TY - JOUR A1 - Wolf, Karen A1 - Braun, Attila A1 - Haining, Elizabeth J. A1 - Tseng, Yu-Lun A1 - Kraft, Peter A1 - Schuhmann, Michael K. A1 - Gotru, Sanjeev K. A1 - Chen, Wenchun A1 - Hermanns, Heike M. A1 - Stoll, Guido A1 - Lesch, Klaus-Peter A1 - Nieswandt, Bernhard T1 - Partially Defective Store Operated Calcium Entry and Hem(ITAM) Signaling in Platelets of Serotonin Transporter Deficient Mice JF - PLoS One N2 - Background Serotonin (5-hydroxytryptamin, 5-HT) is an indolamine platelet agonist, biochemically derived from tryptophan. 5-HT is secreted from the enterochromaffin cells into the gastrointestinal tract and blood. Blood 5-HT has been proposed to regulate hemostasis by acting as a vasoconstrictor and by triggering platelet signaling through 5-HT receptor 2A (5HTR2A). Although platelets do not synthetize 5-HT, they take 5-HT up from the blood and store it in their dense granules which are secreted upon platelet activation. Objective To identify the molecular composite of the 5-HT uptake system in platelets and elucidate the role of platelet released 5-HT in thrombosis and ischemic stroke. Methods: 5-HT transporter knockout mice (5Htt\(^{-/-}\)) were analyzed in different in vitro and in vivo assays and in a model of ischemic stroke. Results In 5Htt\(^{-/-}\) platelets, 5-HT uptake from the blood was completely abolished and agonist-induced Ca2+ influx through store operated Ca\(^{2+}\) entry (SOCE), integrin activation, degranulation and aggregation responses to glycoprotein VI (GPVI) and C-type lectin-like receptor 2 (CLEC-2) were reduced. These observed in vitro defects in 5Htt\(^{-/-}\) platelets could be normalized by the addition of exogenous 5-HT. Moreover, reduced 5-HT levels in the plasma, an increased bleeding time and the formation of unstable thrombi were observed ex vivo under flow and in vivo in the abdominal aorta and carotid artery of 5Htt\(^{-/-}\) mice. Surprisingly, in the transient middle cerebral artery occlusion (tMCAO) model of ischemic stroke 5Htt\(^{-/-}\) mice showed nearly normal infarct volume and the neurological outcome was comparable to control mice. Conclusion Although secreted platelet 5-HT does not appear to play a crucial role in the development of reperfusion injury after stroke, it is essential to amplify the second phase of platelet activation through SOCE and plays an important role in thrombus stabilization. KW - platelets KW - serotonin KW - integrins KW - blood flow KW - collagens KW - platelet activation KW - platelet aggregation KW - ischemic stroke Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-146399 VL - 11 IS - 1 ER - TY - JOUR A1 - Chillo, Omary A1 - Kleinert, Eike Christian A1 - Lautz, Thomas A1 - Lasch, Manuel A1 - Pagel, Judith-Irina A1 - Heun, Yvonn A1 - Troidl, Kerstin A1 - Fischer, Silvia A1 - Caballero-Martinez, Amelia A1 - Mauer, Annika A1 - Kurz, Angela R. M. A1 - Assmann, Gerald A1 - Rehberg, Markus A1 - Kanse, Sandip M. A1 - Nieswandt, Bernhard A1 - Walzog, Barbara A1 - Reichel, Christoph A. A1 - Mannell, Hanna A1 - Preissner, Klaus T. A1 - Deindl, Elisabeth T1 - Perivascular Mast Cells Govern Shear Stress-Induced Arteriogenesis by Orchestrating Leukocyte Function JF - Cell Reports N2 - The body has the capacity to compensate for an occluded artery by creating a natural bypass upon increased fluid shear stress. How this mechanical force is translated into collateral artery growth (arteriogenesis) is unresolved. We show that extravasation of neutrophils mediated by the platelet receptor GPIbα and uPA results in Nox2-derived reactive oxygen radicals, which activate perivascular mast cells. These c-kit+/CXCR-4+ cells stimulate arteriogenesis by recruiting additional neutrophils as well as growth-promoting monocytes and T cells. Additionally, mast cells may directly contribute to vascular remodeling and vascular cell proliferation through increased MMP activity and by supplying growth-promoting factors. Boosting mast cell recruitment and activation effectively promotes arteriogenesis, thereby protecting tissue from severe ischemic damage. We thus find that perivascular mast cells are central