Factors affecting T cell responses induced by fully synthetic glyco-gold-nanoparticles.

We have synthesized and characterized nearly monodisperse and highly pure gold nanoparticles (2 and 5 nm) coated with non-immunoactive mono- and disaccharides, modelled after the capsular polysaccharide of serogroup A of the Neisseria meningitidis bacterium. We have used them to test their ability to induce immune cell responses as a consequence of their multivalency. The results indicate that they are indeed immunoactive and that immunoactivity is strongly dependent on size, and larger, 5 nm nanoparticles perform far better than smaller, 2 nm ones. Immune response (activation of macrophages) initiates with the whole nanoparticle recognition by the surface of antigen-presenting cells, independent of the saccharide oligomerization (or charge) on the nanoparticle surface. The induction of T cell proliferation and the increase of IL-2 levels, a consequence of the expression of MHC II involved in antigen presentation, require the presence of a disaccharide on the nanoparticle, not just a monosaccharide. A possible explanation is that, at this stage, the saccharides are detached from the gold surface. These results may provide leads for designing new saccharide-based, nanoparticle-conjugate vaccines.

Expression of functional GPR35 in human iNKT cells.

The aim of this study was to examine the expression of G protein-coupled receptor (GPR)35 in human invariant natural killer T (iNKT) cells and to determine the functional effects induced by selective activation of this receptor. RT-PCR analysis showed that both human iNKT cells and resting PBMC expressed GPR35; GPR35 protein resulted mostly localized in the plasma membrane, while it internalized in punctate intracellular structures following specific receptor activation (Western blot and immunofluorescence/confocal microscopy analysis). The specific activation of GPR35 by selective receptor agonists [l-kynurenic acid (KYNA)] or 1,4-dihydro-5-(2-propoxyphenyl)-7H-1,2,3-triazolo [4,5-d]pyrimidine-7-one (zaprinast)] functionally correlated with a significant reduction in IL-4 release from alpha-galactosylceramide (alpha-GalCer)-activated human iNKT cells, and this effect resulted mediated by pertussis toxin (PTX)-sensitive Gi/o proteins. In conclusion, our results demonstrate that human iNKT cells express GPR35 functionally active in reducing IL-4 release.

Anti-inflammatory and vascularprotective properties of 8-prenylapigenin.

Flavonoids display several biological activities, but exhibit poor oral absorption and rapid metabolism. To improve their pharmacological profile four C8-prenyl flavonoids, structurally related to the anti-inflammatory lead apigenin, were synthesized, and the two least cytotoxic (IC(50)>30 microM) compounds [8-prenylnaringenin (8-PN) and 8-prenylapigenin (8-PA)] in RAW 264.7 murine macrophages were assayed against a panel of biological targets. The anti-inflammatory properties of these compounds were evaluated in an in vitro model of inflammation [cells exposed to 0.1 microg/ml lipopolysaccharide (LPS) for 24h]. Both 8-PN and 8-PA were equally effective and potent in inhibiting the LPS-induced gene expression [tumor necrosis factor (TNF)-alpha, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2] (RT-PCR) and release (ELISA) of pro-inflammatory mediators [TNF-alpha, NO, prostaglandin (PG)E(2)], through mechanisms involving the inhibition of nuclear factor-kappaB (NF-kappaB) activation (EMSA) and reactive oxygen species accumulation [2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) determination]. One-digit nM concentrations of 8-PN or 8-PA induced a significant increase in the basal production of the atheroprotective prostacyclin (PGI(2)) by human umbilical vein endothelial cells (HUVEC), with maximal effects at 10 nM. Both NS-398, a specific COX-2 inhibitor, and ICI 182 780, a non-selective estrogen receptor antagonist, abolished the activity of these compounds, suggesting a COX- and estrogen receptor-dependent mechanism of activity. 8-PA, a weaker estrogenic compound than 8-PN, resulted only 2-fold less potent than 8-PN in potentiating PGI(2) production by HUVEC, qualifying this C8-prenyl flavonoid as a lead for the rational design of new anti-inflammatory and vascularprotective compounds.

Alpha-galactosylceramide modulates the induction of indoleamine 2,3-dioxygenase in antigen presenting cells.

The glycolipid alpha-galactosylceramide (alpha-GalCer), when presented on CD1 molecules by antigen presenting cells (APCs) to invariant NKT (iNKT cells), is a potent immunomodulator. Indoleamine 2,3-dioxygenase (IDO), an enzyme catalyzing the catabolism of L-tryptophan along the kynurenine pathway, is inducible in APC and represents one of the main endogenous mechanisms of T cell homeostasis, peripheral tolerance and immunosuppression. No data have been published yet on the effect of alpha-GalCer on IDO in APC. We aimed to determine if: (1) alpha-GalCer modulates IDO in APC; (2) the alpha-GalCer-induced effect on IDO correlates with the production by APC of active compounds; (3) the medium from alpha-GalCer-treated APC is able to stimulate iNKT cells. From our results alpha-GalCer alone did not modify IDO expression (RT-PCR) in APC, but when human peripheral blood mononuclear cells (PBMC), monocytes, and monocytic cell lines (THP-1), expressing high levels of CD1d, were treated with interferon-gamma (IFN-gamma) plus alpha-GalCer a significant potentiation of IDO transcription was measured. This effect was not induced by increased IFN-gamma release by APC, and it was functionally correlated with increased L-kynurenine (L-KYN) release by alpha-GalCer-treated CD1d-transfected THP-1 cells. The medium of these cells stimulated iNKT hybridoma cells to release interleukin (IL)-2, while alpha-GalCer alone resulted ineffective. The data demonstrate that alpha-GalCer: (1) does not induce IFN-gamma release by APC; (2) potentiates IFN-gamma-induced IDO expression and function in APC; (2) requires CD1d molecules for inducing these effects; (3) induces the release by APC of compounds active in stimulating iNKT cells.