Organism and molecular-level responses of superoxide dismutase interaction with 2-pentanone

Molecular interaction mechanisms and cellular response of superoxide dismutase and catalase to fluoranthene

As an important raw material and intermediate product of the petrochemical industry, fluoranthene (Fla) can be emitted with industrial activities and has become a typical polycyclic aromatic hydrocarbon enriched in the Chinese topsoil layer, posing a significant threat to sensitive soil biota. Here, multispectral tools and molecular simulation techniques were integrated to elucidate the molecular mechanism of Fla interaction with key antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) at the molecular level. Meanwhile, we further revealed the cellular responses of SOD and CAT and the associated redox states in earthworm (Eisenia fetida) coelomocytes based on the molecular-level results. Our results showed that the exposure to Fla affected the backbone structure of SOD and CAT molecules and resulted in the formation of Fla-SOD polymers as well as an overall reduction in the size of the Fla-CAT binding system. Fla altered the microenvironment around Tyr residues in the SOD molecule and quenched the endogenous fluorescence of Tyr within the CAT molecule. In earthworm coelomocytes, Fla at 60 and 80 μM resulted in a significant elevation of CAT and SOD activities by 114% (p = 0.032) and 6.09% (p = 0.013), respectively. Molecular simulation results suggested that Fla-induced changes in the structure and conformation of SOD and CAT may be the key reason for their altered activities. The related redox homeostasis detection in earthworm coelomocytes indicated that high concentrations (80 μM) of Fla led to a significant accumulation of intracellular ROS (p = 0.018) and resulted in the development of lipid peroxidation. Our work contributes to an in-depth understanding of the biological effect of Fla to sensitive soil fauna, thus providing new ideas for Fla ecological risk prevention and control.

Coupled Lipidomics and Digital Pathology as an Effective Strategy to Identify Novel Adverse Outcome Pathways in Eisenia fetida Exposed to MoS2 Nanosheets and Ionic Mo

Molybdenum disulfide (MoS₂) nanosheets are increasingly applied in several fields, but effective and accurate strategies to fully characterize potential risks to soil ecosystems are lacking. We introduce a coelomocyte-based in vivo exposure strategy to identify novel adverse outcome pathways (AOPs) and molecular endpoints from nontransformed (NTMoS₂) and ultraviolet-transformed (UTMoS₂) MoS₂ nanosheets (10 and 100 mg Mo/L) on the earthworm Eisenia fetida using nontargeted lipidomics integrated with transcriptomics. Machine learning-based digital pathology analysis coupled with phenotypic monitoring was further used to establish the correlation between lipid profiling and whole organism effects. As an ionic control, Na₂MoO₄ exposure significantly reduced (61.2-79.5%) the cellular contents of membrane-associated lipids (glycerophospholipids) in earthworm coelomocytes. Downregulation of the unsaturated fatty acid synthesis pathway and leakage of lactate dehydrogenase (LDH) verified the Na₂MoO₄-induced membrane stress. Compared to conventional molybdate, NTMoS₂ inhibited genes related to transmembrane transport and caused the differential upregulation of phospholipid content. Unlike NTMoS₂, UTMoS₂ specifically upregulated the glyceride metabolism (10.3-179%) and lipid peroxidation degree (50.4-69.4%). Consequently, lipolytic pathways were activated to compensate for the potential energy deprivation. With pathology image quantification, we report that UTMoS₂ caused more severe epithelial damage and intestinal steatosis than NTMoS₂, which is attributed to the edge effect and higher Mo release upon UV irradiation. Our results reveal differential AOPs involving soil sentinel organisms exposed to different Mo forms, demonstrating the potential of liposome analysis to identify novel AOPs and furthermore accurate soil risk assessment strategies for emerging contaminants.

