Backgrounds: Although it is well established that adrenergic stimulation and ß-receptor signaling play important roles for the occurrence of Takotsubo syndrome (TTS), both clinical and experimental data suggested an involvement of signaling mediated by non-ß-adrenoceptors in the pathogenesis of the disease. Here we report that dopamine D1-receptor /protein kinase A (PKA) signaling contributes to catecholamine excess induced endothelial dysfunction via activating small conductance calcium-activated potassium channels (SK1-3).

Methods: Human cardiac microvascular endothelial cells (HCMECs) were treated with 300 µM epinephrine (Epi) to mimic catecholamine excess.  The qPCR, ELISA, flow cytometry and patch clamp analyses were performed.

Results: qPCR and immunostaining detected dopamine D1-receptor in HCMECs. Epi activated SK1-3 channels and suppressed NO production in HCMECs. The Epi-effects could be attenuated by dopamine receptor antagonist SCH23390 (10 µM), suggesting involvement of D1 dopamine receptor in Epi-effects.  The D1-receptor agonist SKF38393 (10 µM) mimicked Epi-effects on SK1-3 channel currents (ISK1-3) or NO production and SCH23390 abolished their effects. These further confirmed the important roles of D1-receptor for endothelial dysfunctions. A PKA blocker (H89, 10 µM) abolished and a PKA activator (8-brom-cAMP, 5 µM) mimicked the effect of the D1-receptor agonist SKF38393, indicating the importance of PKA for D1-receptor effects. A ROS blocker (NAC, 1 mM) blocked and H2O2 (100 µM) mimicked the effect of SKF38393 on ISK1-3. NAC abolished the cAMP-effect, while H89 failed to change the H2O2 effect on ISK1-3, suggesting PKA is upstream factor of ROS in D1-receptor signaling.