Paraquat lung: a reappraisal

Pulmonary histopathology in fatal paraquat poisoning

Paraquat is a potent herbicide widely used in the Indian agriculture industry. Human fatality due to paraquat poisoning is not uncommon in this country. The primary effect of paraquat is on the lungs, and the resultant pulmonary damage leads to the patient's demise. There is a high mortality rate in paraquat poisoning as the treatment is usually supportive with no known antidote. There are limited human studies that have observed the histopathological changes in lungs in paraquat poisoning. The authors have discussed the time-related histopathological changes in lungs in paraquat poisoning on autopsy subjects. The role of anticoagulants and fibrinolytic agents in the treatment of this poisoning has also been discussed.

Characterizing the protracted neurobiological and neuroanatomical effects of paraquat in a murine model of Parkinson's disease

The primary motor symptoms of Parkinson's disease (PD) result from the degeneration of dopamine-producing neurons of the substantia nigra pars compacta (SNc), and often, the loss is asymmetrical, resulting in unilateral tremor presentation. Notably, age is the primary risk factor for PD, and it is likely that the disease ultimately stems from the impact of environmental factors, which interact with the aging process. Recent research has focused on the role of microglia and pro-oxidative responses in dopaminergic neuronal death. In this study, we sought to examine the neurodegenerative, inflammatory, and stress effects of exposure to the etiologically relevant pesticide, paraquat, over time (up to 6 months after injections). We also were interested in whether a high-resolution, 7-Tesla animal magnetic resonance imaging would be sensitive enough to detect the degenerative impact of paraquat. We found that paraquat induced a loss of dopaminergic SNc neurons and activation of microglia that surprisingly did not change over 6 months after the last injection. A long-lasting reduction was evident for body weight, and alterations in organ (lung and heart) weight were evident, which reflect the peripheral impact of the toxicant. The microglial proinflammatory actin-remodeling factor, WAVE2, along with the inflammatory transcription factor, nuclear factor kappa B were also elevated within the brain. Remarkably, the stress hormone, corticosterone, was still significantly elevated 1 month after paraquat, whereas the inflammasome factor, caspase-1, and antigen presentation factor, MFG-E8, both displayed delayed rises after the 6-month time. Using high-resolution magnetic resonance imaging, we detected no striatal changes but modest hemispheric differences in the SNc and time-dependent volumetric enlargement of the ventricles in paraquat-treated mice. These data suggest that paraquat induces long-term nigrostriatal pathology (possibly asymmetric) and inflammatory changes and stress and trophic/apoptotic effects that appear to either increase with the passage of time or are evident for at least 1 month. In brief, paraquat may be a useful nonspecific means to model widespread stress and inflammatory changes related to PD or age-related disease in general, but not the progressive nature of such diseases.

Optimum concentration-response curve metrics for supervised selection of discriminative cellular phenotypic endpoints for chemical hazard assessment

High-content imaging (HCI) provides quantitative and information-rich measurements of chemical effects on human in vitro cell models. Identification of discriminative phenotypic endpoints from cellular features obtained from HCI is required for accurate assessments of potential chemical hazards. However, the use of suboptimal metrics to quantify the concentration-response curves (CRC) of chemicals based on these features may obscure discriminative features, and lead to non-predictive endpoints and poor chemical classifications or hazard assessments. Here, we present a systematic and data-driven study on the performances of different CRC metrics in identifying image-based phenotypic features that can accurately classify the effects of reference chemicals with known in vivo toxicities. We studied four previous HCI in vitro nephro- or pulmono-toxicity datasets, which contain phenotypic feature measurements from different cell and feature types. Within a feature type, we found that efficacy metrics at higher chemical concentrations tend to give higher classification accuracy, whereas potency metrics do not have obvious trends across different response levels. Across different cell and feature types, efficacy metrics generally gave higher classification accuracy than potency metrics and area under the curve (AUC). Our results suggest that efficacy metrics, especially at higher concentrations, are more likely to help us to identify discriminative phenotypic endpoints. Therefore, HCI experiments for toxicological applications should include measurements at sufficiently high chemical concentrations, and efficacy metrics should always be analyzed. The identified features may be used as specific toxicity endpoints for further chemical hazard assessment.

