Characterisation of the Autophagic Response within Human Liver Tissue During Oxidative Stress and HCV Infection
3rd Supervisor: Dr Zania Stamataki
Summary: Hepatitis C Virus (HCV) infection is currently a leading cause for orthotopic liver transplantation. The overwhelming majority of transplant recipients become re-infected, and the disease can frequently become difficult to control with antiviral drugs against a background of host immunosuppression. Therefore an important unmet clinical need exists to investigate novel pathways which may influence HCV infection, survival and replication proximal to the time of transplant surgery.
Autophagy is an evolutionarily conserved intracellular process of lysosomal-dependent degradation of long-lived proteins and cellular organelles. It plays an important role maintaining liver function during normal homeostasis and during potentially injurous processes such as oxidative stress. It is established that primary human hepatocytes exposed to hypoxic conditions in vitro increase basal autophagy via a mechanism dependent on Reactive Oxygen Species (ROS). Furthermore it is suggested that autophagy may also mediate the response of the liver to infectious agents such as HCV. Studies demonstrate that autophagy forms an important component of the innate immune system but it’s precise function remains uncertain. In addition hepatotropic viruses such as HCV and hepatitis B virus (HBV) have developed strategies to subvert and manipulate autophagy presumably for their own survival benefit. Specifically HCV may increase autophagy by inhibiting the autophagy regulatory proteins Akt/mTOR so aiding viral replication. Our preliminary data using human hepatocyte cell lines suggests that HCV infection and autophagy are potentiated under hypoxic conditions. How this observed increase in autophagy during hypoxia regulates HCV infection is not known. This project will investigate the normal autophagic response of primary human hepatocytes both in vivo and in vitro during oxidative stress which model the clinical scenerios encountered during liver transplantation (hypoxia and hypoxia – reoxygenation).
Hypothesis. That primary human hepatocytes and human liver under conditions of oxidative stress (hypoxia and hypoxia-reoxygenation) respond to HCV infection by upregulation of autophagy facilitating viral infection, survival and replication.
Specific Research Questions.
1. Is the increase in HCV infection we observe with the HCV permissive hepatoma cell line Huh-7.5 during hypoxia mediated by changes in cellular autophagy and is the viral infectivity further enhanced during reoxygenation?
2. Do primary human hepatocytes respond in an analogous manner to the human hepatocyte cell line?
3. Does the oxidative stress associated with ischemia reperfusion injury (IRI) seen during liver transplantation result in enhancement of the hepatocyte autophagic response in vivo thereby creating an environment which may promote viral infection?
This position is open to self-funded students only. Current home/EU tuition fees are £3,996 per annum and overseas tuition fees are £16,230 per annum.