Pretreatment with FK506 up-regulates insulin receptors in regenerating rat liver

The tacrolimus-induced glucose homeostasis imbalance in terms of the liver: From bench to bedside

Tacrolimus (TAC), the mainstay of maintenance immunosuppressive agents, plays a crucial role in new-onset diabetes after transplant (NODAT). Previous studies investigating the diabetogenic effects of TAC have focused on the β cells of islets. In this study, we found that TAC contributed to NODAT through directly affecting hepatic metabolic homeostasis. In mice, TAC-induced hypoglycemia rather than hyperglycemia during starvation via suppressing gluconeogenetic genes, suggesting the limitation of fasting blood glucose in the diagnosis of NODAT. In addition, TAC caused hepatic insulin resistance and triglyceride accumulation through insulin receptor substrate (IRS)2/AKT and sterol regulatory element binding protein (SREBP1) signaling, respectively. Furthermore, we found a pivotal role of CREB-regulated transcription coactivator 2 (CRTC2) in TAC-induced metabolic disorders. The restoration of hepatic CRTC2 alleviated the metabolic disorders through its downstream molecules (eg, PCK1, IRS2, and SREBP1). Consistent with the findings from bench, low CRTC2 expression in graft hepatocytes was an independent risk factor for NODAT (odds ratio = 2.692, P = .023, n = 135). Integrating grafts' CRTC2 score into the clinical model could significantly increase the predictive capacity (areas under the receiver operating characteristic curve: 0.71 vs 0.79, P = .048). Taken together, in addition to its impact on pancreatic cells, TAC induces "hematogenous diabetes" via CRTC2 signaling. Liver-targeted management may be of help to prevent or heal TAC-associated diabetes.

MicroRNA profiling of tacrolimus-stimulated Jurkat human T lympocytes

Purpose

This study investigated the Jurkat T cell line expresses cytotoxicity when treated with different concentrations of FK506, and analyzed the expression pattern of microRNA when stimulated by FK506 using the microRNAs microarray, as well as the expression pattern of a gene that is related to the differentiation, activation and proliferation of T cells after being affected by the change of microRNAs.

Methods

To investigate the effects of FK506 on microRNA expression, we purified total RNA of Jurkat cells treated with 20 µM FK506 for 72 hours and used to analyze microRNA profiling by using Agilent's chip.

Results

These results demonstrated that treatment with FK506 markedly induced the down-regulation of 20 microRNAs as well as the up-regulation of 20 microRNAs in a time-dependent manner. The genes that down-regulated by FK506 include let-7a^*, miR-20a^*, and miR-487a. Otherwise miR-202, miR-485-5p, and miR-518c^* are gradually up-regulated in expression. Sanger Institute and DAVIDs bioinformatics indicated that microRNAs regulated the several transcriptomes including nuclear factor of activated T cell-related, T cell receptor/interleukin-2 signaling, and Ca²⁺-calmodulin-dependent phosphatase calcineurin pathways.

Conclusion

As a result of treating FK506 to a Jurkat cell line and running the microRNA microarray, it was found that FK506 not only took part in the suppression of T cell proliferation/activation by inhibiting calcineurin in Jurkat apoptosis, but also affected the microRNAs that are involved in the regulation of various signal transduction pathways.

Xeno-repopulation of Fah -/- Nod/Scid mice livers by human hepatocytes

Functional human hepatocytes xenografted into the liver of mice can be used as a model system to study pharmacokinetics, infection of hepatitis viruses, and the efficacy of hepatitis vaccines. Significant levels of liver xeno-repopulation have been reported in Fah (-/-) Rag2 (-/-) Il2rg (-/-) mice. However, A new model, termed Fah (-/-) Nod/Scid mice, which combines the advantages of liver repopulation in Fah (-/-) mice with the ease of xenotransplantation in Nod/Scid mice was obtained by gradual cross-breeding. Fah (-/-) Nod/Scid mice were easily maintained in breeding colonies and in adult animal care facilities. FK506 treatment combined with gradual withdrawal of NTBC before cell transplantation ensured that Fah (-/-) Nod/Scid mice were susceptible to liver xeno-repopulation by human hepatocytes; the proportion of engrafted human hepatocytes reached 33.6%. The function of the expanded human hepatocytes within the chimeric liver was confirmed by weight curve analysis, the expression of characteristic proteins, and the biochemical analysis of liver function. These results show that Fah (-/-) Nod/Scid mice are an ideal humanized liver mouse model with many useful applications.

