Experimental paraquat poisoning: a histological and electron-optical study of the changes in the lung

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.

Amelioration of paraquat-induced pulmonary fibrosis in mice by regulating miR-140-5p expression with the fibrogenic inhibitor Xuebijing

Intravenous Xuebijing (XBJ) therapy suppresses paraquat (PQ)-induced pulmonary fibrosis. However, the mechanism underlying this suppression remains unknown. This work aimed to analyze the miR-140-5p-induced effects of XBJ injection on PQ-induced pulmonary fibrosis in mice. The mice were arbitrarily assigned to four groups. The model group was administered with PQ only. The PQ treatment group was administered with PQ and XBJ. The control group was administered with saline only. The control treatment group was administered with XBJ only. The miR-140-5p and miR-140-5p knockout animal models were overexpressed. The gene expression levels of miR-140-5p, transglutaminase-2 (TG2), β-catenin, Wnt-1, connective tissue growth factor (CTGF), mothers against decapentaplegic homolog (Smad), and transforming growth factor-β1 (TGF-β1) in the lungs were assayed with quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analysis. The levels of TGF-β1, CTGF, and matrix metalloproteinase-9 (MMP-9) in the bronchoalveolar lavage fluid were assessed by enzyme-linked immunosorbent assay (ELISA). Hydroxyproline (Hyp) levels and pulmonary fibrosis were also scored. After 14 days of PQ induction of pulmonary fibrosis, AdCMV-miR-140-5p, and XBJ upregulated miR-140-5p expression; blocked the expressions of TG2, Wnt-1, and β-catenin; and decreased p-Smad2, p-Smad3, CTGF, MMP-9, and TGF-β1 expressions. In addition, Hyp and pulmonary fibrosis scores in XBJ-treated mice decreased. Histological results confirmed that PQ-induced pulmonary fibrosis in XBJ-treated lungs was attenuated. TG2 expression and the Wnt-1/β-catenin signaling pathway were suppressed by the elevated levels of miR-140-5p expression. This inhibition was pivotal in the protective effect of XBJ against PQ-induced pulmonary fibrosis. Thus, XBJ efficiently alleviated PQ-induced pulmonary fibrosis in mice.

The Ameliorative Effects of Allopurinol on Paraquat-Induced Pulmonary Fibrosis in Rats

Background: Pulmonary fibrosis is described as a chronic idiopathic inflammatory disease of the interstitial lungs. It is associated with a potentially fatal prognosis, and patients show insignificant response to treatment. To treat paraquat (PQ)-induced pulmonary injury and fibrosis, multiple approaches have been used. We aimed to determine the effects of allopurinol (Allo), a xanthine oxidase inhibitor, on PQ-induced pulmonary fibrosis in rats. Methods: A total of 30 female Sprague-Dawley rats were divided randomly into five groups (200±20 g). Group 1 (control) and group 2 (PQ group) were intraperitoneally administered PQ (20 mg/kg) once on day seven without any treatment, while groups 3–5 orally received 50, 100, and 200 mg/kg of Allo seven days before and three weeks following the administration of PQ, respectively. The animals were sacrificed three weeks after PQ administration. For the histopathological analysis and assessment of serum malondialdehyde (MDA) and hydroxyproline (HP) contents, the animals’ blood and lungs were collected. Results: The PQ group showed significantly higher lung HP, serum MDA, and lung index in comparison with the control. Treatment with Allo, especially at 100 and 200 mg/kg, decreased HP, MDA, and lung index significantly, compared to the PQ group. Allo could prevent inflammatory cell infiltration, presence of fibroblasts, and PQ-related alveolar thickening. Conclusion: The results revealed that Allo has potential protective effects on PQ-related pulmonary fibrosis, and the role of xanthine oxidase in the exacerbation of PQ-induced pulmonary fibrosis was confirmed.

Role of bone marrow mesenchymal stem cells in the development of PQ‑induced pulmonary fibrosis

Paraquat (PQ) poisoning‑induced pulmonary fibrosis is one of the primary causes of mortality in patients with PQ poisoning. The potential mechanism of PQ‑induced pulmonary fibrosis was thought to be mediated by inflammation. Recently, bone marrow‑derived mesenchymal stem cells (BMSCs) have been considered as a potential strategy for the treatment of fibrotic disease due to their anti‑inflammatory and immunosuppressive effects. In the present study, an increased accumulation of BMSCs in a mouse model of PQ‑induced pulmonary fibrosis following their transplantation, markedly improving the survival rate of mice with PQ poisoning. In addition, the results indicated that BMSC transplantation may inhibit the production of pro‑inflammatory cytokines, including tumor necrosis factor‑α interleukin (IL)‑1β, IL‑6 and IL‑10 in the lung tissues of PQ‑poisoned mice, and ultimately attenuate the pulmonary fibrosis. In vitro, BMSCs may suppress PQ‑induced epithelial‑to‑mesenchymal transition and protect pulmonary epithelial cells from PQ‑induced apoptosis. These findings suggest that BMSC transplantation may be a promising treatment for pulmonary fibrosis induced by PQ poisoning.

Increased plasma prothrombin time is associated with poor prognosis in patients with paraquat poisoning

BACKGROUND

Paraquat can cause severe injury to vascular endothelial cells and lead to coagulation dysfunction when it is taken into the blood by oral ingestion. In this study, we aim to find a routine coagulation index to serve as an indicator of outcome in patients with acute paraquat poisoning.

METHODS

Between January 2012 and December 2016, 209 patients who attempted suicide by oral ingestion of paraquat were admitted to the emergency room. Routine coagulation indices, including plasma prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (Fbg), thrombin time (TT), and D-dimer were measured to analyze the trend of changes and their relationship with prognosis.

