Bromelain Restores Glutamatergic Homeostasis via Regulation of NR2A, GLT-1, EAAC1, and xCT in Arsenic-Induced Cerebral Cortex and Hippocampal Neurotoxicity

<ns3:p>Background Chronic arsenic exposure interferes with hippocampal-dependent cognition through glutamate excitotoxicity, which in turn interferes with the regulation of receptors and transporters. Bromelain, a combination of proteolytic enzymes derived from Ananas comosus, is known to have neuroprotective effects; however, the mechanisms by which it counteracts glutamate-mediated toxicity in the brain are poorly understood. This study investigated the potential of bromelain to normalize glutamatergic homeostasis and cognitive function in arsenic-treated rats by specifically examining the NMDA receptor subunit NR2A and glutamate transporters GLT-1, EAAC1, and xCT. Methods Seventy-two adult male Wistar rats (200-220 g) were randomly divided into nine groups (n=8 each): control, arsenic-only (20 mg/kg/day sodium arsenite, administered via oral gavage for 14 days), bromelain-only (5, 10, or 15 mg/kg/day, oral gavage), arsenic plus bromelain (at the same doses), and arsenic plus donepezil (2 mg/kg/day, intraperitoneal). Arsenic was coadministered with bromelain and donepezil for 14 consecutive days. The Morris water maze test was used to assess the cognitive performance. Glutamate concentration was measured using sandwich Enzyme-Linked Immunosorbent Assay [ELISA] and total RNA was isolated to perform RT-qPCR to evaluate the expression of NR2A, GLT-1, EAAC1, and xCT. Results Exposure to arsenic impaired spatial memory, increased glutamate levels, and downregulated the expression of NR2A and transporter genes. These effects were reversed by co-treatment with bromelain, especially at 10 mg/kg, which re-established gene expression and lowered glutamate levels. Bromelain at 15 mg/kg was more effective than donepezil in improving glutamate clearance and cognitive performance. Conclusions Bromelain provides multi-target neuroprotection in arsenic neurotoxicity, rescuing glutamatergic homeostasis by coordinated upregulation of NMDA receptor NR2A and the transport network (GLT-1, EAAC1, xCT), accompanied by spatial learning and memory improvement. The demonstrated dose-response, dosing-related superiority over 15 mg/kg donepezil, and lack of overt adverse effects support its translational potential as a safe, plant-based adjunct to excitotoxic diseases and toxin-exposed populations.</ns3:p>