A mixture of anatase and rutile TiO2 nanoparticles induces histamine secretion in mast cells
- Eric Y Chen†1, 2,
- Maria Garnica†1, 2,
- Yung-Chen Wang1, 2,
- Alexander J Mintz1, 2,
- Chi-Shuo Chen1, 2 and
- Wei-Chun Chin1, 2Email author
© Chen et al; licensee BioMed Central Ltd. 2012
Received: 22 July 2011
Accepted: 19 January 2012
Published: 19 January 2012
Histamine released from mast cells, through complex interactions involving the binding of IgE to FcεRI receptors and the subsequent intracellular Ca2+ signaling, can mediate many allergic/inflammatory responses. The possibility of titanium dioxide nanoparticles (TiO2 NPs), a nanomaterial pervasively used in nanotechnology and pharmaceutical industries, to directly induce histamine secretion without prior allergen sensitization has remained uncertain.
TiO2 NP exposure increased both histamine secretion and cytosolic Ca2+ concentration ([Ca2+]C) in a dose dependent manner in rat RBL-2H3 mast cells. The increase in intracellular Ca2+ levels resulted primarily from an extracellular Ca2+ influx via membrane L-type Ca2+ channels. Unspecific Ca2+ entry via TiO2 NP-instigated membrane disruption was demonstrated with the intracellular leakage of a fluorescent calcein dye. Oxidative stress induced by TiO2 NPs also contributed to cytosolic Ca2+ signaling. The PLC-IP3-IP3 receptor pathways and endoplasmic reticulum (ER) were responsible for the sustained elevation of [Ca2+]C and histamine secretion.
Our data suggests that systemic circulation of NPs may prompt histamine release at different locales causing abnormal inflammatory diseases. This study provides a novel mechanistic link between environmental TiO2 NP exposure and allergen-independent histamine release that can exacerbate manifestations of multiple allergic responses.
KeywordsTiO2 nanoparticles mast cell histamine release Ca2+ signaling
Allergic inflammation is a primary pathological feature of many debilitating diseases . Among the numerous active mediators and cytokines that modulate initiation and progression of allergic inflammation, histamine is distinctly potent [1, 2]. Typically, the storage of histamine is restricted to mast cells and circulating basophils [2, 3]. The cardinal pathway of histamine release involves the attachment of IgE-bound allergens to high-affinity FcεRI receptors on mast cells and the crosslinking of adjacent IgE molecules by allergens [1, 2]. Subsequent receptor clustering leads to a complex cascade of intracellular Ca2+ signaling resulting from increased activity of phospholipase C (PLC), generation of diacylglycerol (DAG) (activating PKC) and inositol 1,4,5-trisphosphate (IP3) which mobilizes the ER Ca2+ store and participates in final histamine secretion from mast cells. Activation of histamine receptors (H1, H2, H3 and H4) greatly influences inflammatory responses .
Aside from inducing acute allergic inflammatory responses, histamine also mediates chronic phase progression by augmenting the secretion of pro-inflammatory cytokines such as IL-1α, IL-1β, and IL-6 as well as chemokines like RANTES [1, 4]. Consequential pathologies are expressed in many systems encompassing ocular, airway, skin and GI tracts . Associated disorders may include asthma, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, urticaria, anaphylaxis and food allergies [1, 4, 5]. Possible clinical symptoms include itchiness, increased vascular permeability, edema, leukocyte infiltration, bronchoconstriction and mucus hypersecretion [1, 4, 5]. Therefore, any disturbance to the immunological and/or homeostatic control of histamine release can potentially intensify inflammation leading to health problems.
Recently, numerous epidemiological studies have suggested that pollution associated airborne particulate matter (PM) can aggravate allergic inflammatory responses. Classical examples of allergies indicate that people with asthma and rhinitis are more susceptible to the short term acute effects of particle exposure [6–8]. In line with epidemiological studies, results from animal models also demonstrated that ultrafine particles (one of the major components of PM) can modulate asthmatic responses by exacerbating pulmonary inflammation and airway hyper-responsiveness [9–11]. In an atopic, dermatitis-like, skin lesion mouse model, exposure to titanium dioxide nanoparticles (TiO2 NPs) was found to worsen symptoms by elevating proinflammatory molecules in the skin and increasing serum levels of IgE and histamine . At the same time, exposure to environmental tobacco smoke has been found to increase the risks of rhinoconjunctivitis and allergic conjunctivitis [13, 14]. Moreover, Kulig et al reported that prenatal and postnatal exposure to environmental tobacco smoke in children (< 3 yrs old) was associated with sensitization to food allergens . Despite NPs' ability to potentiate allergic responses, the role that histamine plays in mediation is not clear. More importantly, whether NPs can directly modulate histamine release from mast cells without allergen sensitization remains elusive.
