Aging
Abstract
Recent studies have identified the white adipose tissue (WAT) as an important endocrine organ that regulates energy and glucose metabolism via a number of secreted factors. Mice lacking acyl CoA:diacylglycerol acyltransferase 1 (DGAT1), a key enzyme in mammalian triglyceride synthesis, are protected against diet-induced obesity and glucose intolerance because of increased energy expenditure and enhanced insulin sensitivity. Because DGAT1 is highly expressed in WAT, we hypothesized that DGAT1 deficiency affects the expression of adipocyte-derived factors that regulate energy and glucose metabolism. Here we show that the transplantation of DGAT1-deficient WAT decreases adiposity and enhances glucose disposal in wild-type mice. Analysis of DGAT1-deficient WAT revealed a twofold increase in the expression of adiponectin, a molecule that enhances fatty acid oxidation and insulin sensitivity, and this increase may account in part for the transplantation-induced metabolic changes. Our results highlight the importance of the endocrine function of WAT and suggest that an alteration in this function contributes to the increased energy expenditure and insulin sensitivity in DGAT1-deficient mice.
Authors
Hubert C. Chen, Dalan R. Jensen, Heather M. Myers, Robert H. Eckel, Robert V. Farese Jr.
Abstract
Thyroid function depends on processing of the prohormone thyroglobulin by sequential proteolytic events. From in vitro analysis it is known that cysteine proteinases mediate proteolytic processing of thyroglobulin. Here, we have analyzed mice with deficiencies in cathepsins B, K, L, B and K, or K and L in order to investigate which of the cysteine proteinases is most important for proteolytic processing of thyroglobulin in vivo. Immunolabeling demonstrated a rearrangement of the endocytic system and a redistribution of extracellularly located enzymes in thyroids of cathepsin-deficient mice. Cathepsin L was upregulated in thyroids of cathepsin K–/– or B–/–/K–/– mice, suggesting a compensation of cathepsin L for cathepsin K deficiency. Impaired proteolysis resulted in the persistence of thyroglobulin in the thyroids of mice with deficiencies in cathepsin B or L. The typical multilayered appearance of extracellularly stored thyroglobulin was retained in cathepsin K–/– mice only. These results suggest that cathepsins B and L are involved in the solubilization of thyroglobulin from its covalently cross-linked storage form. Cathepsin K–/–/L–/– mice had significantly reduced levels of free thyroxine, indicating that utilization of luminal thyroglobulin for thyroxine liberation is mediated by a combinatory action of cathepsins K and L.
Authors
Bianca Friedrichs, Carmen Tepel, Thomas Reinheckel, Jan Deussing, Kurt von Figura, Volker Herzog, Christoph Peters, Paul Saftig, Klaudia Brix
Abstract
Previous studies established that IL-5–producing CD4+ T cells play a pivotal role in allergic respiratory inflammation. It was also reported that CD4+ T cells express higher levels of CD44 in the airway than in peripheral blood of patients with allergic respiratory diseases. We have used experimental pulmonary eosinophilia induced in mice by Ascaris suum (Asc) extract to investigate the role of CD44 in the development of allergic respiratory inflammation. Intraperitoneal administration of anti-CD44 mAb prevented both lymphocyte and eosinophil accumulation in the lung. Anti-CD44 mAb also blocked antigen-induced elevation of Th2 cytokines as well as chemokines (CCL11, CCL17) in bronchoalveolar lavage fluid (BALF). Treatment with anti-CD44 mAb inhibited the increased levels of hyaluronic acid (HA) and leukotriene concentrations in BALF that typically result from antigen challenge. Anti-CD44 mAb also blocked antigen-induced airway hyperresponsiveness. An anti-CD44 mAb (IM7) inhibited the HA-binding ability of splenocytes associated with decreased levels of CD44. Soluble CD44 levels in serum were increased in Asc-challenged IM7–treated mice, but not in KM201-treated mice, compared with Asc-challenged rat IgG–treated mice. Ab’s that block CD44-HA binding reduced allergic respiratory inflammation by preventing lymphocyte and eosinophil accumulation in the lung. Thus, CD44 may be critical for development of allergic respiratory inflammation.
