Delineating the role of autophagy in ischemia reperfusion injury

• Applicant: Dr. Christiane Sokollik
• Subject Area: Pediatric and Adolescent Medicine
• Term: Funded in 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 216538522

Despite improved short term outcomes due to advances in immunosuppressive therapy, longterm graft survival in the setting of solid organ transplantation remains unchanged. This is of particular concern for children where with regard to their natural life expectancy an excellent long term outcome is of utmost importance. There is convincing evidence that ischemia reperfusion injury (IRI) which inevitably occurs during solid organ transplantation shapes the later development of long term kidney and liver graft damage. During a transplant, when the organ is harvested from the donor the blood flow is shut down, causing ischemia. Once the organ is surgically placed into the patient and the blood vessels are reconnected, the graft undergoes reperfusion with blood. This results in tissue damage mediated by two main mechanisms. First, ischemia and reperfusion of the organ leads to the formation of toxic material called reactive oxygen species that induce cell death. Secondly, a variety of white blood cells enter the organ causing additional damage. Therefore, an ideal approach to prevent IRI would be to limit effects of both of these pathways. Recent studies indicate that a cellular recycling pathway called autophagy may help to remove the toxic reactive oxygen species that kill cells during ischemia reperfusion injury. Current evidence also indicates that autophagy is a critical regulator of host inflammatory responses and may be able to down-regulate the inflammatory response that occurs during IRI. Therefore, we hypothesize that the induction of autophagy will limit IRI by decreasing reactive oxygen species, danger signal production and white blood cell recruitment. To address this hypothesis we will employ an in- vitro model using primary human endothelial cells and expose them to simulated ischemia reperfusion to measure autophagy induction. We will then alter the degree of autophagy in these cells and determine the production of reactive oxygen species and danger signals. The chemoattraction of white blood cell to these cells will also be determined. To confirm our findings in- vivo, a mouse model will be used where we can manipulate autophagy. After exposure of these mice to ischemia and reperfusion we will harvest blood and tissue to measure danger signal production and the degree of injury. Intravital microscopy will allow us to observe white blood cell attraction and their dynamics in real time. The findings generated from this study will a) help to enhance our understanding of the role of autophagy in ischemia reperfusion injury and b) elucidate the significance of manipulation of autophagy as a novel treatment option to decrease ischemia reperfusion injury. Both will potentially contribute to decrease longterm chronic graft dysfunction in children undergoing liver and kidney transplant.

• DFG Programme: Research Fellowships
• International Connection: Canada
• Host: Professorin Dr. Lisa Robinson