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IN VIVO MECHANISMS OF PARTICULATE MATTER (PM)-INDUCED LUNG AND VASCULAR INJURY
Impact/Purpose:
This research will support efforts to extrapolate between mechanistic studies of PM in vitro and in vivo; and develop sensitive and accurate methods to assess biological effects and mechanisms of injury of various air pollutants, while potentially decreasing the number of animals used in toxicology assessments. The objectives of this study are: 1) to determine the mechanisms by which various emission source particles (oil; coal; diesel) injury the lung and cardiovascular system; 2) to correlate in vivo findings with in vitro data; and 3) to develop more sensitive and accurate methods for determining mechanisms of lung and cardiovascular injury induced by PM.
Description:
Insight into the mechanisms by which ambient particulate matter (PM) mediates its adverse cardiopulmonary effects can provide biological plausibility to epidemiological associations between PM exposure and health effects. Current information on mechanisms of pulmonary injury have been derived from in vitro studies using airway epithelial and alveolar macrophages, in which cellular cytotoxicity and pro-inflammatory responses have been noted. It is presently not known whether mechanisms of PM injury observed in vitro are functional in vivo, making it difficult to extrapolate mechanistic or dose-response relationships obtained in vitro to effects expected in vivo. In addition, current methods to assess PM-induced lung and cardiovascular injury (broncho-alveolar lavage and whole tissue extracts) are insensitive since effects of PM are extremely localized in these tissues, and high doses are required to induce responses. Further, whole tissue extracts obviate mechanistic conclusions by obscuring the specific cell types producing the responses, thus requiring additional studies using in situ approaches to determine the cellular origin of any observed effect(s) in vivo. As observed in vitro, ROFA in rats activated cell signaling pathways (e.g., ERK <) and pro-inflammatory cytokine gene expression. The antioxidant DMTU inhibited ROFA-induced acute lung injury, activation of cell signaling pathways, and pro-inflammatory cytokine expression in vivo. These findings are all consistent with mechanisms observed in vitro. Efforts were initiated to apply Laser Capture Microdissection and develop micro-molecular analyses to provide more sensitive and accurate methods to assess mechanisms of PM-induced lung injury in airways and pulmonary vasculature. In addition, we have microdissected airways from animals exposed to ROFA and developed an approach to assess alterations in cell signaling pathways using protein extract arrays. This analysis detects not only an increase in ERK protein levels but also increased activation of ERK in extracts recovered from airways of ROFA-instilled rats, while ERK activation could not be detected in whole lung protein extracts recovered from rats exposed to the same amount of ROFA.