Effect Of Endotoxin Tolerance Research Articles

The effect of endotoxin tolerance on the expression of chemokine receptor 7 in rats with the acute hepatic failure

Objective To study the effect of endotoxin tolerance (ETT) on chemokine receptor 7 (CXCR7) in the liver tissue of rats with acute liver failure (ALF).Methods SD male rats were randomly divided into three groups:normal group,ALF group and ETT group.The rats in the ETT group and ALF group were injected with lipopolysacharide (LPS) 0.1 mg/kg or saline respectively,one time / day for 5 days.At 24 hours after the 5th-day injection,all rats were injected with D-GalN 800 mg/kg and LPS 8μg/rat.Blood sample and liver tissue were collected on 2,6,12,24 and 48 hours after injection.The gene expressions of CXCR7 in the liver were measured by RT-PCR,and the protein expressions of CXCR7 were determined by Western Blot.The data analysis was performed by LSD,Dunnett's t test.Results The histological damage in the liver tissue was significantly mider in ETT group compared to ALF group.The gene expressions of CXCR7 were significantly milder in ETT group compared to ALF group (2 h:F =29.222,6 h:F=166.892,12 h:F=38.975,24h:F=34.603,48 h:F=18.929,allP＜0.01),but still severer than that of normal group.The CXCR7 protein expression in ALF group and ETT group peaked at 24 hours,but the expression of CXCR7 in ETT group was lower compared with that in in ALF group (2h:F=11.155,6 h:F=42.553,12h:F=17.082,all P＜0.01; 24 h:F=7.242,P＜0.05).Conclusions During the process of endotoxin tolerance,LPS pretreatment and D-GalN can decrease the liver injury,down-regulate the expressions of CXCR7mRNA and CXCR7.This suggests that CXCR7 may play an important role in the ETT. Key words: Endotoxin; Liver failure; Chemokine receptor 7

Impairment of lithium chloride-induced conditioned gaping responses (anticipatory nausea) following immune system stimulation with lipopolysaccharide (LPS) occurs in both LPS tolerant and LPS non-tolerant rats

Anticipatory nausea is a classically conditioned response to a context that has been previously paired with toxin-induced nausea and/or vomiting. When injected with a nausea-inducing drug, such as lithium chloride (LiCl), rats will show a distinctive conditioned gaping response that has been suggested to be an index of nausea. Previous studies have found that immune system activation with an endotoxin, such as lipopolysaccharide (LPS), attenuates LiCl-induced conditioned gaping in rats. The present study examined the acquisition of LiCl-induced conditioned gaping in rats that were either LPS tolerant or LPS non-tolerant, as little is known about the effects of endotoxin tolerance on learning and memory. Male Long-Evan rats were given four systemic injections of LPS (200 μg/kg) or isotonic saline (NaCl) to induce LPS tolerance, indexed with 24 h changes in body weight following treatment. The animals were then given 4 acquisition trials in a LiCl-induced conditioned gaping paradigm. On conditioning days animals were treated with LPS (200 μg/kg) or saline followed 90 min later by injection of LiCl (127 mg/kg) or saline and then placed in a distinctive context for 30 min and their behavior video-recorded. On a drug free test day all animals were again placed in the distinctive context for 10 min and behavior was video-recorded. Gaping responses were scored for all acquisition days and the test day. Spleen and body weights were also obtained for all rats at the end of the experiment. Gaping responses were attenuated in rats treated with LPS in both the LPS tolerant and LPS non-tolerant groups. There were significant negative correlations between spleen weight as well as spleen/body weight ratios, and levels of conditioned gaping responses in LiCl treated rats, but not control rats. These results show that LPS interferes with learning/memory in the anticipatory nausea paradigm in rats that are both LPS tolerant and LPS non-tolerant.

Endotoxin tlerance inhibits lipopolysaccharide-initiated acute pulmonary inflammation and lung injury in rats by the mechanism of nuclear factor-kappaB.

