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Loh CH, Kuo WW, Lin SZ, Shih CY, Lin PY, Situmorang JH, Huang CY. PKC-δ-dependent mitochondrial ROS attenuation is involved as 9-OAHSA combats lipoapotosis in rat hepatocytes induced by palmitic acid and in Syrian hamsters induced by high-fat high-cholesterol high-fructose diet. Toxicol Appl Pharmacol 2023; 470:116557. [PMID: 37207915 DOI: 10.1016/j.taap.2023.116557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 05/08/2023] [Accepted: 05/15/2023] [Indexed: 05/21/2023]
Abstract
Metabolic-associated fatty liver disease (MAFLD) is a global concern, often undetected until reaching an advanced stage. Palmitic acid (PA) is a type of fatty acid that increases and leads to liver apoptosis in MAFLD. However, there is currently no approved therapy or compound for MAFLD. Recently, branched fatty acid esters of hydroxy fatty acids (FAHFAs), a group of bioactive lipids, have emerged as promising agents to treat associated metabolic diseases. This study utilizes one type of FAHFA, oleic acid ester of 9-hydroxystearic acid (9-OAHSA), to treat PA-induced lipoapoptosis in an in vitro MAFLD model using rat hepatocytes and a high-fat high-cholesterol high-fructose (HFHCHFruc) diet in Syrian hamsters. The results indicate that 9-OAHSA rescues hepatocytes from PA-induced apoptosis and attenuates lipoapoptosis and dyslipidemia in Syrian hamsters. Additionally, 9-OAHSA decreases the generation of mitochondrial reactive oxygen species (mito-ROS) and stabilizes the mitochondrial membrane potential in hepatocytes. The study also demonstrates that the effect of 9-OAHSA on mito-ROS generation is at least partially mediated by PKC-δ signaling. These findings suggest that 9-OAHSA shows promise as a therapy for MAFLD.
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Affiliation(s)
- Ching-Hui Loh
- Department of Family Medicine and Medical Research, Buddhist Tzu Chi General Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan; Center for Aging and Health, Buddhist Tzu Chi General Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - Wei-Wen Kuo
- Department of Biological Science and Technology, China Medical University, Taichung, Taiwan
| | - Shinn-Zong Lin
- Bioinnovation Center, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan; Department of Neurosurgery, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | | | - Pi-Yu Lin
- Buddhist Compassion Relief Tzu Chi Foundation, Hualien, Taiwan
| | - Jiro Hasegawa Situmorang
- Cardiovascular and Mitochondrial Related Disease Research Center, Buddhist Tzu Chi General Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan; Center for Biomedical Research, National Research and Innovation Agency (BRIN), Cibinong, Indonesia.
| | - Chih-Yang Huang
- Cardiovascular and Mitochondrial Related Disease Research Center, Buddhist Tzu Chi General Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan; Graduate Institute of Biomedical Sciences, China Medical University, Taichung, Taiwan; Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan; Department of Biotechnology, Asia University, Taichung, Taiwan; Center of General Education, Buddhist Tzu Chi Medical Foundation, Tzu Chi University of Science and Technology, Hualien, Taiwan.
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2
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Black JD, Affandi T, Black AR, Reyland ME. PKCα and PKCδ: Friends and Rivals. J Biol Chem 2022; 298:102194. [PMID: 35760100 PMCID: PMC9352922 DOI: 10.1016/j.jbc.2022.102194] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 06/13/2022] [Accepted: 06/21/2022] [Indexed: 01/06/2023] Open
Abstract
PKC comprises a large family of serine/threonine kinases that share a requirement for allosteric activation by lipids. While PKC isoforms have significant homology, functional divergence is evident among subfamilies and between individual PKC isoforms within a subfamily. Here, we highlight these differences by comparing the regulation and function of representative PKC isoforms from the conventional (PKCα) and novel (PKCδ) subfamilies. We discuss how unique structural features of PKCα and PKCδ underlie differences in activation and highlight the similar, divergent, and even opposing biological functions of these kinases. We also consider how PKCα and PKCδ can contribute to pathophysiological conditions and discuss challenges to targeting these kinases therapeutically.
