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A Phenome-Wide Association Study Uncovers a Pathological Role of Coagulation Factor X during Infection.
Choby JE, Monteith AJ, Himmel LE, Margaritis P, Shirey-Rice JK, Pruijssers A, Jerome RN, Pulley J, Skaar EP
(2019) Infect Immun 87:
MeSH Terms: Acinetobacter Infections, Acinetobacter baumannii, Animals, Disease Models, Animal, Factor X, Host-Pathogen Interactions, Humans, Mice, Mice, Inbred C57BL, Phenotype, Polymorphism, Genetic
Show Abstract · Added April 7, 2019
Coagulation and inflammation are interconnected, suggesting that coagulation plays a key role in the inflammatory response to pathogens. A phenome-wide association study (PheWAS) was used to identify clinical phenotypes of patients with a polymorphism in coagulation factor X. Patients with this single nucleotide polymorphism (SNP) were more likely to be hospitalized with hemostatic and infection-related disorders, suggesting that factor X contributes to the immune response to infection. To investigate this, we modeled infections by human pathogens in a mouse model of factor X deficiency. Factor X-deficient mice were protected from systemic infection, suggesting that factor X plays a role in the immune response to Factor X deficiency was associated with reduced cytokine and chemokine production and alterations in immune cell population during infection: factor X-deficient mice demonstrated increased abundance of neutrophils, macrophages, and effector T cells. Together, these results suggest that factor X activity is associated with an inefficient immune response and contributes to the pathology of infection.
Copyright © 2019 American Society for Microbiology.
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11 MeSH Terms
Structural basis of a potent human monoclonal antibody against Zika virus targeting a quaternary epitope.
Long F, Doyle M, Fernandez E, Miller AS, Klose T, Sevvana M, Bryan A, Davidson E, Doranz BJ, Kuhn RJ, Diamond MS, Crowe JE, Rossmann MG
(2019) Proc Natl Acad Sci U S A 116: 1591-1596
MeSH Terms: Animals, Antibodies, Monoclonal, Antibodies, Neutralizing, Antibodies, Viral, Cryoelectron Microscopy, Disease Models, Animal, Epitopes, Humans, Male, Mice, Mice, Inbred C57BL, Vaccination, Viral Envelope Proteins, Zika Virus, Zika Virus Infection
Show Abstract · Added March 31, 2019
Zika virus (ZIKV) is a major human pathogen and member of the genus in the Flaviviridae family. In contrast to most other insect-transmitted flaviviruses, ZIKV also can be transmitted sexually and from mother to fetus in humans. During recent outbreaks, ZIKV infections have been linked to microcephaly, congenital disease, and Guillain-Barré syndrome. Neutralizing antibodies have potential as therapeutic agents. We report here a 4-Å-resolution cryo-electron microscopy structure of the ZIKV virion in complex with Fab fragments of the potently neutralizing human monoclonal antibody ZIKV-195. The footprint of the ZIKV-195 Fab fragment expands across two adjacent envelope (E) protein protomers. ZIKV neutralization by this antibody is presumably accomplished by cross-linking the E proteins, which likely prevents formation of E protein trimers required for fusion of the viral and cellular membranes. A single dose of ZIKV-195 administered 5 days after virus inoculation showed marked protection against lethality in a stringent mouse model of infection.
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Heme sensing and detoxification by HatRT contributes to pathogenesis during Clostridium difficile infection.
