Preservation solutions alter Mrp2-dependent bile flow in cold ischemic rat livers

BACKGROUND

Previously, decreased organic anion transport through multidrug resistance protein 2 (Mrp2) was observed without any notable cell lysis, even when the livers were stored for 8 hours in University of Wisconsin solution (UW). The aim of this study was to examine the bile flow and its constituents, markers of graft dysfunction without necrosis in cold ischemic livers, using the following preservation media: UW, ET-Kyoto solution (ET-K) and histidine-tryptophan-ketoglutarate solution (HTK).

MATERIALS AND METHODS

Rat livers were stored at 4 degrees C for 8 hours in the preservation media, and reperfused to collect the bile and determine their constituents. Glycyrrhizin (GL) and/or glutathione (GSH) were added to the media as necessary. The transport efficiency of Mrp2 was assessed by the biliary excretion of 5-carboxyfluorescein (CF), a fluoroprobe excreted from Mrp2. The Intracellular distribution of Mrp2 was determined by immunostaining.

RESULTS

Livers stored for 8 hours exhibited significantly decreased bile production and biliary glutathione (GSH) levels without notable cell lysis. CF excretion was significantly delayed in all solutions. However, these markers were remarkably improved by the redistribution of Mrp2 from the cytoplasm to the canalicular membrane, when the livers were exposed to UW in the presence of GL. Moreover, livers exposed to the Kyoto and HTK solutions increased their bile production and organic anion transport in the presence of GL and GSH.

CONCLUSION

These results suggest that the addition of GL and GSH to preservation solutions improves bile production and biliary organic anion transport by increasing Mrp2 localization to the bile canaliculi in post-cold ischemic livers. (248 words).

Impact of cyclosporine on the development of immunosuppressive therapy

With the advent of cyclosporine (CsA) 20 years ago, graft survival increased considerably to more than 80% at 2 years posttransplant. The early formulation of CsA, Sandimmun, is effective in preventing organ rejection, although its absorption profile means it is subject to a high degree of variability. The development of a microemulsion formulation, Neoral, provided a therapy with superior efficacy in kidney, liver, and heart transplantation with an improved pharmacokinetic profile. Calcineurin inhibitors (CNIs), including CsA, have a narrow therapeutic range, so frequent blood measurements to control drug levels are required. Recent research has demonstrated that the measurement of blood CsA concentration at 2 hours postdosing--C2 monitoring--has the potential to optimize efficacy and reduce the side effects associated with CNI use. In heart and de novo kidney transplantation, C2 monitoring may help to further reduce the incidence of acute rejection, while in maintenance renal transplant recipients, C2 monitoring can help to detect overexposure and thus allows safe dose reduction, which may improve blood pressure and renal function. C2 monitoring thus facilitates a better balance between effective Neoral immunosuppression and unwanted side effects. Today, CsA remains the cornerstone of immunosuppression, and ongoing studies aim to further optimize patient management strategies with Neoral. With other trials evaluating the impact of Neoral in combination with newer therapies such as Certican, myfortic, and FTY720, the use of CsA in transplant recipients looks set to continue.

Cyclosporin: an updated review of the pharmacokinetic properties, clinical efficacy and tolerability of a microemulsion-based formulation (neoral)1 in organ transplantation

