COX 2 inhibits the following step in inflammation:

COX-1, expressed constitutively in most cells, is the dominant source of prostanoids for housekeeping functions, such as gastric epithelial cytoprotection and hemostasis. Conversely, COX-2, induced by cytokines, shear stress, and tumor promoters, is the more impoant source of prostanoid formation in inflammation. COX-2 is found in endothelial cells and inflammatory cells. In endothelial cells, COX-2 initiates the synthesis of prostacyclin, a potent vasodilator and inhibitor of platelet aggregation. Ref: Weitz J.I. (2012). Chapter 118. Antiplatelet, Anticoagulant, and Fibrinolytic Drugs. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.