Abstract
In mammals, GPIHBP1 is absolutely essential for transporting lipoprotein lipase (LPL) to the lumen of capillaries, where it hydrolyzes the triglycerides in triglyceride-rich lipoproteins. In all lower vertebrate species (e.g., birds, amphibians, reptiles, fish), a gene for LPL can be found easily, but a gene for GPIHBP1 has never been found. The obvious question is whether the LPL in lower vertebrates is able to reach the capillary lumen. Using purified antibodies against chicken LPL, we showed that LPL is present on capillary endothelial cells of chicken heart and adipose tissue, colocalizing with von Willebrand factor. When the antibodies against chicken LPL were injected intravenously into chickens, they bound to LPL on the luminal surface of capillaries in heart and adipose tissue. LPL was released rapidly from chicken hearts with an infusion of heparin, consistent with LPL being located inside blood vessels. Remarkably, chicken LPL bound in a specific fashion to mammalian GPIHBP1. However, we could not identify a gene for GPIHBP1 in the chicken genome, nor could we identify a transcript for GPIHBP1 in a large chicken RNA-seq data set. We conclude that LPL reaches the capillary lumen in chickens — as it does in mammals — despite an apparent absence of GPIHBP1.
Authors
Cuiwen He, Xuchen Hu, Rachel S. Jung, Mikael Larsson, Yiping Tu, Sandra Duarte-Vogel, Paul Kim, Norma P. Sandoval, Tara R. Price, Christopher M. Allan, Brian Raney, Haibo Jiang, André Bensadoun, Rosemary L. Walzem, Richard I. Kuo, Anne P. Beigneux, Loren G. Fong, Stephen G. Young
Abstract
Birth defects are the leading cause of infant mortality, and they are caused by a combination of genetic and environmental factors. Environmental risk factors may contribute to birth defects in genetically susceptible infants by altering critical molecular pathways during embryogenesis, but experimental evidence for gene-environment interactions is limited. Fetal hyperglycemia associated with maternal diabetes results in a 5-fold increased risk of congenital heart disease (CHD), but the molecular basis for this correlation is unknown. Here, we show that the effects of maternal hyperglycemia on cardiac development are sensitized by haploinsufficiency of Notch1, a key transcriptional regulator known to cause CHD. Using ATAC-seq, we found that hyperglycemia decreased chromatin accessibility at the endothelial NO synthase (Nos3) locus, resulting in reduced NO synthesis. Transcription of Jarid2, a regulator of histone methyltransferase complexes, was increased in response to reduced NO, and this upregulation directly resulted in inhibition of Notch1 expression to levels below a threshold necessary for normal heart development. We extended these findings using a Drosophila maternal diabetic model that revealed the evolutionary conservation of this interaction and the Jarid2-mediated mechanism. These findings identify a gene-environment interaction between maternal hyperglycemia and Notch signaling and support a model in which environmental factors cause birth defects in genetically susceptible infants.
Authors
Madhumita Basu, Jun-Yi Zhu, Stephanie LaHaye, Uddalak Majumdar, Kai Jiao, Zhe Han, Vidu Garg
Abstract
Biological aging is associated with immune activation (IA) and declining immunity due to systemic inflammation. It is widely accepted that HIV infection causes persistent IA and premature immune senescence despite effective antiretroviral therapy and virologic suppression; however, the effects of combined HIV infection and aging are not well defined. Here, we assessed the relationship between markers of IA and inflammation during biological aging in HIV-infected and -uninfected populations. Antibody response to seasonal influenza vaccination was implemented as a measure of immune competence and relationships between IA, inflammation, and antibody responses were explored using statistical modeling appropriate for integrating high-dimensional data sets. Our results show that markers of IA, such as coexpression of HLA antigen D related (HLA-DR) and CD38 on CD4+ T cells, exhibit strong associations with HIV infection but not with biological age. Certain variables that showed a strong relationship with aging, such as declining naive and CD38+ CD4 and CD8+ T cells, did so regardless of HIV infection. Interestingly, the variable of biological age was not identified in a predictive model as significantly impacting vaccine responses in either group, while distinct IA and inflammatory variables were closely associated with vaccine response in HIV-infected and -uninfected populations. These findings shed light on the most relevant and persistent immune defects during virological suppression with antiretroviral therapy.
Authors
Lesley R. de Armas, Suresh Pallikkuth, Varghese George, Stefano Rinaldi, Rajendra Pahwa, Kristopher L. Arheart, Savita Pahwa
Abstract
In rodent models, obesity and hyperglycemia alter cerebral glucose metabolism and glucose transport into the brain, resulting in disordered cerebral function as well as inappropriate responses to homeostatic and hedonic inputs. Whether similar findings are seen in the human brain remains unclear. In this study, 25 participants (9 healthy participants; 10 obese nondiabetic participants; and 6 poorly controlled, insulin- and metformin-treated type 2 diabetes mellitus (T2DM) participants) underwent 1H magnetic resonance spectroscopy scanning in the occipital lobe to measure the change in intracerebral glucose levels during a 2-hour hyperglycemic clamp (glucose ~220 mg/dl). The change in intracerebral glucose was significantly different across groups after controlling for age and sex, despite similar plasma glucose levels at baseline and during hyperglycemia. Compared with lean participants, brain glucose increments were lower in participants with obesity and T2DM. Furthermore, the change in brain glucose correlated inversely with plasma free fatty acid (FFA) levels during hyperglycemia. These data suggest that obesity and poorly controlled T2DM progressively diminish brain glucose responses to hyperglycemia, which has important implications for understanding not only the altered feeding behavior, but also the adverse neurocognitive consequences associated with obesity and T2DM.
