Session: Current Topics in Biological Chemistry:

Many polycyclic aromatic hydrocarbons (PAHs) are toxic environmental chemicals. They absorb ultraviolet light strongly and as such can undergo photochemical reactions that result in the production of reactive oxygen species (ROS). These reactions are in part responsible for PAH toxicity. Many are also highly lipophilic and thus, are readily distributed in the body including within the cellular organelles where they can co-exist and interact with other cellular components such as inorganic ions, chloride salts, and DNA. Such interactions can modulate the toxicity of the PAHs. This report describes the consequences of irradiating 1-pyrenemethylamine hydrochloride in the absence and presence of physiological concentrations of the redox inactive chloride salts NaCl and KCl (350 nm, pH 7.0, 22 °C). Fluorescence experiments using hydroxyphenyl fluorescein (HPF), a specific ROS detecting fluorescence probe, indicate that 1-pyrenemethylamine hydrochloride photosensitizes ROS generation in presence of NaCl with 10 mM and 100 mM salt concentrations resulting in lower generation of ROS while 200 mM of NaCl enhances ROS generation compared to no-salt conditions. Photocleavage studies with the same pyrene dye using pUC19 plasmid in the presence and absence of 50 mM, 150 mM, 250 mM and 400 mM of KCl show that DNA cleavage is progressively enhanced with increasing concentrations of the salt at pH 7.0. Thus, our findings suggest that sodium(I) and potassium(I) chloride salts might have novel pro-oxidant properties that contribute to polycyclic aromatic hydrocarbon phototoxicity in vivo

Kathryn Grant

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