Propolis supplementation attenuates the negative effects of oxidative stress induced by paraquat injection on productive performance and immune function in turkey poults

Paraquat (PQ) is used as a herbicide in agriculture and causes oxidative and inflammatory damage to animal tissues. The current study was conducted to investigate the positive effects of dietary propolis (PR), as a potent naturally produced antioxidant, on growth performance and immune function of turkey poults exposed to oxidative stress induced by PQ injection. Native male turkey poults (n = 120, 49-d-old) were randomly assigned into 4 groups: poults received a basal diet with a daily subcutaneous PQ injection of 5 mg/kg BW for 7 consecutive days (PQ group), an experimental diet containing 1 g/kg PR with a daily subcutaneous PQ injection for 7 days (PR+PQ group), or received the experimental PR diet with a daily subcutaneous injection of 0.5 mL sterile saline for 7 days (PR group); while the control poults received a basal diet with a daily subcutaneous saline injection for 7 consecutive days (C group). The productive performance in the PQ group showed a significant (P < 0.05) reduction in the weight gain (WG) and feed intake (FI), and impaired feed conversion ratio (FCR). Propolis supplementation in the PR+PQ group significantly ameliorated the PQ effects on WG and FCR. Turkey poults of the PQ and PR+PQ groups had a significant augmentation in the blood malondialdehyde (MDA), tumor necrosis factor-α (TNFα), and corticosterone levels, and in contrast, a significant reduction in the triiodothyronine (T₃), when compared to the C group. While propolis significantly reduced the MDA and corticosterone, and increased the T₃ levels in the PR+PQ group compared to the PQ group. Furthermore, the dietary PR supplementation significantly limited the PQ-suppressive effects on cell- and humoral-mediated immunity and lymphocyte proliferation of turkey poults. In addition, propolis supplementation in the PR and PR+PQ groups markedly reversed the PQ-induced DNA fragmentation and heat shock protein 70 (Hsp70) over-expression in blood cells. It can be concluded that PR could improve turkey immunity and performance, particularly under inflammation and oxidative stress induced by PQ exposure.

Neurotoxic Effects Induced by Intracerebral and Systemic Injection of Paraquat in Rats

1 The neurotoxic effects elicited by paraquat after systemic and intracerebral injection were studied in rats.

2 Intrahippocampal microinfusion of paraquat (0.1 μmol) produced behavioural stimulation and electrocortical (ECoG) excitation followed, at 24 h, by multifocal brain damage. Similarly, microinfusion of paraquat (0.2-0.4 μmol) into the locus coeruleus, substantia nigra or into the raphe nuclei, where noradrenergic, dopaminergic and serotonergic neurons are present, respectively, elicited potent excitotoxic effects (n=6 rats per dose and area). A lower dose (0.01 μmol) of the herbicide or injection of the vehicle (1.0 μl) did not produce any behavioural, ECoG or neurodegenerative effect.

3 After systemic administration, paraquat (20 mg kg-1 s.c.) evoked limbic motor seizures and ECoG epileptogenic discharges; in 10 out of 15 treated rats neuronal cell death was observed in the pyriform cortex, but not in other brain regions. A dose of 5 mg kg-1 was ineffective.

4 Among the regions of the brain studied, high concentrations of paraquat were detected in the pyriform cortex 24 h after systemic administration (5.0 and 20 mg kg -1 s.c.) lower levels being observed in the caudate nucleus.

