Nerve growth factor: what is it and what are its functions?

This neurotrophin appears to be related to some psychiatric disorders and diseases.

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

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

What is nerve growth factor?

Nerve growth factor, better known by its acronym as NGF or NGF, is a polypeptide that has been shown to be particularly involved in processes such as 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 mammals, especially involved in those cells that make up the sympathetic nervous system and neurons involved in sensory processes.

What functions does this neurotrophin perform?

As can be guessed from its name, nerve growth factor is primarily responsible for the growth of nerve cells, although it also works to maintain them, make them proliferate and ensure their survival for as long as they are needed.

Its function becomes especially important by ensuring that the cells responsible for transmitting impulses from external stimuli are able to survive for as long as they are needed.The nerve growth factor, i.e., the sensory neurons, and those of the sympathetic system can continue to live.

We will now take a closer look at some of the functions carried out by nerve growth factor.

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 so, it stimulates neuronal proliferation and survival.

The binding between NGF and p75 can give rise to two antagonistic processesThe binding between NGF and p75 can lead to two antagonistic processes, since it can both induce neuronal survival and programmed neuronal death. This has been shown to vary depending on the area of the nervous system.

2. Pancreatic cell proliferation

It has been shown that pancreatic beta cells can present TrkA and p75 receptors, which have an affinity for nerve growth factor.

It has been shown that a decrease in NGF causes these pancreatic cells to begin to die, suggesting that this factor plays a very important role in their survival.which suggests that this factor plays a very important role in their survival.

3. Regulation of the immune system

NGF promotes the regulation of immune processes, whether acquired innately or during the life of the individual.

NGF is released in high doses by the mast cellswhich induces the growth of axons in nociceptive cells, in charge of 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 it induces ovulation in certain mammalian species.

Although it has been seen that this could occur in animals such as llamas, in humans it is not so clear if it can exert 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 not more or less than one year have higher concentrations of nerve growth factor than those who are single or in a relationship for at least one year. than in subjects who are single or have been in a relationship for a longer period of 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 the stress hormone cortisol. Increased Blood cortisol can induce emotions such as euphoria, 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 a 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 protects the interior of the neuron, where the nerve impulse travels. This is why the use of nerve growth factor has been proposed as a treatment to treat and prevent multiple sclerosis. It has also been considered for use in psychiatric disorders such as dementia, depression, schizophrenia, anorexia and bulimia nervosa, autism spectrum disorders and Rett syndrome.

1. Alzheimer's disease

Problems in delivering neuron maintenance signals when NGF is engaged have been related to Alzheimer's disease.

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

This connective cell treatment has been found to be useful in rescuing nerve cells that were vulnerable to death from the disease. to die from the disease.

In some patients, the therapeutic effects of the treatment have been seen to last for almost ten years after treatment. The nerve cells were able to maintain a healthy size, and signals were activated to promote their survival.

2. Schizophrenia

Stress and anxiety are precipitating factors in many mental disorders listed by the DSM-5, and research suggests that a mood influenced by these two emotions affects NGF levels, as well as impairing cognitive function.. Given this, it makes sense that cognitive impairment may be seen in patients with schizophrenia.

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

The fact that NGF plays a role in the reduction of the the reduction of the negative symptomatology of schizophrenia..

3. Rett Syndrome and ASD

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

In Rett patients, lower levels of NGF have been observed in the spinal fluid compared to autistic patients, who have 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.especially in areas such as motor control and cortical functioning. In addition, such treatments improve social communication.

4. Bipolar disorder

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

Low levels of nerve growth factor can be used as a biomarker for the patient's current state.

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". Diabetologia. 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