Methylprednisolone對lipopolysaccharide所誘發慢性發炎大鼠之動脈系統物理性質的影響

Effects of methylprednisolone on mechanical properties of arterial system in lipopolysaccharide-induced chronic inflammatory rats

柯雅惠(Ya-Hui Ko)

指導教授 ： 張國柱

國立臺灣大學/醫學院/生理學研究所/博士(2014年)

https://doi.org/10.6342/NTU.2014.02439

摘要

研究背景與目的：具研究顯示，由內毒素如脂多醣(lipopolysaccharide, LPS)所引起的系統性發炎疾病與心血管疾病發生有關。醣皮質醇(glucocorticoids)是一種普遍用以治療急性或慢性發炎，以及自體免疫疾病的藥物。本篇研究利用脂多醣誘發慢性發炎的雄性Wistar大鼠以探討methylprednisolone(MP，一種合成的醣皮質醇類藥物)對動物動脈管延展性與血管阻力方面的影響。
研究材料與方法：本研究將LPS注入ALZET微型滲透幫浦膠囊並埋入雄性Wistar大鼠右下腹部皮下，每日釋放每公斤體重1毫克LPS，藉由皮下微血管吸收來誘發大鼠產生慢性發炎，LPS處理時間分別為二週及四週。隨機將雄性Wistar大鼠分為三組：(1)假手術組(sham group)；(2)LPS誘發慢性發炎疾病組(LPS group)；(3)LPS誘發慢性發炎合併給予MP治療組(LPS-MP group)，其中MP的給藥劑量與方式為利用腹腔注射方式給予每天每公斤體重5毫克。在第二週及第四週時，進行右頸動脈插管及開胸手術，測量心電圖、主動脈血壓及血流訊號，訊號經由傅立葉轉換後用以分析主動脈輸入阻抗頻譜，並得到描述動脈管彈性的波反射時間(τ)及其它動脈管物理特性參數。實驗後採集血液樣本進行血漿中C反應蛋白(CRP)、介白素-6(IL-6)、一氧化氮(NO)及過氧化亞硝酸鹽(peroxynitrite)的含量分析。利用西方點墨法及組織免疫染色，測量主動脈蛋白質的表現。
研究結果：在脂多醣誘發慢性發炎的疾病組大鼠上發現動脈管總週邊阻力(Rp)下降，血管舒張的情形。此外，動脈管順應性的增加並無伴隨動脈管延展性的改變，顯示在慢性發炎大鼠體內有全身血液容積擴張之現象。研究發現長期給予脂多醣處理的大鼠，主動脈管中蓄積較多的最終糖化終產物(AGEs)及誘導型一氧化氮合成酶(iNOS)，結果產生過量的一氧化氮而造成血管舒張。然而經由計算波反射時間(τ)結果顯示給予脂多醣處理的大鼠，對主動脈管的彈性並無任何影響，推論是產生過多一氧化氮抵消了最終糖化終產物對血管硬化效應，而使動脈管延展性不受絲毫影響。此外，在LPS誘發慢性發炎合併給予MP治療組中發現，雖然動脈管總週邊阻力(Rp)增加，改善周邊血管舒張現象，但減少波反射時間(τ)，顯示MP治療組大鼠主動脈管發生硬化。據研究結果顯示MP治療組大鼠血漿中一氧化氮減少，但主動脈管最終糖化終產物並無顯著下降，可能是導致MP治療組大鼠動脈管延展性變差發生硬化之原因。
結論：在脂多醣誘發慢性發炎的大鼠上若給予methylprednisolone治療，將使主動脈管產生硬化，而在這過程中一氧化氮含量對最終糖化終產物致使主動脈管產生硬化具有關鍵性的影響。

關鍵字

最終糖化終產物 ； 主動脈輸入阻抗頻譜 ； 波傳輸時間 ； 一氧化氮

並列摘要

Background and purpose: It has been shown that systemic inflammation exerted by endotoxins such as lipopolysaccharide (LPS) is associated with cardiovascular diseases. Glucocorticoids are commonly used as therapeutic agents in many acute and chronic inflammatory and autoimmune diseases. The current study investigated the effects of methylprednisolone (a synthetic glucocorticoid) on aortic distensibility and vascular resistance in LPS-induced chronic inflammation in male Wistar rats.
Material and methods: Chronic inflammation was induced by implanting a subcutaneous slow-release ALZET osmotic pump (1 mg/kg/day LPS) for either 2 or 4 weeks. Animals are randomized into three groups: 1) sham, 2) LPS, 3) LPS treated with methylprednisolone (5 mg/kg/day i.p.). Pulsatile aortic pressure and flow signals were measured at different time points, and then were subjected to Fourier transformation for the analysis of aortic input impedance. Arterial wave transit time (τ) was derived to describe the elastic properties of aortas using the impulse response function of the filtered aortic input impedance spectra. At the end of catheterization, blood sample from the animals studied were collected for determination of plasma levels of C-reactive protein (CRP), interleukin-6 (IL-6), nitric oxide (NOx), and peroxynitrite. The aortic protein expression was examined by Western blot and immunohistochemistry.
Results: Vasodilatation occurred in the LPS-infused rats, as evidenced by the fall in total peripheral resistance (Rp). Moreover, an increase in arterial compliance, but lacking of significant changes in aortic distensibility suggested that volume expansion may occur in the animals administered LPS. Long-term LPS challenge enhanced the expression of advanced glycation end products (AGEs) in the aortas. LPS also upregulated the inducible form of nitric oxide synthase (iNOS) to produce high levels of nitric oxide (NO), which resulted in vasodilation. However, LPS challenge did not influence the elastic properties of aortas, as shown by the unaltered τ. The NO-mediated vascular relaxation may counterbalance the AGEs-induced arterial stiffening so that the aortic distensibility remained unaltered. Treating LPS-challenged rats with methylprednisolone prevented peripheral vasodilation, as indicated by increased Rp. However, methylprednisolone produced an increase in aorta stiffness,
as manifested by the significant decline inτ. The diminished aortic distensibility by methylprednisolone paralleled a significant reduction in NO plasma levels, in the absence of any significant changes in AGEs content.
Conclusion: Methylprednisolone stiffens aortas and elastic arteries in LPS-induced chronic inflammation in rats, for NO activity may be dominant as a counteraction of AGEs.

並列關鍵字

advanced glycation end products ； aortic input impedance spectra ； arterial wave transit time ； nitric oxide

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