Effect of in vivo coal dust exposure on arachidonic acid metabolism in the rat alveolar macrophage

Oxygenated metabolites of arachidonic acid (AA) are produced by the alveolar macrophage (AM) and have been shown to mediate inflammatory reactions. We therefore assessed the production of eicosanoids by AM harvested from the lungs of rats exposed to a bituminous coal dust for 2 wk in an inhalation chamber in order to determine if AA metabolism was altered in a manner that may promote an inflammatory response in the lung. Exposure to coal dust resulted in a 66% increase in the number of AM harvested, an increase in thromboxane A2 (TxA2) and leukotriene B4 (LTB4) production to 222% and 181% of control values, respectively, and a decrease in prostaglandin E2 (PGE2) production to 62% of control values. In AM harvested from rats allowed to breath clean air for 2 wk following coal dust exposure, PGE2 production returned to control levels but TxA2 and LTB4 production remained elevated. The TxA2 synthesis inhibitor UK 38,485 reduced TxA2 production in dust-exposed AM both immediately and 2 wk following exposure. Thus, exposure of rats to coal dust significantly alters the metabolism of AA in AM, with potentially important aspects of AA metabolism remaining altered even after a 2-wk recovery period. Based on the established role of eicosanoids in inflammatory and fibrotic processes, these results suggest that the alteration of AM eicosanoid production as a result of the inhalation of coal mine dust may be an important factor in the pathophysiology of coal workers' pneumoconiosis.     

Comparison of low doses of aged and freshly fractured silica on pulmonary inflammation and damage in the rat

Most previous studies of silica toxicity have used relatively high exposure doses of silica. In this study, male rats received by intratracheal instillation either vehicle, aged or freshly fractured silica at a dose of either 5 microg/rat once a week for 12 weeks (total dose=60 microg) or 20 microg/rat once a week for 12 weeks (total dose=240 microg). One week after the last exposure, bronchoalveolar lavage (BAL) was conducted and markers of pulmonary inflammation, alveolar macrophage (AM) activation and pulmonary damage were examined. For rats exposed to a total of 60 microg silica, both aged and freshly fractured silica increased polymorphonuclear leukocytes (PMN) yield and AM activation above control to a similar degree, but no evidence of pulmonary damage, as measured by BAL fluid lactate dehydrogenase activity or albumin concentration, was detected. For rats exposed to 240 microg silica, aged or freshly fractured silica increased PMN yield and AM activation above control. However, zymosan-stimulated and L-NAME sensitive AM chemiluminescence was greater for rats exposed to freshly fractured silica compared to aged silica. Exposure to 240 microg aged or freshly fractured silica also resulted in pulmonary damage, but the extent of this damage did not differ between the two types of silica. The results suggest that exposure of rats to silica levels far lower than those previously examined can cause pulmonary inflammation. In addition, exposure to freshly fractured silica causes greater generation of reactive oxygen species from AM, measured as AM chemiluminescence, in comparison to aged silica, but there is an apparent threshold below which this difference does not occur.     

煤尘对人肺泡上皮细胞DNA损伤作用的体外实验

目的：以体外培养的人肺泡上皮细胞（A549）作为靶细胞，探讨煤尘对DNA的损伤作用。方法：将人肺泡上皮细胞（A549）用3种煤尘作用2h或24h，用MTT法测定细胞存活情况及用单细胞凝胶电泳技术测定DNA链断裂情况；采用两种细胞共培养的方法，用MTT法测定煤尘在巨噬细胞介导作用下对A549细胞存活情况的影响及用单细胞凝胶电泳技术测定DNA链断裂情况。结果：3种煤尘（游离SiO2含量分别为4．33％、1．79％、0．67％）以3种剂量（100、500、1000μg/ml）直接作用于A549细胞24h，在500和1000μg/ml时均可引起细胞存活率的明显下降；直接作用于A549细胞2h或24h及通过巨噬细胞介导作用下A549细胞，均未能引起A549细胞DNA链断裂程度的明显增加。结论：煤尘对A549细胞具有明显的细胞毒性，但不具有明显的遗传毒性。     

Effect of age on leukotriene B4 production in guinea pig whole blood.

