The good thing about free radicals

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Free radicals have long been associated with tissue damage. A new study shows that they also promote regeneration.

Let us start with the basis: every matter consists of atoms. Atoms have a nucleus that is orbited by electrons, just as a satellites orbit our earth. When atoms lose one of their electrons under certain conditions, they become "free radicals". 

They have a craving for electrons and are desperately trying to become complete again. Thus, they "tear" electrons of adjacent molecules and can damage them.

Metabolic processes also take place in the cells of the body, where free radicals are formed by coupling and decoupling electrons.

Free radicals are not just bad
For a long time scientists regarded these free radicals, also called ROS (reactive oxygen species) as "harmful" because of their electron raid. In the meantime, however, they found that they - with the right balance - also have beneficial effects.

The research group around Dr. Simone Di Giovanni (UCL London) has now discovered in an experimental model of axon regeneration that free radicals are even needed for axonal regeneration.

Why? What do they do?
Now it gets difficult: An injury is always accompanied by inflammation and thus an accumulation of inflammatory cells and a ROS production. The team led by Simone di Giovanni was able to show that macrophages (a specific type of inflammatory cell) release oxidative complexes packed in membranes. These are then absorbed by injured axons. In the axons they are transported back into the cell body and unpacked there. They oxidize PTEN, a gene that inhibits regeneration. The oxidation by means of the ROS inactivates PTEN and thus finally stimulates regenerative outgrowth.

What does that mean? What's next?
Free radicals from inflammatory cells that are transported through the axons back to the nucleus are necessary for the outgrowth of the axon after an injury. With this knowledge, research can look for new therapeutic approaches that may also be important for spinal cord injury.

This exciting study was supported by Wings for Life and just published in the prestigious journal Nature Cell Biology.


Source: “Reactive oxygen species regulate axonal regeneration through the release of exosomal NADPH oxidase 2 complexes into injured axons”. Hervera A, De Virgiliis F, Palmisano I, Zhou L, Tantardini E, Kong G, Hutson T, Danzi MC, Perry RB, Santos CXC, Kapustin AN, Fleck RA, Del Río JA, Carroll T, Lemmon V, Bixby JL, Shah AM, Fainzilber M, Di Giovanni S. Nature Cell Biology, February 2018.