Issue published October 17, 2019
- Volume 4, Issue 20
- Previous Issue | Next Issue
- In this issue of JCI Insight, Fiorentino et al. demonstrate that chronic infusion of the glucagon-like peptide 1 receptor agonist exenatide exerts protective effects on pancreatic islet cells and increases insulin sensitivity in non-human primates. The cover image is an electron micrograph of a pancreatic specimen after in vivo treatment with exenatide, with immunogold labeling for the presence of insulin- and proinsulin-containing secretory granules.
On the cover: Exenatide regulates pancreatic islet integrity and insulin sensitivity in baboons
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Research Articles
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Abstract
Deterioration or inborn malformations of the cardiac conduction system (CCS) interfere with proper impulse propagation in the heart and may lead to sudden cardiac death or heart failure. Patients afflicted with arrhythmia depend on antiarrhythmic medication or invasive therapy, such as pacemaker implantation. An ideal way to treat these patients would be CCS tissue restoration. This, however, requires precise knowledge regarding the molecular mechanisms underlying CCS development. Here, we aimed to identify regulators of CCS development. We performed a compound screen in zebrafish embryos and identified tolterodine, a muscarinic receptor antagonist, as a modifier of CCS development. Tolterodine provoked a lower heart rate, pericardiac edema, and arrhythmia. Blockade of muscarinic M3, but not M2, receptors induced transcriptional changes leading to amplification of sinoatrial cells and loss of atrioventricular identity. Transcriptome data from an engineered human heart muscle model provided additional evidence for the contribution of muscarinic M3 receptors during cardiac progenitor specification and differentiation. Taken together, we found that muscarinic M3 receptors control the CCS already before the heart becomes innervated. Our data indicate that muscarinic receptors maintain a delicate balance between the developing sinoatrial node and the atrioventricular canal, which is probably required to prevent the development of arrhythmia.
Authors
Martina S. Burczyk, Martin D. Burkhalter, Teresa Casar Tena, Laurel A. Grisanti, Michael Kauk, Sabrina Matysik, Cornelia Donow, Monika Kustermann, Melanie Rothe, Yinghong Cui, Farah Raad, Svenja Laue, Allessandra Moretti, Wolfram-H. Zimmermann, Jürgen Wess, Michael Kühl, Carsten Hoffmann, Douglas G. Tilley, Melanie Philipp
×Abstract
Myostatin is a negative regulator of muscle growth and metabolism and its inhibition in mice improves insulin sensitivity, increases glucose uptake into skeletal muscle, and decreases total body fat. A recently described mammalian protein called MSS51 is significantly downregulated with myostatin inhibition. In vitro disruption of Mss51 results in increased levels of ATP, β-oxidation, glycolysis, and oxidative phosphorylation. To determine the in vivo biological function of Mss51 in mice, we disrupted the Mss51 gene by CRISPR/Cas9 and found that Mss51-KO mice have normal muscle weights and fiber-type distribution but reduced fat pads. Myofibers isolated from Mss51-KO mice showed an increased oxygen consumption rate compared with WT controls, indicating an accelerated rate of skeletal muscle metabolism. The expression of genes related to oxidative phosphorylation and fatty acid β-oxidation were enhanced in skeletal muscle of Mss51-KO mice compared with that of WT mice. We found that mice lacking Mss51 and challenged with a high-fat diet were resistant to diet-induced weight gain, had increased whole-body glucose turnover and glycolysis rate, and increased systemic insulin sensitivity and fatty acid β-oxidation. These findings demonstrate that MSS51 modulates skeletal muscle mitochondrial respiration and regulates whole-body glucose and fatty acid metabolism, making it a potential target for obesity and diabetes.
Authors
Yazmin I. Rovira Gonzalez, Adam L. Moyer, Nicolas J. LeTexier, August D. Bratti, Siyuan Feng, Congshan Sun, Ting Liu, Jyothi Mula, Pankhuri Jha, Shama R. Iyer, Richard Lovering, Brian O’Rourke, Hye Lim Noh, Sujin Suk, Jason K. Kim, George K. Essien Umanah, Kathryn R. Wagner
×Abstract
The mechanistic target of rapamycin complex 2 (mTORC2) is a potentially novel and promising anticancer target due to its critical roles in proliferation, apoptosis, and metabolic reprogramming of cancer cells. However, the activity and function of mTORC2 in distinct cells within malignant tissue in vivo is insufficiently explored. Surprisingly, in primary human and mouse colorectal cancer (CRC) samples, mTORC2 signaling could not be detected in tumor cells. In contrast, only macrophages in tumor-adjacent areas showed mTORC2 activity, which was downregulated in stromal macrophages residing within human and mouse tumor tissues. Functionally, inhibition of mTORC2 by specific deletion of Rictor in macrophages stimulated tumorigenesis in a colitis-associated CRC mouse model. This phenotype was driven by a proinflammatory reprogramming of mTORC2-deficient macrophages that promoted colitis via the cytokine SPP1/osteopontin to stimulate tumor growth. In human CRC patients, high SPP1 levels and low mTORC2 activity in tumor-associated macrophages correlated with a worsened clinical prognosis. Treatment of mice with a second-generation mTOR inhibitor that inhibits mTORC2 and mTORC1 exacerbated experimental colorectal tumorigenesis in vivo. In conclusion, mTORC2 activity is confined to macrophages in CRC and limits tumorigenesis. These results suggest activation but not inhibition of mTORC2 as a therapeutic strategy for colitis-associated CRC.
