Biomedical subjects

Patricia C Fulkerson

Publications and source records attributed to Patricia C Fulkerson.

13 recordsLinked to original sources

PubMed2006

A central regulatory role for eosinophils and the eotaxin/CCR3 axis in chronic experimental allergic airway inflammation.

To clarify the role and regulation of eosinophils, we subjected several key eosinophil-related genetically engineered mice to a chronic model of allergic airway inflammation aiming to identify results that were independent of the genetic targeting strategy. In particular, mice with defects in eosinophil development (Deltadbl-GATA) and eosinophil recruitment [mice deficient in CCR3 (CCR3 knockout) and mice deficient in both eotaxin-1 and eotaxin-2 (eotaxin-1/2 double knockout)] were subjected to Aspergillus fumigatus-induced allergic airway inflammation. Allergen-induced eosinophil recruitment into the airway was abolished by 98%, 94%, and 99% in eotaxin-1/2 double knockout, CCR3 knockout, and Deltadbl-GATA mice, respectively. Importantly, allergen-induced type II T helper lymphocyte cytokine production was impaired in the lungs of eosinophil- and CCR3-deficient mice. The absence of eosinophils correlated with reduction in allergen-induced mucus production. Notably, by using global transcript expression profile analysis, a large subset (29%) of allergen-induced genes was eosinophil- and CCR3-dependent; pathways downstream from eosinophils were identified, including in situ activation of coagulation in the lung. In summary, we present multiple lines of independent evidence that eosinophils via CCR3 have a central role in chronic allergic airway disease.

Allergens↗

PubMed2006

Persistent effects induced by IL-13 in the lung.

IL-13 overexpression in the lung induces inflammatory and remodeling responses that are prominent features of asthma. Whereas most studies have concentrated on the development of IL-13-induced disease, far fewer studies have focused on the reversibility of IL-13-induced pathologies. This is particularly important because current asthma therapy appears to be poor at reversing lung remodeling. In this manuscript, we used an externally regulatable transgenic system that targets expression of IL-13 to the lung with the aim of characterizing the reversibility process. After 4 wk of doxycycline (dox) exposure, IL-13 expression resulted in mixed inflammatory cell infiltration, mucus cell metaplasia, lung fibrosis, and airspace enlargement (emphysema). After withdrawal of dox, IL-13 protein levels were profoundly reduced by 7 d and below baseline by 14 d. During this time frame, the level of lung eosinophils returned to near normal, whereas macrophages, lymphocytes, and neutrophils remained markedly elevated. IL-13-induced mucus cell metaplasia significantly decreased (91%) 3 wk after withdrawal of dox, showing strong correlation with reduced eosinophil levels. In contrast, IL-13-induced lung fibrosis did not significantly decline 4 wk after dox withdrawal. Importantly, IL-13-induced emphysema persisted, but modestly declined 4 wk after dox. Examination of transcript expression profiles identified a subset of genes that remained increased weeks after transgene expression was no longer detected. Notably, numerous IL-13-induced cytokines and enzymes were reversible (IL-6 and cathepsins), whereas others were sustained (CCL6 and chitinases) after IL-13 withdrawal, respectively. Thus, several hallmark features of IL-13-induced lung pathology persist and are dissociated from eosinophilia after IL-13 overexpression ceases.

Animals↗

PubMed2006

Eotaxin-3 and a uniquely conserved gene-expression profile in eosinophilic esophagitis.

Eosinophilic esophagitis (EE) is an emerging disorder with a poorly understood pathogenesis. In order to define disease mechanisms, we took an empirical approach analyzing esophageal tissue by a genome-wide microarray expression analysis. EE patients had a striking transcript signature involving 1% of the human genome that was remarkably conserved across sex, age, and allergic status and was distinct from that associated with non-EE chronic esophagitis. Notably, the gene encoding the eosinophil-specific chemoattractant eotaxin-3 (also known as CCL26) was the most highly induced gene in EE patients compared with its expression level in healthy individuals. Esophageal eotaxin-3 mRNA and protein levels strongly correlated with tissue eosinophilia and mastocytosis. Furthermore, a single-nucleotide polymorphism in the human eotaxin-3 gene was associated with disease susceptibility. Finally, mice deficient in the eotaxin receptor (also known as CCR3) were protected from experimental EE. These results implicate eotaxin-3 as a critical effector molecule for EE and provide insight into disease pathogenesis.