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Affiliation(s)
- Jennifer D Black
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE.
| | - Trisiani Affandi
- Department of Craniofacial Biology, School of Dental Medicine, University of Colorado Anschutz Medical Campus
| | - Adrian R Black
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE
| | - Mary E Reyland
- Department of Craniofacial Biology, School of Dental Medicine, University of Colorado Anschutz Medical Campus.
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Engin A. Bile Acid Toxicity and Protein Kinases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1275:229-258. [PMID: 33539018 DOI: 10.1007/978-3-030-49844-3_9] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
If the bile acids reach to pathological concentrations due to cholestasis, accumulation of hydrophobic bile acids within the hepatocyte may result in cell death. Thus, hydrophobic bile acids induce apoptosis in hepatocytes, while hydrophilic bile acids increase intracellular adenosine 3',5'-monophosphate (cAMP) levels and activate mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) pathways to protect hepatocytes from apoptosis.Two apoptotic pathways have been described in bile acids-induced death. Both are controlled by multiple protein kinase signaling pathways. In mitochondria-controlled pathway, caspase-8 is activated with death domain-independent manner, whereas, Fas-dependent classical pathway involves ligand-independent oligomerization of Fas.Hydrophobic bile acids dose-dependently upregulate the inflammatory response by further stimulating production of inflammatory cytokines. Death receptor-mediated apoptosis is regulated at the cell surface by the receptor expression, at the death-inducing signaling complex (DISC) by expression of procaspase-8, the death receptors Fas-associated death domain (FADD), and cellular FADD-like interleukin 1-beta (IL-1β)-converting enzyme (FLICE) inhibitory protein (cFLIP). Bile acids prevent cFLIP recruitment to the DISC and thereby enhance initiator caspase activation and lead to cholestatic apoptosis. At mitochondria, the expression of B-cell leukemia/lymphoma-2 (Bcl-2) family proteins contribute to apoptosis by regulating mitochondrial cytochrome c release via Bcl-2, Bcl-2 homology 3 (BH3) interacting domain death agonist (Bid), or Bcl-2 associated protein x (Bax). Fas receptor CD95 activation by hydrophobic bile acids is initiated by reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) signaling. However, activation of necroptosis by ligands of death receptors requires the kinase activity of receptor interacting protein1 (RIP1), which mediates the activation of RIP3 and mixed lineage kinase domain-like protein (MLKL). In this chapter, mainly the effect of protein kinases signal transduction on the mechanisms of hydrophobic bile acids-induced inflammation, apoptosis, necroptosis and necrosis are discussed.
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Affiliation(s)
- Atilla Engin
- Department of General Surgery, Faculty of Medicine, Gazi University, Ankara, Turkey.
