Lung Nonprotein Sulfhydryl Research Articles

Modulation of silica-induced lung injury by reducing lung non-protein sulfhydryls with buthionine sulfoximine

A role for non-protein sulfhydryl moieties (NPSH) (e.g., glutathione) in silica (SI)-induced cellular inflammation and fibrosis was examined in C57B1/6 mice depleted of lung NPSH by buthionine sulfoximine (BSO). Lung NPSH levels in the BSO-treated groups were reduced to approx. 50% of the non-BSO-treated animals. In BSO-treated Si-injected (2 mg/mouse) animals, the number of pulmonary alveolar macrophages (PAM) lavaged from the lungs was significantly increased on day 1 and decreased on day 7. Moreover, BSO-treated Si-exposed mice evidenced significantly more lavage protein and albumin on days 1 and 3, respectively, than non-BSO-treated Si-exposed mice. Si-induced collagen deposition, however, was decreased by 18% in the BSO-treated animals. These data suggest that lung NPSH lessens the potential of silica to elicit acute lung injury.

Depression of glutathione by cold-restraint in mice

The effects of cold-restraint as a physiological stressor on the glutathione (GSH) content of the liver and other tissues were examined in male mice. Mice of the ICR, NIH, ND/4, and B6C3F1 strains subjected to cold-restraint for 2 or 3 h experienced a loss of hepatic GSH concentrations ranging from approximately 15 to 50%. Though 3 of these strains (ICR, NIH, and B6C3F1) experienced hypothermia as result of the cold-restraint treatment, with average decreases in core body temperature ranging from 3.3 to 9.8°C, hepatic GSH levels were depressed in the ND/4 mouse in the absence of changes in core body temperature. The ability of cold-restraint as a stressor to diminsh hepatic GSH therefore could not be attributed simply to hypothermia. The decrease in hepatic GSH from cold-restraint in ND/4 mice was paralleled by a decrease in non-protein sulfhydryl (NPSH) content of the liver. In addition to its effects on liver GSH and NPSH concentrations, 1.5 h of cold-restraint stress significantly depressed plasma, heart, kidney, and lung NPSH concentrations. The extent of NPSH depression was equivalent to the GSH depression in the liver, heart, and kidney, despite the observation that the normal contribution of GSH to total NPSH content in these tissues ranged from a high of 89% (liver) to a low of 49% (heart). These results with cold-restraint in the ND/4 mouse suggest that other stressors may significantly depress cellular concentrations of GSH and other thiols, and may thereby render the affected tissues more susceptible to the toxicity of free radicals, electrophilic xenobiotic metabolites, or reactive oxygen species.

Effects of Depletion of Ascorbic Acid or Nonprotein Sulfhydryls on the Acute Inhalation Toxicity of Nitrogen Dioxide, Ozone, and Phosgene

AbstractThe effect of depleting lung ascorbic acid (AH2) and nonprotein sulfhydryls (NPSH) on the acute inhalation toxicity of nitrogen dioxide (NO2), ozone (O3), and phosgene (COCl2) was investigated in guinea pigs. The increase in bronchoalveolar lavage (BAL) fluid protein (an indicator of alveolar-capillary damage leading to increased permeability) was measured 16–78 h following a 4-h exposure to the gas in animals deficient in AH2 or NPSH. Gas concentrations were chosen that produced low but significant increases in BAL protein. Lung AH2 was lowered to about 20% of control by feeding rabbit chow for 2 wk. Lung NPSH was lowered to about 50% of control by injecting a mixture of buthionine S, R-sulfoximine (BSO) and diethylmaleate (OEM) (2.7 and 1.2 mmol/kg, respectively). BSO/DEM did not affect the lung concentrations of AH2 or α-tocopherol. AH2 depletion caused a fivefold and a threefold enhancement in the toxicity of 5 ppm and 10 ppm NO2, and a sixfold enhancement in the toxicity of 0.5 ppm O3, but di...

The pulmonary effects of buthionine sulfoximine treatment and glutathione depletion in rats.

