Dataset Information

Mitochondrial reactive oxygen species perturb AKT/cyclin D1 cell cycle signaling via oxidative inactivation of PP2A in lowdose irradiated human fibroblasts.

ABSTRACT: Here we investigated the cellular response of normal human fibroblasts to repeated exposure to low-dose radiation. In contrast to acute single radiation, low-dose fractionated radiation (FR) with 0.01 Gy/fraction or 0.05 Gy/fraction for 31 days increased in mitochondrial mass, decreased cellular levels of the antioxidant glutathione and caused persistent accumulation of mitochondrial reactive oxygen species (ROS). Excess ROS promoted oxidative inactivation of protein phosphatase PP2A which in turn led to disruption of normal negative feed-back control of AKT/cyclin D1 signaling in cells treated with long-term FR. The resulting abnormal nuclear accumulation of cyclin D1 causes growth retardation, cellular senescence and genome instability in low-dose irradiated cells. Thus, loss of redox control and subsequently elevated levels of ROS perturb signal transduction as a result of oxidative stress. Our study highlights a specific role of mitochondrial ROS in perturbation of AKT/cyclin D1 cell cycle signaling after low-dose long-term FR. The antioxidants N-acetyl-L-cysteine, TEMPO and mitochondrial-targeted antioxidant Mito-TEMPO provided protection against the harmful cell cycle perturbations induced by low-dose long-term FR.

SUBMITTER: Shimura T

PROVIDER: S-EPMC4823127 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Mitochondrial reactive oxygen species perturb AKT/cyclin D1 cell cycle signaling via oxidative inactivation of PP2A in lowdose irradiated human fibroblasts.

Shimura Tsutomu T Sasatani Megumi M Kamiya Kenji K Kawai Hidehiko H Inaba Yohei Y Kunugita Naoki N

Oncotarget 20160101 3

Here we investigated the cellular response of normal human fibroblasts to repeated exposure to low-dose radiation. In contrast to acute single radiation, low-dose fractionated radiation (FR) with 0.01 Gy/fraction or 0.05 Gy/fraction for 31 days increased in mitochondrial mass, decreased cellular levels of the antioxidant glutathione and caused persistent accumulation of mitochondrial reactive oxygen species (ROS). Excess ROS promoted oxidative inactivation of protein phosphatase PP2A which in tu ...[more]

PMID: 26657292

Similar Datasets

Project description:BACKGROUND:Idiopathic Pulmonary Fibrosis (IPF) is a debilitating disease characterized by exaggerated extracellular matrix deposition and aggressive lung structural remodeling. Disease pathogenesis is driven by fibroblastic foci formation, consequent on growth factor overexpression and myofibroblast proliferation. We have previously shown that both CTGF overexpression and myofibroblast formation in IPF cell lines are dependent on RhoA signaling. As RhoA-mediated regulation is also involved in cell cycle progression, we hypothesise that this pathway is key to lung fibroblast turnover through modulation of cyclin D1 kinetic expression. METHODS:Cyclin D1 expression was compared in primary IPF patient-derived fibroblasts and equivalent normal control cells. Quantitative real time PCR was employed to examine relative expression levels of cyclin D1 mRNA; protein expression was confirmed by western blotting. Effects of Rho signaling were investigated using transient transfection of constitutively active and dominant negative RhoA constructs as well as pharmacological inhibitors. Cellular proliferation of lung fibroblasts was determined by BrdU incorporation ELISA. To further explore RhoA regulation of cyclin D1 in lung fibroblasts and associated cell cycle progression, an established Rho inhibitor, Simvastatin, was incorporated in our studies. RESULTS:Cyclin D1 expression was upregulated in IPF compared to normal lung fibroblasts under exponential growth conditions (p < 0.05). Serum deprivation inhibited cyclin D1 expression, which was restored following treatment with fibrogenic growth factors (TGF-beta1 and CTGF). RhoA inhibition, using a dominant negative mutant and a pharmacological inhibitor (C3 exotoxin), suppressed levels of cyclin D1 mRNA and protein in IPF fibroblasts, with significant abrogation of cell turnover (p < 0.05). Furthermore, Simvastatin dose-dependently inhibited fibroblast cyclin D1 gene and protein expression, inducing G1 cell cycle arrest. Similar trends were observed in control experiments using normal lung fibroblasts, though exhibited responses were lower in magnitude. CONCLUSION:These findings report for the first time that cyclin D1 expression is deregulated in IPF through a RhoA dependent mechanism that influences lung fibroblast proliferation. This potentially unravels new molecular targets for future anti-IPF strategies; accordingly, Simvastatin inhibition of Rho-mediated cyclin D1 expression in IPF fibroblasts merits further exploitation.