Animals↗

PubMed2006

Eosinophils and CCR3 regulate interleukin-13 transgene-induced pulmonary remodeling.

Interleukin (IL)-13 transgene overexpression in the lung induces features of chronic inflammatory lung disorders, including an eosinophil-rich inflammatory cell infiltration, airway hyper-reactivity, and remodeling of the airway (eg, subepithelial fibrosis, goblet cell metaplasia, and smooth muscle hypertrophy and hyperplasia). Here, we aimed to define the role of eosinophils and eosinophil signaling molecules [eg, eotaxins and CC chemokine receptor (CCR) 3] in IL-13-mediated airway disease. To accomplish this, we mated IL-13-inducible lung transgenic mice with mice deficient in eosinophil chemoattractant molecules (eotaxin-1, eotaxin-2, and their receptor CCR3) and with mice genetically deficient in eosinophils (Deltadbl-GATA). We report that in the absence of eotaxin-2 or CCR3, there was a profound reduction in IL-13-induced eosinophil recruitment into the lung lumen. In contrast, in the absence of eotaxin-1, there was a fourfold increase in IL-13-mediated eosinophil recruitment into the airway. IL-13 transgenic mice deficient in CCR3 had a 98% reduction in lung eosinophils. Furthermore, the reduction in pulmonary eosinophils correlated with attenuation in IL-13-induced mucus cell metaplasia and collagen deposition. Mechanistic analysis identified alterations in pulmonary protease and transforming growth factor-beta1 expression in eosinophil-deficient mice. Taken together, these data definitively identify a functional contribution by eosinophils on the effects of chronic IL-13 expression in the lung.

Animals↗

PubMed2005

CXCL9 inhibits eosinophil responses by a CCR3- and Rac2-dependent mechanism.

Recently, inhibitory cytokine pathways for leukocyte chemoattraction and activation have been identified, but there is little insight into the operational mechanisms except for models that rely on simple receptor antagonism. We have previously identified the existence of a murine eosinophil inhibitory pathway mediated by the CXC chemokine ligand 9 (CXCL9, Mig [monokine induced by interferon-gamma]) that impressively blocks eosinophil chemoattraction and function, but the mechanism has remained elusive. We now demonstrate that Mig's inhibitory action extends beyond receptor antagonism alone. Notably, in addition to inhibiting eotaxin-induced filamentous actin (F-actin) formation and chemoattraction, Mig potently blocks platelet activating factor (PAF)- and leukotriene B4 (LTB4)-induced responses. Remarkably, Mig-treated eosinophils display an abnormal F-actin assembly in the absence of agonist stimulation. Additionally, Mig pretreatment inhibits eotaxin-induced activation of the Rho-guanosine triphosphatase (GTPase) Rac, and Rac2-deficient eosinophils demonstrate an impaired transmigration and actin polymerization response to eotaxin stimulation. Furthermore, Mig was unable to inhibit eotaxin-induced responses in Rac2-deficient eosinophils. Finally, using CCR3 gene-targeted cells, Mig's inhibitory activity is demonstrated to be mediated by CC chemokine receptor 3 (CCR3). Thus, by altering agonist-induced signaling and abrogating cytoskeletal reorganization by a Rac2-dependent mechanism, Mig markedly inhibits eosinophil responses to diverse stimuli. These results establish evidence that distinct chemokines can use CCR3 to induce opposing signals in eosinophils.

Actins↗

PubMed2005

Expression and regulation of small proline-rich protein 2 in allergic inflammation.

