免疫球蛋白G4在hydroxychloroquine 治療甲狀腺眼病變的機轉扮演之角色

Abstract

背景簡介： 甲狀腺眼病變（Graves’ orbitopathy, GO）是葛瑞夫氏症（Graves’ disease, GD）常見的表現，不僅造成生理上的症狀，還嚴重影響病人的心理健康及生活品質。甲狀腺眼病變之嚴重度可區分成輕度、中重度及影響視力者，影響視力者可先嘗試用類固醇治療，無效則考慮手術；中重度者之主流治療是使用類固醇或免疫抑制藥物治療；然而輕度甲狀腺眼病變，臨床上內科治療選項有限，常常無藥可用、無計可施， 近期細胞實驗顯示hydroxychloroquine（HCQ）能顯著改善眼眶纖維母細胞（orbital fibroblast）的增生、分化、脂肪生成等變化，是下一個相當具有潛力的GO治療選項，然而HCQ能有效改善眼眶纖維母細胞之中間機轉並不清楚，且臨床上GO病人使用HCQ之效果也可觀察到相當明顯的個體差異。 過去文獻顯示GD與GO病人血清中免疫球蛋白G4（Immunoglobulin G4, IgG4）較高；同時，血清IgG4濃度較高的GO病患，其GO較早被診斷，臨床病程也較為快速且嚴重，對於治療反應也有所差異。GO的病生理機轉與T淋巴球、B淋巴球和甲促素受體抗體（thyroid-stimulating hormone (TSH) receptor antibody）引起的免疫反應有關， HCQ之藥理作用是在於調節免疫反應（immunomodulation），而IgG4也參與了許多先天與後天免疫反應路徑，臨床上HCQ也常被使用在IgG4相關疾病。因此，我們認為HCQ可能可透過IgG4相關路徑來影響或治療GO。 目的： 本研究之假說為HCQ使用後會使血中IgG4產生變化。本假說將藉由前瞻性收集個案，透過個案使用HCQ前後的抽血結果來證實血清中IgG4是否產生變化。 方法： 本研究為一個前瞻性隨機對照臨床試驗，收集輕度甲狀腺眼病變之個案，以二比一的方式分別隨機分配至實驗組與對照組，實驗組使用HCQ藥物六個月，對照組則維持常規GO治療。於用藥前、用藥後第三個月、第六個月時進行抽血並相關基本資料與問卷調查。將比較收案時實驗組與對照組的基本資料是否有差異，IgG4高、低族群在臨床表現的差異，IgG4跟GO相關之臨床重要指標的相關性，比較用藥前、用藥後第三個月、第六個月血清中IgG4和IgG4/IgG比例在實驗組及對照組是否有差異，以及實驗組在使用HCQ之前（收案時）和之後（第三個月、第六個月）血清中IgG4和IgG4/IgG比值是否有所變化。 結果： 實驗組與對照組分別收案人數為47與29人，兩組間基本資料並無差異。若將研究個案依照IgG4中位數（47.32mg/dL）分為高低二組，可發現高IgG4組別罹患GO的時間較長（6.52 ± 6.02年 vs 3.47 ± 4.01年，p = 0.020）。若將個案依照診斷IgG4相關疾病之切點135mg/dL分為高低二組，僅有五位個案被歸類於IgG4高的組別，且其相較於IgG4低的組別有較低的TSH（0.41 (0.22 – 0.66) µIU/mL vs 1.17 (0.52 – 2.20) µIU/mL, p = 0.042）。相關係數分析顯示，IgG4和甲狀腺眼病變生活品質問卷（GO-QoL）的功能分數（r = 0.2656, p = 0.032）呈正相關，IgG4和IgG4/IgG比值則均與罹患GO時間呈正相關（IgG4, r = 0.2465, p = 0.048; IgG4/IgG ratio, r = 0.2906, p = 0.019）。比較實驗組和對照組於收案時、第三個月、第六個月時的血清IgG4和IgG4/IgG比值，結果均無差異。實驗組在使用HCQ前後之比較，於收案時、第三個月、第六個月時的血清IgG4和IgG4/IgG比值均無顯著差異。 討論： 本研究發現高IgG4組罹患GO時間較長，而相關性分析時血清IgG4與較佳的GO-QoL的功能分數呈正相關，同時也與罹患GO時間呈正相關，文獻中提到甲狀腺亢進且血清IgG4高的個案罹患GO的年紀較年輕，因此可能導致罹病時間較長，本研究之發現符合文獻中提到的現象，另可能是因為罹病時間較長因此自身心理較能調適，導致生活品質評分較罹病時間短者佳。另外也發現高IgG4組有較低之TSH，文獻中提到血清IgG4可能與其甲促素受體抗體正相關，可能因此導致甲狀腺亢進較難以被控制而有偏低的TSH。實驗組在使用HCQ前後並無發現血清IgG4有顯著差異，可能是HCQ並不會透過IgG4相關路徑來影響GO，或是以血清IgG4無法代表實際在眼睛當中發生的免疫變化，也可能是本研究個案GO嚴重度及活動度不足，導致無法有顯著差異。 結論： 本研究發現血中IgG4與GO罹病時間呈正相關，以及在GO患者使用HCQ前後，血中IgG4沒有顯著變化。期待進一步研究了解HCQ治療GO的效果、以及HCQ可能影響GO的機轉。