Knippel RJ, Zackular JP, Moore JL, Celis AI, Weiss A, Washington MK, DuBois JL, Caprioli RM, Skaar EP
(2018) PLoS Pathog 14: e1007486
MeSH Terms: Animals, Bacterial Proteins, Clostridium Infections, Clostridium difficile, Genes, Bacterial, Heme, Male, Mice, Mice, Inbred C57BL, Operon, Virulence
Show Abstract · Added April 7, 2019
Clostridium difficile is a Gram-positive, spore-forming anaerobic bacterium that infects the colon, causing symptoms ranging from infectious diarrhea to fulminant colitis. In the last decade, the number of C. difficile infections has dramatically risen, making it the leading cause of reported hospital acquired infection in the United States. Bacterial toxins produced during C. difficile infection (CDI) damage host epithelial cells, releasing erythrocytes and heme into the gastrointestinal lumen. The reactive nature of heme can lead to toxicity through membrane disruption, membrane protein and lipid oxidation, and DNA damage. Here we demonstrate that C. difficile detoxifies excess heme to achieve full virulence within the gastrointestinal lumen during infection, and that this detoxification occurs through the heme-responsive expression of the heme activated transporter system (HatRT). Heme-dependent transcriptional activation of hatRT was discovered through an RNA-sequencing analysis of C. difficile grown in the presence of a sub-toxic concentration of heme. HatRT is comprised of a TetR family transcriptional regulator (hatR) and a major facilitator superfamily transporter (hatT). Strains inactivated for hatR or hatT are more sensitive to heme toxicity than wild-type. HatR binds heme, which relieves the repression of the hatRT operon, whereas HatT functions as a heme efflux pump. In a murine model of CDI, a strain inactivated for hatT displayed lower pathogenicity in a toxin-independent manner. Taken together, these data suggest that HatR senses intracellular heme concentrations leading to increased expression of the hatRT operon and subsequent heme efflux by HatT during infection. These results describe a mechanism employed by C. difficile to relieve heme toxicity within the host, and set the stage for the development of therapeutic interventions to target this bacterial-specific system.
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SIRT2 knockout exacerbates insulin resistance in high fat-fed mice.
Lantier L, Williams AS, Hughey CC, Bracy DP, James FD, Ansari MA, Gius D, Wasserman DH
(2018) PLoS One 13: e0208634
MeSH Terms: Acetylation, Animals, Diet, High-Fat, Energy Metabolism, Insulin, Insulin Resistance, Liver, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Mitochondria, Muscle, Skeletal, Phosphorylation, Proto-Oncogene Proteins c-akt, Sirtuin 2
Show Abstract · Added January 8, 2019
The NAD+-dependent deacetylase SIRT2 is unique amongst sirtuins as it is effective in the cytosol, as well as the mitochondria. Defining the role of cytosolic acetylation state in specific tissues is difficult since even physiological effects at the whole body level are unknown. We hypothesized that genetic SIRT2 knockout (KO) would lead to impaired insulin action, and that this impairment would be worsened in HF fed mice. Insulin sensitivity was tested using the hyperinsulinemic-euglycemic clamp in SIRT2 KO mice and WT littermates. SIRT2 KO mice exhibited reduced skeletal muscle insulin-induced glucose uptake compared to lean WT mice, and this impairment was exacerbated in HF SIRT2 KO mice. Liver insulin sensitivity was unaffected in lean SIRT2 KO mice. However, the insulin resistance that accompanies HF-feeding was worsened in SIRT2 KO mice. It was notable that the effects of SIRT2 KO were largely disassociated from cytosolic acetylation state, but were closely linked to acetylation state in the mitochondria. SIRT2 KO led to an increase in body weight that was due to increased food intake in HF fed mice. In summary, SIRT2 deletion in vivo reduces muscle insulin sensitivity and contributes to liver insulin resistance by a mechanism that is unrelated to cytosolic acetylation state. Mitochondrial acetylation state and changes in feeding behavior that result in increased body weight correspond to the deleterious effects of SIRT2 KO on insulin action.
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16 MeSH Terms
Obesity-induced reduction of adipose eosinophils is reversed with low-calorie dietary intervention.