5 In conclusion, paraquat, given systemically or intracerebrally in rats produces neurodegenerative effects.

Integrated long non-coding RNA analyses identify novel regulators of epithelial-mesenchymal transition in the mouse model of pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal lung disease characterized by aberrant accumulation of fibroblast population and deposition of extra cellular matrix. Increasing evidence support that epithelial‐mesenchymal transition (EMT) of alveolar epithelial cells is a critical process in the pathogenesis of IPF. Although delivery of bleomycin to induce acute lung injury is the most well‐studied animal model of pulmonary fibrosis, there is considerable interest to pursue other models to understand the common and/or specific pathological mechanisms. In this study, we established a mouse model of pulmonary injury and progressive interstitial fibrosis via intraperitoneal injection of paraquat, a widely used herbicide known to cause pulmonary fibrosis in human. Using transcriptome sequencing and microarray analysis, we profiled expression of long non‐coding RNAs (lncRNAs) and identified 513 up‐regulated and 204 down‐regulated lncRNAs in paraquat‐induced fibrotic lung tissues. Gene ontology analysis revealed that the differentially expressed lncRNAs are implicated in cell differentiation, epithelium morphogenesis and wound healing, pathways closely associated with EMT. Furthermore, we identified the evolutionally conserved target genes of two up‐regulated lncRNAs, uc.77 and 2700086A05Rik, as Zeb2 and Hoxa3, respectively, both of which are important modulators of EMT. Consistently, overexpression of uc.77 or 2700086A05Rik in human lung epithelial cells induced EMT as demonstrated by changes in gene and protein expression of various EMT markers and cell morphology. Collectively, our results uncovered a crucial role of lncRNA in the regulation of EMT during lung fibrosis and provide potential avenues for the discovery of novel molecular markers and therapeutic targets for IPF.

A comparative study on toxicity induced by carbosulfan and malathion in Wistar rat liver and spleen

Organophosphorus (OP) and carbamate (CM) pesticides are widely used in agriculture. These pesticides are highly toxic to humans and their residues in food pose potential threat to human health. In this comparative study, we investigated the effect of subchronic exposure of OPs (malathion, MAL) and CM (Carbosulfan, CB) on rat liver and spleen. Biochemical analysis showed that levels of hepatic enzymes (ALT, ALP, LDH and PAL) changed after exposure to the pesticides. In the liver extracts, lipid peroxidation index increased after the treatment by pesticides. Our results indicated that exposure to MAL and CB leads to alteration of liver redox status. Both pesticides induced focal inflammation and fibrosis in the liver. After subchronic administration of MAL (200 mg/kg) and CB (25 mg/kg), systemic inflammation, as depicted by the increase in IFN-δ activity in liver, was observed in both malathion and carbosulfan treated animals. In addition, the results showed that MAL significantly increased TCD4+ and TCD8+ lymphocyte number. It also decreased INF-δ and IL-4 production. However, CB induced a reduction of TCD8+ number and cytokine production in spleen cells. In conclusion, malathion and carbosulfan had significant immunomodulatory properties in the spleen with inflammation and oxidative stress induction in the liver.

Molecular mechanisms of paraquat-induced acute lung injury: a current review

Paraquat is an organic heterocyclic herbicide that is widely used in agriculture, especially in Asian countries. The prevalence of paraquat poisonings has increased dramatically in the past two decades in China. Nearly all paraquat poisonings resulted from intentional or accidental oral administration leading to acute lung injury and, ultimately, acute respiratory distress syndrome. The mortality rate has been reported to be greater than 90%. However, the exact toxic mechanism remains unclear. Herein, we reviewed and summarized the most recent publications related to the molecular mechanisms of paraquat-induced acute lung injury.

Paraquat: a useful tool for the in vivo study of mechanisms of neuronal cell death

The present article reviews the results of experimental studies on paraquat neurotoxicity, started by our group several years ago--when clinical and experimental reports had increased the interest for the possibility that environmental chemicals, including paraquat, may be related to the development of Parkinson's disease-, and which are still continuing since paraquat appears to be a promising tool to study the mechanisms of neuronal cell death in vivo. Our observations have demonstrated that paraquat causes evident neurotoxic effects after intracerebroventricular or intracerebral injection in experimental animals; however, it seems that the herbicide does not exibit a selective neurotoxicity towards the dopaminergic nigro-striatal system since potent behavioural and electrocortical changes are induced by paraquat after injection in brain areas other than the substantia nigra and caudate nucleus. By studying the mechanisms through which paraquat induces neurotoxic effects in vivo, it was shown that either free radical production and activation of cholinergic and glutamatergic transmission may be regarded as related events which play a crucial role in paraquat-induced neurotoxicity. In addition, it was observed that in rats paraquat penetrates the blood-brain barrier following systemic administration to give rise to a differential brain regional distribution; the latter observation rises some concern over the hazard of paraquat as a potential environmental neurotoxin. Indeed, paraquat, administered systemically in rats produces behavioural excitation and brain damage. The brain damage appears to be selective for the pyriform cortex and this does not seem to be strictly related to the high concentrations reached by the herbicide in this area but to the higher vulnerability of this cortical area to the enhanced cholinergic transmission. The recent observation that paraquat, injected into the rat hippocampus, induces the expression of apoptotic neuronal cell death, appears of valuable interest also with a view to paraquat as an useful experimental model in the development of neuroprotective drugs able to block the molecular events which, once activated, are responsible for the induction of neuronal cell death.

