Chitosomes loaded with cranberry proanthocyanidins attenuate the bacterial lipopolysaccharide-induced expression of iNOS and COX-2 in raw 264.7 macrophages
Chitosan binds to negatively charged soy lecithin liposomes by an electrostatic interaction driven by its positively charged amino group. This interaction allows stable covered vesicles (chitosomes) to be developed as a suitable targeted carrier and controlled release system. This study investigated the effect of chitosomes on the activation of cranberry proanthocyanidins (PAC) in Raw 264.7 macrophages. Chitosomes were characterized according to size, zeta potential, PAC-loading, and release properties. Results showed an increase in the net positive charge and size of the liposomes as the concentration of chitosan was increased, suggesting an effective covering of the vesicles by means of electrostatic interactions, as shown by transmission electron microscopy and fluorescence microscopy. About 85% of the PAC that was loaded remained in the chitosomes after release studies for 4 hours in phosphate-buffered saline. Cyclo-oxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) are associated with inflammation. Activated RAW 264.7 macrophages increase the expression of COX-2 and iNOS in response to bacterial infection and inflammation; we, therefore, tested the ability of the PAC-loaded chitosomes to attenuate COX-2 and iNOS expression in LPS (lipopolysaccharide)-stimulated macrophages. Increasing the amount of PAC loaded into the chitosomes caused a dose-dependent attenuation of iNOS and COX-2 expression in LPS-stimulated macrophages. A 2% v/v PAC-loaded chitosomes formulation almost completely attenuated the LPS-induced expression of iNOS and COX-2. PAC-loaded chitosomes were more active than PAC alone, suggesting that the macrophage response to LPS occurs after endocytosis of the PAC-loaded chitosomes.