Zde - 2. lékařská fakulta - Univerzita Karlova

P-78. THE FUNCTIONAL EXPRESSION OF TRPV4 CHANNELS IS SIGNIFICANTLY INCREASEDIN REACTIVE HIPPOCAMPAL ASTROCYTES SEVEN DAYS AFTER CEREBRALHYPOXIA/ISCHEMIAButenko O., Dzamba D., Benesova J., Honsa P., Anderova M.Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences ofthe Czech Republic, Prague, Czech RepublicŠkolitel: Ing. Miroslava Anděrová, CScÚvod: During ischemia/reperfusion, rapid Ca2+ entry in astrocytes can occur via the activation ofvoltage-gated Ca2+ channels, NMDA and P2X7 receptors, Na/Ca2+ exchangers or transient receptorpotential (TRP) channels. Recently, the expression of the TRPV4 channel, a member of the vanilloidsubfamily, was demonstrated in cultured astrocytes and adult rat cortical astrocytes (Benfenati et al.,2007). However, the role of TRPV4 channels in astrocyte pathophysiology was not elucidated yet.Cíl: We studied the functional expression of astrocytic TRPV4 channels in the adult rat hippocampalCA1 region after cerebral hypoxia/ischemia (H/I) induced by bilateral carotid occlusion combined withhypoxic conditions and followed by reperfusion.Materiál a metody: We have compared TRPV4 channel expression in astrocytes of sham-operatedrats (controls) and those 1 hour (1H) or 7 days (7D) after H/I employing immunocyto/histochemicalanalyses, the patch-clamp technique and intracellular Ca2+ imaging on adult hippocampal astrocytesin situ and in vitro.Výsledky: Immunocyto/histochemical analyses revealed the increased expression of TRPV4 channelsin astrocytes 1H and 7D after H/I when compared to controls, coinciding with the developingastrogliosis. Patch-clamp recordings in vitro showed a typical TRPV4 current activated by specificagonist 4αPDD in astrocytes isolated from controls and after H/I; however, a significantly increasedTRPV4 current amplitude/density was detected only in astrocytes 7D after H/I. 4αPDD-inducedcurrents were abolished by the removal of extracellular Ca2+ or the application of RN1734 orRuthenium Red. Ca2+ imaging measurements in vitro confirmed enhanced TRPV4-specific Ca2+entry in astrocytes isolated from animals 7D after H/I. Moreover, an increasing incidence of 4αPDDinducedCa2+ entry was revealed in astrocytes isolated from the ischemic hippocampus. Similarly, inastrocytes in situ, 4αPDD application significantly increased the transient calcium spike rate andTRPV4 current amplitude in astrocytes 7D after H/I.Závěr: Collectively, our data show that TRPV4 cation channels are involved in ischemia-induced Ca2+entry in reactive astrocytes and might be involved in the pathogenic mechanisms of astroglial reactivityfollowing ischemic insult.Podpora projektu: Supported by GACR P303/10/1338, GACR309/08/H079110