Endotoxin concentrations measured by a chromogenic assay in portal and peripheral venous blood in ten dogs with portosystemic shunts

Lipopolysaccharide and toll-like receptor 4 in dogs with congenital portosystemic shunts

Surgical attenuation of a congenital portosystemic shunt (CPSS) results in increased portal vein perfusion, liver growth and clinical improvement. Portal lipopolysaccharide (LPS) is implicated in liver regeneration via toll-like receptor (TLR) 4 mediated cytokine activation. The aim of this study was to investigate factors associated with LPS in dogs with CPSS. Plasma LPS concentrations were measured in the peripheral and portal blood using a limulus amoebocyte lysate (LAL) assay. LPS concentration was significantly greater in the portal blood compared to peripheral blood in dogs with CPSS (P = 0.046) and control dogs (P = 0.002). LPS concentrations in the peripheral (P = 0.012) and portal (P = 0.005) blood of dogs with CPSS were significantly greater than those of control dogs. The relative mRNA expression of cytokines and TLRs was measured in liver biopsies from dogs with CPSS using quantitative PCR. TLR4 expression significantly increased following partial CPSS attenuation (P = 0.020). TLR4 expression was significantly greater in dogs that tolerated complete CPSS attenuation (P = 0.011) and those with good portal blood flow on pre-attenuation (P = 0.004) and post-attenuation (P = 0.015) portovenography. Serum interleukin (IL)-6 concentration was measured using a canine specific ELISA and significantly increased 24 h following CPSS attenuation (P < 0.001). Portal LPS was increased in dogs with CPSS, consistent with decreased hepatic clearance. TLR4 mRNA expression was significantly associated with portal blood flow and increased following surgery. These findings support the concept that portal LPS delivery is important in the hepatic response to surgical attenuation. Serum IL-6 significantly increased following surgery, consistent with LPS stimulation via TLR4, although this increase might be non-specific.

The transhepatic endotoxin gradient is present despite liver cirrhosis and is attenuated after transjugular portosystemic shunt (TIPS)

BACKGROUND

Translocation of gut-derived bacterial products such as endotoxin is a major problem in liver cirrhosis.

METHODS

To assess the hepatic clearance of bacterial products in individuals with cirrhosis, we tested concentrations of Gram-negative bacterial lipopolysaccharide (LPS), LPS-binding protein (LBP), and the precursor of nitric oxide (NO), L-arginine, in a cohort of 8 stable patients with liver cirrhosis before and after elective transjugular portosystemic shunt (TIPS) implantation, including central venous, hepatic venous, and portal venous measurements.

RESULTS

Using an adapted LPS assay, we detected high portal venous LPS concentrations (mean 1743 ± 819 pg/mL). High concentrations of LPS were detectable in the central venous blood (931 ± 551 pg/mL), as expected in persons with cirrhosis. The transhepatic LPS gradient was found to be 438 ± 287 pg/mL, and 25 ± 12% of portal LPS was cleared by the cirrhotic liver. After TIPS, central venous LPS concentrations increased in the hepatic and central veins, indicating shunting of LPS with the portal blood through the stent. This paralleled a systemic increase of L-arginine, whereas the NO synthase inhibitor asymmetric dimethylarginine (ADMA) remained unchanged, suggesting that bacterial translocation may contribute to the pathogenesis of circulatory dysfunction post-TIPS.

CONCLUSIONS

This study provides quantitative estimates of the role of the liver in the pathophysiology of bacterial translocation. The data indicate that the cirrhotic liver retains the capacity for clearance of bacterial endotoxin from the portal venous blood and that TIPS implantation attenuates this clearance. Thus, increased endotoxin concentrations in the systemic circulation provide a possible link to the increased encephalopathy in TIPS patients.

Bacteriological study of the liver in dogs

This study aimed to confirm the possible presence of bacteria in the liver of healthy dogs. Laparotomy was performed in 20 animals admitted for routine abdominal surgery. To be selected for the study, dogs had to be healthy adults without clinical liver disease, signs of infection or macroscopic liver abnormalities. Biopsy samples were histologically and bacteriologically examined. Bacteriological analysis was negative for the livers of eight of the dogs. The remaining animals harboured a diverse bacterial flora in their liver. Twelve bacterial species were identified. Histology showed that the livers of 19 dogs had minor or no abnormalities, and only one animal had interstitial fibrosis and trabecular disarrangement. Histological changes were not related to the presence of bacteria. Thus the results showed that the liver of healthy dogs may harbour different bacterial species. These microorganisms did not cause any detectable manifestation of disease, despite being potential pathogens.

Metabolic, antioxidant, nutraceutical, probiotic, and herbal therapies relating to the management of hepatobiliary disorders

Many nutraceuticals, conditionally essential nutrients, and botanical extracts have been proposed as useful in the management of liver disease. The most studied of these are addressed in terms of proposed mechanisms of action, benefits, hazards, and safe dosing recommendations allowed by current information. While this is an area of soft science, it is important to keep an open and tolerant mind, considering that many major treatment discoveries were in fact serendipitous accidents.

Relationship of the blood endotoxin concentration and prognosis in dogs with pyometra

The blood concentrations of endotoxin in dogs with pyometra (n = 45) were compared with those in healthy dogs (n = 17). The blood endotoxin concentrations in the healthy dogs (n = 17), in those with good prognosis (n = 41) and those with poor prognosis (n = 4) were 3.4 +/- 2.8 pg/ml, 9.5 +/- 11.3 pg/ml and 74.2 +/- 18.3 pg/ml, respectively. The concentrations in the dogs with good prognosis and poor prognosis were significantly (p < 0.01) higher than those in the healthy dogs. The dogs with poor prognosis had significantly (p < 0.01) higher endotoxin concentrations than those with good prognosis. Blood endotoxin concentrations were measured in 9 dogs after surgery, and were found to be decreased. These results suggest the possible involvement of endotoxin in the pathophysiological changes due to pyometra in dogs, and also that the blood endotoxin concentration could be used as a marker to determine prognosis.

Technetium 99m sulfur colloid scintigraphy to evaluate reticuloendothelial system function in dogs with portasystemic shunts

In a retrospective study, technetium 99m sulfur colloid scintigraphy was used to evaluate reticuloendothelial system function in 61 dogs with single congenital and 40 dogs with multiple acquired portasystemic shunts. Whole body reticuloendothelial function was measured by calculating the plasma clearance rate constant from a dynamic study of liver uptake of 99mTc sulfur colloid. Relative liver, spleen, and lung uptake, and a ratio of hepatic:extrahepatic uptake were measured on static equilibrium images. Results were compared with those of a group of 26 normal dogs. Compared with values for the group of normal dogs, the plasma clearance rate constant, relative liver uptake, and hepatic:extrahepatic uptake ratio were significantly decreased, and relative spleen and lung uptake were significantly increased in dogs with portasystemic shunts (P < .0001). The only significant difference between dogs with single congenital versus multiple acquired shunts was that the relative splenic uptake was higher in the former group (P < .0002). Based on these results, we concluded that dogs with portasystemic shunts have significantly impaired reticuloendothelial function. The primary cause of this dysfunction is likely a reduction in effective liver blood flow. Increases in spleen and lung reticuloendothelial activity did occur, but only partially compensated for the reduction of liver reticuloendothelial activity. Possible mechanisms for the increased spleen and lung uptake are discussed.