Induction of c-fos messenger RNA by 3-(N-phenylamino)-1,2-propanediol esters, compounds related to Toxic Oil Syndrome

The Toxic Oil Syndrome (TOS) was a toxic epidemic disease, related to the consumption of rapeseed oil denatured with aniline that affected more than 20,000 people in Spain and resulted in more than 330 deaths after its sudden appearance in 1981. It has been reported that the fatty acid esters of 3-(N-phenylamino)-1,2-propanediol (PAP) have shown a strong association with TOS. These PAP-esters could be absorbed and metabolized in a similar way than phospholipids. This is of interest because some products of phospholipid metabolism are important mediators in downstream pathways involved in the regulation of different nuclear factors. In particular, phospholipase D activity is involved in the activation of c-fos. Thus, we have investigated the effect of different PAP-esters in the induction of c-fos in lung fibroblasts. Results indicate that PAP-esters rapidly induced the expression of c-fos in a dose-dependent manner. In addition, both butanol and propranolol prevent this induction pointing to the involvement of phospholipase D in this activation. These results suggest that deregulation of some nuclear factors such as AP-1 could be involved in the pathogenesis of TOS.

Role of ischemic preconditioning and the portosystemic shunt in the prevention of liver and lung damage after rat liver transplantation

BACKGROUND

This study evaluates whether surgical strategies such as the portosystemic shunt and ischemic preconditioning can protect against hepatic and pulmonary injury associated with liver transplantation.

METHODS

The effect of the portosystemic shunt, ischemic preconditioning, and both surgical procedures together were evaluated in rat liver transplantation. Alanine aminotransferase, hyaluronic acid levels in plasma, adenosine triphosphate and nucleotide levels in liver and edema, malondialdehyde levels, and myeloperoxidase activity were measured 24 hr posttransplantation. Plasmatic tumor necrosis factor (TNF) levels were measured as a possible proinflammatory factor responsible for hepatic and pulmonary damage associated with liver transplantation.

RESULTS

Hepatocyte and cell endothelial damage were observed in liver grafts subjected to 8 hr of cold ischemia. This was associated with increased plasma TNF levels and lung inflammatory response. Portosystemic shunt application in the recipient protected endothelial cells but did not confer an effective protection from hepatocyte damage or reduce the increased plasma TNF levels and lung damage after liver transplantation. However, preconditioning of the donor liver conferred protection against both the endothelial cell and hepatocyte damage observed after liver transplantation. Preconditioning also attenuated the increased plasma TNF release and pulmonary damage. The combination of both surgical strategies resulted in levels of liver injury, TNF, and lung damage similar to those seen after liver transplantation.

CONCLUSIONS

These findings indicate that ischemic preconditioning could be a preferred treatment to reduce hepatic and pulmonary damage associated with liver transplantation. However, this strategy may not be effective in several clinical situations requiring a portosystemic shunt.

Heparin mobilizes xanthine oxidase and induces lung inflammation in acute pancreatitis

OBJECTIVE

To evaluate the effect of low molecular weight heparin on plasma xanthine oxidase concentrations and lung inflammatory response during acute pancreatitis.

DESIGN

Randomized, controlled trial.

SETTING

Experimental laboratory.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

Acute pancreatitis was induced by intraductal administration of 5% sodium taurocholate. Low molecular weight heparin (0, 30, 90, or 300 units/kg) was administered immediately after induction of pancreatitis.

MEASUREMENTS AND MAIN RESULTS

Lipase and xanthine oxidase plasma concentrations were measured 3 hrs after pancreatitis induction. Expression of P-selectin messenger RNA and myeloperoxidase activity as a marker of neutrophil infiltration were determined in the lung. An increase in xanthine oxidase plasma concentrations was observed during pancreatitis. Administration of heparin also increased plasma xanthine oxidase activity in both control and pancreatitis animals. Measures of xanthine oxidase present in the endothelial surface indicate that during pancreatitis, the enzyme is released from the gastrointestinal endothelium. By contrast, heparin mobilizes xanthine oxidase from almost all organs evaluated. Neutrophil infiltration was increased in the lung during pancreatitis. Heparin administration further increased, in a dose-dependent manner, myeloperoxidase activity and P-selectin expression in the lung in animals with pancreatitis. By contrast, in control animals, heparin had no effect on myeloperoxidase activity and did not induce P-selectin up-regulation.

CONCLUSION

During acute pancreatitis, heparin administration might mobilize xanthine oxidase attached to endothelial cells, originating a free radical-generating system in the circulation that would trigger an inflammatory response in the lung.

Adenosine monophosphate-activated protein kinase mediates the protective effects of ischemic preconditioning on hepatic ischemia-reperfusion injury in the rat

Hepatic ischemia-reperfusion (I/R) injury associated with liver transplantation and hepatic resections are an unresolved problem in the clinical practice. Preconditioning is known to preserve energy metabolism in liver during sustained ischemia, but the molecular mechanisms underlying this effect are still unclear. Different metabolic signals, including adenosine monophosphate (AMP) and nitric oxide (NO), have been implicated in preconditioning. AMP-activated protein kinase (AMPK) protects cells by acting as a low-fuel warning system, becoming switched on by adenosine triphosphate (ATP) depletion. NO synthesis is induced by AMPK in the heart during ischemia. The aim of this study was to investigate: 1) whether preconditioning induces AMPK activation; and 2) if AMPK activation leads to ATP preservation and reduced lactate accumulation during prolonged ischemia and its relationship with NO. Preconditioning activated AMPK and concomitantly reduced ATP degradation, lactate accumulation, and hepatic injury. The administration of an AMPK activator, AICAR, before ischemia simulated the benefits of preconditioning on energy metabolism and hepatic injury. The inhibition of AMPK abolished the protective effects of preconditioning. The effect of AMPK on energy metabolism was independent of NO because the inhibition of NO synthesis in the preconditioned group and the administration of the NO donor before ischemia, or to the preconditioned group with previous inhibition of AMPK, had no effect on energy metabolism. Both preconditioning and AICAR pretreatment, through AMPK activation, may be useful surgical and pharmacologic strategies aimed at reducing hepatic I/R injury.

CO2 in static mesenteric venous blood during intestinal ischemia and ischemic preconditioning in rats

During intestinal ischemia, CO2 accumulates in tissue as a result of bicarbonate buffering of anaerobic acid generation. Previous studies have shown that nitric oxide (NO) generated during ischemic preconditioning acts as a glycolytic modulator, thus decreasing tissue lactate production. We studied if ischemic preconditioning induces NO-dependent changes in static mesenteric venous blood Pco2 values and CO2 accumulation during intestinal ischemia. Superior mesenteric venous (smv) acid base variables were studied in 4 groups of rats: a control group (C), an ischemic (90-min period of flow arrest) group (I), an ischemic group subjected to previous ischemic preconditioning (P), and an ischemic group subjected to previous ischemic preconditioning in which nitric oxide synthase (NOS) was inhibited by N-nitro-L-arginine methyl ester (L-NAME) administration (P+N). Preconditioning induced acidosis in smv blood during reperfusion before ischemia, but this effect was counteracted by L-NAME. Group P showed the lowest values of end-ischemic tissue lactate, smv blood CO2 accumulation, and LDH in perfusate, whereas group P+N showed the highest level of LDH in perfusate but the lowest end-ischemic smv blood Pco2 and acidity. We conclude that lower ischemic CO2 accumulation in static smv blood, but not lower end-ischemic Pco2, was related with the protective effect of ischemic preconditioning in our rat model. Thus, the use of stagnant smv blood Pco2 as an indicative of intestinal dysoxia can lead to misinterpretations if a broader acid-base picture is not considered.

