Vascular Permeability Disruption Explored in the Proteomes of Mouse Lungs and Human Microvascular Cells following Acute Bromine Exposure

Bromine (Br₂) is an organohalide found in nature and is integral to many manufacturing processes. Br₂ is toxic to living organisms and high concentrations can prove fatal. To meet industrial demand large amounts of purified Br₂ are produced, transported, and stored worldwide providing a multitude of interfaces for potential human exposure through either accidents or terrorism. To identify the key mechanisms associated with acute Br₂ exposure, we havesurveyed the lung proteomes of C57BL/6 male mice and human lung derived microvascular endothelial cells (HMEC's) at 24 hrs following exposure to Br₂ in concentrations likely to be encountered in the vicinity of industrial accidents. Global discovery proteomics applications, combined with systems biology analysis identified robust and highly significant changes in proteins associated with three biological processes: 1. exosome secretion, 2. inflammation, and 3. vascular permeability. We focused on the latter, conducting physiological studies on isolated perfused lungs harvested from mice 24 hrs post Br₂ exposure. These experiments revealed significant increases in the filtration coefficient (Kf) indicating increased permeability of the pulmonary vasculature. Similarly, confluent monolayers of Br₂ and Br-lipid treated HMEC's exhibited differential levels of ZO-1 that found to be dissociated from cell wall localization, an increase in phosphorylation and internalization of E-cadhedrin, as well as increased actin stress fiber formation, all of which are consistent with increased permeability. Taken as a whole, our discovery proteomics and systems analysis workflow, combined with physiological measurements of permeability, revealed both profound and novel biological changes that contribute to our current understanding of Br₂ toxicity.

Keywords: bromine; discovery proteomics; halogen; systems analysis; vascular permeability.