Buthionine sulfoximine (BSO), an inhibitor of de novo synthesis of glutathione (GSH), was used to deplete rats of GSH and determine the effect of treatment on antioxidant enzyme responses, lung injury, and the susceptibility to concurrent sublethal or lethal hyperoxia. In a preliminary experiment, total lung nonprotein sulfhydryl (NPSH) and GSH levels were measured at various times after single doses of BSO. The lowest concentrations were observed at 12 to 18 h. These experiments were used to establish a repeated dosing protocol for more prolonged GSH depletion. The lungs of rats treated with BSO for 4 days demonstrated markedly decreased GSH and NPSH levels (10 to 40% of control values) and glutathione peroxidase activity (45 to 60% of control values). Superoxide dismutase activities were elevated, glutathione reductase activity was slightly elevated, and catalase activity was unchanged. These changes were dose-responsive. The lungs of treated rats were grossly and microscopically normal. BSO treatment of additional rats did not increase susceptibility to lethal hyperoxia (greater than 98% oxygen). Combined treatment of rats with both BSO and sublethal hyperoxia (80% oxygen) for 4 days did not alter the biochemical responses demonstrated by rats treated solely with BSO. The marked increase in catalase activity obtained after hyperoxia alone was not observed in rats treated with both hyperoxia and BSO. The lungs of saline- and BSO-treated rats exposed to sublethal hyperoxia demonstrated a patchy distribution of slight perivascular and peribronchiolar edema.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of buthionine sulfoximine on the development of ozone-induced pulmonary fibrosis

The capacity of reduced glutathione (GSH) to protect lung tissue against ozone-induced pulmonary fibrosis was investigated. Male B6C3F 1 mice were exposed to 0, 0.2, 0.5, and 1.0 ppm ozone for 23 hr/day for 14 days. During exposures and/or for a period of 90 days after exposures, subgroups of mice at each exposure level were given drinking water containing 30 m M l-buthionine- S,R-sulfoximine (BSO) to lower in vivo levels of GSH. These BSO treatments reduced blood glutamylcysteine synthetase (GCS) activity (regulatory enzyme for GSH biosynthesis) and lung nonprotein sulfhydryl (NPSH) levels in nonexposed animals by approximately half. In contrast, ozone exposures increased blood GCS activity and lung NPSH levels in a concentration-dependent manner, with smaller increases in the BSO-treated mice. Immediately after exposures, an ozone-related inflammatory response was seen in lungs, but no histopathological signs of developing fibrosis were evident. Ninety days later, mice exposed to 1 ppm ozone and not treated with BSO had modest evidence of pulmonary fibrosis. Mice exposed to 1 ppm ozone and treated with BSO during this postexposure period (regardless of BSO treatment during exposures) showed histopathological evidence of exacerbated pulmonary fibrosis, compared to similarly exposed mice not treated with BSO postexposure. These results indicated that interference with the body's normal defense mechanisms against oxidant damage, including suppression of GSH biosynthesis, exacerbates the subsequent development of pulmonary fibrosis.

Pulmonary biochemical effects of inhaled phosgene in rats.

Three exposure regimens were used to study the time course of indicators of lung damage and recovery response to single or repeated exposures to phosgene (COCl2). Rats were sacrificed immediately or throughout a 38-d recovery period after inhalation of 1 ppm COCl2 for 4 h, at intervals during a 7-h exposure to 1 ppm phosgene, or at several time points throughout a 17-d exposure to 0.125 and 0.25 ppm COCl2 (4 h/d, 5 d/wk) and during a 21-d recovery period. Regimen 1 revealed significantly elevated lung wet weight, lung nonprotein sulfhydryl (NPSH) content, and glucose-6-phosphate dehydrogenase (G6PD) activity that stayed elevated for up to 14 d. A significant decrease in body weight and food intake was observed 1 d after exposure. Regimen 2 caused a slight depression in NPSH content but did not affect G6PD activity. Regimen 3 animals showed sustained elevations in lung wet weight, NPSH content, and G6PD activity after 7 d of exposure. No significant changes in these endpoints were observed for the 0.125 ppm COCl2 group. No consistent elevation in hydroxyproline content was seen at either exposure concentration. Light microscopic examination of lung tissue exposed to 0.25 ppm COCl2 for 17 d revealed moderate multifocal accumulation of mononuclear cells in the centriacinar region. In summary, exposure to COCl2 caused changes similar in most ways to those observed for other lower-respiratory-tract irritants.

