Sphingosylphosphorylcholine induces proliferation of human adipose tissue-derived mesenchymal stem cells via activation of JNK

Sphingosylphosphorylcholine (SPC) has been implicated in a variety of cellular responses, including proliferation and differentiation. In this study, we demonstrate that D-erythro-SPC, but not L-threo-SPC, stereoselectively stimulated the proliferation of human adipose tissue-derived mesenchymal stem cells (hADSCs), with a maximal increase at 5 mu M, and increased the intracellular concentration of Ca2+ ([Ca2+](i)) in hADSCs, which do not express known SPC receptors ( i. e., OGR1, GPR4, G2A, and GPR12). The SPC-induced proliferation and increase in [Ca2+] i were sensitive to pertussis toxin (PTX) and the phospholipase C ( PLC) inhibitor U73122, suggesting that PTX-sensitive G proteins, Gi or Go, and PLC are involved in SPC-induced proliferation. In addition, SPC treatment induced the phosphorylation of c-Jun and extracellular signal-regulated kinase, and SPC-induced proliferation was completely prevented by pretreatment with the c-Jun N-terminal kinase (JNK)-specific inhibitor SP600125 but not with the MEK-specific inhibitor U0126. Furthermore, the SPC-induced proliferation and JNK activation were completely attenuated by overexpression of a dominant negative mutant of JNK2, and the SPC-induced activation of JNK was inhibited by pretreatment with PTX or U73122. Treatment of hADSCs with lysophosphatidic acid (LPA) receptor antagonist, Ki16425, had no impact on the SPC-induced increase in [Ca2+](i). However, SPC-induced proliferation was partially, but significantly, attenuated by pretreatment of the cells with Ki16425. These results indicate that SPC stimulates the proliferation of hADSCs through the Gi/Go-PLC-JNK pathway and that LPA receptors may be responsible in part for the SPC-induced proliferation.