Purification and characterization of beta-methylaspartase from Fusobacterium varium

Beta-methylaspartase (EC 4.3.1.2) was purified 20-fold in 35% yield from Fusobacterium varium, an obligate anaerobe. The purification steps included heat treatment, fractional precipitation with ammonium sulfate and ethanol, gel filtration, and ion exchange chromatography on DEAE-Sepharose. The enzyme is dimeric, consisting of two identical 46 kDa subunits, and requires Mg2+ (Km = 0.27+/-0.01 mM) and K+ (Km = 3.3+/-0.8 mM) for maximum activity. Beta-methylaspartase-catalyzed addition of ammonia to mesaconate yielded two diastereomeric amino acids, identified by HPLC as (2S,3S)-3-methylaspartate (major product) and (2S,3R)-3-methylaspartate (minor product). Optimal activity for the deamination of (2S,3S)-3-methylaspartate (Km = 0.51+/-0.04 mM) was observed at pH 9.7. The N-terminal protein sequence (30 residues) of the F. varium enzyme is 83% identical to the corresponding sequence of the clostridial enzyme.

Endochondral ossification of costal cartilage is arrested after chondrocytes have reached hypertrophic stage of late differentiation

Late cartilage differentiation during endochondral bone formation is a multistep process. Chondrocytes transit through a differentiation cascade under the direction of environmental signals that either stimulate or repress progression from one step to the next. In human costal cartilage, chondrocytes reach very advanced stages of late differentiation and express collagen X. However, remodeling of the tissue into bone is strongly repressed. The second hypertrophy marker, alkaline phosphatase, is not expressed before puberty. Upon sexual maturity, both alkaline phosphatase and collagen X activity levels are increased and slow ossification takes place. Thus, the expression of the two hypertrophy markers is widely separated in time in costal cartilage. Progression of endochondral ossification in this tissue beyond the stage of hypertrophic cartilage appears to be associated with the expression of alkaline phosphatase activity. Costal chondrocytes in culture are stimulated by parathyroid hormone in a PTH/PTHrP receptor-mediated manner to express the fully differentiated hypertrophic phenotype. In addition, the hormone stimulates hypertrophic development even more powerfully through its carboxyterminal domain, presumably by interaction with receptors distinct from PTH/PTHrP receptors. Therefore, PTH can support late cartilage differentiation at very advanced stages, whereas the same signal negatively controls the process at earlier stages.

Mitochondria recycle nitrite back to the bioregulator nitric monoxide

Nitric monoxide (NO) exerts a great variety of physiological functions. L-Arginine supplies amino groups which are transformed to NO in various NO-synthase-active isoenzyme complexes. NO-synthesis is stimulated under various conditions increasing the tissue of stable NO-metabolites. The major oxidation product found is nitrite. Elevated nitrite levels were reported to exist in a variety of diseases including HIV, reperfusion injury and hypovolemic shock. Denitrifying bacteria such as Paracoccus denitrificans have a membrane bound set of cytochromes (cyt cd1, cyt bc) which were shown to be involved in nitrite reduction activities. Mammalian mitochondria have similar cytochromes which form part of the respiratory chain. Like in bacteria quinols are used as reductants of these types of cytochromes. The observation of one-e- divergence from this redox-couple to external dioxygen made us to study whether this site of the respiratory chain may also recycle nitrite back to its bioactive form NO. Thus, the aim of the present study was therefore to confirm the existence of a reductive pathway which reestablishes the existence of the bioregulator NO from its main metabolite NO2-. Our results show that respiring mitochondria readily reduce added nitrite to NO which was made visible by nitrosylation of deoxyhemoglobin. The adduct gives characteristic triplet-ESR-signals. Using inhibitors of the respiratory chain for chemical sequestration of respiratory segments we were able to identify the site where nitrite is reduced. The results confirm the ubiquinone/cyt be1 couple as the reductant site where nitrite is recycled. The high affinity of NO to the heme-iron of cytochrome oxidase will result in an impairment of mitochondrial energy-production. "Nitrite tolerance" of angina pectoris patients using NO-donors may be explained in that way.

