探討Thiamet G藥物增強的醣基化作用所調控TNF-α和高糖所誘導之軟骨細胞MMP13表達

Augmented O-GlcNAcylation by Thiamet G downregulates TNF-α and High Glucose induced chondrocyte MMP13 expression

徐小涵(Hsiao-Han Hsu)

指導教授 ： 林能裕

國立臺灣大學/醫學院/解剖學暨細胞生物學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201903534

摘要

關節炎（Osteoarthritis）是一種具有多種風險因素的異質性疾病。其中，肥胖對承受重量和非承受重量之關節都有重大影響。在肥胖者之中由於承受重量過大使脂肪組織和軟骨細胞製造全身性發炎因子和關節炎的發生率有絕對的關係。有研究發現具有心臟代謝異常的肥胖患者的關節炎患病率和發病率高於健康的肥胖患者，這說明新的關節炎表型出現，即代謝綜合症引發的關節炎（Metabolic syndrome associated osteoarthritis），糖尿病患者亦包含在內 [1]。我們假設與代謝
因子異常的狀況包含葡萄糖過量導致毒性和肥胖組織製造促發炎因子TNF-α 對於軟骨前驅細胞所造成之影響。
O-linked β-linked N-acetylglucosamine（乙醯葡萄醣胺）為修飾細胞內蛋白質的醣類結構，簡稱為O-GlcNAc。目前發現受到兩種酵素專一性的調控胞內蛋白質的加醣與去醣作用（乙醯葡萄醣胺轉移酶（O-GlcNAc transferase）負責加醣；乙醯葡萄醣胺水解酶（O-GlcNAcase）負責去醣）。O-GlcNAcylation 作用於胞內蛋白的絲
胺酸（Serine）和蘇胺酸（Threonine）上氫氧基。O-GlcNAcylation 涉及細胞內眾多生理機制，失調後會引起許多疾病產生。本研究旨在探討關節炎中O-GlcNAcylation在關節炎中的角色。我們的研究發現，高糖刺激軟骨前驅細胞使胞內O-GlcNAc 表現提升，同時觀察到發炎反應增強，以藥物Thiamet G 抑制OGA 蛋白活性使胞內O-GlcNAcylation 蛋白累積後能夠改善軟骨前驅細胞發炎現象同時降低發炎因子MMP13 蛋白表現。敲落OGT 基因使O-GlcNAc 不能累積使發炎加劇。
綜合以上結論，我們的結果指出，透過藥物Thiamet G 促進細胞內O-GlcNAc修飾將有助於降低發炎程度。O-GlcNAcylation 是如何調控關節炎相關發炎基因的表現，並且降低發炎表現是我們未來的研究重點。

關鍵字

乙醯葡萄醣胺；乙醯葡萄醣胺轉移酶；乙醯葡萄醣胺水解酶；Thiamet G；腫瘤壞死因子-α；高糖；關節炎

並列摘要

Osteoarthritis (OA) is a heterogeneous disorder with several risk factors. Among them, obesity has a principal impact on both loading and non-loading joints. Mechanical overload and activity of systemic inflammatory mediators derived from chondrocyte or synoviocyte provide clues to the increased incidence and prevalence of OA in obesity. Recently, research found greater OA prevalence and incidence in obese patients with cardiometabolic disturbances than “healthy” obese patients, which led to the description of a new OA phenotype–metabolic syndrome (MetS)-associated OA. Certainly, individual metabolic factors including diabetes may increase the risk of obesity-induced OA. We hypothesized that abnormalities in metabolic factors with metabolic syndrome include excess glucose leading to the effects of toxic and obese tissue on the production of pro-inflammatory TNF-α on chondrocyte precursor cells.

O-GlcNAcylation is a dynamic modification of serine or threonine hydroxyl moieties nucleocytoplasmic proteins by UDP-GlcNAc. The dynamic and inducible cycling of the modification is governed by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), which add and remove the O-GlcNAc (O-linked β-linked N-acetylglucosamine) moiety respectively. The O-GlcNAcylation involes in many important cellular pathways and unbalance of O-GlcNAcylation has implicated in many kinds of diseases. O-GlcNAc glycosylation acts on intracellular proteins of urinium and sulphate. O-GlcNAcylation involves many physiological mechanisms in the cell, which can cause many diseases after dysregulation. This study was to investigate the association of O-GlcNAcylation with chondrocytes in osteoarthritis. Our study found that inhibition of OGA protein activity by the drug Thiamet G can improve the reduction of inflammation after accumulation of intracellular O-GlcNAcylation protein. For instance, high glucose and cellular inflammatory factors stimulate chondrocyte inflammatory response and cause intracellular O-GlcNAc expression rise. Elimination of OGT gene makes O-GlcNAc unable to accumulate and causes an increase in inflammatory response.
Above all, our findings suggest that O-GlcNAcylation regulates inflammation phenotypes of ATDC5 cells through upregulating O-GlcNAc. These results regarding O-GlcNAcylation may also provide an alternative approach for osteoarthritis therapy by modulating O-GlcNAcylation modification.

並列關鍵字

O-GlcNAc ； O-GlcNAc transferase ； O-GlcNAcase ； Thiamet G ； TNF- α ； high glucose ； Osteoarthritis

參考文獻

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