Leukocyte adherence and sequestration following hemorrhagic shock and total ischemia in rats

Evaluation of Mesenteric Microvascular Hyperpermeability Following Hemorrhagic Shock Using Intravital Microscopy

Intravital microscopy is a powerful tool for evaluating vascular hyperpermeability in various vascular beds. Hemorrhagic shock after traumatic injury is known to induce microvascular hyperpermeability, life-threatening edema, and microcirculatory perfusion disturbances. Here we describe the microsurgical and imaging methods to study mesenteric vascular hyperpermeability using intravital microscopy, in a rat model of hemorrhagic shock. In this protocol, hemorrhagic shock is induced by controlled withdrawal of blood to reduce the mean arterial pressure (MAP) to 40 mmHg for 60 min, followed by resuscitation for 60 min. To study the changes in vascular permeability, the rats are given FITC-albumin, a fluorescent tracer, intravenously. The FITC-albumin flux across the vessel wall is measured in mesenteric postcapillary venules by determining intravascular and extravascular fluorescence intensity under intravital microscopy. Intravital microscopic evaluation of high molecular weight FITC-albumin permeability is a reliable indicator of microvascular hyperpermeability.

A Rat Model of Hemorrhagic Shock for Studying Vascular Hyperpermeability

Vascular hyperpermeability is one of the known detrimental effects of hemorrhagic shock, which we continually try to understand, minimize, and reverse. Here, we describe induction of hemorrhagic shock in a rat and studying of its effects on vascular permeability, using intravital microscopy. In this protocol, hemorrhagic shock will be induced by withdrawing blood to reduce the mean arterial pressure (MAP) to 40 mmHg for 60 min followed by resuscitation for 60 min. To study the changes in vascular permeability following hemorrhagic shock, the rats will be given FITC-albumin, a fluorescent tracer, intravenously. Following this, the FITC-albumin flux across the vessel will be measured in mesenteric postcapillary venules by determining fluorescent intensity intravascularly and extravascularly under intravital microscopy.

Serum diamine oxidase as a hemorrhagic shock biomarker in a rabbit model

Background

In prolonged hemorrhagic shock, reductions in intestinal mucosal blood perfusion lead to mucosal barrier damage and systemic inflammation. Gastrointestinal failure in critically ill patients has a poor prognosis, so early assessment of mucosal barrier injury in shock patients is clinically relevant. Unfortunately, there is no serum marker that can accurately assess intestinal ischemia-reperfusion injury.

Objective

The aim of this study was to assess if serum diamine oxidase levels can reflect intestinal mucosal injury subsequent to prolonged hemorrhagic shock.

Methods

Thirty New Zealand white rabbits were divided into three groups: a control group, a medium blood pressure (BP) group (exsanguinated to a shock BP of 50 to 41 mm Hg), and a low BP group (exsanguinated to a shock blood pressure of 40 to 31 mm Hg), in which the shock BP was sustained for 180 min prior to fluid resuscitation.

Results

The severity of hemorrhagic shock in the low BP group was significantly greater than that of the medium BP group according to the post-resuscitation BP, serum tumor necrosis factor (TNF)-α, and arterial lactate. Intestinal damage was significantly more severe in the low BP group according to Chiu’s scoring, claudin-1, intercellular adhesion molecule (ICAM)-1, and myeloperoxidase expression. Serum diamine oxidase was significantly increased in the low BP group compared to the medium BP and control groups and was negatively correlated with shock BP.

Conclusion

Serum diamine oxidase can be used as a serological marker in evaluating intestinal injury and shows promise as an indicator of hemorrhagic shock severity.

Hypothermia caused by slow and limited-volume fluid resuscitation decreases organ damage by hemorrhagic shock

BACKGROUND

Hypothermia frequently occurs during fluid resuscitation of trauma victims, especially in patients with a major blood loss. Recent studies have suggested that mild hypothermia may ameliorate hemorrhagic shock (HS) induced splanchnic damage.

OBJECTIVE

The aim of the present study is to compare the status of body temperature and splanchnic injury under different resuscitation speeds for HS in conscious rats.

METHODS

Experimental study in an animal model of HS. Twenty-four male Wistar-Kyoto rats were used in the study. To mimic HS, 40% of the total blood volume was withdrawn. Fluid resuscitation was given 30 min after blood withdrawal. The rats were randomly divided into three groups; the control group, the 10-min rapid group, and the 12-h slow group.

RESULTS

Levels of blood biochemical parameters, including aspartate transferase (GOT), and alanine transferase (GPT), were measured. Levels of serum tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) were measured and levels of bronchoalveolar lavage fluid (BALF) TNF-α and nitric oxide (NO) were measured by ELISA. The lung, liver and small intestine were examined for pathological changes 48 h after HS.

