Biomedical subjects

Da-Zhong Xu

Publications and source records attributed to Da-Zhong Xu.

At least 19 recordsLinked to original sources

PubMed2006

Amiloride moderates increased gut permeability and diminishes mesenteric lymph-mediated priming of neutrophils in trauma/hemorrhagic shock.

BACKGROUND: Amiloride, an inhibitor of Na+/H+ exchangers and Na+ channels has been shown recently to ameliorate both gut and lung injury in rats subjected to a combined insult of trauma and hemorrhagic shock (T/HS). We have shown previously that mesenteric lymph duct ligation prevents T/HS-induced lung endothelial injury and neutrophil activation, suggesting that toxic inflammatory factors originating from the gut and carried in the lymph are responsible for the lung injury observed after T/HS. This study investigates whether the protective effect of amiloride against T/HS-induced lung injury was associated with decreased lymph toxicity and gut permeability. METHODS: Male rats subjected to trauma (laparotomy) plus hemorrhagic shock (mean arterial pressure, 30 mm Hgx90 min) (T/HS) or trauma plus sham shock (T/SS) and treated with amiloride or its vehicle had their mesenteric lymph duct catheterized. Mesenteric lymph collected before and after shock was assayed for biologic activity on endothelial cells (cytotoxicity and permeability) and neutrophils (respiratory burst activity). Gut permeability was assessed by monitoring plasma concentrations of the fluorescent dye FITC-dextran after its injection into the ileum. RESULTS: Amiloride administration reduced the capacity of post-shock mesenteric lymph to prime neutrophils for an increased respiratory burst. Amiloride failed to decrease the ability of mesenteric lymph to kill endothelial cells or increase their permeability. Amiloride decreased gut permeability. CONCLUSIONS: The mechanisms of the lung protective effect of amiloride in rats undergoing T/HS may be secondary to decreased neutrophil activation, diminished gut permeability, or an effect on the end organ.

Amiloride↗

PubMed2006

Adenosine A2A receptor activation reduces lung injury in trauma/hemorrhagic shock.

OBJECTIVE: Hemorrhagic shock and resuscitation trigger a global ischemia/reperfusion phenomenon, in which various inflammatory processes critically contribute to the ensuing tissue damage. Adenosine is an endogenous nucleoside that is released during shock. Activation of adenosine A(2A) receptors can broadly inactivate inflammatory cascades. The current study was designed to evaluate the effect of A(2A) receptor activation on organ injury and inflammation in the setting of global ischemia/reperfusion elicited by trauma/hemorrhagic shock and resuscitation. DESIGN: Prospective animal study with concurrent control. SETTING: Small animal laboratory. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTIONS: The rats were subjected to a laparotomy (trauma) and 90 mins of hemorrhagic shock or trauma/sham shock. The selective A(2A) receptor agonist CGS-21680 (2-p-(2-carboxyethyl) phenethylamino-5'-N-ethyl-carboxamidoadenosine; 0.5 mg/kg) or its vehicle was injected 30 mins before shock or immediately after resuscitation. At 3 hrs following resuscitation, animals were killed and tissue was harvested for analysis. Lung permeability and pulmonary myeloperoxidase levels were used to quantitate lung injury. Intestinal injury was determined by histologic analysis of terminal ileum. Red blood cell deformability was measured by a laser-assisted ektacytometer. In this assay, a decrease in the elongation index is a marker of decreased red blood cell deformability. MEASUREMENTS AND MAIN RESULTS: Pretreatment with CGS-21680 protected the lung but not the gut against shock-induced injury and prevented the shock-induced decrease in red blood cell deformability. Posttreatment with CGS-21680 ameliorated shock-induced lung injury but failed to prevent gut injury and preserve red blood cell deformability. CONCLUSION: A(2A) receptor agonists may represent a novel therapeutic approach in preventing organ injury following trauma/hemorrhagic shock.

Adenosine↗

PubMed2006

Lymph from a primate baboon trauma hemorrhagic shock model activates human neutrophils.