Periosteally derived osteoblast-like cells differentiate into chondrocytes in suspension culture in agarose

Pluripotent cells from the periosteal layer adjacent to cortical bone attain an osteoblast-like phenotype in culture when reaching confluence in monolayer. It is unknown whether such newly differentiated osteoblast-like cells preserve the chondrogenic potential characteristics for stem cells derived from the periosteum. Primary osteoprogenitor cells derived from bovine metacarpal periosteum were differentiated into alkaline phosphatase-positive osteoblast-like cells by an established monolayer culture protocol. After transfer into suspension culture in agarose gels, the cells differentiated into chondrocytes demonstrated by the production of collagen II, but not of collagen I, as well as alkaline phosphatase activity was abated. Contrarily, with continuation of monolayer culture, the cells maintained their osteoblast-like phenotype and secreted large amounts of collagen I and a minor quantity of collagen III and V. The alkaline phosphatase activity steadily increased during the entire culture period of 2 weeks. Thus, our culture techniques can serve as useful tools to study mechanisms of differentiation by modulating the phenotypic potential of osteogenic cells. The results presented here support the notion that the extracellular environment strongly influences the cell type and its metabolism.

Protection against endotoxemia in rats by a novel tetrahydrobiopterin analogue

We studied the effects of a novel pterin antagonist of NO synthase, the 4-amino analogue of tetrahydrobiopterin (4-ABH4), in a rat model of endotoxic shock and compared its properties with those of N(G)-monomethyl L-arginine (L-NMMA). Treatment with a bolus dose of 4-ABH4 at 2 h after LPS challenge significantly improved the 6-day survival rate, compared with the controls treated with saline. L-NMMA treatment did not significantly influence the survival rate. This bolus treatment, using either compound, had no effect on the plasma nitrite + nitrate or plasma IL-6 levels. The continuous infusion of 4-ABH4 efficiently suppressed the enhanced calcium-dependent/independent NO synthase activities induced by endotoxin in lung homogenates and completely suppressed the increase in plasma nitrite + nitrate caused by endotoxin at 5 h, with no significant difference compared with the L- NMMA treatment. Treatment of RAW264.7 murine macrophages with 4-ABH4 but not with L-NMMA suppressed endotoxin-induced tumor necrosis factor-alpha release by the cells, whereas nitrite in the supernatant decreased in a dose-dependent fashion in both assay systems. Our data show that 4-ABH4, an inhibitor of inducible NO synthase, significantly improves survival in a rat model of endotoxic shock when administered in a bolus dose that does not reduce plasma total nitrite + nitrate levels. Because we observed no overt signs of toxicity and no influence on organ-specific tetrahydrobiopterin levels, we conclude that the novel compound 4-ABH4 is a promising drug candidate for protection against endotoxin-related mortality.

The inflammatory basis of trauma/shock-associated multiple organ failure

Multiple alterations in inflammatory and immunologic function have been demonstrated in clinical and experimental situations after trauma and hemorrhage, in particular the activation of various humoral (e.g. complement, coagulation) and cellular systems (neutrophils, endothelial cells, macrophages). As a consequence of this activation process there is synthesis, expression and release of numerous mediators (toxic oxygen species, proteolytic enzymes, adherence molecules, cytokines), which may produce a generalized inflammation and tissue damage in the body. Mediators are responsible for ongoing interactions of different cell types and for amplification effects through their networks and feedback cycles, finally leading to a sustained inflammation and multiple organ damage in the body. In the setting of trauma/shock, many activators including bacterial as well as non-bacterial factors may be present that will induce local and systemic inflammatory responses. Although the potential role of bacteria/endotoxin translocation and its clinical relevance remains controversial, many lines of evidence support the concept that the gut may be the reservoir for systemic sepsis and subsequent MOF in a number of pathophysiologic states.

[Transfusion of plasma of endotoxin tolerant rats improves survival of hemorrhagic shock in the rat model]

To evaluate the protective effect of endotoxin tolerant plasma after hemorrhagic shock, plasma of endotoxin tolerant animals was used for resuscitation of normal rats. The transfusion of plasma of endotoxin tolerant rats improved the survival rate from 20 to 60 per cent. In the sera of endotoxin tolerant animals a TNF inhibitory activity was detected, which could be transferred by the plasma. This effect may be responsible for the protection to hemorrhagic shock.

[Endotoxin tolerance and hemorrhagic shock in rats]

The aim of the presents study was to investigate the protective capacity of endotoxin tolerance in a hemorrhagic shock model in rats. A pretreatment with low dose endotoxin induces a state of tolerance, which is characterized by decreased TNF alpha production in vivo and in vitro upon subsequent high dose endotoxin challenge. This endotoxin tolerance improves survival after hemorrhagic shock from 22.8% in untreated controls to 68.8 in tolerant rats. The protection was accompanied with the appearance of n TNF alpha inhibitory activity in the serum of endotoxin tolerant animals, which might be responsible for the improved survival after hemorrhagic shock.

