Cyclosporine A가 혈관 반응도에 미치는 영향

Abstract

[한글]

최근에 개발된 cyclosporine A(fungal endecapeptide)는 T 임파구에 관련된 면역 반응만을 선택적으로 봉쇄함으로써 장기 이식 후 혹은 자가 면역 질환의 치료약제로 임상에서 흔히 사용되고 있음에도 불구하고, 신독성과 고혈압 발생등의 부작용때문에 약제 사용에 있어 제한이 되고 있다. 신독성은 신혈관의 저항 증가로 인한 허혈성 손상 때문에 발생하는 것으로 보고되고있으며 고혈압은 혈관의 수축력 증가 흑은 이완력의 감소에 의할 것으로 추측되고 있으나 아직도 이러한 신독성과 고혈압의 병태생리학적 발생기전에 대해서는 정확한 정설이 없다. 따라서 본 연구에서는 cyclosporine A가 혈관 반응도에 미치는

영향과 아울러 그 기전을 알아보고자 cyclosporine A를 투여한 흰쥐의 흥부 대동맥환을 이용하여 norepinephrine을 투여하여 혈관 수축을 유도한 후 acetylcholine에 의한 내피 의존성 이완(endothelium dependent relaxation)과 sodium nitroprusside에 의한 내피 비의존성 이완(endothelium independent relaxation)을 cremophor를 투여한 대조군과 비교하였다. 또한 indomethacin, superoxide dismutase, L-arginine등으로 대동맥환을 전처치한 후와 전처치하기 전과의 내피의존성 이완정도를 비교 관찰하였으며, 아울러 cyclospor

ine A 투여시 norepinephrine에 의한 혈관의 수축력에 변화가 있는지를 관찰하고 cyclosporine A 투여후 혈관의 내피세포와 평활근의 형태학적 변화를 조사하여 다음과 같은 결과를 얻었다.

1. Cyclosporine A 투여군에서 acetylcholine에 의한 내피 의존성 이완이 cremophor 투여군에 비해 의의있게 감소되었다.

2. Cyclosporine A에 의한 내피 의존성 이완 억제는 indomethacin이나 superoxided ismutase 전처치 후에도 회복되지 않았다.

3. Cyclosporine A에 의한 내피 의존성 이완 억제는 nitric oxide의 기질(substrate)인 L-arginine 전처치 후 회복되었다.

4. Cyclosporine A 투여군에서는 cremophor 투여군에 비해 nitroprusside에 의한 내피 비의존성 이완이 의의있게 감소되었다.

5. Cyclosporine A 투여군의 norepinephrine에 의한 혈관 평활근의 수축력은 cremophor 투여군에 비해 차이가 없었다.

6. 형태학적인 변화로는 신동맥에서는 내피세포들의 모양이 커지면서 입방형 모양으로 변하는것이 관찰되었고, 대동맥에서는 내피세포내에 세포질성 공포(cytoplasmic vacuole)의 출현, 내피세포의 기저막으로부터의 박리, phagolysosome의 출현 등이 관찰되었다.

이상의 결과로 cyclosporine A는 내피 의존성 이완을 억제시키는 데 이는 prostaglandin H^^2, thromboxane A^^2 흑은 과산화물 음이온과 같은 내피성 수축 인자(endothelium derived contracting factor)의 증가에 기인한 것이라기 보다는 내피세포내에서의 L-arginine으로부터 내피성 이완 인자(endothelium derived relaxing factor)인 NO의 생성과정에 장애를 초래하고 일부는 혈관 평활근에 직접 작용하여 나타났을 것으로 추측된다.

The effects of cyclosporine A on vascular reactivity

Heung Soo Kim

Department of Medical Science, The Graduate School Yonsei University

(Directed by Professor Dae Suk Han)

Recently introduced cyclosporine A, a fungal endecapeptide, is frequently used

after organ transplantation and in certain autoimmune diseases due to its selective

inhibition of T-cell related immune responses. Despite this advantage, serious side

effects suck as nephrotoxicity and hypertension have limited its use.

Nephrotoxicity was reported to occur due to the increased resistance in renal

arteries resulting in ischemic damage and hypertension due to the increased

vascular contractility or decreased vascular relaxation. However, the exact

pathophysiological mechanisms of these complications remain unclear. This study was

planned to ascertain the effect of cyclosporine A on vascular reactivity and also

its mechanism of action. By using the thoracic aortic segment of cyclosporine

A-treated rat, after contracting the aortic segment with norepinephrine,

endothelium dependent relaxation by acetylcholine was compared with the control

group which was treated with cremophor, the vehicle of cyclosporine A. The effect

of indomethacin, superoxide dismutase, L-arginine on the altered endothelium

dependent relaxation of the cyclosporine A-treated rat was also evaluated by

preincubating each drug and observing differences in vascular relaxation by

acetylcholine. Endothelium independent relaxation by sodium nitroprusside and the

vascular contractility by norepinephrine were compared between cyclosporine

A-treated and control group. Morphological changes in the endothelial cells and the

smooth muscle were also evaluated by light & electron microscope after the

cyclosporine A treatment.

