Induction of vascular injury by Pseudomonas aeruginosa cytotoxin in rabbit lungs is associated with the generation of different leukotrienes and hydroxyeicosatetraenoic acids

Short-chain fatty acids alter tight junction permeability in intestinal monolayer cells via lipoxygenase activation

OBJECTIVE

Involvement of lipoxygenase (LOX) and cyclo-oxygenase (COX) on cellular differentiation or apoptosis induced by butyrate has been reported recently, but the effect on tight junction (TJ) permeability has not been reported. One major activity of butyrate and, to a lesser extent, propionate is to modulate gene transcription via histone acetylation by their histone deacetylase inhibitor activity. In this study, we evaluated the activation of LOX and COX in TJ permeability changes by short-chain fatty acids, butyrate, propionate, and acetate in intestinal monolayer cells and their possible mechanism by histone acetylation.

METHODS

The effects of LOX and COX inhibitors on TJ permeability and the expression of LOX or COX mRNA induced by short-chain fatty acids were investigated in Caco-2 cells using Transwell chambers. The effects of hydroxyeicosatetraenoic acid (a product of LOX) on TJ permeability were also evaluated. The effects of short-chain fatty acids were compared with those of trichostatin A (histone deacetylase inhibitor).

RESULTS

A LOX inhibitor clearly inhibited the effect of butyrate on TJ permeability, whereas COX inhibitors did not. The LOX and COX inhibitors partly inhibited the effects of propionate but not of acetate. Butyrate increased LOX mRNA expression, and hydroxyeicosatetraenoic acid and trichostatin A mimicked its effect.

CONCLUSION

These results suggest that short-chain fatty acids, especially butyrate, induce TJ permeability changes through LOX activation through histone acetylation.

Botulinolysin, a thiol-activated hemolysin produced by Clostridium botulinum, inhibits endothelium-dependent relaxation of rat aortic ring

The effects of botulinolysin (Blyn), a thiol-activated hemolysin produced by Clostridium botulinum, on contractility of rat aortic ring were studied in order to clarify an underlying mechanism of vasoconstriction by the toxin observed previously as an increase in perfusion pressure in isolated rat organs. Blyn (30 hemolytic units/ml; HU/ml) itself did not elicit any apparent change in resting tension of the ring. Contractile tension elicited by a high concentration of phenylephrine in endothelium-intact rings increased significantly after treatment with Blyn (30 HU/ml), while phenylephrine-induced contraction of endothelium-denuded rings was not influenced by toxin treatment. In rings with intact endothelium, acetylcholine (ACh)-induced relaxation was significantly inhibited after treatment with Blyn (30, 10, 1 HU/ml). In contrast, relaxation of denuded rings by sodium nitroprusside was not affected by toxin treatment (30 HU/ml). Arginine (10(-4) M) partly reversed the inhibition of ACh-induced relaxation by the toxin (1 HU/ml). Endothelium-dependent relaxation by histamine or adenosine triphosphate was also inhibited by Blyn (1 HU/ml), but the relaxation elicited by calcium ionophore A23187 was not influenced by the toxin. The results indicate that Blyn acts on endothelium and inhibits agonist-induced endothelium-dependent relaxation of blood vessels.

Coronary vasoconstriction is the most probable cause of death of rats intoxicated with botulinolysin, a hemolysin produced by Clostridium botulinum