Bolus WR, Kennedy AJ, Hasty AH
(2018) Physiol Rep 6: e13919
MeSH Terms: Adipose Tissue, Animals, Caloric Restriction, Cells, Cultured, Eosinophils, Male, Mice, Mice, Inbred C57BL, Obesity, Weight Loss
Show Abstract · Added March 26, 2019
While many studies have characterized the inflammatory disposition of adipose tissue (AT) during obesity, far fewer have dissected how such inflammation resolves during the process of physiological weight loss. In addition, new immune cells, such as the eosinophil, have been discovered as part of the AT immune cell repertoire. We have therefore characterized how AT eosinophils, associated eosinophilic inflammation, and remodeling processes, fluctuate during a dietary intervention in obese mice. Similar to previous reports, we found that obesity induced by high-fat diet feeding reduced the AT eosinophil content. However, upon switching obese mice to a low fat diet, AT eosinophils were restored to lean levels as mice reached the body weight of controls. The rise in AT eosinophils during dietary weight loss was accompanied by reduced macrophage content and inflammatory expression, upregulated tissue remodeling factors, and a more uniformly distributed AT vascular network. Additionally, we show that eosinophils of another metabolically relevant tissue, the liver, did not oscillate with either dietary weight gain or weight loss. This study shows that eosinophil content is differentially regulated among tissues during the onset and resolution of obesity. Furthermore, AT eosinophils correlated with AT remodeling processes during weight loss and thus may play a role in reestablishing AT homeostasis.
© 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
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10 MeSH Terms
A protective human monoclonal antibody targeting the West Nile virus E protein preferentially recognizes mature virions.
Goo L, Debbink K, Kose N, Sapparapu G, Doyle MP, Wessel AW, Richner JM, Burgomaster KE, Larman BC, Dowd KA, Diamond MS, Crowe JE, Pierson TC
(2019) Nat Microbiol 4: 71-77
MeSH Terms: Aedes, Animals, Antibodies, Monoclonal, Antibodies, Neutralizing, Antibodies, Viral, Cell Line, Cercopithecus aethiops, HEK293 Cells, Humans, Male, Mice, Mice, Inbred C57BL, Protein Domains, Vero Cells, Viral Envelope Proteins, West Nile Fever, West Nile Virus Vaccines, West Nile virus
Show Abstract · Added March 31, 2019
West Nile virus (WNV), a member of the Flavivirus genus, is a leading cause of viral encephalitis in the United States. The development of neutralizing antibodies against the flavivirus envelope (E) protein is critical for immunity and vaccine protection. Previously identified candidate therapeutic mouse and human neutralizing monoclonal antibodies (mAbs) target epitopes within the E domain III lateral ridge and the domain I-II hinge region, respectively. To explore the neutralizing antibody repertoire elicited by WNV infection for potential therapeutic application, we isolated ten mAbs from WNV-infected individuals. mAb WNV-86 neutralized WNV with a 50% inhibitory concentration of 2 ng ml, one of the most potently neutralizing flavivirus-specific antibodies ever isolated. WNV-86 targets an epitope in E domain II, and preferentially recognizes mature virions lacking an uncleaved form of the chaperone protein prM, unlike most flavivirus-specific antibodies. In vitro selection experiments revealed a neutralization escape mechanism involving a glycan addition to E domain II. Finally, a single dose of WNV-86 administered two days post-infection protected mice from lethal WNV challenge. This study identifies a highly potent human neutralizing mAb with therapeutic potential that targets an epitope preferentially displayed on mature virions.
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18 MeSH Terms
Role of Bile Acids and GLP-1 in Mediating the Metabolic Improvements of Bariatric Surgery.
Albaugh VL, Banan B, Antoun J, Xiong Y, Guo Y, Ping J, Alikhan M, Clements BA, Abumrad NN, Flynn CR
(2019) Gastroenterology 156: 1041-1051.e4
MeSH Terms: Anastomosis, Surgical, Animals, Anticholesteremic Agents, Bariatric Surgery, Bile Acids and Salts, Blood Glucose, Cholestyramine Resin, Diet, High-Fat, Gallbladder, Glucagon-Like Peptide 1, Glucagon-Like Peptide-1 Receptor, Glucose Tolerance Test, Ileum, Insulin Resistance, Intestines, Lymph, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Receptors, Cytoplasmic and Nuclear, Receptors, G-Protein-Coupled, Signal Transduction, Verrucomicrobia, Weight Loss
Show Abstract · Added January 4, 2019
BACKGROUND & AIMS - Bile diversion to the ileum (GB-IL) has strikingly similar metabolic and satiating effects to Roux-en-Y gastric bypass (RYGB) in rodent obesity models. The metabolic benefits of these procedures are thought to be mediated by increased bile acids, although parallel changes in body weight and other confounding variables limit this interpretation.
