Evaluation of Plasma Opioid and Serum Lipocalin-2 Levels in Pruritic Skin Diseases

Although the opioid system is critical for regulating itch within the central nervous system, its role in managing severe, treatment-resistant itch related to skin diseases is unclear. Serum lipocalin-2 (LCN-2) levels are associated with the visual analogue scale score of itch in patients with psoriasis vulgaris (PSO), but not other itchy skin diseases. Therefore, we herein investigated the relationship between opioids and LCN-2 with itch in pruritic skin diseases.

We assessed plasma levels of β-endorphin and dynorphin A and serum levels of LCN-2 in patients with pruritic skin diseases using enzyme-linked immunosorbent assays.

Plasma dynorphin A levels were significantly reduced in patients with urticaria, and asteatotic dermatitis (AsD), while β-endorphin levels were significantly elevated in those with AsD. The plasma β-endorphin-to-dynorphin A ratio was markedly higher in AsD patients than in healthy controls. Among the patients examined, only those with PSO had significantly elevated serum LCN-2 levels, which correlated with VAS and severity index scores and also with the area of affected skin.

The present results suggest that the ratio of plasma opioids is involved in itch control in AsD patients, and serum LCN-2 levels may be a biomarker for itch and its severity in those with PSO.