TGFβ/Smad signalling in psoriatic epidermis models exposed to salt water soaks and narrowband ultraviolet B radiation

The role of transforming growth factor-β1 (TGFβ1) and Smad signalling has not been established in psoriasis treatment. We aimed to investigate the effect of combined treatment with salt water soaks and ultraviolet radiation on the expression of TGFβ1/Smad signalling proteins in a psoriatic model. We studied mRNA expression (real-time RT-PCR) of TGFβ1, TGFβ receptor type I (TGFβRI), Smad2, Smad3, Smad4, Smad7, minichromosome maintenance protein 7, and involucrin in normal as well as psoriatic epidermis models (PEM) which were treated for three consecutive days with differently concentrated salt water solutions [(3% NaCl; 30% NaCl, 30% Dead Sea salt water (DSSW)] and subsequent narrowband ultraviolet B (NB-UVB). In PEM, TGFβ1 and Smad3 was significantly increased as compared to normal epidermis models. By contrast, TGFβRI mRNA was significantly decreased in PEM. Significant increase of mRNA levels of TGFβ1, TGFβRI, Smad2 and Smad3 was predominantly observed in non-irradiated and irradiated PEM pre-treated with 30% NaCl and/or DSSW which was paralleled by increase of involucrin mRNA. In PEM pre-treated with DSSW, TGFβRI, Smad2, Smad3, Smad4, and Smad7 mRNA was significantly higher in irradiated PEM when compared to non-irradiated samples. It has been shown that TGFβ1/Smad signalling is altered in a psoriatic model and may play a role in the mode of action of salt water soaks and NB-UVB phototherapy of psoriasis.