Photogenotoxicity of Mammalian Cells: A Review of the Different Assays for In Vitro Testing¶

Abstract

During the past several years, phototoxicity has been studied at the molecular level, and these studies have provided new insights in the field of DNA lesion characterization, DNA repair and cell response to ultraviolet (UV)‐induced stress. The development of new antibiotics and antiinflammatory drugs has highlighted the necessity to develop the assessment of phototoxicity in the safety evaluation of new chemical compounds. This paper aims at reviewing the known molecular mechanisms of the cellular response to UV‐induced stress, the in vitro methods that can be proposed and used to screen for toxicity of sunlight and the photosensitization process resulting from the activation of drugs by light. UV sources, biological systems and endpoints of interest in that particular objective are listed. Phototoxic effects span from the cytotoxic–apoptotic effect to the induction of primary DNA damage, DNA repair and a variety of stress genes acting on the cell cycle and the fate of the cell. Ultimately, it can lead to the induction of hereditary DNA modification. A variety of assays are proposed to specifically address all these particular consequences of UV‐induced toxicity.

Unrepaired Cyclobutane Pyrimidine Dimers Do Not Prevent Proliferation of UV‐B‐irradiated Cultured Human Fibroblasts¶

“…It should be emphasized that the proportion of subG 1 cells, expected to represent fibroblasts undergoing apoptosis, was no significantly different from the control either 24 or 48 h after exposure to 500 J m −2 of UV‐B. These observations are in agreement with previous observations that normal human fibroblasts seem refractory to UV‐induced apoptosis (11,29). Using flow cytometry analysis like in our study, a dose of 1400 J m −2 was found to be required to increase the percentage of subG 1 cells from 1.5 to 6.5%.…”

“…A concomitant decrease of 53% in the S/G 2 M population occurred. An opposite trend was observed at 48 h, with a decrease of 6% in G 1 and an increase of 46% in S/G 2 M. On the other hand, no significant difference between irradiated and nonirradiated samples was noted, either at 24 or 48 h, concerning the cell population in the subG 1 phase (1–3%), which corresponds to apoptotic cells (11). It should be mentioned that when cells were irradiated at confluence, arrest in G 2 phase was observed in some experiments (data not shown).…”

A genetic cluster of patients with variant xeroderma pigmentosum with two different founder mutations

“…The capacity of these cells to remove DNA lesions was characterized based on unscheduled DNA synthesis (UDS). Cell cycle and apoptosis assays via cytometry were performed as previously described . Polη expression was evaluated via Western blotting.…”

Genetic Code Expansion of Mammalian Cells with Unnatural Amino Acids

“…Third, light exposure removes the caging group and generates the native, wild‐type protein. Irradiation with >360 nm light has been shown to cause no or minimal damage to biological systems (Meunier et al, ; Forman et al, ).…”