Failure of stress-induced downregulation of Bcl-2 contributes to apoptosis resistance in senescent human diploid fibroblasts

• Published in: Cell death and differentiation Vol. 14; no. 5; pp. 1020 - 1028
• Main Authors: Ryu, S J, Oh, Y S, Park, S C
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.05.2007
• Subjects: Apoptosis; Apoptosis - drug effects; Biochemistry; Cell death; Cells, Cultured; Cellular Senescence - drug effects; Cyclic AMP Response Element-Binding Protein - metabolism; Diploidy; Down-Regulation - drug effects; Down-Regulation - genetics; Fibroblasts - cytology; Fibroblasts - drug effects; Fibroblasts - enzymology; Humans; Hydrogen Peroxide - pharmacology; Kinases; Lymphoma; Membrane Potential, Mitochondrial - drug effects; Molecular biology; Phosphatase; Phosphoprotein Phosphatases - metabolism; Phosphoproteins - metabolism; Protein Phosphatase 2; Proteins; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; Senescence; Standard deviation; Staurosporine - pharmacology; Thapsigargin - pharmacology
• ISSN: 1350-9047; 1476-5403
• DOI: 10.1038/sj.cdd.4402091

We previously reported that senescent human diploid fibroblasts (HDFs) are resistant to apoptosis induced by H(2)O(2) and staurosporine. We report here that senescent HDFs are resistant to thapsigargin-induced apoptosis as well. These agonists caused the reductions in mitochondrial membrane potential (MMP) and in the apoptosis inhibitory protein (B-cell lymphoma) only in young HDFs but not in senescent HDFs. In addition, downregulation of Bcl-2 increased the sensitivity of senescent HDFs to apoptosis induction, suggesting the significant role of Bcl-2 in apoptosis resistance of the senescent HDFs. We further found that P-cAMP response element-binding protein (CREB), a positive regulator of Bcl-2, decreased in stress-induced apoptosis of young HDFs but not in senescent HDFs, and that Bcl-2 was markedly reduced in CREB small interfering RNA (siRNA), transfected senescent HDFs. In addition, activity of protein phosphatase 2A (PP2A), which dephosphorylates p-CREB, significantly increased in young HDFs but not in senescent HDFs treated with H(2)O(2), staurosporine or thapsigargin. Taken together, these results suggest that failure of stress-induced downregulation of Bcl-2 underlies resistance of senescent HDFs to apoptosis.