A nanoparticle coated with sialic acid activates Siglec receptors on macrophages, improving survival from sepsis in mice and reducing inflammation in human tissues.

BackgroundParticulate matter has been shown to stimulate the innate immune system and induce acute inflammation. Therefore, while nanotechnology has the potential to provide therapeutic formulations with improved efficacy, there are concerns such pharmaceutical preparations could induce unwanted inflammatory side effects. Accordingly, we aim to examine the utility of using the proteolytic activity signatures of cysteine proteases, caspase 1 and cathepsin S (CTSS), as biomarkers to assess particulate-induced inflammation.MethodsPrimary peritoneal macrophages and bone marrow-derived macrophages from C57BL/6 mice and ctss −/− mice were exposed to micro- and nanoparticulates and also the lysosomotropic agent, L-leucyl-L-leucine methyl ester (LLOME). ELISA and immunoblot analyses were used to measure the IL-1β response in cells, generated by lysosomal rupture. Affinity-binding probes (ABPs), which irreversibly bind to the active site thiol of cysteine proteases, were then used to detect active caspase 1 and CTSS following lysosomal rupture. Reporter substrates were also used to quantify the proteolytic activity of these enzymes, as measured by substrate turnover.ResultsWe demonstrate that exposure to silica, alum and polystyrene particulates induces IL-1β release from macrophages, through lysosomal destabilization. IL-1β secretion positively correlated with an increase in the proteolytic activity signatures of intracellular caspase 1 and extracellular CTSS, which were detected using ABPs and reporter substrates. Interestingly IL-1β release was significantly reduced in primary macrophages from ctss −/− mice.ConclusionsThis study supports the emerging significance of CTSS as a regulator of the innate immune response, highlighting its role in regulating IL-1β release. Crucially, the results demonstrate the utility of intracellular caspase 1 and extracellular CTSS proteolytic activities as surrogate biomarkers of lysosomal rupture and acute inflammation. In the future, activity-based detection of these enzymes may prove useful for the real-time assessment of particle-induced inflammation and toxicity assessment during the development of nanotherapeutics.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-016-0129-5) contains supplementary material, which is available to authorized users.

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Inhibitors of p38 mitogen‐activated protein kinase (MAPK) are currently being pursued as therapeutics in inflammatory conditions, but many candidates have demonstrated limited efficacy or toxicity issues to date. Nanoformulation of p38 MAPK inhibitors may overcome these challenges, by enabling controlled release and targeted delivery. Thus, the aim of this study was to develop a nanoformulation of the p38 MAPK inhibitor GSK 678361A and subsequently validate its anti‐inflammatory efficacy in vitro, versus the drug in its free format. Poly(lactic‐co‐glycolic acid) nanoparticles encapsulating GSK 678361A were prepared via a salting‐out method and characterised by photon correlation spectroscopy, scanning electron microscopy and high‐performance liquid chromatography. The anti‐inflammatory effect of both free and nanoformulated GSK 678361A was evaluated in cultures of lipopolysaccharide‐stimulated macrophages, with subsequent enzyme‐linked immunosorbent assay analysis of TNF‐α and IL‐6 providing readouts of efficacy. A controlled release nanoformulation of GSK 678361A was successfully developed, with physicochemical characterisation revealing an average particle diameter of 115.5 ± 3.5 nm and polydispersity index of 0.13 ± 0.03, indicative of a homogeneous size distribution. GSK 678361A loading was quantified at 10.1 ± 0.4 µg per mg of poly(lactic‐co‐glycolic acid), equating to an entrapment efficiency of approximately 50%. When tested in cultures of lipopolysaccharide‐stimulated macrophages, GSK 678361A nanoparticles inhibited the production of pro‐inflammatory cytokines to an extent that was largely comparable with the free drug, although superior efficacy of the nanoformulation was observed at selected doses. These studies indicate that GSK 678361A may be successfully nanoformulated without loss of drug activity, warranting further evaluation in models of inflammation in vivo. © 2016 The Authors. Journal of Interdisciplinary Nanomedicine published by John Wiley & Sons Ltd and the British Society for Nanomedicine