A FISH HEPATOMA-CELL LINE (PLHC-1) AS A TOOL TO STUDY CYTOTOXICITY AND CYP1A INDUCTION PROPERTIES OF CELLULOSE AND WOOD CHIP EXTRACTS

Cytotoxicity and CYP1A induction properties of celluloses and wood chi ps were studied with a teleost liver cell line, PLHC-1. Cells were exp osed to acetone extracts of celluloses produced using new bleaching te chniques (elemental chlorine free, ECF; totally chlorine free, TCF) in two sulphate mills or without any bleaching (unbleached, UB) in a sul phite mill. In another set of exposures, celluloses (ECF and TCF bleac hed) and wood chips (from pine and birch) were collected from a sulpha te mill, extracted with acetone, and the extracts used to treat the ce lls. After exposure, O-deethylation of 7-ethoxyresorufin (EROD, a meas ure of cytochrome P4501A (CYP1A) catalytic activity), and total protei n content, a measure of cytotoxicity, were assayed. The presence of th e CYP1A protein in the exposed cells was assessed by immunoblotting. T he cellulose and wood chip extracts were able to cause both cytotoxici ty and EROD induction in the PLHC-1 cells. In the exposures conducted with the material from three different mills, the celluloses made of b irch were more cytotoxic and more potent inducers of EROD activity tha n were the celluloses of pine. Further, UB celluloses increased EROD a ctivity and caused cytotoxicity at lower doses than material bleached with modem bleaching techniques. In the exposures made with material f rom one single mill, there were no clear trends between the celluloses made of pine or birch. Wood chips of pine, however, were more cytotox ic than wood chips of birch. Especially with pine wood chips, cytotoxi city interfered with the induction of EROD activity, thus complicating the evaluation of CYP1A induction. CYP1A protein content was not dete cted in cells exposed to extracts of celluloses or wood chips, possibl y due to low amounts of protein available for the assay. Wood and pulp processing, like bleaching, may change the chemical composition of th e raw material in a way that reduces the potency for biological effect s of the final product, cellulose. This could explain why both UB cell uloses and wood chips were more potent in the cells than ECF or TCF bl eached celluloses. In this study the PLHC-1 cell line showed its poten tial for use in evaluating the biological activity existing in pulp an d paper mill products and raw materials. The identity and source of th e compounds that were able to affect the PLHC-1 cell line remain to be determined. (C) 1998 Elsevier Science Ltd. All rights reserved.