Contact Hypersensitivity Response Research Articles

Interleukin-17 mediated inflammatory responses are required for ultraviolet radiation-induced immune suppression.

Ultraviolet radiation (UVR) induces immunosuppression and is a major factor for development of skin cancer. Numerous efforts have been made to determine mechanisms for UVR-induced immunosuppression and to develop strategies for prevention and treatment of UVR-induced cancers. In the current study, we use IL-17 receptor (IL-17R) deficient mice to examine whether IL-17 mediated responses have a role in UVB (290-320)-induced immunosuppression of contact hypersensitivity responses. Results demonstrate that IL-17 mediated responses are required for UVB-induced immunosuppression of contact hypersensitivity responses. The systemic immune suppression and development of regulatory T cells are inhibited in UVB-treated IL-17R deficient mice compared to wild-type animals. The deficiency in IL-17R inhibits the infiltration and development of a tolerogenic myeloid cell population in UVB-treated skin, which expresses CD11b and Gr-1 and produces reactive oxygen species. We speculate that the development of the tolerogenic myeloid cells is dependent on IL-17-induced chemokines and inflammatory mediators in UVB-treated skin. The inhibition of the tolerogenic myeloid cells may be attributed to the suppression of regulatory T cells in UVR-treated IL-17R(-/-) mice. The findings may be exploited to new strategies for prevention and treatment of UVR-induced skin diseases and cancers.

Abstract 1239: Dietary grape seed proanthocyanidins inhibit UV-induced immune suppression by targeting the development of regulatory T cells in mice

Abstract Immunosuppressive effects of solar ultraviolet (UV) radiation have been implicated in the risk of non-melanoma and melanoma skin cancers in humans. Previously, we have shown that dietary grape seed proanthocyanidins (GSPs) inhibit photocarcinogenesis in mice and inhibit UV-induced suppression of allergic contact hypersensitivity (CHS) response, a prototypic T-cell-mediated immune response. Studies have shown that UV-induced T regulatory (Treg) cells or suppressor T cells have a role in immune suppression and UV-induced skin carcinogenesis is indicated by the demonstration that depletion of UV-induced T-suppressor cells can inhibit UV-induced carcinogenesis. In our continued efforts to investigate the molecular targets responsible for the prevention of immunosuppression in UV exposed mice by GSPs, we have investigated whether GSPs inhibit UV-induced immunosuppression by inhibiting the development or activity of UV-induced Treg cells in mice. To understand the mechanism, C3H/HeN mice were exposed to UV (150 mJ/cm2) radiation on 4 consecutive days with and without treatment of mice with dietary GSPs, mice were sensitized with 2,4-dinitrofluorobenzene (DNFB) 48 h after the last UV exposure, and then sacrificed 5 days after DNFB sensitization. The flow cytometry analysis of lymph node cells indicated that the numbers of Treg cells were reduced in the mice which were given GSPs in diet compared to non-GSPs-treated UV-exposed mice. We then analyzed effects of dietary GSPs (0.5%, w/w) on secretion of cytokines by Treg cells that were isolated from lymph nodes and spleens of mice that were exposed to UVB (150 mJ/cm2). Our ELISA data showed that in comparison to Treg cells isolated from control mice (GSPs-untreated), Treg cells isolated from mice that received GSPs in diet secreted a significantly higher level of IFNγ, while significantly lower levels of interleukin (IL)-10 and TGF-β, which are immunosuppressive in nature. Finally, we used an adoptive transfer approach, wherein draining lymph nodes were harvested from mice that were exposed to UVB on 4 consecutive days with and without GSPs supplementation in diet and sensitized by DNFB onto the UVB-exposed skin. Treg cells were positively selected using magnetic beads and MACS system and transferred into naïve mice that were subsequently challenged by application of DNFB on the ear skin. Naïve recipients that received Treg cells from GSPs-treated, UVB-irradiated donors exhibited CHS response, whereas no significant CHS was observed in mice which were injected Treg cells from UVB alone-exposed mice compared to control group. These data suggest that dietary GSPs inhibit UVB-induced immunosuppression by suppressing the development as well as the functional activation of Treg cells in UV-exposed mice. Citation Format: Santosh K. Katiyar, Tripti Singh, Mudit Vaid. Dietary grape seed proanthocyanidins inhibit UV-induced immune suppression by targeting the development of regulatory T cells in mice. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1239. doi:10.1158/1538-7445.AM2014-1239

