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Kapur A, Beres T, Rathi K, Nayak AP, Czarnecki A, Felder M, Gillette A, Ericksen SS, Sampene E, Skala MC, Barroilhet L, Patankar MS. Oxidative stress via inhibition of the mitochondrial electron transport and Nrf-2-mediated anti-oxidative response regulate the cytotoxic activity of plumbagin. Sci Rep 2018; 8:1073. [PMID: 29348410 PMCID: PMC5773707 DOI: 10.1038/s41598-018-19261-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 12/19/2017] [Indexed: 11/15/2022] Open
Abstract
Plumbagin, an anti-cancer agent, is toxic to cells of multiple species. We investigated if plumbagin targets conserved biochemical processes. Plumbagin induced DNA damage and apoptosis in cells of diverse mutational background with comparable potency. A 3-5 fold increase in intracellular oxygen radicals occurred in response to plumbagin. Neutralization of the reactive oxygen species by N-acetylcysteine blocked apoptosis, indicating a central role for oxidative stress in plumbagin-mediated cell death. Plumbagin docks in the ubiquinone binding sites (Q0 and Qi) of mitochondrial complexes I-III, the major sites for oxygen radicals. Plumbagin decreased oxygen consumption rate, ATP production and optical redox ratio (NAD(P)H/FAD) indicating interference with electron transport downstream of mitochondrial Complex II. Oxidative stress induced by plumbagin triggered an anti-oxidative response via activation of Nrf2. Plumbagin and the Nrf2 inhibitor, brusatol, synergized to inhibit cell proliferation. These data indicate that while inhibition of electron transport is the conserved mechanism responsible for plumbagin's chemotoxicity, activation of Nrf2 is the resulting anti-oxidative response that allows plumbagin to serve as a chemopreventive agent. This study provides the basis for designing potent and selective plumbagin analogs that can be coupled with suitable Nrf2 inhibitors for chemotherapy or administered as single agents to induce Nrf2-mediated chemoprevention.
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Affiliation(s)
- Arvinder Kapur
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792-6188, USA.
| | - Thomas Beres
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792-6188, USA
| | - Kavya Rathi
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792-6188, USA
| | - Amruta P Nayak
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792-6188, USA
- Indian Institute for Science Education and Research, Pune, India
| | - Austin Czarnecki
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792-6188, USA
| | - Mildred Felder
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792-6188, USA
| | - Amani Gillette
- Morgridge Institute for Research and the Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Spencer S Ericksen
- Small Molecule Screening Facility, University of Wisconsin Paul P. Carbone Comprehensive Cancer Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
| | - Emmanuel Sampene
- Department of Biostatistics, University of Wisconsin-Madison, Madison, WI, USA
| | - Melissa C Skala
- Morgridge Institute for Research and the Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Lisa Barroilhet
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792-6188, USA
| | - Manish S Patankar
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792-6188, USA.
