Higher levels of Matrix metallopeptidase (MMP-12), C-X-C motif chemokine ligand-8 (CXCL8), neutrophil elastase, azurocidin 1 (AZU-1), and pro-platelet basic protein (PPBP) were observed in the sputum of ex-smoking asthmatics, which are linked to neutrophilic inflammation. Here, PPBP is linked to inflammatory response.