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Zhang Y, Zhou SQ, Xie MM, Jiang QL, Yang N, Wu R, Zhou J, Xu XR. Licochalcone A alleviates laser-induced choroidal neovascularization by inhibiting the endothelial-mesenchymal transition via PI3K/AKT signaling pathway. Exp Eye Res 2023; 226:109335. [PMID: 36436569 DOI: 10.1016/j.exer.2022.109335] [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: 07/14/2022] [Revised: 10/30/2022] [Accepted: 11/19/2022] [Indexed: 11/27/2022]
Abstract
Choroidal neovascularization (CNV) is a hallmark of wet age-related macular degeneration, which severely impairs central vision. Studies have shown that endothelial-mesenchymal transition (EndMT) is involved in the pathogenesis of CNV. Licochalcone A (lico A), a flavonoid extracted from the root of licorice, shows the inhibition on EndMT, but it remains unclear whether it can suppress the formation of CNV. The aim of this study is to investigate the effects of lico A on laser-induced CNV, and EndMT process in vitro and vivo. We established the model of CNV with a krypton laser in Brown-Norway rats and then intraperitoneally injected lico A. Our experimental results demonstrated that the leakage of CNV was relieved, and the area of CNV was reduced in lico A-treated rats. Cell migration and tube formation in oxidized low-density lipoprotein (Ox-LDL)-stimulated HUVECs were inhibited by lico A and promoted by PI3K activator 740Y-P. The protein expressions of snai1 and α-SMA were increased, and CD31 and VE-cadherin were decreased in the model rats of CNV, but partially reversed after treatment with lico A. The expression of CD31 was decreased and α-SMA was increased in OX-LDL-treated HUVECs, which was further strengthened by 740Y-P, while the expression of CD31 was up-regulated and α-SMA was down-regulated in lico A treated HUVECs. Our data revealed that EndMT process was alleviated by lico A. Meanwhile, PI3K/AKT signaling pathway was activated in model rat of CNV and Ox-LDL-stimulated HUVECs, which can be suppressed with treatment of lico A. Our experimental results confirmed for the first time that lico A has the potential to alleviate CNV by inhibiting the endothelial-mesenchymal transition via PI3K/AKT signaling pathway.
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Affiliation(s)
- Yan Zhang
- Department of Ophthalmology, Jiangsu Province Hospital of Chinese Medicine (Affiliated Hospital of Nanjing University of Chinese Medicine), Nanjing, 210029, China
| | - Si-Qi Zhou
- Department of Ophthalmology, Jiangsu Province Hospital of Chinese Medicine (Affiliated Hospital of Nanjing University of Chinese Medicine), Nanjing, 210029, China
| | - Meng-Meng Xie
- Department of Ophthalmology, Jiangsu Province Hospital of Chinese Medicine (Affiliated Hospital of Nanjing University of Chinese Medicine), Nanjing, 210029, China
| | - Qiu-Le Jiang
- Department of Ophthalmology, Jiangsu Province Hospital of Chinese Medicine (Affiliated Hospital of Nanjing University of Chinese Medicine), Nanjing, 210029, China
| | - Ning Yang
- Department of Ophthalmology, Jiangsu Province Hospital of Chinese Medicine (Affiliated Hospital of Nanjing University of Chinese Medicine), Nanjing, 210029, China
| | - Rui Wu
- Department of Ophthalmology, Jiangsu Province Hospital of Chinese Medicine (Affiliated Hospital of Nanjing University of Chinese Medicine), Nanjing, 210029, China
| | - Jie Zhou
- Department of Ophthalmology, Jiangsu Province Hospital of Chinese Medicine (Affiliated Hospital of Nanjing University of Chinese Medicine), Nanjing, 210029, China
| | - Xin-Rong Xu
- Department of Ophthalmology, Jiangsu Province Hospital of Chinese Medicine (Affiliated Hospital of Nanjing University of Chinese Medicine), Nanjing, 210029, China.
