Study on the effect of thalassotherapy on psoriatic skin

The opioid peptides enkephalins are known to modulate inflammatory reactions as well as the proliferation and differentiation of keratinocytes. In addition, increased enkephalin levels have been demonstrated in psoriatic skin lesions. The aim of this study under J. B. Nissen was to investigate the effect of natural sunlight in combination with salt water baths at the Dead Sea on methionine enkephalin levels (e.n.k.) in psoriatic skin.

Ten patients were treated at the Dead Sea for 4 weeks and keratoma biopsies were taken before and after treatment. The amount of enkephalin extracted from the biopsies was measured by radioimmunoassay.

Dead Sea treatment resulted in complete clinical remission of psoriasis. Immunohistochemical staining of lesion skin showed that the treatment reduced both epidermal thickness/parakeratosis and dermal infiltration of CD3- and CD68-positive cells, although the number of these cells became normal in only two of the ten cases. However, there was only a slight decrease in mean enkephalin levels (21%). Enkephalin levels were increased after Dead Sea treatment in non-lesional psoriatic skin, and immunostaining showed that in some patients treatment induced mild epidermal hyperplasia and dermal infiltration of CD3- and CD68-positive cells. Enkephalin-like immunoreactivity was detected in the cytoplasm of both epidermal keratinocytes and dermal infiltrating cells. To determine whether the relatively high skin enkephalin level after Dead Sea treatment was caused by ultraviolet (UV) radiation, healthy volunteers were exposed to a single dose of UVA and UVB radiation (2 minimal erythema doses). UVA, but not UVB, led to an approximately six-fold increase in mean enkephalin levels in the irradiated skin. Moreover, repeated whole-body UVA irradiation led not only to increased skin enkephalin levels, but also to increased plasma enkephalin levels.

Natural sunlight in combination with salt water baths led to a complete improvement of psoriasis without causing a significant reduction of enkephalin levels in the lesions. In addition, enkephalin levels were increased in the non-lesional skin. These results could be due to a direct stimulatory effect of UVA irradiation on enkephalin formation in the skin. It is possible that the increased circulating enkephalin levels after UV irradiation contribute to the positive effects of UVA irradiation.