CONCLUSIONS

Initially slow rate resuscitation with limited-volume significantly decreased body temperature, serum GOT, GPT, TNF-α, and IL-6 levels, levels of TNF-α, and NO in BALF. Moreover, the slow group had lower injury scores in the lung, liver and small intestine than the rapid group after HS. This finding suggests that mild hypothermia induced by a slow fluid resuscitation rate with limited-volume ameliorates HS-induced splanchnic damage in conscious rats.

Erythropoietin protects severe haemorrhagic shock-induced organ damage in conscious rats

OBJECTIVE

Erythropoietin (EPO) has pleiotropic cytoprotective actions. We investigated the effects of EPO on the physiopathology and cytokine levels after haemorrhagic shock (HS) in conscious rats.

METHODS

Rats received an intravenous injection of 300 U/kg EPO over 10 min followed by HS via withdrawal of 60% of total blood volume from a femoral arterial catheter (6 ml/100 g body weight) over 30 min. Mean arterial pressure (MAP) and heart rate (HR) were monitored continuously for 18 h after the start of blood withdrawal. Levels of biochemical parameters, including haemoglobin, GOT, GPT, BUN, creatinine (Cr), LDH, CPK, and lactate were measured at 30 min before the induction of HS and 0, 1, 3, 6, 9, 12, and 18 h after HS. Cytokine levels, including TNF-alpha and IL-6, in serum were measured at 1, 9, and 18 h after HS. The kidneys, liver, lungs, and small intestine were removed for pathology assessment at 48 h after HS.

RESULTS

HS significantly increased HR, blood GOT, GPT, BUN, Cr, LDH, CPK, lactate, TNF-alpha, and IL-6 levels and decreased haemoglobin and MAP in rats. Pre-treatment with EPO improved survival rate, preserved the MAP, decreased the tachycardia and markers of organ injury, suppressed the release of TNF-alpha and IL-6 after HS in rats.

CONCLUSION

Pre-treatment with EPO suppresses the release of serum TNF-alpha and IL-6, along with decreasing the levels of markers of organ injury associated with HS, with such actions ameliorating HS-induced organ damage in rats.

Lack of Exercise Decreases Survival and Increases Organ Damage After Hemorrhagic Shock in Rats

Inflammatory response secondary to hemorrhagic shock (HS) frequently precedes multiple organ failure and death in trauma patients. Researchers have recognized that exercise benefits immune function. However, the effects of exercise on HSinduced death and organ damage are unknown. In this study, the authors aimed to explore the effects of exercise on survival rate and organ injury after HS. Rats were divided into exercise and nonexercise groups. The exercise group received running training 30 min/day five times/week for 4 weeks. After 4 weeks, researchers withdrew 60% of total blood volume in both groups to mimic HS. Levels of blood aspartate transferase (GOT), alanine transferase (GPT), blood urea nitrogen (BUN), creatinine (Cr), lactic acid dehydrogenase (LDH), creatine kinase—myoglobin (CK-MB), blood glucose, and lactate were measured. The survival rate and injury scores for the liver, kidney, and lung were examined 48 hr after HS. Physical activity was measured in surviving rats from the 3rd to the 7th day after HS. Exercise training significantly increased the survival rate (75% for the exercise group vs. 50% for the nonexercise group) after HS and decreased organ injury. In addition, the exercise group was more active than the nonexercise group after HS.

Melatonin ameliorates hemorrhagic shock-induced organ damage in rats

BACKGROUND

Hemorrhagic shock (HS) followed by resuscitation can result in production of several inflammatory mediators, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), leading to multiple organ dysfunction. Melatonin can attenuate organ damage with its anti-inflammation effects. The present study was designed to investigate the effects of melatonin on the physiopathology and cytokine levels after HS in rats.

METHODS

HS was induced in rats by withdrawing 40% of the total blood volume (6 mL/100 gm body weight) from a femoral artery catheter, immediately followed by intravenous injection of 10mg/kg melatonin. Mean arterial pressure and heart rate were monitored continuously for 48 h after the start of blood withdrawal. Biochemical parameters, including levels of hemoglobulin, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), blood urea nitrogen (BUN), creatinine (Cre), lactic dehydrogenase (LDH), creatine phosphokinase (CPK), and lactate, were determined 30 min before and 0, 1, 3, 6, 12, 24, and 48 h after induction of HS while an equal volume of normal saline was replaced as fluid resuscitation. Cytokine levels including TNF-α and IL-6 in the serum were measured at 1, 24, and 48 h after HS. The kidney, liver, lung, and small intestine were removed for pathology assessment at 48 h after HS.