We have reported that toxic factors in intestinal lymph are responsible for acute lung injury and bone marrow suppression and that they contribute to a systemic inflammatory state based on studies in rodent models of trauma-hemorrhagic shock. Rodent models may not completely reflect the responses of injured patients. Thus, it is important to confirm these findings in primates before applying them to injured human patients with trauma. Thus, we have recently established baboon trauma-hemorrhagic shock (T/HS) and trauma-sham shock (T/SS) models that showed that gut-derived factors carried in the lymph potentiates lung injury and causes human endothelial dysfunction and suppresses human bone marrow progenitor cell growth. Here, we further investigated the effects of these primate lymph samples on human neutrophils. We hypothesized that toxic factors in baboon lymph may prime and/or activate human polymorphonuclear leukocyte (PMN) leading to overproduction of superoxide, thereby contributing to the development of adult respiratory distress syndrome and multiple organ failure. To this effect, we have examined the priming effect of baboon T/HS and T/SS lymph on PMN respiratory burst and expression of adhesion molecule in human neutrophils. The results of these studies indicate that PMN treated with baboon T/HS lymph showed significantly induced respiratory burst responses compared with PMN treated with T/SS lymph or medium when phorbol myristate acetate PMA was applied after lymph pretreatment. Secondly, we found that the expression of CD11b adhesion molecule was increased by incubation with T/HS lymph. These results suggest that baboon lymph from T/HS models can increase respiratory burst and adhesion molecule expression in human PMN, thereby potentially contributing to PMN-mediated organ injury.

Animals↗

PubMed2006

Gut-lymph hypothesis of systemic inflammatory response syndrome/multiple-organ dysfunction syndrome: validating studies in a porcine model.

BACKGROUND: Trauma-hemorrhagic shock (T/HS) mesenteric lymph from rats has multiple biological properties and appears to cause organ injury via the activation of neutrophils and endothelial cells. As the next step in testing the potential clinical relevance of these rodent studies, we utilized a swine T/HS model to determine whether the intestinal lymph results observed in the rodent could be replicated in swine. A porcine model was chosen because the pig and human cardiovascular and gastrointestinal physiology are similar. METHODS: Male pigs were subjected to T/HS and a major intestinal lymph duct was cannulated. Hemorrhagic shock (mean arterial pressure, 40 mm Hg) was performed by withdrawing blood, for 3 hours or until the base deficit reached -5. Animals were then resuscitated in two stages to mimic the prehospital and hospital phases of resuscitation. Mesenteric lymph was collected hourly throughout the experiment and its biological activity was tested on neutrophils (respiratory burst) and endothelial cells (monolayer permeability and cytotoxicity). RESULTS: T/HS lymph but not trauma-sham shock lymph (T/SS) increased neutrophil activation as reflected by an augmented respiratory burst. Likewise T/HS lymph collected at all time points up to 5 hours postshock significantly increased endothelial cell permeability by twofold or greater (p < 0.05), whereas T/HS lymph produced during the first 2 hours postshock was cytotoxic for endothelial cells (viability 70%, p < 0.05 vs. preshock). In contrast, T/SS lymph had no effect on the endothelial cells. CONCLUSION: This large animal model validates rodent studies showing that the shock-injured gut releases biologically active factors into the mesenteric lymph and these factors activate neutrophils and injure endothelial cells.

Animals↗

PubMed2005

Dual effects of mesenteric lymph isolated from rats with burn injury on contractile function in rat ventricular myocytes.

Gut-derived factors in intestinal lymph have been shown to trigger myocardial contractile dysfunction. However, the underlying cellular mechanisms remain unclear. We examined the effects of physiologically relevant concentrations of mesenteric lymph collected from rats with 40% burn injury (burn lymph) on excitation-contraction coupling in rat ventricular myocytes. Burn lymph (0.1-5%), but not control mesenteric lymph from sham-burn animals, induced dual positive and negative inotropic effects depending on the concentrations used. At lower concentrations (<0.5%), burn lymph increased the amplitude of myocyte contraction (1.6 +/- 0.3-fold; n = 12). At higher concentrations (>0.5%), burn lymph initially enhanced myocyte contraction, which was followed by a block of contraction. These effects were partially reversible on washout. The initial positive inotropic effect was associated with a prolongation of action potential duration (measured at 90% repolarization, 2.5 +/- 0.6-fold; n = 10), leading to significant increases in the net Ca2+ influx (1.7 +/- 0.1-fold; n = 8). There were no significant changes in the resting membrane potential. The negative inotropic effect was accompanied by a decrease in the action potential plateau (overshoot decrease by 69 +/- 10%; n = 4) and membrane depolarization. Voltage-clamp experiments revealed that the positive inotropic effects of burn lymph were due to an inhibition of the transient outward K+ currents that prolong action potential duration, and the inhibitory effects were due to a concentration-dependent inhibition of Ca2+ currents that lead to a reduction of action potential plateau. These burn lymph-induced changes in cardiac myocyte Ca2+ handling can contribute to burn-induced contractile dysfunction and ultimately to heart failure.

