Improvement of portal flow and hepatic microcirculatory tissue flow with N-acetylcysteine in dogs with obstructive jaundice produced by bile duct ligation

Role of liver sinusoidal endothelial cells in liver diseases

Liver sinusoidal endothelial cells (LSECs) form the wall of the hepatic sinusoids. Unlike other capillaries, they lack an organized basement membrane and have cytoplasm that is penetrated by open fenestrae, making the hepatic microvascular endothelium discontinuous. LSECs have essential roles in the maintenance of hepatic homeostasis, including regulation of the vascular tone, inflammation and thrombosis, and they are essential for control of the hepatic immune response. On a background of acute or chronic liver injury, LSECs modify their phenotype and negatively affect neighbouring cells and liver disease pathophysiology. This Review describes the main functions and phenotypic dysregulations of LSECs in liver diseases, specifically in the context of acute injury (ischaemia-reperfusion injury, drug-induced liver injury and bacterial and viral infection), chronic liver disease (metabolism-associated liver disease, alcoholic steatohepatitis and chronic hepatotoxic injury) and hepatocellular carcinoma, and provides a comprehensive update of the role of LSECs as therapeutic targets for liver disease. Finally, we discuss the open questions in the field of LSEC pathobiology and future avenues of research.

Therapeutic use of cytoprotective agents in canine and feline hepatobiliary disease

Many medicinal, nutraceutical, and botanic extracts have been used as cytoprotective agents in liver disease. This article explains the mechanisms of action, pertinent pharmacokinetics, side effects, and clinical indications for the use of S-adenosylmethionine, N-acetylcysteine, ursodeoxycholic acid, silymarin, and vitamin E. The literature pertaining to in vitro studies, laboratory animal models, and human and veterinary clinical trials is reviewed with regards to the efficacy and use of these cytoprotective agents in hepatobiliary disease.

N-Acetylcysteine improves disturbed ileal contractility following partial hepatectomy in rats

BACKGROUND AND AIMS

It is well known that disturbed intestinal motility and bacterial overgrowth may occur following partial hepatectomy. These events have been followed by the translocation of enteric bacteria that play a major role in the development of infections. We designed the present study to evaluate the effect of N-acetylcysteine (NAC) on ileal muscle contractility as an indication of intestinal motility.

METHODS

Sprague-Dawley rats were divided into four groups (n = 6): sham, sham plus preoperative intraperitoneal NAC injection, hepatectomy, and hepatectomy plus preoperative intraperitoneal NAC injection. Contractile and relaxant responses in isolated ileal smooth muscle strips were determined using an in vitro muscle technique. Statistical analyses were performed by Kruskal-Wallis and Mann-Whitney U-tests.

RESULTS

Contractile responses to KCl and carbachol were significantly decreased in the ileal strips of the hepatectomy group when compared to the sham-operated control group. The impaired contraction of strips was markedly improved by preoperative NAC treatment. However, neither the electrical field stimulation nor the sodium nitroprusside-mediated relaxant responses changed in any of the groups.

CONCLUSIONS

Our data indicated that disturbed ileal contractility after partial hepatectomy was remedied by preoperative NAC treatment, which in turn might cause attenuation of bacterial translocation.

Yinhu cholagogue mixture combined with endoscopic naso-biliary drainage in treatment of patients with obstructive jaundice: an analysis of 30 cases

AIM: To observe the clinical efficacy and mechanism of Yinhu cholagogue mixture (YCM) combined with endoscopic naso-biliary drainage (ENBD) in the treatment of patients with obstructive jaundice (OJ).

METHODS: A total of 90 OJ patients were randomly divided into surgery control group (n = 30), endoscopy control group (n = 30) and YCM group (n = 30), treated with traditional open surgery, ENBD alone and YCM plus ENBD, respectively. We observed the T-tube and naso-biliary drainage situation, while monitored the serum TBIL, DBIL, AKP, GPT, GOT, LPS and IL-6 levels before and after operation.