Absorption and effects of 3-(N-phenylamino)-1,2-propanediol esters in relation to toxic oil syndrome

Toxic Oil Syndrome (TOS) was an epidemic disease related to the consumption of rapeseed oil denatured with aniline that made its sudden appearance in Spain in 1981. The fatty acid esters of 3-(N-phenylamino)-1,2-propanediol (PAP), which is a chemical class of by-products resulting from the reaction of aniline with oil components, have shown a strong association with TOS-related oils. These compounds also show some structural similarities to platelet-activating factor (PAF). In search of a toxic agent that could explain the widespread systemic effects observed in TOS patients, we investigated the intestinal absorption and biotransformation of the different PAP esters found in TOS-related oil samples and the possible pathophysiological effect of these mediators and their metabolic products if acting as PAF analogs. Results indicate that PAP esters are absorbed in the gastrointestinal tract and are distributed and stored in different organs, particularly in the liver and brown adipose tissue. PAP in these organs showed different patterns of fatty acids, indicating the ability of the gastrointestinal tract to modify the fatty acid composition of the parent PAP. Thus, the fatty acid profile of the PAP esters found in intestine appears to be related to the type of oil used as vehicle. Some of these PAP esters, when a long acyl chain was present in the sn-1 position of the molecule, showed an inhibitory effect on the PAF synthesis. This is an important observation in line with the systemic nature of the disease.

Effects of adenosine on ischaemia-reperfusion injury associated with rat pancreas transplantation

BACKGROUND

During cold preservation, cellular consumption of adenosine triphosphate leads to the accumulation of nucleotides and nucleosides. The precise role of adenosine in modulating the inflammatory response of cold-preserved pancreas after reperfusion remains to be elucidated. The aim of this study was to assess the influence of adenosine on the inflammatory response associated with the process of ischaemia-reperfusion in rat pancreas transplantation.

METHODS

The effect of adenosine from preservation solution on the levels of high-energy nucleotides and their breakdown products after cold ischaemic preservation was determined. In addition, the inflammatory response associated with the process of ischaemia-reperfusion in pancreas transplantation was quantified with and without pretreatment with the adenosine antagonist theophylline, and during preservation of the organ in University of Wisconsin solution with and without adenosine.

RESULTS

Adenosine from preservation solution is able to modify the nucleotide and nucleoside content of preserved pancreas, indicating that adenosine is incorporated and metabolized in tissue. Administration of the adenosine antagonist to transplanted rats moderated the increases in nitrite and nitrate, myeloperoxidase activity and lipoperoxidation levels in the pancreas.

CONCLUSION

Adenosine in the preservation solution may enhance the inflammatory response in rat pancreas transplantation.

Protective effect of ischemic preconditioning on cold preservation and reperfusion injury associated with rat intestinal transplantation

OBJECTIVE

To define the protective effect of ischemic preconditioning on cold ischemia and reperfusion injury associated with intestinal transplantation, and the role of nitric oxide in this process.

SUMMARY BACKGROUND DATA

Ischemia/reperfusion injury continues to be a significant obstacle in small bowel transplantation. Preconditioning is a mechanism that protects against this injury.

METHODS

To study the capacity of preconditioning to prevent cold ischemia-associated injury and the inflammatory response associated with intestinal transplantation, the authors studied a control group of animals, cold ischemia groups with or without previous preconditioning and with or without previous administration of L-NAME or NONOS, and intestinal transplantation groups with or without previous preconditioning and with or without previous administration of L-NAME or NONOS.

RESULTS

Histologic findings and the release of lactate dehydrogenase into the preservation solution showed that preconditioning protects against cold ischemic preservation-associated injury. Preconditioning also prevented the inflammatory response associated with intestinal transplantation, measured by the above parameters and by neutrophil recruitment in the intestine. Inhibition of nitric oxide eliminates the protective effect.

CONCLUSIONS

Preconditioning protects the intestinal grafts from cold preservation and reperfusion injury in the rat intestinal transplantation model. Nitric oxide is involved in this protection.

Soluble receptors released during acute pancreatitis interfere with the detection of tumor necrosis factor-alpha

OBJECTIVE

To evaluate the interfering effect of tumor necrosis factor-alpha soluble receptor when measuring circulating concentrations of tumor necrosis factor-alpha in an experimental model of acute pancreatitis.

DESIGN

Randomized, controlled trial.

SETTING

Experimental laboratory.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

Acute pancreatitis was induced by intraductal administration of 5% sodium taurocholate. Saline was administered in a control group. Serums were overloaded with known amounts of tumor necrosis factor-alpha or macrophage inflammatory protein-2.

MEASUREMENTS AND MAIN RESULTS

Three hours after induction, serum concentrations of free tumor necrosis factor-alpha, total tumor necrosis factor-alpha, and soluble receptor of tumor necrosis factor-alpha were measured. No detectable concentrations of free tumor necrosis factor-alpha were found in any experimental group. By contrast, significant increases in total tumor necrosis factor-alpha and soluble receptor of tumor necrosis factor-alpha were found after induction of pancreatitis. Overloading of serum with tumor necrosis factor-alpha resulted in detection of 50% of the expected concentrations of free tumor necrosis factor-alpha from control animals and only of 5% from the pancreatitis group. Overloading the serum with macrophage inflammatory protein-2 resulted in a detection of 100% of the expected concentrations in both control and treated animals.

CONCLUSION

Circulating soluble receptor of tumor necrosis factor-alpha could interfere with the detection of tumor necrosis factor-alpha in some pathologies, such as pancreatitis, that are associated with increases in soluble receptor of tumor necrosis factor-alpha.

Endogenous nitric oxide and exogenous nitric oxide supplementation in hepatic ischemia-reperfusion injury in the rat

BACKGROUND

Although nitric oxide (NO) is thought to be beneficial in hepatic ischemia-reperfusion (I/R), the mechanisms for this effect are not well established.

METHODS

To investigate the effects of endogenous NO and exogenous NO supplementation on hepatic I/R injury and their pathogenic mechanisms, serum ALT and hyaluronic acid (endothelial cell damage), and hepatic malondialdehyde and H2O2 (oxidative stress), myeloperoxidase activity (leukocyte accumulation), and endothelin (vasoconstrictor peptide opposite to NO) were determined at different reperfusion periods in untreated rats and rats receiving L-NAME, L-NAME+L-arginine, and spermine NONOate (exogenous NO donor).

RESULTS

After reperfusion every parameter increased in untreated animals. Endogenous NO synthesis inhibition by L-NAME increased hepatocyte and endothelial damage as compared to untreated rats, which was reverted and even improved by the addition of L-arginine. Spermine NONOate also improved this damage. However, different mechanisms account for the beneficial effect of endogenous and exogenous NO. Oxidative stress decreased by both L-NAME and L-NAME+L-arginine, but remained unmodified by spermine NONOate. Myeloperoxidase increased by L-NAME and this effect was reverted by the addition of L-arginine, whereas no change was observed with spermine NONOate. Endothelin levels were not modified by L-NAME and L-NAME+L-arginine, but decreased with spermine NONOate.