Action Potentials↗

PubMed2005

Albumin peptide: a molecular marker for trauma/hemorrhagic-shock in rat mesenteric lymph.

Vascular permeability and endothelial cell damage has been shown to occur in rats subjected to trauma with hemorrhagic-shock. Although the factors responsible for the endothelial cell injury are unknown, it has been hypothesized that toxic factors produced in response to hemorrhagic-shock originate in the gut and are absorbed into the mesenteric lymphatics. Consistent with this hypothesis, it has been shown that lymph collected from animals subjected to trauma with hemorrhagic-shock (T/HS) results in a marked decrease in endothelial cell viability both in vitro and in vivo. We therefore compared the lymph collected pre-T/HS to samples collected during, and up to 3h post-T/HS in order to identify a factor present or increased in post-T/HS lymph. This analysis revealed that a single cationic peptide band was significantly increased in post-T/HS lymph, but not in lymph from control animals subjected to trauma without hemorrhagic-shock (T/SS). This peptide was subsequently identified as the N-terminal 24 amino acids of rat serum albumin (RSA) by mass spectrometry and amino acid sequencing. Although the measured increase in the albumin peptide correlates with detectable shock lymph-induced endothelial cell toxicity, the peptide was not toxic to endothelial cells. We therefore propose that the significant increase in the albumin peptide is a marker for post-T/HS lymph-induced endothelial cell toxicity.

Animals↗

PubMed2005

Amiloride combined with small-volume resuscitation with hypertonic saline is superior in ameliorating trauma-hemorrhagic shock-induced lung injury in rats to the administration of either agent alone.

OBJECTIVE: Recognition of the limitations of standard crystalloid resuscitation has led to exploration for alternative resuscitation strategies that might better prevent the development of trauma-hemorrhage-induced organ dysfunction and systemic inflammation. Thus, the goal of this study was to compare the effects of two resuscitation strategies alone and in combination with that of standard resuscitation with Ringer's lactate. These two strategies were intravenous injection of amiloride, an inhibitor of Na/H exchange and epithelial Na channels, and resuscitation with hypertonic saline. DESIGN: Prospective animal study with concurrent control. SETTING: Small animal laboratory. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTIONS: Rats injected with amiloride or its vehicle were subjected to trauma-hemorrhagic shock (T/HS) or trauma sham-shock (T/SS) and resuscitated with Ringer's lactate or hypertonic saline. The T/HS model consisted of a laparotomy plus 90 mins of shock (mean arterial pressure 30 mm Hg). Three hours after the end of the shock or sham-shock period, lung permeability, lung histology, pulmonary neutrophil sequestration, neutrophil CD11b expression, gut injury, and red blood cell rigidification were assessed. MEASUREMENTS AND MAIN RESULTS: Both amiloride and hypertonic saline reduced T/HS-induced pulmonary permeability and neutrophil sequestration, and coadministration of these two agents was more efficacious than administration of the individual agents. In contrast, whereas gut injury was attenuated by both amiloride and hypertonic saline, combined administration of amiloride and hypertonic saline failed to further protect the gut. Additionally, hypertonic saline reduced both neutrophil CD11b expression and red blood cell rigidification, whereas amiloride was without effect. CONCLUSIONS: Combined administration of amiloride and small-volume resuscitation with hypertonic saline may be a strategy worthy of further evaluation in the therapy of shock-induced distant organ injury.

Amiloride↗

PubMed2005

Trauma-hemorrhagic shock mesenteric lymph from rat contains a modified form of albumin that is implicated in endothelial cell toxicity.

It has been proposed that factors originating from the gut after severe trauma/shock are introduced into the systemic circulation through the mesenteric lymphatics and are responsible for the cellular injury and inflammation that culminates in acute multiple organ dysfunction syndrome (MODS). Indeed, it has been shown that lymph collected from shocked but not sham-shocked animals causes endothelial cell death, neutrophil activation, and bone marrow (BM) colony growth suppression in vitro. In an attempt to isolate the factor(s) in lymph responsible for endothelial cell toxicity, lymph from shock and sham animals was fractionated by solid phase extraction (SPE) and ion exchange chromatography (IEX). The separation of shock lymph by both methodologies yielded two fractions having major detectable toxicity to endothelial cells, whereas no toxicity was detected from sham lymph separations by either method. Subsequent analysis of each SPE toxic fraction by gel electrophoresis and mass spectrometry suggests the toxicity is associated with a modified form of rat serum albumin (mod-RSA) and multiple lipid-based factors. Therefore, we have been able to demonstrate by two different separation techniques that shock lymph contains two or more factors that may account for the toxicity to endothelial cells. Further investigations are needed to determine the type of RSA modification and the identity of the lipid factors and their role in MODS.