RESULTS

HS significantly increased the heart rate, blood GOT, GPT, BUN, Cre, LDH, CPK, lactate, TNF-α, and IL-6 levels, and decreased hemoglobulin and mean arterial pressure in rats. Treatment with melatonin preserved the mean arterial pressure, decreased tachycardia, and markers of organ injury, and suppressed the release of TNF-α and IL-6, with no change in hemoglobulin after HS in rats.

CONCLUSION

Treatment with melatonin suppresses the release of serum TNF-α and IL-6, and decreases the levels of markers of organ injury associated with HS, thus ameliorating HS-induced organ damage in rats.

Fluvastatin attenuates severe hemorrhagic shock-induced organ damage in rats

OBJECTIVES

Multiple organ dysfunction resulting from hemorrhagic shock (HS) and subsequent resuscitation was mediated by several inflammatory factors such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10). The present study was designed to investigate the protective effects of fluvastatin on these mediators after HS in rats.

METHODS

The experimental rats were randomly divided into three groups. The vehicle group received only vitamin K without HS, the HS-control group received vitamin K and HS, and the HS-experimental group received both vitamin K and fluvastatin (1mg/kg) before HS. HS was produced by bleeding from a femoral arterial catheter to remove 60% of total blood volume (6ml/100g BW) over 30min. The mean arterial pressure (MAP) and heart rate (HR) were monitored continuously for 12h after the start of blood withdrawal. The biochemical parameters, including arterial blood gas, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), blood urea nitrogen (BUN), creatinine (Cre), lactic dehydrogenase (LDH), creatine phosphokinase (CPK), and lactate were obtained at 30min before induction of HS and at 0, 1, 3, 6, 9 and 12h after HS. Equal volume of normal saline was given to replace blood volume loss. Cytokine levels including TNF-alpha and IL-10 in serum were measured at 1h after HS. Kidney, liver, lung and small intestine were removed for pathology examination at 48h after HS.

RESULTS

HS significantly increased HR, blood GOT, GPT, BUN, Cre, LDH, CPK, lactate, TNF-alpha and IL-10 levels, and also induced metabolic acidosis and decreased MAP in rats. Pre-treatment with fluvastatin was found to improve survival rate, preserved MAP, decreased the markers of organ injury, suppressed the release of TNF-alpha and increased IL-10 after HS in rats.

CONCLUSION

Pre-treatment with fluvastatin can suppress the release of serum TNF-alpha and can also increase serum IL-10 level to protect HS-induced multi-organ damage in rats.

Influence of sex and age on morphological organ damage after hemorrhagic shock

Immune function after hemorrhagic shock (shock) and subsequent sepsis is proofed to be sex- and age-related, showing an enhanced immune function and better survival of young females and a deteriorating immune response in advanced age. However, it remains unclear if the observed sex- and age-related effects observed on the immune function mirror the histomorphological changes of the affected organs. To scrutinize a possible association, male and female CBA/J mice (young, 2-3 months; aged 18-19 months) were subjected to shock (35 + 5 mmHg for 90 min and fluid resuscitation) or sham operation. At 48 h after shock, histological specimen at definite sites were harvested (lung, small bowel, liver, and kidney) and immediately stored in 10% formalin. After paraffin embedding, hematoxylin-eosin stain and immunohistochemical stains (vascular cell adhesion molecule 1 [VCAM-1], cluster of differentiation 44 [CD44], signal transducers and activators of transcription 3 [STAT-3]) were performed. In both sexes, aged animals developed significantly increased (P < 0.05) tissue damage in all analyzed organs compared with young mice. Sex differences were noticed in the lungs of young mice, showing a significantly (P < 0.05) lower organ damage score in female animals. Sex-related differences were found for VCAM-1 and cluster of differentiation 44 expression, whereas age-related changes were observed for STAT-3. These results demonstrate that the severity of tissue damage caused by hemorrhagic shock is influenced by sex- and age-related effects. Variances in the VCAM-1 and STAT-3 expression suggest that improved immune function in female and young subjects may be responsible for less shock-induced tissue damage.

