Increased levels of enkephalin following natural sunlight (combined with salt water bathing at the Dead Sea) and ultraviolet A irradiation

The opioid peptides enkephalins have been shown to modulate inflammatory re sponses and keratinocyte proliferation and differentiation. Furthermore, in creased levels of enkephalin are present in psoriatic lesions. The purpose of the present study was to determine the effect of natural sunlight combin ed with salt water bathing in the Dead Sea on the methionine-enkephalin (e. n.k.) level in psoriatic skin. Ten patients were treated at the Dead Sea fo r 4 weeks, and keratotome biopsies were obtained before and after treatment . The amount of enkephalin extracted from the biopsies was measured bq radi oimmunoassay. Treatment at the Dead Sea resulted in a complete clinical cle arance of psoriasis, and immunohistochemical stainings of lesional skin sho wed that the treatment decreased both epidermal thickness/parakeratosis and the dermal infiltration of CD3- and CD68-positive cells, although the numb er of CD3- and CD68-positive cells became normal in only two of the 10 case s. However, there was only a slight decrease in the mean enk levels (21%). Furthermore, the level of enk was high in non-lesional psoriatic skin after treatment at the Dead Sea, and immunostaining showed that, in some patient s, the treatment induced a mild epidermal hyperplasia and a dermal infiltra tion of CD3- and CD68-positive cells. Enkephalin-like immunoreactivity was detected in the cytoplasm of both epidermal keratinocytes and dermal infilt rating cells. To determine whether the relatively high skin enk levels afte r treatment at the Dead Sea was caused by ultraviolet (UV) radiation, norma l volunteers were exposed to a single dose of UVA and UVB (2 minimal erythe ma doses), WA, but not UVB, irradiation stimulated the mean enk level in th e irradiated skin by about sixfold. Furthermore, multiple whole-body UVA ir radiations not only resulted in increased skin levels of enk, but also in i ncreased plasma levels. In conclusion, natural sunlight combined with salt water bathing cleared psoriasis without causing a significant decrease in l esional enk levels. Furthermore, non-lesional enk levels were increased. Th ese findings may be the result of a direct stimulatory effect of UVA irradi ation on enk formation in the skin. It is possible that the increased circu lating levels of enk after UV exposure may contribute to the beneficial eff ects of UVA irradiation.