CONCLUSIONS

These results suggest that, although both endogenous and exogenous NO exert a protective role in experimental hepatic I/R injury, the mechanisms of the beneficial effect of the two sources of NO are different.

Fructose-1,6-biphosphate in rat intestinal preconditioning: involvement of nitric oxide

BACKGROUND AND AIMS

Inhibition of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by nitric oxide (NO) in intestinal preconditioning could modify the rate of formation of glycolytic intermediates. Fructose-1,6-biphosphate (F16BP) is a glycolytic intermediate that protects tissue from ischaemia/reperfusion injury. We evaluated if F16BP may be endogenously accumulated as a consequence of GAPDH inhibition by NO during intestinal preconditioning in rats.

METHODS

We assessed: (1) effect of preconditioning on F16BP content; (2) effect of NO on GAPDH activity before and during sustained ischaemia; and (3) protective effect of F16BP in control, ischaemic, and preconditioned animals with or without administration of N-nitro-L-arginine methyl ester (L-NAME), NO donor, or F16BP.

RESULTS

Preconditioned rats showed a significant transient decrease in GAPDH activity and also maintained basal F16BP levels longer than ischaemic rats. L-NAME administration to preconditioned rats reversed these effects. F16BP administration to ischaemic rats decreased protein release in the perfusate. Administration of F16BP to L-NAME treated rats attenuated the harmful effect of L-NAME.

CONCLUSIONS

Our study indicates that F16BP may be endogenously accumulated in preconditioned rats as a consequence of inhibition of GAPDH by NO, and this may contribute to the protection observed in intestinal preconditioning.

Storage time and deodorization temperature influence the formation of aniline-derived compounds in denatured rapeseed oils

In 1981 an epidemic, named Toxic Oil Syndrome, occurred in Spain as a result of ingestion of rapeseed oil denatured with 2% aniline, which had been imported for industrial use but was fraudulently diverted and processed for human consumption. Two groups of chemical compounds have been identified in the ingested toxic oil: fatty acid anilides and amino-propanediol derivatives. The objective of this work was to assess the effect of several refining process variables on the formation of 3-(N-phenylamino)-1,2-propanediol (PAP) esters. The amount of PAP esters in aniline-denatured oil increased dramatically when oil was heated from 250 degrees C to 300 degrees C. However, the ones formed when 300 degrees C was reached were lost during processing at that temperature. The level maintained during the operation time at 300 degrees C was higher in denatured samples stored for 3 weeks before refining than in denatured samples stored only for 1 week. Anilides were also analyzed. We found that anilides decreased very little with distillation time. In this paper we discuss the influence of storage time prior to refining and of elevated refining temperature, such as temperatures that might occur in close proximity to a deodorizer coil.

Preconditioning protects against systemic disorders associated with hepatic ischemia-reperfusion through blockade of tumor necrosis factor-induced P-selectin up-regulation in the rat

Previous studies indicate that ischemic preconditioning protects against lung injury resulting from hepatic ischemia-reperfusion (I/R) through inhibition of tumor necrosis factor (TNF) release from Kupffer cells. The present study investigated whether this effect is limited to the lung or is a generalized systemic response and explores the molecular mechanisms involved. Hepatic I/R led to an increase in neutrophil accumulation in liver, lung, and splanchnic organs. Although preconditioning did not modify neutrophil infiltration in liver during reperfusion, it conferred protection against hepatic injury associated with I/R. In remote organs, preconditioning abrogated the increase in P-selectin up-regulation, preventing neutrophil infiltration and thus reducing the oxidative stress and microvascular disorders following hepatic I/R in these organs. Administration of Abs against P-selectin or TNF previous to ischemia had the same effects as preconditioning. The effects of preconditioning on the blockade of P-selectin up-regulation probably results from inhibition of systemic TNF release from Kupffer cells. Supplementation of TNF abolished the benefits of preconditioning, whereas the injurious effects of TNF were prevented by previous blockade of P-selectin. The results of the present study suggest that ischemic preconditioning protects the liver against I/R injury by a mechanism independent of adhesion molecule expression and neutrophil accumulation. In remote organs, however, hepatic preconditioning prevents inflammatory damage by reducing the systemic TNF release from the liver and thus preventing P-selectin up-regulation.

Strategies to modulate the deleterious effects of endothelin in hepatic ischemia-reperfusion

BACKGROUND

This study evaluates whether bosentan (endothelin [ET] receptor antagonist) or preconditioning (mechanism that inhibits the postischemic ET release) could reduce the microvascular disorders and the injurious effects of tumor necrosis factor (TNF) associated with hepatic ischemia-reperfusion (I/R).

METHODS

Hepatic I/R was induced in rats and the effects of bosentan or preconditioning on the deleterious effects of ET in hepatic I/R were evaluated. Transaminase and TNF levels in plasma; edema, vascular permeability, lactate, ET, and TNF levels in liver; and edema and myeloperoxidase activity levels in lung were measured after hepatic reperfusion.

RESULTS

The administration of bosentan or the induction of preconditioning previous to I/R attenuated the increase in vascular permeability, edema and lactate levels observed in liver after I/R. However, the addition of ET before preconditioning abolished its benefits. Preconditioning prevented both the increase in hepatic TNF and its release from the liver into the systemic circulation. This resulted in an attenuation of liver and lung damage. Addition of ET or TNF to the preconditioned group abolished the benefits of preconditioning, whereas the previous inhibition of TNF release with GdCl3 in the preconditioned group pretreated with ET did not modify the effects of preconditioning. The inhibition of ET with bosentan prevented the increase of both hepatic and plasma TNF, thus attenuating the liver and lung injury, whereas TNF addition abolished the benefits of bosentan.

CONCLUSIONS

These findings suggest that both bosentan and preconditioning, by inhibition of ET could attenuate the microvascular disorders and the deleterious effect of TNF on the liver and lung elicited by hepatic I/R.

Pancreatitis induces HSP72 in the lung: role of neutrophils and xanthine oxidase

The aim of this work was to evaluate the systemic Hsp72 expression in rat lung and liver in vivo in a model of acute pancreatitis and investigate the possible involvement of xanthine oxidase and neutrophils in this process. Pancreatitis was induced by intraductal administration of 5% sodium taurocholate and samples of lung and liver were obtained 1 and 3 h later. In some groups of rats circulating xanthine oxidase was inhibited with oxypurinol, and neutrophil recruitment was blocked with a monoclonal antibody against P-selectin. Hsp72 expression was assessed by means of Western blot and immunohistochemistry. Results showed Hsp72 induction in lung, but not in liver, shortly after pancreatitis. Hsp72-induced expression was located in bronchial epithelium, alveolar macrophages, infiltrating neutrophils, and blood vessels. Oxypurinol and the antibody against P-selectin prevented pancreatitis-induced lung Hsp72 overexpression suggesting that Hsp72 induction is mediated by neutrophil infiltration into the lungs.

