Paraquat poisonings: mechanisms of lung toxicity, clinical features, and treatment

CT imaging as a prognostic indicator for patients with pulmonary injury from acute paraquat poisoning

OBJECTIVE

CT imaging may be an effective diagnostic method for assessing the extent and progression of pulmonary injury in patients with acute paraquat (PQ) poisoning.

METHODS

A retrospective review of 78 patients with acute PQ poisoning (survivor group, n=42; non-survivor group, n=36) was conducted to examine the lung segment involvement and CT image characteristics from baseline (first CT scan at a mean of 2.4 days after poisoning) to treatment time (second CT scan 3 days after the first). We examined the association between prognosis and pulmonary lesions indicated by characteristic effusion, fibrosis and consolidation in CT images.

RESULTS

Significant differences were apparent in CT images at baseline and after 3 days between the survivor and the non-survivor groups, with higher levels of pulmonary segment involvement, effusion, consolidation and fibrosis observed in the non-survivor group at baseline (p<0.05). The non-survivor group also showed rapid lesion progression. The receiver operating characteristic curve indicated that the best prognostic value of baseline CT scanning was achieved when performed 2-3 days following the initial exposure.

CONCLUSION

Prognosis correlated with increasing lung segment involvement, extent of disease characteristics visualised using CT and speed of lesion progression from baseline. Prognostic evaluation using CT scanning can be used to effectively provide earlier treatment for patients at risk for severe complications associated with PQ toxicity, such as acidosis; leukocytosis; and renal, hepatic and pancreatic failures.

ADVANCES IN KNOWLEDGE

Chest CT scan can be used 2-3 days following acute PQ poisoning to determine prognosis.

Environmental factors and unhealthy lifestyle influence oxidative stress in humans--an overview

Oxygen is the most essential molecule for life; since it is a strong oxidizing agent, it can aggravate the damage within the cell by a series of oxidative events including the generation of free radicals. Antioxidative agents are the only defense mechanism to neutralize these free radicals. Free radicals are not only generated internally in our body system but also trough external sources like environmental pollution, toxic metals, cigarette smoke, pesticides, etc., which add damage to our body system. Inhaling these toxic chemicals in the environment has become unavoidable in modern civilization. Antioxidants of plant origin with free radical scavenging properties could have great importance as therapeutic agents in several diseases caused by environmental pollution. This review summarizes the generation of reactive oxygen species and damage to cells by exposure to external factors, unhealthy lifestyle, and role of herbal plants in scavenging these reactive oxygen species.

The dose of cyclophosphamide for treating paraquat-induced rat lung injury

BACKGROUND/AIMS

Cyclophosphamide (CP) is a promising treatment for severe cases of paraquat (PQ) poisoning. We investigated the effective dose of CP for mitigating PQ-induced lung injury.

METHODS

Adult male Sprague-Dawley rats were allocated into five groups: control, PQ (35 mg/kg, intraperitoneal injection), and PQ + CP (1.5, 15, or 30 mg/kg). The dimensions of lung lesions were determined using X-ray microtomography (micro-CT), and histological changes and cytokine levels were recorded.

RESULTS

The micro-CT results showed that 15 mg/kg CP was more effective than 1.5 mg/kg CP for treating PQ-induced lung injury. At a dose of 1.5 mg/kg, CP alleviated the histological evidence of inflammation and altered superoxide dismutase activity. Using 15 mg/kg CP reduced the elevated catalase activity and serum transforming growth factor (TGF)-β1 level.

CONCLUSIONS

A CP dose of > 15 mg/kg is effective for reducing the severity of PQ-induced lung injury as determined by histological and micro-CT tissue examination, possibly by modulating antioxidant enzyme and TGF-β1 levels.

Paraquat-induced pulmonary fibrosis starts at an early stage of inflammation in rats

AIM

To investigate the starting point of paraquat-induced pulmonary fibrosis in rats.

MATERIALS & METHODS

A total of 96 healthy Sprague-Dawley rats were randomly divided into eight groups (n = 12 in each group) including a control and paraquat-poisoning group. Control rats received treatment with saline. Samples were collected at 2, 6, 12, 24, 48, 72 and 120 h after paraquat administered by lavage. All lung tissues were stained with hematoxylin-eosin and Masson's trichrome. Collagen III expressed in bronchoalveolar lavage fluid was detected by ELISA. The α-smooth muscle actin in lung tissue was detected by western blotting.