Activated protein C attenuates microvascular injury during systemic hypoxia

In response to hypoxia, an inflammatory cascade is initiated and microvascular injury ensues. Specifically, within 10 min, leukocyte adherence to the endothelium begins, and leukocyte emigration and vascular leak soon follow. Activated protein C (APC) has been reported to have both anticoagulant and anti-inflammatory properties. Activated protein C is best described in its role as a treatment for sepsis. However, it has been used, with some success, in experimental models of hypoxic injury. We hypothesized that APC would be protective against microvascular injury during systemic hypoxia. Randomized prospective animal study. Adult male Sprague-Dawley rats. To characterize the microvascular response to APC exposure during hypoxia, four rat groups were used: saline control, APC infusion alone (100 mg/kg bolus), hypoxia alone (10% O2), and simultaneous hypoxia + APC infusion. Measurements of leukocyte adherence (no. per 100-microm venule), leukocyte emigration (no. per 4,000 microm(2)), and venular leak by fluorescein isothiacyanate-labeled albumin (Fo/Fi) were performed during intravital microscopy of the intact venular bed. Leukocyte adherence decreased from 14.5 (+/-1.2) cells/100-microm venule in hypoxic rats to 4.4 (+/-1.5) cells/100-microm venule in those treated with both hypoxic gas and APC infusion (P < 0.001). Similarly, leukocyte emigration in hypoxic rats reached 12.3 (+/- 2.2) cells/4,000-microm(2) venule, but was reduced to 3.5 (+/-0.3) cells/4,000-microm(2) venule (P <.001). Venular permeability to protein was also significantly decreased in the APC-treated group from 0.82 (+/-0.14) to 0.25 (+/-0.14) (P < 0.001). The infusion of APC attenuates the inflammatory response during systemic hypoxia at the microvascular level, as evidenced by measurements of leukocyte adherence, emigration, and venular permeability. Further investigation is needed to examine the potential role of APC in the treatment of hypoxic injury.

Angiopoietin-1 inhibits intrinsic apoptotic signaling and vascular hyperpermeability following hemorrhagic shock

Studies from our laboratory demonstrated the involvement of intrinsic apoptotic signaling in hyperpermeability following hemorrhagic shock (HS). Angiopoietin 1 (Ang-1), a potent inhibitor of hyperpermeability, was recently shown to inhibit apoptosis. The purpose of our study was to determine the effectiveness of Ang-1 in attenuating HS-induced hyperpermeability and its relationship to apoptotic signaling. HS was induced in rats by withdrawing blood to reduce the mean arterial pressure to 40 mmHg for 1 h, followed by reperfusion. Mesenteric postcapillary venules were examined for changes in hyperpermeability by intravital microscopy. Mitochondrial release of second mitochondrial derived activator of caspases (smac) and cytochrome c were determined by Western blot and ELISA, respectively. Caspase-3 activity was determined by fluorometric assay. Parallel studies were performed in rat lung microvascular endothelial cell (RLMEC) monolayers, utilizing HS serum and the proapoptotic Bcl-2 homologous antagonist/killer [BAK (BH3)] peptide as inducers of hyperpermeability. In rats, Ang-1 (200 ng/ml) attenuated HS-induced hyperpermeability versus the HS group ( P < 0.05). Ang-1 prevented HS-induced collapse of mitochondrial transmembrane potential (ΔΨm), smac and cytochrome c release, and caspase-3 activity ( P < 0.05). In RLMEC monolayers, HS serum and BAK (BH3) peptide both induced hyperpermeability that was inhibited by Ang-1 ( P < 0.05). Ang-1 attenuated HS and BAK (BH3) peptide-induced collapse of ΔΨm, smac release, cytochrome c release, activation of caspase-3, and vascular hyperpermeability. In vivo, BAK (BH3) induced vascular hyperpermeability that was attenuated by Ang-1 ( P < 0.05). These findings suggest that Ang-1's role in maintaining microvascular endothelial barrier integrity involves the intrinsic apoptotic signaling cascade.

LEUKOCYTE-ENDOTHELIUM INTERACTIONS AFTER HEMORRHAGIC SHOCK/REPERFUSION AND CECAL LIGATION/PUNCTURE

Hemorrhagic shock/reperfusion (HS/R) followed by sepsis triggers systemic microcirculatory disturbances that may induce multiple organ failure. The present study evaluated the effects of HS/R and cecal ligation and puncture, followed by necrotic cecal resection/peritoneal lavage (REL) on leukocyte-endothelium interactions at the mesentery. Eighty-one anesthetized Wistar rats (200-250 g) were randomly assigned to a first injury: (1) control-HS-no hemorrhagic shock/no reperfusion group, (2) HS/blood-HS/R with 25% shed blood, and (3) HS/blood + LR-HS/R with 25% of the shed blood + lactated Ringer's solution, 3x shed blood volume. Twenty-four hours post-HS/R, animals were submitted to cecal ligation and puncture and, 24 h thereafter, to REL. Leukocyte-endothelium interactions were assessed by intravital microscopy and intercellular adhesion molecule (ICAM) 1 and P-selectin expression by immunohistochemistry. Lungs were observed for ICAM-1 expression and neutrophil infiltration. Single and double injury induced significant increases in rolling (approximately 2-fold), adherent (approximately 5-fold), and migrated leukocytes (approximately 7-fold); ICAM-1 expression (approximately 1/2-fold), and P-selectin expression (approximately 1/2-fold) at the mesentery compared with control-HS group. REL normalized leukocyte-endothelium interactions at the mesentery in single-injured animals. However, in double-injured rats, adherence and migration of leukocytes decreased but did not normalize. Similar results were observed on ICAM-1 expression and neutrophil infiltration in the lungs from these animals. In conclusion, the current in vivo observation of the mesenteric microcirculation after a double injury followed by REL is a suitable model for the systematic evaluation of the inflammatory reaction at local and distant sites. In addition, data presented herein emphasized the importance of surgical removal of the septic focus in controlling the otherwise lethal sepsis-induced multiple organ dysfunction syndrome.