Background: Graves' orbitopathy (GO) is a common manifestation of Graves' disease (GD) and not only causes physical symptoms but also severely affects patients' mental health and quality of life. However, for mild GO, there are limited options for medical treatment, often leaving patients without effective medications or strategies. Recent cell study has shown that hydroxychloroquine (HCQ) can significantly improve the proliferation, differentiation, and adipogenesis of orbital fibroblasts, mak-ing it a promising treatment option for GO. However, the exact mechanisms through which HCQ affects orbital fibroblast are unclear. Previous studies have shown that patients with GD and GO have higher levels of serum immunoglobulin G4 (IgG4). Furthermore, GO patients with higher levels of se-rum IgG4 are diagnosed of GO earlier, have a more rapid and severe clinical course, and show differences in treatment response. The pathophysiology of GO is associated with immune reactions involving T lymphocytes, B lymphocytes, and thyroid-stimulating hormone (TSH) receptor antibodies. The pharmacological effect of HCQ is mainly immunomodulation, and IgG4 is involved in innate and adaptive immunity. Also, HCQ is commonly used in treatment for IgG4-related diseases. Therefore, we hypothesize that HCQ may affect the pathophysiology of GO through IgG4-related pathways. Objective: The hypothesis of this study is that HCQ treatment results in changes in serum IgG4 levels. We aim to verify this hypothesis by a prospective study to compare the serum IgG4 levels before and after HCQ treatment in patients with mild GO. Methods: This study was a prospective randomized controlled clinical trial enrolling pa-tients with mild GO. The participants were randomly assigned in a 2:1 ratio to the treatment group (receiving HCQ for six months) or the control group (receiving stand-ard of care for GO). Blood samples, relevant basic information and questionnaire sur-veys were collected at baseline, the third month, and the sixth month. We aim to inves-tigate the baseline characteristics between the treatment and control groups, differ-ences in clinical manifestations between the high and low IgG4 subgroups, the correla-tion between IgG4 and clinically important indicators of GO, differences in serum IgG4 and IgG4/IgG ratio between the treatment and control groups at baseline, the third month, and the sixth month, and changes in serum IgG4 and IgG4/IgG ratio in the treatment group before, 3 months, and 6 months after HCQ treatment. Results: The treatment group and the control group consisted of 47 and 29 individuals, re-spectively, with no significant differences in baseline characteristics between the two groups. When the study cases were divided into high and low groups based on the me-dian IgG4 level (47.32 mg/dL), it was found that the high IgG4 group had a longer du-ration of GO (6.52 ± 6.02 years vs 3.47 ± 4.01 years, p = 0.020). When the cases were divided into high and low groups based on an IgG4 level of 135 mg/dL, the diagnostic threshold of IgG4-related disease, only five cases were classified as high IgG4, and these cases had significantly lower TSH levels compared to the low IgG4 group (0.41 (0.22 – 0.66) µIU/mL vs 1.17 (0.52 – 2.20) µIU/mL, p = 0.042). There was a positive correlation between IgG4 and the functional subscale of the Graves' Ophthalmopathy Quality of Life questionnaire (GO-QoL) (r = 0.2656, p = 0.032), and both IgG4 and IgG4/IgG ratio were positively correlated with the duration of GO (IgG4, r = 0.2465, p = 0.048; IgG4/IgG ratio, r = 0.2906, p = 0.019). Comparison within the treatment group before and after the use of HCQ showed no significant differences in serum IgG4 and IgG4/IgG ratio at baseline, third month, and sixth month. Discussion: This study revealed that the high IgG4 group had a longer duration of GO, and se-rum IgG4 levels were positively correlated with better functional scores on the GO-QoL in correlation analysis. Additionally, IgG4 levels were positively correlated with the duration of GO. Literature suggested that individuals with Graves' hyperthyroidism and elevated serum IgG4 levels tend to develop GO at a younger age, which potentially led to the result of a longer duration of GO and better quality-of-life as compared to those with low IgG4 in the present study. Another finding was that the high IgG4 group had lower levels of TSH. Literature suggested that elevated serum IgG4 levels were positively associated with TSH receptor antibodies, which could make it more difficult for hyperthyroidism to be controlled and result in lower TSH levels. In the treatment group, no significant differences in serum IgG4 levels were found before and after the use of HCQ. This suggested that HCQ may not affect the pathophysiology of GO through IgG4-related pathway. Another possibility was that serum IgG4 levels may not represent the actual immunological changes in the eyes. It was also possible that the severity and activity of GO was too low to see the differences of serum IgG4 after HCQ treatment. Conclusion: This study revealed the positive correlation between serum IgG4 and the duration of GO. However, there was no change on serum IgG4 before and after treatment of HCQ. Further research is warranted to examine the efficacy of HCQ on treating GO patients and the underlying mechanism by which HCQ affect GO.