Secretory leukocyte peptidase inhibitor (SLPI)

Secretory leukocyte peptidase inhibitor (SLPI) is a highly cationic, cysteine-rich single-chain protein produced by epithelial cells and secreted at high levels at mucosal surfaces, including the respiratory, gastrointestinal, and reproductive tracts[1][2][5][7]. SLPI inhibits a range of serine proteases—especially neutrophil elastase—protecting tissues from proteolytic damage during inflammation and various infections[1][2]. It also exhibits broad-spectrum antimicrobial activity against bacteria, fungi, and viruses, and is implicated in anti-inflammatory regulation via modulation of NF-κB signaling[2][5][6]. SLPI functions as a major defense molecule in mucosal immunity and plays roles in wound healing, cell proliferation, and apoptosis. The protein has clinical relevance in inflammatory lung diseases, several human cancers (where overexpression can correlate with tumor aggressiveness), and infection protection (HIV, HPV, bacterial pneumonia). SLPI's gene is located on chromosome 20q12-13.2 in humans[2][3]. Recombinant SLPI is under investigation for therapeutic use in inflammatory and respiratory disease, but is not yet approved as a drug. SLPI expression can serve as a biomarker for disease activity in inflammation, infection, and cancer[1][7].

Other names

AntileukoproteinaseSecretory leukocyte protease inhibitorWAP four-disulfide core domain protein 4WFDC4ALPMPIHUSI-IALK1BLPIHUSI-1Mucus proteinase inhibitorProtease inhibitor WAP4Seminal proteinase inhibitor

Direct inhibition of serine proteases (e.g., binding and inactivation of neutrophil elastase); Anti-inflammatory activity through suppression of NF-κB signaling pathways; Enhancement of glutathione synthesis and reduction of matrix metalloproteinases and prostaglandin E2; Interference with viral entry and replication by protein-protein interactions (e.g., blocking HIV and HPV uptake)