Albumins↗

PubMed2005

Store-operated calcium channel inhibition attenuates neutrophil function and postshock acute lung injury.

BACKGROUND: A wide variety of neutrophil (PMN) functions are regulated by cytosolic calcium concentration. Calcium channel blockade might therefore decrease postshock inflammation but could also limit important cardiovascular compensations. PMN Ca2+ entry occurs, however, through store-operated calcium entry (SOCE) channels rather than the voltage operated (L-type) channels that regulate cardiovascular tone. We hypothesized that SOCE inhibition might suppress postshock PMN activation, lessening lung injury without compromising cardiovascular performance. METHODS: Human PMNs were treated in vitro with N-propargyl-nitrendipine (MRS1845 [MRS]) a dihydropyridine Ca2+ channel blocker with relative specificity for SOCE channels. Calcium flux was measured by fura fluorescence. Chemotaxis was studied in modified Boyden chambers. Respiratory burst was studied by dihydrorhodamine fluorescence. Exploratory studies were then performed where rats were subjected to trauma and hemorrhagic shock (T/HS) (laparotomy, then hemorrhage to a mean arterial pressure of 30-40 mm Hg for 90 minutes) after pretreatment with MRS or vehicle given intraperitoneally at laparotomy. In vivo PMN CD11b expression was then assayed by flow cytometry and lung injury was assessed as percentage Evans blue dye leak 3 hours after resuscitation. The shed blood volume required to achieve standardized hypotension was measured. RESULTS: In vitro, MRS suppressed human PMN SOCE without affecting calcium store release; it suppressed chemotaxis (60 +/- 6 vs. 150 +/- 15 x 10(3) PMNs/well, p = 0.002) and suppressed respiratory burst (62 +/- 11% vs. 100%, p < 0.05) at IC50 concentrations similar to those needed to suppress SOCE. In subsequent in vivo rat studies, MRS decreased postshock PMN CD11b expression from 397 +/- 93 to 268 +/- 39 MFU mean flourescent units (p < 0.05) and decreased lung Evans blue dye permeability from 8.1 +/- 1.9% to 3.4 +/- 0.1% (p < 0.05). MRS had no noticeable effect on the relationship between blood pressure and blood loss, with shed blood volume remaining almost identical (26 +/- 2 mL/kg vs. 27 +/- 3 mL/kg, p = not significant). CONCLUSION: Modulation of PMN Ca2+ entry by means of selective SOCE channel inhibition attenuates PMN inflammatory responses in vitro. In vivo, SOCE channel blockade attenuates trauma and hemorrhagic shock-induced PMN priming and lung injury without gross evidence of hemodynamic side effects. The relative specificity of SOCE channel blockade for "nonexcitable" cells such as PMNs may make it a valuable form of chemoprophylaxis for the inflammatory consequences of hemorrhagic shock in trauma patients.

Animals↗

PubMed2005

Small volume resuscitation with hypertonic saline is more effective in ameliorating trauma-hemorrhagic shock-induced lung injury, neutrophil activation and red blood cell dysfunction than pancreatitic protease inhibition.

BACKGROUND: Recognition of the limitations of standard crystalloid resuscitation has led to the search for alternative resuscitation strategies that might better limit the development of trauma-hemorrhage-induced organ dysfunction and systemic inflammation. Thus, the goal of this study was to compare the effects of two resuscitation strategies alone, and in combination, with those of standard resuscitation with Ringers lactate (RL). The two strategies were small volume resuscitation with hypertonic saline (HTS) and intraluminal inhibition of pancreatic proteases with the serine protease inhibitor nafamostat. METHODS: Male rats were subjected to trauma-hemorrhagic shock (T/HS) or trauma sham-shock (T/SS) and resuscitated with RL, HTS, nafamostat, or the combination of HTS and nafamostat. The T/HS model consisted of a laparotomy plus 90 minutes of shock (MAP 30 mm Hg). Three hours after the end of the shock or sham-shock period, lung permeability, pulmonary neutrophil sequestration, neutrophil activation, red blood cell deformability, and gut injury were assessed. RESULTS: Both HTS and nafamostat reduced T/HS-induced pulmonary permeability and neutrophil sequestration, as well as neutrophil activation as compared with resuscitation with RL. However, HTS was more effective than nafamostat in reducing T/HS-induced acute lung injury and neutrophil activation. Additionally, HTS, but not nafamostat, reduced T/HS-induced RBC rigidification. Lastly, gut injury after T/HS was reduced to the greatest extent by the combination of HTS plus nafamostat. CONCLUSION: Small volume resuscitation with HTS is more effective than RL and nafamostat in limiting T/HS-induced acute lung injury, neutrophil activation and red blood cell injury.

