[Effects of Interaction of Zinc and Cadmium on Growth and Cadmium Accumulation of Brassica campestris L.]

The interaction between different elements is an efficient means to control the heavy metal accumulation in crops. Phosphorus (P) and zinc (Zn), as essential nutrient elements of plants, have been shown to have important impacts on cadmium (Cd) accumulation in crops through interactions with each other. However, the function of the simultaneous interaction of P, Zn, and Cd on vegetable growth and Cd accumulation remains unclear. Herein, using a single-factor level design with two alternating fixed factors, pot experiments were conducted to study the impact and mechanism of this simultaneous interaction at different levels of P, Zn, and Cd on Brassica campestris L. growth, antioxidant enzyme activity, and Zn and Cd accumulation with neutral purple soil as the substrate. The results showed that the addition of an appropriate amount of P and Zn could promote the growth of Brassica campestris L. and inhibit its Cd accumulation, through different mechanisms. P mainly reduced the Cd availability in soil and improved the crop resistance, whereas Zn mainly promoted the dilution effect by the crop growth and its physiological antagonism. The antioxidant capacity of Brassica campestris L. was significantly inhibited when 1 mg·kg-1 exogenous Cd was added to the soil, along with decreased activities of CAT and POD and high accumulation of MDA. Notably, both P and Zn could improve the antioxidant capacity and relieve Cd toxicity by increasing CAT activity, without obviously influencing POD activity. The highest yield of Brassica campestris L. (55.72 g·pot-1) was attained when the ratio of stress concentration for exogenous P, Zn, and Cd[ω(Cd):ω(Zn):ω(P)] was 1:10:200. Furthermore, the Cd content in the edible part was also lower than the national standard requirement of 50 µg·kg-1for Cd in green leafy vegetables (GB 2762-2017). In addition, the accumulation of Cd was further decreased when the proportion of P and Zn was increased, along with a decreased yield of the vegetable. Therefore, a proper application of P and Zn fertilizers could simultaneously reduce Cd accumulation and increase crop yield and thus contribute to achieving safe vegetable production.

[Effects of Water Management on the Transformation of Iron Oxide Forms in Paddy Soils and Its Coupling with Changes in Cadmium Activity].

The transformation of iron oxide forms in the process of soil water management in paddy fields has an important impact on soil cadmium (Cd) activity and accumulation in rice. The test soil for this experiment was purple paddy soil in southwest China contaminated with exogenously added Cd. Through indoor cultivation experiments, the effects of water management (continuous flooding, CW; alternating wet and dry, DW) combined with iron oxide application (goethite, G-Fe; iron powder, Fe) on the pH, redox state (Eh, pe+pH), iron oxide form conversion, and Cd bioavailability changes in Cd-contaminated soil were studied. Meanwhile, the coupling relationship between the transformation of iron oxide form and the evolution of soil Cd activity driven by water management were also analyzed. The results showed that DTPA-Cd content was decreased by 17.7%-39.2% after 93 days of flooding, indicating that CW could significantly reduce soil Cd bioavailability. CW combined with Fe or G-Fe application significantly enhanced the passivating effect on soil Cd. Among them, the DTPA-Cd content of G-Fe application was reduced by 24.3% compared with that of the CK after 14 d of flooding; thus, G-Fe was effective in short-term passivation. The reduction in DTPA-Cd content of Fe application was 39.2% after 93 d of flooding, so Fe was able to passivate soil Cd continuously. It was also found that the application of iron oxides under alternating wet and dry conditions had no passivating effect on soil Cd. Furthermore, based on correlation analysis, the formation of amorphous iron (Feo) (P<0.01) was verified as the main reason for the change in Cd bioavailability of Cd in the soil:firstly, the soil pH gradually declined to 7.4, and the soil was kept at reduction conditions under CW, which promoted the morphology transformation from the crystalline state (Fec) to Feo. This transformation subsequently pushed the Cd transformation from the exchangeable state to the iron-manganese combined state and thus resulted in the significant decrease in Cd bioavailability. Meanwhile, the content and proportion of Feo were also significantly increased by the application of CW combined with Fe or G-Fe, thus further enhancing its Cd passivating effect on the soil. This research provides a scientific basis for the optimal water management and the application of iron-containing passivation agent in the safe use of Cd-contaminated paddy soils.

