Modulation of bacterial ghosts – induced nitric oxide production in macrophages by bacterial ghost‐delivered resveratrol

The present study aimed to investigate the capacity of resveratrol (RV) delivered into macrophages by bacterial ghosts (BGs), representing intact empty nonliving envelopes of Gram‐negative bacteria, to modulate nitric oxide (NO) production related to the presence of the pathogen‐associated molecular patterns on the surface of BGs. Incubation of the murine macrophage cell line RAW 264.7 with BGs leads to a dose‐dependent activation of inducible NO synthase. To modify BG‐induced NO formation in RAW 264.7 cells by RV; BGs were loaded with RV (RV‐BGs) and incubated with murine macrophages in a dose‐dependent manner. RV‐BGs delivering RV to the target macrophages significantly reduced BG‐induced NO production with concentration of RV more than one order of magnitude lower than the amount of RV capable of reducing NO formation when applied directly. Moreover, no cytotoxic impact of BGs on the viability of RAW 264.7 cells added to macrophages alone or loaded with RV was detected after a mutual 24 h incubation, whereas cell viability slightly decreased (~ 10%) when RV concentrations of 30 μm alone were applied. The results obtained in the present study clearly indicate that the intracellular delivery of RV by BGs significantly enhances the total RV effect. The present study demonstrates that NO formation induced after internalization of BGs by macrophages can be effectively modulated by RV loaded inside BGs and delivered directly to the cytosol of target cells. Low doses of RV presented within the BG's envelope significantly decreased generation of NO without having a cytotoxic impact on the viability of phagocytic cells