Cyclosporin is a lipophilic cyclic polypeptide immunosuppressant that interferes with the activity of T cells chiefly via calcineurin inhibition. The original oil-based oral formulation of this drug (Sandimmun)l was characterised by high intra- and interpatient pharmacokinetic variability, with poor bioavailability in many patients; a novel microemulsion formulation (Neoral)1 was therefore developed to circumvent these problems. Studies show increases, attributable chiefly to improved absorption in patients who absorb the drug only poorly from the original formulation, in mean systemic exposure to cyclosporin with the microemulsion, with no clinically significant differences in tolerability or drug interaction profiles. Cyclosporin microemulsion is at least as effective as the oil-based formulation in renal, liver and heart transplant recipients, with trends towards decreased incidence of acute rejection with the microemulsion formulation in some (statistically significant in a few) trials. Cyclosporin microemulsion and tacrolimus appear to have similar efficacy in preventing acute rejection episodes in most renal, pancreas-kidney, liver and heart transplant recipients. However, there are indications of superior efficacy for tacrolimus in some trials, particularly in the prevention of severe acute rejection and in Black transplant recipients. Current 12-month data also indicate equivalent efficacy of sirolimus in renal transplantation. Conversion from the oil-based to microemulsion formulation in stable renal, liver and heart transplant recipients is achievable with no change in acute rejection rates. The addition of an anti-interleukin-2 receptor monoclonal antibody and/or mycophenolate mofetil to cyclosporin microemulsion plus corticosteroids decreases rates of acute rejection; corticosteroid withdrawal without increased acute rejection rates was also achieved on the addition of these agents in some trials. Pharmacoeconomic analyses have shown savings in direct healthcare costs in kidney or liver transplantation when cyclosporin microemulsion is used in preference to the oil-based formulation, although studies incorporating indirect costs or expressing costs in terms of therapeutic outcomes are currently unavailable.

CONCLUSIONS

The introduction of cyclosporin microemulsion has consolidated the place of the drug as a mainstay of therapy in all types of solid organ transplantation; research into optimisation of outcomes through more effective therapeutic monitoring in patients receiving this formulation is ongoing. Several novel immunosuppressants have been introduced in recent years: further clinical and pharmacoeconomic research will be needed to clarify the relative positioning of these agents, particularly with respect to specific patient groups. Other new drugs (basiliximab/daclizumab and mycophenolate mofetil) offer particular advantages when used in combination with cyclosporin.

The effects of liver transplantation and cyclosporine on bile formation and lipid composition: an experimental study in the rat

BACKGROUND/AIMS

Hepatic graft dysfunction is a major management problem in the early post-liver transplantation period. Our aims were to study how liver transplantation per se affects bile formation, and to investigate the role of cyclosporine in the pathogenesis of early graft dysfunction.

METHODS

Syngeneic liver transplantation used male Lewis rats. Two weeks after transplantation, the rats were randomly assigned to receive either daily subcutaneous injections of cyclosporine 10 mg/kg for 1 week (n=8), or daily saline injections (Placebo, n=8). 24-h bile collections were performed 18 h after the last injection. Eight non-transplanted rats served as controls.

RESULTS

Liver transplantation per se (Placebo) significantly increased basal bile flow (51%), particularly that portion which was bile salt-independent flow (81%), but did not impair bile salt kinetics or biliary lipid composition. Cyclosporine reduced basal bile flow and bile salt-independent flow by 41% and 30%, respectively. Bile salt synthesis was 52% suppressed, leading to a 22% decrease in the bile salt pool size. The recycling frequency of the bile salt pool was unaffected. The drug inhibited bile salt (37%) and phospholipid (23%) outputs; cholesterol secretion remained unaltered. This significantly elevated the cholesterol saturation of bile (25%).

CONCLUSIONS

Liver transplantation per se is choleretic and does not impair bile formation or lipid composition in this inbred rat model. Parenteral administration of high-dose cyclosporine induces cholestasis by inhibiting bile salt secretion and BSIF. Bile salt synthesis is down-regulated and the bile salt pool size decreased. The drug adversely affects biliary lipid composition by differential inhibition of bile salt and phospholipid outputs relative to an unchanged cholesterol secretion.