Therapeutic Tissue Regeneration by a Macrophage Colony-Stimulating Factor Fc Conjugate

Therapeutic Tissue Regeneration by a Macrophage Colony-Stimulating Factor Fc Conjugate

β-Arrestin 2 Inhibits Proinflammatory Chemokine Production and Attenuates Contact Allergic Inflammation in the Skin

β-Arrestins participate in G-protein receptor signaling and act as adapter proteins that direct the recruitment, activation, and scaffolding of various cytoplasmic signaling complexes. β-Arrestin 2-deficient (Arrb2(-/-)) mice show decreased T-cell recruitment into allergic lung tissue but increased neutrophil infiltration into wounded skin. Given these opposing effects in different immune cell subsets, we investigated the role of β-arrestin 2 in the regulation of contact hypersensitivity responses. We observed significantly increased allergic ear swelling to the obligate contact sensitizers DNFB and FITC in Arrb2(-/-) compared with wild-type mice. Immunohistological analyses revealed strikingly increased neutrophil infiltration with abundant subcorneal pustules in inflamed ear tissue of DNFB-allergic Arrb2(-/-) mice. Experiments involving adoptive transfers of sensitized lymphocytes and bone marrow chimeric mice indicated that β-arrestin 2 exerts its anti-inflammatory effects predominantly through radioresistant, skin-resident cells in the challenge phase of contact hypersensitivity. As a potential mechanism, we found that primary cultures of β-arrestin 2-deficient keratinocytes secreted higher levels of neutrophil-attracting chemokines including CXCL1/KC in response to T cell-derived cytokines in vitro. These experimental results support a model in which β-arrestin 2 inhibits the production of proinflammatory chemokines, which limits the recruitment of myeloid immune cells and thereby attenuates allergic skin inflammation.

Tc1-mediated contact sensitivity reaction, its mechanism and regulation

The contact hypersensitivity reaction (CHS) to haptens is a classic example of cell-mediated immune response. In the effector phase, two stages can be distinguished: an early component, that appears only 2 hours after subsequent contact with the hapten, and the late component that develops approximately 24 hours later which is mediated by TCRαβ+ cells. The effector lymphocytes may be CD4+ T helper 1 (Th1) cells or CD8+ T cytotoxic 1 (Tc1) cells, which depends on the employed hapten and/or mice strain. NKT lymphocytes play the crucial role in the CHS initiation, by supporting B1 cells in the antigen-specific IgM antibodies production. The development of an early component is essential for the recruitment of T effector (Teff) cells to the side of hapten deposition and for the complete expansion of inflammatory reaction. The CHS reaction is under T regulatory (Treg) cells control, both in the induction phase as well as in the effector phase. A new view of a negative regulation of the Tc1 mediated CHS response is based on the suppression induced by epicutaneous (EC) application of protein antigen. The DNP-BSA skin application, on a gauze patch, leads to a state of immunosuppression. This maneuver results in rising the population of Treg cells with TCRαβ+CD4+CD25+Foxp3+ phenotype. The mechanism of suppression requires direct contact between Treg cells and Teff cells and the participation of CTLA-4 molecule is also necessary. The described method of evoking immune tolerance via EC immunization may contribute to elaborate a new method of allergic contact dermatitis therapy. This is because of its effectiveness, ease of induction and non-invasive protein antigen application.

