Researchers at the Icahn School of Medicine at Mount Sinai have identified a molecular mechanism that restricts the ability of injured neurons to regrow damaged axons, according to findings published in the journal Nature. The discovery suggests that blocking the aryl hydrocarbon receptor (AHR) could promote nerve regeneration and improve functional recovery following damage to peripheral nerves or the spinal cord.
A Molecular Brake on Nerve Regeneration
Axons act as long fibers that transmit vital signals between nerve cells across the central and peripheral nervous systems. When these extensions are severed or crushed, recovery depends entirely on whether the neuron can rebuild its physical connections. In adult mammals, however, that regenerative capacity remains severely limited. According to the Mount Sinai team, injuries to peripheral nerves or the spinal cord frequently result in long-lasting or permanent losses of movement and sensation because neurons struggle to rebuild.
The study points to AHR as the important regulator controlling this limitation. “When neurons are injured, they must deal with stress while also trying to regrow their axons,” said Hongyan Zou, MD, PhD, Professor of Neurosurgery and Neuroscience at the Icahn School of Medicine at Mount Sinai and the study’s senior author. “We discovered that AHR functions like a brake that shifts neurons toward managing stress rather than rebuilding damaged connections.” Active AHR signaling suppresses axon growth, but when researchers removed AHR or blocked it with drugs, damaged fibers regenerated more successfully. Mouse models involving peripheral nerve damage and spinal cord injury showed clear improvements in movement and sensory recovery after AHR suppression.
The Tradeoff Between Cellular Survival and Repair
Additional experiments conducted by the team explained the exact mechanics behind this cellular brake. Following an injury, AHR supports a protective response that helps neurons maintain protein quality control, a biological process known as proteostasis. While this internal system protects injured cells from immediate cellular stress, it simultaneously restricts the production of new proteins required to rebuild axons.
Without active AHR, neurons switch priorities. They ramp up protein production and activate biological pathways linked directly to growth and axon regeneration. This regenerative shift relies on an additional factor called HIF-1α, which regulates genes involved in metabolism and tissue repair. “This discovery shows that neurons use AHR to balance survival and regeneration,” Dr. Zou explained. By releasing the AHR brake, researchers can push neurons into a state that favors repair.
An Unexpected Role for a Toxin Sensor
AHR was initially discovered for its ability to detect environmental toxins and pollutants, known as xenobiotics. The new findings demonstrate that the protein’s biological role reaches far beyond environmental sensing. Inside neurons, AHR connects external environmental responses directly to the internal cellular machinery that determines whether damaged axons can successfully regenerate.
Did you know? Several drugs designed to inhibit AHR are already undergoing clinical trials for other conditions, raising the possibility that researchers could investigate similar compounds as treatments for spinal cord and peripheral nerve injuries in the future, according to the study authors.
Moving Toward Clinical Applications
While the discovery opens new therapeutic avenues, the research remains at an early stage. Additional studies are required before AHR-targeting strategies can be evaluated in human patients. Future work will test how effectively AHR inhibitors perform across different forms of neural injury, determine precise treatment timing and dosages, and examine how suppressing the protein impacts other surrounding cells involved in the injury response.
The Mount Sinai research team also plans to investigate AHR-blocking drugs and gene-therapy methods designed to reduce AHR activity specifically within neurons. These upcoming strategies aim to determine whether targeted interventions can further enhance axon recovery following spinal cord injuries, strokes, and other neurological diseases.
Frequently Asked Questions
What is an axon?
Axons are long extensions of nerve cells that transmit communication signals throughout the central and peripheral nervous systems.
What does the aryl hydrocarbon receptor (AHR) do in injured neurons?
According to researchers at Mount Sinai, AHR acts as a molecular brake that prioritizes cellular stress management and protein quality control over axonal regrowth.
Are treatments utilizing AHR inhibitors available now?
No. While drugs that inhibit AHR are currently in clinical trials for other medical conditions, using them to treat nerve and spinal cord injuries remains in the early research phase.
Stay Informed on Breakthrough Research
Explore our latest coverage on neuroscience, emerging medical treatments, and clinical trials by subscribing to our updates.
Worth a look