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4
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Liu S, Shen M, Li C, Wei Y, Meng X, Li R, Cao Y, Wu W, Liu H. PKCδ contributes to oxidative stress-induced apoptosis in porcine ovarian granulosa cells via activating JNK. Theriogenology 2019; 131:89-95. [PMID: 30965208 DOI: 10.1016/j.theriogenology.2019.03.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 03/23/2019] [Accepted: 03/25/2019] [Indexed: 01/21/2023]
Abstract
Oxidative stress-induced apoptosis of granulosa cells (GCs) is believed to be an important cause of follicular atresia. Our previous work showed that the c-Jun N-terminal kinase (also known as JNK) might promote apoptosis in GCs during oxidative stress. The aim of this study was to investigate the upstream signaling required for JNK-mediated GCs apoptosis during oxidative stress. Since PKCδ and ASK1 have been suggested to regulate JNK activity in some types of cells, we hypothesized that PKCδ and ASK1 might contribute to JNK-dependent apoptosis in GCs suffering oxidative stimulation. To test this assumption, porcine GCs obtained from healthy follicles were treated with H2O2 alone, or together with inhibitors against PKCδ and JNK, and then collected for cell viability assay, TUNEL staining, immunoprecipitation, western blotting, or JNK activity detection in vitro. The current results showed that the cell viability loss, DNA fragmentation, morphological shrinkage, and nuclear condensation in H2O2-treated porcine GCs was correlated with enhanced activation of JNK. Although ASK1 was supposed to be a JNK activator, we found no definite role of ASK1 in JNK-induced GCs apoptosis during oxidative stress. Further investigations revealed that H2O2-mediated PKCδ activation was required for the apoptotic death of porcine GCs. Particularly, the pro-apoptotic effects of PKCδ on porcine GCs might be achieved by activating the mitochondrial pathway. Importantly, we found that p-PKCδ acts as an upstream activator of JNK in H2O2-treated porcine GCs. However, JNK has no regulatory effect on PKCδ activity. Taken together, our findings provided a novel model of GCs apoptosis involving the activation of PKCδ/JNK/mitochondrial apoptosis axis during oxidative stress.
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Affiliation(s)
- Shuo Liu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Ming Shen
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Chengyu Li
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Yinghui Wei
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Xueqing Meng
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Rongyang Li
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Yan Cao
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Wangjun Wu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Honglin Liu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, PR China.
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5
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Wang C, Yang M, Zhao J, Li X, Xiao X, Zhang Y, Jin X, Liao M. Bile salt (glycochenodeoxycholate acid) induces cell survival and chemoresistance in hepatocellular carcinoma. J Cell Physiol 2018; 234:10899-10906. [PMID: 30548625 DOI: 10.1002/jcp.27905] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 10/24/2018] [Indexed: 12/15/2022]
Affiliation(s)
- Chengzhi Wang
- Key Laboratory of Nanobiological Technology of Chinese Ministry of Health, Xiangya Hospital, Central South University Changsha Hunan People's Republic of China
- Department of Nephrology Blood Purification Center, Xiangya Hospital, Central South University Changsha Hunan People's Republic of China
| | - Manyi Yang
- Key Laboratory of Nanobiological Technology of Chinese Ministry of Health, Xiangya Hospital, Central South University Changsha Hunan People's Republic of China
| | - Jinfeng Zhao
- Key Laboratory of Nanobiological Technology of Chinese Ministry of Health, Xiangya Hospital, Central South University Changsha Hunan People's Republic of China
| | - Xia Li
- Department of Nephrology Blood Purification Center, Xiangya Hospital, Central South University Changsha Hunan People's Republic of China
| | - Xiangcheng Xiao
- Department of Nephrology Blood Purification Center, Xiangya Hospital, Central South University Changsha Hunan People's Republic of China
| | - Yang Zhang
- Hepatobiliary and Enteric Surgery Center Xiangya Hospital, Central South University Changsha Hunan People's Republic of China
| | - Xin Jin
- Key Laboratory of Nanobiological Technology of Chinese Ministry of Health, Xiangya Hospital, Central South University Changsha Hunan People's Republic of China
| | - Mingmei Liao
- Key Laboratory of Nanobiological Technology of Chinese Ministry of Health, Xiangya Hospital, Central South University Changsha Hunan People's Republic of China
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Zhou M, Zhang Q, Zhao J, Liao M, Wen S, Yang M. Phosphorylation of Bcl-2 plays an important role in glycochenodeoxycholate-induced survival and chemoresistance in HCC. Oncol Rep 2017; 38:1742-1750. [PMID: 28731137 DOI: 10.3892/or.2017.5830] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 06/22/2017] [Indexed: 12/12/2022] Open
Abstract
Hepatocellular carcinoma (HCC) is a highly malignant tumor and can evolve rapidly to resistance to chemotherapies. Glycochenodeoxycholate (GCDA), which is toxic and hydrophobic, is the main ingredient in the bile and associated with carcinogenesis of gastrointenstinal tumors. Bcl-2 is the most important anti-apoptotic protein and overexpressed in various human tumors. In the present study, we found that GCDA can induce the chemoresistance of human liver cancer cells and specific depletion of Bcl-2 by RNA interference blocks GCDA-stimulated chemoresistance, which indicate the pivotal role of Bcl-2 in such process. Mechanistically, GCDA simultaneously stimulates phosphorylation of Bcl-2 at Ser70 site and activates extracellular signal-regulated kinase 1/2 (ERK1/2), and inhibition of ERK1/2 by PD98059 (MAPK/ERK1/2 inhibitor) or siRNA (targeting ERK1/2) suppresses GCDA-stimulated phosphorylation of Bcl-2 and significantly attenuates the survival and chemoresistance induced by GCDA in liver cancer cells. Thus, GCDA-induced survival and chemoresistance of liver cancer cells may occur through activation of Bcl-2 by phosphorylation at Ser70 site through MAPK/ERK1/2 pathway, which may contribute to the development of human liver cancer and chemoresistance.