Epicutaneous Immunization with TNP-Ig and Zymosan Induces TCRαβ+ CD4+ Contrasuppressor Cells That Reverse Skin-Induced Suppression via IL-17A

Background: Our previous work showed that epicutaneous (EC) immunization with protein antigen e.g. TNP-conjugated mouse immunoglobulin (TNP-Ig) in the form of a patch prior to hapten sensitization inhibits Th1-mediated contact hypersensitivity (CHS) in mice. We also found that suppression of CHS was mediated by TCRαβ+ CD4+ CD8+ T suppressor cells producing TGF-β. The aim of this study was to investigate the role of innate immunity in the suppression of CHS. Methods: Mice were immunized by applying gauze patches containing protein antigen alone or in the presence of zymosan, and were then tested for the CHS response. Adoptive cell transfer experiments were used to study the mechanisms involved in the reversal of skin-induced suppression. The influence of EC immunization on cytokine production by lymph node cells was measured by ELISA. Results: We found that EC immunization with TNP-Ig and zymosan before trinitrophenyl chloride sensitization reverses skin-induced suppression, demonstrated in vivo and in vitro. The reversal of skin-induced suppression was transferable by antigen-specific TCRαβ+ CD4+ T contrasuppressor cells. Furthermore, we showed that the contrasuppression was IL-17A-dependent and TLR2- and MyD88-independent. Conclusions: Our work strongly suggests that EC immunization with protein antigen and zymosan reverses skin-induced suppression and that this approach may be a potential tool to increase the immunogenicity of weakly immunogenic antigens.

Lack of transglutaminase 2 diminished T‐cell responses in mice

Transglutaminase 2 (TG2) has been reported to play a role in dendritic cell activation and B-cell differentiation after immunization. Its presence and role in T cells, however, has not been explored. In the present study, we determined the expression of TG2 on mouse T cells, and evaluated its role by comparing the behaviours of wild-type and TG2(-/-) T cells after activation. In our results, naive T cells minimally expressed TG2, expression of which was increased after activation. T-cell proliferation, expression of activation markers such as CD69 and CD25, and secretions of interleukin-2 and interferon-γ were suppressed in the absence of TG2, presumably due, in part, to diminished nuclear factor-κB activation. These effects on T cells seemed to be reflected in the in vivo immune response, the contact hypersensitivity reaction elicited by 2,4-dinitro-1-fluorobenzene, with lowered peak responses in the TG2(-/-) mice. When splenic T cells from mice immunized with tumour lysate-loaded wild-type dendritic cells were re-challenged ex vivo with the same antigen, the profile of surface markers including CD44, CD62L, and CD127 strongly indicated lesser generation of memory CD8(+) T cells in TG2(-/-) mice. In the TG2(-/-) CD8(+) T cells, moreover, Eomes expression was markedly decreased. These results indicate possible roles of TG2 in CD8(+) T-cell activation and CD8(+) memory T-cell generation.

Cannabinoid 1 receptors in keratinocytes attenuate fluorescein isothiocyanate-induced mouse atopic-like dermatitis.

Atopic dermatitis is a chronic inflammatory disease characterized by an impaired epidermal barrier function combined with a chronic Th2-type inflammatory response and an intense pruritus. Here, we used an experimental mouse model for Th2-type contact hypersensitivity (CHS) to fluorescein isothiocyanate (FITC) to investigate the potential role of cannabinoid 1 receptors (CB1) in the pathophysiology of mouse atopic-like dermatitis. Mice lacking CB1 receptors globally (Cnr1(-/-) ) or specifically in keratinocytes (KC-Cnr1(-/-) ) as well as wild-type (WT) control mice were sensitized and challenged with FITC. We examined ear swelling responses, transepidermal water loss, Th2-type skin inflammatory responses and serum IgE levels. Both Cnr1(-/-) and KC-Cnr1(-/-) showed enhanced CHS responses to FITC and a delayed epidermal barrier repair when compared with WT mice. mRNA levels for IL-4, thymic stromal lymphopoietin (TSLP) and CCL8, as well as eosinophil activity, were significantly increased in inflamed ear tissue of FITC-challenged Cnr1(-/-) and KC-Cnr1(-/-) mice. Importantly, CB1 receptor-deficient keratinocytes secreted increased levels of TSLP, a proinflammatory mediator that drives Th2-type skin inflammation in atopic dermatitis, under basal and Th2-type inflammatory conditions. Taken together, our results demonstrate that CB1 receptors in keratinocytes help to maintain epidermal barrier homoeostasis and attenuate Th2-type allergic inflammatory responses. Based on our work, we propose that enhanced epidermal allergen penetrance cooperates with increased production of TSLP and CCL8 by epidermal keratinocytes for the induction of type 2 CD4+ T helper cells. Our results place keratinocytes at the cross-roads of outside-in and inside-out pathophysiologic mechanisms of atopic dermatitis.