Authors
Shigeki Katoh, Nobuhiro Matsumoto, Kumiko Kawakita, Akira Tominaga, Paul W. Kincade, Shigeru Matsukura
Abstract
Characteristic of both chronic wounds and acute wounds that fail to heal are excessive leukocytosis and reduced matrix deposition. Estrogen is a major regulator of wound repair that can reverse age-related impaired wound healing in human and animal models, characterized by a dampened inflammatory response and increased matrix deposited at the wound site. Macrophage migration inhibitory factor (MIF) is a candidate proinflammatory cytokine involved in the hormonal regulation of inflammation. We demonstrate that MIF is upregulated in a distinct spatial and temporal pattern during wound healing and its expression is markedly elevated in wounds of estrogen-deficient mice as compared with intact animals. Wound-healing studies in mice rendered null for the MIF gene have demonstrated that in the absence of MIF, the excessive inflammation and delayed-healing phenotype associated with reduced estrogen is reversed. Moreover, in vitro assays have shown a striking estrogen-mediated decrease in MIF production by activated murine macrophages, a process involving the estrogen receptor. We suggest that estrogen inhibits the local inflammatory response by downregulating MIF, suggesting a specific target for future therapeutic intervention in impaired wound-healing states.
Authors
Gillian S. Ashcroft, Stuart J. Mills, KeJian Lei, Linda Gibbons, Moon-Jin Jeong, Marisu Taniguchi, Matthew Burow, Michael A. Horan, Sharon M. Wahl, Toshinori Nakayama
Abstract
Pituitary tumors cause considerable morbidity due to local invasion, hypopituitarism, or hormone hypersecretion. In many cases, no suitable drug therapies are available, and surgical excision is currently the only effective treatment. We show here abundant expression of nuclear hormone receptor PPAR-γ in all of 39 human pituitary tumors. PPAR-γ activating thiazolidinediones (TZDs) rosiglitazone and troglitazone induced G0-G1 cell-cycle arrest and apoptosis in human, rat somatolactotroph, and murine gonadotroph pituitary tumor cells, and suppressed in vitro hormone secretion. In vivo development and growth of murine somatolactotroph and gonadotroph tumors, generated by subcutaneous injection of prolactin-secreting (PRL-secreting) and growth hormone–secreting (GH-secreting) GH3 cells, luteinizing hormone–secreting (LH-secreting) LβT2 cells, and α-T3 cells, was markedly suppressed in rosiglitazone-treated mice, and serum GH, PRL, and LH levels were attenuated in all treated animals (P < 0.009). These results demonstrate that PPAR-γ is an important molecular target in pituitary adenoma cells and PPAR-γ ligands inhibit tumor cell growth and GH, PRL, and LH secretion in vitro and in vivo. TZDs are proposed as novel oral medications for managing pituitary tumors.
Authors
Anthony P. Heaney, Manory Fernando, Shlomo Melmed
Abstract
Studies in rodents have implicated various cytokines as paracrine mediators of increased osteoclastogenesis during estrogen deficiency, but increases in RANKL, the final effector of osteoclastogenesis, have not been demonstrated. Thus, we isolated bone marrow mononuclear cells expressing RANKL on their surfaces by two-color flow cytometry using FITC-conjugated osteoprotegerin-Fc (OPG-Fc-FITC) as a probe. The cells were characterized as preosteoblastic marrow stromal cells (MSCs), T lymphocytes, or B lymphocytes by using Ab’s against bone alkaline phosphatase (BAP), CD3, and CD20, respectively, in 12 premenopausal women (Group A), 12 early postmenopausal women (Group B), and 12 age-matched, estrogen-treated postmenopausal women (Group C). Fluorescence intensity of OPG-Fc-FITC, an index of the surface concentration of RANKL per cell, was increased in Group B over Groups A and C by two- to threefold for MSCs, T cells, B cells, and total RANKL-expressing cells. Moreover, in the merged groups, RANKL expression per cell correlated directly with the bone resorption markers, serum C-terminal telopeptide of type I collagen and urine N-telopeptide of type I collagen, in all three cell types and inversely with serum 17β-estradiol for total RANKL-expressing cells. The data suggest that upregulation of RANKL on bone marrow cells is an important determinant of increased bone resorption induced by estrogen deficiency.
