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.