RESULTS

The results showed that the PT and APTT values in the ≥30 mL group were significantly greater than those in the <30 mL group (both P < .01). Within 1 week of admission, PT and APTT values gradually decreased, while Fbg levels gradually increased. Univariate and multivariate Cox regression analysis indicated that sex, ingestion volume, and PT were independent predictors of mortality within 40 days. The cumulative survival rates differed significantly (P = .001) between patients with PT <12 seconds and PT ≥12 seconds.

CONCLUSIONS

Coagulation status in patients with PQ poisoning was closely related to prognosis. Routine monitoring of coagulation function, particularly PT in plasma, is helpful for analysis of the condition and prognosis of patients with PQ poisoning.

Alveolar Proteinosis and Phospholipidoses of the Lungs

Three pulmonary disease conditions result from the accumulation of phospholipids in the lung. These conditions are the human lung disease known as pulmonary alveolar proteinosis, the lipoproteinosis that arises in the lungs of rats during acute silicosis, and the phospholipidoses induced by numerous cationic amphiphilic therapeutic agents. In this paper, the status of phospholipid metabolism in the lungs during the process of each of these lung conditions has been reviewed and possible mechanisms for their establishment are discussed. Pulmonary alveolar proteinosis is characterized by the accumulation of tubular myelin-like multilamellated structures in the alveoli and distal airways of patients. These structures appear to be formed by a process of spontaneous assembly involving surfactant protein A and surfactant phospholipids. Structures similar to tubular myelin-like multilamellated structures can be seen in the alveoli of rats during acute silicosis and, as with the human condition, both surfactant protein A and surfactant phospholipids accumulate in the alveoli. Excessive accumulation of surfactant protein A and surfactant phospholipids in the alveoli could arise from their overproduction and hypersecretion by a subpopulation of Type II cells that are activated by silica, and possibly other agents. Phospholipidoses caused by cationic amphiphilic therapeutic agents arise as a result of their inhibition of phospholipid catabolism. Inhibition of phospholipases results in the accumulation of phospholipids in the cytoplasm of alveolar macrophages and other cells. While inhibition of phospholipases by these agents undoubtedly occurs, there are many anomalous features, such as the accumulation of extracellular phospholipids and surfactant protein A, that cannot be accounted for by this simplistic hypothesis.

Liver X Receptor Agonist TO901317 Attenuates Paraquat-Induced Acute Lung Injury through Inhibition of NF-κB and JNK/p38 MAPK Signal Pathways

Paraquat (PQ) is a widely used herbicide with extremely high poisoning mortality mostly from acute lung injury (ALI) or progressive pulmonary fibrosis. Toxicity mechanisms remain unclear, but a redox cycling process that generates reactive oxygen species (ROS) is involved, as are inflammation and cell apoptosis. We established an ALI mouse model by intraperitoneal injection of PQ (28 mg/kg) and then investigated the effects of a potent liver X receptor (LXR) agonist, TO901317 (5 or 20 mg/kg), injected intraperitoneally 30 min after PQ administration. Poisoned mice exhibited severe lung tissue lesions and edema, significant neutrophilic (PMNs) infiltration, and release of the proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). PQ administration also decreased activity of antioxidases, including superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferases (GSTs), and increased lipid peroxidation as evaluated by malondialdehyde (MDA) levels. PQ exposure induced upregulation of the proapoptotic gene Bax and downregulation of the antiapoptotic gene Bcl-2, leading to marked cell apoptosis in the lung tissues. TO901317 treatment reversed all these effects through inhibition of PQ-induced nuclear factor kappa B (NF-κB) and JNK/p38 mitogen-activated protein kinase (MAPK) activation. The LXR agonist TO901317 had potent antioxidant, anti-inflammatory, and antiapoptotic effects against PQ-induced ALI.

Curcumin inhibits paraquat induced lung inflammation and fibrosis by extracellular matrix modifications in mouse model

OBJECTIVE

Paraquat (PQ), a potent herbicide can cause severe toxicity. We report here that fibroproliferation phase of acute lung injury (ALI) is initiated much earlier (within 48 h) after PQ intoxication than previously reported (after 2 weeks) and we aimed to study the protective effects of intranasal curcumin as new therapeutic strategy in mouse model.

METHODS

Mice (Park's strain) were divided into five experimental groups (I) control, received only saline (0.9 % NaCl) (II) PQ, mice intoxicated with PQ (50 mg/kg, i.p., single dose); (III) curcumin, treated with curcumin (5 mg/kg, i.n) an hour before PQ administration; (IV)Veh, DMSO (equal volume to curcumin) given an hour before PQ exposure; (V) DEXA, mice treated with dexamethasone (1 mg/kg, i.p) before an hour of PQ intoxication. After 48 h of the PQ exposure, all mice were sacrificed and samples were analyzed.

RESULTS

Pretreatment with intranasal curcumin (5 mg/kg) could modify the PQ-intoxication (50 mg/kg, i.p) induced structural remodeling of lung parenchyma at an early phase of acute lung injury. Significant increase in inflammatory cell count, reactive oxygen species and hydroxyproline levels were decreased after curcumin pretreatment (all p < 0.05). Histological examination and zymography results were also found consistent.

CONCLUSION

Our results show that curcumin pretreatment decreased the expression of alpha smooth muscle actin (α-SMA), matrix metalloproteinases-9 (MMP-9) and changed the expression of tissue inhibitors of metalloproteinase (TIMP-1) after PQ intoxication. Single toxic dose of PQ has initiated fibroproliferation within 48 h and intranasal curcumin may prove as new therapeutic strategy for PQ induced ALI and fibroproliferation.

