S. S. Abdelhamid1, X. Sun1, J. Scioscia1, J. Darby1, Z. Secunda1, H. Moheimani1, B. Al Matour1, J. Mulla1, U. Kar1, J. Das1, T. Billiar1 1University Of Pittsburgh, Pittsburgh, PA, USA
Introduction: An extensive release of metabolites and DAMPs into the circulation after severe hemorrhagic shock drives the systemic inflammatory response. Caspases 1 and 11 inflammasomes are multiprotein oligomers that cleave GasderminD, a downstream protein that forms pores in the plasma membrane. These pores contribute to the release of DAMPs and other cellular constituents into the circulation after severe injury. Elucidating the mechanisms that activate GasderminD cleavage in response to trauma and how caspases contribute to this activation could identify targets to reduce the systemic inflammatory response to severe injury.
Methods: Unmanipulated C57BL6/J controls and mice subjected to severe hemorrhagic shock (3 hours, 25 mmHG) with soft tissue injury (HS/T) were included in this study. Groups were divided into wild type, GasderminD-/-, Caspase-1-/-, and Caspase-11-/-. Each group included a total of 6 mice (3 males, 3 females) for a total of 48 mice. Plasma was isolated 30 minutes after resuscitation and sent for untargeted metabolomic analysis (Metabolon, NC, n = 902 metabolites). Dimension reduction and clustering analysis was used on R.
Results: Metabolites across several superpathways and classes were analyzed between groups. Circulating amino acid levels were significantly increased in WT HS/T mice compared to GasderminD-/- mice (p< 0.05), indicating a high turnover of proteins following severe shock driven by GasderminD. Deletion of Caspase 1 or Caspase 11 each resulted in a minimal partial reversal of the release of metabolites after HS/T. This suggests that inflammasomes involving caspases 1 and 11 are important for trauma induced cell disruption and release of metabolites.
Conclusion: Our findings point to an important role for inflammatory caspases in the systemic storm that takes place following hemorrhagic shock with tissue injury. Because GasderminD is a known effector of both the canonical (Caspase1) and non-canonical (caspase 11) inflammasome, it is likely that both pathways contribute to GasderminD activation/cleavage. The association with amino acid release also points to a role of these pathways in proteolysis after injury.