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Affiliation(s)
- Maojun Zhou
- Key Laboratory of Cancer Proteomics of Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410008, P.R. China
| | - Qi Zhang
- Department of Hepatobiliary and Pancreatic Surgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, P.R. China
| | - Jinfeng Zhao
- Key Laboratory of Nanobiological Technology of Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410008, P.R. China
| | - Mingmei Liao
- Key Laboratory of Nanobiological Technology of Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410008, P.R. China
| | - Sailan Wen
- Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
| | - Manyi Yang
- Key Laboratory of Nanobiological Technology of Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410008, P.R. China
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7
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Zhan B, Kong C, Zhang Z, Dong X, Zhang N. Inhibition of PKCα reduces the ability of migration of kidney cancer cells but has no impact on cell apoptosis. Exp Ther Med 2017; 13:2473-2479. [PMID: 28565866 DOI: 10.3892/etm.2017.4258] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 01/20/2017] [Indexed: 12/29/2022] Open
Abstract
Kidney cancer is among the most important causes of cancer-associated mortality worldwide. The present study aimed to evaluate protein kinase C α (PKCα) expression in kidney cancer tissues and cell lines, and its significance in apoptosis and migration. Expression of PKCα was analyzed using quantitative polymerase chain reaction and western blotting. In addition, the inhibitor of PKCα (calphostin C and GO6976) was used to treat kidney cancer cells. The ACHN cell line was generated with PKCα-small-interfering RNA (siRNA) and a stable expression of PKCα, in order to facilitate the analysis of apoptosis and migration of PKCα during knockdown and inactivation. Flow cytometry was used to determine the rates of apoptosis. Immunohistochemical staining was used to identify the localization of PKCα in renal clear cell carcinoma and normal sections. PKCα expression in normal tissues was found to be greater than in cancerous tissues. Furthermore, apoptosis was not promoted with PKCα inhibitors or PKCα-siRNA treatment, and a decrease of the migration ability was observed following transfection with PKCα-dominant negative. The results indicated that inhibition of PKCα might not contribute to apoptosis progression in kidney carcinoma.
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Affiliation(s)
- Bo Zhan
- Department of Urology, The First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Chuize Kong
- Department of Urology, The First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Zhe Zhang
- Department of Urology, The First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Xiao Dong
- Department of Urology, The First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Naiwen Zhang
- Department of Urology, The First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
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8
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Liver Cholesterol Overload Aggravates Obstructive Cholestasis by Inducing Oxidative Stress and Premature Death in Mice. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2016; 2016:9895176. [PMID: 27635189 PMCID: PMC5011220 DOI: 10.1155/2016/9895176] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 07/13/2016] [Indexed: 12/14/2022]
Abstract
Nonalcoholic steatohepatitis is one of the leading causes of liver disease. Dietary factors determine the clinical presentation of steatohepatitis and can influence the progression of related diseases. Cholesterol has emerged as a critical player in the disease and hence consumption of cholesterol-enriched diets can lead to a progressive form of the disease. The aim was to investigate the impact of liver cholesterol overload on the progression of the obstructive cholestasis in mice subjected to bile duct ligation surgery. Mice were fed with a high cholesterol diet for two days and then were subjected to surgery procedure; histological, biochemical, and molecular analyses were conducted to address the effect of cholesterol in liver damage. Mice under the diet were more susceptible to damage. Results show that cholesterol fed mice exhibited increased apoptosis and oxidative stress as well as reduction in cell proliferation. Mortality following surgery was higher in HC fed mice. Liver cholesterol impairs the repair of liver during obstructive cholestasis and aggravates the disease with early fatal consequences; these effects were strongly associated with oxidative stress.