Project description:The cyclin D1 oncogene encodes the regulatory subunit of a holoenzyme that phosphorylates and inactivates the Rb protein and promotes progression through G1 to S phase of the cell cycle. Several prostate cancer cell lines and a subset of primary prostate cancer samples have increased cyclin D1 protein expression. However, the relationship between cyclin D1 expression and prostate tumor progression has yet to be clearly characterized. This study examined the effects of manipulating cyclin D1 expression in either human prostatic epithelial or stromal cells using a tissue recombination model. The data showed that overexpression of cyclin D1 in the initiated BPH-1 cell line increased cell proliferation rate, but did not elicit tumorigenicity in vivo. However, overexpression of cyclin D1 in Normal Prostate Fibroblasts (NPF) that were subsequently recombined with BPH-1 did induce malignant transformation of the epithelial cells. The present study also showed that recombination of BPH-1 + cyclin D1 overexpressing fibroblasts (NPF cyclin D1) resulted in permanent malignant transformation of epithelial cells (BPH-1 NPF-cyclin D1 cells) similar to that seen with Carcinoma Associated Fibroblasts (CAFs). Microarray analysis showed that the expression profiles between CAFs and NPF cyclin D1 cells were highly concordant including cyclin D1 upregulation. These data indicated that the tumor-promoting activity of cyclin D1 may be tissue-specific. Keywords: cyclin D1; stromal-epithelial interactions; prostate cancer; cDNA microarray NPF cyclin D1 cells were generated from NPFs, which were isolated from two different patient samples; CAFs were isolated from two different patient samples as well. RNA was isolated from NPFs, CAFs, and NPF cyclin D1 cells using total RNA isolation kit (Qiagen). Custom spotted cDNA microarrays were constructed as previously described (True, L., Coleman, I., Hawley, S., Huang, C. Y., Gifford, D., Coleman, R., Beer, T. M., Gelmann, E., Datta, M., Mostaghel, E., Knudsen, B., Lange, P., Vessella, R., Lin, D., Hood, L., and Nelson, P. S. A molecular correlate to the Gleason grading system for prostate adenocarcinoma. Proc Natl Acad Sci U S A, 103: 10991-10996, 2006) using a non-redundant set of 6,700 prostate-derived cDNA clones identified from the Prostate Expression Data Base (PEDB), a public sequence repository of expressed sequence tag data derived from human prostate cDNA libraries. Total RNA was amplified through one round of linear amplification using the MessageAmp aRNA kit (Ambion, Austin, TX). Sample quality and quantification was assessed by agarose gel electrophoresis and absorbance at A260. Cy3 and Cy5 labeled cDNA probes were made from 4 M-BM-5g of amplified RNA. Two NPF cyclin D1 and two CAF samples (labeled with Cy3) were hybridized head-to-head with an NPF control sample labeled with Cy5. Probes were hybridized competitively to microarrays under a coverslip for 16 h at 63M-BM-0C. Fluorescent array images were collected for both Cy3 and Cy5 by using a GenePix 4000B fluorescent scanner, and image intensity data were gridded and extracted using GenePix Pro 4.1 software. Differences in gene expression between NPF cyclin D1/NPF and CAF/NPF groups were determined using a two-sample t-test with Significance Analysis of Microarrays (SAM) software (http://www-stat.stanford.edu/_tibs/SAM/) with a False Discovery Rate (FDR) of M-bM-^IM-$ 10% considered significant (Tusher, PNAS, 2001). Similarities in gene expression between NPF cyclin D1/NPF and CAF/NPF groups were determined using a one-sample t-test in SAM with an FDR of M-bM-^IM-$ 0.1% considered significant. These results were reduced to unique genes by eliminating all but the highest scoring clones for each gene. A Pearson correlation coefficient was calculated in Excel to assess the strength of the linear relationship between NPF cyclin D1/NPF and CAF/NPF average log2 ratios.

Dataset Information

Mitochondrial reactive oxygen species perturb AKT/cyclin D1 cell cycle signaling via oxidative inactivation of PP2A in lowdose irradiated human fibroblasts.

Publications

Mitochondrial reactive oxygen species perturb AKT/cyclin D1 cell cycle signaling via oxidative inactivation of PP2A in lowdose irradiated human fibroblasts.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets