Dopamine regulates cell cycle regulatory proteins via cAMP, Ca ²⁺/PKC, MAPKs, and NF-κB in mouse embryonic stem cells

This study examined the effect of dopamine on DNA synthesis and its related signal cascades in mouse embryonic stem (ES) cells. Dopamine inhibited DNA synthesis in both a dose-and time-dependent manner. Dopamine, SKF 38393 (D1 receptor agonist), and quinpirole (D2 receptor agonist) decreased the level of [³H]-thymidine incorporation. The level of cyclic adenosine 3, 5-monophosphate (cAMP) was increased by SKF 38393 but not by quinpirole. The protein kinase C (PKC) protein was translocated from the cytosolic fraction to the membrane compartment by dopamine. Dopamine also increased [Ca ²⁺]_i, which was blocked by EGTA (an extracellular Ca ²⁺ chelator), BAPTA-AM (an intracellular Ca²⁺ chelator), nifedipine (a L-type Ca²⁺ channel blocker), SQ 22536 [an adenylyl cyclase (AC) inhibitor] and neomycin [a phospholipase C (PLC) inhibitor]. Dopamine, SKF 38393, and quinpirole increased the level of p44/42 mitogen-activated protein kinases (MAPKs), p38 MAPK, and stress-activated protein kinase/Jun-N-terminal kinase (SAPK/JNK) phosphorylation. Dopamine also increased level of H₂O₂ formation and activated the transcription factor family NF-κB. Moreover, SKF 38393, quinpirole, and dopamine inhibited cell cycle regulatory proteins, which is consistent with the change in the level of [³H]-thymidine incorporation observed. Thedopamine-induced decrease in cyclin E, cyclin-dependent protein kinase-2 (CDK-2), and cyclin D1, CDK-4 were blocked by pertussis toxin (G protein inhibitor), SQ 22536, neomycin, bisindolylmaleimide I (PKC inhibitor), SB 203580 (p38 MAPK inhibitor), PD 98059 (p44/42 inhibitor), and SP 600125 (SAPK/JNK inhibitor). In conclusion, dopamine inhibits DNA synthesis in mouse ES cells via the cAMP, Ca²⁺/PKC, MAPKs, and NF-κB signaling pathways.