukosequestration after burn injury may improve clinical outcomes by limiting remote tissue injury.

P-selectin mediates intestinal ischemic injury by enhancing complement deposition

BACKGROUND

Ischemia and reperfusion injury of rodent intestine is complement mediated. P-selectin antagonism reduces local injury, yet neutrophil depletion does not. This study tests the thesis that the protective mechanism of P-selectin antagonists involves complement inhibition.

METHODS

We subjected rats (n = 86) to 50 minutes of complete mesenteric ischemia and 4 hours of reperfusion. Treatment with a monoclonal antibody (PB1.3) against P-selectin reduced intestinal injury as judged by 125I-albumin permeability index (7.33 +/- 0.40) compared with saline solution treatment (11.4 +/- 0.49) (p < 0.05).

RESULTS

However, intestinal neutrophil sequestration assessed by myeloperoxidase assay was unchanged. Immunohistochemistry revealed that mucosal C5b-9 was deposited in animals treated with saline solution and was absent in the sham group. PB1.3 treatment reduced C5b-9 deposition in the intestinal mucosa compared with that in animals treated with saline solution (p < 0.05). Neutrophil-dependent remote lung injury assessed by 125I-albumin permeability and pulmonary myeloperoxidase assay were not significantly reduced by PB1.3. Treatment with a soluble form of P-selectin ligand, sialyl Lewisx (sLex), reduced intestinal myeloperoxidase (0.065 +/- 0.006) compared with saline solution treatment (0.136 +/- 0.02) (p < 0.05), but it did not reduce permeability. Remote lung permeability was reduced (4.52 +/- 0.65 x 10(-3)) by sLex compared with saline solution treatment (6.11 +/- 0.41 x 10(-3)) (p < 0.05).

CONCLUSIONS

Antagonizing the lectin domain of P-selectin and thereby neutrophil adhesion was without local benefit in this model. In contrast, PB1.3 exerted a novel antagonism of P-selectin and reduced complement deposition.