RESULTS: On the 14^th d after sugery, LPS, IL-6 levels and the liver function markers such as TBIL, DBIL, AKP, GPT and GOT in all the patients decreased obviously, and these indexes were markedly lower in YCM group than those in the surgery control group and endoscopy control group (0.07 ± 0.01 vs 0.12±0.03, 0.13 ± 0.03; 166.5 ± 31.62 vs 230.2 ± 41.08, 225.6 ± 42.69; 24.3 ± 7.91 vs 43.3 ± 9.49, 46.7 ± 11.07; 12.6 ± 4.74 vs 32.2 ± 6.33, 46.7 ± 11.07; 67.5 ± 25.30 vs 102.5 ± 36.37, 114.9 ± 39.53; 36.8 ± 14.23 vs 79.0 ± 35.88, 82.3 ± 34.79; 46.2 ± 11.07 vs 84.5 ± 34.79, 80.3 ± 31.62, respectively; P < 0.05 or 0.01); there were no marked differences between the two control groups. On the 5^th d after operation, combined therapy was superior to the other two treatments in bile drainage (P < 0.05 or 0.01), but there was no significant difference between the two control groups.

CONCLUSION: YCM in combination with ENBD can effectively restore liver function, promote bile excretion and lower LPS and IL-6 levels in OJ patients.

Effects of N-acetylcysteine administration in hepatic microcirculation of rats with biliary cirrhosis

BACKGROUND/AIMS

Increased intrahepatic resistance (IHR) in cirrhosis is due to fibrosis and hepatic endothelial dysfunction (HED). Besides producing fibrosis, increased reactive oxygen species (ROS) promotes ROS-related nitration of anti-oxidative enzymes in cirrhotic livers. Tyrosine nitration (nitrotyrosilation)-related inactivation of anti-oxidative enzymes is increased in cirrhotic livers. This study investigates effects of N-acetylcysteine (NAC) administrations in bile-duct-ligation (BDL) rats.

METHODS

This study measured portal venous pressure (PVP), IHR, hepatic endothelial function, hepatic levels of anti-oxidants and oxidants, type III procollagen (PIIIP), proteins expression of thromboxane synthase (TXS), nitrotyrosine, manganese superoxide dismutase (MnSOD), and hepatic NOx and thromboxane A(2) (TXA(2)) production in perfusates.

RESULTS

The improvement of HED was associated with decreased PVP and IHR, hepatic protein and mRNA levels of PIIIP, protein expression of TXS and nitrotyrosine, oxidants and production of TXA(2) in NAC-treated BDL rat livers. Conversely, hepatic NOx production, anti-oxidants, and protein expression of MnSOD were increased in NAC-treated BDL rat livers.

CONCLUSIONS

In NAC-treated cirrhotic rats, the decrease in IHR was mainly caused by its anti-oxidative effect-related prevention of hepatic fibrogenesis associated with the decrease of oxidants-related nitrotyrosilation and improvement of HED.

Effect of N-acetylcysteine on blood and tissue lipid peroxidation in lipopolysaccharide-induced obstructive jaundice

In obstructive jaundice, free radical production is increased and antioxidative activity is reduced. N-Acetylcysteine (NAC) has a beneficial effect with anti-inflammatory and antioxidant activity, acting as a free radical scavenger. NAC inhibits inducible nitric oxide synthase, suppresses cytokine expression/release, and inhibits adhesion molecule expression and nuclear factor kappa B. The aim of this study was to investigate the effects of NAC on liver/renal tissue and serum lipid peroxidation in lipopolysaccharide (LPS)-induced obstructive jaundice. We randomized 60 rats into 6 groups: group 1, Sham; group 2, obstructive jaundice (OJ) induced after bile-duct ligation; group 3, OJ + NAC (100 mg kg- 1 subcutaneously); group 4, OJ + LPS (10 mg kg-1); group 5, OJ + NAC + LPS; and group 6, OJ + LPS + NAC. For each group, the biochemical markers of lipid peroxidation and the antioxidant products were measured in serum and liver/renal tissue after sacrifice. Almost all lipid peroxidation products levels were increased and antioxidant products levels were decreased in groups who received LPS (groups 4, 5, and 6), but the effect was less remarkable when NAC was administered before LPS (group 5). The same trend was seen for groups with OJ +/- LPS who did not received NAC or received it after induced toxemia (groups 2, 4, and 6) as compared to groups 1 and 3. Moreover, in the case of OJ + LPS, rats treated with NAC before LPS (group 5) had lower lipid peroxidation products levels and higher antioxidant products levels as compared to those who did not received NAC (group 4). This phenomenon was not reproducible with NAC administered after LPS (group 6). Thus, results of this study showed that NAC prevents the deleterious effects of LPS in obstructive jaundice by reducing lipid peroxidation in serum and liver/renal tissue if administered before LPS. Nonetheless, NAC failed to prevent the lipid peroxidation in the case of established endotoxemia in obstructive jaundice.

