In this study, we report the role of DNA methyltransferase 1 (DNMT1) in ultraviolet A (UVA)-induced senescence in human dermal fibroblasts (HDFs). We show that DNMT1 expression was significantly reduced during UVA-induced senescence, and this senescence could be alleviated or aggravated by the up- or down-regulation of DNMT1, respectively. Expression of the transcription factor zinc finger E-bo...

UVA (320-400 nm) represents the main spectral component of solar UV radiation, induces pre-mutagenic DNA lesions and is classified as Class I carcinogen. Recently, discussion arose whether UVA induces DNA double-strand breaks (dsbs). Only few reports link the induction of dsbs to UVA exposure and the underlying mechanisms are poorly understood. Using the Comet-assay and γH2AX as markers for dsb...

Cells from patients with the inherited disorder, Fanconi's anemia (FA), were analyzed for endonucleases which recognize DNA interstrand cross-links and monoadducts produced by psoralen plus UVA irradiation. Two chromatin-associated DNA endonuclease activities, defective in their ability to incise DNA-containing adducts produced by psoralen plus UVA light, have been identified and isolated in nu...

Retinal damage by light has two distinct action spectra, one peaking in the ultraviolet-A (UVA) and the other in the mid-visible wavelengths (green light). Here we show in a single animal species, the Long Evans rat, that UVA and green light can produce histologically dissimilar types of damage. UVA light in particular produces severe retinal damage at low irradiation levels. Furthermore, the m...

The skin cancer incidence has increased substantially over the past decades and the role of ultraviolet (UV) radiation in the etiology of skin cancer is well established. Ultraviolet B radiation (280–320 nm) is commonly considered as the more harmful part of the UV-spectrum due to its DNA-damaging potential and well-known carcinogenic effects. Ultraviolet A radiation (320–400 nm) is still regar...

BACKGROUND The health effects of Amaranth Oil (AO) are attributed to its specific chemical composition. That makes it an outstanding natural product for the prevention and treatment of ultraviolet (UV) irradiation-related pathologies such as sunburn, photoaging, photoimmunosuppression, and photocarcinogenesis. Most of the studies are taken on animal model, and there is a lack of research on the...

The effect of the hydroxymethylglutaryl-CoA (HMG-CoA) inhibitor lovastatin on the UVA-induced photocytotoxicity has been investigated in cultured human N.C.T.C. 2544 keratinocytes. In the absence of irradiation, 5 x 10(-7) M lovastatin did not exhibit any significant cytotoxic effect towards this cell line. Although the drug cannot act as a photosensitizer, because it does not absorb in the UVA...

PURPOSE The action spectrum of ultraviolet radiation mainly responsible for melanoma induction is unknown, but evidence suggests it could be ultraviolet A (UVA), which has a different geographic distribution than ultraviolet B (UVB). This study assessed whether melanoma mortality rates are more closely related to the global distribution of UVA or UVB. METHODS UVA and UVB radiation and age-adj...

The thymidine analogue 4-thiothymidine (S(4)TdR) is a photosensitizer for UVA radiation. The UV absorbance spectrum of S(4)TdR and its incorporation into DNA suggests that it might act synergistically with nonlethal doses of UVA to selectively kill hyperproliferative or cancerous skin cells. We show here that nontoxic concentrations of S(4)TdR combine with nonlethal doses of UVA to kill prolife...

Ultraviolet A (UVA) (320-400 nm) radiation is known to cause cutaneous aging and skin cancer. We studied the effect of UVA (365 nm) radiation on the human epidermis by focusing on keratinocyte gap junction-mediated intercellular communication (GJIC). We observed a dose-dependent 10-fold decrease in GJIC induced by UVA in normal human keratinocytes. This decrease in GJIC was associated with time...