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Bonam SR, Mastrippolito D, Georgel P, Muller S. Pharmacological targets at the lysosomal autophagy-NLRP3 inflammasome crossroads. Trends Pharmacol Sci 2024; 45:81-101. [PMID: 38102020 DOI: 10.1016/j.tips.2023.11.005] [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: 11/06/2023] [Revised: 11/14/2023] [Accepted: 11/14/2023] [Indexed: 12/17/2023]
Abstract
Many aspects of cell homeostasis and integrity are maintained by the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome. The NLRP3 oligomeric protein complex assembles in response to exogenous and endogenous danger signals. This inflammasome has also been implicated in the pathogenesis of a range of disease conditions, particularly chronic inflammatory diseases. Given that NLRP3 modulates autophagy, which is also a key regulator of inflammasome activity, excessive inflammation may be controlled by targeting this intersecting pathway. However, specific niche areas of NLRP3-autophagy interactions and their reciprocal regulatory mechanisms remain underexplored. Consequently, we lack treatment methods specifically targeting this pivotal axis. Here, we discuss the potential of such strategies in the context of autoimmune and metabolic diseases and propose some research avenues.
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Affiliation(s)
- Srinivasa Reddy Bonam
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Dylan Mastrippolito
- CNRS-University of Strasbourg, Biotechnology and Cell Signaling, Illkirch, France; Strasbourg Institute of Drug Discovery and Development (IMS), Strasbourg, France
| | - Philippe Georgel
- CNRS-University of Strasbourg, Biotechnology and Cell Signaling, Illkirch, France; Strasbourg Institute of Drug Discovery and Development (IMS), Strasbourg, France; Fédération Hospitalo-Universitaire (FHU) OMICARE, Fédération de Médecine Translationnelle de Strasbourg (FMTS), Strasbourg University, Strasbourg, France
| | - Sylviane Muller
- CNRS-University of Strasbourg, Biotechnology and Cell Signaling, Illkirch, France; Strasbourg Institute of Drug Discovery and Development (IMS), Strasbourg, France; Fédération Hospitalo-Universitaire (FHU) OMICARE, Fédération de Médecine Translationnelle de Strasbourg (FMTS), Strasbourg University, Strasbourg, France; University of Strasbourg Institute for Advanced Study (USIAS), Strasbourg, France.
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2
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Ranasinghe R, Mathai M, Zulli A. Revisiting the therapeutic potential of tocotrienol. Biofactors 2022; 48:813-856. [PMID: 35719120 PMCID: PMC9544065 DOI: 10.1002/biof.1873] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 05/13/2022] [Indexed: 12/14/2022]
Abstract
The therapeutic potential of the tocotrienol group stems from its nutraceutical properties as a dietary supplement. It is largely considered to be safe when consumed at low doses for attenuating pathophysiology as shown by animal models, in vitro assays, and ongoing human trials. Medical researchers and the allied sciences have experimented with tocotrienols for many decades, but its therapeutic potential was limited to adjuvant or concurrent treatment regimens. Recent studies have focused on targeted drug delivery by enhancing the bioavailability through carriers, self-sustained emulsions, nanoparticles, and ethosomes. Epigenetic modulation and computer remodeling are other means that will help increase chemosensitivity. This review will focus on the systemic intracellular anti-cancer, antioxidant, and anti-inflammatory mechanisms that are stimulated and/or regulated by tocotrienols while highlighting its potent therapeutic properties in a diverse group of clinical diseases.
