Targeted counteracting of overactive macrophages by melittin stable-loaded solid lipid nanoparticles alleviates cytokine storm and acute inflammatory injury

The continuous activation of macrophages play a critical role in the pathogenesis of cytokine storm (CS). Considering that CS results from the participation of multiple cytokines, the therapeutic effect of a single cytokine or its receptor-targeted blockade therapy remains uncertain. Melittin, which can systematically suppress the overexpression of proinflammatory mediators via inhibiting the mitogen-activated protein kinase and nuclear factor kappa-B pathways in activated macrophages, shows great potential in alleviating CS and acute inflammatory injury (AII). However, its clinical application is limited by its hemolytic activity, non-specific cytotoxicity and lack of targeting. In this study, a folic acid-modified and melittin stable-loaded solid lipid nanoparticle (Fa-MpG@LNP) with a core-shell structure was developed for CS control via targeted inhibition of the overproduction of proinflammatory mediators in activated macrophages with specific expression of folate receptor-β. The resultant Fa-MpG@LNP showed ideal physicochemical properties and stability, low hemolytic activity and non-specific cytotoxicity, and it can specifically bind to lipopolysaccharide (LPS)-stimulated macrophages and effectively reduce the elevated levels of proinflammatory mediators. After intravenous administration, the Fa-MpG@LNP accumulated at inflamed tissue and significantly downregulate the overproduction of proinflammatory cytokines in tissue-infiltrated macrophages, resulting in a significant decrease of cytokine concentration in inflamed tissue and serum in LPS-induced acute pneumonia mice, and finally alleviate AII with undetectable toxic side effects. These results indicate the clinical application potential of Fa-MpG@LNP in alleviating CS and its related symptoms.