The inhibitory effect of naringenin on atopic dermatitis induced by DNFB in NC/Nga mice

Aims

Atopic dermatitis (AD) is a chronic and relapsing inflammatory dermatitis characterized by pruritic and eczematous skin lesions. Here, we investigated the therapeutic effect of the fruit flavonoid naringenin on DNFB induced atopic dermatitis mice model.

Main methods

AD-like skin lesion was induced by repetitive skin contact with DNFB in NC/Nga mice and the effects of the fruit flavonoid naringenin were evaluated on the basis of histopathological findings of skin, ear swelling and cytokine production of CD4⁺T cells.

Key findings

Intraperitoneal injection of naringenin for one week after DNFB challenge significantly lowered ear swelling and improved back skin lesions. In addition, naringenin significantly suppressed production of interferon-gamma (IFN-γ) by activated CD4⁺ T cells and serum IgE level. Furthermore, naringenin reduced DNFB-induced infiltration of eosinophils, mast cells, CD4⁺ T cells, and CD8⁺ T cells in skin lesions.

Significance

Naringenin may suppress the development of AD-like skin lesions in DNFB-treated NC/Nga mice by reducing IFN-γ production of activated CD4⁺ T cells, serum IgE levels and infiltration of immune cells to skin lesion.     

7,8,4′-Trihydroxyisoflavone Attenuates DNCB-Induced Atopic Dermatitis-Like Symptoms in NC/Nga Mice

Atopic dermatitis (AD) is characterized by chronic highly pruritic and relapsing inflammatory skin lesions. Despite its growing prevalence, therapeutic treatments remain limited. Natural immune modulators from herbal extracts or derivatives may be useful for treating AD symptoms. This study examined the effect of 7,8,4′-trihydroxyisoflavone (7,8,4′-THIF), a metabolite of soy isoflavone daidzin, on AD-like symptoms. Repeated epicutaneous application of 2,4-dinitrochlorobenzene (DNCB) was performed on the ear and dorsal skin of NC/Nga mice to induce AD-like symptoms and skin lesions, and 7,8,4′-THIF (200 and 400 nmol) or tacrolimus (100 µg) was applied topically for 3 weeks to assess their anti-pruritic effects. We found that 7,8,4′-THIF alleviated DNCB-induced AD-like symptoms as quantified by skin lesion, dermatitis score, ear thickness, and scratching behavior. Histopathological analysis demonstrated that 7,8,4′-THIF decreased DNCB-induced eosinophil and mast cell infiltration into skin lesions. We also found that 7,8,4′-THIF significantly alleviated DNCB-induced loss of water through the epidermal layer. In addition to reducing the DNCB-induced increase in serum IgE, 7,8,4′-THIF also lowered skin lesion levels of the chemokine thymus and activation regulated chemokine; Th2 cytokines interleukin (IL)-4, IL-5, and IL-13; and Th1 cytokines IL-12 and interferon-γ. These results suggest that 7,8,4′-THIF might be a potential therapeutic candidate for the treatment of atopic dermatitis.     

Reactive nitrogen species formation in eosinophils and imbalance in nitric oxide metabolism are involved in atopic dermatitis-like skin lesions in NC/Nga mice

Nitric oxide (NO) and reactive nitrogen species (RNS) have been implicated in the pathogenesis of inflammatory diseases. However, the involvement of NO and RNS in atopic dermatitis (AD), a pruritic inflammatory skin diseases, is not fully understood. In this study, we investigated the contribution of NO and RNS to the development of AD-like skin lesions in NC/Nga mice, an animal model for human AD. AD-like skin lesions were observed in NC/Nga mice kept under conventional conditions but not in specific pathogen-free conditions. The expression of inducible NO synthase (iNOS) and endothelial NOS (eNOS) proteins was upregulated in the dermal lesions, and that of neuronal NOS (nNOS) was downregulated in the epidermal lesions of the skin. Although the concentrations of NO2(-) and NO3(-) were lower, protein-bound nitrotyrosine content was significantly increased in the skin lesions. Immunohistochemical localization of nitrotyrosine was observed in almost all eosinophils. These results suggest that RNS formation in eosinophils and imbalance of NO metabolism are involved in the pathogenesis of AD-like skin lesions in NC/Nga mice.     

