ASK1/2 signaling promotes inflammation in a mouse model of neutrophilic dermatosis

Mice homozygous for the Tyr208Asn amino acid substitution in the carboxy terminus of Src homology region 2 (SH2) domain-containing phosphatase 1 (SHP-1) (referred to as Ptpn6(spin) mice) spontaneously develop a severe inflammatory disease resembling neutrophilic dermatosis in humans. Disease in Ptpn6(spin) mice is characterized by persistent footpad swelling and suppurative inflammation. Recently, in addition to IL-1 alpha and IL-1R signaling, we demonstrated a pivotal role for several kinases such as SYK, RIPK1, and TAK1 in promoting inflammatory disease in Ptpn6(spin) mice. In order to identify new kinases involved in SHP-1-mediated inflammation, we took a genetic approach and discovered apoptosis signal-regulating kinases 1 and 2 (ASK1 and ASK2) as novel kinases regulating Ptpn6-mediated footpad inflammation. Double deletion of ASK1 and ASK2 abrogated cutaneous inflammatory disease in Ptpn6(spin) mice. This double deletion further rescued the splenomegaly and lymphomegaly caused by excessive neutrophil infiltration in Ptpn6(spin) mice. Mechanistically, ASK regulates Ptpn6(spin)-mediated disease by controlling proinflammatory signaling in the neutrophils. Collectively, the present study identifies SHP-1 and ASK signaling crosstalk as a critical regulator of IL-1 alpha-driven inflammation and opens future avenues for finding novel drug targets to treat neutrophilic dermatosis in humans.