Transforming growth factor-beta inhibits apoptosis induced by beta-amyloid peptide fragment 25-35 in cultured neuronal cells.
Previously, we demonstrated that transforming growth factor-beta (TGF-beta) pretreatment protects neuroblastoma cell lines, human hNT neurons, and primary rat embryo hippocampal neurons (REHIPs) from degeneration caused by incubation with beta-amyloid peptide (Abeta). Here we present evidence suggesting that TGF-beta interferes with an apoptotic pathway induced by Abeta. TGF-beta preteatment decreases the amount of DNA laddering seen following Abeta treatment in neuroblastoma cells, while in REHIPs, TGF-beta decreases the number of positive cells detected in situ by Klenow labelling following Abeta treatment. RT-PCR shows that in REHIPs, Abeta decreases mRNA expression of Bcl-2, as well as the ratio of Bcl-xL/Bcl-xS, with little effect on Bax expression. These changes are expected to promote apoptosis. When REHIPs are incubated with TGF-beta before addition of Abeta, the Bcl-xL/Bcl-xS ratio and Bcl-2 levels are increased compared to cells treated with Abeta alone. Again there is little effect on Bax expression. Western blotting and immunohistochemistry experiments also show that TGF-beta maintains increased levels of Bcl-2 and Bcl-xL protein in REHIPs even in the presence of Abeta. This pattern of gene expression should function to decrease apoptosis. Similarly, RT-PCR analysis of mRNA prepared from hNT cells shows that TGF-beta pretreatment before addition of Abeta maintains a higher level of Bcl-2 expression and an increased Bcl-xL/Bcl-xS ratio as compared to cells treated with Abeta alone. In neuronal cell types treated with Abeta, TGF-beta appears to regulate expression of genes in the Bcl-2 family to favor an anti-apoptotic pathway.
Kim
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Laboratory of Cell Regulation and Carcinogenesis, National Cancer Institute, Building 41/Room C-629, 41 Library Dr MSC 5055, Bethesda, MD 20892, USA. flanderk@dce41.nci.nih.gov
Kim
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Ren
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Hawver
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Flanders
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KC
D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects*; D019254:Genes, bcl-2; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D051379:Mice; D009447:Neuroblastoma / Q000473:pathology; D009474:Neurons / Q000187:drug effects* / Q000473:pathology; D010446:Peptide Fragments / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
D016229:Amyloid beta-Peptides; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C494827:Bax protein, mouse; C494828:Bax protein, rat; C494812:Bcl2l1 protein, mouse; C494813:Bcl2l1 protein, rat; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016212:Transforming Growth Factor beta; C074636:amyloid beta-protein (25-35); D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein