Arsenic exposure induced anxiety-like behaviors in male mice via influencing the GABAergic Signaling in the prefrontal cortex

Abstract

Arsenic contamination in drinking water causes a global public health problem. Emerging evidence suggests that arsenic may act as an environmental risk factor for anxiety disorders. However, the exact mechanism underlying the adverse effects has not been fully elucidated. This study aimed to evaluate the anxiety-like behaviors of mice exposed to arsenic trioxide (As₂O₃), to observe the neuropathological changes, and to explore the link between the GABAergic system and behavioral manifestations. For this purpose, male C57BL/6 mice were exposed to various doses of As₂O₃ (0, 0.15, 1.5, and 15 mg/L) through drinking water for 12 weeks. Anxiety-like behaviors were assessed using the open field test (OFT), light/dark choice test, and elevated zero maze (EZM). Neuronal injuries in the cerebral cortex and hippocampus were assessed by light microscopy with H&E and Nissl staining. Ultrastructural alteration in the cerebral cortex was assessed by transmission electron microscope (TEM). The expression levels of GABAergic system-related molecules (i.e., glutamate decarboxylase, GABA transporter, and GABA_B receptor subunits) in the prefrontal cortex (PFC) were determined by qRT-PCR and western blotting. Arsenic exposure showed a striking anxiogenic effect on mice, especially in the group exposed to 15 mg/L As₂O₃. Light microscopy showed neuron necrosis and reduced cell counts. TEM revealed marked ultrastructural changes, including the vacuolated mitochondria, disrupted Nissl bodies, an indentation in the nucleus membrane, and delamination of myelin sheath in the cortex. In addition, As₂O₃ influenced the GABAergic system in the PFC by decreasing the expression of the glutamate decarboxylase 1 (GAD1) and the GABA_B2 receptor subunit, but not the GABA_B1 receptor subunit. To sum up, sub-chronic exposure to As₂O₃ is associated with increased anxiety-like behaviors, which may be mediated by altered GABAergic signaling in the PFC. These findings shed light on the mechanisms responsible for the neurotoxic effects of arsenic and therefore more cautions should be taken.

Keywords: Anxiety-like behaviors; Arsenic; Brain nuclei; GABAergic signaling.