# Evaluation of Phototoxicity of Short-Wavelength Laser Light Utilizing PCNA Accumulation

## TL;DR

This study evaluates the harmful effects of short-wavelength laser light on cells by measuring PCNA accumulation, showing that toxicity depends on cell cycle phase and light intensity.

## Contribution

A novel method for quantitatively assessing phototoxicity using PCNA accumulation in live cells during the S phase of the cell cycle.

## Key findings

- PCNA accumulation occurs only when the cell nucleus in the S phase is irradiated.
- Higher PCNA accumulation was observed at 375 nm compared to 405 nm laser wavelengths.
- PCNA accumulation correlates with laser intensity and can predict 24 h cell viability.

## Abstract

In recent years, diseases such as age-related macular degeneration and retinal pigment degeneration caused by excessive exposure to short-wavelength visible light have become significant concerns. With the aim of quantitatively evaluating the toxicity of short-wavelength light, proliferating cell nuclear antigen (PCNA) accumulation at the irradiation site was investigated using live cell imaging techniques to irradiate individual living cells with short-wavelength laser light. By examining the dependency of PCNA accumulation on the irradiation site within the cells and their cell cycle, it was observed that PCNA accumulation occurred only when the cell nucleus of cells in the S phase of the cell cycle was irradiated. We investigated the accumulation of PCNA at the laser irradiation site using laser light at wavelengths of 405 nm and 375 nm, with intensities ranging from 0.5 μW to 9.0 μW. The results confirmed an increase in PCNA accumulation with increasing intensity, and a higher accumulation was observed with laser light irradiation at a wavelength of 375 nm compared to 405 nm. By comparing the PCNA accumulation and 24 h cell viability, we demonstrated the feasibility of quantitatively assessing laser light toxicity through the measurement of PCNA accumulation.