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.

Range-finding risk assessment of inhalation exposure to nanodiamonds in a laboratory environment.

This study considers fundamental methods in occupational risk assessment of exposure to airborne engineered nanomaterials. We discuss characterization of particle emissions, exposure assessment, hazard assessment with in vitro studies, and risk range characterization using calculated inhaled doses and dose-response translated to humans from in vitro studies. Here, the methods were utilized to assess workers' risk range of inhalation exposure to nanodiamonds (NDs) during handling and sieving of ND powder. NDs were agglomerated to over 500 nm particles, and mean exposure levels of different work tasks varied from 0.24 to 4.96 µg·m(-3) (0.08 to 0.74 cm(-3)). In vitro-experiments suggested that ND exposure may cause a risk for activation of inflammatory cascade. However, risk range characterization based on in vitro dose-response was not performed because accurate assessment of delivered (settled) dose on the cells was not possible. Comparison of ND exposure with common pollutants revealed that ND exposure was below 5 µg·m(-3), which is one of the proposed exposure limits for diesel particulate matter, and the workers' calculated dose of NDs during the measurement day was 74 ng which corresponded to 0.02% of the modeled daily (24 h) dose of submicrometer urban air particles.

Smad3 signal transducer regulates skin inflammation and specific IgE response in murine model of atopic dermatitis.

Atopic dermatitis (AD) is a common chronic inflammatory skin disease characterized by itchy, dry, and inflamed skin. Transforming growth factor (TGF)-beta is an important fibrogenic and immunomodulatory factor that regulates cellular processes in the injured and inflamed skin. This study examines the role of the TGF-beta-Smad signaling pathway using Smad3-deficient mice in a murine model of AD. Dermatitis was induced in mice by epicutaneous application of ovalbumin (OVA) applied in a patch to tape-stripped skin. OVA-specific IgE and IgG2a antibody levels were measured by ELISA. Skin biopsies from sensitized skin areas were used for RNA isolation, histology, and immunohistochemical examination. The thickness of dermis was significantly reduced in OVA-sensitized skin of Smad3-/- mice. The defect in the dermal thickness was accompanied by a decrease in the expression of mRNA for proinflammatory cytokines IL-6 and IL-1beta in the OVA-sensitized skin. In contrast, the number of mast cells was significantly increased in OVA-sensitized skin of Smad3-/- mice, which also exhibited elevated levels of OVA-specific IgE. These results demonstrate that the Smad3-pathway regulates allergen-induced skin inflammation and systemic IgE antibody production in a murine model AD. The Smad3 signaling pathway might be a potential target in the therapy of allergic skin diseases.

Smad3 -signalling and Th2 cytokines in normal mouse airways and in a mouse model of asthma.

This study investigates the role of Smad3 signalling for the T-helper2 (Th2) cytokine homeostasis in normal lungs and in a mouse model of asthma. We used mice deficient for Smad3, a central part of the major signal transduction pathway for TGF-beta and other related cytokines, and a mouse model for allergic asthma with ovalbumin (OVA) as the antigen. Compared to wild type mice, naive (unmanipulated) Smad3-/- mice exhibited significantly increased levels of proinflammatory cytokines and IL-4 as well as the Th2 associated transcription factor GATA-3 in the lung tissue and bronchoalveolar lavage (BAL). In the asthma model, mucin secretion and airway hyperresponsiveness (AHR) after allergen exposure was significantly increased in the Smad3-/- mice as compared to wild type (WT) mice. IL-4 levels in Smad3-/- were similar to those encountered in WT mice but IL-13 levels were decreased in the airways of OVA sensitized Smad3-/- mice compared to corresponding WT mice. The results indicate that a lack of Smad3 dependent signalling in the normal state will lead to an increase in the GATA-3 levels and as a result of this the levels of IL-4 increase. However, the lack of Smad3 also seems to inhibit expression of some cytokines, especially IL-13. Our results also indicate that in the inflammatory state TGF-beta or related cytokines functions to counterbalance the effects of IL-4 rather than to critically regulate its expression.

Intranasal exposure to Stachybotrys chartarum enhances airway inflammation in allergic mice.

RATIONALE: Exposure to building dampness, often associated with growth of microbes such as Stachybotrys chartarum, has been linked to respiratory symptoms. We have shown previously in a murine model that exposure to S. chartarum can induce lung inflammation characterized by infiltration of neutrophils and lymphocytes; this process is regulated by proinflammatory cytokines and leucocyte-attracting chemokines. OBJECTIVES: Because an atopic predisposition may influence the response to microbes, we examined the effects of S. chartarum on allergic mice in an experimental model. BALB/c mice were sensitized to ovalbumin by intraperitoneal injections and exposed for 3 wk to spores of S. chartarum. MEASUREMENTS AND MAIN RESULTS: Numbers of eosinophils and neutrophils were drastically increased in bronchoalveolar fluid from these mice as compared with the ovalbumin-sensitized/challenged mice or those exposed to S. chartarum without ovalbumin sensitization. Histologic sections showed severe granulomatous inflammatory cell infiltrates in all compartments of the lung, including peribronchial, perivascular, and alveolar spaces. The mRNA levels of proinflammatory cytokines interleukin-1beta and tumor necrosis factor alpha and the chemokine CCL3/MIP-1alpha were also markedly increased in the lungs. Despite the enhancement of the pulmonary inflammatory reaction, exposure to S. chartarum spores significantly down-regulated airway hyperresponsiveness and showed a tendency to decrease levels of Th2 cytokines in the lung. CONCLUSION: Exposure to S. chartarum modulates the inflammatory reaction and airway hyperresponsiveness, depending on the allergic status of the exposed mice.