Non-Functionalized Ultrasmall Silica Nanoparticles Directly and Size-Selectively Activate T Cells.

Sub-micron-sized silica nanoparticles, even as small as 10-20 nm in diameter, are well-known for their activation of mononuclear phagocytes. In contrast, the cellular impact of those <10 nm [ i.e.

Pro-inflammatory adjuvant properties of pigment-grade titanium dioxide particles are augmented by a genotype that potentiates interleukin 1β processing.

Background: Pigment-grade titanium dioxide (TiO) particles are an additive to some foods (E171 on ingredients lists), toothpastes, and pharma-/nutraceuticals and are absorbed, to some extent, in the human intestinal tract. TiO can act as a modest adjuvant in the secretion of the pro-inflammatory cytokine interleukin 1β (IL-1β) when triggered by common intestinal bacterial fragments, such as lipopolysaccharide (LPS) and/or peptidoglycan. Given the variance in human genotypes, which includes variance in genes related to IL-1β secretion, we investigated whether TiO particles might, in fact, be more potent pro-inflammatory adjuvants in cells that are genetically susceptible to IL-1β-related inflammation.

Imaging flow cytometry assays for quantifying pigment grade titanium dioxide particle internalization and interactions with immune cells in whole blood.

Pigment grade titanium dioxide is composed of sub-micron sized particles, including a nanofraction, and is widely utilized in food, cosmetic, pharmaceutical, and biomedical industries. Oral exposure to pigment grade titanium dioxide results in at least some material entering the circulation in humans, although subsequent interactions with blood immune cells are unknown. Pigment grade titanium dioxide is employed for its strong light scattering properties, and this work exploited that attribute to determine whether single cell-particle associations could be determined in immune cells of human whole blood at "real life" concentrations.

Reduction of T-Helper Cell Responses to Recall Antigen Mediated by Codelivery with Peptidoglycan the Intestinal Nanomineral-Antigen Pathway.

Naturally occurring intestinal nanomineral particles constituently form in the mammalian gut and trap luminal protein and microbial components. These cargo loaded nanominerals are actively scavenged by M cells of intestinal immune follicles, such as Peyer's patches and are passed to antigen-presenting cells. Using peripheral blood mononuclear cell populations as an model of nanomineral uptake and antigen presentation, we show that monocytes avidly phagocytose nanomineral particles bearing antigen and peptidoglycan (PGN), and that the presence of PGN within particles downregulates their cell surface MHC class II and upregulates programmed death receptor ligand 1.

Synthetic mimetics of the endogenous gastrointestinal nanomineral: Silent constructs that trap macromolecules for intracellular delivery.

Amorphous magnesium-substituted calcium phosphate (AMCP) nanoparticles (75-150nm) form constitutively in large numbers in the mammalian gut. Collective evidence indicates that they trap and deliver luminal macromolecules to mucosal antigen presenting cells (APCs) and facilitate gut immune homeostasis. Here, we report on a synthetic mimetic of the endogenous AMCP and show that it has marked capacity to trap macromolecules during formation.

Intestinal APCs of the endogenous nanomineral pathway fail to express PD-L1 in Crohn's disease.

Crohn's disease is a chronic inflammatory condition most commonly affecting the ileum and colon. The aetiology of Crohn's disease is complex and may include defects in peptidoglycan recognition, and/or failures in the establishment of intestinal tolerance. We have recently described a novel constitutive endogenous delivery system for the translocation of nanomineral-antigen-peptidoglycan (NAP) conjugates to antigen presenting cells (APCs) in intestinal lymphoid patches.

Pharmaceutical/food grade titanium dioxide particles are absorbed into the bloodstream of human volunteers.

Background: Exposure to persistent engineered nano and micro particles via the oral route is well established. Animal studies have demonstrated that, once ingested, a small proportion of such particles translocate from the gastrointestinal tract to other tissues. Exposure to titanium dioxide is widespread via the oral route, but only one study has provided indirect evidence (total titanium analyses) of absorption into the blood stream in humans.

An endogenous nanomineral chaperones luminal antigen and peptidoglycan to intestinal immune cells.

In humans and other mammals it is known that calcium and phosphate ions are secreted from the distal small intestine into the lumen. However, why this secretion occurs is unclear. Here, we show that the process leads to the formation of amorphous magnesium-substituted calcium phosphate nanoparticles that trap soluble macromolecules, such as bacterial peptidoglycan and orally fed protein antigens, in the lumen and transport them to immune cells of the intestinal tissue.

Artefactual nanoparticle activation of the inflammasome platform: in vitro evidence with a nano-formed calcium phosphate.

Aim: To determine whether in vitro experimental conditions dictate cellular activation of the inflammasome by apatitic calcium phosphate nanoparticles.

Material & Methods: The responses of blood-derived primary human cells to in situ-formed apatite were investigated under different experimental conditions to assess the effect of aseptic culture, cell rest and duration of particle exposure. Cell death and particle uptake were assessed, while IL-1β and caspase 1 responses, with and without lipopolysaccharide prestimulation, were evaluated as markers of inflammasome activation.

Immuno-inhibitory PD-L1 can be induced by a peptidoglycan/NOD2 mediated pathway in primary monocytic cells and is deficient in Crohn's patients with homozygous NOD2 mutations.

Peptidoglycan (PGN) is a ubiquitous bacterial membrane product that, despite its well known pro-inflammatory properties, has also been invoked in immuno-tolerance of the gastrointestinal tract. PGN-induced mucosal IL-10 secretion and downregulation of Toll like receptors are potential mechanisms of action in the gut but there are few data on tolerogenic adaptive immune responses and PGN. Here, using blood-derived mononuclear cells, we showed that PGN induced marked cell surface expression of PD-L1 but not PD-L2 or CD80/CD86, and specifically in the CD14(+) monocytic fraction.

Origin and fate of dietary nanoparticles and microparticles in the gastrointestinal tract.

Humans have evolved with oral exposure to dietary microparticles and nanoparticles as a normal occurrence but the ever-growing exploitation of nanotechnology is likely to increase exposure further, both qualitatively and quantitatively. Moreover, unlike the situation with respirable particles, relatively little is known about gastrointestinal intake and handling of nanoparticles. With a long term interest in gut exposure and responses to dietary microparticles, our group is now applying its expertise to nanoparticles in the gastrointestinal tract.

Dietary microparticles and their impact on tolerance and immune responsiveness of the gastrointestinal tract.

Dietary microparticles are non-biological bacterial-sized particles of the gastrointestinal lumen that occur due to endogenous formation (calcium phosphate) or following oral exposure (exogenous microparticle). In the UK, about 40 mg (10(12)) of exogenous microparticles are ingested per person per day, through exposure to food additives, pharmaceutical/supplement excipients or toothpaste constituents. Once ingested, exogenous microparticles are unlikely to pass through the gastrointestinal tract without adsorbing to their surfaces some ions and molecules of the intestinal lumen.

Low dietary calcium levels modulate mucosal caspase expression and increase disease activity in mice with dextran sulfate sodium induced colitis.

Dietary calcium (Ca) positively modulates the susceptibility to colon cancer, but its effects on related or earlier colonic pathologies, such as inflammation and mucosal dysregulation, are poorly understood. We tested the effects of differing dietary Ca levels on acute dextran sulfate sodium (DSS)-induced colitis in mice. BALB/c mice received a normal Ca (NCa) diet (0.