Effects of dietary supplementation with glutamate and aspartate on diquat-induced oxidative stress in piglets

This study aimed to investigate the protective effects of dietary glutamate and aspartate supplementations on diquat-induced oxidative stress in piglets. Diquat injection significantly reduced growth performance, including body weight, average daily weight gain, and feed intake (P<0.05). Meanwhile, diquat administration induced oxidative stress evidenced by the decreased serum nitric oxide (NO) and elevated malondialdeyhde (MDA) concentration (P<0.05). Furthermore, diquat-induced oxidative stress disrupted intestinal absorption system and decreased serum threonine, serine, and glycine levels. Dietary supplementation with glutamate improved final body weight, antioxidant system, and expressions of amino acids transporters and enhanced serum glutamate concentration compared with diquat group (P<0.05). While aspartate failed to alleviate diquat-induced oxidative stress, growth depression, and dysfunction of nutrients absorption except for liver relative weight. In conclusion, dietary supplementation with glutamate confers beneficial effects on diquat-induced oxidative stress in piglets, while aspartate exhibits little effects.

Nrf2 regulates an adaptive response protecting against oxidative damage following diquat-mediated formation of superoxide anion

Mouse embryonic fibroblasts derived from Nrf2-/- mice (N0) and Nrf2+/+ mice (WT) have been used to characterize both basal and diquat (DQ)-induced oxidative stress levels and to examine Nrf2 activation during exposure to DQ-generated superoxide anion. Microarray analysis revealed that N0 cells have similar constitutive mRNA expression of genes responsible for the direct metabolism of reactive oxygen species but decreased expression of genes responsible for the production of reducing equivalents, repair of oxidized proteins and defense against lipid peroxidation, compared to WT cells. Nonetheless, the basal levels of ROS flux and oxidative damage biomarkers in WT and N0 cells were not different. Diquat dibromide (DQ), a non-electrophilic redox cycling bipyridylium herbicide, was used to generate intracellular superoxide anion. Isolated mitochondria from both cell lines exposed to DQ produced equivalent amounts of ROS, indicating a similar cellular capacity to generate ROS. However, N0 cells exposed to DQ for 24-h exhibited markedly decreased cell viability and aconitase activity as well as increased lipid peroxidation and glutathione oxidation, relative to WT cells. 2',7'-Dichlorofluorescein fluorescence was not increased in WT and N0 cells after 30-min of DQ exposure. However, increased levels of ROS were detected in N0 cells but not WT cells after 13-h of DQ treatment. Additionally, total glutathione concentrations increased in WT, but not N0 cells following a 24-h exposure to DQ. DQ exposure resulted in activation of an antioxidant response element-luciferase reporter gene, as well as induction of Nrf2-regulated genes in WT, but not N0 cells. Thus the enhanced sensitivity of N0 cells does not reflect basal differences in antioxidative capacity, but rather an impaired ability to mount an adaptive response to sustained oxidative stress.

Diquat poisoning of dairy cattle by topical application

This case report describes poisoning of dairy cattle from a dermal challenge of 50 to 100 mg/kg body weight diquat. Five of 36 cattle exposed, demonstrated clinical signs of intoxication, dehydration, and death over 5 days. Diquat poisoning of cattle by the dermal route has not previously been reported.

Chronic ingestion of a potential food contaminant induces gastrointestinal inflammation in rats: role of nitric oxide and mast cells

Chronic ingestion of xenobiotics could be pathogenic in the gastrointestinal tract. Recently, we showed that acute low administration of a food contaminant (diquat) induced intestinal secretion involving mast cells and nitric oxide. This work aimed to determine in rats: (1) the influence of a low level (0.1 mg/kg/day per os) chronic ingestion of diquat on gastrointestinal immune cells, and (2) the participation of nitric oxide synthases (NOS) in these effects. Diquat increased both gastric and jejunal myeloperoxidase activities, tissue histamine in vitro release after stimulation by 48/80, and mast cell numbers. Diquat did not alter gastric NOS but increased intestinal inducible NOS (iNOS) activity. L-NAME prevented diquat-induced gastric and intestinal mastocytosis and gastric but not intestinal inflammation. L-NAME reduced gastric constitutive NOS (cNOS) activity and reestablished control iNOS activity. Chronic low level ingestion of diquat induces a low-grade gastric and intestinal inflammation with mastocytosis and enhancement of intestinal iNOS activity.