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Chen M, Xiao J, El-Seedi HR, Woźniak KS, Daglia M, Little PJ, Weng J, Xu S. Kaempferol and atherosclerosis: From mechanism to medicine. Crit Rev Food Sci Nutr 2022; 64:2157-2175. [PMID: 36099317 DOI: 10.1080/10408398.2022.2121261] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Natural products possess pleiotropic cardiovascular protective effects owing to their anti-oxidation, anti-inflammation and anti-thrombotic properties. Kaempferol, (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one), is a kind of naturally occurring flavonoid existing in many common fruits and vegetables (e.g., onions, broccoli, strawberries and grapes) and particularly in traditional Chinese medicine as exemplified by Ginkgo biloba. Epidemiological, preclinical and clinical studies have revealed an inverse association between the consumption of kaempferol-containing foods and medicines and the risk of developing cardiovascular diseases. Numerous translational studies in experimental animal models and cultured cells have demonstrated a wide range of pharmacological activities of kaempferol. In this article, we reviewed the antioxidant, anti-inflammatory and cardio-protective activities of kaempferol and elucidated the potential molecular basis of the therapeutic capacity of kaempferol by focusing on its anti-atherosclerotic effects. Overall, the review presents the health benefits of kaempferol-containing plants and medicines and reflects on the potential of kaempferol as a possible drug candidate to prevent and treat atherosclerosis, the underlying pathology of most cardiovascular diseases.
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Affiliation(s)
- Meijie Chen
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Clinical Research Hospital of Chinese Academy of Sciences (Hefei), University of Science and Technology of China, Hefei, Anhui, China
| | - Jianbo Xiao
- Department of Analytical Chemistry and Food Science, University of Vigo, Vigo, Spain
| | - Hesham R El-Seedi
- Pharmacognosy Group, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
- International Research Center for Food Nutrition and Safety, Jiangsu University, Zhenjiang, China
| | | | - Maria Daglia
- International Research Center for Food Nutrition and Safety, Jiangsu University, Zhenjiang, China
- Department of Pharmacy, University of Napoli Federico II, Naples, Italy
| | - Peter J Little
- School of Pharmacy, University of Queensland, Pharmacy Australia Centre of Excellence, Woolloongabba, QLD, Australia
| | - Jianping Weng
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Clinical Research Hospital of Chinese Academy of Sciences (Hefei), University of Science and Technology of China, Hefei, Anhui, China
| | - Suowen Xu
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Clinical Research Hospital of Chinese Academy of Sciences (Hefei), University of Science and Technology of China, Hefei, Anhui, China
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Dang KR, Wu T, Hui YN, Du HJ. Newly-found functions of metformin for the prevention and treatment of age-related macular degeneration. Int J Ophthalmol 2021; 14:1274-1280. [PMID: 34414094 PMCID: PMC8342286 DOI: 10.18240/ijo.2021.08.20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 05/11/2021] [Indexed: 12/18/2022] Open
Abstract
Metformin (MET), a first-line oral agent used to treat diabetes, exerts its function mainly by activating adenosine monophosphate-activated protein. The accumulation of oxidized phospholipids in the outer layer of the retina plays a key role in retinal pigment epithelium (RPE) cells death and the formation of choroidal neovascularization (CNV), which mean the development of age-related macular degeneration (AMD). Recent studies have shown that MET can regulate lipid metabolism, inhibit inflammation, and prohibit retinal cell death and CNV formation due to various pathological factors. Here, newly discovered functions of MET that may be used for the prevention and treatment of AMD were reviewed.