INTRAVENOUS ANESTHESIA INHIBITS LEUKOCYTE-ENDOTHELIAL INTERACTIONS AND EXPRESSION OF CD11B AFTER HEMORRHAGE

Hemorrhage increases adhesion of leukocytes to the venular endothelium, mediated by increased expression of the Mac-1 integrin complex (CD18/CD11b) present on leukocytes. Anesthetic agents may possess anti-inflammatory properties. Hence, this study determined the effects of i.v. anesthesia on leukocyte adhesion after hemorrhage in relation to expression of CD11b.

METHODS

Male Wistar rats were (n = 57) anesthetized i.v. with propofol (Diprivan) and fentanyl, ketamine, or thiopental. During anesthesia, 10% of total blood volume was removed and intravital microscopy used to observe the rat mesentery and measure leukocyte (neutrophils) rolling and adhesion in postcapillary venules (15 - 25 microm). Flow cytometry was also used to determine CD11b expression on neutrophils from blood removed at the end of these experiments (n = 25) or blood incubated with anesthetic agents and activated with platelet activating factor ex vivo (0.1 micromol/L) (n = 24).

RESULTS

Hemorrhage increased leukocyte adhesion (stationary count per 150 microm) in rats anesthetized with thiopental (baseline, 3.4 +/- 1.2; hemorrhage, 6.7 +/- 2.0; P < 0.05) but not in those receiving either ketamine (baseline, 3.6 +/- 1.3; hemorrhage, 3.3 +/- 1.3) or propofol/fentanyl (baseline, 6.2 +/- 2.0; hemorrhage, 5.8 +/- 0.8). Neutrophils collected from thiopental-treated rats had elevated CD11b expression with thiopental (mean fluorescence baseline, 67.5 +/- 1.3; hemorrhage, 83.6 +/- 5.3; P < 0.05) but not with propofol/fentanyl (mean fluorescence baseline, 69.1 +/- 1.3; hemorrhage, 65.9 +/- 1.6), and ketamine-treated rats (mean fluorescence baseline, 74.3 +/- 2.1; hemorrhage, 74.8 +/- 1.1). Ketamine also inhibited upregulation of CD11b with platelet activating factor ex vivo.

CONCLUSIONS

After hemorrhage, leukocyte adhesion and CD11b expression increased during thiopental anesthesia, but propofol/fentanyl and ketamine protected against hemorrhage-induced leukocyte adhesion. The anti-inflammatory effect of ketamine was mediated by direct inhibition of CD11b expression on leukocytes.

Hydroxyethyl starch inhibits neutrophil adhesion and transendothelial migration

A resuscitation strategy that significantly alters the state of neutrophil (PMN) activation may impact organ function and survivability after shock. Various resuscitative fluids have been shown to elicit a severe immune activation and an upregulation of cellular injury markers, whereas other fluids have been shown to be protective. Recent studies have demonstrated that hydroxyethyl starch (HES), an artificial colloid, may exert significant anti-inflammatory effects, whereas conflicting studies with the same substance have shown an increase in PMN activation. Successful manipulation of the early immune events associated with hemorrhage and resuscitation will require a better understanding of the possible pro- or anti-inflammatory effects of resuscitation fluids. Our study investigated the effect of HES directly on PMN and cultured vascular endothelial cells in vitro. The effect of HES on PMN surface expression of CD11b and L-selectin was measured by flow cytometry. PMN activation response to HES was measured using a shape-change assay in response to formyl-methionyl-leucyl-phenylalanine (f-MLP). The effect of HES on endothelial cell surface expression of E-selectin, P-selectin, vascular cell adhesion molecule-1(VCAM-1), and intracellular adhesion molecule-1 (ICAM-1) was evaluated by enzyme-linked immunoabsorbant assay. PMN rolling, adhesion, and migration events were measured using direct microscopy under conditions simulating microvascular flow. PMN surface expression of CD11b and L-selectin in whole blood samples and isolated PMNs were unaffected by exposure to HES. HES had no effect on the normal f-MLP dose-dependent increase in PMN activation. In the absence of IL-1 stimulation, there was a small but statistically significant (P < 0.05) increase in ICAM-1 after exposure to HES. After stimulation with IL-1 (10 U/mL), HES had no effect on the expression of P-selectin, E-selectin, ICAM-1, or VCAM-1. Under simulated microvascular flow conditions in vitro, HES significantly diminished the PMN tethering rate (P < 0.05) and the transendothelial migration rate (P < 0.05) in a dose-dependent manner. HES significantly alters the function of the PMN at the interface of the PMN responding to activated endothelium. The effect occurs, surprisingly, without a coincident effect on the state of PMN activation or a significant change in the surface expression of the adhesion molecules responsible for PMN-endothelial interaction.

