Francesca Alessandrini

Genome-wide, large-scale production of mutant mice by ENU mutagenesis

In the post-genome era, the mouse will have a major role as a model system for functional genome analysis. This requires a large number of mutants similar to the collections available from other model organisms such as Drosophila melanogaster and Caenorhabditis elegans. Here we report on a systematic, genome-wide, mutagenesis screen in mice. As part of the German Human Genome Project, we have undertaken a large-scale ENU-mutagenesis screen for dominant mutations and a limited screen for recessive mutations. In screening over 14,000 mice for a large number of clinically relevant parameters, we recovered 182 mouse mutants for a variety of phenotypes. In addition, 247 variant mouse mutants are currently in genetic confirmation testing and will result in additional new mutant lines. This mutagenesis screen, along with the screen described in the accompanying paper, leads to a significant increase in the number of mouse models available to the scientific community. Our mutant lines are freely accessible to non-commercial users (for information, see http://www.gsf.de/ieg/groups/enu-mouse.html).

Health Effects of Ambient Particulate Matter—Biological Mechanisms and Inflammatory Responses to In Vitro and In Vivo Particle Exposures

In this article, we review and analyze different modes of exposure to ultrafine particles in order to assess particle-induced inflammatory responses and the underlying mechanisms in vitro and in vivo. Based on results from monocytic cells cultured under submerged conditions, we discuss (1) the impact of particle properties such as surface area and oxidative potential on lipid metabolism as a highly sensitive regulatory pathway and (2) the interference of diesel exhaust particles with toll-like receptor-mediated inflammatory responses. Furthermore, new developments of air–liquid interface exposure used as an alternative approach to simulate cell particle interactions are presented. In addition to the in vitro approaches, animal exposure studies are described that apply selected mouse models to elucidate potential allergic and inflammatory pulmonary responses and mast-cell-related mechanisms after particle exposure. Long-term inhalation of ultrafine particles might lead to irreversible changes in lung structure and function. Clinical studies addressing the characteristics of inflammatory airway cells are a promising approach to understand underlying pathophysiological mechanisms in chronic obstructive pulmonary disease. Finally, a potential outcome of human particle exposure is chronic cough in children. Here, discrimination between asthmatic and nonasthmatic cough by means of immunological parameters appears to be an important step toward improving diagnosis and therapy.

Role of Oxidative Stress in Ultrafine Particle–induced Exacerbation of Allergic Lung Inflammation

RATIONALE The effects of ultrafine particle inhalation on allergic airway inflammation are of growing interest. The mechanisms underlying these effects are currently under investigation. OBJECTIVES To investigate the role of oxidative stress on the adjuvant activity of inhaled elemental carbon ultrafine particles (EC-UFPs) on allergic airway inflammation. METHODS Ovalbumin-sensitized mice were exposed to EC-UFPs (504 microg/m(3) for 24 h) or filtered air immediately before allergen challenge and systemically treated with N-acetylcysteine or vehicle before and during EC-UFP inhalation. Allergic inflammation was measured up to 1 week after allergen challenge by means of bronchoalveolar lavage, cytokine/total protein assays, lung function, and histology. Isoprostane levels in lung tissue served to measure oxidative stress. Transmission electron microscopy served to localize EC-UFPs in lung tissue and both electrophoretic mobility shift assay and immunohistochemistry to quantify/localize nuclear factor-kappaB (NF-kappaB) activation. MEASUREMENTS AND MAIN RESULTS In sensitized and challenged mice EC-UFP inhalation increased allergen-induced lung lipid peroxidation and NF-kappaB activation in addition to inflammatory infiltrate, cytokine release, and airway hyperresponsiveness. Prominent NF-kappaB activation was observed in the same cell types in which EC-UFPs were detected. N-acetylcysteine treatment significantly reduced the adjuvant activity of EC-UFPs. In nonsensitized or sensitized but not challenged mice EC-UFP exposure induced a moderate increase in isoprostanes but no significant effect on other parameters of lung inflammation. CONCLUSIONS Our findings demonstrate a critical role for oxidative stress in EC-UFP-induced augmentation of allergen-induced lung inflammation, where EC-UFP exposure has potentiating effects in lung allergic inflammation. Our data support the concept that allergic individuals are more susceptible to the adverse health effects of EC-UFPs.