Animals↗

PubMed2005

Na+,K+-ATPase activity is inhibited in cultured intestinal epithelial cells by endotoxin or nitric oxide.

Na+K+-ATPase is an important enzyme serving vital functions in various mammalian tissues, including the intestine. We have previously documented that endotoxin (LPS) and nitric oxide (NO) can induce enterocyte injury in vitro. To examine whether alterations Na+,K+-ATPase activity might be involved in LPS- or NO-induced enterocyte dysfunction, we carried out four series of experiments. The first set of experiments documented that LPS decreases IEC-6 Na+,K+-ATPase activity at concentrations as low as 0.10 microg/ml. The second set of experiments tested whether exposure of IEC-6 cells to the exogenous NO donor, S-Nitroso-N-acetylpenicillamine (SNAP), would decrease IEC-6 Na+,K+-ATPase activity. The results of these experiments documented that SNAP significantly decreased IEC-6 Na+,K+-ATPase activity in a dose-dependent fashion at a threshold inhibitory concentration of 0.1 mM, and there was an inverse correlation between Na+,K+-ATPase activity and NO concentrations in the medium. Since enterocytes contain iNOS, and LPS can increase iNOS activity, the third set of experiments examined the relationship between LPS-induced inhibition of Na+),K+-ATPase activity and NO production by the IEC-6 cells. These results showed that LPS increased IEC-6 NO production in both a dose- and time-dependent fashion and an inverse correlation existed between LPS-induced NO production and decreased Na+,K+-ATPase activity. Addition of the NOS inhibitor, L-NNA, prevented the LPS-induced decrease in Na+,K+ATPase activity, suggesting that NO is involved in the decrease of Na+,K+-ATPase activity observed in the IEC-6 cells incubated with LPS. One mechanism by which the increased NO concentrations could have contributed to the decrease in Na+,K+ATPase activity, after the addition of LPS or SNAP, is via the production of peroxynitrite during the reaction of NO with superoxide. This notion was supported by studies showing that SNAP- and LPS-induced decreases in IEC-6 Na+,K+-ATPase activity could be blocked by adding superoxide dismutase to the medium. The last set of experiments tested whether the inhibition of Na+,K+-ATPase activity with the specific Na+,K+-ATPase inhibitor ouabain would increase the permeability of an IEC-6 monolayer. IEC-6 monolayer permeability was increased by ouabain, but only at a high concentration. In conclusion, these studies indicate that LPS or the NO donor, SNAP, inhibit Na+,K+-ATPase activity and this inhibition is at least partly related to peroxynitrite production. These studies also suggest that LPS-induced NO production by the IEC-6 cells decreases IEC-6 Na+,K+-ATPase activity in an autocrine fashion.

Animals↗

PubMed2004

The female intestine is more resistant than the male intestine to gut injury and inflammation when subjected to conditions associated with shock states.

Having documented that proestrus female rats are more resistant to shock-induced acute gut and hence lung injury than male rats, we tested the hypothesis that the female gut is more resistant to injury and produces less of an inflammatory response than the male gut when exposed to conditions associated with shock states (hypoxia and acidosis) utilizing the ex vivo Ussing chamber system. Ileal mucosal membranes harvested from normal male and female rats mounted in Ussing chamber systems were exposed to normoxia or 40 min of hypoxia at a normal pH (pH 7.3) or acidosis (pH 6.8). Cytokine and nitric oxide levels in the serosal compartment of the Ussing chamber were measured at the end of the 3-h experimental period to assess the immunoinflammatory response, whereas FITC-dextran (mol wt 4,300) was employed to assess barrier function. Histomorphological changes were used to quantitate gut mucosal injury. Hypoxia, acidosis, or hypoxia plus acidosis was associated with a significant increase in proinflammatory cytokine production [interleukin (IL)-6, tumor necrosis factor, and macrophage inflammatory protein (MIP)-2] by the male compared with the female intestinal segments. In contrast, the female gut manifested a higher anti-inflammatory response (nitric oxide and IL-10) and improved intestinal barrier function as well as less evidence of mucosal injury than the male intestinal segments. Administration of estradiol or the testosterone receptor antagonist, flutamide, to male rats abrogated the increase in gut injury and the increased IL-6 and MIP-2 response observed after hypoxia plus acidosis. These results suggest that gender differences in the ex vivo intestinal response to stresses, such as hypoxia and acidosis, exist and that the administration of estradiol or blockade of the testosterone receptor to male rats mitigates these gender differences.

