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 pigment-dependent. 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-1α), delayed effects were observed with a secretion decreased 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.

Tattoos are trending, and in the USA 25% of people aged 18 to 50 are tattooed. The more people get tattoos, the more skin injuries are discovered and reported in the literature. The short-term and localized effects are well known, but injection of tattoo inks can be associated to long-term risks. In this article, we investigated three cobalt pigments, which constitute a wide range of colors found in tattoos: Pigment Violet 14 (purple), Pigment Green19 (green), and Pigment Blue 28 (blue). After injection, macrophages are among the first cells to come in contact with pigments. We thus tested the effects of cobalt-based pigments on the macrophage cell line J774A1. In order to detect delayed effects, we compared two exposure schemes: acute exposure for 24 hours and with a 3 days post-exposure recovery period. The conjunction of these two schemes allowed the investigation of delayed or sustained effects of the pigments. Pigment dissolution and cobalt release was very variable from one pigment to another, Pigment Violet 14 and Pigment Green19 being easily dissolved, while Pigment Blue 28 dissolved much more slowly. The cytotoxicity of the pigments correlated well with their dissolution. All pigments induced functional effects on macrophages, which were largely pigment-dependent. For example, Pigment Green19 and Pigment Blue 28 showed a delayed effect on the phagocytic capacity of the cells. All three pigments induced a low but significant secretion of tumor necrosis factor, but the effect was transient. Conversely, Pigment Violet 14 and Pigment Blue 28 induced a sustained secretion of interleukin 6, although at low levels. The pigments also induced changes in some important membrane markers of macrophages such as CD11b, PdL-1 or CD206. In conclusion, the pigments induced functional perturbations in macrophages, sometimes persistent over time after exposure, even at non-toxic doses.