Stress found to send harmful enzymes to the brain

Levels of the enzyme MMP8 increased in the blood of stressed mice Keystone / Leandre Duggan

In the event of stress, immune cells channel harmful enzymes into the brain, where it influences certain neurons, according to a Zurich study. In mice, this leads to changes in behaviour: they withdraw into themselves and avoid social contact.

This newly discovered link between body and mind in stress-related mental illness could lead to new treatments for depression, according to a press release from the University of Zurich (UZH).

In the study, published on Wednesday in the specialist journal Nature, the UZH-led research team showed that levels of the enzyme MMP8 increased in the blood of stressed mice.

“We observed the same change in patients suffering from depression,” said Flurin Cathomas, first author of the study, according to the UZH press release. In his view, this shows that the results are also relevant to humans.

+ Is Switzerland becoming the ‘burn-out nation’?

In mice, the researchers also found that in the event of stress, more monocytes migrated to the brain – in particular to the region of the reward centre. Monocytes belong to the group of white blood cells and are part of the innate immune system. They produce the enzyme MMP8.

The mice concerned behaved in the same way as depressed people. The scientists demonstrated in their study that the enzyme was indeed responsible for the change in behaviour by suppressing the MMP8 gene in certain mice. These mice did not change their behaviour despite the stress.

+ More animal experiments with severe pain suffering

As part of their studies on humans, the researchers now want to gain more knowledge about the interaction between the brain, the immune system and the psyche. But many more studies are still needed before these results can be applied in clinical practice, the UZH concluded.

How we work

This news story has been written and carefully fact-checked by an external editorial team. At SWI swissinfo.ch we select the most relevant news for an international audience and use automatic translation tools such as DeepL to translate it into English. Providing you with automatically translated news gives us the time to write more in-depth articles. You can find them here. 

If you want to know more about how we work, have a look here, and if you have feedback on this news story please write to [e-mail].