Mechanism Of Pb²⁺ Removal And Cytotoxicity Alleviation By L. Plantarum CCFM8661

With Pb pollution aggravating and Pb-poinsoning cases increasing, human health threaten by Pb-contaminated food has aroused public attention. In a previous study, we identified one lactic acid bacteria(LAB) strain with Pb2+ biosorption ability via screening. It was reported, for the first time, that Lactobacillus plantarum CCFM8661 exerted a significant protective effect against lead toxicity in mice. Many researches indicate Pb was mainly absorbed in gastrointestinal tract. Meanwhile, LABs also played their beneficial function in that place. Therefore our study was conducted to clarify the Pb removal and cytotoxicity alleviation mechanism of L. plantarum CCFM8661.In this study, we demonstrated the Pb2+ binding ability of L. plantarum CCFM8661 using large-scale screening. In the single-metal binding study, the affinity of L. plantarum CCFM8661 to the six divalent cations, from most to least was Pb2+> Fe2+> Zn2+> Mn2+> Mg2+>Ca2+. As the result of binary-metal binding study, the interference with Pb2+ binding was observed with the attendance of Fe2+, Mn2+ and Ca2+. However, L. plantarum CCFM8661 still preferred to bind Pb2+ in these situation. The result of desorption experiment showed the Pb2+ binding was stable and the bioaccumulation also took place during the process.The scanning electron microscope(SEM) images showed the obvious morphological changes of bacterial cells after Pb2+ treated, while the transmission electron microscope(TEM) images presented that large amounts of Pb deposits were obviously seen on the surface of bacterial cells, and a few could also been observed within the cells. The comparison of the different cellular components binding ability also demonstrated the cell walls(the Pb2+ removal of cell wall was 73.79%) played a significant role in the Pb2+ binding. The FTIR results and the group modification study confirmed the interaction of the amino and carboxyl groups of the biomass with the Pb ions. The Langmuir–Fraundlich dual isotherm model and the pseudo second-order rate mode provides the closest fit to the equilibrium data indicating that physical and chemical sorption take place simultaneously.In addition, the protective effect of L. plantarum CCFM8661 against Pb toxicity were conducted in Pb-exposed intestinal cell model. As the result, Pb exposure can reduce intestinal cell viability, generate reactive oxygen species(ROS) and down-regulate the tight junction protein expression including ZO-1 and Occludin at gene and protein level. With the intervention and the therapy of this strain, the cell viability and the cell ROS level were recovered. Moreover, the strain can regulate the tight junction protein expression at gene and protein level. Therefore, the intestinal barrier was well protected and inhibited Pb absorption and toxicity.This paper studied the mechanism of Pb removal and cytotoxicity alleviation by L. plantarum CCFM8661. The results provide the reference for mechanism study of heavy metal alleviation by LAB and lay the foundation for the further research.