In this study, the effect of endotoxin tolerance on lipopolysaccharide (LPS)-initiated pulmonary inflammation, the local production of tumour necrosis factor-alpha (TNF-alpha) and the cytokine-induced neutrophil attractant (CINC), as well as the activation of nuclear factor-kappaB (NF-kappaB) and its subunit composition, were examined in vivo. Endotoxin tolerance was reproduced by four consecutive daily intraperitoneal injections of 0.6 mg/kg of Escherichia coli 055:B5 LPS. Compared with control rats, endotoxin-tolerant rats failed to increase the permeability of pulmonary microvascular or recruit neutrophil to lung tissue upon restimulation with 6 mg/kg of LPSs. Pretreatment with LPSs inhibited the protein level of TNF-alpha in bronchoalveolar lavage fluid (BALF) and mRNA expression of CINC in lung tissue in response to subsequent LPS stimulation. These changes were accompanied by the suppression of activation of NF-kappaB, including the low level of total amount of DNA-binding activity and high percentage of non-transactive p50 homodimers. These data demonstrate that endotoxin tolerance can alleviate the LPS-induced acute neutrophilic pulmonary inflammation in rats and can inhibit the proinflammatory cytokines in lung and suggest that endotoxin tolerance might result from the unresponsiveness of NF-kappaB and persistent high percentage of p50 homodimers. Therefore, the phenomenon of endotoxin tolerance might be used as a strategy for the prevention or treatment of LPS-associated acute respiratory distress syndrome in which excessive or dysregulated inflammation leads to acute lung injury.

Effects of endotoxin tolerance on liver function after hepatic ischemia/reperfusion injury in the rat

It is known that endotoxin tolerance prevents lethality after ischemia/reperfusion injuries (e.g., myocardial infarction) in laboratory animals. We used a rat model of partial hepatic ischemia/reperfusion to investigate whether endotoxin tolerance prevents associated lethality and disorders of liver function. Prospective animal study. University research facility. Male Sprague-Dawley rats. Hepatic ischemia was initiated by atraumatic clipping across the portal venous and hepatic arterial blood supply to the left lateral lobe for 90 mins. The common bile duct was canalized, and in a second set of experiments the bile duct of the left lateral lobe was canalized selectively. Bile flow, bile acids, and transaminases were determined during ischemia and 300 mins of reperfusion in endotoxin-tolerant and -nontolerant rats. Endotoxin-nontolerant animals showed a 50% lethality after hepatic ischemia/reperfusion injuries. All endotoxin-tolerant rats survived and did not react with any change in bile flow, showing a constant flow. The amount of bile acids in the common bile duct was reduced during ischemia and regained the concentrations of sham-operated animals 60 mins after reperfusion. From 180 mins after reperfusion, the difference between endotoxin-tolerant and -nontolerant animals was statistically significant. When bile acid concentration was determined in the ischemic left lateral lobe, ischemia/reperfusion was found to significantly decrease in endotoxin-nontolerant rats 60 mins after reperfusion. In contrast, endotoxin-tolerant rats produced normal amounts of bile acids 60 mins after reperfusion. At 120 mins after reperfusion, the amount of bile acids in the formerly ischemic left lateral lobe was more than normal. In this model of partial hepatic ischemia/reperfusion, endotoxin tolerance prevents ischemia/reperfusion injury-associated lethality and local disorders of liver function. This phenomenon induced by endotoxin tolerance may be useful in liver surgery to prevent ischemia/reperfusion injury.

Endotoxin tolerance protects against local hepatic ischemia/reperfusion injury in the rat

Liver surgery and liver transplantation as well as circulatory shock are often associated with hepatic ischemia/reperfusion (I/R) injury. Recent evidence suggests that TNF-α plays a central role in I/R injury and, therefore, down-regulation of TNF-α seems to be a promising way to protect against the deleterious consequences of I/R. Endotoxin tolerance represents a state of unresponsiveness to endotoxin and is associated with diminished TNF-α production. Thus, the effect of endotoxin tolerance on hepatic I/R injury of the liver was investigated in a rat model. I/R injury was induced by temporary ischemia of the left lateral liver lobe for 90 min followed by a 3 h observation period of reperfusion. I/R injury resulted in functional hepatic disorder characterized by a decrease both in bile flow and bile acid concentration and 50% mortality. This was prevented by induction of endotoxin tolerance. Hepatic TNF-α mRNA expression after I/R of the liver was determined by RT-PCR. In untreated rats, TNF-α mRNA was induced in the liver 60 min after reperfusion and further increased until 3 h after reperfusion. In contrast, in endotoxin-tolerant rats, no increases in TNF-α mRNA expression were detected. This suggests that induction of endotoxin tolerance protects against hepatic I/R injury possibly via down-regulation of intra-organ TNF-α expression.