We evaluated the effect of age on eicosanoid production in guinea pig blood. Heparinized blood from 7-10-day, 6-week, or 6-month-old guinea pigs was incubated with 150 microM arachidonic acid (AA) for 5 min, followed by stimulation with A23187 (20 micrograms/mL) for an additional 10 min at 37 degrees. The reaction was terminated by centrifugation, and the production of plasma leukotriene (LT) B4 and C4, prostaglandin E2 (PGE2), and thromboxane B2 (TXB2) was determined by enzyme-linked immunoassay (ELISA). LTC4, PGE2, and TXB2 formation were unaffected by age. In marked contrast, production of LTB4 was increased 4- to 5-fold as age increased from 7-10 days (9.51 +/- 2.07 ng/mL) or 6 weeks (8.83 +/- 1.81 ng/mL) to 6 months (40.57 +/- 9.66 ng/mL). To determine the effect of age on the total eicosanoid product profile, blood was stimulated in the presence of [14C]AA, and plasma metabolites were separated by reverse-phase high pressure liquid chromatography (RP-HPLC) and quantitated using on-line radiochemical detection. In addition to increased LTB4 production, a modest increase in 12-hydroxyeicosatetraenoic acid (12-HETE) production was also observed in the 6-month-old animals. Previous studies have demonstrated interference of 12-HETE in the immunoassay of LTB4. Therefore, to validate the authenticity of the plasma leukotriene ELISA measurements, samples were precipitated with methanol and fractionated by RP-HPLC. The fractions co-eluting with [3H]LTB4 or [3H]LTC4 were dried under vacuum and reconstituted in ELISA buffer, and leukotrienes were quantitated. As seen previously, following HPLC purification LTB4 production remained significantly elevated in the 6-month-old guinea pigs, whereas LTC4 production was unaffected by age. To further document the selectivity of this effect on LTB4 production, we evaluated the effect of increasing age on cyclooxygenase or phospholipase A2 (PLA2) activity. Neither cyclooxygenase nor PLA2 activity was elevated as animals matured. In conclusion, the capacity of whole blood to produce LTB4, but not LTC4, TXB2, or PGE2, was elevated markedly in older animals.     

Effects of diesel exhaust particles (DEP), carbon black, and silica on macrophage responses to lipopolysaccharide: evidence of DEP suppression of macrophage activity

The effects of diesel exhaust particle (DEP) exposure on alveolar macrophage (AM) response to ex vivo and in vivo lipopolysaccharide (LPS) challenge were determined by monitoring LPS-stimulated production of interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha). The roles of the insoluble particulate and the organic compounds of DEP in altering pulmonary responses were evaluated by comparing the DEP-induced pulmonary responses to those of carbon black (CB), a carbonaceous particle with few adsorbed organic compounds, or to silica, a known pneumotoxic dust. Male Sprague-Dawley rats were exposed to a single intratracheal dose (5 or 35 mg/kg body weight) of DEP, CB, or silica, or to saline vehicle. Rats were sacrificed 1, 3, or 7 d postexposure. To study the responsiveness to the bacterial product LPS, AM isolated from particle-exposed rats were challenged ex vivo with LPS (0.1 microg/10(6) AM) and LPS-stimulated cytokine release was monitored. In addition, rats were exposed intratracheally to a single dose of DEP (5 mg/kg) and 3 d later exposed in vivo to 1 mg/kg LPS for 3 h prior to measurement of cytokine production by AM. DEP exposure resulted in neutrophil infiltration and elevated levels of albumin and lactate dehydrogenase (LDH) activity in the bronchoalveolar lavage fluid; these responses were not substantially different from those elicited by CB or silica exposure. AM from DEP-exposed rats showed increased spontaneous production of IL-1, but not TNF-alpha, while the opposite was true for CB or silica. Upon ex vivo challenge with LPS, AM from DEP-exposed rats showed a significant decrease in the secretion of TNF-alpha and, to a lesser extent, IL-1, compared to the sum of the DEP and LPS effects. In contrast, AM from CB- or silica-exposed rats did not show this decreased responsiveness to subsequent LPS challenge. This inhibitory action of DEP on LPS-stimulated AM production of IL-1 and TNF-alpha was further confirmed by the results obtained from rats exposed to both DEP and LPS in vivo. In summary, these results indicate that while DEP, CB, and silica all induce pulmonary inflammatory responses due to particle stimulation, only DEP suppress AM cytokine release in response to LPS stimulation. The contrasting cellular response with respect to DEP and CB exposures may be due to the presence of adsorbed organic compounds on DEP, which may contribute to the increased susceptibility of hosts to pulmonary infections after DEP exposure.     

