1. Division of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea & Westminster Hospital, London, UK.
2. Department of Anaesthesiology, Southwest Hospital, Army Medical University, Chongqing, China.
3. Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Zhejiang, China.
4. Department of Anaesthesiology, Shenzhen Second People's Hospital/the First Affiliated Hospital of Shenzhen University, Health Science Centre, Shenzhen, China.
5. Department of Anaesthesiology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China.
* These authors contributed equally to this work; HLZ, JTG and DMA share senior authorship.
Background: Effective preservation strategies to ameliorate lung graft ischaemia injury are needed to rescue 'extended criteria' or 'marginal' lung grafts, and to improve recipient outcomes after transplantation.
Methods: Lung grafts from male Lewis rats were extracted after 40 min of cardiocirculatory death, and healthy human lung tissues were collected from patients undergoing a lobectomy. Lung samples were then preserved in a 4°C preservation solution supplemented with 0.1 nM Dexmedetomidine (Dex, α2-adrenoceptor agonist) for 16 h. In vitro, human lung epithelial A549 cells were preserved in the 4°C preservation solution with 0.1 nM Dex for 24 h, then re-cultured in the cell culture medium at 37°C to mimic the clinical scenario of cold ischaemia and warm reperfusion. Lung tissues and cells were then analysed with various techniques including western blot, immunostaining and electron microscope, to determine injuries and the protection of Dex.
Results: Prolonged warm ischaemia after cardiocirculatory death initiated Rip kinase-mediated necroptosis, which was exacerbated by cold storage insult and enhanced lung graft injury. Dex supplementation significantly reduced necroptosis through upregulating Nrf2 activation and reducing oxidative stress, thereby significantly improving lung graft morphology. Dex treatment also attenuated endoplasmic reticulum stress, stabilised lysosomes and promoted cell membrane resealing function, consequently reducing cell death and inflammatory activation after hypothermic hypoxia-reoxygenation in A549 cells.
Conclusions: Inhibition of regulated cell death through Dex supplementation to the graft preservation solution improves allograft quality which may aid to expand the donor lung pool and enhance lung transplant outcomes per se.
Keywords: Donation after cardiocirculatory death, Lung transplantation, Ischaemia reperfusion injury, Regulated cell death, Dexmedetomidine.