Paraquat Poisoning in Patients With HIV Infection: A Case Report and Literature Review

Paraquat poisoning is very severe. Most victims, including those who have ingested a small amount, will die from Paraquat poisoning. The cause of death in the majority of such cases is lung fibrosis. Paraquat poisoning in patients with positive human immunodeficiency virus (HIV) infection status has seldom been reported. Herein, we report a case of an HIV patient with Paraquat poisoning who had an excellent outcome even without standard treatment. Currently, only 3 such cases have been reported in the literature and in each case there was a good outcome, which was not expected according to predictive models. A possible mechanism may involve the relative lack of functional macrophages in HIV patients, which would tend to result in much less severe lung injury. None of the available predictive models of Paraquat poisoning appear to be appropriate for HIV patients.Paraquat poisoning in HIV patients may have better survival due to less lung injury.

The preventive effect of atorvastatin on paraquat-induced pulmonary fibrosis in the rats

PURPOSE

Pulmonary fibrosis is a potentially lethal inflammatory disease and there has been no effective medication for this progressive disease up to now. As a model, different therapeutic approaches have been applied for paraquat-induced pulmonary injury and fibrosis. Atorvastatin besides cholesterol-lowering effects possesses anti-inflammatory and anti-oxidant properties. The current study was designed to investigate the preventive anti-fibrotic effects of atorvastatin on paraquat-induced pulmonary fibrosis in rats.

METHODS

The rats were randomly divided into five experimental groups. Group I, control group (saline), group II received a single oral dose of 20 mg/kg paraquat with no treatment and III, IV and V groups received atorvastatin at the doses of 10, 20, and 40 mg/kg/day orally one week before and three weeks after paraquat administration, respectively. The rats were sacrificed 21 days after paraquat. Lung hydroxyproline and serum levels of malondialdehyde (MDA) were determined and lung indices and semi-quantitative histopathological changes were evaluated.

RESULTS

Paraquat could significantly increase the serum MDA and lung hydroxyproline levels. Elevated content of tissue hydroxyproline and serum levels of malondialdehyde induced by paraquat, attenuated by atorvastatin at the doses of 10, 20 and 40 mg/kg. Furthermore, histopathological findings and the amount of lung indices showed the beneficial preventive role of atorvastatin in rat pulmonary fibrosis induced by paraquat.

CONCLUSION

In conclusion, the present data show that atorvastatin alleviate the toxic effects of paraquat under the experimental circumstances and may be a useful agent in cases who are in contact or poisoned with paraquat.

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.

Edaravone attenuates paraquat-induced lung injury by inhibiting oxidative stress in human type II alveolar epithelial cells

BACKGROUND

Edaravone (3-methyl-1-penyl-2-pyrazolin-5-one) is a potent free-radical scavenger and has the antioxidant ability to inhibit lipid peroxidation. The study aimed to examine the effect of edaravone on protecting the acute injury of human type II alveolar epithelial cells (A549 cells) induced by paraquat (PQ) and the change of production of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD).

METHODS

A549 cells were cultured and divided into PQ group (group P), edaravone-treated group (group E) and normal control group (group C). The cells in group P were exposed to paraquat (600 μmol/L), and the cells in group E were treated with edaravone (100 μmol/L) additionally, and no drug intervention was given to the cells in group C. Real-time monitoring by LSCM was used to detect the cell response and the intracellular dynamic change of ROS level in A549 cells after administration of PQ and edaravone. And the levels of SOD and MDA were detected respectively by biochemistry colorimetry. Data were expressed as mean ± standard error of the mean. Statistical analysis was carried out with the soft SPSS 16.0.

RESULTS

The concentration of intracellular ROS significantly increased when PQ was given to A549 cells. But after administration of edaravone, the concentration of intracellular ROS was decreased. Compared to the PQ group, the levels of SOD in the edaravone group were significantly increased while the levels of MDA were markedly decreased.

CONCLUSIONS

Paraquat can increase the oxidative stress, and induce the lipid peroxidation of A549 cells. Edaravone has the effect to scavenge reactive oxygen species, and to protect against the PQ-induced lung toxicity.

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.

Studies of the interaction between paraquat and bovine hemoglobin

The interaction between paraquat (PQ) and bovine hemoglobin (BHb) was investigated using fluorescence and UV/vis absorption spectroscopy. The reactivity of the heme centers with superoxide anions formed by PQ was judged on the basis of the decrease of the Soret band. The experimental results showed that the fluorescence quenching of BHb by PQ was a result of the formation of PQ-BHb complex; static quenching was confirmed to result in the fluorescence quenching. The binding site number n, apparent binding constant K(A) and corresponding thermodynamic parameters were measured at different temperatures. The process of binding PQ molecule on BHb was a spontaneous molecular interaction procedure in which entropy increased and Gibbs free energy decreased. Hydrophobic and electrostatic interactions played a major role in stabilizing the complex. The effect of PQ on the conformation of BHb was analyzed using synchronous fluorescence spectroscopy.

Antifibrotic effect of captopril and enalapril on paraquat-induced lung fibrosis in rats

Although different treatment modalities have been implemented for pulmonary fibrosis, the results have not been promising and these conditions have been considered untreatable and irreversible. Thus, a plethora of new drugs has been tried for the control of this condition in recent years. This study examined the effects of two angiotensin-converting enzyme inhibitors, captopril and enalapril, on paraquat-induced pulmonary fibrosis in rats, through biochemical and histopathological parameters. Male albino Wistar rats were divided into eight groups (n = 4-5 each), including control, paraquat, captopril alone, captopril treatment and pre-treatment, enalapril alone, enalapril treatment and pre-treatment. After 21 days of treatment, the lungs were removed and the levels of hydroxyproline, glutathione and lipid peroxidation were determined. Angiotensin-converting enzyme inhibitors showed no effect on glutathione and lipid peroxidation. The results also demonstrated that captopril and enalapril improved pulmonary fibrosis as shown by histopathology, as well as a decreased content of hydroxyproline (P < 0.001) in the lung tissue. In conclusion, the present findings suggest that the antifibrotic effect of these drugs may be related to the inhibition of angiotensin-converting enzyme.

