- Open Access
Effects of nitric oxide synthase inhibitor ω-Nitro-L-Arginine Methyl Ester, on silica-induced inflammatory reaction and apoptosis
© Wang and Leigh; licensee BioMed Central Ltd. 2006
- Received: 24 December 2005
- Accepted: 07 November 2006
- Published: 07 November 2006
Although nitric oxide is overproduced by macrophages and neutrophils after exposure to silica, its role in silica-induced inflammatory reaction and apoptosis needs further clarification. In this study, rats were intratracheally instilled with either silica suspension or saline to examine inflammatory reactions and intraperitoneally injected with ω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthases, or saline to examine the possible role of nitric oxide production in the reaction.
Results showed that silica instillation induced a strong inflammatory reaction indicated by increased total cell number, number of neutrophils, protein concentration and lactate dehydrogenase (LDH) activity in bronchoalveolar lavage fluid (BALF). There were no significant differences in these indices between silica-instilled groups with and without L-NAME injection (p > 0.05) except LDH level. The results also showed that apoptotic leucocytes were identified in BALF cells of silica-instilled groups whereas no significant difference was found between silica-instilled groups with and without L-NAME injection in the apoptotic reaction (p > 0.05). Silica instillation significantly increased the level of BALF nitrite/nitrate and L-NAME injection reduced this increase.
Intratracheal instillation of silica caused an obvious inflammatory reaction and leucocyte apoptosis, but these reactions were not influenced by intraperitoneal injection of L-NAME and reduced production of NO. This supports the possibility that silica-induced lung inflammation and BALF cell apoptosis are via NO-independent mechanisms.
- Nitric Oxide
- Intratracheal Instillation
- Apoptotic Neutrophil
- BALF Cell
- Asbestos Fibre
Silica exposure results in an initial inflammatory reaction and subsequent fibrosis. During this process, various agents such as cytokines and free radicals are produced and these agents in turn regulate the development of the inflammation and fibrosis . Nitric oxide (NO), a small molecule with multiple biologic functions, has been shown to be overproduced by alveolar macrophages and neutrophils as well as other cell types after exposure to intratracheal instillation of silica [2–4]. It has also been demonstrated that γ-interferon and TNF-α, which are produced in silica-induced response , can induce synthesis of NO .
NO is a molecule that can readily pass through the cell membrane and exert its action on cells. It is involved in vessel dilatation, inhibition of platelet aggregation  and host defence. It is also an apoptosis inducer for some cell types . Since silica-induced apoptosis of bronchoalveolar leucocytes has already been demonstrated  and probably has a role in the evolution of silica-induced inflammation and fibrosis, NO may induce leucocyte apoptosis to regulate these pathological reactions. However, there are also evidences that some apoptotic change occurs via a nitric oxide-independent pathway [10, 11]. It is not known whether leucocyte apoptosis in silica-induced inflammation occurs via the nitric oxide-dependent or independent pathway.
Although NO seems to be beneficial by induction of apoptosis in inflammatory cells, the NO produced in a silica-induced lung reaction may be harmful. That is because nitric oxide can combine with superoxide to form peroxynitrite free radical and this substance can cause severe lung damage [2, 12, 13]. Indeed, other harmful agents such as asbestos fibres  and ozone , which induce lung damage, have been demonstrated to enhance production of NO in vitro and in vivo although the role of NO in the process is uncertain. Even in the case of peroxynitrite, its exact role in pathological processes is contradictive. Current knowledge indicates that both NO and peroxynitrite may have dual or beneficial and harmful effects in inflammatory reactions depending on situation.
ω-nitro-L-arginine methyl ester (L-NAME) is a NO synthase inhibitor and inhibits the production of NO by inducible NO synthase and constitutive NO synthase. In silica-induced inflammatory reaction, inducible NO synthase gene expression increases in alveolar leucocytes and the production of NO is likely to be via the increased gene expression of NO synthase . In the present study, silica-induced inflammation and apoptosis were quantified in intratracheally (it) silica-instilled rats with and without L-NAME injection to see if this compound could inhibit the inflammatory reaction and apoptosis.
Nitrite/nitrate level in BALF
In this study, a strong inflammatory reaction was induced following silica instillation. At the administered dosage, L-NAME failed to influence the silica-induced inflammation indices. The L-NAME dosage was above the effective dosage in similar studies for the inhibition of lung injury [16–19] and actually reduced the level of nitrite/nitrate in BALF from silica-instilled rats in this experiment.