Pulmonary response to inhaled silica or titanium dioxide.

The pulmonary response to mineral dust inhalation was investigated by characterizing markers of lung injury and inflammation, macrophage activation, dust clearance, and histopathology. Rats were exposed (6 hr/day x 5 days) to air or 50 mg/m3 crystalline silica (SiO2) or titanium dioxide (TiO2). At 7, 14, 28, and 63 days after exposure, bronchoalveolar lavage fluid (BALF) was analyzed for lactate dehydrogenase (LDH), total protein, and N-acetylglucosaminidase, as well as cell number, type, and viability. Alveolar macrophages (AM) obtained in BALF were cultured with or without LPS and release of interleukin-1 (IL-1) and fibronectin was determined. Histopathology was conducted at 28 and 63 days. The exposure protocol resulted in 1.8-1.9 mg of mineral dust being deposited in the pulmonary region. Clearance of SiO2 was significantly less than TiO2. SiO2 increased BALF neutrophils (Days 14, 28, and 63), total protein (Days 28 and 63), and LDH and lymphocytes (Day 63). SiO2 increased AM-derived fibronectin release (Day 63) and LPS-induced IL-1 release (all time points), but not spontaneous release of IL-1. TiO2 did not change BALF biochemical or cellular parameters or AM secretory activity. Histopathology revealed minimal interstitial inflammation with SiO2 and no significant response in control or TiO2 rats. These results demonstrate the pulmonary response to inhaled SiO2 can be differentiated from the relatively innocuous TiO2 by changes in BALF markers of injury and inflammation further supporting the use of BALF analysis to make relative assessments of pulmonary toxicity. The stimulation of macrophage fibronectin release by the fibrogenic dust SiO2 and not TiO2 is consistent with a role for this glycoprotein in lung injury and repair. Last, the early and persistent effect of SiO2 on LPS-induced AM IL-1 release indicates this response may represent a sensitive early marker of dust-induced changes in the AM population.     

Response of alveolar macrophages to in vitro exposure to freshly fractured versus aged silica dust: the ability of Prosil 28, an organosilane material, to coat silica and reduce its biological reactivity.

We have reported previously that crushing or grinding crystalline silica results in the generation of silica-based radicals on the particulate surface and that these radicals can generate hydroxyl radicals in aqueous solution. Data in the present study indicate that freshly ground silica is more cytotoxic and is a more potent activator of alveolar macrophages than comparably sized aged silica. That is, compared to aged silica, fresh silica is 4.2-fold more potent in decreasing the membrane integrity of macrophages; is 50% more potent in activating hydrogen peroxide secretion by macrophages; and is 4.6-fold more potent in stimulating cellular chemiluminescence. Prosil 28, an organosilane material, is an effective coating agent for fresh silica. It decreases the cytotoxicity of fresh silica by as much as 78% and decreases the ability of fresh silica to induce chemiluminescence from alveolar macrophages by 58%. The data suggest that surface radicals associated with freshly cleaved dust may be an important factor in the induction of pulmonary disease. Furthermore, treating dust with coating agents may substantially decrease toxicity.     

