Abstract MP17: TLR4 May Play A Role In Accelerated Atherosclerosis In Beta Thalassemia

Abstract

Beta Thalassemia (BT) is an autosomal recessive hemoglobinopathy that affects 80 million people worldwide. Children with BT display an increase in carotid-intima media thickness, an early sign suggestive of premature atherosclerosis. However, it is unknown if there is a direct relationship between BT and atherosclerotic disease. BT has increased free heme leading to ROS generation directly or via Toll Like Receptor (TLR4) activation, but the role of heme in disease progression in BT is poorly characterized. The aim of this study is to evaluate the progression of atherosclerosis in BT mice and the potential role of TLR4. Atherosclerosis was induced by implementing short (ST) and long term (LT) models. In our ST model, both BT ( Hbb th-3 ) and wild type (b6) male/female littermates (n=5) were fed a Paigen high fat diet (PD) for 8 weeks. On week 2, mice were injected with AAV8-PCSK9 to knockdown the LDL receptor. On weeks 4-8, mice were treated with Angiotensin ll via subcutaneous osmotic pumps implantation. The LT model was performed by placing mice on 3 months of PD with PCSK9 overexpression. Atherosclerosis was evaluated by atherosclerotic plaque lesion area of the descending aorta via en face analysis, histology of the aortic roots, and RT-qPCR of inflammatory markers. In addition, to evaluate the possible contribution of TLR4 in atherosclerosis, bone marrow transplants were performed by grafting WT and BT bone marrow (n=2-4) to both b6 and TLR4 -/- mice, and atherosclerosis was performed as described in our LT model.In our ST model, aortic en face analysis revealed elevated plaque accumulation in BT mice (WT: 22 ± 4% plaque area vs. Thal: 45 ± 11% plaque area, p = .024). Aortic root (H&E) analysis did not display a significant difference in our ST model, but it was significantly increased in the LT model. Gene expression profiling indicated a significant increase in both IL-6 and CD-68 (p<0.041) in BT mice. In our BMT experiments, we saw a significant decrease in aortic root plaque in TLR4 -/- mice with Thal BM (.24 ± .06 mm 2 ) compared to wild type mice with Thal BM (.39 ± .07 mm 2 ). Our data demonstrate for the first time that the underlying pathophysiology of BT clearly leads to accelerated atherosclerosis and suggest TLR4 is playing a role in atherosclerotic development in BT.