Genuine traditional Korean medicine,Naju Jjok (Chung-Dae,Polygonum tinctorium) improves 2,4-dinitrofluorobenzene-induced atopic dermatitis-like lesional skin

PurposeNaju Jjok (NJJ, Polygonum tinctorium) is a clear heat and release toxin medicinal. It has been used to treat various inflammatory diseases and as a dye in clothing in traditional Korean medicine. However, the effect of NJJ on atopic dermatitis (AD) has not been elucidated. Therefore, we examined whether NJJ would have an inhibitory effect on AD using the mimic AD murine model and in vitro model.MethodsWe treated NJJ on 2,4-dinitrofluorobenzene (DNFB)-induced AD-like skin lesions in NC/Nga mice, phorbol myristate acetate/calcium ionophore A23187-stimulated human mast cell line (HMC-1) cells, and anti-CD3/anti-CD28-stimulated splenocytes. Histological analysis, ELISA, PCR, and Western blot analysis were performed.ResultsThe oral administration with NJJ suppressed the total clinical severity in DNFB-induced AD-like lesional skin. NJJ significantly suppressed the levels of inflammatory mRNA and protein in AD-like lesional skin. NJJ significantly suppressed the levels of IgE and interleukin-4 in the serum of DNFB-induced AD mice. The expression of mast cells-derived caspase-1 was suppressed by NJJ in AD-like lesional skin. In addition, topical application with NJJ improved clinical symptoms in DNFB-induced AD mice. The topical application with NJJ significantly suppressed the levels of IgE and histamine in the serum of DNFB-induced AD mice. NJJ suppressed the production and mRNA expression of TSLP by blockade of caspase-1 signal pathway in the activated HMC-1 cells. Furthermore, NJJ significantly decreased the production of tumor necrosis factor-α from the stimulated splenocytes.ConclusionsIn conclusion, these results propose curative potential of natural dye, NJJ by showing the scientific evidence on anti-AD effect of NJJ which has been used traditionally.     

Development of atopic dermatitis-like skin lesions in STAT6-deficient NC/Nga mice

Atopic dermatitis (AD) is a pruritic inflammatory skin disease characterized by elevation of plasma levels of total IgE, infiltration of mast cells and eosinophils, and the expression of cytokines by Th2 T cells. However, the role of Th2 cells in the pathogenesis of AD is not fully understood. In this study we examined the NC/Nga (NC) mouse model of AD and established STAT6-deficient (SATA6(-/-)) NC mice to investigate the relevance of IL-4-mediated immune responses. Surprisingly, these mice elicited AD-like skin lesions at equivalent frequency and time of onset compared with normal NC littermates. Histological features of the lesion in STAT6(-/-) NC mice fulfilled the criteria for the pathogenesis of AD, although these mice fail to produce IgE and Th2 cytokines. The lymph nodes proximal to the regions of skin that developed lesions exhibited massive enlargement elicited by the accumulation of activated IFN-gamma-secreting T cells. Moreover, caspase I, IL-18, IL-12, and IFN-gamma are found to be highly expressed at the skin lesion, occurring simultaneously with elevation of eotaxin 2 and CCR3 expression. Therefore, the Th2-mediated immune response is not necessary for the development of AD-like skin disease in NC mice. The skin microenvironment that favored IFN-gamma production tightly correlates with the skin disease in NC mice through the infiltration of eosinophils.     

