Mitochondrial dysfunction from malathion and chlorpyrifos exposure is associated with degeneration of GABAergic neurons in Caenorhabditis elegans

6-PPD quinone at environmentally relevant concentrations induced damage on longevity in C. elegans: Mechanistic insight from inhibition in mitochondrial UPR response

6-PPD quinone (6-PPDQ) exists widely in water environment media, causing acute lethality to some aquatic species. Long-term exposure to 6-PPDQ reduced the lifespan of Caenorhabditis elegans. However, the molecular basis for mitochondrial control of 6-PPDQ toxicity remains largely unclear. Using HSP-6 as marker of mitochondrial unfolded protein response (mt UPR), we observed activation of mt UPR by 0.1 and 1 μg/L 6-PPDQ and inhibition in mt UPR by 10 μg/L 6-PPDQ. Additionally, increased atfs-1, ubl-5, and dve-1 expressions were caused by 0.1 and 1 μg/L 6-PPDQ and decreased expressions of these genes were induced by 10 μg/L 6-PPDQ. Neuronal and intestinal RNA interference (RNAi) of hsp-6 caused susceptibility to 6-PPDQ toxicity on longevity, and atfs-1, ubl-5, and dve-1 acted in neurons and intestine to modulate mt UPR and 6-PPDQ toxicity on longevity. Meanwhile, 6-PPDQ (1 and 10 μg/L) increased expressions of histone methyltransferase genes met-2 and set-6, and decreased expressions of histone demethylase genes jmjd-1.2 and jmjd-3.1. Neuronal RNAi of set-6 and intestinal RNAi of met-2 accelerated hsp-6, atfs-1, ubl-5, and dve-1 expressions and extended lifespan of 6-PPDQ exposed nematodes. In contrast, neuronal RNAi of jmjd-1.2 and jmjd-3.1 and intestinal RNAi of jmjd-1.2 suppressed these 4 gene expressions and reduced lifespan of 6-PPDQ exposed nematodes o. In nematodes, RNAi of hsp-6 could also enhance mitochondrial dysfunction and mitochondrial reactive oxygen species (ROS) induced by 6-PPDQ. Therefore, 6-PPDQ caused damage on longevity was associated with suppression in mt UPR, which was under regulation of certain histone methylation related signals.

Combinational exposure to hydroxyatrazine increases neurotoxicity of polystyrene nanoparticles on Caenorhabditis elegans

Using Caenorhabditis elegans as an animal model, we investigated combinational effect between 2-hydroxyatrazine (HA) and polystyrene nanoparticle (PS-NP) on function and development of D-type motor neurons. Exposure to HA (10 and 100 μg/L) alone caused decreases in body bend, head thrash, and forward turn and increase in backward turn. Exposure to 100 μg/L HA also caused neurodegeneration of D-type motor neurons. Moreover, combinational exposure to HA (0.1 and 1 μg/L) induced enhancement in PS-NP (10 μg/L) toxicity in inhibiting body bend, head thrash, and forward turn, and in increasing backward turn. In addition, combinational exposure to HA (1 μg/L) could result in neurodegeneration of D-type motor neurons in PS-NP (10 μg/L) exposed nematodes. Combinational exposure to HA (1 μg/L) and PS-NP (10 μg/L) increased expressions of crt-1, itr-1, mec-4, asp-3, and asp-4, which govern the induction of neurodegeneration. Moreover, combinational exposure to HA (0.1 and 1 μg/L) strengthened PS-NP (10 μg/L)-induced decreases in glb-10, mpk-1, jnk-1, and daf-7 expressions, which encode neuronal signals regulating response to PS-NP. Therefore, our results demonstrated the effect of combinational exposure to HA and nanoplastics at environmentally relevant concentrations in causing toxic effect on nervous system in organisms.

Ecological threat caused by malathion and its chiral metabolite in a honey bee-rape system: Stereoselective exposure risk and the mechanism revealed by proteome

Honey bees play an important role in the ecological environment. Regrettably, a decline in honey bee colonies caused by chemical insecticides has occurred throughout the world. Potential stereoselective toxicity of chiral insecticides may be a hidden source of danger to bee colonies. In this study, the stereoselective exposure risk and mechanism of malathion and its chiral metabolite malaoxon were investigated. The absolute configurations were identified using an electron circular dichroism (ECD) model. Ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used for chiral separation. In pollen, the initial residues of malathion and malaoxon enantiomers were 3571-3619 and 397-402 μg/kg, respectively, and R-malathion degraded relatively slowly. The oral LD₅₀ values of R-malathion and S-malathion were 0.187 and 0.912 μg/bee with 5 times difference, respectively, and the malaoxon values were 0.633 and 0.766 μg/bee. The Pollen Hazard Quotient (PHQ) was used to evaluate exposure risk. R-malathion showed a higher risk. An analysis of the proteome, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and subcellular localization, indicated that energy metabolism and neurotransmitter transport were the main affected pathways. Our results provide a new scheme for the evaluation of the stereoselective exposure risk of chiral pesticides to honey bees.