The results in this study may be an indication that although nitric oxide may be an important marker in the development of lung injury, it does not play a pivotal role in silica-induced inflammation under the conditions of this experiment. In a previous study with a rat model , intratracheal instillation of silica (100 mg/kg BW)caused overproduction of both superoxide and nitric oxide 24 hours later. Nitric oxide has been demonstrated to be able to combine with superoxide to form peroxynitrite which is a much stronger harmful agent to lung tissue [21, 22]. However, NO synthase inhibitor L-NAME did not reduce lung inflammatory reactions in the present study although the level of nitrite/nitrate in BALF from silica-instilled rats was reduced by the drug. L-NAME had also been shown to decrease NO as well as peroxynitrite production in silica-induced acute lung injury  in a previous study. The damaging role of NO or peroxynitrite in silica-induced lung injury could not be verified by injection of L-NAME which has been widely used as a NO synthase inhibitor. The dependency of silica-induced lung inflammation on NO or peroxynitrite is open to question.
NO has been demonstrated to cause apoptosis . Induction of inducible NO synthase by exogenous agent can also lead to cell death by apoptosis . Macrophages cause apoptosis of other cell types through the release of nitric oxide . In silica-induced inflammation, increase in inducible nitric oxide synthase activity, nitric oxide overproduction and leucocyte apoptosis have all been demonstrated [26, 27]. This suggests that there is a probability that the silica-induced nitric oxide might induce neutrophil apoptosis to regulate the evolution of the silica-induced inflammation. However, in this experiment, L-NAME did not influence leucocyte apoptosis significantly. Since the dosage is well above effective and actually reduced the BALF level of nitrite/nitrate, it is possible that nitric oxide plays only a minor role in the leucocyte apoptosis of silica-induced inflammation.
It is noted that chemicals can cause cell apoptosis by either nitric oxide-dependent or nitric oxide-independent mechanisms . For example, bisphosphonates induce apoptosis in mouse macrophage-like cells in vitro by an nitric oxide-independent pathway . These workers demonstrated that the apoptosis induced by bisphosphonates was not due to increased synthesis of NO and could not be prevented by inhibitors of NO synthase. NO also failed to induce apoptosis in oligodendrocytes .
Peroxynitrite can be produced in silica-induced lung injury and this endogenous substance can induce either necrosis [31, 32] or apoptosis[33–36]. In this experiment, L-NAME did not influence either leucocyte apoptosis or lung inflammation significantly. Since peroxynitrite might be overproduced in silica-induced inflammation of this study and L-NAME actually reduced the overproduction of NO, there is a possibility that leucocyte apoptosis in silica-induced inflammation was via a peroxynitrite-independent pathway.
It is interesting that L-NAME at an effective dosage, failed to influence silica-induced inflammation as well as leucocyte apoptosis. This supports the hypothesis that the regulation of apoptosis might influence the evolution of silica-induced inflammation. For example, in a previous study, it was demonstrated that enhancement of apoptosis by IL-10 accelerated the resolution of acute inflammation induced by LPS . It was noted that L-NAME inhibited silica-induced LDH activity increase in BALF in this experiment. This inhibition may also be related to a NO-independent pathway since it has been demonstrated that L-NAME can reduce LDH release by cultured cells independent of NO reduction [38, 39].
In regard to the role of NO in injuries caused by various invading agents, conflicting results have been presented. A number of experiments showed that NO was harmful to the exposed cells or tissues  whereas some experiments indicated that NO actually played a protective role to the exposed tissues or cells [40, 41]. Moreover, in an in vitro study NO was demonstrated to play a dichotomous role in asbestos induced harmful effects . The result of this study was the outcome of four weeks after one off exposure of silica and continuing administration of L-NAME. Although this study did not directly measure the activity of NO synthases, the production of NO estimated by nitrite/nitrate level in BALF was dramatically reduced by the injection of L-NAME. Since it has been reviewed that direct link between silica-induced NO production and pathogenesis was obtained using iNOS knockout mice, and iNOS knockout provided protection in sub-chronic exposure of silica but not in acute exposure , the complexity of NO synthases in silica-induced inflammation is shown. Further studies are needed to reveal the exact role of NO in silica-induced harmful effects.
