Biomedical subjects

Elizabeth Galbreath

Publications and source records attributed to Elizabeth Galbreath.

7 recordsLinked to original sources

PubMed2006

Death receptor-6 regulates the development of pulmonary eosinophilia and airway inflammation in a mouse model of asthma.

Death receptor-6 (DR6), a member of the death domain-containing TNFR superfamily, is highly expressed in lymphoid tissues and regulated upon lymphocyte activation. Targeted disruption of DR6 results in enhanced CD4(+) T cell proliferation and T helper 2 (Th2) differentiation in vitro, whereas the in vivo role of DR6 in regulating Th2 cell differentiation and effector function remains largely unknown. In the current study, we used a Th2-skewed allergic airway inflammation model induced by ovalbumin (OVA) sensitization and challenge to compare the inflammatory response in the lung of both wild type (WT) and DR6(-/-) mice. DR6(-/-) mice were protected from the development of airway inflammation as evidenced by attenuated eosinophil accumulation and reduced mucus-producing cells in the lining airways of allergen-challenged animals. Consistent with these observations, a profound reduction of Th2 cytokine production (IL-5 and IL-13) was detected in the bronchoalveolar lavage fluid (BAL). Furthermore, a significant increase in the frequency of IFN-gamma secreting cells was observed in the DR6(-/-) mouse lungs after OVA challenge, which may account for the reduced pulmonary Th2 cytokine production. These data point to a critical role of DR6 in regulating airway inflammation in the OVA-induced mouse model of asthma.

Animals↗

PubMed2004

5-Hydroxytryptamine1B receptor-mediated contraction of rabbit saphenous vein and basilar artery: role of vascular endothelium.

This study characterizes the sumatriptan-sensitive [5-hydroxytryptamine (5-HT)(1B/1D)] receptor in rabbit saphenous vein and basilar artery. (S)-(-)-1-[2-[4-(4-Methoxy-phenyl)-piperazin-1-yl]-ethyl]isochroman-6-carboxylic acid methylamide (PNU-109291), a 5-HT(1D) subtype-selective agonist (human K(i) = 2.5 +/- 0.07 nM), did not contract either tissue, whereas o-methoxyphenylpiperazide derivative 4F (MPPA-4F), a 5-HT(1B) subtype-selective antagonist (human K(i) = 4.6 +/- 0.6 nM) potently inhibited sumatriptan-induced contraction in the saphenous vein and basilar artery. These results suggested that sumatriptan-induced contraction was mediated via the 5-HT(1B) receptor in these blood vessels. 5-HT(1B) receptor-mediated contraction was then compared in endothelium-intact and denuded vessels to evaluate the role of the endothelium in regulating sumatriptan-induced contractility in these tissues. The presence of an intact endothelium inhibited 5-HT(1B)-induced contraction in both tissues. Endothelial denudation or nitric-oxide synthase inhibition with N(omega) nitro-L-arginine methyl ester (L-NAME) (100 microM) increased the efficacy and potency of sumatriptan in the saphenous vein and basilar artery. Surprisingly, in endothelial-denuded vascular tissues, L-NAME (100 microM) also significantly increased the maximal 5-HT(1B) receptor-induced contraction in both tissues, with no effect on potency of sumatriptan. The effect of L-NAME after endothelial denudation may reflect the presence of a low density of residual endothelial cells as estimated by CD31 antibody staining combined with the modulating effect of nitric oxide released from nonendothelial cells in vascular tissue. Endothelial modulation was specific to 5-HT(1B) receptors because removal of the endothelium did not significantly alter contraction to norepinephrine, histamine, prostaglandin, or potassium chloride in the saphenous vein or basilar artery.

Animals↗

PubMed2003

LY317615 decreases plasma VEGF levels in human tumor xenograft-bearing mice.

Angiogenesis plays an important role in tumor growth. Angiogenic growth factors may be useful as biomarkers of antiangiogenic activity since their plasma concentrations correlate with the efficacy of treatments directed toward angiogenic targets. SW2 small-cell lung carcinoma (SCLC), Caki-1 renal cell carcinoma and HCT-116 colon carcinoma tumors produce measurable plasma VEGF, bFGF and TGFbeta in nude mice. Mice bearing these human tumor xenografts were treated orally twice daily with the PKCbeta inhibitor, LY317615 (days 14-30 for SW2 and HCT116, and days 21-39 for Caki-1). Plasma was collected every 3 days from control and treated mice. LY317615 significantly decreased plasma VEGF levels in mice bearing SW2 SCLC and Caki-1 renal cell carcinoma compared to control plasma concentrations beginning 5-7 days after initiating therapy. VEGF plasma levels remained suppressed after termination of LY317615 treatment and for the duration of the study (an additional 2 to 3 weeks). Plasma VEGF levels in mice bearing HCT116 xenografts were not altered by LY317615 treatment and plasma bFGF and TGF-beta were not altered by LY317615 in any of the animals. As shown by CD31 immunohistochemical staining, LY317615 decreased intratumoral vessel density by nearly 40% in all three tumors. Only the Caki-1 tumor responded to single-agent LY317615 therapy with a measurable tumor growth delay. Thus, unexpectedly inhibition of PKCbeta in vivo led to decreased VEGF production that persisted after therapy as well as to decreased intratumoral vessels. Plasma VEGF was a weak marker of response to LY317615, and plasma bFGF and TGFbeta were not markers of LY317615 activity.

Angiogenesis Inhibitors↗

PubMed2003

LIGHT-deficiency impairs CD8+ T cell expansion, but not effector function.