TiO2 NPs have been extensively utilized in the nano-technological and pharmaceutical arenas and are one of the main components in many household commodities and personalized products [16, 17]. The enormous annual global production of TiO2 broadens the possibilities of occupational and environmental exposures . As a common constituent of PM10, TiO2 NPs are widely known for their potential hazardous effects, which manifest biologically via inflammatory responses . TiO2 NPs size, surface area and crystalline structure ascribe cellular nanotoxicity [20–23]. In addition to respiratory inhalation, NPs can enter the human body via alternative routes such as: direct penetration through skin, ingestion and injection . Animal studies have shown that intra-tracheally instilled TiO2 and other NPs can possibly transmigrate from lung to systemic circulation [25–27]. Upon entering blood circulation, NPs can infiltrate multiple organs, potentially directly stimulating mast cells, a critical effector, exacerbating pathological consequences . As such, TiO2 NPs were selected as ideal model particles for our study.
Previously, we have demonstrated that TiO2 NPs can trigger a cascade of cytosolic Ca2+ signaling leading to mucin secretion . In the present study, we aim to investigate the impact of NPs on histamine secretion from RBL-2H3 mast cells. We hypothesize that TiO2 NPs can directly induce histamine release without prior allergen sensitization via a Ca2+-mediated pathway.
TiO2 NP characterization
TiO2 NP-Induced [Ca2+]C increase
Extracellular source of [Ca2+]C increase
The source of elevated [Ca2+]C was identified by stimulating RBL-2H3 cells with TiO2 NPs in Ca2+-free Hanks' buffer with EGTA added to chelate traces of Ca2+. Figure 2B demonstrates that TiO2 NPs (0.1 mg/ml-1 mg/ml) failed to induce a significant increase in [Ca2+]C, when compared with the 160% increase observed in normal Hanks' buffer (Figure 2A). Our data suggested that the extracellular Ca2+ pool was the primary source of the observed [Ca2+]C increase. We then examined if TiO2 NPs can induce extracellular Ca2+ influx via membrane channels, in particular L-type Ca2+ channels. Blocking the channels with CdCl2 (200 μM) markedly inhibited the rise in [Ca2+]C by approximately 75% (Figure 2C). Subsequent pre-treatment of cells with nifedipine or verapamil (L-type Ca2+ channel blockers) also hampered the rise in [Ca2+]C elicited by TiO2 NPs (Figure 2D and 2E). Nonetheless, the incomplete blockage of Ca2+ influx with membrane channel blockers suggests a possible Ca2+ leakage through perturbed cell membranes. To confirm that TiO2 NPs can instigate membrane disruption, thereby permitting unspecific extracellular Ca2+ entry, a fluorescent calcein dye was used to assess cytosolic leakage. Results showed a dye permeation ratio increase from approximately 5 to 12% with a TiO2 NP concentration ranging from 0.1 to 1 mg/ml (Figure 2F).
Induction of oxidative stress and associated Ca2+ influx
The IP3-IP3 receptor as a histamine-release pathway
Ca2+ dependency of TiO2 NP-induced histamine secretion
Recently, a growing epidemic of exacerbated allergic inflammatory diseases have been closely linked with the exposure to airborne PM pollution [5, 7, 8]. Many prior investigations have focused on the hazardous effects of NPs. These reports have primarily been either epidemiological studies that draw correlations between clinical manifestations and exposure to environmental pollutants or immunological studies that examine the release of inflammatory cytokines and subsequent recruitment of immune cells using allergen-sensitized mice with PM or NP insults [7, 9, 10]. Few studies have systematically investigated the role of histamine secretion from mast cells during NP challenge and its role in mediating allergic inflammation. By using allergen-sensitized animal models, these studies overlooked the NP's potential to directly stimulate histamine release from mast cells without prior allergen sensitization or IgE production. In addition, the associated underlying cellular mechanisms leading to the final degranulation are not clear. TiO2 NPs have previously been shown to trigger mucin secretion, pulmonary inflammatory responses and emphysema-like pathology [17, 18, 29, 30]. In this study, we demonstrate that TiO2 NPs can directly stimulate histamine release from RBL-2H3 mast cells via a Ca2+- dependent pathway.
Allergic inflammatory diseases encompass a multifactorial interplay between many elements/systems; our study focuses on how TiO2 NPs can directly trigger histamine release from mast cells and its potential to exacerbate allergic symptoms. This effect is due to histamine's ability to affect the physiology and pathology of a wide range of cells via corresponding receptors that are widely expressed on airway and vascular muscle cells, hepatocytes, chondrocytes, endothelial cells, epithelial cells, neutrophil, eosinophils, monocytes, macrophage, dendritic cells, and T and B cells . We found that TiO2 NPs can significantly induce histamine release from RBL-2H3 cells in a dose dependent manner (Figure 5A). Our data is corroborated by evidence documenting more severe TiO2 NP-induced inflammation with elevated release of inflammatory cytokines than that of TiO2 of micrometric dimensions [31, 32]. The TiO2 NP-elicited mast cell degranulation also appeared to be a Ca2+-dependent process, as indicated by a major attenuation in histamine secretion when pretreated with BAPTA (Figure 5B). The importance of Ca2+ in stimulus-secretion coupling mechanisms is well documented [33, 34]. We and others have reported that NPs increase [Ca2+]C prior to cellular exocytosis [17, 35]. As TiO2 concentrations increased from 0.1 to 1 mg/ml, a sustained elevation in [Ca2+]C was observed (Figure 2A). Our data demonstrated that [Ca2+]C increased as a function of TiO2 concentration and coincided with the measurements of histamine secretion (Figure 5A). The TiO2 NPs used in our study consisted of a mixture of anatase/rutile crystalline forms which have been shown to impose greater cellular toxicity . Although phase composition, surface chemistry and purity may play important roles in influencing nanotoxicity, dependence on additional physical parameters such as particle size, surface area and concentration have all been reported [20, 21, 36–38]. However, the mechanism by which TiO2 NPs trigger intracellular mast cell Ca2+ signaling is not clear.
