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Journal of Clinical Investigation RSS feed -- Current issue

CSF-1–dependant donor-derived macrophages mediate chronic graft-versus-host disease
  By: Kylie A. Alexander, Ryan Flynn, Katie E. Lineburg, Rachel D. Kuns, Bianca E. Teal, Stuart D. Olver, Mary Lor, Neil C. Raffelt, Motoko Koyama, Lucie Leveque, Laetitia Le Texier, Michelle Melino, Kate A. Markey, Antiopi Varelias, Christian Engwerda, Jonathan S. Serody, Baptiste Janela, Florent Ginhoux, Andrew D. Clouston, Bruce R. Blazar, Geoffrey R. Hill, Kelli P.A. MacDonald

Chronic GVHD (cGVHD) is the major cause of late, nonrelapse death following stem cell transplantation and characteristically develops in organs such as skin and lung. Here, we used multiple murine models of cGVHD to investigate the contribution of macrophage populations in the development of cGVHD. Using an established IL-17–dependent sclerodermatous cGVHD model, we confirmed that macrophages infiltrating the skin are derived from donor bone marrow (F4/80+CSF-1R+CD206+iNOS). Cutaneous cGVHD developed in a CSF-1/CSF-1R–dependent manner, as treatment of recipients after transplantation with CSF-1 exacerbated macrophage infiltration and cutaneous pathology. Additionally, recipients of grafts from Csf1r–/– mice had substantially less macrophage infiltration and cutaneous pathology as compared with those receiving wild-type grafts. Neither CCL2/CCR2 nor GM-CSF/GM-CSFR signaling pathways were required for macrophage infiltration or development of cGVHD. In a different cGVHD model, in which bronchiolitis obliterans is a prominent manifestation, F4/80+ macrophage infiltration was similarly noted in the lungs of recipients after transplantation, and lung cGVHD was also IL-17 and CSF-1/CSF-1R dependent. Importantly, depletion of macrophages using an anti–CSF-1R mAb markedly reduced cutaneous and pulmonary cGVHD. Taken together, these data indicate that donor macrophages mediate the development of cGVHD and suggest that targeting CSF-1 signaling after transplantation may prevent and treat cGVHD.

CD4+ and CD8+ T cell–dependent antiviral immunity requires STIM1 and STIM2
  By: Patrick J. Shaw, Carl Weidinger, Martin Vaeth, Kevin Luethy, Susan M. Kaech, Stefan Feske

Calcium signaling is critical for lymphocyte function, and intracellular Ca2+ concentrations are regulated by store-operated Ca2+ entry (SOCE) through Ca2+ release–activated Ca2+ (CRAC) channels. In patients, loss-of-function mutations in CRAC channel components ORAI1 and STIM1 abolish SOCE and are associated with recurrent and chronic viral infections. Here, using mice with conditional deletion of Stim1 and its homolog Stim2 in T cells, we determined that both components are required for the maintenance of virus-specific memory CD8+ T cells and recall responses following secondary infection. In the absence of STIM1 and STIM2, acute viral infections became chronic. Early during infection, STIM1 and STIM2 were required for the differentiation of naive CD8+ T cells into fully functional cytolytic effector cells and mediated the production of cytokines and prevented cellular exhaustion in viral-specific CD8+ effector T cells. Importantly, memory and recall responses by CD8+ T cells required expression of STIM1 and STIM2 in CD4+ T cells. CD4+ T cells lacking STIM1 and STIM2 were unable to provide “help” to CD8+ T cells due to aberrant regulation of CD40L expression. Together, our data indicate that STIM1, STIM2, and CRAC channel function play distinct but synergistic roles in CD4+ and CD8+ T cells during antiviral immunity.

