Neuroprotective effects of plasma-activated N-acetylcysteine against streptozotocin-induced behavioral deficits in rats: Attenuation of oxidative stress and cholinergic dysfunction

N-Acetylcysteine (NAC), a thiol-containing antioxidant, has demonstrated neuroprotective potential in various neurological disorders. Recently, cold atmospheric plasma (CAP) technology has emerged as a promising approach for modifying the physicochemical properties of biomolecules. This study investigated the neuroprotective effects of plasma-activated N-acetylcysteine (PAN) in a rat model of intracerebroventricular streptozotocin (icv-STZ)-induced cognitive impairment, with particular emphasis on redox homeostasis and cholinergic function. The physicochemical properties of PAN were characterized using FTIR, LC-MS/MS, and DPPH assay. Male rats received a single icv-STZ injection (3 mg/kg) on day 0, followed by oral administration of NAC or PAN (50 mg/kg) every other day for three weeks. Cognitive performance and anxiety-like behaviors were assessed using the shuttle box, novel object recognition, and elevated plus maze tests. Subsequently, oxidative stress indices (TAC, GSH, SOD, CAT, MDA, NO), cholinergic markers (AChE activity, ACh levels), and the expression of AChE, α7 nAChR, Nrf2, Keap1 and BDNF genes were quantified in the hippocampus and cerebral cortex. FTIR and LC-MS/MS analyses revealed plasma-induced chemical modifications in NAC, resulting in the generation of novel compounds. The DPPH assay further demonstrated superior radical scavenging activity of PAN compared with NAC. Behaviorally, PAN administration significantly alleviated STZ-induced cognitive deficits and anxiety-like behaviors. Biochemically, PAN normalized TAC, GSH, MDA, NO, and ACh levels, increased CAT and SOD activities, and reduced AChE activity. At the transcriptional level, PAN upregulated α7 nAChR, Nrf2 and BDNF expression while downregulating AChE and Keap1. Collectively, these findings suggest that PAN mitigates behavioral impairments in the icv-STZ rat model of Alzheimer's disease, potentially through attenuation of oxidative stress and restoration of cholinergic neurotransmission.