Nitrogen dioxide exposure and lung antioxidants in ascorbic acid-deficient guinea pigs

We have previously found that ascorbic acid (AA) deficiency in guinea pigs enhances the pulmonary toxicity of nitrogen dioxide (NO 2). The present study showed that exposure to NO 2 (4.8 ppm, 3 hr) significantly increased lung lavage fluid protein (a sensitive indicator of pulmonary edema) only in guinea pigs fed rabbit chow (a diet not supplemented with vitamin C) for at least 7 days, at which time lung AA was about 50% of normal. The rabbit chow diet did not cause reduced body weight as did commercial synthetic scorbutic diets, even when they were supplemented with AA. After 14 days of feeding rabbit chow, lung AA was reduced to 15% of control. At this time, α-tocopherol (AT) in the same lungs was reduced to 85% of control, and lung nonprotein sulfhydryls (NPSH) were increased to 114% of control. Exposure of the guinea pigs to NO 2 (4.5 ppm, 16 hr) increased wet lung weight and further altered the antioxidants in deficient (but not normally fed) animals in the following manner: NPSH content was increased to 130% of control, AT was decreased to 74% of control, and AA was increased from 15 to 50% of control. These findings suggest that depletion of AA in guinea pigs removes an important defense against NO 2. The lung appears to be able to partially compensate for the dietary lack of antioxidant by accumulating AA from other tissues and by increasing NPSH concentrations. However, sufficient exposure to NO 2 leads to oxidation of AT and pulmonary edema. Conditions in which NO 2 produced edema were accompanied by only a slight consumption of AT, and no detectable oxidation of lung AA or NPSH.

Oxidant lung injury: intervention with sulfhydryl reagents.

Intracellular pools of reduced sulfhydryl compounds are taxed in protective and repair processes during oxidant lung injury. To determine the efficacy of exogenous sulfhydryl compounds in preventing the toxic effects of high oxygen exposure on lung, the cell permeable sulfhydryl compounds, cysteamine (CYS) or N-acetylcysteine (NaC), were infused continuously in rats during exposure to 1 atm O2. CYS caused a reduction in mortality compared to vehicle treated-oxygen exposed rats at seven days (56% vs 78% respectively). At 48 hours, CYS reduced oxidant-induced pulmonary edema, measured by wet to dry weight ratios, and prevented oxidation of lung nonprotein sulfhydryls. NaC was even more effective in reducing mortality compared to vehicle treated-oxygen exposed rats (28% vs 78% respectively). In contrast to this beneficial effect of sulfhydryl compounds in oxygen toxicity, oxidant injury due to paraquat poisoning was exacerbated. Mortality increased in mice and rats given paraquat and treated with CYS. We speculate that this effect may be due to the ability of paraquat to accept reducing equivalents directly from CYS, thereby increasing reactive oxygen generated from reduced paraquat.

Nonprotein sulfhydryl alterations in F-344 rats following acute methyl chloride inhalation