This study demonstrated that L-NAME, a nitric oxide synthase inhibitor, did not influence the inflammatory reaction and apoptosis of neutrophils after exposure to intratracheal silica in rats at the dosage of 15 mg/kg/day for four weeks. Because this dosage was more than10 times of L-NAME ED 50 and it actually reduced the production of NO in silica-instilled lungs, NO probably played little role in the development of inflammation and leucocyte apoptosis in silica-induced harmful effects. The result is inconsistent with a number of previous studies which support the concept that NO can harm lung tissue in silica-induced effects by combining with superoxide to form peroxynitrite. We conclude that silica-induced harmful effects are probably caused by NO or peroxynitrite independent pathways in the rat model established by intratracheal instillation.
Experimental animals and group
The animals used in the experiments were male Wistar rats. They were purchased from the animal breeding facility of The University of New South Wales (Little Bay, NSW) and held in presterilised cages in the animal holding facility of the National Institute of Occupational Health and Safety. Sterilised food and water were supplied ad libitum. Experimental protocols involving rats were in accordance with the University of Sydney regulations and approved by The Animal Care Ethics Committee (ACEC) of The University of Sydney (ACEC number: WOR/7-95/2/2182).
In this study, body weights of the rats at the start of the experiment were 224–235 grams. The rats were grouped by randomised block design into four groups (each of 5): (1) it saline + ip saline; (2) it saline + ip L-NAME; (3) it silica + ip saline; (4) it silica + ip L-NAME.
Preparation of dust suspensions
Min-U-Sil 5 silica was obtained from Silica Corp, Berkeley Springs, West Virginia (particle size range was 0.6–8.0 μm, 98% < 5 μm diameter; purity was 99.5% α-quartz by X-ray diffraction). A 12.5 mg amount of dust was suspended in 0.5 ml saline or 0.5 ml saline alone, sterilised by autoclave and vortexed before injection. The preparation was free of endotoxin.
Intratracheal instillation and intraperitoneal injection
Rats were anesthetised by ip injection of a mixture of ketamine (100 mg/kg) and xylazine (3.3 mg/kg, Sigma Chemical Company, St Louis, MO, USA). Before use, the chemicals were dissolved in saline and sterilised by filtration. Intratracheal instillation was performed by a procedure of tracheal exposure. After shaving, the skin in the ventral aspect of the neck was incised in the midline. The trachea was exposed through blunt dissection. Using a 1 ml disposable syringe with a #26 needle, 12.5 mg silica dust dissolved in 0.5 ml of saline, or saline alone, was injected. The incision was sutured with interrupted silk sutures immediately after the injection and the rat was kept in a 30°C incubator until it regained consciousness. Immediately after the recovery of the instilled rats from anasthesia, saline or L-NAME dissolved in saline was ip injected at a dosage of 15 mg/kg. Thereafter, the injection was conducted daily at the same dosage for 4 weeks.
Randomly-selected rats were anesthetised with an ip injection of 75 mg/kg of pentobarbital when 4 weeks observation period completed. Laparotomy was performed and the abdominal aorta was exposed. The rats were killed by transection of the aorta. There was no significant difference in body weight among the different groups of rats in each experiment when sacrificed.
After sacrifice, an incision was made into the neck region and the trachea was exposed by trimming of surrounding tissue. A piece of suturing thread was passed under the exposed trachea. A small opening was made by cutting in a lengthwise direction just below the larynx and in transverse direction just below and connected to the lengthwise incision. An 18-gauge needle in plastic tubing was placed into the opening and pushed through the trachea towards the lung. The needle was secured in place with the thread by ligation. A 5 ml volume of phosphate buffered saline (PBS) was injected into the needle with a 5 ml syringe for lavage. The injection process was finished within one minute and the fluid was kept in the lung for an additional minute. The withdrawal process was also finished in one minute. In total, two aliquots of 5 ml PBS were used for the lavage of each rat. The recovered fluid of each rat was pooled and the volume recorded. The recovered volume of BALF was between 9.0 to 9.7 ml and no significant difference could be detected among the different groups of rats in the recovered volume.
Counting of BALF cells
The total cell number was counted with a haemocytometer. A 50 μl volume of obtained lavage fluid was transferred to a plastic vial and mixed with the same amount of trypan blue solution (Sigma Chemical Company, St Louis, MO, USA). The well-mixed fluid then was transferred to a haemocytometer and the BALF cells were counted under a microscope.
