Immobilization of cadmium and lead by Lactobacillus rhamnosus GR-1 mitigates apical-to-basolateral heavy metal translocation in a Caco-2 model of the intestinal epithelium

Abstract

Heavy metals are highly toxic elements that contaminate the global food supply and affect human and wildlife health. Purification technologies are often too expensive or not practically applicable for large-scale implementation, especially in impoverished nations where heavy metal contamination is widespread. Lactobacillus rhamnosus GR-1 (LGR-1) was shown in previous work to reduce heavy metal bioaccumulation in a Tanzanian cohort of women and children through indeterminant mechanisms. Here, it was hypothesized that LGR-1 could sequester the heavy metals lead (Pb) and cadmium (Cd), thereby reducing their absorption across intestinal epithelium. LGR-1 and other lactobacilli significantly reduced the amount of Pb and Cd in solution at all concentrations tested (0.5 mg/L-50 mg/L) and exhibited sustained binding profiles over a 48-hour period. Relative binding efficiency of LGR-1 decreased as Pb concentration increased, with an absolute minimum binding threshold apparent at concentrations of 2 mg/L and above. Electron microscopy revealed that Pb formed irregular cell-surface clusters on LGR-1, while Cd appeared to form intracellular polymeric clusters. Additionally, LGR-1 was able to significantly reduce apical-to-basolateral translocation of Pb and Cd in a Caco-2 model of the intestinal epithelium. These findings demonstrate the absorbent properties of LGR-1 can immobilize Pb and Cd, effectively reducing their translocation across the intestinal epithelium in vitro. Oral administration of heavy metal-binding Lactobacillus spp. (many of which are known human symbionts and strains of established probiotics) may offer a simple and effective means to reduce the amount of heavy metals absorbed from foods in contaminated regions of the world.

Cadmium and Selenate Exposure Affects the Honey Bee Microbiome and Metabolome, and Bee-Associated Bacteria Show Potential for Bioaccumulation

“…Previous studies have examined the effects of cadmium on the microbes associated with mice (76) and spiders (44) and the effects of selenate on bumble bee microbes (35). Host-associated microbes can detoxify or sequester toxic metals, including arsenic (47), selenate (35), lead and chromium (48), copper (49), and cadmium (50)(51)(52). Our research extends this work by showing that bee-associated microbes can be affected by metal(loid) exposure and are able to bioaccumulate some of these compounds and that the metabolome is changed in response to selenate and cadmium poisoning.…”

“…As many of the honey bee gut microbes were resilient to metal or metalloid challenge, we next determined whether common bee-associated bacteria can remove these toxicants from their immediate environment. The potential for bacteria to protect their host from toxic metal exposure through bioaccumulation is an emerging topic of investigation in several systems, including humans (51,85), mice (49,52), and insects (48). We exposed strains of bee-associated bacteria to cadmium in vitro and found that all assayed taxa removed a significant amount of cadmium from their growth media after 2 days of incubation.…”

“…Likewise, various Lactobacillus spp. can accumulate copper (49), cadmium (50)(51)(52), aluminum (53), and chromium (54), which suggests that members of this genus have the potential to be administered as probiotics to reduce metal burden in the host.…”

A multi-omic cohort as a reference point for promoting a healthy human gut microbiome

“…One potential explanation for the association with desirable cardiometabolic and psychological scores observed in our study for yogurt or milk is the production of metabolites such as folate and GABA by S. thermophilus , Bifidobacterium and Lactobacillus 90, 91 . Moreover, Lactobacilli have been reported to sequester heavy metals including lead and cadmium 92 . All of these live or dead probiotics could potentially exert functions on the immune system or even the brain.…”

Probiotics against alleviation of lead toxicity: recent advances

“…Pb absorption and immobilization reducing its translocation across the intestinal epithelium in vitro Daisley et al, 2019…”