Endothelial deficiency of L1 reduces tumor angiogenesis and promotes vessel normalization
  By: Elena Magrini, Alessandra Villa, Francesca Angiolini, Andrea Doni, Giovanni Mazzarol, Noemi Rudini, Luigi Maddaluno, Mina Komuta, Baki Topal, Hans Prenen, Melitta Schachner, Stefano Confalonieri, Elisabetta Dejana, Fabrizio Bianchi, Massimiliano Mazzone, Ugo Cavallaro

While tumor blood vessels share many characteristics with normal vasculature, they also exhibit morphological and functional aberrancies. For example, the neural adhesion molecule L1, which mediates neurite outgrowth, fasciculation, and pathfinding, is expressed on tumor vasculature. Here, using an orthotopic mouse model of pancreatic carcinoma, we evaluated L1 functionality in cancer vessels. Tumor-bearing mice specifically lacking L1 in endothelial cells or treated with anti-L1 antibodies exhibited decreased angiogenesis and improved vascular stabilization, leading to reduced tumor growth and metastasis. In line with these dramatic effects of L1 on tumor vasculature, the ectopic expression of L1 in cultured endothelial cells (ECs) promoted phenotypical and functional alterations, including proliferation, migration, tubulogenesis, enhanced vascular permeability, and endothelial-to-mesenchymal transition. L1 induced global changes in the EC transcriptome, altering several regulatory networks that underlie endothelial pathophysiology, including JAK/STAT-mediated pathways. In particular, L1 induced IL-6–mediated STAT3 phosphorylation, and inhibition of the IL-6/JAK/STAT signaling axis prevented L1-induced EC proliferation and migration. Evaluation of patient samples revealed that, compared with that in noncancerous tissue, L1 expression is specifically enhanced in blood vessels of human pancreatic carcinomas and in vessels of other tumor types. Together, these data indicate that endothelial L1 orchestrates multiple cancer vessel functions and represents a potential target for tumor vascular-specific therapies.

Peptide-siRNA nanocomplexes targeting NF-κB subunit p65 suppress nascent experimental arthritis
  By: Hui-fang Zhou, Huimin Yan, Hua Pan, Kirk K. Hou, Antonina Akk, Luke E. Springer, Ying Hu, J. Stacy Allen, Samuel A. Wickline, Christine T.N. Pham

The NF-κB signaling pathway is implicated in various inflammatory diseases, including rheumatoid arthritis (RA); therefore, inhibition of this pathway has the potential to ameliorate an array of inflammatory diseases. Given that NF-κB signaling is critical for many immune cell functions, systemic blockade of this pathway may lead to detrimental side effects. siRNAs coupled with a safe and effective delivery nanoplatform may afford the specificity lacking in systemic administration of small-molecule inhibitors. Here we demonstrated that a melittin-derived cationic amphipathic peptide combined with siRNA targeting the p65 subunit of NF-κB (p5RHH-p65) noncovalently self-assemble into stable nanocomplexes that home to the inflamed joints in a murine model of RA. Specifically, administration of p5RHH-p65 siRNA nanocomplexes abrogated inflammatory cytokine expression and cellular influx into the joints, protected against bone erosions, and preserved cartilage integrity. The p5RHH-p65 siRNA nanocomplexes potently suppressed early inflammatory arthritis without affecting p65 expression in off-target organs or eliciting a humoral response after serial injections. These data suggest that this self-assembling, largely nontoxic platform may have broad utility for the specific delivery of siRNA to target and limit inflammatory processes for the treatment of a variety of diseases.

Human satellite cells have regenerative capacity and are genetically manipulable
  By: Andreas Marg, Helena Escobar, Sina Gloy, Markus Kufeld, Joseph Zacher, Andreas Spuler, Carmen Birchmeier, Zsuzsanna Izsvák, Simone Spuler

Muscle satellite cells promote regeneration and could potentially improve gene delivery for treating muscular dystrophies. Human satellite cells are scarce; therefore, clinical investigation has been limited. We obtained muscle fiber fragments from skeletal muscle biopsy specimens from adult donors aged 20 to 80 years. Fiber fragments were manually dissected, cultured, and evaluated for expression of myogenesis regulator PAX7. PAX7+ satellite cells were activated and proliferated efficiently in culture. Independent of donor age, as few as 2 to 4 PAX7+ satellite cells gave rise to several thousand myoblasts. Transplantation of human muscle fiber fragments into irradiated muscle of immunodeficient mice resulted in robust engraftment, muscle regeneration, and proper homing of human PAX7+ satellite cells to the stem cell niche. Further, we determined that subjecting the human muscle fiber fragments to hypothermic treatment successfully enriches the cultures for PAX7+ cells and improves the efficacy of the transplantation and muscle regeneration. Finally, we successfully altered gene expression in cultured human PAX7+ satellite cells with Sleeping Beauty transposon–mediated nonviral gene transfer, highlighting the potential of this system for use in gene therapy. Together, these results demonstrate the ability to culture and manipulate a rare population of human tissue-specific stem cells and suggest that these PAX7+ satellite cells have potential to restore gene function in muscular dystrophies.