[Screening and Evaluation of Methods for Determining Available Lead (Pb) and Cadmium (Cd) in Farmland Soil].

The accumulation of heavy metals in crops is largely dependent on the availability of heavy metals in soils. Due to the differences of soil types and pollution characteristics, there is no widely recognized method for the determination of the bio-available heavy metals in soils such as Pb and Cd. In order to screen and establish suitable methods, the extractable abilities of five extractants (CaCl2, NH4OAc, HCl, EDTA, and DTPA) and Gradient Diffusion Film Technology (DGT) on four typical farmland soils with very different properties in Chongqing (acid purple soil, neutral purple soil, calcareous yellow soil and calcareous purple soil) were systematically compared. Simultaneously, pot experiments were carried out with Lolium perenne L. as an indicator plant to explore the relationship between the extractable soil Pb and Cd and their accumulation in plants. The feasibility of the tested methods were evaluated based on the extractability and co-relationships. The results showed that the extractability of the tested extractants for soil Pb and Cd varied a lot. HCl showed highest extractability on Pb in acid purple soil and calcareous yellow soil, while EDTA did the best in neutral purple soil and calcareous purple soil; HCl showed best extractability in all soils except calcareous purple soil, where EDTA was the best. Considering the correlation between the extraction amount and uptake by plant, all the extraction methods could be applied for the evaluation of the bioavailability of soils Pb and Cd except CaCl2 for Pb due to its weak extractability for Pb for a specific soil type. For the comparison of heavy bioavailability in different soil types, EDTA-extractable Pb and DGT-extractable Cd were recommended due to their well co-relationships between extractable amount in soil and uptake by plant (Lolium perenne L.) as indicated by the correlation coefficients of 0.941 and 0.919, respectively. HCl was relatively suitable as Cd extractant compared to others if DGT method could not be used.

Protective Properties of FOXO1 Inhibition in a Murine Model of Non-alcoholic Fatty Liver Disease Are Associated With Attenuation of ER Stress and Necroptosis.

AIM: The pathogenesis of non-alcoholic fatty liver disease is currently unclear, however, lipid accumulation leading to endoplasmic reticulum stress appears to be pivotal in the process. At present, FOXO1 is known to be involved in NAFLD progression. The relationship between necroptosis and non-alcoholic steatohepatitis has been of great research interest more recently. However, whether FOXO1 regulates ER stress and necroptosis in mice fed with a high fat diet is not clear. Therefore, in this study we analyzed the relationship between non-alcoholic steatohepatitis, ER stress, and necroptosis. MAIN METHODS: Male C57BL/6J mice were fed with an HFD for 14 weeks to induce non-alcoholic steatohepatitis. ER stress and activation of necroptosis in AML12 cells were evaluated after inhibition of FOXO1 in AML12 cells. In addition, mice were fed with AS1842856 for 14 weeks. Liver function and lipid accumulation were measured, and further, ER stress and necroptosis were evaluated by Western Blot and Transmission Electron Microscopy. KEY FINDINGS: Mice fed with a high fat diet showed high levels of FOXO1, accompanying activation of endoplasmic reticulum stress and necroptosis. Further, sustained PA stimulation caused ER stress and necroptosis in AML12 cells. At the same time, protein levels of FOXO1 increased significantly. Inhibition of FOXO1 with AS1842856 alleviated ER stress and necroptosis. Additionally, treatment of mice with a FOXO1 inhibitor ameliorated liver function after they were fed with a high fat diet, displaying better liver condition and lighter necroptosis. SIGNIFICANCE: Inhibition of FOXO1 attenuates ER stress and necroptosis in a mouse model of non-alcoholic steatohepatitis.