Lisinopril ameliorates paraquat-induced lung fibrosis

BACKGROUND

Paraquat is a controversial and one of the most commonly used herbicides in the world. Although liver, kidney, heart and CNS are affected, lung damage resulting to pulmonary fibrosis is the usual cause of deaths in the cases with intoxication. The mechanism of paraquat toxicity is not clear but probably includes the induction of lipid peroxidation of unsaturated fatty acids. Lisinopril, an angiotensin-converting enzyme inhibitor (ACEI), an antihypertensive drug, has beneficial effects on the treatment of fibrosis. The antifibrotic effect of lisinopril has shown to be due to inhibition of synthesis of angiotensin II that causes stimulation of fibroblast proliferation and collagen synthesis.

METHOD

Male albino Wistar rats were used in the experiments (weighing 150-300 g). The animals were divided into 5 groups: group I received saline, group II received lisinopril (1 mg/kg; po), group III was given a single i.p. dose of 20 mg/kg paraquat, group IV (treatment group) received lisinopril after single a i.p. dose of 20 mg/kg paraquat, and group V (pre-treatment group) received lisinopril before a single i.p. dose of 20 mg/kg paraquat. After 21 days of treatment, the level of hydroxyproline and the degree of lipid peroxidation were determined in the lung tissue of the animals and the lungs were examined histologically for fibrosis.

RESULT

Paraquat caused a significant increase in hydroxyproline content and lisinopril significantly decreased the amount hydroxyproline (p<0.001) in the lung tissue of the rats. The histological examination also indicated that lisinopril can effectively protect the paraquat-induced lung fibrosis. The lipid peroxidation levels in the lung were not significantly changed when compared to the control group.

CONCLUSION

The antifibrotic effect of lisinopril may be due to inhibition of angiotensin II or proline moiety, which is a common structural in all ACEI, drugs.

Decreasing the oxidant stress from paraquat in isolated perfused rat lung using captopril and niacin

The abilities of captopril and niacin to protect against the lung toxicity of paraquat (PQ) were studied. The anti-oxidative action of captopril, an angiotensin-converting enzyme inhibitor, appears to be attributable to the sulphahydryl group (SH) in the compound, which gives captopril the ability to scavenge reactive oxygen species. Niacin replenishes the NAD and ATP depletion caused by reactive oxygen species. PQ causes lung damage in man and in several species of laboratory animals. The damage is initially manifested by hemorrhage and edema, and later by consolidation of the lung and fibrosis development. In this study, the lungs of male Wistar rats (250-300 g in weight) were perfused by Krebs-Ringer buffer alone (control), niacin (150 microM), captopril (10 microM) and PQ (600 microM) in perfusion fluid, and the biochemical changes that occurred in isolated rat lung were examined within 1 h and compared to PQ alone. The results show that captopril significantly decreases the lung weight/body weight ratio when used as a pretreatment and a post-treatment to captopril (p<0.0001). The results also show that captopril (10 microM) and niacin (150 microM) significantly decreases PQ-induced lung toxicity. Lactate dehydrogenase (LDH) activity significantly decreased in treatment groups as compared to the PQ group (p<0.0001). This study suggests that paraquat causes increased lipid peroxidation and LDH activity and decreased glutathione (GSH) and total protein in isolated perfused rat lung. These effects are reduced under these experimental conditions by captopril and niacin.

The role of sodium cromolyn in treatment of paraquat-induced pulmonary fibrosis in rat

Paraquat is a non-selective herbicide which is widely used in agriculture. It has potential of producing pulmonary fibrosis. In this study the therapeutic effect of different doses of sodium cromolyn on the development of paraquat-induced pulmonary fibrosis was investigated. In order to produce lung fibrosis, rats were given single oral dose of paraquat (40 mg kg(-1)). Two groups of animals were nebulised with 6 or 8 mg day(-1) cromolyn (divided into two doses per day) 5 days prior and 2 weeks after paraquat treatment. Control animals were given equivalent volume of normal saline and treated with cromolyn similar to the test groups. Rats were killed at the end of treatment course and lung tissues were tested histologically and biochemically. Histological examination of paraquat-treated animals showed marked infiltration of inflammatory cells in the alveolar spaces, septal thickening and fibrosis. Lesions were evident in many places of sections. Sodium cromolyn could markedly reduce such damages in lung tissue. Lung weight, hydroxyproline and collagen content of lung tissues were elevated significantly (P < 0.05) in paraquat group compared with control group. In cromolyn-treated groups such factors were near to control value and were significantly lower than paraquat group (P < 0.05). Results of this study indicate that sodium cromolyn can decrease the fibrogenic effect of paraquat on lung. Such effect may be due to the stabilising of mast cells and inhibition of inflammatory mediators by sodium cromolyn.

A case of paraquat poisoning and subsequent fatality presenting to an emergency department

Paraquat (1,1'-dimethyl-4,4'-dipyridylium) is an herbicide associated with both accidental and intentional ingestion, leading to severe and often fatal toxicity. Prognosis is largely dependent on the amount of paraquat absorbed. Rapid identification of the symptoms of paraquat toxicity (burns or ulceration at the site of ingestion or injection, acute respiratory distress, and renal failure) can facilitate early treatment intervention to limit absorption. We report a case of a 71-year-old man with a suicidal ingestion of paraquat 2 days prior to presentation. Serum paraquat levels, time elapsed since ingestion, and clinical symptoms all indicated poor prognosis. The patient developed severe respiratory distress and progressive renal failure, and died 6 days after admission to the hospital.