Authors
Guitty Eghbali-Fatourechi, Sundeep Khosla, Arunik Sanyal, William J. Boyle, David L. Lacey, B. Lawrence Riggs
Abstract
The γ-melanocyte-stimulating hormone (γ-MSH) is a natriuretic peptide derived from the N-terminal region of proopiomelanocortin (POMC). Evidence suggests that it may be part of the coordinated response to a low-sodium diet (LSD). We tested the effect of the HSD (8% NaCl) compared with LSD (0.07%) on mean arterial pressure (MAP) in mice with targeted disruption of the PC2 gene (PC2–/–), necessary for processing of POMC into γ-MSH, or the melanocortin receptor 3 gene (Mc3r–/–; the receptor for MSH). In wild-type mice, HSD for 1 week did not alter MAP versus LSD mice, but plasma γ-MSH immunoreactivity was more than double the LSD value. In contrast, in PC2–/– mice, MAP on the LSD was not greater than in wild-type mice, but plasma γ-MSH was reduced to one-seventh the wild-type value. On the HSD, MAP rose to a markedly hypertensive level while plasma γ-MSH concentration remained severely depressed. Intravenous infusion of γ-MSH (0.2 pmol/min) for 30 min to PC2–/– mice after 1 week of HSD lowered MAP from hypertensive levels to normal; infusion of α-MSH at the same rate had no effect. Injection of 60 fmol of γ-MSH into the lateral cerebral ventricle of hypertensive mice also lowered MAP to normal. Administration of a stable analogue of γ-MSH intra-abdominally by microosmotic pump to PC2–/– mice prevented the development of hypertension when ingesting the HSD. In mice with targeted disruption of the Mc3r gene, the HSD also led to marked hypertension accompanied by elevated plasma levels of γ-MSH; infusion of exogenous γ-MSH to these mice had no effect on MAP. These results strongly suggest that PC2-dependent processing of POMC into γ-MSH is necessary for the normal response to the HSD. γ-MSH deficiency results in marked salt-sensitive hypertension that is rapidly improved with exogenous γ-MSH through a central site of action. α-MSH infused at the same rate had no effect on MAP, indicating that the hypertension is a specific consequence of impaired POMC processing into γ-MSH. Absence of Mc3r produces γ-MSH resistance and hypertension on the HSD. These findings demonstrate a novel pathway mediating salt-sensitivity of blood pressure.
Authors
Xi-Ping Ni, David Pearce, Andrew A. Butler, Roger D. Cone, Michael H. Humphreys
Abstract
The dissemination of IgA-dependent immunity between mucosal sites has important implications for mucosal immunoprotection and vaccine development. Epithelial cells in diverse gastrointestinal and nonintestinal mucosal tissues express the chemokine MEC/CCL28. Here we demonstrate that CCR10, a receptor for MEC, is selectively expressed by IgA Ab-secreting cells (large s/cIgA+CD38hiCD19int/–CD20–), including circulating IgA+ plasmablasts and almost all IgA+ plasma cells in the salivary gland, small intestine, large intestine, appendix, and tonsils. Few T cells in any mucosal tissue examined express CCR10. Moreover, tonsil IgA plasmablasts migrate to MEC, consistent with the selectivity of CCR10 expression. In contrast, CCR9, whose ligand TECK/CCL25 is predominantly restricted to the small intestine and thymus, is expressed by a fraction of IgA Ab-secreting cells and almost all T cells in the small intestine, but by only a small percentage of plasma cells and plasmablasts in other sites. These results point to a unifying role for CCR10 and its mucosal epithelial ligand MEC in the migration of circulating IgA plasmablasts and, together with other tissue-specific homing mechanisms, provides a mechanistic basis for the specific dissemination of IgA Ab-secreting cells after local immunization.
