A new technique of bronchial microsampling and proteomic analysis of epithelial lining fluid in a rat model of acute lung injury

Abstract

The standard technique to evaluate the proteins present in epithelial lining fluid (ELF) is bronchoalveolar lavage (BAL). Bronchoscopic microsampling (BMS) method has been developed for humans as a less invasive alternative. We establish the usefulness of a rat bronchial microsampling (rBMS) to evaluate various proteins in ELF in lipopolysaccharide (LPS)-induced lung injury models in rats. In the first experiment of this study, we validate that whether the rBMS can obtain information from ELF in place of BAL. Tumor necrosis factor (TNF)-α concentrations were increased in the rBMS samples similar to BAL 1 and 3h after LPS instillation. In the second part of this study, a proteomic analysis of the rBMS, using the Protein ChipR system, revealed the presence of proteins whose molecular weights corresponded to TNF-related proteins in the LPS-treated rats. In rats treated with a TNF-α converting enzyme inhibitor, the concentrations of these proteins in rBMS decreased or disappeared. In the third experiment, rBMS was performed without tracheostomy at 6 and 24h after instillation of LPS, and a rat multiple cytokines assay system detected heterogeneous variations in the concentrations of interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, TNF-αand interferon (IFN)-γ in ELF. The cytokine profile was significantly modified by pre-treatment with dexamethasone. This new rBMS technique could be used to measure TNF-α in LPS-induced acute lung injury (ALI) as well as for proteomic analysis, without sacrificing the rats. Furthermore, this procedure enables the serial collection of ELF, which would allow the examination of time-dependent cytokine variations in rat ALI model.