Influence of age on the passage of paraquat through the blood-brain barrier in rats: a distribution and pathological examination

Experiments were performed to determine the extent of paraquat entry into the brain of neonatal and elderly rats, as compared with adult rats, which may be dependent on the efficacy of the blood-brain barrier. A single, median lethal dose (20 mg/kg s.c.) of paraquat containing [14C]paraquat was administered to neonatal (10 day old), adult (3 month old) and elderly (18 month old) rats. In contrast to the adult and elderly rats where paraquat levels fell over the 24 h post-dosing period to negligible levels, paraquat concentrations in neonatal brains did not decrease with time between 0.5 and 24 h following dosing. The distribution of [14C]paraquat was measured in selective brain regions using quantitative autoradiography in all three age groups of rats, 30 min and 24 h following dosing. Autoradiography demonstrated that brain paraquat distributions were similar in the rat age groups. Most of the paraquat was confined to regions outside the blood-brain barrier and to brain regions that lack a complete blood-brain barrier e.g. dorsal hypothalamus, area postrema and the anterior olfactory bulb. Between 0.5 h and 24 h following dosing, paraquat concentrations in deeper brain structures, some distance away from the sites of entry, began to slowly increase in all the rat age groups. By 24 h following dosing, a majority of brain regions examined using quantitative autoradiography revealed significantly higher paraquat concentrations in neonatal brains as compared to brain regions of adult and elderly rats. Despite increased paraquat entry into neonatal brain, we could find no evidence for paraquat-induced neuronal cell damage following a detailed histopathological examination of perfused-fixed brains. In conclusion, impaired blood-brain barrier integrity in neonatal brain thus permitting more paraquat to enter than in adult brain, did not result in neuronal damage.

Modulation of cyclophosphamide-induced early lung injury by curcumin, an anti-inflammatory antioxidant

Cyclophosphamide causes lung injury in rats through its ability to generate free radicals with subsequent endothelial and epithelial cell damage. In order to observe the protective effects of a potent anti-inflammatory antioxidant, curcumin (diferuloyl methane) on cyclophosphamide-induced early lung injury, healthy, pathogen free male Wistar rats were exposed to 20 mg/100 g body weight of cyclophosphamide, intraperitoneally as a single injection. Prior to cyclophosphamide intoxication oral administration of curcumin was performed daily for 7 days. At various time intervals (2, 3, 5 and 7 days post insult) serum and lung samples were analyzed for angiotensin converting enzyme, lipid peroxidation, reduced glutathione and ascorbic acid. Bronchoalveolar lavage fluid was analyzed for biochemical constituents. The lavage cells were examined for lipid peroxidation and glutathione content. Excised lungs were analyzed for antioxidant enzyme levels. Biochemical analyses revealed time course increases in lavage fluid total protein, albumin, angiotensin converting enzyme (ACE), lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase, alkaline phosphatase, acid phosphatase, lipid peroxide levels and decreased levels of glutathione (GSH) and ascorbic acid 2, 3, 5 and 7 days after cyclophosphamide intoxication. Increased levels of lipid peroxidation and decreased levels of glutathione and ascorbic acid were seen in serum, lung tissue and lavage cells of cyclophosphamide groups. Serum angiotensin converting enzyme activity increased which coincided with the decrease in lung tissue levels. Activities of antioxidant enzymes were reduced with time in the lungs of cyclophosphamide groups.(ABSTRACT TRUNCATED AT 250 WORDS)

PGI2 production and angiotensin converting enzyme activity in cultured porcine pulmonary artery endothelial cells treated with paraquat

The herbicide paraquat (PQ) is known to cause acute pulmonary edema at toxic dose and to induce morphologic changes in alveolar epithelial cells, even in the early phase of toxicity. However, whether the pulmonary vascular endothelial cells are specifically vulnerable to PQ is still controversial. To investigate the direct toxic and metabolic effects of PQ on pulmonary vascular endothelial cells, cultured porcine pulmonary artery endothelial cells (PPAEC) were evaluated. A dose of 10(-4) M of PQ inhibited the growth of endothelial cells. The thrombin- and bradykinin-stimulated production of prostacyclin (PGI2) by PPAEC was significantly enhanced, and the angiotensin converting enzyme (ACE) activity of cell lysate of PPAEC was significantly suppressed after incubation for 24 h with 10(-4) M PQ. No further enhancement of PGI2 production in response to thrombin after 48 h of incubation was demonstrated. These alterations in arachidonic acid metabolism and ACE activity did not result from the cytotoxicity of PQ, because the release of lactate dehydrogenase (LDH) into the culture medium increased only after 72 h incubation with PQ. Incubation for more than 48 h induced an obvious toxis effect on PPAEC.

Protection of rats against the effects of alpha-naphthylthiourea (ANTU) by elevation of non-protein sulphydryl levels

We have investigated the influence of the elevation of pulmonary glutathione (GSH) levels on the toxicity of the rodenticide alpha-naphthylthiourea (ANTU) to rat lung. Administration of phorone (diisopropylidene acetone; 200 mg/kg i.p.) caused an initial depletion of both pulmonary and hepatic GSH followed after 48 hr by a marked elevation in both tissues, due most probably to a compensatory rebound synthesis. In control rats, ANTU produced a dose-dependent lethality, hydrothorax and loss of ability of lung tissue to accumulate adenosine and spermidine (markers of endothelial and epithelial cell function, respectively). These effects were prevented or markedly ameliorated when ANTU was given 48 hr after pretreatment with phorone. The mechanism of the protection by phorone pretreatment against ANTU-induced pulmonary toxicity is unclear. It may be due, in part, to elevated GSH levels in pulmonary endothelial cells and, in addition, to increased detoxification of ANTU in the liver, resulting in a decreased availability to the lung.