Previous experimental evidence suggests that ultrafine carbon black and ZnO NPs can induce extracellular Ca2+ influx through activated voltage-gated Ca2+ channels [35, 39]. The question of whether TiO2 NPs can trigger a similar process is unclear. Our experiments confirmed that [Ca2+]C failed to increase significantly when cells were treated with TiO2 NPs in Ca2+-free Hanks' solution (Figure 2B) or blocked with CdCl2 (a general Ca2+ channel blocker) (Figure 2C) . We then demonstrated that TiO2 NPs can activate L-type voltage-gated Ca2+ channels on mast cells, allowing extracellular Ca2+ influx into the cytosol (Figure 2D and 2E). The ROS generated in response to NP exposure has been attributed to the opening of membrane Ca2+ channels [17, 35, 39, 40]. Our data revealed that TiO2 NPs elevated cytosolic ROS levels (Figure 3A) and that the involvement of oxidative stress could modulate intracellular Ca2+ homeostasis by activating L-type Ca2+ channels (Figure 3B). Supporting our results, Hussain and colleagues also reported that TiO2 NPs can exert oxidative effects under abiotic conditions . Other studies have shown that TiO2 NPs increase intracellular ROS production in various cells by causing mitochondrial injuries, such as impaired mitochondrial membrane permeability, a decrease in mitochondrial potential, mitochondrial respiratory dysfunction and downregulation of SOD (superoxide dismutase) and GSH (glutathione) levels [41, 42]. ROS are thought to affect Ca2+ signaling possibly by oxidation of thiol groups of membrane channels and changing the intra-molecular bonding of proteins and lipids [43, 44]. Moreover, it has been suggested that ROS can impact membrane Ca2+ channels and Ca2+ binding proteins . In addition to ROS formation, direct damage to cell membrane integrity by lipid peroxidation may be an alternative route for extracellular Ca2+ entry [22, 39]. Co-administration of TiO2 NPs and fluorescent calcein dye resulted in an augmented calcein permeation ratio (Figure 2F). The calcein data corroborates with previous publications showing that TiO2 NPs can perturb the lipid bilayer, perhaps by forming transient pores that may account for the portion of Ca2+ increase that could not be completely abolished by blocking L-type Ca2+ channels [17, 45].
An initial upsurge in [Ca2+]C from extracellular influx is usually relayed by a secondary Ca2+ release from internal organelles . However, the question of how TiO2 NPs transduce Ca2+ signals in mast cells involving common secondary messengers remains unanswered. Heretofore, we demonstrated that TiO2 NPs could stimulate PLC and IP3 receptor activities in mast cells, resulting in secondary amplification of cytosolic Ca2+. Data from Figure 4A-C showed that cells incubated with U73122, 2-APB and Xestospongin notably inhibited TiO2 NP-triggered Ca2+ rise and histamine secretion (Figure 5B). Activation of PLC can be explained by the stimulation from ROS [47, 48]. Alternatively, a localized increase in [Ca2+]C has been shown to trigger PLC, thereby generating IP3 and DAG . Collectively, these results point toward the contribution from ER Ca2+ stores. Figure 4D revealed that depleting the ER internal store with Thapsigargin significantly diminished TiO2 NPs stimulated cytosolic Ca2+ increase and subsequent histamine secretion (Figure 5B). Our data indicates that the ER dependent IP3-IP3 receptor pathway is critically involved in amplifying (or sustaining) the initial cytosolic Ca2+ rise and subsequent histamine release.
Our findings revealed a new mechanism depicting how TiO2 NPs can potentially exacerbate many allergic inflammatory responses and perhaps non-allergic inflammatory disorders. Mast cell exposure to TiO2 NPs can activate membrane L-type Ca2+ channels, induce ROS production and stimulate PLC activity. Influx of extracellular Ca2+ raises [Ca2+]C, and when coupled with the IP3-IP3 receptor pathway, can trigger the release of ER resident Ca2+ and subsequent histamine secretion. These results suggest that mast cell degranulation of histamine may be significantly augmented and intensified in NP exposed tissues with or without IgE antibody-based sensitization. This model may also provide a new explanation for chronic inflammatory diseases elicited by airborne PM. The inhaled NPs can circulate and accumulate in various organs thereby elevating the risks of activating mast cell degranulation in other tissues [25, 50, 51]. As a result, NP exposure may worsen the mast cell associated inflammatory symptoms involving arthritis, atherosclerosis and coronary diseases [52–54]. Finally, our results suggest that a new immunoregulatory system may be considered since NPs can directly trigger inflammatory mediators, thereby bypassing traditional immuno-stimulation by allergens.