Slide preparation, staining and differential counting
A 100 μl volume of the BALF was placed on a slide by Cytospin centrifugation immediately after the lavage (600 rpm, 5 min, Shandon, USA). At least two slides were prepared from each rat and stained with Diff-Quik (Lab. Aids Pty. Ltd., Narrabeen, Australia). The interval between sacrifice of rat to placement of BALF on slides was approximately 15 min.
The slides were read under oil immersion (× 1000). Five hundred leucocytes were counted to determine the frequency of different types of cells by their morphology.
Measurement of BALF protein
The supernatant of centrifuged BALF was placed in 400 μl polyethylene tubes, in duplicate. The protein concentration was measured by Lowry's method  using bovine serum albumin as a standard. The measurement was conducted 1 day after lavage.
Measurement of lactate dehydrogenase
BALF was centrifuged (3000 rpm, 15 min) and the supernatant was used for measurement of LDH activity. The measurement was performed with a CentrifiChem System 400 using a kit method (Trace Scientific Pty. Ltd., Sydney, Australia) and determined within 3 days after lavage. LDH measurements were performed within 3 days after lavage. The samples were kept in ice during operation and stored in -20°C freezer.
Identification of apoptosis
The slides were blind-coded before the scoring of apoptotic leucocytes. A minimum of 1000 leucocytes were counted for the occurrence of cells with apoptotic features. A minimum of 500 neutrophils were counted to determine the percentage of apoptotic neutrophils. Apoptotic features included formation of condensed chromatin bodies with sharp edges and convolution of the cell surface [45, 46]. Apoptotic macrophages and neutrophils were differentiated by morphology. Apoptotic macrophages were generally larger in size, with clear and non-ciliated cell borders. The key point in discriminating apoptotic macrophages from apoptotic neutrophils is the cytoplasm staining with Diff-Quik. The cytoplasm of apoptotic macrophages is a blue colour, similar to the non-apoptotic macrophages. The cytoplasm of apoptotic neutrophils is light yellow, similar to non-apoptotic neutrophils. Morphological apoptosis of the cells in BALF was confirmed by agarose gel electrophoresis of extracted genomic DNA. In the electrophoresis, cells in BALF with morphological apoptosis showed a ladder pattern, whereas cells without morphological apoptosis lacked such an eletrophoretic feature.
Scoring of macrophages with engulfed apoptotic cells
A total of 1000 macrophages were counted for the incidence of macrophages with engulfed cells or apoptotic bodies. The proportion of macrophages with engulfed cells or bodies in 1000 counted macrophages was calculated.
Effect of L-NAME injection on production of NO metabolites
To examine the effects of L-NAME administration on production of NO in silica-instilled lungs, forty male Wistar rats were used to obtain BALF for the measurement of nitrite/nitrate levels. Body weights of these rats at the start of the experiment were 209–220 grams. The rats were grouped by randomised block design into four groups for intratracheal instillation and ip injection (each of 10): (1) it saline + ip saline; (2) it saline + ip L-NAME; (3) it silica + ip saline; (4) it silica + ip L-NAME. At two weeks after instillation, 5 rats in each group were randomly selected and killed for lavage. At four weeks after instillation, all the remaining rats were killed and lavaged. The lavage fluid was used for the measurement of nitrite/nitrate level within two hours. The procedures in instillation, injection, killing and lavage were exactly the same as described above.
Nitrite/nitrate levels in the obtained BALF were measured by a Total Nitric Oxide and Nitrate/Nitrite Parameter Assay Kit (R&D System, Minneapolis MN, USA) with conversion of nitrate to nitrite by nitrate reductase. Absorbances were measured at 540 nm with ELISA microplate reader (Titertek Multiskan MCC/340).
The results are expressed as means ± standard error (se). Student-Newman-Keul's test was used for multiple comparison of different animal groups of each index with the software package Instat because this test method is suitable for multiple comparison. Analyses of variance were also conducted by this software. Statistical significance was preset at p < 0.05.
The authors would like to thank Dr Tony Bonin for useful discussion during the implementation of this study. This study was partially supported by Dust Diseases Board Research Grants Scheme.