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Affiliation(s)
- Ranmali Ranasinghe
- Institute of Health and Sport, College of Health and MedicineVictoria UniversityMelbourneVictoriaAustralia
| | - Michael Mathai
- Institute of Health and Sport, College of Health and MedicineVictoria UniversityMelbourneVictoriaAustralia
| | - Anthony Zulli
- Institute of Health and Sport, College of Health and MedicineVictoria UniversityMelbourneVictoriaAustralia
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3
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Lucci A, Vera MC, Comanzo CG, Lorenzetti F, Ferretti AC, Ceballos MP, Quiroga AD, Alvarez MDL, Carrillo MC. Delta-tocotrienol enhances the antitumor effects of interferon alpha through ROS and Erk/MAPK signaling pathways in hepatocellular carcinoma cells. Can J Physiol Pharmacol 2021; 100:453-463. [PMID: 34932399 DOI: 10.1139/cjpp-2021-0606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The complexity of hepatocellular carcinoma (HCC) signaling and the failure of pharmacological therapeutics reveal the significance of establishing new anti-cancer strategies. Interferon alpha (IFN α) has been used as adjuvant therapy for reducing HCC recurrence and improving survival. Delta-tocotrienol (δ-tocotrienol), a natural unsaturated isoform of vitamin E, is a promising candidate for cancer treatment. In this study, we evaluated whether the combination of δ-tocotrienol with IFN α displays significant advantages in the treatment of HCC cells. Results showed that the combination significantly decreased cell viability, migration and invasion of HCC cells compared to single therapies. Combining δ-tocotrienol and IFN α enhanced the decrease in proliferating cell nuclear antigen (PCNA) and matrix metalloproteinases MMP-7 and MMP-9. The combination also produced an enhancement of apoptosis together with increased Bax/Bcl-xL ratio and ROS generation. δ-tocotrienol induced Notch1 activation and changes in Erk and p38 MAPK signaling status. Blocking experiments confirmed that ROS and Erk are involved, at least in part, in the anticancer effects of the combined treatment. In conclusion, the combination of δ-tocotrienol with IFN α therapy showed promising results for HCC cells treatment, which makes the combination of cytokine-based immunotherapy with natural products a potential strategy against liver cancer.
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Affiliation(s)
- Alvaro Lucci
- Consejo Nacional de Investigaciones Científicas y Técnicas, 62873, Instituto de Fisiología Experimental (IFISE), Rosario, Santa Fe, Argentina.,Rosario National University Faculty of Biochemistry and Pharmaceutical Sciences, 63029, Rosario, Argentina;
| | - Marina C Vera
- Consejo Nacional de Investigaciones Científicas y Técnicas, 62873, Instituto de Fisiología Experimental (IFISE), Rosario, Santa Fe, Argentina.,Rosario National University Faculty of Biochemistry and Pharmaceutical Sciences, 63029, Rosario, Argentina;
| | - Carla G Comanzo
- Consejo Nacional de Investigaciones Científicas y Técnicas, 62873, Instituto de Fisiología Experimental (IFISE), Rosario, Santa Fe, Argentina.,Rosario National University Faculty of Biochemistry and Pharmaceutical Sciences, 63029, Rosario, Argentina;
| | - Florencia Lorenzetti
- Consejo Nacional de Investigaciones Científicas y Técnicas, 62873, Instituto de Fisiología Experimental (IFISE), Rosario, Santa Fe, Argentina.,Rosario National University Faculty of Biochemistry and Pharmaceutical Sciences, 63029, Rosario, Argentina;
| | - Anabela C Ferretti
- Rosario National University Faculty of Biochemistry and Pharmaceutical Sciences, 63029, Rosario, Argentina;
| | - María Paula Ceballos
- Consejo Nacional de Investigaciones Científicas y Técnicas, 62873, Instituto de Fisiología Experimental (IFISE), Rosario, Santa Fe, Argentina.,Rosario National University Faculty of Biochemistry and Pharmaceutical Sciences, 63029, Rosario, Argentina;
| | - Ariel D Quiroga