Extracellular pressure stimulates colon cancer cell adhesion in vitro and to surgical wounds by Src (sarcoma protein) activation

BACKGROUND

We hypothesized that pressure stimulates colon cancer cell adhesion to surgical wounds.

METHODS

We quantitated adhesion of murine 26/51 transplantable colon cancer cells by cell counting or chromium 51-labeling. Tumor cells were added to murine surgical wounds after 30 minutes preincubation under ambient or 15 mm Hg increased pressure. Src activation was assayed by immunoblotting for phosphorylated Src and inhibited by 4-amino-5-(4chlorophenyl)-7-(t-butyl)pyrazolo-[3-4-d]pyrimidine (PP2).

RESULTS

Pressure stimulated colon 26/51 cell adhesion to murine wounds by 43% to 52% (n = 9, P <0.05 each). Pressure stimulated Src phosphorylation by 39% +/- 4% (n = 5, P = 0.004) in colon 26 cells. The Src inhibitor PP2 (20 mumol/L) did not inhibit Src phosphorylation at ambient pressure but prevented pressure stimulation of Src phosphorylation. Src blockade by PP2 did not affect basal adhesion of either tumor to murine wounds but completely blocked pressure stimulation of adhesion (n = 4, P <0.001 each).

CONCLUSIONS

Increased pressure may activate cancer adhesion to surgical wounds via Src. Src antagonists might inhibit this process.

Influence of ionic and non-ionic radiographic contrast media on leukocyte adhesion molecules

BACKGROUND: Many papers have focused on the importance of granulocytes in the process of reperfusion and ischemia. Most of the clinical studies measured several parameters of this process during and after coronary angiography, without taking into account the effect of the radiographic contrast media (RCM) used during this procedure. MATERIALS AND METHODS: We performed a randomized patient study (n = 37) to evaluate the effect of ionic and non-ionic RCM on granulocyte adhesion during coronary angiography. We also evaluated the influence of the ionicity and osmolarity of the different substances on granulocyte adhesion molecules in in vitro experiments. RESULTS: The osmolarity of patient serum samples increased from 302 +/- 1 to 309 +/- 1 mOsm/kg (p < 0.05) after infusion of RCM. The CD11b expression in the samples of the non-ionic RCM treated group increased from 221 +/- 21 MFI to 377 +/- 30 MFI (p < 0.05) measured as the absolute mean fluorescence intensity (MFI), yet did not alter significantly in the ionic RCM group. In contrast, the in vitro experiments showed a reduction of the CD11b expression from 360 +/- 70 MFI to 149 +/- 30 MFI (p < 0.05) in the ionic RCM group. CONCLUSIONS: The upregulation of adhesion molecules was significantly reduced in vivo with ionic RCM, while ionic substances caused opposite effects in vitro. This effect should be taken into account when performing leukocyte functional analysis of samples taken during angiography.

Heme-oxygenase-1 mRNA expression affects hemorrhagic shock-induced leukocyte adherence

BACKGROUND

Hemorrhagic shock-related leukocyte adherence to endothelial cells is a key step in microvascular injury-related organ damage. Heme-oxygenase-1 (HO-1) metabolizes heme, a potent cytotoxic agent, to carbon monoxide and biliverdin. We hypothesized that changing HO-1 expression would change leukocyte adherence after hemorrhagic shock.

METHODS

Rats were administered hemin, zinc protoporphyrin, or vehicle 6 hours before surgery. HO-1 expression was determined by reverse-transcriptase polymerase chain reaction in various tissues. Shock was induced in urethane-anesthetized animals by decreasing mean arterial blood pressure to 40 mm Hg for 60 minutes, followed by standard resuscitation measures. Leukocyte adherence was measured by intravital microscopy in rat mesenteric venules.

