Angiotensin II Increases Expression of 1C Subunit of L-Type Calcium Channel Through a Reactive Oxygen Species and cAMP Response Element–Binding Protein–Dependent Pathway in HL-1 Myocytes

Angiotensin II (Ang II) is involved in the pathogenesis of atrial fibrillation (AF). L-type calcium channel (LCC) expression is altered in AF remodeling. We investigated whether Ang II modulates LCC current through transcriptional regulation, by using murine atrial HL-1 cells, which have a spontaneous calcium transient, and an in vivo rat model. Ang II increased LCC 1C subunit mRNA and protein levels and LCC current density, which resulted in an augmented calcium transient in atrial myocytes. An 2-kb promoter region of LCC 1C subunit gene was cloned to the pGL3 luciferase vector. Ang II significantly increased promoter activity in a concentrationand time-dependent manner. Truncation and mutational analysis of the LCC 1C subunit gene promoter showed that cAMP response element (CRE) ( 1853 to 1845) was an important cis element in Ang II-induced LCC 1C subunit gene expression. Transfection of dominant-negative CRE binding protein (CREB) (pCMV-CREBS133A) abolished the Ang II effect. Ang II (1 mol/L, 2 hours) induced serine 133 phosphorylation of CREB and binding of CREB to CRE and increased LCC 1C subunit gene promoter activity through a protein kinase C/NADPH oxidase/reactive oxygen species pathway, which was blocked by the Ang II type 1 receptor blocker losartan and the antioxidant simvastatin. In the rat model, Ang II infusion increased LCC 1C subunit expression and serine 133 phosphorylation of CREB, which were attenuated by oral losartan and simvastatin. In summary, Ang II induced LCC 1C subunit expression via a protein kinase C–, reactive oxygen species–, and CREB-dependent pathway and was blocked by losartan and simvastatin. (Circ Res. 2007;100:1476-1485.)