A novel population of myeloid Gr-1+ cells expressing FasL and perforin mediate contact hypersensitivity responses in skin (CAM5P.236)

Abstract Allergic contact hypersensitivity (CHS) is a CD8 T cell mediated response to hapten sensitization and challenge of the skin. Hapten-primed CD8 cell infiltration into the skin challenge site requires prior Gr-1+ cell infiltration into the site. Despite WT levels of CD8 priming, sensitized gld/perforin-/- mice have no CHS to hapten challenge. The response is restored in these mice by transfer of WT bone marrow derived Gr-1+ cells at the time of hapten challenge. The goal of this study was to further characterize these Gr-1+ cells. Gr-1+cells were purified from the bone marrow of sensitized and challenged mice by depletion of CD3+, B220+, NK1+, F4/80+, and Ly6G+ cells. qRT-PCR and Western Blot analyses confirm expression of FasL and perforin by the negatively selected cells that are 90% Gr-1+CXCR2+. Flow cytometry analyses indicate the FasL+ cells within this population express CD11c, CXCR2, CCR2, Ly6C, and CX3CR1. These Gr-1+cells, but not neutrophils, induce apoptosis of cultured endothelial cells. Transfer of these Gr-1+ myeloid cells to sensitized gld/perforin-/- mice during hapten challenge induces expression of the T cell chemoattractants CCL1, CCL2, and CCL5 in the challenged skin. These results describe a novel population of bone marrow derived Gr-1+CXCR2+ myeloid cells expressing FasL and perforin that induce expression of the chemoattractants required to direct hapten-primed T cell infiltration into the challenged skin site to mediate CHS.

ASK1 promotes the contact hypersensitivity response through IL-17 production.

Contact hypersensitivity (CHS) is a form of delayed-type hypersensitivity triggered by the response to reactive haptens (sensitization) and subsequent challenge (elicitation). Here, we show that ASK1 promotes CHS and that suppression of ASK1 during the elicitation phase is sufficient to attenuate CHS. ASK1 knockout (KO) mice exhibited impaired 2,4-dinitrofluorobenzene (DNFB)-induced CHS. The suppression of ASK1 activity during the elicitation phase through a chemical genetic approach or a specific inhibitory compound significantly reduced the CHS response to a level similar to that observed in ASK1 KO mice. The reduced response was concomitant with the strong inhibition of production of IL-17, a cytokine that plays an important role in CHS and other inflammatory diseases, from sensitized lymph node cells. These results suggest that ASK1 is relevant to the overall CHS response during the elicitation phase and that ASK1 may be a promising therapeutic target for allergic contact dermatitis and other IL-17-related inflammatory diseases.

Severity of polymorphic light eruption in pre‐ and post‐menopausal women: a comparative study

