Neutrophil Elastase Cleaves Laminin-332 (laminin-5) Generating Peptides That Are Chemotactic for Neutrophils

Proteolytic processing of laminin-332 by matrix metalloproteinase (MMP)-2 and MMP-14 has been shown to yield fragments that are promigratory for epithelial cells. During acute and chronic inflammation, proteases are elaborated by neutrophils and macrophages that can degrade basement membranes. We investigated the susceptibility of laminin-332 to degradation by the following neutrophil and macrophage proteases: neutrophil elastase (NE), cathepsin G, proteinase-3, and MMPs-2, -8, -9, and -12. Protease-specific differences were seen in the capacity to cleave the individual chains of laminin-332. NE and MMP-12 showed the greatest activity toward the gamma2 chain, generating a fragment similar in size to the gamma2x fragment generated by MMP-2. The digestion pattern of laminin-332 by degranulated neutrophils was nearly identical to that generated with NE alone. Digestion by supernatants of degranulated neutrophils was blocked by an inhibitor of NE, and NE-deficient neutrophils were essentially unable to digest laminin-332, suggesting that NE is the major neutrophil-derived protease that degrades laminin-332. In vivo, laminin gamma2 fragments were found in the bronchoalveolar lavage fluid of wild-type mice treated with lipopolysaccharide, whereas that obtained from NE-deficient mice showed a different cleavage pattern. In addition, NE cleaved a synthetic peptide derived from the region of human laminin gamma2 containing the MMP-2 cleavage site, suggesting that NE may generate laminin-332 fragments that are also promigratory. Both laminin-332 fragments generated by NE digestion and NE-digested laminin gamma2 peptide were found to be chemotactic for neutrophils. Collectively, these data suggest that degradation of laminin-332 by NE generates fragments with important biological activities.