MMP-12 polarizes neutrophil signalome towards an apoptotic signature

While macrophages are well-known to polarize across the inflammatory spectrum, neutrophils have only recently been found to activate in a similar fashion in response to pro- or anti-inflammatory stimuli. Matrix metalloproteinase (MMP)-12 mediates neutrophil physiology with direct signaling mechanisms yet to be investigated. We hypothesized MMP-12 may modify neutrophil signaling. Bone marrow neutrophils were stimulated with interleukin (IL-1 beta; pro-inflammatory), IL-4 (anti-inflammatory), or MMP-12. The secretome was mapped by multi-analyte profiling and intracellular signaling evaluated by array. IL-1 beta induced a cytokine-mediated inflammatory LPS-like signalome, with upregulation of pro-inflammatory cytokines such as interferon gamma (IFN gamma,15.2-fold,p = 0.001), chemokine (C-X-C motif) ligand 1 (CXCL1,8.4-fold,p - 0.005), and tumor necrosis factor alpha (TNF alpha,11.2-fold,p = 0.004). IL-4 induced strong intracellular signaling with upregulation of mitogen-activated protein kinase kinase (MEK1;1.9-fold,p = 0.0005) and downregulation of signal transducer and activator of transcription 4 (STAT4;0.77-fold,0.001). MMP-12 increased IL-4 secretion 20-fold and induced a robust apoptotic neutrophil signalome with upregulation of forkhead box O1 (FOXO1;1.4-fold,p < 0.0001) and downregulation of WNT signaling with MMP-12 cleavage of the adherens junction components beta-catenin, cahderin-3, and catenin-alpha 2. In conclusion, neutrophils shifted phenotype by stimuli, with MMP-12 inducing a unique apoptotic signalome with higher resemblance to the anti-inflammatory signalome. Significance: This study revealed that neutrophils demonstrate unique polarization signaling responses to specific stimuli, with the matrix metalloproteinase (MMP)-12 signalome showing similarity to the IL-4 signalome. MMP-12 polarized neutrophils towards a strong apoptotic signature by upregulating FOXO1 and downregulating WNT signaling. Our results highlight that neutrophils display more plasticity than previously appreciated.

Automated summary

Neutrophils display unique polarization signaling responses to specific stimuli, with the MMP-12 signalome showing similarity to the IL-4 signalome. MMP-12 polarized neutrophils towards a strong apoptotic signature by upregulating FOXO1 and downregulating WNT signaling. These results highlight the plasticity of neutrophils beyond previous understanding.