The effects of norepinephrine on the proliferation, lipid-uptake and mRNA expression of inflammatory markers in vascular smooth muscle cells

Background: Cardiovascular disease (CVD) is the leading, global cause of death. Elevated levels of norepinephrine (NE) are associated with CVDs such as coronary heart disease with atherosclerosis as the underlying mechanism. Oxidised low-density lipoprotein (OxLDL) has been shown to play an integral role in the formation of atherosclerosis within the vasculature. Previous studies suggest a decrease in NE by renal denervation is associated with enhanced atherosclerosis in mice and NE has anti-inflammatory effects. Therefore, we hypothesised that NE may protect against atherosclerosis. This study aimed to investigate the effects of NE on cellular proliferation, OxLDL uptake and mRNA expression of inflammatory markers in mouse aortic vascular smooth muscle cells (VSMCs), a key cell type involved in atherosclerosis. Methods: Mouse aortic VSMCs were cultured and treated with NE for three consecutive days. Cell proliferation was measured using the trypan blue exclusion and MTS proliferation assays. VSMCs were exposed to fluorescence-labelled OxLDL in the presence or absence of NE for 24 hours. Cellular uptake of fluorescence-labelled OxLDL was visualised by confocal microscopy and analysed for mean fluorescence intensity using ImageJ. To investigate the involvement of NE receptors, theMaster