Biomedical subjects

Julia K L Walker

Publications and source records attributed to Julia K L Walker.

8 recordsLinked to original sources

PubMed2006

Leukocyte-derived IL-10 reduces subepithelial fibrosis associated with chronically inhaled endotoxin.

Endotoxin (LPS), a Gram-negative cell wall component, has potent proinflammatory properties. Acute LPS exposure causes airway inflammation; chronic exposure causes airway hyperreactivity and remodeling. IL-10 is an important antiinflammatory cytokine, which is decreased in patients with airway disease, such as asthma and cystic fibrosis. To examine the physiologic and therapeutic role of IL-10 in acute and chronic LPS-induced airway disease. Mice were exposed to aerosolized LPS once or daily for 4 wk. Endpoints were airway inflammation, airway reactivity to methacholine, extracellular matrix protein expression, and histologic analysis. IL-10-deficient mice developed significantly enhanced airway cellularity and remodeling when compared with C57BL/6 mice after chronic LPS inhalation. However they demonstrated less airway hyperreactivity associated with higher inducible nitric oxide synthase (iNOS), endothelial NOS (eNOS), and lung lavage fluid nitrite levels. In a bone marrow transplantation model, the IL-10 antiinflammatory effect was dependent on the hematopoietic but not on the parenchymal IL-10 expression. Induced epithelial human IL-10 expression protected from the LPS effects and led to decreased collagen production. IL-10 attenuates chronic LPS-induced airway inflammation and remodeling. Physiologically, the antiinflammatory effect of IL-10 is mediated by hematopoietic cells. Therapeutically, adenovirus-driven expression of human IL-10 in airway epithelia is sufficient for its protective effect on inflammation and remodeling. The role of IL-10 on airway hyperreactivity is complex: IL-10 deficiency protects against LPS-induced hyperreactivity, and is associated with higher eNOS, iNOS, and airway nitrate levels.

Adenoviridae↗

PubMed2006

Multistrain genetic comparisons reveal CCR5 as a receptor involved in airway hyperresponsiveness.

Asthma is a ubiquitous disease with a broad range of clinical phenotypes. To better understand the complex genetic and environmental interactions underlying asthma, we compared the gene-gene interactions of four genetically distinct mouse strains that demonstrate biologically distinct responses to allergen. Using DNA microarrays and knock-out mouse studies, we showed that CCR5 plays a definitive role in the development of ovalbumin-induced allergic airway inflammatory disease. In addition, gene expression profiling data have revealed other potential novel targets for therapeutics-based research and has enhanced the understanding of the molecular mechanisms underlying the etiology of "asthma."

Animals↗

PubMed2005

Morphine side effects in beta-arrestin 2 knockout mice.

Morphine is a potent analgesic, yet, like most opioid narcotics, it exerts unwanted side effects such as constipation and respiratory suppression, thereby limiting its clinical utility. Pharmacological approaches taken to preserve the analgesic properties, while eliminating the unwanted side effects, have met with very limited success. Here, we provide evidence that altering mu opioid receptor regulation may provide a novel approach to discriminate morphine's beneficial and deleterious effects in vivo. We have previously reported that mice lacking the G protein-coupled receptor regulatory protein, beta-arrestin 2, display profoundly altered morphine responses. beta-Arrestin 2 knockout mice have enhanced and prolonged morphine analgesia with very little morphine tolerance. In this report, we examine whether the side effects of morphine treatment are also augmented in this animal model. Surprisingly, the genetic disruption of opioid receptor regulation, while enhancing and prolonging analgesia, dramatically attenuates the respiratory suppression and acute constipation caused by morphine.

Animals↗

PubMed2005

Toll-like receptor 4 antagonist (E5564) prevents the chronic airway response to inhaled lipopolysaccharide.

Although chronic inhalation of endotoxin or lipopolysaccharide (LPS) causes all of the classic features of asthma, including airway hyperreactivity, airway inflammation, and airway remodeling, the mechanisms involved in this process are not clearly understood. The objective of this study was to determine whether intratracheal treatment with LPS antagonist (E5564, a lipid A analog) prevented the development of chronic endotoxin-induced airway disease in a mouse model of environmental airway disease. Pretreatment with 10 and 100 microg of E5564 was found to inhibit the airway response (hyperreactivity and inflammation) for up to 48 h after the administration of the compound. Repeated dosing with 50 microg of E5564 intratracheally did not cause any measurable toxicity. Therefore, in a chronic experiment, mice were treated with either E5564 (50 microg) or vehicle three times weekly for 5 wk and simultaneously daily exposed to either LPS (4.65 +/- 0.30 microg/m3) or saline aerosol. E5564 was effective in decreasing the airway hyperreactivity to methacholine, the air space neutrophilia, the interleukin-6 in the lung lavage fluid, and the neutrophil infiltration of the airways 36 h after 5 wk of LPS inhalation. Less collagen deposition was observed in the airways of E5564-treated mice compared with vehicle-treated mice after a 4-wk recovery period. Our results indicate that E5564, a Toll-like receptor 4 antagonist, minimizes the physiological and biological effects of chronic LPS inhalation, suggesting a therapeutic role for competitive LPS antagonists in preventing or reducing endotoxin-induced environmental airway disease.

Administration, Inhalation↗

PubMed2004

The role of Toll-like receptor 4 in environmental airway injury in mice.

