Ion channels and transporters modulate migration, ramification, and apoptosis in microglial cells / eingereicht von: Susanna Zierler

• VerfasserIn: Zierler, Susanna
• Place / Publishing House: 2007
• Year of Publication: 2007
• Language: English
• Classification: 44.45 - Immunologie; 42.15 - Zellbiologie; 42.63 - Tierphysiologie
• Physical Description: 158 Bl.; Ill., graph. Darst.
• Notes: Abweichender Titel laut Übersetzung der Verfasserin/des Verfassers
• Other title: Ionenkanäle und Transporter modulieren Migration, Ramifizierung und Apoptose in Mikroglia
• ac_no: AC05034357
• Hierarchical level: Monograph
• Statement of Responsibility: eingereicht von: Susanna Zierler

ger: In the developing fetal brain as well as during inflammation microglia, immune competent cells of the brain, show a highly proliferative and phagocytotic activity. During ontogenesis microglial progenitors differentiate into ramified cells, while following acute inflammation microglia are proposed to either, migrate into blood vessels, transform into a resting state, or undergo apoptosis. Thus, one strategy to reduce microglial cell number might be migration into the circulatory system. An initial step of cell migration is the formation of a lamellipodium. Volume changes are essential for sprouting of a lamellipodium. Because volume regulation is associated with modulation of chloride conductances, we focused on the impact of chloride conductances on the formation of a lamellipodium. We identified swelling activated chloride channels using a hypoosmotic solution via patch clamp techniques and KCl cotransporters (KCC) using RT-PCR in the microglial cell line, BV-2. These chloride conductances were reversibly inhibited by DIOA, a routinely used blocker of KCC, and flufenamic acid, which blocks swelling activated chloride channels. Interestingly, BV-2 cells exposed to an isoosmotic KCl solution, leading to an inversion of KCl cotransport and, thus, to a water influx, rapidly formed a vibrant lamellipodium, which was inhibited by blockade of chloride conductances.<br />Microglia in conventional cell culture show an amoeboid phenotype and have to be secondarily inactivated. We demonstrated that the phorbol ester, PMA, a commonly used activator for protein kinase C (PKC), induced ramification in BV-2 cells. None of the PKC inhibitors used, counteracted PMA-induced ramification. Therefore, we assume that a PMA-binding protein, excluding PKC isoforms, is critical for the structural remodelling of microglial cells. To investigate, whether ion channels and transporters are associated with the transformation from an amoeboid to a ramified phenotype, we evaluated the contributions of ion conductances to the PMA-dependent ramification. Blockade of chloride currents suppressed microglial ramification. Further, we induced a multipolar morphology of BV-2 cells culturing them in three-dimensional environment. Induction of apoptosis is another strategy to control proliferative activity of microglial cells. Since very little is known about cell death in microglia, we investigated the mechanism of apoptosis in BV-2 cells. Therefore, we studied the ultrastructural distribution of chromatin during apoptosis, using UV-irradiation as a trigger of apoptosis. Moreover, we induced programmed cell death in microglial cells via ammonia and distinct tocopherol analogues, respectively. Because microglia play an essential part in neuroinflammatory diseases, it is of great interest to evaluate their activation status. Migration, ramification or apoptosis are possible mechanisms to control the proliferative and inflammatory activity of microglial cells.<br /> eng: In the developing fetal brain as well as during inflammation microglia, immune competent cells of the brain, show a highly proliferative and phagocytotic activity. During ontogenesis microglial progenitors differentiate into ramified cells, while following acute inflammation microglia are proposed to either, migrate into blood vessels, transform into a resting state, or undergo apoptosis. Thus, one strategy to reduce microglial cell number might be migration into the circulatory system. An initial step of cell migration is the formation of a lamellipodium. Volume changes are essential for sprouting of a lamellipodium. Because volume regulation is associated with modulation of chloride conductances, we focused on the impact of chloride conductances on the formation of a lamellipodium. We identified swelling activated chloride channels using a hypoosmotic solution via patch clamp techniques and KCl cotransporters (KCC) using RT-PCR in the microglial cell line, BV-2. These chloride conductances were reversibly inhibited by DIOA, a routinely used blocker of KCC, and flufenamic acid, which blocks swelling activated chloride channels. Interestingly, BV-2 cells exposed to an isoosmotic KCl solution, leading to an inversion of KCl cotransport and, thus, to a water influx, rapidly formed a vibrant lamellipodium, which was inhibited by blockade of chloride conductances.<br />Microglia in conventional cell culture show an amoeboid phenotype and have to be secondarily inactivated. We demonstrated that the phorbol ester, PMA, a commonly used activator for protein kinase C (PKC), induced ramification in BV-2 cells. None of the PKC inhibitors used, counteracted PMA-induced ramification. Therefore, we assume that a PMA-binding protein, excluding PKC isoforms, is critical for the structural remodelling of microglial cells. To investigate, whether ion channels and transporters are associated with the transformation from an amoeboid to a ramified phenotype, we evaluated the contributions of ion conductances to the PMA-dependent ramification. Blockade of chloride currents suppressed microglial ramification. Further, we induced a multipolar morphology of BV-2 cells culturing them in three-dimensional environment. Induction of apoptosis is another strategy to control proliferative activity of microglial cells. Since very little is known about cell death in microglia, we investigated the mechanism of apoptosis in BV-2 cells. Therefore, we studied the ultrastructural distribution of chromatin during apoptosis, using UV-irradiation as a trigger of apoptosis. Moreover, we induced programmed cell death in microglial cells via ammonia and distinct tocopherol analogues, respectively. Because microglia play an essential part in neuroinflammatory diseases, it is of great interest to evaluate their activation status. Migration, ramification or apoptosis are possible mechanisms to control the proliferative and inflammatory activity of microglial cells.