Dual targeting of iNOS and Src tyrosine kinase as a superior therapeutic strategy against soman-induced long-term neurotoxicity: multimodal biomarker, imaging, and neurobehavioral outcome analyses

Acute exposure to the organophosphate nerve agent (OPNA) soman (GD) triggers severe and persistent brain injury characterized by seizures, oxidative stress, and structural and functional network alterations, collectively described as the brain’s “SOS” response, despite timely administration of standard medical countermeasures that prevent lethality but fail to halt chronic neuropathology. In this study, we tested whether adjunct therapy with two mechanistically distinct agents, 1400W, a selective inducible nitric oxide synthase inhibitor, and saracatinib (SAR), a Src family kinase inhibitor, administered alone or in combination at reduced doses, could disrupt the progression of this pathological cascade. Mixed-sex adult Sprague Dawley rats were exposed to soman (132 μg/kg, s.c.) followed by atropine and HI-6 within one minute and midazolam one hour later, after which animals received vehicle, 1400W, SAR, or combination therapy. Behavioral outcomes were assessed at 5–6 weeks, structural and functional MRI at 8–9 weeks, and spontaneous recurrent seizures were quantified by EEG from 10–18 weeks post-exposure. Soman exposure resulted in widespread disruptions of resting-state functional connectivity (rsFC, as measured by functional MRI) across amygdalar, cortical, hippocampal, and thalamic networks, which correlated negatively with oxidative stress markers. Treatment with 1400W alone or in combination with SAR robustly restored rsFC across regions, while SAR alone selectively improved hippocampal connectivity, with combination therapy providing the greatest preservation of both functional and structural MRI measures. Restored connectivity correlated with improved behavioral performance and reduced oxidative stress, whereas increased cortical connectivity predicted higher seizure burden, consistent with maladaptive network reorganization. Neuroinflammatory and neurodegenerative markers also correlated with alterations in rsFC. Effect size–driven, cross-domain analyses support a combinatorial therapeutic strategy and highlight systems-level MRI as a translational biomarker for evaluating interventions against OPNA-induced neurotoxicity.