Abstract
Prolonged exposure to ultraviolet radiation on human skin can lead to mutations in DNA, photoaging, suppression of the immune system, and other damage up to skin cancer (melanoma, basal cell, and squamous cell carcinoma). We reviewed the state of knowledge of the damaging action of UVB and UVA on DNA, and also the mechanisms of DNA repair with the participation of the DNA-photolyase enzyme or of the nucleotide excision repair (NER) system. In the course of evolution, most mammals lost the possibility of DNA photoreparation due to the disappearance of DNA photolyase genes, but they retained closely related cryptochromes that regulate the transcription of the NER system enzymes. We analyze the published relationships between DNA photolyases/cryptochromes and carcinogenesis, as well as their possible role in the prevention and treatment of diseases caused by UV radiation.
Highlights
Introduction and CryptochromesBiomedicinesThe constant destructive impact of various adverse environmental factors causes the disturbance of the normal functioning of living cells [1,2,3]
It was found that chronic exposure to solar radiation is the most important environmental factor involved in the pathogenesis of actinic keratosis and squamous cell carcinoma [9]
Both pathways require the involvement of a large number of enzymes, and as a result, the process stretches over time to several hours, the processes triggered by CPD dimers, for example, melanogenesis, have time to start in cells
Summary
Targets of UV radiation in living organisms can be various photoactive molecules, for example, pterins, folates, flavins, porphyrins, aromatic amino acids, etc. (Figure 1), as well as biopolymers: proteins and nucleic acids [11,12]. (Figure 1), as well as biopolymers: proteins and nucleic acids [11,12] Such photoactive molecules transfer into an excited state after the light absorption, and the excess energy can be utilized in several ways, among which three main options are of biological significance. (2) Important biologically active molecules can undergo partial chemical modification (as happens with DNA, see Section 2.2 and Figure 2) or be completely destroyed, which can lead to a deficiency of these molecules in the body. This is especially true for those substances that cannot be synthesized in the human body. Porphyrins (Figure 1) are well-known photosensitizers in medicine, and their ability to generate ROS underlies the photodynamic cancer therapy [15]
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