METHODS - Global G protein-coupled bile acid receptor-1 null (Tgr5) and intestinal-specific farnesoid X receptor null (Fxr) mice on high-fat diet as well as wild-type C57BL/6 and glucagon-like polypeptide 1 receptor deficient (Glp-1r) mice on chow diet were characterized following GB-IL.
RESULTS - GB-IL induced weight loss and improved oral glucose tolerance in Tgr5, but not Fxr mice fed a high-fat diet, suggesting a role for intestinal Fxr. GB-IL in wild-type, chow-fed mice prompted weight-independent improvements in glycemia and glucose tolerance secondary to augmented insulin responsiveness. Improvements were concomitant with increased levels of lymphatic GLP-1 in the fasted state and increased levels of intestinal Akkermansia muciniphila. Improvements in fasting glycemia after GB-IL were mitigated with exendin-9, a GLP-1 receptor antagonist, or cholestyramine, a bile acid sequestrant. The glucoregulatory effects of GB-IL were lost in whole-body Glp-1r mice.
CONCLUSIONS - Bile diversion to the ileum improves glucose homeostasis via an intestinal Fxr-Glp-1 axis. Altered intestinal bile acid availability, independent of weight loss, and intestinal Akkermansia muciniphila appear to mediate the metabolic changes observed after bariatric surgery and might be manipulated for treatment of obesity and diabetes.
Copyright © 2019 AGA Institute. Published by Elsevier Inc. All rights reserved.
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Increased Ripk1-mediated bone marrow necroptosis leads to myelodysplasia and bone marrow failure in mice.
Wagner PN, Shi Q, Salisbury-Ruf CT, Zou J, Savona MR, Fedoriw Y, Zinkel SS
(2019) Blood 133: 107-120
MeSH Terms: Animals, BH3 Interacting Domain Death Agonist Protein, Bone Marrow, Bone Marrow Diseases, Cells, Cultured, Cytokines, Hematopoietic Stem Cells, Inflammation, Mice, Mice, Inbred C57BL, Mice, Knockout, Myelodysplastic Syndromes, Necrosis, Receptor-Interacting Protein Serine-Threonine Kinases, bcl-2 Homologous Antagonist-Killer Protein
Show Abstract · Added December 11, 2018
Hematopoiesis is a dynamic system that requires balanced cell division, differentiation, and death. The 2 major modes of programmed cell death, apoptosis and necroptosis, share molecular machinery but diverge in outcome with important implications for the microenvironment; apoptotic cells are removed in an immune silent process, whereas necroptotic cells leak cellular contents that incite inflammation. Given the importance of cytokine-directed cues for hematopoietic cell survival and differentiation, the impact on hematopoietic homeostasis of biasing cell death fate to necroptosis is substantial and poorly understood. Here, we present a mouse model with increased bone marrow necroptosis. Deletion of the proapoptotic Bcl-2 family members Bax and Bak inhibits bone marrow apoptosis. Further deletion of the BH3-only member Bid (to generate triple-knockout [TKO] mice) leads to unrestrained bone marrow necroptosis driven by increased Rip1 kinase (Ripk1). TKO mice display loss of progenitor cells, leading to increased cytokine production and increased stem cell proliferation and exhaustion and culminating in bone marrow failure. Genetically restoring Ripk1 to wild-type levels restores peripheral red cell counts as well as normal cytokine production. TKO bone marrow is hypercellular with abnormal differentiation, resembling the human disorder myelodysplastic syndrome (MDS), and we demonstrate increased necroptosis in MDS bone marrow. Finally, we show that Bid impacts necroptotic signaling through modulation of caspase-8-mediated Ripk1 degradation. Thus, we demonstrate that dysregulated necroptosis in hematopoiesis promotes bone marrow progenitor cell death that incites inflammation, impairs hematopoietic stem cells, and recapitulates the salient features of the bone marrow failure disorder MDS.