Leukotriene B4 and prostaglandin E2 mediate the inflammatory response of rabbit skin to intradermal arachidonic acid.

1. Acute inflammation was induced in rabbit skin by intradermal injection of arachidonic acid. 2. Inflammation was assessed by the local accumulation of intravenously-injected 125I-serum albumin (plasma extravasation) and histologically (polymorphonuclear leucocyte, PMNL infiltration). 3. Leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) were extracted from skin and fractionated using C18 mini-columns. They were quantitated by specific radioimmunoassays and authenticated by reversed-phase high performance liquid chromatography analysis. 4. Maximally elevated levels of LTB4 and PGE2 were detected in skin 5 min after arachidonic acid injection. At subsequent times the eicosanoid content of the skin decreased. 5. The decrease in the eicosanoid content of the skin was due to rapid clearance (t 1/2 approximately 5 min) via the microvasculature and not a consequence of metabolism. 6. The concentration of LTB4 and PGE2 measured in inflamed skin was sufficient to account for the plasma extravasation and PMNL infiltration induced by arachidonic acid. The model therefore is useful for evaluating the anti-inflammatory efficacy of inhibitors of arachidonic acid metabolism including 5-lipoxygenase inhibitors. 7. The consequences of the rapid clearance of LTB4 from inflammatory sites are discussed with respect to its measurement in inflammatory disease and its role as an acute inflammatory mediator.     

A comparison of the anti-inflammatory activity of selective 5-lipoxygenase inhibitors with dexamethasone and colchicine in a model of zymosan induced inflammation in the rat knee joint and peritoneal cavity.

Intraperitoneal and intra-articular (knee joint) injection of zymosan in the rat caused two phases of increased vascular permeability, a rapid increase (0.25-0.5 h) and a secondary increase (2-3 h) which was temporally associated with the onset of leukocyte infiltration. Intraperitoneal injection of zymosan led to a single peak of eicosanoid production (LTB4, C4, D4, E4 and 6-oxo-PGF1 alpha) which was maximal at 0.125-0.25 h. Intra-articular injection led to an initial peak of LTB4 production (maximal at 0.25 h) and a secondary peak of LTB4 and PGE2 production (maximal at 3 h). Oral administration of the 5-lipoxygenase (5-LO) inhibitors phenidone, BW A4C (N-hydroxy-N-[3-(3-phenoxyphenyl)-2-propenyl] acetamide), A63162 (N-hydroxy-N-[1-(4-(phenylmethoxy) phenyl)ethyl] acetamide and ICI 207 968 (2-[3-pyridylmethyl]-indazolinone inhibited LTB4 production in A23187 stimulation blood ex vivo. The glucocorticosteroid dexamethasone had no effect in this model. The initial phase of increased vascular permeability in the peritoneal cavity and LTB4 production was dose dependently inhibited by the 5-LO inhibitors phenidone, BW A4C, A63162, and ICI 207 968 but not by dexamethasone or colchicine. The initial phase of increased permeability in the joint was unaffected by phenidone, BW A4C, dexamethasone or colchicine. However the latter two drugs inhibited the later phase of increased permeability and leukocyte infiltration in the joint and peritoneal cavity. These results demonstrate that zymosan induces eicosanoid production in vivo but the relative importance of these mediators varies depending on the inflammatory site.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lung cell reactions in guinea pigs exposed to tobacco smoke and silica dust or bacterial lipopolysaccharides

