Dysregulation of natural killer cells’ receptor expression and cytotoxic function by hydroxychloroquine

Abstract

Abstract Background and Aim: Natural killer (NK) cells are crucial players of the innate immune system, especially in the fight against tumors and infections. Besides, NK cells are known to contribute in inflammatory processes associated with multiple diseases. The drug hydroxychloroquine (HCQ) has been repurposed to be used for the treatment of malaria, autoimmune diseases, and COVID-19 infection. However, its direct mechanism of action on NK cells remains unknown. In this study, we aimed to examine the effects of HCQ on NK cell activity and function. Materials and Methods: The human NK cell line NK92 was cultured and treated with HCQ at 1, 5, and 10 μM for 24 and 48 hours. Then, NK92 cell viability, NKG2D and CD107a expression, as well as NK92 cell cytotoxicity were assessed. Also, IFN-γ production was measured by ELISA after HCQ treatment. Statistical analysis was performed where p<0.05 was considered statistically significant. Results: Upon treatment with different concentrations of HCQ for 48 hours, NK92 cell viability significantly decreased in a dose-dependent manner, with the lowest viability noted at 10 μM of HCQ. Additionally, NKG2D and CD107a expression were significantly reduced upon treatment with 5 and 10 μM of HCQ. Similarly, the cytotoxicity of NK92 cells against K562 cells was reduced at both 5:1 and 10:1, effector to target (E: T) cell ratios, when 10 μM HCQ was used. In contrast, IFN-γ levels were significantly increased upon the treatment with 1, 5, and 10 μM HCQ. Conclusion: This study highlights the effect of HCQ on activating receptor expression, cytotoxicity, and IFN-γ production of NK cells. Despite being an immunomodulatory drug, more studies are needed to further understand HCQ’s effects on NK cells and perhaps other effector cells. None