30 June 2008

At your age, Grandfather, it is harmful to lack of sleep!

Scientists at the University of Pennsylvania have found that in the brain cells of old mice, the mechanism of response of unstructured proteins (unfolded protein response, UPR), which is a reaction to stress caused by lack of sleep, is disrupted.

This discovery suggests that in older people, lack of sleep can aggravate already, as a rule, impaired protective reactions to abnormal folding of protein molecules, the frequency of which increases as the cell ages. The accumulation and aggregation of abnormal proteins in the cell is associated with many diseases, including Alzheimer's and Parkinson's diseases.

The response of unstructured proteins is part of a "quality control system" that monitors protein synthesis in the endoplasmic reticulum. When too many amino acid chains accumulate inside the reticulum or in case of any other failures, the endoplasmic reticulum uses a response mechanism of unstructured proteins that slows down the synthesis process and gives the reticulum the opportunity to get rid of excess amino acid chains. If the mechanism does not work, the process of self–destruction of the cell is triggered - apoptosis.

The authors demonstrated that lack of sleep does not disrupt the response of unstructured proteins in 10-week-old mice, while there is no accumulation of improperly folded protein molecules in the endoplasmic reticulum of cortical cells. At the same time, in old 2-year-old mice with a lack of sleep, the response mechanism of unstructured proteins could not cope with its function, and abnormal proteins clogged the endoplasmic reticulum. In old animals, on which lack of sleep did not have a stressful effect, violations of the response of unstructured proteins preceding the experiment were revealed.

The sleep of mice consists in short periods of passivity during the day and night. On average, a mouse sleeps one hour for every two hours of wakefulness. To create a lack of sleep, scientists constantly watched the animals and gently pushed the mice falling asleep with a brush, returning them to the activity phase.

After 3, 6, 9 and 12 hours of sleep deprivation, some of the animals were killed and the protein composition of their brain cells was analyzed. After 6 hours of insomnia, protein synthesis in the brain cells of young mice was blocked by the auxiliary protein (chaperone protein) BiP/GRP78, which indicated a full response of unstructured proteins. In old mice, on the contrary, the protein BiP/GRP78 was not detected and protein synthesis was observed in the endoplasmic reticulum.

Compared with young animals, older mice also had fewer proteins correcting abnormally folded protein molecules and more proteins causing cell death. Thus, sleep deprivation activates several processes in the aging brain at once, the overall result of which is the accumulation of abnormal proteins.

The authors believe that in the aging brain, the effect they have identified with a high degree of probability aggravates the already error-prone systems of folding and splitting protein molecules. As part of their next work, they plan to test the possibility of slowing down aging and reducing the effects of sleep deficiency by introducing key proteins with protective functions into cells.

Portal "Eternal youth" www.vechnayamolodost.ru based on EurekAlert materials


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