Hepatic preconditioning preserves energy metabolism during sustained ischemia

We evaluated the possibility that ischemic preconditioning could modify hepatic energy metabolism during ischemia. Accordingly, high-energy nucleotides and their degradation products, glycogen and glycolytic intermediates and regulatory metabolites, were compared between preconditioned and nonpreconditioned livers. Preconditioning preserved to a greater extent ATP, adenine nucleotide pool, and adenylate energy charge; the accumulation of adenine nucleosides and bases was much lower in preconditioned livers, thus reflecting slower adenine nucleotide degradation. These effects were associated with a decrease in glycogen depletion and reduced accumulation of hexose 6-phosphates and lactate. 6-Phosphofructo-2-kinase decreased in both groups, reducing the availability of fructose-2, 6-bisphosphate. Preconditioning sustained metabolite concentration at higher levels although this was not correlated with an increased glycolytic rate, suggesting that adenine nucleotides and cAMP may play the main role in the modulation of glycolytic pathway. Preconditioning attenuated the rise in cAMP and limited the accumulation of hexose 6-phosphates and lactate, probably by reducing glycogen depletion. Our results suggest the induction of metabolic arrest and/or associated metabolic downregulation as energetic cost-saving mechanisms that could be induced by preconditioning.

Effect of peritoneal lavage and lymph ligature on systemic complications of experimental acute pancreatitis

We studied the involvement of ascitic fluid on the systemic effects of experimental acute pancreatitis. This has been achieved by comparing the effectiveness of either peritoneal lavage or lymphatic ligature on preventing changes in systemic vascular permeability. Three hours after induction of pancreatitis, we found increases in vascular permeability in the pancreas, lung, and intestine. Both peritoneal lavage and lymphatic ligature were able to prevent the changes observed in the lung and intestine and the increases on plasma levels of lipase and amylase, suggesting a similar involvement for lymphatic draining and peritoneal absorption pathways. In addition, we evaluated the effect of intraperitoneal deposition into health rats of pancreatitis-associated ascitic fluid collected from rats with experimental acute pancreatitis. A significant increase in plasma amylase and lipase levels could be observed but no changes in vascular permeability were found. Altogether, these results indicate that transperitoneal absorption of toxic mediators from the ascitic fluid is not enough to explain the systemic damage induced by acute pancreatitis.

H(2)O(2) and PARS mediate lung P-selectin upregulation in acute pancreatitis

P-selectin and circulating xanthine oxidase are involved in the process of neutrophil infiltration into the lung associated with acute pancreatitis. This study investigated the mediators that trigger the upregulation of P-selectin in this process. Pancreatitis was induced in rats by intraductal administration of 5% sodium taurocholate. P-selectin expression was measured using radiolabeled antibodies. Neutrophil infiltration and PAF levels were also evaluated. The role of superoxide radical, H(2)O(2), or the enzyme poly (ADP-ribose) synthetase (PARS) on these processes was determined in groups of animals treated with the corresponding inhibitors. Pancreatitis was associated with an increase in P-selectin expression in the lung. Inhibition of PARS or H(2)O(2) abrogated P-selectin upregulation, PAF generation, and neutrophil recruitment. Superoxide dismutation prevented neutrophil recruitment and PAF generation, but had no effect on P-selectin expression. We conclude that during acute pancreatitis, upregulation of P-selectin in the pulmonary endothelium is triggered by H(2)O(2) and PARS activity.

Constitutive nuclear factor-kappaB activity in human upper airway tissues and nasal epithelial cells

Respiratory epithelial cells are actively involved in the host defence and inflammatory reactions of the airways. Nuclear factor-kappaB (NF-kappaB) is a transcription factor that plays a pivotal role in many cellular responses to environmental changes. The inducible nitric oxide synthase (iNOS) isoform has been implicated in airway inflammation as well as in normal airway function. In this study, the hypothesis that NF-kappaB may be associated with iNOS expression in airway epithelium, not only in inflammatory processes but also under physiological conditions was examined. NF-kappaB deoxyribonucleic acid-binding activity was assayed by means of electrophoretic mobility shift assay (EMSA) and iNOS expression examined using immunohistochemical techniques in healthy nasal mucosa and chronically inflamed nasal polyps. Further NF-kappaB activity was assayed; by means of EMSA, in nasal epithelial cells isolated from both tissues. NF-kappaB was activated in nasal polyps, but also to the same extent in healthy nasal mucosa. Uniform iNOS expression was localized within the airway epithelium in both inflamed and noninflamed tissues. Along with iNOS expression, concomitant NF-kappaB activation was found in nasal epithelial cells obtained from both tissues and no differences were observed when nasal mucosa and nasal polyp were compared. These results suggest that constitutive nuclear factor-kappaB and concurrent inducible nitric oxide synthase expression in epithelial cells may play a physiological role in airway function.

Role of P-selectin and ICAM-1 in pancreatitis-induced lung inflammation in rats: significance of oxidative stress

OBJECTIVE

To investigate the role of P-selectin and intercellular adhesion molecule-1 (ICAM-1) in the pathogenesis of lung injury associated with pancreatitis, and the relation between xanthine oxidase-derived oxidants and expression of these adhesion molecules.

SUMMARY BACKGROUND DATA

In acute pancreatitis, acute respiratory distress syndrome occurs in the early stages of disease. This process is mediated by neutrophil infiltration.

METHODS

Pancreatitis was induced in rats by intraductal administration of 5% sodium taurocholate. ICAM-1 and P-selectin expression was measured using radiolabeled monoclonal antibodies. Neutrophil infiltration and plasma levels of xanthine oxidase were also evaluated.

RESULTS

Pancreatitis induces increases in P-selectin expression in lung, whereas ICAM-1 is unchanged from baseline levels. Immunoneutralization of either P-selectin or ICAM-1 prevents the infiltration of neutrophils into the lung. Xanthine and xanthine oxidase activity were increased after induction of pancreatitis. Xanthine oxidase inhibition prevents the upregulation of P-selectin in lung and neutrophil infiltration.

CONCLUSIONS

During acute pancreatitis, P-selectin is upregulated in the pulmonary endothelium and is a key determinant of leukocyte recruitment. Constitutive ICAM-1 is also involved in the process of cell infiltration into the lung. The increased expression of P-selectin appears to be triggered by a mechanism dependent on free radicals generated by xanthine oxidase released by the damaged pancreas.

Protective effect of liver ischemic preconditioning on liver and lung injury induced by hepatic ischemia-reperfusion in the rat

This study evaluates whether preconditioning could modulate the injurious effects of tumor necrosis factor (TNF) on liver and lung following hepatic ischemia-reperfusion (I/R) by inhibiting hepatic postischemic TNF release. The inhibition of hepatic TNF release from Kupffer cells with gadolinium chloride (GdCl(3)) previous to ischemia maintained TNF at control levels, attenuating the increases in transaminases, vascular permeability, and edema associated with hepatic I/R injury. TNF addition reverted this beneficial effect, indicating the implication of the TNF released mainly from Kupffer cells in hepatic I/R injury. Preconditioning prevented hepatic TNF increases, thus attenuating the liver injury, while TNF addition abolished the benefits of preconditioning. Inhibition of nitric oxide (NO) synthesis abolished the effect of preconditioning, whereas GdCl(3) addition avoided the injurious effect of NO inhibition. In addition, NO administration before I/R offered similar results to those found in preconditioning, while TNF addition abolished the benefits of NO. Thus, the effect of preconditioning on TNF release after hepatic I/R is mediated by NO. Inhibition of hepatic TNF release from Kupffer cells with GdCl(3) prevented both the increase in plasma TNF and the injurious effect in lung seen after hepatic I/R, and these effects were reverted with TNF addition. Preconditioning resulting in reduced hepatic TNF levels prevented the systemic TNF release, thus reducing the lung damage following hepatic I/R. However, TNF addition abolished the protective effect of preconditioning on lung injury. These findings indicate that preconditioning attenuates hepatic postischemic TNF release from Kupffer cells, thus probably reducing the liver and lung injury following hepatic I/R, and that this effect of preconditioning is mediated by NO.