Authors
Eric J. Kunkel, Chang H. Kim, Nicole H. Lazarus, Mark A. Vierra, Dulce Soler, Edward P. Bowman, Eugene C. Butcher
Abstract
The rapid and selective accumulation of neutrophils into the lungs is thought to underlie the pulmonary failure that leads to sepsis-related death. In this study we investigated whether neutrophil TLR4 is important in LPS-induced pulmonary neutrophil recruitment by creating chimeric mice (transferring bone marrow between TLR4+/+ and TLR4–/– mice). In TLR4+/+ mice receiving TLR4–/– bone marrow, 6 weeks after transplant TLR4 was absent in all circulating leukocytes as well as in resident macrophages (these mice were termed LeukocyteTLR4–/–), and these cells were completely nonresponsive to LPS. In TLR4–/– mice receiving TLR4+/+ bone marrow, endothelial cells but not leukocytes were deficient in TLR4 (EndotheliumTLR4–/–). Surprisingly, systemic LPS (0.5 mg/kg) induced a dramatic increase in neutrophil sequestration into the lungs of LeukocyteTLR4–/– mice over the first 4 hours. Concomitantly, numbers of circulating leukocytes decreased by 90%. By contrast, EndotheliumTLR4–/– mice showed very little increase in neutrophil sequestration in the lungs, suggesting that endothelium rather than leukocyte TLR4 was important. Intravital microscopy of peripheral microcirculation in the cremaster muscle revealed about 30-fold more leukocyte–endothelial cell interactions in LPS-treated EndotheliumTLR4–/– mice than in LPS-treated LeukocyteTLR4–/– mice. This is consistent with less sequestration of leukocytes into the lungs of EndotheliumTLR4–/– mice. In conclusion, our data challenge the view that LPS directly activates neutrophils to trap in lungs and suggest a far more important role than previously appreciated for the endothelial cells.
Authors
Graciela Andonegui, Claudine S. Bonder, Francis Green, Sarah C. Mullaly, Lori Zbytnuik, Eko Raharjo, Paul Kubes
Abstract
Comparing lymphocyte responses to allergenic and nonallergenic foods could reveal the differences between pathogenic and normal immune responses to foods. Defining the cytokine-producing phenotypes of peanut-specific lymphocytes from peanut-allergic children, children who outgrew peanut allergy, and children who have always tolerated peanuts may be useful for understanding the mechanisms of food tolerance. Investigating immune responses against foods is hindered, however, by the fact that circulating food antigen–specific lymphocytes are very rare. In a novel approach we used carboxyfluorescein succinimidyl ester to detect peanut-specific lymphocytes by flow cytometry. We confirmed that these cells are indeed peanut specific by cloning. Peanut-allergic donors show Th2 polarization of cytokine production by peanut-specific cells (IFN-γ low, TNF-α low, IL-4 high, IL-5 high, IL-13 high). Conversely, nonallergic children and children who have outgrown their allergy show Th1 skewing to peanut antigens (IFN-γhigh, TNF-α high, IL-4 low, IL-5 low, IL-13low), similarly to nonallergenic food antigens (β-lactoglobulin, OVA). This finding suggests that peanut antigens do not intrinsically induce Th2 skewing, but that the type of response depends upon the donor’s allergic status. In conclusion, food allergic status is characterized by a Th2 response whereas Th1-skewed responses underlie oral tolerance.
Authors
Victor Turcanu, Soheila J. Maleki, Gideon Lack
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ISSN: 0021-9738 (print), 1558-8238 (online)