RESULTS

Hemin, hemorrhagic shock, and the combination resulted in significantly increased HO-1 expression, whereas zinc-protoporphyrin (ZNPP) resulted in significantly decreased leukocyte adherence. After hemorrhagic shock and hemin administration, leukocyte adherence was significantly decreased 60 minutes into resuscitation (7.92 +/- 2.29 vs. 4.84 +/- 0.71 cells/100 microm, p < 0.05) and significantly increased after ZNPP plus shock (14.08 +/- 3.95, p <or= 0.01).

CONCLUSION

The results demonstrate that hemin increases and ZNPP decreases HO-1 mRNA expression and attenuates hemorrhagic shock-induced leukocyte adherence, whereas ZNPP decreases it. These results suggest that by changing HO-1 expression, leukocyte adherence resulting from oxidant injury may be altered.

In vivo visualization of reactive oxidants and leukocyte-endothelial adherence following hemorrhagic shock

The generation of oxygen radicals during leukocyte-endothelial cell interaction is considered to represent one of the fundamental steps of microvascular injury following ischemia and reperfusion. Indirect evidence also suggests that this relationship may be important following hemorrhagic shock. The purpose of this study was to characterize the temporal changes of reactive oxygen species (ROS) in the mesenteric microvascular endothelium, in vivo, as a consequence of hemorrhagic shock and reperfusion, and to correlate this ROS production to leukocyte adherence. Following a control period, blood was withdrawn to reduce the mean arterial pressure to 40 mmHg for 1 h in urethane-anesthetized rats. Mesenteric venules in a transilluminated segment of small intestine were examined to quantitate changes in ROS generation and leukocyte adherence. Sprague-Dawley rats were injected with dihydrorhodamine 123, a hydroperoxide-sensitive fluorescent probe that is trapped within viable cells as a nonfluorescent form and then converted to the mitochondrion-selective form rhodamine 123 by hydroperoxides. The fluorescent light emission from rhodamine 123 was recorded with digital microscopy and downloaded to a computerized image analysis program. Our results demonstrated an 80% increase in ROS generation beginning within 5 min into resuscitation and a 10-fold increase in leukocyte adherence that occurred at 10 min after resuscitation. Both ROS generation and leukocyte adherence were attenuated with pre-shock administration of platelet activating factor (PAF) antagonist, WEB 2086, and the CD11/CD18a antibody, anti-LFA-1beta. Our findings suggest that ROS production in endothelial cells is increased during reperfusion following hemorrhagic shock and that the mechanism of expression is mediated in part by both PAF expression and subsequent leukocyte adherence.

Reoxygenating microvascular endothelium exhibits temporal dissociation of NF-kappaB and AP-1 activation

Alterations of cellular redox balance in microvascular endothelium results in changes of essential cell functions. These alterations may arise, in part, due to modifications in the pattern of gene expression produced by transcription factor activation. Endothelium subjected to hypoxia/reoxygenation becomes redox imbalanced, thereby leading to activation and perhaps production of a proinflammatory state. A human dermal microvascular endothelial cell line (HMEC-1) was exposed to 6 h of hypoxia (3% O(2)) followed by return to normoxia atmospheric conditions. Reactive oxygen species (ROS) generation (dichlorofluoroscein epifluorescence) was immediate and significant following reoxygenation. Electrophoretic mobility shift assays revealed activation of the oxidant sensitive transcription factors NFkappaB and AP-1, though importantly, peak activation of each factor was separated temporally by greater than 60 min. NFkappaB activation occurred without degradation of the inhibitory protein IkappaBalpha. Reoxygenating HMEC-1 exhibited a greater than 500-fold increase in polymorphonuclear neutrophil (PMN) adhesion when compared to normoxic controls. Exposure of reoxygenating HMEC-1 to the antioxidant pyrrolidine dithiocarbamate produced complete abrogation of NFkappaB activation and the intensive PMN adhesion observed in untreated, posthypoxic HMEC-1. Though rexoygenation stress induced significant upregulation of PMN adhesion, no upregulation of interleukin-8 production was observed. Our results suggest that ROS generation occurring in endothelium following onset of reoxygenation stress signals activation of key transcription factors and that their activation takes place in a temporal fashion. The temporal feature of transcription factor activation may be key to production of a postischemic proinflammatory state.

