1 research outputs found
Photoisomerization of retinoic acid and its influence on regulation of human keratinocyte growth and differentiation
71-76Retinoic acid constantly undergoes structural
inter-conversions among the geometrical isomers (all-trans-retinoic acid,
9-cis- retinoic acid, 11-cis-retinoic acid , 13-cis- retinoic
acid and 9-13-di-cis-retinoic acid) by photoisomerization under natural
light. Geometric isomers of retinoic acid thus formed showed different effects on
human epidermal keratinocyte growth and differentiation. The ability of the
isomers to inhibit the synthesis of cornified envelope (terminal event in the keratinocyte
differentiation program) changed rapidly when illuminated by white fluorescent light.
The 11-cis-retinoic acid had a 3-fold stronger activity to inhibit the growth
of keratinocytes than the other geometric isomers. On the other hand, all-trans-
retinoic acid, 9-cis-retinoic acid and 9-13-di-cis-retinoic
acid exhibited a 3-fold greater ability to inhibit synthesis of involucrin,
transglutaminase and the cornified envelopes. The regulation of keratin expression
by the geometric isomers of retinoic acids was extremely complex. Level of
keratin -1 (K1) mRNA was increased by 11-cis- retinoic acid and 13-cis-retinoic
acid, but suppressed by 9, 13-di-cis-retinoic acids while all-trans-retinoic
acid and 9-cis-retinoic acid had no effect. Level of keratin-10 (K10)
mRNA was strongly inhibited by all-trans-retinoic acid, 9-cis-retinoic acid
and 11-cis-retinoic acid as compared to 13-cis-retinoic acid
and 9, 13-di-cis-retinoic acids. The mRNA level of keratin-14 (K14) was
suppressed by all-trans-retinoic acid, 9-cis-retinoic acid
and 11-cis-retinoic acid but not influenced by 13-cis-retinoic
acid and 9, 13-di-cis-retinoic acid. Natural light induced structural
inter-conversions among the geometric isomers of retinoic acids in tissues especially
the skin, might play a crucial role in the regulation of growth and differentiation
of keratinocytes