Endotoxin tolerance protects against local hepatic ischemia/reperfusion injury in the rat.

Liver surgery and liver transplantation as well as circulatory shock are often associated with hepatic ischemia/reperfusion (I/R) injury. Recent evidence suggests that TNF-alpha plays a central role in I/R injury and, therefore, down-regulation of TNF-alpha seems to be a promising way to protect against the deleterious consequences of I/R. Endotoxin tolerance represents a state of unresponsiveness to endotoxin and is associated with diminished TNF-alpha production. Thus, the effect of endotoxin tolerance on hepatic I/R injury of the liver was investigated in a rat model. I/R injury was induced by temporary ischemia of the left lateral liver lobe for 90 min followed by a 3 h observation period of reperfusion. I/R injury resulted in functional hepatic disorder characterized by a decrease both in bile flow and bile acid concentration and 50% mortality. This was prevented by induction of endotoxin tolerance. Hepatic TNF-alpha mRNA expression after I/R of the liver was determined by RT-PCR. In untreated rats, TNF-alpha mRNA was induced in the liver 60 min after reperfusion and further increased until 3 h after reperfusion. In contrast, in endotoxin-tolerant rats, no increases in TNF-alpha mRNA expression were detected. This suggests that induction of endotoxin tolerance protects against hepatic I/R injury possibly via down-regulation of intra-organ TNF-alpha expression.

Arachidonic acid turnover in peritoneal macrophages is altered in endotoxin-tolerant rats

Peritoneal macrophages from endotoxin-tolerant rats have been found to exhibit depressed metabolism of arachidonic acid (AA) to prostaglandins and thromboxane in response to endotoxin. The effect of endotoxin tolerance on AA turnover in peritoneal macrophages was investigated by measuring [ 14C]AA incorporation and release from membrane phospholipids. Endotoxin tolerance did not affect the amount of [ 14C]AA incorporated into macrophages (30 min−24h). However, the temporal incorporation of [ 14C]AA into individual phospholipid pools (15 min−24 h) was altered. In endotoxin-tolerant macrophages, [ 14C]AA incorporation into phosphatidylcholine (PC) (2, 4, 24 h) and phosphatidylethanolamine (PE) (8 h) was increased, while the incorporation into phosphatidylserine (PS) (2–24 h) was reduced ( P < 0.005) compared to control macrophages. There was no change in [ 14C]AA incorporation into phosphatidylinositol (PI). Following 2 or 24 h of incorporation of [ 14C]AA, macrophages were incubated (3 h) with endotoxin (50 μg/ml) or A23187 (1 μM), and [ 14C]AA release was measured. Endotoxin-tolerant macrophages released decreased ( P < 0.05) amounts of [ 14C]AA in response to both endotoxin and the calcium ionophore A23187 compared to controls. Control macrophages in response to endotoxin released [ 14C]AA from PC, PI and PE. In contrast, tolerant cells released [ 14C]AA only from PC ( P < 0.05). A23187 released [ 14C]AA from all four pools in the control cells, but only from PC and PE in the tolerant cells. These data demonstrate that endotoxin tolerance alters the uptake and release of AA from specific macrophage phospholipid pools. These results suggest that changes in AA turnover and/or storage are associated with endotoxin tolerance.

Lipopolysaccharide tolerance inhibits eye inflammation. II. Preliminary studies on the mechanism.

The effect of endotoxin tolerance on ocular inflammation was studied in rabbits. Compared with a control group, a passive Arthus reaction in tolerant rabbits was characterized by a sharp decline in the expected increase in vascular permeability and slightly reduced leukocyte extravasation. Aqueous humor withdrawal (paracentesis) and intravitreal injection of prostaglandin E2 were also examined in lipopolysaccharide (LPS)-tolerant rabbits; in both circumstances, ocular protein exudation was decreased. These studies suggest that the prostaglandin system is particularly affected in the ocular responses of LPS-tolerant rabbits, and raise the possibility that other phenomena described in LPS tolerance may have a similar basis.

Lipopolysaccharide tolerance inhibits eye inflammation. I. Reduced immune complex or lipopolysaccharide effects.