Liver xeno-repopulation with human hepatocytes in Fah-/-Rag2-/- mice after pharmacological immunosuppression

Functional human hepatocytes xeno-engrafted in mouse liver can be used as a model system to study hepatitis virus infection and vaccine efficacy. Significant liver xeno-repopulation has been reported in two kinds of genetically modified mice that have both immune deficiency and liver injury-induced donor hepatocyte selection: the uPA/SCID mice and Fah(-/-) Rag2(-/-)Il2rg(-/-) mice. The lack of hardy breeding and the overly elaborated technique in these two models may hinder the potential future application of these models to hepatitis virus infection and vaccination studies. Improving the transplantation protocol for liver xeno-repopulation from human hepatocytes will increase the model efficiency and application. In this study, we successfully apply immunosuppressive drug treatments of anti-asialo GM1 and FK506 in Fah(-/-)Rag2(-/-) mice, resulting in significant liver xeno-repopulation from human hepatocytes and human fetal liver cells. This methodology decreases the risk of animal mortality during breeding and surgery. When infected with hepatitis B virus (HBV) sera, Fah(-/-)Rag2(-/-) mice with liver xeno-repopulation from human hepatocytes accumulate significant levels of HBV DNA and HBV proteins. Our new protocol for humanized liver could be applied in the study of human hepatitis virus infection in vivo, as well as the pharmacokinetics and efficacy of potential vaccines.

RNAi-mediated silencing of insulin receptor substrate-4 enhances actinomycin D- and tumor necrosis factor-alpha-induced cell death in hepatocarcinoma cancer cell lines

Insulin receptor substrate-4 (IRS-4) transmits signals from the insulin-like growth factor receptor (IGF-IR) and the insulin receptor (IR) to the PI3K/AKT and the ERK1/2 pathways. IRS-4 expression increases dramatically after partial hepatectomy and plays an important role in HepG2 hepatoblastoma cell line proliferation/differentiation. In human hepatocarcinoma, IRS-4 overexpression has been associated with tumor development. Herein, we describe the mechanism whereby IRS-4 depletion induced by RNA interference (siRNA) sensitizes HepG2 cells to treatment with actinomycin D (Act D) and combined treatment with Act D plus tumor necrosis factor-alpha (TNF-alpha). Similar results have been obtained in HuH 7 and Chang cell lines. Act D therapy drove the cells to a mitochondrial-dependent apoptotic program involving cytochrome c release, caspase 3 activation, PARP fragmentation and DNA laddering. TNF-alpha amplifies the effect of Act D on HepG2 cell apoptosis increasing c-jun N-terminal kinase (JNK) activity, IkappaB-alpha proteolysis and glutathione depletion. IRS-4 depleted cells that were treated with Act D showed an increase in cytochrome c release and procaspase 3 and PARP proteolysis with respect to control cells. The mechanism involved in IRS-4 action is independent of Akt, IkappaB kinase and JNK. IRS-4 down regulation, however, decreased gamma-glutamylcysteine synthetase content and cell glutathione level in the presence of Act D plus TNF-alpha. These results suggest that IRS-4 protects HepG2 cells from oxidative stress induced by drug treatment.

Effect of the immunosuppressants on hepatocyte proliferation and apoptosis in a young animal model of liver regeneration: an immunohistochemical study using tissue microarrays

Hepatocyte proliferation and apoptosis (programmed cell death) occur during the liver parenchyma regeneration and the liver size modeling is mainly controlled by hepatocyte apoptosis. The purpose of the present study was to verify the influence of immunosuppressant drugs on these phenomena by utilizing tissue microarray techniques. Thirty-six weaning rats (age 21-23 days, weight 30-50 g) were divided into six groups: control, sham, hepatectomy, hepatectomy plus solumedrol, hepatectomy plus CsA, and hepatectomy plus Tac. The animals were killed one day after hepatectomy, and the remnant livers were weighed and harvested for tissue microarray sections. Liver cell proliferation was evaluated by staining for PCNA and apoptosis was detected by the TUNEL method. It was verified that CsA promoted a decrease in the liver weight, Tac and CsA decreased the proliferation index of hepatocytes, and glucocorticoid had no significant effects. The apoptosis index was not altered by hepatectomy or immunosuppressants. Our data indicate that, in the growing rat, CsA and Tac have negative effects on hepatocyte proliferation and have no effect on the hepatocyte apoptosis.