Surface modifications of silica nanoparticles are crucial for their inert versus proinflammatory and immunomodulatory properties.

Background Silica (SiO2) nanoparticles (NPs) are widely used in diverse industrial and biomedical applications. Their applicability depends on surface modifications, which can limit potential health problems. Objective To assess the potential impact of SiO2 NP exposure and NPs chemical modifications in allergic airway inflammation. Methods Mice were sensitized by five repetitive intraperitoneal injections of ovalbumin/aluminum hydroxide (1 μg) over 42 days, then intratracheally instilled with plain or modified SiO2 NPs (50 μg/mouse), and subsequently aerosol challenged for 20 minutes with ovalbumin. One or 5 days later, allergic inflammation was evaluated by cell differentiation of bronchoalveolar lavage fluid, lung function and gene expression and histopathology, as well as electron and confocal microscopy of pulmonary tissue. Results Plain SiO2 NPs induced proinflammatory and immunomodulatory effects in vivo, highlighted by enhanced infiltration of inflammatory cells in the bronchoalveolar lavage fluid, induction of a pulmonary T helper type 2 (Th2) cytokine pattern, differentiation of type 2 macrophages, and by morphological changes in the lung of sensitized mice. These effects were dramatically attenuated using surface-functionalized NPs with amino and phosphate groups, but not with polyethylene glycol. The role of macrophages in taking up SiO2 NPs was confirmed by flow cytometry, confocal microscopy, and gene expression analysis. Conclusion Our data suggest that amino and phosphate surface modifications, but not polyethylene glycol (PEG), mitigate the proinflammatory and immunomodulatory effect of SiO2 NPs in allergic airway inflammation, paving the way for new strategies in the production of nanomaterials with lower health impact for humans.

Effects of ultrafine particles-induced oxidative stress on Clara cells in allergic lung inflammation

BackgroundClara cell protein (CC16), the main secretory product of bronchiolar Clara cells, plays an important protective role in the respiratory tract against oxidative stress and inflammation. The purpose of the study was to investigate the role of elemental carbon ultrafine particles (EC-UFP)-induced oxidative stress on Clara cells and CC16 in a mouse model of allergic lung inflammation.MethodsOvalbumin (OVA)-sensitized mice were exposed to EC-UFP (507 μg/m3 for 24 h) or filtered air immediately prior to allergen challenge and systemically treated with N-acetylcysteine (NAC) or vehicle prior and during EC-UFP inhalation. CC16 was measured up to one week after allergen challenge in bronchoalveolar lavage fluid (BALF) and in serum. The relative expression of CC16 and TNF-α mRNA were measured in lung homogenates. A morphometrical analysis of mucus hypersecretion and electron microscopy served to investigate goblet cell metaplasia and Clara cell morphological alterations.ResultsIn non sensitized mice EC-UFP inhalation caused alterations in CC16 concentration, both at protein and mRNA level, and induced Clara cell hyperplasia. In sensitized mice, inhalation of EC-UFP prior to OVA challenge caused most significant alterations of BALF and serum CC16 concentration, BALF total protein and TNF-α relative expression compared to relevant controls; their Clara cells displayed the strongest morphological alterations and strongest goblet cell metaplasia occurred in the small airways. NAC strongly reduced both functional and morphological alterations of Clara cells.ConclusionOur findings demonstrate that oxidative stress plays an important role in EC-UFP-induced augmentation of functional and morphological alterations of Clara cells in allergic lung inflammation.

