eATP/P2X7R axis drives nanoparticle induced neutrophil recruitment in the pulmonary microcirculation

Exposure to nanoparticles (NPs) is frequently associated with adverse cardiovascular effects. In contrast, NPs in nanomedicine hold great promise for precise lung-specific drug delivery, especially considering the extensive pulmonary capillary network that facilitates interactions with bloodstream-suspended particles. Therefore, exact knowledge about interactions and effects of engineered NPs with the pulmonary microcirculation are instrumental for future application of this technology in patients. To unravel the real-time dynamics of intravenously delivered NPs and their effects in the pulmonary microvasculature, we employed intravital microscopy of the mouse lung. PEG amine-modified quantum dots (aQDs) with a low potential for biomolecule and cell interactions and carboxyl-modified quantum dots (cQDs) with a high interaction potential were used, representing two different NP subtypes. Only aQDs triggered rapid neutrophil recruitment in microvessels and their subsequent recruitment to the alveolar space. Application of specific inhibitors revealed that the aQDs induced neutrophil recruitment was linked to cellular degranulation, TNF-α, and DAMP release into the circulation, particularly extracellular ATP (eATP). Stimulation of the ATP-gated P2X7R induced the expression of E-selectin on microvascular endothelium with the subsequent E-selectin depended neutrophilic immune response. Leukocyte integrins (LFA-1 and MAC-1) mediated adhesion and reduction in neutrophil crawling velocity on the vascular surface. In summary, this study unravels the complex cascade of neutrophil recruitment during NP-induced sterile inflammation. Thereby we demonstrate novel adverse effects for NPs in the pulmonary microcirculation and provide critical insights for optimizing NP-based drug delivery and therapeutic intervention strategies, to ensure their efficacy and safety in clinical applications. ### Competing Interest Statement The authors have declared no competing interest.