This study examined the effect of acute methyl chloride (MeCl) inhalation on F-344 rat tissue nonprotein sulfhydryl (NPSH), largely reduced glutathione. Rats were exposed to MeCl concentrations of 1500, 500, or 100 ppm. A 6-hr exposure to 1500 ppm of MeCl decreased the NPSH content of liver, kidney, and lungs to 17, 27, and 30% of control values, respectively, while 500 ppm MeCl lowered the liver, kidney, and lung NPSH to 41, 59, and 55% of control values, respectively, demonstrating a concentration-related effect. Blood NPSH did not differ from controls in either of these groups. No statistically significant changes from controls in tissue or blood NPSH were observed following a 100-ppm MeCl exposure. The extent of tissue NPSH loss was dependent on exposure duration. Liver and kidney NPSH returned to control NPSH concentrations within 8 hr following exposure of 1500 ppm MeCl. Pretreatment of rats with Aroclor-1254 or SKF-525A did not alter the MeCl-induced decrease in tissue NPSH. These data indicate that MeCl reacts extensively with tissue NPSH in vivo in a concentration-related fashion following acute inhalation exposure. The most likely NPSH constituent with which MeCl reacts is reduced glutathione. The finding that blood NPSH was not affected, in contrast to liver, kidney, or lung NPSH, indicates a tissue-specific reaction between MeCl and sulfhydryl groups, a reaction in which the tissue enzyme glutathione- S-alkyltransferase may play a role.

Glutathione and non-protein sulfhydryl in cerebral cortex and lung in mice exposed to high oxygen pressure

Mice were exposed to 6 atm of 100% O 2, and killed at the onset of hyperactivity, convulsions, and 10(s) post convulsions. Examination of brain cortex from mice killed at these stages of O 2 toxicity revealed no change in oxidized glutathione (GSSG), non-protein sulfhydryls (NPSH), total glutathione (GSH + GSSG), the GSH/GSSG ratio, glutathione reductase and glutathione peroxidase. Mice exposed to 4 atm for 1 h or 6 atm for 16 min exhibited a 36% and 33% decrease in lung NPSH respectively, but no change in cortical NPSH was observed. Although intraventricular diethylmaleate (DEM) decreased cerebral NPSH 72%, no change in the susceptibility of mice to O 2 convulsions was found. Disulfiram, an effective O 2 convulsive protectant had no effect on either cortical NPSH or total glutathione.

Potentiation of acrylate ester toxicity by prior treatment with the carboxylesterase inhibitor triorthotolyl phosphate (TOTP)

The ability of the carboxylesterase inhibitor TOTP to modify the metabolism, mortality, and sulfhydryl depletion resulting from inhalation of acrylate esters was investigated in male rats. Methyl acrylate and ethyl acrylate were enzymatically hydrolyzed by plasma and by homogenates of rat liver, lung, and kidney, with highest activity found in liver homogenates. Hydrolysis of methyl and ethyl acrylate by tissue homogenates from rats treated with TOTP was inhibited in a dose-dependent manner. Pretreatment of rats with 125 mg/kg of TOTP potentiated the lethal action of inhaled methyl acrylate and ethyl acrylate. In the 72-hr period following termination of a 4-hr exposure to 500, 750, or 1000 ppm methyl acrylate the respective mortality rates in TOTP pretreated rats were 83, 100, and 100% compared with 0, 17, and 67% mortality in corn oil-pretreated rats. The acrylate esters reacted with glutathione in vitro and decreased tissue nonprotein sulfhydryl (NPSH) in vivo. The depletion of NPSH by inhaled acrylate esters was most pronounced in lung compared with that in liver, kidney, or blood. TOTP pretreatment significantly enhanced acrylate ester-induced decreases in tissue NPSH concentrations. In rats exposed for 4 hr to 135, 370, 490, or 720 ppm methyl acrylate, lung NPSH was reduced 34, 55, 69, and 83%, respectively, in TOTP-pretreated rats versus 0, 26, 27, and 52%, respectively, in corn oil-pretreated rats. Kidney NPSH following exposure to acrylate esters was significantly altered only in TOTP-pretreated rats. These studies demonstrate that carboxylesterases are important in the detoxification of methyl acrylate and ethyl acrylate and that exposure to inhibitors of carboxylesterases may potentiate the adverse effects of these esters.

