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BackgroundTiO2 particles are commonly used as dietary supplements and may contain up to 36% of nano-sized particles (TiO2-NPs). Still impact and translocation of NPs through the gut epithelium is poorly documented.ResultsWe show that, in vivo and ex vivo, agglomerates of TiO2-NPs cross both the regular ileum epithelium and the follicle-associated epithelium (FAE) and alter the paracellular permeability of the ileum and colon epithelia. In vitro, they accumulate in M-cells and mucus-secreting cells, much less in enterocytes. They do not cause overt cytotoxicity or apoptosis. They translocate through a model of FAE only, but induce tight junctions remodeling in the regular ileum epithelium, which is a sign of integrity alteration and suggests paracellular passage of NPs. Finally we prove that TiO2-NPs do not dissolve when sequestered up to 24 h in gut cells.ConclusionsTaken together these data prove that TiO2-NPs would possibly translocate through both the regular epithelium lining the ileum and through Peyer’s patches, would induce epithelium impairment, and would persist in gut cells where they would possibly induce chronic damage.

Evidence suggests that endothelin-1 (ET-1) plays an essential role in brain inflammation. However, whether ET-1 contributes directly to blood-brain barrier (BBB) breakdown remains to be elucidated. Using an in vitro BBB model consisting of co-cultures of human primary astrocytes and brain microvascular endothelial cells (BMVECs), we first investigated the expression of ET-1 by BMVECs upon stimulation with tumour necrosis factor (TNF)-a, which plays an essential role in the induction and synthesis of ET-1 during systemic inflammatory responses. Increased ET-1 mRNA was detected in the human BMVECs 24 h after TNF-a treatment. This was correlated with an increase in ET-1 levels in the culture medium, as determined by sandwich immunoassay. Both TNF-a and ET-1 increased the permeability of human BMVECs to a paracellular tracer, sucrose, but only in the presence of astrocytes.The increase in BMVEC permeability by TNF-a was partially prevented by antibody neutralization of ET-1 and completely by monoclonal antibody against IL-1b. Concomitantly, TNF-a induced IL-1b mRNA expression by astrocytes in co-culture and this effect was partially prevented by ET-1 antibody neutralization. In parallel experiments, treatment of human primary astrocytes in single cultures with ET-1 for 24 h induced IL-1b mRNA synthesis and IL-1b protein secretion in the cell culture supernatant. Taken together, these results provide evidence for paracrine actions involving ET-1, TNF-a and IL-1b between human astrocytes and BMVECs, which may play a central role in BBB breakdown during CNS inflammation. Keywords: blood-brain barrier, endothelin-1, interleukin-1b, neuropathogenesis, tumour necrosis factor-a. Endothelin-1 (ET-1) is a 21-amino-acid peptide considered to belong to the cytokine family. Isolated from endothelial cells, ET-1 has been found to be one of the most potent vasoconstrictor peptides in humans (Yanagisawa et al. 1988). In addition, ET-1 has been implicated as a mediator of cerebrovascular responses in ischaemic stroke and subarachnoid haemorrhage (Masaoka et al. 1989;Kohno et al. 1990;Suzuki et al. 1990;Yasuda et al. 1990;Lampl et al. 1997). ET-1 also exerts a wide spectrum of effects on non-vascular tissues, including those of the CNS. Recent evidence demonstrated the neuropathological significance of ET-1, as shown by the correlation between increased blood-brain barrier (BBB) permeability (Narushima et al. 1999;Chi et al. 2001), and increased ET-1 levels in CSF and CNS parenchyma (Rolinski et al. 1999), although its prime role in this process and the underlying mechanisms remain to be elucidated.The role of cytokines such as interleukin (IL)-1b and tumour necrosis factor (TNF)-a in the neuropathogenesis of brain inflammation is well established (Griffin et al. 1994;Boven et al. 1999). IL-1b has been shown to be associated with the pathophysiology of demyelinating disorders such as Abbreviations used: BBB, blood-brain barrier; BMVEC, brain microvascular endothelial cell; ELISA, enzyme-linked immunosorbent assay; ET-1, endo...

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