Culture of RBL-2H3 Mast Cells
The RBL-2H3 rat mast cell line (ATCC, Manassas, VA, USA) is a widely-used mast cell model that responds to stimuli by secreting histamine and other mediators . RBL-2H3 cells elicit a potent immune allergic response following crosslinking of their IgE-bound FcεRI by multivalent allergens . Cells were cultured in 15 cm cell culture plates (VWR, CA, USA) in MEM medium (Invitrogen, CA, USA) supplemented with L-glutamine, 1% penicillin/streptomycin and 10% heat inactivated fetal bovine serum (FBS) (Invitrogen, CA, USA). Cultures were incubated in a humidified incubator at 37°C/5% CO2. Cell counts were performed using trypan blue (Sigma-Aldrich, MO, USA) exclusion and a Bright-Line haemocytometer.
Nanoparticles and Characterization
A mixture of anatase and rutile forms of ultrafine titanium (IV) dioxide (< 100 nm diameter by Brunauer Emmett Teller (BET) method, purity of 99.5% trace metals basis) (Cat No. 634662) (Sigma-Aldrich, MO, USA) was used in this study because this form has been shown to result in more severe cellular injuries . The TiO2 NPs have a primary crystalline size of 100 nm (maximum), specific surface area of 46.3 m2/g (as determined by BET), equivalent spherical diameter of 100 nm (maximum) and a trace metallic impurities of 1000 ppm (maximum) (information from Sigma). All TiO2 NP samples were reconstituted in Hanks' buffer (Invitrogen, CA, USA) and sonicated for approximately 1 minute immediately before usage. The concentrations used were 1 mg/ml, 0.75 mg/ml, 0.5 mg/ml, 0.25 mg/ml, and 0.1 mg/ml. All sizes of NP suspension were independently confirmed using homodyne dynamics laser scattering (DLS) as described in the previous study . Morphology and size of TiO2 NP powder were determined by transmission electron microscope (JEOL JEM-2010 HRTEM, MA, USA) and analyzed using an analysisPRO (Olympus, PA, USA).
Cells were seeded at 1 × 105 cells per well in a 24-well plate, and incubated for 24 hrs in MEM medium supplemented with 10% FBS. Following 24 hr incubation, the MEM medium was removed from the cells and the culture was rinsed with Hanks' solution twice before use.
Measurement of cytosolic Ca2+ concentrations induced by TiO2 exposure
All experiments were performed in dark conditions. The cells were loaded with a Rhod-2 AM dye (1 μM) (Kd = 570 nM, λEx = 552 nm and λEm = 581) (Invitrogen, CA, USA) for 45 minutes. After the dye loading, the cells were rinsed and incubated with either normal Hanks' or Ca2+-free Hanks' solution, and treated with the appropriate TiO2 NP concentrations. All Ca2+ signaling experiments were carried out on a thermoregulated stage at 37°C mounted on a Nikon microscope (Nikon Eclipse TE2000- U, Tokyo, Japan). RBL-2H3 cells were then incubated with cadmium chloride (200 μM; Sigma-Aldrich, MO, USA) to block the membrane Ca2+ channels , followed by TiO2 NP stimulation. To test the interaction between TiO2 and L-type membrane Ca2+ channels, nifedipine (10 μM; Sigma-Aldrich, MO, USA) and verapamil (100 μM; Sigma-Aldrich, MO, USA), L-type Ca2+ channel blockers [17, 39] were applied to RBL-2H3 cells, independently, prior to the exposure of TiO2. Antioxidant N-acetylcysteine (NAC, 250 μM; Sigma-Aldrich, MO, USA) was also added to RBL-2H3 cells to study the involvement of reactive oxygen species (ROS) [17, 39], possibly generated as a result of TiO2 stimulation, and the activation of Ca2+ channels. Thapsigargin (100 nM; Sigma-Aldrich, MO, USA) was used to deplete the ER Ca2+ content in order to investigate the contribution of the internal ER Ca2+ pool [17, 56]. In order to test the involvement of secondary messenger molecules in intensifying a Ca2+ response, U73122 (PLC blocker) (10 μM; Sigma-Aldrich, MO, USA), Aminoethoxydiphenyl borate (2-APB) (50 μM; Sigma-Aldrich, MO, USA) and Xestospongin C (IP3 receptor blockers) (20 μM; VWR, CA, USA) were pre-incubated with cells prior to TiO2 NP exposure [56, 57].
