The Evaluation of Acute Lung Injury Induced by Nitrogen Mustard in Mouse Precision Cut Lung Slices

Abstract

Nitrogen Mustard (NM; mechlorethamine hydrochloride) is a cytotoxic alkylating agent known to cause progressive pulmonary injury. Its toxic properties elicit extensive tissue remodeling within the respiratory tract, contributing to the development of chronic lung disease. Precision-Cut Lung Slices (PCLS) represent an ex vivo alternative to in vivo studies, minimizing animal numbers while increasing experimental replicates, which is advantageous for mechanistic toxicology studies and evaluating potential therapeutics. PCLS are three-dimensional excerpts of the lung that include all resident cell types; they remain viable in culture for up to 14 days, allowing for evaluation of functional activity, structural alterations and cytotoxicity. In the present studies, PCLS were used to assess NM-induced lung injury and alterations in pulmonary mechanics. C57BL/6 mice were euthanized, the lungs filled with agarose, isolated after congealment, and sliced (300 mM in thickness); slices were cultured in Dulbecco's Modified Eagle's Medium (DMEM) and Ham's F-12 Nutrient Mixture (DMEM/F-12). Twenty-four hours later, PCLS were treated with NM (1, 10, and 100 mM) for one hour, washed, refed with medium and cultured for 3 days. NM caused a dose-related increase in cytotoxicity and a decrease in mitochondrial activity as measured by lactate dehydrogenase (LDH) and WST-1 assays, respectively. Analysis of histologic sections revealed that NM caused damage to the airway epithelium; this was associated with decreased mRNA expression of collagen1A1 and collagen3A1, markers of tissue repair. To determine if these changes were linked to altered pulmonary function, we measured airway responsiveness using video microscopy. In these studies, changes in airway area after stimulation with increasing concentrations of methacholine were assessed in cross-sectional airways. Consistent with structural alterations, NM caused a ~30% decrease in maximal airway contraction after methacholine, relative to control, indicating a loss in airway smooth muscle function. These data demonstrate that PCLS can be used effectively to mechanistically assess the progression of injury induced by NM. Further understanding of the progression of damage and repair processes following exposure to mustards is essential in order to develop therapeutics for treating pulmonary toxicity.