Asthma is a complex inflammatory pulmonary disorder that is on the rise despite intense ongoing research. We aimed to elucidate novel pathways involved in the pathogenesis of asthma. Employing asthma models induced by different allergens (ovalbumin and Aspergillus fumigatus), we uncovered the involvement of two members of the small proline-rich protein (SPRR) family, SPRR2a and SPRR2b, known to be involved in epithelial differentiation but not allergic disease. In situ hybridization revealed induction of SPRR2 signal in a subset of bronchial epithelial cells and mononuclear cells associated with inflammation after allergen challenge. Allergen-induced SPRR2 mRNA accumulation in the lung occurred in a time-dependent manner, with peak expression 10-96 h after a second ovalbumin challenge. Transgenic overexpression of interleukin (IL)-13 in the lungs resulted in a marked increase of SPRR2 expression, and allergen-induced SPRR2 expression was significantly decreased in IL-13-deficient mice. Studies in gene-targeted mice revealed that allergen-induced SPRR2 was dependent upon STAT6. Finally, we aimed to determine if the induction of SPRR2 by allergen was tissue specific. Notably, SPRR2 was markedly increased in the small intestine after induction of allergic gastrointestinal inflammation. Thus, SPRR2 is an allergen- and IL-13-induced gene in experimental allergic responses that may be involved in disease pathophysiology.

Allergens↗

PubMed2005

Identification of a cooperative mechanism involving interleukin-13 and eotaxin-2 in experimental allergic lung inflammation.

Pulmonary eosinophilia, a hallmark pathologic feature of allergic lung disease, is regulated by interleukin-13 (IL-13) as well as the eotaxin chemokines, but the specific role of these cytokines and their cooperative interaction are only partially understood. First, we elucidated the essential role of IL-13 in the induction of the eotaxins by comparing IL-13 gene-targeted mice with wild type control mice by using an ovalbumin-induced model of allergic airway inflammation. Notably, ovalbumin-induced expressions of eotaxin-1 and eotaxin-2 mRNA in the lungs were almost completely dependent upon IL-13. Second, in order to address the specific role of eotaxin-2 in IL-13-induced pulmonary eosinophilia, we generated eotaxin-2 gene-deficient mice by homologous recombination. Notably, in contrast to observations made in eotaxin-1-deficient mice, eotaxin-2-deficient mice had normal base-line eosinophil levels in the hematopoietic tissues and gastrointestinal tract. However, following intratracheal IL-13 administration, eotaxin-2-deficient mice showed a profound reduction in airway eosinophilia compared with wild type mice. Most interestingly, the level of peribronchial lung tissue eosinophils in IL-13-treated eotaxin-2-deficient mice was indistinguishable from wild type mice. Furthermore, IL-13 lung transgenic mice genetically engineered to be deficient in eotaxin-2 had a marked reduction of luminal eosinophils. Mechanistic analysis identified IL13-induced eotaxin-2 expression by macrophages in a distinct lung compartment (luminal inflammatory cells) compared with eotaxin-1, which was expressed solely in the tissue. Taken together, these results demonstrate a cooperative mechanism between IL-13 and eotaxin-2. In particular, IL-13 mediates allergen-induced eotaxin-2 expression, and eotaxin-2 mediates IL-13-induced airway eosinophilia.

Animals↗

PubMed2004

Pulmonary chemokine expression is coordinately regulated by STAT1, STAT6, and IFN-gamma.

The expression of distinct chemokines within the asthmatic lung suggests that specific regulatory mechanisms may mediate various stages of asthmatic disease. Global transcript expression profiling was used to define the spectrum and kinetics of chemokine involvement in an experimental murine model of asthma. Seventeen chemokines were induced in the lungs of allergen-inoculated mice, as compared with saline-treated mice. Two (CXCL13 and CCL9) of the 17 identified chemokines have not previously been associated with allergic airway disease. Seven (7 of 17; CCL2, CCL7, CCL9, CCL11, CXCL1, CXCL5, CXCL10) of the allergen-induced chemokines were induced early after allergen challenge and remained induced throughout the experimental period. Three chemokines (CXCL2, CCL3, and CCL17) were induced only during the early phase of the inflammatory response after the initial allergen challenge, while seven chemokines (CCL6, CCL8, CCL12, CCL22, CXCL9, CXCL12, and CXCL13) were increased only after a second allergen exposure. Unexpectedly, expression of only three chemokines, CCL11, CCL17, and CCL22, was STAT6 dependent, and many of the identified chemokines were overexpressed in STAT6-deficient mice, providing an explanation for the enhanced neutrophilic inflammation seen in these mice. Notably, IFN-gamma and STAT1 were shown to contribute to the induction of two STAT6-independent chemokines, CXCL9 and CXCL10. Taken together, these results show that only a select panel of chemokines (those targeting Th2 cells and eosinophils) is positively regulated by STAT6; instead, many of the allergen-induced chemokines are negatively regulated by STAT6. Collectively, we demonstrate that allergen-induced inflammation involves coordinate regulation by STAT1, STAT6, and IFN-gamma.

