2023-09-30 09:03:03
In today’s episode of “Unsterblich,” biochemist Renée Schroeder explains exactly how cell death works, why it can be altruistic and why it is so important for eternal youth.
Cells have genes to send themselves to death in a controlled manner. A programmed cell death. Planned suicide. This process is called apoptosis.
Necrosis and apoptosis
The ancient Greeks had already noticed that there are two types of death: necrosis, which is death through accident and disease, and apoptosis, which is the controlled cell death when the leaves fall off in autumn or the skin between the toes disappears. Apoptosis is a type of cell suicide and is essential in animal development. In most cases, many more cells are produced than needed and the excess are broken down in a controlled manner. During apoptosis, no inflammatory substances are secreted that damage the neighboring tissue, as is the case with necrosis. So it is a natural and intentional process. Dying as part of the natural development of the organism. And necessary if you want to stay young.
Altruism in bacteria – the suicide module
Bacterial cells already have genetically controlled cell death. When a bacterial colony becomes stressed and threatened, the suicide module switches on. Around 80 to 90% of the cells commit suicide. The other cells can survive because they get resources and they change their metabolism. When the stress is over, a new phase of growth begins. In the meantime, they can wait quietly in a state where they do little.
Poison and antidote in balance
This suicide module is very simple: it consists of two genes, one coding for a poison and the second for an antidote. These are called toxin and antitoxin. As long as everything is in balance, the poison and antidote bind to each other and neutralize each other. The antidote is usually slightly more unstable than the poison, which means that as soon as both substances can no longer be produced, the antidote breaks down faster than the poison. The poison remains and kills the cell.
Is that altruistic?
Altruism is defined as a selfless way of thinking and acting and unselfishness. It is an antithesis to egoism. Whether altruism even exists is questioned by many philosophers. It would have to presuppose a voluntary decision, because if selflessness is forced, it loses its altruistic character. Whether bacteria and individual cells can make “voluntary decisions” remains to be seen. In any case, many bacteria have a system for committing self-death in order for the colony to survive. All bacteria in a colony are almost identical, clones so to speak. In the long term, the advantage is that the colony and therefore the clone survives. And this process places the survival of the colony above the survival of the individual bacterium. From an evolutionary perspective, such behavior makes a lot of sense! It prevails in evolution – with or without intention.
Apoptosis in higher cells
Animal and human cells also have genes for programmed cell death. These are very important for many normal processes in the body. Apoptosis is an essential part of our metabolism and immune system. The average adult loses between 50 and 70 billion cells every day through apoptosis.
The 2002 Nobel Prize in Medicine was awarded to Sydney Brenner, H. Robert Horvitz and John Sulston for their work identifying genes that control apoptosis. The genes were identified through studies on the worm Caenorhabditis elegans. We humans have homologs of these genes that are necessary in the regulation of apoptosis. Since apoptosis cannot be stopped once it has begun, this process requires very precise regulation. Apoptosis can be initiated in two ways. In the intrinsic pathway, the cell kills itself because it senses cell stress, while in the extrinsic pathway, the cell kills itself due to signals from other cells. Both pathways induce cell death by activating caspases, which are enzymes that break down proteins.
Apoptotic processes are always necessary during embryonic development: for example, when fingers are formed, entire cell populations, namely the skin between the fingers, are eliminated through apoptosis. Apoptosis is also responsible for the regression of the uterus following delivery or the rejection of the endometrium during menstruation.
However, if apoptosis is incorrectly regulated, it can be involved in the development of many diseases. Apoptotic cell destruction plays a major undesirable role in osteoporosis, in the destruction of the T cells of the immune system, in neurodegenerative diseases such as Parkinson’s or in rheumatism. But suppressing apoptosis can also lead to diseases such as cancer.
Apoptosis is a ubiquitous process that must be regulated very precisely. It is essential for life, but can also lead to illness and be fatal.
When cells are attacked by viruses, they usually switch on apoptosis, killing themselves so that the virus cannot multiply and infect neighboring cells. But there are viruses, such as the baculovirus, which infect the organism, penetrate the host cell and switch off apoptosis. This is how the evolution of the virus works!
We have already learned that it is necessary for old cells to go into apoptosis. If they don’t, they promote aging and cause a number of age-related diseases.
In order for us to become immortal, cells must be able to die. Controlled death is therefore part of eternal youth.
Title image: Renée Schroeder
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