Acidosis↗

PubMed2004

A study of the biologic activity of trauma-hemorrhagic shock mesenteric lymph over time and the relative role of cytokines.

BACKGROUND: Gut-derived factors in intestinal lymph have been recently shown to cause lung injury, activate neutrophils, and injure endothelial cells in rats subjected to hemorrhagic shock (T/HS). However, the time course of the appearance and disappearance of these factors in intestinal lymph is unclear. Thus the goal of this study was to characterize the biologic activity of T/HS lymph collected at various times during and after shock. METHODS: Male rats subjected to trauma (laparotomy) plus hemorrhagic shock (mean arterial pressure, 90 mm Hg x 90 min) (T/HS) or trauma plus sham shock (T/SS) had their mesenteric lymph duct catheterized. Mesenteric lymph collected before shock, during shock, and hourly for 6 hours after shock was assayed for cytokine levels (tumor necrosis factor, granulocyte-macrophage colony-stimulating factor, interleukin-1, and transforming growth factor-beta) as well as biologic activity on endothelial cells (cytotoxicity and permeability) and neutrophils (CD11b adhesion molecule expression and respiratory burst activity). RESULTS: T/HS, but not T/SS, lymph injured endothelial cells and activated neutrophils, although the cytokine levels did not differ between the T/HS and T/SS lymph samples. The biologic activity of T/HS lymph appeared during the shock (gut ischemic) period. The temporal pattern of activity varied on the basis of the biologic activity being tested, with the neutrophil-activating properties of the T/HS lymph persisting longest. CONCLUSIONS: These results suggest that gut ischemia itself is sufficient to induce the production of biologically active T/HS lymph and that the temporal pattern of biologic activity varies over time on the basis of the property being tested. Consequently, studies directed at identifying the active factors in T/HS lymph must take these temporal patterns of activity into account.

Animals↗

PubMed2004

Female sex hormones protect red blood cells from damage after trauma-hemorrhagic shock.

BACKGROUND: Trauma/hemorrhagic shock (T/HS) is known to cause changes in red blood cell (RBC) deformability and resting shape. Our previous studies have shown that proestrus female rats are more protected from shock-induced RBC damage than diestrus females or males. However, it is unclear whether female or male sex hormones can influence the severity of these alterations. METHODS: Red blood cell deformability and shape were examined in proestrus female rats, and oophorectomized female rats, as well as in castrated and non-castrated male rats (5-10 animals per group) subjected to T/HS. Red blood cell deformability was measured by laser ektacytometry whereas erythrocyte shape was evaluated by scanning electron microscopy. RESULTS: Proestrus female rats subjected to T/HS did not show either significant RBC deformability changes (decrease in elongation index) or shape alterations (increase in the percentage of reversibly and irreversibly changed cells). Oophorectomized rats demonstrated more severe RBC changes than did non-oophorectomized rats. The degree of RBC damage was the same in castrated and non-castrated males, which was significantly worse than in proestrus females. CONCLUSIONS: Removal of female sex hormones increases the severity of T/HS-induced RBC changes, indicating that female sex hormones protect against RBC damage. In contrast, male sex hormones do not appear to modulate T/HS RBC dysfunction.

Analysis of Variance↗

PubMed2004

Trauma-hemorrhagic shock-induced up-regulation of endothelial cell adhesion molecules is blunted by mesenteric lymph duct ligation.