Inhalation of toxins commonly found in air pollution contributes to the development and progression of asthma and environmental airway injury. In this study, we investigated the requirement of toll-like receptor 4 (TLR4) in mice for pulmonary responses to three environmental toxins: aerosolized lipopolysaccharide, particulate matter (residual oil fly ash), and ozone. The physiologic and biologic responses to these toxins were evaluated by the extent of airway responsiveness, neutrophil recruitment to the lower respiratory tract, changes in inflammatory cytokines, and the concentration of protein in the lavage fluid. Genetically engineered, TLR4-deficient mice (C57BL/6(TLR4-/-)) were unresponsive to inhaled lipopolysaccharide, except for minimal increases in some inflammatory cytokines. In contrast, C57BL/6(TLR4-/-) mice did not differ from wild-type mice in their airway response to instilled residual oil fly ash or acute ozone exposure; however, we found that, despite a robust inflammatory response, C57BL/6(TLR4-/-) mice are protected against the development of airway hyperresponsiveness after subchronic ozone exposure. These data demonstrate in the mouse that the requirement of TLR4 for pulmonary inflammation depends on the nature of the toxin and appears specific to toxin and exposure conditions.

Animals↗

PubMed2003

Allergen-induced airway disease is mouse strain dependent.

We investigated the development of airway hyperreactivity (AHR) and inflammation in the lungs of nine genetically diverse inbred strains of mice [129/SvIm, A/J, BALB/cJ, BTBR+(T)/tf/tf, CAST/Ei, C3H/HeJ, C57BL/6J, DBA/2J, and FVB/NJ] after sensitization and challenge with ovalbumin (OVA). At 24, 48, and 72 h post-OVA exposure, the severity of AHR and eosinophilic inflammation of the mouse strains ranged from relatively unresponsive to responsive. The severity of the airway eosinophilia of some strains did not clearly correlate with the development of AHR. The temporal presence of T helper type 2 cytokines in lung lavage fluid also varied markedly among the strains. The levels of IL-4 and IL-13 were generally increased in the strains with the highest airway eosinophilia at 24 and 72 h postexposure, respectively; the levels of IL-5 were significantly increased in most of the strains with airway inflammation over the 72-h time period. The differences of physiological and biological responses among the inbred mouse strains after OVA sensitization and challenge support the hypothesis that genetic factors contribute, in part, to the development of allergen-induced airway disease.

Allergens↗

PubMed2003

Beta-arrestin-2 regulates the development of allergic asthma.

Asthma is a chronic inflammatory disorder of the airways that is coordinated by Th2 cells in both human asthmatics and animal models of allergic asthma. Migration of Th2 cells to the lung is key to their inflammatory function and is regulated in large part by chemokine receptors, members of the seven-membrane-spanning receptor family. It has been reported recently that T cells lacking beta-arrestin-2, a G protein-coupled receptor regulatory protein, demonstrate impaired migration in vitro. Here we show that allergen-sensitized mice having a targeted deletion of the beta-arrestin-2 gene do not accumulate T lymphocytes in their airways, nor do they demonstrate other physiological and inflammatory features characteristic of asthma. In contrast, the airway inflammatory response to LPS, an event not coordinated by Th2 cells, is fully functional in mice lacking beta-arrestin-2. beta-arrestin-2-deficient mice demonstrate OVA-specific IgE responses, but have defective macrophage-derived chemokine-mediated CD4+ T cell migration to the lung. This report provides the first evidence that beta-arrestin-2 is required for the manifestation of allergic asthma. Because beta-arrestin-2 regulates the development of allergic inflammation at a proximal step in the inflammatory cascade, novel therapies focused on this protein may prove useful in the treatment of asthma.

Animals↗

PubMed2002

Vasoactive intestinal polypeptide type-1 receptor regulation. Desensitization, phosphorylation, and sequestration.

The vasoactive intestinal polypeptide type-1 (VPAC(1)) receptor is a class II G protein-coupled receptor, distinct from the adrenergic receptor superfamily. The mechanisms involved in the regulation of the VPAC(1) receptor are largely unknown. We examined agonist-dependent VPAC(1) receptor signaling, phosphorylation, desensitization, and sequestration in human embryonic kidney 293 cells. Agonist stimulation of cells overexpressing this receptor led to a dose-dependent increase in cAMP that peaked within 5-10 min and was completely desensitized after 20 min. Cells cotransfected with the VPAC(1) receptor (VPAC(1)R) and G protein-coupled receptor kinases (GRKs) 2, 3, 5, and 6 exhibited enhanced desensitization that was not evident with GRK 4. Immunoprecipitation of the epitope-tagged VPAC(1) receptor revealed dose-dependent phosphorylation that was increased with cotransfection of any GRK. Agonist-stimulated internalization of the VPAC(1)R peaked in 10 min, and neither overexpressed beta-arrestin nor its dominant-negative mutant altered internalization. However, a dynamin-dominant negative mutant did inhibit VPAC(1) receptor internalization. Interestingly, VPAC(1)R specificity in desensitization was not evident by study of the overexpressed receptor; however, we determined that human embryonic kidney 293 cells express an endogenous VPAC(1)R that did demonstrate dose-dependent GRK specificity. Therefore, VPAC(1) receptor regulation involves agonist-stimulated, GRK-mediated phosphorylation, beta-arrestin translocation, and dynamin-dependent receptor internalization. Moreover, study of endogenously expressed receptors may provide information not evident in overexpressed systems.

Arrestins↗