Tachykinins may play a role in psoriasis per se, in addition to pruritus in this disease. Targeting the combined NK-1 and NK-2 receptors might be a possible treatment.

Psoriasis is a chronic inflammatory disease in which pruritus is a common symptom. Pruritus may be associated with the gamma-aminobutyric acid (GABA) system. The distribution of GABA and its GABA(A) receptor (R) was studied in involved and non-involved psoriatic skin, as well as normal healthy control skin, using an immunohistochemistry technique. Pruritus was determined using a visual analog scale. Inflammatory cells immunoreactive for the GABA ligand and the GABA(A) R were increased (P < 0.01, respectively) in the involved skin. Cells stained for GABA ligand were mostly macrophages with some lymphocytes, while cells stained for GABA(A) R were macrophages, neutrophils or lymphocytes. There was a positive correlation when comparing GABA ligand (P = 0.05) and GABA(A) R (P < 0.05) expressing inflammatory cells, with pruritus. The GABA ligand and its GABA(A) R may play a role for the pathogenesis of psoriasis as well as for pruritus in this disease.

Objective To identify pathoaetiological neuroimmune mechanisms in patients with atopic dermatitis (AD) and chronic stress, focusing at nerve density, sensory neuropeptides, and the serotonergic system. Methods Eleven patients with AD with histories of stress worsening were included. Biopsies from involved and non-involved skin were processed for immunohistochemistry. Salivary cortisol test was done as a marker for chronic stress. Results There were more acanthosis and fewer nerve fibres in epidermis and papillary dermis of involved compared with non-involved skin. Whereas there was no significant change in the number of substance P and calcitonin generelated peptide-positive nerve fibres between the involved and non-involved skin, there was an increase in the epidermal fraction of 5-hydroxtrytamine 1A (5-HT1A) receptor and serotonin transporter protein (SERT) immunoreactivity in the involved skin. The number of 5-HT2AR, CD3-positive cells, and SERTpositive cells, most of them being CD3 positive, was increased in involved skin. There was an increase in mast cells in the involved skin, and these cells were often located close to the basement membrane. There was a strong tendency to a correlation between 5-HT2AR positive cells in the papillary dermis of involved skin and low cortisol ratios, being an indicator of chronic stress. Conclusion A changed innervation and modulation of the serotonergic system are indicated in chronic atopic eczema also during chronic stress.