鐵調素，作為關鍵的鐵調節激素，在維持外周系統的鐵平衡中具有重要作用。外周鐵調素的表達受到多種因素的平衡調節，包括鐵的狀態，炎症，造血活動和缺氧。這一激素肽在腦內的存在和廣泛分佈，提示它可能在腦鐵平衡中也發揮作用。本研究檢測了炎症是否對腦內鐵調素表達起調節作用，從而影響腦鐵代謝。 / 在本研究的第一部分，我們檢測了炎症是否調節腦內鐵調素的表達，以及這種調節作用在腦內是否具有區域特異性。利用脂多糖（一種廣泛使用的炎症誘導劑）誘導的炎症模型，我們發現腦室內注射脂多糖可區域特異性地誘導腦內鐵調素的表達，即誘導皮層和黑質的鐵調素表達，而海馬的鐵調素水準無顯著改變。與此相伴隨的是腦內膜鐵轉運蛋白區域特異性的表達下降。此外，我們發現脂多糖處理引起的腦內鐵調素表達升高發生在神經元而不是星形膠質細胞內。這些發現提示，炎症能夠區域特異性地上調腦內鐵調素表達，上調的鐵調素轉而下調特定腦區膜鐵轉運蛋白的表達。 / 在本研究的第二部分，我們檢測了離體水準上炎症對原代皮層神經元和MES23.5多巴胺能細胞鐵調素表達的影響。我們觀察了炎症對這些細胞鐵調素和膜鐵轉運蛋白表達的作用。我們發現脂多糖不增加原代皮層神經元鐵調素的表達。但在與BV-2小膠質細胞共培養的條件下，原代皮層神經元的鐵調素表達水準經脂多糖刺激後上升。我們檢測了一系列可能由小膠質釋放的促炎細胞因數對神經元鐵調素表達的影響。結果表明，白介素-6介導了脂多糖誘導的神經元鐵調素表達升高的作用。我們進一步發現，白介素-6在短時間內直接增加神經元鐵調素表達和降低膜鐵轉運蛋白表達。最後我們進一步探究了白介素-6對腦內鐵調素表達的調控機制，發現在原代皮層神經元和MES23.5多巴胺能細胞中白介素-6誘導的鐵調素表達是通過信號轉導和轉錄啟動因數3信號通路介導的。 / 綜上所述，我們的研究結果表明，炎症在調節腦內鐵調素表達和控制腦內鐵轉運中發揮重要的作用。在腦內，炎症區域特異性地誘導鐵調素表達上調和膜鐵轉運蛋白表達下調。白介素-6/ 信號轉導和轉錄啟動因數3這一信號通路介導了在炎症情況下腦內鐵調素表達。這些發現加強了我們對於腦內鐵調素表達的調節過程的理解，並提供了一種新的關於鐵調素在腦內抗炎作用的治療觀點。 / Hepcidin, as the central iron regulatory hormone, plays a key role in maintaining peripheral iron homeostasis. The expression of hepcidin in the periphery is regulated by multiple factors homeostatically, including iron status, inflammation, erythropoietic activity and hypoxia. The presence and widespread distribution of this peptide in the brain suggests that hepcidin may also have an essential role in brain iron homeostasis. In this study we tested the hypothesis that inflammation exerts an important role in the regulation of brain hepcidin expression, which might alter brain iron metabolism. / To investigate whether inflammation could regulate brain hepcidin expression and whether this regulatory role is regionally specific in the brain, in the first part of study, we explored the effects of lipopolysaccharides (LPS), a widely used inflammation-inducing agent, on hepcidin expression in different brain regions of the rat brain in vivo. We found that intracerebroventricular (i.c.v.) injection of LPS induced brain hepcidin expression regionally specifically, that is, in the cortex and substantia nigra but not in the hippocampus. This effect was accompanied by a regionally specific decrease in brain ferroportin expression. Besides, brain hepcidin was found to be increased in neurons but not in astrocytes by LPS treatment. These findings indicate that inflammation could up-regulate brain hepcidin expression regionally specifically in the brain, which in turn down-regulates ferroportin expression in specific brain regions. / In the second part, we investigated the effects of inflammation on hepcidin expression in primary cortical neurons and MES23.5 dopaminergic cells in vitro. The expression of hepcidin as well as ferroportin was observed. We found that LPS did not increase hepcidin expression in primary cortical neurons. However, LPS induced neuronal hepcidin expression with the presence of BV-2 microglia cells. We examined the effects of a series of pro-inflammatory cytokines which could be released by microglia cells, on hepcidin expression, and found that interleukin-6 (IL-6) mediated neuronal hepcidin expression induced by LPS. Furthermore, we found that IL-6 directly increased hepcidin expression and decreased ferroportin expression in an acute manner. Finally, we further investigated the mechanisms underlying the regulatory effects of IL-6 on brain hepcidin expression, and found that IL-6-induced hepcidin expression is via signal transducer and activator of transcription-3 (STAT3) signaling in primary cortical neurons and MES23.5 dopaminergic cells. / In conclusion, the results of the present study implied that inflammation plays an important role in regulating brain hepcidin expression and controlling brain iron transport. In the brain, hepcidin up-regulation and ferroportin down-regulation is induced by inflammation in a regionally specific way. IL-6/ STAT3 signaling pathway is essential for brain hepcidin expression during inflammation. These findings enhance our understanding of the regulatory process of hepcidin in the brain, and provide a new therapeutic perspective of hepcidin in anti-inflammation in the brain. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / He, Xuan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 110-128). / Abstracts also in Chinese. / ABSTRACT OF THESIS ENTITLED --- p.II / ACKNOWLEDGENENTS --- p.VII / TABLE OF CONTENTS --- p.VIII / LIST OF FIGURES --- p.XII / LIST OF ABBREVIATIONS --- p.XV / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Introductory statement --- p.1 / Chapter 1.2 --- Hepcidin in the periphery --- p.1 / Chapter 1.2.1 --- Biological functions of hepcidin --- p.3 / Chapter 1.2.2 --- Regulation of hepcidin synthesis --- p.10 / Chapter 1.2.2.1 --- Regulation of hepcidin by iron --- p.10 / Chapter 1.2.2.2 --- Regulation of hepcidin by inflammation --- p.17 / Chapter 1.2.2.3 --- Regulation of hepcidin by anemia, erythropoiesis and hypoxia --- p.21 / Chapter 1.2.3 --- Misregulation of hepcidin --- p.25 / Chapter 1.2.3.1 --- Hepcidin deficiency --- p.25 / Chapter 1.2.3.2 --- Hepcidin excess --- p.27 / Chapter 1.3 --- Hepcidin in the brain --- p.28 / Chapter 1.4 --- Neuroinflammation --- p.30 / Chapter 1.5 --- Summary --- p.33 / Chapter 1.6 --- Objectives . --- p.34 / Chapter CHAPTER 2 --- MATERIALS AND METHODS --- p.36 / Chapter 2.1 --- Animal experiments --- p.36 / Chapter 2.1.1 --- Intracerebroventricular LPS injection --- p.36 / Chapter 2.1.2 --- Animal sacrifice and sample collection --- p.37 / Chapter 2.2 --- Cell cultures --- p.38 / Chapter 2.2.1 --- Primary cortical neurons culture --- p.38 / Chapter 2.2.2 --- BV-2 microglia cells --- p.39 / Chapter 2.2.3 --- MES23.5 dopaminergic cells --- p.39 / Chapter 2.3 --- Western blot analysis --- p.40 / Chapter 2.4 --- ELISA measurement --- p.42 / Chapter 2.5 --- Immunohistochemistry --- p.43 / Chapter 2.6 --- Statistical analysis --- p.44 / Chapter CHAPTER 3 --- IN VIVO STUDY OF THE EFFECTS OF INFLAMMATION ON BRAIN HEPCIDIN EXPRESSION --- p.46 / Chapter 3.1 --- ABSTRACT. --- p.46 / Chapter 3.2 --- INTRODUCTION --- p.47 / Chapter 3.3 --- MATERIALS AND METHODS --- p.48 / Chapter 3.4 --- RESULTS --- p.50 / Chapter 3.4.1 --- LPS injection induced hepcidin expression in neurons in the cortex and substantia nigra but not in the hippocampus of the rat brain --- p.50 / Chapter 3.4.2 --- LPS injection did not induce hepcidin expression in astrocytes in the cortex, hippocampus and substantia nigra of the rat brain --- p.51 / Chapter 3.4.3 --- LPS injection induced hepcidin up-regulation and ferroportin down-regulation in the cortex and substantia nigra but not in the hippocampus of the rat brain --- p.52 / Chapter 3.4.4 --- LPS injection induced IL-6 production and STAT3 phosphorylation in the cortex, hippocampus and substantia nigra of the rat brain --- p.53 / Chapter 3.5 --- DISCUSSION --- p.54 / Chapter CHAPTER 4 --- IN VITRO STUDY OF THE MECHANISMS UNDERLYING THE EFFECTS OF INFLAMMATION ON BRAIN HEPCIDIN EXPRESSION --- p.72 / Chapter 4.1 --- ABSTRACT --- p.72 / Chapter 4.2 --- INTRODUCTION --- p.73 / Chapter 4.3 --- MATERIALS AND METHODS --- p.74 / Chapter 4.4 --- RESULTS --- p.76 / Chapter 4.4.1 --- IL-6 mediated LPS-induced hepcidin expression in primary cortical neurons with the presence of BV-2 microglia --- p.76 / Chapter 4.4.2 --- IL-6 induced hepcidin up-regulation and ferroportin down-regulation in primary cortical neurons in an acute manner --- p.77 / Chapter 4.4.3 --- Inhibition of STAT3 activity suppressed IL-6-induced hepcidin up-regulation and ferroportin down-regulation in primary cortical neurons --- p.79 / Chapter 4.4.4 --- IL-6 rather than other cytokines induced STAT3 activation in primary cortical neurons --- p.80 / Chapter 4.4.5 --- Inhibition of STAT3 activity suppressed IL-6-induced hepcidin up-regulation and ferroportin down-regulation in MES23.5 dopaminergic cells --- p.80 / Chapter 4.5 --- DISCUSSION --- p.81 / Chapter CHAPTER 5 --- GENERAL DISCUSSION --- p.102 / REFERENCE --- p.110
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_328569 |
| Date | January 2013 |
| Contributors | He, Xuan., Chinese University of Hong Kong Graduate School. Division of Biomedical Sciences. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography |
| Format | electronic resource, electronic resource, remote, 1 online resource (xviii, 128 leaves) : ill. (some col.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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