Spinosad insecticide: subchronic and chronic toxicity and lack of carcinogenicity in CD-1 mice

The potential toxicologic and oncogenic effects of spinosad, a natural fermentation product with insecticidal properties, were investigated. The 13-week toxicity study consisted of groups of 10 CD-1 mice/sex provided diets containing 0, 0.005, 0.015, 0.045, or 0.12% spinosad (Study 1). The 0.12% group was terminated on Test Day 44 due to mortality and overt clinical signs of toxicity. An 18-month chronic oncogenicity study consisted of groups of 50 CD-1 mice/sex provided diets containing 0, 0.0025, 0.008, or 0.036% spinosad (Study 2). Two interim groups of 10 mice/sex/group were terminated after 3 and 12 months. Females given 0.036% were terminated on Day 455 due to markedly lower body weights and feed consumption, as well as excessive mortality. Because of the early termination of the female high-dose group, additional groups of 10 male and female mice (12-month interim necrospy) and 50 male and female mice (18-month necropsy) were provided diets containing 0, 0.0008, or 0.024% spinosad (Study 3) to fully assess potential chronic toxicity and oncogenicity. Standard toxicologic parameters were evaluated consistent with existing regulatory guidelines. The primary effect in the 13-week and 18-month studies was intracellular vacuolation of histiocytic and epithelial cells in numerous tissues and organs at doses of > or = 0.015%. The histological vacuolation corresponded to ultrastructural lysosomal lamellar inclusion bodies. This alteration was consistent with phospholipidosis, a condition that results from accumulation of polar lipids in lysosomes. Lesions with no apparent direct relation to vacuolation were hyperplasia of the glandular mucosa of the stomach, skeletal muscle myopathy, bone marrow necrosis, and anemia with associated splenic hematopoiesis. The incidence of tumors in mice given spinosad was not increased relative to controls at any dose level. The no observed effect level for the 13-week study was 0.005% (6 mg/kg/day) spinosad, and for the chronic toxicity/oncogenicity study was 0.008% (11 mg/kg/day) spinosad for male and female CD-1 mice.

Spinosad insecticide: subchronic and chronic toxicity and lack of carcinogenicity in Fischer 344 rats

Spinosad is an insecticide derived from a naturally occurring bacterium via fermentation. The toxicity of spinosad was characterized in subchronic and chronic toxicity/oncogenicity studies conducted according to standard toxicology regulatory guidelines. Subchronic toxicity was evaluated in groups of 10 Fischer 344 rats/sex given feed containing 0, 0.05, 0.1, 0.2, or 0.4% spinosad (Study 1) or 0, 0.003, 0.006, 0.012, or 0.06% spinosad (Study 2) for 13 weeks. Lower body weights and increased mortality occurred in rats given 0.4% spinosad. Microscopic effects were observed in the adrenal glands, liver, lymphoid cells, reproductive tissues, kidney, thyroid, stomach, lung, and skeletal muscle of rats given > or = 0.05% spinosad, and consisted primarily of vacuolation of cells; however, degenerative, regenerative, and/or inflammatory changes were also noted in some tissues. Vacuolation within a number of tissues was ultrastructurally characterized by an increase in size and number of lysosomes that contained extensive membranous whorls consistent with phospholipidosis. The no observed effect level (NOEL) in the 13-week studies was 0.012% (24 mg/kg/day) spinosad. Chronic toxicity and oncogenicity were evaluated in groups of 60 Fischer 344 rats/sex given feed containing 0, 0.005, 0.02, 0.05, or 0.1% spinosad for up to 2 years. Rats given 0.1% spinosad for 1 year had microscopic effects similar to those observed in the subchronic studies. Vacuolation and inflammation of the thyroid gland also occurred in rats given 0.05% spinosad for 1 year. Excessive mortality occurred in rats from the oncogenicity study given 0.1% spinosad by 21 months, and surviving rats were euthanized because the maximum tolerated dose had been exceeded. Rats given 0.05% spinosad for 2 years had vacuolation and/or inflammation involving the thyroid, lymphoid tissue, and lung. Rats given 0.05% spinosad had similar numbers of neoplasms as control rats, indicating that spinosad was not carcinogenic at dose levels up to 0.05%. The NOEL at 2 years was 0.005% (2.4 mg/kg/day) spinosad.

Drug-induced phospholipidosis: are there functional consequences?

Phospholipidosis induced by drugs with a cationic amphiphilic structure is a generalized condition in humans and animals that is characterized by an intracellular accumulation of phospholipids and the concurrent development of concentric lamellar bodies. The primary mechanism responsible for the development of phospholipidosis is an inhibition of lysosomal phospholipase activity by the drugs. While the biochemical and ultrastructural features of the condition have been well characterized, much less effort has been directed toward understanding whether the condition has adverse effects on the organism. While there are a few cationic amphiphilic drugs that have been reported to cause phospholipidosis in humans, the principal concern with this condition is in the pharmaceutical industry during preclinical testing. While this class of drugs should technically be referred to as cationic lipophilic, the term cationic amphiphilic is widely used and recognized in this field, and for this reason, the terminology cationic amphiphilic drugs (CADs) will be employed in this Minireview. The aim of this Minireview is to provide an evaluation of the state of knowledge on the functional consequences of CAD-induced phospholipidosis.

Pulmonary responses to single versus multiple intratracheal instillations of silica in rats

The pulmonary toxicity of particles is often studied using a single intratracheal instillation of the material. It was hypothesized that smaller multiple intratracheal administrations of silica would result in differences in pulmonary responses as compared to a single large intratracheal administration. In the first of a series of experiments, the pulmonary responses in male F344 rats to a single intratracheal instillation of crystalline silica (5 mg/100 g body weight) given on d 0 were compared with those resulting from 5 consecutive daily intratracheal administrations of the dust (1 mg/100 g body weight/d) with the initial dose given on d 0. Controls received saline intratracheally. In the second experiment, the dose was reduced to 1 mg/100 g body weight for the single-dose protocol and 0.2 mg/100 g body weight/d for 5 consecutive days for the multiple-dose protocol. In both experiments, responses were assessed on d 14. In the third experiment, the doses were the same as the first experiment, but the responses were assessed on d 28. The indices of toxicity were cellular differentials recovered by bronchoalveolar lavage, which is an index of inflammation, and the level of albumin in the bronchoalveolar lavage fluid, a measure of damage to the capillary-epithelial barrier. At the higher dose of silica, similar levels of inflammation and lung damage were evident in both dosing protocols. Less severe responses occurred at the lower dose. The comparative pattern between the single and multiple dosing protocols was similar in all three experiments. Since only minor differences were noted in the pulmonary responses when the responses to the single- and multiple-dose protocols were compared, data indicate that the multiple-dose protocol does not offer any advantages over the single-dose protocol.

A characterization of amiodarone-induced pulmonary toxicity in F344 rats and identification of surfactant protein-D as a potential biomarker for the development of the toxicity

Amiodarone (AD) is gaining support as a first-line antiarrhythmic drug despite its potentially fatal pulmonary toxicity involving inflammation and fibrosis. The goals of this study were to characterize a rat model of AD-induced pulmonary toxicity (AIPT) and identify a serum biomarker to aid in the diagnosis of the onset of pulmonary toxicity. Male F344 rats were instilled intratracheally with AD (6.25 mg/kg with a 3.125 mg/ml solution) in sterile water or the sterile water vehicle on days 0 and 2, a protocol that led to the development of pulmonary fibrosis on day 28 in the AD-treated animals. Animals were killed on days 3, 5, 6, 7, or 10 and bronchoalveolar lavage (BAL) was performed. Recovery of alveolar macrophages and eosinophils was increased on days 3 and 5, while neutrophil recovery and albumin levels in the first BAL fraction were significantly elevated only on day 3. BAL cells recovered from AD-treated rats at day 3 produced more phorbol myristate acetate-stimulated luminol-dependent chemiluminescence (LDCL) over 20 min than BAL cells from control rats. Experiments using specific inhibitors implicated superoxide and nitric oxide in at least part of the LDCL response. Serum levels of surfactant protein-D (SP-D), a surfactant-associated protein, were increased concurrently with the inflammatory response in the lungs. These findings indicate that this model exhibits transient pulmonary inflammation and damage, with the potential for elevated oxidant production in the lungs and subsequent pulmonary fibrosis. Also, SP-D is proposed as a specific biomarker to monitor the onset of AIPT in this model.

