N-acetyl cysteine protects against chlorine-induced tissue damage in an ex vivo model

High-level concentrations of chlorine (Cl₂) can cause life-threatening lung injuries and the objective in this study was to understand the pathogenesis of short-term sequelae of Cl₂-induced lung injury and to evaluate whether pre-treatment with the antioxidant N-acetyl cysteine (NAC) could counteract these injuries using Cl₂-exposed precision-cut lung slices (PCLS). The lungs of Sprague-Dawley rats were filled with agarose solution and cut into 250 μm-thick slices that were exposed to Cl₂ (20-600 ppm) and incubated for 30 min. The tissue slices were pre-treated with NAC (5-25 mM) before exposure to Cl₂. Toxicological responses were analyzed after 5 h by measurement of LDH, WST-1 and inflammatory mediators (IL-1β, IL-6 and CINC-1) in medium or lung tissue homogenate. Exposure to Cl₂ induced a concentration-dependent cytotoxicity (LDH/WST-1) and IL-1β release in medium. Similar cytokine response was detected in tissue homogenate. Contraction of larger airways was measured using electric-field-stimulation method, 200 ppm and control slices had similar contraction level (39 ± 5%) but in the 400 ppm Cl₂ group, the evoked contraction was smaller (7 ± 3%) possibly due to tissue damage. NAC-treatment improved cell viability and reduced tissue damage and the contraction was similar to control levels (50 ± 11%) in the NAC treated Cl₂-exposed slices. In conclusion, Cl₂ induced a concentration-dependent lung tissue damage that was effectively prevented with pre-treatment with NAC. There is a great need to improve the medical treatment of acute lung injury and this PCLS method offers a way to identify and to test new concepts of treatment of Cl₂-induced lung injuries.