Authors
Janice J. Hwang, Lihong Jiang, Muhammad Hamza, Elizabeth Sanchez Rangel, Feng Dai, Renata Belfort-DeAguiar, Lisa Parikh, Brian B. Koo, Douglas L. Rothman, Graeme Mason, Robert S. Sherwin
Abstract
Genetic defects in the synaptic scaffolding protein gene, SHANK2, are linked to a variety of neuropsychiatric disorders, including autism spectrum disorders, schizophrenia, intellectual disability, and bipolar disorder, but the molecular mechanisms underlying the pleotropic effects of SHANK2 mutations are poorly understood. We generated and characterized a line of Shank2 mutant mice by deleting exon 24 (Δe24). Shank2Δe24–/– mice engage in significantly increased locomotor activity, display abnormal reward-seeking behavior, are anhedonic, have perturbations in circadian rhythms, and show deficits in social and cognitive behaviors. While these phenotypes recapitulate the pleotropic behaviors associated with human SHANK2-related disorders, major behavioral features in these mice are reminiscent of bipolar disorder. For instance, their hyperactivity was augmented with amphetamine but was normalized with the mood stabilizers lithium and valproate. Shank2 deficiency limited to the forebrain recapitulated the bipolar mania phenotype. The composition and functions of NMDA and AMPA receptors were altered at Shank2-deficient synapses, hinting toward the mechanism underlying these behavioral abnormalities. Human genetic findings support construct validity, and the behavioral features in Shank2 Δe24 mice support face and predictive validities of this model for bipolar mania. Further genetic studies to understand the contribution of SHANK2 deficiencies in bipolar disorder are warranted.
Authors
Andrea L. Pappas, Alexandra L. Bey, Xiaoming Wang, Mark Rossi, Yong Ho Kim, Haidun Yan, Fiona Porkka, Lara J. Duffney, Samantha M. Phillips, Xinyu Cao, Jin-dong Ding, Ramona M. Rodriguiz, Henry H. Yin, Richard J. Weinberg, Ru-Rong Ji, William C. Wetsel, Yong-hui Jiang
Abstract
Cellular therapies based on permanent genetic modification of conventional T cells have emerged as a promising strategy for cancer. However, it remains unknown if modification of T cell subsets, such as Tregs, could be useful in other settings, such as allograft transplantation. Here, we use a modular system based on a chimeric antigen receptor (CAR) that binds covalently modified mAbs to control Treg activation in vivo. Transient expression of this mAb-directed CAR (mAbCAR) in Tregs permitted Treg targeting to specific tissue sites and mitigated allograft responses, such as graft-versus-host disease. mAbCAR Tregs targeted to MHC class I proteins on allografts prolonged islet allograft survival and also prolonged the survival of secondary skin grafts specifically matched to the original islet allograft. Thus, transient genetic modification to produce mAbCAR T cells led to durable immune modulation, suggesting therapeutic targeting strategies for controlling alloreactivity in settings such as organ or tissue transplantation.
Authors
Antonio Pierini, Bettina P. Iliopoulou, Heshan Peiris, Magdiel Pérez-Cruz, Jeanette Baker, Katie Hsu, Xueying Gu, Ping-Ping Zheng, Tom Erkers, Sai-Wen Tang, William Strober, Maite Alvarez, Aaron Ring, Andrea Velardi, Robert S. Negrin, Seung K. Kim, Everett H. Meyer
Abstract
Sickle cell disease (SCD) results from a point mutation in the β-globin gene forming hemoglobin S (HbS), which polymerizes in deoxygenated erythrocytes, triggering recurrent painful vaso-occlusive crises and chronic hemolytic anemia. Reactivation of fetal Hb (HbF) expression ameliorates these symptoms of SCD. Nuclear factor (erythroid derived-2)–like 2 (Nrf2) is a transcription factor that triggers cytoprotective and antioxidant pathways to limit oxidative damage and inflammation and increases HbF synthesis in CD34+ stem cell–derived erythroid progenitors. We investigated the ability of dimethyl fumarate (DMF), a small-molecule Nrf2 agonist, to activate γ-globin transcription and enhance HbF in tissue culture and in murine and primate models. DMF recruited Nrf2 to the γ-globin promoters and the locus control region of the β-globin locus in erythroleukemia cells, elevated HbF in SCD donor–derived erythroid progenitors, and reduced hypoxia-induced sickling. Chronic DMF administration in SCD mice induced HbF and increased Nrf2-dependent genes to detoxify heme and limit inflammation. This improved hematological parameters, reduced plasma-free Hb, and attenuated inflammatory markers. Chronic DMF administration to nonanemic primates increased γ-globin mRNA in BM and HbF protein in rbc. DMF represents a potential therapy for SCD to induce HbF and augment vasoprotection and heme detoxification.
