Studies on Thymine‐derived Uv Photoproducts in Dna—i. Formation and Biological Role of Pyrimidine Adducts in Dna

Abstract

Abstract— Pyrimidine (Pyr) adducts constitute a significant fraction of the photoproducts formed in DNA exposed to far UV light. The primary and secondary DNA structure affects the rate of Pyr adduct formation; for example, it increases with decreasing (Ade + Thy)/(Gua + Cyt) of the DNA and with increasing dehydration, and it is greater in double‐stranded than in single‐stranded DNA. Pyrimidine adducts do not appear to be involved in inter‐strand cross‐links, and 313 nm‐induced photolysis of Pyr adducts does not cause strand breakage. The action spectrum for Pyr adduct formation is qualitatively similar to that for Pyr < > Pyr formation; the calculated quantum yields for its formation is essentially wavelength independent over the range 254 nm to 280 nm, but decreased somewhat at shorter wavelengths (240 nm). The biological role of Pyr adducts is still not clear. The data suggest that either Pyr adducts and their photolysis products are not lethal, or that both are lethal but can be repaired under certain conditions.

IL-18 Reduces Ultraviolet Radiation-Induced DNA Damage and Thereby Affects Photoimmunosuppression

“…This applies primarily for UV-induced immunosuppression. Suppression of the induction of CHS by UV radiation can be prevented by the application of DNA repair enzymes (9,26). The same applies for the UV-induced release of the immunosuppressive cytokine IL-10 (44).…”

“…UV induces two major types of DNA lesions, 6-4 photoproducts and cyclobutane pyrimidine dimers (CPD), with the latter being the predominant lesions (26). Southwestern dot blot analysis using an Ab directed against CPD revealed that in DNA samples extracted 3.5 and 6 h after UVB exposure, respectively, UV-induced DNA damage was significantly reduced upon IL-18 treatment (data not shown).…”

DNA damage, death receptor activation and reactive oxygen species contribute to ultraviolet radiation-induced apoptosis in an essential and independent way

“…For years, it was proposed that UVB-induced DNA damage is the only mediator of UVB-induced cell death. UVB induces two types of lesions in chromosomal DNA, 56 -44 photoproducts and cyclobutane pyrimidine dimers (CPD), the latter being the predominant ones (Patrick, 1977). The majority of DNA lesions are removed by the nucleotide excision repair (de Laat et al, 1999).…”

Paulownia tomentosa (Princess Tree) Extract Reduces DNA Damage and Induces DNA Repair Processes in Skin Cells

“…The ultraviolet radiation component of sunlight is the most important environmental inducer of damage in the skin. Ultraviolet radiations can induce damage on DNA bases by direct absorption of photons resulting in the direct effect of cyclobutane pyrimidine dimers (CPD) or the 6-4 photoproducts formation both created by dimerization of contiguous pyrimidines on the DNA [2,3]. Ultraviolet radiation can also induces significant damage to skin cells through the generation of Reactive Oxygen Species (ROS) which produce secondary damage to DNA nucleobases and the sugar phosphate backbone [2].…”

“…Among the harmful environmental factors, solar ultraviolet radiation (UVR) is the major one causing cellular and molecular modifications in the skin like photo-aging and eventually leading to genomic instability and cancer ( [3,82]. UV-induced generation of Reactive Oxygen Species (ROS) such as O 2 , H 2 O 2 , OH° in the skin, develops oxidative stress when their formation exceeds the antioxidant defense ability.…”