- Consejo Nacional de Investigaciones Científicas y Técnicas, 62873, Instituto de Fisiología Experimental (IFISE), Rosario, Santa Fe, Argentina.,Rosario National University Faculty of Biochemistry and Pharmaceutical Sciences, 63029, Rosario, Argentina.,Universidad Abierta Interamericana, 28178, Centro de Altos Estudios en Ciencias Humanas y de la Salud. Sede Rosario, Rosario, Santa Fe, Argentina;
| | - Maria de Lujan Alvarez
- Consejo Nacional de Investigaciones Científicas y Técnicas, 62873, Instituto de Fisiología Experimental (IFISE), Rosario, Santa Fe, Argentina.,Rosario National University Faculty of Biochemistry and Pharmaceutical Sciences, 63029, Morfología, Rosario, Santa Fe, Argentina.,Universidad Abierta Interamericana, 28178, Centro de Altos Estudios en Ciencias Humanas y de la Salud. Sede Rosario, Rosario, Santa Fe, Argentina;
| | - María Cristina Carrillo
- Consejo Nacional de Investigaciones Científicas y Técnicas, 62873, Instituto de Fisiología Experimental (IFISE), Rosario, Santa Fe, Argentina.,Rosario National University Faculty of Biochemistry and Pharmaceutical Sciences, 63029, Rosario, Santa Fe, Argentina;
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4
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Ji X, Yao H, Meister M, Gardenhire DS, Mo H. Tocotrienols: Dietary Supplements for Chronic Obstructive Pulmonary Disease. Antioxidants (Basel) 2021; 10:883. [PMID: 34072997 PMCID: PMC8228218 DOI: 10.3390/antiox10060883] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 05/16/2021] [Accepted: 05/18/2021] [Indexed: 12/21/2022] Open
Abstract
Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide. Emphysema and chronic bronchitis are the two major phenotypes of COPD, which have many symptoms, such as dyspnea, chronic cough, and mucus overproduction. Emphysema is characterized by the destruction of the alveolar wall, while chronic bronchitis is characterized by limitations in expiratory airflow. Cigarette smoking is the most significant risk factor for the pathogenesis of COPD in the developed world. Chronic inflammation contributes to the onset and progression of the disease and furthers the risk of comorbidities. Current treatment options and prevention strategies for COPD are very limited. Tocotrienols are a group of vitamin E molecules with antioxidant and anti-inflammatory properties. Individual tocotrienols (α, γ, and δ) have shown their ability to attenuate inflammation specifically via suppressing nuclear factor-κB-mediated cytokine production. The δ- and γ-forms of tocotrienols have been indicated as the most effective in the prevention of macrophage infiltration, production of reactive oxygen species, and cytokine secretion. This review briefly discusses the pathogenesis of COPD and the role of inflammation therein. Furthermore, we summarize the in vitro and in vivo evidence for the anti-inflammatory activity of tocotrienols and their potential application to COPD management. Coupled with the bioavailability and safety profile of tocotrienols, the ability of these compounds to modulate COPD progression by targeting the inflammation pathways renders them potential candidates for novel therapeutic approaches in the treatment of COPD patients.
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Affiliation(s)
- Xiangming Ji
- Department of Nutrition, Byrdine F. Lewis College of Nursing and Health Professions, Georgia State University, Atlanta, GA 30303, USA; (M.M.); (H.M.)
| | - Hongwei Yao
- Department of Molecular Biology, Cell Biology & Biochemistry, Division of Biology and Medicine, Brown University, Providence, RI 02912, USA;
| | - Maureen Meister
- Department of Nutrition, Byrdine F. Lewis College of Nursing and Health Professions, Georgia State University, Atlanta, GA 30303, USA; (M.M.); (H.M.)
| | - Douglas S. Gardenhire
- Department of Respiratory Therapy, Byrdine F. Lewis College of Nursing and Health Professions, Georgia State University, Atlanta, GA 30303, USA;
| | - Huanbiao Mo
- Department of Nutrition, Byrdine F. Lewis College of Nursing and Health Professions, Georgia State University, Atlanta, GA 30303, USA; (M.M.); (H.M.)