The pathophysiology of lethal intoxication by botulinolysin (Blyn) was studied using anesthetized rats and isolated rat organs. Intravenous injection of 10,000 and 1000 hemolytic units (HU) of Blyn killed rats rapidly while 100 HU of the toxin did not. Congestion and edema of lungs were observed at autopsies of the rats killed by intoxication. Hemoglobinemia was obvious in rats injected with 1000 HU of Blyn but not in rats with 10,000 HU. Electrocardiograms of the intoxicated rats showed depression of T waves but not changes characteristic of hyperpotassemia. All the rats injected with the above doses of Blyn showed a rapid fall in arterial blood pressure (BP) immediately after the toxin injection, and BP soon recovered in rats injected with 100 HU, partially and transiently in rats with 1000 HU, and not in rats with 10,000 HU of Blyn. Perfusion of Blyn (1 HU/ml) to isolated rat hearts caused a rapid and marked increase in perfusion pressure and cessation of spontaneous heart beat. Acetylsalicylic acid (10(-3) M) and quinacrine dihydrochloride (10(-5) M) did not essentially influence the effects of Blyn on the isolated hearts, but verapamil (10(-6) M) inhibited at least the initial increase in perfusion pressure elicited by Blyn. Spontaneous contractions of the isolated atria were little influenced by Blyn (60 HU/ml). Perfusion pressures of isolated kidneys, lungs and livers were also increased by Blyn (1 HU/ml). The results indicate that Blyn caused vasoconstriction but had little direct effect on myocardium. Based on the above findings, we conclude that coronary vasoconstriction elicited by direct action of Blyn causes acute cardiac dysfunction leading to systemic hypotension and death of the intoxicated animals.

Effects of two different inhibitors of the arachidonic acid metabolism on platelet sequestration in endotoxic shock

Metabolites of arachidonic acid are known to play an important part in the pathogenesis of organ injury in endotoxic shock. We compared the effects of the classical cyclooxygenase inhibitor aspirin with that of the dual cyclooxygenase and lipoxygenase inhibitor ketoprofen on the behavior of platelets tagged with 111In-labeled oxine in multiple organs during endotoxin shock. Three groups of sheep (n = 7 in each) were anesthetized before being subjected to endotoxin shock. Group E had no drug treatment (shock controls), group KET received ketoprofen and group ASP received aspirin treatment. In the lungs and in the liver of group E there was a marked sequestration of platelets, which started in both organs immediately after administration of endotoxin and continued throughout the study. In the treated groups, however, the response to endotoxin was both delayed and reduced compared with the untreated shock controls. The first changes in platelet activity were noted after more than 1 h in the treated groups. Four hours after administration of endotoxin, platelet activity (sequestration) had increased in the lungs by 102 +/- 14% in group E, 53 +/- 11% in group ASP and 20 +/- 13% in group KET (P < 0.01, P < 0.01 and P < 0.05 respectively compared to baseline). Corresponding values for the liver were 52 +/- 16% in group E, 22 +/- 19% in group ASP and -2 +/- 12% in group KET (P < 0.01, P < 0.01 and P > 0.05 respectively compared with baseline).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of indomethacin on increases in leukotriene B4 and pulmonary edema in response to phorbol ester administration in dogs

The administration of leukotrienes (LTs) into the pulmonary circulation results in edema formation and increased vascular permeability. We reported previously that the administration of phorbol myristate acetate (PMA, 20 micrograms/kg) to intact anesthetized dogs results in a reduction in circulating white blood cells as well as the development of pulmonary edema concomitant with the appearance of LTs in the lungs. In contrast, when a smaller dose of PMA (10 micrograms/kg) was administered, neither extravascular lung water nor LTs increased, although there was a similar reduction in circulating white blood cells. In the present study, we used a property of indomethacin, namely, its capacity to augment the formation of LTs, to examine further the relationship between LT generation and pulmonary edema formation in response to PMA administration. In intact pentobarbital-anesthetized dogs pretreated with saline (N = 9), the administration of PMA at a dose of 10 micrograms/kg, i.v., did not result in any change in extravascular lung water or in LTB4 present in bronchoalveolar lavage fluid (BALF). In contrast, in six animals pretreated with indomethacin (5 mg/kg), the administration of this dose of PMA resulted in increases in both extravascular lung water (P < 0.05) and LTB4 (P < 0.05) in BALF. These results provide support for the hypothesis that leukotrienes are requisite for PMA-induced increases in extravascular lung water.

