Adaptive immune response is involved in kainic acid-induced hippocampal injury in C57BL/6 mice

Wei ZHU; Xiangyan CUI; Jie ZHU

ABSTRACT

BACKGROUND:

Kainic acid (KA)-induced hippocampal injury in rodents is a good model for studying human neurodegenerative diseases. Although many studies have evidenced that inflammatory molecules and responses participate in and accelerated the process of disease, it is still unclear whether adaptive immune response, especially immune competent cells, such as T and B cells, is involved in the pathogenesis of neurodegenerative diseases.

OBJECTIVE:

To observe the roles of B and T cell subsets in KA-induced hippocampal neurodegeneration.

DESIGN:

Randomized controlled animal trial.5ETTING Department of Otolaryngology and Head, and Department of Neurology, First Hospital, Jilin University; Division of Geriatrics, Department of Neurotec, Huddinge Hospital, Karolinska Institute.MATERrALS This trial was conducted in the Department of Neurotec, Huddinge Hospital, Karolinska Institute during June to September 2000. Twenty male C57 BL/6 mice (wide-type), and knockout mice CD4(-/-) (n =17), CD8(-/-)(n =19), CD4/CD8(-/-) (n =15) and Igh-6(-/-) (n =14) of C57BL/6 background were involved in this trial. They were aged 5 to 6 weeks,weighing 18 to 20 g. Three age- and body mass-matched C57BL/6 mice received water as controls. Reagent and instruments KA (Sigma, USA). Bicolor flow cytometer and CellQuest (Becton Dickinson, CA, USA).

METHODS:

① Eighty-five anesthetized mice were slowly administrated with 7.69 g/L KA by micropipette which was connected to nose of mouse at the dose of 48 mg/kg. Three control C57BL/6 mice received the same amount of water intranasally. ②Clinical symptoms of mice were monitored. Seizures were graded using a 6-point scale, 0 normal; 6 death.③After 4 to 5 hours of administration of KA, surface immunofluorescence staining of spleen cells was measured with flow cytometer. ④After 7 days of administration of KA, all the mice were anesthetized, and their brains were harvested,then fixed and embedded. For assessment of the severity and extent of hippocampal neurodegeneration by Nissl's staining, the sections were scored by a semiquantitative grading system with a 6-point scale 0 normal; 6 severe loss of neurons (more than 40% neuron loss in area CA3); ⑤One-factor analysis of variance was used for the comparison of difference among groups and students' t test was used between two groups.MAIN OUTCOME

MEASURES:

Clinical grade, hippocampal neuropathological changes and the molecular expression of splenic monocytes of mice in each group.

RESULTS:

Eighty-five mice were involved in the result analysis. ① Clinical grade All CD4 (-/-) mice displayed severe seizures, and their clinical symptoms were significantly severer than those of wild type mice (P ＜ 0.01). Clinical scores of CD4/CD8 (-/-) mice were significantly lower than those of wide-type mice (P ＜ 0.01). However, the responses of CD8 (-/-) and Igh-6 (-/-) mice did not differ notably from those of the wild-type mice. The clinical grade of control mice was the lowest. ②Hippocampal neuropathological changes Neurodegeneration was the mildest in CD4/CD8 (-/-) mice and severest in Igh-6 (-/-) mice. ③ Spleen cell subsets changes the number of splenic CD4+T cells was significantly increased in CD8(-/-) mice and wide-type mice (before and after administration of KA 8.4%,14.2%;18.2%,31.5%); CD8+T cells were up-regulated in Igh-6(-/-) mice ( before and after administration 2.1% and 7.4%); B cells rose numerically in CD4(-/-) (Before and after administration 22.7% and 32.8%).

CONCLUSION:

Aadaptive immune response is involved in the KA-induced hippocampal neurodegeneration in mice, and B and T cell subsets contribute differently to the pathogenesis.