Manipulation Of Macrophage Polarization By Peptide-Coated Gold Nanoparticles And Its Protective Effects On Acute Lung Injury

Background and objetive: Acute lung injury(ALI)and its more severe form of acute respiratory distress syndrome(ARDS)are common respiratory conditions in critically ill patients with a mortality rate reaching 40%.To date,there are no effective drug treatments for theses condtions.Studies have shown that macrophage polarization in the lung plays an important role in the initiation,development and progression of ALI/ARDS.Regulating the activation and polarization of macrophages is expected to be a new strategy for the treatment of ALI/ARDS.Lately,we developed a novel class of anti-inflammatory nanoparticles that can effectively inhibit Toll-like receptor(TLR)pathways in macrophages.They were made of gold nanoparticles(GNPs)and peptides,forming peptide-GNP hybirds(P12).This study aimed to explore the effect of P12 on macrophage polarization and its protective role in ALI mice,providing a new strategy to develop an effective clinical treatment for ALI/ARDS.Methods: The physicochemical characterizations of the size and zeta-potential of the bare GNPs and peptide-coated GNPs were conducted with transmission electron microscopy and dynamic light scattering techniques.The classical ALI mouse model was established by intratracheal injection of lipopolysaccharide(LPS,10 mg/kg)for 24 h,and the bronchoalveolar lavage fluid(BALF)cytology,pulmonary histopathology analysis,lung wet/dry weight ratio and cytokine level analysis by Luminex were conducted to evalulate the protective effects of P12.In the same ALI mouse model,pulmonary macrophages of mice were depleted to confirm whether they play a critical role in the in-vivo antiinflammatory action of P12.In addition,the effects of P12 on the polarization of mouse bone marrow derived macrophages(BMDMs)were assessed by ELISA and q RT-PCR,while those on pulmonary macrophage polarization were measured by multi-color flow cytometry and immunofluorescence staining.Results: We first confirmed that P12 could reduce lung inflammation and damage by decreasing the infiltration of inflammatory cells and enhancing the level of antiinflammatory cytokine(IL-10)in the lung.We then found that P12 injected into the airway primarily targeted macrophages in the lung to exert anti-inflammatory effects.In addition,in the ex vivo cell culture model,P12 was able to drive the polarization of BMDMs toward anti-inflammatory M2 phenotype.In the ALI mouse model,P12 could increase the alveolar M2 macrophages and reduce both the alveolar and interstitial M1 macrophages in the BALF and lung tissues.Conclusions: Peptide-coated GNPs(P12)were able to induce M2 macrophage polarization in vitro and in vivo.In the LPS-induced ALI mouse model,P12 could effectively alleviated lung inflammation by targeting pulmonary macrophages to reduce their inflammatory responses and promote their polarization to anti-inflammatory M2 type.This study provided a novel bioactive nanodevice to manipulate macrophage polarization to the M2 type to regulate the acute inflammatory reaction in the lung,which is expected to be a new effective therapeutic strategy to treat ALI/ARDS.