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No description available.

No description available.

Liver transplantation was first performed in 1963 (1) as an experimental treatment for end stage liver disease. Three patients were transplanted, all of whom died within 3 weeks. Since then it has become an established therapy resulting in improved quality of life (2), with 675 transplants from cadaveric donors taking place in the UK in 2001 and 706 in 2002 (3). This level of activity compares with 10 years ago when 502 liver transplants were performed in 1992. Figures released for survival up to the year 2000 show that early (1 year) survival has improved to 88% for patients transplanted from 1998 – 1999, with 3 year survival for the period 1996 – 1997 being 73% and 5 year survival for the period 1994 – 1995 being 64% (3). This improvement is probably due to a combination of factors such as improved surgical and anaesthetic technique, changes in medical management after transplantation, the improved recognition of other harmful factors like hypertension, choice of immune suppression and better prediction of patients in whom liver transplantation is not likely to be appropriate such as those with cholangiocarcinoma or multiple large hepatocellular carcinomas. [Taken from Introduction]

This thesis sought to investigate novel methods for protecting the liver from ischaemia reperfusion injury in the context of liver transplantation. Research in the heart, brain and kidneys has suggested that hypoxia inducible factor (HIF) may play a key role in the delayed phase of ischaemic preconditioning and can protect organs for up to 3 days. However, although there is good evidence for the potential of HIF to protect organs from ischaemia, the HIF pathway still presents some what of a paradox because it targets both pro-death (e.g. BNIP3,NIX) as well as pro-survival genes (e.g. HO-I, EPO). HIF is primarily controlled by 3 oxygen dependent prolyl hydroxylases (PHD 1 , PHD2, PHD3), and inhibition of these prolyl hydroxylases leads to HIF activation. It was hypothesised that differential inhibition of PHD 1,2 or 3 may result in selective gene regulation and may confer greater or less protection against ischaemia reperfusion injury. To investigate this hypothesis mouse embryonic fibroblasts (MEFs) were isolated from PHDl, 2, and 3 knock-out (KO) embryos and compared to MEFs derived from WT littermate controls. In these MEFs, cell growth and proliferation, as well as cell survival following exposure to anoxia and inducers of apoptosis was studied. The principal findings were that PHD2 is the dominant regulator of HIF in normoxia. PHD2 knock-out MEFs exhibited glycolytic metabolism and had a lower oxygen consumption compared to wild-type MEFs. Gene array studies confirmed the dominant role of PHD2 but also demonstrated that PHD 1 upregulates a number of HIF target genes, albeit to a lesser extent than PHD2. There were no differences, however, in susceptibility to hypoxic injury in the PHDl, 2, and 3 knock-out MEFs compared to wild-type controls. A further aim of the study was to investigate whether prolyl hydroxylase inhibition using dimethyloxalyglycerine (DMOG) may protect the liver in a rodent model of ischaemia reperfusion injury. DMOG effectively upregulated HIF and IllF target genes. Serum transaminases (AST and AL T) were significantly lower in the DMOG treated animals compared to the normal saline treated controls 24 hours following ischaemia. This protection was similar to the protection conferred by surgically induced ischaemic preconditioning. This thesis provides important insights into the individual function of the prolyl hydroxylases and provides preliminary evidence that prolyl hydroxylase inhibitors may be useful in the treatment of ischaemia reperfusion injury in liver transplantation.