Oral Presentation 2019 Hunter Cell Biology Meeting

Activation of mitochondrial apoptotic signalling to trigger inflammation (#28)

Kate Lawlor 1 2 , James Vince 3 4 , Dominic De Nardo 3 4 , Wenqing Gao 5 , Angelina Vince 3 , Cathrine Hall 3 , Kate McArthur 6 , Daniel Simpson 3 4 , Swarna Lekha Vijayaraj 3 4 , Lisa Lindqvist 3 4 , Philippe Bouillet 3 4 , Mark Rizzacasa 7 , Si Ming Man 8 , John Silke 3 4 , Seth Masters 3 4 , Guillaume Lessene 3 4 , David Huang 3 4 , Daniel Gray 3 4 , Benjamin Kile 6 , Feng Shao 5
  1. Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia
  2. Department of Molecular and Translational Science, Monash University, Clayton, VIC, Australia
  3. The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
  4. Department of Medical Biology, The University of Melbourne, Parkville, VIC, Australia
  5. National Institute of Biological Sciences, Beijing, China
  6. Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
  7. School of Chemistry, The Bio21 Institute, The University of Melbourne, Melbourne, VIC, Australia
  8. John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia

Apoptotic cell death is classically regarded as immunologically silent. The mitochondrial or “intrinsic” apoptotic pathway is an evolutionarily conserved, BCL-2 family regulated, process that promotes the death and phagocytic clearance of stressed, damaged or infected cells. BAX and BAK-mediated mitochondrial membrane damage is essential for mitochondrial apoptosis, and is required for the downstream activation of apoptotic effector caspase activity. Consequently, the study of BAX/BAK regulation in cancer cells has resulted in the development of rationally designed BH3-mimetics compounds that trigger BAX/BAK to induce cancer cell death. However, research into the consequences of activating mitochondrial apoptosis in innate immune cells, such as macrophages, is less well studied. Using a range of targeted BH3-mimetic compounds, and other cancer chemotherapeutics, we have discovered the key pro-survival BCL-2 family members required to prevent spontaneous BAX/BAK apoptotic cell death in macrophages. Unexpectedly, we also observed that BAX/BAK signaling in macrophages triggers the activation of inflammasome-associated caspase, caspase-1, resulting in the activation and release of the pro-inflammatory cytokine, interleukin-1b (IL-1b). Using a panel of mice deficient in apoptotic signaling machinery, inflammasome sensor proteins or inflammatory caspases, we have defined a novel pathway by which BAX/BAK can cause inflammation via NLRP3 inflammasome activation. We believe this molecular pathway may underpin observations linking chemotherapeutic and cellular stress responses to inflammasome and IL-1b-driven inflammation.