Silica-induced pulmonary inflammation in rats: activation of NF-kappa B and its suppression by dexamethasone

The goal of this study was to examine the relationship of the transcriptional regulatory factor nuclear factor-kappaB (NF-kappa B) to the early inflammatory events involved with silica exposure. Male F-344 rats received an intratracheal (i.t.) instillation of silica (100 mg/kg in a volume of 1 ml/kg) of saline. At 1, 3, 6, and 18 h postinstillation, and the rats were sacrificed and underwent bronchoalveolar lavage (BAL) for functional analysis of inflammation. Beginning at 1 h postinstillation, the silica-instilled (Si) rats displayed significant increases in neutrophils in BAL fluid compared to the saline controls. BAL cells from the Si group displayed a significant increase in luminol-dependent chemiluminescence (LDCL) compared to the controls. NF-kappa B activation was measurable at 3 h postinstillation, and this activation continued throughout the 18-h time course. Treatment with dexamethasone (5 mg/kg) at -3 h prior to silica instillation, at the time of instillation (0 h), and +1.5 h postinstillation resulted in both a reduction in NF-kappa B expression (by 70%) at 3 h postinstillation and corresponding reductions in LDCL, BAL cell count, and BAL neutrophils. These results show that activation of NF-kappa B is associated with silica-induced pulmonary inflammation, and the inhibition of its activation correlates temporally with suppression of inflammation.

Modulation of silica-induced pulmonary toxicity by dexamethasone-containing liposomes

Human exposure to silica (SI) is of great occupational concern because it is marked by pulmonary inflammation and fibrosis. Our objective was to determine if early pharmacological intervention altered the inflammatory and fibrotic responses to silica in rats. Male Fisher-344 rats received intratracheal (IT) instillations of the anti-inflammatory steroid, dexamethasone (DEX), incorporated into a novel liposomal (LIP) delivery system (DEX-LIP), or buffer as control (HBSS) on Day-1 and every fourth day until euthanization. On Day 0, the DEX-LIP group received IT instillations of SI (10 mg/100g body wt, DEX-LIP-SI); half of the HBSS group received SI (10 mg/100g body wt, HBSS-SI) and the other half saline (HBSS-SAL). On Day 10 or 20, bronchoalveolar lavage (BAL) was performed for cellular, biochemical, and functional analyses of inflammation and damage. HBSS-SI rats had significant elevations in the neutrophil cell count over HBSS-SAL rats at both times. DEX-LIP treatment markedly reduced these values, indicating that DEX-LIP protected against SI-induced inflammation. In contrast, DEX-LIP did not protect against biochemical (albumin concentration, and beta-glucuronidase and lactate dehydrogenase activities) and functional (luminol-dependent chemiluminescence) indices of SI-induced damage. At Day 20, the DEX-LIP treatment significantly reduced the SI-induced increase in right lung/total body weight ratio and right lung hydroxyproline content, a biochemical index of fibrosis. This attenuation of fibrosis was confirmed histopathologically on preserved left lungs from these same animals. These results show that administration of liposomes containing dexamethasone attenuated SI-induced pulmonary inflammation and fibrosis in rats, and that this protection is independent of some biochemical and functional parameters of damage.

Exposure to crystalline silica or treatment with chlorphentermine increases vitamin E levels in rat alveolar lavage materials

Previous studies have shown that vitamin E may be an integral part of lung surfactant and may function to protect this material from oxidant damage. Therefore, we measured the vitamin E levels in alveolar lavage materials from rats exposed to crystalline silica or treated with chlorphentermine (CP), two treatments that are known to increase surfactant phospholipids (PL) by different mechanisms. Silica exposure leads to increased PL synthesis, and CP treatment causes a reduction in PL degradation. Two different silica preparations, HCL-washed and unwashed silica, were used because exposure to each of them leads to different degrees of phospholipidosis. Exposure to HCL-washed silica results in a more than 17-fold increase in lavage PL and protein levels and a 12.2-fold increase in the amount of vitamin E. Exposure to unwashed silica leads to an approximately 7-fold increase in PL and proteins and a 5.8-fold increase in lavage vitamin E. Following treatment of rats with CP, there is a 15- to 19-fold increase in lavage PL and proteins and a 13.6-fold increase in vitamin E. When the results are expressed as micrograms vitamin E per milligram of lavage PL or protein, there is not much difference between controls and each treatment group. Because surfactant synthesis occurs in the endoplasmic reticulum, we also measured vitamin E in lung microsomes. Both silica exposure and CP treatment also lead to 1.8- to 2.5-fold increases, respectively, in the lung microsomal levels of vitamin E. These results demonstrate that alveolar lavage vitamin E levels are elevated along with lavage PL and proteins, and lung microsomal vitamin E levels are increased following exposure of rats to silica or treatment of the animals with CP.

An evaluation of possible mechanisms underlying amiodarone-induced pulmonary toxicity

The effectiveness of amiodarone in the treatment of cardiac arrhythmias is limited due to the development of pulmonary toxicity. Although the biochemical and morphologic characteristics associated with amiodarone-induced pulmonary toxicity (AIPT) are well-defined, the mechanisms underlying this disorder remain unknown. This review focuses on proposed mechanisms of AIPT, in particular (i) direct cellular damage; (ii) the role of phospholipidosis; (iii) the correlation between drug burden and toxicity; (iv) the role of the immune system; (v) the generation of oxidants; (vi) changes in membrane properties; and (vii) miscellaneous biochemical considerations. Additional discussion of the role of amiodarone's primary metabolite, desethylamiodarone, in AIPT and the involvement of preexisting lung dysfunction in the susceptibility to AIPT is included. With a clearer understanding of the possible contributions of these mechanisms to AIPT, it may be possible to develop strategies to alleviate toxicity and prolong the usefulness of amiodarone in the treatment of cardiac arrhythmias.

Effects of amiodarone-induced phospholipidosis on pulmonary host defense functions in rats

The effect of the induction of pulmonary phospholipidosis by amiodarone on selected pulmonary host defense functions was studied in male Fischer-344 rats. One week of daily amiodarone treatment resulted in a 4.5-fold increase in total phospholipid in alveolar macrophages recovered from the lungs by bronchoalveolar lavage. The presence of the phospholipidosis had no effect on the phagocytosis of heat-killed yeast cells, the induction of luminol-dependent chemiluminescence, or the spontaneous release of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), or spontaneous and LPS-stimulated release of IL-1 by alveolar macrophages in vitro. In contrast, the LPS-stimulated release of IL-6 and TNF-alpha by phospholipidotic alveolar macrophages was enhanced compared with control cells. The pulmonary clearance of Listeria monocytogenes following intratracheal administration of the bacteria was not affected by the phospholipidotic condition. It appears that, in the context of the functions studied, the induction of pulmonary phospholipidosis by amiodarone does not impair pulmonary host defense processes in rats, and may actually be associated with the augmentation of some activities.

