Solar UV radiation: differential effectiveness of UVB subcomponents in causing cell death, micronucleus induction and delayed expression of heritable damage in human hybrid cells.
OBJECTIVE
To determine the effectiveness of two UV spectra with different UVB components for cell kill and micronucleus induction in irradiated human HeLaxskin fibroblast (CGL1) hybrid cells and their progeny. To determine the presence of reactive oxygen species (ROS) in the progeny of the irradiated cells at various post-irradiation times and their relationship with induced delayed biological effects.


METHODS
A commercial solar ultraviolet simulator was used. Two different filters were employed: the first transmitted radiation with lambda>284nm and the second radiation with lambda>293nm. The resulting spectra have different UVB components (lambda between 284 and 320nm, 19 W/m(2), and between 293 and 320nm, 13 W/m(2)) and the same UVA component (lambda between 320 and 400nm, 135 W/m(2)). CGL1 cells were irradiated with various doses. Clonogenic survival and micronucleus formation were scored in the irradiated cells and their progeny. ROS were detected by incubation of cultures at various post-irradiation times with dichlorodihydrofluorescein diacetate followed by flow cytometric measurement of the final product, dichlorofluorescein.


RESULTS
The biological effectiveness of the lambda>284nm spectrum was higher by a factor of 3 compared to the lambda>293nm spectrum for cell kill, and by a factor of 5 for micronucleus induction. No delayed cell death or micronucleus formation was found in the progeny of cells exposed to lambda>293nm, while a large and dose-dependent effect was found in the progeny of cells exposed to lambda>284nm for both of these endpoints. ROS levels above those in unirradiated controls were found only in the progeny of cells exposed to the lambda>284nm spectrum.


CONCLUSIONS
The spectrum with lambda>284nm was more effective than that with lambda>293nm for induction of cell kill and micronucleus formation in the directly irradiated cells as well as induction of delayed effects in the progeny in the form of delayed reproductive death and micronucleus formation. The presence of ROS in the progeny of the irradiated cells may be the cause of the delayed effects.
Bettega
D
D
Dipartimento di Fisica, Università degli Studi di Milano and INFN, Via Celoria 16, 20133 Milano, Italy.
Calzolari
P
P
Belloni
F
F
Di Lena
F
F
Genchi
S
S
Lupi
M
M
Massariello
P
P
Orsini
S
S
Tallone
L
L
Tomasoni
D
D
Ubezio
P
P
Redpath
J L
JL
D016923:Cell Death / Q000528:radiation effects*; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D006801:Humans; D006822:Hybrid Cells; D048629:Micronuclei, Chromosome-Defective / Q000528:radiation effects*; D017382:Reactive Oxygen Species; D013472:Sunlight; D014466:Ultraviolet Rays
D017382:Reactive Oxygen Species; D004247:DNA