In order to investigate the possibility of the synergistic effects of tobacco smoke and/or silica dust (SiO2) or bacterial endotoxins (LPS), guinea pigs were exposed to combinations of these agents. A 15-day exposure to SiO2 alone caused a decrease in intracellular lysosomal enzymes of alveolar macrophages (AM) and an increase of lysosomal enzymes detected in lung lavage fluid which was present 16 weeks after exposure. The effect was the same in animals which received SiO2 in combination with tobacco smoke. Exposure to LPS caused an increase in the number of neutrophils recovered in lavage fluid. The increase in neutrophils was less in animals previously exposed to tobacco smoke alone or in combination with LPS. Acute exposure to LPS also caused an increase in lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase and acid phosphatase activity detectable in lung lavage fluid. The increase was less pronounced in animals previously exposed to smoke. Cathepsin D was increased in AM after tobacco smoke exposure alone and was decreased to below control values of the animals which received an acute LPS exposure.     

Contributory role of lung pleura to release of anaphylactic mediators from guinea pig lung in response to ovalbumin or A23187.

Previous findings revealed greater contractile responses of guinea pig lung pleural surface strips to antigen or A23187 challenge than denuded lung parenchymal strips (lung strip devoid of any pleura). Moreover, we have identified a high density of mast cells distributed throughout the lung pleura. The present study examined mediators released from guinea pig lung pleural surface and denuded lung parenchyma fragments in response to immunologic challenge with ovalbumin (OA) or non-immunologic challenge with the ionophore A23187. Histamine levels were measured radioenzymatically; leukotrienes (LTs), prostaglandins (PGs) and thromboxane B2 (TXB2), a stable metabolite of thromboxane A2 (TXA2), were quantitated using an enzyme immunoassay. Histamine release reached a maximal level 3-5 min after OA challenge, whereas A23187-induced histamine release increased gradually in a time-dependent manner. Similar kinetics were observed in the release of LTs, PGs and TXA2. Pleural surface released a substantially (P < 0.05) greater amount of histamine to both challenges than denuded parenchyma. Moreover, histamine content in pleural surface was significantly (P < 0.05) higher than in denuded parenchyma. Pleural surface also released considerably (P < 0.05) more LTB4, LTC4, and LTE4 in response to OA and A23187 than denuded parenchyma. In contrast, pleural surface and denuded parenchyma released equivalent amounts of PGD2, PGE2, PGF2 alpha, and TXA2 in response to both challenges. The rank order of leukotriene release was LTC4 > LTE4 > LTB4, whereas that of prostanoid release was TXA2 > PGD2 > or = PGF2 alpha > PGE2. We conclude that pleural surface is the major source of histamine and leukotrienes released from guinea pig lung in vitro in response to OA and A23187, whereas both pleural surface and denuded parenchyma participate to the same extent in prostaglandin and TXA2 production after such challenges.     

Differential release of eicosanoids by bradykinin, arachidonic acid and calcium ionophore A23187 in guinea-pig isolated perfused lung

The effects of infusions of bradykinin (0.2 microM), calcium ionophore A23187 (0.5 microM) and arachidonic acid (13 microM) on the release of eicosanoids from the guinea-pig isolated perfused lung were investigated using radioimmunoassay for thromboxane B2 (TXB2), 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha), PGE2, leukotriene B4 (LTB4) and LTC4 and bioassay using the superfusion cascade. Bradykinin released more 6-oxo-PGF1 alpha than TXB2, whereas arachidonic acid and ionophore released more TXB2 than 6-oxo-PGF1 alpha. The time course of eicosanoid release varied with the stimulus: bradykinin and arachidonic acid produced an immediate release, whereas the ionophore showed a slower onset of release. Although the amounts of LTB4 and LTC4 released by the ionophore were very low according to radioimmunoassays, there was evidence from the bioassay of release of a leukotriene-like substance, thought to be LTD4. The leukotriene antagonist FPL 55712 lacks specificity in the guinea-pig trachea; at the concentration used (2 microM) it antagonized contractions of the tracheal strip to PGE2 as well as to LTC4. Our results show that in the guinea-pig perfused lung the metabolism of exogenous arachidonic acid is both qualitatively and quantitatively different from the metabolism of endogenous arachidonic acid; furthermore, the profile of eicosanoid production is stimulus-dependent.     