Comparative evaluation of amiodarone-induced phospholipidosis and drug accumulation in Fischer-344 and Sprague-Dawley rats

Amiodarone (AD) and its major metabolite, desethylamiodarone (desethylAD), are both phospholipogenic. The present study was undertaken to evaluate the comparative susceptibilities of male Fischer-344 and Sprague-Dawley rats to AD-induced phospholipidosis in alveolar macrophages (AMs), liver and kidney tissue and the concomitant accumulation of AD and desethylAD in these cells, tissues and plasma. Rats were administered AD (100 mg/kg/day, p.o.) for 1 week. Plasma concentrations of AD and desethylAD were approximately 4- and 12-fold higher, respectively, in Fischer-344s compared to Sprague-Dawleys 24 h after the last dose. AD and desethylAD levels in AMs were approximately 12- and 25-fold higher, respectively, in Fischer-344s than Sprague-Dawleys. In the liver and kidney, levels of both compounds were also significantly higher in Fischer-344s than Sprague-Dawleys. Ultrastructural features indicative of phospholipidosis were not observed consistently in any tissue except AMs from treated Fischer-344s. AM total phospholipid increased nearly 5-fold in Fischer-344s, while Sprague-Dawleys showed no increase over control. AMs from both strains incubated with 10 microM AD or desethylAD in vitro were not significantly different in their accumulation of the compounds. When incubated with AD or desethylAD, the lysosomal phospholipases A1 partially purified from AMs of both strains were equally sensitive to inhibition as measured by the drug concentration giving 50% inhibition in activity (IC50). The results of this study indicate that at the same administered dose, AD and desethylAD, accumulate to higher tissue levels and are more phospholipogenic in male Fischer-344 rats than in male Sprague-Dawley rats. The basis for the high susceptibility of Fischer-344 rats to AM-induced phospholipidosis is unknown at present but appears not to be related to biochemical or cellular features of the AMs.

Characteristics of the acute-phase pulmonary response to silica in rats

Exposure to silica, a cytotoxic and fibrogenic mineral dust, has been demonstrated to cause pulmonary inflammation and damage to the lung tissue. In contrast to the long-term consequences, little information exists on the sequence of inflammatory/damaging events occurring acutely after exposure to silica. The purpose of this study was to determine the minimum time after the administration of silica that the inflammatory/damage response is detectable and the temporal relationship of these processes. Male Fischer 344 rats were dosed intratracheally with silica (2.5 or 10 mg/100 g body weight) or saline vehicle. At 2 and 4 h after instillation, both cellular (total cell count and neutrophil count) and biochemical (total protein, albumin, and beta-glucuronidase and lactate dehydrogenase activities) parameters of inflammation and damage were evaluated in the bronchoalveolar lavage fluid. At 2 h, total protein levels were elevated at both silica doses, but all other parameters were unchanged; however, 4 h after silica exposure all parameters were elevated over those of the saline control. In a further attempt to characterize the inflammatory/damage processes, luminol-dependent chemiluminescence (LDCL) was performed on aliquots of chopped lung. At 2 h after silica instillation, phorbol myristate acetate-stimulated lung tissue from silica-treated rats had no increase in light production when compared to controls, whereas after 4 h there were significant increases in LDCL activity in both dose groups when compared to controls. The addition of superoxide dismutase (SOD) decreased LDCL activity of the 2.5 mg/100 g group by 59% (2 h) and 66% (4 h), and of the 10 mg/100 g group by 49% (2 h) and 73% (4 h). Alternatively, the addition of N-omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase, decreased the 2.5 mg/100 g group by 52% (2 h) and 60% (4 h). The 10 mg/100 g group was decreased by 67% (2 h), but only exhibited a 12% reduction at 4 h. SOD and L-NAME also inhibited the background LDCL in saline-treated rats. These reductions in LDCL activity indicate that reactive oxygen and nitrogen species play a role in the acute phase pulmonary response from silica. The results of this study indicate that the initial stages of damage begin to appear by 2 h, but damage and inflammation are definitive by 4 h after administration of silica in rats.

Subchronic pulmonary inflammation and fibrosis induced by silica in rats are attenuated by amiodarone

A previous study demonstrated that the acute phase of silica-induced lung injury in rats can be attenuated by concomitant administration of amiodarone, a cationic amphiphilic drug that inhibits phospholipase activity in the lungs. The purpose of the present study was to determine whether continued amiodarone administration could inhibit subchronic silica-induced lung injury and fibrosis. Male Fischer-344 rats were administered amiodarone (150 mg/kg, p.o., 5 days/week) for 14 days and were then instilled with silica (100 mg/kg) intratracheally. Amiodarone treatment then continued for 60 days. Injury was evaluated by parameters in bronchoalveolar lavage fluid and fibrosis was assessed by lung hydroxyproline content and trichrome staining of collagen. Within the bronchoalveolar lavage fluid, amiodarone treatment resulted in significant decreases in silica-induced elevations in albumin levels, lactate dehydrogenase activity, beta-glucuronidase activity, and neutrophil influx. Amiodarone treatment resulted in significant reductions in silica-induced increases in lung weight and hydroxyproline levels; the diminution of fibrosis due to amiodarone treatment was confirmed histologically. These results indicate that subchronic pulmonary inflammation and fibrosis induced by silica in the rat can be attenuated by the concomitant administration of amiodarone.

Metabolism of amiodarone following intratracheal instillation in hamsters

Intratracheal instillation of the antiarrhythmic drug amiodarone (AD) in hamsters is an established animal model of AD-induced pulmonary fibrosis. A metabolite of AD, desethylamiodarone (dAD), has also been shown to produce pulmonary fibrosis in this model. It was previously reported that following intratracheal instillation of AD in hamsters, metabolite could not be detected in lung tissue. However, in studies in our laboratory dAD was detected following instillation of AD. The goal of the present study was to monitor the distribution of AD and dAD to lung and liver within 1 h of AD instillation and to investigate the site of AD metabolism. Both AD and dAD were detected in the lung and liver within 5 min of AD instillation; lung and liver concentrations of AD and dAD were also quantified at 30 and 60 min following AD instillation. Incubation of lung and liver microsomes with AD showed that the liver is a probable site of AD metabolism following the intratracheal administration of AD to hamsters.

Pulmonary responses to amiodarone in hamsters: comparison of intratracheal and oral administrations

Amiodarone (AD) has been shown to produce a transient pulmonary fibrosis in hamsters after intratracheal (i.t.) instillation. The goal of this study was to examine bronchoalveolar lavage (BAL) parameters during the development of fibrosis after i.t. AD in hamsters and to examine the responses to oral AD in hamsters for comparison to responses to i.t. AD in an effort to explore the roles of inflammation, phospholipidosis, and lung drug burden in AD-induced pulmonary disease. Two i.t. instillations on Days 0 and 7 of AD in hamsters produced fibrosis as characterized by elevated lung hydroxyproline content and variable increases in lavage macrophage, neutrophil, and eosinophil number through Day 28. Intratracheal AD also increased the permeability of the alveolar-capillary barrier as evidenced by an increase in BAL fluid albumin only on Day 8. Pulmonary phospholipidosis was not induced by i.t. AD and only small amounts of AD and its metabolite desethyl-AD (dAD) were detected in lung tissue through Day 10 after instillation on Days 0 and 7. The repeated oral administration of AD did not result in pulmonary fibrosis during the 35-day course of this study. Oral AD did cause a sustained increase in BAL fluid neutrophil number; other BAL cells were only slightly affected. Oral AD did not increase BAL fluid albumin content but a prominent BAL cell phospholipidosis was noted. Measurement of AD and dAD in lung tissue demonstrated a substantial accumulation of drug and metabolite after oral treatment with AD. The results of this study indicate that lung drug burden, pulmonary phospholipidosis, and lung neutrophil influx are not crucial factors in the development of AD-induced pulmonary fibrosis in hamsters. This study supports the possible involvement of physical damage to the lung and/or pulmonary eosinophilia in the generation of AD-induced pulmonary fibrosis in hamsters.

In vivo and in vitro reversibility of chlorphentermine-induced phospholipidosis in rat alveolar macrophages

Chlorphentermine (CP) is a cationic, amphiphilic drug (CAD) that has been studied widely for its ability to induce phospholipidosis, a disorder characterized by excessive accumulation of cellular phospholipid and ultrastructural development of lysosomal lamellar bodies (LLBs) in the cell. The accumulation of inducing drug correlates with increasing phospholipids. In the present study, we examined the reversibility of this disorder in rat alveolar macrophages (AMs) following a 7-day treatment (30 mg/kg/day, ip). The reversibility of phospholipidosis was examined under in vivo conditions and under in vitro conditions in cell cultures for a period of up to 12 days. There was a marked reduction in cellular CP levels and phospholipid content after 4 days of recovery, both in vivo and in vitro; however, there was no indication of significant loss of LLBs. Beyond this time point, ultrastructural recovery from phospholipidosis lagged behind the biochemical recovery temporally and was somewhat less rapid in vitro than in vivo. By 12 days of recovery, AMs from both groups had recovered biochemically, but a moderate level of LLBs was still present in some AMs in the in vitro recovery group. The results of this study indicate that there are more similarities than differences when comparing the recovery of phospholipidotic cells in vitro to that occurring in vivo. We conclude that the use of cell cultures may prove valuable in studying the reversibility of CAD-induced phospholipidosis.

