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- Title
The Role of Active Oxygen (<sup>1</sup>0<sub>2</sub> and 0·<sub>2</sub><sup>-</sup>) Induced by Crude Coal Tar and Its Ingredients Used in Photochemotheraphy of Skin Diseases.
- Authors
Joshi, Prakash C.; Pathak, Madhu A.
- Abstract
Crude coal tar (CCT) and certain photoreactive ingredients of CCT are photosensitizing agents used in the treatment of skin diseases (psoriasis, atopic eczema, etc.). Limited information is available in elucidating the mode of action of CCT in clearing psoriasis or causing skin photosensitization reactions. The production of singlet oxygen (1O2) and superoxide radicals (O·2- or HO2), the formation of interstrand cross-links (ICL) in DNA, and the skin photosensitization reaction caused by CCT or the ingredients present in tar preparations have been examined. Both type I (oxygen-independent) and type II (sensitized reactions requiring molecular oxygen) reactions are induced by CCT. Our data show that CCT and some of the photoreactive ingredients present in CCT produce 1O2, 0·2-, and ICL in DNA upon exposure to UVA radiation. Based on the equivalent concentration, the efficiency of various agents to produce 1O2 was of the following order: hematoporphyrin > phenanthridine > acridine > methylene blue > CCT > fluoranthrene > anthracene > pyrene > 8-methoxypsoralen > anthralin > chloroquine > anthralin dimer. The 0·2- formation with CCT and its ingredients was also of the same order except for anthracene which was found to be a strong producer of 0·2-. The therapeutic effectiveness of CCT appears to be due to: (a) its cytotoxic effects, and (b) the production of 1O2, 0·2-, and ICL by CCT and its photo-reactive ingredients. The-skin photosensitizing (smarting, edema, and erythema responses) and carcinogenic properties of CCT may also be related to the production of 1O2 and 0·2- and the formation of ICL which appear to be responsible for inducing the damage to the DNA and cell membrane.
- Subjects
COAL-tar colors; PHOTOCHEMOTHERAPY; DRUG therapy; PHOTOSENSITIZATION; SKIN diseases; HEMATOPORPHYRIN
- Publication
Journal of Investigative Dermatology, 1984, Vol 82, Issue 1, p67
- ISSN
0022-202X
- Publication type
Article
- DOI
10.1111/1523-1747.ep12259146