Apoptosis of endothelial cells triggers a caspase-dependent anti-apoptotic paracrine loop active on VSMC

• Published in: The FASEB journal Vol. 18; no. 6; p. 705
• Main Authors: Raymond, Marc-André, Désormeaux, Anik, Laplante, Patrick, Vigneault, Normand, Filep, Janos G, Landry, Karine, Pshezhetsky, Alexey V, Hébert, Marie-Josée
• Format: Journal Article
• Language: English
• Published: United States 01.04.2004
• Subjects: Animals; Apoptosis; bcl-X Protein; Biological Factors - metabolism; Caspases - metabolism; Endothelium, Vascular - cytology; Endothelium, Vascular - enzymology; Endothelium, Vascular - metabolism; Heparan Sulfate Proteoglycans - chemistry; Heparan Sulfate Proteoglycans - physiology; Humans; Mitogen-Activated Protein Kinases - metabolism; Models, Biological; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - metabolism; Paracrine Communication; Proto-Oncogene Proteins c-bcl-2 - metabolism; Rats; Tumor Suppressor Protein p53 - metabolism
• ISSN: 1530-6860
• DOI: 10.1096/fj.03-0573fje

Increased endothelial apoptosis and decreased apoptosis of vascular smooth muscle cells (VSMC) are central to initiation of myo-intimal thickening. We hypothesized that apoptosis of endothelial cells (EC) induces the release of anti-apoptotic mediator(s) active on VSMC. We found that serum-free medium conditioned by apoptotic EC decreases apoptosis of VSMC compared with fresh serum-free medium. Inhibition of endothelial apoptosis during conditioning with a pan-caspase inhibitor ZVAD-FMK blocked the release of the anti-apoptotic factor(s) active on VSMC. VSMC exposed to serum-free medium conditioned by apoptotic EC showed increased ERK 1/2 phosphorylation, enhanced Bcl-xl expression, and inhibition of p53 expression. Fractionation of the conditioned medium followed by mass spectral analysis identified one bioactive component as a C-terminal fragment of the domain V of perlecan. Serum-free medium supplemented with either a synthetic peptide containing the EGF motif of the domain V of perlecan or chondroitin 4-sulfate, a glycosaminoglycan anchored on the domain V of perlecan, increased ERK 1/2 phosphorylation and Bcl-xl protein levels while inhibiting apoptosis of VSMC. These results suggest that a proteolytic activity developing downstream of activated caspases in apoptotic EC initiates degradation of pericellular proteoglycans and liberation of bioactive fragments with a robust impact on inhibition of VSMC apoptosis.