Attenuation of acute inflammatory effects of silica in rat lung by 21-aminosteroid, U74389G

Chemical alteration of the glucocorticoid, methylprednisolone, has led to the introduction of a new class of compounds called the 21-aminosteroids (21-ASs). The purpose of this study was to investigate the effect of the 21-AS, U74389G, on silica-induced acute lung injury. Male Fischer 344 rats were treated intraperitoneally with saline or U74389G in a total dose of 15 mg/kg divided into three injections of 5 mg/kg separated by 4 h. Following the first treatment, animals from the two groups were intratracheally instilled with silica (10 mg/100 g body wt in 0.5 ml of saline) or saline vehicle (0.5 ml). Twenty-four hours after the instillations, bronchoalveolar lavage (BAL) was performed. In the animals not receiving U74389G, marked increases in total protein, beta-glucuronidase, and lactate dehydrogenase (LDH) activities and number of neutrophils (PMNs) were demonstrated in the BAL fluid of the silica-treated animals compared to their controls. Silica also caused dramatic increases in the luminol-dependent chemiluminescence (CL) of lung tissue and BAL cells. The CL reaction was decreased by superoxide dismutase (SOD) and N-nitro-L-arginine methyl ester hydrochloride (L-NAME), a nitric oxide (NO) synthase inhibitor. In animals treated with U74389G, there was attenuation of the silica-induced increases in biochemical, cellular, and chemiluminescent indices of damage. This study demonstrates that U74389G significantly reduces acute lung injury caused by the intratracheal instillation of silica, and this drug may be of potential value for treatment of lung diseases in which damage caused by reactive oxygen species has been implicated.

Acute pulmonary inflammation in hamsters following intratracheal administration of amiodarone

The use of the antiarrythmic drug amiodarone (AD) has been limited by the propensity of the drug to cause severe lung damage. AD has been shown to produce a transient pulmonary fibrosis in hamsters after intratracheal instillation. The goal of this study was to characterize the early inflammatory events associated with the administration of AD. Male Syrian hamsters that were instilled intratracheally with AD or saline vehicle underwent bronchoalveolar lavage (BAL). Total cells, macrophages, and eosinophils obtained by BAL were elevated by AD treatment at day 3. At both days 1 and 3 after instillation, AD-treated animals had significant elevations in neutrophil number. BAL fluid albumin was significantly elevated at day 1 in treated animals. Chemiluminescence (CL) performed on cells obtained by BAL showed an increase in CL of AD-treated samples compared to controls in phorbol myristate acetate (PMA) stimulated CL. PMA-induced increases in responsiveness were diminished by superoxide dismutase and catalase. These results indicate that oxidants such as superoxide and hydrogen peroxide may be involved in this inflammatory process. The results of this study show that intratracheal instillation of AD results in an inflammatory response that can be assessed by cellular, biochemical, and functional means.

Introduction of luminol-dependent chemiluminescence as a method to study silica inflammation in the tissue and phagocytic cells of rat lung

The inhalation of silica has been shown to produce a dramatic inflammatory and toxic response within the lungs of humans and laboratory animals. A variety of cellular and biochemical parameters are used to assess the silica-induced lung injury. The purpose of this paper is to introduce the use of luminol-dependent chemiluminescence as a new method to study inflammation in both phagocytic cells and lung tissue recovered from silica-exposed animals. Chemiluminescence, or the emission of light, accompanies the release of reactive forms of oxygen when phagocytic cells are challenged. In this study, male Fischer 344 rats were intratracheally instilled with either silica (10 mg/100 g bw) or saline vehicle. One day after the instillations, a marked increase in the chemiluminescence was observed in the lung tissue and bronchoalveolar lavage cells recovered from the silica-treated animals when compared with the saline controls. The light reaction was markedly decreased by either superoxide dismutase of N-nitro-arginine methyl ester hydrochloride. Superoxide dismutase is involved in the enzymatic breakdown of superoxide anion, while N-nitro-L-arginine methyl ester hydrocholoride, a nitric oxide synthase inhibitor, prevents the formation of nitric oxide. When superoxide anion and nitric oxide react, they form the highly oxidizing substance peroxynitrite. This study then implicates peroxynitrite as an agent that may be responsible for some of the oxidant lung injury that is associated with silica exposure. The use of luminol-dependent chemiluminescence may prove valuable as a method to measure the earliest events in the inflammatory process, and may be an adjunct in studying the mechanisms that produce inflammation.

Effect of short-term exogenous pulmonary surfactant treatment on acute lung damage associated with the intratracheal instillation of silica

The objective of our study was to investigate whether coating the surface of silica with Survanta, a commercially available, bovine pulmonary surfactant, would reduce the in vitro cytotoxicity to alveolar macrophages (AMs), as well as attenuate lung damage in vivo following intratracheal instillation of silica. In the in vitro studies, alveolar macrophages from male Fischer 344 rats were incubated for 1 and 24 h with native or Survanta-treated silica (0.5 mg/ml). At both time points, the native, uncoated silica caused a dramatic loss of AM viability. The AMs were protected, however, when the silica was treated with the Survanta surfactant. This protective effect was significantly greater after 1 h when compared with 24 h. In the in vivo studies, a high dose of silica (10 mg/100 g body weight) was suspended in Survanta and intratracheally instilled into the lungs of male Fischer 344 rats. A number of biochemical and cellular parameters were measured within the bronchoalveolar lavage fluid (BALF) 1 and 14 d after the instillation exposures to assess lung damage. One day after the instillations, the suspension of silica in Survanta resulted in significant reductions in the silica-induced increases in total protein, beta-glucuronidase activity, and influx of neutrophils (PMNs) into the airspaces of the lungs. Fourteen days after the instillation exposures, this protective effect was lost. When Survanta was instilled into the lungs 15 min after the intratracheal instillation of silica, a significant reduction also was demonstrated in the silica-induced elevations in BALF total protein, beta-glucuronidase activity, and influx of PMNs 1 d after the instillation exposures. In an attempt to protect silica-exposed lungs over a longer period of time, Survanta was instilled into the lung 15 min after the silica instillation, and then every other day over a 7-d treatment period. Twenty-four hours after the last Survanta instillation, slight but significant decreases in the silica-induced elevations in BALF total protein and beta-glucuronidase activity were observed. The Survanta treatment, however, had no effect in preventing the infiltration of PMNs into the airspaces of the lungs. The results of this study indicate that artificially coating the silica with surfactant phospholipid offers short-term protection against its toxicity under both in vitro and in vivo conditions.

A toxicologic approach for evaluating cases of sick building syndrome or multiple chemical sensitivity

The nonspecificity of symptoms and exposures commonly reported as "sick building syndrome" is very similar to that reported for the condition termed "multiple chemical sensitivity (MCS)." In many instances health care practitioners are divided on the reality of the latter. As in all scientific cases of possible cause-and-effect relationships, an organized, dispassionate approach should be used to evaluate each claim of MCS. Most obviously, known medical conditions must be ruled out before chemical "sensitivity" is proposed. Also, several questions on the toxicology of the chemical exposure must be addressed. Although temporality may be apparent (toxicity followed exposure), the time frame for the appearance of symptoms must be appropriate to the exposure conditions and chemical(s) involved. The chemical(s) must have known or reasonably inferred properties to cause the claimed effect. The dose(s) received must be adequate to effect a response (dose-response characteristics). Alternate causation must be evaluated thoroughly, that is, are there other more logical explanations for the symptoms? In contrast to single-chemical exposures, exposure to mixtures of chemicals, as commonly found in sick buildings, is very difficult to evaluate. However, a rational, scientific approach to cause-and-effect questions will help avoid erroneous and subjective decision making.