Acute inhalation toxicity of 2-chloro-1,3-butadiene (chloroprene): Effects on liver and lung

2-Chloro-1,3-butadiene (chloroprene, CBD), a major industrial chemical used in synthetic chlorinated rubber production, is acutely hepatotoxic. Fasted rats were exposed to concentrations of 100, 150, 225, and 300 ppm CBD for 4 hr and killed at 24 hr. Liver injury as measured by increased serum sorbitol dehydrogenase (SDH) activity was apparent in animals exposed to 225 and 300 ppm CBD. Non-protein sulfhydryl (NPSH) concentrations in liver were increased 24 hr after all exposures. Lung NPSH concentrations were decreased significantly after 100- and 300-ppm exposure. Serum lactate dehydrogenase (LDH) activity was increased after exposure to 300 ppm. When this same enzyme was measured in lung lavage fluid from animals killed 24 hr after exposure, no elevation was detected. Thus, acute lung injury did not manifest itself with a release of LDH into the airway at this time. Alternatively, airway injury may have resolved by 24 hr. Aroclor 1254 (PCB) pretreatment prevented liver injury (SDH elevation, liver enlargement, and NPSH rebound) following exposure to 100 and 300 ppm CBD. Lung NPSH was not decreased by CBD exposure of PCB-pretreated, fasted rats. The pattern of CBD toxicity is comparable to 1,1-dichloroethylene toxicity.

Biochemical effects of intratracheal instillation of cadmium chloride on rat lung

Selected biochemical parameters in rat lung tissue were examined after intratracheal instillation of 0.5 μmole/kg of cadmium chloride (CdCl 2), which produces levels of approximately 10 μg Cd/g of lung wet weight 1 hr following instillation. Lungs were examined 2 hr, 1 day, 3 days and 7 days after CdCl 2 instillation and compared with matched controls receiving saline instillations. Cytosolic lysosomal enzymes, Superoxide dismutase (SOD), catalase, and glutathione (GSH) peroxidase-associated enzymes increased significantly 24 hr after CdCl 2 insult. Peak increases of enzyme activities occurred about 3 days after CdCl 2 instillation. Levels of lung nonprotein sulfhydryl (NPSH) groups, thiobarbituric acid (TBA)-reactive products, protein and DNA increased after CdCl 2 instillation in a similar manner. By 7 days most measured biochemical parameters either remained at the peak 3-day values or decreased toward normal levels. The biochemical changes are consistent with known reported CdCl 2-induced edema and inflammation accompanied by phagocyte recruitment into lung tissue and reparative proliferation of lung cell types.

Comparative effects of hyperbaric oxygen and pentylenetetrazol on lung weight and non-protein sulfhydryl content of experimental animals

Rats convulsed by hyperbaric oxygen (OHP) or by pentylenetetrazol (PTZ) suffer consolidative lung damage. This effect and its moderation by pretreatment of the animals with protective compounds were quantitated by measuring lung weight and lung non-protein sulfhydryl (NPSH) content; liver NPSH content was also measured. Changes in lung weight were also examined in mice, guinea pigs, and rabbits treated with these two agents. Rats and mice convulsed by either OHP or PTZ suffered a similar degree of lung damage. This effect was absent when exposures did not lead to onset of convulsive seizures. In contrast, guinea pigs and rabbits convulsed by OHP for similar times sustained considerably less lung damage. PTZ-induced convulsions in these two species did not lead to significant increases in lung weight. Rats convulsed with OHP or PTZ had an identical loss of NPSH (44 %) from lung but much less loss (25 %) from liver. The liver NPSH loss was duplicated by non-convulsive OHP treatment, while lung NPSH content was relatively unaffected by such exposures. Starvation for 18 hr depleted liver NPSH levels but led to no greater loss of this component under OHP. Lung weight increases and lung NPSH loss due to PTZ were prevented by prior administration of compounds, (e.g. 5-hydroxytryptamine), known to prevent effects of OHP. The experimental data were contrasted with the results of clinical experience with human patients. The conclusion was reached that the gross aspects of OHP-induced lung damage in animals are probably attributable to some mechanism other than direct oxidative attack upon pulmonary structures.