Abstract 16157: Connexin 43 Acts as a Counter Regulatory Molecule of Caveolin- 1 in the Control of Angiogenesis
Background: Apart from an important component of the gap junction, connexin 43 (Cx43) has been known to regulate other cellular functions like cell proliferation. This regulatory role of Cx43 could be of much importance in therapeutic situations like wound healing. On the other hand, recently it has been shown that caveolin-1 (Cav-1) acts as a negative regulator of angiogenesis. The aim of the present study was whether Cx43 acts as a counter regulator of Cav-1 in the control of endothelial cell proliferation and migration.
Methods and results: Inhibition of Cx43 with niflumic acid, flufenamic acid and 18-α-glycyrrhetinic acid (50 µM for 48 hrs) in cultured human umbilical vein endothelial cells (HUVEC) resulted in a decreased phosphorylation of p42/44 MAPK and increased expression of Cav-1(western blot). Furthermore inhibition of Cx43 resulted in 50±7% decrease (n=5; p<0.05 for all further parameters) in cell proliferation (crystal violet assay), 48±5% decrease in migration (migration assay) and 49±6% decrease in tube formation of endothelial cells (Matrigel assay) compared to control. Similar results were obtained with specific inhibition of Cx43 by mimetic peptides (Gap26 and Gap27; 0.25 µg/ml). Accordingly inhibition of MEK/ERK pathway with PD98059 (10 µM, 48 hrs) resulted in an increased expression of Cav-1, a reduction in Cx43 expression and impaired cell proliferation, migration and sprouting of endothelial cells. Contrariwise, down-regulation of Cav-1 by small interference RNA resulted in an increased expression of Cx43 and increased phosphorylation of p42/44 MAPK. Accordingly the cell number increased by 35±5% compared to controls.
Conclusion: The data of the present study shows that Cav-1 suppresses the cell proliferation via suppression of Cx43 activity upstream to p42/44 MAPK. Knockdown of Cav-1 results in loss of this suppressive activity of Cav-1 and cells undergo cell cycle progression. This counter regulatory role of Cx43 can be of importance in therapeutic angiogenesis.
- © 2011 by American Heart Association, Inc.