Trace metal uptake by native plants growing on a brownfield in France: zinc accumulation by Tussilago farfara L.

Several human activities such as mining, smelting, or transportations lead to trace metal pollution in soil. The presence of these pollutants can represent environmental and organism health risks. Phytoextraction can be used to remediate trace metal-contaminated soils. It uses the plants' ability to remove trace metals from soil and to accumulate them in their shoots, which can then be harvested. We studied the spontaneous vegetation growing on a brownfield located in France. The use of native plants is interesting since spontaneous vegetation is already well adapted to the site's environmental conditions leading to a better survival and growth than non-native plants. Ten native plant species were sampled, and the Cr, Cu, Cd, Ni, Pb, and Zn concentrations present in their shoots were measured. In order to determine the plant's capacity to extract trace metals from the soil, the bioconcentration factor (BCF) was calculated for each plant and trace metal. Plants with a BCF greater than 1 are able to accumulate trace metals in their shoots and could be a good candidate to be used in phytoextraction. Results underscored one new accumulator plant for Zn, Tussilago farfara L., with a BCF value of 3.069. No hyperaccumulator was found among the other sampled plants. Our preliminary study showed that T. farfara is able to accumulate zinc in its shoots. Moreover, this native plant is a pioneer species able to quickly colonize various habitats by vegetative multiplication. That is why T. farfara  L. could be interesting for zinc phytoextraction and could be worth further studies.

Phagocytic activity of human macrophages and Drosophila hemocytes after exposure to the neonicotinoid imidacloprid.

Neonicotinoid insecticides are increasingly used in modern pest control and in conventional agriculture. Their residues are frequently found in our environment and in our food leading to chronic exposure of pollinating insects and humans. Indeed, evidence has become stronger that chronic exposure to neonicotinoids might have a direct impact on the immune response of invertebrates and vertebrates. Therefore, we compared the cellular immune response of human macrophages (THP-1) and Drosophila melanogaster hemocytes (Schneider 2 cells) after exposure to four different concentrations of the neonicotinoid imidacloprid. Cells were immune activated with LPS (lipopolysaccharide) of Escherichia coli to compare the phagocytic activity of immune activated and non-activated cells during pesticide exposure. Drosophila cells were more strongly affected by the insecticide than human macrophages. Even though imidacloprid showed an adverse effect on phagocytosis on both cells while immune activated, it decreased phagocytosis in Drosophila cells at shorter exposure time and without immune activation.

Imidacloprid intensifies its impact on honeybee and bumblebee cellular immune response when challenged with LPS (lippopolysacharide) of Escherichia coli.

Insect hemocytes play an important role in insects' defense against environmental stressors as they are entirely dependent on their innate immune system for pathogen defense. In recent years a dramatic decline of pollinators has been reported in many countries. The drivers of this declines appear to be associated with pathogen infections like viruses, bacteria or fungi in combination with pesticide exposure. The aim of this study was thus to investigate the impact of imidacloprid, a neonicotinoid insecticide, on the cellular immune response of two pollinators (Apis mellifera and Bombus terrestris) during simultaneous immune activation with LPS (lipopolysaccharide) of Escherichia coli. For this purpose the phagocytosis capacity as well as the production of H2O2 and NO of larval hemocytes, exposed to five different imidacloprid concentrations in vitro, was measured. All used pesticide concentrations showed a weakening effect on phagocytosis with but also without LPS activation. Imidacloprid decreased H2O2 and increased NO production in honeybees. Immune activation by LPS clearly reinforced the effect of imidacloprid on the immune response of hemocytes in all three immune parameters tested. Bumblebee hemocytes appeared more sensitive to imidacloprid during phagocytosis assays while imidacloprid showed a greater impact on honeybee hemocytes during H2O2 and NO production.