The effect of PUVA treatment on acid hydrolases in human polymorphonuclear leukocytes

The activity of intracellular acid hydrolases in polymorphonuclear leukocytes (PMNL) from psoriatic patients and normal control subjects was determined. No significant differences between healthy and psoriatic individuals were detected, but a slight decrease in acid hydrolase activity was found in PMNL of psoriasis patients during PUVA therapy. PUVA treatment of PMNL in vitro at intensities that may be achieved in situ in the epidermis led to intracellular inactivation of acid hydrolases, which was not due to secretion of the enzymes or cell damage. The decrease in PMNL hydrolase activity appeared to be evoked by PUVA-generated reactive oxygen species because reduced glutathione prevented this decrease. The activity of free extracellular acid hydrolases was not affected by PUVA, and the superoxide production of PUVA-treated PMNL was increased. These results suggest that intracellular inactivation of acid hydrolases and possibly other lysosomal enzymes in PMNL or monocytes infiltrating the epidermis may contribute to the antipsoriatic activity of PUVA therapy.