RESULTS

A rat model of paraquat poisoning was established. Histological examination results indicated that lung fibrosis started in rats 2 h after paraquat poisoning. Compared with the control group, the collagen III protein in bronchoalveolar lavage fluid was significantly upregulated in the 2-h group (α = 0.05) and the same level was maintained in the other poisoning groups. The expression of α-smooth muscle actin in the lung tissue was significantly increased in the 12-h group (α = 0.05) and remained at the same level after 12 h.

CONCLUSION

The paraquat-induced pulmonary fibrosis in rats began at an early stage of inflammation. The therapy of antifibrosis should be applied at an early time of paraquat poisoning.

Prognostic value of initial arterial lactate level and lactate metabolic clearance rate in patients with acute paraquat poisoning

OBJECTIVE

The aim of this study is to evaluate the prognostic value of initial arterial lactate level and 12-hour lactate metabolic clearance rate (MCR) in patients with acute paraquat poisoning.

METHODS

A total of 204 patients with acute paraquat poisoning were admitted to the Emergency Intensive Care Unit at The First Affiliated Hospital of China Medical University from January 2009 to December 2011.

RESULTS

The overall mortality rate was 72.5% (148/204) during a 28-day follow-up period; only 56 of 204 patients with acute paraquat poisoning survived. The initial arterial lactate level was higher in nonsurvivors than in survivors (P = .026). The 12-hour lactate MCR was lower in nonsurvivors than in survivors (P = .040). The initial arterial lactate level (P = .004) and 12-hour lactate MCR (P < .001) were associated with increased risk in 28-day mortality. In the receiver operating characteristic curve analysis, the initial arterial lactate level had an area of 0.749 (95% confidence interval, 0.714-0.856) and a cutoff concentration at 2.5 mmol/L (sensitivity = 84.6%, specificity = 79.2%, Youden index = 0.64). The 12-hour lactate MCR had an area of 0.871 (95% confidence interval, 0.807-0.935), and the cutoff was at 13.5% (sensitivity = 87.1%, specificity = 84.3%, Youden index = 0.71).

CONCLUSIONS

The initial arterial lactate level and 12-hour lactate MCR had good predictive powers in evaluating the prognosis of patients with acute paraquat poisoning, which may prove to be simpler and more practical tools in assessing the severity of paraquat poisoning.

Paraquat poisoning in pediatric patients

OBJECTIVE

This observational study examined the outcome of Taiwanese pediatric patients with paraquat poisoning and compared these data with the published data on paraquat poisonings from other international poisoning centers.

METHODS

We performed a retrospective study on children with acute paraquat poisoning that were admitted to the Chang Gung Memorial Hospital during a period of 10 years (2000-2010). Of the 193 paraquat poisoning patients, only 6 were children.

RESULTS

The mean age was 8.85 ± 5.55 (1-15.6) years. Younger patients had accidentally swallowed paraquat, whereas older patients had intentionally ingested paraquat. Most patients were referred within a relatively short period (0.5-2.0 hours). Paraquat poisoning was associated with high morbidity and often resulted in severe complications, including acute respiratory distress syndrome and multiple-organ failure. The complications included shock (50.0%), hypoxemia (33.3%), respiratory failure (33.3%), nausea/vomiting (16.7%), abdominal pain (33.3%), hepatitis (66.7%), gastrointestinal tract bleeding (33.3%), acute renal failure (33.3%), and seizures (16.7%). Patients were treated aggressively with a standard detoxification protocol consisting of gastric lavage, active charcoal, charcoal hemoperfusion, and cyclophosphamide and steroid pulse therapies. Secondary bacterial infections were common after hospitalization and included sepsis (33.3%), pneumonia (33.3%), and urinary tract infection (50.0%). In the end, 2 patients (33.3%) died from multiple-organ failure, despite intensive resuscitation.

CONCLUSIONS

Our data (mortality rate, 33.3%) are comparable to the data of other published reports from other international poison centers. Evidently, a prompt diagnosis of paraquat poisoning and an immediate institution of a detoxification protocol is a prerequisite for a favorable outcome.

New formulation of paraquat with lysine acetylsalicylate with low mammalian toxicity and effective herbicidal activity

BACKGROUND

Currently, the commercial formulations of the herbicide paraquat are highly toxic to humans, and no effective antidote is available for paraquat poisoning. The aim of the present study was to develop a safe formulation, combining paraquat and the known antidote lysine acetylsalicylate. The toxicity of a mixture of Gramoxone® (20% paraquat) and lysine acetylsalicylate in adult Wistar male rats and the herbicidal efficacy against grass lawn (50% of Poa pratensis and 50% of Festuca arundinacea) were evaluated. This new formulation was administered to Wistar rats by gavage at 125 mg kg(-1) of paraquat ion and lysine acetylsalicylate at 79, 158 or 316 mg kg(-1) body weight, and the survival rate was observed for 30 days.