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Affiliation(s)
- Kuan-Rong Dang
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Tong Wu
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Yan-Nian Hui
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Hong-Jun Du
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
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Zhai S, Zhang XF, Lu F, Chen WG, He X, Zhang CF, Wang CZ, Yuan CS. Chinese medicine GeGen-DanShen extract protects from myocardial ischemic injury through promoting angiogenesis via up-regulation of VEGF/VEGFR2 signaling pathway. JOURNAL OF ETHNOPHARMACOLOGY 2021; 267:113475. [PMID: 33068653 DOI: 10.1016/j.jep.2020.113475] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/01/2020] [Accepted: 10/12/2020] [Indexed: 06/11/2023]
Abstract
HEADINGS ETHNOPHARMACOLOGICAL RELEVANCE Coronary heart disease (CHD) usually refers to myocardial ischemia or myocardial necrosis caused by coronary artery stenosis. GeGen and DanShen (GD) are popular Chinese herbs for the treatment of angina pectoris and myocardial infarction (MI). This sentence needs to be a separate paragraph. AIM OF THE STUDY This study was to investigate the role of GD extract in promoting ischemic myocardial angiogenesis, and to explore its signaling mechanism, so as to provide a more reliable scientific basis for the clinical treatment of ischemic cardiovascular disease. MATERIALS AND METHODS GD extract was initially analyzed by HPLC-Q-TOF MS. In vitro, migration assay and tube formation assay were subsequently used to detect the angiogenesis activity of GD extract in human umbilical vein endothelial cells (HUVECs). Following the in vitro study, an MI rat model was established by ligating the left anterior descending coronary artery (LAD), immediately followed by a 4-week daily GD extract treatment by intragastric administration. After the animal sacrifice, hematoxylin-eosin (HE) staining was conducted to observe the pathological changes of the infarct margin. Besides, the MI area was measured by 2,3,5-triphenyltetrazoliumchloride (TTC) staining. The microvascular density (MVD) was also quantified through CD31 immunohistochemistry. Moreover, the levels of VEGF, TXB2 and 6-keto-PGF1α in serum were detected by enzyme-linked immunosorbent assay. The expression of VEGFR2 and ERK were detected by immunohistochemistry as well. RESULTS In vitro study, GD extract was found to induce significant angiogenesis in HUVECs. In vivo, smaller infarct size was found in treatment groups than that of the model group, and the protein expression of VEGFR2 as well as ERK in the marginal zone of MI in treatment groups were significantly increased. The morphological changes of myocardium were observed with a significant growth in the number of new blood vessels. Regarding the effect of GD extract, the serum levels of CK, LDH and TXB2 were consequently reduced, whereas the levels of VEGF, 6-keto-PGF1α were significantly increased. CONCLUSIONS Based on the findings of this study, GD extract had a protective effect against MI in rats. The possible mechanism is to promote angiogenesis by regulating the VEGF/VEGFR2 signaling pathway after MI occurrence.
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Affiliation(s)
- Shuo Zhai
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Xiao-Fan Zhang
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Fang Lu
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Wei-Guo Chen
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Xin He
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative Region of China.
| | - Chun-Feng Zhang
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China.
| | - Chong-Zhi Wang
- Tang Center of Herbal Medicine Research and Department of Anesthesia & Critical Care, University of Chicago, Chicago, IL, 60637, USA
| | - Chun-Su Yuan
- Tang Center of Herbal Medicine Research and Department of Anesthesia & Critical Care, University of Chicago, Chicago, IL, 60637, USA
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Zhang S, Li L, Chen W, Xu S, Feng X, Zhang L. Natural products: The role and mechanism in low-density lipoprotein oxidation and atherosclerosis. Phytother Res 2020; 35:2945-2967. [PMID: 33368763 DOI: 10.1002/ptr.7002] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 10/30/2020] [Accepted: 12/13/2020] [Indexed: 12/11/2022]
Abstract
Atherosclerosis is a chronic inflammatory, metabolic, and epigenetic disease, which leads to the life-threatening coronary artery disease. Emerging studies from bench to bedside have demonstrated the pivotal role of low-density lipoprotein (LDL) oxidation in the initiation and progression of atherosclerosis. This article hereby reviews oxidation mechanism of LDL, and the pro-atherogenic and biomarker role of oxidized LDL in atherosclerosis. We also review the pharmacological effects of several representative natural products (vitamin E, resveratrol, quercetin, probucol, tanshinone IIA, epigallocatechin gallate, and Lycopene) in protecting against LDL oxidation and atherosclerosis. Clinical and basic research supports the beneficial effects of these natural products in inhibiting LDL oxidation and preventing atherosclerosis, but the data are still controversial. This may be related to factors such as the population and the dosage and time of taking natural products involved in different studies. Understanding the mechanism of LDL oxidation and effect of oxidized LDL help researchers to find novel therapies against atherosclerosis.
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Affiliation(s)
- Shengyu Zhang
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Lingli Li
- Department of Pharmacy, Anhui Provincial Hospital, Anhui Medical University, Hefei, China
| | - Wenxu Chen
- Department of Pharmaceutics, College of Pharmacy, Anhui University of Chinese Medicine, Hefei, China
| | - Suowen Xu
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Xiaojun Feng
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Lei Zhang
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China.,Department of Pharmacy, Anhui Provincial Hospital, Anhui Medical University, Hefei, China
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Wu T, Dang KR, Wang YF, Lyu BZ, Xu WQ, Dou GR, Zhou J, Hui YN, Du HJ. A modified laser-induced choroidal neovascularization animal model with intravitreal oxidized low-density lipoprotein. Int J Ophthalmol 2020; 13:1187-1194. [PMID: 32821671 DOI: 10.18240/ijo.2020.08.03] [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: 12/18/2019] [Accepted: 05/08/2020] [Indexed: 10/23/2022] Open
Abstract
AIM To investigate whether intravitreal injection of oxidized low-density lipoprotein (OxLDL) can promote laser-induced choroidal neovascularization (CNV) formation in mice and the mechanism involved, thereby to develop a better animal model. METHODS C57BL6/J mice were randomized into three groups. Immediately after CNV induction with 532 nm laser photocoagulation, 1.0 µL of OxLDL [100 µg/mL in phosphate-buffered saline (PBS)] was intravitreally injected, whereas PBS and the same volume low-density lipoprotein (LDL; 100 µg/mL in PBS) were injected into the vitreous as controls. Angiogenic and inflammatory cytokines were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting (WB) after 5d, and CNV severity was analyzed by choroid flat mount and immunofluorescence staining after 1wk. In vitro, retinal pigment epithelial (RPE) cell line (ARPE19) were treated with OxLDL (LDL as control) for 8h. Angiogenic and inflammatory cytokine levels were measured. A specific inhibitor of lectin-like oxidized low-density lipoprotein receptor 1 (LOX1) was used to evaluate the role of LOX1 in this process. RESULTS At 7d after intravitreal injection of 1 µL (100 µg/mL) OxLDL, T15-labeled OxLDL was mainly deposited around the CNV area, and the F4/80-labeled macrophages, the CD31-labeled vascular endothelial cells number and CNV area were increased. Meanwhile, WB and qRT-PCR results showed that vascular endothelial growth factor (VEGF), CC chemokine receptor 2 (CCR2), interleukin-6 (IL-6), IL-1β, and matrix metalloproteinase 9 (MMP9) expressions were increased, which was supported by in vitro experiments in RPE cells. LOX1 inhibitors significantly reduced expressions of inflammatory factors IL-1β and VEGF. CONCLUSION A modified laser-induced CNV animal model is established with intravitreal injection of 1 µL (100 µg/mL) of OxLDL at 7d, which at least partially through LOX1. This animal model can be used as a simple model for studying the role of OxLDL in age-related macular degeneration.
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Affiliation(s)
- Tong Wu
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Kuan-Rong Dang
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Ya-Fen Wang
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Bao-Zhen Lyu
- Department of Anatomy and Histology and Embryology, Xi'an Health School, Xi'an 710032, Shaanxi Province, China
| | - Wen-Qin Xu
- The Orbital Disease Institute of the Third Medical Center of PLA General Hospital, Beijing 100039, China
| | - Guo-Rui Dou
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Jian Zhou
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Yan-Nian Hui
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Hong-Jun Du
- Department of Ophthalmology, Xijing Hospital, Eye Institute of Chinese PLA, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
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Hsu YJ, Lin CW, Cho SL, Yang WS, Yang CM, Yang CH. Protective Effect of Fenofibrate on Oxidative Stress-Induced Apoptosis in Retinal-Choroidal Vascular Endothelial Cells: Implication for Diabetic Retinopathy Treatment. Antioxidants (Basel) 2020; 9:antiox9080712. [PMID: 32764528 PMCID: PMC7464418 DOI: 10.3390/antiox9080712] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 07/28/2020] [Accepted: 08/04/2020] [Indexed: 12/24/2022] Open
Abstract
Diabetic retinopathy (DR) is an important microvascular complication of diabetes and one of the leading causes of blindness in developed countries. Two large clinical studies showed that fenofibrate, a peroxisome proliferator-activated receptor type α (PPAR-α) agonist, reduces DR progression. We evaluated the protective effects of fenofibrate on retinal/choroidal vascular endothelial cells under oxidative stress and investigated the underlying mechanisms using RF/6A cells as the model system and paraquat (PQ) to induce oxidative stress. Pretreatment with fenofibrate suppressed reactive oxygen species (ROS) production, decreased cellular apoptosis, diminished the changes in the mitochondrial membrane potential, increased the mRNA levels of peroxiredoxin (Prx), thioredoxins (Trxs), B-cell lymphoma 2 (Bcl-2), and Bcl-xl, and reduced the level of B-cell lymphoma 2-associated X protein (Bax) in PQ-stimulated RF/6A cells. Western blot analysis revealed that fenofibrate repressed apoptosis through cytosolic and mitochondrial apoptosis signal-regulated kinase-1 (Ask)-Trx-related signaling pathways, including c-Jun amino-terminal kinase (JNK) phosphorylation, cytochrome c release, caspase 3 activation, and poly (ADP-ribose) polymerase-1 (PARP-1) cleavage. These protective effects of fenofibrate on RF/6A cells may be attributable to its anti-oxidative ability. Our research suggests that fenofibrate could serve as an effective adjunct therapy for ocular oxidative stress-related disorders, such as DR.