Authors
Karl Katholnig, Birgit Schütz, Stephanie D. Fritsch, David Schörghofer, Monika Linke, Nyamdelger Sukhbaatar, Julia M. Matschinger, Daniela Unterleuthner, Martin Hirtl, Michaela Lang, Merima Herac, Andreas Spittler, Andreas Bergthaler, Gernot Schabbauer, Michael Bergmann, Helmut Dolznig, Markus Hengstschläger, Mark A. Magnuson, Mario Mikula, Thomas Weichhart
×Abstract
During pregnancy the maternal pancreatic islets of Langerhans undergo adaptive changes to compensate for gestational insulin resistance. Kisspeptin has been shown to stimulate insulin release, through its receptor, GPR54. The placenta releases high levels of kisspeptin into the maternal circulation, suggesting a role in modulating the islet adaptation to pregnancy. In the present study we show that pharmacological blockade of endogenous kisspeptin in pregnant mice resulted in impaired glucose homeostasis. This glucose intolerance was due to a reduced insulin response to glucose as opposed to any effect on insulin sensitivity. A β cell–specific GPR54-knockdown mouse line was found to exhibit glucose intolerance during pregnancy, with no phenotype observed outside of pregnancy. Furthermore, in pregnant women circulating kisspeptin levels significantly correlated with insulin responses to oral glucose challenge and were significantly lower in women with gestational diabetes (GDM) compared with those without GDM. Thus, kisspeptin represents a placental signal that plays a physiological role in the islet adaptation to pregnancy, maintaining maternal glucose homeostasis by acting through the β cell GPR54 receptor. Our data suggest reduced placental kisspeptin production, with consequent impaired kisspeptin-dependent β cell compensation, may be a factor in the development of GDM in humans.
Authors
James E. Bowe, Thomas G. Hill, Katharine F. Hunt, Lorna I.F. Smith, Sian J.S. Simpson, Stephanie A. Amiel, Peter M. Jones
×Abstract
Epicardial adipose tissue (EAT) is the visceral fat depot of the heart. Inflammation of EAT is thought to contribute to coronary artery disease (CAD). Therefore, we hypothesized that the EAT of patients with CAD would have increased inflammatory gene expression compared with controls without CAD. Cardiac surgery patients with (n = 13) or without CAD (n = 13) were consented, and samples of EAT and subcutaneous adipose tissue (SAT) were obtained. Transcriptomic analysis was performed using Affymetrix Human Gene 1.0 ST arrays. Differential expression was defined as a 1.5-fold change (ANOVA P < 0.05). Six hundred ninety-three genes were differentially expressed between SAT and EAT in controls and 805 in cases. Expression of 326 genes was different between EAT of cases and controls; expression of 14 genes was increased in cases, while 312 were increased in controls. Quantitative reverse transcription PCR confirmed that there was no difference in expression of CCL2, CCR2, TNF-α, IL-6, IL-8, and PAI1 between groups. Immunohistochemistry showed more macrophages in EAT than SAT, but there was no difference in their number or activation state between groups. In contrast to prior studies, we did not find increased inflammatory gene expression in the EAT of patients with CAD. We conclude that the specific adipose tissue depot, rather than CAD status, is responsible for the majority of differential gene expression.
Authors
Timothy P. Fitzgibbons, Nancy Lee, Khanh-Van Tran, Sara Nicoloro, Mark Kelly, Stanley K.C. Tam, Michael P. Czech
×Abstract
Dendritic cells (DCs) are crucial to balance protective immunity and autoimmune inflammatory processes. Expression of CD83 is a well-established marker for mature DCs, although its physiological role is still not completely understood. Using a DC-specific CD83–conditional KO (CD83ΔDC) mouse, we provide new insights into the function of CD83 within this cell type. Interestingly, CD83-deficient DCs produced drastically increased IL-2 levels and displayed higher expression of the costimulatory molecules CD25 and OX40L, which causes superior induction of antigen-specific T cell responses and compromises Treg suppressive functions. This also directly translates into accelerated immune responses in vivo. Upon Salmonella typhimurium and Listeria monocytogenes infection, CD83ΔDC mice cleared both pathogens more efficiently, and CD83-deficient DCs expressed increased IL-12 levels after bacterial encounter. Using the experimental autoimmune encephalomyelitis model, autoimmune inflammation was dramatically aggravated in CD83ΔDC mice while resolution of inflammation was strongly reduced. This phenotype was associated with increased cell influx into the CNS accompanied by elevated Th17 cell numbers. Concomitantly, CD83ΔDC mice had reduced Treg numbers in peripheral lymphoid organs. In summary, we show that CD83 ablation on DCs results in enhanced immune responses by dysregulating tolerance mechanisms and thereby impairing resolution of inflammation, which also demonstrates high clinical relevance.
