TNFα counteracts interleukin-10 anti-inflammatory pathway through the NOX2-Lyn-SHP-1 axis in human monocytes

TNF alpha-mediated signaling pathways play a pivotal role in the pathogenesis of inflammatory diseases such as rheumatoid arthritis (RA) and inflammatory bowel disease (IBD) by promoting phagocyte inflammatory functions, notably cytokine release and reactive oxygen species (ROS) production by NOX2. In contrast, interleukin10 (IL-10), a powerful anti-inflammatory cytokine, potently shuts down phagocyte activation, making IL-10 an attractive therapeutic candidate. However, IL-10 therapy has shown limited efficacy in patients with inflammatory diseases. Here, we report that TNF alpha blocks IL-10 anti-inflammatory pathways in human monocytes, thereby prolonging inflammation. TNF alpha decreased IL-10-induced phosphorylation of STAT3 and consequently IL-10-induced expression of the major anti-inflammatory factor, SOCS3. Decreased STAT3 phosphorylation was due to a SHP1/2 phosphatase, as NSC-87877, a SHP1/2 inhibitor, restored STAT3 phosphorylation and prevented the TNF alpha-induced inhibition of IL-10 signaling. TNF alpha activated only SHP1 in human monocytes and this activation was NOX2-dependent, as diphenyleneiodonium, a NOX2 inhibitor, suppressed SHP1 activation and STAT3 dephosphorylation triggered by TNF alpha. ROS-induced activation of SHP1 was mediated by the redoxsensitive kinase, Lyn, as its inhibition impeded TNF alpha-induced SHP1 activation and STAT3 dephosphorylation. Furthermore, H2O2 recapitulated TNF alpha-inhibitory activity on IL-10 signaling. Finally, NSC-87877 dampened collagen antibody-induced arthritis (CAIA) in mice. These results reveal that TNF alpha disrupts IL-10 signaling by inducing STAT3 dephosphorylation through a NOX2-ROS-Lyn-SHP1 axis in human monocytes and that inhibition of SHP1/2 in vivo protects against CAIA. These new findings might explain the poor efficacy of IL-10 therapy in patients with inflammatory diseases and suggest that anti-TNF alpha agents and SHP1/2 inhibitors could improve the therapeutic use of IL-10.