Nitric oxide inhibition ameliorates cortical proteomic changes in the Cntnap2^-/- and Shank3^Δ4–22 mouse models of autism spectrum disorder

Background: Autism spectrum disorder (ASD) is a neurodevelopmental disorder with a strong genetic component, and over a thousand associated genes have been identified, including CNTNAP2 and SHANK3. Our previous work using Cntnap2^-/- and Shank3^Δ4–22 ASD mouse models implicated dysregulated nitric oxide (NO) signaling in ASD-related behaviors, which were improved by inhibition of neuronal nitric oxide synthase (nNOS) with 7-Nitroindazole (7-NI). However, the molecular mechanisms linking NO signaling to ASD pathology remain poorly defined. Methods: We performed mass spectrometry-based global proteomic profiling of cortical tissue from both mouse models under baseline conditions and following 7-NI treatment. Systems biology and bioinformatics analyses were used to identify differentially expressed proteins, enriched pathways, and treatment-responsive networks. Cross-model comparisons were performed to assess molecular convergence and overlap with human ASD-risk genes. Behavioral and biochemical assessments were reanalyzed to evaluate ASD-like phenotypes and treatment effects. Results: Treatment with 7-NI improved ASD-like behavioral deficits in Cntnap2 and Shank3 mutant mice, including increased sociability and reduced anxiety-like behavior. 7-NI was also associated with attenuation of cortical protein alterations across synaptic, neuronal, and metabolic pathways, shifting subsets of dysregulated proteins toward wild-type expression levels. Despite distinct genetic mutations, the two models converged at the protein and pathway levels, including treatment-responsive proteins encoded by high-confidence human ASD risk genes. Limitations: Analyses were restricted to cortical tissue; additional brain regions may reveal complementary mechanisms. Mass spectrometry may underrepresent low-abundance proteins; larger sample sizes could improve statistical power. Potential off-target effects of 7-NI should also be considered. Conclusions: These findings show that nNOS inhibition improves ASD-like behaviors and is associated with partial normalization of altered cortical proteins across two genetically distinct ASD mouse models that display convergent molecular changes, including proteins encoded by high-confidence ASD risk genes.