Sleeping little causes the brain to destroy itself
Many people think that sleeping little has no important consequences, other than that it causes a feeling of fatigue that can be quite bearable for some people. However, lack of sleep causes alterations in the functioning of the brain which are not always easy to detect but which are associated with serious long-term problems.
A recent study that has been carried out at the Polytechnic University of Marche, in Italy, provides relevant information about this fact. According to the authors, sleep little can make a substance called glia "eat" healthy neuronal connections (the so-called "synapses"), affecting neuronal connectivity and increasing the risk of developing neurological disorders such as dementia. The glia is composed of cells of the nervous system called glial cells that normally ensure that everything works as it should, but certain alterations seem to modify their behavior.
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Glial cells: astrocytes and microglia
In order to understand the discoveries made by this research it is necessary to have clear the functions of the glial cells in the nervous system. The study focuses specifically on the role of two of them: astrocytes and microglia.
Glial cells or neuroglia They are specialized in providing support to neurons , which are very effective in neuronal transmission but highly limited in other senses. Different types of glia give neurons a solid structure, accelerate synaptic connections and maintain the balance of the extracellular environment of the nervous system.
Astrocytes are a type of glia that is located in the central nervous system, that is, in the brain and spinal cord. In addition to being part of the blood-brain barrier that nourishes and protects neurons, astroglia eliminates unnecessary synapses to promote the regeneration of damaged tissues.
Microglial cells or microglia are also located in the central nervous system. They are considered part of the immune system for their ability to phagocytose ("eat") waste products and damaged cells, which is very important to protect the body from pathogens, infections and other threats.
The study by Bellesi and collaborators
The research team of the Polytechnic University of Marche, headed by Michele Bellesi, studied the effects of lack of sleep in mice comparing the brains of three sets of experimental subjects using measurement techniques and three-dimensional representation.
The rodents of one of the groups were able to sleep freely. Those in the second had been kept awake for 8 hours when they needed to sleep, while those in the third were deprived of sleep for a period of 5 days. This last group had the objective of simulating the lack of chronic sleep.
The study focused on analyzing the differences in the activity of glial cells depending on the degree of sleep deprivation, particularly that of astrocytes and microglia, which Bellesi's team and other research groups had previously related to brain degeneration.
The researchers found that the intensity of phagocytosis increased with that of sleep deficit . Thus, while the astrocytes were active in 6% of the synapses of the mice that had been able to sleep, they were 7% in the mice with a slight deprivation and in 13.5% in the group of lack of chronic sleep
On the other hand, Bellesi and his collaborators also identified an increase in microglia activity. This may be even more relevant than the phagocytosis carried out by the astrocytes, since the excess in the function of the microglia It is related to the development of neurodegenerative diseases , as we will explain later.
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Background of this investigation
Previously, Bellesi's team had found that the genes that lead astrocytes to initiate the phagocytosis process are expressed more intensely under conditions of sleep deprivation. However, until now they had not been able to demonstrate direct connection between the activity of this glial cell and lack of sleep .
Studies had also been published, both with rodents and with humans, which suggested a causal relationship between sleeping poorly and an increase in nervous system inflammation. The research of the Bellesi team provides the important information that this inflammation is due to an increase in microglia activity.
This type of glia has received much attention from the scientific community because of the role of chronic inflammation in various neurodegenerative diseases, particularly Alzheimer's and Parkinson's. The functions of microglia they become destructive instead of regenerative when the amount of brain damage is excessive.
Implications of the findings
Synthetically, the results of this study suggest that the activity of certain glial cells intensifies under conditions of sleep deprivation. These data connect in turn with the known fact that if astrocytes or microglia act in excess can cause long-term brain damage .
In the case of astrocytes, Bellesi's team found that little sleep can cause phagocytosis of healthy synapses as well as irrelevant connections and waste products. This leads to a worsening of neuronal transmission that would become more marked the more the sleep deficit is maintained.
The excessive activity of the microglia has been related to neurodegenerative diseases such as Alzheimer's dementia. This seems to be due to the fact that the inflammatory responses provoked by this glial cell predispose to the development of major damage if they are maintained for too long.
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Bibliographic references:
- Bellesi, M .; from Vivo, L .; Chini, M .; Gilli, F .; Tononi, G. & Cirelli, C. (2017). Sleep loss promotes astrocytic phagocytosis and microglial activation in cerebral cortex mouse. Journal of Neuroscience, 37 (21): 5263-73.
