THE EFFECT OF IQMIK-DERIVED TRANSITION METALS ON ROS PRODUCTION IN HUMAN GINGIVAL EPITHELIAL CELLS

Of all adult Alaska Native persons who use smokeless tobacco, 35% use only iqmik, a smokeless tobacco mixture unique to Alaska since the time of first contact with non-Native peoples. Iqmik is a combination of cured tobacco leaf mixed with the ash of punk fungus (Phellinus igniarius), alder or willow bushes, or driftwood. The ash component of iqmik contains higher levels of toxic transition metals, such as cadmium (Cd), cobalt (Co), and nickel (Ni), than leaf tobacco. Cells exposed to these transition metals show elevated reactive oxygen species (ROS). The purpose of this research was to determine the degree to which iqmik, punk ash and tobacco leaf induce ROS in exposed primary human gingival epithelial cells (HGEP), and the degree to which transition metals may play a role in this redox response. We hypothesized that exposure of HGEP to artificial human saliva extracts of these compounds would lead to absorption of Cd, Co and Ni, elevating ROS production. Samples of iqmik, tobacco and punk ash and artificial human saliva extracts of these compounds were analyzed by ICP-MS following microwave-assisted acid digestion. Intracellular redox status was quantified using H₂DCFDA in cells exposed to artificial saliva extracts of iqmik, tobacco and punk ash, or aqueous solutions of metals salts (1ppm), CdCl₂, CoCl₂ and NiCl₂. Significantly higher concentrations of Cd, Co and Ni were isolated in punk ash and iqmik than in tobacco leaf. Artificial saliva extracts of iqmik produced significantly more ROS than extracts of tobacco leaf and punk ash. The level of ROS triggered by the mixture iqmik was greater than additive compared to that triggered by the individual constituents, ash and tobacco. Treatment with 1ppm CoCl₂ produced significantly greater ROS than CdCl₂ or NiCl₂ treatment, suggesting that Co within the punk ash may account for more of the iqmik triggered ROS than either Cd or Ni.