The researchers found that a protein known as the aryl hydrocarbon receptor, or AHR, acts like a molecular “brake” that limits the ability of injured nerve cells to regrow damaged axons.

The findings, published in the journal Nature, suggest that blocking AHR could help damaged nerves regenerate and improve movement and sensation following nerve or spinal cord injuries.

Axons are long extensions of nerve cells that carry signals between different parts of the nervous system.

When these structures are damaged or severed, the ability of neurons to rebuild them plays an important role in determining how much a person can recover.

However, adult mammals have a limited ability to regenerate damaged axons.

This is one of the reasons injuries to nerves and the spinal cord can result in long-lasting or permanent problems with movement and sensation.

The new study found that AHR plays an important role in this process.

According to the researchers, when neurons are injured, they must balance two competing needs.

They need to protect themselves from cellular stress while also producing the proteins necessary to rebuild their damaged connections.

The researchers discovered that AHR pushes neurons toward managing stress rather than rebuilding their axons.

When scientists removed AHR from neurons or used drugs to block its activity, damaged nerve fibers were able to regenerate more effectively.

Experiments in mice with peripheral nerve injuries and spinal cord injuries also showed that suppressing AHR was associated with improved movement and sensation.

The researchers found that AHR normally supports a protective process known as proteostasis, which helps cells maintain protein quality during stress.

While this response helps injured neurons survive, it can also reduce the production of new proteins needed for axon growth.

When AHR was blocked, neurons appeared to change their priorities. They increased the production of proteins and activated biological pathways linked to growth and nerve regeneration.

The researchers also identified HIF-1α as an important factor in this process. HIF-1α helps regulate genes involved in metabolism and tissue repair.

Hongyan Zou, a professor of neurosurgery and neuroscience at Mount Sinai and the study's senior author, said the findings show how neurons balance survival and regeneration following injury.

AHR was initially known for its role in detecting environmental toxins and pollutants.

The new findings suggest that the protein has a broader role inside neurons, where it helps connect environmental signals with cellular processes that determine whether damaged axons can regenerate.

The discovery could eventually contribute to new treatments for nerve injuries.

Some drugs designed to inhibit AHR are already being investigated in clinical trials for other medical conditions, raising the possibility that similar approaches could eventually be studied for nerve and spinal cord injuries.

However, the researchers stressed that the work is still at an early stage.

More studies are needed to determine the appropriate timing and dosage of AHR inhibitors and to understand how blocking the protein affects other cells involved in the body's response to injury.

The Mount Sinai team plans to investigate AHR-blocking drugs and gene therapy approaches that could reduce AHR activity specifically in neurons.

Researchers hope these approaches could eventually help improve recovery from spinal cord injuries, stroke and other neurological conditions.