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Angiotensin II increases calponin expression in cultured rat vascular smooth muscle cells
C R di Gioia1, W M van de Greef, G Sperti
1Istituto di Cardiologia, Università Cattolica, Rome, Italy.
Abstract:
Angiotensin II (Ang II) action on vascular smooth muscle cells is not limited to contraction, but includes long term effects such as hypertrophy and hyperplasia. This implies a complex pattern of gene modulation, which remains largely unknown. We used the mRNA differential display method to screen rat aortic smooth muscle cells cultured with or without Ang II. We demonstrated that Ang II induces the expression of calponin, a 34-kD protein, which has been shown to regulate smooth muscle cell contraction and to be a marker of smooth muscle cell differentiation. We demonstrated this induction both at gene and protein level in vascular smooth muscle cells. Calponin mRNA was dose-dependently induced by Ang II, with an effect still evident at 5 x 10(-9)M, and it did not require active protein synthesis, since cycloheximide treatment did not suppress this induction. Calponin gene expression was maximal at 3 h, while protein expression was maximal at 8 h. Calponin expression was completely abolished by the AT1 receptor antagonist, losartan, at 1 x 10(-6)M. Our data demonstrate that Ang II increases calponin gene expression and protein level in rat aortic smooth muscle cells in vitro.
Insights
Angiotensin II (Ang II) significantly increases calponin gene and protein expression in rat aortic smooth muscle cells. This finding reveals a key molecular mechanism underlying Ang II
Area of Science:
- Vascular biology
- Molecular cardiology
- Cellular signaling
Background:
- Angiotensin II (Ang II) influences vascular smooth muscle cells beyond contraction, affecting hypertrophy and hyperplasia.
- The underlying gene modulation patterns for these long-term effects are not well understood.
Purpose of the Study:
- To investigate the impact of Ang II on gene expression in rat aortic smooth muscle cells.
- To identify specific genes modulated by Ang II in vascular smooth muscle cells.
Main Methods:
- Utilized mRNA differential display to screen gene expression changes in rat aortic smooth muscle cells.
- Cultured cells with and without Ang II, assessing gene and protein levels of calponin.
- Employed cycloheximide to test the requirement for active protein synthesis and losartan to block AT1 receptors.
Main Results:
- Ang II dose-dependently induced calponin gene expression, detectable at 5 x 10(-9)M.
- Calponin induction occurred without requiring active protein synthesis.
- Calponin gene expression peaked at 3 hours, while protein expression peaked at 8 hours.
- Losartan completely blocked Ang II-induced calponin expression, confirming AT1 receptor involvement.
Conclusions:
- Angiotensin II significantly upregulates calponin gene and protein expression in rat aortic smooth muscle cells in vitro.
- Calponin induction by Ang II is an early, direct effect mediated via the AT1 receptor.
- This study highlights calponin as a key target gene in Ang II-mediated vascular smooth muscle cell modulation.