Further studies of lipid peroxidation in human paraquat poisoning

Ingestion poisoning related lung injury- a pictorial review

Poison ingestion is a medical emergency requiring immediate care in the emergency department. Respiratory symptoms with ingested poisons can occur due to aspiration, cardiopulmonary effects, or direct lung toxicity due to injury of the alveolar epithelium. Chest imaging (chest radiographs/CT) is usually performed in the emergency setting to evaluate such symptoms. It is often impossible to elicit the nature of the poison ingested by the patients due to their unconscious state. Identification of the culprit poison can expedite the patient's management towards a specific antidote or help understand the underlying mechanism causing the pulmonary symptoms. The imaging manifestations depend on the underlying mechanisms, varying for each ingested poison, forming an imaging signature which has not been adequately discussed in existing literature. Poisons like paraquat and organophosphate are important to differentiate as indiscriminate use of oxygen therapy in the former can exacerbate the lung injury caused by redox cycling. In this pictorial assay, we present the chest imaging spectrum of commonly ingested poisons, and further suggest algorithmic approach towards identification of common poisons based on their chest imaging.

Transplantation of endothelial progenitor cells attenuated paraquat-induced acute lung injury via miR-141-3p-Notch-Nrf2 axis

Background

Paraquat (PQ) presents with high toxicity for humans and animals, and the lungs become the main target organ by the poisoning of PQ leading to acute lung injury. Endothelial progenitor cells (EPCs) were proved to have the repair function on acute lung injury (ALI). We aimed to invatigate the underlying mechanism of EPCs in PQ-induced ALI involving miR-141-3p.

Methods

Endothelial progenitor cells were isolated from peripheral blood of C57BL/6J mice and identified by flow cytometry. Lung wet-to-dry (W/D) weight ratios, lung injury score and the number of total leukocyte and the number of neutrophils in BALF were used to analyze the degree of lung injury. The transfection was performed with Lipofectamine 2000. The levels of miRNA and mRNA were determined by qRT-PCR, and the protein levels were detected by Western blot assay.

Results

Endothelial progenitor cells alleviated lung wet-to-dry (W/D) weight ratios, lung injury score and the number of total leukocyte and the number of neutrophils in BALF in PQ-induced ALI mice. EPCs inhibited miR-141-3p expression, and enhanced the levels of Notch-Nrf2 axis in PQ-induced ALI mice. MiR-141-3p knockdown reversed the PQ induced-inhibition on Notch-1 and Hesr1 expression. MiR-141-3p over-expression could inhibit the expression of Notch-1 pathway significantly in the pulmonary epithelial cell line MLE-12. Both miR-141-3p over-expression and si-Notch-1 abolished the protection effect of EPCs on lung injury induced by PQ in vivo.

Conclusions

Endothelial progenitor cells could provide therapeutic effect on PQ-induced ALI via miR-141-3p-Notch-Nrf2 Axis.

Eukaryotic translation initiation factor 2 subunit α (eIF2α) inhibitor salubrinal attenuates paraquat-induced human lung epithelial-like A549 cell apoptosis by regulating the PERK-eIF2α signaling pathway

Paraquat (PQ), as one of the most widely used herbicides in the world, can cause severe lung damage in humans and animals. This study investigated the underlying molecular mechanism of PQ-induced lung cell damage and the protective role of salubrinal. Human lung epithelial-like A549 cells were treated with PQ for 24h and were pre-incubated with salubrinal for 2h, followed by 500μM of PQ treatment. Silencing eIF2α gene of the A549 cells with siRNA interference method was conducted. Cell morphology, cell viability, apoptosis and caspase-3 activity were assessed by different assays accordingly thereafter. The expression of PERK, p-PERK, ATF6, c-ATF6, IRE1α, p-IRE1α, CHOP, GRP78, p-eIF2α and β-actin was assayed by western blot. The data showed that PQ significantly reduced A549 cell viability, changed cell morphology, induced cell apoptosis and significantly upregulated the levels of GRP78, CHOP, p-PERK, c-ATF6 and p-IRE1α. However, 30μM salubrinal could attenuate the effects of PQ on damages to A549 cells through upregulating p-eIF2α. In contrast, knocking down eIF2α gene inhabited the effects of salubrinal. These results suggest that PQ-induced A549 cell apoptosis involved endoplasmic reticulum (ER) stress, specially the PERK-eIF2α pathway. Salubrinal attenuated A549 cells from PQ-induced damages through regulation of the PERK-eIF2α signaling.

