How Probiotics Inhibit Cadmium Absorption and Protect the Intestinal Barrier Original paper

Cadmium (Cd), one of the most common toxic and nonessential elements, is widely distributed in the environment, as an agricultural and industrial pollutant, seriously threatens the health of intestine¹.

What was studied?

This original research article investigated how probiotics inhibit cadmium absorption, not only by directly binding cadmium but also by reducing intestinal uptake and strengthening the gut barrier. The central hypothesis proposed that probiotics both sequester Cd in the gut and preserve intestinal barrier integrity, thereby lowering Cd accumulation in the body².

The study applied complementary models: in vitro (laboratory-based cell culture) and in vivo (animal experiments).

In vitro, human intestinal epithelial HT-29 cells were exposed to Cd with and without treatment by Lactobacillus plantarum CCFM8610. Researchers assessed cytotoxicity, oxidative stress, inflammatory responses, and tight junction integrity to evaluate how probiotics inhibit cadmium absorption at the cellular level.

In vivo, C57BL/6 mice received environmentally relevant doses of Cd along with oral administration of different L. plantarum strains (CCFM8610, CCFM11, and CCFM8614), which differed in their Cd-binding and antioxidative properties. The experiments measured Cd levels in feces, liver, and kidney, while also evaluating gut barrier function, immune regulation, and inflammatory markers. Together, these findings provided mechanistic insights into how probiotics inhibit cadmium absorption and protect host health.

Who was studied?

The study involved two main subject groups. In vitro experiments were conducted using the human intestinal epithelial cell line HT-29, a widely accepted model for studying gut barrier function and toxicological responses. For the animal experiments, adult male C57BL/6 mice were used, a standard laboratory mouse strain for toxicology and immunology research. Mice were randomly assigned to five groups: a control group, a Cd-only group, and three groups each receiving Cd plus one of the three L. plantarum strains. Each group contained 10 animals. The probiotic strains administered differed in their abilities to bind Cd and to counteract oxidative stress, providing insight into the relative importance of these probiotic characteristics in mitigating Cd toxicity.

Most important findings

The study provided robust evidence that probiotics, particularly L. plantarum CCFM8610, can reduce Cd absorption through two complementary mechanisms: direct intestinal Cd sequestration and protection of the gut barrier. In HT-29 cells, both intervention (simultaneous) and therapy (post-exposure) treatments with CCFM8610 significantly alleviated Cd-induced cytotoxicity, reduced reactive oxygen species (ROS) and lipid peroxidation, and restored tight junction protein distribution (ZO-1 and claudin-1). Inflammatory cytokine levels (TNF-α, IL-1β, IL-6, IL-8) were also reduced in probiotic-treated cells.

In vivo, all three L. plantarum strains increased fecal Cd excretion and reduced Cd accumulation in liver and kidney tissues of mice, but strains with both high Cd-binding and antioxidative activity (especially CCFM8610) were most effective. Cd exposure disrupted gut barrier function, as shown by decreased expression of tight junction genes, increased gut permeability (measured by FITC-dextran and endotoxin translocation), and heightened intestinal inflammation. Probiotic treatment reversed these effects, restoring tight junction gene expression, reducing permeability, and normalizing cytokine and secretory IgA levels. Notably, the antioxidative property of the probiotic strains was crucial: even strains with lower Cd-binding but higher antioxidative activity (CCFM8614) provided significant protection, highlighting multiple modes of probiotic action.

Key implications

For heavy metal certification programs and industry, this study offers critical insights into the mechanisms by which probiotic supplementation can mitigate dietary Cd exposure. The data demonstrate that probiotics can function as a preventive strategy against Cd uptake not solely through biosorption but also by maintaining gut barrier integrity and attenuating oxidative and inflammatory damage induced by Cd. This dual-action approach suggests that probiotic products, particularly those with both strong Cd-binding and antioxidative properties, could be developed as functional food supplements to reduce the bioavailability of Cd from contaminated food or water. For regulatory bodies, these findings support the inclusion of probiotic intervention as a non-invasive, dietary-based strategy in heavy metal risk management and public health guidelines. The research further underscores the importance of characterizing probiotic strains for both metal-binding and antioxidative capacities when certifying or recommending them for heavy metal mitigation.

Citation

Zhai Q, Tian F, Zhao J, Zhang H, Narbad A, Chen W. Oral administration of probiotics inhibits absorption of the heavy metal cadmium by protecting the intestinal barrier. Applied and Environmental Microbiology. 2016;82(14):4429-4440. doi:10.1128/AEM.00695-16.