Protective effect of ozone treatment on the injury associated with hepatic ischemia-reperfusion: antioxidant-prooxidant balance

The effects of ozone treatment on the injury associated to hepatic ischemia-reperfusion (I/R) was evaluated. Ozone treatment (1 mg/kg daily during 10 days by rectal insufflation) is shown to be protective as it attenuated the increases in transaminases (AST, ALT) and lactate levels observed after I/R. I/R leads to a decrease in endogenous antioxidant (SOD and glutathione) and an increase in reactive oxygen species (H2O2) with respect to the control group. However, ozone treatment results in a preservation (glutathione) or increase (SOD) in antioxidant defense and maintains H2O2 at levels comparable to those in the control group. The present study reports a protective effect of ozone treatment on the injury associated to hepatic I/R. The effectiveness of ozone could be related to its action on endogenous antioxidants and prooxidants balance in favour of antioxidants, thus attenuating oxidative stress.

Modification of glyceraldehyde-3-phosphate dehydrogenase in response to nitric oxide in intestinal preconditioning

BACKGROUND

Previous studies have demonstrated that intestinal preconditioning is triggered by an initial increase in nitric oxide synthesis. This confers resistance to the organ in face of a subsequently sustained period of ischemia-reperfusion. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key enzyme in the glycolytic cascade that could be modulated by nitric oxide. The purpose of the present study is to evaluate a possible inhibitory effect on intestinal GAPDH by the nitric oxide generated during preconditioning. This could lead to a reduction of lactate accumulation during subsequent ischemia.

METHODS

GAPDH activity was measured after intestinal preconditioning, and the effect of nitric oxide synthase inhibition was evaluated.

RESULTS

Preconditioning induced a significant, but transient, decrease in GAPDH activity. This effect appears to be correlated with a reduced amount of lactate accumulation during ischemia. Inhibition of nitric oxide synthesis reversed these changes. In addition, increased synthesis of nitric oxide was detected after preconditioning.

CONCLUSIONS

In summary, this study indicates that nitric oxide generated during ischemic preconditioning could act as a glycolytic modulator during subsequent ischemia, through its effect on GAPDH activity.

Activation of alveolar macrophages in lung injury associated with experimental acute pancreatitis is mediated by the liver

OBJECTIVE

To evaluate (1) whether alveolar macrophages are activated as a consequence of acute pancreatitis (AP), (2) the implication of inflammatory factors released by these macrophages in the process of neutrophil migration into the lungs observed in lung injury induced by AP, and (3) the role of the liver in the activation of alveolar macrophages.

SUMMARY BACKGROUND DATA

Acute lung injury is the extrapancreatic complication most frequently associated with death and complications in severe AP. Neutrophil infiltration into the lungs seems to be related to the release of systemic and local mediators. The liver and alveolar macrophages are sources of mediators that have been suggested to participate in the lung damage associated with AP.

METHODS

Pancreatitis was induced in rats by intraductal administration of 5% sodium taurocholate. The inflammatory process in the lung and the activation of alveolar macrophages were investigated in animals with and without portocaval shunting 3 hours after AP induction. Alveolar macrophages were obtained by bronchoalveolar lavage. The generation of nitric oxide, leukotriene B4, tumor necrosis factor-alpha, and MIP-2 by alveolar macrophages and the chemotactic activity of supernatants of cultured macrophages were evaluated.

RESULTS

Pancreatitis was associated with increased infiltration of neutrophils into the lungs 3 hours after induction. This effect was prevented by the portocaval shunt. Alveolar macrophages obtained after induction of pancreatitis generated increased levels of nitric oxide, tumor necrosis factor-alpha, and MIP-2, but not leukotriene B4. In addition, supernatants of these macrophages exhibited a chemotactic activity for neutrophils when instilled into the lungs of unmanipulated animals. All these effects were abolished when portocaval shunting was carried out before induction of pancreatitis.

CONCLUSION

Lung damage induced by experimental AP is associated with alveolar macrophage activation. The liver mediates the alveolar macrophage activation in this experimental model.

The protective role of adenosine in inducing nitric oxide synthesis in rat liver ischemia preconditioning is mediated by activation of adenosine A2 receptors

This study aims to determine if the protective role of adenosine in liver ischemic preconditioning is mediated by the activation of adenosine receptors and to ascertain which of these receptors is implicated in the process. Administration of adenosine A1 and A2 receptor antagonists to preconditioned animals indicates that hepatic preconditioning is mediated by the activation of adenosine A2 receptors. Propentofylline (an inhibitor of adenosine transport into cells) in the preconditioned group, subjected to previous administration of an adenosine A2 receptor antagonist, prevented the negative effect of the latter on the protection offered by preconditioning. An increase of NO production was detected just immediately after hepatic preconditioning, and the administration of an adenosine A2 receptor antagonist to the preconditioning group prevented this increase, thus abolishing the protective effect of preconditioning. However, the administration of a NO donor to the preconditioned group subjected to previous administration of the adenosine A2 receptor antagonist was able to maintain the preconditioning effects. In conclusion, these results indicate that, in preconditioning, the protective effect of adenosine could be a result of an increase in extracellular adenosine. This in turn would induce the activation of adenosine A2 receptors, which, by eliciting an increase in NO generation, would protect against the injury associated with hepatic ischemia-reperfusion.

Free radicals generated by xanthine oxidase mediate pancreatitis-associated organ failure

In the present study we evaluate the possibility that xanthine oxidase released by damaged pancreas could act as a source of oxidative damage in systemic tissues during the early stages of acute pancreatitis. This was accomplished by evaluating the effects of xanthine oxidase inhibition with oxypurinol infused into the portal vein. Under these conditions, we inhibited the enzyme before it reached the liver and other distant organs, without inducing changes in the severity of pancreatic damage. Results indicate that pancreatitis parallels increases in xanthine oxidase activity in plasma. Superoxide radicals generated by this enzyme appears to be involved in the decrease of reduced glutathione levels in the plasma and liver. In addition, xanthine oxidase inhibition prevents the infiltration of neutrophils into the lungs. We conclude that oxygen free radicals generated by xanthine and xanthine oxidase released to the bloodstream are involved in the systemic organ failure associated with acute pancreatitis.

Quantitative peptide bioanalysis using column-switching nano liquid chromatography/mass spectrometry

Many endogenous peptides are circulating in bodily fluids at the low pmol l-1 range, placing high demands on the bioanalytical procedure. In order to analyze these minute concentrations in complex matrices, a miniaturized liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) bioanalysis method was developed using custom-made nanoLC columns (75 microns i.d.) and a micro-electrospray interface (micro ESI). To be able to analyze large sample volumes in order to cope with low biological analyte concentrations, the nanoLC/ESI-MS method was coupled to an on-line preconcentration (PC) system based on a strong anion-exchange material. This method was used to analyze endothelin peptides (ETs) in complex matrices, which are potent vasoconstrictors of M(r) approximately 2500 Da. The ET isoforms could be simultaneously analyzed with detection limits down to 30 pmol l-1 in cell supernatants (1.5 fmol on column). The method was linear from 50 to 2000 pmol l-1 with correlation coefficients of 0.99 for two of the three endothelin isoforms. Several other parameters, such as matrix effects and recovery, were also investigated.