Estrogens stimulate serotonin neurons to inhibit binge-like eating in mice
  By: Xuehong Cao, Pingwen Xu, Mario G. Oyola, Yan Xia, Xiaofeng Yan, Kenji Saito, Fang Zou, Chunmei Wang, Yongjie Yang, Antentor Hinton Jr., Chunling Yan, Hongfang Ding, Liangru Zhu, Likai Yu, Bin Yang, Yuxin Feng, Deborah J. Clegg, Sohaib Khan, Richard DiMarchi, Shaila K. Mani, Qingchun Tong, Yong Xu

Binge eating afflicts approximately 5% of US adults, though effective treatments are limited. Here, we showed that estrogen replacement substantially suppresses binge-like eating behavior in ovariectomized female mice. Estrogen-dependent inhibition of binge-like eating was blocked in female mice specifically lacking estrogen receptor-α (ERα) in serotonin (5-HT) neurons in the dorsal raphe nuclei (DRN). Administration of a recently developed glucagon-like peptide-1–estrogen (GLP-1–estrogen) conjugate designed to deliver estrogen to GLP1 receptor–enhanced regions effectively targeted bioactive estrogens to the DRN and substantially suppressed binge-like eating in ovariectomized female mice. Administration of GLP-1 alone reduced binge-like eating, but not to the same extent as the GLP-1–estrogen conjugate. Administration of ERα-selective agonist propylpyrazole triol (PPT) to murine DRN 5-HT neurons activated these neurons in an ERα-dependent manner. PPT also inhibited a small conductance Ca2+-activated K+ (SK) current; blockade of the SK current prevented PPT-induced activation of DRN 5-HT neurons. Furthermore, local inhibition of the SK current in the DRN markedly suppressed binge-like eating in female mice. Together, our data indicate that estrogens act upon ERα to inhibit the SK current in DRN 5-HT neurons, thereby activating these neurons to suppress binge-like eating behavior and suggest ERα and/or SK current in DRN 5-HT neurons as potential targets for anti-binge therapies.

Disposable platform provides visual and color-based point-of-care anemia self-testing
  By: Erika A. Tyburski, Scott E. Gillespie, William A. Stoy, Robert G. Mannino, Alexander J. Weiss, Alexa F. Siu, Rayford H. Bulloch, Karthik Thota, Anyela Cardenas, Wilena Session, Hanna J. Khoury, Siobhán O’Connor, Silvia T. Bunting, Jeanne Boudreaux, Craig R. Forest, Manila Gaddh, Traci Leong, L. Andrew Lyon, Wilbur A. Lam

BACKGROUND. Anemia, or low blood hemoglobin (Hgb) levels, afflicts 2 billion people worldwide. Currently, Hgb levels are typically measured from blood samples using hematology analyzers, which are housed in hospitals, clinics, or commercial laboratories and require skilled technicians to operate. A reliable, inexpensive point-of-care (POC) Hgb test would enable cost-effective anemia screening and chronically anemic patients to self-monitor their disease. We present a rapid, stand-alone, and disposable POC anemia test that, via a single drop of blood, outputs color-based visual results that correlate with Hgb levels.

METHODS. We tested blood from 238 pediatric and adult patients with anemia of varying degrees and etiologies and compared hematology analyzer Hgb levels with POC Hgb levels, which were estimated via visual interpretation using a color scale and an optional smartphone app for automated analysis.

RESULTS. POC Hgb levels correlated with hematology analyzer Hgb levels (r = 0.864 and r = 0.856 for visual interpretation and smartphone app, respectively), and both POC test methods yielded comparable sensitivity and specificity for detecting any anemia (n = 178) (<11 g/dl) (sensitivity: 90.2% and 91.1%, specificity: 83.7% and 79.2%, respectively) and severe anemia (n = 10) (<7 g/dl) (sensitivity: 90.0% and 100%, specificity: 94.6% and 93.9%, respectively).

CONCLUSIONS. These results demonstrate the feasibility of this POC color-based diagnostic test for self-screening/self-monitoring of anemia.


