Nerve growth factor: what is it and what functions does it have

Nerve growth factor is a neurotrophin whose main function is to ensure the proper functioning of the nervous system through the maintenance and regulation of neuronal processes, especially their growth and survival.

It is found in various parts of the body and has been associated with various functions, some of them frankly surprising. If you want to know more, we invite you to continue reading this article.

• Related article: "Neurotrophins: what are they, functions and what types are there"

What is nerve growth factor?

Nerve growth factor, better known by its acronym as NGF or FCN, is a polypeptide that has been shown to be especially involved in processes such as the growth, development, maintenance, and survival of nerve cells.

This substance was discovered in 1956 by Rita Levi-Montalcini and Stanley Cohen, who observed that this protein is found in the nervous system of children. mammals, especially involved in those cells that are forming the sympathetic nervous system and the neurons involved in the processes sensory.

What functions does this neurotrophin perform?

As can be assumed from its name, nerve growth factor is responsible, above all, for the growth of nerve cells, although it also works to maintain them, make them proliferate and guarantee their survival during the time in which they are to be used. need.

Its function becomes especially important ensuring that the cells responsible for transmitting the impulse from external stimuli, that is, the sensory neurons, and those of the sympathetic system can continue to live.

Here we will take a more in-depth look at some of the functions that nerve growth factor performs.

1. Neuronal proliferation

NGF causes some genes to be expressed, such as the bcl-2 gene, by coupling to the TrkA receptor (read as 'Track'). By doing this, it stimulates the proliferation and survival of the neuron.

The union between NGF and p75 can give rise to two antagonistic processes, since it can both induce the survival of the neuron and its programmed death. This has been seen to vary depending on the area of ​​the nervous system.

• You may be interested: "Types of neurons: characteristics and functions"

2. Proliferation of pancreatic cells

It has been shown that the beta cells of the pancreas can present TrkA and p75 receptors, which have an affinity towards the nerve growth factor.

It has been proven that a decrease in NGF causes these cells of the pancreas to begin to die, which suggests that this factor plays a very important role in their survival.

3. Regulation of the immune system

NGF promotes the regulation of immunological processes, be they acquired innately or during the life of the individual.

NGF is released in high doses by mast cells, which induces the growth of axons in nociceptive cells, responsible for detecting harmful stimuli. This increases the sensation of pain in inflamed areas.

4. Ovulation

NGF is found abundantly in semen, which has led several studies to consider the idea that this induces ovulation in certain species of mammals.

Although it has been seen that this could occur in animals such as llamas, in humans it is not so clear if it can exercise some kind of real function or if it is a phenomenon that once had its biological importance but is now something vestigial.

5. Romantic love

It has been seen that people who have been in a romantic relationship for a period of no more than or less than a year have higher concentrations of nerve growth factor than in subjects who are single or have a partner for a longer time.

NGF can indirectly stimulate the expression of adrenocorticotrophic hormone (ACTH) in the hypothalamic-pituitary-adrenal axis, increasing vasopressin secretion.

In turn, ACTH stimulates the secretion of cortisol, the stress hormone. By increasing cortisol in the blood, emotions such as euphoria can be induced, which coincides with the first symptoms of romantic love.

Research results

In animal models, nerve growth factor has been shown to prevent and reduce damage from degenerative diseases. NGF promotes nerve regeneration in rats. In addition, in inflammatory diseases, NGF is increased, having the function of reducing the symptoms of inflammation.

It has also been seen that it could be involved in the repair of myelin, the substance that is responsible for protecting the interior of the neuron, where the nerve impulse travels. This is why the use of nerve growth factor has been considered as a treatment to treat and prevent multiple sclerosis. The option of using it in psychiatric disorders, such as dementias, depression, schizophrenia, anorexia and bulimia nervosa, autism spectrum disorders and rett syndrome.

1. Alzheimer disease

Problems emitting maintenance signals from the neuron when the NGF is coupled have been linked to Alzheimer's disease.

That is why it has been proposed, as a therapeutic tool, to incorporate tissue cells into the brain of patients genetically modified connective tissue to secrete nerve growth factor, promoting the growth of new fibers neural.

This connective cell treatment has been found useful in rescuing nerve cells that were vulnerable to dying. because of the disease.

In some patients it has been seen that the therapeutic effects of the treatment lasted almost ten years after its application. The nerve cells managed to maintain a healthy size, and signals were activated to promote their survival.

• You may be interested: "Alzheimer's: causes, symptoms, treatment and prevention"

2. Schizophrenia

Stress and anxiety are precipitating factors in many DSM-5 mental disorders, and research suggests that a mood influenced by these two emotions affect NGF levels, in addition to impairing cognitive functions. Given this, it makes sense that cognitive decline can be seen in patients with schizophrenia.

It has been seen that patients with this disorder, once they are under treatment with atypical antipsychotics, their NGF levels are increased, although this effect has not been seen in those who are treated with antipsychotics typical. Patients with atypical antipsychotics show a more significant cognitive improvement compared to those who do not receive such medication.

The fact that the NGF intervenes in reducing the negative symptoms of schizophrenia.

3. Rett syndrome and ASD

In Rett syndrome and autism spectrum disorders (ASD) there are certain differences in terms of levels of nerve growth factor that can be found in various areas of the nervous system of patients.

In patients with Rett, lower levels of NGF have been observed in the spinal fluid compared to autistic patients, who present properly normal levels.

Pharmacological therapies to regulate NGF in people with Rett syndrome have been shown to be effective, especially in areas such as motor control and functioning at the cortical level. In addition, these types of treatments improve social communication.

4. Bipolar disorder

In the Bipolar disorder Altered levels of neurotrophins have been shown to pose problems in brain plasticity. In patients with the disorder it has been seen that have reduced levels of NGF, especially in the manic phase. This leads to an irritable mood, increased energy, and less subjective need for sleep.

Low levels of nerve growth factor can be used as a biomarker to determine the current status of the patient.

Patients with bipolar disorder treated with lithium have higher concentrations of NGF in the prefrontal cortex, limbic system, hippocampus, and amygdala.

Bibliographic references:

• Aloe, L., Rocco, M. L., Balzamino, B. O., & Micera, A. (2015). Nerve Growth Factor: A Focus on Neuroscience and Therapy. Current neuropharmacology, 13 (3), 294–303. doi: 10.2174 / 1570159x13666150403231920
• Freeman R. S., Burch R. L., Crowder R. J., Lomb D. J., Schoell M. C., Straub J. A., Xie L. (2004). "NGF deprivation-induced gene expression: after ten years, where do we stand?". Progress in Brain Research. 146: 111–26. doi: 10.1016 / S0079-6123 (03) 46008-1
• Sanes DH, Thomas AR, Harris WA (2011). "Naturally-occurring neuron death". Development of the Nervous System, Third Edition. Boston: Academic Press. pp. 171–208. ISBN 978-0-12-374539-2
• Pierucci D, Cicconi S, Bonini P, Ferrelli F, Pastore D, Matteucci C, Marselli L, Marchetti P, Ris F, Halban P, Oberholzer J, Federici M, Cozzolino F, Lauro R, Borboni P, Marlier LN (2001). "NGF-withdrawal induces apoptosis in pancreatic beta cells in vitro". Diabetology. 44 (10): 1281–95. doi: 10.1007 / s00125010065
• Ratto MH, Leduc YA, Valderrama XP, van Straaten KE, Delbaere LT, Pierson RA, Adams GP (Sep 2012). "The nerve of ovulation-inducing factor in semen". Proceedings of the National Academy of Sciences of the United States of America. 109 (37): 15042–7. doi: 10.1073 / pnas.1206273109