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A Novel In Vitro Model of the Alveolar Capillary Region: Bridging the Gap Between Inhalation Toxicology and Cardiovascular Disease
Citation:
Vitucci, E. AND S. McCullough. A Novel In Vitro Model of the Alveolar Capillary Region: Bridging the Gap Between Inhalation Toxicology and Cardiovascular Disease. Society of Toxicology Annual Meeting, San Diego, California, March 27 - 31, 2022.
Impact/Purpose:
Presentation of recent advances with the alveolar-capillary exposure region (ACRE) organotypic in vitro model.
Description:
An estimated 3.5-million people die annually from air pollution-induced cardiovascular disease (API-CVD); however, the molecular mechanisms driving API-CVD remain unclear. To identify these mechanisms, we developed a novel in vitro model of the lung that mimics the in vivo exposure scenario and that represents the interface of the respiratory and cardiovascular system, the alveolar capillary region (ACR). This organotypic model includes human alveolar-like epithelial cells (H441), human lung fibroblasts, and human lung microvascular endothelial cells (HULEC). We hypothesized that air pollutant exposure of the alveolar H441 cells would induce endothelial dysfunction in the capillary HULEC, a common precursor to CVD. To test this, we exposed confluent monolayers of H441 cells to the ubiquitous air pollutant, diesel exhaust particulates (DEP), and investigated the effect of this alveolar DEP (Alv-DEP) exposure on the H441 and the underlying HULEC. Alv-DEP exposure induced the expression of several anti-oxidants such as HMOX1 and NQO1 and activated the NRF2 and MAPK pathways in the H441 and the HULEC. In addition, reactive oxygen species accumulated in the HULEC and the secretion of the proinflammatory mediator IL8 was induced, suggesting Alv-DEP causes endothelial redox dysfunction and proinflammatory activation. To investigate these mechanisms of endothelial dysfunction further we performed siRNA knockdown of NRF2 in the HULEC. We identified a significant reduction in the HULEC anti-oxidant expression and in IL8 expression. As IL8 is a known target of MAPK signaling, we pharmacologically inhibited MAPK activation in the HULEC, but found no significant reduction in expression. Inhibition of MAPK activation in the H441, however, did significantly reduce both HULEC antioxidant expression and IL8 expression and secretion. Together, these data suggest alveolar epithelial MAPK signaling may be driving endothelial antioxidant and proinflammatory response through endothelial NRF2 signaling. Ultimately, these data suggest that secreted epithelial mediators may drive endothelial redox dysfunction and may promote systemic inflammation. As endothelial redox dysfunction and systemic inflammation are important precursor steps towards CVD development, these data suggest that alveolar epithelial cells may be an important cell type to target for prevention and therapeutic strategies against inhaled toxicants. Does not reflect EPA policy.