FUNDING. This work was funded by the FDA-funded Atlantic Pediatric Device Consortium, the Georgia Research Alliance, Children’s Healthcare of Atlanta, the Georgia Center of Innovation for Manufacturing, and the InVenture Prize and Ideas to Serve competitions at the Georgia Institute of Technology.

TGF-β prevents T follicular helper cell accumulation and B cell autoreactivity
  By: Mark J. McCarron, Julien C. Marie

T follicular helper (Tfh) cells contribute to the establishment of humoral immunity by controlling the delivery of helper signals to activated B cells; however, Tfh development must be restrained, as aberrant accumulation of these cells is associated with positive selection of self-reactive germinal center B cells and autoimmunity in both humans and mice. Here, we show that TGF-β signaling in T cells prevented Tfh cell accumulation, self-reactive B cell activation, and autoantibody production. Using mice with either T cell–specific loss or constitutive activation of TGF-β signaling, we demonstrated that TGF-β signaling is required for the thymic maturation of CD44+CD122+Ly49+CD8+ regulatory T cells (Tregs), which induce Tfh apoptosis and thus regulate this cell population. Moreover, peripheral Tfh cells escaping TGF-β control were resistant to apoptosis, exhibited high levels of the antiapoptotic protein BCL2, and remained refractory to regulation by CD8+ Tregs. The unrestrained accumulation of Tfh cells in the absence of TGF-β was dependent on T cell receptor engagement and required B cells. Together, these data indicate that TGF-β signaling restrains Tfh cell accumulation and B cell–associated autoimmunity and thereby controls self-tolerance.

TMEM14C is required for erythroid mitochondrial heme metabolism
  By: Yvette Y. Yien, Raymond F. Robledo, Iman J. Schultz, Naoko Takahashi-Makise, Babette Gwynn, Daniel E. Bauer, Abhishek Dass, Gloria Yi, Liangtao Li, Gordon J. Hildick-Smith, Jeffrey D. Cooney, Eric L. Pierce, Kyla Mohler, Tamara A. Dailey, Non Miyata, Paul D. Kingsley, Caterina Garone, Shilpa M. Hattangadi, Hui Huang, Wen Chen, Ellen M. Keenan, Dhvanit I. Shah, Thorsten M. Schlaeger, Salvatore DiMauro, Stuart H. Orkin, Alan B. Cantor, James Palis, Carla M. Koehler, Harvey F. Lodish, Jerry Kaplan, Diane M. Ward, Harry A. Dailey, John D. Phillips, Luanne L. Peters, Barry H. Paw

The transport and intracellular trafficking of heme biosynthesis intermediates are crucial for hemoglobin production, which is a critical process in developing red cells. Here, we profiled gene expression in terminally differentiating murine fetal liver-derived erythroid cells to identify regulators of heme metabolism. We determined that TMEM14C, an inner mitochondrial membrane protein that is enriched in vertebrate hematopoietic tissues, is essential for erythropoiesis and heme synthesis in vivo and in cultured erythroid cells. In mice, TMEM14C deficiency resulted in porphyrin accumulation in the fetal liver, erythroid maturation arrest, and embryonic lethality due to profound anemia. Protoporphyrin IX synthesis in TMEM14C-deficient erythroid cells was blocked, leading to an accumulation of porphyrin precursors. The heme synthesis defect in TMEM14C-deficient cells was ameliorated with a protoporphyrin IX analog, indicating that TMEM14C primarily functions in the terminal steps of the heme synthesis pathway. Together, our data demonstrate that TMEM14C facilitates the import of protoporphyrinogen IX into the mitochondrial matrix for heme synthesis and subsequent hemoglobin production. Furthermore, the identification of TMEM14C as a protoporphyrinogen IX importer provides a genetic tool for further exploring erythropoiesis and congenital anemias.

