原形態C反應蛋白(native C-reactive protein, nCRP) 是ㄧ種五聚體構造的急性期蛋白質。當身體發炎時，會從肝臟大量表現出來，在血漿的濃度會上升到原本得一百倍或更多。而在發炎的組織處，會產生出另一種以單體蛋白形式存在的修飾或單體C反應蛋白(modified CRP或monomeric CRP, mCRP)。無論如何，原形態C反應蛋白和單體C反應蛋白，兩者已被報導具有相當不一樣的生物活性，兩個異構體更被認為在先天免疫反應以及冠狀動脈硬化 (atherosclerosis) 的疾病進程等發炎疾病上扮演重要的角色。嗜中性白血球 (neutrophil) 可以藉由釋放毒殺分子來摧毀外來的病原體，即活化的嗜中性白血球經由NADPH氧化酵素(NADPH oxidase) 可以消耗氧氣來產生大量的氧活性分子 (reactive oxygen species, ROS)。其中NADPH oxidase的細胞質蛋白的磷酸化並且轉移到細胞膜部分組裝起來，可以使得NADPH氧化酵素處在準備好的狀態。當嗜中性白血球受到第二個刺激後，便可以產生更多的氧活性分子，這樣的過程就稱為”priming effect”。處在primed狀態的嗜中性白血球，將可以更容易的產生快速且強力的毒殺作用。本篇研究主要就是要探討C反應蛋白異構體對於嗜中性白血球是否有priming或者活化的作用。首先，我們發現原形態C反應蛋白對於嗜中性白血球或者分化後的HL-60細胞株具有priming的作用，且是ㄧ個劑量依賴姓的反應，可以明顯增加PMA刺激後的呼吸爆發 (respiratory burst)。進一步探討其分子機制，確認原形態的C反應蛋白可以促使NADPH氧化酵素內的細胞質內蛋白p47phox的磷酸化，而且是經由p38 MAPK的路徑。相較之下，發現單體C反應蛋白具有良好的活化作用，並經由ERK路徑，但幾乎不能prime嗜中性白血球。而在FcgammaR拮抗實驗中，原形態C反應蛋白媒介的priming作用在dHL-60上的FcgammaR並沒有顯著的功能。這篇研究顯露出C反應蛋白異構體在嗜中性白血球活化上，扮演不同的角色。

Native C-reactive protein (nCRP) is a pentameric acute phase protein expressed at high serum concentrations in inflammation. At inflammatory sites, another form of CRP termed modified or monomeric CRP (mCRP) is expressed and represents a monomeric structure. However, nCRP and mCRP have quite different bioactivities. Both isoforms are proposed to play roles in innate immunity and may participate in the pathogenesis of atherosclerosis and other diseases related with inflammation. Neutrophils can destroy pathogens by releasing microbicidal molecules in inflammation. Activated neutrophils consume oxygen and generate reactive oxygen species (ROS) by activating leukocyte NADPH oxidase. Phosphorylation as well as translocation of cytosolic components of leukocyte NADPH oxidase prepares neutrophils for subsequent stimulations. This step is termed “priming effect” which enhance the ROS production when neutrophils are triggered. In primed state, neutrophils easily perform fast and powerful microbicidal activity. Here, we investigated the potential role of CRP isoforms for priming and triggering neutrophil. We found that nCRP mediates priming of granulocyte and DMSO-differentiated HL-60 for PMA-induced respiratory burst. This effect is dosage-dependent. The priming mechanism of nCRP transduced through the phosphorylation of the cytosolic subunit p47phox, via p38 MAPK pathway. In contrast, mCRP triggers neutrophils via ERK, but have little effect in priming neutrophil. We also showed that FcgammaR on dHL-60 had no function in nCRP-mediated priming effect. This study revealed the different roles of CRP isoforms in neutrophil activation.

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