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9
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Webster CRL, Anwer MS. Hydrophobic bile acid apoptosis is regulated by sphingosine-1-phosphate receptor 2 in rat hepatocytes and human hepatocellular carcinoma cells. Am J Physiol Gastrointest Liver Physiol 2016; 310:G865-73. [PMID: 26999807 PMCID: PMC4895872 DOI: 10.1152/ajpgi.00253.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 03/14/2016] [Indexed: 01/31/2023]
Abstract
The hepatotoxic bile acid glycochenodeoxycholate (GCDC) modulates hepatocyte cell death through activation of JNK, Akt, and Erk. The nonhepatotoxic bile acid taurocholate activates Akt and Erk through the sphingosine-1-phosphate receptor 2 (S1PR2). The role of the S1PR2 in GCDC-mediated apoptosis and kinase activation is unknown. Studies were done in rat hepatocytes, HUH7 cells, and HUH7 cells stably transfected with rat Ntcp (HUH7-Ntcp). Cells were treated with GCDC and apoptosis was monitored morphologically by Hoechst staining and biochemically by immunoblotting for the active cleaved fragment of caspase 3. Kinase activation was determined by immunoblotting with phospho-specific antibodies. JTE-013, an inhibitor of S1PR2, significantly attenuated morphological evidence of GCDC-induced apoptosis and prevented caspase 3 cleavage in rat hepatocytes and HUH7-Ntcp cells. In hepatocytes, JTE-013 mildly suppressed, augmented, and had no effect on GCDC-induced JNK, Akt, and Erk phosphorylation, respectively. Similar results were seen in HUH7-Ntcp cells except for mild suppression of JNK and Erk phosphorylation. Knockdown of S1PR2 in HUH7-Ntcp augmented Akt, inhibited JNK, and had no effect on Erk phosphorylation. GCDC failed to induce apoptosis or kinase activation in HUH7 cells. In conclusion, SIPR2 inhibition attenuates GCDC-induced apoptosis and inhibits and augments GCDC-induced JNK and Akt phosphorylation, respectively. In addition, GCDC must enter hepatocytes to mediate cell death or activate kinases. These results suggest that SIPR2 activation is proapoptotic in GCDC-induced cell death but that this effect is not due to direct ligation of the S1PR2 by the bile acid.
