Characterization of cationic amino acid transporters (hCATs) 1 and 2 in human skin.

In the present study, we characterized the distribution of human cationic amino acid transporters 1 (hCAT1) and 2 (hCAT2) in healthy skin and compared it to psoriatic skin lesions by means of immunohistochemistry. Moreover, we tested the hypothesis that L -arginine and L -ornithine influence the expression and synthesis of hCAT1 and hCAT2 in cell culture experiments by means of real-time-PCR and Western blot. Immunohistochemical comparison between healthy and psoriatic skin revealed a decreased amount of hCAT1, especially in the stratum granulosum of psoriatic skin; the distribution pattern of hCAT2 was not significantly affected in psoriatic skin. Cell culture experiments showed that supraphysiological concentrations of 15 mM L -arginine (72 h) lead to a significant increase of the hCAT1-mRNA and protein expression, whereas other concentrations had no significant influence. In contrast, L -arginine concentrations of 2 mM led to a significant increase of the hCAT2B mRNA-expression after 24 h. However, 48 and 72 h revealed no significant changes and high concentrations (15 mM L -arginine) led to a significant downregulation of the hCAT2B transporter over all time points analyzed. L -ornithine had no effect on the hCAT1 expression of mRNA and protein level. On the other hand the expression of hCAT2B was significantly up regulated at a 5-mM concentration of L -ornithine at all analyzed time points. Other concentrations had no effect. For the first time, the findings yield data about hCAT1 and hCAT2 on protein-level and suggest that L -arginine is a worthwhile object of studies, which investigated L -arginine as a possible therapeutic agent to reduce psoriatic symptoms.