The Role of Salivary and Intestinal Complement System Inhibitors in the Midgut Protection of Triatomines and Mosquitoes
The Role of Salivary and Intestinal Complement System Inhibitors in the Midgut Protection of Triatomines and Mosquitoes
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DOI：
10.1371/journal.pone.0006047
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发表时间：
2009-06-25
期刊：
影响因子：
3.7
通讯作者：
Gontijo, Nelder Figueiredo
中科院分区：
文献类型：
--
作者：
Barros, Veruska Cavalcanti;Assumpcao, Jessica Goes;Gontijo, Nelder Figueiredo
噬血节肢动物的唾液中含有直接或间接参与吞血过程的生物分子，其中包括一些补体系统抑制剂。这些抑制剂最明显的功能是保护中肠免受补体的伤害。为了研究这一假说，巴西三角草若虫被迫在抑制物对中肠的保护被绕过的情况下摄取人类血清。在这种情况下，补体损伤了中肠前上皮，导致细胞死亡。一旦一些昆虫，如埃及伊蚊没有唾液抑制物，我们就假设存在肠道抑制物。用一种能确定补体因子(C1q、C3b或C4b)在微板上连接的补体激活剂分子表面沉积水平的免疫学方法，研究了埃及按蚊的肠道以及其他三种三藻(巴西毛滴虫、致病毛滴虫和罗氏罗氏沼虾)的唾液和肠道中的抑制活性。这一方法允许确定沿着补体级联的激活阶段的哪些点被抑制。正如预期的那样，埃及斑潜蝇肠道中的可溶性物质能够通过经典途径和替代途径抑制C3b的沉积。从三聚氰胺中获得的唾液或可溶性肠道内容物不能通过经典途径抑制C1q的沉积。三种三聚氰胺的肠道内容物均能抑制经典途径的C4b沉积。另一方面，只有巴西毛滴虫唾液能抑制C4b的沉积。所有三聚氰胺的唾液和肠道内容物都能抑制C3b在经典途径和替代途径中的沉积。从肠细胞膜中提取的物质都不能抑制C3b在经典途径中的沉积。补体抑制剂的存在可能会产生重要的生物学后果，本文将对此进行详细讨论。
Saliva of haematophagous arthropods contain biomolecules involved directly or indirectly with the haematophagy process, and among them are encountered some complement system inhibitors. The most obvious function for these inhibitors would be the protection of the midgut against injury by the complement. To investigate this hypothesis, Triatoma brasiliensis nymphs were forced to ingest human serum in conditions in which the protection of midgut by the inhibitors is bypassed. In these conditions, the anterior midgut epithelium was injured by the complement, causing cell death. Once some insects such as Aedes aegypti have no salivary inhibitors, we hypothesized the existence of intestinal inhibitors. The inhibitory activity was investigated in the intestine of A. aegypti as well as in the saliva and intestine of other three triatomine species (T. brasiliensis, T. infestans and Rhodnius prolixus) using an immunological method able to determine the level of deposition of some complement factors (C1q, C3b, or C4b) on the surface of complement activator molecules linked to microplates. This methodology permitted to identify which points along the activation phase of the complement cascade were inhibited. As expected, soluble contents of A. aegypti's intestine was capable to inhibit C3b deposition by the classical and alternative pathways. Saliva or soluble intestinal contents, obtained from triatomines were unable to inhibit C1q deposition by the classical pathway. C4b deposition by the classical pathway was inhibited by the intestinal contents from the three triatomines. On the other hand, only T. brasiliensis saliva inhibited C4b deposition. Both, saliva and intestinal contents from all triatomines were able to inhibit C3b deposition in the classical and alternative pathways. None of the material extracted from the intestinal cell membranes from the triatomines inhibited C3b deposition in the classical pathway. The existence of complement inhibitors may have important biological consequences which are discussed in detail.