TOPICAL OR ORAL-ADMINISTRATION WITH AN EXTRACT OF POLYPODIUM-LEUCOTOMOS PREVENTS ACUTE SUNBURN AND PSORALEN-INDUCED PHOTOTOXIC REACTIONS ASWELL AS DEPLETION OF LANGERHANS CELLS IN HUMAN SKIN

Sunburn, immune suppression, photoaging, and skin cancers result from uncontrolled overexposure of human skin to solar ultraviolet radiation (UVR). Preventive measures, including photoprotection, are helpful an d can be achieved by topical sunscreening agents, Polypodium leucotomo s (PL) has been used for the treatment of inflammatory diseases and ha s shown some in vitro and in vivo inmunomodulating properties. Its ben eficial photoprotective effects in the treatment of vitiligo and its a ntioxidant properties encouraged us to evaluate in vivo the potentiall y useful photoprotective property of natural extract of PL after topic al application or oral ingestion. Twenty-one healthy volunteers [eithe r untreated or treated with oral psoralens (8-MOP or 5-MOP)] were enro lled in this study and exposed to solar radiation for evaluation of th e following clinical parameters: immediate pigment darkening (IPD), mi nimal erythema dose (MED), minimal melanogenic dose (MMD), and minimal phototoxic dose (MPD) before and after topical or oral administration of FL. Immunohistochemical assessment of CD1a-expressing epidermal ce lls were also performed. PL was found to be photoprotective after topi cal application as well as oral administration. PL increased UV dose r equired for IPD (P<0.01), MED (P<0.001) and MPD (P<0.001). After oral administration of FL, MED increased 2.8+/-0.59 times and MPD increased 2.75+/-0.5 and 6.8+/-1.3 times depending upon the type of psoralen us ed, Immunohistochemical study revealed photoprotection of Langherhans cells by oral as well as topical FL. The observed photoprotective acti vities of oral or topical PL reveal a new avenue in examining the pote ntially useful field of systemic photoprotection and suggests that PL can be used as adjunct treatment and can make photochemotherapy and ph ototherapy possibly safe and effective when the control of cutaneous p hototoxicity to PUVA or UVB is a limiting factor in such phototherapie s.