MMP-12 processing of human ELR⁺ CXC chemokines. (A) Analysis of MMP-12 proteolysis of human CXCL1, -2, -3, -5, -6, -7, and -8 incubated with or without 1 μmol/L prinomastat (MMPI) as a control on silver-stained 15% Tris-Tricine SDS-PAGE gel. Black horizontal lines separate individual gels. (B) Identification of human and murine MMP-12 cleavage products by MALDI-TOF MS. Deconvolution of mass spectrometry data revealed that MMP-12 cleaved 6 human ELR⁺ CXC chemokines in, or downstream of, the ELR motif. Cleavage products generated by proteolysis within the ELR motif are highlighted in bold. Arrows indicate human and murine MMP-12 cleavage sites.