RIP1-driven autoinflammation targets IL-1α independently of inflammasomes and RIP3

The protein-tyrosine phosphatase SHP-1 has critical roles in immune signalling, but how mutations in SHP-1 cause inflammatory disease in humans remains poorly defined(1). Mice homozygous for the Tyr208Asn amino acid substitution in the carboxy terminus of SHP-1 (referred to as Ptpn6(spin) mice) spontaneously develop a severe inflammatory syndrome that resembles neutrophilic dermatosis in humans and is characterized by persistent footpad swelling and suppurative inflammation(2,3). Here we report that receptor-interacting protein 1 (RIP1)-regulated interleukin (IL)-1 alpha production by haematopoietic cells critically mediates chronic inflammatory disease in Ptpn6(spin) mice, whereas inflammasome signalling and IL-1 beta-mediated events are dispensable. IL-1 alpha was also crucial for exacerbated inflammatory responses and unremitting tissue damage upon footpad microabrasion of Ptpn6(spin) mice. Notably, pharmacological and genetic blockade of the kinase RIP1 protected against wound-induced inflammation and tissue damage in Ptpn6(spin) mice, whereas RIP3 deletion failed to do so. Moreover, RIP1-mediated inflammatory cytokine production was attenuated by NF-kappa B and ERK inhibition. Together, our results indicate that wound-induced tissue damage and chronic inflammation in Ptpn6(spin) mice are critically dependent on RIP1-mediated IL-1 alpha production, whereas inflammasome signalling and RIP3-mediated necroptosis are dispensable. Thus, we have unravelled a novel inflammatory circuit in which RIP1-mediated IL-1 alpha secretion in response to deregulated SHP-1 activity triggers an inflammatory destructive disease that proceeds independently of inflammasomes and programmed necrosis.