Efficient Immuno-Modulation of TH1/TH2 Biomarkers in 2,4-Dinitrofluorobenzene-Induced Atopic Dermatitis: Nanocarrier-Mediated Transcutaneous Co-Delivery of Anti-Inflammatory and Antioxidant Drugs

The present study was conducted with the aim to investigate the immuno-modulatory and histological stabilization effects of nanocarrier–based transcutaneous co-delivery of hydrocortisone (HC) and hydroxytyrosol (HT). In this investigation, the clinical and pharmacological efficacies of nanoparticle (NP)-based formulation to alleviate 2,4-dinitrofluorobenzene (DNFB)-induced atopic dermatitis (AD) was explored by using an NC/Nga mouse model. Ex vivo visual examination of AD induction in experimental mice indicated remarkable control of NP-based formulations in reducing pathological severity of AD-like skin lesions. Therapeutic effectiveness of NP-based formulations was also evaluated by comparing skin thickness of AD-induced NP-treated mice (456±27 µm) with that of atopic mice (916±37 µm). Analysis of the immuno-spectrum of AD also revealed the dominance of NP-based formulations in restraining immunoglobulin-E (IgE), histamine, prostaglandin-E₂ (PGE₂), vascular endothelial growth factor-α (VEGF-α), and T-helper cells (T_H1/T_H2) producing cytokines in serum and skin biopsies of tested mice. These anti-AD data were further supported by histological findings that revealed alleviated pathological features, including collagen fiber deposition, fibroblasts infiltration, and fragmentation of elastic fibers in experimental mice. Thus, NP-mediated transcutaneous co-delivery of HC and HT can be considered as a promising therapy for managing immunological and histological spectra associated with AD.     

Inability of IL-12 to down-regulate IgE synthesis due to defective production of IFN-gamma in atopic NC/Nga mice.

NC/Nga mice raised in nonsterile circumstances spontaneously suffer from atopic dermatitis-like skin lesions with IgE hyperproduction. We investigated effects of rIL-12 on the IgE production in NC/Nga mice. rIL-12 administration was successful to suppress the increase of IgE levels in BALB/c mice immunized with OVA and aluminum hydroxide, but failed to abrogate that in NC/Nga mice. Both in vivo and in vitro IFN-gamma production induced by rIL-12 was less in NC/Nga mice than in BALB/c mice. Addition of rIFN-gamma to rIL-4 and LPS completely abrogated IgE production by B cells of BALB/c mice, but was insufficient to suppress it by B cells of NC/Nga mice. In splenic cells pretreated with Con A, STAT4 was phosphorylated at the tyrosine residue by addition of rIL-12, which was more weakly inducible in NC/Nga mice than in BALB/c mice. Finally, we examined the preventive ability of rIL-12 on the clinical aspects of atopic dermatitis in NC/Nga mice. rIL-12 administration resulted in exacerbation of development of the skin lesions and IgE production in NC/Nga mice raised in nonsterile circumstances. These results suggest that defective production of IFN-gamma by T cells less sensitive to IL-12 and low responsiveness of B cells to IFN-gamma may contribute to IgE hyperproduction in NC/Nga mice, and that IL-12 may have no ability to improve the clinical aspects of NC/Nga mice.     

Suppression of skin lesions by transdermal application of CpG-oligodeoxynucleotides in NC/Nga mice, a model of human atopic dermatitis

Atopic dermatitis (AD) is a pruritic inflammatory skin disease characterized by an elevation of the total IgE level in plasma, the infiltration of mast cells and eosinophils, and the expression of cytokines by Th2 cells. NC/Nga mice kept in conventional conditions are known to develop skin lesions resembling human AD. We examined in this study the alterations of immune response in NC/Nga mice kept in conventional conditions, following transdermal application of CpG-oligodeoxynucleotides (ODN), which plays a critical role in immunity via the augmentation of Th1-type and suppression of Th2-type responses. CpG-ODN remarkably changed the immune response from type Th2 to Th1 as determined from cytokine mRNA and Ab levels. The serum IgE level was decreased and the expression of IgG2a was up-regulated. The application of CpG-ODN to the skin also decreased inflammatory infiltration of mast cells, and suppression in the skin lesions was observed. Furthermore, the generation of regulatory T cells, which are considered immune suppressive T cells, was observed in the skin on treatment with CpG-ODN. These results suggested CpG-ODN is effective for immunotherapy in patients with AD, which is characterized by Th2-dominated inflammation.     

