Reduced dietary Ca, Cu, Zn, Mn, and Mg bioavailability but increased Fe bioavailability with polyethylene microplastic ingestion in a mouse model: Changes in intestinal permeability and gut metabolites.

Microplastics emerge as a new environmental and human health crisis. Minimal research exists on effects of microplastic ingestion on the oral bioavailability of minerals (Fe, Ca, Cu, Zn, Mn, and Mg) in the gastrointestinal tract via impacting intestinal permeability, mineral transcellular transporters, and gut metabolites. Here, mice were exposed to polyethylene spheres of 30 and 200 µm (PE-30 and PE-200) in diet (2, 20, and 200 µg PE g-1) for 35 d to determine the microplastic effects on mineral oral bioavailability. Results showed that for mice fed diet amended with PE-30 and PE-200 at 2-200 µg g-1, Ca, Cu, Zn, Mn, and Mg concentrations in the small intestine tissue were 43.3-68.8 %, 28.6-52.4 %, 19.3-27.1 %, 12.9-29.9 %, and 10.2-22.4 % lower compared to control mice, suggesting hampered bioavailability of these minerals. In addition, Ca and Mg concentrations in mouse femur were 10.6 % and 11.0 % lower with PE-200 at 200 µg g-1. In contrast, Fe bioavailability was elevated, as suggested by significantly (p < 0.05) higher Fe concentration in the intestine tissue of mice exposed to PE-200 than control mice (157-180 vs. 115 ± 7.58 µg Fe g-1) and significantly (p < 0.05) higher Fe concentrations in liver and kidney with PE-30 and PE-200 at 200 µg g-1. Following PE-200 exposure at 200 µg g-1, genes coding for duodenal expression of tight junction proteins (e.g., claudin 4, occludin, zona occludins 1, and cingulin) were significantly up-regulated, possibility weakening intestinal permeability to Ca, Cu, Zn, Mn, and Mg ions. The elevated Fe bioavailability was possibly related to microplastic-induced greater abundances of small peptides in the intestinal tract, which inhibited Fe precipitation and elevated Fe solubility. Results showed that microplastic ingestion may cause Ca, Cu, Zn, Mn, and Mg deficiency but Fe overload via altering intestinal permeability and gut metabolites, posing a threat to human nutrition health.

Oxidative stress, defense response, and early biomarkers for lead-contaminated soil in Vicia faba seedlings.

Chemical analyses and biological measurements were investigated in leaves of Vicia faba seedlings exposed to extraneous lead (Pb) at 0 to 2,000 mg/kg of soil for a month. The results showed that superoxide radical (O*(2)(-)) production, increased along with total Pb in leaves and available Pb in soil, resulted in enhancement of malondialdehyde and carbonyl groups. Antioxidant enzymes, including corresponding isoenzymes and heat shock protein 70 (hsp 70), were also enhanced to some extent. Significant changes were detected in the patterns and intensities of guaiacol peroxidase isoenzymes, while superoxide dismutase, catalase, and ascorbate peroxidase isoenzymes only changed intensities. Superoxide dismutase activities increased with the increase of extraneous Pb at 0 to 500 mg/kg of soil and tended to decline thereafter, which might be responsible for the decrease of hydrogen peroxide and accumulation of O*(2)(-). Guaiacol peroxidase and ascorbate peroxidase enzymes were upregulated to become major scavengers of excess hydrogen peroxide on the condition of decreased catalase activities. Levels of hsp 70 were well correlated with Pb contents in leaves (r=0.777), O*(2)(-) accumulation (r = 0.985, p<0.01), and carbonyl groups (r=0.920, p<0.01) under extraneous Pb at 0 to 250 mg/kg of soil, suggesting that hsp 70 induced by O*(2)(-) was possibly involved in disposal of denatured proteins. The results showed that O*(2)(-), hsp 70, and guaiacol peroxidase isoenzymes had the most sensitive responses in the seedlings and these parameters could be potential early biomarkers of soil Pb contamination.

[Effects of free-air CO2 enrichment on phosphine emission from rice field].

Phosphine, a trace gas, has been proved to commonly exist in environment. Under free air carbon dioxide enrichment (FACE) condition, the phosphine fluxes were investigated on the function of different nitrogen fertilizer application, NN (normal N, 250 kg/hm2) and LN (low N, 125 kg/hm2). Results showed that phosphine fluxes and concentrations in flourishing stages, both tillering stage and elongation stage, were higher than in slowly growing stages. The highest phosphine flux of (155.2 +/- 22.71) ng/(m2 x h) was observed in tillering stage in NN zone of the FACE area. The highest average phosphine flux of (41.72 +/- 7.006) ng/(m2 x h) was observed in NN zone of FACE area, while the lowest average phosphine flux of (- 1.485 +/- 6.229) ng/(m2 x h) could be detected in LN zone of the ambient area. CO2 enrichment can obviously improve the phospine emission. The nitrogen fertilizing level doesn't play an important role in phosphine emission. Both net fluxes and concentrations of phosphine had obviously positive correlation with temperature. A one-day phosphine flux and concentration experiment was carried out in ripening stage. The result showed that light was the prominent factor influencing phosphine concentration in daytime.