What is Apoptosis?

What Does Apoptosis Mean

We explain what apoptosis is, what it does and what its phases are. Also, neuronal apoptosis and differences with necrosis.

Apoptosis is a controlled process of cell death.

What is apoptosis

Apoptosis is the cellular self-destruction mechanism that allows the body to control the development and growth of cells to rule out those with dangerous abnormalities or 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, by withdrawing growth factors, losing some type of suppressive activity or by cutting off its contact with the cells that surround it.
  • Positive induction. By activating 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 a cell suicide, and leaving the immune system to deal with the “remains” of the eliminated cells.

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

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Apoptosis function

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

  • Get rid of abnormal cells that have been born atrophied, have abnormalities or 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 fulfill 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 the tissue must be lost or separated. Thus, for example, the fingers are formed, which are initially united by a membrane: the cells of the latter must be programmed to die and separate each member. It is also what happens to the uterine endometrium during menstruation.

Phases of apoptosis

Apoptosis has two recognizable phases, which are:

  • Decision phase. The apoptosis process begins with the reception by certain cells of a death signal, that is, an instruction to commit suicide. Then she must "decide" if she survives or starts the death processes. For this, mitochondria are fundamental organelles: they generate multiprotein complexes that release intramitochondrial content such as cytochrome C, certain hormones of the caspase family and other triggers of apoptosis.
  • Execution phase. Once the cell has “decided” to die, a process of degradation of 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 , culminating in cellular autolysis, that is, with the cell disintegrating itself, leaving behind molecular residues that the immune system will take over.

Apoptosis and 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 is a case of unscheduled and unwanted cell death , known as tissue death, 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.

Necrosis can occur from various causes : uncontrolled bacterial infections , the 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 extremely cold. These cases often lead to amputation, as the necrosis spreads throughout the body and can cause a general septic reaction (generalized infection).

Neural apoptosis

Cells in 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 these types of cells in the body is much slower and more sporadic than the rest of the ordinary cells of the body.

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, many mental ailments that often 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 malfunction of 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 injuries that contribute to the perpetuation of the problem.

The scientific experimentation currently devoted to studying the great efforts apoptosis, foreseeing the eventual cure of these and other related ailments such as cancer.

Apoptosis and cancer

Various internal or external causes can lead to the appearance of defective cells, generally carriers of damaged DNA. The cell tries to repair the damage caused by the damaged DNA or, if impossible, sentences itself to programmed death . Thus, the body prevents defective cells from reproducing, spreading the genetic failure.

Should the intended mechanisms fail, the same immune system can exert pressure to force the cell to undergo apoptosis. If the process is successful, the proliferation of possible cancer cells, for example, is prevented.

The problem is that many precancerous cells do not respond to internal or external apoptosis signals , thus proceeding to divide uncontrollably and generate tumors, crazed masses of cells reproducing non-stop.

For this reason, many current cancer studies focus on understanding why cancer cells block their natural apoptosis functions. A possible cure would be to intervene externally to reignite the process , without the need for highly destructive and invasive therapies such as radiotherapy or chemotherapy.

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