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Chen YT, Su YC, Chang ML, Tsai PF, Kung JT. Low-Level MHC Class II Expression Leads to Suboptimal Th Cell Response, Increased Autoaggression, and Heightened Cytokine Inducibility. J I 2017; 198:1928-1943. [DOI: 10.4049/jimmunol.1600967] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 12/26/2016] [Indexed: 01/27/2023]
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Patwardhan RS, Sharma D, Checker R, Sandur SK. Mitigation of radiation-induced hematopoietic injury via regulation of cellular MAPK/phosphatase levels and increasing hematopoietic stem cells. Free Radic Biol Med 2014; 68:52-64. [PMID: 24287141 DOI: 10.1016/j.freeradbiomed.2013.11.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 10/31/2013] [Accepted: 11/05/2013] [Indexed: 11/22/2022]
Abstract
Here we describe a novel strategy for mitigation of ionizing radiation-induced hematopoietic syndrome by suppressing the activity of MKP3, resulting in ERK activation and enhanced abundance of hematopoietic stem cells, using the antioxidant flavonoid baicalein (5,6,7-trihydroxyflavone). It offered complete protection to mouse splenic lymphocytes against radiation-induced cell death. Inhibitors of ERK and Nrf-2 could significantly abrogate baicalein-mediated radioprotection in lymphocytes. Baicalein inhibited phosphatase MKP3 and thereby enhanced phosphorylation of ERK and its downstream proteins such as Elk and Nrf-2. It also increased the nuclear levels of Nrf-2 and the mRNA levels of its dependent genes. Importantly, baicalein administration to mice before radiation exposure led to significant recovery of loss of bone marrow cellularity and also inhibited cell death. Administration of baicalein increased the hematopoietic stem cell frequency as measured by side-population assay and also by antibody staining. Further, baicalein offered significant protection against whole-body irradiation (WBI; 7.5Gy)-induced mortality in mice. Interestingly, we found that baicalein works by activating the same target molecules ERK and Nrf-2 both in vitro and in vivo. Finally, administration of all-trans-retinoic acid (inhibitor of Nrf-2) significantly abrogated baicalein-mediated protection against WBI-induced mortality in mice. Thus, in contrast to the generalized conception of antioxidants acting as radioprotectors, we provide a rationale that antioxidants exhibit pleiotropic effects through the activation of multiple cellular signaling pathways.
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Affiliation(s)
- R S Patwardhan
- Radiation Biology and Health Sciences Division, Modular Laboratories, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Deepak Sharma
- Radiation Biology and Health Sciences Division, Modular Laboratories, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Rahul Checker
- Radiation Biology and Health Sciences Division, Modular Laboratories, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Santosh K Sandur
- Radiation Biology and Health Sciences Division, Modular Laboratories, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.
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Khan NM, Poduval TB. Bilirubin augments radiation injury and leads to increased infection and mortality in mice: molecular mechanisms. Free Radic Biol Med 2012; 53:1152-69. [PMID: 22819982 DOI: 10.1016/j.freeradbiomed.2012.07.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 07/08/2012] [Indexed: 01/15/2023]
Abstract
Our earlier results demonstrated that clinically relevant concentrations of unconjugated bilirubin (UCB) possessed immunotoxic effects. Whole-body irradiation (WBI) with 1 to 6 Gy leads to acute radiation syndrome, immunosuppression, and makes the host susceptible to infection. Since hyperbilirubinemia has been shown to be associated with several types of cancer, the present studies were undertaken to evaluate the radiomodifying effects of UCB in radiation-exposed mice having elevated levels of UCB. Pretreatment of splenic lymphocytes with UCB (1-50 μM at UCB/BSA ratio <1) augmented radiation-induced DNA strand breaks, MMP loss, calcium release, and apoptosis. Combination treatment of mice with UCB (50mg/kg bw) followed by WBI (2 Gy) 0.5h later, resulted in significantly increased splenic atrophy, bone marrow aplasia, decreased counts of peritoneal exudate cells, and different splenocyte subsets such as CD3+ T, CD4+ T, CD8+ T, CD19+ B, and CD14+ macrophages as compared to either UCB or WBI treatment. Hematological studies showed that WBI-induced lymphopenia, thrombocytopenia, and neutropenia were further aggravated in the combination treatment group. UCB pretreatment of mice potentiated WBI-induced apoptosis and decreased WBI-induced loss of functional response of various immune cells leading to augmentation of immunosuppression and infection susceptibility caused by WBI. In an acute bacterial peritonitis model, UCB pretreatment of mice significantly increased WBI-induced proinflammatory cytokines, nitric oxide, and peritoneal bacterial load resulting in increased infection and death. Studies using the pharmacological inhibitor of p38MAPK demonstrated the involvement of p38MAPK activation in the inflammatory cascade of peritonitis. These findings should prove useful in understanding the potential risk to hyperbilirubinemic patients during radiotherapy and victims of acute radiation exposure in the course of radiation accidents.
