Endothelin-1 and its A and B receptors: are they possibly involved in vitiligo?

Endothelin-1 (ET-1), expressed by keratinocytes, has paracrine effects on melanocytes. The endothelin 1-axis [ET-1, endothelin A receptor (ETAR) and endothelin B receptor (ETBR)] is thought to play a role in the depigmentation process occurring in vitiligo, with no studies on the cutaneous protein expression of this axis in the disease. The aim of the present study was to compare the expression of ET-1 axis in lesional and perilesional normal epidermis of vitiligo patients with healthy controls. Ten patients with non-segmental stable vitiligo and ten healthy controls were included. Skin biopsies from all subjects were studied immunohistochemically for ET-1, ETAR and ETBR expression. No significant difference was detected in the rate of expression and the degree of staining of ET-1 axis in controls compared with each of lesional vitiligo and perilesional normal epidermis (P>0.05). There was no statistically significant difference between lesional vitiligo and perilesional normal epidermis regarding to the rates of ET-1, ETAR and ETBR expression (P=0.82, P=0.5 and P=0.99, respectively). Semi-quantitative analysis of ETAR revealed higher staining grades in lesional compared with perilesional normal epidermis, with a statistically significant difference (P=0.04). There was no statistically significant difference between the two groups regarding the staining grades of ET-1 and ETBR (P>0.05 for both markers). A highly significant positive correlation was found between ET-1 and ETAR (r =0.99, P<0.05) and between ET-1 and ETBR (r=0.87, P<0.05). The study demonstrated unaltered expression of ET-1 axis in keratinocytes in lesional vitiligo and perilesional normal epidermis. Additional studies on the differential expression of this axis in keratinocytes and melanocytes are therefore required.