Calcein dye leakage measurements
RBL-2H3 cells were seeded at a density of 1 × 105 cells per well in a 24-well plate and cultured for 24 hrs. TiO2 prepared with calcein fluorescent dye (50 μM) (Invitrogen, CA, USA) in Hanks' buffer was incubated with the cells for 5 minutes at 37°C. Calcein is a biological inert green-fluorescent molecule of a molecular mass of 623 Daltons and an estimated molecular radius of 0.6 nm . The TiO2 NP solution containing calcein dye was then removed and the cells were rinsed twice with PBS to remove any possible remnants of the dye. Subsequently, the cells were loaded with Hoechst (10 μM) (Sigma-Aldrich, MO, USA), a fluorescent nucleus dye, for 5 minutes at 37°C, and were then rinsed thoroughly . Fresh Hanks' solution was added into each well before taking fluorescent images of calcein and Hoechst loaded cells with a Nikon fluorescence microscope. Afterwards, a percentage of calcein loaded cells against total number of cells, as determined by the Hoechst dye, was calculated for each of the TiO2 NP concentrations used in the experiment.
Intracellular reactive oxygen species (ROS) production
ROS production was evaluated by fluorescence microscopy using oxidation of CM-H2DCFDA dye (Invitrogen, CA, USA). The cells (1 × 105 cells/well) were cultured for 24 hrs before being rinsed with PBS solution. Hanks' buffer, containing TiO2 NPs at concentrations ranging from 0-0.75 mg/ml, was then incubated with the cells for 15 minutes in 37°C followed by PBS washing and loading with 2 μM CM-H2DCFDA dye for 30 minutes. Fluorescent images of ROS generated in cells were captured and analyzed by calculating the ratio of increase in fluorescent intensity between TiO2 NP treatment and control groups.
Histamine detection with enzyme linked immunosorbent assay (ELISA) preparation
The cells were seeded at a density of 1 × 105 cells density in a 24-well plate and cultured for 24 hrs. RBL-2H3 cells were then rinsed with PBS and pre-treated with BAPTA-AM (50 μM) (Invitrogen, CA, USA), Thapsigargin (SERCA pump inhibitor), U73122, 2-APB, or Xestospongin for 20 minutes in the same manner. Cells were stimulated for 5 minutes with the appropriate TiO2 NP concentrations (0-0.75 mg/ml) which were prepared in PBS. The histamine-containing supernatant was collected and centrifuged to remove any remaining TiO2 NPs. The supernatant was then incubated in a 96-well plate overnight at 4°C. The rest of the assay was carried out in accord to Neogen ELISA instructions pertaining to the histamine kit (Neogen Corp, MI, USA).
After staining the treated cells, image analysis was performed with an inverted Nikon Eclipse TE2000-U fluorescent microscope. Each photo was taken at a magnification of 200 × and analyzed using SimplePCI (Compix Inc., Imaging Systems, Sewickle, PA, USA). The data shown is a representative of Ca2+ signals of more than 200 cells and the experiments were conducted independently for at least 3 times.
The data was presented as means ± SD. Each experiment was performed independently at least three times. Statistical significance was determined using a Student's t-test analysis with p values < 0.05 (GraphPad Prism 4.0, GraphPad Software, Inc., San Diego, CA, USA).
The authors gratefully thank David Ojcius for careful reading of the manuscript. We also thank Mike Dunlap from IMF for assistance with TEM imaging. This study was supported by grants from NIH (1R15HL095039), NSF (CBET-0932404) and the UC CITRIS Program. EYC, MG and CSC were supported by UC Merced GRC summer fellowships, NIH NHLBI URS and Center of Excellence on Health Disparities (1P20MD005049-01 from the National Center on Minority Health and Health Disparities).
- Galli SJ, Tsai M, Piliponsky AM: The development of allergic inflammation. Nature 2008, 454: 445–454. 10.1038/nature07204PubMed CentralPubMedView Article
- Jones BL, Kearns GL: Histamine: new thoughts about a familiar mediator. Clin Pharmacol Ther 2011, 89: 189–197. 10.1038/clpt.2010.256PubMedView Article
- Williams JI, Gow JA, Klier SM, McCue SL, Salapatek AM, McNamara TR: Non-clinical pharmacology, pharmacokinetics, and safety findings for the antihistamine bepotastine besilate. Curr Med Res Opin 2010, 26: 2329–2338. 10.1185/03007995.2010.486753PubMedView Article
- Jutel M, Akdis M, Akdis CA: Histamine, histamine receptors and their role in immune pathology. Clin Exp Allergy 2009, 39: 1786–1800. 10.1111/j.1365-2222.2009.03374.xPubMedView Article
- Holgate ST: The epidemic of allergy and asthma. Nature 1999, 402: B2–4. 10.1038/35037000PubMedView Article
- von Klot S, Wolke G, Tuch T, Heinrich J, Dockery DW, Schwartz J, Kreyling WG, Wichmann HE, Peters A: Increased asthma medication use in association with ambient fine and ultrafine particles. Eur Respir J 2002, 20: 691–702. 10.1183/09031936.02.01402001PubMedView Article
- Spira-Cohen A, Chen LC, Kendall M, Lall R, Thurston GD: Personal Exposures to Traffic-Related Air Pollution and Acute Respiratory Health Among Bronx School Children with Asthma. Environ Health Perspect 2011.