Polymorphic light eruption (PLE) is approximately four times more common in women than in men and often begins in young adult life. It is hypothesized that patients with PLE have an inherent resistance to UVL-induced immunosuppression, which is a physiological phenomenon in normal healthy individuals. Consequently, in PLE there is a delayed-type hypersensitivity reaction to a UVL-modified skin antigen, which results in an inflammatory reaction and a variable rash. The female hormone, 17β-oestradiol, has been shown to inhibit UVL-induced physiological suppression of contact hypersensitivity responses. This has been postulated to account for the female preponderance of PLE. If 17β-oestradiol plays a significant part in the disease, one might hypothesize that the severity of PLE might reduce in women after menopause. To compare the severity of PLE in pre-menopausal women with that in post-menopausal women. Eighteen pre-menopausal and 18 post-menopausal women with PLE had their Polymorphic Light Eruption Severity Index (PLESI) scored by a single investigator. Pre-menopausal women (mean age 40years; range 25-50) had a mean PLESI of 54.8 (range 0-86, SD 20.2). Post-menopausal women (mean age 63years; range 53-78) had a mean PLESI of 36.8 (range 0-74, SD 18.2). A significant difference in mean PLESI values between pre- and post-menopausal women was noted (18.0; 95% CI 4.9-31.0; P = 0.008). At the time of the study, three subjects in the pre-menopausal group and one subject in the post-menopausal group were on oestrogen preparations. Even after excluding the four patients on oral oestrogens, there remained a statistically significant difference in the mean PLESI scores between the pre-menopausal and post-menopausal groups (55.10 vs. 36.64; difference of 18.46, 95% CI: 4.0-32.91; P = 0.014). The severity of PLE was significantly less in post-menopausal women as compared with pre-menopausal women.

Tobacco Smoke–Induced Immunologic Changes May Contribute to Oral Carcinogenesis

ObjectiveThe objective of this study was to determine if tobacco smoke (TS), a risk factor for cancers of the aerodigestive tract, may contribute to oral carcinogenesis, in part, by suppressing...

IDO2 is critical for IDO1-mediated T-cell regulation and exerts a non-redundant function in inflammation

IDO2 is implicated in tryptophan catabolism and immunity but its physiological functions are not well established. Here we report the characterization of mice genetically deficient in IDO2, which develop normally but exhibit defects in IDO-mediated T-cell regulation and inflammatory responses. Construction of this strain was prompted in part by our discovery that IDO2 function is attenuated in macrophages from Ido1 (-/-) mice due to altered message splicing, generating a functional mosaic with implications for interpreting findings in Ido1 (-/-) mice. No apparent defects were observed in Ido2 (-/-) mice in embryonic development or hematopoietic differentiation, with wild-type profiles documented for kynurenine in blood serum and for immune cells in spleen, lymph nodes, peritoneum, thymus and bone marrow of naive mice. In contrast, upon immune stimulation we determined that IDO1-dependent T regulatory cell generation was defective in Ido2 (-/-) mice, supporting Ido1-Ido2 genetic interaction and establishing a functional role for Ido2 in immune modulation. Pathophysiologically, both Ido1 (-/-) and Ido2 (-/-) mice displayed reduced skin contact hypersensitivity responses, but mechanistic distinctions were apparent, with only Ido2 deficiency associated with a suppression of immune regulatory cytokines that included GM-CSF, G-CSF, IFN-γ, TNF-α, IL-6 and MCP-1/CCL2. Different contributions to inflammation were likewise indicated by the finding that Ido2 (-/-) mice did not phenocopy Ido1 (-/-) mice in the reduced susceptibility of the latter to inflammatory skin cancer. Taken together, our results offer an initial glimpse into immune modulation by IDO2, revealing its genetic interaction with IDO1 and distinguishing its non-redundant contributions to inflammation.

Crosstalk between contact hypersensitivity reaction and antidepressant drugs

Allergic contact dermatitis is a delayed-type hypersensitivity reaction mediated by hapten-specific T cells. Many cell types, inflammatory mediators and cytokines are involved in this reaction. Contact hypersensitivity is a self-limited reaction and can be regulated at different levels. Because it is known that disturbances in the immune system underpin the onset of depression and that antidepressant drugs have immunomodulatory effects, it can be hypothesized that antidepressants may have some efficacy in the treatment of contact hypersensitivity. There are some reports on the effectiveness of antidepressants in the inhibition of cutaneous sensitization in mice, and the aim of this narrative review is to assess the evidence for the effectiveness of antidepressant drugs in reducing the recurrence of contact hypersensitivity reactions.