Neurodegeneration produced by intrahippocampal injection of paraquat is reduced by systemic administration of the 21-aminosteroid U74389F in rats

The behavioural, electrocortical (ECoG) and neurodegenerative effects of intrahippocampal injection of paraquat, a well-known free radical producing agent, were studied in rats. Injection of paraquat (100 nmol) into one dorsal hippocampus produced limbic motor and ECoG seizures. These effects were accompanied at 24 h by severe damage to CA1, CA3 and CA4 hippocampal pyramidal neurones and dentate gyrus granule cells. In comparison to the cell number counted in control, untreated, side of the hippocampus, significant (P < 0.05) neuronal loss was observed in the CA1 and CA3 pyramidal cell layers of the treated hippocampus. A lower dose of the herbicide (10 nmol) did not produce consistent motor and ECoG effects and in no instance was significant neuronal loss observed. A pretreatment with U74389F [21-4-(2,6-di-l-pyrrodinyl-4-pyridinyl)-1-piperazinyl-pregna-1,4,9 (11)triene-3,20-dione monomethansulfonate] (30 mg/kg i.p., 15 min before paraquat) completely protected rats from motor and ECoG epileptogenic effects induced by intrahippocampal paraquat (100 nmol). This dose of U74389F also reduced the hippocampal damage typically produced by paraquat and no significant neuronal loss was reported in the CA1 and CA3 pyramidal cell layers. A lower dose of U74389F (10 mg/kg i.p.) did not afford any protection against the epileptogenic effects produced by paraquat (100 nmol); in these animals hippocampal damage was still evident though neuronal loss did not reach statistical significance. In conclusion, the present data show that systemic administration of U74389F possesses neuroprotective effects against seizures and neurodegeneration typically elicited by intrahippocampal injection of paraquat.

Determination of paraquat in rat brain by high-performance liquid chromatography

The applications of a method based on ion-pair solid-phase extraction and reversed-phase HPLC are reported. The method was used to measure paraquat concentrations in discrete brain areas at different times after its systemic administration in rats. In addition, the method was employed in the determination of paraquat levels in whole-brain samples from rats of various ages systemically treated with several doses of the herbicide.

Intra-nigral infusion of Cu-free superoxide dismutase prevents paraquat-induced behavioural stimulation and ECoG epileptogenic discharges in rats

In adult rats, with cannulae chronically implanted by a stereotactic instrument into the substantia nigra (pars compacta), the electrocortical (ECoG) and behavioural effects elicited by intranigral infusion of paraquat and the prevention of these effects by prior administration into the same site of different types of superoxide dismutase, were studied. Paraquat (50 micrograms) produced an intense pattern of behavioural stimulation, contralateral circling and repetitive discharges of high voltage ECoG spikes. The effects of paraquat were abolished in all of the animals pretreated into the same site with copper-free superoxide dismutase. Pretreatment with native Cu, Zn-superoxide dismutase prolonged significantly the latency of onset but did not prevent the behavioural stimulation and ECoG spikes evoked by paraquat. On the contrary, pretreatment with albumin or saline did not confer any protection against the neurotoxicological changes induced by paraquat. In conclusion, the present experiments showed that motor, ECoG and lethal effects of paraquat were completely prevented by Cu-free superoxide dismutase, suggesting that the central effects of this herbicide are in some way related to the release in the brain of copper and/or other transition metal ions.