Inhibitory Effects of Heartwood Extracts of Broussonetia kazinoki Sieb on the Development of Atopic Dermatitis in NC/Nga Mice

We investigated the effects of a topically applied extract of the heartwood of Broussonetia kazinoki Sieb (B. kazinoki) on atopic dermatitis (AD)-like skin lesions induced by an extract of the house-dust mite Dermatophagoides farina in NC/Nga mice. We found that topically applied B. kazinoki extract suppressed the histological manifestations of AD-like skin lesions, and decreased the levels of plasma immunoglobulin E (IgE) and interleukin-4 (IL-4) in the mice. Moreover, B. kazinoki inhibited the induction of thymus-and-activation-regulated chemokine (TARC/CCL17), macrophage-derived chemokine (MDC/CCL22), and regulated-on-activation-normal T cell-expressed-and-secreted chemokine (RANTES/CCL5) in HaCaT cells activated by tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). In conclusion, our results suggest that B. kazinoki extract has therapeutic advantages in the treatment of AD.     

Pyridone 6, a pan-JAK inhibitor, ameliorates allergic skin inflammation of NC/Nga mice via suppression of Th2 and enhancement of Th17

Atopic dermatitis (AD) is a common pruritic inflammatory disease triggered by a defective skin barrier and immunodysregulation. AD has been considered a typical example of a Th2 response associated with allergic disease. In the early phases of the disease, symptoms include IgE hyperproduction, eosinophil accumulation, and mast cell activation; in the chronic phase, a Th1-dominant immune response is also observed at the sites of AD skin lesions. The role of IL-17-producing Th (Th17) cells in AD has not been established. In the current study, we found that pyridone 6 (P6), a pan-JAK inhibitor, delayed the onset and reduced the magnitude of skin disease in an AD-like skin-disease model of NC/Nga mice. P6 reduced IFN-γ and IL-13, whereas it enhanced IL-17 and IL-22 expression. In vitro, P6 also inhibited both Th1 and Th2 development, whereas it promoted Th17 differentiation from naive T cells when present within a certain range of concentrations. This was probably because P6 strongly inhibited STAT1, STAT5, and STAT6 phosphorylation, whereas STAT3 phosphorylation was less efficiently suppressed by P6 at the same concentration. Furthermore, IL-22 protects keratinocytes from apoptosis induced by IFN-γ, and administration of IL-17 and IL-22 partially ameliorated skin diseases in NC/Nga mice. These results suggested that the JAK inhibitor P6 is therapeutic for AD by modulating the balance of Th2 and Th17.     

Effect of Mouse Strain in a Model of Chemical-induced Respiratory Allergy

The inhalation of many types of chemicals is a leading cause of allergic respiratory diseases, and effective protocols are needed for the detection of environmental chemical–related respiratory allergies. In our previous studies, we developed a method for detecting environmental chemical–related respiratory allergens by using a long-term sensitization–challenge protocol involving BALB/c mice. In the current study, we sought to improve our model by characterizing strain-associated differences in respiratory allergic reactions to the well-known chemical respiratory allergen glutaraldehyde (GA). According to our protocol, BALB/c, NC/Nga, C3H/HeN, C57BL/6N, and CBA/J mice were sensitized dermally with GA for 3 weeks and then challenged with intratracheal or inhaled GA at 2 weeks after the last sensitization. The day after the final challenge, all mice were euthanized, and total serum IgE levels were assayed. In addition, immunocyte counts, cytokine production, and chemokine levels in the hilar lymph nodes (LNs) and bronchoalveolar lavage fluids (BALF) were also assessed. In conclusion, BALB/c and NC/Nga mice demonstrated markedly increased IgE reactions. Inflammatory cell counts in BALF were increased in the treated groups of all strains, especially BALB/c, NC/Nga, and CBA/J strains. Cytokine levels in LNs were increased in all treated groups except for C3H/HeN and were particularly high in BALB/c and NC/Nga mice. According to our results, we suggest that BALB/c and NC/Nga are highly susceptible to respiratory allergic responses and therefore are good candidates for use in our model for detecting environmental chemical respiratory allergens.     