Authors
Andreas B. Wild, Lena Krzyzak, Katrin Peckert, Lena Stich, Christine Kuhnt, Alina Butterhof, Christine Seitz, Jochen Mattner, Niklas Grüner, Maximilian Gänsbauer, Martin Purtak, Didier Soulat, Thomas H. Winkler, Lars Nitschke, Elisabeth Zinser, Alexander Steinkasserer
×Abstract
miR-511-3p, encoded by CD206/Mrc1, was demonstrated to reduce allergic inflammation and promote alternative (M2) macrophage polarization. Here, we sought to elucidate the fundamental mechanism by which miR-511-3p attenuates allergic inflammation and promotes macrophage polarization. Compared with WT mice, the allergen-challenged Mrc1–/– mice showed increased airway hyperresponsiveness (AHR) and inflammation. However, this increased AHR and inflammation were significantly attenuated when these mice were pretransduced with adeno-associated virus–miR-511-3p (AAV–miR-511-3p). Gene expression profiling of macrophages identified Ccl2 as one of the major genes that was highly expressed in M2 macrophages but antagonized by miR-511-3p. The interaction between miR-511-3p and Ccl2 was confirmed by in silico analysis and mRNA-miR pulldown assay. Further evidence for the inhibition of Ccl2 by miR-511-3p was given by reduced levels of Ccl2 in supernatants of miR-511-3p–transduced macrophages and in bronchoalveolar lavage fluids of AAV–miR-511-3p–infected Mrc1–/– mice. Mechanistically, we demonstrated that Ccl2 promotes M1 macrophage polarization by activating RhoA signaling through Ccr2. The interaction between Ccr2 and RhoA was also supported by coimmunoprecipitation assay. Importantly, inhibition of RhoA signaling suppressed cockroach allergen–induced AHR and lung inflammation. These findings suggest a potentially novel mechanism by which miR-511-3p regulates allergic inflammation and macrophage polarization by targeting Ccl2 and its downstream Ccr2/RhoA axis.
Authors
Danh C. Do, Jie Mu, Xia Ke, Karan Sachdeva, Zili Qin, Mei Wan, Faoud T. Ishmael, Peisong Gao
×Abstract
Depletion of epithelial cells after lung injury prompts proliferation and epithelial mesenchymal transition (EMT) of progenitor cells, and this repopulates the lost epithelial layer. To investigate the cell proliferative function of human oncoprotein MDM2, we generated mouse models targeting human MDM2 expression in either lung Club or alveolar cells after doxycycline treatment. We report that MDM2 expression in lung Club or alveolar cells activates DNA replication specifically in lung progenitor cells only after chemical- or radiation-induced lung injury, irrespective of their p53 status. Activation of DNA replication by MDM2 triggered by injury leads to proliferation of lung progenitor cells and restoration of the lost epithelial layers. Mouse lung with no Mdm2 allele loses its ability to replicate DNA, whereas loss of 1 Mdm2 allele compromises this function, demonstrating the requirement of endogenous MDM2. We show that the p53-independent ability of MDM2 to activate Akt signaling is essential for initiating DNA replication in lung progenitor cells. Furthermore, MDM2 activates the Notch signaling pathway and expression of EMT markers, indicative of epithelial regeneration. This is the first report to our knowledge demonstrating a direct p53-independent participation of MDM2 in progenitor cell proliferation and epithelial repair after lung injury, distinct from a p53-degrading antiapoptotic effect preventing injury.
Authors
Shilpa Singh, Catherine A. Vaughan, Christopher Rabender, Ross Mikkelsen, Sumitra Deb, Swati Palit Deb
×Abstract
Intrathecal (IT) delivery and pharmacology of antisense oligonucleotides (ASOs) for the CNS have been successfully developed to treat spinal muscular atrophy. However, ASO pharmacokinetic (PK) and pharmacodynamic (PD) properties remain poorly understood in the IT compartment. We applied multimodal imaging techniques to elucidate the IT PK and PD of unlabeled, radioactively labeled, or fluorescently labeled ASOs targeting ubiquitously expressed or neuron-specific RNAs. Following lumbar IT bolus injection in rats, all ASOs spread rostrally along the neuraxis, adhered to meninges, and were partially cleared to peripheral lymph nodes and kidneys. Rapid association with the pia and arterial walls preceded passage of ASOs across the glia limitans, along arterial intramural basement membranes, and along white-matter axonal bundles. Several neuronal and glial cell types accumulated ASOs over time, with evidence of probable glial accumulation preceding neuronal uptake. IT doses of anti-GluR1 and anti-Gabra1 ASOs markedly reduced the mRNA and protein levels of their respective neurotransmitter receptor protein targets by 2 weeks and anti-Gabra1 ASOs also reduced binding of the GABAA receptor PET ligand 18F-flumazenil in the brain over 4 weeks. Our multimodal imaging approaches elucidate multiple transport routes underlying the CNS distribution, clearance, and efficacy of IT-dosed ASOs.