Allergens↗

PubMed2004

Expression and regulation of a disintegrin and metalloproteinase (ADAM) 8 in experimental asthma.

Asthma, a complex chronic inflammatory pulmonary disorder, is on the rise despite intense ongoing research. To elucidate novel pathways involved in asthma pathogenesis, we used transcript expression profiling in a murine model of asthma. Employing asthma models induced by different allergens (ovalbumin and Aspergillus fumigatus) we uncovered the involvement of ADAM8, a member of a disintegrin and metalloproteinase (ADAM) family. In situ hybridization of mouse lungs revealed strong ADAM8 induction in peribronchial and perivascular inflammatory cells as well as in bronchiolar epithelial cells following allergen challenge. Sequence analysis of lung ADAM8 cDNA identified a novel splice variant of ADAM8 that contained an additional exon in juxtaposition to the transmembrane domain. Allergen-induced ADAM8 mRNA accumulation in the lung was dose- and time-dependent. Transgenic or pharmacologic delivery of interleukin (IL)-4 or IL-13 to the lungs resulted in a marked increase of ADAM8 expression. Gene-targeted mice studies revealed that ovalbumin-induced ADAM8 was largely dependent upon signal transducer and activator of transcription (STAT) 6 and the IL-4 receptor alpha-chain. Thus, ADAM8 is an allergen-, IL-4-, and IL-13-induced gene in the experimental asthmatic lung. Taken together with the role of ADAM33 in asthma, these results suggest that allergic lung responses involve the interplay of diverse members of the ADAM family.

ADAM Proteins↗

PubMed2004

Negative regulation of eosinophil recruitment to the lung by the chemokine monokine induced by IFN-gamma (Mig, CXCL9).

Experimental analysis of allergic airway inflammation (AAI) in animals and humans is associated with coordinate gene induction. Using DNA microarray analysis, we have identified a large panel of AAI signature genes. Unexpectedly, the allergen-challenged lung (a T helper 2 microenvironment) was found to be associated with the expression of T helper 1-associated CXCR3 ligands, monokine induced by IFN-gamma (Mig), and IFN-gamma-inducible protein of 10 kDa (IP-10). Here we report that Mig functions as a negative regulator of murine eosinophils. Whereas Mig was not able to induce chemotaxis of eosinophils, pretreatment with Mig induced a dose-dependent inhibition of chemoattractant-induced eosinophil transmigration in vitro. Moreover, i.v. administration of low doses of Mig ( approximately 10-30 microg/kg) induced strong and specific dose-dependent inhibition of chemokine-, IL-13-, and allergen-induced eosinophil recruitment and, conversely, neutralization of Mig before allergen challenge increased airway eosinophilia. Importantly, Mig also inhibited a CCR3-mediated functional response in eosinophils. These results indicate that the ultimate distribution and function of inflammatory cells within the allergic lung is dictated by a balance between positively and negatively regulatory chemokines. The identification of a naturally occurring eosinophil inhibitory chemokine pathway in vivo provides a strategic basis for future therapeutic consideration.

Allergens↗

PubMed2004

Transcript signatures in experimental asthma: identification of STAT6-dependent and -independent pathways.

