In vitro cardiotoxicity of residual oil fly ash

by 1978- Knuckles, Travis Lee

Knuckles, Travis Lee. In Vitro Cardiotoxicity of Residual Oil Fly Ash. (Under the direction of Kenneth B. Adler and Kevin L. Dreher). Epidemiological studies have shown an association between air pollution particulate matter (PM) and adverse cardiovascular effects. Although numerous mechanisms have been proposed, the actual mechanism(s), as well as emission sources and associated causal properties by which PM affects the cardiovascular system, remain elusive. At least some adverse PM health effects can be attributed to bioavailable constituents, most notably the transition metal content of the particles. Toxicological studies in rats using residual oil fly ash (ROFA) combustion source particles show extrapulmonary effects ranging from thermoregulatory alterations to fatal cardiac arrhythmias. Exposure of rats to ROFA via intratracheal instillation lead to a rapid and transient increase in plasma metal content as early as 15 minutes post-exposure, suggesting that PM constituents are bioavailable to both the systemic circulation and perfused organs. However, the impact of this systemic exposure on extrapulmonary organs at the cellular and molecular levels is unknown. In this study, cardiomyocytes derived from 1-day-old rat pups were exposed in order to determine the direct effects of a particle-free residual oil fly ash leachate (ROFA-L). Using concentrations of leachates relevant to amounts that were found in the plasma of rats following pulmonary deposition, this study has shown that ROFA bioavailable constituents induce cytotoxicity in cardiomyocyte cultures in a dose response relationship from 25µg/mL to 1.56µg/mL of ROFA-L. The cardiomyocyte cytotoxicity due to ROFA-L exposure was not found to be mediated by the major metal constituents nor was the cytotoxicity oxidant dependant at lower doses. The cytotoxic effects of ROFA-L were enhanced with the addition of a tyrosine kinase inhibitor, genistein. Acute noncytotoxic doses of ROFA-L altered global gene expression consistent with cardiac myocyte electrophysiological remodeling, oxidative stress, and cell survival. Genomic alterations were found to correlate with changes in transcription factor activation. These acute changes in both transcription factor activation and gene expression could lead to possible chronic consequences for the cardiac myocyte. In Vitro Cardiotoxicity of Residual Oil Fly Ash. By Travis Lee Knuckles A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the Degree of Doctor of Philosophy Comparative Biomedical Sciences Raleigh 2005 _______________________ Kenneth Adler Chair Advisory Committee ________________________ Kevin L. Dreher _______________________ Damian Shea ________________________ Philip Sannes