Authors
Curt Mazur, Berit Powers, Kenneth Zasadny, Jenna M. Sullivan, Hemi Dimant, Fredrik Kamme, Jacob Hesterman, John Matson, Michael Oestergaard, Marc Seaman, Robert W. Holt, Mohammed Qutaish, Ildiko Polyak, Richard Coelho, Vijay Gottumukkala, Carolynn M. Gaut, Marc Berridge, Nazira J. Albargothy, Louise Kelly, Roxana O. Carare, Jack Hoppin, Holly Kordasiewicz, Eric E. Swayze, Ajay Verma
×Abstract
Chromatin modifiers act to coordinate gene expression changes critical to neuronal differentiation from neural stem/progenitor cells (NSPCs). Lysine-specific methyltransferase 2D (KMT2D) encodes a histone methyltransferase that promotes transcriptional activation and is frequently mutated in cancers and in the majority (>70%) of patients diagnosed with the congenital, multisystem intellectual disability disorder Kabuki syndrome 1 (KS1). Critical roles for KMT2D are established in various non-neural tissues, but the effects of KMT2D loss in brain cell development have not been described. We conducted parallel studies of proliferation, differentiation, transcription, and chromatin profiling in KMT2D-deficient human and mouse models to define KMT2D-regulated functions in neurodevelopmental contexts, including adult-born hippocampal NSPCs in vivo and in vitro. We report cell-autonomous defects in proliferation, cell cycle, and survival, accompanied by early NSPC maturation in several KMT2D-deficient model systems. Transcriptional suppression in KMT2D-deficient cells indicated strong perturbation of hypoxia-responsive metabolism pathways. Functional experiments confirmed abnormalities of cellular hypoxia responses in KMT2D-deficient neural cells and accelerated NSPC maturation in vivo. Together, our findings support a model in which loss of KMT2D function suppresses expression of oxygen-responsive gene programs important to neural progenitor maintenance, resulting in precocious neuronal differentiation in a mouse model of KS1.
Authors
Giovanni A. Carosso, Leandros Boukas, Jonathan J. Augustin, Ha Nam Nguyen, Briana L. Winer, Gabrielle H. Cannon, Johanna D. Robertson, Li Zhang, Kasper D. Hansen, Loyal A. Goff, Hans T. Bjornsson
×Abstract
Kabuki syndrome 1 (KS1) is a Mendelian disorder of the epigenetic machinery caused by mutations in the gene encoding KMT2D, which methylates lysine 4 on histone H3 (H3K4). KS1 is characterized by intellectual disability, postnatal growth retardation, and distinct craniofacial dysmorphisms. A mouse model (Kmt2d+/βGeo) exhibits features of the human disorder and has provided insight into other phenotypes; however, the mechanistic basis of skeletal abnormalities and growth retardation remains elusive. Using high-resolution micro-CT, we show that Kmt2d+/βGeo mice have shortened long bones and ventral bowing of skulls. In vivo expansion of growth plates within skulls and long bones suggests disrupted endochondral ossification as a common disease mechanism. Stable chondrocyte cell lines harboring inactivating mutations in Kmt2d exhibit precocious differentiation, further supporting this mechanism. A known inducer of chondrogenesis, SOX9, and its targets show markedly increased expression in Kmt2d–/– chondrocytes. By transcriptome profiling, we identify Shox2 as a putative KMT2D target. We propose that decreased KMT2D-mediated H3K4me3 at Shox2 releases Sox9 inhibition and thereby leads to enhanced chondrogenesis, providing a potentially novel and plausible explanation for precocious chondrocyte differentiation. Our findings provide insight into the pathogenesis of growth retardation in KS1 and suggest therapeutic approaches for this and related disorders.
Authors
Jill A. Fahrner, Wan-Ying Lin, Ryan C. Riddle, Leandros Boukas, Valerie B. DeLeon, Sheetal Chopra, Susan E. Lad, Teresa Romeo Luperchio, Kasper D. Hansen, Hans T. Bjornsson
×Abstract
Intestinally derived glucagon-like peptide-1 (GLP-1), encoded by the preproglucagon (Gcg) gene, is believed to function as an incretin. However, our previous work questioned this dogma and demonstrated that pancreatic peptides rather than intestinal Gcg peptides, including GLP-1, are a primary regulator of glucose homeostasis in normal mice. The objective of these experiments was to determine whether changes in nutrition or alteration of gut hormone secretion by bariatric surgery would result in a larger role for intestinal GLP-1 in the regulation of insulin secretion and glucose homeostasis. Multiple transgenic models, including mouse models with intestine- or pancreas tissue–specific Gcg expression and a whole-body Gcg-null mouse model, were generated to study the role of organ-specific GLP-1 production on glucose homeostasis under dietary-induced obesity and after weight loss from bariatric surgery (vertical sleeve gastrectomy; VSG). Our findings indicated that the intestine is a major source of circulating GLP-1 after various nutrient and surgical stimuli. However, even with the 4-fold increase in intestinally derived GLP-1 with VSG, it is pancreatic peptides, not intestinal Gcg peptides, that are necessary for surgery-induced improvements in glucose homeostasis.