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5
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Shrungeswara AH, Unnikrishnan MK. Energy Provisioning and Inflammasome Activation: The Pivotal Role of AMPK in Sterile Inflammation and Associated Metabolic Disorders. Antiinflamm Antiallergy Agents Med Chem 2020; 20:107-117. [PMID: 32938355 DOI: 10.2174/1871523019666200916115034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 07/02/2020] [Accepted: 08/19/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND Body defenses and metabolic processes probably co-evolved in such a way that rapid, energy-intensive acute inflammatory repair is functionally integrated with energy allocation in a starvation/ infection / injury-prone primitive environment. Disruptive metabolic surplus, aggravated by sedentary lifestyle induces chronic under-activation of AMPK, the master regulator of intracellular energy homeostasis. Sudden increase in chronic, dysregulated 'sterile' inflammatory disorders probably results from a shift towards calorie rich, sanitized, cushioned, injury/ infection free environment, repositioning inflammatory repair pathways towards chronic, non-microbial, 'sterile', 'low grade', and 'parainflammation'. AMPK, (at the helm of energy provisioning) supervises the metabolic regulation of inflammasome activation, a common denominator in lifestyle disorders. DISCUSSION In this review, we discuss various pathways linking AMPK under-activation and inflammasome activation. AMPK under-activation, the possible norm in energy-rich sedentary lifestyle, could be the central agency that stimulates inflammasome activation by multiple pathways such as 1: decreasing autophagy, and accumulation of intracellular DAMPs, (particulate crystalline molecules, advanced glycation end-products, oxidized lipids, etc.) 2: stimulating a glycolytic shift (pro-inflammatory) in metabolism, 3: promoting NF-kB activation and decreasing Nrf2 activation, 4: increasing reactive oxygen species (ROS) formation, Unfolded Protein Response (UPR) and Endoplasmic Reticulum (ER) stress. CONCLUSION The 'inverse energy crisis' associated with calorie-rich, sedentary lifestyle, advocates dietary and pharmacological interventions for treating chronic metabolic disorders by overcoming / reversing AMPK under-activation.
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Affiliation(s)
- Akhila H Shrungeswara
- Department of Pharmacy Practice, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
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6
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Tan SW, Israf Ali DAB, Khaza'ai H, Wong JW, Vidyadaran S. Cellular uptake and anti-inflammatory effects of palm oil-derived delta (δ)-tocotrienol in microglia. Cell Immunol 2020; 357:104200. [PMID: 32979761 DOI: 10.1016/j.cellimm.2020.104200] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 08/17/2020] [Accepted: 08/18/2020] [Indexed: 02/06/2023]
Abstract
Tocopherols long dominated studies on vitamin E, although interest has shifted to tocotrienols. It was previously shown that δ-tocotrienol derived from palm oil reduced nitric oxide released by BV2 microglia as early as 18 h after lipopolysaccharide stimulation. The current study measured δ-tocotrienol uptake by BV2 over a 24 h incubation period and its anti-inflammatory effects on primary microglia. Uptake of 17.5 μg/mL δ-tocotrienol by BV2 microglia began as early as 5 min and rose steeply to 21 ± 3% of the amount administered at 24 h. The amount of δ-tocotrienol retained in the lipopolysaccharide-stimulated microglia at 24 h was 14 ± 2%, with no substantial difference seen in unstimulated microglia. The same δ-tocotrienol regimen reduced nitric oxide levels by 82% at 24 h after lipopolysaccharide stimulation (p < 0.05). This was accompanied by decreased inducible nitric oxide synthase protein expression by 67 ± 5% compared to untreated controls (p < 0.05). In primary microglia, δ-tocotrienol downregulated IL-1β production, but TNF-α and IL-6 were not affected. δ-Tocotrienol also reduced prostaglandin E2 production by ~78%% and decreased transcription of COX-2 and 5-LOX, but not COX-1. This study showed the anti-inflammatory effects of δ-tocotrienol derived from palm oil and opens up interest for tocotrienol supplementation to reduce the effects of inflammatory conditions.