Hepatic preconditioning in rats is defined by a balance of adenosine and xanthine

The present work investigates the relationship between adenosine, nitric oxide (NO), and free radicals during ischemic preconditioning in rat liver. For this purpose, we evaluated: 1) the efficacy of different periods of preconditioning; 2) the changes in the concentration of adenine nucleotides during preconditioning; 3) the importance of adenosine and xanthine concentrations in the induction of preconditioning; and 4) the possible effect of xanthine oxidase-derived superoxide anion on NO during preconditioning. Results show that just a 10- to 15-minute period of ischemia followed by 10-minute reperfusion prevents the ischemic damage that would be induced by a subsequent 90 minutes of ischemia followed by 90 minutes of reperfusion. Administration of xanthine or metabolization of endogenous adenosine abolishes the protective effect of preconditioning. When rats have been subjected to a period of preconditioning not within the effective time window (10-15 minutes), and thus offering no protection, the administration of a NO donor was found to restore the protection. The dose needed to restore protection appears to be proportional to the endogenous xanthine concentration. In addition, when xanthine oxidase was inhibited, preconditioning effectively offered protection in front of ischemia and reperfusion, independently of the xanthine concentration. Altogether, this indicates that the time window of ischemia capable to induce preconditioning in liver is defined by the relative tissue concentrations of adenosine and xanthine. The lower limit of this window (10 minutes) is defined by the amount of adenosine able to induce NO generation. Its upper limit (15 minutes) is defined by the concentration of xanthine able to remove the generated NO.

Quantitative electrospray LC-MS and LC-MS/MS in biomedicine

The use of electrospray LC-MS and LC-MS/MS for the quantitative determination of two low molecular weight (< 500 Da) organic compounds in human plasma (Lovastatin) and cell supernatants (Arachidonic acid) and medium molecular weight (> 2000 Da) endogenous peptides (Endothelins) in supernatants of human umbilical vein endothelial cell cultures is reported. These methods make use either of deuterium labelled or structurally similar molecules as internal standards for quantitation and one or more pre-purification steps previous the LC-MS analysis. Linear calibration curves and detection limits around 50 pg ml(-1) were obtained in all three cases.

Arachidonic acid metabolites in CSF in hypoxic-ischaemic encephalopathy of newborn infants

The aim of this study was to evaluate the cerebral synthesis of eicosanoids in the asphyctic newborn and to investigate the relation between the prostanoid profiles in cerebrospinal fluid (CSF) and the appearance and severity of hypoxic-ischaemic encephalopathy (HIE). Levels of 6-keto-PGF(1-alpha), TXB2, PGE2 and PGF(2-alpha), in CSF were measured in 40 full term newborns during the first day of life. Thirty of these newborns had birth asphyxia and were divided into three groups: 10 without HIE, 12 with mild HIE and 8 with moderate-severe HIE. They were compared to a control group of 10 non-hypoxic newborns. Determinations of the metabolites in CSF were performed by RIA and expressed as pg/ml (mean +/- SD). The CSF TXB2 (thromboxane A2 metabolite) in asphyxiated newborns was always higher than in the control group (28.12 +/- 10.6), and related to the severity of HIE (p = 0.005): without HIE (50.84 +/- 16.4; p = 0.02), mild HIE (80.65 +/- 12.64; p < 0.01) and moderate-severe HIE (178.14 +/- 20.5; p < 0.01). The CSF 6-keto-PGF(1-alpha) (prostacyclin metabolite) in asphyxiated newborns was always higher than in the control group (80.55 +/- 12.56), but indirectly related to the severity of HIE: without HIE (240.95 +/- 28.12; p < 0.01), mild HIE (183.65 +/- 30.1; p < 0.01) and moderate-severe HIE (140.55 +/- 25.12; p < 0.01). In the moderate-severe HIE group, the increase in TXB2 was higher than the rise in 6-keto-PGF(1-alpha).

Leukotriene generation and neutrophil infiltration after experimental acute pancreatitis

The role of 5-lipoxygenase metabolites of arachidonic acid in the inflammatory response associated with experimental acute pancreatitis has been evaluated. For this purpose, an experimental necrohemorrhagic pancreatitis was induced in rats by intraductal administration of 5% sodium taurocholate. Neutrophil infiltration was detected in pancreas at 1 and 3 h after the induction of pancreatitis. This was concomitant with increased levels of leukotriene B4 and peptide leukotrienes (C4, D4 and E4). In lung, similar increases in neutrophil infiltration were detected but only 3 h after acute pancreatitis induction, and no changes in leukotriene B4 nor peptide leukotrienes were apparent at this time. These results suggest that after induction of acute pancreatitis, 5-lipoxygenase metabolites could play a role in the inflammatory response in the pancreas, but they are not involved in the inflammatory response in lung.

Eicosanoid production by placental and amnion tissues from control and non-insulin-dependent diabetic rats. Influence of oxytocin in the incubating medium

Eicosanoid production by intrauterine tissues from control and neonatal-streptozotocin induced diabetic rats during late pregnancy was evaluated. In diabetic placenta the release of 6-keto-PGF1alpha was found diminished when compared to controls. In addition, LTB4 generation was increased in diabetic placenta. No alterations in the production of TXA2, PGE2, PGE1 and PGF2alpha was found when diabetic and control placenta were compared. In amnion tissue a decreased generation of 6-keto-PGF1alpha was observed in the diabetic group, but no alteration in any other eicosanoid evaluated was found. Oxytocin (5 mU/ml, in vitro), which increases prostaglandin synthesis in rabbit and human amnion tissues, did not modify eicosanoid generation in control rat amnion. In contrast, in diabetic amnion the presence of oxytocin further decreased the release of 6-keto-PGF1alpha and diminished PGE1 generation. The present results suggest that this mildly diabetic state induces alterations in eicosanoid production in intrauterine tissues, abnormalities probably enhanced during parturition, when endogenous concentrations of oxytocin are elevated.

Influence of nitric oxide synthase and kinin antagonists on metabolic parameters in chronic streptozotocin-induced diabetes mellitus

In vivo administration of HOE 140 (a new bradykinin receptor antagonist) and L-NAME (nitric oxide synthase inhibitor) was performed in chronic streptozotocin-diabetic rats. Basal increases (in umol.g dw-1) in liver (45.0 +/- 3.4.1) and uterine (40.0 +/- 2.95) triglyceride levels in diabetic animals vs control (liver: 34.0 +/- 3.87; uterus: 30.2 +/- 4.01) were partially prevented by L-NAME (p < 0.01), HOE 140 (p < 0.01) and L-NAME + HOE 140 (p < 0.01). High glycogen levels (in mg.g dw-1) observed in diabetic uterine tissue (3.07 +/- 0.90), and decreased glycogen content detected in diabetic liver (11.64 +/- 1.50) vs. control (uterus: 1.59 +/- 0.15, liver: 17.25 +/- 0.87) were unaffected. Uterine 14CO2 production from 14C-U-Glucose (in uCi.mg dw), which is lower in diabetic (35.0 +/- 5.12) than in control (50.12 +/- 4.54) tissues, was improved by HOE 140 (p < 0.05) and L-NAME+HOE 140 (p < 0.05), while hepatic glucose oxidation was not increased by the drugs. Glycemia levels were decreased in diabetic rats injected with L-NAME and L-NAME plus HOE 140. Pancreatic 6-Keto-prostaglandin F1 alpha to Thromboxane B2 ratio was lower in diabetic animals than in controls, and L-NAME and/or HOE 140 treatment prevented the decrement. These findings suggest that vasoactive compounds might prevent streptozotocin-induced damage in pancreatic tissue from chronic diabetic rats.