The analysis of polygenic diseases such as asthma poses a challenging problem. In an effort to provide unbiased insight into disease pathogenesis, we took an empirical approach involving transcript expression profiling of lung tissue from mice with experimental asthma. Asthmatic responses were found to involve sequential induction of 4.7% of the tested genome; notably, there was ectopic expression of a series of genes not previously implicated in allergic or pulmonary responses. Genes were widely distributed throughout all chromosomes, but preferentially included genes involved in immunity, development, and homeostasis. When asthma was induced by two independent experimental regimens, unique gene transcript profiles were found depending upon the mode of disease induction. However, the majority of genes were common to both models representing an asthma signature genome. Analysis of STAT6-deficient mice revealed that an unexpectedly large segment of the asthma genes were STAT6 independent; this correlated with sustained inflammatory events in these mice. Notably, induction of asthma in STAT6-deficient mice resulted in gene induction not seen in wild-type mice. These results raise concern that therapeutic blockade of STAT6 in the asthmatic setting may reprogram the genetic signature, resulting in alternative lung pathology, which we indeed observed in STAT6-deficient mice. These results provide unprecedented insight into the complex steps involved in the pathogenesis of allergic airway responses; as such, these results have significant therapeutic and clinical implications.

Administration, Intranasal↗

PubMed2004

Role of TC21/R-Ras2 in enhanced migration of neurofibromin-deficient Schwann cells.

The neurofibromatosis type 1 tumor suppressor protein neurofibromin, is a GTPase activating protein for H-, N-, K-, R-Ras and TC21/R-Ras2 proteins. We demonstrate that Schwann cells derived from Nf1-null mice have enhanced chemokinetic and chemotactic migration in comparison to wild-type controls. Surprisingly, this migratory phenotype is not inhibited by a farnesyltransferase inhibitor or dominant-negative (dn) (N17)H-Ras (which inhibits H-, N-, and K-Ras activation). We postulated that increased activity of R-Ras and/or TC21/R-Ras2, due to loss of Nf1, contributes to increased migration. Mouse Schwann cells (MSCs) express R-Ras and TC21/R-Ras2 and their specific guanine exchange factors, C3G and AND-34. Infection of Nf1-null MSCs with a dn(43N)R-Ras adenovirus (to inhibit both R-Ras and TC21/R-Ras2 activation) decreases migration by approximately 50%. Conversely, expression of activated (72L)TC21/R-Ras2, but not activated (38V)R-Ras, increases migration, suggesting a role of TC21/R-Ras2 activation in the migration of neurofibromin-deficient Schwann cells. TC21/R-Ras2 preferentially couples to the phosphatidylinositol 3-kinase (PI3-kinase) and MAP kinase pathways. Treatment with a PI3-kinase or MAP kinase inhibitor reduces Nf1-null Schwann cell migration, implicating these TC21 effectors in Schwann cell migration. These data reveal a key role for neurofibromin regulation of TC21/R-Ras2 in Schwann cells, a cell type critical to NF1 tumor pathogenesis.

Animals↗

PubMed2004

Foxa2 regulates alveolarization and goblet cell hyperplasia.

The airways are lined by several distinct epithelial cells that play unique roles in pulmonary homeostasis; however, the mechanisms controlling their differentiation in health and disease are poorly understood. The winged helix transcription factor, FOXA2, is expressed in the foregut endoderm and in subsets of respiratory epithelial cells in the fetal and adult lung. Because targeted mutagenesis of the Foxa2 gene in mice is lethal before formation of the lung, its potential role in lung morphogenesis and homeostasis has not been determined. We selectively deleted Foxa2 in respiratory epithelial cells in the developing mouse lung. Airspace enlargement, goblet cell hyperplasia, increased mucin and neutrophilic infiltration were observed in lungs of the Foxa2-deleted mice. Experimental goblet cell hyperplasia caused by ovalbumin sensitization, interleukin 4 (IL4), IL13 and targeted deletion of the gene encoding surfactant protein C (SP-C), was associated with either absent or decreased expression of Foxa2 in airway epithelial cells. Analysis of lung tissue from patients with a variety of pulmonary diseases revealed a strong inverse correlation between FOXA2 and goblet cell hyperplasia. FOXA2 is required for alveolarization and regulates airway epithelial cell differentiation in the postnatal lung.

Animals↗