Correlation between lipid peroxidation and morphological manifestation of paraquat-induced lung injury in rats

Biochemical and morphological studies of rat lung were performed to determine the role of lipid peroxidation in the in vivo lung toxicity of paraquat. Two injections of 20 mg/kg paraquate were administered intraperitoneally every other day. While notable epithelial damage in the lungs was observed on the day after the second paraquat injection and progressed through the 5th day, the concentration of lipid peroxides in the rat lungs did not increase by the 3rd day after the injection. The lipid peroxide concentrations increased after the 5th day post-injection, and reached the maximum concentrations on the 7th day, when the damaged alveolar surface had been mostly repaired by regenerative pneumocytes. On the other hand, the delayed increase of lung lipid peroxides in paraquat-treated rats paralleled the increased number of macrophages in the lung, which reached maximum numbers on the 7th day. Glutathione peroxidase activity in the lungs also increased with a similar time course. Macrophages from the lungs contained a large amount of engulfed degradation products and cellular debris, and immunohistochemical study showed high glutathione peroxidase content on the 5th and 7th days. These results suggest that lipid peroxidation is a relatively late event in the in vivo paraquat-treated lung and that the delayed increase of lipid peroxides in the lungs occurs from the phagocytic activities of macrophages rather than from toxic cell injury.

Pulmonary fibrosis induced in the hamster by amiodarone and desethylamiodarone

Associated with amiodarone use is pneumonitis which may progress to life-threatening pulmonary fibrosis. Desethylamiodarone, a metabolite, whose role in the etiology of amiodarone-induced pulmonary toxicity has been unclear, also possesses antiarrhythmic activity and could potentially be used as an antiarrhythmic drug itself. We have used a single intratracheal administration of equimolar amounts of amiodarone or desethylamiodarone (1.83 mumol) to male golden Syrian hamsters to investigate the fibrogenicity of desethylamiodarone. Animals were terminated at 1, 7, 14, 21, and 28 days post-treatment, and toxicity was assessed by measurement of lung hydroxyproline content and by histological techniques. Amiodarone and desethylamiodarone significantly increased lung hydroxyproline content over vehicle control animals by 21 days (33 and 58% respectively). While amiodarone-treated lungs had hydroxyproline contents similar to control levels at 28 days, desethylamiodarone-treated lungs remained elevated (44% over control values). Quantitative histologic examination revealed that lungs from desethylamiodarone-treated animals displayed a greater toxic effect, while trichrome staining confirmed the increased deposition of interstitial collagen in these same animals. These results may be due to the higher affinity of the lung for desethylamiodarone and thus a prolonged exposure. The findings indicate that, in the hamster, both compounds are toxic by this route and that desethylamiodarone is not a nontoxic metabolite. Further, use of desethylamiodarone as an antiarrhythmic agent may not be devoid of the adverse effects associated with amiodarone.

Effects of paraquat on canine bronchoalveolar lavage fluid

Bronchoalveolar lavage (BAL) recovers the epithelial lung fluid of the lower respiratory tract. In this study, we have used BAL to detect early pulmonary injury in beagle dogs following an intravenous infusion of 10 mg paraquat dichloride/kg bodyweight. Bronchoalveolar lavage was performed twice in 11 dogs, 60 hr before and 34 hr after an intravenous infusion of paraquat dichloride (n = 8) or saline (n = 3). The dogs were studied in three groups: (1) paraquat only (n = 4); (2) paraquat plus hemoperfusion (n = 4); and (3) hemoperfusion only (n = 3). Because hemoperfusion, a treatment used for paraquat poisoning, could have effects on BAL independent of paraquat, we evaluated the effects on BAL fluid of this procedure performed separately from and together with administration of paraquat. We examined cytology, proteins, enzymes, and glutathione in the BAL fluid and expressed all results per milliliter of aspirated lavage fluid. Hemoperfusion did not alter the BAL fluid. In contrast, in dogs studied 34 hr after administration of paraquat, total cell counts, alveolar macrophage and neutrophil counts, and concentrations of total protein, albumin, ACE, LDH, and ALP were increased. Bronchoalveolar lavage in the dog provides an excellent tool with which to detect early paraquat-induced pulmonary injury. The same technique could be useful for sequential monitoring of other types of pulmonary disease and injury.

The accumulation and localisation of putrescine, spermidine, spermine and paraquat in the rat lung. In vitro and in vivo studies

Putrescine was accumulated into the isolated perfused rat lung by a temperature dependent process. The uptake obeyed saturation kinetics for which an apparent Km of 14 microM and Vmax of 48 nmol/g wet wt/hr was derived. After rats were dosed subcutaneously with [14C]putrescine, it was accumulated in the lung to concentrations greater than that in the plasma with the highest amount found between 3 and 12 hr. From 3 hr after dosing until 24 hr, there was a progressive increase in 14C label incorporated into spermidine, indicating that putrescine was converted to spermidine. Using autoradiographic techniques in lung slices the [3H]oligoamines were found in the alveolar epithelial type II. Clara and very probably the alveolar type I cells. With [3H]paraquat, the presence was detected only in the alveolar type II cells. Likewise, in the isolated perfused rat lung or following s.c. dosing of rats with [3H]putrescine the radiolabel was located only in the alveolar type II cell. We have suggested that the most likely explanation for the differences in localisation of label between in vitro and in vivo studies resulted from the use of [3H] label of different specific activity. Consequently we have concluded that the cell types with the ability of accumulate paraquat and oligoamines were the alveolar epithelial type I and type II cells and Clara cells.

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.

