Light‐induced cytotoxicity of 16 polycyclic aromatic hydrocarbons on the US EPA priority pollutant list in human skin HaCaT keratinocytes: Relationship between phototoxicity and excited state properties

Abstract

The photocytotoxicity of 16 polycyclic aromatic hydrocarbons (PAHs) on the priority pollutant list of the United States Environmental Protection Agency (US EPA) were tested in human skin HaCaT keratinocytes. A selected PAH was mixed with HaCaT cells and irradiated with a solar simulator lamp for a dose equivalent to 5 min of outdoor sunlight and the cell viability was determined immediately and also after 24 h of incubation. For the cells without incubation after the treatments, it is found that all PAHs with three rings or less, except anthracene, are not photocytotoxic, while the four or five-ring PAHs (except chrysene), benz [a]fluorenthene, fluorenthene, and pyrene, are photocytotoxic to the human skin HaCaT keratinocytes. If the cells were incubated for 24 h after the treatments, the photocytotoxic effect of the PAHs was greatly amplified in comparison to the nonincubated cells. For the 24 h incubated cells, all PAHs except naphthalene exhibit photocytotoxicity to some extent. Exposure to 5 μM of the 4-and 5-ring PAHs (except chrysene) and 3-ring anthracene more than 80% of the cells lose viability. The photocytotoxicity of the PAHs correlates well with several of their excited state properties: light absorption, excited singlet-state energy, excited triplet-state energy, and HOMO-LUMO energy gap. All the photocytotoxic PAHs absorb light at >300 nm, in the solar UVB and UVA region. There is a threshold for each of the three excited state descriptors of a photocytotoxic PAH: singlet energy <355 kJ/mol (corresponding to 337 nm light), triplet energy <230 kJ/mol (corresponding to 520 nm light), HOMO-LUMO gap <3.6 eV (corresponding to 344 nm light) obtained at the Density Functional Theory B3LYP/6-31G(d) level.

DNA damage and repair of human skin keratinocytes concurrently exposed to pyrene derivatives and UVA light

“…The relative photocytotoxicity is: 1-HP ~ 1-AP ~ Pyrene > 1-BP > 1-NP. These results are similar to the previously reported in both HaCaT and Jurkat cells using some of the similar compounds 2,36,37 .…”

“…Co-exposure to pyrene and light irradiation causes human skin keratinocyte cells to become non-viable in a pyrene dose dependent manner 2 . It is suggested that damages to cellular constituents DNA, protein and lipids are the main reasons leading to phototoxicity 6,7 .…”

A study of the phototoxic effect of Benzo[a] Pyrene on bacteria

“…Photodegradation of PAHs may be due in addition to UVA rays as well as visible light, and this is especially true in the case of PAHs with a higher content of aromatic rings, which are photosensitized upon radiation with a wavelength >400 nm [32][33][34].…”

Light-induced toxic effects of tamoxifen: A chemotherapeutic and chemopreventive agent

“…The cell culture method was reported in a previous publication [30, 31]. After the HaCaT cells grew to a concentration of no less than 1×10 5 cells/mL, the cells were harvested and centrifuged at 2000 rpm for 5 min.…”