- Cysteine protease cathepsin F is expressed in human atherosclerotic lesions, is secreted by cultured macrophages, and modifies low density lipoprotein particles in vitro. Oörni, K., Sneck, M., Brömme, D., Pentikäinen, M.O., Lindstedt, K.A., Mäyränpää, M., Aitio, H., Kovanen, P.T. J. Biol. Chem. (2004)