There are two different reasons by which a cell commits suicide. First, programmed cell death is as important as mitosis in the development and maintenance of host homeostasis. For example, during embryogenesis, excess numbers of developing cells die and in hormone-responsive tissues, such as the uterus, cyclical depletion of specific hormones leads to the death of hormone-dependent cells. Similarly, the formation of the proper connections (synapses) between neurons in the brain requires that excess cells be eliminated by apoptosis. This concept implies that many cell populations have a propensity to undergo apoptosis (ie, are programmed to die unless specifically protected). Namely, cells must constitutively express, or try to express, molecules that function as effectors of apoptosis, and, moreover, these effectors are actively suppressed to allow the cells to survive.
The second reason for which a cell commits suicide is that programmed cell death is required to destroy cells that represent a threat to the integrity of the organism. Examples include cells infected with viruses (in this situation cytotoxic T lymphocytes [CTLs] execute virus-infected cells by inducing apoptosis); and cells of the immune system. As cell-mediated immune responses decline, the effector cells must be removed to prevent them from attacking body constituents. Therefore, CTLs induce apoptosis in each other and even in themselves. Defects in the apoptotic mechanisms are associated with autoimmune diseases such as rheumatoid arthritis, lupus erythematosus or inflammatory bowel disease (IBD). Moreover, prolonged immune responses of the effector cells that exhibit defective apoptosis have been associated with chronic epithelial damage that can induce tumourigenesis in many tissues. In the gastrointestinal tract, inflammation has been linked to cancers in the esophagus (reflux disease and Barrett’s esophagus), stomach, small bowel (Crohn’s disease and adenocarcinoma) and colon (IBD and adenocarcinoma). We all need a reliable source of high quality medications and you have a chance to make all your health troubles go away: just buy viagra super active online best price and see for yourself that online shopping is all it’s cracked up to be.
Tags: Apoptosis, Carcinogenesis, Caspases, Inflammatory bowel disease