Significant increase of Kuppfer cells associated with loss of Na+,K+-ATPase activity in rat hepatic allograft rejection

Ischemia-Reperfusion Injury and Ischemic-Type Biliary Lesions following Liver Transplantation

Ischemia-reperfusion (I-R) injury after liver transplantation (LT) induces intra- and/or extrahepatic nonanastomotic ischemic-type biliary lesions (ITBLs). Subsequent bile duct stricture is a significant cause of morbidity and even mortality in patients who underwent LT. Although the pathogenesis of ITBLs is multifactorial, there are three main interconnected mechanisms responsible for their formation: cold and warm I-R injury, injury induced by cytotoxic bile salts, and immunological-mediated injury. Cold and warm ischemic insult can induce direct injury to the cholangiocytes and/or damage to the arterioles of the peribiliary vascular plexus, which in turn leads to apoptosis and necrosis of the cholangiocytes. Liver grafts from suboptimal or extended-criteria donors are more susceptible to cold and warm I-R injury and develop more easily ITBLs than normal livers. This paper, focusing on liver I-R injury, reviews the risk factors and mechanisms leading to ITBLs following LT.

Serum cholestasis markers as predictors of early outcome after liver transplantation

BACKGROUND

Early cholestasis is not uncommon after liver transplantation and usually signifies graft dysfunction. The aim of this study was to determine if serum synthetic and cholestatic parameters measured at various time points after transplantation can predict early patient outcome, and graft function.

METHODS

The charts of 92 patients who underwent 95 liver transplantations at Rabin Medical Center between 1991 and 2000 were reviewed. Findings on liver function tests and levels of serum bilirubin, alkaline phosphatase (ALP), and gamma glutamyl transpeptidase (GGT) on days 2, 10, 30, and 90 after transplantation were measured in order to predict early (6 months) patient outcome (mortality and sepsis) and initial poor functioning graft. Pearson correlation, chi(2) test, and Student's t-test were performed for univariate analysis, and logistic regression for multivariate analysis.

RESULTS

Univariate analysis. Serum bilirubin >/=10 mg/dL and international normalized ratio (INR) >1.6 on days 10, 30, and 90, and high serum ALP and low albumin levels on days 30 and 90 were risk factors for 6-month mortality; serum bilirubin >/=10 mg/dL on days 10, 30, and 90, high serum ALP, high GGT, and low serum albumin, on days 30 and 90, and INR >/=1.6 on day 10 were risk factors for sepsis; high serum alanine aminotransferase, INR >1.6, and bilirubin >/=10 mg/dL on days 2 and 10 were risk factors for poor graft function. The 6-month mortality rate was significantly higher in patients with serum bilirubin >/=10 mg/dL on day 10 than in patients with values of <10 mg/dL (29.4% vs. 4.0%, p = 0.004). Patients who had sepsis had high mean serum ALP levels on day 30 than patients who did not (364.5 +/- 229.9 U/L vs. 70.8 +/- 125.6 U/L, p = 0.005). Multivariate analysis. Significant predictors of 6-month mortality were serum bilirubin >/=10 mg/dL [odds ratio (OR) 9.05, 95% confidence intervals (CI) 1.6-49.6] and INR >1.6 (OR 9.11, CI 1.5-54.8) on day 10; significant predictors were high serum ALP level on day 30 (OR 1.005, 1.001-1.01) and high GGT level on day 90 (OR 1.005, CI 1.001-1.01). None of the variables were able to predict initial poor graft functioning.

CONCLUSIONS

Several serum cholestasis markers may serve as predictors of early outcome of liver transplantation. The strongest correlation was found between serum bilirubin >/=10 mg/dL on day 10 and early death, sepsis, and poor graft function. Early intervention in patients found to be at high risk may ameliorate the high morbidity and mortality associated with early cholestasis.

