This team of biologists from the Massachusetts Institute of Technology (MIT) offers us a real remote control of the hormones sometimes responsible for mental health disorders, such as adrenaline and cortisol. remotely control the release of these hormones from the adrenal gland, using magnetic nanoparticles. The approach presented in the journal Science Advances will help to learn more about how the release of hormones affects mental health and to open up new ways to treat these hormone-related disorders.

It is known that abnormal levels of stress hormones like adrenaline and cortisol are linked to a variety of mental disorders including depression and post-traumatic stress disorder (PTSD). The MIT researchers therefore looked at the possibility of treating these disorders by modulating the function of peripheral organs, rather than intervening more invasively in the central nervous system.

The team has developed magnetic nanoparticles (see white squares in the visual) which can be injected into the adrenal gland and which, when exposed to a weak magnetic field, heat slightly, activating heat-sensitive channels which trigger the release of hormones. In essence, the technique can stimulate an organ “deep” in the body but minimally invasive.

Magnetothermal stimulation to modulate the function of the adrenal cells
The laboratory of lead author Polina Anikeeva, an MIT professor of materials science and engineering, has already designed several new magnetic nanomaterials, including particles that can release drugs at specific times in specific sites in the body. Here, his team wanted to explore the idea of ​​treating brain disorders by manipulating organs which are outside the central nervous system but which influence it by the release of hormones. This is the case, in particular of the hypothalamic-pituitary-adrenal (HHS) axis, which regulates the stress response in mammals. Hormones secreted by the adrenal gland, including cortisol and adrenaline, play an important role in depression, stress, and anxiety.

Treating certain neurological disorders “on the periphery”, by modulating local pathways rather than the global circuits of the central nervous system, this is the principle of this research: in order to be able to modulate the release of hormones, the researchers targeted ion channels that control the flow of calcium into the adrenal cells. These ion channels can be activated by a variety of stimuli, including heat. When calcium flows through open channels into the adrenal cells, the cells begin to pump hormones. It is therefore a question of modulating the influx of calcium into the adrenal cells.

To stimulate these heat-sensitive channels, which occur naturally in the adrenal cells, the researchers designed nanoparticles in magnetite, a type of iron oxide which forms tiny magnetic crystals of 1 / 5,000 of the thickness of a hair human. Scientists show in rats that when injected directly into the adrenal glands, these particles stay there for at least 6 months. When the rats are exposed to a weak magnetic field, the particles heat up by around 6 ° C, which is enough to trigger the opening of the calcium channels without damaging the surrounding tissues. The targeted heat channel here, known as TRPV1, is present in many sensory neurons throughout the body, including pain receptors. TRPV1 stimulation triggers a hormonal surge which doubles cortisol levels and increases norepinephrine levels by 25%. These two effects lead to a measurable increase in the animals’ heart rate.

Use the technique against stress and pain: this hormone release technique could treat PTSD and other disorders in a much less invasive way than brain implants, for example, which electrically stimulate the release of hormones. The technique could find another application in the treatment of pain, because in the pain receptors there are also heat-sensitive ion channels.