α₁-Adrenoceptor stimulation enhances leukemia inhibitory factor-induced proliferation of mouse-induced pluripotent stem cells.

Since the clinical use of induced pluripotent stem (iPS) cells may overcome the current obstacles in stem cell-based therapy, the molecular mechanisms that regulate iPS cell proliferation are of great interest. Therefore, in the present study, we determined the involvement of α(1)-adrenoceptor in the proliferation of mouse iPS cells. The selective α(1)-adrenoceptor agonist l-phenylephrine dose-dependently increased the proliferation of mouse iPS cells cultured in a medium with leukemia inhibitory factor (LIF). Pretreatment with either selective α(1)-adrenoceptor antagonists or protein kinase C (PKC) inhibitors significantly inhibited l-phenylephrine-induced DNA synthesis. The treatment with an IP(3) receptor agonist significantly enhanced LIF-induced DNA synthesis. On the other hand, we confirmed that the intracellular calcium level was increased by the treatment with l-phenylephrine. Thus, intracellular calcium release or PKC activation induced by α(1)-adrenoceptor activation may lead to the enhancement of DNA synthesis. In addition, pretreatment with mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor PD98059 or phosphatidylinositol-3 phosphate kinase (PI3K) inhibitor LY294002 significantly inhibited l-phenylephrine-induced DNA synthesis. Treatment with l-phenylephrine significantly increased Akt or p44/42 MAPK phosphorylation. α(1)-Adrenoceptor expression in mouse iPS cells was confirmed by immunofluorescence staining and western blotting analysis. In mouse iPS cells cultured with LIF, stimulation with l-phenylephrine significantly increased the proportion of cells in the S and G(2)/M phases and decreased that in the G(1) phase. These results suggest that stimulation with α(1)-adrenoceptor may enhance DNA synthesis and proliferation of mouse iPS cells cultured with LIF via augmentation of both the MEK/MAPK and the PI3K/Akt pathways.