초록
외부 병원체의 침입에 의한 병원독소로 발병된 뇌염증에서 미성숙뇌는 성숙뇌에서 보다 많은 백혈구의 침윤을 일으킨다. 케모카인은 뇌염증부위로 염증세포의 침윤을 매개하는 물질이다. 본 연구는 미성숙뇌의 뇌염증에서 백혈구침윤의 기전을 연구하기 위하여 내독소로 유발된 뇌염증에서 케모카인의 일종인 MCP-1, $MIP-1{\alpha}$, MIP-2의 발현을 연구하였다. 신생쥐와 성숙쥐의 미상핵 국소에 LPS $(0.5\;{\mu}g/{\mu}l)$를 정위주사 한 후 시간대별로 RT-PCR과 면역조직화학검사을 통하여 각각 mRNA상과 단백질상에서의 발현을 비교분석하였다. 광학현미경상 LPS 주입 후 6 시간 후부터 주사부위의 염증세포의 침윤이 시작되었으며 24 시간 후에 가장 뚜렷한 현상을 보였다. RT-PCR 결과, MCP-1, $MIP-1{\alpha}$, MIP-2 mRNA 발현은 24 시간 때에 최고치를 나타냈었다. 미성숙뇌의 각 케모카인의 mRNA발현은 성숙뇌에 비해 MCP-1은 약 2.6배, $MIP-1{\alpha}$는 약 1.4배, MIP-2는 약 1.2배 발현양이 더 많다. 면역조직화학검사는 광학현미경결과와 RT-PCR결과와 상응하여 각 케모카인들이 24 시간 때에 가장 양성반응이 뚜렷이 나타났다. 이러한 현상은 뇌염증에서 백혈구의 침윤은 케모카인을 생성하는 소교세포, 성상세포, 내피세포 등의 영향을 받는 기전에 의하여 조절되었다는 것을 나타내며 이들 케모카인 형성환경의 역할을 명확히 밝히고 질병의 진행에서 케모카인의 활성을 조정하는 방법을 연구하면 향후 뇌염증을 포함한 여러 가지질환에서 신경세포의 손상을 막는 치료법의 개발이 가능하게 될 것이다.
Severe brain injuries induced by toxin pose one of the most important problems on our health care because of their high morbidity and mortality, are implicated to leucocyte infiltration more premature or immature brain than mature brain. Chemokines are the induction meditators for infiltration of inflammatory cells to the inflammation sites. In order to study the mechanism of leucocyte infiltration, the expression of several chemokines, MCP-1, $MIP-1{\alpha}$ and MIP-2 was studied in lipopolysaccharide(LPS)-stimulated neonatal and adult brain. One week old Sprague-Dawley rats or adult male rats weighing 300-350 g were used for the experiment. After anesthetization, $1\;{\mu}l$ LPS (0.5 mg/ml) subsequently was injected in the right caudate nucleus of the brain with stereotaxic frame. Animals were sacrificed at 6 hours, 24 hours, and 72 hours after injection. The present study was carried out using RT-PCR for the mRNA and immunohistochemistry for the expression of the proteins. In the neonatal rat brain, prominent interstitial edema with significant accumulation of leukocytes was detected at 24 and 72 hours after LPS injection. A semiquantitative analysis of RT-PCR revealed that the MCP-1, $MIP-1{\alpha}$, and MIP-2 mRNA expression peaked at 24 hours in neonatal and adult rat brain. Neonatal rats showed about 2.6, 1.4, and 1.2 times more expression of the MCP-1, $MIP-1{\alpha}$, and MIP-2 than that of the adult rats in the brain tissue. Immunohistochemical analysis also showed that MCP-1 immunoreactivity was paralleled with the RT-PCR results. MCP-1 protein was significantly detected at 24 and 72 hours in the brain parenchyma. $MIP-1{\alpha}$protein was highly expressed at 24 hours. The results of leukocyte infiltration in H&E stain was parallelled with that of the immunohistochemistry. Chemokine proteins were markedly detected at 24 hours after injection of LPS and neutrophil influx into intraparenchymal was prominent at 24 hours. These results suggest that the leukocyte infiltration in the intracranial infection may be controlled by mechanisms influenced by chemokine producing cells in the central nervous system such as microglia, astrocyte and endothelial cell.
