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Alternative
Toxicology - Endpoint: Phototoxicity Testing
In Vitro
3T3 NRU Phototoxicity Test
Phototoxicity
can be defined as a toxic response to a substance after the
first exposure to certain chemicals and subsequent exposure
to light, or that is induced by skin irradiation after systemic
administration of a chemical. The in vitro 3T3 Neutral Red
Uptake (NRU) phototoxicity test is used to identify the phototoxic
potential of a test substance after exposure to light. The
test is based on a comparison of the cytotoxicity of a chemical
in the presence and in the absence of a non-cytotoxic dose
of UVA. Cytotoxicity in this test is expressed as a concentration-dependant
reduction of the uptake of the vital dye, Neutral Red in Balb/c
3T3 cells when measured 24 hours after treatment with the
test substance and irradiation.
The 3T3 NRU Phototoxicity test is used
for the assessment of phototoxic potential as indicated in
the OECD Guideline for the Testing of Chemicals, No. 432 “In
Vitro 3T3 NRU phototoxicity test” and the Method B40
of Annex V to Directive 67/548/EEC (Council Directive 2000/33/EEC).
SkinEthic
Human Reconstituted Epidermal (HRE) Model
The HRE Model
is an appropriate model for the determination of phototoxic
potency of formulations containing known phototoxic ingredients
(e.g. intended for photo-dynamic therapy), or for screening
of products prior to assessment of photoallergenicity in
vivo.
With this model it is possible to apply the product directly
to the surface of the epidermis and then to irradiate the tissue
with ultra-violet or visible light. The degree of phototoxic
response can then be assessed by multi endpoint analysis (see
above).
