Stress sensitivity in patients with atopic dermatitis in relation to the translocator protein 18 kDa (TSPO)

Atopic dermatitis (AD) is a chronic inflammatory skin disease, characterized by pruritic and eczematous skin lesions and dermatitis that worsens under stressful conditions. However, the relation of these symptoms to an individual's stress sensitivity is not well understood. On the other hand, expression of the translocator protein (18 kDa) (TSPO), formerly known as the peripheral-type benzodiazepine receptor, has been used as a biological marker of trait anxiety and stress sensitivity. The present study was designed to address this issue by examining TSPO in patients with AD. Fifty-two patients with AD (30 male and 22 female) and 163 healthy volunteers (89 male and 74 female) participated in this study. State-Trait Anxiety Inventory (STAI) scores were significantly higher in patients with AD, especially male patients, than in healthy subjects. The expression of platelet TSPO, as determined with a binding assay with [(3)H] PK11195, was also significantly higher in patients with AD, indicating that AD is a stress-responsive disease. In genomic analysis using lymphocytes, a single-nucleotide polymorphism of the human TSPO gene at exon 4 (485G>A), which is presumably associated with an individual's stress sensitivity, showed significantly lower frequencies of G/G and higher frequencies of G/A in patients with AD than in healthy subjects. The severity of AD, as determined with the Scoring of Atopic Dermatitis index, was correlated with TSPO expression in male patients with the G/A phenotype. In conclusion, the present study provides new evidence that variation in the TSPO gene affects susceptibility to AD.