Regulation of Paraquat for wheat crop contamination

Unveiling the ototoxic effects of paraquat on zebrafish larva

Paraquat is a widely utilized herbicide in agricultural fields posing a significant impact on human health and the environment due to its potent oxidant properties. Rampant paraquat usage leads to serious health hazards to farmers and the ecosystem, particularly the water bodies. Paraquat exposure can damage dopaminergic neurons causing Parkinson's disease in humans and other animal models. Extensive research has been done regarding the mode of action, pathophysiology and molecular mechanisms of paraquat-induced Parkinson's disease. Meanwhile, the ototoxic effect of paraquat remains poorly understood. Potential ototoxins can cause sensorineural hearing loss, one of the most common sensory disabilities in humans. In this study, we investigated the harmful effects of paraquat on neuromast hair cells in zebrafish larvae, a powerful model organism for auditory research. We treated sub-lethal concentrations (125 μM to 1000 μM) of paraquat to 3 and 4 dpf zebrafish larvae to investigate its ototoxic effects via rheotaxis behavioral assay, neuromast staining and scanning electron microscopy. The behavioral assay findings showed a drastic decline in the rheotaxis behavior in all the concentrations of paraquat-treated larvae. Furthermore, DASPEI neuromast vital staining displayed a dose-dependent reduction in the neuromast hair cells as we increased the paraquat concentration. The scanning electron microscope data revealed the significant shortening of kinociliary length, a decrease in stereociliary density and changes in semilunar peridermal cell morphology signifying the damaging effects of paraquat at the cellular level. Collectively, the behavioral, anatomical and morphological studies highlight the potential ototoxic effects of paraquat on zebrafish neuromast hair cells, further signifying its potential role in causing hearing loss in humans.

Multi-medium residues and ecological risk of herbicides in a typical agricultural watershed of the Mollisols region, Northeast China

The widespread use of herbicides impacts non-target organisms, promotes weed resistance, posing a serious threat to the global goal of green production in agriculture. Although the herbicide residues have been widely reported in individual environmental medium, their presence across different media has received scant attention, particularly in Mollisols regions with intensive agricultural application of herbicides. A systematic investigation was conducted in this study to clarify the occurrence of herbicide residues in soil, surface water, sediments, and grains from a typical agricultural watershed in the Mollisols region of Northeast China. Concentrations of studied herbicides ranged from 0.30 to 463.49 μg/kg in soil, 0.31-29.73 μg/kg in sediments, 0.006-1.157 μg/L in water, and 0.32-2.83 μg/kg in grains. Among these, Clomazone was the most priority herbicide detected in soil, sediments, and water, and Pendimethalin in grains. Crop types significantly affected the residue levels of herbicides in grains. Clomazone posed high ecological risks in soil and water, with 86.4 % of water samples showing high risks from herbicide mixtures (RQ > 1). These findings aid in enhancing our comprehension of the pervasive occurrence and potential ecological risks of herbicides in different media within typical agricultural watersheds, providing detailed data to inform the development of targeted mitigation strategies.

A potential mechanism clue to the periodic storm from microglia activation and progressive neuron damage induced by paraquat exposure

Paraquat (PQ), is characterized by neurotoxicity, which increases the potential risk of Parkinson's disease (PD) exposure in the long-term and low doses. Triggering microglia activation and neuroinflammation is deemed an early event resulting in PD. However, the underlying pathogenesis of PD by PQ is not clear yet. In this article, C57BL/6J mice treated with PQ could successfully act out Parkinson-like. In addition, we observed the fluorescence intensity enhancement of Iba-1 activated microglia with released pro-inflammatory, all ahead of both the damage of dopaminergic neurons in the substantia nigra and corpus striatum of the brain. Surprisingly, the injection of minocycline before PQ for many hours not only can effectively improve the neurobehavioral symptoms of mice but inhibit the activation of microglia and the release of pro-inflammatory substances, even controlling the gradual damage and loss of neurons. A further mechanism of minocycline hampered the expression levels of key signaling proteins PI3K, PDK1, p-AKT, and CD11b (the receptor of microglia membrane recognition), while a large number of inflammatory factors. Our results suggested that the CD11b/PI3K/NOX2 pathway may be a clue that microglia-mediated inflammatory responses and neuronal damage in a PQ-induced abnormal behavior Parkinson-like mouse.

Integrated physiological and metabolomic analysis reveals new insights into toxicity pathways of paraquat to Microcystis aeruginosa

Chemical pollutants, such as herbicides, released into the aquatic environment adversely affect the phytoplankton community structure. While majority of herbicides are specifically designed to target photosynthetic processes, they also can be toxic to phytoplankton; however, despite the photosynthetic toxicity, some herbicides can target multiple physiological processes. Therefore, a full picture of toxicity pathway of herbicide to phytoplankton is necessary. In the present study, the cyanobacterium Microcystis aeruginosa was exposed to two levels (17 μg L^-1 (EC₁₀) and 65 μg L^-1 (EC₅₀)) of paraquat for 72 h. The physiological and metabolic responses were analyzed to elucidate the toxicity pathway and establish the adverse outcome pathway of paraquat to M. aeruginosa. The results revealed that enhanced glycolysis (upregulation of pyruvic acid level) and tricarboxylic acid cycle (upregulation of the levels of malic acid, isocitric acid and citric acid) exposed to EC₁₀ level of paraquat, which probably acted as a temporary strategy to maintain a healthy energy status in M. aeruginosa cells. Meanwhile, the expressions of glutathione and benzoic acid were enhanced to scavenge the excessive reactive oxygen species (ROS). Additionally, the accumulation of pigments (chlorophyll a and carotenoid) might play a supplementary role in the acclimation to EC₁₀ level paraquat treatment. In cells exposed to paraquat by EC₅₀ level, the levels of SOD, CAT, glutathione and benzoic acid increased significantly; however, the ROS exceeded the tolerance level of antioxidant system in M. aeruginosa. The adverse effects were revealed by inhibition of chlorophyll a fluorescence, the decreases in several carbohydrates (e.g., glucose 1-phosphate, fructose and galactose) and total protein content. Consequently, paraquat-induced oxidative stress caused the growth inhibition of M. aeruginosa. These findings provide new insights into the mode of action of paraquat in M. aeruginosa.