SLPI (secretory leukocyte peptidase inhibitor) is a multifunctional serine protease inhibitor with broad biological roles in immunity and tissue homeostasis. SLPI contains a whey acidic protein (WAP) domain that enables potent inhibition of neutrophil serine proteases including elastase, cathepsin G, and proteinase 3 1. Beyond protease inhibition, SLPI exhibits antimicrobial activity against mycobacteria and modulates inflammatory responses by suppressing NF-κB-mediated gene transcription in response to bacterial lipopolysaccharide 23. SLPI expression is upregulated by pro-inflammatory cytokines (IL-1, IL-6, TNF-α) and plays critical roles in tissue repair and wound healing by limiting protease-induced damage 45. In inflammatory lung diseases such as cystic fibrosis and COPD, SLPI protects airways from neutrophil-derived proteolytic damage while controlling excessive inflammation 6. Recent evidence reveals that α2-adrenergic signaling drives pathological SLPI production in cartilage, promoting hypertrophic degeneration and contributing to osteoarthritis progression; SLPI deletion prevents this cartilage degeneration 7. Additionally, while SLPI's anti-inflammatory and antimicrobial functions protect mucosal barrier tissues, excessive expression may promote epithelial tumor metastasis 8. These diverse functions position SLPI as a promising therapeutic target across multiple disease contexts.