Opioid receptors expression in the skin of haemodialysis patients suffering from uraemic pruritus

Background Uraemic pruritus is a common symptom in patients with chronic kidney disease undergoing haemodialysis (HD) treatment. Etiopathogenesis of uraemic pruritus is complex and not fully explained, but there are reports indicating a possible role of peripheral opioid system in its pathomechanism. Objectives This study was undertaken to analyse the expression of mu- and kappa-opioid receptors in the skin of HD patients with and without uraemic pruritus. Methods Forty patients suffering from chronic kidney disease, treated with haemodialysis (21 pruritic and 19 non-pruritic), were included. The expression of mu- and kappa-opioid receptors in their skin was evaluated with immunohistochemistry. Results The significant (P < 0.02) decrease in kappa-opioid receptor expression was shown in the skin of pruritic patients in comparison with the skin of those without itch (1.07 +/- 0.62 and 1.66 +/- 0.85, respectively). Moreover, there was a significant negative correlation between intensity of pruritus and expression of kappa-opioid receptors (r = -0.63, P = 0.002). There was no difference in the expression of mu-opioid receptor expression in the skin of pruritic and non-pruritic HD patients. Conclusions This study indicates that changes in peripheral opioid system may play an important role in the uraemic itch pathogenesis and that future studies are necessary to fully understand this mechanism.