Molecular switch in neurons found to limit the regrowth of damaged axonal fibers

Researchers from the Icahn School of Medicine at Mount Sinai have discovered a molecular switch in neurons that limits the regrowth of damaged axonal fibers. The findings, published in the journal Nature [https://doi.org/ 10.1038/s41586-026-10295-z], show that blocking a protein called the aryl hydrocarbon receptor (AHR) may help neural regeneration and restore function after injuries to the peripheral nerves or spinal cord.

Axons are the long fibers that carry signals between nerve cells, or neurons, in both central and peripheral nervous systems. Axons are essential for communication in the nervous system. When they are cut or damaged, recovery depends on the neuron's ability to regrow these fibers.

But neurons in adult mammals have a limited ability to regrow their axonal connections so

injuries to the nerves or spinal cord often lead to long-lasting or permanent loss of movement or sensation. Scientists have long been trying to understand why this repair process is so restricted.

In the new study, investigators found that AHR acts as a key regulator that determines how neurons respond after injury.

When neurons are injured, they must deal with stress while also trying to regrow their axons. We discovered that AHR functions like a brake that shifts neurons toward managing stress rather than rebuilding damaged connections."

Hongyan Zou, MD, PhD, Professor of Neurosurgery, and Neuroscience, at the Icahn School of Medicine at Mount Sinai and study's senior author

The research team showed that when AHR signaling is active, it slows down axon growth. But when the researchers removed AHR from neurons or blocked it with drugs, axonal fibers regrew more effectively. In mouse models of peripheral nerve injury and spinal cord injury, inhibiting AHR also improved recovery of motor and sensory function.

Further experiments revealed how this process works. After injury, AHR helps neurons protect themselves by maintaining protein quality control-a process known as proteostasis. While this protective response helps neurons cope with stress, it also reduces the production of new proteins needed for growth.

When AHR is turned off, neurons shift their strategy. They begin producing more new proteins and activate growth-related pathways that support axon regeneration. The researchers also found that this growth response depends on another factor called HIF-1α, which helps regulate genes involved in metabolism and tissue repair.

"This discovery shows that neurons use AHR to balance survival and regeneration," Dr. Zou explained. "By releasing this brake, we can push neurons into a state that favors repair."

AHR was originally identified as a sensor that detects environmental toxins and pollutants, termed xenobiotics. The new findings suggest that AHR also plays an unexpected role inside neurons by integrating environmental sensing and regenerative capability to regrow axons after injury.

The study is an early step toward possible treatments. Several drugs that block AHR are already being tested in clinical trials for other diseases, raising the possibility that they could eventually be studied for nerve or spinal cord injuries.

More research is needed before this approach can be used in patients. Future studies will examine how effective AHR inhibitors are in different types of neural damage, determine the best timing and dosage for treatment, and assess the impact on other cells after injury.

The Mount Sinai research team plans to test AHR-blocking drugs and gene-therapy strategies designed to reduce AHR activity in neurons. The goal of this next stage of research is to determine whether these approaches can further boost axon regrowth and improve recovery after spinal cord injury, stroke, or other neurological diseases.