regulators of shear stress-induced arteriogenesis by orchestrating leukocyte function and growth factor/cytokine release, thus providing a therapeutic target for treatment of vascular occlusive diseases. KW - Mast cells Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-164800 VL - 16 IS - 8 ER - TY - JOUR A1 - Stritt, Simon A1 - Nurden, Paquita A1 - Favier, Remi A1 - Favier, Marie A1 - Ferioli, Silvia A1 - Gotru, Sanjeev K. A1 - van Eeuwijk, Judith M.M. A1 - Schulze, Harald A1 - Nurden, Alan T. A1 - Lambert, Michele P. A1 - Turro, Ernest A1 - Burger-Stritt, Stephanie A1 - Matsushita, Masayuki A1 - Mittermeier, Lorenz A1 - Ballerini, Paola A1 - Zierler, Susanna A1 - Laffan, Michael A. A1 - Chubanov, Vladimir A1 - Gudermann, Thomas A1 - Nieswandt, Bernhard A1 - Braun, Attila T1 - Defects in TRPM7 channel function deregulate thrombopoiesis through altered cellular Mg\(^{2+}\) homeostasis and cytoskeletal architecture JF - Nature Communications N2 - Mg\(^{2+}\) plays a vital role in platelet function, but despite implications for life-threatening conditions such as stroke or myocardial infarction, the mechanisms controlling [Mg\(^{2+}\)]i in megakaryocytes (MKs) and platelets are largely unknown. Transient receptor potential melastatin-like 7 channel (TRPM7) is a ubiquitous, constitutively active cation channel with a cytosolic α-kinase domain that is critical for embryonic development and cell survival. Here we report that impaired channel function of TRPM7 in MKs causes macrothrombocytopenia in mice (Trpm7\(^{fl/fl-Pf4Cre}\)) and likely in several members of a human pedigree that, in addition, suffer from atrial fibrillation. The defect in platelet biogenesis is mainly caused by cytoskeletal alterations resulting in impaired proplatelet formation by Trpm7\(^{fl/fl-Pf4Cre}\) MKs, which is rescued by Mg\(^{2+}\) supplementation or chemical inhibition of non-muscle myosin IIA heavy chain activity. Collectively, our findings reveal that TRPM7 dysfunction may cause macrothrombocytopenia in humans and mice. KW - Cytoskeleton KW - homeostasisIon channels KW - thrombopoiesis Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-173843 VL - 7 ER - TY - JOUR A1 - Viera, Jonathan Trujillo A1 - El-Merahbi, Rabih A1 - Nieswandt, Bernhard A1 - Stegner, David A1 - Sumara, Grzegorz T1 - Phospholipases D1 and D2 Suppress Appetite and Protect against Overweight JF - PLoS ONE N2 - Obesity is a major risk factor predisposing to the development of peripheral insulin resistance and type 2 diabetes (T2D). Elevated food intake and/or decreased energy expenditure promotes body weight gain and acquisition of adipose tissue. Number of studies implicated phospholipase D (PLD) enzymes and their product, phosphatidic acid (PA), in regulation of signaling cascades controlling energy intake, energy dissipation and metabolic homeostasis. However, the impact of PLD enzymes on regulation of metabolism has not been directly determined so far. In this study we utilized mice deficient for two major PLD isoforms, PLD1 and PLD2, to assess the impact of these enzymes on regulation of metabolic homeostasis. We showed that mice lacking PLD1 or PLD2 consume more food than corresponding control animals. Moreover, mice deficient for PLD2, but not PLD1, present reduced energy expenditure. In addition, deletion of either of the PLD enzymes resulted in development of elevated body weight and increased adipose tissue content in aged animals. Consistent with the fact that elevated content of adipose tissue predisposes to the development of hyperlipidemia and insulin resistance, characteristic for the pre-diabetic state, we observed that Pld1\(^{-/-}\) and Pld2\(^{-/-}\) mice present elevated free fatty acids (FFA) levels and are insulin as well as glucose intolerant. In conclusion, our data suggest that deficiency of PLD1 or PLD2 activity promotes development of overweight and diabetes. KW - enzyme regulation KW - insulin resistance KW - body weight KW - mouse models KW - bioenergetics KW - insulin KW - hypothalamus KW - adipose tissue Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-179729 VL - 11 IS - 6 ER -