| Development of new pharmaceutical strategies to attenuate acute phase hepatic ischemia-reperfusion injury in liver transplantation using small-for-size grafts is always important to expand the liver donor pools in split liver transplantation for adult patients.Cell survival Akt ( protein kinase B) signaling is important for intracellular homeostasis. Akt plays a critical role in controlling the balance between survival and apoptosis. Akt activation has been demonstrated to be a key mediator in an-tiapoptotic signaling during liver regeneration and to prevent cardiac ischemia-reprefusion injury. Activation of Akt signaling pathway during the early phase after liver transplantation using small-for-size grafts might be important to rescue the grafts from injury. Up to now, no pharmaceutical treatment targeting on cell survival/apoptosis pathways has been studied in liver transplantation using small-for-size grafts.FTY720 ( 2-amino-2-[ 2-( 4-octylphenyl) ethyl ] -1, 3-propanediol hydro-chloride ) is synthetically derived from myriocin (ISP-1 ) , a metabolite isolated from the ascomycete, Isaria sinclarii. FTY720 is a novel irnmunomodulator, which has been demonstrated to prolong allograft survival in a variety of solid organ transplant models. Recently, FTY720 was found to be able to prevent ischemia-reperfusion injury in liver and kidney models with a similar mechanism. However, the exact protective mechanism, especially the effect of FTY720 on hepatocytes has not been extensively studied. In the current study, we aim to probe into the protective mechanism of FTY720 in a rat liver transplantation model using small-for-size grafts by investigation of cell signaling pathways related to survival, apoptosis and acute phase inflammatory response.MethodAnimal model and Surgical procedure: Male inbred Lewis rats were used as donors and recipients. The experiment was conducted in two groups of rats: control group ( n = 22) and FTY720 treatment group ( n = 18 ). A rat model of small-for-size non-arterialized orthotopic liver transplantation without veno-ve-nous bypass was used. . The median lobe and right lobe of the liver were selected to be the graft and the median ratio of the graft weight to the recipient liver weight (graft weight ratio) was 39% (range 3645%). In the FTY720 treatment group, 1 mg/kg FTY720 in 1 ml of saline was given intravenously at 20 minutes before graft harvesting in the donor, immediately before liver harvesting in the recipient and immediately after reperfusion in the recipient. The same a-mount of saline was given in the control group at the same time points.Survival study; Six rats in the FTY720 group and 10 rats in the control group were used for survival study. Rats that had lived for more than 7 days after transplantation were considered survivors.Detection method: Liver tissues and blood were sampled at 6 and 24 hours after reperfusion for hepatic gene detection, morphologic examination, and liver function tests. Six rats were included at each time point for the treatment group and control group, respectively. Intragraft protein levels of signaling pathways of cell survival (Akt) , apoptosis (Caspase) and inflammatory response (MAPK) were detected by Western-blot. Intracellular expression of Phospho-Aktser473, A20, inducible nitric oxide synthase (iNOS) and endothelial nitric oxide syn-thase (eNOS) were detected by immunostaining. Morphological study was examined by HE and electron microscopy. Hepatic apoptosis was compared by TUNEL assay.ResultsFTY720 improved 7-day graft survival; Seven-day graft survival rate was significantly improved by FTY720 treatment from 40% (4/10) in the controlgroup to 100% (6/6) (p = 0.034).FTY720 significantly improved liver function: FTY720 treatment significantly decreased the serum levels of ALT and AST at 24 hours after liver transplantation (ALT: 1215 (722-1289) vs 1970 (709-3170) U/L, p=0.035; AST: 851 (582-1089) vs 1840 (1207-4090) U/L, p =0.011). The serum level of total bilirubin was significantly lower at 6 h...
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