ABSTRACT
Cationic lipids are efficient tools to introduce nucleic acids and proteins into cells. Elucidation of the mechanism and cellular pathways associated with such transport has been relatively tedious, even though significant progress has been made in the characterization of the intracellular trafficking of lipid/DNA complexes. Surprisingly little is known about the effects of these delivery vectors on cell functioning. In this report, we show that both cationic lipids and cationic lipid/DNA complexes mobilize the intracellular calcium. Removal of extracellular calcium did not significantly abolish this effect and preincubating cells with thapsigargin led to a decrease in [Ca2+]i, indicating that calcium was released mainly from internal calcium stores sensitive to thapsigargin. Pretreatment of the cells with the phospholipase C inhibitor U73122, blocked the [Ca2+]i rise, suggesting an inositol dependent mechanism.
Subject(s)
Calcium Signaling/drug effects , Calcium/metabolism , Cations/metabolism , Cytosol/metabolism , Lipid Metabolism , Transfection , Biological Transport , Cations/chemistry , Enzyme Inhibitors/pharmacology , Estrenes/chemistry , Estrenes/pharmacology , Genetic Vectors/metabolism , Humans , Inositol Phosphates/metabolism , K562 Cells , Lipids/chemistry , Liposomes , Models, Biological , Pyrrolidinones/chemistry , Pyrrolidinones/pharmacology , Thapsigargin/chemistry , Thapsigargin/pharmacology , Type C Phospholipases/antagonists & inhibitors , Type C Phospholipases/metabolismABSTRACT
It has been shown that a preinjection of diC14-amidine cationic liposomes decreased TNF-alpha secretion induced by lipoplexes intravenous injection. We showed here that free cationic liposomes inhibit CpG sequences- or lipopolysaccharides-induced TNF-alpha secretion by macrophages. Surprisingly, this effect was strictly dependent on serum. Free cationic liposomes alone did not reveal any anti-inflammatory activity. Low-density lipoproteins and triglyceride-rich lipoproteins were identified as the serum components that confer to the liposomes an anti-inflammatory activity. Lipid fractions of these lipoproteins were able to reproduce the effect of the total lipoproteins and could inhibit, in association with diC14-amidine liposomes, the CpG-induced TNF-alpha secretion. Serum components confer to cationic liposomes new properties that can be used to modulate the inflammatory response directed against CpG sequences and lipopolysaccharides.