The effect of endotoxin tolerance on ocular inflammation was studied in rabbits. A single intravenous (IV) injection of endotoxin (bacterial lipopolysaccharide [LPS]) produced a mild acute iridocyclitis. Repeated daily (five to seven days) IV injections of LPS (5 micrograms extracted from Salmonella typhimurium) led to a state of refractoriness or LPS "tolerance," and ocular inflammation was no longer produced. In contrast to controls, in rabbits tolerant to LPS, IV LPS failed to elevate prostaglandin E2, thromboxane B2, or chemotactic factors in the aqueous humor. Rabbits tolerant to LPS also resisted the increase in vascular permeability normally induced by an ocular reversed passive Arthus reaction. These results demonstrated that LPS tolerance can induce anti-inflammatory effects in the eye.

Effects of endotoxin tolerance on hepatic excretory function: In vivo study

Induction of endotoxin tolerance in rats led to reductions in bile flow and BSP excretion. BSP serum retention or storage of BSP in the liver was not affected. Although serum alanine aminotransferase (ALT) activity was slightly elevated in endotoxin-tolerant rats, the levels of serum aspartate amino-transferase (AST) and hepatic 5'-nucleotidase were normal. These in vivo data support the validity of in vitro studies demonstrating the cholestatic effects of endotoxin and the viewpoint that endotoxin may be responsible for the cholestatic jaundice associated with Gram-negative bacterial infections.

Effects of endotoxin tolerance on the hemodynamic changes associated with glycerol administration.

Rats made tolerant to endotoxin are partially protected from the histologic and functional injury that usually accompanies intramuscular administration of glycerol. Glycerol nephrotoxicity appears to correlate with the reductions in renal blood flow and cardiac output which follow injection. Studies were undertaken to determine if endotoxin tolerance would alter these hemodynamic abnormalities. A radiolabelled microsphere technique was employed to measure cardiac output and regional blood flow. Endotoxin-tolerant rats had higher cardiac outputs and renal blood flows and lower renovascular resistances than control rats when studied 90 min after intramuscular glycerol. These observations may partially explain the reduced nephrotoxicity of glycerol in rats made tolerant to endotoxin.

The effect of endotoxin tolerance on some serum constitutents of cows

The serum levels of total protein, total iron-binding capacity and copper increased significantly in cows as a result of injections of E. coli endotoxin whereas the level of urea-N decreased. Magnesium, potassium, sodium, calcium and inorganic phosphate showed no significant change. The increase in total protein was investigated by Sephadex G200 gel filtration studies, polyacrylamide gel electrophoresis and single radial immunodiffusion assays. IgG increased by 22 per cent, IgM by 30 per cent and total transferrin by 74 per cent, whereas IgA decreased by 25 per cent. Other proteins (α- and β-globulins) increased in the serum. The increased immunoglobulin levels were partly due to the formation of antibody to endotoxin; this antibody could be removed by adsorption with endotoxin. Non-specific immunoglobulins were formed also; the examination of absorbed sera showed them to be mainly of the IgG class.

Effect of endotoxin tolerance on the lead acetate-induced endotoxin hypersensitivity of rats.

Effect of endotoxin tolerance on the lead acetate-induced endotoxin hypersensitivity of rats.

EFFECT OF ENDOTOXIN-TOLERANCE, CORTISONE, AND THOROTRAST ON RELEASE OF ENZYMES FOR SUBCELLULAR PARTICLES OF MOUSE LIVER.

Carbon tetrachloride-induced leakage of 2 acid-hydrolases from mouse liver lysosomes, in vito, was inhibited by chronic pretreatment of the mice with endotoxin. Cortisone-pretreatment inhibited the release of one of the enzymes. Pretreatment of the mice with Thorotrast, a reticulo-endothelial-blocking agent which neutralizes tolerant states, had the opposite effect and caased accelerated release of acid-hydrolases from liver lysosomes of tolerant as well as normal animals. None of the 3 agents studied produced comparable changes in the rate of leakage of soluble dehydrogenases from mouse liver mitochondria. It is suggested that stabilization of hepatic lysosomal membranes in endotoxin-tolerant animals represents a selective response of these particles to repeated small doses of the toxin and plays an important role in the development of tolerance to this agent. (auth)