- Downs SH, Schindler C, Liu LJ, Keidel D, Bayer-Oglesby L, Brutsche MH, Gerbase MW, Keller R, Kunzli N, Leuenberger P, et al.: Reduced exposure to PM10 and attenuated age-related decline in lung function. N Engl J Med 2007, 357: 2338–2347. 10.1056/NEJMoa073625PubMedView Article
- Archer AJ, Cramton JL, Pfau JC, Colasurdo G, Holian A: Airway responsiveness after acute exposure to urban particulate matter 1648 in a DO11.10 murine model. Am J Physiol Lung Cell Mol Physiol 2004, 286: L337–343. 10.1152/ajplung.00202.2003PubMedView Article
- Hussain S, Vanoirbeek JA, Luyts K, De Vooght V, Verbeken E, Thomassen LC, Martens JA, Dinsdale D, Boland S, Marano F, et al.: Lung exposure to nanoparticles modulates an asthmatic response in a mouse model of asthma. Eur Respir J 2011.
- Jin C, Shelburne CP, Li G, Potts EN, Riebe KJ, Sempowski GD, Foster WM, Abraham SN: Particulate allergens potentiate allergic asthma in mice through sustained IgE-mediated mast cell activation. J Clin Invest 2011.
- Yanagisawa R, Takano H, Inoue K, Koike E, Kamachi T, Sadakane K, Ichinose T: Titanium dioxide nanoparticles aggravate atopic dermatitis-like skin lesions in NC/Nga mice. Exp Biol Med (Maywood) 2009, 234: 314–322. 10.3181/0810-RM-304View Article
- Hugg TT, Jaakkola MS, Ruotsalainen RO, Pushkarev VJ, Jaakkola JJ: Parental smoking behaviour and effects of tobacco smoke on children's health in Finland and Russia. Eur J Public Health 2008, 18: 55–62. 10.1093/eurpub/ckm053PubMedView Article
- Simoni M, Baldacci S, Puntoni R, Pistelli F, Farchi S, Lo Presti E, Pistelli R, Corbo G, Agabiti N, Basso S, et al.: Respiratory symptoms/diseases and environmental tobacco smoke (ETS) in never smoker Italian women. Respir Med 2007, 101: 531–538. 10.1016/j.rmed.2006.06.021PubMedView Article
- Kulig M, Luck W, Lau S, Niggemann B, Bergmann R, Klettke U, Guggenmoos-Holzmann I, Wahn U: Effect of pre- and postnatal tobacco smoke exposure on specific sensitization to food and inhalant allergens during the first 3 years of life. Multicenter Allergy Study Group, Germany. Allergy 1999, 54: 220–228. 10.1034/j.1398-9995.1999.00753.xPubMedView Article
- Kaida T, Kobayashi K, Adachi M, Suzuki F: Optical characteristics of titanium oxide interference film and the film laminated with oxides and their applications for cosmetics. J Cosmet Sci 2004, 55: 219–220.PubMed
- Chen EY, Garnica M, Wang YC, Chen CS, Chin WC: Mucin secretion induced by titanium dioxide nanoparticles. PLoS One 2011, 6: e16198. 10.1371/journal.pone.0016198PubMed CentralPubMedView Article
- Hussain S, Thomassen LC, Ferecatu I, Borot MC, Andreau K, Martens JA, Fleury J, Baeza-Squiban A, Marano F, Boland S: Carbon black and titanium dioxide nanoparticles elicit distinct apoptotic pathways in bronchial epithelial cells. Part Fibre Toxicol 2010, 7: 10. 10.1186/1743-8977-7-10PubMed CentralPubMedView Article
- Ahn MH, Kang CM, Park CS, Park SJ, Rhim T, Yoon PO, Chang HS, Kim SH, Kyono H, Kim KC: Titanium dioxide particle-induced goblet cell hyperplasia: association with mast cells and IL-13. Respir Res 2005, 6: 34. 10.1186/1465-9921-6-34PubMed CentralPubMedView Article
- Sayes CM, Wahi R, Kurian PA, Liu Y, West JL, Ausman KD, Warheit DB, Colvin VL: Correlating nanoscale titania structure with toxicity: a cytotoxicity and inflammatory response study with human dermal fibroblasts and human lung epithelial cells. Toxicol Sci 2006, 92: 174–185. 10.1093/toxsci/kfj197PubMedView Article
- Jiang J, Oberdorster G, Elder A, Gelein R, Mercer P, Biswas P: Does Nanoparticle Activity Depend upon Size and Crystal Phase? Nanotoxicology 2008, 2: 33–42. 10.1080/17435390701882478PubMed CentralPubMedView Article
- Gurr JR, Wang AS, Chen CH, Jan KY: Ultrafine titanium dioxide particles in the absence of photoactivation can induce oxidative damage to human bronchial epithelial cells. Toxicology 2005, 213: 66–73. 10.1016/j.tox.2005.05.007PubMedView Article
- Hussain S, Boland S, Baeza-Squiban A, Hamel R, Thomassen LC, Martens JA, Billon-Galland MA, Fleury-Feith J, Moisan F, Pairon JC, Marano F: Oxidative stress and proinflammatory effects of carbon black and titanium dioxide nanoparticles: role of particle surface area and internalized amount. Toxicology 2009, 260: 142–149. 10.1016/j.tox.2009.04.001PubMedView Article
- Pujalte I, Passagne I, Brouillaud B, Treguer M, Durand E, Ohayon-Courtes C, L'Azou B: Cytotoxicity and oxidative stress induced by different metallic nanoparticles on human kidney cells. Part Fibre Toxicol 2011, 8: 10. 10.1186/1743-8977-8-10PubMed CentralPubMedView Article
- Choi HS, Ashitate Y, Lee JH, Kim SH, Matsui A, Insin N, Bawendi MG, Semmler-Behnke M, Frangioni JV, Tsuda A: Rapid translocation of nanoparticles from the lung airspaces to the body. Nat Biotechnol 2010, 28: 1300–1303. 10.1038/nbt.1696PubMed CentralPubMedView Article
