Cui, J. Y. Y. | bioRxiv Science

bioRxiv2025

Cadmium-induced gut dysbiosis precedes the onset of hippocampus-dependent learning and memory deficits in mice

BackgroundCadmium (Cd) is a heavy metal recognized as a neurotoxicant. However, the mechanisms underlying its neurotoxicity remain poorly understood. The gut-brain axis, a bidirectional communication pathway between the central nervous system and the gut microbiome, has been linked to various neurological disorders. Because the gut microbiome is a known target of Cd, it is important to investigate whether the gut-brain axis mechanistically contributes to the Cd-induced neurotoxicity. ObjectiveIn our initial exploration of the role of the gut-brain axis in modulating Cd neurotoxicity on cognition, we investigated whether Cd exposure induces gut dysbiosis before the onset of cognitive deficits and explored the potential link between gut microbiome alterations and Cd-induced cognitive deficits. MethodsAdult male mice were exposed to 3 mg/L Cd via drinking water for nine weeks. Behavioral assessments were conducted throughout the exposure period to evaluate cognitive function. Fresh fecal pellets were collected weekly to monitor changes in the gut microbiome composition. The effects of Cd on the hippocampus and intestine were analyzed using transcriptomics and mass spectrometry (MS)-based metabolomics. ResultsCd exposure resulted in hippocampus-dependent learning and memory deficits, first observed at four weeks into exposure. RNA sequencing of the hippocampus at the terminal time point revealed reduced expression of genes involved in cognition and neuroinflammation in Cd exposed mice. Metagenomic shotgun sequencing showed that Cd-induced gut dysbiosis preceded the onset of cognitive impairments, with specific bacterial species associated with Cd-induced cognitive deficits. Furthermore, Cd exposure reduced the expression of genes involved in intestinal barrier integrity, increased inflammatory cytokines levels, and altered the levels of neuroactive microbial metabolites. ConclusionOur study is the first to show that Cd exposure triggers gut microbial shifts before the onset of cognitive deficits, accompanied by increased intestinal permeability and elevated proinflammatory biomarkers in both the intestine and brain at the terminal time point. These findings suggest a potential critical role of gut-brain axis in modulating Cd neurotoxicity and underscore the need for future research to elucidate the mechanistic involvement of gut microbiome as a potential target for mitigating Cd-induced cognitive decline.

systems biology↗

bioRxiv2023

In Vivo Tissue Distribution of Microplastics and Systemic Metabolomic Alterations After Gastrointestinal Exposure

Global plastic use has consistently increased over the past century with several different types of plastics now being produced. Much of these plastics end up in oceans or landfills leading to a substantial accumulation of plastics in the environment. Plastic debris slowly degrades into microplastics (MPs) that can ultimately be inhaled or ingested by both animals and humans. A growing body of evidence indicates that MPs can cross the gut barrier and enter into the lymphatic and systemic circulation leading to accumulation in tissues such as the lungs, liver, kidney, and brain. The impacts of mixed MPs exposure on tissue function through metabolism remains largely unexplored. To investigate the impact of ingested MPs on target metabolomic pathways, mice were subjected to either polystyrene microspheres or a mixed plastics (5 {micro}m) exposure consisting of polystyrene, polyethylene and the biodegradability and biocompatible plastic, poly-(lactic-co-glycolic acid). Exposures were performed twice a week for four weeks at a dose of either 0, 2, or 4 mg/week via oral gastric gavage. Our findings demonstrate that, in mice, ingested MPs can pass through the gut barrier, be translocated through the systemic circulation, and accumulate in distant tissues including the brain, liver, and kidney. Additionally, we report on the metabolomic changes that occur in the colon, liver and brain which show differential responses that are dependent on dose and type of MPs exposure. Lastly, our study provides proof of concept for identifying metabolomic alterations associated with MPs exposure and adds insight into the potential health risks that mixed MPs contamination may pose to humans.

pharmacology and toxicology↗