Acute silica toxicity: attenuation by amiodarone-induced pulmonary phospholipidosis

Exposure to the toxic mineral dust silica has been shown to produce an acute inflammatory response in the lungs of both humans and laboratory animals. Coating silica with phospholipids reduces its toxicity when studied with in vitro systems. The drug amiodarone increases phospholipid within the cells, airways, and alveoli of the lungs. This increase in phospholipid is due to amiodarone's ability to inhibit phospholipase activity within alveolar macrophages (AMs) and whole lung. The purpose of this study was to determine whether the amiodarone-induced increase in pulmonary phospholipid would protect the lungs from acute damage caused by the intratracheal instillation of silica. Treatment of male Fischer 344 rats with amiodarone for 14 days caused an increase in phospholipid content in bronchoalveolar lavage fluid and AMs compared to vehicle-treated controls. The rats were then instilled with silica or saline vehicle. At both 1 and 14 days after silica exposure, pulmonary phospholipidosis was associated with a marked reduction in acute silica-induced pulmonary damage as assessed by biochemical parameters in bronchoalveolar lavage fluid, however, the influx of neutrophils into the airspaces was not reduced. Four times more phospholipid was bound to the silica recovered from amiodarone-treated rats compared to controls. The results of these in vivo experiments indicate that pulmonary phospholipidosis attenuates the acute damage associated with the intratracheal instillation of silica in rats. By using an in vitro cell culture system, we demonstrated that, in contrast to control AMs, phospholipidotic AMs were significantly more resistant to the cytotoxicity of surfactant-coated silica.(ABSTRACT TRUNCATED AT 250 WORDS)

The inhibition of silica-induced lung inflammation by dexamethasone as measured by bronchoalveolar lavage fluid parameters and peroxynitrite-dependent chemiluminescence

The inhalation of silica has been shown to produce a dramatic inflammatory and toxic response within the lungs of humans and laboratory animals. Currently, no effective treatment exists for workers who may have been exposed to the inhalation of silica. The objective of this study was to develop an animal model in which we could evaluate the effect that anti-inflammatory steroids have on the acute silica-induced pulmonary inflammatory response. Male Fischer 344 rats were pretreated with either dexamethasone (2 mg/kg) or saline vehicle (i.p.) on days 1, 3, and 5. On day 6, the animals from the two groups were then intratracheally instilled with either silica (20 mg/0.5 ml saline vehicle) or saline vehicle (0.5 ml). Twenty-four hours after the instillations in the non-steroid group, significant increases occurred in total protein, total number of cells, neutrophils, and lymphocytes recovered from the lungs of animals treated with silica compared to saline controls. Silica also caused dramatic increases in the luminol-dependent chemiluminescence (LDCL) of lung tissue and bronchoalveolar lavage (BAL) cells. The LDCL reaction was markedly decreased by either superoxide dismutase (SOD) or N-nitro-L-arginine methyl ester hydrochloride (L-NAME). SOD is involved in the enzymatic breakdown of superoxide anion, while L-NAME, a nitric oxide (NO) synthase inhibitor, prevents the formation of NO. When the superoxide anion and NO react, they form the highly oxidizing substance peroxynitrite. This study then implicates peroxynitrite as an agent which may be involved in the silica-induced oxidant lung injury.(ABSTRACT TRUNCATED AT 250 WORDS)

X-ray microanalysis of cultured alveolar macrophages with phospholipidosis

When administered to humans and animals, the iodine-containing drug amiodarone can cause pulmonary toxicity. As part of the pulmonary response to amiodarone, the drug and its principal metabolite, desethylamiodarone, accumulate in alveolar macrophages. Little is known about the susceptibility of lungs with preexisting damage to amiodarone administration. A number of chemicals can cause pulmonary phospholipidosis in humans and animals. To study the effect of a preexisting phospholipidosis on the intracellular accumulation of amiodarone and desethylamiodarone, rats were treated with chlorphentermine to induce a phospholipidosis in alveolar macrophages. The cells were recovered from the lungs by pulmonary lavage and placed in cell culture. They were then exposed to the same concentration of either amiodarone or desethylamiodarone. The intracellular distribution of each drug was quantified by measuring the associated iodine signal using X-ray microanalysis of freeze-dried cryosections of cells. Both drugs accumulated in lipid-rich amorphous bodies which correspond to lysosomally derived lamellar structures observed in conventional plastic sections. The level of desethylamiodarone exceeded that of amiodarone in the amorphous bodies. With both drugs, a higher concentration of iodine was present at the outer edges of the amorphous bodies compared to that in the center core. This suggests that the drugs are unable to freely penetrate the performed structures. By monitoring the concentrations of sodium and potassium ions within the nucleus, it was determined that chlorphentermine treatment disrupted the ionic distribution in the cells. Exposure to amiodarone, but not desethylamiodarone, resulted in further changes in sodium and potassium levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of amiodarone administration during lactation in Fischer-344 rats

The antiarrhythmic drug, amiodarone, was administered (35 mg/kg, p.o.) once daily to lactating Fischer-344 rats for either the first 7 days of lactation, the first 14 days of lactation, or for the full 24-day lactational period. Treatment with amiodarone resulted in a decrease in maternal weight gain compared to pair-fed vehicle-treated controls, however, neonatal weight gain was not affected. The concentration of amiodarone in the maternal milk was approx. 6-fold higher than its primary metabolite, desethylamiodarone. Plasma levels of amiodarone and desethylamiodarone were higher in maternal rats compared to neonates. Both amiodarone and desethylamiodarone were distributed to neonatal tissues through lactational transfer. The levels of desethylamiodarone were higher in neonatal lung compared to liver at all treatment times. They were also elevated above amiodarone in neonatal lung at all treatment times. The amiodarone levels in neonatal lung and liver were similar.

Retrograde extrapolation of blood alcohol data: an applied approach

Retrograde extrapolation is a mathematical process, based on sound scientific principles, that is used routinely in pharmacology, toxicology, and clinical medicine. This process may be applied to the situation of ethyl alcohol consumption with reliability when reasonable assumptions are made concerning absorption rates, elimination rates, and patterns of alcohol consumption, including drinking duration and volume consumed. By utilizing an established range of values for the elimination rate of alcohol of 0.015-0.020 g/dl/h, a relatively narrow range of extrapolated blood alcohol concentrations (BACs) can be determined in situations where the time frame in question is after peak alcohol absorption into the blood. A wider range of elimination rates of 0.01-0.03 g/dl/h may be applied and will satisfy the possibility of nonlinear kinetics within an individual; however, this wider range will have little practical effect on the predicted BACs. When the time point in question is prior to peak absorption, a wider range of predicted BAC values will result. The extent of this range will be influenced by the amount of information available concerning the temporal pattern of alcohol consumption. Reported drinking volumes are notoriously inaccurate and, in fact, are of little practical use. Given the parameters of body weight and time duration between initiation of drinking and determination of the BAC, the number of "drinks" consumed may be reliability calculated. Retrograde extrapolation is applicable in the forensic setting with scientific reliability when reasonable and justifiable assumptions are utilized.

