Apoptosis (Meaning and Explanation)

We explain what apoptosis is, what function it has and what its phases are. Furthermore, neuronal apoptosis and differences with necrosis.

cell apoptosis — Apoptosis is a controlled process of cell death.

What is apoptosis?

Apoptosis It is the mechanism of cellular self-destruction that allows the body to control the development and growth of cells to discard those that present anomalies or dangerous defects. This process of programmed cell death operates through genetically controlled cellular signals and has an important preventive function in the body.

This process can occur in the body in two ways:

Negative induction. By isolating the cell destined to die, that is, removing growth factors, losing some type of suppressive activity or cutting its contact with the cells that surround it.
Positive induction. Through the activation of proteins or other types of organic compounds that trigger cell death, or even the reception of conflicting signals by the cell marked to die.

In both cases, apoptosis occurs in orderly and methodical terms not chaotic, following strict guidelines of cellular suicide, and leaving the immune system to deal with the “remains” of the eliminated cells.

It is, then, a natural process that It is part of the body's protection and renewal mechanisms. It usually does not represent significant damage to any cellular system, since, if necessary, young cells of the same type as those eliminated are being produced at the same rate.

Apoptosis function

Apoptosis is a vital planning role of the organism, which fulfills the following functions:

Get rid of abnormal cells who were born stunted, who have anomalies or who have been infected with viruses or have suffered damage to their DNA.
Eliminate some old and defective cells and replace them with new cells that perform the same function, keeping the body healthy. This is particularly important in the case of the body's defense cells, which can develop a tendency to attack healthy tissues by mistake.
Proceed to the formation of the organism during key stages of its development, such as various embryonic stages in which tissue must be lost or separated. Thus, for example, fingers are formed, which are initially joined by a membrane: the cells of the latter must be programmed to die and separate each limb. This is also what happens to the uterine endometrium during menstruation.

Phases of apoptosis

Apoptosis has two recognizable phases, which are:

Decision phase The process of apoptosis begins with the reception by specific cells of a death signal, that is, an instruction to commit suicide. Then she must “decide” whether to survive or initiate the death processes. For this, mitochondria are essential organelles: they generate multiprotein complexes that release intramitochondrial content such as cytochrome C, certain hormones of the caspase family and other factors that trigger apoptosis.
Execution phase Once the cell has “decided” to die, a process of degradation of the chromatin proteins begins inside it, setting in motion everything secreted in the previous phase by the mitochondria. This involves a series of ordered biochemical reactions, which culminate in cellular autolysis, that is, with the cell disintegrating itself, and leaving behind molecular residues that the immune system will take care of.

Apoptosis and necrosis

cell apoptosis tissue necrosis — Necrosis is a chaotic process that does not affect individual cells but entire tissues.

Apoptosis and necrosis should not be confused. The first is a natural, healthy and orderly process. On the contrary, necrosis It is a case of unscheduled and unwanted cell death known as tissue death, and which puts the integrity of the organism at risk.

The fundamental difference is that necrosis is a chaotic, accidental and irreversible process in which the cells of some tissue begin to die en masse.

The necrosis can occur for various reasons: uncontrolled bacterial infections, interruption of blood flow to certain tissues (vascular accidents) or the action of toxins such as poisons, lethal substances or high-level ionizing radiation.

It is also common when a person's extremities have been exposed to too intense cold. These cases often lead to amputation, as the necrosis spreads throughout the body and can cause a general septic reaction (generalized infection).

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Neuronal apoptosis

Cells of the nervous system and brain, called neurons, also go through the natural process of apoptosis in which old neurons are supplanted by young ones. However, the generation of this type of cells in the body is much slower and sporadic than the rest of the ordinary cells of the organism.

Consequently, over time, our nervous system deteriorates causing loss of brain efficiency, delayed nervous reaction or even loss of certain functions, as becomes very evident in advanced old age. In fact, numerous mental ailments that usually afflict people in old age, such as senile dementia, depend on this process.

There are other pathologies, such as epilepsy or Alzheimer's disease, in which this process is combined with a defective functioning of the glial cells, responsible for absorbing and discarding the remains of dead neurons, preventing them from causing problems.

Thus, in these diseases, waste accumulates and interferes with the regular functioning of the brain, causing the loss of brain mass or leaving scars and lesions that contribute to the perpetuation of the problem.

Scientific experimentation currently dedicates great efforts to the study of apoptosis, anticipating the eventual cure of these and other related ailments, such as cancer.

Apoptosis and cancer

Various internal or external causes can cause the appearance of defective cells, generally carrying damaged DNA. The cell attempts to repair the damage caused by the damaged DNA or, if this is impossible, it sentences itself to programmed death. Thus, the body prevents defective cells from reproducing, spreading the genetic defect.