Facilitation of Survival in a Rat Fulminant Hepatic Failure Model by Combination Therapy Using Recombinant G-CSF and Tacrolimus

The mortality rate of fulminant hepatic failure (FHF) is high because of retarded liver regeneration. Recombinant human granulocyte colony-stimulating factor (rHuG-CSF) and tacrolimus are known to be immunosuppressive and supportive to liver regeneration. We investigated the effects of their combination therapy in a rat FHF model with a 68% partial hepatectomy and 24% liver necrosis. All rats without drug pretreatment died within 55 h. The median time was prolonged from 37 to 52 h by rHuG-CSF (250 microg/kg/day s.c. on days -5 to 0) and to 46 h by tacrolimus (0.5 mg/kg/day i.m. on days -2 to 0). Notably, the combination therapy facilitated DNA biosynthesis and survival prolongation, with a median of 77 h. The interferon-gamma (IFN-gamma) protein levels and natural killer cell (NK) activity in the liver were low at 12 h, and no further inhibition was detected by any treatment. Tacrolimus significantly upregulated the mRNA levels of insulin receptors and transforming growth factor-alpha (TGF-alpha), whereas rHuG-CSF did not. Regarding tissue remodeling-related factors, rHuG-CSF upregulated mRNA levels of vascular endothelial growth factor (VEGF) and matrix metalloproteinase- 9 (MMP-9), whereas tacrolimus did not. The combination treatment upregulated protein levels of both insulin receptors and VEGF. These results suggest that tacrolimus improves the hepatocyte replication and rHuG-CSF contributes to tissue reconstitution, and this combination therapy directly facilitates liver regeneration in the FHF model.

Insulin receptor substrate-4 signaling in quiescent rat hepatocytes and in regenerating rat liver

This study was designed to characterize insulin receptor substrate-4 (IRS-4) in isolated rat hepatocytes and to examine its role in liver regeneration. Subcellular fractionation revealed that 85% of IRS-4 is located at isolated hepatocyte plasma membranes. The distribution of IRS-4 among intracellular compartments remained unchanged in insulin-stimulated cells. Two bands corresponding to 145 and 138 kd were observed in immunoblotting experiments. Immunoprecipitation of hepatocyte lysates with a highly specific antibody against IRS-4 led to an insulin and insulin-like growth factor 1 (IGF-1)-dependent increase in phosphotyrosine residues of the 145-kd band. IRS-4 was found to be associated with Src homology 2 (SH2) domain-containing proteins (phosphatidylinositol 3-kinase [PI 3-kinase] and Src homology phosphatase [SHP-2]) and with protein kinase C zeta (PKC zeta). Insulin and IGF-1 elicited a rapid and dose-dependent binding of these 3 proteins to IRS-4. These data suggest that IRS-4 is insulin-/IGF-1-activated by phosphorylation and not by translocation, inducing the recruitment of SH2 domain-containing proteins and PKC zeta to the membrane. To evaluate the possible role of IRS-4 in liver regeneration, we also examined this system after partial hepatectomy (PH). One day after PH, IRS-1 expression increased, consistent with a stimulatory role in the regenerative process, whereas it decreased 7 days after liver resection. This drastic IRS-1 depletion occurred at the expense of increased IRS-2 and IRS-4 expression 7 days after PH. In addition, at this period of time after surgery, the in vivo insulin stimulation of remnant rat livers showed an increase in IRS-4/PI 3-kinase association. Given that 1 and 7 days after PH isolated hepatocytes responded similarly to insulin in terms of induced cell proliferation, a compensatory role is proposed for IRS-2/4 induction. In conclusion, IRS-4 is activated by insulin and IGF-1-like IRS-1 in rat hepatocytes, and the induced expression of IRS-4 is a compensatory mechanism that plays a role in conditions of liver regeneration.