Functional expression of the serotonin 5-HT 7 receptor in human glioblastoma cell lines

Abstract

1 Serotonin 5-HT 7 receptors are present in astrocytes. Understanding their role in this type of cell would greatly benefit from the identification of astroglial cell lines expressing this receptor type. 2 The aim of the present study was to assess the expression of native 5-HT 7 receptors and 5-HT 7 receptor mRNA in a number of human glioblastoma cell lines, by means of cAMP measurements, Western blot analysis and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. 3 5-Hydroxytryptamine (5-HT), 5-carboxamidotryptamine (5-CT), 5-methoxytryptamine (5-MeOT) and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) induced concentration- dependent stimulations of cAMP accumulation in the human glioblastoma cell lines, U-373 MG, U-138 MG, U-87 MG, DBTRG-05MG, T98G, H4, CCF-STTG1 and Hs 683. The rank order of potency was 5-CT>5-HT = 5-MeOT≫8-OH-DPAT. 4 The effect of 5-CT was inhibited in a concentration-dependent manner by the selective 5-HT 7 receptor antagonist SB-269970 in all human glioblastoma cells. Schild analyses yielded slope factors close to unity (0.89-1.13) and pA 2 values of 8.69-9.05. 5 Western blot analysis revealed the presence of immunoreactive bands corresponding to the human 5-HT 7 receptor in extracts of all human glioblastoma cell lines. 6 The presence of the three splice variants of the 5-HT 7 receptor (5-HT 7(a/b/d)) was visualized by RT-PCR analysis with specific primers in all human glioblastoma cell lines. 7 In conclusion, human glioblastoma cell lines express functional 5-HT 7 receptors and the three splice variants of the corresponding mRNA. These cell lines could serve as model systems of native 5-HT 7 receptors in glial cells to investigate their putative role in processes like release of neurotrophic factors or inflammatory cytokines.