Inhibitory effects of polysaccharide-rich extract of Phragmites rhizoma on atopic dermatitis-like skin lesions in NC/Nga mice

AimsPhragmites rhizoma was reported to have anti-oxidative and free radical scavenging activity. It also has been traditionally used to suppress inflammation. In the present study, we aimed to evaluate the topical effects of the polysaccharide-rich extract of P. rhizoma (PEP) on atopic dermatitis.Main methodsWe induced AD-like skin lesions by an extract of the house-dust mite Dermatophagoides farinae (Dfb) in NC/Nga mice, and then performed macroscopic analysis, immunohistochemical staining and measurement of total serum IgE and cytokine production by ELISA.Key findingsTopically applied PEP suppressed dermatitis with a decrease in dermatitis score and scratch number. The histological manifestations of atopic skin lesions including thickened epidermis and increased numbers of mast cells, polymorphonuclear leukocytes and nerve fibers were significantly attenuated. The activation of IgE and the levels of cytokines such as IFN-γ IL-4 and IL-10 were also decreased.SignificanceOur results indicated that PEP might have an inhibitory effect on atopic dermatitis-like lesion and be a promising natural resource in the treatment of atopic dermatitis.     

Effect of dendritic cells treated with CpG ODN on atopic dermatitis of Nc/Nga mice

Atopic dermatitis (AD) is a chronic inflammatory skin disease and the pathogenesis of AD is associated with the release of various cytokines/chemokines due to activated Th(2) immune responses. Synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG dinucleotide in the context of particular base sequence (CpG motifs) are known to have the immunostimulatory activities in mice and to convert from Th(2) to Th(1) immune responses in AD. We aimed to investigate that CpG ODN, especially phosphodiester form, can stimulate the protective immunity in NC/Nga mice with AD. We isolated BMDCs from NC/Nga mice and then, cultured with GM-CSF and IL-4 for 6 days, and treated for 2 days by either phosphorothioate ODN or phosphodiester ODN. CpG ODN-treated DCs resulted in more production of IL-12. When CpG ODN-treated DCs were intravenously injected into the NC/Nga mice, the NC/Nga mice with CpG ODN-treated DCs showed significant improvement of AD symptoms and decrease of IgE level. Histopathologically, the NC/Nga mice skin with CpG ODN-treated DCs showed the decreased IL-4 and TARC expression comparing with non-injected mice. These results may suggest that phosphodiester CpG ODN-treated DCs might function as a potent adjuvant for AD in a mouse model.     

Deletion polymorphisms in the promoter region of Fcgamma receptor IIB is not associated with antigen-specific IgG2a and IgG2b antibody responses in NC/Nga mice

Fcgamma receptor (R) IIB, a low-affinity FcR for IgG, inhibits B cell Ag R (BCR)-mediated activation when these two receptors are cross-linked by Ag and IgG-containing immune complexs (ICs). We found deletion polymorphisms in the promoter region of fcgr2b in NC/Nga mice, a model for human atopic dermatitis. NC/Nga mice produced significantly higher levels of ovalbumin (OVA)-specific IgG, IgG2a and IgG2b than did BALB/c mice. Analysis of (BALB/c x NC/Nga)F1 x BALB/c or (BALB/c x NC/Nga) F1 x NC/Nga backcross mice revealed that deletion polymorphisms of fcgr2b in NC/Nga mice does not directly regulate hyper OVA-specific IgG2a and IgG2b Ab responses.     