OBJECTIVE: Previous studies have shown that mesenteric lymph duct ligation prevents trauma-hemorrhagic shock-induced lung injury and neutrophil activation. Since endothelial cells rapidly express adhesion molecules, such as P-selectin and intercellular adhesion molecule-1, after shock, and because trauma-hemorrhagic shock-induced lung injury appears to involve neutrophil-endothelial cell interactions, we tested the hypothesis that lymph duct ligation would diminish trauma-hemorrhagic shock-induced P-selectin and intercellular adhesion molecule-1 expression in the lung and other organs. DESIGN: Prospective animal study with concurrent control. SETTING: Small animal laboratory. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTIONS: Four groups of male rats were studied: trauma (laparotomy) plus sham shock, trauma-sham shock plus lymph duct ligation, trauma-hemorrhagic shock (90 mins of shock at 30 mm Hg), and trauma-hemorrhagic shock plus lymph duct ligation. At 3 or 24 hrs after trauma-hemorrhagic shock or trauma-sham shock, lung, heart, liver, kidney, intestinal, and other visceral concentrations of P-selectin and intercellular adhesion molecule-1 expression were measured using the dual radiolabeled monoclonal antibody technique. MEASUREMENTS AND MAIN RESULTS: At 3 and 24 hrs, trauma-hemorrhagic shock increased endothelial cell P-selectin and intercellular adhesion molecule-1 adhesion molecule expression in the lung and liver. At 3 and 24 hrs after trauma-hemorrhagic shock, intercellular adhesion molecule-1 expression was increased in the heart, spleen, pancreas, intestine, and kidney, whereas at 24 hrs, but not 3 hrs, P-selectin expression also was increased in these organs. Lymph duct ligation prevented trauma-hemorrhagic shock-induced increased adhesion molecule expression in all of these organs with the exception of intestinal P-selectin expression. CONCLUSIONS: Trauma-hemorrhagic shock-induced increases in endothelial cell P-selectin and intercellular adhesion molecule-1 expression in the lung and liver as well as other tissues appear to be related to factors liberated from the ischemic gut and carried in intestinal lymph.

Analysis of Variance↗

PubMed2004

Hemorrhagic shock induces endothelial cell apoptosis, which is mediated by factors contained in mesenteric lymph.

OBJECTIVE: Trauma-hemorrhagic shock is one of the leading causes of acute respiratory distress syndrome. This syndrome is associated with disruption of the alveolar barrier consisting of both epithelial and endothelial cells, which leads to a major increase in epithelial and microvascular permeability in the lungs. Although alveolar epithelial cell apoptosis has been documented as a contributing factor to this increase in permeability, it is unclear whether endothelial cell apoptosis occurs following trauma-hemorrhagic shock and, if so, the source of factors leading to this process. DESIGN: Prospective animal study with concurrent control. SETTING: Small-animal laboratory. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTIONS: Trauma-hemorrhagic shock in rats was induced by laparotomy followed by blood withdrawal to achieve a mean arterial blood pressure of 30 mm Hg for 90 mins. At the end of the shock period, the rats were resuscitated, and 3 hrs later lungs were taken for histologic analysis. In other experiments, mesenteric lymph was collected from trauma-hemorrhagic shock and trauma-sham shock rats, and the biological activity of these lymph samples was tested for their ability to kill cultured endothelial cells or endothelial cells of isolated femoral veins. MEASUREMENTS AND MAIN RESULTS: Trauma-hemorrhagic shock triggered endothelial cell apoptosis in the lung as assessed using the Tunnel assay as well as by light and electron microscopic analysis. Since our previous studies have documented that mesenteric lymph is a major contributor to lung injury following shock, we also tested the hypothesis that factors in the mesenteric lymph were responsible for the endothelial cell apoptosis-inducing effect of shock. Preventing the mesenteric lymph from reaching the lung by mesenteric lymph duct ligation decreased endothelial cell apoptosis. Mesenteric lymph obtained from rats subjected to trauma-hemorrhagic shock elicited apoptosis in cultured endothelial cells and when placed into isolated femoral vein as well as increased endothelial cell monolayer permeability. CONCLUSIONS: Trauma-hemorrhagic shock induces endothelial as well as epithelial cell apoptosis in the lung via factors contained in the mesenteric lymph, thereby contributing to the pathophysiology of the acute respiratory distress syndrome.

Animals↗

PubMed2004

The role of lymph factors in lung injury, bone marrow suppression, and endothelial cell dysfunction in a primate model of trauma-hemorrhagic shock.