Monoclonal antibody to endotoxin attenuates hemorrhage-induced lung injury and mortality in rats

OBJECTIVES

To determine the possible role of enteric bacteria-derived endotoxin in the pathogenesis of the lung injury and mortality in rats following hemorrhagic shock and resuscitation.

DESIGN

Prospective, randomized study.

SETTING

Animal laboratory of an institute for research traumatology.

SUBJECTS

Male Sprague-Dawley rats, weighing 450 to 480 g.

INTERVENTIONS

Anesthetized rats were subjected to a prolonged hemorrhagic shock (mean arterial pressure of 30 to 35 mm Hg for 180 mins) followed by resuscitation. A murine monoclonal antibody to lipopolysaccharide from Escherichia coli and Salmonella, WN1 222-5, was administered at a total dose of 5 mg/kg i.v., starting at the onset of shock (WN1 group). The control group was treated similarly to the WN1 group but received saline at the same volume as WN1 222-5.

MEASUREMENTS AND MAIN RESULTS

The 48-hr mortality rate was significantly reduced by WN1 222-5 treatment (28.6% in the treatment group vs. 78.6% in the control group; p = .0169). The characteristic lung injury in this model was significantly reduced in the WN1 group, as assessed by microscopic histopathologic examination increase in lung wet weight (7.60 +/- 0.47 g/kg in the control group vs. 5.14 +/- 0.31 g/kg in the WN1 group; p = .0002), and pulmonary neutrophilic infiltration (myeloperoxidase activity: 1835 +/- 567 mU/g wet weight in the control group vs. 891 +/- 212 mU/g wet weight in the WN1 group).

CONCLUSIONS

These data suggest that a) endotoxin derived from enteric bacteria might play an important role in the pathogenesis of lung injury; and b) antiendotoxin agents, such as WN1 222-5, appear to protect against endogenous bacterial endotoxin-related disorders in severe hemorrhagic shock in rats.

IL-6 release after intestinal ischemia/reperfusion in rats is under partial control of TNF

Although there is much evidence to substantiate the view that tumor necrosis factor (TNF) plays a pivotal role in the pathogenesis of multiple organ injury subsequent to intestinal ischemia/reperfusion (I/R), it is still unclear whether TNF is involved in triggering the release of other inflammatory mediators in this condition. The current study was designed to determine the potential effects of TNF blockade, by means of monoclonal antibody (TNF MoAb) treatment, on plasma interleukin 6 (IL-6) in rats after acute intestinal I/R injury. Anesthetized rats underwent 75-min occlusion of superior mesenteric artery followed by 6 hr of reperfusion. The animals were treated with TNF MoAb or control protein at a dose of 20 mg/kg i.v. 30 min before the onset of I/R. Similar IL-6 responses in both the portal and the systemic circulation were observed in animals subjected to intestinal I/R, who showed a progressive increase in plasma IL-6 concentration upon release of the clamp. In animals receiving TNF MoAb before I/R, the subsequent IL-6 release following reperfusion was significantly blunted compared to the levels in controls (P < 0.05). The present study demonstrates that the activation and/or release of IL-6 in the setting of acute gut I/R may, at least in part, be mediated via TNF-dependent mechanisms, providing further evidence that a complex interaction exists between TNF and IL-6.

Significance of TNF in hemorrhage-related hemodynamic alterations, organ injury, and mortality in rats

To evaluate the role of tumor necrosis factor-alpha (TNF-alpha) in hemodynamic alterations, multiple organ damage, and mortality caused by hemorrhagic shock, we employed a monoclonal antibody to TNF-alpha (TNF-alpha MAb) in anesthetized rats subjected to prolonged hemorrhagic shock (mean arterial pressure of 30-35 mmHg for 180 min) followed by resuscitation over 50 min. Treatment of rats with 20.0 mg/kg TNF-alpha MAb 15 min after the end of resuscitation significantly decreased the total peripheral resistance index (P = 0.031) and provided remarkable protection from multiple organ damage compared with controls. The 48-h survival rate was significantly higher in the treatment group (73.3%) than in the control group (26.7%; P = 0.029). The results suggest that TNF-alpha induced by hemorrhagic shock in rats is an important mediator of pathophysiological alterations associated with cardiovascular abnormalities, multiple organ injury, and even lethality. Postresuscitation treatment with TNF-alpha MAb, even after an initial TNF-alpha formation had occurred, significantly attenuated the cardiovascular consequences and improved the survival rate. Thus monoclonal antibodies to TNF-alpha might provide new prospects in the treatment of hemorrhage-related disorders.

