cis-Urocanic acid does not induce the expression of immunosuppressive cytokines in murine keratinocytes.
trans-Urocanic acid (UCA) acts as a chromophore for UV radiation in the epidermis and isomerizes to cis-UCA which then initiates some of the changes leading to UV-induced immunosuppression. The mechanism of the immunomodulation by cis-UCA is unknown at present, but one possibility is that the interaction between cis-UCA and keratinocytes causes the release of immunosuppressive cytokines locally. To test this hypothesis, PAM-212 cells, a murine keratinocyte cell line, were incubated with 0.10-100 micrograms/mL trans- and cis-UCA for 6 or 24 h, respectively. The expression of interleukin (IL)-10, transforming growth factor (TGF)-beta and tumor necrosis factor (TNF)-alpha messenger RNA (mRNA) was then measured by reverse transcription-polymerase chain reaction in comparison with the mRNA for the house-keeping gene, beta-actin. No change or significant induction of any of the cytokine messages occurred. However, the expression of IL-10 messenger RNA (mRNA) was induced 24 h after UVB irradiation (300 J/m2) and that of TNF-alpha mRNA occurred 6 h after treatment with phorbol myristate acetate. The expression of IL-10 protein was also examined by immunostaining in both PAM-212 cells and B16-F10 murine melanoma cells between 3 and 48 h after incubation with 10 and 100 micrograms/mL cis- and trans-UCA. No alteration was seen with either isomer at either concentration. In contrast, UVB irradiation of both cell lines resulted in a marked increase in intracellular IL-10 protein at 24 and 48 h. Therefore the upregulation of the immunosuppressive cytokines, IL-10, TNF-alpha and TGF-beta, in keratinocytes is unlikely to be the mechanism by which cis-UCA induces immunosuppression in mice.
Zak-Prelich
M
M
Department of Dermatology, Medical University of Lodz, Poland.
Norval
M
M
Venner
T J
TJ
Bisset
Y
Y
Walker
C
C
Rafferty
T S
TS
Sauder
D N
DN
McKenzie
R C
RC
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000187:drug effects*; D016753:Interleukin-10 / Q000235:genetics*; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects*; D051379:Mice; D012333:RNA, Messenger; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000235:genetics*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*; D014560:Urocanic Acid / Q000494:pharmacology*
D017931:DNA Primers; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D014560:Urocanic Acid