Abstract
PurposeTo characterize the effects of benzalkonium chloride (BAK) in THP-1 differentiated cells in vitro.MethodsMacrophages were obtained after differentiation of THP-1 cells, a human monocytic leukemia cell line. Macrophages were exposed for 24 h to 33 nM (10−5%) benzalkonium chloride (BAK), 10 nM dinitrochlorobenzene (DNCB), 100 ng/mL lipopolysaccharide (LPS), 5 ng/mL tumor necrosis factor alpha (TNF-α) or phosphate buffered saline (PBS) as controls. The expression of CD11b, CD11c, CD33 and CD54 was evaluated using immunohistochemistry and flow cytometry (FCM). Phagocytosis function was analyzed using carboxylate-modified fluorescent microspheres and quantified by FCM. Migration was evaluated in cocultures with conjunctival epithelial cells. Cytokine production was detected and quantified in culture supernatants using a human cytokine array.ResultsStimulation of THP-1-derived macrophages with a low concentration of BAK increased CD11b and CD11c expression and decreased CD33. Macrophages exposed to BAK, LPS and TNF-α had increased phagocytosis. In contrast to LPS, BAK and TNF-α increased macrophage migration. Cytokines in supernatants of macrophages exposed to BAK revealed an increased release of CCL1, CCL4/MIP-1β, TNF-α, soluble CD54/ICAM-1 and IL-1β.Conclusion In vitro, BAK has a direct stimulating effect on macrophages, increasing phagocytosis, cytokine release, migration and expression of CD11b and CD11c. Long-term exposure to low concentrations of BAK should be considered as a stimulating factor responsible for inflammation through macrophage activation.
Highlights
Inflammatory and immune cells are involved in the pathophysiological mechanisms of ocular surface diseases [1]
THP-1 cells were differentiated into macrophages after phorbol myristate acetate (PMA) stimulation
Total cytotoxity expressed by PMA differentiated THP-1 cells exposed during 24 hours to benzalkonium chloride (BAK) at 33 nM was 39.364% and to DNCB at 10 nM was 29.561.8% (Table 1)
Summary
Inflammatory and immune cells are involved in the pathophysiological mechanisms of ocular surface diseases [1]. Alongside dendritic cells and B-lymphocytes, they are antigenpresenting cells [2] They produce inflammatory mediators and exhibit heterogeneity in their phenotype depending on the local environment. Macrophages are localized in the stroma and can interact closely with conjunctival epithelial cells, playing an important role in ocular surface diseases. Allergic conjunctivitis has been shown to be associated with excessive macrophage infiltration in the conjunctiva [3,4]. In trachoma, they are known to increase local production of connective tissue growth factor (CTGF), basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) [5]
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