Nitric oxide enhances endothelin production in pancreas transplantation

The role of endothelin and its relationship with nitric oxide (NO) production in ischemia-reperfusion associated with pancreas transplantation has been explored. For this purpose, pancreatic levels of endothelin were evaluated in an experimental model of pancreas transplantation after different periods of cold preservation. The effects of NO synthase inhibition were also evaluated. Results show posttransplantation increases in lipase and endothelin production. The release of lipase and endothelin was only prevented by NG-nitro-L-arginine methyl ester after a short ischemic period. Thus, endothelin synthesis could be a consequence of stimulation with NO in the ischemia-reperfusion associated with pancreas transplantation.

Prostanoids and free radicals in Cl4C-induced hepatotoxicity in rats: effect of astilbin

A beneficial effect of flavonoids in Cl(4)C-induced hepatoxicity in rats has been reported. In this communication we have evaluated the protective effect of astilbin, an active flavonoid isolated from a crude extract of Hymenaea martiana, as well as its action on liver arachidonate metabolism in Cl(4)C-treated rats. The following groups of rats were studied: Group I = controls; Group II = Astilbine-treated animals (40 mg/Kg); Group III = Cl(4)C-treated at 1 ml/kg; Group IV = Astilbine + ClC4 and Group V = Vitamine E (50 mg/Kg) + Cl(4)C-treated animals. Histological findings, superoxide dismutase activity, lipoperoxides and prostanoid profiling studies revealed that the hepatoprotective effect of astilbine was higher than that of vitamin E. Astilbine was capable to restore lipoperoxides and tissue prostanoids to basal values.

Protective effect of preconditioning on the injury associated to hepatic ischemia-reperfusion in the rat: role of nitric oxide and adenosine

The effects of ischemic preconditioning on rat liver integrity, as well as the implication of nitric oxide (NO) and adenosine in this process, has been evaluated. Preconditioning before ischemia-reperfusion prevented the increases in alanine transaminase (ALT), aspartate transaminase (AST), and lactate dehydrogenase (LDH) levels, but did not modify blood flow. Adenosine or NO administration previous to hepatic ischemia-reperfusion simulated the effect of preconditioning, whereas inhibition of adenosine or NO synthesis abolished the protective effect of hepatic preconditioning. Nevertheless, inhibition of adenosine and simultaneous administration of NO in preconditioned animals offered similar results to those found in the preconditioned group, indicating that, in the absence of adenosine, NO is able to maintain the preconditioning benefits. It is suggested that, in preconditioning, adenosine stimulates NO production to protect against the injury associated with ischemia-reperfusion.

Free radical enhancement promotes leucocyte recruitment through a PAF and LTB4 dependent mechanism

In the present investigation we studied the concerted role of superoxide anion, platelet activating factor (PAF) and leukotriene B4 (LTB4) in the mechanism that results in polymorphonuclear leucocyte accumulation induced by oxygen free radicals in rat pancreas. This was done by comparing the effects of a PAF antagonist (BN-52021), a LTB4 inhibitor (MK-886) and superoxide dismutase (SOD) in a experimental rat model of inflammation elicited by the oxygen free radicals induced via infusion of xanthine/xanthine oxidase. Also, the effect of independent LTB4 infusion has been studied. The results show that increases in polymorphonuclear cell infiltration (evaluated by tissue histology), myeloperoxidase and LTB4 levels induced in pancreas by infusion of xanthine/xanthine oxidase were abolished by the administration of either the PAF antagonist, the LTB4 inhibitor, or SOD. The fact that BN-52021 could prevent neutrophil recruitment and LTB4 synthesis suggests that PAF is a necessary step for subsequent LTB4 synthesis and polymorphonuclear leucocyte accumulation.

Quantitative analysis of mevinolinic acid in human plasma by high-performance liquid chromatography coupled with negative-ion electrospray tandem mass spectrometry

Mevinolinic acid (MVA), the major active metabolite of Lovastatin in human blood, is analysed by microbore high-performance liquid chromatography coupled to electrospray tandem mass spectrometry. Quantification is carried out by using methylmevinolinic acid (MMVA) as internal standard. Positive- and negative-ion mass spectra of these compounds are shown. Because of the higher sensitivity obtainable, the negative-ion mode is selected for the analysis. Solid-phase extraction cartridges are used off-line to prepurify and concentrate the sample and a microbore (1 x 100 mm) reversed-phase column is used for chromatography. Tandem mass spectrometry is carried out in the precursor-ion mode using a selected-reaction monitoring procedure. The [M-H]- precursor ions for MVA and MMVA are selected in the first quadrupole analyser and the second analyser is focused on the common product ion at m/z 319. Detection and quantification limits are ca. 50 pg/mL and ca. 200 pg/mL respectively. An example of the application of the method to the routine analysis of samples from a bioequivalence study is also shown.

Liver ischemic preconditioning is mediated by the inhibitory action of nitric oxide on endothelin

The concerted involvement of both NO and endothelin in the protective effect of preconditioning against hepatic ischemia-reperfusion induced injury has been evaluated in this study. Thus hepatic ischemia-reperfusion or preconditioning plus ischemia-reperfusion was induced in rats and the effect of nitric oxide administration or inhibition with addition of the endothelin antagonist Bosentan was evaluated. Results show that the increases in plasma GPT release after ischemia-reperfusion were prevented after preconditioning. Inhibition of nitric oxide abolished the effect of preconditioning, addition of the endothelin antagonist abolished the injurious effect of NO inhibition. Also, increased synthesis of endothelin has been detected after ischemia-reperfusion, and addition of NO or preconditioning prevented this increase, suggesting that increases of NO inhibit endothelin synthesis. Altogether this indicates that hepatic preconditioning is mediated by the inhibitory action of nitric oxide on endothelin levels.

Intestinal preconditioning is mediated by a transient increase in nitric oxide

The effect of ischemic preconditioning on the intestine, as well the implantation of nitric oxide and prostacyclin in this process has been evaluated. Thus, intestinal ischemia-reperfusion was induced in rats, and the protection conferred by previous preconditioning was evaluated. In addition, the effect of nitric oxide inhibition and the administration of nitric oxide were determined. Results show that the increases observed in LDH release after ischemia-reperfusion were prevented after preconditioning. Inhibition of nitric oxide synthesis abolished the protective effect of preconditioning, and nitric oxide administration replicated this effect. Also, an increased synthesis of nitric oxide has been detected after preconditioning. Increases in 6 keto PGF1 alpha were independent of nitric oxide. Altogether indicates that preconditioning is triggered by an initial increase in nitric oxide synthesis.