The effect of N-acetylcysteine on pulmonary lipid peroxidation and tissue damage

BACKGROUND

We aimed to investigate the effect of N-acetylcysteine (NAC) on pulmonary lipid peroxidation and tissue damage in experimental obstructive jaundice (OJ) stimulated by lipopolysaccharide (LPS) in this study.

MATERIALS AND METHODS

We randomized 40 rats into five groups. Group A: Sham (n = 8); group B: OJ (n = 8); group C: OJ + lipopolysaccharide (LPS; n = 8); group D: OJ + NAC + LPS (n = 8); group E: OJ + LPS + NAC (n = 8). OJ was performed by common bile duct ligation and division in all groups except the sham group. At the fifth day, the rats were jaundiced. At the fifth day of OJ, LPS was injected 10 mg/kg intraperitoneally to the rats and at the tenth day, the rats were sacrificed in group C. In group D; at the fifth day of OJ, NAC was started 100 mg/kg subcutaneously and the same dose NAC injection repeated every day for 5 days. At the tenth day of OJ, LPS was injected 10 mg/kg intraperitoneally to the rats and then after 6 h they were sacrificed. In group E; 10 mg/kg LPS was administered intraperitoneally at fifth day of OJ and after then NAC was started 100 mg/kg subcutaneously and the same dose NAC injection repeated every day for 5 days and at the tenth day, the rats were sacrificed. Tissue samples were harvested through a midline incision, and lungs were resected and examined histopathologically and immunohistochemically for tissue damage scoring. The blood was taken by cardiac puncture and malondialdehyde (MDA), myeloperoxidase (MPO), and levels of total antioxidant status were detected with biochemical methods to evaluate lung tissue damage.

RESULTS

Increase in lung and serum MDA and MPO levels, as well as decrease in total antioxidant status, were observed in groups B and C when compared with the sham group (P = 0.0001, for each comparison). Furthermore, the lung tissue damage was observed in the same groups by histopathological examination when compared with sham group. There was significant decrease at serum and lung MPO and MDA levels after the NAC application in groups D and E, when compared with group C (P = 0.0001, for each comparison). Antioxidant status in groups D and E were increased in the presence of NAC (P = 0.0001, for each comparison). Lung histology was prevented relatively in group D when compared with groups B and C.

CONCLUSION

Results of the study indicate that NAC has protective effect on pulmonary lipid peroxidation and tissue damage before and after LPS administration.

N-acetylcysteine attenuates bacterial translocation after partial hepatectomy in rats

BACKGROUND

Translocating enteric bacteria have been suggested as playing a major role in the development of infections after partial hepatectomy. We investigated the effect of N-acetylcysteine (NAC) on bacterial translocation (BT) and intestinal mucosa as the first line of defense against BT.

MATERIALS AND METHODS

We compared four groups of eight Sprague-Dawley male rats each: sham, control (partially hepatectomized), partial hepatectomy plus preoperative single-dose NAC, and a fourth that received partial hepatectomy with a preoperative single-dose NAC plus treatment with NAC for 2 days. Microorganism counts of tissues, lung injury score, lung tissue glutathione, and malondialdehyde levels and microscopy of intestinal mucosa were studied at the end of 48 h.

RESULTS

Microorganism count in the lung and mesenteric lymph node cultures and lung injury score were significantly higher in the control group when compared with the sham, third, and fourth groups (lung: 9919.6 versus 0.0, 2912.9, 1550.0 cfu/g tissue; mesenteric lymph nodes: 8458.3 versus 0.0, 89.0, 88.9 cfu/g tissue; lung injury score: 3.25 versus 0.5, 1.13, 1.75). In the control group, the villous height of the distal ileal mucosa was significantly shorter than the sham group (65.25 versus 75.25 microm) and the difference from groups 3 and 4 was not statistically significant. Neutrophil infiltration in the distal ileal mucosa of the control group was significantly higher than the sham, third and fourth groups (3.13 versus 0.25, 0.38 and 1.0).

