Abstract Body (Do not enter title and authors here): Background: Age is the most important risk factor for coronary artery disease (CAD), independent of traditional risk factors such as hypertension, diabetes (DM), hyperlipidemia and smoking, through poorly understood mechanisms. Medin, a cleavage product of MFGE8 protein that forms the most common human amyloid, accumulates in the vasculature with age, including the coronary arteries. Although medin amyloid has been implicated in various diseases such as Alzheimer’s disease, vascular dementia and aortic aneurysms, its role in CAD remains unknown. Medin was shown to induce changes characteristic of vascular aging, such as endothelial and smooth muscle dysfunction in human donor cerebral arteries. Medin also induced proinflammatory activation of human brain microvascular endothelial cells through NFκB activation .
Aims: To determine the effects of medin on pro-inflammatory and prothrombotic activation of human coronary artery endothelial cells (HCAECs).
Methods: Primary HCAECs (passages 6-8) were exposed for 20 hours to physiologic doses of recombinant medin (0.5, 1 and 5 µM) and gene expression of pro-inflammatory proteins (IL-6, IL-8, IL-1b and intercellular adhesion molecule (ICAM)-1), prothrombotic protein (plasminogen activator inhibitor (PAI)-1) and anticoagulant membrane protein thrombomodulin were quantified using rtPCR and compared. Separately, HCAECs were exposed to medin (0.5, 1 and 5 µM) with or without small molecule specific inhibitor of NFκB (RO106-9920, 10 uM) for 20 hours and protein expression of IL-6 in conditioned media was measured using ELISA.
Results: Medin caused dose-dependent increases in gene expressions of pro-inflammatory cytokines IL-6, IL-8, IL-1b, ICAM-1 (Figure 1 A-D). Medin caused a dose-dependent increase in PAI-1 and a dose-dependent decrease in thrombomodulin (Fig. 1 E-F). Co-treatment with RO106-9920 prevented medin-induced increase in IL-6 protein expression (Fig. 1G).
Conclusions: Medin induces pro-inflammatory and prothrombotic activation of human coronary artery endothelial cells. The proinflammatory activation is likely NFκB-dependent. Medin is a promising potential novel mediator of CAD and vascular aging.