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New agents in
photoprotection
Rosen, Cheryl1
Toronto Western Hospital, University of Toronto1
Abstract-
Photoprotection involves a group of sun protective behaviours, including
seeking shade, use of sunglasses, protective clothing and then appropriate
use of sunscreens. New methods of protection are being developed. i)
Primary prevention programs are aimed at changing behaviour in the sun.
The effectiveness of these health promotion programs is being studied.
ii) There are new agents for increasing the protective capacity of clothing.
Compounds, known as Tinosorb FR/FD, with both UVB- and UVA-absorbing
moieties can be added to detergents or fabric conditioning rinses for
use during laundering. These compounds bind to fabric and absorb UV.
iii) New sunscreen compounds have been developed which absorb and scatter
UV. Most recently there has been an emphasis on UVA protection, photostability,
and microfine particle size to increase reflection. iv) There are new
UV protective compounds for topical cutaneous use, that do not act as
typical sunscreening agents i.e. absorbing UVB/A. Polyphenols from green
tea and black tea have been shown to protect against several endpoints
in in vitro and in vivo model systems, including a decrease in the formation
of skin tumours in chronically UV-irradiated mice. (-)-epigallocatechin-3-gallate,
a green tea polyphenol (GTP), appears to alter the signal transduction
pathways induced by UVB, inhibiting the UVB-induction of c-fos and the
UVB-induced activation of MAP kinase. In humans exposed to 2 MED dose
of solar simulated UV, topical GTP provided protection against erythema,
sunburn cell formation, Langerhan cell depletion and DNA damage. DNA
repair enzymes, both T4 endonuclease V (T4N5) and photolyase, have been
encapsulated in liposomes and shown to catalyze removal of cyclobutane
pyrimidine dimmers in humans. T4N5 lotion decreased skin cancer formation
in a murine model and provided protection to patients with xeroderma
pigmentosum. The poly/oligosaccharides in Aloe barbadensis extracts
have been shown in a murine model to prevent UV-induced immunosuppression
and to inhibit the UVB-induced phosphorylation of JNK kinase. The antioxidants
alpha-tocopherol and ascorbate have been shown to be photoprotective
in certain in vivo and in vitro assays. Further evidence is required
to support their use as photoprotective agents in humans.
Keywords: photoprotection
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