M2 muscarinic receptors inhibit cell proliferation in human glioblastoma cell lines

In the present work we investigated the expression of M2 muscarinic receptor subtype in two glioblastoma cell lines and its role in the control of cell proliferation. The M2 receptor transcript and protein expression was studied using RT-PCR and western blot analysis. 3[H]-thymidine incorporation was used to evaluate cell proliferation in the presence or in the absence of M2 agonist arecaidine. We demonstrated that M2 receptor is expressed in both cell lines, although U251 cells show a higher expression level, compared to U87 cells. The activation of M2 receptors by the agonist arecaidine decreases cell growth in a dose and time dependent manner. The anti-proliferative effect of arecaidine is also confirmed by the significant decrease of 3[H]-thymidine incorporation in both cell lines. Moreover the M2 antagonist gallamine counteracts the arecaidine effects confirming M2 receptor involvement in glioma cell growth inhibition. These data suggest a role for M2 receptors in the inhibition of glioma cell proliferation and the possibility of exploiting these receptors as new promising tools for glioblastoma therapy.