Thromboxane A2 up-regulates neutrophil elastase release in Syrian hamsters with trinitrobenzene sulfonic acid-induced colitis

Neutrophil elastase (NE) is a factor that aggravates colitis. We investigated the influence of thromboxane A2 (TXA2) and leukotriene B4 (LTB4) on NE release in Syrian hamsters with trinitrobenzene sulfonic acid-induced colitis. Colonic specimens with colitis were incubated with U-46619 (a TXA2 analogue) or LTB4 in vitro and NE release was examined. As a result, U-46619 increased NE release, while LTB4 had no effect. The NE release induced by U-46619 was inhibited by a TP-receptor antagonist. To demonstrate that TXA2 caused NE release in vivo as well, while LTB4 did not, colitis animals were treated with nordihydroguaiaretic acid (NDGA), a dual inhibitor of cyclooxygenase/lipoxygenase; and colonic luminal TXB(A)2 and LTB4 levels and NE activity were determined. The TXB(A)2 level was significantly correlated with NE activity, while no correlation was found between LTB4 and NE activity. An inhibitory effect of NDGA on the ulcer area was also observed, and NE activity was significantly correlated with the ulcer area. The suppression of TXA2 production by NDGA may result in the inhibition of NE release so that colonic tissue damage becomes less severe. Regulation of NE release is a new biological action of TXA2 that has not been reported before.     

Differential production of leukotriene B4 or prostaglandin E2 by WKYMVm or serum amyloid A via formyl peptide receptor-like 1

Serum amyloid A (SAA) and Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm) have been reported as formyl peptide receptor-like 1 (FPRL1) ligands. WKYMVm but not SAA stimulated superoxide generation by human neutrophils. In terms of the downstream signalings triggered by WKYMVm and SAA, both agonists stimulated cytosolic phospholipase A2-mediated arachidonic acid release, a precursor of leukotriene B4 (LTB4) and prostaglandin E2 (PGE2). WKYMVm also strongly stimulated LTB4 production in human neutrophils without affecting PGE2 production, whereas SAA strongly stimulates cyclooxygenase-2 (COX-2) expression and PGE2 production but not LTB4 production. In terms of the receptors responsible for the differential actions of these two agonists, we found that FPRL1 is involved in the production of LTB4 by WKYMVm and PGE2 production by SAA. This study demonstrates that the chemoattractant receptor, FPRL1, can be differentially regulated by distinct ligands to generate different lipid mediators, and thus, different immune responses.     

Pharmacological profile of SK&F 105809, a dual inhibitor of arachidonic acid metabolism

The effects of SK&F 105809, 6,7,-dihydro-2-[4(methylsulfinyl) phenyl]-3-(4-pyridyl) -5[H]-pyrrolo[1,2-a] imidazole, on eicosanoid metabolism, inflammatory responses, algesia and ulcer formation are described. SK&F 105809 was determined to be a prodrug for the sulfide metabolite SK&F 105561 which is an inhibitor of 5-lipoxygenase (5-LO) and prostaglandin H (PGH) synthase activities seen with both the isolated enzyme (IC50S 3 microM) and human monocyte production of the eicosanoids leukotriene B4 (LTB4, IC50 1.0 microM) and prostaglandin E2 (PGE2, IC50 0.1 microM). In-vivo conversion of SK&F 105809 to the active principle SK&F 105561 was observed in both mice and rats. SK&F 105809 inhibited LTB4 and PGE2 production in vivo in inflammatory exudates as well as the production of LTB4 and thromboxane B2 (TxB2) ex vivo in rat blood. SK&F 105809 inhibited oedema and inflammatory-cell infiltration in arachidonic acid-induced inflammation in the mouse ear and rat paw as well as in carrageenan- and monosodium urate crystal-induced peritonitis. SK&F 105809 was also effective in inhibiting mouse collagen-induced arthritis and associated acute-phase reactant protein. At the same time, these acute and chronic models of inflammation were found to be resistant to the action of selective cyclooxygenase inhibitors such as naproxen. In addition, SK&F 105809 possessed analgesic activity in phenylquinone-induced abdominal constriction assay and inhibited indomethacin-induced ulcers.     