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Affiliation(s)
- Ying-Jung Hsu
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, No. 1, Jen Ai Road Section 1, Taipei 100, Taiwan; (Y.-J.H.); (C.-W.L.); (W.-S.Y.)
| | - Chao-Wen Lin
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, No. 1, Jen Ai Road Section 1, Taipei 100, Taiwan; (Y.-J.H.); (C.-W.L.); (W.-S.Y.)
- Department of Ophthalmology, National Taiwan University Hospital, No. 7, Zhongshan South Road, Taipei 100, Taiwan;
| | - Sheng-Li Cho
- Department of Internal Medicine, National Taiwan University Hospital, No. 7, Zhongshan South Road, Taipei 100, Taiwan;
| | - Wei-Shiung Yang
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, No. 1, Jen Ai Road Section 1, Taipei 100, Taiwan; (Y.-J.H.); (C.-W.L.); (W.-S.Y.)
- Department of Internal Medicine, National Taiwan University Hospital, No. 7, Zhongshan South Road, Taipei 100, Taiwan;
| | - Chung-May Yang
- Department of Ophthalmology, National Taiwan University Hospital, No. 7, Zhongshan South Road, Taipei 100, Taiwan;
| | - Chang-Hao Yang
- Department of Ophthalmology, National Taiwan University Hospital, No. 7, Zhongshan South Road, Taipei 100, Taiwan;
- Correspondence: ; Tel.: +886-2-23123456 (ext. 63193)
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EMT and EndMT: Emerging Roles in Age-Related Macular Degeneration. Int J Mol Sci 2020; 21:ijms21124271. [PMID: 32560057 PMCID: PMC7349630 DOI: 10.3390/ijms21124271] [Citation(s) in RCA: 118] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/12/2020] [Accepted: 06/14/2020] [Indexed: 02/06/2023] Open
Abstract
Epithelial–mesenchymal transition (EMT) and endothelial–mesenchymal transition (EndMT) are physiological processes required for normal embryogenesis. However, these processes can be hijacked in pathological conditions to facilitate tissue fibrosis and cancer metastasis. In the eye, EMT and EndMT play key roles in the pathogenesis of subretinal fibrosis, the end-stage of age-related macular degeneration (AMD) that leads to profound and permanent vision loss. Predominant in subretinal fibrotic lesions are matrix-producing mesenchymal cells believed to originate from the retinal pigment epithelium (RPE) and/or choroidal endothelial cells (CECs) through EMT and EndMT, respectively. Recent evidence suggests that EMT of RPE may also be implicated during the early stages of AMD. Transforming growth factor-beta (TGFβ) is a key cytokine orchestrating both EMT and EndMT. Investigations in the molecular mechanisms underpinning EMT and EndMT in AMD have implicated a myriad of contributing factors including signaling pathways, extracellular matrix remodelling, oxidative stress, inflammation, autophagy, metabolism and mitochondrial dysfunction. Questions arise as to differences in the mesenchymal cells derived from these two processes and their distinct mechanistic contributions to the pathogenesis of AMD. Detailed discussion on the AMD microenvironment highlights the synergistic interactions between RPE and CECs that may augment the EMT and EndMT processes in vivo. Understanding the differential regulatory networks of EMT and EndMT and their contributions to both the dry and wet forms of AMD can aid the development of therapeutic strategies targeting both RPE and CECs to potentially reverse the aberrant cellular transdifferentiation processes, regenerate the retina and thus restore vision.
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