RESULTS

The survival rate of the paraquat group was only 40%, while lysine acetylsalicylate provided effective protection, with full survival observed in the groups that received 125 mg kg(-1) of paraquat ion and 316 mg kg(-1) of lysine acetylsalicylate. Both formulations of paraquat, either in the absence or in the presence of lysine acetylsalicylate, provided the same herbicidal activity against the tested herbal species.

CONCLUSIONS

The present formulation of paraquat containing lysine acetylsalicylate, significantly decreases mammalian toxicity while maintaining effective herbicidal activity.

ARE-inducing phenol antioxidant TC-13 improves survival of Drosophila melanogaster in oxidative stress

The effects of hydrophilic synthetic antioxidant TC-13 sodium (3'-(3'-tert-butyl-4'-hydroxyphenyl)propylthiosulfonate on survival of various strains of Drosophila melanogaster were studied under conditions of oxidative stress induced with H(2)O(2)and paraquat. In a concentration of 1%, TC-13 significantly improved survival of Canton S males treated with H(2)O(2)and in a concentration of 0.2% it improved survival of H(2)O(2)-stressed Oregon R females. The protective effect of the antioxidant under conditions of paraquat-induced stress was observed in Canton S females and Oregon R flies of both genders. Addition of T-13 to diets led to prolongation of the maximum lifespan of insects in the majority of the experiment variants. A relationship between the protective effects of TC-13 and the genotype, gender, and environmental conditions was detected.

On the methodological limitations of detecting oxidative stress: effects of paraquat on measures of oxidative status in greenfinches

Oxidative stress (OS) is widely believed to be responsible for generation of trade-offs in evolutionary ecology by means of constraining investment into a number of components of fitness. Yet the progress in understanding the true role of OS in ecology and evolution has remained elusive. Interpretation of current findings is particularly hampered by the scarcity of experiments demonstrating which of the many available parameters of oxidative status respond most sensitively to and are relevant for measuring OS. We addressed these questions in wild-caught captive greenfinches (Carduelis chloris) by experimental induction of OS by administration of the pro-oxidant compound paraquat with drinking water. Treatment induced 50% of mortality and a significant drop in body mass and an increase in oxidative DNA damage and glutathione levels in erythrocytes among the survivors of the high paraquat (0.2 g/L during 7 days) group. Three days after the end of the treatment, paraquat had no effect on peroxidation of lipids (plasma malondialdehyde), carbonylation of proteins (in erythrocytes), parameters of plasma antioxidant protection (TAC and OXY), uric acid or carotenoids. Our findings of an increase in one marker of damage and one marker of protection from the multitude of measured variables indicate that detection of OS is difficult even under most stringent experimental induction of oxidative insult. We hope that this study highlights the need for reconsideration of over-simplistic models of OS and draws attention to the limitations of detection of OS due to time-lagged and hormetic up-regulation of protective mechanisms. This study also underpins the diagnostic value of measurement of oxidative damage to DNA bases and assessment of erythrocyte glutathione levels.

Enhanced expression of cystine/glutamate transporter in the lung caused by the oxidative-stress-inducing agent paraquat

