Heavy Metal Toxicity in an Insect Cell Line (Methyl-HgCl, HgCl2, CdCl2 and CuSO4)

Abstract

We have analyzed the toxicity, uptake and intracellular effects of CdCl 2 , HgCl 2 , MeHgCl and CuSO 4 in a cell line of the Asian tiger mosquito Aedes albopictus. Cell proliferation was drastically inhibited by CdCl 2 and MeHgCl while HgCl 2 showed only a moderate effect. Acute toxicity tests showed that membrane integrity was severely affected in cells treated with low doses of HgCl 2 and MeHgCl. Uptake of both mercury species occurred via simple diffusion while cadmium entered the cells through mediated transport. CdCl 2 , HgCl 2 and CuSO 4 , but not MeHgCl induced microtubulesupported neurite-like extensions in the Aedes cells. The metals induced some general intracellular pathologies such as mitochondrial alterations, nuclear deformation and increased lysosomal profiles. Mitochondrial swelling and severe RER dilatation by proteinaceous material was most pronounced in cadmium-treated cells. These morphological features were accompanied by lactate production and induction of a 78-kDa protein (possibly Grp78/BiP). The latter may represent a stress defense system that leads to a positive shift of the cell viability curve. Unlike other treatments, CuSO 4 -treated cells showed massive apoptosis characterized by nuclear chromatin condensation and DNA laddering. IntroductionMany insect species accumulate heavy metals from the environment in their body. Therefore, their role in food webs as well as their potential to serve as bioindicators have been widely studied (McGeoch 1998). However, less is known about the fate of the heavy metals at the cellular level in insects. A major advantage of using insect cell cultures for this purpose is that this method allows for controlled exposure of cells to precise metal concentrations for a specific amount of time. In this chapter, we will describe the general toxicity, uptake kinetics, subcellular distribution and physiological effects of several heavy metals in a cell line of the Asian tiger mosquito Aedes albopictus.In a series of dye exclusion tests and cell proliferation assays on mercury-, methylmercury-, and cadmium-treated cells, we found that they showed widely different toxicity patterns. Sublethal doses of the tested heavy metals showed a profound effect on general cell morphology: long, neurite-like, microtubule-supported extensions were induced (except for MeHgCl-treated cells). At the subcellular level, many general, stress-related pathologies were found, such as nuclear chromatin clumping, indentation and dilatation of the perinuclear cisternae, increase of ribosomal density, and lysosomal and RER volume. Cd-treated cells specifically showed clear mitochondrial condensation and swelling, suggesting impairment of aerobic function which was confirmed by increased lactic acid levels in the culture medium. Proteinaceous substance that we found in the dilated RER cisternae may represent the ER stress protein Grp78/BiP. Cells exposed to MeHgCl showed particular cytoplasmic tube-like structures of unknown function and the appearance of blebs suggested microtubul...

Ultrastructural Alterations of Midgut Epithelium, But Not Greater Wing Fluctuating Asymmetry, in Paper Wasps (Polistes dominula) from Urban Environments

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“…In the tiger mosquito Aedes albopictus Skuse (Diptera), metals such as Cd and Hg induce intracellular pathologies similar to those found in P. dominula from the urban sites, i.e. mitochondrial alterations, nuclear deformation and increased lysosomal profiles (Braeckman, 2011). We also found great cytoplasm vacuolization in the urban wasps.…”

Biochemical and histological alterations induced by nickel oxide nanoparticles in the ground beetle Blaps polychresta (Forskl, 1775) (Coleoptera: Tenebrionidae)

“…The irregulation of the nuclear envelopes and karyorrhexis indicate a pathway of cell death [87,88]. Some authors attributed apoptosis to metal accumulation [89,90], which is in agreement with our results. Research has proven the relation between exposure to metals and the prevalence of apoptosis [91,92].…”

Bioaccumulation of Cadmium Affects Development, Mating Behavior, and Fecundity in the Asian Corn Borer, Ostrinia furnacalis

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