Endotoxins and liver disease

Inverse association between serum concentrations of actin-free vitamin D-binding protein and the histopathological extent of fibrogenic liver disease or hepatocellular carcinoma

BACKGROUND AND AIM

Next to its role as a carrier protein for vitamin D and its plasma metabolites, the primary function of vitamin D-binding protein (DBP; Gc-globulin) is to serve and to bind and neutralize extracellular monomeric actin (G-actin) released from necrotic cells, which in its long filamentous form (F-actin) triggers coagulation. We, therefore, investigated the kinetics of serum concentrations of actin-free DBP during the pathogenetic sequence from liver fibrosis to hepatocellular carcinoma (HCC) to initiate a discussion on a hypothetical association of serum concentrations of actin-free DBP and, thus, altered actin clearance in the circulation, and an increased risk of thrombosis in patients with functional liver insufficiency.

RESULTS

Our data show that serum levels of actin-free DBP are decreased in patients with liver fibrosis (n=288) and HCC (n=102) compared with healthy controls (n=120 and n=63) and nonliver disease sick (n=312) and that the level of decrease correlates with the severity of disease as determined according to the score by the French METAVIR Cooperative Study Group staging system for hepatic fibrosis or the Edmondson-Steiner's grading system for the assessment of HCC.

CONCLUSION

Although further, in particular, longitudinal studies are still necessary to back up our data, the presented findings suggest that decreasing levels of the actin-scavenger DBP could potentially contribute to the thrombophilic predisposition frequently observed in patients with chronic fibrogenic liver disease and HCC.

Acute-phase response alters the disposition kinetics of cefepime following intravenous administration to rabbits

The effect of experimentally induced fever on the pharmacokinetics of cefepime administered intravenously at a dose of 75 mg/kg bw was studied in six healthy rabbits. The study was conducted in two consecutive phases, separated by a washout period of 2 weeks. Infection was induced by the intravenous inoculation of 5 x 10(8) cfu of Escherichia coli 24 h before the pharmacokinetic investigation was carried out. Serial blood samples for cefepime concentration determination were obtained for 48 h following drug administration. The concentrations of cefepime in the plasma were determined by a quantitative microbiological assay using an agar-gel diffusion method employing Bacillus subtilis ATCC 6633 as the test organism, with a level of detectability of approximately 0.10 microg/ml. Cefepime plasma concentrations versus time were evaluated by non-compartmental methods using WinNonLin. Cefepime was well tolerated and no serious adverse events were observed. Rectal temperature increased 1 degree C 24 h post injection in infected animals. Highly significant differences in the blood plasma concentrations of cefepime were observed between febrile and healthy animals at all the sampling times. This could explain the greater area under the plasma level-time curve of the drug in febrile compared with healthy animals. The results from pharmacokinetic calculations showed that both the distribution volume at steady state (V (dss)) and body clearance (CL(tot)) were affected in febrile as compared to healthy animals. The mean values of V (dss) and CL(tot) of cefepime in healthy rabbits were 1.168 L/kg and 0.303 L/kg/h, respectively. As compared with healthy animals, the mean estimates of V (dss) (0.917 L/kg) and CL(tot) (0.205 L/kg per h) of cefepime were significantly lower, whereas t (1/2lambda), MRT and AUMC were significantly higher in febrile rabbits. It is concluded that, although experimental infection had an effect on the disposition kinetics of cefepime in healthy and febrile rabbits, this was not sufficiently pronounced to require alteration of the dosage during disease.

Evaluation of heparin immobilized chitosan-PEG microbeads for charcoal encapsulation and endotoxin removal

A technique is described to encapsulate activated charcoal for hemoperfusion to be used in an artificial liver support. Activated charcoal was encapsulated within chitosan-PEG matrix and subsequently surface modified with PGE1 or heparin (hep-AC-PEGCB) via the glutaraldehyde functionalities. This novel matrix was used as the supports for perfusion of endotoxin, under a flow rate of 30 ml/mt. Endotoxin adsorption was quantitatively measured by the method of Limulus Amebocyte lysate test. It seems, the hep-AC-PEGCB may be a good adsorbent system for the removal of toxic endotoxin, and the system may be useful for detoxification of blood. The hep-AC-PEGCB matrix had improved biocompatibility as demonstrated from their hemolytic potential and charcoal release. However, further studies are needed to determine their behaviour under clinical conditions.

Activated charcoal microcapsules and their applications

Activated charcoal, long known to the ancients as a substance of therapeutic value in a variety of maladies, has recently been "rediscovered" to be of great value in medical applications. Activated charcoal hemoperfusion is effective in blood purification for removal of various circulating toxic materials and waste metabolites, directly. However, particulate release and platelet adhesion prevent its continued clinical use. Polymeric coatings or microencapsulation of charcoal within polymers have improved their blood compatibility. Chitosan encapsulated activated charcoal (ACCB) beads have been extensively investigated in our group for the removal of various toxins such as urea, creatinine, uric acid, bilirubin, etc. This article highlights various methods of microencapsulation procedures of activated charcoal and the importance of this novel material for a variety of biomedical applications. Further, this review provides an insight to the future perspectives for using them in clinical practice.