Effect of nodakenin on atopic dermatitis-like skin lesions

Nodakenin, derived from the roots of Angelica gigas Nakai, is an important natural resource and medicinal material with anti-allergic and anti- inflammatory activities. We have previously shown that nodakenin inhibits IgE/Ag-induced degranulation in mast cells. In this study, we investigated the inhibitory effect of nodakenin on 2,4-dinitrochlorobenzene (DNCB)-induced atopic dermatitis (AD)- like skin lesions in ICR mice. Scratching behavior, skin severity score, blood IgE level, and skin thickness were improved in DNCB-induced AD-like ICR mice. Our results showed that nodakenin suppressed the increase of AD-like skin lesions in ICR mice. These results suggest that nodakenin may be a potential therapeutic resource for AD as well as an adjunctive agent to control itching associated with AD.     

Effect of Pyeongwee-San (KMP6) on 2,4-dinitrofluorobenzene-induced atopic dermatitis-like skin lesions in NC/Nga mice

AimsRecently, some studies reported that digestive tract disease is closely associated with atopic dermatitis (AD). Pyeongwee-San (KMP6) is a Korean medicine, which has come onto the drugstore for the treatment of digestive tract disease. The aim of the present study was to examine whether KMP6 could suppress 2,4-dinitrofluorobenzene (DNFB)-induced AD-like skin lesions in NC/Nga mice.Main methodsMice were sensitized with DNFB by applying to shaved dorsal skin. At that time, the drugs or saline were orally administrated to DNFB-applied mice.Key findingsThe administration of KMP6 or glycyrrhizic acid (GL), a major component of KMP6, inhibited the scratching number in DNFB-induced AD model. The mRNA expressions of interleukin (IL)-4, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and CCR3 were upregulated by DNFB sensitization, but the upregulated mRNA expressions were significantly reduced by the administration of KMP6 or GL. In addition, the levels of IgE, histamine, and IL-4 were significantly reduced by the administration of KMP6 or GL in serum of DNFB-induced AD model. However, the level of IFN-γ in serum was significantly increased by KMP6 or GL. KMP6 or GL also significantly inhibited the numbers of inflammatory cells, mast cells, and protein level of IL-4 in lesions of DNFB-induced AD model. Finally, KMP6 or GL significantly decreased the productions of IL-4, IFN-γ, and TNF-α in anti-CD3 plus anti-CD28 antibody-stimulated splenocytes.SignificanceKMP6 showed anti-atopic potential in this setting; hence we suggest it as a potential prospect for anti-atopic agent besides being just a medicine for the stomach and bowels.     

Therapeutic effect of tyndallized Lactobacillus rhamnosus IDCC 3201 on atopic dermatitis mediated by down‐regulation of immunoglobulin E in NC/Nga mice

The therapeutic effect of oral administration of Lactobacillus rhamnosus IDCC 3201 tyndallizate (RHT3201) on atopic dermatitis (AD)‐like skin lesions in NC/Nga mice were investigated. After induction of dermatitis in NC/Nga mice with house‐dust mite extract, each group was fed RHT3201 with 1 × 10⁸, 1 × 10⁹, or 1 × 10¹⁰ cells orally once a day for 8 weeks. Dermatitis scores and frequency of scratching were improved by oral feeding with RHT3201. In contrast to the control group, RHT3201‐fed mice showed significantly down‐regulated mast cell numbers and serum immunoglobulin E (IgE) concentrations had significantly less IL4 in their axillary lymph node cells. The therapeutic effect of RHT3201 was found to be dose‐dependent. These findings indicate that RHT3201 has potential for treating AD.     