Authors
Ki-Suk Kim, Chelsea R. Hutch, Landon Wood, Irwin J. Magrisso, Randy J. Seeley, Darleen A. Sandoval
×Abstract
Tissue engineering may address organ shortages currently limiting clinical transplantation. Off-the-shelf engineered vascularized organs will likely use allogeneic endothelial cells (ECs) to construct microvessels required for graft perfusion. Vasculogenic ECs can be differentiated from committed progenitors (human endothelial colony-forming cells or HECFCs) without risk of mutation or teratoma formation associated with reprogrammed stem cells. Like other ECs, these cells can express both class I and class II major histocompatibility complex (MHC) molecules, bind donor-specific antibody (DSA), activate alloreactive T effector memory cells, and initiate rejection in the absence of donor leukocytes. CRISPR/Cas9-mediated dual ablation of β2-microglobulin and class II transactivator (CIITA) in HECFC-derived ECs eliminates both class I and II MHC expression while retaining EC functions and vasculogenic potential. Importantly, dually ablated ECs no longer bind human DSA or activate allogeneic CD4+ effector memory T cells and are resistant to killing by CD8+ alloreactive cytotoxic T lymphocytes in vitro and in vivo. Despite absent class I MHC molecules, these ECs do not activate or elicit cytotoxic activity from allogeneic natural killer cells. These data suggest that HECFC-derived ECs lacking MHC molecule expression can be utilized for engineering vascularized grafts that evade allorejection.
Authors
Jonathan Merola, Melanie Reschke, Richard W. Pierce, Lingfeng Qin, Susann Spindler, Tania Baltazar, Thomas D. Manes, Francesc Lopez-Giraldez, Guangxin Li, Laura G. Bracaglia, Catherine Xie, Nancy Kirkiles-Smith, W. Mark Saltzman, Gregory T. Tietjen, George Tellides, Jordan S. Pober
×Abstract
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by pathologic T cell–B cell interactions and autoantibody production. Defining the T cell populations that drive B cell responses in SLE may enable design of therapies that specifically target pathologic cell subsets. Here, we evaluated the phenotypes of CD4+ T cells in the circulation of 52 SLE patients drawn from multiple cohorts and identified a highly expanded PD-1hiCXCR5–CD4+ T cell population. Cytometric, transcriptomic, and functional assays demonstrated that PD-1hiCXCR5–CD4+ T cells from SLE patients are T peripheral helper (Tph) cells, a CXCR5– T cell population that stimulates B cell responses via IL-21. The frequency of Tph cells, but not T follicular helper (Tfh) cells, correlated with both clinical disease activity and the frequency of CD11c+ B cells in SLE patients. PD-1hiCD4+ T cells were found within lupus nephritis kidneys and correlated with B cell numbers in the kidney. Both IL-21 neutralization and CRISPR-mediated deletion of MAF abrogated the ability of Tph cells to induce memory B cell differentiation into plasmablasts in vitro. These findings identify Tph cells as a highly expanded T cell population in SLE and suggest a key role for Tph cells in stimulating pathologic B cell responses.
Authors
Alexandra V. Bocharnikov, Joshua Keegan, Vanessa S. Wacleche, Ye Cao, Chamith Y. Fonseka, Guoxing Wang, Eric S. Muise, Kelvin X. Zhang, Arnon Arazi, Gregory Keras, Zhihan J. Li, Yujie Qu, Michael F. Gurish, Accelerating Medicines Partnership (AMP) RA/SLE Network, Michelle Petri, Jill P. Buyon, Chaim Putterman, David Wofsy, Judith A. James, Joel M. Guthridge, Betty Diamond, Jennifer H. Anolik, Matthew F. Mackey, Stephen E. Alves, Peter A. Nigrovic, Karen H. Costenbader, Michael B. Brenner, James A. Lederer, Deepak A. Rao
×Abstract
It is proposed that the impaired sympathoadrenal response to hypoglycemia induced by recurrent insulin-induced hypoglycemia (RH) is an adaptive phenomenon induced by specific changes in microRNA expression in the ventromedial hypothalamus (VMH). To test this hypothesis, genome-wide microRNAomic profiling of the VMH by RNA-sequencing was performed in control rats and rats treated for RH. Differential expression analysis identified microRNA-7a-5p and microRNA-665 as potential mediators of this phenomenon. To further test this hypothesis, experiments were conducted consisting of targeted lentiviral-mediated overexpression of microRNA-7a-5p and downregulation of microRNA-665 in the VMH. Hyperinsulinemic hypoglycemic clamp experiments demonstrated that targeted overexpression of microRNA-7a-5p (but not downregulation of microRNA-665) in the VMH of RH rats restored the epinephrine response to hypoglycemia. This restored response to hypoglycemia was associated with a restoration of GABAA receptor gene expression. Finally, a direct interaction of microRNA-7a-5p with the 3′-UTR of GABAA receptor α1-subunit (Gabra1) gene was demonstrated in a luciferase assay. These findings indicate that (a) the impaired sympathoadrenal response RH induces is associated with changes in VMH microRNA expression and (b) microRNA-7a-5p, possibly via direct downregulation of GABA receptor gene expression, may serve as a mediator of the altered sympathoadrenal response to hypoglycemia.
