Cardiac microvascular endothelial cells express a functional Ca+ -sensing receptor

Area of Science:

• Cardiovascular Biology
• Cellular Physiology
• Molecular Pharmacology

Background:

• Extracellular calcium (Ca2+) plays a critical role in regulating vascular tone, but the precise mechanisms remain incompletely understood.
• Endothelium-dependent control of vascular tone is a key factor in cardiovascular health.
• Identifying novel receptors involved in calcium signaling within endothelial cells is crucial for understanding vascular regulation.

Purpose of the Study:

• To investigate the presence and functionality of the extracellular calcium-sensing receptor (CaSR) in cardiac microvascular endothelial cells (CMEC).
• To determine if CaSR activation in CMEC leads to changes in intracellular calcium concentrations and influences vascular tone.
• To elucidate the signaling pathways involved in CaSR-mediated responses in CMEC.

Main Methods:

• Detection of CaSR mRNA using reverse transcription-polymerase chain reaction (RT-PCR).
• Identification of CaSR protein expression via immunocytochemical analysis.
• Assessment of intracellular Ca2+ mobilization using the calcium-sensitive fluorochrome Fura-2/AM in response to CaSR agonists and modulators.

Main Results:

• CaSR mRNA and protein were successfully detected in CMEC.
• CaSR agonists (spermine, Gd3+, La3+, neomycin) induced a heterogeneous intracellular Ca2+ signal.
• This Ca2+ signal was dependent on inositol 1,4,5-trisphosphate (InsP3) signaling and intracellular Ca2+ stores, and was modulated by the Na+/Ca2+ exchanger.
• Allosteric activators of CaSR potentiated the response to CaSR agonists.

Conclusions:

• Cardiac microvascular endothelial cells express a functional CaSR.
• The CaSR in CMEC is capable of responding to physiological agonists.
• Activation of CaSR mobilizes intracellular Ca2+ from InsP3-sensitive stores, suggesting a role in the endothelium-dependent control of vascular tone.