Unilateral paraquat-induced lung fibrosis: evolution of changes in lung fibronectin and collagen after graded degrees of lung injury

We describe a model of pulmonary fibrosis in which doses of paraquat ranging from 0.001 mg/kg to 1.0 mg/kg were instilled into the right lung of rats. Lung injury, as measured by right lung lavage albumin content and differential neutrophil count, ranged from undetectable to extremely severe, depending on the dose. Lung fibrosis, as assessed by collagen content and electron microscopy, showed similar dose-response effects. Mortality was minimal. Lavage fibronectin increased after high doses of paraquat, peaked at 2 d postinjury, decreased sharply after 3 d and was normal by 7 d. The temporal pattern was similar to that for albumin. Cultured alveolar macrophages obtained at 4 d postinjury did not have significant increases in fibronectin release. Tissue fibronectin content increased more slowly than lavage fibronectin, peaking at 4 d postinjury, and was still elevated at 7 and 14 d postinjury. Incorporation of [35S]methionine into tissue fibronectin by lung explants obtained at different times postinjury showed a similar time course. Lung collagen content increased steadily between 4 and 14 d postinjury. We conclude that, in our model, graded degrees of lung injury and fibrosis can be produced by varying the dose of unilaterally instilled paraquat and that the increases in lavage fibronectin were related mainly to capillary permeability whereas increases in tissue fibronectin represented parenchymal synthesis. The time course of changes in lung tissue fibronectin and collagen was consistent with the proposed roles of fibronectin in tissue repair and fibrosis. The ability of our model to produce graduated degrees of lung injury and fibrosis should be useful in further studies on the pathogenesis of postinjury lung fibrosis.

Intraluminal fibrosis in interstitial lung disorders

The histopathologic and ultrastructural features of intraluminal organizing and fibrotic changes were studied in open lung biopsies and autopsy specimens from 373 patients with interstitial lung disorders, including hypersensitivity pneumonitis (n = 44), idiopathic pulmonary fibrosis (n = 92), collagen-vascular diseases (n = 20), chronic eosinophilic pneumonia (n = 10), pulmonary histiocytosis X (n-90), pulmonary sarcoidosis (n = 62), pneumoconioses (n = 25), Legionnaire's disease (n = 5), drug- and toxin-induced pneumonitis (n = 4), radiation-induced pneumonitis (n = 2), lymphangioleiomyomatosis (n = 11), and chronic organizing pneumonia of unknown cause (n = 8). Three patterns of intraluminal organization and fibrosis were recognized: 1) intraluminal buds, which partially filled the alveoli, alveolar ducts and/or distal bronchioles; 2) obliterative changes, in which loose connective tissue masses obliterated the lumens of alveoli, alveolar ducts or distal bronchioles, and 3) mural incorporation of previously intraluminal connective tissue masses, which fused with alveolar, alveolar ductal, or bronchiolar structures and frequently became reepithelialized. All three patterns had common morphologic features, suggesting that, regardless of their severity, they resulted from a common pathogenetic mechanism, ie, the migration of activated connective tissue cells, through defects in the epithelial lining and its basement membrane, from the interstitial into the intraluminal compartment. Intraluminal buds were observed most frequently in hypersensitivity pneumonitis, chronic eosinophilic pneumonia, and organizing pneumonia of unknown cause. Mural incorporation and, to a lesser extent, obliterative changes were observed in most interstitial disorders and were very prominent in idiopathic pulmonary fibrosis. Mural incorporation and obliterative changes play an important role in pulmonary remodeling, especially when several adjacent alveoli and/or other air spaces are involved. Under these circumstances, intraluminal organization can mediate the fusion of adjacent alveolar structures by intraluminal connective tissue.

The duration of the pulmonary paraquat toxicity--enhancement effect of O2 in the rat

The duration of the pulmonary paraquat toxicity-enhancement effect of O2 has been examined in Wistar rats. In one experiment, various groups of normal animals were given a single dose (5 mg/kg body wt) of paraquat and after different periods were exposed to continuous breathing of normobaric 74% O2 in airtight chambers until dead or up to 10 days. In a reverse experiment, a large number of rats were first exposed for 6 days to continuous breathing of normobaric 74% O2 and were then separated into various groups which received a single dose of paraquat (5 mg/kg body wt) after various periods of breathing normal air, ranging from 0 to 96 hr. The extent of pulmonary damage in both experiments was evaluated by histologic examination and by biochemical determination of total collagen content of the lungs. It was found that the duration of the pulmonary damage induced by paraquat that is enhanced by continuous breathing of high O2 concentration lasts 24 to 48 hr. It was also observed that 12 to 24 hr after paraquat administration and continuous breathing of high O2 concentration pulmonary lesions are severe and extensive, and in animals surviving 6 or more days there was also incipient interstitial fibrosis. The reverse sequence of treatment (O2 + paraquat) resulted in no mortality and no pulmonary lesions. Additional controls treated with each of the pulmonary toxins alone also revealed no lung changes.

