Birch pollen-specific subcutaneous immunotherapy reduces ILC2 frequency but does not suppress IL-33 in mice.

BACKGROUND: The underlying mechanism of allergen-specific subcutaneous immunotherapy (SCIT) is not yet fully understood, but suppression of allergen-specific Th2 cells and production of allergen-specific IgG4 antibodies are two hallmarks. The impact on the innate arm of the immune system is far less clear. OBJECTIVE: The aim of this study was to investigate the effect of birch pollen (BP) SCIT on the innate immune response in a BP SCIT mouse model. METHODS: Mice with birch pollen-induced allergic airway inflammation received weekly subcutaneous immunotherapy injections with birch pollen extract (BPE) adsorbed to alum. The effect of the BP SCIT on innate cytokine levels in lung, the number and the functionality of ILC2s and the airway inflammation was determined. RESULTS: Mice with BP allergy had an increased level of the innate cytokines IL-33, IL-25, GM-CSF and IL-5+ ILC2s in the lungs. BP SCIT suppressed the number of IL-5+ ILC2s, mast cell tryptase release, Th2 cytokine production, eosinophil recruitment and peribronchial inflammatory infiltrates. In contrast, innate cytokine production and collagen deposition in the airways were not affected. CONCLUSION AND CLINICAL RELEVANCE: BP SCIT is able to suppress the adaptive and part of the innate immune response, but this is not sufficient to inhibit collagen deposition and the IL-33 expression in the airways in mice.

Indoor Pollutant Hexabromocyclododecane Has a Modest Immunomodulatory Effect on House Dust Mite Induced Allergic Asthma in Mice.

Hexabromocyclododecane (HBCD) has been recognized as an indoor pollutant. HBCD is added as a flame retardant to many consumer products and leaches from the products into house dust. HBCD might be potentially hazardous to the airways because of inhalation of house dust. Sensitization to house dust mite (HDM) is a risk factor for the development of allergic asthma. In this study, we examined whether HBCD can affect the immune response to HDM allergens. Bone-marrow-derived dendritic cells (BMDCs) were exposed simultaneously to HBCD and HDM in vitro. HBCD enhanced oxidative stress in HDM-pulsed BMDCs, which was accompanied by a higher production of Interleukin (IL)-6 and -10. Adoptive transfer of HDM/HBCD-exposed BMDCs into naïve mice resulted in enhanced levels of IL-17A after inhalational challenge with HDM. Direct mucosal exposure to HBCD during HDM inhalation enhanced IL-4 or IL-17A production, depending on the HDM extract used, but did not aggravate the eosinophilic airway inflammation or airway hyper-reactivity. Our results indicate that exposure to HBCD can have a mild immune-modulating effect by enhancing the inflammatory cytokine production in response to inhaled HDM in mice.

Birch pollen immunotherapy in mice: inhibition of Th2 inflammation is not sufficient to decrease airway hyper-reactivity.

BACKGROUND: Suppression of Th2 cytokine production by allergen-specific Th2 cells is considered to be critical for the suppression of allergic symptoms by subcutaneous immunotherapy. The aim of this study was to develop a mouse model for birch pollen (BP) immunotherapy to elucidate the underlying mechanisms that contribute to the improvement of clinical symptoms. METHODS: Mice with BP-induced allergic airway inflammation received weekly subcutaneous immunotherapy (SCIT) injections with BP extract (BPE) adsorbed to alum. The effect of an increasing dose of BPE adsorbed to a fixed concentration of alum on the suppression of airway inflammation and airway hyper-responsiveness (AHR) was determined. After 2, 4, 6 or 8 immunotherapy injections, the mice were rechallenged with the same allergen and all hallmarks of allergic asthma were evaluated. RESULTS: Suppression of the immunological parameters by immunotherapy was dependent on the BPE dose. Two injections were sufficient to suppress IL-4, IL-5, IL-13, IL-10 and IFN-γ production, eosinophil recruitment and peribronchial inflammatory infiltrates. BP-specific immunoglobulins were upregulated, but this was not sufficient to reduce AHR. Eight injections were needed to suppress AHR. The gradual reduction in AHR was inversely associated with the increase of BP IgG2a. CONCLUSIONS: BP SCIT induces an early suppression of Th2-mediated eosinophilic airway inflammation, but AHR is only effectively reduced after continued SCIT conceivably by allowing IgG2a antibody titres to build up.

SPG4 gene promoter regulation via Elk1 transcription factor.

The most common cause of autosomal dominant hereditary spastic paraplegia, that is characterized with axonal degeneration in corticospinal tracts and posterior columns, is known to be caused by mutations in the SPG4 gene which encodes spastin, a microtubule severing ATPase belonging to AAA family. Spastin promotes the formation of microtubule networks that are essential for axon growth and branching which are important for neuronal plasticity. Mutations observed in SPG4 gene of hereditary spastic paraplegia patients have been shown to cause reduced spastin levels. In addition to mutations, transcriptional regulation of spastin gene expression may also affect spastin level. ETS (E Twenty Six-specific)-domain transcription factor, Elk1, has been shown to be important for synaptic plasticity and interact with microtubules. In this study, we aimed to identify the critical promoter regions of SPG4 gene and effects of Elk on SPG4 gene expression. We identified 700 bp TATA-less promoter including a critical CpG island as an optimal promoter, and deletion of the CpG island gradually decreased the SPG4 promoter activity. In addition, we identified the binding sites of Elk1 on the SPG4 promoter by EMSA. Over-expression of Elk1 showed that it repressed the SPG4 promoter and also decreased spastin protein level in SHSY-5Y cells.