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Affiliation(s)
- Shi Wei Tan
- Neuroinflammation Group, Immunology Laboratory, Department of Pathology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia
| | - Daud Ahmad Bin Israf Ali
- Cell Signaling Laboratory, Department of Biomedical Science, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia
| | - Huzwah Khaza'ai
- Biochemistry Laboratory, Department of Biomedical Science, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia
| | - Jia Woei Wong
- Attest Research Sdn Bhd, Kompleks EUREKA, Universiti Sains Malaysia, 11800 Minden, Pulau Pinang, Malaysia
| | - Sharmili Vidyadaran
- Neuroinflammation Group, Immunology Laboratory, Department of Pathology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia.
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7
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Wallert M, Börmel L, Lorkowski S. Inflammatory Diseases and Vitamin E-What Do We Know and Where Do We Go? Mol Nutr Food Res 2020; 65:e2000097. [PMID: 32692879 DOI: 10.1002/mnfr.202000097] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 06/26/2020] [Indexed: 12/14/2022]
Abstract
Inflammation-driven diseases and related comorbidities, such as the metabolic syndrome, obesity, fatty liver disease, and cardiovascular diseases cause significant global burden. There is a growing body of evidence that nutrients alter inflammatory responses and can therefore make a decisive contribution to the treatment of these diseases. Recently, the inflammasome, a cytosolic multiprotein complex, has been identified as a key player in inflammation and the development of various inflammation-mediated disorders, with nucleotide-binding domain and leucine-rich repeat pyrin domain (NLRP) 3 being the inflammasome of interest. Here an overview about the cellular signaling pathways underlying nuclear factor "kappa-light-chain-enhancer" of activated B-cells (NF-κB)- and NLRP3-mediated inflammatory processes, and the pathogenesis of the inflammatory diseases atherosclerosis and non-alcoholic fatty liver disease (NAFLD) is provided; next, the current state of knowledge for drug-based and dietary-based interventions for treating cardiovascular diseases and NAFLD is discussed. To date, one of the most important antioxidants in the human diet is vitamin E. Various in vitro and in vivo studies suggest that the different forms of vitamin E and also their derivatives have anti-inflammatory activity. Recent publications suggest that vitamin E-and possibly metabolites of vitamin E-are a promising therapeutic approach for treating inflammatory diseases such as NAFLD.
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Affiliation(s)
- Maria Wallert
- Department of Nutritional Biochemistry and Physiology, Institute of Nutritional Science, Friedrich Schiller University Jena, Jena, 07743, Germany.,Competence Cluster for Nutrition and Cardiovascular Health (nutriCARD), Halle-Jena-Leipzig, Germany
| | - Lisa Börmel
- Department of Nutritional Biochemistry and Physiology, Institute of Nutritional Science, Friedrich Schiller University Jena, Jena, 07743, Germany.,Competence Cluster for Nutrition and Cardiovascular Health (nutriCARD), Halle-Jena-Leipzig, Germany
| | - Stefan Lorkowski
- Department of Nutritional Biochemistry and Physiology, Institute of Nutritional Science, Friedrich Schiller University Jena, Jena, 07743, Germany.,Competence Cluster for Nutrition and Cardiovascular Health (nutriCARD), Halle-Jena-Leipzig, Germany
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8
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Chin KY, Wong SK, Japar Sidik FZ, Abdul Hamid J, Abas NH, Mohd Ramli ES, Afian Mokhtar S, Rajalingham S, Ima Nirwana S. The Effects of Annatto Tocotrienol Supplementation on Cartilage and Subchondral Bone in an Animal Model of Osteoarthritis Induced by Monosodium Iodoacetate. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2019; 16:ijerph16162897. [PMID: 31412648 PMCID: PMC6720523 DOI: 10.3390/ijerph16162897] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Revised: 08/08/2019] [Accepted: 08/09/2019] [Indexed: 12/18/2022]
Abstract
Osteoarthritis is a degenerative joint disease which primarily affects the articular cartilage and subchondral bones. Since there is an underlying localized inflammatory component in the pathogenesis of osteoarthritis, compounds like tocotrienol with anti-inflammatory properties may be able to retard its progression. This study aimed to determine the effects of oral tocotrienol supplementation on the articular cartilage and subchondral bone in a rat model of osteoarthritis induced by monosodium iodoacetate (MIA). Thirty male Sprague-Dawley rats (three-month-old) were randomized into five groups. Four groups were induced with osteoarthritis (single injection of MIA at week 0) and another served as the sham group. Three of the four groups with osteoarthritis were supplemented with annatto tocotrienol at 50, 100 and 150 mg/kg/day orally for five weeks. At week 5, all rats were sacrificed, and their tibial-femoral joints were harvested for analysis. The results indicated that the groups which received annatto tocotrienol at 100 and 150 mg/kg/day had lower histological scores and cartilage remodeling markers. Annatto tocotrienol at 150 mg/kg/day significantly lowered the osteocalcin levels and osteoclast surface of subchondral bone. In conclusion, annatto tocotrienol may potentially retard the progression of osteoarthritis. Future studies to confirm its mechanism of joint protection should be performed.
