Panneerselvam M.,University of California at San Diego |
Ali S.S.,University of California at San Diego |
Ali S.S.,Helmy Institute for Medical science |
Finley J.C.,University of California at San Diego |
And 6 more authors.
Molecular Nutrition and Food Research | Year: 2013
Scope: The flavanol (-)-epicatechin (Epi), a component of cacao, has cardiac protective benefits in humans. Our previous study demonstrated Epi has δ-opioid receptor (DOR) binding activity and promotes cardiac protection. Here we examined the effects of 10 days of Epi treatment on: cardiac mitochondrial respiration, reactive oxygen species production, calcium swelling, and mitochondrial membrane fluidity. Methods and results: Mice were randomized into four groups: (i) control (saline), (ii) naltrindole (Nalt; DOR antagonist), (iii) Epi, and (iv) Epi + Nalt and received 1 mg/kg Epi or water via oral gavage. Nalt groups received 5 mg/kg ip per day for 10 days. Significant increases in mitochondrial respiration and enhanced free radical production during state 3 respiration were observed with Epi. Additionally, we observed significant increases in rigidity of mitochondrial membranes and resistance to calcium-induced mitochondrial swelling with Epi treatment. Blocking the DOR with Nalt resulted in decreases in all of the observed parameters by Epi treatment. Conclusion: These findings indicate that Epi induces an integrated response that includes metabolic and structural changes in cardiac mitochondria resulting in greater functional capacity via DOR. Mitochondrial targeted effects of epicatechin may explain the physiologic benefit observed on cardiac protection and support epicatechin's potential clinical application as a cardiac protective mimetic. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source
Alagoz M.,University of Sussex |
Chiang S.-C.,University of Sussex |
Sharma A.,University of Sussex |
El-Khamisy S.F.,University of Sussex |
And 2 more authors.
PLoS ONE | Year: 2013
Accumulation of peptide-linked DNA breaks contributes to neurodegeration in humans. This is typified by defects in tyrosyl DNA phosphodiesterase 1 (TDP1) and human hereditary ataxia. TDP1 primarily operates at single-strand breaks (SSBs) created by oxidative stress or by collision of transcription machinery with topoisomerase I intermediates (Top1-CCs). Cellular and cell-free studies have shown that Top1 at stalled Top1-CCs is first degraded to a small peptide resulting in Top1-SSBs, which are the primary substrates for TDP1. Here we established an assay to directly compare Top1-SSBs and Top1-CCs. We subsequently employed this assay to reveal an increased steady state level of Top1-CCs in neural cells lacking Atm; the protein mutated in ataxia telangiectasia. Our data suggest that the accumulation of endogenous Top1-CCs in Atm-/- neural cells is primarily due to elevated levels of reactive oxygen species. Biochemical purification of Top1-CCs from neural cell extract and the use of Top1 poisons further confirmed a role for Atm during the formation/resolution of Top1-CCs. Finally, we report that global transcription is reduced in Atm-/- neural cells and fails to recover to normal levels following Top1-mediated DNA damage. Together, these data identify a distinct role for ATM during the formation/resolution of neural Top1-CCs and suggest that their accumulation contributes to the neuropathology of ataxia telangiectasia. © 2013 Alagoz et al. Source
Fridolfsson H.N.,University of California at San Diego |
Kawaraguchi Y.,University of California at San Diego |
Ali S.S.,University of California at San Diego |
Ali S.S.,Helmy Institute for Medical science |
And 19 more authors.
FASEB Journal | Year: 2012
We show here that the apposition of plasmamembrane caveolae and mitochondria (first noted in electron micrographs >50 yr ago) and caveolae-mitochondria interaction regulates adaptation to cellular stress by modulating the structure and function of mitochondria. In C57Bl/6 mice engineered to overexpress caveolin specifically in cardiac myocytes (Cav-3 OE), localization of caveolin to mitochondria increases membrane rigidity (4.2%; P<0.05), tolerance to calcium, and respiratory function (72% increase in state 3 and 23% increase in complex IV activity; P<0.05), while reducing stress-induced generation of reactive oxygen species (by 20% in cellular superoxide and 41 and 28% in mitochondrial superoxide under states 4 and 3, respectively; P<0.05) in Cav-3 OE vs. TGneg. By contrast, mitochondrial function is abnormal in caveolin-knockout mice and Caenorhabditis elegans with null mutations in caveolin (60% increase free radical in Cav-2 C. elegans mutants; P<0.05). In human colon cancer cells, mitochondria with increased caveolin have a 30% decrease in apoptotic stress (P<0.05), but cells with disrupted mitochondria-caveolin interaction have a 30% increase in stress response (P<0.05). Targeted gene transfer of caveolin to mitochondria in C57Bl/6 mice increases cardiac mitochondria tolerance to calcium, enhances respiratory function (increases of 90% state 4, 220% state 3, 88% complex IV activity; P<0.05), and decreases (by 33%) cardiac damage (P<0.05). Physical association and apparently the transfer of caveolin between caveolae and mitochondria is thus a conserved cellular response that confers protection from cellular damage in a variety of tissues and settings. © FASEB. Source
Meisenberg C.,University of Sussex |
Ward S.E.,University of Sussex |
Schmid P.,University of Sussex |
Schmid P.,Queen Mary, University of London |
And 3 more authors.