Discernment scheme for paraquat poisoning: A five-year experience in Shiraz, Iran

AIM

To evaluate various schemes for paraquat poisoning and different variables that influence the outcome of acute paraquat poisoning.

METHODS

In a cross-sectional study, the information about all cases of acute paraquat poisoning who were admitted to teaching hospitals affiliated to Shiraz University of Medical Sciences, in a five year period (September 2010 to September 2015) were evaluated. The variables included: Demographic data, medical assessment, therapeutic options, laboratory findings, and the outcomes. Data were analyzed using SPSS, version 22. Significant difference between groups was tested using t-test for continues outcomes and χ² test for categorical. The significance level was considered to be P < 0.05.

RESULTS

A total of 104 patients (66.3% male) were evaluated. The mean age of the female patients was 22.81 ± 9.87 years and the male patients’ was 27.21 ± 11.06 years. Ninety seven (93.3%) of all the cases were suicide attempts with mortality rate of 43.2%. Despite the necessity for emergency hemodialysis during the first 6 h of intoxication, none of the patients had dialysis during this time. Immunosuppressive and corticosteroid medications were not administrated in adequate dosage in 31.1% and 60% of the patients, respectively. Ingestion of more than 22.5 cc of paraquat and increase in creatinine level were the most important predictors of mortality.

CONCLUSION

Treatment should start immediately for these patients. Moreover, creating a clinical guideline according to the findings can have an impact on the treatment procedure which seems to be necessary.

Ulinastatin suppresses endoplasmic reticulum stress and apoptosis in the hippocampus of rats with acute paraquat poisoning

Lung injury is the main manifestation of paraquat poisoning. Few studies have addressed brain damage after paraquat poisoning. Ulinastatin is a protease inhibitor that can effectively stabilize lysosomal membranes, prevent cell damage, and reduce the production of free radicals. This study assumed that ulinastatin would exert these effects on brain tissues that had been poisoned with paraquat. Rat models of paraquat poisoning were intraperitoneally injected with ulinastatin. Simultaneously, rats in the control group were administered normal saline. Hematoxylin-eosin staining showed that most hippocampal cells were contracted and nucleoli had disappeared in the paraquat group. Fewer cells in the hippocampus were concentrated and nucleoli had disappeared in the ulinastatin group. Western blot assay showed that expressions of GRP78 and cleaved-caspase-3 were significantly lower in the ulinastatin group than in the paraquat group. Immunohistochemical findings showed that CHOP immunoreactivity was significantly lower in the ulinastatin group than in the paraquat group. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining showed that the number of apoptotic cells was reduced in the paraquat and ulinastatin groups. These data confirmed that endoplasmic reticular stress can be induced by acute paraquat poisoning. Ulinastatin can effectively inhibit this stress as well as cell apoptosis, thereby exerting a neuroprotective effect.

Inhibitory effects of rosiglitazone on paraquat-induced acute lung injury in rats

AIM

To investigate the effects of the PPAR-γ agonist rosiglitazone on acute lung injury induced by the herbicide paraquat (PQ) and the underlying mechanisms of action.

METHODS

Male Sprague-Dawley rats were injected with PQ (20 mg/kg, ip). Rosiglitazone (3 or 10 mg/kg, ip) was administered 1 h before PQ exposure. Peripheral blood was collected at 4, 8, 24 and 72 h after PQ exposure for measuring the levels of MDA, TNF-α and IL-1β, and the SOD activity. Lung tissues were collected at 72 h after PQ exposure to determine the wet-to-dry (W/D) ratios and lung injury scores, as well as the protein levels of NF-κBp65, PPAR-γ, Nrf2, IκBα and pIκBα.

RESULTS

At 72 h after PQ exposure, the untreated rats showed a 100% cumulative mortality, whereas no death was observed in rosiglitazone-pretreated rats. Moreover, rosiglitazone pretreatment dose-dependently attenuated PQ-induced lung edema and lung histopathological changes. The pretreatment significantly reduced the levels of TNF-α, IL-1β and MDA, increased SOD activity in the peripheral blood of PQ-treated rats. The pretreatment also efficiently activated PPAR-γ, induced Nrf2 expression and inhibited NF-κB activation in the lung tissues of PQ-treated rats. Furthermore, the pretreatment dose-dependently inhibited IκB-α degradation and phosphorylation, thus inhibiting NF-κB activation.

CONCLUSION

Pretreatment with rosiglitazone protects rats against PQ-induced acute lung injury by activating PPAR-γ, inducing Nrf2 expression and inhibiting NF-κB activation.

Medical management of paraquat ingestion

Poisoning by paraquat herbicide is a major medical problem in parts of Asia while sporadic cases occur elsewhere. The very high case fatality of paraquat is due to inherent toxicity and lack of effective treatments. We conducted a systematic search for human studies that report toxicokinetics, mechanisms, clinical features, prognosis and treatment. Paraquat is rapidly but incompletely absorbed and then largely eliminated unchanged in urine within 12-24 h. Clinical features are largely due to intracellular effects. Paraquat generates reactive oxygen species which cause cellular damage via lipid peroxidation, activation of NF-κB, mitochondrial damage and apoptosis in many organs. Kinetics of distribution into these target tissues can be described by a two-compartment model. Paraquat is actively taken up against a concentration gradient into lung tissue leading to pneumonitis and lung fibrosis. Paraquat also causes renal and liver injury. Plasma paraquat concentrations, urine and plasma dithionite tests and clinical features provide a good guide to prognosis. Activated charcoal and Fuller's earth are routinely given to minimize further absorption. Gastric lavage should not be performed. Elimination methods such as haemodialysis and haemoperfusion are unlikely to change the clinical course. Immunosuppression with dexamethasone, cyclophosphamide and methylprednisolone is widely practised, but evidence for efficacy is very weak. Antioxidants such as acetylcysteine and salicylate might be beneficial through free radical scavenging, anti-inflammatory and NF-κB inhibitory actions. However, there are no published human trials. The case fatality is very high in all centres despite large variations in treatment.

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.

Liposomal Antioxidants for Protection against Oxidant-Induced Damage

Reactive oxygen species (ROS), including superoxide anion, hydrogen peroxide, and hydroxyl radical, can be formed as normal products of aerobic metabolism and can be produced at elevated rates under pathophysiological conditions. Overproduction and/or insufficient removal of ROS result in significant damage to cell structure and functions. In vitro studies showed that antioxidants, when applied directly and at relatively high concentrations to cellular systems, are effective in conferring protection against the damaging actions of ROS, but results from animal and human studies showed that several antioxidants provide only modest benefit and even possible harm. Antioxidants have yet to be rendered into reliable and safe therapies because of their poor solubility, inability to cross membrane barriers, extensive first-pass metabolism, and rapid clearance from cells. There is considerable interest towards the development of drug-delivery systems that would result in the selective delivery of antioxidants to tissues in sufficient concentrations to ameliorate oxidant-induced tissue injuries. Liposomes are biocompatible, biodegradable, and nontoxic artificial phospholipid vesicles that offer the possibility of carrying hydrophilic, hydrophobic, and amphiphilic molecules. This paper focus on the use of liposomes for the delivery of antioxidants in the prevention or treatment of pathological conditions related to oxidative stress.

Protective Effects of Liposomal N-Acetylcysteine against Paraquat-Induced Cytotoxicity and Gene Expression

Paraquat (PQ) is a herbicide that preferentially accumulates in the lung and exerts its cytotoxicity via the generation of reactive oxygen species (ROS). There is no specific treatment for paraquat poisoning. Attempts have been made to increase the antioxidant status in the lung using antioxidants (e.g., superoxide dismutase, vitamin E, N-acetylcysteine) but the outcome from such treatments is limited. Encapsulation of antioxidants in liposomes improves their therapeutic potential against oxidant-induced lung damage because liposomes facilitate intracellular delivery and prolong the retention of entrapped agents inside the cell. In the present study, we compared the effectiveness of conventional N-acetylcysteine (NAC) and liposomal-NAC (L-NAC) against PQ-induced cytotoxicity and examined the mechanism(s) by which these antioxidant formulations conferred cytoprotection. The effects of NAC or L-NAC against PQ-induced cytotoxicity in A549 cells were assessed by measuring cellular PQ uptake, intracellular glutathione content, ROS levels, mitochondrial membrane potential, cellular gene expression, inflammatory cytokine release and cell viability. Pretreatment of cells with L-NAC was significantly more effective than pretreatment with the conventional drug in reducing PQ-induced cytotoxicity, as indicated by the biomarkers used in this study. Our results suggested that the delivery of NAC as a liposomal formulation improves its effectiveness in counteracting PQ-induced cytotoxicity.

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

Paraquat dichloride (methyl viologen; PQ) is an effective and widely used herbicide that has a proven safety record when appropriately applied to eliminate weeds. However, over the last decades, there have been numerous fatalities, mainly caused by accidental or voluntary ingestion. PQ poisoning is an extremely frustrating condition to manage clinically, due to the elevated morbidity and mortality observed so far and due to the lack of effective treatments to be used in humans. PQ mainly accumulates in the lung (pulmonary concentrations can be 6 to 10 times higher than those in the plasma), where it is retained even when blood levels start to decrease. The pulmonary effects can be explained by the participation of the polyamine transport system abundantly expressed in the membrane of alveolar cells type I, II, and Clara cells. Further downstream at the toxicodynamic level, the main molecular mechanism of PQ toxicity is based on redox cycling and intracellular oxidative stress generation. With this review we aimed to collect and describe the most pertinent and significant findings published in established scientific publications since the discovery of PQ, focusing on the most recent developments related to PQ lung toxicity and their relevance to the treatment of human poisonings. Considerable space is also dedicated to techniques for prognosis prediction, since these could allow development of rigorous clinical protocols that may produce comparable data for the evaluation of proposed therapies.

Consecutive administration of paraquat to rats induces enhanced cholesterol peroxidation and lung injury

It is our hypothesis that as a consequence of increased oxidative stress, rats develop lung injury with increased cholesterol-derived hydroperoxides and oxysterols in lung after consecutive exposure of the rats to paraquat. To test this we administered 10 mg/kg of paraquat i.p. once or seven times (once a day) to Wistar rats. Rats were killed, and lung tissue was collected 24 h after the last paraquat injection. We found that in response to consecutive paraquat doses, there were significant increases in 7alpha- and 7beta-hydroperoxycholest-5-en-3beta-ol (7alpha-OOH and 7beta-OOH; P=0.01) as well as 7alpha- and 7beta-hydroxycholesterol (7alpha-OH and 7beta-OH; P=0.01), and 7-ketocholesterol (7-keto; P=0.03). In addition, pulmonary hemorrhage, thickening of alveolar septum, and inflammatory cell infiltration of macrophages were observed. This is the first report showing enhanced cholesterol peroxidation and lung injury of rats due to consecutive doses of paraquat.

Role of heat shock protein 60 (HSP60) on paraquat intoxication

The possibility of establishing a new method of treatment against pulmonary fibrosis caused by acute paraquat intoxication, which takes into consideration the role of heat shock protein 60 (HSP60), was investigated in paraquat-exposed rat lung mitochondria. In polyacrylamide electrophoresis, mitochondrial protein bands appeared, especially in the range of molecular weight 60 kDa and higher, whereas protein bands disappeared in the 20-40 kDa range on the 4th day after paraquat exposure. The protein profile was normalized on the 7th day and no remarkable changes were seen thereafter up to the 56th day. The changes seen during the observation period were thought to reflect the course of paraquat-induced dysfunction and subsequent repair. The malondialdehyde concentration in mitochondria decreased until the 7th day but subsequently increased and recovered to normal levels by the 56th day. The relative density of HSP60 increased until the 7th day but subsequently decreased and recovered to normal levels by the 56th day. These two parameters therefore showed symmetrical changes. The change in the malondialdehyde concentration was thought to reflect the course of activation of the antioxidation function in mitochondria and the progression of repair. The change in the relative density of HSP60 was thought to have increased to repair the proteins affected by the paraquat radical and to have normalized with the progression of healing. These results suggest that HSP60 may play an important role in preventing the progression of pulmonary fibrosis induced by paraquat.

Inhaled nitric oxide in advanced paraquat intoxication

No effective treatment is available for adult respiratory distress syndrome, pulmonary hypertension and progressive lung fibrosis in severe paraquat poisoning. A potentially beneficial effect of nitric oxide inhalation on the mean pulmonary artery pressure and gas exchange in a subject with advanced paraquat intoxication is reported. Eight days after the suicidal ingestion of an unknown dose of paraquat, a 52-year-old female had a PaO2 < or = 50 mm Hg despite ventilation with an FiO2 of 1 and a positive end-expiratory pressure of 14 to 18 cm H2O. After administration of 25 ppm nitric oxide, PaO2 increased and the mean pulmonary artery pressure and the right-to-left shunt decreased. Discontinuation of nitric oxide resulted in rapid reversal. Ventilatory function was stabilized for three days during nitric oxide inhalation but the patient developed massive pleural effusions and died on d 11 during an interruption of nitric oxide therapy. The response of serious paraquat intoxications to nitric oxide therapy may merit further study. A remarkable post-mortem finding was extensive myonecrosis supporting prolonged muscular retention of paraquat with toxic myopathy or neuromyopathy as a late manifestation of paraquat toxicity.

Protective effect of liposome-associated alpha-tocopherol against paraquat-induced acute lung toxicity

The present study was undertaken to investigate whether alpha-tocopherol, entrapped in liposomes and delivered directly to the lung, could protect against paraquat-induced lung damage in the rat. Plain liposomes (composed of dipalmitoylphosphatidylcholine, DPPC) or DPPC/alpha-tocopherol liposomes were administered intratracheally to animals 24 hr prior to an intraperitoneal injection of paraquat (20 mg/kg); rats were killed 24 or 48 hr after paraquat treatment. Results of this study showed that lungs of animals treated with paraquat were damaged extensively as evidenced by an increase in lung weight and a significant reduction in lung angiotensin-converting enzyme (ACE) activity and cytochrome P450 concentration. Furthermore, paraquat treatment resulted in a significant decrease in reduced glutathione (GSH) concentrations and a marked elevation in microsomal lipid peroxidation levels as measured by the formation of diene conjugates. Pretreatment of rats with DPPC liposomes alone did not alter significantly the paraquat-induced changes of all parameters examined. On the other hand, pretreatment of rats with DPPC/alpha-tocopherol liposomes 24 hr prior to paraquat challenge resulted in a significant increase in pulmonary alpha-tocopherol concentrations and antagonized paraquat-induced changes in lipid peroxidation, GSH/GSSG ratio, lung ACE activity and cytochrome P450 concentrations. Results of this study suggested that alpha-tocopherol, delivered directly to the lung in a liposomal formulation 24 hr prior to paraquat administration, confers protection against paraquat-induced lung damage.

Pulmonary edema after Escherichia coli peritonitis correlates with thiobarbituric-acid-reactive materials in bronchoalveolar lavage fluid

We developed a new model of acute lung injury caused by live Escherichia coli peritonitis in guinea pigs. Arterial blood gas determinations, arterial blood pressure, and white blood cell counts were monitored serially for 12 h after the injection of either 2 x 10(9) E. coli J96 or saline. Lung water, albumin concentration in bronchoalveolar lavage fluid (BALF) and in lung tissue, WBC counts in BALF, and thiobarbituric-acid-reactive materials (TBARM) in plasma, lung tissue, and BALF were examined. Increased TBARM might be associated with pulmonary injury and are produced either by the generation of lipoperoxides secondary to oxygen-free radicals or as metabolic byproducts of prostanoid metabolism. Lung tissue sections were studied by light microscopy. E. coli peritonitis, as compared with control animals, caused significant peripheral neutropenia, histopathologic evidence of lung inflammation, acidosis, and hypotension. The wet-to-dry lung ratio was increased in the peritonitis group when compared with that in the control group (p less than 0.01). Pulmonary edema in the peritonitis group was associated with significantly increased albumin concentrations in BALF and lung tissue. We report the new finding of increased TBARM concentrations in BALF after E. coli peritonitis (p less than 0.01 and p less than 0.05, respectively). In contrast, plasma TBARM concentrations were unchanged. The levels of TBARM in the BALF correlated significantly with both lung water (p less than 0.01) and lung tissue albumin concentration (p less than 0.01). The measurement of elevated TBARM in BALF may allow acute lung injury to be detected. We conclude that this model may be useful for further studies of acute lung injury caused by E. coli peritonitis.

Failure of haemoperfusion and haemodialysis to prevent death in paraquat poisoning. A retrospective review of 42 patients

In this review the efficacy of haemoperfusion in the treatment of paraquat poisoning is addressed. 42 reports containing sufficient information of paraquat-poisoned patients were evaluated. These reports, from 35 patients reported in the literature and 7 new cases, were chosen for the following reasons: the timed plasma paraquat concentrations were known, patient outcome was known, and details of haemoperfusion were available. In some cases, haemodialysis was also performed. The plasma paraquat concentrations and the specific times post-ingestion were plotted on a contour graph that predicts the probability of survival. Comparison of the predicted probability of survival versus the actual outcome showed that haemoperfusion, single or repeated, did not affect patient survival. None of the patients whose initial plasma concentrations were greater than 3 mg/L paraquat survived, regardless of the time after ingestion that the concentrations were measured, and despite haemoperfusion. Therefore, such patients might not be considered for haemoperfusion because of their uniformly bad prognosis, despite the procedure being used, and because of the morbidity, discomfort and cost associated with it. Clearly, the need for better techniques to remove paraquat and to prevent the consequences of the metabolic effects of the compound are required urgently before the treatment of the paraquat-poisoned patient will be successful.