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Immunohistochemical detection of 4-hydroxyaminoquinoline 1-oxide-DNA adducts in mouse tissues in vivo
1Second Department of Surgery, Hyogo College of Medicine, Nishinomiya, Japan.
Abstract:
4-Hydroxyaminoquinoline 1-oxide (4HAQO)-DNA adducts were immunohistochemically demonstrated in the nuclei of various organs of mice with the use of an antibody directed against 4HAQO-modified DNA. Specificity of the immunostaining was confirmed by several tests, including preincubation of the antibody with 4HAQO-modified DNA or related molecules and digestion of the sections with DNase. 4HAQO dissolved in isotonic solution and injected sc into an isolated portion of the mouse skin clamped off with ring-shaped forceps resulted in dose-dependent generation of DNA adducts in the nuclei of epithelial cells, fibroblasts, and panniculus carnosus cells. Nuclear staining was absent in animals given injections of isotonic solution only, and the intensity of staining correlated well with the level of unscheduled DNA synthesis demonstrated autoradiographically. 4HAQO-DNA adducts were observed in all target organs of 4HAQO tumorigenesis (i.e., lung, trachea, pancreas, uterus, vagina, skin, and colon) after injection of the carcinogen. Nuclear staining was absent or low in nontarget organs, including the liver and brain. Considerable variation was found in staining levels between cell types and different anatomic locations of cells within each target organ. The intensity of immunohistochemical staining correlated well with numbers of 4HAQO-DNA adducts measured by the radiolabeling technique.
Insights
Immunohistochemistry detected 4-hydroxyaminoquinoline 1-oxide (4HAQO)-DNA adducts in mouse organs. This method accurately identified carcinogen-DNA adducts in target organs, correlating with tumorigenesis.
Area of Science:
- Toxicology
- Molecular Biology
- Immunohistochemistry
Background:
- 4-Hydroxyaminoquinoline 1-oxide (4HAQO) is a carcinogen.
- Understanding the distribution and formation of 4HAQO-DNA adducts is crucial for carcinogenicity studies.
Purpose of the Study:
- To develop and validate an immunohistochemical method for detecting 4HAQO-DNA adducts in mouse tissues.
- To correlate the presence of these adducts with carcinogen exposure and tumorigenesis.
Main Methods:
- Immunohistochemistry using a specific antibody against 4HAQO-modified DNA.
- Specificity was confirmed through antibody preincubation and DNase digestion.
- Correlation with unscheduled DNA synthesis (autoradiography) and radiolabeling techniques.
Main Results:
- 4HAQO-DNA adducts were successfully localized in the nuclei of various cells in target organs (lung, trachea, pancreas, uterus, vagina, skin, colon).
- Dose-dependent adduct formation was observed after subcutaneous injection.
- Staining intensity correlated with DNA synthesis and adduct levels measured by radiolabeling.
- Adducts were absent or low in non-target organs (liver, brain).
Conclusions:
- Immunohistochemistry is a reliable method for visualizing 4HAQO-DNA adducts in vivo.
- The distribution of adducts in target organs supports the role of 4HAQO in carcinogenicity.
- This technique aids in understanding the mechanism of 4HAQO-induced carcinogenesis.