Chronic psychological stress suppresses contact hypersensitivity: Potential roles of dysregulated cell trafficking and decreased IFN-γ production

Increasing evidence shows that psychological stress can have dramatic impacts on the immune system, particularly the cutaneous immune response in dermatological disorders. While there have been many studies examining the impact of acute psychological stress on contact hypersensitivity there are relatively few studies concerning the impact of chronic psychological stress. Furthermore, the local immunological mechanisms by which chronic psychological stress impacts contact hypersensitivity still remain to be explored. Here we show that restraint-induced chronic psychological stress stimulates activation of the hypothalamus-pituitary-adrenal axis and delays weight gain in female BALB/c mice. We observed that chronic psychological stress reduces the cutaneous immune response as evidence by reduced ear swelling. This correlated with a significant decrease in the inflammatory cell infiltrate. On the other hand, chronic psychological stress does not influence T cell proliferation, activation, or sensitivity to corticosterone but does increase CD4(+) and CD8(+) T cell percentages in draining lymph nodes during a contact hypersensitivity reaction. Chronic psychological stress induces a decrease in overall circulating white blood cells, lymphocytes, and monocytes during a contact hypersensitivity reaction suggesting extravasation from the circulation. Finally, we found markedly reduced local IFN-γ production in chronically stressed animals. Based on these findings we propose that chronic psychological stress reduces contact hypersensitivity due to dysregulated cell trafficking and reduced production of IFN-γ.

The VEGF-C/VEGFR3 signaling pathway contributes to resolving chronic skin inflammation by activating lymphatic vessel function

BackgroundThe functions of lymphatic vessels are to drain the protein-rich lymph from the extracellular space, to maintain normal tissue pressure, and to mediate the immune response, particularly in inflammatory conditions. ObjectiveTo evaluate the function of the vascular endothelial growth factor (VEGF)-C/VEGF receptor (VEGFR)-3 signaling pathway in chronic skin inflammation. MethodsWe used adenovirus-mediated VEGF-C or VEGFR3-immunoglobulin (Ig) production and investigated the effects of VEGF-C/VEGFR3 signaling on the resolution of inflammation using the experimental chronic contact hypersensitivity (CHS) reaction mouse model. ResultsVEGF-C gene transfer promoted significant reduction of ear swelling and ear weight in CHS reaction-induced skin inflammation. Although, there was no significant difference in the number of lymphatic vessels, the number of infiltrating CD11b-positive inflammatory cells was significantly reduced in the VEGF-C group, which suggested that VEGF-C upregulated the drainage of interstitial fluid and inflammatory cells via lymphatic vessels. Furthermore, blockade of VEGFR3 expression resulted in a significant delay in the recovery from CHS reaction-induced skin inflammation. Lymphatic vessel size was enlarged and a significant increase of infiltrating CD11b inflammatory cells was observed in mice with VEGFR3-Ig gene transfer compared to control mice. These results suggested that blockade of VEGFR3 inhibited the drainage function of the lymphatic system. ConclusionThis study provides evidence that VEGF-C/VEGFR3 signaling plays an important role in the resolution of skin inflammation; the regulation of lymphatic function may have a great therapeutic potential in inflammatory skin diseases.

Contact sensitizing potential of pyrogallol and 5-amino-o-cresol in female BALB/c mice

Hair dye components such as pyrogallol and cresol have been shown previously to promote allergic reactions such as rashes, dermal inflammation, irritation and dermatitis. The objective of this study was to determine the contact sensitization potential of pyrogallol (PYR) and 5-amino-o-cresol (AOC) when applied dermally to female BALB/c mice. Measurement of the contact hypersensitivity response was initially accomplished using the local lymph node assay. For PYR, significant increases in the proliferation of lymph node cells were observed at concentrations of 0.5% (w/v) and higher. For AOC, borderline increases, albeit significant, in auricular lymph node cell proliferation were observed at 5% and 10%. Results from the irritancy assay suggested that PYR, but not AOC, was an irritant. To further delineate whether PYR was primarily an irritant or a contact sensitizer, the mouse ear swelling test (MEST) was conducted. A significant increase in mouse ear thickness was observed at 72h following challenge with 0.5% PYR in mice that had been sensitized with 5% PYR. In contrast, no effects were observed in the MEST in mice sensitized and challenged with the highest achievable concentration of AOC (10%). Additional studies examining lymph node subpopulations and CD86 (B7.2) expression by B cells further support the indication that PYR was a sensitizer in BALB/c mice. The results demonstrate that PYR is both a sensitizer and an irritant in female BALB/c mice. However, the contact sensitization potential of AOC is minimal in this strain of mouse.