Immunotoxicity of organophosphate flame retardants TPHP and TDCIPP on murine dendritic cells in vitro.

Organophosphate flame retardants (PFRs) are commonly used as alternatives for the banned polybrominated diphenyl ethers (PBDEs) and are ubiquitously detected in indoor dust. PFRs can be potentially hazardous to respiratory health via the inhalation of house dust. Dendritic cells (DCs) are crucial in the immunological defense against pathogens in the airways. In respiratory allergy however, an aberrant immune response is induced against innocuous proteins, like house dust mite allergens. In this study, we examined whether exposure to PFRs Triphenylphosphate (TPHP) and Tris(1,3-dichloroisopropyl) phosphate (TDCIPP) affected activation/maturation of DCs at steady state and during exposure to house dust mite allergens (HDM). Bone marrow-derived dendritic cells (BMDCs) were exposed to a concentration range of each PFR (0.1-100 µM) with or without HDM in vitro to analyze the effect on the expression of major histocompatibility complex class II (MHCII), co-stimulatory molecules and cytokine production. Concentrations of TPHP and TDCIPP of ≥50 µM were cytotoxic to BMDCs. At these cytotoxic concentrations, TPHP exposure induced an activated phenotype in steady state DCs, while HDM exposed DCs acquired a tolerogenic phenotype. In contrast, TDCIPP exposure had no effect at steady state DCs but suppressed the expression of MHCII, costimulatory molecules, and the IL-6 production in HDM exposed DCs. The cytotoxic concentrations induced the anti-oxidant enzyme hemeoxigenase-1, which is a marker for oxidative stress. These results demonstrate that PFRs can be immunotoxic for DCs and suggest the necessity to evaluate the effects on the immune system on a cellular level during the risk assessment of these alternative flame retardants.

Indoor pollutant hexabromocyclododecane enhances house dust mite-induced activation of human monocyte-derived dendritic cells.

The indoor pollutant hexabromocyclododecane (HBCD) has been added as flame retardant to many consumer products but detaches and accumulates in house dust. Inhalation of house dust leads to exposure to house dust mite (HDM) allergens in the presence of HBCD. Activation of dendritic cells is crucial in the sensitization to HDM allergens. The current study examined whether exposure to HBCD affected activation/maturation of HDM-exposed human dendritic cells (DC). Human monocyte-derived DC (moDC) were exposed simultaneously to HDM and a concentration range of HBCD (0.1-20 µM) in vitro. HDM exposure of moDC induced expression of co-stimulatory molecule CD80 and production of pro-inflammatory cytokines interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α. However, simultaneous exposure of moDC to HBCD and HDM enhanced the expression of antigen presenting molecule HLA-DR, co-stimulatory molecule CD86 and pro-inflammatory cytokine IL-8 depending on the dose of HBCD. Our results indicate that simultaneous exposure of HDM and HBCD can enhance the antigen presentation and maturation/activation of DC.

Katanin-p80 gene promoter characterization and regulation via Elk1.

Katanin is an ATPase family member protein that participates in microtubule severing. It has heterodimeric structure consisting of 60 kDa (katanin-p60) and 80 kDa (katanin-p80) subunits encoded by KATNA1 and KATNB1 genes, respectively. Katanin-p60 has the enzymatic activity for microtubule severing, whereas katanin-p80 consists of multiple domains with different functions such as targeting katanin-p60 to the centrosome, augmenting microtubule severing by katanin-p60, and even suppressing microtubule severing. Despite the various important functions of katanin-p80, its transcriptional regulation has not been studied yet. Elk1 transcription factor has been shown to interact with microtubules and regulate the transcription of another microtubule severing protein, spastin. In spite of katanin's importance, and structural and functional similarities to spastin, there is no study on the transcriptional regulation of katanin yet. In this study, we aimed to characterize KATNB1 promoter and analyze the effects of Elk1 on katanin-p80 expression. We identified a 518- bp TATA-less promoter including a critical CpG island and GC boxes as an optimal promoter, and sequential deletion of CpG island and the GC elements gradually decreased the KATNB1 promoter activity. In addition, we showed Elk1 binding on the KATNB1 promoter by EMSA. We found that Elk1 activated KATNB1 promoter, and increased both mRNA and protein levels of katanin-p80 in SH-SY5Y cells. On the other hand, KCl treatment increasing SUMOylation decreased KATNB1 promoter activity. Since microtubule severing is an important cellular mechanism of which malfunctions result in serious diseases such as spastic paraplegia, Alzheimer's disease and cell cycle related disorders, identification of KATNB1 transcriptional regulation is crucial in understanding the coordination of microtubule severing activity by different proteins in the cells.