A cautionary note on the resolution of paraquat lung damage after radiotherapy

We have been able to model the lung damage caused by paraquat in our mice and have found a dose-related increase in lung damage after PQ. Unfortunately we have not found a radiation dose or optimum time for irradiation which shows a reduction of the PQ lung damage.

Sequential bilateral lung transplantation for paraquat poisoning. A case report. The Toronto Lung Transplant group

A 31-year-old nurseryman developed progressive respiratory failure secondary to paraquat poisoning after repeated and prolonged exposure. Ventilatory assistance proved inadequate to maintain satisfactory oxygenation, and extracorporeal membrane oxygenator support was instituted. A right lung transplantation was performed, but the transplant subsequently was damaged when lethal levels of paraquat entered the bloodstream from muscle reservoirs. Membrane oxygenation was reinstituted for 19 days during which time charcoal hemoperfusion reduced paraquat levels to the undetectable range. A left lung transplantation was then performed, after which pulmonary gas exchange no longer posed a problem. The patient subsequently developed a progressive, severe, toxic myopathy with generalized weakness and inability to maintain spontaneous ventilation. Death occurred from a cerebrovascular accident after a trachea-innominate artery fistula, 93 days after the initial lung transplantation and 71 days after the second one. The development of progressive toxic myopathy following severe Paraquat poisoning has not been previously recognized, presumably because most victims of fatal paraquat poisoning survive only a brief period.

Patterns of pulmonary structural remodeling after experimental paraquat toxicity. The morphogenesis of intraalveolar fibrosis

For a study of the evolution of interstitial and intraalveolar fibrosis, ultrastructural and immunohistochemical observations were made of the lungs of 16 cynomolgous monkeys given 1 or 2 injections of 10 mg/kg of paraquat and sacrificed 2 days to 8 weeks later. At 2-3 days, alveolar epithelial cells were denuded in many areas, and fibronectin was conspicuous in alveolar spaces. At 1 week, fibroblasts and inflammatory cells were migrating through gaps in the denuded epithelial basement membranes; Type II cells were regenerating in some areas. At 3-4 weeks, alveoli developing intraalveolar fibrosis contained many myofibroblasts, collagen fibrils, and small elastic fibers; fibrotic alveolar walls were lined by metaplastic squamous cells and bronchiolar epithelial cells. Spiraling collagen fibrils were found in interstitium but not in alveolar spaces, which suggests that they were formed from breakdown of collagen. Newly formed intraalveolar collagen was mainly Type I. At 8 weeks, intraalveolar fibrosis had led to extensive remodeling, with new glandlike alveoli lined by Type II cells; alveoli without intraalveolar fibrosis had more normal architecture. Thus, intraalveolar fibrosis in paraquattreated lung is mediated by intraalveolar migration of interstitial cells, through gaps in the epithelial basement membranes, after epithelial injury. This is followed by connective tissue synthesis on the luminal side of the epithelial basement membrane, by differentiation of interstitial cells into myofibroblasts and smooth-muscle cells, by incorporation of areas of intraalveolar fibrosis into the interstitium, and by coalescence of alveolar walls. Intraalveolar fibrosis is more important than interstitial fibrosis in the structural remodeling that occurs in paraquattreated lung, because it results in obliteration of alveoli, coalescence of alveolar walls, and loss of functional alveolar-capillary units.

Pesticide lung: a pilot investigation of fruit-growers and farmers during the spraying season

A fruit-grower with large, atypical lung infiltrations and lung fibrosis triggered off an investigation of fruit-growers during the spraying season. An interview was carried out together with a Wright peak flow meter test and an x-ray examination of the chest. No fewer than 156 spray preparations were used by the group; individual fruit-growers used between three and 27. In connection with spraying, 41% of subjects had one or other type of symptom; peak flow was reduced in 19% and x-ray changes were seen in 24%. A questionnaire was returned by 132 of 235 farmers. Of these, 60 had worked with biocides, 72 had not. A non-significant higher frequency of symptoms was found among those who used biocides. The results would indicate that biocides (or "pesticides") can give rise to a lung disease, "biocide lung," which comprises (1) pneumonia, radiologically demonstrable by more or less transient round infiltrations and (2) chronic progressive lung fibrosis.