The mechanism of a defective IFN-gamma response to bacterial toxins in an atopic dermatitis model, NC/Nga mice, and the therapeutic effect of IFN-gamma, IL-12, or IL-18 on dermatitis

NC/Nga (NC) mice raised under conventional conditions (Conv. NC mice) spontaneously develop dermatitis similar to human atopic dermatitis, whereas NC mice raised under the specific pathogen-free conditions do not develop dermatitis. In the present study, we show that the representative Th1 cytokine, IFN-gamma levels in the sera of NC mice, injected with either staphylococcal enterotoxin B or endotoxin (LPS), to be severalfold lower than those of normal mice. The low IFN-gamma response to staphylococcal enterotoxin B was correlated to the lack of regular Vbeta8(+) T cells and Vbeta8(+) NK T cells, and the low IFN-gamma response to LPS was correlated to an impaired IL-18 production of macrophages. The CD3-stimulated IL-4 production from liver and spleen T cells from Conv. NC mice in vitro was greatly augmented. The serum IL-4 levels of untreated Conv. NC mice also were higher than those of normal mice and specific pathogen-free NC mice. Treatment of Conv. NC mice either with IFN-gamma, IL-12, or IL-18 twice a week from 4 wk of age substantially inhibited the elevation of the serum IgE levels, serum IL-4 levels, and dermatitis, and IL-12 or IL-18 treatment also reduced the in vitro IL-4 production from CD3-stimulated liver T cells. The systemic deficiency in the Th1 response to bacterial stimulation thus leads to a Th2-dominant state and may induce an abnormal cellular immune response in the skin accompanied with an overproduction of IgE and a susceptibility to dermatitis in NC mice.     

Low susceptibility of NC/Nga mice to the lipopolysaccharide-mediated lethality with D-galactosamine sensitization and the involvement of fewer natural killer T cells

The LPS-mediated lethality of NC/Nga mice, having fewer NKT cells, was examined by using d-galactosamine (d-GalN)-sensitization. The NC/Nga mice were not killed by a simultaneous administration of d-GalN and LPS whereas all C57BL/6 (B6) control mice were killed. The injection of d-GalN and LPS failed to elevate the levels of serum alanine aminotransferase and caspase 3 in the liver tissues of NC/Nga mice. Further, the nitric oxide (NO) level of the d-GalN- and LPS-injected NC/Nga mice was much lower than those of the B6 mice. The expression of an inducible NO synthase (iNOS) was significantly reduced in the livers of NC/Nga mice. However, there was no significant difference in LPS-induced TNF-α production between B6 mice and NC/Nga mice. The NC/Nga mice had an impaired expression of IFN-γ protein and mRNA in response to d-GalN and LPS. The pretreatment with α-galactosylceramide (α-GalCer), which activates Vα14(+) NKT cells and induces the production of IFN-γ, rendered NC/Nga mice more susceptible to the LPS-mediated lethality. The livers of NC/Nga mice had fewer NKT cells compared to B6 mice. Taken together, it is suggested that the resistance of NC/Nga mice to the LPS-mediated lethality with d-GalN sensitization depended on the impaired IFN-γ production caused by fewer NKT cells and reduced NO production that followed.     

Scratching of their skin by NC/Nga mice leads to development of dermatitis

Effects of scratching behavior on dermatitis, transepidermal water loss (TEWL) and serum IgE concentrations were examined in NC/Nga (NC) mice with toenails (WIT) and without toenails (WOT). The first study was a preventive treatment done to cut off hind toenails before dermatitis induction and the second study was a therapeutic treatment by cutting off hind toenails of NC mice with severe dermatitis. In the preventive study, scratching behavior significantly increased in both WIT and WOT after dermatitis induction. Skin severity score, TEWL, number of mast cells and serum IgE concentration statistically increased in WIT but not in WOT after dermatitis induction. Histological changes coincided with the skin severity score in WIT, while no changes were observed in WOT. In the therapeutic study, skin severity score in WOT but not in WIT statistically decreased after cutting off the hind toenails. TEWL and numbers of mast cells in WOT were statistically lower compared with findings in WIT. Thus scratching up the skin with toenails seemed to be the most important factor leading to dermatitis in NC mice.