Do you want to live a long life? I know that I do. There are so many movies to watch, so many planets to explore. To live a long, uninterrupted life in a healthy body, we need good tissue, obviously. Don’t have to look long for things that destroy our tissue: infections, wounds, cosmic rays, bad dish soap. But to keep our bodies alive and fresh, the majority of our cells actually kill themselves from within, daily. Most of the time, cell death is not a bad thing; it’s a necessary component of survival.
Like the tapes in Mission:Impossible, cells have self-destruction programs, which they use to clear the way for the future cell generations. Apoptosis is the usual method of tissue self-destruction. It’s also been studied the most. A failure of apoptosis can have a deleterious effect on our bodies. Without enough of it, what’s otherwise normal cell growth can become cancer. Autoimmune disease can develop – think celiac, lupus, type I diabetes. All are unfortunate, tragic outcomes.
There are, however, non-apoptosis means of cell suicide. Scientists are researching these, and their findings can have implications for the treatment of cancer and autoimmune diseases. One alternative method, called necroptosis, resembles the mechanisms of cell death triggered by external events, like wounds. Necroptosis and apoptosis are deeply intertwined. In fact, an enzyme that triggers apoptosis can also trigger necroptosis. Nevertheless, some potent viruses can turn off apoptosis, and necroptosis then acts as a back-up generator, chugging along to destroy its cell despite everything.
Autophagy is the next interesting cell suicide method. Here, a second membrane grows inside the cell’s original membrane, which then withers away. The cell recycles its innards, reincarnating multiple times with the same physical materials. This path to cell death is particularly active in starvation conditions. In a way, this self-destruction acts as self-preservation.
When cells self-destroy, does method matter? Yes. While apoptosis can be anti-inflammatory, necroptosis and other processes are inflammatory. Non-apoptotic cell deaths lack a mechanism that tells surrounding tissue to eat old cell debris, which is a necessary process called phagocytosis. Too little phagocytosis can have unfortunate consequences, pus being a mild example.
Scientists have yet to identify a way to monitor which cell death process is taking place within a live organism at any particular moment. Apoptosis is still crucial, but its alternatives burst with potential benefits for the future of medicine.
Source: Tait SW, Ichim G, Green DR. Die another way–non-apoptotic mechanisms of cell death. J Cell Sci. 2014;127(Pt 10):2135-44.