Journal of Cancer Science and Therapy | Year: 2014
Background and objective: Small cell lung cancer (SCLC) is one of the most challenging tumors to treat due to high proliferation rate, early metastatic dissemination and rapid development of chemotherapy resistance. The current treatment protocols involve the use of topoisomerase 1 (TOP1) poisons such as irinotecan and topotecan in combination with platinum-based compounds. TOP1 poisons kill cancer cells by trapping TOP1 on DNA, generating lethal DNA double-strand breaks. A potential mechanism employed by cancer cells to resist killing by TOP1 poisons is to overexpress enzymes involved in the repair of TOP1-DNA breaks. Tyrosyl DNA phosphodiesterase 1 (TDP1) is a key player in this process and despite its importance, no data is currently available to correlate TDP1 protein and mRNA levels with catalytic activity in SCLC. In addition, it is not known if TDP1 and TOP1 protein levels correlate with the cellular response of SCLC to TOP1 based therapies. Methods and results: We report a remarkable variation in TDP1 and TOP1 protein levels in a panel of SCLC cell lines. TDP1 protein level correlates well with TDP1 mRNA and TDP1 catalytic activity, as measured by two newly developed independent activity assays, suggesting the potential utility of immunohistochemistry in assessing TDP1 levels in SCLC tissues. We further demonstrate that whilst TDP1 protein level alone does not correlate with topotecan sensitivity, TDP1/TOP1 ratio correlates well with sensitivity in 8 out of 10 cell lines examined. Conclusion: This study provides the first cellular analyses of TDP1 and TOP1 in SCLC and suggests the potential utility of TDP1/TOP1 ratio to assess the response of SCLC to topotecan. The establishment and validation of an easy-to-use TDP1 enzymatic assay in cell extracts could be exploited as a diagnostic tool in the clinic. These findings may help in stratifying patients that are likely to benefit from TOP1 poisons and TDP1 inhibitors currently under development. Source
Mahmoud A.M.,Cairo University |
Mahmoud A.M.,Helmy Institute for Medical science |
Aboul-Soud M.A.M.,Cairo University |
Aboul-Soud M.A.M.,King Saud University |
And 4 more authors.
International Journal of Oncology | Year: 2016
The merging of high-throughput gene expression techniques, such as microarray, in the screening of natural products as anticancer agents, is considered the optimal solution for gaining a better understanding of the intervention mechanism. Red yeast rice (RYR), a Chinese dietary product, contains a mixture of hypocholesterolemia agents such as statins. Typically, statins have this effect via the inhibition of HMG-CoA reductase, the key enzyme in the biosynthesis of cholesterol. Recently, statins have been shown to exhibit various beneficial antineoplastic properties through the disruption of tumor angiogenesis and metastatic processes. Mevinolin (MVN) is a member of statins and is abundantly present in RYR. Early experimental trials suggested that the mixed apoptotic/necrotic cell death pathway is activated in response to MVN exposure. In the current study, the cytotoxic profile of MVN was evaluated against MCF-7, a breast cancer-derived cell line. The obtained results indicated that MVN-induced cytotoxicity is multi-factorial involving several regulatory pathways in the cytotoxic effects of MVN on breast cancer cell lines. In addition, MVN-induced transcript abundance profiles inferred from microarrays showed significant changes in some key cell processes. The changes were predicted to induce cell cycle arrest and reactive oxygen species generation but inhibit DNA repair and cell proliferation. This MVN-mediated multi-factorial stress triggered specific programmed cell death (apoptosis) and DNA degradation responses in breast cancer cells. Taken together, the observed MVN-induced effects underscore the potential of this ubiquitous natural compound as a selective anticancer activity, with broad safety margins and low cost compared to benchmarked traditional synthetic chemotherapeutic agents. Additionally, the data support further pre-clinical and clinical evaluations of MVN as a novel strategy to combat breast cancer and overcome drug resistance. Source