The results are as follow:

1. The endothelium dependent relaxation by acetylcholine was decreased

significantly in the cyclosporine A-treated group compared with the

cremophor-treated group.

2. Suppression of endothelium dependent relaxation in the cyclosporine A-treated

group was not reversed even after the preincubation with indomethacin and

superoxide dismutase.

3. Suppression of endothelium dependent relaxation in the cyclosporine A-treated

group was recovered following preincubation with L-arginine, the substrate of NO.

4. The endothelium independent relaxation by nitroprusside was also decreased in

the cyclosporine A-treated group compared with the cremophor-treated group.

5. No significant changes in vascular contractility by norepinephrine were noted

in the cyclosporine A-treated group.

6. Morphological chanties after the cyclosporine A treatment were mainly observed

in the vascular endothelial cells; cuboidal changes of the endothelial cells in the

renal artery and appearance of cytoplasmic vacuoles and phagolysosome within the

endothelial cells, detachment of the endothelial cells from the basement membrane

in the aorta.

From the above results, it can be concluded that the main effect of cyclosporine

A on the vascular reactivity is inhibition of endothelium dependent relaxation and

its principal mechanism of action seems to be the defect in the NO forming

mechanism from the L-arginine caused by cyclosporine A rather than the increased

activity of the EDCF such as prostaglandin H^^2, thromboxane A^^2 or superoxide

anion.

[영문]

Recently introduced cyclosporine A, a fungal endecapeptide, is frequently used after organ transplantation and in certain autoimmune diseases due to its selective inhibition of T-cell related immune responses. Despite this advantage, serious side

effects suck as nephrotoxicity and hypertension have limited its use.

Nephrotoxicity was reported to occur due to the increased resistance in renal arteries resulting in ischemic damage and hypertension due to the increased vascular contractility or decreased vascular relaxation. However, the exact pathophysiological mechanisms of these complications remain unclear. This study was planned to ascertain the effect of cyclosporine A on vascular reactivity and also its mechanism of action. By using the thoracic aortic segment of cyclosporine

A-treated rat, after contracting the aortic segment with norepinephrine, endothelium dependent relaxation by acetylcholine was compared with the control group which was treated with cremophor, the vehicle of cyclosporine A. The effect of indomethacin, superoxide dismutase, L-arginine on the altered endothelium dependent relaxation of the cyclosporine A-treated rat was also evaluated by preincubating each drug and observing differences in vascular relaxation by acetylcholine. Endothelium independent relaxation by sodium nitroprusside and the vascular contractility by norepinephrine were compared between cyclosporine A-treated and control group. Morphological changes in the endothelial cells and the smooth muscle were also evaluated by light & electron microscope after the cyclosporine A treatment.

The results are as follow:

1. The endothelium dependent relaxation by acetylcholine was decreased significantly in the cyclosporine A-treated group compared with the cremophor-treated group.

2. Suppression of endothelium dependent relaxation in the cyclosporine A-treated group was not reversed even after the preincubation with indomethacin and superoxide dismutase.

3. Suppression of endothelium dependent relaxation in the cyclosporine A-treated group was recovered following preincubation with L-arginine, the substrate of NO.

4. The endothelium independent relaxation by nitroprusside was also decreased in the cyclosporine A-treated group compared with the cremophor-treated group.

5. No significant changes in vascular contractility by norepinephrine were noted in the cyclosporine A-treated group.

6. Morphological chanties after the cyclosporine A treatment were mainly observed in the vascular endothelial cells; cuboidal changes of the endothelial cells in the renal artery and appearance of cytoplasmic vacuoles and phagolysosome within the

endothelial cells, detachment of the endothelial cells from the basement membrane in the aorta.

From the above results, it can be concluded that the main effect of cyclosporine A on the vascular reactivity is inhibition of endothelium dependent relaxation and its principal mechanism of action seems to be the defect in the NO forming mechanism from the L-arginine caused by cyclosporine A rather than the increased

activity of the EDCF such as prostaglandin H^^2, thromboxane A^^2 or superoxide anion.