Inhalation of rod-like carbon nanotubes causes unconventional allergic airway inflammation.

BACKGROUND: Carbon nanotubes (CNT) represent a great promise for technological and industrial development but serious concerns on their health effects have also emerged. Rod-shaped CNT are, in fact, able to induce asbestos-like pathogenicity in mice including granuloma formation in abdominal cavity and sub-pleural fibrosis. Exposure to CNT, especially in the occupational context, happens mainly by inhalation. However, little is known about the possible effects of CNT on pulmonary allergic diseases, such as asthma. METHODS: We exposed mice by inhalation to two types of multi-walled CNT, rigid rod-like and flexible tangled CNT, for four hours a day once or on four consecutive days. Early events were monitored immediately and 24 hours after the single inhalation exposure and the four day exposure mimicked an occupational work week. Mast cell deficient mice were used to evaluate the role of mast cells in the occurring inflammation. RESULTS: Here we show that even a short-term inhalation of the rod-like CNT induces novel innate immunity-mediated allergic-like airway inflammation in healthy mice. Marked eosinophilia was accompanied by mucus hypersecretion, AHR and the expression of Th2-type cytokines. Exploration of the early events by transcriptomics analysis reveals that a single 4-h exposure to rod-shaped CNT, but not to tangled CNT, causes a radical up-regulation of genes involved in innate immunity and cytokine/chemokine pathways. Mast cells were found to partially regulate the inflammation caused by rod-like CNT, but also alveaolar macrophages play an important role in the early stages. CONCLUSIONS: These observations emphasize the diverse abilities of CNT to impact the immune system, and they should be taken into account for hazard assessment.

Functional Beta2-Integrins Restrict Skin Inflammation In Vivo.

Beta2-integrins and the important integrin regulator kindlin-3 are essential for leukocyte trafficking, but the role of beta2-integrins in regulating inflammation is still incompletely understood. Here, we have investigated skin inflammation in a mouse model where the kindlin-3 binding site in the beta2-integrin has been mutated (TTT/AAA-beta2-integrin knock-in), leading to expressed but dysfunctional integrins. We show that, surprisingly, neutrophil trafficking into the inflamed skin in a contact hypersensitivity model is normal in these mice, although trafficking of T cells and eosinophils into the skin is reduced. Instead, expression of dysfunctional integrins leads to increased mast cell and dendritic cell numbers in the skin, increased inflammatory cytokine production in the inflamed skin in vivo, and in mast cells in vitro. Furthermore, expression of dysfunctional integrins leads to increased dendritic cell activation and migration to lymph nodes and increased Th1 responses in vivo. Therefore, the kindlin-3/integrin interaction is important for trafficking of T cells and eosinophils but not absolutely required for neutrophil trafficking into the inflamed skin. Functional beta2-integrins also have a major role in restricting the immune response in the inflamed skin and lymph nodes in vivo, likely through effects on mast cell and dendritic cell numbers and activation.