Again, the microflora is to blame

Intestinal bacteria were blamed for the development of multiple sclerosis

Daria Spasskaya, N+1

Two articles in the journal Proceedings of the National Academy of Sciences linked the initiation of multiple sclerosis with the gut microbiota. Scientists from the University of California in the USA and the Max Planck Institute in Germany not only associated a certain group of bacteria with the likelihood of developing the disease, but also showed how bacteria inhabiting the human intestine modulate T-cell immunity and trigger the process of inflammation. Briefly about these works tells Science.

Multiple sclerosis is an immune–mediated disease of the central nervous system in which T-lymphocytes attack the myelin sheaths of nerves. As a result, nerve fibers lose the ability to conduct an impulse, and the "information flows" between the brain and the periphery are interrupted. The destruction of white matter is also observed in the brain. On MRI images, the lesions (sclera) look like "plaques" or "holes" – they are one of the characteristic signs of multiple sclerosis. Another essential sign of the disease is inflammation, which is a consequence of the activation of T-lymphocytes.

What is the cause of the development of multiple sclerosis, it was still unclear. It is known that, although the disease is not considered hereditary, there is a genetic predisposition to it. The probability that both will get sick in a pair of twins is much higher in monozygotic (identical) twins than in fraternal twins. It is believed that most often sclerosis occurs in genetically predisposed people in the presence of certain external factors that cause the start of the process.

In recent years, the development of the disease has been associated with the influence of microbiota. For example, transgenic mice, which eventually manifest one of the variants of the disease, do not get sick if they are raised in sterile conditions and their intestines are not populated with bacteria.

To test the effect of intestinal microbes on the development of multiple sclerosis, German scientists studied the composition of the microbiota of 34 monozygotic twin pairs. In each pair, one of the twins suffered from multiple sclerosis, and the other was healthy. Microbiota samples were taken from the participants and its species composition was analyzed using sequencing. It turned out that the number of bacteria Akkermansia muciniphila increased in the intestines of the sick participants who did not receive special treatment.

Biota samples from five pairs of twins were planted in sterile mice with a model of spontaneous autoimmune brain inflammation (mouse model of multiple sclerosis). In mice infected with microbes from sick donors, the disease developed much more often than in animals infected with "healthy" microbiota. Scientists have found that the level of the anti-inflammatory signaling molecule interleukin-10 (IL-10) is reduced in diseased mice. The reason for this was discovered by the authors of the second work, published simultaneously with the work of the Germans.

The incidence of autoimmune encephalomyelitis in mice that have been transplanted microbiota from healthy people (HD) or patients with multiple sclerosis (MS). When inhibited by interleukin-10 (anti-IL10) antibodies, mice with a "healthy" microbiota were also more likely to get sick. Kerstin Berer et al / PNAS 2017.

American scientists conducted a similar experiment on a twice as large sample. The authors compared the microbiomes of 71 healthy people and 71 patients with multiple sclerosis, and also observed in patients an excess of bacteria Akkermansia muciniphila, and in addition, Acinetobacter calcoaceticus. Also, the number of bacteria was reduced in patients Parabacteroides distasonis. Scientists treated the precursors of lymphocytes with bacterial extracts and found that under the action of components specific to patients with sclerosis, these cells less often develop into lymphocytes producing IL-10. Instead, extracts from Akkermansia and Acinetobacter stimulated differentiation into pro-inflammatory lymphocytes.

In sum, these studies suggest that the composition of the intestinal microbiota may be an "external factor" stimulating the development of multiple sclerosis. Certain types of microbes are able to modulate the immune response in the body, spurring or suppressing inflammation. Perhaps a targeted change in the species composition of intestinal bacteria (for example, with the help of fecal transplantation) will help reduce the incidence of the disease, which affects two and a half million people in the world.

Despite the fact that there is a therapy that makes life easier for patients, there is no medicine that would completely cure the disease. We wrote about how doctors are trying to treat multiple sclerosis by "rebooting the immune system", and that a new therapy strategy may be the stimulation of myelin-producing cells.

Portal "Eternal youth" http://vechnayamolodost.ru  15.09.2017