Crucial role for human Toll-like receptor 4 in the development of contact allergy to nickel

A novel DC therapy with manipulation of MKK6 gene on nickel allergy in mice

Background

Although the activation of dermal dendritic cells (DCs) or Langerhans cells (LCs) via p38 mitogen-activated protein kinase (MAPK) plays a crucial role in the pathogenesis of metal allergy, the in vivo molecular mechanisms have not been identified and a possible therapeutic strategy using the control of dermal DCs or LCs has not been established. In this study, we focused on dermal DCs to define the in vivo mechanisms of metal allergy pathogenesis in a mouse nickel (Ni) allergy model. The effects of DC therapy on Ni allergic responses were also investigated.

Methods and Finding

The activation of dermal DCs via p38 MAPK triggered a T cell-mediated allergic immune response in this model. In the MAPK signaling cascade in DCs, Ni potently phosphorylated MAP kinase kinase 6 (MKK6) following increased DC activation. Ni-stimulated DCs could prime T cell activation to induce Ni allergy. Interestingly, when MKK6 gene-transfected DCs were transferred into the model mice, a more pronounced allergic reaction was observed. In addition, injection of short interfering (si) RNA targeting the MKK6 gene protected against a hypersensitivity reaction after Ni immunization. The cooperative action between T cell activation and MKK6-mediated DC activation by Ni played an important role in the development of Ni allergy.

Conclusions

DC activation by Ni played an important role in the development of Ni allergy. Manipulating the MKK6 gene in DCs may be a good therapeutic strategy for dermal Ni allergy.

Functions of Toll-like receptors as an inborn immunity component and their participation in the pathogenesis of dermatoses of different etiologies

In addition to serving as a mechanical barrier protecting our organism from the damaging effect of different factors, our skin also takes part in immune reactions developing in case of microbial intervention. Toll-like receptors (TLR) mediating recognition of molecular structures of pathogens are expressed in skin cells of different types initiating the development of adaptive immune reactions when associated with different ligands. The review presents data on the structure and functions of TLR, their localization in skin compartments and their role in the pathogenesis of skin diseases being of infectious etiology and non-infectious origin.

In vitro Toxicity Testing in the Twenty-First Century

The National Research Council (NRC) article “Toxicity Testing in the 21st Century: A vision and A Strategy” (National Research Council, 2007) was written to bring attention to the application of scientific advances for use in toxicity tests so that chemicals can be tested in a more time and cost efficient manner while providing a more relevant and mechanistic insight into the toxic potential of a compound. Development of tools for in vitro toxicity testing constitutes an important activity of this vision and contributes to the provision of test systems as well as data that are essential for the development of computer modeling tools for, e.g., system biology, physiologically based modeling. This article intends to highlight some of the issues that have to be addressed in order to make in vitro toxicity testing a reality in the twenty-first century.

Prophylactic vaccines mimic synthetic CpG oligonucleotides in their ability to modulate immune responses

Synthetic oligonucleotide ligands that bind to toll-like receptors are known to modulate the immune response via the activation of antigen presenting cells, and were therefore proposed as a novel form of vaccine adjuvant. Clinical-grade they are, however, not readily available. Here, we show that commonly used prophylactic vaccines for infectious diseases like measles, mumps and tuberculosis exhibit the same immune modulating behavior as synthetic CpG oligonucleotides in terms of their ability to stimulate IFN-α production and plasmacytoid dendritic cell maturation. Featuring the additional advantages of low-cost and proven safety, these vaccines could therefore be attractive alternatives to CpG oligonucleotides as adjuvants for immunotherapy. This previously undiscovered characteristic of prophylactic vaccines also sheds new light on the mechanisms by which they operate and is extremely interesting for vaccine development. Moreover, the finding that prophylactic vaccines trigger TLRs like synthetic oligonucleotides opens the possibility to predict the immune response of new vaccines.

Absorption of nickel, chromium, and iron by the root surface of primary molars covered with stainless steel crowns

Objective. The purpose of this study was to analyze the absorption of metal ions released from stainless steel crowns by root surface of primary molars. Study Design. Laboratory research: The study included 34 primary molars, exfoliated or extracted during routine dental treatment. 17 molars were covered with stainless-steel crowns for more than two years and compared to 17 intact primary molars. Chemical content of the mesial or distal root surface, 1 mm apically to the crown or the cemento-enamel junction (CEJ), was analyzed. An energy dispersive X-ray spectrometer (EDS) was used for chemical analysis. Results. Higher amounts of nickel, chromium, and iron (5-6 times) were found in the cementum of molars covered with stainless-steel crowns compared to intact molars. The differences between groups were highly significant (P < .001). Significance. Stainless-steel crowns release nickel, chromium, and iron in oral environment, and the ions are absorbed by the primary molars roots. The additional burden of allergenic metals should be reduced if possible.

Lack of the purinergic receptor P2X(7) results in resistance to contact hypersensitivity

Engagement of P2X₇ on mouse dendritic cells, presumably by ATP released in response to contact allergen, is needed for IL-1β production and the sensitization phase of contact hypersensitivity.

Sensitization to contact allergens requires activation of the innate immune system by endogenous danger signals. However, the mechanisms through which contact allergens activate innate signaling pathways are incompletely understood. In this study, we demonstrate that mice lacking the adenosine triphosphate (ATP) receptor P2X₇ are resistant to contact hypersensitivity (CHS). P2X₇-deficient dendritic cells fail to induce sensitization to contact allergens and do not release IL-1β in response to lipopolysaccharide (LPS) and ATP. These defects are restored by pretreatment with LPS and alum in an NLRP3- and ASC-dependent manner. Whereas pretreatment of wild-type mice with P2X₇ antagonists, the ATP-degrading enzyme apyrase or IL-1 receptor antagonist, prevents CHS, IL-1β injection restores CHS in P2X₇-deficient mice. Thus, P2X₇ is a crucial receptor for extracellular ATP released in skin in response to contact allergens. The lack of P2X₇ triggering prevents IL-1β release, which is an essential step in the sensitization process. Interference with P2X₇ signaling may be a promising strategy for the prevention of allergic contact dermatitis.