Oxytocin Downregulates the CaV1.2 L-Type Ca2+ Channel via Gi/cAMP/PKA/CREB Signaling Pathway in Cardiomyocytes

Abstract

Oxytocin (OT) and its receptor (OTR) are expressed in the heart and are involved in the physiological cardiovascular functional system. Although it is known that OT/OTR signaling is cardioprotective by reducing the inflammatory response and improving cardiovascular function, the role of OT in the cardiac electrical excitation modulation has not been clarified. This study investigates the molecular mechanism of the action of OT on cardiomyocyte membrane excitation focusing on the L-type Ca2+ channel. Our methodology uses molecular biological methods and a patch-clamp technique on rat cardiomyocytes with OT, combined with several signal inhibitors and/or activators. Our results show that long-term treatment of OT significantly decreases the expression of Cav1.2 mRNA, and reduces the L-type Ca2+ channel current (ICa.L) in cardiomyocytes. OT downregulates the phosphorylated component of a transcription factor adenosine-3′,5′-cyclic monophosphate (cAMP) response element binding protein (CREB), whose action is blocked by OTR antagonist and pertussis toxin, a specific inhibitor of the inhibitory GTP-binding regulators of adenylate cyclase, Gi. On the other hand, the upregulation of Cav1.2 mRNA expression by isoproterenol is halted by OT. Furthermore, inhibition of phospholipase C (PLC) was without effect on the OT action to downregulate Cav1.2 mRNA—which suggests a signal pathway of Gi/protein kinase A (PKA)/CREB mediated by OT/OTR. These findings indicate novel signaling pathways of OT contributing to a downregulation of the Cav1.2-L-type Ca2+ channel in cardiomyocytes.

Repeated oxytocin prevents central sensitization by regulating synaptic plasticity via oxytocin receptor in a chronic migraine mouse model

“…As OTR belongs to the G protein-coupled receptor superfamily, the long-term OT treatment could activate Gαi proteins of OTR and inhibit AC1 activity [ 58 ]. However, the activation of the AC1/PKA/pCREB pathway in acute and chronic pain induces postsynaptic LTP to enhance synaptic transmission efficiency, thus resulting in central sensitization [ 59 , 60 ].…”

“…While previous studies have reported that OT may activate gamma-aminobutyric acid (GABA)ergic interneurons in the spinal dorsal horn and promote GABA release to inhibit the function of postsynaptic glutamate receptors, including NMDA receptors [ 52 , 61 ]. A recent study has demonstrated that long-term treatment with OT can downregulate the expression of PKA and pCREB in neonatal cardiomyocytes [ 58 ]. Comparison of the different mechanisms mentioned above implies that the effect of long-term treatment with OT may be different from the short-term or single-dose reatment.…”

Protein Kinase C Regulates Expression and Function of the Cav3.2 T-Type Ca2+ Channel during Maturation of Neonatal Rat Cardiomyocyte

“…Neonatal rat cardiomyocytes were prepared as described previously [ 10 , 11 ]. Neonatal ventricular myocytes were prepared from 2-8-days-old Wistar rats and maintained at 37 °C under 5% CO 2 in Dulbecco’s modified Eagle’s medium (DMEM) that was supplemented with 10% fetal bovine serum for 24 h, followed by an additional 24 h incubation in DMEM with or without protein kinase inhibitor, or a protein kinase activator (see the figure insets).…”

Enhanced BDNF Actions Following Acute Hypoxia Facilitate HIF-1α-Dependent Upregulation of Cav3-T-Type Ca2+ Channels in Rat Cardiomyocytes

“…All animal experiments confirmed to the Guidelines for the Care and Use of Animals at Oita University, and the NIH guidelines were approved by the institutional committee. Neonatal rat cardiomyocytes were enzymatically isolated and cultured as previously described [ 37 , 38 , 39 ]. After 24 h of culture, >70% of the cells adhered to the substrates and started to exhibit spontaneous beating.…”