Authors
Sriram Krishnamoorthy, Betty Pace, Dipti Gupta, Sarah Sturtevant, Biaoru Li, Levi Makala, Julia Brittain, Nancy Moore, Benjamin F. Vieira, Timothy Thullen, Ivan Stone, Huo Li, William E. Hobbs, David R. Light
Abstract
Eosinophilic esophagitis (EoE) is an allergic inflammatory disease of the esophagus mediated by an IL-13–driven epithelial cell transcriptional program. Herein, we show that the cytoskeletal protein synaptopodin (SYNPO), previously associated with podocytes, is constitutively expressed in esophageal epithelium and induced during allergic inflammation. In addition, we show that the SYNPO gene is transcriptionally and epigenetically regulated by IL-13 in esophageal epithelial cells. SYNPO was expressed in the basal layer of homeostatic esophageal epithelium, colocalized with actin filaments, and expanded into the suprabasal epithelium in EoE patients, where expression was elevated 25-fold compared with control individuals. The expression level of SYNPO in esophageal biopsies correlated with esophageal eosinophil density and was improved following anti–IL-13 treatment in EoE patients. In esophageal epithelial cells, SYNPO gene silencing reduced epithelial motility in a wound healing model, whereas SYNPO overexpression impaired epithelial barrier integrity and reduced esophageal differentiation. Taken together, we demonstrate that SYNPO is induced by IL-13 in vitro and in vivo, is a nonredundant regulator of epithelial cell barrier function and motility, and is likely involved in EoE pathogenesis.
Authors
Mark Rochman, Jared Travers, J. Pablo Abonia, Julie M. Caldwell, Marc E. Rothenberg
Abstract
Fibrous cap smooth muscle cells (SMCs) protect atherosclerotic lesions from rupturing and causing thrombosis, while other plaque SMCs may have detrimental roles in plaque development. To gain insight into recruitment of different plaque SMCs, we mapped their clonal architecture in aggregation chimeras of eGFP+Apoe–/– and Apoe–/– mouse embryos and in mice with a mosaic expression of fluorescent proteins in medial SMCs that were rendered atherosclerotic by PCSK9-induced hypercholesterolemia. Fibrous caps in aggregation chimeras were found constructed from large, endothelial-aligned layers of either eGFP+ or nonfluorescent SMCs, indicating substantial clonal expansion of a few cells. Similarly, plaques in mice with SMC-restricted Confetti expression showed oligoclonal SMC populations with little intermixing between the progeny of different medial SMCs. Phenotypes comprised both ACTA2+ SMCs in the cap and heterogeneous ACTA2– SMCs in the plaque interior, including chondrocyte-like cells and cells with intracellular lipid and crystalline material. Fibrous cap SMCs were invariably arranged in endothelium-aligned clonal sheets, confirming results in the aggregation chimeras. Analysis of the clonal structure showed that a low number of local medial SMCs partake in atherosclerosis and that single medial SMCs can produce several different SMC phenotypes in plaque. The combined results show that few medial SMCs proliferate to form the entire phenotypically heterogeneous plaque SMC population in murine atherosclerosis.
Authors
Kevin Jacobsen, Marie Bek Lund, Jeong Shim, Stine Gunnersen, Ernst-Martin Füchtbauer, Mads Kjolby, Laura Carramolino, Jacob Fog Bentzon
Abstract
The monocyte lineage is essential to normal wound healing. Macrophage inhibition or knockout in mice results in impaired wound healing through reduced neovascularization, granulation tissue formation, and reepithelialization. Numerous studies have either depleted macrophages or reduced their activity in the context of wound healing. Here, we demonstrate that by increasing the number of macrophages or monocytes in the wound site above physiologic levels via pullulan-collagen composite dermal hydrogel scaffold delivery, the rate of wound healing can be significantly accelerated in both wild-type and diabetic mice, with no adverse effect on the quality of repair. Macrophages transplanted onto wounds differentiate into M1 and M2 phenotypes of different proportions at various time points, ultimately increasing angiogenesis. Given that monocytes can be readily isolated from peripheral blood without in vitro manipulation, these findings hold promise for translational medicine aimed at accelerating wound healing across a broad spectrum of diseases.
Authors
Michael S. Hu, Graham G. Walmsley, Leandra A. Barnes, Kipp Weiskopf, Robert C. Rennert, Dominik Duscher, Michael Januszyk, Zeshaan N. Maan, Wan Xing Hong, Alexander T.M. Cheung, Tripp Leavitt, Clement D. Marshall, Ryan C. Ransom, Samir Malhotra, Alessandra L. Moore, Jayakumar Rajadas, H. Peter Lorenz, Irving L. Weissman, Geoffrey C. Gurtner, Michael T. Longaker
No posts were found with this tag.