- Li Y, Li J, Yin J, Li W, Kang C, Huang Q, Li Q: Systematic influence induced by 3 nm titanium dioxide following intratracheal instillation of mice. J Nanosci Nanotechnol 2010, 10: 8544–8549. 10.1166/jnn.2010.2690PubMedView Article
- Oberdorster G, Sharp Z, Atudorei V, Elder A, Gelein R, Lunts A, Kreyling W, Cox C: Extrapulmonary translocation of ultrafine carbon particles following whole-body inhalation exposure of rats. J Toxicol Environ Health A 2002, 65: 1531–1543. 10.1080/00984100290071658PubMedView Article
- Barlow PG, Clouter-Baker A, Donaldson K, Maccallum J, Stone V: Carbon black nanoparticles induce type II epithelial cells to release chemotaxins for alveolar macrophages. Part Fibre Toxicol 2005, 2: 11. 10.1186/1743-8977-2-11PubMed CentralPubMedView Article
- Chen HW, Su SF, Chien CT, Lin WH, Yu SL, Chou CC, Chen JJ, Yang PC: Titanium dioxide nanoparticles induce emphysema-like lung injury in mice. FASEB J 2006, 20: 2393–2395. 10.1096/fj.06-6485fjePubMedView Article
- Moon C, Park HJ, Choi YH, Park EM, Castranova V, Kang JL: Pulmonary inflammation after intraperitoneal administration of ultrafine titanium dioxide (TiO 2 ) at rest or in lungs primed with lipopolysaccharide. J Toxicol Environ Health A 2010, 73: 396–409. 10.1080/15287390903486543PubMedView Article
- Oberdorster G, Ferin J, Gelein R, Soderholm SC, Finkelstein J: Role of the alveolar macrophage in lung injury: studies with ultrafine particles. Environ Health Perspect 1992, 97: 193–199.PubMed CentralPubMedView Article
- Oberdorster G, Ferin J, Lehnert BE: Correlation between particle size, in vivo particle persistence, and lung injury. Environ Health Perspect 1994,102(Suppl 5):173–179. 10.1289/ehp.94102s5173PubMed CentralPubMedView Article
- Abdullah LH, Conway JD, Cohn JA, Davis CW: Protein kinase C and Ca 2+ activation of mucin secretion in airway goblet cells. Am J Physiol 1997, 273: L201–210.PubMed
- Petersen CC, Toescu EC, Petersen OH: Different patterns of receptor-activated cytoplasmic Ca 2+ oscillations in single pancreatic acinar cells: dependence on receptor type, agonist concentration and intracellular Ca 2+ buffering. Embo J 1991, 10: 527–533.PubMed CentralPubMed
- Stone V, Tuinman M, Vamvakopoulos JE, Shaw J, Brown D, Petterson S, Faux SP, Borm P, MacNee W, Michaelangeli F, Donaldson K: Increased calcium influx in a monocytic cell line on exposure to ultrafine carbon black. Eur Respir J 2000, 15: 297–303. 10.1034/j.1399-3003.2000.15b13.xPubMedView Article
- Kobayashi N, Naya M, Endoh S, Maru J, Yamamoto K, Nakanishi J: Comparative pulmonary toxicity study of nano-TiO(2) particles of different sizes and agglomerations in rats: different short- and long-term post-instillation results. Toxicology 2009, 264: 110–118. 10.1016/j.tox.2009.08.002PubMedView Article
- Oberdorster G, Oberdorster E, Oberdorster J: Nanotoxicology: an emerging discipline evolving from studies of ultrafine particles. Environ Health Perspect 2005, 113: 823–839. 10.1289/ehp.7339PubMed CentralPubMedView Article
- Monteiller C, Tran L, MacNee W, Faux S, Jones A, Miller B, Donaldson K: The pro-inflammatory effects of low-toxicity low-solubility particles, nanoparticles and fine particles, on epithelial cells in vitro: the role of surface area. Occup Environ Med 2007, 64: 609–615. 10.1136/oem.2005.024802PubMed CentralPubMedView Article
- Huang CC, Aronstam RS, Chen DR, Huang YW: Oxidative stress, calcium homeostasis, and altered gene expression in human lung epithelial cells exposed to ZnO nanoparticles. Toxicol In Vitro 2009, 24: 45–55.PubMedView Article
- Donaldson K, Stone V, Borm PJ, Jimenez LA, Gilmour PS, Schins RP, Knaapen AM, Rahman I, Faux SP, Brown DM, MacNee W: Oxidative stress and calcium signaling in the adverse effects of environmental particles (PM10). Free Radic Biol Med 2003, 34: 1369–1382. 10.1016/S0891-5849(03)00150-3PubMedView Article
- Shukla RK, Sharma V, Pandey AK, Singh S, Sultana S, Dhawan A: ROS-mediated genotoxicity induced by titanium dioxide nanoparticles in human epidermal cells. Toxicol In Vitro 2011, 25: 231–241. 10.1016/j.tiv.2010.11.008PubMedView Article
- Freyre-Fonseca V, Delgado-Buenrostro NL, Gutierrez-Cirlos EB, Calderon-Torres CM, Cabellos-Avelar T, Sanchez-Perez Y, Pinzon E, Torres I, Molina-Jijon E, Zazueta C, et al.: Titanium dioxide nanoparticles impair lung mitochondrial function. Toxicol Lett 2011, 202: 111–119. 10.1016/j.toxlet.2011.01.025PubMedView Article
- Kourie JI: Interaction of reactive oxygen species with ion transport mechanisms. Am J Physiol 1998, 275: C1–24.PubMed
- Palaniappan PR, Pramod KS: The effect of titanium dioxide on the biochemical constituents of the brain of Zebrafish (Danio rerio): An FT-IR study. Spectrochim Acta A Mol Biomol Spectrosc 2011.