Alterations in prostacyclin and thromboxane formation by chronic cigarette smoke exposure: temporal relationships and whole smoke vs. gas phase

Chronic cigarette smoke exposure in vivo causes decreased conversion of [14C]arachidonic acid (AA) to prostacyclin (PGI2) by isolated aortic tissue and increased conversion to thromboxane (TXA2) by isolated platelets from rats. Alterations in the PGI2/TXA2 balance may be part of the mechanism through which smoking increases the risk of cardiovascular disease. To study the influence of smoke exposure duration on this response, male rats were exposed daily to 10 puffs of freshly generated cigarette smoke. Animals were killed after 1, 4, 14, 28 and 57 days of smoke exposure and 3, 7, 14 and 28 days after cessation of the 57-day of smoke-exposure regimen. Elevated carboxyhemoglobin levels during the smoke-exposure sessions verified smoke (gas phase) inhalation. Statistically significant alterations in prostacyclin synthesis preceded those of thromboxane. A decrease of 20-25% (P less than 0.05) in PGI2 production from [14C]AA in isolated aortic tissue was found beginning 28 days after smoke was initiated and quickly rebounded when smoke exposure was terminated. Increased production of TXA2 from [14C]AA by isolated platelets became statistically significant (P less than 0.05) on the 57th day and returned to normal 7-14 days after cessation of smoke exposure. To determine the effect of gas phase constituents on the PGI2/TXA2 balance a second series of experiments divided male and female Sprague-Dawley rats into sham, whole smoke and gas phase groups. Gas phase was produced by passing whole smoke through a Cambridge filter to remove particulate matter. Per cent COHb averaged 1.4 for sham, 7.8 for whole smoke and 9.4 for gas phase groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Internalization, cytotoxicity, apoptosis, and tumor necrosis factor-alpha expression in rat alveolar macrophages exposed to various dusts occurring in the ceramics industry

In 1997 The International Agency for Research on Cancer classified some exposures to crystalline silica as carcinogenic to humans. Such exposures were acknowledged to be very variable, and even in the same monograph it was admitted that coal dust, containing as much as 20% quartz, could not be classified. Clearly there is a need to develop methods for assessing any risks posed by various silica containing dusts in different workplaces. A European collective research project, SILICERAM, was launched with the aim of assessing the toxicity of various dusts in the ceramics industry and improving worker protection. This study examined the effect of particles, namely, DQ12 quartz, China clay, feldspar, and a sample resembling a typical mixture used in the ceramic industry (a "contrived sample" or CS), on NR8383, a rat alveolar macrophage (AM) cell line. Titanium dioxide and aluminum oxide were also used as negative controls. Confocal microscopy observations showed internalization of DQ12 and CS in NR8383. Cell viability decreased dramatically after a 2-h incubation exposure period with DQ12 (-71%). CS was less toxic than DQ12 at 2 h. China clay and feldspar were slightly cytotoxic to NR8383 cells. DQ12 induced apoptosis, with a smaller effect of CS and China clay. TNFalpha gene expression was analyzed by RT-PCR. DQ12, at a noncytotoxic dose of 10 microg/cm(2), induced a significant expression of TNFalpha (+2 times increase). In contrast, similar doses of CS and China clay did not produce a significant increase, while TiO2 and Al2O3 displayed no effect. Co-treatment with 10 microM aluminum lactate significantly reduced the effects of silica-containing particles on cytotoxicity, apoptosis, and TNFalpha expression.     