CONCLUSIONS

The parenteral use of NAC attenuates bacterial translocation after partial hepatectomy in rats. Attenuation of the lung injury after partial hepatectomy in NAC-treated groups might be attributable to both anti-inflammatory effect and the effect on BT.

Systemic, pulmonary, and hepatosplanchnic effects of N-acetylcysteine during long-term porcine endotoxemia

OBJECTIVE

Controversial data have been reported on the effects of N-acetylcysteine in patients with septic shock. We therefore investigated the systemic, pulmonary, and hepatosplanchnic hemodynamic, gas exchange, and metabolic effects of N-acetylcysteine during long-term, volume-resuscitated, hyperdynamic porcine endotoxemia, which mimics the features of hyperdynamic human sepsis.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

Investigational animal laboratory.

SUBJECTS

Eighteen pigs were randomized to receive endotoxin alone (controls, n = 9) or endotoxin plus N-acetylcysteine (n = 9).

INTERVENTIONS

Anesthetized, mechanically ventilated, and instrumented animals received continuous intravenous endotoxin and were resuscitated with hydroxyethylstarch to keep mean arterial pressure >60 mm Hg. After 12 hrs of endotoxemia, they were randomized to receive either placebo or N-acetylcysteine (150 mg/kg loading dose over 1 hr followed by 20 mg.kg-1.hr-1 for 11 hrs).

MEASUREMENTS AND MAIN RESULTS

Before as well as 12, 18, and 24 hrs after starting the endotoxin infusion, systemic, pulmonary, and hepatosplanchnic hemodynamics, oxygen exchange, and metabolism as well as nitric oxide, glutathione, and 8-isoprostane concentrations were assessed. N-acetylcysteine failed to improve any of the variables of the systemic, pulmonary, or hepatosplanchnic hemodynamics, gas exchange, and metabolism. Although N-acetylcysteine significantly elevated glutathione concentration, it did not influence the 8-isoprostane concentrations and even further reduced hepatic venous pH.

CONCLUSIONS

Despite the increased glutathione concentration, N-acetylcysteine did not improve systemic, pulmonary, and hepatosplanchnic hemodynamics, oxygen exchange, and metabolism. When compared with previous reports in the literature, a different timing of N-acetylcysteine administration and/or an ongoing or even N-acetylcysteine-induced aggravation of oxidative stress may account for this result.

Management of paracetamol overdose: current controversies

Paracetamol (acetaminophen) is one of the most frequently used analgesics, and is the most commonly used substance in self-poisoning in the US and UK. Paracetamol toxicity is manifested primarily in the liver. Treatment with N-acetyl-cysteine (NAC), if started within 10 hours from ingestion, can prevent hepatic damage in most cases. Pharmacokinetic data relating plasma paracetamol concentration to time after ingestion have been used to generate a 'probable hepatoxicity line' to predict which cases of paracetamol overdose will result in hepatotoxicity and should be treated with NAC. However, later studies use a 25% lower line as their 'possible hepatotoxicity line'. Although adopting the original line may save considerable resources, further studies are needed to determine whether such an approach is safe. On the basis of the metabolism of paracetamol, several risk factors for paracetamol toxicity have been proposed. These risk factors include long term alcohol (ethanol) ingestion, fasting and treatment with drugs that induce the cytochrome P450 2E1 enzyme system. Although some studies have suggested that these risk factors may be associated with worse prognosis, the data are inconclusive. However, until further evidence is available, we suggest that the lower line should be used when risk factors are present. In Canada and the UK, the intravenous regimen for NAC is used almost exclusively; in the US, an oral regimen is used. Both regimens have been shown to be effective. There is no large scale study with direct comparison between these 2 therapeutic protocols and controversy still exists as to which regimen is superior. During the last few years there has been an increase in the number of reports of liver failure associated with prolonged paracetamol administration for therapeutic reasons. The true incidence of this phenomenon is not known. We suggest testing liver enzyme levels if a child has received more than 75 mg/kg/day of paracetamol for more than 24 hours during febrile illness, and to treat with NAC when transaminase levels are elevated. Paracetamol overdose during pregnancy should be treated with either oral or intravenous NAC according to the regular protocols in order to prevent maternal, and potentially fetal, toxicity. Unless severe maternal toxicity develops, paracetamol overdose does not appear to increase the risk for adverse pregnancy outcome.