Aims: Azelnidipine, a third-generation dihydropyridine calcium channel blocker (DHP CCB), has a characteristic hypotensive effect that persists even after it has disappeared from the plasma, which is thought to be due to its high hydrophobicity. However, because azelnidipine is unique, it might have other unknown effects on L-type Cav1.2 channels that result in the long-lasting decrease of blood pressure. The aim of this study was to investigate the potential quantitative modification of Cav1.2 by azelnidipine.
Main methods: HEK293 cells were used to express Cav1.2 channels. Immunocytochemical analysis was performed to detect changes in the surface expression of the pore-forming subunit of the Cav1.2 channel, Cav1.2α1c. Western blotting analysis was performed to evaluate changes in expression levels of total Cav1.2α1c and Cavβ2c.
Key findings: The surface expression of Cav1.2α1c was markedly reduced by treatment with azelnidipine, but not with other DHP CCBs (amlodipine and nicardipine). Results obtained with a dynamin inhibitor and an early endosome marker suggested that the reduction of surface Cav1.2α1c was not likely caused by internalization. Azelnidipine reduced the total amount of Cav1.2α1c protein in HEK293 cells and rat pulmonary artery smooth muscle cells. The reduction of Cav1.2α1c was rescued by inhibiting proteasome activity. In contrast, azelnidipine did not affect the amount of auxiliary Cavβ2c subunits that function as a chaperone of Cav1.2.
Significance: This study is the first to demonstrate that azelnidipine reduces the expression of Cav1.2α1c, which might partly explain its long-lasting hypotensive effect.
Keywords: Azelnidipine; Ca(v)1.2; Ca(v)β; Dihydropyridines; Hypotensive effect; Proteasomal degradation.
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