Probiotic Lactobacillus johnsonii BS15 Prevents Memory Dysfunction Induced by Chronic High-Fluorine Intake through Modulating Intestinal Environment and Improving Gut Development

Abstract

In recent years, the influence of chronic fluorosis on the brain has been widely reported. Our study aimed to demonstrate the potential mechanism underlying the impairment of memory function by excessive fluorine intake. We also evaluated whether improvement of intestinal microflora could be a potential therapy to prevent the negative influences from the perspective of gut-brain axis. Male ICR mice were randomly divided into three groups and administered with either phosphate buffered saline (PBS) (Control and F groups) or Lactobacillus johnsonii BS15 (FP group; daily amounts of 1 × 10⁹ CFU/mL), a probiotic strain, by oral gavage throughout a 98-day experimental period. Sodium fluoride (100 mg/L) was added to the drinking water of the F and FP groups. Animals were sacrificed for sampling with or without water avoidance stress (WAS) at two phases of the experiment and behavioral tests including T-maze test and passive avoidance test were also performed. Based on the results of behavioral tests, probiotic reversed the fluorine-induced memory dysfunction. In addition, L. johnsonii BS15 also increased the antioxidant capacities (serum and hippocampal tissue) and hippocampal synaptic plasticity-related mRNA expression after excessive fluoride ingestion. Moreover, the increased colonization of L. johnsonii BS15 also protected the small intestines from the damages of growth performance, visceral indexes, intestinal development, digestive, and secretory functions by changing the structure of the microflora and then improving intestinal permeability and integrity. L. johnsonii BS15 also improved the ability of flourosis mice against psychological stress indicated by the changes in behavioral tasks, hippocampal antioxidant levels, and synaptic plasticity-related mRNA expressions. Lactobacillus johnsonii BS15 intake appears as a promising way to ameliorate fluorine-induced memory dysfunction, especially under psychological stress.

Keywords: Fluorosis; Gut-brain axis; Memory impairment; Probiotic; Psychological stress.