LIGHT, a newly identified member of the tumor necrosis factor (TNF) family, is expressed on activated T lymphocytes. To evaluate how LIGHT contributes to T cell functions, we generated LIGHT-deficient (LIGHT(-/-)) mice using gene targeting. Disruption of LIGHT significantly reduced CD8(+) T cell-cycle progression, leading to reduced proliferation to anti-CD3, anti-CD3/anti-CD28 or allogeneic stimulation, whereas proliferation of CD4(+) T cells remained unchanged. In contrast to the observed proliferative defects, isolated CD8(+) T cells from LIGHT(-/-) mice displayed normal cytotoxic effector function development when compared to wild-type CD8(+) T cells. Underlying a potential mechanism of reduced CD8(+) T cell proliferation, LIGHT(-/-) CD8(+) T cells displayed reduced surface levels of CD25 and a diminished ability to proliferate in response to exogenous IL-2. Furthermore, addition of IL-12 to LIGHT(-/-) CD8(+) T cell cultures could not ameliorate this proliferative defect. These results reveal a potential mechanism of action for LIGHT as a positive regulator of CD8(+) T cell expansion, but not lytic effector function development.

Animals↗

PubMed2002

Accelerated onset and increased severity of acute graft-versus-host disease following adoptive transfer of DR6-deficient T cells.

DR6 is a recently identified member of the TNFR family. In a previous study, we have shown that DR6 KO mice have enhanced CD4(+) T cell proliferation and Th2 cytokine production. Acute graft-vs-host disease (GVHD) results from the activation and expansion of alloreactive donor T cells following bone marrow transplantation. In this article, we demonstrate that the transfer of donor T cells from DR6 KO mice into allogeneic recipient mice in a parent into an F(1) model of acute GVHD results in a more rapid onset of GVHD with increased severity. Recipients of DR6 KO T cells exhibit earlier systemic symptoms of GVHD, more rapid weight loss, earlier histopathological organ damage in the thymus, spleen, and intestines, and earlier mortality. The rapid onset of GVHD in these mice may be attributable to the enhanced activation and expansion of DR6 KO CD4(+) and CD8(+) T cells. Our findings support the hypothesis that DR6 serves as an important regulatory molecule in T cell immune responses. The identification and use of DR6 ligands and/or agonistic Abs to DR6 may represent useful therapeutics in the treatment of T cell-mediated diseases such as GVHD.

Acute Disease↗

PubMed2002

Vasoactive intestinal polypeptide/pituitary adenylate cyclase-activating peptide receptor 2 deficiency in mice results in growth retardation and increased basal metabolic rate.

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are two closely related peptides that bind two homologous G protein-coupled receptors, VIP/PACAP receptor 1 (VPAC1R) and VIP/PACAP receptor II (VPAC2R), with equally high affinity. Recent reports suggest that VPAC2R plays a role in circadian rhythm and T cell functions. To further elucidate the functional activities of VPAC2R, we generated VPAC2R-deficient mice by deleting exons VIII-X of the VPAC2R gene. The VPAC2R-deficient mice showed retarded growth and had reduced serum IGF-I levels compared with gender-matched, wild-type siblings. The mutant mice appeared healthy and fertile at a young adult age. However, older male mutant mice exhibited diffuse seminiferous tubular degeneration with hypospermia and reduced fertility rate. The mutant mice appeared to have an increase in insulin sensitivity. VPAC2R-deficient mice had increased lean mass and decreased fat mass with reduced serum leptin levels. Indirect calorimetry experiments showed that the respiratory quotient values immediately following the transition into the dark cycle were significantly higher in male knockout mice for about 4 h. Additionally, male and female VPAC2R-deficient mice presented an increased basal metabolic rate (23% and 10%, respectively) compared with their wild-type siblings. Our results suggest that VPAC2R plays an important role in growth, basal energy expenditure, and male reproductive functions.

Amino Acid Sequence↗

PubMedDate not supplied

Use of genetically engineered mice in drug discovery and development: wielding Occam's razor to prune the product portfolio.

Genetically engineered mice (GEMs) that either overexpress (transgenic) or lack (gene-targeted, or "knock-out") genes are used increasingly in industry to investigate molecular mechanisms of disease, to evaluate innovative therapeutic targets, and to screen agents for efficacy and/or toxicity. High throughput GEM construction in drug discovery and development (DDD) serves two main purposes: to test whether a given gene participates in a disease condition, or to determine the function(s) of a protein that is encoded by an expressed sequence tag (EST, an mRNA fragment for a previously uncharacterized protein). In some instances, phenotypes induced by such novel GEMs also may yield clues regarding potential target organs and toxic effects of potential therapeutic molecules. The battery of tests used in phenotypic analysis of GEMs varies between companies, but the goal is to define one or more easily measured endpoints that can be used to monitor the disease course--especially during in vivo treatment with novel drug candidates. In many DDD projects, overt phenotypes are subtle or absent even in GEMs in which high-level expression or total ablation of an engineered gene can be confirmed. This outcome presents a major quandary for biotechnology and pharmaceutical firms: given the significant expense and labor required to generate GEMs, what should be done with "negative" constructs? The 14th century philosophical principle known as Occam's razor-that the simplest explanation for a phenomenon is likely the truth-provides a reasonable basis for pruning potential therapeutic molecules and targets. In the context of DDD, Occam's razor may be construed to mean that correctly engineered GEMs lacking obvious functional or structural phenotypes have none because the affected gene is not uniquely essential to normal homeostasis or disease progression. Thus, a "negative" GEM construct suggests that the gene under investigation encodes a ligand or target molecule without significant therapeutic potential. This interpretation indicates that, at least in a market-driven industrial setting, such "negative" projects should be pruned aggressively so that resources may be redirected to more promising DDD ventures.

Animals↗