Liposomes as immunomodulator - Inhibitory effect of liposomes on NO production from macrophages

Liposomes have been artificially made into membranous vesicles composed ess entially of naturally occurring phospholipids and have been found to serve as a carrier of drugs and an immunological adjuvant, After being intravenou sly injected, they are quickly removed from the blood circulation and trapp ed by Kupffer cells of the liver and macrophages of spleen. However, the ch anges liposomes exert in these cells with which liposomes interact remain u nresolved. To clarify this point is very important to assure the safe use o f liposomes as drug carriers. Macrophages have many unique functions, and n itric oxide (NO) produced by NO synthase (NOS) which is induced in response to some cytokines and bacterial products such as lipopolysaccharide (LPS) is responsible for the bactericidal, tumoricidal and immune regulatory acti vities, On the other hand, overexpressed NO is implicated in the developmen t of atherosclerosis, DNA injury, and hypotension associated with septic sh ock, This article focuses on the effects of liposomes on NO production from LPS-stimulated mice peritoneal macrophages in vitro; we found that liposom es composed of phosphatidylserine inhibit NO production. We also discuss th e mechanism of the inhibitory activity of liposomes.