P. Redondo et al., EFFECTS OF LOW CONCENTRATIONS OF CIS-UROCANIC ACID AND TRANS-UROCANICACID ON CYTOKINE ELABORATION BY KERATINOCYTES, Photodermatology, photoimmunology & photomedicine, 12(6), 1996, pp. 237-243
The urocanic acid cis isomer (cis-UCA) is a possible cutaneous photore
ceptor for the immunomodulatory phenomena that follow ultraviolet B ir
radiation. Several experiments in animals show an inhibitory action of
cis-UCA on cellular immunity. However, the action of cis-UCA on the s
ynthesis of cytokines in keratinocytes remains unknown. Long-term cult
ures of normal human keratinocytes were prepared in a serum-free mediu
m, and stimulated with 1 mu g/ml of phorbol 12-myristate 13-acetate (T
PA) and UCA or UVB-UCA (10-100 mu g/ml). Synthesis of the following cy
tokines was measured using ELISA and Northern blot techniques: TNF-alp
ha, IL-1 alpha, IL-1 beta, IL-6, IL-8 and TGF-beta 1. TPA increased TN
F-alpha protein levels in culture supernatants. No changes in IL-1 alp
ha and IL-1 beta protein levels were detected in basal culture superna
tant after TPA stimulus. TPA augmented RNA expression for TNF-alpha, I
L-1 alpha, IL-1 beta and TGF-beta 1. UCA isomers did not induce cytoki
ne changes in protein synthesis. Expression of IL-1 alpha and IL-1 bet
a genes was increased after exposure to 100 mu g/ml UVB-UCA (70 mu g/m
l cis-UCA). A slight increase in TNF-alpha RNA expression was detected
when the dose of UVB-UCA reached 100 mu g/ml. No effects on cytokine
synthesis were found after UCA stimulus. These results suggest that lo
w doses of cis-UCA do not effect cytokine synthesis by keratinocytes.