Intrahepatic cholestasis after liver transplantation

Cholestasis is a common sequela of liver transplantation. Although the majority of cases remain subclinical, severe cholestasis may be associated with irreversible liver damage, requiring retransplantation. Therefore, it is essential that clinicians be able to identify and treat the syndromes associated with cholestasis. In this review, we consider causes of intrahepatic cholestasis. These may be categorized by time of occurrence, namely, within 6 months of liver transplantation (early) and thereafter (late), although there may be an overlap in their causes. The causes of intrahepatic cholestasis include ischemia/reperfusion injury, bacterial infection, acute cellular rejection, cytomegalovirus infection, small-for-size graft, drugs for hepatotoxicity, intrahepatic biliary strictures, chronic rejection, hepatic artery thrombosis, ABO blood group incompatibility, and recurrent disease. The mechanisms of cholestasis in each category and the clinical presentation, diagnosis, treatment, and outcome are discussed in detail.

CD40L (CD154) expression in human liver allografts during chronic ductopenic rejection

The CD40-CD40L (CD154) interaction plays a pivotal role in the effector mechanisms of allograft rejection. Blockade of the CD40/CD40L costimulatory pathway prevents the development of chronic allograft rejection in several animal transplant models. The relevance of in situ CD40 and CD40L expression in human liver allografts was assessed by immunohistochemistry during ductopenic chronic rejection (CR). In CR allograft specimens (n = 8), marked CD40L expression was detected on Kupffer cells (KCs) and sinusoidal macrophages with a unique centrilobular distribution (P <.001). The CD40L+ KCs and macrophages were shown to be CD68+ after immunohistochemical analysis of serial sections with anti-CD68 monoclonal antibody. Moderate staining of vascular and sinusoidal endothelial cells and mononuclear infiltrates was observed in some CR cases. These findings were in contrast to the absence of CD40L expression in controls (n = 11) consisting of stable liver allograft and normal liver tissue specimens. Only occasional CD40 expression in some cases of CR and controls was observed. In CR, CD40L (CD154) expression is manifested on KCs and macrophages. The present novel data show another important cellular source of CD40L expression and suggest a potential role of KCs/macrophages and CD40/CD40L costimulatory interactions in the pathogenesis of chronic rejection ductopenic liver allograft.

Impairment of peroxisomal structure and function in rat liver allograft rejection: prevention by cyclosporine

BACKGROUND

During allograft rejection, cytokines and lipid mediators contribute to cell injury and organ failure. Peroxisomes play a crucial role in lipid metabolism, including the degradation of lipid mediators by peroxisomal beta-oxidation. Therefore, we investigated the alterations of hepatic peroxisomes after allogeneic rat liver transplantation.

METHODS

MHC-incompatible Dark Agouti (RT1a) donor rats and Lewis (RT1(1)) recipient rats were used for allogeneic transplantation. For immunosuppression, a group of these animals received cyclosporine (CsA) intraperitoneally (1 mg/kg body weight per day). Lewis rats were used for isogeneic transplant combination. Ten days after transplantation, livers were investigated using morphometrical methods for determination of peroxisomal diameter and volume density. The activities of peroxisomal catalase (CAT) and acyl-coenzyme A oxidase (AOX) were determined, and the corresponding proteins were evaluated by quantitative immunocytochemistry and immunoblotting. The expressions of mRNAs encoding CAT and AOX were investigated by Northern blotting.

RESULTS

The volume density and diameter of peroxisomes were significantly decreased in allogeneic transplanted livers but were unchanged in CsA-treated animals. Both the activities of CAT and AOX and their protein levels were significantly reduced in liver allografts. Moreover, the corresponding mRNA levels of CAT and AOX were decreased significantly in liver allografts, whereas CsA treatment led to an increase of those mRNAs. Isogeneic transplanted livers showed only a slight reduction of the corresponding enzyme values.

CONCLUSIONS

Peroxisomes are severely affected both morphologically and functionally after allogeneic liver transplantation. These results suggest that impairment of peroxisomal lipid beta-oxidation could contribute to the pathogenesis of the rejection process by decreased catabolism of lipid mediators involved in the regulation of the inflammatory response. CsA, in addition to its immunosuppressive effects, may contribute to allograft survival by maintenance of those important peroxisomal functions.