Thesis #21

The influence of the polyunsaturated fatty acids (PUFA) linoleic acid,
arachidonic acid, α-linolenic acid and γ-linolenic acid on pigmentation
was examined using different in vitro models: monolayer cultures of B16
mouse melanoma cells, monolayer cultures of normal human melanocytes
and a commercially available reconstructed pigmented epidermis
that consists of normal, human-derived epidermal keratinocytes (NHEK)
and melanocytes (NHM) which have been cul tured to form a multilayered,
highly differentiated model of the human epidermis that exhibits in
vivo - l ike morphological and ultrastructural characteristics.
We used two different sublines of B16 origin called B16-F1 and B16-F10
for our experiments. In both sublines 25 μM of the PUFA listed above
showed two distinct effects on melanogenesis of the cells: 1) the secretion
of intracellularly produced melanin into the extracellular culture
fluid was enhanced, and 2) the intracellular melanin content was decreased.
The stimulation of melanin secretion was highest after an incubation
time of 24 h, whereas the reduction of intracellular melanin was
most effective after 72 h. α-Linolenic acid and γ-linolenic acid decreased
intracellular melanin content more effectively than arachidonic acid
and linoleic acid. Futhermore intracellular melanin content of murine
melanoma cells was reduced more effectively in B16-F10 subline.
In both sublines tyrosinase activity was not affected, whereas tyrosinase
content was reduced. Tyrosinase mRNA level of B16-F1 cells was
decreased by linoleic and arachidonic acid. None of the fatty acids had
an influence on tyrosinase mRNA levels of B16-F10 cel l s .
None of the polyunsaturated fatty acids at a concentration of 100 μM
affected the melanogenesis of monolayer cul tures of NHM when measuring
the changes in mRNA level, content and activity of tyrosinase and
in the amount of intracellular pigment. In addition the polyunsaturated
fatty acids did not inhibit the pigmentation of the reconstructed pigmented
epidermis.