PDF(Pubmed)
Abstract：
A major Streptococcus pneumoniae pathogenic factor is the cholesterol-dependent cytolysin pneumolysin, binding membrane cholesterol and producing permanent lytic or transient pores. During brain infections, vascular damage with variable ischemia occurs. The role of ischemia on pneumolysin\'s pore-forming capacity remains unknown. In acute brain slice cultures and primary cultured glia, we studied acute toxin lysis (via propidium iodide staining and LDH release) and transient pore formation (by analyzing increases in the intracellular calcium). We analyzed normal peripheral tissue glucose conditions (80 mg%), normal brain glucose levels (20 mg%), and brain hypoglycemic conditions (3 mg%), in combinations either with normoxia (8% oxygen) or hypoxia (2% oxygen). At 80 mg% glucose, hypoxia enhanced cytolysis via pneumolysin. At 20 mg% glucose, hypoxia did not affect cell lysis, but impaired calcium restoration after non-lytic pore formation. Only at 3 mg% glucose, during normoxia, did pneumolysin produce stronger lysis. In hypoglycemic (3 mg% glucose) conditions, pneumolysin caused a milder calcium increase, but restoration was missing. Microglia bound more pneumolysin than astrocytes and demonstrated generally stronger calcium elevation. Thus, our work demonstrated that the toxin pore-forming capacity in cells continuously diminishes when oxygen is reduced, overlapping with a continuously reduced ability of cells to maintain homeostasis of the calcium influx once oxygen and glucose are reduced.
摘要：
肺炎链球菌的主要致病因素是胆固醇依赖性细胞溶素，结合膜胆固醇并产生永久性溶解或瞬时孔。在脑部感染期间,血管损伤与可变缺血发生。缺血对肺炎球菌溶素成孔能力的作用尚不清楚。在急性脑切片培养和原代培养的神经胶质细胞中，我们研究了急性毒素裂解（通过碘化丙啶染色和LDH释放）和瞬时孔形成（通过分析细胞内钙的增加）。我们分析了正常的外周组织葡萄糖状况（80mg％），正常脑葡萄糖水平（20mg％），和大脑低血糖条件（3毫克％），与常氧（8％氧气）或缺氧（2％氧气）的组合。在80毫克％的葡萄糖，缺氧通过肺炎球菌溶血素增强细胞溶解。在20毫克％的葡萄糖，缺氧不影响细胞裂解，但非溶解性孔形成后钙的恢复受损。只有3毫克%的葡萄糖，在常氧症期间，肺炎球菌溶血素是否产生更强的裂解。在低血糖（3mg％葡萄糖）条件下，肺炎球菌溶血素引起较温和的钙增加，但是修复工作不见了。小胶质细胞比星形胶质细胞结合更多的肺炎球菌溶血素，并且通常显示出更强的钙升高。因此，我们的工作表明，当氧气减少时，细胞中的毒素成孔能力不断降低，一旦氧气和葡萄糖减少，细胞维持钙内流稳态的能力不断降低。
