rogrammed cell death, or apoptosis, is an important component of various cellular processes. These include embryonic development, hormone-dependent atrophy, normal mature cell turnover, proper development and functioning of the immune system. Apoptosis can also occur as a defense mechanism, such as in immune responses or when cells are damaged by disease or chemical agents. However, many human diseases and conditions can be linked to an increase or decrease in the normal levels of apoptosis. For example, neurodegenerative diseases, ischemic damage, autoimmune disorders and many types of cancer have been attributed to inappropriate levels of apoptosis. Apoptotic cells can be recognized by defined morphological changes such as cellular shrinking, chromatin condensation, and eventually cell fragmentation into small apoptotic bodies.
One of the early events in apoptosis is the translocation of phosphatidylserine (PS) from inside the cell to the outer membrane. This change provides a signal to macrophages favoring phagocytosis over the inflammatory response. The PS translocation in apoptosis can be detected by using labeled annexin V. Annexin V is a 36 kDa human protein that binds specifically, in a calcium-dependent manner, with nanomolar affinity to externalized PS.
Annexin-Vivo™ 750 was developed by conjugating annexin V with a NIR fluorophore. This agent has been developed to enable in vivo visualization and quantification of the membrane-bound phospholipid, PS, exposed in the outer leaflet of the cell membrane lipid bilayer during the early stages of apoptosis. It can provide an effective in vivo imaging tool for the rapid detection of therapeutic efficacy in a variety of pathological conditions (including cancer, stroke, atherosclerosis, myocardial ischemia, and liver toxicity), facilitating the discovery and characterization of novel therapeutics.