Dissociation of pentameric to monomeric C-reactive protein localizes and aggravates inflammation: in vivo proof of a powerful proinflammatory mechanism and a new anti-inflammatory strategy.

BACKGROUND: The relevance of the dissociation of circulating pentameric C-reactive protein (pCRP) to its monomeric subunits (mCRP) is poorly understood. We investigated the role of conformational C-reactive protein changes in vivo. METHODS AND RESULTS: We identified mCRP in inflamed human striated muscle, human atherosclerotic plaque, and infarcted myocardium (rat and human) and its colocalization with inflammatory cells, which suggests a general causal role of mCRP in inflammation. This was confirmed in rat intravital microscopy of lipopolysaccharide-induced cremasteric muscle inflammation. Intravenous pCRP administration significantly enhanced leukocyte rolling, adhesion, and transmigration via localized dissociation to mCRP in inflamed but not noninflamed cremaster muscle. This was confirmed in a rat model of myocardial infarction. Mechanistically, this process was dependent on exposure of lysophosphatidylcholine on activated cell membranes, which is generated after phospholipase A2 activation. These membrane changes could be visualized intravitally on endothelial cells, as could the colocalized mCRP generation. Blocking of phospholipase A2 abrogated C-reactive protein dissociation and thereby blunted the proinflammatory effects of C-reactive protein. Identifying the dissociation process as a therapeutic target, we stabilized pCRP using 1,6-bis(phosphocholine)-hexane, which prevented dissociation in vitro and in vivo and consequently inhibited the generation and proinflammatory activity of mCRP; notably, it also inhibited mCRP deposition and inflammation in rat myocardial infarction. CONCLUSIONS: These results provide in vivo evidence for a novel mechanism that localizes and aggravates inflammation via phospholipase A2-dependent dissociation of circulating pCRP to mCRP. mCRP is proposed as a pathogenic factor in atherosclerosis and myocardial infarction. Most importantly, the inhibition of pCRP dissociation represents a promising, novel anti-inflammatory therapeutic strategy.

Lipopolysaccharide-induced radical formation in the striatum is abolished in Nox2 gp91phox-deficient mice.

Encephalopathy associated with septic shock as well as psychiatric disorders can be caused by the central nervous formation of reactive oxygen species (ROS) associated with inflammation. The systemic application of lipopolysaccharide (LPS, 100 mug/kg i.p.) also serves as a model for major depression and results in enhanced inflammatory processes. which are characterized by the stimulation of microglia or macrophages that then impair normal brain function. The aim of the present study was to analyze the effect of peripherally applied LPS on the central nervous formation of ROS and IL-6 in wild-type mice and in mice lacking the NADPH oxidase Nox2 subunit gp91phox. Microdialysis was performed in the striatum of the mice. Central nervous ROS were detected by electron spin resonance spectroscopy using 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH) as reactant, which was infused via a microdialysis probe. IL-6 was measured in microdialysis samples by an immunoassay. Finally, blood samples were taken by heart puncture to detect IL-6 in plasma. In the wild-type mice, LPS significantly increased the ROS formation in the striatum of wild-type mice and resulted in a significantly enhanced IL-6 production. In the mice lacking the NADPH oxidase Nox2 subunit gp91phox, LPS did not enhance ROS formation, while central IL-6 was significantly increased. IL-6 plasma values were enhanced in both types of mice. In conclusion, the gp91phox-containing NADPH oxidase complex is involved in the central nervous ROS formation after peripheral LPS stimulation and might be a pharmacological target in patients with septic shock.