Lung fibrosis induced by diquat after intratracheal administration

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

Concentration-dependent respiratory response of guinea pigs to paraquat aerosol

Six groups of male English smooth-haired guinea pigs were exposed to a paraquat aerosol for 4 h. Concentrations of the paraquat ion aerosols ranged from 0.83 to 2.07 mg/m3. Over 85% of the particles in the aerosol were found to be under 0.65 micron. Tidal volume and respiratory frequency of each animal were measured prior to exposure, immediately following exposure, and 18 h following exposure. These parameters were monitored during air breathing and a 10% CO2 challenge using a whole body plethysmograph fitted with a head chamber. A concentration-related decrease in tidal volume and increase in respiratory frequency were found 18 h following exposure when breathing air and the CO2 mixture. Inspection of the flow-volume (V-VT) loops showed abnormal rectangular shapes 18 h following exposure, also varying with the concentration and indicative of lung restriction with a hyperventilation pattern. This study provides quantitative information on the respiratory toxicity following a paraquat inhalation exposure and qualitative description of its effect on the respiratory pattern. The measurements made may be of value in the search of antidotes for this important herbicide.

A retrospective study of proliferative interstitial lung disease of horses in Florida

Proliferative and fibrosing interstitial lung disease was diagnosed in 20 horses submitted for necropsy between 1982 and 1985. Most of the horses were foals ranging from 3 days to 6 months in age. Six adult horses were affected. The macroscopic and microscopic characteristics of the lesions consisted of proliferative interstitial pneumonia and were similar to those of atypical interstitial pneumonia of ruminants. Based on morphologic features of the lesions, a toxic etiology is suspected for the induction of this naturally acquired primary equine lung disorder, but could not be specifically discovered by historical information.

A light and electron microscopic study of the regenerative epithelium in the intrahepatic bile duct. Experimental study of local direct instillation of paraquat into the intrahepatic bile ducts of rats

To date, no reliable report on the regeneration of the intrahepatic bile duct epithelium following damage to the duct has been published. In this study, a direct instillation of paraquat dichloride into the intrahepatic bile ducts of rats was carried out, and the livers were examined under light and electron microscopy. One hour after treatment, the biliary epithelia showed degeneration and necrosis, and these changes remained for a considerable period in a large majority of the ducts examined. Three weeks after instillation, low columnar epithelium consisting of hyperchromatic nuclei and eosinophilic cytoplasm was present in a medium-sized bile duct, which was collared by marked periductal fibrosis. Electron microscopically, the eosinophilic epithelium showed a marked increase in the number of rough endoplasmic reticula, ribosomes, mitochondria, and filamentous structures, suggesting an active viability of the cell. Subsequently, the eosinophilic cells were replaced by normal-appearing epithelium, not associated with the periductal fibrosis. The data suggest that an epithelial regeneration occurred in the intrahepatic duct following injury and that this activity may be similar to that of the extrahepatic bile duct epithelium.

Morphological and biochemical correlates of chemical induced injury in the lung. A discussion

We have reviewed some of the factors which contribute to lung damage by various toxicants. These include disposition of the chemical, its metabolism, individual cell type susceptibility and the potential for the tissue to repair. We have discussed the use of biochemical parameters to measure the functional activity of individual cell types in order to predict the damage to specific cell types and concluded that careful morphological analysis of lung tissue is likely to provide a more sensitive and informative measure of specific cell type injury. However, in order to investigate the mechanism of toxicity of pulmonary toxicants it is essential to establish the primary biochemical event that leads to cell damage and morphological change. The importance of separating the relevant biochemical change(s) from the cascade of biochemical events associated with dead and dying cells and the reparative response of the lung is emphasised.

Bipyridylium herbicide toxicity in vitro: comparative study of the cytotoxicity of paraquat and diquat toward the pulmonary alveolar macrophage

In vitro exposure of adult rat alveolar macrophages to either paraquat or diquat resulted in concentration dependent cytotoxicity (cell death). The herbicide paraquat, however was statistically significantly more potent toward these cells than was diquat. The LC50 value for paraquat (8-h exposure, 37 degrees C) was determined to be 0.94 mM [95% confidence interval (C.I.) 0.79-1.12 mM], whereas the corresponding LC50 value for diquat was 1.97 mM (C.I. 1.58-2.51 mM). Interestingly, diquat was shown to enter these cells to a much greater extent than was paraquat. The latter data, while seemingly contradictory to the above findings, is consistent with other reported findings in this study that show that cell respiration, as measured by loss of oxygen consumption, was more sensitive to diquat than it was to paraquat. Also, only paraquat cytotoxicity was found to be dependent on oxygen tension and could be altered by the presence of antioxidant enzymes in the culture medium. Both compounds, however, were found to be equipotent toward purified mitochondria. Both paraquat and diquat were able to uncouple oxidative phosphorylation and induce active oxygen species (superoxide anions and hydrogen peroxide) from this organelle. It is concluded that free-radical pathology is the most likely mechanism of action by which paraquat is cytotoxic toward these cells, but that diquat poisoning probably originates from some other mode of action.