In mammalian cultured cells, the activity of a cystine/glutamate transporter, designated System xc(-), has been shown to be essential for maintaining intracellular glutathione levels and the extracellular cystine/cysteine redox balance. The substrate-specific subunit of this transporter, xCT, is strongly induced by various stimuli, including oxidative stress, which suggests that xCT is one of the adaptive cellular defense systems against these types of stress. Embryonic fibroblasts from xCT-deficient mice fail to survive unless a cysteine precursor, N-acetylcysteine, is present. However, it is unclear whether xCT has similar functions in vivo because xCT-deficient mice are apparently normal. In this study, we investigated the phenotype of the xCT-deficient mice under paraquat-induced oxidative stress. At a paraquat dose of 45mg/kg, the survival rate of the xCT-deficient mice was significantly lower than that of the wild-type mice. Under this condition, total glutathione (the reduced form of glutathione (GSH)+the oxidized form of GSH) levels in the lungs of the xCT-deficient mice were lower than those in the lungs of the wild-type mice. Histopathological examinations showed that paraquat administration worsened the alveolar structure of the xCT-deficient mice compared with the wild-type mice. After paraquat treatment, obvious 8-hydroxy-2'-deoxyguanosine and 4-hydroxy-2-nonenal reactivity was detected in the lungs of the xCT-deficient mice. Although xCT expression was slightly detectable in the lungs of the normal wild-type mice, paraquat administration induced xCT mRNA expression in the lung. Constitutive expression of xCT mRNA was detected in alveolar macrophages isolated from the pulmonary lavage fluid of the wild-type mice, and paraquat administration strongly enhanced xCT mRNA expression in these cells. GSH levels in bronchoalveolar lavage fluid were significantly higher in the paraquat-treated wild-type mice than in the paraquat-treated xCT-deficient mice. These results suggest that xCT contributes to the maintenance of glutathione levels in lungs and the glutathione redox state as a protective system against paraquat toxicity in vivo.

Increased expression of SVCT2 in a new mouse model raises ascorbic acid in tissues and protects against paraquat-induced oxidative damage in lung

A new transgenic mouse model for global increases in the Sodium Dependent Vitamin C transporter 2 (SVCT2) has been generated. The SVCT2-Tg mouse shows increased SVCT2 mRNA levels in all organs tested and correspondingly increased ascorbic acid (ASC) levels in all organs except liver. The extent of the increase in transporter mRNA expression differed among mice and among organs. The increased ASC levels did not have any adverse effects on behavior in the SVCT2-Tg mice, which did not differ from wild-type mice on tests of locomotor activity, anxiety, sensorimotor or cognitive ability. High levels of SVCT2 and ASC were found in the kidneys of SVCT2-Tg mice and urinary albumin excretion was lower in these mice than in wild-types. No gross pathological changes were noted in kidneys from SVCT2-Tg mice. SVCT2 immunoreactivity was detected in both SVCT2 and wild-type mice, and a stronger signal was seen in tubules than in glomeruli. Six treatments with Paraquat (3x10 and 3x15 mg/kg i.p.) were used to induce oxidative stress in mice. SVCT2-Tg mice showed a clear attenuation of Paraquat-induced oxidative stress in lung, as measured by F(2)-isoprostanes. Paraquat also decreased SVCT2 mRNA signal in liver, lung and kidney in SVCT2-Tg mice.

Paraquat-induced convulsion and death: a report of five cases

Paraquat (PQ) is a potent toxicant for humans, and poisoning with PQ is associated with high mortality. Patients with severe PQ-induced poisoning may die of multiple organ failure involving the circulatory and respiratory systems. Death resulting from epilepsy-like convulsions, which are infrequently noted reported with PQ poisoning, is observed clinically with this condition. This study presents the clinical data of five patients with severe PQ-induced poisoning who died of epilepsy-like convulsions, and related publications were reviewed in order to investigate the pathogenesis, clinical manifestations, and prognosis of these convulsions. Our results may help prevent this event and improve the success of treatment.

Quantification of paraquat in postmortem samples by gas chromatography-ion trap mass spectrometry and review of the literature

Paraquat (PQ) is an herbicide implicated in numerous fatalities, mainly caused by voluntary ingestion. Several methods have been used to quantify PQ in plasma and urine samples of intoxicated humans as a predictor of clinical outcome. There is no validated method for the analysis of PQ in postmortem samples. Therefore, the aim of this study was to develop an analytical method, using gas chromatography-ion trap mass spectrometry (GC-IT/MS) after solid-phase extraction, to quantify PQ in postmortem samples, namely in whole blood, urine, liver, lung and kidney, to cover the routes of distribution, accumulation and elimination of PQ. The method proved to be selective as there were no interferences of endogenous compounds with the same retention time as PQ and ethyl paraquat (internal standard). The regression analysis for PQ was linear in the range 0-10 µg/mL. The detection limits ranged from 0.0076 µg/mL for urine to 0.047 µg/mL for whole blood, and the recoveries were suitable for forensic analysis. The proposed GC-IT/MS method provided an accurate and simple assay with adequate precision and recovery for the quantification of PQ in postmortem samples. The proof of applicability was performed in two fatal PQ intoxications. A review of the analytical methods for the determination of quaternary ammonium herbicides is also provided for a better understanding of the presently available techniques.