- Kelly CV, Leroueil PR, Orr BG, Banaszak Holl MM, Andricioaei I: Poly(amidoamine) dendrimers on lipid bilayers II: Effects of bilayer phase and dendrimer termination. J Phys Chem B 2008, 112: 9346–9353. 10.1021/jp8013783PubMed CentralPubMedView Article
- Berridge MJ, Irvine RF: Inositol trisphosphate, a novel second messenger in cellular signal transduction. Nature 1984, 312: 315–321. 10.1038/312315a0PubMedView Article
- Lu SP, Lin Feng MH, Huang HL, Huang YC, Tsou WI, Lai MZ: Reactive oxygen species promote raft formation in T lymphocytes. Free Radic Biol Med 2007, 42: 936–944. 10.1016/j.freeradbiomed.2006.11.027PubMedView Article
- Muller G, Wied S, Jung C, Over S: Hydrogen peroxide-induced translocation of glycolipid-anchored (c)AMP-hydrolases to lipid droplets mediates inhibition of lipolysis in rat adipocytes. Br J Pharmacol 2008, 154: 901–913.PubMed CentralPubMedView Article
- Ashby MC, Craske M, Park MK, Gerasimenko OV, Burgoyne RD, Petersen OH, Tepikin AV: Localized Ca 2+ uncaging reveals polarized distribution of Ca 2+ -sensitive Ca 2+ release sites: mechanism of unidirectional Ca 2+ waves. J Cell Biol 2002, 158: 283–292. 10.1083/jcb.200112025PubMed CentralPubMedView Article
- Kumar R, Roy I, Ohulchanskky TY, Vathy LA, Bergey EJ, Sajjad M, Prasad PN: In vivo biodistribution and clearance studies using multimodal organically modified silica nanoparticles. ACS Nano 2010, 4: 699–708. 10.1021/nn901146yPubMed CentralPubMedView Article
- Semmler-Behnke M, Kreyling WG, Lipka J, Fertsch S, Wenk A, Takenaka S, Schmid G, Brandau W: Biodistribution of 1.4- and 18-nm gold particles in rats. Small 2008, 4: 2108–2111. 10.1002/smll.200800922PubMedView Article
- Woolley DE: The mast cell in inflammatory arthritis. N Engl J Med 2003, 348: 1709–1711. 10.1056/NEJMcibr023206PubMedView Article
- Hansson GK, Robertson AK, Soderberg-Naucler C: Inflammation and atherosclerosis. Annu Rev Pathol 2006, 1: 297–329. 10.1146/annurev.pathol.1.110304.100100PubMedView Article
- Ozben B, Erdogan O: The role of inflammation and allergy in acute coronary syndromes. Inflamm Allergy Drug Targets 2008, 7: 136–144. 10.2174/187152808785748128PubMedView Article
- Passante E, Frankish N: The RBL-2H3 cell line: its provenance and suitability as a model for the mast cell. Inflamm Res 2009, 58: 737–745. 10.1007/s00011-009-0074-yPubMedView Article
- Nguyen T, Chin WC, Verdugo P: Role of Ca 2+ /K + ion exchange in intracellular storage and release of Ca 2+ . Nature 1998, 395: 908–912. 10.1038/27686PubMedView Article
- Divangahi M, Balghi H, Danialou G, Comtois AS, Demoule A, Ernest S, Haston C, Robert R, Hanrahan JW, Radzioch D, Petrof BJ: Lack of CFTR in skeletal muscle predisposes to muscle wasting and diaphragm muscle pump failure in cystic fibrosis mice. PLoS Genet 2009, 5: e1000586. 10.1371/journal.pgen.1000586PubMed CentralPubMedView Article
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