Differential activity of nitric oxide synthase in human nasal mucosa and polyps

Nitric oxide (NO) plays an important regulatory role in airway function and seems to be implicated in the pathophysiology of several airway diseases. To better understand the involvement of NO in the upper airways, we examined the presence of nitric oxide synthase (NOS) activity in human nasal mucosa and nasal polyp tissues. Nasal mucosa was obtained from seven patients undergoing septoplasty, and nasal polyps came from nine patients following polypectomy. NOS activity was quantified in tissue homogenates using the citrulline release assay and localized in tissue sections using reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry. The results showed that nasal polyps (n = 9) contained higher levels of total NOS activity (mean +/- SD 5.94 +/- 5.71, range 1.29-18.0 pmol.min-1.mg protein) than nasal mucosa tissues (n = 7) (0.28 +/- 0.22, range 0.01-0.57 pmol.min-1.mg protein). In addition, nasal polyps mainly contained inducible NOS activity (4.67 +/- 4.57, range 1.23-15.5 pmol.min-1.mg protein) whereas in nasal mucosa all NOS activity detected was in constitutive form. In both cases, NOS activity was localized in the epithelial cells. Since NO synthase is induced in inflamed upper airways, we conclude that NO may be an important inflammatory mediator in the respiratory system and that the epithelium may be a source of NO production in the human upper airways.

Nitric oxide enhances 12-HETE versus LTB4 generation in pancreatic transplantation

The role of nitric oxide in lipoxygenase metabolism after a process of ischemia-reperfusion in pancreas transplantation has been evaluated in this study. Sprague-Dawley rats were randomized into three groups, as follows: Group I--Control animals not surgically manipulated; Group II.--Pancreas transplantation, after 12 h of organ preservation; Group III.--Same as II but with administration of NG-nitro-L-arginine methyl esther (a nitric oxide synthase inhibitor) (10 mg/Kg) prior to organ revascularization. The results show post-transplantation increases in leukotriene B4 and 12-hydroxyeicosatraenoic acid levels in pancreatic tissue. Nitric oxide synthase inhibition reversed the increases in 12-hydroxyeicosatetraenoic acid, but was unable to modify leukotriene B4 increases suggesting the existence of a direct effect of nitric oxide on the 12-lipoxygenase metabolism in pancreas transplantation.

Hepatic involvement in pancreatitis-induced lung damage

The role of liver in the respiratory dysfunction associated with acute pancreatitis has been evaluated. For this purpose, an experimental necrohemorrhagic pancreatitis was induced in rats by intraductal administration of 3.5% sodium taurocholate. Additionally, a portocaval shunt was performed before induction of acute pancreatitis to prevent the initial passage through the liver of substances released by the pancreas. Twelve hours after the induction of pancreatitis, increases in lung prostacyclin and thromboxane B2 synthesis, decreased lung superoxide dismutase activity, and increases in plasma phospholipase A2 activity were found. In addition, inflammatory injury was evidenced in lung by histopathological analysis. The portocaval shunt was able to prevent the metabolic changes and ameliorate the inflammatory process in the lung, suggesting that the liver plays an active role in the systemic inflammatory response to acute pancreatitis.

Role of xanthine oxidase and eicosanoids in development of pancreatic ischemia-reperfusion injury

The implication of different eicosanoids and oxygen free radicals in the development of pancreatic injury after an ischemia-reperfusion process has been evaluated. For this purpose we have compared the effect of allopurinol and indomethacin administration on the pancreatic levels of eicosanoids in a rat model of pancreatic ischemia-reperfusion. After 60 min of pancreatic ischemia and 2 h of reperfusion, significant increases in 6-keto-PGF1 alpha, PGE2, and LTB4 in pancreas tissue were detected. Allopurinol before the ischemic period reduced 6-keto-PGF1 alpha, PGE2, and LTB4 levels to the range of basal values, while prior indomethacin treatment significantly reduced 6-keto-PGF1 alpha and PGE2 levels, with LTB4 remaining unmodified. Increased postischemic plasma lipases were also significantly reduced by allopurinol to the range of sham-operated animals whereas indomethacin did not modify these levels. The data suggest a role for lipoxygenase metabolites in the development of pancreatic injury and the importance of the enzyme xanthine oxidase as an inductor of eicosanoid biosynthesis.

Comparative study of different thermospray interfaces with carbamate pesticides: Influence of the ion source geometry

Sixteen carbamate pesticides that belong to four chemical classes (oxime-N-methylcarbamates, aryl N-methylcarbamates, N-phenylcarbamates, and methyl esters of substituted carbamic acids) were investigated via three different commercially available thermospray interfaces and ion sources that exhibit wide differences in source geometry. Comparisons were made between the three interfaces with respect to ion formation and sensitivity of detection. Experimental parameters were standardized to obtain comparable experimental conditions. Very similar mass spectra for most carbamates were obtained that illustrate independence from the geometry of the ionization and desolvation chambers of the interfaces. These findings are in sharp contrast to several literature reports. However, thermally labile carbamates gave unsatisfactory results with regard to spectral compatibility between the interfaces. Such differences were due to thermally assisted hydrolysis reactions that occur in the vaporizer probe prior to ionization and reflect differences in the vaporizer designs. The study proves conclusively that comparable spectra can be obtained under thermospray with different interfaces and mass spectrometers.

Biomedical and biochemical applications of liquid chromatography-mass spectrometry

This review centres on the application of various LC-MS and LC-MS-MS techniques to the study and solution of practical problems in biomedical research. For this purpose it covers a selection of publications in this area included in the MEDLINE database for the period 1991-mid-1994. As shown herein, LC-MS is increasingly gaining in importance in the biomedical field, especially after the revolution brought about by the introduction of the new liquid-phase atmospheric pressure ionization (API) techniques, such as electrospray (ES) and ionspray. The information in this database shows that thermospray (TS), which clearly dominated LC-MS coupling in the 1980s, is on a downward trend relative to the more modern API techniques which will certainly dominate this application field in the present decade. Studies on drug metabolism, therapeutic drug monitoring and pharmacology have been traditionally carried out by GC-MS. However, LC-MS has lately been replacing classical GC-MS techniques in many of these applications. For instance, LC-ES-MS has greatly facilitated the application of both qualitative and quantitative LC-MS methods to highly polar molecules. This is possible without the need to resort to elaborate sample handling and derivatization procedures for relatively high-molecular-mass compounds such as drug conjugates, biosynthetic and natural peptides and therapeutic proteins obtained by recombinant DNA technology, all of them formerly totally inaccessible to the standard GC-MS or LC-MS methods. With regard to studies on metabolism and biochemical phenomena of endogenous compounds, LC-ES-MS is also becoming very strong in the analysis of structural biopolymers such as peptides, proteins, glycoproteins and glycolipids, and also lower molecular mass compounds such as fatty acids, vitamins, steroids and nucleic acids. For example, structural verification of post-translational modifications in proteins can be efficiently obtained in the time frame of an LC run and suitable MS methods for the location of glycopeptide-containing fractions in proteolytic digests of glycoproteins have been developed. Interesting examples are also shown of the use of LC-MS in clinical studies and the determination of biological markers of disease.

Altered levels of urinary prostanoids in lead-exposed workers

This paper describes the alteration of the urinary excretion of prostanoids in workers occupationally exposed to lead. For this purpose, the following groups were studied: Group 1 (n = 62): controls; Group 2 (n = 29): risk group; and Group 3 (n = 69): exposed group. Urine samples were collected for prostanoid analysis and lead blood levels were analyzed. Our results demonstrate that urinary excretion of prostanoids is already altered even at levels of lead in blood = 200 micrograms/l. Owing to their sensitivity, urinary prostanoids could be useful markers of early renal changes associated with lead exposure. However, underlying mechanisms should be elucidated and the health significance of such changes should be assessed before any conclusion is drawn.