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Affiliation(s)
- Kok-Yong Chin
- Department of Pharmacology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Cheras 56000, Malaysia.
| | - Sok Kuan Wong
- Department of Pharmacology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Cheras 56000, Malaysia
| | | | - Juliana Abdul Hamid
- Department of Pharmacology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Cheras 56000, Malaysia
| | - Nurul Hafizah Abas
- Department of Pharmacology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Cheras 56000, Malaysia
| | - Elvy Suhana Mohd Ramli
- Department of Anatomy, Faculty of Medicine, Universiti Kebangsaan Malaysia, Cheras 56000, Malaysia
| | - Sabarul Afian Mokhtar
- Department of Orthopedics and Traumatology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Cheras 56000, Malaysia
| | - Sakthiswary Rajalingham
- Department of Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Cheras 56000, Malaysia
| | - Soelaiman Ima Nirwana
- Department of Pharmacology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Cheras 56000, Malaysia
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Vitamin E δ-tocotrienol inhibits TNF-α-stimulated NF-κB activation by up-regulation of anti-inflammatory A20 via modulation of sphingolipid including elevation of intracellular dihydroceramides. J Nutr Biochem 2018; 64:101-109. [PMID: 30471562 DOI: 10.1016/j.jnutbio.2018.10.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 09/30/2018] [Accepted: 10/29/2018] [Indexed: 12/24/2022]
Abstract
Nuclear factor-κB (NF-κB) regulates inflammation and cell survival, and is considered a potential target for anti-inflammatory and anti-cancer therapy. δ-Tocotrienol (δTE), a vitamin E form, has been shown to inhibit NF-κB, but the mechanism underlying this action is not clear. In the present study, we show that δTE inhibited TNF-α-induced activation of NF-κB and LPS-stimulated IL-6 in a dose- and time-dependent manner in Raw 264.7 macrophages. δTE potently inhibited TNF-α-induced phosphorylation of transforming growth factor β-activated kinase 1 (TAK1), an upstream kinase essential for the activation of NF-κB. Interestingly, δTE significantly increased the expression of A20 and to a less extent, cylindromatosis (CYLD), both of which are inhibitors of NF-κB. The importance of induction of A20 in δTE's anti-NF-κB effect is validated in A20 knockout cells where δTE's inhibition of NF-κB was largely diminished. In pursuit of the cause for A20 induction, we found that δTE treatment caused rapid and persistent elevation of dihydroceramides, while decreased ceramides initially but increased ceramides during prolonged treatment. These changes of sphingolipids were accompanied by increased cellular stress markers. Importantly, δTE's induction of A20 and inhibition of NF-κB activation were partially counteracted by myriocin, a potent inhibitor of de novo synthesis of sphingolipids, indicating a critical role of sphingolipid modulation in δTE-mediated effects. Since dihydroceramide has been shown to induce A20 and inhibit NF-κB in RAW cells, we conclude that that δTE inhibits NF-κB activation by enhancing its negative regulator A20 as a result of modulating sphingolipids especially elevation of dihydroceramides.
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