SORCS1 is necessary for normal insulin secretory granule biogenesis in metabolically stressed β-cells
  By: Melkam A. Kebede, Angie T. Oler, Trillian Gregg, Allison J. Balloon, Adam Johnson, Kelly Mitok, Mary Rabaglia, Kathryn Schueler, Donald Stapleton, Candice Thorstenson, Lindsay Wrighton, Brendan J. Floyd, Oliver Richards, Summer Raines, Kevin Eliceiri, Nabil G. Seidah, Christopher Rhodes, Mark P. Keller, Joshua L. Coon, Anjon Audhya, Alan D. Attie

We previously positionally cloned Sorcs1 as a diabetes quantitative trait locus. Sorcs1 belongs to the Vacuolar protein sorting-10 (Vps10) gene family. In yeast, Vps10 transports enzymes from the trans-Golgi network (TGN) to the vacuole. Whole-body Sorcs1 KO mice, when made obese with the leptinob mutation (ob/ob), developed diabetes. β-Cells from these mice had a severe deficiency of secretory granules (SGs) and insulin. Interestingly, a single secretagogue challenge failed to consistently elicit an insulin secretory dysfunction. However, multiple challenges of the Sorcs1 KO ob/ob islets consistently revealed an insulin secretion defect. The luminal domain of SORCS1 (Lum-Sorcs1), when expressed in a β-cell line, acted as a dominant-negative, leading to SG and insulin deficiency. Using syncollin-dsRed5TIMER adenovirus, we found that the loss of Sorcs1 function greatly impairs the rapid replenishment of SGs following secretagogue challenge. Chronic exposure of islets from lean Sorcs1 KO mice to high glucose and palmitate depleted insulin content and evoked an insulin secretion defect. Thus, in metabolically stressed mice, Sorcs1 is important for SG replenishment, and under chronic challenge by insulin secretagogues, loss of Sorcs1 leads to diabetes. Overexpression of full-length SORCS1 led to a 2-fold increase in SG content, suggesting that SORCS1 is sufficient to promote SG biogenesis.

Longistatin in tick saliva blocks advanced glycation end-product receptor activation
  By: Anisuzzaman, Takeshi Hatta, Takeharu Miyoshi, Makoto Matsubayashi, M. Khyrul Islam, M. Abdul Alim, M. Abu Anas, M. Mehedi Hasan, Yasunobu Matsumoto, Yasuhiko Yamamoto, Hiroshi Yamamoto, Kozo Fujisaki, Naotoshi Tsuji

Ticks are notorious hematophagous ectoparasites and vectors of many deadly pathogens. As an effective vector, ticks must break the strong barrier provided by the skin of their host during feeding, and their saliva contains a complex mixture of bioactive molecules that paralyze host defenses. The receptor for advanced glycation end products (RAGE) mediates immune cell activation at inflammatory sites and is constitutively and highly expressed in skin. Here, we demonstrate that longistatin secreted with saliva of the tick Haemaphysalis longicornis binds RAGE and modulates the host immune response. Similar to other RAGE ligands, longistatin specifically bound the RAGE V domain, and stimulated cultured HUVECs adhered to a longistatin-coated surface; this binding was dramatically inhibited by soluble RAGE or RAGE siRNA. Treatment of HUVECs with longistatin prior to stimulation substantially attenuated cellular oxidative stress and prevented NF-κB translocation, thereby reducing adhesion molecule and cytokine production. Recombinant longistatin inhibited RAGE-mediated migration of mouse peritoneal resident cells (mPRCs) and ameliorated inflammation in mouse footpad edema and pneumonia models. Importantly, tick bite upregulated RAGE ligands in skin, and endogenous longistatin attenuated RAGE-mediated inflammation during tick feeding. Our results suggest that longistatin is a RAGE antagonist that suppresses tick bite–associated inflammation, allowing successful blood-meal acquisition from hosts.

Neurotrophin receptor p75NTR mediates Huntington’s disease–associated synaptic and memory dysfunction
  By: Verónica Brito, Albert Giralt, Lilian Enriquez-Barreto, Mar Puigdellívol, Nuria Suelves, Alfonsa Zamora-Moratalla, Jesús J. Ballesteros, Eduardo D. Martín, Nuria Dominguez-Iturza, Miguel Morales, Jordi Alberch, Sílvia Ginés