Mechanistic insights into pyridine exposure induced toxicity in model Eisenia fetida species: Evidence from whole-animal, cellular, and molecular-based perspectives

Pyridine and its derivatives are widely used in many applications and inevitably cause extreme scenarios of serious soil contamination, which pose a threat to soil organisms. Still, the eco-toxicological effects and underlying mechanisms of pyridine-caused toxicity toward soil fauna have not been well established. Thus, earthworms (Eisenia fetida), coelomocytes, and oxidative stress-related proteins were selected as targeted receptors to probe the ecotoxicity mechanism of extreme pyridine soil exposure targeted to earthworms by using a combination of in vivo animal experiments, cell-based in vitro tests, in vitro functional and conformational analyses, and in silico analyses. The results showed that pyridine caused severe toxicity to E. fetida at extreme environmental concentrations. Exposure of pyridine induced excessive ROS formation in earthworms, causing oxidative stress and various deleterious effects, including lipid damage, DNA injury, histopathological change, and decreased defense capacity. Also, pyridine destroyed the cell membrane of earthworm coelomic cells and triggered a significant cytotoxicity. Importantly, the intracellular ROS (e.g., O₂^-, H₂O₂, and OH·^-) was release-activated, which eventually inducing oxidative stress effects (lipid peroxidation, inhibited defense capacity, and genotoxicity) through the ROS-mediated mitochondrial pathway. Moreover, the antioxidant defence mechanisms in coelomocytes responded quickly to reduce ROS-mediated oxidative injury. It was conformed that the abnormal expression of targeted genes associated with oxidative stress in coelomic cells was activated after pyridine exposure. Particularly, we found that the normal conformation (particle sizes, intrinsic fluorescence, and polypeptide backbone structure) of CAT/SOD was destroyed by the direct binding of pyridine. Furthermore, pyridine bound easily to the active center of CAT, but preferentially to the junction cavity of two subunits of SOD, which is considered to be a reason for impaired protein function in cells and in vitro. Based on these evidences, the ecotoxicity mechanisms of pyridine toward soil fauna are elucidated based on multi-level evaluation.

The effect of TiO2NPs on cloransulam-methyl toxicity to earthworm (Eisenia fetida)

Cloransulam-methyl is a new herbicide and has broad application prospect. However, the effect of cloransulam-methyl on earthworm have yet to be clarified. As more and more titanium dioxide nanoparticles (TiO₂NPs) enter the soil, cloransulam-methyl and TiO₂NPs have a risk of co-exposure, but the effect of TiO₂NPs on cloransulam-methyl toxicity is unknown. In the study, the ecotoxicity of cloransulam-methyl (0.1, 1 mg kg^-1) on earthworm and the effect of TiO₂NPs (10 mg kg^-1) on cloransulam-methyl toxicity was investigated after exposure for 28 and 56 d. Exposure tests showed cloransulam-methyl and cloransulam-methyl + TiO₂NPs promoted the accumulation of reactive oxygen species, malondialdehyde and 8-hydroxydeoxyguanosine, increased the activities of superoxide dismutase and catalase, resulted in lipid peroxidation and DNA damage. Besides, the results at the genetic level showed cloransulam-methyl and cloransulam-methyl + TiO₂NPs altered the expression of physiologically-related genes, which demonstrated that cloransulam-methyl and cloransulam-methyl + TiO₂NPs induced oxidative stress and cell apoptosis, and disturbed the normal reproduction in earthworm. The results of comprehensive toxicity comparison indicated cloransulam-methyl and TiO₂NPs co-exposure has higher toxicity compared to cloransulam single exposure. Our results suggest that TiO₂NPs can enhance the toxicity of cloransulam-methyl on Eisenia fetida in terms of oxidative stress, cell apoptosis and reproduction aspects. Based on above studies, it is of great importance for evaluating the risk of cloransulam-methyl co-exposure with TiO₂NPs in soil.

Hydroxylated polycyclic aromatic hydrocarbons possess inhibitory activity against alpha-glucosidase: An in vitro study using multispectroscopic techniques and molecular docking

Alpha-glucosidase (GAA) activity can be affected by exogenous substances. Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) are typical metabolites of PAHs that can enter the body through various routes. The effects of 1-hydroxynaphthalene (1-OHNap) and 1-hydroxypyrene (1-OHPyr) on GAA activity and the potential mechanisms were investigated viamultispectroscopic methods and molecular docking. First-order derivative synchronous spectrofluorimetry was successfully applied to analyze the fluorescence quenching of GAA in the GAA-1-OHNap and GAA-1-OHPyr systems. 1-OHNap and 1-OHPyr had strong inhibitory effects on GAA activity. GAA could bind with 1-OHNap and 1-OHPyr in 1:1 mode with binding constants of 3.97 × 10⁴ and 9.42 × 10⁴ L/mol at 298 K. Hydrophobic interactions and hydrogen bonds played pivotal roles in the interactions. 1-OHNap was located closer to the active site of GAA than 1-OHPyr. This work suggests that the disturbance of glycometabolism by exogenous pollutants in the human body is worthy of attention and further investigation.

