Protective effects of oral administration of lactic acid bacteria strains against methylmercury-induced intestinal toxicity in a murine model

The utilization of lactic acid bacteria has been proposed to mitigate the burden of heavy metal exposure through processes probably involving chelation and reduced metal bioaccessibility. We evaluated the effects of daily intake of two strains of lactobacilli (Lactobacillus intestinalis LE1 or Lactobacillus johnsonii LE2) on intestinal toxicity during methylmercury (MeHg) exposure through drinking water (5 mg/L) for two months in mice. MeHg exposure resulted in inflammation and oxidative stress at the colon, as well as an increase in intestinal permeability accompanied by decreased fecal short -chain fatty acids (SCFA). The administration of the strains resulted in a differential protective effect that, based on their chelation capacity, supported the existence of additional mechanisms of action besides chelation. Both strains reduced IL-1 beta levels and oxidative stress, while LE1 lowered TNF-alpha, diminished MeHg-induced mucus over -secretion triggered by the IL-4/IL-13/STAT6 pathway, reduced intestinal permeability, and ameliorated inflammation and oxidative stress, probably by acting on the Keap1/ Nrf2/ARE pathway. Administration of LE1 partially restored SCFA contents, which could be partly responsible for the positive effects of this strain in alleviating MeHg toxicity. These results demonstrate that lactobacilli strains can be useful tools in reducing the intestinal toxicity of MeHg, the main mercurial form conveyed by food.