AbstractsBiology & Animal Science

Microglial purinergic signaling in mouse models of CD39 deficiency and schizophrenia

by Petya Georgieva




Institution: Freie Universität Berlin
Department: FB Biologie, Chemie, Pharmazie
Degree: PhD
Year: 2015
Record ID: 1108238
Full text PDF: http://edocs.fu-berlin.de/diss/receive/FUDISS_thesis_000000099041


Abstract

Microglia are the immune competent cells of the central nervous system (CNS). In response to many exogenous and endogenous molecules and in pathologies they can become activated, migrate to the location of the stimuli, release cytokines and become phagocytic. One of the most important molecules, released from other cell types, is adenosine triphosphate (ATP), which is sensed by microglia via purinergic receptors and modulates their activity and function. ATP is degraded on the cell surface by CD39, which is expressed in the CNS only by microglia. In the firrst part of my thesis, I studied how Cd39 deletion affects purinergic signaling in cultured microglia. I found that microglia devoid of CD39 are more sensitive to low concentrations of ATP, but do not show changes in the expression of purinergic receptors. Absence of CD39 leads to higher amounts of ATP found in the supernatants of microglia upon medium change. In astrocyte-microglia co-cultures, astrocytes are the main source of ATP, while microglia are responsible for its rapid and effective removal. Lack of microglial CD39 enzyme also leads to a larger spread of the ATP-mediated astrocytic calcium waves. Taken together, I could show that microglial CD39 is an important regulator of autocrine and paracrine ATP signaling both in microglia and astrocytes. Moreover I found that both Cd39 gene expression and protein activity are strongly reduced in a pro-inflammatory context, which led me to the second part of my thesis. Here I investigated ATP-related microglia function in a maternal immune activation (MIA) mouse model of schizophrenia. In adult MIA offspring ATP-induced microglial phagocytosis was impaired. Calcium imaging experiments with freshly isolated microglia confirmed that the cells from MIA offspring exhibit reduced sensitivity to ATP. In addition, mRNA expression of Cd39 and P2ry12 was increased in microglia from MIA offspring. In summary, microglia in this mouse model of schizophrenia exhibit an altered ATP-related phenotype, which points toward a purinergic disbalance in the brain of these animals. Mikroglia sind die immunkompetenten Zellen im zentralen Nervensystem (ZNS). Sie können durch die Anwesenheit von verschiedenen exogenen und endogenen Signalen aktiviert werden, zum Beispiel in verschiedenen Krankheiten des ZNS, zu der Quelle der Signalen migrieren, Zytokine freisetzen und phagozytische Aktivität aufweisen. Eines der wichtigsten Gefahrensignale ist Adenosintriphosphat (ATP), welches von Zellen freigesetzt werden kann. Es wirkt über verschiedene purinerge Rezeptoren, welche von Mikroglia exprimiert werden, und kann die Aktivität und Funktion von Mikroglia beeinflussen. ATP wird an der Zelloberfläche von CD39 abgebaut, einem Enzym, welches im ZNS nur von Mikroglia produziert wird. Im ersten Teil meiner Arbeit untersuchte ich wie die Deletion von Cd39 die purinerge Signalgebung in Kulturmikroglia verändert. Ich konnte feststellen, dass die Cd39 Expression und Proteinaktivität in einem pro-inflammatorischen Kontext stark reduziert sind.…