*In partial fulfillment of the requirement for the PhD degree.
DIETARY HISTIDINE INCREASES MOUSE SKIN UROCANIC ACID LEVELS AND ENHANCES UVB-INDUCED IMMUNE SUPPRESSION OF CONTACT HYPERSNSITIVITY
Article first published online: 2 JAN 2008
Photochemistry and Photobiology
Volume 53, Issue 4, pages 431–438, April 1991
How to Cite
Reilly, S. K. and Da Fabo, E. C. (1991), DIETARY HISTIDINE INCREASES MOUSE SKIN UROCANIC ACID LEVELS AND ENHANCES UVB-INDUCED IMMUNE SUPPRESSION OF CONTACT HYPERSNSITIVITY. Photochemistry and Photobiology, 53: 431–438. doi: 10.1111/j.1751-1097.1991.tb03653.x
- Issue published online: 2 JAN 2008
- Article first published online: 2 JAN 2008
- Received 22 January 1991; accepted 25 January 1991
Urocanic Acid (UCA) exists in mammalian skin primarily as the trans isomer and is photoisomerized to cis UCA upon UVB absorption. Our previous studies indicated that the photoiaomerization of UCA is the initiating event in UVB-induced suppression of cell-mediated immunity (tUCA cUCA immune suppression). The purpose of this study was to verify the role of UCA in UV-induced immune suppression of contact hypersensitivity (CHS) in BALB/c mice. Since UCA is a metabolite of the amino acid L-histidine, we reasoned that increased dietary levels of histidine should raise skin tUCA levels. If skin tUCA is the UVB photoreceptor for immune suppression, this increase should enhance UV-induced suppression of CHS. HPLC analysis of skin from BALB/c mice given a histidine-rich diet (10%) showed that the total amount of UCA is significantly higher in these animals than in mice fed a normal diet. Further, levels of suppression of CHS of 3% and 49% in control fad mice, induced by 4.8 and 7.2 kJ/m2 UVB were significantly increased to 21% and 71% respectively in histidine-fed animals at these same UVB doses. These findings provide additional support for the UCA model for immune suppression, and provide the first evidence that UV-induced immune suppression can be enhanced by a dietary component, L-histidine.