The Role of Peptide- and Peptidomimetic-based Cathepsin-C Inhibitors in Inhibition of Necrosis

Abstract

The two most known forms of cell death are apoptosis and necrosis. Apoptosis is a controlled form of cell death. Necrosis was previously thought to be a more disorderly form of self-destruction. Recent research, however, suggests that the process of necrosis is much more controlled than it has been understood to be. In fact, this systematic necrotic process plays a critical role in many harmful health conditions. For example, it is involved in the obstruction of blood vessels, neurodegenerative diseases, infection, inflammatory diseases, exposure to toxins, and cancer. This study builds on research done by Prof. Ilana Natan at Ben-Gurion University and Prof. Amnon Albeck at Bar-Ilan University. Their research identified increased elastaselike proteolytic activity in cells exposed to necrosis inducers. In necrosis, proteolytic enzymes catalyze the hydrolysis of peptide bonds in proteins and peptides. It follows that the development of protease inhibitors may be important in the treatment of various disease states. This study focuses on the inhibition of a specific enzyme, Cathepsin C, which is a cysteine protease. Six inhibitors of the enzyme Cathepsin C were synthesized to be used in several experiments. The preliminary experiment tested if the compounds inhibited Cathepsin C’s activity when the enzyme was isolated. Then, the compounds were tested in live cells. In the first live cell experiment, rat heart cells in simulated hypoxic conditions were incubated with the inhibitors. In the second live cell experiment, the compounds were incubated with PC-12 cells in which necrosis was induced by toxic KCN, or potassium cyanide. KCN is a substance that is toxic to cells because it interferes with the activity of cytochrome c oxidase, thereby inhibiting oxidative phosphorylation and cellular respiration. 4 The last experiment involved exploring how protective effects of the compounds vary depending on the compound concentration. These experiments shed light on the role of Cathepsin C and proteases in the controlled process of necrosis. Furthermore, identifying the cellular processes and key enzymes involved in necrotic cell death will not only provide insight into the mechanism of necrosis, but will also direct the development of drugs that prevent necrosis.