Secretory leukocyte protease inhibitor inhibits neutrophil apoptosis

This is the authors' abstract. We don't add key points for this paper.

BACKGROUND AND OBJECTIVE: The secretory leukocyte protease inhibitor (SLPI) is a major anti-elastase barrier at the epithelial surfaces of upper respiratory tract. In addition to its anti-protease activity, SLPI has been shown to express anti-bacterial, anti-viral and anti-inflammatory properties. METHODS: We measured SLPI concentration in nasal lavage fluid of healthy volunteers after challenge with endotoxin (LPS) and evaluated SLPI effects in vitro on neutrophil chemotaxis, adhesion, cytokine (IL-8) release and apoptosis. RESULTS: SLPI concentration in nasal lavage (n = 9) 2, 6 and 24 h after the challenge with LPS (25 µg) increased from 32% to 238% compared with baseline (226 ± 71 ng/mL). In vitro, SLPI (20-80 µg/mL) induced neutrophil chemotaxis (sixfold, P < 0.001) and decreased neutrophil apoptosis by 73% (P = 0.006), relative to controls. However, SLPI had no affect on IL-8 release or neutrophil adhesion to fibronectin. SLPI-positive immunoreactivity was co-localized with neutrophils in lung specimens from patients with COPD. CONCLUSIONS: Our findings indicate upregulation of SLPI in response to LPS in nasal secretions and show anti-apoptotic effects of SLPI in primary human neutrophils suggesting a new role of SLPI during neutrophilic inflammation.