The online version of this article (doi:10.1186/cc10356) contains supplementary material, which is available to authorized users.
The authors declare that they have no competing interests.
MPC participated in the study design and coordination, carried out the molecular genetic studies and functional assays, and helped to draft the manuscript. VT carried out the MP number experiments and functional assays and helped to draft the manuscript. CD carried out the MP number experiments. IW and DW contributed patient samples. JT helped to draft the manuscript. CHT conceived of the study and participated in its design and coordination and helped to draft the manuscript. All authors read and approved the final manuscript.
Activated protein C (APC) induces release of microparticles (MP) from primary physiological cells, which are found in patients undergoing treatment with recombinant human APC (rhAPC) for severe sepsis. We hypothesised that APC on these circulating MPs activate endothelial protease-activated receptor 1 (PAR1) to induce anti-apoptotic and anti-inflammatory properties that can improve patient outcome.
This was an experimental study on clinical samples in an intensive care setting, and included patients with severe sepsis who fulfilled criteria for treatment with rhAPC. The number of CD13+ MPs from the patients were analysed to determine their origin. They were also quantified for endothelial protein C receptor (EPCR) and APC expression. Clinical relevance of these MPs were ascertained by comparing survival between the group receiving rhAPC (n = 25) and a control group of untreated patients (n = 25). MPs were also incubated with endothelial cells to analyse apoptotic gene expression, cytoprotection and anti-inflammatory effects.
rhAPC treatment induced a significant increase in circulating MP-associated EPCR by flow cytometry (P < 0.05) and by quantitative ELISA (P < 0.005). APC expression also showed significant increases (P < 0.05). Numerically, CD13+ MPs were higher in rhAPC-treated survivors versus non-survivors. However, the number of non-survivors was low and this was not significantly different. APC on MPs was demonstrated to induce anti-apoptotic and endothelial barrier effects through the activation of endothelial PAR1.
rhAPC treatment in patients with sepsis significantly increases circulating EPCR + MPs. These MPs were noted to express APC, which has specific anti-apoptotic and anti-inflammatory effects, with a non-significant correlative trend towards survival. This suggests that MPs could disseminate APC function and activate endothelial PAR1 at distal vascular sites.
Additional file 1:Supplementary information. Supplementary materials and methods, and figure legend [17, 18, 45–48]. (DOCX 16 KB)
Additional file 2:Supplementary Figure S1. The proportion of free versus bound rhAPC on microparticles. Comparison of results obtained from patient samples to in vitro derived MPs. (TIFF 31 KB)
Additional file 3:Supplementary table S1. Genes modulated by APC (free or microparticle [MP]-bound from patients). Microarray results. (DOCX 17 KB)
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- The clinical and functional relevance of microparticles induced by activated protein C treatment in sepsis
Cheng Hock Toh
- BioMed Central
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