Early cellular events in pulmonary fibrosis

In this review we have surveyed recent investigations of early cellular events in pulmonary fibrosis both in animal models and in human diseases. Analysis of the interactions of the numerous cell types in the lung following injury is an almost overwhelmingly complex enterprise. In the animal models experimental design has a profound effect on results, making it difficult to compare studies when species, fibrogenic agent, dose, route of exposure, schedule of administration, time course, and analytical methods may not be equivalent. In human diseases we are rarely able to obtain data at precisely the same time point in the course of the disease even among patients in the same study, and possible confounding variables present are legion. Transcending these difficulties for the moment, can we draw any conclusions from our current knowledge of early cellular interactions in pulmonary fibrosis? What is striking is not that there are so many agents that can potentially induce pulmonary fibrosis, but that the lung has such capabilities for recovery. Although the major effector cells may all initially participate in damaging the lung and initiating fibrosis, there is evidence that they may also have the capacity to participate in subsequent repair. Macrophages may initially recruit fibroblasts and stimulate them to proliferate, only to suppress them subsequently. Macrophage production of prostaglandins can lead to suppression of macrophage, neutrophil and lymphocyte responses, thus attenuating tissue injury and the development of fibrosis. Neutrophils may initially release toxic metabolites and enzymes that damage parenchyma. However, there is evidence that they may later play a role in attenuating fibrosis, perhaps through collagenase secretion, or through as yet unknown mechanisms. Lymphocytes may initially participate in a number of damaging ways by secreting chemoattractants for other cells and participating in destructive autoimmune processes. However, there is evidence that subpopulations of T cells may dramatically shift during the course of fibrosis, leading to attenuation of the process. It may thus be useful to consider irreversible pulmonary fibrosis as the end result of a process in which the balance of normal injury/repair mechanisms is disrupted. There is clearly no single "fibrogenic event." Rather, there seem to be a number of places where disruption of balance/repair processes may begin. In diseases of unknown etiology such as sarcoidosis or IPF, loss of control may occur at the genetic level, leading to the destructive alveolitis that is the apparent precursor of fibrosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Paraquat toxicity

Paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride) is marketed as a contact herbicide. Although it has proved safe in use there have been a number of cases of poisoning after the intentional swallowing of the commercial product. The most characteristic feature of poisoning is lung damage, which causes severe anoxia and may lead to death. The specific toxicity to the lung can be explained in part by the accumulation of paraquat into the alveolar type I and type II epithelial cells by a process that has been shown to accumulate endogenous diamines and polyamines. When accumulated, paraquat undergoes an NADPH-dependent, one-electron reduction to form its free radical, which then reacts avidly with molecular oxygen to reform the cation and produce superoxide anion, which in turn will dismutate to form H2O2. This may lead to the formation of more reactive (and hence toxic) radicals which have the potential to cause lipid peroxidation and lead to cell death. Biochemical changes provoked by paraquat in the lung suggest that it causes a rapid, pronounced and prolonged oxidation of NADPH that initiates compensatory biochemical processes in the lung. NADPH may be further depleted as it is consumed in an attempt to detoxify H2O2 or lipid hydroperoxides. Thus it is possible that with toxic levels of paraquat in the cell, compensatory biochemical processes are insufficient to maintain levels of NADPH consistent either with cell survival or with the ability to detoxify H2O2 or prevent lipid peroxidation.

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.

Mitochondrial injury of pulmonary alveolar epithelial cells in acute paraquat intoxication

The primary ultrastructural changes in pulmonary alveolar epithelial cells are described in paraquat-injected rats. Within 6-12 hr a single intravenous injection of 40 mg/kg paraquat dichloride caused selective mitochondrial swelling and loss of intramitochondrial granules within 24 hr in alveolar Type II cells. As the mitochondrial injury advanced, microvilli disappeared from apical plasma membrane followed by a cell destruction and detachment from basement membrane. This was accompanied by secondary damage to Type II cells and interstitial cells. These results indicate that paraquat may affect primarily the Type II cells and the first lesion produced occurs in mitochondria.

Fine structural changes in cryptogenic fibrosing alveolitis and asbestosis

Lung biopsies from 17 patients with cryptogenic fibrosing alveolitis of a cellular rather than fibrotic pattern were examined by transmission electron microscopy in the hope that such cases would show features of pathogenetic significance. Further selection was made by choosing minimally affected areas. There was no ultrastructural evidence of immune complex deposition but alveolar epithelial and capillary damage was frequently found (17 and 14 of the 17 cases respectively). Alveolar epithelial injury consisted of patchy necrosis and regenerative hyperplasia. Alveolar capillary injury consisted of cytoplasmic swelling and basement membrane thickening and reduplication. Many of these features have not been emphasized in previous reports and their prominence in early stages of the disease suggest that they may have pathogenetic significance, possible mechanisms of which are discussed. Similar findings identified during the course of this study in 8 asbestos workers suggest that similar pathogenetic mechanisms may operate in asbestosis.

Paraquat and ferritin-dependent lipid peroxidation

A lipid peroxidation system consisting of phospholipid liposomes, paraquat, ADP, and NADPH-cytochrome P450 reductase was constituted using ferritin as the sole source of iron. Lipid peroxidation was completely inhibited by superoxide dismutase, essentially not affected by mannitol, but markedly stimulated by catalase. Similar effects of these scavenging agents were observed in incubations void of ADP. These data suggest that O2-, produced by the redox cycling of paraquat, can release iron from ferritin and thereby promote lipid peroxidation. The effects of catalase and mannitol suggest that the initiation of peroxidation, in either the presence or absence of ADP, is not significantly dependent upon the hydroxyl radical produced via an iron-catalyzed Haber-Weiss reaction.

Sequential pathological changes induced in rats with the anti-cancer drug I, 3-bis (2-chloroethyl)-I-nitrosourea (BCNU)

The pathology of pulmonary toxicity induced by the anticancer drug 1, 3-bis(2-chloroethyl)-1-nitrosourea (BCNU) was studied in F344 rats. The compound was administered in a multiple-dose regimen comparable to the dose schedule commonly given patients. Morphological aspects were investigated by light and electron microscopy in a serial sacrifice experiment. All animals developed pulmonary fibrosis accompanied by formation of peribronchial and peribronchiolar foci of granulomatous tissue. The first morphologically detectable changes were identified in alveolar type II cells and were suggestive of disturbed surfactant synthesis. Endothelial damage accompanied by pronounced plasma cell infiltration developed subsequently and was followed by the development of diffuse interstitial fibrosis.