title: 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]anthracene, dibenzo[a,h]anthracene, benzo[ghi]perylene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, benzo[b]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 microM 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.
authors.affiliation: Department of Chemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Shuguang
authors.initials: S
authors.lastname: Wang
authors.forename: Yinghong
authors.initials: Y
authors.lastname: Sheng
authors.forename: Manliang
authors.initials: M
authors.lastname: Feng
authors.forename: Jerzy
authors.initials: J
authors.lastname: Leszczynski
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Tachikawa
authors.forename: Hongtao
authors.initials: H
authors.lastname: Yu
mesh_terms: D002461:Cell Line, Transformed; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000737:chemistry / Q000633:toxicity*; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000528:radiation effects*; D015394:Molecular Structure; D009152:Mutagenicity Tests; D009153:Mutagens / Q000737:chemistry / Q000633:toxicity; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry / Q000633:toxicity*; D012867:Skin / Q000187:drug effects / Q000528:radiation effects; D013997:Time Factors; D018675:Toxicity Tests / Q000379:methods; D014466:Ultraviolet Rays; D014481:United States; D014484:United States Environmental Protection Agency
chemical_list: D004785:Environmental Pollutants; D009153:Mutagens; D011084:Polycyclic Aromatic Hydrocarbons