Efficacy of charcoal hemoperfusion in paraquat poisoning

We studied the efficiency of in vitro and in vivo charcoal hemoperfusion for the removal of paraquat. At a flow rate of 200 ml/min, 93-99% of paraquat in 4 L of solution (5, 10, 100 ppm) was removed in less than 160 min. The disappearance half-time was 16 min 10 sec. At 100 ml/min, it was 49 min 30 sec. Of 23 paraquat poisoning cases, 15 patients underwent hemoperfusion (HP) of which 10 died of respiratory failure within 28 days (7.6 +/- 2.9) and 5 survived without pulmonary complications. Of eight patients who did not receive HP, six died of respiratory failure within 97 days (33.4 +/- 18.8), even when their general condition was good upon admission. Two who vomited the ingested paraquat immediately survived without HP, and their paraquat concentration in urine was less than one ppm on admission. In one patient, whose paraquat concentration in blood was followed serially, 99% of the paraquat was removed from circulating blood by a single hemoperfusion. We conclude that charcoal hemoperfusion is effective for the removal of paraquat from blood in vivo and from solution in vitro. Hemoperfusion may also improve survival after paraquat ingestion, but further data are needed.

Hepatic injury associated with paraquat toxicity in humans

Thirteen patients are reported who developed evidence of hepatic damage after exposure to paraquat and subsequently died. At autopsy, the main changes involved the bile excretory pathways. Ten of the thirteen cases had cholestasis, usually localized to the centrilobular zone. There was cholangiocellular injury involving the small and medium-sized bile ducts in portal areas. It consisted of shrinkage of cells, poor definition of outline, separation from the basement membrane, desquamation of cells into the lumen, infiltration of the wall by neutrophils and possible loss of integrity of the basement membrane. These bile duct lesions have not been previously described in association with paraquat toxicity. On the basis of the overall histologic findings in this study and extrapolation from experimental studies, it is hypothesized that paraquat injury to the liver is biphasic; it is initially hepatocellular but becomes cholangiocellular after the first 2 days.

The changing pattern of paraquat poisoning in man

The clinical and pathological findings are described in 14 patients who died between 6 hours and 26 days after drinking paraquat. Respiratory failure and delayed pulmonary fibrosis have become the hallmark of this poison, but were not the common mode of death in this series. Toxic myocarditis, renal tubular necrosis and centrilobular liver cell damage were significant factors in the eight deaths which occurred within 5 days of paraquat ingestion. Similar abnormalities plus respiratory failure caused the two deaths which occurred 5 and 6 days after consumption of the poison. Respiratory failure was the sole cause of death in only four patients who died 8 to 26 days after drinking paraquat, although the lungs showed pathological changes in all cases. The patients who died in multisystem failure, with one exception, had drunk larger quantities of paraquat than those who survived for a longer period and died in respiratory failure.

Cerebral damage in paraquat poisoning

This is the first report on cerebral changes in eight patients who died of paraquat poisoning. These included generalized oedema, haemorrhages (both subependymal and subarachnoid), glial reactions (microglial activity and astrocytic response) and meningeal inflammation. Oedema and haemorrhage were the most consistent and significant findings; they suggest that paraquat may damage the cerebral blood vessels. The distribution of haemorrhages was unusual and resembled that seen in thiamine deficiency.

Biochemical and morphological correlation of oxidant-induced pulmonary injury: low dose exposure to paraquat, oxygen, and ozone

The authors compared the temporal pattern of low-dose oxidant-induced lung injury in rats after exposure to either 1 ppm ozone or 100% oxygen for 24 hr or from treatment with paraquat (20 mg/kg, intraperitoneally). Histological abnormalities in airways, parenchyma, and blood vessels were evaluated from coded and randomized sections and compared with appropriate controls. Drug metabolism by lung endoplasmic reticulum was studied in similarly treated rats as another index of lung injury. Exposure to oxygen caused no discernible morphological or biochemical abnormalities. Exposure to ozone caused histological lesions which appeared early and resolved by 7 to 14 days, whereas paraquat-induced lesions were first evident at about 7 to 14 days. Abnormalities in drug metabolism followed a similar pattern. Low-dose oxidant exposure from ozone and paraquat produce similar histological and biochemical lesions in rat lungs but with distinct temporal patterns.

