Bacterial endotoxic substances from periodontopathic bacteria and their effects on host cells

包括牙龈卟啉单胞菌在内的革兰氏阴性厌氧菌的选定物种与牙周病的发病机制有关。牙龈卟啉单胞菌脂多糖（PgLPS）是由独特的组分组成，具有独特的免疫生物学活性。C3 H/HeJ小鼠脾B淋巴细胞对大肠杆菌内毒素（Escherichia coli LPS，EcLPS）反应低下，但在暴露于PgLPS后，脾B淋巴细胞增殖。由于牙周炎病变的特征是B淋巴细胞/浆细胞数量增加，因此阐明LPS刺激的机制，特别是LPS刺激后B细胞活化的信号转导机制是重要的。然而，在本研究中，我们首先检测了PgLPS对LPS应答的C3 H/HeN和LPS低应答的C3 H/HeJ小鼠脾B淋巴细胞酪氨酸蛋白磷酸化的分子效应。结果表明，PgLPS诱导了两种小鼠B淋巴细胞中所选膜蛋白的酪氨酸磷酸化，包括表观分子量为24.8kDa和26.0kDa的磷酸化蛋白（p24.8和p26.0），而EcLPS仅诱导了C3 H/HeN B淋巴细胞中的p24.8和p26.0。这些结果表明，PgLPS通过与C3 H/HeN B淋巴细胞相同的酪氨酸磷酸化途径诱导C3 H/HeJ B淋巴细胞活化，而EcLPS的触发信号不能被转导以启动酪氨酸蛋白磷酸化。结果表明，fimbrilin基因的分子结构是不同源的，这表明在fimbrilin基因的分子修饰应该发生在牙龈卟啉单胞菌菌株的体外传代和维护。

Selected species of Gram-negative anaerobes including Porphyromonas gingivalis have been implicated in the pathogenesis of periodontal diseases. We have shown that P.gingivalis lipopolysaccharide (PgLPS) are composed of unique constituents and exhibit characteristic immunobiological activities. Splenic B lymphocytes from C3H/HeJ mice known to be hyporesponsive to Escherichia coli LPS (EcLPS) did proliferate after exposure to PgLPS.Since periodontitis lesions are characterized as infiltration with increased numbers of B lymphocytes/plasma cells, it is important to elucidate the mechanisms of stimulation with LPS,especially the mechanisms of signal transduction in terms of B cell activation upon stimulation with LPS.However, the intracellular signals generated by LPS have not yet been well defined.In the present study, we first examined the molecular effect of PgLPS on the tyrosineprotein phosphorylation in the splenic B lymphocytes from LPS-responsive C3H/HeN and LPS-hyporesponsive C3H/HeJ mice. The results indicated that PgLPS induced tyrosine phosphorylation of selected membrane proteins that included the phosphoproteins with apparent molecular masses of 24.8kDa and 26.0kDa (p24.8 and p26.0) in the B lymphocytes from both strains of mice, while EcLPS induced p24.8 and p26.0 in C3H/HeN B lymphocytes only. These findings suggest that through the same tyrosine phosphorylation pathway as observed in C3H/HeN B lymphocytes, PgLPS induced the activation of C3H/HeJ B lymphocytes in which a trigger signal by EcLPS could not be transduced to initiate tyrosine protein phosphorylation.Second, we examined immunochemical specificity of LPS and the molecular property of the gene encoding the fimbrilin of P.gingivalis strains. The seults showed that the molecular structure of the fimbrilin genes was not homologous, suggesting that molecular modifications in the fimbrilin gene should occur during in vitro passages and maintenance of strains of P.gingivalis.