Endotoxins (lipopolysaccharides, LPSs) are potent bacterial poisons, and they are always present in the intestine in considerable numbers. Stress, such that as a resulting from multiple injuries, burns, hypovolemia, hypoxia, intestinal ischemia, and surgery can lead to a breakdown of the gut barrier, allowing endotoxins to enter the systemic circulation via translocation. However, estimating the biological activity of translocated circulating endotoxins and identification of the mechanisms regulating their biological activities remain complex problems. CD14 has been found to exist as a soluble protein in the serum and as a glycosylphosphatidylinositol (GPI)-anchored protein of myeloid lineage cells. It plays key roles in both LPS-induced activation and in LPS internalization by cells. In this article, we outline: (i) the biological activity of circulating endotoxin; and (ii) the role of membrane and/or soluble CD14 regulating the bioactivity of circulating endotoxin in a human model of postoperative endotoxemia.
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