Total and Regional Deposition of Ultrafine Particles in a Mouse Model of Allergic Inflammation of the Lung

Epidemiological studies have shown an association between ambient particle inhalation and adverse respiratory heath effects. Inhalation of ultrafine particles (UFP, diameter <100 nm) has been suggested to contribute to exacerbation of allergic airway inflammation. Here we analyze the potential effects of allergen sensitization and challenge on total and regional deposition of UFP in the lung. Ovalbumin (OVA)-sensitized and nonsensitized mice were exposed for 1 h to ultrafine iridium particles radiolabeled with 192Ir (UF-Ir) (0.2 mg m−3) at 2 different time points either before or after allergen (OVA) challenge. Additional sensitized and nonsensitized mice were exposed to UF-Ir without allergen challenge. Lung total and regional UF-Ir deposition were calculated according to the distribution of radioactivity in the body and in the excreta during 3 days following UF-Ir inhalation. OVA-sensitized mice showed a 21% relative increase of total UF-Ir deposited fraction compared to nonsensitized mice. When UF-Ir inhalation was performed after allergen challenge, no difference in total UF-Ir deposited fraction between sensitized and nonsensitized mice was detectable. Furthermore, no differences in extrathoracic deposition or in regional particle deposition were detected between all experimental groups. This study indicates that allergen sensitization alone can affect UFP deposition in the lungs. Whether higher UFP deposition in sensitized individuals compared to nonsensitized individuals or whether other factors, like alterations in long-term clearance kinetics, contribute substantially to the susceptibility of allergic individuals to particle exposure has yet to be elucidated.

ENU Mouse Mutagenesis: Generation of Mouse Mutants with Aberrant Plasma IgE Levels

Background: The ENU Mouse Mutagenesis Project aims at a large-scale, systematic production of mouse mutants using the alkylating agent ethyl-nitrosourea (ENU). Offspring of mutagenized mice are subjected to a multiparameter screen to detect alterations in various phenotypes with the ultimate goal of identifying novel genes relevant for the expression of the phenotype. Using this approach, we have analyzed plasma IgE concentrations to identify mouse mutants with aberrant plasma IgE levels. Methods and Results: ENU-mutagenized male C3HeB/FeJ were mated to wild-type females to produce F1 offspring. F1 animals were analyzed for alterations in their plasma IgE concentrations that showed a dominant mode of inheritance, or bred further to screen for recessive phenotypes. Plasma IgE concentrations were determined by ELISA and a normal range for plasma IgE was established using C3HeB/FeJ wild-type animals. So far we have tested 6568 F1 animals. Repeated testing confirmed a stable aberrant IgE phenotype in 124 animals. To confirm the genetic basis of the observed phenotype, these mice were subjected to confirmation crossing. Currently we have established 9 independent mutant mouse lines (3 with high plasma IgE and 6 with plasma IgE below detection limit) that have been genetically confirmed and additional 24 variant mouse lines are currently undergoing confirmation testing. Conclusion: ENU mouse mutagenesis allowed us to generate and identify mouse mutants with aberrant plasma IgE levels, which may be used to characterize novel genes involved in IgE regulation and may serve as animal models for IgE-mediated diseases.

Specific CD8 T Cells in IgE-mediated Allergy Correlate with Allergen Dose and Allergic Phenotype

