Basic Knowledge of Lipopolysaccharide (LPS)

(9) Wounds and LPS

LPS is not toxic when it enters via the mouth or skin. Rather, it contributes to the activation of innate immunity. However, when injected into the blood, strong inflammation occurs depending on the amount used. However, what if you have a wound on your stomach or skin? Can LPS enter the blood through this wound and become inflamed?

In conclusion, given that free LPS is present around the wound, it is very difficult to transfer it from the wound to the blood while maintaining enough biological activity to induce inflammation.

As mentioned in the “Structure and function of LPS” section, LPS is a component embedded in the cell wall of gram-negative bacteria and comprises sugars and lipids. There are fats and proteins in the body that bind to lipids (typically LDL, which carries cholesterol). The lipid part, which is also the active center of LPS, is trapped by fat and LDL and becomes inactive. This can also be observed in the fact that after mixing LPS with blood, LPS amount cannot be successfully detected (*1). In addition, it has no strong biological activity.

Live gram-negative bacteria must intervene for LPS to be transported to the blood or organs. When living bacteria invade the body, multiply, and lyse, a large amount of LPS (which cannot be suppressed by lipid-binding proteins) is released while maintaining biological activity.

Therefore, unless there are live bacteria, the presence of LPS around the wound is unlikely to cause inflammation.

（*1）Endotoxemia—menace, marker, or mistake? J Leukoc Biol.100(4): 687–698 (2016)