Learning and memory deficits are early clinical manifestations of Huntington’s disease (HD). These cognitive impairments have been mainly associated with frontostriatal HD pathology; however, compelling evidence provided by several HD murine models suggests that the hippocampus may contribute to synaptic deficits and memory dysfunction in HD. The neurotrophin receptor p75NTR negatively regulates spine density, which is associated with learning and memory; therefore, we explored whether disturbed p75NTR function in the hippocampus could contribute to synaptic dysfunction and memory deficits in HD. Here, we determined that levels of p75NTR are markedly increased in the hippocampus of 2 distinct mouse models of HD and in HD patients. Normalization of p75NTR levels in HD mutant mice heterozygous for p75NTR prevented memory and synaptic plasticity deficits and ameliorated dendritic spine abnormalities, likely through normalization of the activity of the GTPase RhoA. Moreover, viral-mediated overexpression of p75NTR in the hippocampus of WT mice reproduced HD learning and memory deficits, while knockdown of p75NTR in the hippocampus of HD mice prevented cognitive decline. Together, these findings provide evidence of hippocampus-associated memory deficits in HD and demonstrate that p75NTR mediates synaptic, learning, and memory dysfunction in HD.

Protein kinase LKB1 promotes RAB7-mediated neuropilin-1 degradation to inhibit angiogenesis
  By: Imoh S. Okon, Kathleen A. Coughlan, Cheng Zhang, Cate Moriasi, Ye Ding, Ping Song, Wencheng Zhang, Guangpu Li, Ming-Hui Zou

After internalization, transmembrane receptors (TMRs) are typically recycled back to the cell surface or targeted for degradation. Efficient TMR trafficking is critical for regulation of several processes, including signal transduction pathways, development, and disease. Here, we determined that trafficking of the angiogenic receptor neuropilin-1 (NRP-1) is abrogated by the liver kinase B1 (LKB1), a serine-threonine kinase of the calcium calmodulin family. We found that aberrant NRP-1 expression in tumor cells from patients with lung adenocarcinoma is associated with decreased levels of LKB1. In cultured lung cells, LKB1 accentuated formation of a complex between NRP-1 and RAB7 in late endosomes. LKB1 specifically bound GTP-bound RAB7, but not a dominant-negative GDP-bound form of RAB7, promoting rapid transfer and lysosome degradation of NRP-1. siRNA-mediated depletion of RAB7 disrupted the transfer of NRP-1 to the lysosome, resulting in recovery of the receptor as well as increased tumor growth and angiogenesis. Together, our findings indicate that LKB1 functions as a RAB7 effector and suppresses angiogenesis by promoting the cellular trafficking of NRP-1 from RAB7 vesicles to the lysosome for degradation. Furthermore, these data suggest that LKB1 and NRP-1 have potential as therapeutic targets for limiting tumorigenesis.

Maternal diet-induced microRNAs and mTOR underlie β cell dysfunction in offspring
  By: Emilyn U. Alejandro, Brigid Gregg, Taylor Wallen, Doga Kumusoglu, Daniel Meister, Angela Chen, Matthew J. Merrins, Leslie S. Satin, Ming Liu, Peter Arvan, Ernesto Bernal-Mizrachi

A maternal diet that is low in protein increases the susceptibility of offspring to type 2 diabetes by inducing long-term alterations in β cell mass and function. Nutrients and growth factor signaling converge through mTOR, suggesting that this pathway participates in β cell programming during fetal development. Here, we revealed that newborns of dams exposed to low-protein diet (LP0.5) throughout pregnancy exhibited decreased insulin levels, a lower β cell fraction, and reduced mTOR signaling. Adult offspring of LP0.5-exposed mothers exhibited glucose intolerance as a result of an insulin secretory defect and not β cell mass reduction. The β cell insulin secretory defect was distal to glucose-dependent Ca2+ influx and resulted from reduced proinsulin biosynthesis and insulin content. Islets from offspring of LP0.5-fed dams exhibited reduced mTOR and increased expression of a subset of microRNAs, and blockade of microRNA-199a-3p and -342 in these islets restored mTOR and insulin secretion to normal. Finally, transient β cell activation of mTORC1 signaling in offspring during the last week of pregnancy of mothers fed a LP0.5 rescued the defect in the neonatal β cell fraction and metabolic abnormalities in the adult. Together, these findings indicate that a maternal low-protein diet alters microRNA and mTOR expression in the offspring, influencing insulin secretion and glucose homeostasis.

