Cyclosporine a augments P-glycoprotein expression in the regenerating rat liver

mTOR inhibitor therapy: Does it prevent HCC recurrence after liver transplantation?

Prevention of hepatocellular carcinoma (HCC) recurrence after liver transplantation is a clinical priority. The importance of the mammalian target of rapamycin (mTOR) pathway in cell growth and survival makes it a logical target for antitumor strategies, as borne out by clinical data in various types of malignancy. A number of studies have indicated that the mTOR inhibitors everolimus and sirolimus suppress cell proliferation and tumor growth in animal models of HCC. Coadministration of an mTOR inhibitor could permit lower dosing of chemotherapeutic agents in HCC management, and trials in non-transplant HCC population are exploring combined used with various agents including sorafenib, the vascular endothelial growth factor inhibitor bevacizumab and conventional agents. In terms of a preventive effect after liver transplantation for HCC, data from retrospective studies and non-randomized prospective analyses in which patients received an mTOR inhibitor with concomitant calcineurin inhibitor therapy have indicated that HCC recurrence rates and overall survival may be improved compared to a standard calcineurin inhibitor regimen. Meta-analyses have supported these findings, but controlled trials are required before any firm conclusions can be drawn. In two of the three randomized trials which have assessed de novo mTOR inhibitor therapy after liver transplantation, there was a numerically lower rate of HCC recurrence by one year post-transplant in patients given an mTOR inhibitor versus the control arm, but absolute numbers were low. Overall, based on the available data from retrospective studies, meta-analyses, and post-hoc assessments of randomized trials, it appears advisable to consider mTOR inhibition-based immunosuppression after transplantation for HCC, particularly in patients who exceed the Milan criteria. Prospective data are awaited.

Enhancement of P-glycoprotein expression by hepatocyte transplantation in carbon tetrachloride-induced rat liver

The multidrug resistance protein P-glycoprotein (P-gp) is physiologically expressed at the bile canalicular membrane of the liver, where it participates in the biliary excretion of various lipophilic drugs. Chronic exposure to carbon tetrachloride (CCI(4)) is known to induce hepatic fibrosis resulting in hepatotoxicity. This study focuses on the effects of CCI(4) and hepatic transplantation (HT) on the P-gp expressions in rat liver. Male SD rats were treated with CCI(4) to induce liver damage for 3, 7, 14, 21, and 28 days, respectively. Immunohistochemistry revealed that P-gp was widely distributed in the liver and was spread from the cytoplasm to cell membrane of the rat liver. Western blot showed remarkable increase of P-gp expression in 3 days CCI(4)-treated rats, whereas, a continuous decrease in the P-gp expression was seen in 7, 14, 21, and 28 days CCI(4)-treated rats. After HT with cells from the normal rat liver, the level of P-gp increased comparing with those from the sham operation. Blood biochemistry showed decreased levels of serum alanine transaminase, aspartate transaminase, and alkaline phosphatase and increased serum levels of triglyceride and total protein, which indicated the improved function of the liver damaged by CCI(4). These results illustrate the variation of the expression of P-gp in CCI(4)-induced hepatic damage and an increase of P-gp level after HT in the toxic liver induced by CCI(4). We hypothesized that P-gp may play a protective role in the process of liver injury. HT can be beneficial to ameliorate the rat liver functional damage induced by CCI(4).

Changes in mitochondrial ultrastructure and malondialdehyde level in regenerating liver tissue in rats

AIM: To investigate the role of mitochondria permeability transition (MPT) in liver regeneration.

METHODS: One hundred and five male Sprague-Dawley rats were randomly divided into three groups: partial hepatectomy (PH) group, cyclosporin A (CsA) group and sham-operated (SH) group. Animals in the PH and CsA groups underwent 2/3 partial hepatectomy. Animals in the CsA group were administered CsA before the surgery. The animals in each group were further divided into seven sub-groups. Ultrastructural morphology of mitochondria in remnant liver after PH was determined by electron microscopy. The content of malondialdehyde (MDA) in liver tissue was also measured.

RESULTS: Remarkable changes were observed in the morphology and ultrastructure of the liver mitochondria at 24 h after PH, including conspicuous swelling, increased membrane permeability, reduced number of cristae, and matrix vacuolation. At 72 h, moderate mitochondrial swelling was observed, while, at other time points, mild mitochondrial swelling was seen. Mitochondrial permeability increased at 0, 3 and 6 h in the CsA group, but decreased at 24 and 72 h when compared with the PH group. Similar changes in endoplasmic reticulum were also noted. The content of MDA increased at 3 h after PH, peaked at 24 h, and then decreased and returned to normal level at 120 h. The contents of MDA at all time points in the CsA group were significantly higher than those in the PH group.

