<h4>Background</h4>We aimed to test the effect of hydroxychloroquine (HCQ) treatment on atherosclerosis and plasma lipids in apolipoprotein E deficient (ApoE<sup>-/-</sup>) mice, defining the aortic expression of endothelial nitric oxide synthase (eNOS) and hypoxia inducible factor-1 alpha (HIF-1α).<h4>Methods</h4>Forty-seven (47) mice were divided into two treatment groups: an HCQ group administered 10 mg/kg/day in drinking water for 16 weeks and a control group with no HCQ. Here, NOS3 is linked to atherosclerosis.