The role of pentraxin-3 as a prognostic biomarker in paraquat poisoning

Paraquat poisoning has been a public health problem in both the developing and developed countries. Pentraxin 3 is a member of the pentraxin family which is expressed as part of the acute-phase response that begins after injury, trauma, and infection. The aim of our study is to determine whether PTX3 levels can be a significant marker of pulmonary fibrosis and outcome of survival in paraquat poisoning. To measure the plasma paraquat level, we collected serum of the patients immediately after admission. EDTA plasma samples for checking the plasma PTX3 concentration were taken before and after the 1st hemoperfusion and after the 2nd hemoperfusion therapy. PTX3 concentrations in EDTA plasma were determined using a commercial solid-phase enzyme-linked immunosorbent assay (ELISA). Plasma paraquat concentration was higher in survivors than in non-survivors (p<0.05). Maximal plasma PTX3 level was significantly higher in the pulmonary fibrosis group, and plasma PTX3 was significantly increased throughout hemoperfusion therapy (p<0.01). Moreover, increase in PTX3 was greater in non-survivors than survivors (p<0.05). Our results show that PTX3 is a useful biomarker of severity and outcome predictor in paraquat poisoning.

Simple and sensitive liquid chromatography-tandem mass spectrometry methods for quantification of paraquat in plasma and urine: application to experimental and clinical toxicological studies

Simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods have been developed and validated for quantification of paraquat (PQ) in plasma and urine. Plasma and urine sample preparation were carried out by one-step protein precipitation using cold acetonitrile (-20 to -10 °C). After centrifugation, an aliquot of 10 μL of supernatant was injected into a Kinetex™ hydrophilic interaction chromatography (HILIC) column with a KrudKatcher™ Ultra in-line filter. The chromatographic separation was achieved using the mobile phase mixture of 250 mM ammonium formate (with 0.8% aqueous formic acid) in water and acetonitrile at a flow rate of 0.3 mL/min. Detection was performed using an API2000 triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode via an electrospray ionization (ESI) source. The calibration curve was linear over the concentration range of 10-5000 ng/mL, with an LLOQ of 10 ng/mL. The inter- and intra-day precision (% R.S.D.) were <8.5% and 6.4% for plasma and urine, respectively with the accuracies (%) within the range of 95.1-102.8%. PQ in plasma and urine samples was stable when stored at -70 °C for three freeze-thaw cycles. The methods were successfully applied to determine PQ concentration in rat and human samples.

The protective effect of C-phycocyanin on paraquat-induced acute lung injury in rats

To investigate the potential protective effect of C-phycocyanin (PC) on paraquat (PQ)-induced acute lung injury, rats were divided into control, PQ-treated and PQ+PC-treated groups. Rats in PQ-treated group were orally administered with 50mg/kg PQ, and rats in PQ+PC-treated group were intraperitoneally injected with 50mg/kg PC after administration of PQ. At 8, 24, 48 and 72h after treatments, GSH-Px and SOD activities, MDA levels in plasma and BALF, HYP, NF-κB, IκB-α and TNF-α contents in lung tissues were measured. The pathological changes in lung were observed. After treatment with PC, the levels of MDA and the relative contents of NF-κB and TNF-α were significantly decreased, the activities of GSH-Px and SOD and the relative contents of IκB-α were significantly increased. The degree of rat lung damage was obviously reduced in PQ+PC-treated group. The results suggested that PC treatment significantly attenuated PQ-induced acute lung injury.

Inhibition of myotube formation by paraquat in the myoblast cell line C2C12

Paraquat (PQ) is one of the most frequently used pesticides in worldwide. In most countries, PQ is used without restrictions. To investigate the effect of PQ on myogenesis, cultures of C2C12, a useful model to study differentiation of myoblasts into myotubes, were exposed to various concentrations of PQ. Myotube formation did not occur in the presence of 50 µM PQ. Although cell death was not observed at this concentration, growth inhibition was evident in the growth medium. Production of myosin heavy chain, a myogenesis marker protein, decreased dose dependently with the concentration of PQ, which was added to the C2C12 cell culture during differentiation. Inhibition of myogenesis by PQ was not reversed by the addition of ascorbic acid. These results show that PQ is a strong inhibitor of muscle differentiation in vitro.

