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Letters to the Editor |
Letter to the Editor
Letter in Response to Bisoendial et al: "Activation of Inflammation and Coagulation After Infusion of C-Reactive Protein in Humans"
The Department of Pharmacology, Therapeutics, and Toxicology, Wales Heart Research Institute, Cardiff University, Wales College of Medicine, Cardiff, United Kingdom
To the Editor:
With interest we read the recent report by Bisoendial et al in Circulation Research regarding their observation that infusion of C reactive protein (CRP) into humans induces the release of inflammatory mediators and coagulation factors.1 The CRP used in this study was generated in Escherichia coli, therefore there is a major possibility of the CRP being contaminated with bacterial products. Although the authors tried to remove endotoxin contamination using gel-filtration, in our opinion this is not a very rigorous method. The kinetics of Bisoendial et al observations suggests that endotoxin contamination and not CRP itself is responsible for their observations. This is especially clear considering the levels of CRP found in the plasma and the kinetics of IL-6 and IL-8 induction. The authors observe a continuous presence of CRP, which even increases after 24 hours, most likely attributable to the generation of CRP in the volunteer. If, as the authors suggest, their observation is caused by CRP itself, this would suggest that CRP can directly or indirectly increase its own synthesis; this would be a self-perpetuating effect and CRP levels would keep increasing until maximal achievable levels were obtained. However, IL-6 and IL-8 levels peak after 4 hours and are back to baseline levels at 8 hours. If CRP were responsible for the increased expression of these cytokines, levels would not peak, but because of the continuous and increasing levels of CRP, IL-6, and IL-8 levels would keep increasing similar to CRP. The kinetics of the increase in CRP, IL-6, and IL-8 levels can be completely explained by the presence of small amounts of endotoxin contamination. Endotoxin, because it would be removed from the circulation, would only cause a temporary increase in IL-6 and IL-8 whereas CRP would increase after 24 hours.
We and others have shown that contamination of commercial E coli–derived CRP is responsible for numerous effects previously ascribed to CRP2–7 and that endotoxin contamination is responsible for chemokine and cytokine secretion in vitro.2,7 It has been shown that contaminations of protein with minute amounts of endotoxin can increase cytokine secretion.8 In conclusion, we suggest that the events observed by Bisoendial et al are most likely caused by endotoxin contamination of their CRP preparation and that the results of this study have to be interpreted with great care.
References
1. Bisoendial RJ, Kastelein JJ, Levels JH, Zwaginga JJ, van den Bogaard B, Reitsma PH, Meijers JC, Hartman D, Levi M, Stroes ES. Activation of inflammation and coagulation after infusion of C-reactive protein in humans. Circ Res. 2005; 96: 714–716.
2. Nagoshi Y, Kuwasako K, Cao YN, Kitamura K, Eto T. Effects of C-reactive protein on atherogenic mediators and adrenomedullin in human coronary artery endothelial and smooth muscle cells. Biochem Biophys Res Commun. 2004; 314: 1057–1063.[CrossRef][Medline] [Order article via Infotrieve]
3. van den Berg CW, Taylor KE, Lang D. C-reactive protein induced in vitro vasorelaxation is an artefact caused by the presence of sodium azide in commercial preparations. Arterioscler Thromb Vasc Biol. 2004; 24: e168–e171.
4. van den Berg CW, Taylor KE. Letter regarding article by Li et al, "C-reactive protein upregulates complement-inhibitory factors in endothelial cells". Circulation. 2004; 110: e542.
5. Swafford AN Jr, Bratz IN, Knudson JD, Rogers PA, Timmerman JM, Tune JD, Dick GM. C-reactive protein does not relax vascular smooth muscle: effects mediated by sodium azide in commercially available preparations. Am J Physiol Heart Circ Physiol. 2005; 288: H1786–H1795.
6. Lafuente N, Azcutia V, Matesanz N, Cercas E, Rodriguez-Manas L, Sanchez-Ferrer CF, Peiro C. Evidence for sodium azide as an artifact mediating the modulation of inducible nitric oxide synthase by C-reactive protein. J Cardiovasc Pharmacol. 2005; 45: 193–196.[CrossRef][Medline] [Order article via Infotrieve]
7. Taylor KE, Giddings JC, van den Berg CW. C-reactive protein-induced in vitro endothelial cell activation is an artefact caused by azide and lipopolysaccharide. Arterioscler Thromb Vasc Biol. 2005; 25: 1225–1230.
8. Bausinger H, Lipsker D, Ziylan U, Manie S, Briand JP, Cazenave JP, Muller S, Haeuw JF, Ravanat C, de la Salle H, Hanau D. Endotoxin-free heat-shock protein 70 fails to induce APC activation. Eur J Immunol. 2002; 32: 3708–3713.[CrossRef][Medline] [Order article via Infotrieve]
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  R. Bisoendial, J. Kastelein, and E. Stroes Letter to the Editor: In response to van den Berg et al: Circ. Res., September 30, 2005; 97(7): e71 - e71. [Full Text] [PDF]
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