Authors
Rahul Agrawal, Griffin Durupt, Dinesh Verma, Michael Montgomery, Adriana Vieira-de Abreu, Casey Taylor, Sankar Swaminathan, Simon J. Fisher
×Abstract
Atrial fibrillation (AF) is the most common heart rhythm disorder and a major cause of stroke. Unfortunately, current therapies for AF are suboptimal, largely because the molecular mechanisms underlying AF are poorly understood. Since the autonomic nervous system is thought to increase vulnerability to AF, we used a rapid atrial pacing (RAP) canine model to investigate the anatomic and electrophysiological characteristics of autonomic remodeling in different regions of the left atrium. RAP led to marked hypertrophy of parent nerve bundles in the posterior left atrium (PLA), resulting in a global increase in parasympathetic and sympathetic innervation throughout the left atrium. Parasympathetic fibers were more heterogeneously distributed in the PLA when compared with other left atrial regions; this led to greater fractionation and disorganization of AF electrograms in the PLA. Computational modeling revealed that heterogeneously distributed parasympathetic activity exacerbates sympathetic substrate for wave break and reentry. We further discovered that levels of nerve growth factor (NGF) were greatest in the left atrial appendage (LAA), where AF was most organized. Preferential NGF release by the LAA — likely a direct function of frequency and regularity of atrial stimulation — may have important implications for creation of a vulnerable AF substrate.
Authors
Georg Gussak, Anna Pfenniger, Lisa Wren, Mehul Gilani, Wenwei Zhang, Shin Yoo, David A. Johnson, Amy Burrell, Brandon Benefield, Gabriel Knight, Bradley P. Knight, Rod Passman, Jeffrey J. Goldberger, Gary Aistrup, J. Andrew Wasserstrom, Yohannes Shiferaw, Rishi Arora
×Abstract
Meningiomas are the most common adult primary tumor of the central nervous system, but there are no known effective medical therapies for recurrent meningioma, particularly for World Health Organization grade II and III tumors. Meningiomas arise from the meninges, located outside the blood-brain barrier, and therefore may be directly targeted by antibody-mediated immunotherapy. We found that programmed cell death ligand 1 (PD-L1) was highly expressed in multiple human malignant meningioma cell lines and patient tumor samples. PD-L1 was targeted with the anti–PD-L1 antibody avelumab and directed natural killer cells to mediate antibody-dependent cellular cytotoxicity (ADCC) of PD-L1–expressing meningioma tumors both in vitro and in vivo. ADCC of meningioma cells was significantly increased in target cells that upregulated PD-L1 expression and, conversely, abrogated in tumor cells that were depleted of PD-L1. Additionally, the high-affinity natural killer cell line, haNK, outperformed healthy donor NK cells in meningioma ADCC. Together, these data support a clinical trial designed to target PD-L1 with avelumab and haNK cells, potentially offering a novel immunotherapeutic approach for patients with malignant meningioma.
Authors
Amber J. Giles, Shuyu Hao, Michelle Padget, Hua Song, Wei Zhang, John Lynes, Victoria Sanchez, Yang Liu, Jinkyu Jung, Xiaoyu Cao, Rika Fujii, Randy Jensen, David Gillespie, Jeffrey Schlom, Mark R. Gilbert, Edjah K. Nduom, Chunzhang Yang, John H. Lee, Patrick Soon-Shiong, James W. Hodge, Deric M. Park
×Abstract
Increased fibrosis is a characteristic remodeling response to biomechanical and neurohumoral stress and a determinant of cardiac mechanical and electrical dysfunction in disease. Stress-induced activation of cardiac fibroblasts (CFs) is a critical step in the fibrotic response, although the precise sequence of events underlying activation of these critical cells in vivo remain unclear. Here, we tested the hypothesis that a βIV-spectrin/STAT3 complex is essential for maintenance of a quiescent phenotype (basal nonactivated state) in CFs. We reported increased fibrosis, decreased cardiac function, and electrical impulse conduction defects in genetic and acquired mouse models of βIV-spectrin deficiency. Loss of βIV-spectrin function promoted STAT3 nuclear accumulation and transcriptional activity, and it altered gene expression and CF activation. Furthermore, we demonstrate that a quiescent phenotype may be restored in βIV-spectrin–deficient fibroblasts by expressing a βIV-spectrin fragment including the STAT3-binding domain or through pharmacological STAT3 inhibition. We found that in vivo STAT3 inhibition abrogates fibrosis and cardiac dysfunction in the setting of global βIV-spectrin deficiency. Finally, we demonstrate that fibroblast-specific deletion of βIV-spectrin is sufficient to induce fibrosis and decreased cardiac function. We propose that the βIV-spectrin/STAT3 complex is a determinant of fibroblast phenotype and fibrosis, with implications for remodeling response in cardiovascular disease (CVD).