Wld(S) reduces paraquat-induced cytotoxicity via SIRT1 in non-neuronal cells by attenuating the depletion of NAD

Wld^S is a fusion protein with NAD synthesis activity, and has been reported to protect axonal and synaptic compartments of neurons from various mechanical, genetic and chemical insults. However, whether Wld^S can protect non-neuronal cells against toxic chemicals is largely unknown. Here we found that Wld^S significantly reduced the cytotoxicity of bipyridylium herbicides paraquat and diquat in mouse embryonic fibroblasts, but had no effect on the cytotoxicity induced by chromium (VI), hydrogen peroxide, etoposide, tunicamycin or brefeldin A. Wld^S also slowed down the death of mice induced by intraperitoneal injection of paraquat. Further studies demonstrated that Wld^S markedly attenuated mitochondrial injury including disruption of mitochondrial membrane potential, structural damage and decline of ATP induced by paraquat. Disruption of the NAD synthesis activity of Wld^S by an H112A or F116S point mutation resulted in loss of its protective function against paraquat-induced cell death. Furthermore, Wld^S delayed the decrease of intracellular NAD levels induced by paraquat. Similarly, treatment with NAD or its precursor nicotinamide mononucleotide attenuated paraquat-induced cytotoxicity and decline of ATP and NAD levels. In addition, we showed that SIRT1 was required for both exogenous NAD and Wld^S-mediated cellular protection against paraquat. These findings suggest that NAD and SIRT1 mediate the protective function of Wld^S against the cytotoxicity induced by paraquat, which provides new clues for the mechanisms underlying the protective function of Wld^S in both neuronal and non-neuronal cells, and implies that attenuation of NAD depletion may be effective to alleviate paraquat poisoning.

Severe paraquat poisoning: clinical and radiological findings in a survivor

Paraquat is a nonselective contact herbicide of great toxicological importance, being associated with high mortality rates, mainly due to respiratory failure. We report the case of a 22-year-old male admitted to the emergency room with a sore throat, dysphagia, hemoptysis, and retrosternal pain after the ingestion of 50 mL of a paraquat solution, four days prior to admission. Chest CT scans revealed pulmonary opacities, pneumomediastinum, pneumothorax, and subcutaneous emphysema. The patient was submitted to two cycles of immunosuppressive therapy with cyclophosphamide, methylprednisolone, and dexamethasone. The pulmonary gas exchange parameters gradually improved, and the patient was discharged four weeks later. The clinical and tomographic follow-up evaluations performed at four months after discharge showed that there had been further clinical improvement. We also present a brief review of the literature, as well as a discussion of the therapeutic algorithm for severe paraquat poisoning.

Feasibility Assessment of Micro-Electrode Chip Assay as a Method of Detecting Neurotoxicity in vitro

Detection and characterization of chemically induced toxic effects in the nervous system represent a challenge for the hazard assessment of chemicals. In vivo, neurotoxicological assessments exploit the fact that the activity of neurons in the central and peripheral nervous system has functional consequences. And so far, no in vitro method for evaluating the neurotoxic hazard has yet been validated and accepted for regulatory purpose. The micro-electrode array (MEA) assay consists of a culture chamber into which an integrated array of micro-electrodes is capable of measuring extracellular electrophysiology (spikes and bursts) from electro-active tissues. A wide variety of electrically excitable biological tissues may be placed onto the chips including primary cultures of nervous system tissue. Recordings from this type of in vitro cultured system are non-invasive, give label free evaluations and provide a higher throughput than conventional electrophysiological techniques. In this paper, 20 substances were tested in a blinded study for their toxicity and dose-response curves were obtained from fetal rat cortical neuronal networks coupled to MEAs. The experimental procedure consisted of evaluating the firing activity (spiking rate) and modification/reduction in response to chemical administration. Native/reference activity, 30 min of activity recording per dilution, plus the recovery points (after 24 h) were recorded. The preliminary data, using a set of chemicals with different mode-of-actions (13 known to be neurotoxic, 2 non-neuroactive and not toxic, and 5 non-neuroactive but toxic) show good predictivity (sensitivity: 0.77; specificity: 0.86; accuracy: 0.85). Thus, the MEA with a neuronal network has the potency to become an effective tool to evaluate the neurotoxicity of substances in vitro.