Accumulation of amiodarone and desethylamiodarone by rat alveolar macrophages in cell culture

Amiodarone is a clinically effective antiarrhythmic drug shown to cause lung damage in humans and animals. While the mechanism of this pulmonary toxicity is unknown, it may be associated with the accumulation of amiodarone and its principal metabolite, desethylamiodarone, by alveolar macrophages. In the present study, characteristics of the uptake of these drugs by rat alveolar macrophages in vitro were examined. The alveolar macrophages were collected by pulmonary lavage from male Fischer 344 rats. Amiodarone and desethylamiodarone were incubated separately (2.5 microM) with the cells in culture for 1, 2, 4 and 18 hr. High performance liquid chromatography was used to measure drug uptake. At 1 and 2 hr, the uptake of desethylamiodarone by alveolar macrophages was significantly greater (P less than 0.05) than that of amiodarone, but over time, the accumulation of amiodarone began to approach that of desethylamiodarone and was not significantly different by 4 hr. To simulate a more physiological situation, plasma levels achieved in the adult male rat after 1 week of amiodarone treatment (150 mg/kg) were used. Amiodarone (1.95 micrograms/mL) and desethylamiodarone (0.80 microgram/mL) were added together into the cell culture. At 1 and 18 hr, the ratio of desethylamiodarone/amiodarone uptake was significantly greater (P less than 0.05) than in incubation medium containing no cells, indicating an enhanced uptake of desethylamiodarone. Metabolic inhibitors (KCN, 2,4-dinitrophenol, and ouabain) and other cationic, amphiphilic drugs (chlorcyclizine, chlorphentermine, and imipramine) were added individually to the cell cultures containing amiodarone or desethylamiodarone. During 1 hr of incubation, these agents had no effect in blocking the accumulation of amiodarone and desethylamiodarone in the cells. The efflux of amiodarone or desethylamiodarone was measured from cells following incubation for 4 hr with each drug. After this time, the medium was replaced with drug-free medium, and the cells were incubated for another 24 hr. Sixty-three percent of amiodarone was lost as compared to only 31% of desethylamiodarone over the 24-hr period (P less than 0.05). The results of this study are suggestive of a preferential uptake and retention of desethylamiodarone as compared to amiodarone. The accumulation of the drugs appears not to be due to active transport or associated with any carrier protein involved in the transport of other structurally-related compounds.

Influence of a pre-existing phospholipidosis on the accumulation of amiodarone and desethylamiodarone in rat alveolar macrophages

Amiodarone is an antiarrhythmic drug that concentrates in the lungs and can cause pulmonary damage in humans. The purpose of the present study was to examine the influence of a pre-existing lung pathology on the pulmonary accumulation of amiodarone and its primary metabolite, desethylamiodarone. To study this problem, male Fischer 344 rats were administered chlorphentermine to induce a phospholipidosis in the alveolar macrophages of the lungs. The accumulation of amiodarone and desethylamiodarone in phospholipidotic alveolar macrophages was measured following 5 weeks of amiodarone administration. When calculated on a per cell basis, the levels of both drugs were increased over 10-fold in phospholipid-laden macrophages compared to cells from control rats in which a phospholipidosis was not present. When phospholipidotic macrophages were exposed to amiodarone and desethylamiodarone in vitro, both drugs were accumulated to a higher level than occurred in cells from control rats. The results of this study demonstrate that the presence of a pre-existing phospholipidosis results in an enhanced accumulation of amiodarone and desethylamiodarone in rat alveolar macrophages.

Effects of amiodarone administration during pregnancy in Fischer 344 rats

Amiodarone is a class III anti-arrhythmic compound that is iodinated, cationic and amphiphilic in nature. The clinical use of amiodarone may be associated with various side-effects, including pulmonary and hepatic toxicity. Use of this compound during pregnancy may therefore place the fetus at risk through in utero exposure. This study was designed to observe any gross developmental effects that may be caused by the administration of amiodarone to Fischer 344 rats during pregnancy, investigate the placental transfer of amiodarone and its principal metabolite, desethylamiodarone and determine the levels of amiodarone and desethylamiodarone in the maternal and newborn lung, liver and plasma. To conduct this study, 35 mg/kg of amiodarone was administered daily to pregnant rats for either the last 7 days of pregnancy, the last 14 days of pregnancy, or for the full 22 days of pregnancy. Drug treatment had no effect on the length of gestation or litter size. Maternal weight gain was decreased only when amiodarone was administered during the last 7 days of gestation. The birthweights of the offspring were decreased, however, crown to rump length was unaffected. Both amiodarone and desethylamiodarone accumulated in the offspring through placental transfer. The levels of both compounds were greater in maternal and newborn lung when compared to maternal and newborn liver, respectively. The maternal lung and liver concentrations of both compounds were significantly higher than the respective newborn concentrations. The newborn plasma concentrations of amiodarone and desethylamiodarone were significantly lower than maternal levels indicating that the placenta may not be totally permeable to the two drugs.

Response of rat lungs to amiodarone: preferential accumulation of amiodarone and desethylamiodarone in alveolar macrophages

Treatment of humans with the antiarrhythmic drug amiodarone can cause pulmonary pathology and toxicity. The disorder is associated with the accumulation of phospholipid, amiodarone, and its principal metabolite desethylamiodarone in lung tissue. To better understand the response of the lung to amiodarone administration, the distribution of total phospholipid, amiodarone, and desethylamiodarone was determined in the lungs of male Fischer 344 rats as a function of treatment time with amiodarone. Rats were treated with amiodarone for 2 days, 1 week, or 9 weeks and the proportional accumulation of the three materials was measured in four fractions: (1) the residual lavaged lung, (2) the alveolar macrophage fraction, and (3) the sedimentable and (4) the nonsedimentable acellular lavage materials. The alveolar macrophage fraction demonstrated a preferential accumulation of phospholipid and both drugs. When isolated alveolar macrophages and type II cells were compared on a per cell basis, alveolar macrophages accumulated significantly more of the drugs and phospholipid throughout the treatment period. The results of this study illustrate the important role played by the alveolar macrophage in the sequestration of amiodarone and desethylamiodarone in rat lung.

Application of X-ray microanalysis to the study of drug uptake in cell culture

X-ray microanalysis has been used previously to study the accumulation of iodine in alveolar macrophages of rats treated with the iodinated drug, amiodarone. Due to metabolism of the drug in vivo, primarily to desethylamiodarone, it was not possible to identify the source of the iodine signal. In the present study we have utilized primary cell cultures of alveolar macrophages to study the intracellular accumulation of each of these drug species in vitro. Neither drug is metabolized by these cells in culture, permitting characterization of the accumulation of each independent of the other. Cells were incubated with equimolar concentrations of either amiodarone or desethylamiodarone for 42 hr, and X-ray microanalysis of freeze-dried cryosections of cells was used to quantify accumulation by monitoring the iodine signal associated with each drug. For both drug exposures, the highest iodine content was present in amorphous bodies and dense granules, consistent with the pattern following in vivo exposure. Higher levels of desethylamiodarone, compared to amiodarone, were measured in all compartments of the cells. The results of the in vitro investigation further demonstrate the utility of X-ray microanalysis in the study of the cellular response to amiodarone and desethylamiodarone.

Response of alveolar macrophages to amiodarone and desethylamiodarone, in vitro

Administration of the antiarrhythmic drug amiodarone to humans or animals may result in lung damage. Amiodarone is metabolized to desethylamiodarone and other minor metabolites. Because amiodarone and the metabolites accumulate in the lungs, it is not possible to ascertain the role of each of these compounds in the induction of toxicity. In the present study, we utilized primary cell cultures of rat alveolar macrophages to study the actions of amiodarone and desethylamiodarone individually and in combination. Neither drug species was metabolized by the cells over 42 h in culture thereby permitting assessment of the actions of each. Both drugs induced the formation of lamellar inclusions, indicative of the development of cellular phospholipidosis. Desethylamiodarone appeared to induce formation of the structures in a shorter period of time than did amiodarone, although given adequate exposure, the two drugs produced similar responses. At shorter times of exposure and lower concentrations, desethylamiodarone was more cytotoxic than amiodarone as assessed by the release of lactate dehydrogenase. The two in combination resulted in cytotoxicity that was more than additive. The results of this study indicate that in vitro cultures of alveolar macrophages may be quite useful in studying the role these cells play in the pulmonary toxicity associated with amiodarone therapy. Additionally, this study supports the idea that a significant portion of the toxicity may result from the actions of desethylamiodarone.

