CONSTITUTIVE ENDOTHELIAL AND INDUCIBLE NITRIC-OXIDE SYNTHASE IN INFLAMMATORY DERMATOSES

We have used immunohistochemistry to localize the expression of the co nstitutive endothelial and inducible forms of the enzyme nitric oxide synthase (NOS) in skin from involved and uninvolved sites in patients with atopic dermatitis (AD) and allergic contact dermatitis (CD), Endo thelial NOS (eNOS) immunoreactivity was localized to vascular endothel ium in the dermis of both involved and uninvolved skin from all patien ts. Inducible NOS (iNOS) immunoreactivity was found to be closely asso ciated with the upper dermal microvasculature in all the involved AD b iopsies, but only in two of 10 uninvolved AD biopsies, CD biopsies wer e taken from 10 positive skin patch test sites and iNOS immunoreactivi ty was detected in all of these, iNOS immunoreactivity was detected in only one of the negative patch test biopsies. Both the extent and int ensity of iNOS immunoreactivity was lower in CD than in AD skin lesion s. The presence of eNOS in the skin is necessary for constitutive NO-m ediated dilatation of the dermal vasculature, Induction of iNOS in the dermal endothelium and in perivascular inflammatory cells may be sign ificant with respect to the roles of NO in both the vasodilatory compo nent of the inflammatory response and in the modulation of immune resp onses in the skin.