- Fubini B, Hubbard A: Reactive oxygen species (ROS) and reactive nitrogen species (RNS) generation by silica in inflammation and fibrosis. Free Radic Biol Med 2003, 34: 1507–1516. 10.1016/S0891-5849(03)00149-7PubMedView ArticleGoogle Scholar
- Zeidler P, Hubbs A, Battelli L, Castranova V: Role of inducible nitric oxide synthase-derived nitric oxide in silica-induced pulmonary inflammation and fibrosis. J Toxicol Environ Health A 2004, 67: 1001–1026. 10.1080/15287390490447296PubMedView ArticleGoogle Scholar
- Blackford JA Jr., Antonini JM, Castranova V, Dey RD: Intratracheal instillation of silica up-regulates inducible nitric oxide synthase gene expression and increases nitric oxide production in alveolar macrophages and neutrophils. Am J Respir Cell Mol Biol 1994, 11: 426–431.PubMedView ArticleGoogle Scholar
- Castranova V, Huffman LJ, Judy DJ, Bylander JE, Lapp LN, Weber SL, Blackford JA, Dey RD: Enhancement of nitric oxide production by pulmonary cells following silica exposure. Environ Health Perspect 1998, 106 Suppl 5: 1165–1169.PubMedView ArticleGoogle Scholar
- Davis GS, Pfeiffer LM, Hemenway DR: Interferon-gamma production by specific lung lymphocyte phenotypes in silicosis in mice. Am J Respir Cell Mol Biol 2000, 22: 491–501.PubMedView ArticleGoogle Scholar
- Feng HM, Walker DH: Interferon-gamma and tumor necrosis factor-alpha exert their antirickettsial effect via induction of synthesis of nitric oxide. Am J Pathol 1993, 143: 1016–1023.PubMed CentralPubMedGoogle Scholar
- Naseem KM, Bruckdorfer KR: Hydrogen peroxide at low concentrations strongly enhances the inhibitory effect of nitric oxide on platelets. Biochem J 1995, 310 ( Pt 1): 149–153.Google Scholar
- Tada Y, Mori T, Shinogi T, Yao N, Takahashi S, Betsuyaku S, Sakamoto M, Park P, Nakayashiki H, Tosa Y, Mayama S: Nitric oxide and reactive oxygen species do not elicit hypersensitive cell death but induce apoptosis in the adjacent cells during the defense response of oat. Mol Plant Microbe Interact 2004, 17: 245–253.PubMedView ArticleGoogle Scholar
- Leigh J, Wang H, Bonin A, Peters M, Ruan X: Silica-induced apoptosis in alveolar and granulomatous cells in vivo. Environ Health Perspect 1997, 105 Suppl 5: 1241–1245.PubMedView ArticleGoogle Scholar
- Terenzi F, Diaz-Guerra MJ, Casado M, Hortelano S, Leoni S, Bosca L: Bacterial lipopeptides induce nitric oxide synthase and promote apoptosis through nitric oxide-independent pathways in rat macrophages. J Biol Chem 1995, 270: 6017–6021. 10.1074/jbc.270.11.6017PubMedView ArticleGoogle Scholar
- Washo-Stultz D, Hoglen N, Bernstein H, Bernstein C, Payne CM: Role of nitric oxide and peroxynitrite in bile salt-induced apoptosis: relevance to colon carcinogenesis. Nutr Cancer 1999, 35: 180–188. 10.1207/S15327914NC352_13PubMedView ArticleGoogle Scholar
- Beckman JS, Beckman TW, Chen J, Marshall PA, Freeman BA: Apparent hydroxyl radical production by peroxynitrite: implications for endothelial injury from nitric oxide and superoxide. Proc Natl Acad Sci U S A 1990, 87: 1620–1624. 10.1073/pnas.87.4.1620PubMed CentralPubMedView ArticleGoogle Scholar
- Koppenol WH, Moreno JJ, Pryor WA, Ischiropoulos H, Beckman JS: Peroxynitrite, a cloaked oxidant formed by nitric oxide and superoxide. Chem Res Toxicol 1992, 5: 834–842. 10.1021/tx00030a017PubMedView ArticleGoogle Scholar
- Thomas G, Ando T, Verma K, Kagan E: Asbestos fibers and interferon-gamma up-regulate nitric oxide production in rat alveolar macrophages. Am J Respir Cell Mol Biol 1994, 11: 707–715.PubMedView ArticleGoogle Scholar
