INCREASED FORMATION OF MDA-DNA ADDUCTS IN ANILINE-INDUCED SPLENIC TOXICITY

Huaxian Ma, M.S., J. Wang, M.D., P.J. Boor, M.D. and M.F. Khan, Ph.D.

Department of Pathology, UTMB

Background: Malondialdehyde (MDA), one of the most abundant lipid preoxidation-derived aldehydes, is known to be mutagenic and carcinogenic. MDA can transfer an oxopropenyl group to guanine residues of DNA to yield pyrimodopurinone (M1G) adducts. M1G is a biologically important adduct that serves as a useful dosimeter of MDA-induced DNA modifications. Previous studies have shown that aniline exposure leads to increased lipid preoxidation and DNA damage in the spleen. However, formation and contribution of MDA-DNA adducts in aniline-induced splenic toxicity are not known. Objective: The focus of this study was to evaluate if aniline-induced increased lipid peroxidation also leads to increased formation of MDA-DNA adducts in the spleen. Methods: Male SD rats were subchronically exposed to aniline (0.5 mmol/kg/day via drinking water for 30 days), while controls received drinking water only. Quantitation of M1G in the DNA samples from control and aniline-treated rats was done using an enzyme-linked immunosorbent assay (ELISA) and by using an anti-MDA-DNA monoclonal antibody. Results: M1G levels in the spleen of aniline-treated rats showed remarkable increases, which were 4.1 fold or 315% greater than the controls. To further validate our M1G ELISA results, immunohisto-chemistry of MDA-DNA adducts was also performed. MDA-DNA adduct-specific immunostaining showed more nuclear staining in the red pulp areas of the spleens of aniline-treated rats compared to the controls. Conclusions: Our study clearly shows that aniline treatment leads to significant increases in MDA-DNA adduct formation in the spleen, suggesting greater DNA base modification by MDA. Formation of MDA-DNA adducts may serve as a biomarker of DNA damage by MDA, and also presents a potential mechanism in the pathogenesis of aniline-induced fibrosarcomas in the spleen. This work was supported by grant ES006476 from NIEHS (NIH).