Secretory leukocyte protease inhibitor (SLPI)

Secretory leukocyte protease inhibitor (SLPI) is a small, cationic, secreted protein that functions as a serine protease inhibitor, providing critical protection for epithelial tissues at mucosal surfaces against inflammatory damage from enzymes like neutrophil elastase and cathepsins. It is widely expressed in respiratory, gastrointestinal, and genitourinary tracts, as well as in fluids including saliva, seminal plasma, and nasal and bronchial secretions. SLPI also displays broad antimicrobial activity—including antiviral action against HIV—and regulates inflammation by inhibiting NF-κB-dependent gene transcription in immune cells. In disease states, SLPI contributes to defense against lung tissue degradation, infection control, and maintenance of epithelial integrity, but overexpression in cancer can promote tumor progression and metastasis. Therapeutically, recombinant SLPI is under investigation for conditions where protease imbalance leads to tissue destruction, such as cystic fibrosis, emphysema, asthma, and potentially heart failure. SLPI levels serve as biomarkers of inflammation, infection, and tumor aggressiveness.

Other names

AntileukoproteinaseSecretory leukoprotease inhibitorMucus protease inhibitorBronchial secretory inhibitorHuman seminal inhibitor ICervix uteri secretion inhibitor

Inhibition of serine proteases, reducing tissue damage from inflammation. Down-regulation of NF-κB-mediated gene transcription to prevent excessive inflammatory response. Antimicrobial effects, including the inhibition of HIV entry and replication. Modulation of immune cell responses (macrophage activation and cytokine release).