Neuronal changes in psoriasis exacerbation.

Background: The nervous system contributes to inflammatory skin diseases. Objective The aim of this investigation was to study the neuronal contribution to psoriasis at the remission and exacerbation phases.

Methods: We examined the expression of the neuronal markers protein gene product 9.5 (PGP 9.5), growth-associated protein-43 (GAP-43) and substance P, in addition to its receptor (R), neurokinin-1R (NK-1R) in psoriatic skin from seven female patients at remission and exacerbation, using immunohistochemistry.

Results: The number of epidermal PGP 9.5 immunoreactive nerve fibres in the involved skin during exacerbation was decreased (P < 0.01) compared to involved skin at remission and non-involved skin at the exacerbation phase. GAP-43-positive nerve fibres were decreased (P < 0.05) in the involved skin in contrast to non-involved skin, during exacerbation. Substance P expression was seen on both immunoreactive nerve fibres and cells with a down-regulation (P < 0.01) in the number of positive nerve fibres in the involved skin compared to non-involved skin, at the exacerbation phase. The number of substance P-positive cells was slightly lower in the involved skin at exacerbation than at remission. The number of NK-1R immunoreactive cells was increased (P < 0.01) in the involved skin in contrast to non-involved skin, at the exacerbation phase.

Conclusion: Our findings suggest a crosstalk between the nervous system and inflammation during psoriasis exacerbation in the form of an altered expression of nerve fibres, substance P and its NK-1R.