Disseminated intravascular coagulation in liver cirrhosis

We measured thrombin-antithrombin III complex (TAT), soluble fibrin (SF) and D-dimer levels in 51 patients with liver cirrhosis to determine whether these tests provide new evidence for the presence of disseminated intravascular coagulation (DIC) in liver cirrhosis. TAT levels (median, range) were increased in the patient group (4.2 micrograms/l, 1.8-60.0) compared to the reference group (2.0 micrograms/l, range 1.5-7.6 micrograms/l). SF levels (0 nmol/l, range 0-80 nmol/l) were also increased in the patients as compared to the controls (0 nmol/l, 0), but there was no correlation between TAT and SF levels (r = 0.23, p less than 0.98). TAT levels did not correlate with AT-III levels (r = -0.36, p less than 0.49), but there was an inverse correlation between SF and AT-III (r = 0.60, p less than 0.001). If AT-III levels were above 0.30 U/ml, SF levels remained low, whereas SF levels were increased in patients with AT-III levels below 0.30 U/ml. These findings suggest that if sufficient AT-III is present, thrombin formation is adequately controlled, whereas at low levels of AT-III, thrombin escapes inactivation by AT-III and may act upon fibrinogen, leading to the formation of SF and a low-grade DIC. SF levels correlated well with D-dimer levels (r = 0.55, p less than 0.001), which is consistent with DIC and secondary fibrinolysis.

IN CONCLUSION

(1) thrombin formation is increased in liver cirrhosis, as indicated by increased TAT levels in 21 of 51 patients; (2) the plasma concentration of AT-III appears to be of major importance for the development of DIC. The present study provides evidence for DIC in severe liver cirrhosis when AT-III levels are less than 0.30 U/ml.

Vasoconstrictive effect of portal blood in isolated dog kidney

Humoral vasoactive substances coming from portal blood have been considered as a possible cause of renal dysfunction in cirrhotic patients. We have thus investigated the effect of perfusion of portal blood from anesthetized dogs on the isolated kidney functions. Both kidneys of a dog were simultaneously perfused on 2 Nizet's pump oxygenators, one kidney serving as control for the other. Renal blood flow was decreased in kidneys perfused with portal blood, as compared to the paired control kidneys perfused with sus-hepatic blood (group A experiments). Addition of polymyxin B to the portal blood restored the renal blood flow to the control level (group B experiments). No significant changes appeared between experimental and control kidneys for glomerular filtration rate, urine output, sodium and water excretion, renin activity, angiotensin II levels, plasmatic PGE2 levels, in group A as well as in group B. We conclude that portal blood of dogs contains vasoactive substances reducing renal blood flow; their action is mediated neither by the renin-angiotensin system nor by changes in renal PGE2 production. The complete abolition of this effect by Polymyxin suggests that these substances may be endotoxins.

Endotoxin-induced liver injury in aged and subacutely hypervitaminotic A rats

The plasma disappearance of endotoxin and endotoxin-induced hepatic injury were studied in two rat models: the aging rat and the subacutely hypervitaminotic A rat. The choice of these models was based on their respective association with a decreased or increased Kupffer cell endocytic activity. The half-life of endotoxin (E. coli O26: B6, phenol extracted) in plasma was significantly prolonged in aged rats as measured by both the Limulus assay (t1/2 = 2.1 +/- 0.1 h in 3-6-month-old, and 3.3 +/- 0.3 h in 24-36-month-old rats) and 51Cr-labeled endotoxin radioactivity assay (t1/2 = 5.3 +/- 0.3 h in 3-6-month old and 7.7 +/- 0.6 h in 24 36-month-old rats). In subacute hypervitaminosis A, the half-life of endotoxin was significantly decreased in the Limulus assay (t1/2 = 2.1 +/- 0.1 h in 3-6-month old and 1.4 +/- 0.2 h in subacutely hypervitaminotic A rats), but not in the radioactivity assay (t1/2 = 5.3 +/- 0.3 h in 3-6-month-old and 5.0 +/- 0.4 h in subacutely hypervitaminotic A rats). Hundred percent mortality was observed at a dose of 2 mg endotoxin/100 g body wt. in old rats, but not in young rats. Only 1 of 7 young subacutely hypervitaminotic A rats died following injection of this dose of endotoxin. The dose of endotoxin which caused only minimal parenchymal liver cell injury in young rats induced substantial parenchymal cell injury in old rats and subacutely hypervitaminotic A rats as determined by both histological and biochemical parameters. It is concluded that some basic characteristics of experimental animals, such as age and nutritional status, can dramatically influence the sensitivity to endotoxin and this is not necessarily correlated with the rate of endotoxin clearance.

The characteristic pattern of aspartate aminotransferase and alanine aminotransferase in the bitch with the cystic hyperplasia-pyometra complex: effect of medical or surgical treatment

In 75 clinically normal unspayed female control dogs between two and eleven years old the average plasma level of aspartate aminotransferase (AST) was 21.6 +/- 5.7 (+/- SD) IU/l, of alanine aminotransferase (ALT) 40.4 +/- 13.0 IU/l and of the AST/ALT ratio 0.6 +/- 0.2. These values showed only minor changes over years. In 96 bitches with the cystic hyperplasia-pyometra complex there was a very significant increase of the AST, decrease of the ALT and increase of the AST/ALT ratio. The changes were more pronounced in 62 clinically ill bitches with typical endometritis post oestrum, in 18 dogs with gram negative organisms in the uterus and in 53 bitches with white blood cell (WBC) levels higher than 40 X 10(9)/1. Renal failure had no influence on the specific changed values. The changed values returned either temporarily to normal after prostaglandin (PGF2 alpha)-treatment or definitely after ovariohysterectomy.