Authors
Nehal J. Patel, Drew M. Nassal, Amara D. Greer-Short, Sathya D. Unudurthi, Benjamin W. Scandling, Daniel Gratz, Xianyao Xu, Anuradha Kalyanasundaram, Vadim V. Fedorov, Federica Accornero, Peter J. Mohler, Keith J. Gooch, Thomas J. Hund
×Abstract
Lung cancer remains the leading cause of cancer-related death in the United States. Although the alveolar macrophage (AM) comprises the major resident immune cell in the lung, few studies have investigated its role in lung cancer development. We recently discovered a potentially novel mechanism wherein AMs regulate STAT-induced inflammatory responses in neighboring epithelial cells (ECs) via secretion and delivery of suppressors of cytokine signaling 3 (SOCS3) within extracellular vesicles (EVs). Here, we explored the impact of SOCS3 transfer on EC tumorigenesis and the integrity of AM SOCS3 secretion during development of lung cancer. AM-derived EVs containing SOCS3 inhibited STAT3 activation as well as proliferation and survival of lung adenocarcinoma cells. Levels of secreted SOCS3 were diminished in lungs of patients with non–small cell lung cancer and in a mouse model of lung cancer, and the impaired ability of murine AMs to secrete SOCS3 within EVs preceded the development of lung tumors. Loss of this homeostatic brake on tumorigenesis prompted our effort to “rescue” it. Provision of recombinant SOCS3 loaded within synthetic liposomes inhibited proliferation and survival of lung adenocarcinoma cells in vitro as well as malignant transformation of normal ECs. Intratumoral injection of SOCS3 liposomes attenuated tumor growth in a lung cancer xenograft model. This work identifies AM-derived vesicular SOCS3 as an endogenous antitumor mechanism that is disrupted within the tumor microenvironment and whose rescue by synthetic liposomes can be leveraged as a potential therapeutic strategy for lung cancer.
Authors
Jennifer M. Speth, Loka R. Penke, Joseph D. Bazzill, Kyung Soo Park, Rafael Gil de Rubio, Daniel J. Schneider, Hideyasu Ouchi, James J. Moon, Venkateshwar G. Keshamouni, Rachel L. Zemans, Vibha N. Lama, Douglas A. Arenberg, Marc Peters-Golden
×Abstract
Efferocytosis, or phagocytic clearance of dead/dying cells by brain-resident microglia and/or infiltrating macrophages, is instrumental for inflammation resolution and restoration of brain homeostasis after stroke. Here, we identify the signal transducer and activator of transcription 6/arginase1 (STAT6/Arg1) signaling axis as a potentially novel mechanism that orchestrates microglia/macrophage responses in the ischemic brain. Activation of STAT6 was observed in microglia/macrophages in the ischemic territory in a mouse model of stroke and in stroke patients. STAT6 deficiency resulted in reduced clearance of dead/dying neurons, increased inflammatory gene signature in microglia/macrophages, and enlarged infarct volume early after experimental stroke. All of these pathological changes culminated in an increased brain tissue loss and exacerbated long-term functional deficits. Combined in vivo analyses using BM chimeras and in vitro experiments using microglia/macrophage-neuron cocultures confirmed that STAT6 activation in both microglia and macrophages was essential for neuroprotection. Adoptive transfer of WT macrophages into STAT6-KO mice reduced accumulation of dead neurons in the ischemic territory and ameliorated brain infarction. Furthermore, decreased expression of Arg1 in STAT6–/– microglia/macrophages was responsible for impairments in efferocytosis and loss of antiinflammatory modality. Our study suggests that efferocytosis via STAT6/Arg1 modulates microglia/macrophage phenotype, accelerates inflammation resolution, and improves stroke outcomes.
