Leflunomide之抗發炎及其抗血小板凝集作用

Anti-inflammatory and Antiplatelet effects of Leflunomide

陳秀貞(Shiu-Jen Chen)

指導教授 ： 鄭建業

中原大學/理學院/化學研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400646

摘要

中文摘要
Leflunomide (LEF)為新型抗發炎及免疫調節劑屬於異噁唑類 (isoxazole)化合物，臨床上常用於器官移植時的免疫抑制劑及治療類風濕關節炎和自體免疫相關疾病的治療藥。雖有文獻指出leflunomide具有抗發炎效果，然而其真正的作用機轉仍不甚明確；因此，本論文第一部份研究主題是利用carrageenan所誘發的動物模式來進一步探討leflunomide的抗發炎及止痛機轉，結果證實leflunomide能有效的預防及改善carrageenan所引起的大白鼠足蹠發炎性疼痛，其作用機轉可能包括：(1)抑制發炎足蹠組織內誘發型cyclooxygenase-2及inducible nitric oxide synthase的表現，進而降低足蹠組織液中prostaglandin E2及nitrate的濃度(2)可增加發炎組織液中interleukin-10的生成及具有抑制tumor necrosis factor-α生成的趨勢(3)減少發炎組織內myeloperoxidase活性，故可減少嗜中性白血球在發炎組織的聚集。
已知cyclooxygenase pathway在血小板的活化過程中，亦扮演一重要角色，由於leflunomide可抑制cyclooxygenase活性，故可推論leflunomide應有抑制血小板凝集之可能。然而，截至目前為止，尚無這方面的文獻發表；因此本研究的第二主題乃探討leflunomide對血小板凝集反應的影響。結果證實leflunomide能明顯抑制arachidonic acid或collagen所引起的兔子血小板凝集反應，其IC50約為50 µM，其可能參與的作用機轉包括：(1)可經由抑制cyclooxygenase及thromboxane synthase的活性而抑制thromboxane A2的生成 (2)增加血小板細胞膜的流動性 (3)抑制血小板表面glycoprotein Ⅱb/Ⅲa (GP Ⅱb/Ⅲa)的表現(4)抑制細胞內鈣離子的流動性等。總結，本研究證明leflunomide確實為一有效的抗發炎止痛劑，亦是血小板凝集抑制劑。

關鍵字

抗發炎 ； 抗血小板凝集 ； leflunomide ； 鹿角菜

並列摘要

英文摘要
The isoxazole derivative leflunomide is a novel immunomodulating and anti-inflammatory agent currently being used for treatment of the transplant rejection immunosuppressive agent, rheumatoid arthritis, autoimmune diseases and transplant rejection. However, the true anti-inflammatory mechanism of leflunomide is still unclear. Therefore, the first aim of this study is to evaluate whether leflunomide has analgesic effect in a rat model of carrageenan-evoked theremal hyperalgesia and further investigates the possible mechanisms invoved. Our results show that the pre- or post-treatment with leflunomide significantly inhibits the carrageenan-evoked thermal hyperalgesia. The possible mechanisms may be associated with the decreased formation of nitric oxide and prostaglandin E2 due to the attenuation of inducible nitric oxide synthase and cyclooxygenase-2 protein expression in carrageenan-injected rat paws. Furthermore, leflunomide also suppresses the formation of tumor necrosis factor-alpha and increases the interleukin-10 production in the paw exudates. The myeloperoxidase activity in carrageenan-injected paws is also inhibited by leflunomide.
The second aim of this study is to investigate whether leflunomide has antiplatelet effect and further explores the possible mechanisms involved. Preincubation of the rabbit washed platelet with leflunomide (10 ~ 100 µM) inhibits the dose-dependent platelet aggregation that is induced by arachidonic acid (100 µM) or collagen (10 µg/mL) with IC50 about 50 µM. Our data further indicate that the possible anti-aggregatory mechanisms may include (1) inhibition of thromboxane B2 formation through the suppressing of cyclooxygenase and thromboxane synthase activity of platelets (2) increase of platelat membrane fluidity (3) attenuation of the platelet surface glycoprotein Ⅱb/Ⅲa (GPⅡb/Ⅲa) expression (4) suppression of intraplatelet calcium mobilization. This study demonstrates that leflunomide is not only an effective anti-inflammatory and analgesic agent but also an antiplatelet aggregatory inhibitor.

並列關鍵字

leflunomide ； antiplatelet aggregation ； anti-inflammatory ； carrageenan

參考文獻

8. 洪秀儀、陳拯：類風濕性關節炎的治療趨勢。

9. Adunyah, B. E.; Dean, W. L. Inositol trisphosphate-induced Ca2+ release from human platelet membrane. Biochem. Biophys. Res. Commun. 1985; 128: 1274-1280.

10. Baeuerle, P. A. The inducible transcription activator NF-kappa B: regulation by distinct protein subunits. Biochem. Biophys. Acta. 1991; 1072: 63-80.

11. Beckman, J. S.; Beckman, T. W.; Chen, J.; Marshall, P. A.; Freeman, B. A. Apparent hydroxyl radical production by peroxynitrite: implications for endothelial injury from nitric oxide and superoxide. Proc. Natl. Acad. Sci. USA. 1990; 87(4): 1620-1624.

12. Berridge, M. J. Inositol triphosphate and diacylglycerol as second messenger. Biochem. J. 1983; 220: 124-134.