Oxylipins and metabolites from pyroptotic cells act as promoters of tissue repair

Pyroptosis is a lytic cell death mode that helps limit the spread of infections and is also linked to pathology in sterile inflammatory diseases and autoimmune diseases. During pyroptosis, inflammasome activation and the engagement of caspase-1 lead to cell death, along with the maturation and secretion of the inflammatory cytokine interleukin 1β (IL-1β). The dominant effect of IL-1β in promoting tissue inflammation has clouded the potential influence of other factors released from pyroptotic cells. Here, using a system where macrophages are induced to undergo pyroptosis without IL-1β/⍺ release (denoted Pyro-1), we uncover unexpected beneficial effects of the Pyro-1 secretome. First, we noted that the Pyro-1 supernatants upregulated gene signatures linked to migration, cellular proliferation, and wound healing. Consistent with this gene signature, Pyro-1 supernatants boosted migration of primary fibroblasts and macrophages, as well as faster wound closure in vitro, and improved tissue repair in vivo. In mechanistic studies, lipidomics and metabolomics of the Pyro-1 supernatants identified the presence of both oxylipins and metabolites, linking them to pro-wound healing effects. Focusing specifically on the oxylipin prostaglandin E2 (PGE2), we find that PGE2 synthesis is induced de novo during pyroptosis, downstream of caspase-1 activation, and COX2 activity; further, PGE2 synthesis occurs late in pyroptosis, with its release dependent on Gasdermin D pores opened during pyroptosis. As for the pyroptotic metabolites, they link to immune cell infiltration into the wounds, and polarization to CD301+ macrophages. Collectively, these data advance the concept that the pyroptotic secretome 1 Mehrotra et al., Page No. possesses oxylipins and metabolites with tissue repair properties that may be harnessed therapeutically. Supernatants from Live, apoptotic or pyroptotic cells were generated by triggering them with LeTox (and their live untreated coounterparts). Mo BMDMs were treated for 4h with the supernatants thus generated followed by RNAseq.