- Pendino KJ, Laskin JD, Shuler RL, Punjabi CJ, Laskin DL: Enhanced production of nitric oxide by rat alveolar macrophages after inhalation of a pulmonary irritant is associated with increased expression of nitric oxide synthase. J Immunol 1993, 151: 7196–7205.PubMedGoogle Scholar
- Walley KR, McDonald TE, Higashimoto Y, Hayashi S: Modulation of proinflammatory cytokines by nitric oxide in murine acute lung injury. Am J Respir Crit Care Med 1999, 160: 698–704.PubMedView ArticleGoogle Scholar
- Hogaboam CM, Chensue SW, Steinhauser ML, Huffnagle GB, Lukacs NW, Strieter RM, Kunkel SL: Alteration of the cytokine phenotype in an experimental lung granuloma model by inhibiting nitric oxide. J Immunol 1997, 159: 5585–5593.PubMedGoogle Scholar
- Hogaboam CM, Gallinat CS, Bone-Larson C, Chensue SW, Lukacs NW, Strieter RM, Kunkel SL: Collagen deposition in a non-fibrotic lung granuloma model after nitric oxide inhibition. Am J Pathol 1998, 153: 1861–1872.PubMed CentralPubMedView ArticleGoogle Scholar
- Nunes H, Lebrec D, Mazmanian M, Capron F, Heller J, Tazi KA, Zerbib E, Dulmet E, Moreau R, Dinh-Xuan AT, Simonneau G, Herve P: Role of nitric oxide in hepatopulmonary syndrome in cirrhotic rats. Am J Respir Crit Care Med 2001, 164: 879–885.PubMedView ArticleGoogle Scholar
- Antonini JM, Van Dyke K, Ye Z, DiMatteo M, Reasor MJ: Introduction of luminol-dependent chemiluminescence as a method to study silica inflammation in the tissue and phagocytic cells of rat lung. Environ Health Perspect 1994, 102 Suppl 10: 37–42.PubMedView ArticleGoogle Scholar
- Maeda H, Akaike T: Nitric oxide and oxygen radicals in infection, inflammation, and cancer. Biochemistry (Mosc) 1998, 63: 854–865.Google Scholar
- Lee J: Inducible nitric oxide synthase mRNA expression and nitric oxide production in silica-induced acute inflammatory lung injury. Korean-Journal-of-Physiology-and-Pharmacology 1998, 2: 233–239.Google Scholar
- Brune B, Mohr S, Messmer UK: Protein thiol modification and apoptotic cell death as cGMP-independent nitric oxide (NO) signaling pathways. Rev Physiol Biochem Pharmacol 1996, 127: 1–30.PubMedView ArticleGoogle Scholar
- Hu J, Van Eldik LJ: S100 beta induces apoptotic cell death in cultured astrocytes via a nitric oxide-dependent pathway. Biochim Biophys Acta 1996, 1313: 239–245. 10.1016/0167-4889(96)00095-XPubMedView ArticleGoogle Scholar
- Aliprantis AO, Diez-Roux G, Mulder LC, Zychlinsky A, Lang RA: Do macrophages kill through apoptosis? Immunol Today 1996, 17: 573–576. 10.1016/S0167-5699(96)10071-2PubMedView ArticleGoogle Scholar
- Srivastava KD, Rom WN, Jagirdar J, Yie TA, Gordon T, Tchou-Wong KM: Crucial role of interleukin-1beta and nitric oxide synthase in silica-induced inflammation and apoptosis in mice. Am J Respir Crit Care Med 2002, 165: 527–533.PubMedView ArticleGoogle Scholar
- Wiethoff AJ, Reed KL, Webb TR, Warheit DB: Assessing the role of neutrophil apoptosis in the resolution of particle-induced pulmonary inflammation. Inhal Toxicol 2003, 15: 1231–1246.PubMedView ArticleGoogle Scholar
- Bosca L, Hortelano S: Mechanisms of nitric oxide-dependent apoptosis: involvement of mitochondrial mediators. Cell Signal 1999, 11: 239–244. 10.1016/S0898-6568(98)00064-3PubMedView ArticleGoogle Scholar
- Rogers MJ, Chilton KM, Coxon FP, Lawry J, Smith MO, Suri S, Russell RG: Bisphosphonates induce apoptosis in mouse macrophage-like cells in vitro by a nitric oxide-independent mechanism. J Bone Miner Res 1996, 11: 1482–1491.PubMedView ArticleGoogle Scholar
- Mitrovic B, Ignarro LJ, Vinters HV, Akers MA, Schmid I, Uittenbogaart C, Merrill JE: Nitric oxide induces necrotic but not apoptotic cell death in oligodendrocytes. Neuroscience 1995, 65: 531–539. 10.1016/0306-4522(94)00491-MPubMedView ArticleGoogle Scholar