MicroRNA-182 drives metastasis of primary sarcomas by targeting multiple genes
  By: Mohit Sachdeva, Jeffrey K. Mito, Chang-Lung Lee, Minsi Zhang, Zhizhong Li, Rebecca D. Dodd, David Cason, Lixia Luo, Yan Ma, David Van Mater, Rebecca Gladdy, Dina C. Lev, Diana M. Cardona, David G. Kirsch

Metastasis causes most cancer deaths, but is incompletely understood. MicroRNAs can regulate metastasis, but it is not known whether a single miRNA can regulate metastasis in primary cancer models in vivo. We compared the expression of miRNAs in metastatic and nonmetastatic primary mouse sarcomas and found that microRNA-182 (miR-182) was markedly overexpressed in some tumors that metastasized to the lungs. By utilizing genetically engineered mice with either deletion of or overexpression of miR-182 in primary sarcomas, we discovered that deletion of miR-182 substantially decreased, while overexpression of miR-182 considerably increased, the rate of lung metastasis after amputation of the tumor-bearing limb. Additionally, deletion of miR-182 decreased circulating tumor cells (CTCs), while overexpression of miR-182 increased CTCs, suggesting that miR-182 regulates intravasation of cancer cells into the circulation. We identified 4 miR-182 targets that inhibit either the migration of tumor cells or the degradation of the extracellular matrix. Notably, restoration of any of these targets in isolation did not alter the metastatic potential of sarcoma cells injected orthotopically, but the simultaneous restoration of all 4 targets together substantially decreased the number of metastases. These results demonstrate that a single miRNA can regulate metastasis of primary tumors in vivo by coordinated regulation of multiple genes.

Plasma fibronectin supports hemostasis and regulates thrombosis
  By: Yiming Wang, Adili Reheman, Christopher M. Spring, Jalil Kalantari, Alexandra H. Marshall, Alisa S. Wolberg, Peter L. Gross, Jeffrey I. Weitz, Margaret L. Rand, Deane F. Mosher, John Freedman, Heyu Ni

Plasma fibronectin (pFn) has long been suspected to be involved in hemostasis; however, direct evidence has been lacking. Here, we demonstrated that pFn is vital to control bleeding in fibrinogen-deficient mice and in WT mice given anticoagulants. At the site of vessel injury, pFn was rapidly deposited and initiated hemostasis, even before platelet accumulation, which is considered the first wave of hemostasis. This pFn deposition was independent of fibrinogen, von Willebrand factor, β3 integrin, and platelets. Confocal and scanning electron microscopy revealed pFn integration into fibrin, which increased fibrin fiber diameter and enhanced the mechanical strength of clots, as determined by thromboelastography. Interestingly, pFn promoted platelet aggregation when linked with fibrin but inhibited this process when fibrin was absent. Therefore, pFn may gradually switch from supporting hemostasis to inhibiting thrombosis and vessel occlusion following the fibrin gradient that decreases farther from the injured endothelium. Our data indicate that pFn is a supportive factor in hemostasis, which is vital under both genetic and therapeutic conditions of coagulation deficiency. By interacting with fibrin and platelet β3 integrin, pFn plays a self-limiting regulatory role in thrombosis, suggesting pFn transfusion may be a potential therapy for bleeding disorders, particularly in association with anticoagulant therapy.

Mast cells aggravate sepsis by inhibiting peritoneal macrophage phagocytosis
  By: Albert Dahdah, Gregory Gautier, Tarik Attout, Frédéric Fiore, Emeline Lebourdais, Rasha Msallam, Marc Daëron, Renato C. Monteiro, Marc Benhamou, Nicolas Charles, Jean Davoust, Ulrich Blank, Bernard Malissen, Pierre Launay

Controlling the overwhelming inflammatory reaction associated with polymicrobial sepsis remains a prevalent clinical challenge with few treatment options. In septic peritonitis, blood neutrophils and monocytes are rapidly recruited into the peritoneal cavity to control infection, but the role of resident sentinel cells during the early phase of infection is less clear. In particular, the influence of mast cells on other tissue-resident cells remains poorly understood. Here, we developed a mouse model that allows both visualization and conditional ablation of mast cells and basophils to investigate the role of mast cells in severe septic peritonitis. Specific depletion of mast cells led to increased survival rates in mice with acute sepsis. Furthermore, we determined that mast cells impair the phagocytic action of resident macrophages, thereby allowing local and systemic bacterial proliferation. Mast cells did not influence local recruitment of neutrophils and monocytes or the release of inflammatory cytokines. Phagocytosis inhibition by mast cells involved their ability to release prestored IL-4 within 15 minutes after bacterial encounter, and treatment with an IL-4–neutralizing antibody prevented this inhibitory effect and improved survival of septic mice. Our study uncovers a local crosstalk between mast cells and macrophages during the early phase of sepsis development that aggravates the outcome of severe bacterial infection.

