The Dissociation of Pentameric to Monomeric C-Reactive Protein Localizes and Aggravates Inflammation: In vivo Proof of a Powerful Pro-Inflammatory 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 CRP changes in vivo.
Methods and Results—We identified mCRP in inflamed human striated muscle, human atherosclerotic plaque and in infarcted myocardium (rat and human) and its co-localization with inflammatory cells, suggesting 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 in non-inflamed cremaster muscle, This was confirmed in a rat model of myocardial infarction. Mechanistically, this process was dependent on exposure of lysophosphatidyl¬choline on activated cell membranes, which is generated following phospholipase A2 (PLA2) activation. These membrane changes could be visualized intravitally on endothelial cells, as well as the co-localized mCRP generation. Blocking PLA2 abrogated CRP dissociation and thereby blunted CRP's pro-inflammatory effects. Identifying the dissociation process as a therapeutic target, we stabilized pCRP using 1,6-bis-phosphocholin-hexane, which prevented dissociation in vitro and in vivo, and consequently inhibited generation and pro-inflammatory activity of mCRP and notably, inhibited mCRP deposition and inflammation in rat myocardial infarction.
Conclusions—These results provide in vivo evidence for a novel mechanism localizing and aggravating inflammation via PLA2-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.
- C-reactive protein
- C-reactive protein
- myocardial infarction
- Received October 31, 2013.
- Revision received March 27, 2014.
- Accepted April 18, 2014.