All of the following are mediators of acute inflammation except

ref Robbins 9/e p83 Myeloperoxidase (MPO) is a heme-containing enzyme that, in the presence of peroxide and halide ions, is effective in killing various microorganisms; in addition, it exes a wide variety of extracellular functions. Polymorphonuclear leukocytes (PMN) are the main source of this enzyme.