Swiss scientists have discovered, in a mouse model of MS, how exposure to low temperatures forces the body to divert its resources from the immune system towards maintaining body heat, which alleviates the symptoms of the disease
Change focus. That is what a group of scientists from the University of Geneva-UNIGE (Switzerland) saying to treat multiple sclerosis. It’s about diverting interest from the immune system, whose malfunction causes this autoimmune disease, with something else. And they propose the cold.
In evolutionary biology, the “life history theory”, first proposed in the 1950s, posits that when the environment is favorable, the resources used by any organism are dedicated to growth and reproduction. On the contrary, in a hostile environment, resources are transferred to so-called maintenance programs, such as energy conservation and defense against external attacks.
What now researchers from the UNIGE is to apply this concept in a specific field of medicine: the erroneous activation of the immune system that causes autoimmune diseases.
By studying mice with a model of multiple sclerosis, the scientists discovered how exposure to low temperatures forced the body to divert its immune system resources toward maintaining body heat.
In fact, during the cold, the immune system decreased its harmful activity, which considerably attenuated the course of the autoimmune disease.
These results open the way to a fundamental biological concept on the allocation of energy resources.
Autoimmune diseases occur when the immune system attacks the body’s own organs. For example, type 1 diabetes, for example, is caused by the mistaken destruction of insulin-producing cells in the pancreas.
Multiple sclerosis is the most common autoimmune disease of the central nervous system (consisting of the brain and spinal cord). The ailment is characterized by the destruction of myelin, which is a protector of nerve cells and is important for the correct and rapid transmission of electrical signals. Therefore, its loss leads to neurological disability, including paralysis.
“The defence mechanisms of our body against the hostile environment are energetically expensive and can be constrained by trade-offs when several of those are activated. The organism may therefore have to prioritise resource allocation into different defence programmes depending on their survival values,” as explained by Mirko Trajkovski, lead author of the study.
His team thought this may be of particular interest to autoimmunity, where the introduction of an additional energy-costly program can elicit a milder immune response and thereby affect disease. In other words, “Could we divert the energy used by the body when the immune system fails?”
To test their hypothesis, the scientists subjected mice suffering from experimental autoimmune encephalomyelitis, a model of human multiple sclerosis, to a relatively cooler environment, around 10 ° C after an acclimatization period of gradually lowering the ambient temperature.
“After a few days, we observed a clear improvement in the clinical severity of the disease as well as in the extent of demyelination observed in the central nervous system,” said Doron Merkler, co-author of the work.
In addition, he highlights, “The animals did not have any difficulty in maintaining their body temperature at a normal level, but, singularly, the symptoms of locomotor impairments dramatically decreased, from not being able to walk on their hind paws to only a slight paralysis of the tail”.
The researchers explain that the immune response is based, among other things, on the ability of so-called antigen-presenting monocytes to instruct T cells on how to recognize foreign elements that need to be fought off.
In autoimmune diseases, however, self-antigens are mistaken for foreign ones.
In this study, points out Mirko Trajkovski, “We show that cold modulates the activity of inflammatory monocytes by decreasing their antigen presenting capacity, which rendered the T cells, a cell type with critical role in autoimmunity, less activated”.
That is, by forcing the body to increase its metabolism to maintain body heat, cold robs the immune system of resources. This causes a decrease in harmful immune cells and thus improves the symptoms of the disease.
“While the concept of prioritising the thermogenic over the immune response is evidently protective against autoimmunity, it is worth noting that cold exposure increases susceptibility to certain infections. Thus, our work could be relevant not only for neuroinflammation, but also other immune-mediated or infectious diseases, which warrants further investigation,” added Trajkovski.
The truth is that an increase in autoimmune diseases has been observed for some time. The improvement in living conditions in Western countries, which has been noted in recent decades, has gone hand in hand with an increase in cases of autoimmune diseases.
“While this increase is undoubtedly multifactorial, the fact that we have an abundance of energy resources at our disposal may play an important but as yet poorly understood role in autoimmune disease development,” concluded Doro Merkler.
The researchers will now continue their research to answer the million-dollar question: Can their discoveries be applied to develop a clinical application for humans?
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