Secretion and composition of bile after human liver transplantation: studies on the effects of cyclosporine and tacrolimus

Cyclosporine (CsA) and tacrolimus (FK506) have recently been reported to inhibit canalicular transport of bile acids in vitro and thereby possibly induce cholestasis. A relative reduction of chenodeoxycholic acid (CDCA) has been observed after liver transplantation when CsA is used as immunosuppressant. We tested the hypothesis that CsA induces cholestasis and reduces CDCA secretion as compared with treatment with monoclonal antibodies (OKT3), and that CsA differs from FK506 with regard to its effects on biliary lipid secretion. Bile flow, biliary lipid secretion rates, and biliary bile acid composition were determined during the first 10 days after transplantation in 29 liver transplant recipients. Two prospective randomized studies were performed that compared CsA and OKT3 and compared CsA- and FK506-based regimens. In study 1, bile acid output averaged 0.75+/-0.15 micromol/min in the CsA I group and 0.54+/-0.11 micromol/min in the OKT3 group on postoperative day 1. Bile flow and bile acid output then increased, and there was no significant difference between the two groups. The relative proportion of CDCA decreased to the same extent in both groups. In study 2, mean bile acid outputs on postoperative day 1 were 0.57+/-0.26 micromol/min and 0.55+/-0.15 micromol/min in the CsA 2 and FK506 groups, respectively. The following increase in bile acid secretion was significantly larger in the FK506 group. After transplantation, the relative proportion of CDCA decreased with time in both groups, but the reduction was more rapid in the FK506 group. In conclusion, CsA did not inhibit bile secretion during short-term treatment after liver transplantation. Compared with patients given CsA-based treatment, patients with FK506-based treatment recovered bile secretion more rapidly.

Influence of liver transplantation and cyclosporin on bile secretion--an experimental study in the rat

Bile secretion is reduced after liver transplantation. It has been suggested that this is due either to the effect of cyclosporin or to the damage to the liver graft during preservation and reperfusion. The aim of this study was to explore the influence of cyclosporin as well as of liver transplantation on bile secretion. Bile flow was studied in an experimental model in the rat. In syngeneic liver-transplanted animals, the bile flow was increased compared to the bile flow in the control group (1.29 +/- 0.09 ml/h vs 0.66 +/- 0.03 ml/h; P < 0.01), mainly due to an increased bile acid-independent flow (0.76 ml/h vs 0.50 ml/h; P < 0.01). The findings in the liver-transplanted rats contrasted with those in a group of nontransplanted animals treated with cyclosporin. Cyclosporin treatment resulted in a reduced bile acid-independent fraction (0.37 ml/h vs 0.50 ml/h, P < 0.05) of the bile flow, although no biochemical signs of hepatotoxicity were present. This reduction in the bile acid-independent fraction could, however, not be demonstrated when cyclosporin was given to a group of liver-transplanted rats, although a reduced total bile flow was recorded in the 1st hour measurements. In contrast to previous studies, we found that the cyclosporin vehicle (Cremophor EL), when administered chronically, induced a higher bile flow than that in the control rats. This effect was not seen in the transplanted rats. Our findings in this experimental rat model indicate that cyclosporin will influence and reduce bile secretion and bile acid secretion even if no other signs of liver dysfunction are present. On the other hand, the preservation and reperfusion in this model resulted in an increased bile flow, while bile acid secretion remained constant.

Raised pressure in the bile ducts after orthotopic liver transplantation

Biliary complications are common after orthotopic liver transplantation. Bile leakage in the immediate postoperative period and on removal of the T-tube could possibly be caused by a raised bile duct pressure. In order to test this hypothesis, bile duct pressure was studied in seven consecutive liver transplant patients. During the operation, the common bile duct was anastomosed end-to-end over a T-tube. The initial bile duct pressure measurement was performed a median of 12 days (range 10-17 days) after the transplantation and on one or two more occasions during the following 3 months. Seven cholecystectomized gallstone patients with indwelling T-tubes were used as controls. The bile duct pressure at the level of the xiphoid process in the transplanted group was 7.7 +/- 1.4 cm H2O and in the control group 0.5 +/- 0.8 cm H2O (P < 0.001). The initially increased bile duct pressure after liver transplantation decreased with time (P < 0.05) towards normal during the following 3 months. The raised pressure may increase the risk of bile leakage in the postoperative period.