Studies in rodent models of trauma-hemorrhagic shock (T/HS) have shown that factors contained in the intestinal lymph are responsible for acute lung injury and bone marrow suppression, and that they contribute to a systemic inflammatory state. Because results observed in rodent T/HS models may not fully reflect the response of injured patients, it is necessary to determine if these results can be replicated in primates before the institution of invasive studies in humans. Thus, the three goals of this study were to determine if diversion of thoracic duct lymph reduced T/HS-induced lung injury; to compare the biologic activity of thoracic duct lymph from baboons subjected to T/HS or trauma sham-shock (T/SS); and to compare the biologic activity and composition of plasma from baboons subjected to T/SS, T/HS, and T/HS with thoracic duct lymph drainage. Three groups of baboons were studied: T/SS plus lymph diversion via a thoracic duct catheter, T/HS, and T/HS plus lymph diversion (T/HS-LD). The trauma component consisted of a neck dissection with resection of the proximal clavicle plus a laparotomy. HS was to a mean arterial pressure of 40 mmHg and was maintained at 40 mmHg until the base excess reached -5 mEq or the total shock period reached 3 h. Volume resuscitation was carried out by reinfusing the shed blood plus crystalloids. Before, during, and after the T/HS or T/SS period, blood and lymph samples were obtained for analysis, and lung samples were harvested for measurement of lung wet-to-dry ratio at 5 h after the end of the shock period. Diversion of thoracic duct lymph prevented T/HS-induced lung injury as reflected in lung wet-to-dry weight ratios (T/SS = 4.6 +/- 0.5; T/HS+LD = 4.8 +/- 0.7; T/HS = 5.4 +/- 0.6; P < 0.05). Lymph from the T/HS group collected during the early postshock period was cytotoxic for human endothelial cells (HUVECs; 16% vs. 100% survival in T/SS lymph) and increased HUVEC monolayer permeability almost 2-fold (P < 0.01). T/HS lymph and plasma also suppressed red blood cell (erythroid burst-forming unit) and white blood cell (granulocyte-monocyte colony-forming unit) progenitor cell growth of human bone marrow to approximately 50% of control, whereas T/SS lymph and plasma were not suppressive (P < 0.05). Plasma cytokine levels were increased to a similar degree in the two T/HS groups. Thus, in a primate model of T/HS, gut-derived factors carried in the lymph potentiates lung injury and endothelial dysfunction, and suppresses bone marrow progenitor cell growth.

Animals↗

PubMed2004

Persistent HIF-1alpha activation in gut ischemia/reperfusion injury: potential role of bacteria and lipopolysaccharide.

In both animal models of hemorrhagic shock and clinical settings, shock-induced gut ischemia has been implicated in the development of the systemic inflammatory response syndrome and distant organ injury, yet the factors transducing these events remain to be fully determined. Because hypoxia-inducible factor (HIF-1), a transcription factor composed of oxygen-labile HIF-1alpha and constitutive HIF-1beta subunits, regulates the physiologic/pathophysiologic response to hypoxia and ischemia, we examined the HIF-1 response in two rat models of gut ischemia-reperfusion. We found that ileal nuclear HIF-1alpha protein levels were induced in rats subjected to trauma (laparotomy) plus hemorrhagic shock for 90 min relative to their trauma sham-shock and naïve counterparts and that this trauma hemorrhagic shock-induced mucosal HIF-1alpha protein response persisted after 1 h and 3 h of reperfusion. Likewise, in a model of isolated gut ischemia-reperfusion injury, where the superior mesenteric artery was occluded for 45 min, nuclear HIF-1alpha were induced in the gut mucosa relative to their sham counterparts and persisted after 1 h and 3 h or reperfusion. Similar to the in vivo response, in vitro hypoxia induced HIF-alpha expression in three different enterocyte cell lines (rat IEC-6 and human Caco-2 and HT-29 cell lines). However, in contrast to the in vivo response, HIF-1 expression rapidly disappeared on subsequent reoxygenation. Because in vivo enterocytes are exposed to bacteria, we tested whether the in vitro HIF-1alpha response would persist on reoxygenation if the enterocytes were cocultured with bacteria. P. aeruginosa, an enteric bacterium, markedly induced enterocyte HIF-1alpha protein levels under normoxic conditions. Furthermore, the addition of P. aeruginosa during either the hypoxic or reoxygenation phase prevented the degradation of HIF-1alpha protein levels. Moreover, the observation that lipopolysaccharide induced HIF-1alpha expression in a time-dependent manner in IEC-6 cells indicated that the induction of HIF-1 by exposure to P. aeruginosa is not dependent on bacterial viability. In conclusion, these results suggest that HIF-1alpha activation is an early reperfusion-independent event in models of gut ischemia-reperfusion and that this HIF-1alpha response is potentiated by the presence of P. aeruginosa or lipopolysaccharide.

Animals↗