Prostaglandin E2 inhibits and indomethacin and aspirin enhance, A23187-stimulated leukotriene B4 synthesis by rat peritoneal macrophages

1. The calcium ionophore, A23187, stimulated leukotriene B4 (LTB4), thromboxane B2 (TxB2) and prostaglandin E2 (PGE2) synthesis by 4 day carrageenin-elicited rat peritoneal macrophages. 2. At concentrations of 2 x 10(-7)-2 x 10(-5) M indomethacin and aspirin enhanced A23187-stimulated LTB4 synthesis and inhibited PGE2 and TXB2 formation. 3. PGE2 inhibited A23187-stimulated LTB4 and TXB2 formation as well as the augmentation of LTB4 release caused by aspirin and indomethacin. However, PGE2 was ineffective when the cells were challenged with arachidonic acid (AA). 4. Dibutyryl adenosine 3':5'-cyclic monophosphate (db-cyclic AMP) partially inhibited A23187-stimulated LTB4 production. 5. Our results suggest that PGE2 inhibits macrophage LTB4 synthesis by limiting the availability of AA. Indomethacin and aspirin, possibly by removing the regulatory effect of PGE2, promote the synthesis of the pro-inflammatory LTB4.     

Oxygen-derived free radical-induced vasoconstriction by thromboxane A2 in aorta of the spontaneously hypertensive rat

This study was performed to clarify the mechanism of vasoconstriction induced by oxygen-derived free radicals in spontaneously hypertensive rats. The isometric tension of aortic rings from spontaneously hypertensive rats and Wistar-Kyoto rats was measured in Krebs-Henseleit solution. Oxygen-derived free radicals were generated by mixing xanthine and xanthine oxidase. The removal of endothelium enhanced the contractions induced by oxygen-derived free radicals. The inhibition of nitric oxide production with NG-nitro-L-arginine methyl ester (10(-4) M) enhanced the contractions. Treatment with the thromboxane A2 (TXA2) synthetase inhibitor OKY-046 (10(-4) M) or RS-5186 (10(-4) M) markedly reduced the contractions. Treatment with the cyclooxygenase inhibitor indomethacin (10(-5) M) and a TXA2/prostaglandin H2 (PGH2) receptor antagonist, ONO-3708 (10(-6) M), completely abolished the oxygen-derived free radical-induced contractions. In contrast, treatment with the PGI2 synthetase inhibitor tranylcypromine (10(-4) M) did not attenuate the oxygen-derived free radical-induced contractions. Whether endothelium was present or not, the release of TXB2, PGE2, and 6-keto-PGF1alpha, but not PGF2alpha, was increased by the production of oxygen-derived free radicals. Catalase and the hydroxyl radical scavenger deferoxamine plus mannitol markedly inhibited the oxygen-derived free radical-induced contractions. These results suggest that oxygen-derived free radical-induced vasoconstriction in spontaneously hypertensive rat aorta is caused by TXA2 and PGH2 released in smooth muscle.     

Eicosanoid production and phospholipase A2 secretion by peritoneal macrophages from rats with adjuvant-induced arthritis.

The effect of adjuvant-induced arthritis on rat peritoneal macrophage (RPM) function with respect to [14C]arachidonic acid (AA) release, leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) production, and secreted phospholipase A2 (PLA2) activity was investigated. Twice as many cells were lavaged from the peritoneal cavity of arthritic rats 21 days post-adjuvant injection than were lavaged from normal rats. PGE2 production was increased two-fold in Ca++ ionophore-stimulated RPM from the adjuvant animals as compared with RPM from control animals. However, PLA2 secretion, LTB4 production and [14C]AA release were unchanged. These results suggest that PGE2 production, rather than LTB4 production or PLA2 secretion, is preferentially enhanced in Ca++ ionophore-stimulated RPM from arthritic rats and may, therefore, reflect a major role for PGE2 in adjuvant-induced arthritis. However, the presence of increase numbers of macrophages and their associated products, including PLA2 and LTB4, may also contribute to the inflammatory process in this disease.