CONCLUSION: The changes in mitochondrial ultrastructure and MDA level are closely associated with MPT during live regeneration in rats, especially prominent at 24 h after PH. The changes in mitochondrial ultrastructure and MDA level in liver tissue is possibly related to the initiation of liver regeneration after PH.

Interleukin-2 treatment effect on imatinib pharmacokinetic, P-gp and BCRP expression in mice

The aim of this study was to investigate the effect that recombinant interleukin-2 (rIL-2) (0.16 MUI/injection) had on the pharmacokinetics of imatinib (IM) in plasma. In this study, IM was given orally to mice at a dose of 150 mg/kg once a day for 11 days (from day 1 to 11) either alone or in combination with intraperitoneal injections of rIL-2 twice a day from day 8 to 11. Pharmacokinetic parameters were determined using WinNonLin software. Areas under the curve were compared using Bailer's method. The repeated administration of the rIL-2+IM combination was shown to have two pharmacokinetic advantages compared with repeated IM doses alone. In addition to the pharmacodynamic interest of this treatment, we found that the combined treatment significantly increased the IM Cmax (P<0.05) and significantly increased the IM trough concentration (C(24 h)) (P<0.01), which was always above the minimum therapeutic IM concentration (1 mumol/l) in plasma. Those pharmacokinetic modifications may be explained, in part, by a decrease in the P-glycoprotein expression in the three intestinal segments of the mice (duodenum, P<0.01; jejunum, P<0.05; and ileum, P<0.05) and a decrease in BCRP expression in the duodenum segment (P<0.05) due to rIL-2. In another experiment, we found a significant induction of intestinal P-glycoprotein expression in mice that had been given IM orally (150 mg/kg) twice a day for 11 days. It would be interesting to further investigate the IM disposition associated with rIL-2 treatment for clinical applications.

Role of pharmacogenetics of ATP-binding cassette transporters in the pharmacokinetics of drugs

Interindividual differences of drug response are an important cause of treatment failures and adverse drug reactions. The identification of polymorphisms explaining distinct phenotypes of drug metabolizing enzymes contributed in part to the understanding of individual variations of drug plasma levels. However, bioavailability also depends on a major extent from the expression and activity of drug transport across biomembranes. In particular efflux transporters of the ATP-binding cassette (ABC) family such as ABCB1 (P-glycoprotein, P-gp), the ABCC (multidrug resistance-related protein, MRP) family and ABCG2 (breast cancer resistance protein, BCRP) have been identified as major determinants of chemoresistance in tumor cells. They are expressed in the apical membranes of many barrier tissue such as the intestine, liver, blood-brain barrier, kidney, placenta, testis and in lymphocytes, thus contributing to plasma, liquor, but also intracellular drug disposition. Since expression and function exhibit a broad variability, it was hypothesized that hereditary variances in the genes of membrane transporters could explain at least in part interindividual differences of pharmacokinetics and clinical outcome of a variety of drugs. This review focuses on the functional significance of single nucleotide polymorphisms (SNP) of ABCB1, ABCC1, ABCC2, and ABCG2 in in vitro systems, in vivo tissues and drug disposition, as well as on the clinical outcome of major indications.

Co-administration of cyclosporine A alleviates thioacetamide-induced liver injury

AIM: To investigate the effects of cyclosporine A (CsA) on thioacetamide (TAA)-induced liver injury.

METHODS: CsA was co-administrated (7.5 μg/kg body weight per day, i.p.) into rat to investigate the role of CsA on TAA-(200 mg/kg body weight per 3 d for 30 d, i.p.)induced liver injury.

RESULTS: The data show that TAA caused liver fibrosis in rat after 30 d of treatment. CsA alleviates the morphological changes of TAA-induced fibrosis in rat liver. The blood glutamyl oxaloacetic transaminase (GOT)/glutamyl pyruvic transaminase (GPT) in the TAA-injury group is elevated compared to that of the normal rat. Compared with the TAA-injury group, the blood GOT/GPT and TGFβ1 (by RT-PCR analysis) are reduced in the CsA plus TAA-treated rat. The level of the transforming growth factor receptor I (TGFβ-R1) in the CsA plus TAA-treated group shows higher than that in the TAA only group, but shows a lower level of the fibroblast growth factor receptor 4 (FGFR4) in the CsA plus TAA-treated group, when using the Western blot analysis. After immunostaining of the frozen section, TGFβ-R1 and FGFR4 are more concentrated in rat liver after CsA plus TAA injury.

CONCLUSION: This result suggests that CsA has an alleviated effect on TAA-induced liver injury by increasing the multidrug resistance P-glycoprotein and could be through the regulation of TGFβ-R1 and FGFR4.