PTGS2 and aneurysm: In addition to COX2, the expression of EP2 which is the receptor-mediating COX2–PGE2–NFkB signaling involved in ectatic arterial remodeling during aneurysm formation [3], was observed in the mural SMC layer, in the endothelium of small and large bAVM vessels, as well as in the inflammatory cells surrounding bAVM vessels (Fig. 3).