The immunotoxicity of cobalt-chrome (CoCr) particles generated from prosthetic implants in differentiated HL-60 cells
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Contributing OfficeNational Center for Toxicological Research
Abstract
Metals, such as cobalt and chromium, are present in prosthetic implants that are used to replace damaged hips, knees, and shoulders. However, there is continued concern about particles and metal ions produced from wear damage of these implants that may impact the success of prosthetic implants in clinical practice. The long-term exposure to these leachants may negatively affect the safety of these implants. Biodistribution and cellular internalization of leachants are key factors in determining the intracellular interactions with different cellular organelles and the leachant’s effect on cell function. Among these, phagocytic function of macrophages, which is an important component of the host’s response to microbial pathogens, is critical for tissue hemostasis. In addition, the ability of nanomaterials to recruit immune cells has an important role in all phases of the immune response. Therefore, testing the capability of nanomaterials to recruit immune cells and induce phagocytosis helps in predicting their influence on the immune cell response. The aim of this study was to develop a model to test the effect of CoCr particles generated from prosthetic hip implants on the phagocytic function of macrophages and to test the chemoattractant capability of these particles to recruit neutrophils in vitro. Herein, we differentiated human acute promyelocytic leukemia cells (HL-60 cells) to macrophage-like cells by exposing them to vitamin D3 and phorbol myristate acetate (PMA). We optimized the differentiation method by exposing HL-60 cells to different doses of vitamin D3 and PMA with varying exposure times. Differentiated macrophage-like cells were evaluated morphologically and functionally by testing the phagocytic function using luminol-dependent chemiluminescence with zymosan A. The combination of vitamin D3 (150 nM) for 24 h followed by a 4 h supplementation with PMA (5 nM) showed the best phagocytic function. For testing the chemoattractant capability of CoCr particles, HL-60 cells were differentiated to neutrophil-like cells by exposing them to all-trans retinoic acid (ATRA) and dimethyl sulfoxide (DMSO). The neutrophil-like cells differentiated from HL-60 cells by a 4-day ATRA treatment showed a better chemotactic function compared to those treated with DMSO. The macrophage-like cells derived from HL-60 cells were exposed to different concentrations of CoCr particles (6.25, 12.5, and 25 μg/ml) for 24 hours followed by the addition of opsonized zymosan A to evaluate the effect of the particles on the phagocytic function. Results showed a dose dependent inhibition of the phagocytic function for the macrophage-like cells after exposure to CoCr particles. The internalization was also evaluated by microscopy. Different concentrations of CoCr particles (6.25, 12.5, and 25 μg/ml) showed no chemoattractant capacity to neutrophil-like cells differentiated from HL-60 cells. These results indicate that CoCr particles had an inhibitory effect on the phagocytic function of macrophages which brings more attention to the immunotoxic effect of these particles.