Vaginally applied diquat intoxication

CASE REPORT

We report the case of a woman who introduced 20 mL of diquat concentrate intravaginally. Abdominal pain, vomiting, diarrhea, burning chest pains, and somnolence appeared within the first 24 hours. The vulva and vagina were corrosively inflamed. Acute renal failure appeared on the third day and was treated by 6 hemodialyses over 6 days. The patient was dysarthric with spastic tetraparesis for 3 months. The electroencephalogram, diffusely slow on day 3, was normal on day 28. The electromyoneurogram was normal at all times. Biopsy of a peripheral nerve performed on day 57 following intoxication showed no myelin or axonal alterations.

Lung fibrosis induced by diquat after intratracheal administration

Diquat toxicity to lung was evaluated at various intervals after intratracheal administration to rats. Twelve hours after the injection, both type I and type II pneumocytes developed degenerative changes which were similar in nature to those induced by paraquat. A much larger dose of diquat, however, was needed for the changes compared to paraquat, which is known to be actively taken up by the lung. This morphological evidence suggests that diquat may cause alveolar damage by the same mechanism as paraquat, although it is not actively taken up by the lung. Moreover, initial alveolar damage induced by diquat was followed by lung fibrosis, as with paraquat. Since paraquat is a well known fibrogenic agent, the common property of these two agents in alveolar damage may be a key to interpreting the development of lung fibrosis.

Biliary excretion of glutathione and glutathione disulfide in the rat. Regulation and response to oxidative stress

Regulation of the biliary excretion of reduced glutathione (GSH) and glutathione disulfide (GSSG) and responses to selected model toxins were examined in male Sprague-Dawley rats. In control and phenobarbital-pretreated rats in which the intrahepatic concentration of GSH was modulated by the administration of diethyl maleate or acetaminophen, the biliary concentration of GSH was consistently lower than, but directly proportional to, the intrahepatic concentration of GSH. Furthermore, increments in bile flow produced by the infusion of sulfobromophthalein (BSP)-glutathione were associated with proportional increases in the biliary excretion of GSH, suggesting that GSH passes into bile passively along a concentration gradient. In contrast, GSSG appears to be secreted into bile against a steep concentration gradient. An increased hepatic production and biliary excretion of GSSG resulted from the administration of t-butyl hydroperoxide. Measurement of biliary GSSG and BSP during a constant infusion of the GSH adduct of BSP indicated that GSSG shares a common excretory mechanism with GSH adducts. Diquat, nitrofurantoin, and paraquat also markedly stimulated the biliary excretion of GSSG. On a molar basis, these compounds generated much more GSSG than a direct substrate for glutathione peroxidase such as t-butyl hydroperoxide, indicating that the compounds undergo redox-cycling with concomitant production of hydrogen peroxide. Aminopyrine (0.8 mmol/kg) also significantly increased biliary GSSG. This increase, however, was associated with a proportional increase in bile flow and in the biliary excretion of GSH such that the GSSG/GSH ratio in bile did not change. Acetaminophen and chloroform, two compounds generating electrophilic metabolites that deplete intrahepatic GSH, led to a progressive decrease in the biliary excretion of GSH and GSSG. Furosemide and dimethylnitrosamine, the electrophilic metabolites of which do not deplete hepatic GSH, minimally altered biliary GSH and GSSG. Similarly, carbon tetrachloride and iproniazid, which yield organic radical metabolites that can peroxidize membrane lipids, did not increase the biliary excretion of GSSG. This finding indicates that membrane-bound lipid hydroperoxides may not be good substrates for glutathione peroxidases. The measurement of the biliary excretion of GSSG and of the GSSG/GSH ratio in bile is a sensitive index of oxidative stress in vivo and thus complements other in vivo parameters for the study of reactive intermediates of xenobiotics such as the determination of covalent binding, the formation of lipid hydroxy acids, and the depletion of intracellular GSH.

Recovery from inhalation of diquat aerosol

A patient developed high fever, cough, changing consolidations on chest roentgenograms, jaundice, and skin rash following inhalation of diquat aerosol. To our knowledge this is the first report of diquat inhalation and only the second report of aerosol damage from any part of the dipyridyl herbicides.