A small molecule in the brain may help explain why some cellular systems shift out of balance in autism.

Researchers at the Hebrew University of Jerusalem found that nitric oxide, a common brain signal, can trigger a chain reaction inside neurons when its activity rises too high, ScienceDaily reports. The molecule usually helps cells communicate. In this case, it appears to alter a protective protein and weaken a key cellular brake.

The study, published in Molecular Psychiatry, focused on three parts of that chain: nitric oxide, the TSC2 protein, and the mTOR pathway. mTOR helps regulate cell growth and protein production. When it becomes too active, neurons may struggle to function and communicate as they should.

Scientists found a possible molecular chain reaction linked to autism biology.

The Cellular Brake Starts To Fail

The team found that nitric oxide can chemically modify TSC2 through a process called S-nitrosylation. That change marks TSC2 for removal. With less TSC2 in place, the brake on mTOR weakens.

EurekAlert reports that when researchers lowered nitric oxide signaling in neurons, the TSC2 modification was blocked and mTOR activity moved back toward normal. The team also engineered a version of TSC2 that resisted the nitric oxide-related chemical tag. That change helped preserve TSC2 levels and reduced the downstream effects tied to excessive mTOR activity.

The work adds detail to earlier findings from the same lab. In 2023, Hebrew University researchers reported a direct connection between nitric oxide levels in the brain and autism indicators in mouse models, human stem cells, and clinical blood samples, Hebrew University reported.

A tiny brain signal may push key cellular systems into overdrive.

Earlier Research Pointed To Nitric Oxide

That earlier work showed that autism-like indicators rose as nitric oxide increased in the brain. When researchers lowered nitric oxide in controlled animal models, those indicators decreased, according to The Jerusalem Post.

Advanced Science News reported that the 2023 research also found changes in neuronal proteins, dendritic spine density, anxiety-related behavior, social behavior, and novelty seeking in autism models. The new study narrows the question further. It identifies a specific route by which nitric oxide may disrupt one of the cell’s major control systems.

Autism is diverse, and one pathway will not explain every case.

Human Samples Add Weight To The Findings

The 2026 study also examined samples from children with autism, including children with SHANK3 mutations and children with idiopathic autism. The researchers found reduced TSC2 levels and increased mTOR signaling, a pattern that matched their lab findings.

The research remains early. It does not explain all autism. It does not offer an approved treatment.

That caution matters. Autism has many genetic and environmental influences, and any future drug target would need extensive testing. Still, outside experts have noted that the nitric oxide research is notable because it draws from cells, animal models, and human samples, The Times of Israel reports.

For now, the finding gives scientists a sharper map. A tiny signal may disable a cellular brake. That may help explain why one pathway in autism can spin too fast.