TGF-beta(1) downregulates PTHrP in coronary endothelial cells

Area of Science:

• Cardiovascular Biology
• Endocrinology
• Molecular Biology

Background:

• Parathyroid hormone-related peptide (PTHrP) is present in the cardiovascular system, particularly in coronary endothelial cells.
• The regulatory factors influencing cardiac PTHrP expression remain largely unexamined.
• Transforming growth factor-beta(1) (TGF-β1) is implicated in various cardiovascular conditions.

Purpose of the Study:

• To investigate the effect of TGF-β1 on ventricular PTHrP expression.
• To explore the relationship between TGF-β1, PTHrP, and cardiac hypertrophy in different physiological and pathophysiological states.

Main Methods:

• Isolation of rat coronary endothelial cells for in vitro analysis.
• Immunoblotting and RT-PCR to quantify PTHrP protein and mRNA levels.
• Studies in transgenic mice overexpressing TGF-β1 and in spontaneously hypertensive rats (SHR-SP).
• Investigation of ventricular PTHrP in a rat model of pressure-induced cardiac hypertrophy (aortic banding).

Main Results:

• TGF-β1 caused a concentration-dependent decrease in PTHrP protein in cultured coronary endothelial cells within 24 hours.
• Transgenic mice overexpressing TGF-β1 exhibited reduced ventricular PTHrP protein and mRNA.
• In aging SHR-SP rats, increased TGF-β1 correlated with downregulated ventricular PTHrP mRNA.
• Pressure-induced cardiac hypertrophy without TGF-β1 induction led to transiently increased ventricular PTHrP.
• PTHrP expression was reduced under all conditions involving TGF-β1 exposure to coronary endothelial cells.

Conclusions:

• TGF-β1 downregulates PTHrP expression in ventricular coronary endothelial cells.
• Cardiac PTHrP expression does not correlate with cardiac hypertrophy.
• The downregulation of PTHrP by TGF-β1 is significant for the paracrine functions of PTHrP in the ventricle.