A CYCLIC PEPTIDE ANALOG OF LOOP-III OF PDGF-BB CAUSES APOPTOSIS IN HUMAN FIBROBLASTS

A cyclic peptide analogue of platelet-derived growth factor-BE (PDGF-B E), Fl [(IVRKK81)-I-77-C-(RKIE76)-R-73], has recently been shown to in hibit specifically [I-125]PDGF-BB/receptor binding, and PDGF-BB-induce d DNA synthesis in cells expressing PDGF receptors, Here we demonstrat e that P1 induces apoptosis in exponentially growing human fibroblasts as confirmed by characteristic changes in cell and nuclear morphology , by TUNEL staining and by flow cytometry, Following incubation with P 1 (100 mu M), the percentage of cells exhibiting DNA fragmentation inc reased from 24% after 8 h to 76% after 28 h as exponentially growing c ells progressed through the cell cycle, We conclude from these finding s taken together that apoptosis accounts for the major proportion of P I-induced cell death, Omission of the Cys residue from P1 or replaceme nt by Ser did not alter the potency of the peptide confirming that pep tide dimerisation is not important for its activity, PDGF-BB, EGF, FGF , thrombin and foetal bovine serum were not able to rescue cells from the effects of Fl, Fl is a useful tool for investigation of the balanc e of cellular proliferation/apoptosis in wound healing, atherosclerosi s and restenosis, and constitutes a basis from which to design compoun ds with greater potency. (C) 1997 Federation of European Biochemical S ocieties.