Immediate and sustained effects of cobalt and zinc-containing pigments on macrophages
Résumé
Pigments are among the oldest nanoparticulate products known to mankind, and their
use in tattoos is also very old. Nowadays, 25% of American people aged 18 to 50 are
tattooed, which poses the question of the delayed effects of tattoos. In this article, we
investigated three cobalt [Pigment Violet 14 (purple color)] or cobalt alloy pigments
[Pigment Blue 28 (blue color), Pigment Green 14 (green color)], and one zinc pigment
[Pigment White 4 (white color)] which constitute a wide range of colors found in tattoos.
These pigments contain microparticles and a significant proportion of submicroparticles
or nanoparticles (in either aggregate or free form). Because of the key role of macrophages
in the scavenging of particulate materials, we tested the effects of cobalt- and zinc-based
pigments on the J774A.1 macrophage cell line. In order to detect delayed effects, we
compared two exposure schemes: acute exposure for 24 hours and an exposure for 24
hours followed by a 3-day post-exposure recovery period. The conjunction of these two
schemes allowed for the investigation of the delayed or sustained effects of pigments. All
pigments induced functional effects on macrophages, most of which were pigmentdependent.
For example, Pigment Green 19, Pigment Blue 28, and Pigment White 4
showed a delayed alteration of the phagocytic capacity of cells. Moreover, all the pigments
tested induced a slight but significant increase in tumor necrosis factor secretion. This
effect, however, was transitory. Conversely, only Pigment Blue 28 induced both a short
and sustained increase in interleukin 6 secretion. Results showed that in response to
bacterial stimuli (LPS), the secretion of tumor necrosis factor and interleukin 6 declined
after exposure to pigments followed by a recovery period. For chemoattractant cytokines
(MCP-1 or MIP-1a), delayed effects were observed with a secretion decreased in
Frontiers in presence of Pigment Blue 28 and Pigment violet 14, both with or without LPS stimuli. The
pigments also induced persisting changes in some important macrophage membrane
markers such as CD11b, an integrin contributing to cell adhesion and immunological
tolerance. In conclusion, the pigments induced functional disorders in macrophages,
which, in some cases, persist long after exposure, even at non-toxic doses.
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