Transglutaminase activity regulates atherosclerotic plaque composition at locations exposed to oscillatory shear stress

ObjectiveAtherosclerosis preferentially develops at sites of disturbed blood flow. We tested the hypothesis that transglutaminase activity plays a role in plaque development at these locations.Methods and resultsExposure of endothelial cells to steady flow (7 dynes/cm2) was associated with relatively low transglutaminase activity, whereas under low oscillatory flow (1.3 ± 2.6 dynes/cm2) endothelial cells showed a >4-fold higher level of transglutaminase activity. Under oscillatory flow, transglutaminase activity increased the expression of the chemokine MCP-1 (CCL2). In vivo, oscillatory flow was induced by placement of a tapered perivascular cast around the carotid artery of type 2 transglutaminase (TGM2) knockout mice and WT counterparts. After 2 days, significantly less monocytes adhered to the endothelium in TGM2 knockout mice as compared to WT. In a more chronic setting, ApoE knockout mice that were equipped with the flow-modifying cast developed lesions proximal to the cast (low shear stress), and distal to the cast (oscillatory shear stress). Inhibition of transglutaminase induced a marked reduction in macrophage and fat content in distal lesions only. In addition, lesion size was increased in this area, which was attributed to an increase in smooth muscle content.ConclusionOscillatory shear stress increases endothelial transglutaminase activity. In turn, transglutaminase activity affects the expression of MCP-1 in vitro and monocyte recruitment in vivo. In a mouse model of atherosclerosis, transglutaminase activity has a major effect on plaque composition under oscillatory shear stress.

► Transglutaminase activity is higher in endothelial cells under oscillatory flow. ► Inhibition of transglutaminase decreases the expression of MCP-1. ► In vivo, less monocytes adhere to the endothelium in TG2 knockout mice. ► ApoE knockout mice are equipped with a flow-modifying cast to induce lesions. ► Transglutaminase affects plaque composition under oscillatory shear stress only.