SUBCHRONIC EFFECTS OF SMOKELESS TOBACCO EXTRACT (STE) ON HEPATIC LIPID-PEROXIDATION, DNA-DAMAGE AND EXCRETION OF URINARY METABOLITES IN RATS

The oral use of moist smokeless tobacco products (snuff) is causally a ssociated with cancer of the mouth, lip, nasal cavities, esophagus and gut. The mechanism by which smokeless tobacco constituents produce ge netic and tissue damage is not known. Recent studies in our laboratori es have shown that an aqueous extract of smokeless tobacco (STE) activ ates macrophages with the resultant production of reactive oxygen spec ies (ROS), including nitric oxide. Furthermore, the administration of acute doses of STE (125-500 mg/kg) to rats induces dose dependent incr eases in mitochondrial and microsomal lipid peroxidation, enhances DNA single strand breaks, and significantly increases the urinary excreti on of the lipid metabolites malondialdehyde, formaldehyde, acetaldehyd e and acetone. Since the use of tobacco is a chronic process, the effe cts of an aqueous extract of STE in rats following low dose exposure w ere examined. Female Sprague-Dawley rats were treated orally with 25 m g STE/kg every other day for 105 days. The effects of subchronic treat ment of STE on hepatic microsomal and mitochondrial lipid peroxidation and the incidence of hepatic nuclear DNA damage were assessed. Lipid peroxidation increased 1.4- to 3.3-fold in hepatic mitochondria and mi crosome with STE treatment between 0 and 105 days with respect to cont rol animals while hepatic DNA single strand breaks increased up to 3.4 -fold. Maximum increases in lipid peroxidation and DNA single strand b reaks occurred between 75 and 90 days of treatment. Urinary excretion of the four lipid metabolites malondialdehyde, formaldehyde, acetaldeh yde and acetone was monitored by high pressure liquid chromatography ( HPLC) with maximum increases being observed between 60 and 75 days of treatment. The results clearly indicate that low dose subchronic admin istration of STE induces an oxidative stress resulting in tissue damag ing effects which may contribute to the toxicity and carcinogenicity o f STE. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.