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Affiliation(s)
- Cynthia R L Webster
- Department of Clinical Science, Cummings School of Veterinary Medicine at Tufts University, Grafton, Massachusetts; and
| | - M Sawkat Anwer
- Department of Biomedical Science, Cummings School of Veterinary Medicine at Tufts University, Grafton, Massachusetts
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10
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Sousa T, Castro RE, Pinto SN, Coutinho A, Lucas SD, Moreira R, Rodrigues CMP, Prieto M, Fernandes F. Deoxycholic acid modulates cell death signaling through changes in mitochondrial membrane properties. J Lipid Res 2015; 56:2158-71. [PMID: 26351365 DOI: 10.1194/jlr.m062653] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Indexed: 12/21/2022] Open
Abstract
Cytotoxic bile acids, such as deoxycholic acid (DCA), are responsible for hepatocyte cell death during intrahepatic cholestasis. The mechanisms responsible for this effect are unclear, and recent studies conflict, pointing to either a modulation of plasma membrane structure or mitochondrial-mediated toxicity through perturbation of mitochondrial outer membrane (MOM) properties. We conducted a comprehensive comparative study of the impact of cytotoxic and cytoprotective bile acids on the membrane structure of different cellular compartments. We show that DCA increases the plasma membrane fluidity of hepatocytes to a minor extent, and that this effect is not correlated with the incidence of apoptosis. Additionally, plasma membrane fluidity recovers to normal values over time suggesting the presence of cellular compensatory mechanisms for this perturbation. Colocalization experiments in living cells confirmed the presence of bile acids within mitochondrial membranes. Experiments with active isolated mitochondria revealed that physiologically active concentrations of DCA change MOM order in a concentration- and time-dependent manner, and that these changes preceded the mitochondrial permeability transition. Importantly, these effects are not observed on liposomes mimicking MOM lipid composition, suggesting that DCA apoptotic activity depends on features of mitochondrial membranes that are absent in protein-free mimetic liposomes, such as the double-membrane structure, lipid asymmetry, or mitochondrial protein environment. In contrast, the mechanism of action of cytoprotective bile acids is likely not associated with changes in cellular membrane structure.
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Affiliation(s)
- Tânia Sousa
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal
| | - Rui E Castro
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
| | - Sandra N Pinto
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal
| | - Ana Coutinho
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal Departamento de Química e Bioquímica, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
| | - Susana D Lucas
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
| | - Rui Moreira
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
| | - Cecília M P Rodrigues
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
| | - Manuel Prieto
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal
| | - Fábio Fernandes
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal
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11
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Wong TY, Lin SM, Leung LK. The Flavone Luteolin Suppresses SREBP-2 Expression and Post-Translational Activation in Hepatic Cells. PLoS One 2015; 10:e0135637. [PMID: 26302339 PMCID: PMC4547722 DOI: 10.1371/journal.pone.0135637] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Accepted: 07/24/2015] [Indexed: 11/18/2022] Open
Abstract
High blood cholesterol has been associated with cardiovascular diseases. The enzyme HMG CoA reductase (HMGCR) is responsible for cholesterol synthesis, and inhibitors of this enzyme (statins) have been used clinically to control blood cholesterol. Sterol regulatory element binding protein (SREBP) -2 is a key transcription factor in cholesterol metabolism, and HMGCR is a target gene of SREBP-2. Attenuating SREBP-2 activity could potentially minimize the expression of HMGCR. Luteolin is a flavone that is commonly detected in plant foods. In the present study, Luteolin suppressed the expression of SREBP-2 at concentrations as low as 1 μM in the hepatic cell lines WRL and HepG2. This flavone also prevented the nuclear translocation of SREBP-2. Post-translational processing of SREBP-2 protein was required for nuclear translocation. Luteolin partially blocked this activation route through increased AMP kinase (AMPK) activation. At the transcriptional level, the mRNA and protein expression of SREBP-2 were reduced through luteolin. A reporter gene assay also verified that the transcription of SREBF2 was weakened in response to this flavone. The reduced expression and protein processing of SREBP-2 resulted in decreased nuclear translocation. Thus, the transcription of HMGCR was also decreased after luteolin treatment. In summary, the results of the present study showed that luteolin modulates HMGCR transcription by decreasing the expression and nuclear translocation of SREBP-2.
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Affiliation(s)
- Tsz Yan Wong
- Food and Nutritional Sciences Programme, School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, Hong Kong S.A.R., People's Republic of China
| | - Shu-mei Lin
- Dept. of Food Science, National Chiayi University, Chiayi City, Taiwan, (R.O.C.)
| | - Lai K. Leung
- Food and Nutritional Sciences Programme, School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, Hong Kong S.A.R., People's Republic of China
- Biochemistry Programme, School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, Hong Kong S.A.R., People's Republic of China
- * E-mail:
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