The IL-33/ST2 pathway in CNS : Traumatic brain injury and brain tumour

Interleukin 33 (IL-33) is a dual function cytokine. It is a member of the IL-1 family and it acts as a pro-inflammatory factor (18 kilo Dalton, 18 kD) like other cytokines in IL-1 family. IL-33 is also a transcription factor (32 kD - form) which can suppress or activate gene transcription in diverse cases. A variety of cell types and tissues in the central nervous system (CNS) can release IL-33 after injury. The 18 kD IL-33 binds to the membrane receptor protein ST2 ligand, then regulates downstream gene expression, triggers cytokine synthesis, and modulates the immune system response. After traumatic brain injury (TBI) in the CNS, glial cells become key players in the nervous tissue response. Astrocytes undergo activation, proliferation, release pro-inflammatory factors and, as a consequence, a glial scar barrier around the injury is formed. Simultaneously, resting microglia are activated and able to remove debris. Lastly, oligodendrocytes together with microglia and astrocytes are activated and communicate with the immune system. In addition, as a severe kind of injury to the CNS, brain tumours share some similar characteristics of brain injury, such as hypoxia and inflammation. Therefore, IL-33 may play a role in neuroinflammation and also in brain tumours. In this project, our aim was to investigate the role of IL-33 and the IL-33/ST2 pathway in traumatic brain injury and brain tumours (e.g glioma). We found that IL-33 can influence the CNS immune resonse, and may be important in CNS pathology.