Surfactant protein D (SP-D) alters cellular uptake of particles and nanoparticles

Abstract

Surfactant protein D (SP-D) is primarily expressed in the lungs and modulates pro- and anti-inflammatory processes to toxic challenge, maintaining lung homeostasis. We investigated the interaction between NPs and SP-D and subsequent uptake by cells involved in lung immunity. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) measured NP aggregation, particle size and charge in native human SP-D (NhSP-D) and recombinant fragment SP-D (rfhSP-D). SP-D aggregated NPs, especially following the addition of calcium. Immunohistochemical analysis of A549 epithelial cells investigated the co-localization of NPs and rfhSP-D. rfhSP-D enhanced the co-localisation of NPs to epithelial A549 cells in vitro. NP uptake by alveolar macrophages (AMs) and lung dendritic cells (LDCs) from C57BL/6 and SP-D knock-out mice were compared. AMs and LDCs showed decreased uptake of NPs in SP-D deficient mice compared to wild-type mice. These data confirmed an interaction between SP-D and NPs, and subsequent enhanced NP uptake.

Keywords::

• Nanoparticles
• particle characterisation
• nanotoxicology
• mechanistic toxicology
• surfactant protein D

Acknowledgements

This work was funded under the Joint Environment and Human Health programme (NERC-EPSRC Project NE-E009395-1), funded by agencies of the UK Government: the Natural Environment Research Council (NERC), Department for Environment Food and Rural Affairs (Defra), Environment Agency (EA), Ministry of Defence (MOD) and the Medical Research Council (MRC). We gratefully acknowledge this financial support of the MRC ITTP Toxicology Unit for Z McKenzie. The European Centre for the Environment and Human Health (part of the Peninsula College of Medicine and Dentistry which is a joint entity of the University of Exeter, the University of Plymouth and the NHS in the South West) is supported by investment from the European Regional Development Fund and the European Social Fund Convergence Programme for Cornwall and the Isles of Scilly. MK and HWC developed the concepts in all the detailed experiments. MK, HWC and KK wrote and managed the proposal outlining the experimental design. MK and PD designed the DLS and ESEM experiments. PD prepared the materials and conducted the DLS and ESEM measurements; MK, KK and PD jointly interpreted and synthesised the protein-NP data to form conclusions. RAM, HWC, JM, ZM and MK designed the A549, AM, and LDC experiments. ZM conducted the A549 experiments; RD conducted the LDC experiments; and RAM conducted the AM experiments. MK, RAM, JM and HWC jointly interpreted and synthesised the cell data to form the protein-NP manuscript. MK, PD, RAM, JM, KK and HWC jointly revised the manuscript critically for important intellectual content.