Exosomes in the Pathogenesis of Diabetic Atherosclerosis & its Treatment Opportunities

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The goal of this proposal is to understand why people with diabetes develop severe fatty-rich plaques called atherosclerosis in arteries. Accelerated atherosclerosis has been linked to several types of cardiovascular diseases that cause disabilities and premature death amongst diabetic individuals. Unfortunately, such serious medical problems are very frequent among veterans enrolled in the VHA Health Care System as they are almost three times more likely to develop diabetes than people in the general population. One reason that has been identified to enhance atherosclerosis among diabetic individuals is high blood sugar, also called “hyperglycemia”. But exactly how hyperglycemia enhances atherosclerosis is not known. Our recent research focus has centered on exploring the role of microvesicles released by cells, called “exosomes”, as a source of inflammation in atherosclerosis. Preliminary findings presented in our revised grant proposal show that human diabetic subjects diagnosed with advance peripheral atherosclerotic cardiovascular disease accumulate pro-inflammatory exosomes in their bloodstream. Our findings also show that diabetic mice accumulate pro-inflammatory exosomes in their bloodstream. Furthermore, our findings show that such diabetic plasma exosomes can increase the number of white blood cells that accumulate in arteries when they are infused into non-diabetic mice. Interestingly, our data demonstrate that pro-inflammatory exosomes can be produced by macrophages cultured in glucose-rich medium that simulates diabetic hyperglycemia. Remarkably, our data also show that macrophages can produce anti-inflammatory exosomes when they cultured in medium that contains protective cytokines such as interleukin-4. Based on our extensive new findings, we propose to explore whether diabetic hyperglycemia enhances the progression of atherosclerosis through exosomes that communicate pro-inflammatory signaling in the immune system and the vessel wall. We also aim to produce exosomes that can serve to overcome the effects of hyperglycemia to suppress the progression of diabetic atherosclerosis. In our First Aim we will define the extent to which hyperglycemia causes the production of proinflammatory exosomes in the bloodstream of veterans suffering from advanced atherosclerotic disease. We will do the same by studying mouse models of diabetes. Next, we will test the ability of diabetic plasma exosomes to enhance vascular inflammation and atherosclerosis when infused into hyperlipidemic mice. We will also test whether macrophages cultured in medium that contains elevated levels of glucose or bad cholesterol called oxLDL, will produce exosomes that can induce atherosclerosis when infused into non-diabetic mice. Lastly, we will explore if a class of signaling molecule called microRNA carried by exosomes are responsible for their inflammatory signaling. In our Second Aim we will seek to produce therapeutic exosomes. Our strategy will consist of isolating exosomes from macrophages cultured in medium that contains protective factors including interleukin-4. Our second strategy will be to produce bioengineered exosomes from cultured macrophage tailored to produce desired levels of protective miRNA and test whether such exosomes can exert anti-inflammatory properties to reduce the progression of atherosclerosis in diabetic mice.