Pseudomonas aeruginosa cytotoxin as a pathogenicity factor in a systemic infection of leukopenic mice

The effect of Pseudomonas aeruginosa cytotoxin was assessed in leukopenic outbred Swiss male mice (20 g) using a high cytotoxin-producing strain (PA158) and its cytotoxin-deficient isogenic mutant (PA114F5) generated by Tn7::Tn5 transposon mutagenesis of PA158. Leukopenia was induced by intraperitoneal (i.p.) administration of cyclophosphamide (150 micrograms/g). Anesthetized mice were infected via a 4 mm incision on the shaved back with 300 CFU/mouse (9 LD50; expected death rate 85%). Precleared mouse cytotoxin-specific heat inactivated rabbit polyclonal antibody (RPA) was administered i.p. (0.2 ml) 24 hr before challenge. Controls received i.p. normal rabbit serum, RPA, cyclophosphamide alone, or a sham procedure. Challenge with the high cytotoxin-producing strain PA158 caused earlier and a significantly greater mortality than that observed with a cytotoxin-deficient strain PA114F5 (P < 0.01). Cytotoxin-specific polyclonal antibody was protective. Pretreatment with antibody decreased the mortality rate following challenge with PA158 from 88.9% to 27.8% (P < 0.01). Pretreatment with antibody decreased the mortality rate following challenge with PA114F5 from 27.8% to 5.6% (P < 0.05). These results demonstrate that P. aeruginosa cytotoxin contributes to the pathogenicity of the organism and that cytotoxin antibody is protective in a systemic P. aeruginosa infection in leukopenic mice.

Amelioration of respiratory and circulatory changes in established endotoxic shock by ketoprofen

In an intensive-care setting we studied the effects of ketoprofen, a dual inhibitor of cyclooxygenase and lipoxygenase, on circulatory and respiratory changes during established endotoxic shock in sheep. Two groups (n = 7 in each) were exposed to E. coli endotoxin, which caused a sharp increase in pulmonary artery pressure (200%; PAP), intrapulmonary shunt fraction (300%; QS/QT%), and oxygen extraction ratio (50%; VO2/DO2%). There was also a significant decrease in mean arterial pressure (25%; MAP), respiratory compliance (60%; CT), arterial oxygen tension (65%; PaO2), and oxygen delivery index (15%; DO2) in both groups. After 30 min of endotoxin infusion, group K received ketoprofen, 2.5 mg/kg b.w. i.v., while group E served as shock controls. After 4 h there had been a significant improvement in MAP, PaO2, DO2, QS/QT%, and CT in the ketoprofen-treated group compared with the controls (P < 0.01). In addition, the oxygen extraction ratio normalised in group K, but remained 70-100% increased in group E (P < 0.01). The wet-to-dry weight ratios of the lungs and the liver were significantly lower in the ketoprofen-treated group compared with the controls (P < 0.05). It was concluded that ketoprofen significantly ameliorated the respiratory and circulatory effects of established endotoxic shock in sheep.

Effects of ketoprofen on respiratory and circulatory changes in endotoxic shock

OBJECTIVE

To study the effects of ketoprofen, a dual inhibitor of the arachidonic acid metabolism, on hemodynamic and respiratory changes during endotoxic shock.

DESIGN

Prospective, randomised, controlled study using an established intact animal model of endotoxic shock in sheep.

SETTING

An animal laboratory in a university hospital.

INTERVENTIONS

4 groups were studied (n = 7 in each). Group K received ketoprofen and group A received aspirin 30 min before start of endotoxin infusion. Group E received endotoxin, but no drug treatment. Group C received neither endotoxin nor drug treatment. All the animals were anaesthetised with ketamine, had controlled ventilation with FiO2 = 0.5 and received Ringer's lactate at an infusion rate that would keep the pulmonary capillary wedge pressure constant.

RESULTS

Both ketoprofen and aspirin prevented the early rise in pulmonary arterial pressure that occurred in group E a few minutes after start of i.v. infusion of endotoxin. Furthermore, ketoprofen prevented any significant changes in arterial blood pressure, arterial oxygen tension, oxygen delivery index, oxygen extraction ratio, respiratory compliance, intrapulmonary shunt fraction, and platelet counts that occurred in group E. Aspirin, on the other hand, provided only partial and time limited (1-2 h) protection against these changes. Wet-to-dry weight ratios of the lungs were significantly lower in the ketoprofen treated than in the untreated shock controls and the aspirin treated animals.

CONCLUSION

Ketoprofen completely prevented the changes in hemodynamics and respiratory function observed in control-endotoxin-treated animals.