© 2019 by The American Society of Hematology.
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15 MeSH Terms
Pancreatic islet-autonomous insulin and smoothened-mediated signalling modulate identity changes of glucagon α-cells.
Cigliola V, Ghila L, Thorel F, van Gurp L, Baronnier D, Oropeza D, Gupta S, Miyatsuka T, Kaneto H, Magnuson MA, Osipovich AB, Sander M, Wright CEV, Thomas MK, Furuyama K, Chera S, Herrera PL
(2018) Nat Cell Biol 20: 1267-1277
MeSH Terms: Animals, Cell Differentiation, Cell Plasticity, Cell Proliferation, Female, Glucagon-Secreting Cells, Insulin, Insulin-Secreting Cells, Islets of Langerhans, Male, Mice, Inbred C57BL, Mice, Knockout, Mice, SCID, Mice, Transgenic, Signal Transduction, Smoothened Receptor
Show Abstract · Added November 6, 2018
The mechanisms that restrict regeneration and maintain cell identity following injury are poorly characterized in higher vertebrates. Following β-cell loss, 1-2% of the glucagon-producing α-cells spontaneously engage in insulin production in mice. Here we explore the mechanisms inhibiting α-cell plasticity. We show that adaptive α-cell identity changes are constrained by intra-islet insulin- and Smoothened-mediated signalling, among others. The combination of β-cell loss or insulin-signalling inhibition, with Smoothened inactivation in α- or δ-cells, stimulates insulin production in more α-cells. These findings suggest that the removal of constitutive 'brake signals' is crucial to neutralize the refractoriness to adaptive cell-fate changes. It appears that the maintenance of cell identity is an active process mediated by repressive signals, which are released by neighbouring cells and curb an intrinsic trend of differentiated cells to change.
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16 MeSH Terms
Attenuation of diet-induced hypothalamic inflammation following bariatric surgery in female mice.
Herrick MK, Favela KM, Simerly RB, Abumrad NN, Bingham NC
(2018) Mol Med 24: 56
MeSH Terms: Animals, Bariatric Surgery, Diet, High-Fat, Female, Hypothalamus, Inflammation, Mice, Inbred C57BL, Obesity
Show Abstract · Added April 11, 2019
BACKGROUND - Exposure of rodents to chronic high-fat diet (HFD) results in upregulation of inflammatory markers and proliferation of microglia within the mediobasal hypothalamus. Such hypothalamic inflammation is associated with metabolic dysfunction, central leptin resistance, and maintenance of obesity. Bariatric surgeries result in long-term stable weight loss and improved metabolic function. However, the effects of such surgical procedures on HFD-induced hypothalamic inflammation are unknown. We sought to characterize the effects of two bariatric surgical procedures, Roux-en-Y gastric bypass (RYGB) and biliary diversion (BD-IL), in female mice with particular emphasis on HFD-induced hypothalamic inflammation and microgliosis.
METHODS - RYGB and BD-IL were performed on diet-induced obese (DIO) mice. Quantitative RT-PCR and fluorescent microscopy were used to evaluate hypothalamic inflammatory gene expression and microgliosis. Results were compared to lean (CD), DIO sham-surgerized mice (DIO-SHAM), and dietary weight loss (DIO-Rev) controls.
RESULTS - In female mice, RYGB and BD-IL result in normalization of hypothalamic inflammatory gene expression and microgliosis within 8 weeks of surgery, despite ongoing exposure to HFD. Paralleling these results, the hypothalamic expression levels of the orexigenic neuropeptide Agrp and the anorexic response of surgical mice to exogenous leptin were comparable to lean controls (CD). In contrast, results from DIO-Rev mice were comparable to DIO-SHAM mice, despite transition back to standard rodent show and normalization of weight.
CONCLUSION - Bariatric surgery attenuates HFD-induced hypothalamic inflammation and microgliosis and restores leptin sensitivity, despite ongoing exposure to HFD.
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