Large vessel vasculitis is a disease that causes damage to blood vessels. This damage to blood vessels can increase the risk of patients with LVV developing cardiovascular disease, including heart attacks and strokes. A chemical produced in the body called endothelin may contribute to this increase in cardiovascular disease risk by causing the vessels to stiffen and blood pressure to increase. It has previously been shown that by blocking the effects of endothelin, vessel stiffness and blood pressure improve. Bosentan is a tablet that blocks the effects of endothelin. The investigators plan to assess blood vessel function in those with LVV and participants without LVV. Participants with LVV will then be given Bosentan for 6 weeks to evaluate its impact on blood vessel function.