PIXE Analysis in Different Stages of Psoriatic Skin

Abstract

Elemental distribution in psoriatic skin varies with the functional state of the keratinocytes, e.g., electrolytes influence cell metabolism and cell proliferation, and trace elements play a crucial role in a great number of enzymes. Elemental distribution in pinpoint lesions, old plaques, and uninvolved skin of 5 psoriatic patients and 4 healthy controls was studied by means of PIXE (proton-induced x-ray emission) analysis. This technique allows the simultaneous detection of elements with an atomic number greater than or equal to 14 along the epidermis and dermis in freeze-dried skin biopsies. Trace elements such as Fe, Cu, and Zn were determined down to a level of 1 ppm. In comparison with uninvolved skin, concentrations of P and K were elevated in psoriatic epidermis. In addition, increased levels of K were correlated with the stage of the psoriatic lesion. Zinc concentrations were significantly elevated in pinpoint lesions. The Zn concentration profiles within the epidermis and upper dermis showed high correlation to the P concentration profiles. Iron levels were decreased in old psoriatic plaques, whereas Cu concentrations varied considerably. In comparison to the controls, Cl concentrations were markedly decreased in the dermis of involved and uninvolved psoriatic skin, whereas epidermal Cl levels were unaffected. As high K levels prevent the Ca-induced differentiation of keratinocytes, high K levels may be the cause of the high cell differentiation in psoriatic skin. Elevated DNA- and RNA-polymerases might be the cause of elevated Zn levels in pinpoint lesions.