Redox cycling and increased oxygen utilization contribute to diquat-induced oxidative stress and cytotoxicity in Chinese hamster ovary cells overexpressing NADPH-cytochrome P450 reductase

Diquat and paraquat are nonspecific defoliants that induce toxicity in many organs including the lung, liver, kidney, and brain. This toxicity is thought to be due to the generation of reactive oxygen species (ROS). An important pathway leading to ROS production by these compounds is redox cycling. In this study, diquat and paraquat redox cycling was characterized using human recombinant NADPH-cytochrome P450 reductase, rat liver microsomes, and Chinese hamster ovary (CHO) cells constructed to overexpress cytochrome P450 reductase (CHO-OR) and wild-type control cells (CHO-WT). In redox cycling assays with recombinant cytochrome P450 reductase and microsomes, diquat was 10-40 times more effective at generating ROS compared to paraquat (K(M)=1.0 and 44.2μM, respectively, for H(2)O(2) generation by diquat and paraquat using recombinant enzyme, and 15.1 and 178.5μM, respectively for microsomes). In contrast, at saturating concentrations, these compounds showed similar redox cycling activity (V(max)≈6.0nmol H(2)O(2)/min/mg protein) for recombinant enzyme and microsomes. Diquat and paraquat also redox cycle in CHO cells. Significantly more activity was evident in CHO-OR cells than in CHO-WT cells. Diquat redox cycling in CHO cells was associated with marked increases in protein carbonyl formation, a marker of protein oxidation, as well as cellular oxygen consumption, measured using oxygen microsensors; greater activity was detected in CHO-OR cells than in CHO-WT cells. These data demonstrate that ROS formation during diquat redox cycling can generate oxidative stress. Enhanced oxygen utilization during redox cycling may reduce intracellular oxygen available for metabolic reactions and contribute to toxicity.

Therapeutic hypothermia attenuates acute lung injury in paraquat intoxication in rats

AIM OF THE STUDY

Paraquat intoxication induces acute lung injury and numerous fatalities have been reported. The mechanism of toxic effect of paraquat is oxidative injury and inflammation. Therapeutic hypothermia has been known to have antioxidant and anti-inflammatory effects. This study was designed to evaluate the effect of therapeutic hypothermia on paraquat intoxication.

METHODS

Male Sprague-Dawley rats were given 50 mg/kg of paraquat intraperitoneally and divided into the normothermia (36-38°C) group and the hypothermia (30-32°C) group after 1h of paraquat administration. The hypothermia group underwent 2 h of hypothermia followed by 2 h of rewarming. In the survival study, mortality was observed for 24 h after paraquat administration. An in the second experiment, lung tissues and plasma were harvested at 6 h after paraquat administration.

RESULTS

The 12 h survival rate was significantly higher in the hypothermia group than in the normothermia group (100% vs. 50%, p<0.05), but survival rates for 24 h were not different. Acute lung injury score was lower in the hypothermia group than in the normothermia group (p<0.05). Thmalondialdehyde contents of lung tissues, plasma interleukin-6 and nitrite/nitrate concentrations were significantly decreased in the HT group compared to the NT group (p<0.05).

CONCLUSION

Therapeutic hypothermia delayed early mortality and attenuated acute lung injury in paraquat intoxication.

Saturated hydrogen saline protects rats from acute lung injury induced by paraquat

BACKGROUND

Paraquat (PQ) intoxication causes lung oxidative stress damage. Saturated hydrogen saline, a newly explored antioxidant, has been documented to play a powerful antioxidant role in preventing oxidative stress damage. This study aimed to investigate the protective effects and the possible mechanisms of intoxication on rats with acute lung injury (ALI) caused by paraquat poisoning.

METHODS

Thirty PQ poisoned rats were randomly divided into a PQ intoxication group (intoxication group), a saturated hydrogen saline intervention group (intervention group), and a control group, with 10 rats in each group. The first two groups accepted an intragastric administration of PQ at a dose of 50 mg/kg for every single rat, and the control group was fed with a same volume of normal saline. Five mL/kg of saturated hydrogen saline was given to the intervention group three times a day by peritoneal injection for three days after intoxication. Arterial blood gas was detected on the third day. The rats were executed and their lungs were taken for measurement of wet dry weight ratio, homogenate malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OhdG). Histological changes of the lungs were also observed.

RESULTS

Compared with the control group, the intoxication group had more serious hypoxemia, greater wet/dry weight ratio, higher MDA level, higher expression of 8-OhdG and more severe lung damage (P<0.01 or P<0.05). However, after intervention with saturated hydrogen saline, poisoned animals turned to have lighter hypoxemia, smaller wet/dry weight ratio, lower MDA level, lower expression of 8-OhdG, and milder lung damage (P<0.01 or P<0.05).

CONCLUSIONS

Saturated hydrogen saline is effective in preventing acute lung injury caused by PQ. Possibly, it can neutralize toxic oxygen radicals selectively and alleviate the oxidative stress injury induced by PQ.

