The protein tyrosine phosphatase Lyp/PTPN22 drives TNFα-induced priming of superoxide anions production by neutrophils and arthritis.

Neutrophils are essential for host defense against infections, but they also play a key role in acute and chronic inflammation. The protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene encodes the lymphoid-specific tyrosine phosphatase (Lyp) and a genetic single-nucleotide polymorphism of PTPN22 rs2476601 (R620W) has been associated with several human autoimmune diseases, including rheumatoid arthritis (RA). Here, we investigated the role of Lyp in TNFα-induced priming of neutrophil ROS production and in the development of arthritis using new selective Lyp inhibitors. Results show that Lyp-selective inhibitors (IC-11 and compound 8b), inhibited TNFα-induced priming of neutrophil superoxide anion production. TNFα induced an increase of Lyp protein expression in human neutrophils isolated from healthy donors. Key pathways involved in neutrophil priming were investigated. Lyp-selective inhibitors, inhibited TNFα-induced p47phox phosphorylation on Ser345, ERK1/2 phosphorylation and Pin1 activation. Interestingly, Lyp expression was increased in neutrophils isolated from synovial fluid of RA patients and Lyp inhibitors, I-C11 and compound 8b prevented superoxide anion production by endogenously primed neutrophils isolated from synovial fluid of RA. Moreover, IC-11 significantly prevented collagen antibody-induced arthritis in mice. These results show that Lyp expression is increased in inflammatory neutrophils, Lyp is involved in TNFα-induced excessive ROS production by neutrophils and its inhibition protected mice against arthritis. Inhibition of Lyp could be a therapeutic strategy in inflammatory arthritis.