Surface Defects Regulate the in Vivo Bioenergetic Response of Earthworm Eisenia fetida Coelomocytes to Molybdenum Disulfide Nanosheets

Abstract

Two-dimensional molybdenum disulfide (2D MoS2) nanomaterials are seeing increased use in several areas, and this will lead to their inevitable release into soils. Surface defects can occur on MoS2 nanosheets during synthesis or during environmental aging processes. The mechanisms of MoS2 nanosheet toxicity to soil invertebrates and the role of surface defects in that toxicity have not been fully elucidated. We integrated traditional toxicity end points, targeted energy metabolomics, and transcriptomics to compare the mechanistic differences in the toxicity of defect-free and defect-rich MoS2 nanosheets (DF-MoS2 and DR-MoS2) to Eisenia fetida using a coelomocyte-based in vivo assessment model. After organism-level exposure to DF-MoS2 for 96 h at 10 and 100 mg Mo/L, cellular reactive oxygen species (ROS) levels were elevated by 25.6–96.6% and the activity of mitochondrial respiratory electron transport chain (Mito-RETC) complex III was inhibited by 9.7–19.4%. The tricarboxylic acid cycling and glycolysis were also disrupted. DF-MoS2 preferentially up-regulated subcellular component motility processes related to microtubules and caused mitochondrial fission. Unlike DF-MoS2, DR-MoS2 triggered an increased degree of mitochondrial fusion, as well as more severe oxidative stress. The activities of Mito-RETC complexes (I, III, IV, V) associated with oxidative phosphorylation were significantly inhibited by 22.8–68.6%. Meanwhile, apoptotic pathways were activated upon DR-MoS2 exposure, which together with the depolarization of mitochondrial membrane potential, mediated significant apoptosis. In turn, genes related to cellular homeostasis and energy release were up-regulated to compensate for DR-MoS2-induced energy deprivation. Our study indicates that MoS2 nanosheets have nanospecific effects on E. fetida and also that the role of surface defects from synthesis or that accumulate from environmental impacts needs to be fully considered when evaluating the toxicity of these 2D materials.

Earthworm Coelomocyte Internalization of MoS2 Nanosheets: Multiplexed Imaging, Molecular Profiling, and Computational Modeling

“…Unlike P-NSMoS 2 , V-NSMoS 2 specifically induced membrane stress and mitochondrial motility processes. Sun et al demonstrated that surface defects induced by UV irradiation can enhance the in vivo bioenergetic toxicity of NSMoS 2 for earthworm coelomocytes, including stronger electron-transfer interference and ROS accumulation . The impacted biological pathway was verified by assaying cellular uptake at low temperatures (Figure C), demonstrating that the V-NSMoS 2 uptake is associated with energy consumption.…”

“…Coelomocyte viability significantly decreased to 84.0, 76.0, and 82.1% of the control following 24 h of in vitro exposure to 50 μg of Mo/mL P-NSMoS 2 , V-NSMoS 2 , and ionic Mo, respectively (Figure B). The cellular uptake of nanomaterials is thought to be an initiating event of cytotoxicity. , Our previous work reported the oxidative stress and energy metabolism disturbance in the coelomocytes as part of the overall response of earthworms upon in vivo exposure to NSMoS 2 and that vacancy defects enhanced such toxicity potential . However, it is challenging to track the real-time interaction of NSMoS 2 with coelomocytes in vivo , thus hampering the effort to establish a mechanistic connection between the observed toxicity and cellular uptake behavior.…”

“…Co., Ltd., Jiangsu, China, and V-NSMoS 2 were prepared by UV irradiation (Text S1). Two types of NSMoS 2 were characterized as detailed in Text S2. To visualize cellular uptake, fluorescence-labeled P-NSMoS 2 or V-NSMoS 2 were synthesized by a carboxylamine coupling reaction .…”

“…NSMoS 2 exert adverse effects on terrestrial plants, inhibiting the growth and nutrient uptake by maize (Zea mays) and reprogramming carbon and nitrogen metabolism in rice (Oryza sativa L.). , Soil invertebrates are generally recognized as more sensitive models for toxicity assessment than plants, allowing for a more dynamic exposure scenario. Earthworms are ubiquitous sentinel species in soil, providing an active defense against xenobiotics and coordinating the in vivo homeostasis mainly through the free-circulating coelomocytes in the coelom. , We have previously demonstrated that Eisenia fetida absorb NSMoS 2 via dermal and oral routes, with subsequent accumulation in the gut . This whole-animal exposure to NSMoS 2 can alter the coelomocyte mitochondrial dynamics and inhibit the activity of complex III in the respiratory electron transport chain, further disrupting the cellular energy metabolic processes.…”

“…by providing additional physical and chemical reaction sites. − The design of vacancies includes single (e.g., sulfur vacancies) or aggregated atomic vacancies (e.g., surface defects and nanopores). NSMoS 2 are amenable for enhanced catalytic and photovoltaic properties through vacancy engineering due to their highly ordered lattice structure. , NSMoS 2 enriched with atomic vacancies may exhibit entirely distinct biological effects compared to pristine NSMoS 2 . ,, For example, surface defects in NSMoS 2 induced stronger in vivo bioenergetic toxicity to earthworms, specifically increased rates of coelomocytes apoptosis . Similarly, Shi et al reported that nanopores on NSMoS 2 can enhance their antibacterial ability by facilitating electron transfer with biofilms …”