Authors
Wei Cai, Xuejiao Dai, Jie Chen, Jingyan Zhao, Mingyue Xu, Lili Zhang, Boyu Yang, Wenting Zhang, Marcelo Rocha, Toshimasa Nakao, Julia Kofler, Yejie Shi, R. Anne Stetler, Xiaoming Hu, Jun Chen
×Abstract
Itch induces scratching that removes irritants from the skin, whereas pain initiates withdrawal or avoidance of tissue damage. While pain arises from both the skin and viscera, we investigated whether pruritogenic irritant mechanisms also function within visceral pathways. We show that subsets of colon-innervating sensory neurons in mice express, either individually or in combination, the pruritogenic receptors Tgr5 and the Mas-gene–related GPCRs Mrgpra3 and Mrgprc11. Agonists of these receptors activated subsets of colonic sensory neurons and evoked colonic afferent mechanical hypersensitivity via a TRPA1-dependent mechanism. In vivo intracolonic administration of individual TGR5, MrgprA3, or MrgprC11 agonists induced pronounced visceral hypersensitivity to colorectal distension. Coadministration of these agonists as an “itch cocktail” augmented hypersensitivity to colorectal distension and changed mouse behavior. These irritant mechanisms were maintained and enhanced in a model of chronic visceral hypersensitivity relevant to irritable bowel syndrome. Neurons from human dorsal root ganglia also expressed TGR5, as well as the human ortholog MrgprX1, and showed increased responsiveness to pruritogenic agonists in pathological states. These data support the existence of an irritant-sensing system in the colon that is a visceral representation of the itch pathways found in skin, thereby contributing to sensory disturbances accompanying common intestinal disorders.
Authors
Joel Castro, Andrea M. Harrington, TinaMarie Lieu, Sonia Garcia-Caraballo, Jessica Maddern, Gudrun Schober, Tracey O’Donnell, Luke Grundy, Amanda L. Lumsden, Paul Miller, Andre Ghetti, Martin S. Steinhoff, Daniel P. Poole, Xinzhong Dong, Lin Chang, Nigel W. Bunnett, Stuart M. Brierley
×Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) emerged in 2012 in Saudi Arabia and has caused over 2400 cases and more than 800 deaths. Epidemiological studies identified diabetes as the primary comorbidity associated with severe or lethal MERS-CoV infection. Understanding how diabetes affects MERS is important because of the global burden of diabetes and pandemic potential of MERS-CoV. We used a model in which mice were made susceptible to MERS-CoV by expressing human DPP4, and type 2 diabetes was induced by administering a high-fat diet. Upon infection with MERS-CoV, diabetic mice had a prolonged phase of severe disease and delayed recovery that was independent of virus titers. Histological analysis revealed that diabetic mice had delayed inflammation, which was then prolonged through 21 days after infection. Diabetic mice had fewer inflammatory monocyte/macrophages and CD4+ T cells, which correlated with lower levels of Ccl2 and Cxcl10 expression. Diabetic mice also had lower levels of Tnfa, Il6, Il12b, and Arg1 expression and higher levels of Il17a expression. These data suggest that the increased disease severity observed in individuals with MERS and comorbid type 2 diabetes is likely due to a dysregulated immune response, which results in more severe and prolonged lung pathology.
Authors
Kirsten A. Kulcsar, Christopher M. Coleman, Sarah E. Beck, Matthew B. Frieman
×Abstract
The glucagon-like peptide-1 receptor agonist exenatide improves glycemic control by several and not completely understood mechanisms. Herein, we examined the effects of chronic intravenous exenatide infusion on insulin sensitivity, β cell and α cell function and relative volumes, and islet cell apoptosis and replication in nondiabetic nonhuman primates (baboons). At baseline, baboons received a 2-step hyperglycemic clamp followed by an l-arginine bolus (HC/A). After HC/A, baboons underwent a partial pancreatectomy (tail removal) and received a continuous exenatide (n = 12) or saline (n = 12) infusion for 13 weeks. At the end of treatment, HC/A was repeated, and the remnant pancreas (head-body) was harvested. Insulin sensitivity increased dramatically after exenatide treatment and was accompanied by a decrease in insulin and C-peptide secretion, while the insulin secretion/insulin resistance (disposition) index increased by about 2-fold. β, α, and δ cell relative volumes in exenatide-treated baboons were significantly increased compared with saline-treated controls, primarily as the result of increased islet cell replication. Features of cellular stress and secretory dysfunction were present in islets of saline-treated baboons and absent in islets of exenatide-treated baboons. In conclusion, chronic administration of exenatide exerts proliferative and cytoprotective effects on β, α, and δ cells and produces a robust increase in insulin sensitivity in nonhuman primates.
Authors
Teresa Vanessa Fiorentino, Francesca Casiraghi, Alberto M. Davalli, Giovanna Finzi, Stefano La Rosa, Paul B. Higgins, Gregory A. Abrahamian, Alessandro Marando, Fausto Sessa, Carla Perego, Rodolfo Guardado-Mendoza, Subhash Kamath, Andrea Ricotti, Paolo Fiorina, Giuseppe Daniele, Ana M. Paez, Francesco Andreozzi, Raul A. Bastarrachea, Anthony G. Comuzzie, Amalia Gastaldelli, Alberto O. Chavez, Eliana S. Di Cairano, Patrice Frost, Livio Luzi, Edward J. Dick, Glenn A. Halff, Ralph A. DeFronzo, Franco Folli