[Effects of amniotic fluid embolism-like plasma on isolated perfused rabbit lungs]

OBJECTIVE

In order to investigate whether amniotic fluid could induce the release of mediators from blood cells which would damage the lungs, an isolated perfused rabbit lung (IPRL) was exposed to amniotic fluid embolism-like plasma (AFEP) and the injury of AFEP to lungs and the protective effects of ibuprofen were studied.

METHODS

10 ml human amniotic fluid and 50 ml heparized rabbit blood were incubated together with or without ibuprofen (600 micrograms) at 37 degrees C for 30 min and centrifuged. Supernatants were taken and were referred to as AFEP or ibuprofen AFEP. IPRL was perfused with AFEP, ibuprofen AFEP, simple amniotic fluid (SAF), supernatant of amniotic fluid (SnAF), rabbit plasma (RP) and control NS. The changes of pulmonary artery pressure (PAP), respiratory pressure (RP) and lung weight were recorded by computer and compared with control NS group.

RESULTS

In groups of SAF, SnAF and RP PAPs were slightly elevated (0.13-0.6 kPa, P > 0.05), and lung weights were not changed. AFEP induced the increase of PAP (3.52 +/- 0.64 kPa, P < 0.05) and lung weight (4.0 +/- 1.0 g, P < 0.01) with the development of lung edema. Administration of ibuprofen prevented partially the APEP-induced increase of PAP (1.87 +/- 0.43 kPa, P < 0.05) and lung weight (0.4 +/- 0.3 g, P < 0.01).

CONCLUSION

Amniotic fluid may induce the release of mediators from blood cells, and the latter is the important cause resulting in the pathological changes of lungs in amniotic fluid embolism. Ibuprofen may reduce partially the APEP-induced lung injury.

Differential effects of parathyroid hormone fragments on collagen gene expression in chondrocytes

The effect of parathyroid hormone (PTH) in vivo after secretion by the parathyroid gland is mediated by bioactive fragments of the molecule. To elucidate their possible role in the regulation of cartilage matrix metabolism, the influence of the amino-terminal (NH2-terminal), the central, and the carboxyl-terminal (COOH-terminal) portion of the PTH on collagen gene expression was studied in a serum free cell culture system of fetal bovine and human chondrocytes. Expression of alpha1 (I), alpha1 (II), alpha1 (III), and alpha1 (X) mRNA was investigated by in situ hybridization and quantified by Northern blot analysis. NH2-terminal and mid-regional fragments containing a core sequence between amino acid residues 28-34 of PTH induced a significant rise in alpha1 (II) mRNA in proliferating chondrocytes. In addition, the COOH-terminal portion (aa 52-84) of the PTH molecule was shown to exert a stimulatory effect on alpha1 (II) and alpha1 (X) mRNA expression in chondrocytes from the hypertrophic zone of bovine epiphyseal cartilage. PTH peptides harboring either the functional domain in the central or COOH-terminal region of PTH can induce cAMP independent Ca2+ signaling in different subsets of chondrocytes as assessed by microfluorometry of Fura-2/AM loaded cells. These results support the hypothesis that different hormonal effects of PTH on cartilage matrix metabolism are exerted by distinct effector domains and depend on the differentiation stage of the target cell.

Evaluation of a soluble E-selectin enzyme-linked immunosorbent assay under posttraumatic conditions

