Lipid Peroxidation-derived Adducts Research Articles

Demonstration of ethanol‐induced protein adducts in oral leukoplakia (pre‐cancer) and cancer

Excessive alcohol consumption is a common cause for upper gastrointestinal tract cancers. However, the primary mechanisms of alcohol-induced carcinogenesis have remained poorly defined. We examined the generation and subcellular distribution of protein adducts with acetaldehyde (AA), the first metabolite of ethanol, and end products of lipid peroxidation, malondialdehyde (MDA) and 4-hydroxynonenal (HNE), from oral biopsy specimens obtained from 36 subjects (11 British, 25 Japanese) reporting alcohol misuse. All patients had been diagnosed with oral pre-cancer (leukoplakia, n = 7) or squamous cell carcinoma (SCC; n = 29). Automated immunostaining for AA, MDA and HNE adducts was performed using monospecific antibodies. Positive staining for AA, MDA and HNE adducts was observed in the dysplastic or malignant epithelial cells, HNE being relatively the most abundant adduct species. The subgroup of Japanese patients had higher levels of AA and MDA, although not HNE, than the British sample. When the material was divided to those with SCC or leukoplakia, MDA adducts but not the other antigens were more prominent in the former group. Significant correlations were found between the different adducts (AA vs. MDA, r = 0.68, P < 0.001; AA vs. HNE, r = 0.47, P < 0.01 and MDA vs. HNE, r = 0.59, P < 0.001). In addition, cytochrome P450 2E1 staining was found in these samples, correlating with both AA and MDA adducts. The data indicates that AA- and lipid peroxidation-derived adducts are formed in oral tissues of alcohol misusers with oral leukoplakia and cancer. The findings also support a pathogenic role of AA and excessive oxidative stress in carcinogenesis.

Lipid peroxidation dominates the chemistry of DNA adduct formation in a mouse model of inflammation

In an effort to define the prevalent DNA damage chemistry-associated chronic inflammation, we have quantified 12 DNA damage products in tissues from the SJL mouse model of nitric oxide (NO) overproduction. Using liquid chromatography-mass spectrometry/MS and immunoblot techniques, we analyzed spleen, liver and kidney from RcsX-stimulated and control mice for the level of the following adducts: the DNA oxidation products 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), guanidinohydantoin (Gh), oxazolone (Ox); 5-guanidino-4-nitroimidazole (NitroIm); spiroiminodihydantoin (Sp) and M(1)dG; the nitrosative deamination products 2'-deoxyxanthosine, 2'-deoxyoxanosine (dO), 2'-deoxyinosine and 2'-deoxyuridine and the lipid peroxidation-derived adducts 1,N(6)-etheno-deoxyadenosine and 1,N(2)-etheno-deoxyguanosine. The levels of dO, Gh, Ox, NitroIm and Sp were all below a detection limit of approximately 1 lesion per 10(7) bases. Whereas there were only modest increases in the spleens of RcsX-treated compared with control mice for the nucleobase deamination products (10-30%) and the DNA oxidation products 8-oxodG (10%) and M(1)dG (50%), there were large (3- to 4-fold) increases in the levels of 1,N(6)-etheno-deoxyadenosine and 1,N(2)-etheno-deoxyguanosine. Similar results were obtained with the liver and with an organ not considered to be a target for inflammation in the SJL mouse, the kidney. This latter observation suggests that oxidative and nitrosative stresses associated with inflammation can affect tissues at a distance from the activated macrophages responsible for NO overproduction during chronic inflammation. These results reveal the complexity of NO chemistry in vivo and support an important role for lipids in the pathophysiology of inflammation.

Early alcoholic liver injury: formation of protein adducts with acetaldehyde and lipid peroxidation products, and expression of CYP2E1 and CYP3A.

The formation of protein adducts with reactive aldehydes resulting from ethanol metabolism and lipid peroxidation has been suggested to play a role in the pathogenesis of alcoholic liver injury. To gain further insight on the contribution of such aldehydes in alcoholic liver disease, we have compared the appearance of acetaldehyde, malondialdehyde, and 4-hydroxynonenal adducts with the expression of cytochrome P-450IIE1, and cytochrome P-4503A enzymes in the liver of rats fed alcohol with a high-fat diet for 2 to 4 weeks according to the Tsukamoto-French procedure and in control rats (high-fat liquid diet or no treatment). Urine alcohol and serum aminotransferase levels were recorded, and the liver pathology was scored from 0 to 10 according to the presence of steatosis, inflammation, necrosis, and fibrosis. The ethanol treatment resulted in the accumulation of fat, mild necrosis and inflammation, and a mean liver pathology score of 3 (range: 1 to 5). Liver specimens from the ethanol-fed animals with early alcohol-induced liver injury were found to contain perivenular, hepatocellular acetaldehyde adducts. Malondialdehyde and 4-hydroxynonenal adducts were also present showing a more diffuse staining pattern with occasional sinusoidal reactions. In the control animals, a faint positive reaction for the hydroxynonenal adduct occurred in some of the animals fed the high fat diet, whereas no specific staining was observed in the livers from the animals receiving no treatment. Expression of both CYP2E1 and CYP3A correlated with the amount of protein adducts in the liver of alcohol-treated rats. Distinct CYP2E1-positive immunohistochemistry was seen in 3 of 7 of the ethanol-fed animals. In 5 of 7 of the ethanol-fed animals, the staining intensities for CYP3A markedly exceeded those obtained from the controls. The present findings indicate that acetaldehyde and lipid peroxidation-derived adducts are generated in the early phase of alcohol-induced liver disease. The formation of protein adducts appears to be accompanied by induction of both CYP2E1 and CYP3A.