Effect of narrowband ultraviolet B therapy on serum levels of CD26/dipeptidyl-peptidase IV and truncated forms of substance P in psoriasis patients with pruritus

Purpose: While pruritus affects approximately 60-90% of psoriasis patients, the pathogenesis of the condition remains unclear. CD26/dipeptidyl-peptidase IV (CD26/DPPIV) and truncated forms of substance P (SP) have been reported to play an important role in the pathogenesis of psoriatic itch. The aim of this study was to determine the serum levels of soluble CD26/DPPIV and truncated forms of SP in response to narrowband ultraviolet B (NBUVB) therapy.

Patients and methods: The peripheral blood of 13 participants with moderate to severe psoriasis (psoriasis area and severity index (PASI) ≥10) who presented with pruritus symptoms and 12 psoriasis-free participants were collected. Seven of the 13 patients agreed to be treated with NBUVB. The PASI was evaluated. Additionally, the clinical assessment of itch was performed with the visual analog scale (VAS) and the itch severity scale (ISS).

Results: The results showed that the levels of truncated SP were significantly higher in participants with psoriasis compared to participants without psoriasis. (302.20±56.87 vs 234.96±78.01 pg/ml, p<0.05). After irradiation, truncated SP significantly decreased from 288.85±66.22 pg/ml to 252.13±49.78 pg/ml, p<0.05. The CD26/DPPIV levels were lower in psoriasis participants compared to the healthy participants (526.34±145.35 vs 593.19±84.92 ng/ml, p>0.05) and increased significantly after NBUVB therapy (518.13±173.0 ng/ml to 592.7±193.9 ng/ml, p<0.05). NBUVB therapy caused alterations to the serum levels of truncated SP and CD26/DPPIV.

Conclusion: The decreased serum levels of truncated SP and increased levels of CD26/DPPIV post-NBUVB treatment observed in this study provides insight into the underlying molecular mechanisms of the treatment; this may be used in the prospective monitoring and development of improved psoriasis-related pruritus therapeutics. Further studies, comprising a larger cohort, are required to confirm these results.