The up-regulation of E-selectin, one of the adhesion molecules on the endothelium, is an important event in the mediation of the inflammatory response. Because the presence of E-selectin cannot be determined directly in vivo except by invasive biopsy techniques, the only available information concerning its activity is the serum level of the soluble form. Therefore we tried to measure soluble E-selectin levels in trauma and sepsis situations, where endothelial activation is supposed to occur. We have investigated the soluble E-selectin levels in a group of patients undergoing the trauma associated with cardiac surgery and the use of extracorporeal circulation, some of whom developed a systemic inflammatory response syndrome (SIRS). We have also confirmed that our enzyme-linked immunosorbent assay (ELISA) will detect the levels of soluble E-selectin that are produced as a result of the exposure of cultured human umbilical endothelial cells to even low levels of endotoxin. The data presented in this paper indicate that in patients with SIRS after extracorporeal circulation, the levels of circulating soluble E-selectin are numerically higher but---at least in this group of patients---not statistically significantly different from the levels in patients who have undergone the surgery. These results suggest that the measurement of serum levels of soluble E-selectin is not a reliable method for monitoring the onset of SIRS in patients having undergone surgical trauma, although we have confirmed that our ELISA will detect the levels of soluble E-selectin that are produced as a result of the exposure of cultured human endothelial cells to even low levels of endotoxin.

Endogenous modulators of TNF and IL-1 response are under partial control of TNF in baboon bacteremia

Tumor necrosis factor (TNF) and interleukin (IL)-1 are two cytokines for which naturally occurring inhibitors have been identified. The present study was undertaken to evaluate the extent to which scavenging of TNF in bacteremia attenuates the plasma levels of IL-1 receptor antagonist (IL-1ra) and soluble TNF receptors (sTNFR). Ten male baboons received 2 x 10(9) colony-forming units/kg live Escherichia coli over 2 h and were subjected to either placebo or anti-TNF antibody (anti-TNF Ab) treatment (1 mg/kg CDP571, Celltech, UK) 2 h before E. coli infusion (observation time: 72h). IL-1ra (range: 50-100 ng/ml) and sTNFR (range: 55kDa, 20-25 ng/ml; 75 kDa, 30-35 ng/ml) release was more sustained than that of IL-1 and TNF and was significantly attenuated by anti-TNF treatment, as were the circulating levels of IL-1, IL-8, and monocyte chemotactic peptide-1 (MCP-1) in the anti-TNF Ab group. We conclude that the increase in circulating natural cytokine modulators observed in nonhuman primate bacteremia is under the partial control of endogenous TNF because it was influenced by anti-TNF pretreatment. This attenuation is comparable to the anti-TNF effect on the chemokine MCP-1.

Early detection of anastomotic leaks after colorectal surgery by measuring endotoxin in the drainage fluid

BACKGROUND/AIMS

Early detection of anastomotic leaks after colorectal anastomosis is essential for adequate intervention to prevent peritonitis. We investigated whether the measurement of endotoxin (LPS) concentrations in the drainage has any value for the early detection of anastomotic leaks.

MATERIALS AND METHODS

Twenty two patients with colorectal anastomosis were enrolled in this study, 3 developed clinically established signs of anastomotic leaks and 19 recovered without complications. LPS concentrations in the drainage, the total daily excreted LPS amounts, leukocyte and thrombocyte counts, plasma urea and creatinine, and body temperature were measured for up to 8 days after surgery and tested for their value to detect anastomotic leaks.

RESULTS

LPS concentrations in the drainage fluid and daily excreted LPS amounts of patients with anastomotic leaks were significantly higher compared to the group without anastomotic leaks. On the third postoperative day, LPS concentrations ranged from 5270 to 6750 pg/ml in patients with anastomotic leaks and from 1 to 1848 pg/ml in patients without complications. Total daily excreted LPS amounts were 270-675 ng/day in patients with anastomotic leak and 0-92 ng/day in patients without anastomotic leaks. Both LPS-related parameters allowed reliable detection of anastomotic leaks on day 3 after surgery (Student's t-Test, p < 0.0005), while leukocyte and thrombocyte counts, plasma urea and creatinine, and body temperatures of both patient groups were not significantly different at any time (p > 0.05).

CONCLUSION

We found that the measurement of LPS concentrations in the drainage and the daily excreted LPS amount could be valuable parameters for the early detection of anastomotic leaks as early as on the third post-operative day.