Bone marrow stromal cell bioactivation and detoxification of the benzene metabolite hydroquinone: comparison of macrophages and fibroblastoid cells

Bone marrow stroma consists predominately of two cell types, macrophages and fibroblastoid stromal cells, which regulate the growth and differentiation of myelopoietic cells via the production of growth factors. We have previously shown that macrophages are more sensitive than fibroblastoid stromal cells (LTF cells) to the toxic effects of the benzene metabolite hydroquinone. In this study, the role of selective bioactivation and/or deactivation in the macrophage-selective effects of hydroquinone was examined. LTF and macrophage cultures were incubated with 10 microM [14C]hydroquinone to examine differential bioactivation. After 24 hr, the amount of 14C covalently bound to acid-insoluble macromolecules was determined. Macrophages had 16-fold higher levels of macromolecule-associated 14C than did LTF cells. Additional experiments revealed that hydroquinone bioactivation to covalent-binding species was hydrogen peroxide dependent in macrophage homogenates. Covalent binding in companion LTF homogenates was minimal, even in the presence of excess hydrogen peroxide. These data suggest that a peroxidative event was responsible for bioactivation in macrophages and, in agreement with this, macrophages contained detectable peroxidase activity whereas LTF cells did not. Bioactivation of [14C]hydroquinone to protein-binding species by peroxidase was confirmed utilizing purified human myeloperoxidase in the presence of hydrogen peroxide and ovalbumin as a protein source. High performance liquid chromatographic analysis of incubations containing purified myeloperoxidase, hydroquinone, and hydrogen peroxide showed that greater than 90% of hydroquinone was removed and could be detected stoichometrically as 1,4-benzoquinone. 1,4-Benzoquinone was confirmed as a reactive metabolite formed from hydroquinone in macrophage incubations using excess GSH and trapping the reactive quinone as its GSH conjugate, which was measured by high performance liquid chromatography with electrochemical detection. The activity of DT-diaphorase, a quinone reductase that has been invoked as a protective mechanism in quinone-induced toxicity, was 4-fold higher in LTF cells than macrophages. These data suggest that the macrophage-selective toxicity of hydroquinone results from higher levels of peroxidase-mediated bioactivation and/or lower levels of DT-diaphorase-mediated detoxification.

Quantitative X-ray microanalysis of alveolar macrophages after long-term treatment with amiodarone

Treatment with the iodine-containing antiarrhythmic drug, amiodarone, can cause pulmonary toxicity. Alveolar macrophages are particularly susceptible to formation of lipidrich lamellar bodies in amiodarone-treated animals. Amiodarone and several of its metabolites accumulate in the cell. Previously, we have reported that the technique of X-ray microanalysis is useful in monitoring the distribution of iodine in freeze-dried cryosections of alveolar macrophages from Fischer 344 rats 24 hr after a single dose of amiodarone. In the present study, we examine the effects of longer term amiodarone treatment of 1 or 9 weeks. Substantial changes in iodine distribution occur in the cells with increasing length of drug treatment. High concentrations of iodine are found early in the lamellar bodies. The iodine levels in the nuclei slowly increase with the length of treatment, and after 9 weeks of treatment, approach those found in the lamellar bodies. It is possible that this accumulation of iodine in the nuclei is due to the presence of polar metabolites. In addition, the potassium concentration in the cell decreases and the sodium increases with treatment duration. These changes in cations are most likely due to altered ion transport in the macrophages by the inhibition of membrane Na-K-ATPase by the drug and its principal metabolite, desethylamiodarone.

Macrophage regulation of myelopoiesis is altered by exposure to the benzene metabolite hydroquinone

Hydroquinone, a myelotoxic metabolite of benzene, decreases the ability of murine bone marrow stromal cells to support myelopoiesis in vitro. Bone marrow stroma consists of macrophages and fibroblastoid stromal cells that participate coordinately in regulating myelopoiesis. The goal of this study was to determine if macrophage or fibroblastoid cell function is more sensitive to the myelotoxic actions of hydroquinone. To address this question, we developed purified populations of macrophages and fibroblastoid stromal cells and treated each population with hydroquinone. These cells were reconstituted together with nontreated cells of the opposite type and assayed for their ability to support the formation of granulocyte and macrophage colonies in an agar overlay. Reconstituted cultures containing hydroquinone-treated macrophages supported fewer colonies than did corresponding cultures containing untreated macrophages. Reconstituted cultures containing hydroquinone-treated fibroblastoid stromal cells were not affected. Moreover, hydroquinone reduced detectable interleukin-1 activity in purified macrophage cultures stimulated with lipopolysaccharide. These results indicate that hydroquinone selectively interferes with macrophage function possibly, in part, via alteration of macrophage interleukin-1 secretion.

A review of the biology and toxicologic implications of the induction of lysosomal lamellar bodies by drugs

Over 30 drugs of differing pharmacologic action are capable of inducing lamellar bodies of lysosomal origin in cells of animals and humans. The structures develop because of a drug-induced impairment in lysosomal phospholipid catabolism. Toxicity frequently accompanies the induction of these bodies. However, little information exists as to whether their development or presence is causally linked to the cellular or tissue dysfunction. This review examines the biological aspects of the induction of lysosomal lamellar bodies by drugs and considers the toxicologic implications of their presence in cells.

Amiodarone-induced pulmonary toxicity in rats: biochemical and pharmacological characteristics

Treatment of humans with the antiarrhythmic drug, amiodarone (AD), may result in the development of pulmonary toxicity. To characterize this response, male Fischer 344 rats were treated with AD for 1, 3, 9, and 16 weeks. AD induces a twofold increase in the level of pulmonary phospholipid after 3 weeks of treatment. Continued administration results in only a small increase above this level. All classes of phospholipids are elevated; phosphatidylcholine displays the largest increase, both quantitatively and as a relative increase over the control level. Both AD and its principal metabolite, desethylAD, are sequestered in the lungs following AD treatment. The relative levels are similar at all time points except 16 weeks, where the relative amount of AD is decreased. After 3 weeks of AD, female 344 rats show the same increase in pulmonary phospholipid as males. While similar levels of desethyAD are sequestered in the lungs of both sexes, AD levels are much lower in female lungs. Evidence is presented to suggest that desethylAD may play an important role in the induction of the phospholipidosis. The activity of Na+,K+-ATPase in the lungs is inhibited by 75% after 9 weeks of AD while the activity of the acid hydrolase, beta-N-acetylglucosaminidase is increased significantly at this time point. All biochemical changes are reversible with values returning to control levels 2 weeks after termination of a 3-week AD treatment protocol. Measurable levels of AD and desethylAD are present in lung tissue after 5 weeks of recovery.

Iodine in rat alveolar macrophages following amiodarone treatment: quantitative X-ray microanalysis

The techniques of cryomicrotomy and X-ray microanalysis were used to quantitatively measure the subcellular distribution of iodine in rat alveolar macrophages following a single administration of the iodine-containing antiarrhythmic drug, amiodarone. When frozen, dried sections were analyzed, small amounts of iodine were found throughout the alveolar macrophages, but the major accumulations were observed in amorphous bodies and dense granules. The highest to lowest accumulation is in the following order: amorphous bodies (90 mmole I/kg dry wt) greater than dense granules (50 mmole I/kg dry wt) greater than nucleus = cytosol (10 mmoles I/kg dry wt). The amorphous bodies can contain high and low levels of iodine and the granules are found to have high and low levels of iron. Granules with the high and low levels of iron and amorphous bodies with the high and low levels of iodine can be found in the same cells. X-ray microanalysis proved useful in describing the intracellular distribution of iodine-labeled species following amiodarone administration.