Targeting VE-PTP activates TIE2 and stabilizes the ocular vasculature
  By: Jikui Shen, Maike Frye, Bonnie L. Lee, Jessica L. Reinardy, Joseph M. McClung, Kun Ding, Masashi Kojima, Huiming Xia, Christopher Seidel, Raquel Lima e Silva, Aling Dong, Sean F. Hackett, Jiangxia Wang, Brian W. Howard, Dietmar Vestweber, Christopher D. Kontos, Kevin G. Peters, Peter A. Campochiaro

Retinal and choroidal neovascularization (NV) and vascular leakage contribute to visual impairment in several common ocular diseases. The angiopoietin/TIE2 (ANG/TIE2) pathway maintains vascular integrity, and negative regulators of this pathway are potential therapeutic targets for these diseases. Here, we demonstrated that vascular endothelial-protein tyrosine phosphatase (VE-PTP), which negatively regulates TIE2 activation, is upregulated in hypoxic vascular endothelial cells, particularly in retinal NV. Intraocular injection of an anti–VE-PTP antibody previously shown to activate TIE2 suppressed ocular NV. Furthermore, a small-molecule inhibitor of VE-PTP catalytic activity (AKB-9778) activated TIE2, enhanced ANG1-induced TIE2 activation, and stimulated phosphorylation of signaling molecules in the TIE2 pathway, including AKT, eNOS, and ERK. In mouse models of neovascular age-related macular degeneration, AKB-9778 induced phosphorylation of TIE2 and strongly suppressed NV. Ischemia-induced retinal NV, which is relevant to diabetic retinopathy, was accentuated by the induction of ANG2 but inhibited by AKB-9778, even in the presence of high levels of ANG2. AKB-9778 also blocked VEGF-induced leakage from dermal and retinal vessels and prevented exudative retinal detachments in double-transgenic mice with high expression of VEGF in photoreceptors. These data support targeting VE-PTP to stabilize retinal and choroidal blood vessels and suggest that this strategy has potential for patients with a wide variety of retinal and choroidal vascular diseases

Proteinase 3–dependent caspase-3 cleavage modulates neutrophil death and inflammation
  By: Fabien Loison, Haiyan Zhu, Kutay Karatepe, Anongnard Kasorn, Peng Liu, Keqiang Ye, Jiaxi Zhou, Shannan Cao, Haiyan Gong, Dieter E. Jenne, Eileen Remold-O’Donnell, Yuanfu Xu, Hongbo R. Luo

Caspase-3–mediated spontaneous death in neutrophils is a prototype of programmed cell death and is critical for modulating physiopathological inflammatory responses; however, the underlying regulatory pathways remain ill defined. Here we determined that in aging neutrophils, the cleavage and activation of caspase-3 is independent of the canonical caspase-8– or caspase-9–mediated pathway. Instead, caspase-3 activation was mediated by serine protease proteinase 3 (PR3), which is present in the cytosol of aging neutrophils. Specifically, PR3 cleaved procaspase-3 at a site upstream of the canonical caspase-9 cleavage site. In mature neutrophils, PR3 was sequestered in granules and released during aging via lysosomal membrane permeabilization (LMP), leading to procaspase-3 cleavage and apoptosis. Pharmacological inhibition or knockdown of PR3 delayed neutrophil death in vitro and consistently delayed neutrophil death and augmented neutrophil accumulation at sites of inflammation in a murine model of peritonitis. Adoptive transfer of both WT and PR3-deficient neutrophils revealed that the delayed death of neutrophils lacking PR3 is due to an altered intrinsic apoptosis/survival pathway, rather than the inflammatory microenvironment. The presence of the suicide protease inhibitor SERPINB1 counterbalanced the protease activity of PR3 in aging neutrophils, and deletion of Serpinb1 accelerated neutrophil death. Taken together, our results reveal that PR3-mediated caspase-3 activation controls neutrophil spontaneous death.

Kazutoshi Mori and Peter Walter receive the 2014 Albert Lasker Basic Medical Research Award
  By: Corinne L. Williams

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