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Affiliation(s)
- Nazir M Khan
- Immunology and Hyperthermia Section, Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
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Wilankar C, Sharma D, Checker R, Khan NM, Patwardhan R, Patil A, Sandur SK, Devasagayam TPA. Role of immunoregulatory transcription factors in differential immunomodulatory effects of tocotrienols. Free Radic Biol Med 2011; 51:129-43. [PMID: 21536125 DOI: 10.1016/j.freeradbiomed.2011.03.038] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 03/01/2011] [Accepted: 03/28/2011] [Indexed: 12/20/2022]
Abstract
Tocotrienols have been shown to possess antioxidant, antitumor, cardioprotective, and antiproliferative effects. This report describes novel immunomodulatory effects of tocotrienols in murine lymphocytes. γ-Tocotrienol (GT) was more effective in suppressing concanavalin A (Con A)-induced T cell proliferation and cytokine production compared to α-tocotrienol (AT) when present continuously in the culture. GT inhibited T cell activation markers and costimulatory molecule. GT modulated intracellular glutathione in lymphocytes, and the suppressive effects of GT could not be abrogated by thiol or nonthiol antioxidants, indicating a poor link between anti-inflammatory properties of tocotrienols and cellular redox status. It was also observed that GT suppressed Con A-induced activation of NF-κB, AP-1, and NF-κB-dependent gene expression. Cellular uptake studies with tocotrienols showed higher accumulation of GT compared to AT. Similar immunosuppressive effects of GT were also observed when administered to mice. In contrast, transient exposure of lymphocytes to GT (4 h) resulted in higher survival and proliferation of lymphocytes in vitro and in vivo in syngeneic and allogeneic hosts. This was attributed to the ability of GT to induce NF-κB, AP-1, and mTOR activation in lymphocytes upon transient exposure. Our results demonstrated that antioxidants such as tocotrienols may exhibit pleiotropic effects by activating multiple mechanisms in cells.
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Affiliation(s)
- Chandan Wilankar
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400085, India
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Checker R, Sharma D, Sandur SK, Khan NM, Patwardhan RS, Kohli V, Sainis KB. Vitamin K3 suppressed inflammatory and immune responses in a redox-dependent manner. Free Radic Res 2011; 45:975-85. [DOI: 10.3109/10715762.2011.585647] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Checker R, Sharma D, Sandur SK, Subrahmanyam G, Krishnan S, Poduval TB, Sainis KB. Plumbagin inhibits proliferative and inflammatory responses of T cells independent of ROS generation but by modulating intracellular thiols. J Cell Biochem 2010; 110:1082-93. [PMID: 20564204 DOI: 10.1002/jcb.22620] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Plumbagin inhibited activation, proliferation, cytokine production, and graft-versus-host disease in lymphocytes and inhibited growth of tumor cells by suppressing nuclear factor-kappaB (NF-kappaB). Plumbagin was also shown to induce reactive oxygen species (ROS) generation in tumor cells via an unknown mechanism. Present report describes a novel role of cellular redox in modulation of immune responses in normal lymphocytes by plumbagin. Plumbagin depleted glutathione (GSH) levels that led to increase in ROS generation. The decrease in GSH levels was due to direct reaction of plumbagin with GSH as evinced by mass spectrometric and HPLC analysis. Further, addition of plumbagin to cells resulted in decrease in free thiol groups on proteins and increase in glutathionylation of proteins. The suppression of mitogen-induced T-cell proliferation and cytokine (IL-2/IL-4/IL-6/IFN-gamma) production by plumbagin was abrogated by thiol antioxidants but not by non-thiol antioxidants confirming that thiols but not ROS play an important role in biological activity of plumbagin. Plumbagin also abrogated mitogen-induced phosphorylation of ERK, IKK, and degradation of IkappaB-alpha. However, it did not affect phosphorylation of P38, JNK, and AKT. Our results for the first time show that antiproliferative effects of plumbagin are mediated by modulation of cellular redox. These results provide a rationale for application of thiol-depleting agents as anti-inflammatory drugs.
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Affiliation(s)
- Rahul Checker
- Radiation Biology & Health Sciences Division, Bio-Medical Group, Bhabha Atomic Research Centre, Mumbai 400085, Maharashtra, India
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