Comparison of endothelial activation during endotoxic and posttraumatic conditions by serum analysis of soluble E-selectin in nonhuman primates

Because the presence of E-selectin, which is one of the adhesion molecules on the endothelium, cannot be determined directly in vivo except by invasive biopsy techniques, the only available kinetic information concerning its activity is the serum level of the soluble form. Therefore we tried to measure soluble E-selectin levels and compare the degree of endothelial activation in a trauma and endotoxic situation, where endothelial activation is supposed to occur. To perform these studies, an enzyme-linked immunosorbent assay with two monoclonal antibodies was set up and used in (1) a model of endotoxic shock in baboons (n = 8) (1.5 mg/kg Escherichia coli endotoxin as a 10-minute intravenous infusion), (2) a hemorrhagic traumatic shock model in baboons (n = 6), where trauma was simulated by infusion of zymosan-activated serum and hemorrhage. Soluble E-selectin was released in vivo after the application of endotoxin, and it reached a peak level after 24 hours (13.82 +/- 5.38 ng/ml). In baboons with hemorrhagic shock, much lower levels (5.03 +/- 1.98 ng/ml) of soluble E-selectin were found. A lower soluble E-selectin level indicates a lower level of endothelial activation after experimental hemorrhagic traumatic shock (with endotoxin translocation from the gut) as compared with endotoxic shock probably caused by much lower endotoxin levels in traumatic shock.

Monoclonal antibody to tumor necrosis factor-alpha attenuates hemodynamic dysfunction secondary to intestinal ischemia/reperfusion in rats

OBJECTIVE

To evaluate the effects of monoclonal antibody to tumor necrosis factor (TNF)-alpha on the hemodynamic alterations and survival rate in rats subjected to intestinal ischemia/reperfusion.

DESIGN

Prospective, randomized study.

SETTING

Animal laboratory of an institute for research in traumatology.

SUBJECTS

Male Sprague-Dawley rats, weighing 430 to 460 g.

INTERVENTIONS

Anesthetized rats underwent 75 mins of superior mesenteric artery occlusion followed by 6 hrs of reperfusion. The animals were treated intravenously with either TNF-alpha monoclonal antibody (TN3, 20 mg/kg) or the control protein (albumin, 20 mg/kg) 30 mins before the onset of ischemia.

MEASUREMENTS AND MAIN RESULTS

Pretreatment with TNF-alpha monoclonal antibody significantly attenuated the decreases in blood pressure and cardiac index (p < .01) compared with controls, for < or = 6 hrs after reperfusion. Stroke volume remained stable in the TNF-alpha monoclonal antibody-treated group and was significantly higher than in the control group at 0.5, 5, and 6 hrs after reperfusion (p < .05 at 0.5 and 5 hrs and p < .01 at 6 hrs). No differences in vascular resistance index values were observed between the two groups at any point in time (p > .05). After intestinal ischemia/reperfusion injury, both the portal and systemic TNF concentrations in the control animals were completely neutralized by TNF-alpha monoclonal antibody treatment. The 72-hr survival rate was significantly (p < .01) better in the treatment group (90%, 9/10) than in the control group (20%, 2/10).

CONCLUSIONS

These results suggest that intestinal ischemia/reperfusion injury can lead to increased TNF release into both the portal and the systemic circulation, which may be an important factor contributing to the development of hemodynamic dysfunction. Pretreatment with TNF-alpha monoclonal antibody significantly attenuates the cardiovascular consequences and improves the survival rate after acute intestinal ischemia/reperfusion injury.

Systemic inflammatory response syndrome after cardiac operations

BACKGROUND

A systemic inflammatory response after open heart operation may be responsible for hyperdynamic circulatory instability and organ dysfunction. To what extent mediator release is involved needs to be clarified.

METHODS

Ten patients with postoperative hyperdynamic circulatory dysregulation (group I) requiring application of alpha-constrictors and 10 patients with routine cardiac procedures and stable postoperative hemodynamic indices (group II) were analyzed for mediator release and metabolic and hemodynamic changes until the third postoperative day.

RESULTS

Group I patients showed a significantly increased cardiac index and decreased systemic vascular resistance after bypass (cardiac index, group I: 5.2 +/- 1.2 L.min-1.m-2, group II: 2.5 +/- 1.6 L.min-1.m-2; systemic vascular resistance, group I: 495 +/- 204 dyne.s. cm-5, group II: 1,356 +/- 466 dyne.s.cm-5) and at 3 hours (cardiac index, group I: 4.4 +/- 0.8 L.min-1.m-2, group II: 2.9 +/- 0.6 L.min-1.m-2; systemic vascular resistance, group I: 567 +/- 211 dyne.s.cm-5, group II: 1,053 +/- 273 dyne.s.cm-5). Significantly higher serum levels of interleukin-6 were assessed in group I (postbypass, group I: 6,812 +/- 9,293 pg/mL, group II: 295 +/- 303 pg/mL; 3 hours, group I: 3,474 +/- 5,594 pg/mL, group II: 286 +/- 296 pg/mL). Concentrations of elastase, tumor necrosis factor, soluble tumor necrosis factor receptor, and interleukin-8 were elevated in group I (not significant). Early postoperative levels of soluble E-selectin and soluble intercellular adhesion molecule were also higher in group I (not significant). Continuously increased levels of endotoxin could be detected in only 3 of 10 patients in group I. Severe lactic acidosis (> or = 5 mmol/L) occurred in group I only.

CONCLUSIONS

Postoperative hyperdynamic instability after open heart operations appears to be associated with a certain pattern of mediator release. In particular, interleukin-6 appears to be involved in circulatory dysregulation and metabolic derangement.

Comparison of the efficacy of pentoxifylline and albifyllin (HWA 138) on endotoxin-induced cytokine production, coagulation disturbances, and mortality

We have evaluated two different xanthine derivatives, pentoxifylline (POF) and albifyllin (HWA), in rat endotoxemia for their ability to reduce 1) cytokine formation, 2) coagulation disturbances, and 3) mortality. The animals were injected with lipopolysaccharide (LPS) (15 mg/kg i.p.) and received HWA or POF (25, 50, or 100 mg/kg) or saline 30 min before LPS administration. The plasma tumor necrosis factor levels were significantly reduced and in a similar manner by pretreatment with HWA or POF in vivo as well as in vitro. Neither the coagulation disturbance nor the characteristic leukopenia that follow an LPS challenge were significantly influenced by the xanthine derivatives. At a dose of 100 mg/kg, the 6 day mortality was significantly reduced by HWA to 36% but only attenuated by POF to 55% as compared to 80% in the control group. The similar effect of both agents on cytokine formation and coagulation disturbances indicate that, at least to a substantial degree, other mechanisms may account for the significant protection of rats against endotoxin-induced mortality by HWA only. HWA 138 may, therefore, be a new powerful agent against endotoxin-related disorders and mortality.

Animal models as the basis of pharmacologic intervention in trauma and sepsis patients

With limited resources and the current concerns about using animals for research purposes, the needs must be clear when setting up trauma and sepsis experiments for pharmacologic interventions. Such interventions are performed typically for four reasons: (1) to study the pathophysiologic role of certain mediators (which can be influenced by pharmacologic agents); (2) to study the therapeutic efficacy of treatment strategies; (3) to study the overall safety of new drugs under trauma/sepsis conditions, which are adjunct studies to standard toxicology; (4) to test new diagnostic procedures in a defined trauma or sepsis setting. Intervention in the inflammatory response may be performed at several levels: (1) at the primary induction site (e.g., by antilipopolysaccharide or by preventing complement activation); (2) at the intermediate mediator level (e.g., by antitumor necrosis factor); (3) at the final mediator level (e.g. , by block of polymorphonuclear neutrophil elastase, and (4) at the target (e.g., by membrane stabilization or enhanced antioxidant defense).

Significance of NO in hemorrhage-induced hemodynamic alterations, organ injury, and mortality in rats

In an attempt to evaluate the role of nitric oxide (NO) in pathophysiological alterations and multiple organ damage caused by hemorrhagic shock, we employed NG-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthase, in anesthetized rats subjected to a prolonged hypovolemic insult (30-35 mmHg for 180 min). Infusion of 2.0 mg/kg L-NMMA at the end of resuscitation diminished the fall in mean arterial pressure (MAP) and significantly increased the cardiac index and stroke volume, together with remarkable protection from multiple organ damage compared with the controls. The 48-h survival rate was significantly improved from 26.7% in the control group to 68.8% in the treatment group (P < 0.05). In contrast, the high dose of 20.0 mg/kg L-NMMA resulted in a strong blood pressure response, but a marked reduction in cardiac index and stroke volume concomitant with an increased total peripheral resistance index within the observation period, and tended to increase damage to various organs at 2 h after treatment. In addition, marked elevation in both endotoxin and tumor necrosis factor levels were observed in animals subjected to shock insult. The results suggest that NO induced by hemorrhagic shock in rats is an important mediator for pathophysiological alterations associated with cardiovascular abnormalities, multiple organ dysfunction, and even lethality. Regulation of NO generation and use of NO inhibitors might provide new aspects in the treatment of hemorrhage-related disorders, whereas the administration of L-NMMA would be either deleterious or salutary in a dose-dependent manner.