Reactive Oxygen Species and Aging in Caenorhabditis elegans: Causal or Casual Relationship?

The free radical theory of aging proposes a causal relationship between reactive oxygen species (ROS) and aging. While it is clear that oxidative damage increases with age, its role in the aging process is uncertain. Testing the free radical theory of aging requires experimentally manipulating ROS production or detoxification and examining the resulting effects on lifespan. In this review, we examine the relationship between ROS and aging in the genetic model organism Caenorhabditis elegans, summarizing experiments using long-lived mutants, mutants with altered mitochondrial function, mutants with decreased antioxidant defenses, worms treated with antioxidant compounds, and worms exposed to different environmental conditions. While there is frequently a negative correlation between oxidative damage and lifespan, there are many examples in which they are uncoupled. Neither is resistance to oxidative stress sufficient for a long life nor are all long-lived mutants more resistant to oxidative stress. Similarly, sensitivity to oxidative stress does not necessarily shorten lifespan and is in fact compatible with long life. Overall, the data in C. elegans indicate that oxidative damage can be dissociated from aging in experimental situations.

Collection of biological samples in forensic toxicology

Forensic toxicology is the study and practice of the application of toxicology to the purposes of the law. The relevance of any finding is determined, in the first instance, by the nature and integrity of the specimen(s) submitted for analysis. This means that there are several specific challenges to select and collect specimens for ante-mortem and post-mortem toxicology investigation. Post-mortem specimens may be numerous and can endow some special difficulties compared to clinical specimens, namely those resulting from autolytic and putrefactive changes. Storage stability is also an important issue to be considered during the pre-analytic phase, since its consideration should facilitate the assessment of sample quality and the analytical result obtained from that sample. The knowledge on degradation mechanisms and methods to increase storage stability may enable the forensic toxicologist to circumvent possible difficulties. Therefore, advantages and limitations of specimen preservation procedures are thoroughfully discussed in this review. Presently, harmonized protocols for sampling in suspected intoxications would have obvious utility. In the present article an overview is given on sampling procedures for routinely collected specimens as well as on alternative specimens that may provide additional information on the route and timing of exposure to a specific xenobiotic. Last, but not least, a discussion on possible bias that can influence the interpretation of toxicological results is provided. This comprehensive review article is intented as a significant help for forensic toxicologists to accomplish their frequently overwhelming mission.

Molecular mechanisms of pesticide-induced neurotoxicity: Relevance to Parkinson's disease

Pesticides are widely used in agricultural and other settings, resulting in continued human exposure. Pesticide toxicity has been clearly demonstrated to alter a variety of neurological functions. Particularly, there is strong evidence suggesting that pesticide exposure predisposes to neurodegenerative diseases. Epidemiological data have suggested a relationship between pesticide exposure and brain neurodegeneration. However, an increasing debate has aroused regarding this issue. Paraquat is a highly toxic quaternary nitrogen herbicide which has been largely studied as a model for Parkinson's disease providing valuable insight into the molecular mechanisms involved in the toxic effects of pesticides and their role in the progression of neurodegenerative diseases. In this work, we review the molecular mechanisms involved in the neurotoxic action of pesticides, with emphasis on the mechanisms associated with the induction of neuronal cell death by paraquat as a model for Parkinsonian neurodegeneration.

The efficacy of high doses of vitamin C in patients with paraquat poisoning

Paraquat (PQ) poisoning is an extremely difficult condition to manage clinically because of the lack of effective treatments. The purpose of this study was to assess the effect of high doses of vitamin C in combination with anti-inflammatory and immunosuppressant therapy in patients with PQ poisoning. The medical records of 134 patients who presented to the emergency department within 24 hours after PQ poisoning were reviewed retrospectively. The 57 patients presented between January 2004 and September 2005 were group 1; they received pulse therapy, which included cyclophosphamide and methylprednisolone, followed by the administration of dexamethasone over 2 weeks. The 77 patients that presented between October 2005 and January 2008 were group 2; they received the above-mentioned therapy and high-dose vitamin C for 2 weeks. There was no difference in the distribution of baseline variables between the 2 groups. However, group 2 showed a significant reduction in acute kidney injury related to PQ. Furthermore, a multivariate logistic regression analysis showed that the addition of vitamin C to the treatment was significantly associated with an increased survival of the patients. Larger trials will be needed to verify the effect of high-dose vitamin C on survival in patients with PQ poisoning.