- Delaney CA, Tyrberg B, Bouwens L, Vaghef H, Hellman B, Eizirik DL: Sensitivity of human pancreatic islets to peroxynitrite-induced cell dysfunction and death. FEBS Lett 1996, 394: 300–306. 10.1016/0014-5793(96)00977-5PubMedView ArticleGoogle Scholar
- Estevez AG, Radi R, Barbeito L, Shin JT, Thompson JA, Beckman JS: Peroxynitrite-induced cytotoxicity in PC12 cells: evidence for an apoptotic mechanism differentially modulated by neurotrophic factors. J Neurochem 1995, 65: 1543–1550.PubMedView ArticleGoogle Scholar
- Ye Y, Estevez AG: Nitrotyrosine containing proteins in PC12 cells after exposure to peroxynitrite. Society for Neuroscience Abstract Viewer and Itinerary Planner 2002, 303: 17.Google Scholar
- Shin JT, Barbeito L, MacMillan-Crow LA, Beckman JS, Thompson JA: Acidic fibroblast growth factor enhances peroxynitrite-induced apoptosis in primary murine fibroblasts. Arch Biochem Biophys 1996, 335: 32–41. 10.1006/abbi.1996.0479PubMedView ArticleGoogle Scholar
- Zhuang S, Simon G: Peroxynitrite-induced apoptosis involves activation of multiple caspases in HL-60 cells. Am J Physiol Cell Physiol 2000, 279: C341–51.PubMedGoogle Scholar
- Lin KT, Xue JY, Nomen M, Spur B, Wong PY: Peroxynitrite-induced apoptosis in HL-60 cells. J Biol Chem 1995, 270: 16487–16490. 10.1074/jbc.270.28.16487PubMedView ArticleGoogle Scholar
- Cox G: IL-10 enhances resolution of pulmonary inflammation in vivo by promoting apoptosis of neutrophils. Am J Physiol 1996, 271: L566–71.PubMedGoogle Scholar
- Shimizu S, Nomoto M, Yamamoto T, Momose K: Reduction by NG-nitro-L-arginine of H2O2-induced endothelial cell injury. Br J Pharmacol 1994, 113: 564–568.PubMed CentralPubMedView ArticleGoogle Scholar
- Seif-el-Nasr M, Fahim AT: Antioxidant effect of N omega-nitro-L-arginine methyl ester (L-NAME) on global cerebral ischemia in a rat model. Arzneimittelforschung 2001, 51: 628–632.PubMedGoogle Scholar
- Wishah K, Malur A, Raychaudhuri B, Melton AL, Kavuru MS, Thomassen MJ: Nitric oxide blocks inflammatory cytokine secretion triggered by CD23 in monocytes from allergic, asthmatic patients and healthy controls. Ann Allergy Asthma Immunol 2002, 89: 78–82.PubMedView ArticleGoogle Scholar
- Peng HB, Spiecker M, Liao JK: Inducible nitric oxide: an autoregulatory feedback inhibitor of vascular inflammation. J Immunol 1998, 161: 1970–1976.PubMedGoogle Scholar
- Dorger M, Allmeling AM, Kiefmann R, Schropp A, Krombach F: Dual role of inducible nitric oxide synthase in acute asbestos-induced lung injury. Free Radic Biol Med 2002, 33: 491–501. 10.1016/S0891-5849(02)00844-4PubMedView ArticleGoogle Scholar
- Zeidler PC, Castranova V: Role of nitric oxide in pathological responses of the lung to exposure to environmental/occupational agents. Redox Rep 2004, 9: 7–18. 10.1179/135100004225003879PubMedView ArticleGoogle Scholar
- Lowry OH, Rosebrough NJ, Farr AL, Randall RJ: Protein measurement with the Folin phenol reagent. J Biol Chem 1951, 193: 265–275.PubMedGoogle Scholar
- Newman SL, Henson JE, Henson PM: Phagocytosis of senescent neutrophils by human monocyte-derived macrophages and rabbit inflammatory macrophages. J Exp Med 1982, 156: 430–442. 10.1084/jem.156.2.430PubMedView ArticleGoogle Scholar
- Savill JS, Wyllie AH, Henson JE, Walport MJ, Henson PM, Haslett C: Macrophage phagocytosis of aging neutrophils in inflammation. Programmed cell death in the neutrophil leads to its recognition by macrophages. J Clin Invest 1989, 83: 865–875.PubMed CentralPubMedView ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.