Effect of WEB 2086 on leukocyte adherence in response to hemorrhagic shock in rats

BACKGROUND

The pathogenesis of generalized microvascular injury after hemorrhagic shock is known to involve the generation of platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine [PAF]). The release of PAF is manifested in several ways, including by increased vascular permeability, altered vascular reactivity, and increased leukocyte adherence to the endothelium. WEB 2086 is a PAF antagonist that has been shown experimentally to improve survival after hemorrhagic shock. The purpose of this study was to examine the efficacy of WEB 2086 in attenuating leukocyte adherence before, during, and after hemorrhagic shock.

METHODS

After a control period, blood was withdrawn to reduce the mean arterial pressure to 40 mm Hg for 30 minutes in urethane-anesthetized rats. Mesenteric venules in a transilluminated segment of the small bowel were examined to quantitate leukocyte adherence using intravital microscopy.

RESULTS

In sham-operated rats (control), there was minimal to no leukocyte adherence throughout the experiment. Hemorrhagic shock resulted in a significant increase in leukocyte adherence postshock during resuscitation (10.9 +/- 1.8 cells/100 microm, p < 0.01) when compared with controls. WEB 2086, when given before shock, significantly attenuated leukocyte adherence (0.1 +/- 0.08 cells/100 microm, p < 0.01) when compared with hemorrhagic shock alone. This effect of WEB 2086 on adherence could be demonstrated even when it was given during (3.5 +/- 0.9 cells/100 microm, p < 0.01) and 10 minutes into (5.8 +/- 1.1 cells/100 microm, p < 0.05) hemorrhagic shock.

CONCLUSION

Our findings suggest that WEB 2086 may be of therapeutic benefit against the microvascular damage sustained after hemorrhagic shock.

The local effect of PAF on leukocyte adherence to small bowel mesenteric venules following intra-abdominal contamination

We have previously demonstrated that intra-abdominal contamination increases neutrophil infiltration into the gastrointestinal tract. The purpose of our current study was twofold: 1) to determine if leukocyte adherence to the mesenteric microvasculature occurred by local peritoneal contamination or by systemic mechanisms; and 2) to assess the role of platelet activation factor (PAF) in this process. Rats underwent cecal ligation and puncture (CLP), and 4 h after the procedure we used intravital microscopy to visualize the mesenteric microcirculation. Cecal ligation and puncture increased leukocyte adherence (22.3+/-5.5 leukocytes/100 microm) vs. sham (2.3+/-0.9, P < 0.05). WEB-2086, a PAF receptor antagonist, prevented this increase (6.47+/-4.8, P < 0.05). To assess if leukocyte adherence was due to topical effects, we performed similar experiments with the small bowel exteriorized. In such cases, CLP did not increase leukocyte adherence (1.2+/-0.8 vs. 1.4+/-0.9). In addition, topical application of highly diluted fecal matter (1:1000) increased leukocyte adherence (4.8+/-1.2) vs. control (0.6+/-0.3, P < 0.05). Our study demonstrates that leukocyte adherence in the mesenteric microcirculation following intra-abdominal contamination is due to direct topical exposure to fecal matter, and it is mediated by PAF.

Protection against hemorrhagic shock in mice genetically deficient in poly(ADP-ribose)polymerase

Hemorrhagic shock (HS) and resuscitation leads to widespread production of oxidant species. Activation of the enzyme poly(ADP-ribose) polymerase (PARP) has been shown to contribute to cell necrosis and organ failure in various disease conditions associated with oxidative stress. We tested the hypothesis whether PARP activation plays a role in the multiple organ dysfunction complicating HS and resuscitation in a murine model of HS and resuscitation by using mice genetically deficient in PARP (PARP(-/-)) and their wild-type littermates (PARP(+/+)). Animals were bled to a mean blood pressure of 45 mmHg (1 mmHg = 133 Pa) and resuscitated after 45 min with isotonic saline (2x volume of shed blood). There was a massive activation of PARP, detected by poly(ADP-ribose) immunohistochemistry, which localized to the areas of the most severe intestinal injury, i.e., the necrotic epithelial cells at the tip of the intestinal villi, and colocalized with tyrosine nitration, an index of peroxynitrite generation. Intestinal PARP activation resulted in gut hyperpermeability, which developed in PARP(+/+) but not PARP(-/-) mice. PARP(-/-) mice were also protected from the rapid decrease in blood pressure after resuscitation and showed an increased survival time, as well as reduced lung neutrophil sequestration. The beneficial effects of PARP suppression were not related to a modulation of the NO pathway nor to a modulation of signaling through IL-6, which similarly increased in both PARP(+/+) and PARP(-/-) mice exposed to HS. We propose that PARP activation and associated cell injury (necrosis) plays a crucial role in the intestinal injury, cardiovascular failure, and multiple organ damage associated with resuscitated HS.