Iron-induced Oxidative Stress and Anxiety-like Behavior in Wistar Rats Following Systemic Iron Administration

Iron is a trace element essential to many physiological functions in the human body and notably in the brain, where it participates in important metabolic processes. Iron content in the brain is strictly regulated and disruption of these mechanisms can result in iron deficiency or iron excess. Iron accumulation has been hypothesized to be involved in the pathogenesis of various neurodegenerative diseases. In the rat model, repeated systemic iron administration produces iron excess in brain regions involved in spatial cognitive/memory functions. Cognitive deficits are thought to result from iron-induced oxidative stress. It has been also suggested that disruption of iron homeostasis modulates anxiety-like behaviors in humans and animals, but the underlying mechanisms remain unclear. We thus examined the effect of a 15-day 30 mg/kg/day iron administration on anxiety-like behavior using four novelty-based behavioral models of anxiety, i.e. the light/dark room test, unfamiliar environment test, elevated plus-maze, and open-field test. We measured iron accumulation and several biomarkers of oxidative stress (antioxidant enzymes: catalase CAT, superoxide dismutase SOD, and a product of lipid peroxidation: malondialdehyde MDA) in four regions of interest (ROIs) including the hippocampus, prefrontal cortex, striatum and cerebellum. Compared to controls, iron-treated rats exhibited higher anxiety-like behaviors, had increased iron content, and altered biomarkers of oxidative stress (higher MDA and lower CAT and SOD) in the ROIs, in particular, the medial prefrontal cortex and hippocampus, which are known to be involved in the anxiety/fear circuit. These results contribute to establish the link between iron systemic administration, iron excess in the brain, oxidative stress, and anxiety-like behavior, which is a common comorbidity of neurodegenerative disorders.