In vitro: The Modulating Effect of Myricetin on the Atherosclerosis Related Processes in THP1 Macrophages

Aims: To assess the anti-atherosclerotic effects of Myricetin (pharmaceutical) in human THP-1 macrophages following IFN-γ or MCP-1 stimulation.

Study Design: The protective effects of myricetin against atherosclerosis was evaluated using the humanTHP-1 macrophages and studying the following parameters namely, cell viability, cell proliferation, cell migration, inflammation related gene expression and cholesterol efflux in vitro.

Place and Duration of Study: THP-1 cell line: Department of biochemistry (faculty of science), Cell Culture Unit, Experimental Biochemistry Unit (King Fahad Medical Research Centre), King Abdul Aziz University, between September 2019 and September 2020.

Methodology: The THP-1 cell lines were differentiated into macrophages by incubation with PMA (160 nM) for 24 hours. The viability percentage was determined using Pierce LDH cytotoxicity assay kit, the percentage change in macrophages proliferation was evaluated by crystal violet dye, the RNA was extracted then the cDNA was synthesized and the quantitative real time polymerase chain reaction (qRT-PCR) was done for inflammation-related genes, ICAM-1 and MCP-1. The percentage of monocyte migration and cholesterol efflux were also calculated.

Results: Cytotoxicity assays demonstrated no significant toxicity with myricetin at 25μM and 50 μM concentrations on THP-1 macrophages. The quantitative real-time RT-PCR (qRT-PCR) demonstrated a significant increase in interferon gamma (IFN-γ) mediated expression of both intercellular adhesion molecule (ICAM-1) and monocyte chemo-attractant protein-1 (MCP-1) by 2.1 and 7.1 fold respectively, compared to the control. Treatment with myricetin (25 μM and 50 μM) significantly inhibited the IFN-γ induced overexpression of ICAM-1 by 42.86% & 71.34% and MCP-1 by 53.52% & 87.32% respectively. Myricetin (25 μM) significantly reduced the migration of monocytes by 33.66% compared to MCP-1. The cholesterol efflux from THP-1 macrophages treated with myricetin was significantly increased by 47% and 57% in the absence and presence of IFN-γ, respectively compared to the control.

Conclusion: Myricetin has anti-inflammatory effects and supports cholesterol efflux, which can help in prevention of atherosclerosis. Furthermore, myricetin did not exhibit any cytotoxic effects and therefore is a safe phytochemical which can complement conventional therapeutics.