ABSTRACT
Spinocerebellar ataxia type-3 or Machado-Joseph disease (SCA3/MJD) is an autosomal dominant neurodegenerative disease caused by triplet nucleotide expansion. The expansion of the polyglutamine tract near the C terminus of the MJD1 gene product, ataxin-3, above a threshold of 40 glutamine repeats causes neuronal loss and degeneration. The expanded ataxin-3 forms aggregates, and nuclear inclusions, within neurons, possibly due to the misfolding of mutant proteins. Here we report upon the behavioral test changes related to truncated and expanded forms of MJD protein (MJDtr) in Drosophila, and show that expanded MJDtr, when expressed in the nervous system, causes characteristic locomotor dysfunction and anosmia. This phenomenon has not been previously reported in humans or in transgenic Drosophila models. In addition, the in vivo expression of the antiapoptotic gene bcl-2 showed no evidence of ameliorating the deleterious effect of MJDtr-Q78s, either in the eye or in the nervous system. The study shows that such Drosophila transgenic models express olfactory dysfunction and ataxic behavior as observed in human patients.
Subject(s)
Behavior, Animal/physiology , Drosophila/metabolism , Nerve Tissue Proteins/metabolism , Peptides/metabolism , Trinucleotide Repeat Expansion/physiology , Animals , Animals, Genetically Modified , Apoptosis/genetics , Ataxin-3 , Disease Models, Animal , Eye Abnormalities/genetics , Eye Abnormalities/metabolism , Machado-Joseph Disease/genetics , Machado-Joseph Disease/metabolism , Machado-Joseph Disease/physiopathology , Movement Disorders/genetics , Movement Disorders/metabolism , Movement Disorders/physiopathology , Nerve Degeneration/genetics , Nerve Degeneration/metabolism , Nerve Degeneration/physiopathology , Nerve Tissue Proteins/genetics , Nervous System/metabolism , Nervous System/pathology , Nervous System/physiopathology , Neurons/metabolism , Neurons/pathology , Nuclear Proteins , Olfaction Disorders/genetics , Olfaction Disorders/metabolism , Olfaction Disorders/physiopathology , Peptides/genetics , Proto-Oncogene Proteins c-bcl-2/genetics , Proto-Oncogene Proteins c-bcl-2/metabolism , Repressor ProteinsABSTRACT
c-Myc is known to control cell proliferation and apoptosis, and much effort has been focused on elucidating the mechanisms by which c-Myc works. In this study, we show that c-Myc expression is induced by many cellular insults, including cisplatin, doxorubicin, paclitaxel, 5-flourouracil, H(2)O(2), and radiation, and the enhanced expression of c-Myc protects against cell death caused by these cellular insults through ornithine decarboxylase (ODC) induction. To investigate the cellular protective role of c-Myc, we constructed a stable transfectant of ODC, one of the many transcriptional targets of c-Myc in cells, and found that enhanced expression of ODC inhibited cell death induced by cellular insults such as cisplatin, H(2)O(2,) and radiation. We also found that cisplatin activated nuclear factor-kappaB, and this subsequently induced c-Myc expression, resulting in the blocking of apoptosis through ODC induction. The results herein, therefore, strongly suggest another role for c-Myc in a stress-response function; that is, it promotes cell survival under stressful conditions.
Subject(s)
Ornithine Decarboxylase/biosynthesis , Proto-Oncogene Proteins c-myc/physiology , Antineoplastic Agents/pharmacology , Cell Survival/physiology , Cisplatin/pharmacology , Enzyme Induction , Gene Expression/drug effects , Humans , NF-kappa B/metabolism , Ornithine Decarboxylase/metabolism , Proto-Oncogene Proteins c-myc/genetics , Tumor Cells, CulturedABSTRACT
PURPOSE: To investigate whether 2'-benzoyl-oxycinnamaldehyde (BCA) induces apoptosis in human retinal pigment epithelial (hRPE) cells and has an antiproliferative effect in a proliferative vitreoretinopathy (PVR) model in the rabbit. METHODS: Fifty percent growth inhibition doses of hRPE cells at 50%, 75%, and 100% confluence were determined by MTT assay. Apoptosis in hRPE cells induced by BCA was shown by DAPI staining. Expression of p53, p21, Bcl-2, GADD45, cyclin D, phospho-MAP kinase, cdk2, and Akt1 at various concentrations of BCA in cultured hRPE cells was examined by immunoblot analysis. In the efficacy study, 2.0 x 10(5) rabbit RPE cells were injected into the vitreous cavity after gas compression, and the eyes subsequently received either sham injections or 600 micro M BCA. Fundus examination was performed before and 1, 7, 14, 21, and 28 days after BCA injection. The toxicity studies were conducted by the same protocol as used for the efficacy evaluation but without the RPE cell injection. Simultaneous electroretinograms were recorded on days 1, 7, 14, 21, and 28 after exposure to the drug. RESULTS: BCA treatment induced apoptosis in hRPE cells. Furthermore, an increase in p53 expression, phosphorylation of Bcl-2, and downregulation of Akt1 expression were observed in BCA-induced apoptotic cells. BCA effectively prevented the proliferation of rabbit RPE cells in the experimental PVR model. BCA exhibited a wide safety margin, showing no evidence of causing retinal toxicity, even at the 600- micro M concentration. CONCLUSIONS: The results of this study suggest that BCA effectively inhibits proliferation of RPE cells and has a very wide safety margin, indicating a potential therapeutic usefulness in treating PVR.
