N-Dodecanoyl-L-homoserine lactone (C12-HSL) is a small diffusible signalling molecule involved in quorum sensing, thereby controlling gene expression and affecting cellular metabolism in bacteria. In addition to regulating bacterial functions, C12-HSL activates NF-kappaB in RAW 264.7 macrophages, increasing the expression of TNF-alpha, interleukin-1beta (IL-1beta) and IL-8, while other lactones do not. In addition, C12-HSL alters cell cycling and metabolism of human keratinocyte (HaCaT) cells. It is important to note that C12-HSL is distinct from N-3-oxo-dodecanoyl-L-homoserine lactone, which is produced at different times in biofilm development and has different cellular effects.