Amiodarone-induced phospholipidosis in rat alveolar macrophages

Humans treated with the antiarrhythmic drug amiodarone may develop pulmonary toxicity accompanied by the presence of alveolar macrophages (AM) containing lamellar inclusions. This cellular response is indicative of the development of a drug-induced phospholipidosis. To characterize this response of the AM, Fischer-344 rats were treated with amiodarone, and the macrophages were recovered by pulmonary lavage. The development of phospholipidosis was dose- and time-dependent and was reversible. Daily treatment for 1 wk (5 days/wk) at 150 mg/kg resulted in a 5-fold increase in total phospholipid in the cells. Phospholipid levels were increased only slightly more through 9 wk of treatment. Cells were filled with lamellar inclusions and contained areas of amorphous granular and membranous material. Individual classes of phospholipids were all increased during the development of phospholipidosis. When expressed as mumol/10(7) cells, phosphatidylcholine demonstrated the largest increase. Levels of amiodarone and its major metabolite, desethylamiodarone, increased in AM in parallel with the increase in phospholipid. From 3 days through 9 wk of treatment, the level of desethylamiodarone was always higher than that of amiodarone. Treatment with desethylamiodarone also induced phospholipidosis in AM. Administration of phenobarbital along with amiodarone for 1 wk caused a reduction in the levels of amiodarone, desethylamiodarone, and phospholipid in the cells. The molar ratio of amiodarone to phospholipid was decreased, whereas the molar ratio of desethylamiodarone to phospholipid remained unchanged. Taken together, the results indicate that, along with amiodarone, desethylamiodarone and/or its metabolites may play an important role in the phospholipidosis induced in AM when rats are treated with amiodarone.

Association of chlorphentermine with phospholipids in rat alveolar lavage materials, alveolar macrophages and type II cells

Administration of chlorphentermine to rats leads to an increase in the phospholipid content of pulmonary surfactant materials and alveolar macrophages. It is known that this drug binds to pure phospholipids and prevents their degradation by phospholipases. Therefore, experiments were carried out to determine if chlorphentermine binds to surfactant phospholipids in vitro and to measure the in vivo association of drug with phospholipids in alveolar lavage materials from rats injected with [14C]chlorphentermine. The presence of chlorphentermine in alveolar macrophages, type II cells and other small pneumocytes (a population of lung cells which does not include alveolar macrophages or type II cells) from treated animals was also assessed. Binding of the drug to surfactant phospholipids, as measured with the fluorescent probe, 1-anilino-8-naphthalene sulfonate, occurs in vitro and does not differ in various subfractions of alveolar lavage materials isolated by differential centrifugation. Following daily administration of chlorphentermine to rats for 3 days, the drug appears to be associated with surfactant phospholipids such that the molar ratio is 1:100 (chlorphentermine/phospholipid). Chlorphentermine is also associated with alveolar macrophages (molar ratio, 1:18) and type II cells (molar ratio, 1:33). Not much drug is associated with the population of other lung cells (molar ratio, 1:333). In alveolar macrophages, approx. 70% of the drug seems to be bound to phospholipid and/or sequestered in subcellular organelles. However, only 20% of the chlorphentermine is bound and/or sequestered in type II cells. The results of these experiments suggest that following chlorphentermine administration, the drug is associated with phospholipids in acellular pulmonary lavage materials, alveolar macrophages and type II cells. This drug-phospholipid interaction may impair phospholipid degradation and lead to a phospholipidosis in surfactant materials and alveolar macrophages.

Chlorphentermine suppresses the phosphatidylinositol pathway in concanavalin A-activated mouse splenic lymphocytes

We have previously demonstrated that the chlorphentermine (CP)1-induced impairment in lymphocyte blastogenesis involves drug-induced inhibition of an event which occurs very early during lymphocyte activation. An early event, which is associated with mitogen-induced lymphocyte activation, involves the hydrolysis of phosphatidylinositol by phospholipase C to yield inositol phosphates and diacylglycerol as products. Inositol phosphates and diacylglycerol then function as mediators of a trans-membrane signal for the continuation of the cellular response. It was the purpose of the present study to determine the effects of CP on this phosphatidylinositol pathway. We demonstrated that formation of inositol phosphates in lymphocytes increases progressively above control over a 2 hour period following concanavalin A (Con A)-stimulation. In contrast, lymphocytes pre-incubated with 10(-5)M CP for 60 min, then stimulated with Con A for 2 hours in the presence of 10(-5)M CP, exhibit a significantly depressed inositol phosphate formation. In addition, CP also inhibited the activity of phospholipase C (IC50 = 0.58 mM), the enzyme responsible for the formation of inositol phosphates during lymphocyte activation. Further, lymphocytes activated in a manner that bypasses the phosphatidylinositol pathway are not inhibited by 10(-7)M or 10(-9)M CP as are cells activated with Con A. These results suggest that the suppression of the phosphatidylinositol pathway may be involved in the inhibition by CP of lymphocyte blastogenesis induced by Con A.

Alterations in rat alveolar surfactant phospholipids and proteins induced by administration of chlorphentermine

Chlorphentermine is a cationic amphiphilic drug which produces a phospholipid storage disorder in rat lungs. Experiments were carried out to characterize changes in the composition of acellular alveolar lavage materials and to study possible mechanisms by which pulmonary surfactant phospholipidosis is produced by administration of the drug. Following ten daily injections of chlorphentermine (25 mg/kg body weight), there are 12.2- and 13.6-fold increases of pulmonary lavage total phospholipids and disaturated phosphatidylcholines (disaturated PC), respectively. In addition, there is a 2.8-fold increase in total protein and a 12.7-fold increase in the surfactant apoprotein group with molecular weights from 28,000 to 32,000. We measured incorporation of labeled palmitate, choline and glycerol into disaturated PC in type II cells and alveolar macrophages isolated from control and chlorphentermine-treated animals. The drug does not affect the incorporation of labeled substrates into disaturated PC in either cell type. However, in alveolar macrophages there is a decrease in the rate of intracellular degradation of recently synthesized disaturated PC in chlorphentermine-treated animals. The drug also inhibits the phospholipase-induced catabolism of rat surfactant disaturated PC which occurs during incubation of alveolar lavage fluid in vitro at 37 degrees C. When the lavage fluid is divided into subfractions by differential centrifugation, a larger percentage of the phospholipid is distributed in the less sedimentable subfractions in chlorphentermine-treated animals relative to controls, suggesting the accumulation of older surfactant materials. These results suggest that chlorphentermine-induced phospholipidosis of pulmonary surfactant materials is due to decreased rates of phospholipid degradation.

Role of phospholipase A inhibition in amiodarone pulmonary toxicity in rats

Amiodarone is effective in the treatment of ventricular and supraventricular arrhythmias. In man its clinical use is associated with the accumulation of phospholipid-rich multilamellar inclusions in various tissues including lung, liver and others. This report presents evidence showing that amiodarone is a potent inhibitor of lysosomal phospholipase A from rat alveolar macrophages, J-744 macrophages and rat liver. When compared with other cationic amphiphilic agents which are known to produce phospholipidosis, amiodarone is one of the most potent inhibitors yet discovered. The subcellular localization of amiodarone has been determined in lung and its distribution was consistent with a lysosomal localization. It is hypothesized that amiodarone causes cellular phospholipidosis by concentrating in lysosomes and inhibiting phospholipid catabolism.

Role of the alveolar macrophage in the induction of pulmonary phospholipidosis by chlorphentermine. II. Drug uptake into cells in vitro

This study was conducted to further assess the role of the alveolar macrophage in the induction of pulmonary phospholipidosis by the cationic amphiphilic drug, chlorphentermine (CP). Alveolar macrophages were collected from normal rats by pulmonary lavage, allowed to attach to glass cover slips and incubated with CP in vitro at 37 degrees C. The uptake of CP was measured using [14C]CP. Uptake is rapid, reaching equilibrium by 2 min resulting in the concentration of CP within the cells. The process is temperature-dependent being depressed markedly at 2 degrees C. Two components of uptake were identified. Below 0.2 mM CP, a carrier-mediated mechanism and diffusion are involved whereas, at concentrations above 0.2 mM, the carrier is saturated and diffusion predominates, with the intracellular binding of CP to membranes probably responsible for the striking sequestration. The carrier-mediated component obeys Michaelis-Menten kinetics, does not appear to require Na+ and is not affected by metabolic inhibitors. This is consistent with the concept that the process occurs by facilitated diffusion. Metabolism of CP does not play a role in the accumulation of the drug. The transport system is different from those involved in glucose, nucleoside or amino acid uptake. Total initial uptake was inhibited by the three cationic amphilic drugs tested, iprindole, chlorcyclizine and imipramine indicating that cationic amphiphilic drugs may share a common uptake system.