RATIONALE Studies in humans and rodents have indicated a causative role for CD8(+) T cells in IgE-mediated allergic inflammation, but their function is still controversial. OBJECTIVES To analyze the role of allergen-specific CD8(+) T cells during the development of allergic airway inflammation in two parallel but diverging outcome models. METHODS We used H2-Kb SIINFEKL (OVA(257-264)) multimers to analyze induction, natural distribution, and phenotype of allergen-specific CD8(+) T cells in a murine C57BL/6 model of ovalbumin (OVA)-induced allergic airway inflammation using low-dose or high-dose OVA sensitization. MEASUREMENTS AND MAIN RESULTS The low-dose protocol was characterized by a significant induction of total and OVA-specific IgE, eosinophilic airway inflammation, IL-4 levels in bronchoalveolar lavage fluid. And significant alterations in lung function. The high dose protocol was characterized by a significant reduction of the allergic phenotype. Using OVA(257-264) H2-Kb multimers, we observed lung and airway infiltrating OVA-specific CD8(+) T cells showing an effector/effector-memory phenotype. The high-dose protocol caused significantly higher infiltration of allergen-specific CD8(+) cells to the airways and enhanced their cytotoxicity. Adoptive transfer with CD8(+) T cells from transgenic OT-I mice to TAP1(-/-) or wild-type mice showed their migration to the lungs and TAP1-dependent proliferation after OVA-aerosol exposure. TAP1(-/-) mice defective in CD8(+) T cells showed exacerbated symptoms in the low-dose sensitization model. CONCLUSIONS Allergen-specific CD8(+) T cells seem to protect from allergic inflammation in the lungs. Their number, which is dependent on the sensitization dose, appears to be a critical predictor for the severity of the allergic phenotype.

Identification of immunological relevant phenotypes in ENU mutagenized mice

Abstract. The immunology screen focuses on the identification of novel gene products involved in the mammalian immune response and on the establishment of mouse models for immunological disorders. For this purpose, high throughput and semi-automated techniques were developed and optimized for low cost per sample and reproducibility. All assays are designed to be nonconsumptive and are based on peripheral blood or direct PCR amplification.

Ultrafine particles affect the balance of endogenous pro- and anti-inflammatory lipid mediators in the lung: in-vitro and in-vivo studies.

BackgroundExposure to ultrafine particles exerts diverse harmful effects including aggravation of pulmonary diseases like asthma. Recently we demonstrated in a mouse model for allergic airway inflammation that particle-derived oxidative stress plays a crucial role during augmentation of allergen-induced lung inflammation by ultrafine carbon particle (UfCP) inhalation. The mechanisms how particle inhalation might change the inflammatory balance in the lungs, leading to accelerated inflammatory reactions, remain unclear. Lipid mediators, known to be immediately generated in response to tissue injury, might be strong candidates for priming this particle-triggered change of the inflammatory balance.MethodsWe hypothesize that inhalation of UfCP may disturb the balance of pro- and anti-inflammatory lipid mediators in: i) a model for acute allergic pulmonary inflammation, exposing mice for 24 h before allergen challenge to UfCP inhalation (51.7 nm, 507 μg/m3), and ii) an in-vitro model with primary rat alveolar macrophages (AM) incubated with UfCP (10 μg/1 x 106 cells/ml) for 1 h. Lungs and AM were analysed for pro- and anti-inflammatory lipid mediators, namely leukotriene B4 (LTB4), prostaglandin E2 (PGE2), 15(S)-hydroxy-eicosatetraenoic acid (15(S)-HETE), lipoxin A4 (LXA4) and oxidative stress marker 8-isoprostane by enzyme immunoassays and immunohistochemistry.ResultsIn non-sensitized mice UfCP exposure induced a light non-significant increase of all lipid mediators. Similarly but significantly in rat AM all lipid mediators were induced already within 1 h of UfCP stimulation. Also sensitized and challenge mice exposed to filtered air showed a partially significant increase in all lipid mediators. In sensitized and challenged mice UfCP exposure induced highest significant levels of all lipid mediators in the lungs together with the peak of allergic airway inflammation on day 7 after UfCP inhalation. The levels of LTB4, 8-isoprostane and PGE2 were significantly increased also one day after UfCP exposure. Immunohistochemistry localized highest concentrations of PGE2 especially in AM one day after UfCP exposure.ConclusionOur results suggest that UfCP exposure affects the balance between pro- and anti-inflammatory lipid mediators. In allergic mice, where the endogenous balance of pro- and anti-inflammatory mediators is already altered, UfCP exposure aggravates the inflammation and the increase in anti-inflammatory, pro-resolving lipid mediators is insufficient to counterbalance the extensive inflammatory response. This may be a contributing mechanism that explains the increased susceptibility of asthmatic patients towards particle exposure.