Connective tissue growth factor (IGFBP-rP2) expression and regulation in cultured bovine endothelial cells

Media from large vessel endothelial cells (pulmonary artery, aorta) contained intact connective tissue growth factor (CTGF) and a dominant 19-kDa band. N-terminal analysis of the 19-kDa band showed sequence corresponding to CTGF amino acid 181-190, suggesting that the 19-kDa band represented a proteolytic fragment of CTGF. Intact CTGF was increased by cAMP but not by transforming growth factor-beta (TGF beta). CTGF messenger RNA (mRNA) was not changed by cAMP nor TGF beta. In two microvessel endothelial cells, mRNA was found at low levels by PCR and Northern analysis, but no CTGF protein was seen on Western analysis. In the microvessel cells, TGF beta increased and cAMP did not change CTGF mRNA levels, with neither TGF beta nor cAMP increasing CTGF protein. The discordance between protein and mRNA levels in large vessel and microvessel endothelial cells was mostly explained by the effects of cAMP and TGF beta on media proteolytic activity; in large vessel cells, cAMP inhibited degradation of CTGF, whereas in microvessel cells, TGF beta and cAMP stimulated proteolytic activity against CTGF. We conclude that in large vessel endothelial cells, cAMP increased intact CTGF protein by inhibiting degradation of CTGF, whereas TGF beta stimulated neither CTGF mRNA nor protein; in microvessel cells, TGF beta increased CTGF mRNA, while both TGF beta and cAMP stimulated CTGF degradation.