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

一些革兰氏阴性厌氧菌，包括牙龈卟啉单胞菌，已经与牙周病的发病机制有关。我们已经证明，牙龈假单胞菌脂多糖(PgLPS)由独特的成分组成，并显示出独特的免疫生物学活性。由于牙周炎病变以B淋巴细胞/浆细胞增多为特征，因此阐明LPS刺激的机制，特别是LPS刺激下B细胞活化的信号转导机制是非常重要的。然而，目前对LPS产生的细胞内信号还没有明确的定义。在本研究中，我们首先研究了PgLPS对LPS反应的C3H/HEN和低反应的C3HEJ小鼠B淋巴细胞酪氨酸蛋白磷酸化的分子作用。结果表明，PgLPS可诱导两种小鼠B淋巴细胞膜蛋白的酪氨酸磷酸化，其中包括表观分子质量为24.8 kDa和26.0 kDa的磷蛋白(p24.8和p26.0)，而EcLPS仅诱导C3H/HEN B淋巴细胞的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淋巴细胞的激活，而ECLPS的触发信号不能传递启动酪氨酸蛋白磷酸化的信号。其次，我们检测了LPS的免疫化学特异性和牙龈假单胞菌Fimbrin基因的分子特性。结果表明，牙龈假单胞菌fimbrlin基因的分子结构并不同源，提示fimbrlin基因的分子修饰应在牙龈假单胞菌的体外传代和维持过程中进行。

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.