대뇌 국소 허혈성 병변이 후속되는 전뇌 허혈 손상에 미치는 보호 효과

Abstract

[한글]

반복 허혈 손상 모델은 일과성 허혈증이나 다발성 뇌경색 등의 질환과 유사한 특성을 가지고 있어 허혈 손상의 기전을 밝히는 연구에 유용하게 이용되고 있으며, 특히 gerbil에서 5분간의 양측 경동맥 결찰을 통한 전뇌 허혈 손상을 반복하여 가함으로 후속되는 허혈 손상에 대한 보호 효과가 유도됨이 보고된 바 있다. 이러한 보호 효과의 기전은 아직 정확히 밝혀져 있지 않으나 초기 허혈 손상으로 인한 heat shock protein이나 proto-oncogen의 발현, 다양한 신경 영양 물질과 cytokine등이 관여 할 것이라는 보고가 있으며 최근에는 세포 배양을 통해 연구되어진 성상 세포의 역활이 이러한 기전에 중요하게 작용 할 것으로 생각되어 지고 있다. 따라서 본 연구에서는 gerbil을 이용하여 미세 자성체주입법을 통한 국소 허혈성 병변을 일으키고 1일, 3일, 그리고 7일 후각 집단 별로 다시 5분 간의 후속되는 전뇌 허혈 손상을 주어 국소 허혈과 전뇌 허혈을 혼합한 반복 허혈 손상 모델을 설정함으로 선행되는 국소 허혈성 병변에 의한 신경 세포 변성의 보호 효과를 검토해 보았다. 또한 이러한 보호 효과에 관여하는 많은 요소 중에서 국소 허혈 손상으로 유발된 성상 세포의 증식 정도가 보호 효과와 관련이 있는지 비교 평가해 보았다. 그 결과 hematoxylin-eosin 염색을 이용해 평가한 해마 CAI의 신경 세포 변성은 전뇌 허혈 손상 만을 준 경우에서는 양측 모두 일정하였으나, 국소 허혈 손상을 전처치 한 집단에서는 동일한정도의 전뇌 허혈 손상을 받았음에도 불구하고 피질 경색의 동측에 비해 반대측 해마 CAI 부위에서 심하게 나타나 국소 피질 경색으로 인한 보호 효과가 있음을 확인 하였다. 또한 신경 세포 손상에 대한 보호 효과는 허혈 손상 간의 시간 간격에 따라 정량적인 차이가 있어서, 7일에 비해 1일과 3일 후 더욱 뚜렷한 효과를 보이고 있었다. 그러나

성상 세포의 증식도를 평가하기 위해 시행한 GFAP(glial fibrillary acidic protein)항체 면역조직화학 염색법 결과, 국소 피질 경색으로 활성화되는 성상세포는 1일과 3일째 보다는 7일째 더욱 뚜렷하여 허혈 손상의 보호 효과와 시간 경과가 일치하지 않았다. 따라서 GFAP 면역조직화학 염색법만으로는 허혈 손상의 보호 효과와 관련된 성상 세포의 기능적인 평가를 충분히 반영하지 못할 것으로 사료되며 이는 향후 cytokine이나 효소활성도의 측정등 다양한 방법을 퉁해 고찰되어야 할것으로 사료된다.

The protective effect of cortical infarction to the neuronal damage following

subsequent global ischemic insult in the Gerhil

Kyung Ho Yu

Department of Medicine The Graduate School, Yonsei University

(Directed by Professor Byung In Lee)

Prior brief ischemic insult was reported to protect the hippocampal CAI neurons

from delayed neuronal death following global ischemia. Mechanisms of such

protective effects have, however, remained unclear. The study was conducted to

confirm whether the preceding cortical infarction exerts protective effects on the

adjacent hippocampal CAI neurons against the subsequent global ischemia and to

relate the role of reactive astrocytosis to the mechanisms of protective effects.

Male, Mongolian gerbils, aged 12∼15 weeks and weighing 70∼90 g, were anesthetized

with ketamine by intraperitoneal injections, and a small cortical infarction in the

unilateral parietal cortex was made by infusing magnetic ferrite particles, which

were followed by subsequent global ischemia for 5 minutes on 1, 3, and 7 days

later. One week following the subsequent global ischemia, the neuronal degeneration

in the hippocampal CAI regions was examined by Hematoxylin-eosin stain.

Immunohistochemistry using GFAP-antibody was carried out to evaluate the temporal

course of astrocytic reactivity after 1, 3, and 7 days of cortical infarction. The

neuronal degeneration of CAI region in the ipsilateral hippocampus preceded by the

cortical infarction was less severe than those in the contralateral ones. The

difference of neuronal degeneration between both of hemispheres was clearly more

prominent in animals whose global ischemia was induced at 1 and 3 days after the

cortical infarction than 7 days. However, the reactivity of GFAP was minimal at 1

day but markedly increased at 3 and 7 days after the cortical infarction. This

present study confirmed that the preceding cortical infarction protected the

adjacent ipsilateral CAI neurons from the subsequent global ischemic insult with

its protective effect being most remarkable at 1 and 3 days but less appreciable at

7 days after cortical infarction. However, the degree of reactive astrocytosis

measured by GFAP Immunohistochemistry did not correlate well with the degree of

neuroprotection, thus it did not fully account for the mechanisms of such

protective effect.

[영문]

Prior brief ischemic insult was reported to protect the hippocampal CAI neurons from delayed neuronal death following global ischemia. Mechanisms of such protective effects have, however, remained unclear. The study was conducted to confirm whether the preceding cortical infarction exerts protective effects on the adjacent hippocampal CAI neurons against the subsequent global ischemia and to relate the role of reactive astrocytosis to the mechanisms of protective effects.

Male, Mongolian gerbils, aged 12∼15 weeks and weighing 70∼90 g, were anesthetized with ketamine by intraperitoneal injections, and a small cortical infarction in the unilateral parietal cortex was made by infusing magnetic ferrite particles, which were followed by subsequent global ischemia for 5 minutes on 1, 3, and 7 days later. One week following the subsequent global ischemia, the neuronal degeneration in the hippocampal CAI regions was examined by Hematoxylin-eosin stain.

Immunohistochemistry using GFAP-antibody was carried out to evaluate the temporal course of astrocytic reactivity after 1, 3, and 7 days of cortical infarction. The neuronal degeneration of CAI region in the ipsilateral hippocampus preceded by the

cortical infarction was less severe than those in the contralateral ones. The difference of neuronal degeneration between both of hemispheres was clearly more prominent in animals whose global ischemia was induced at 1 and 3 days after the

cortical infarction than 7 days. However, the reactivity of GFAP was minimal at 1 day but markedly increased at 3 and 7 days after the cortical infarction. This present study confirmed that the preceding cortical infarction protected the adjacent ipsilateral CAI neurons from the subsequent global ischemic insult with

its protective effect being most remarkable at 1 and 3 days but less appreciable at 7 days after cortical infarction. However, the degree of reactive astrocytosis measured by GFAP Immunohistochemistry did not correlate well with the degree of

neuroprotection, thus it did not fully account for the mechanisms of such protective effect.