The brain relies on countless chemical messages to keep its networks running smoothly. You can imagine this system similar to traffic lights guiding cars through a busy city. The new study focused on nitric oxide, a common chemical messenger in the brain. Researchers have found that in some cases of autism, elevated levels of this molecule may no longer act as a beneficial signal, but instead act more like a “button turned off” state.
When nitric oxide triggers this chain of events, an important protective protein called TSC2 begins to disappear. TSC2 normally helps regulate a major cellular control system known as mTOR, which manages processes such as cell proliferation and protein production. Without this safety net, mTOR activity could surge beyond normal levels. The encouraging finding is that when scientists blocked this particular step in the chain reaction, cellular activity returned to a healthier balance. The results give researchers a clearer idea of ​​where to focus when studying the biology of autism and possible future treatments.
Communication between nitric oxide and the brain
Nitric oxide is normally the brain’s silent helper. These small molecules move easily between cells, helping to fine-tune communication and keeping neural circuits responsive. But new research from the Hebrew University of Jerusalem suggests that in certain cases of autism spectrum disorder (ASD), nitric oxide can trigger biochemical sequences that push critical cellular systems into hyperactivity.
The study was led by Professor Haitham Amal, Satel Family Professor of Neuroscience, and PhD student Shashank Ojha was the first author. This study molecular psychiatryone of the leading journals in psychiatry and part of the Nature Publishing Group. The researchers investigated how three key components interact in brain cells: nitric oxide, the protective protein TSC2, and the mTOR pathway, which plays a central role in controlling cell growth and protein production.
Scientists have long suspected that aberrant mTOR signaling is involved in ASD. What is not clear are the biological pathways linking risk factors and these changes in the brain.
How nitric oxide changes the TSC2 protein
To investigate this mechanism, the research team focused on a biochemical process known as S-nitrosylation. This process occurs when nitric oxide binds to proteins and changes their behavior.
Using systems-level analysis of proteins, the researchers found that many proteins connected to the mTOR pathway were affected by this modification. This observation led them to take a closer look at TSC2. Under normal conditions, TSC2 acts as a brake to keep mTOR activity under control.
Their experiments showed that nitric oxide can modify TSC2 and mark it for removal from cells. Decreasing TSC2 levels weakens its braking effect and increases mTOR signaling. Because mTOR regulates protein production and other important cellular activities, excessive activation can interfere with neuronal function and communication.
interrupt a molecular chain reaction
The researchers then investigated whether this pathway could be disrupted. They used a pharmacological method to reduce the production of nitric oxide in neurons.
When nitric oxide signaling was reduced, TSC2 modification no longer occurred. As a result, mTOR activity returned to normal levels. The researchers also observed changes in protein translation and improvements in measures related to autism-related cellular effects in their experimental system.
As a complementary strategy, the scientists designed a modified version of the TSC2 protein that resists nitric oxide-related modifications. Blocking that single chemical tag maintained normal TSC2 levels and attenuated downstream changes associated with excessive mTOR signaling. These results support the idea that this particular modification may play an important role in driving the pathway.
Evidence from children with autism
This study also included clinical samples from children diagnosed with ASD. These samples were taken from children with SHANK3 mutations and children with idiopathic ASD (cases with no known single genetic cause). Participants were recruited by Dr. Adi Alan.
The researchers identified patterns in these samples that were consistent with laboratory findings. In particular, we observed decreased TSC2 levels and increased activity of the mTOR signaling pathway. These observations add real-world relevance to the molecular mechanisms identified in the study.
“Autism is not one condition with one cause, and we do not expect one pathway to explain all cases,” said Professor Haitham Amal. “However, by identifying a clearer sequence of events for how nitric oxide-related changes affect TSC2 and, by extension, key regulators like mTOR, we hope to provide a more precise map for future research and, ultimately, more targeted treatment ideas.”
New directions in autism research
This finding highlights the potential importance of developing nitric oxide inhibitors as possible tools for ASD research and treatment. By identifying a specific nitric oxide-TSC2-mTOR relationship, this study provides a new framework for understanding how cellular signaling becomes imbalanced in autism.
A clearer picture of this biological pathway could also help scientists identify new targets for therapy and guide future research aimed at restoring normal signaling in the brain.
About Autism Spectrum Disorder (ASD)
ASD is a neurodevelopmental condition associated with differences in social communication and behavior. The condition varies widely from person to person, and many genetic and biological factors can influence risk and outcome.
Researchers are increasingly studying cellular pathways such as mTOR because they play a critical role in how brain cells grow, adapt, and form connections. Understanding these pathways may open new possibilities for future treatments.