Identification and characterization of two types of triacylglycerol lipase genes from Neocaridina denticulata sinensis

Triacylglycerol lipases (TGLs) can catalyze the hydrolysis reaction of triacylglycerol serving multiple functions in most organisms. Based on the genomic and transcriptomic databases of Neocaridina denticulata sinensis, two TGL genes from N. denticulata sinensis designated NdTGL1 and NdTGL2 were identified and characterized. NdTGL1 showed the highest expression in the stomach, followed by the testis and hepatopancreas, and NdTGL2 exhibited the maximum expression in the hepatopancreas, followed by the stomach and heart. Under the stimulation of copper ion, the expression of NdTGL1 peaked at 12 h and the expression of NdTGL2 elevated significantly at 24 h after stimulation (P < 0.05). It is speculated that NdTGLs may play an important role in the stress response of N. denticulata sinensis. Challenged with Vibrio parahaemolyticus, the expression profiles of NdTGL1 and NdTGL2 in the hepatopancreas was different, which indicates that the immune response of the V. parahaemolyticus challenge might lead to changes in triglyceride metabolism. The recombinant NdTGL (recNdTGL1 and recNdTGL2) were obtained and the enzymatic characterization of recNdTGL1 and recNdTGL2 were determined. The common maximum activity and stability of the recNdTGL1 and recNdTGL2 were observed at 45 °C and 10 °C, respectively. Both recNdTGL1 and recNdTGL2 exhibited the highest activity at pH 10.0. Furthermore, the recNdTGL1 and recNdTGL2 displayed the maximum stability at pH 5.0 and pH 8.0, respectively. In presence of different metal ions, the enzyme activity of recNdTGL1 and recNdTGL2 were inhibited by Cu²⁺ and Zn²⁺, and decreased by about 25%. Studies on the triacylglycerol lipases of N. denticulata sinensis provide theoretical support for studies related to fat metabolism in crustaceans and studies on response mechanism of digestive enzymes to microbial pathogens.

Behavioral, histopathological, genetic, and organism-wide responses to phenanthrene-induced oxidative stress in Eisenia fetida earthworms in natural soil microcosms

Phenanthrene (PHE) contamination not only changes the quality of soil environment but also threatens to the soil organisms. There is lack of focus on the eco-toxicity potential of this contaminant in real soil in the current investigation. Here, we assessed the toxic effects of PHE on earthworms (Eisenia fetida) in natural soil matrix. PHE exhibited a relatively high toxicity to E. fetida in natural soil, with the LC₅₀ determined to be 56.68 mg kg^-1 after a 14-day exposure. Excessive ROS induced by PHE, leading to oxidative damage to biomacromolecules in E. fetida, including lipid peroxidation, protein carbonylation, and DNA damage. The antioxidant defense system (total antioxidant capacity, glutathione S-transferase, peroxidase, catalase, carboxylesterase, and superoxide dismutase) in E. fetida responded quickly to scavenge excess ROS and free radicals. Exposure to PHE resulted in earthworm avoidance responses (2.5 mg kg^-1) and habitat function loss (10 mg kg^-1). Histological observations indicated that the intestine, body wall, and seminal vesicle in E. fetida were severely damaged after exposure to high-dose PHE. Moreover, earthworm growth (weight change) and reproduction (cocoon production and the number of juvenile) were also inhibited after exposure to this pollutant. Furthermore, the integrated toxicity of PHE toward E. fetida at different doses and exposure times was assessed by the integrated biomarker response (IBR), which confirmed that PHE is more toxic to earthworms in the high-dose and long-term exposure groups. Our results showed that PHE exposure induced oxidative stress, disturbed antioxidant defense system, and caused oxidative damage in E. fetida. These effects can trigger behavior changes and damage histological structure, finally cause growth inhibition, genotoxicity, and reproductive toxicity in earthworms. The strength of this study is the comprehensive toxicity evaluation of PHE to earthworms and highlights the need to investigate the eco-toxicity potential of exogenous environmental pollutants in a real soil environment.