Pulmonary effects of contact exposure to paraquat: a clinical and experimental study

The clinical and pathological features of a patient who died from the effects of percutaneous absorption of paraquat are described. The toxin was absorbed during the spraying of vineyards. Nine of his co-workers, less heavily exposed, were investigated. The transfer factor for carbon monoxide was reduced in six. Lung biopsy of two showed medial hypertrophy of the pulmonary arteries with evidence of fresh and organised thrombi. In one there was also interstitial fibrosis. We designed an experimental animal model to investigate these findings. Low concentrations of paraquat were applied to the skin of rats over a nine-week period. The lungs were examined postmortem, and the medial thickness of the muscular pulmonary arteries was expressed as a percentage of their external diameters. In randomly encountered (large and small) pulmonary arteries the mean percentage medial thickness (MT%) was 11·99±0·41% (SEM) in controls and 25·28±0·94% in test rats (p<0·001). In the large muscular pulmonary arteries the MT% in the control rats was 13·6±0·49% and in the test rats 25·9±1·44% (p<0·001). In the small pulmonary arteries the values were: controls 9·0±0·73% and tests 14·2±1·35% (p<0·05). One test rat which died spontaneously showed pulmonary infarction from thrombosis. We concluded that paraquat absorbed through the skin in low dosage over a prolonged period can produce pulmonary arterial lesions in man and rat. This contrasts with the familiar pathological findings of acute high dose ingestion. These findings have important bearings on the use of this herbicide in agriculture.

Further clinical observations on the pulmonary effects of paraquat ingestion

Five patients are reported who developed evidence of acute lung damage after proved ingestion of paraquat. In two the lung changes resolved; in one an aspiration pneumonia occurred, which was successfully treated, while two developed fatal pulmonary oedema. These pulmonary complications after paraquat intoxication appear more common than the progressive pulmonary fibrosis previously described. It is suggested that acute pulmonary oedema is a response to large doses, usually of Gramoxone, that subclinical lung changes result from small doses, usually of Weedol, and that pulmonary fibrosis occurs after intermediate doses. Preliminary data on plasma paraquat concentrations suggest that these are of value in prognosis.

Pulmonary ultrastructure of the late aspects of human paraquat poisoning

The pulmonary ultrastructure of the late aspects of a case of human paraquat poisoning is investigated and compared with normal human pulmonary ultrastructure. Alveoli in the paraquat patient are numerically reduced in comparison to the control. They are filled with edematous proteinaceous plasma-like fluid containing erythrocytes, macrophages, leukocytes, fibroblast-like cells, platelets, and fibrin. These alveoli are lined by granular pneumocytes. Interstitial areas in the paraquat patient are greatly expanded and there are no alveolar septums. Interstitial areas contain proteinaceous plasma-like material, collagen, fibrin, platelets, mature fibroblasts, plasma cells, many leukocytes, numerous erythrocytes, and capillaries. Capillary permeability seems to be enhanced in the paraquat patient either by vesicles forming transendothelial channels or pores or by disruption of endothelial cells.

Pulmonary histological appearances in fatal paraquat poisoning

The paper describes the histological appearances in the lungs from 11 fatal cases of paraquat poisoning. The study originated as an attempt to define the sequential changes in the condition and, from them, to assess the mode of action of the herbicide in the human. The main features of the "paraquat lung" include haemorrhage, extrusion of macrophages, oedema, "honeycombing", fibrosis and, rarely, epithelial hyperplasia. The indications are that the changes are progressive once a threshold tissue concentration has been reached. The appearances are compared to those in poisoning by hyperbaric oxygen and it is hypothesized that the toxic action of paraquat is to sensitize the lungs to oxygen at atmospheric pressure.

The pathology of the lung in paraquat poisoning

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