Contact Hypersensitivity to Oxazolone Provokes Vulvar Mechanical Hyperalgesia in Mice

The interplay among pain, allergy and dysregulated inflammation promises to yield significant conceptual advances in immunology and chronic pain. Hapten-mediated contact hypersensitivity reactions are used to model skin allergies in rodents but have not been utilized to study associated changes in pain perception in the affected skin. Here we characterized changes in mechanical hyperalgesia in oxazolone-sensitized female mice challenged with single and repeated labiar skin exposure to oxazolone. Female mice were sensitized with topical oxazolone on their flanks and challenged 1-3 times on the labia. We then measured mechanical sensitivity of the vulvar region with an electronic pressure meter and evaluated expression of inflammatory genes, leukocyte influx and levels of innervation in the labiar tissue. Oxazolone-sensitized mice developed vulvar mechanical hyperalgesia after a single labiar oxazolone challenge. Hyperalgesia lasted up to 24 hours along with local influx of neutrophils, upregulation of inflammatory cytokine gene expression, and increased density of cutaneous labiar nerve fibers. Three daily oxazolone challenges produced vulvar mechanical hyperalgesic responses and increases in nerve density that were detectable up to 5 days post-challenge even after overt inflammation resolved. This persistent vulvar hyperalgesia is resonant with vulvodynia, an understudied chronic pain condition that is remarkably prevalent in 18-60 year-old women. An elevated risk for vulvodynia has been associated with a history of environmental allergies. Our pre-clinical model can be readily adapted to regimens of chronic exposures and long-term assessment of vulvar pain with and without concurrent inflammation to improve our understanding of mechanisms underlying subsets of vulvodynia and to develop new therapeutics for this condition.

Effects of intestinal bacteria-derived p-cresyl sulfate on Th1-type immune response in vivo and in vitro

Protein fermentation by intestinal bacteria generates various compounds that are not synthesized by their hosts. An example is p-cresol, which is produced from tyrosine. Patients with chronic kidney disease (CKD) accumulate high concentrations of intestinal bacteria-derived p-cresyl sulfate (pCS), which is the major metabolite of p-cresol, in their blood, and this accumulation contributes to certain CKD-associated disorders. Immune dysfunction is a CKD-associated disorder that frequently contributes to infectious diseases among CKD patients. Although some studies imply pCS as an etiological factor, the relation between pCS and immune systems is poorly understood. In the present study, we investigated the immunological effects of pCS derived from intestinal bacteria in mice. For this purpose, we fed mice a tyrosine-rich diet that causes the accumulation of pCS in their blood. The mice were shown to exhibit decreased Th1-driven 2, 4-dinitrofluorobenzene-induced contact hypersensitivity response. The concentration of pCS in blood was negatively correlated with the degree of the contact hypersensitivity response. In contrast, the T cell-dependent antibody response was not influenced by the accumulated pCS. We also examined the in vitro cytokine responses by T cells in the presence of pCS. The production of IFN-γ was suppressed by pCS. Further, pCS decreased the percentage of IFN-γ-producing Th1 cells. Our results suggest that intestinal bacteria-derived pCS suppressesTh1-type cellular immune responses.

Route-dependent systemic and local immune effects following exposure to solutions prepared from titanium dioxide nanoparticles

Nanoparticle titanium dioxide (nano-TiO2) is a white pigment widely used in foods, sunscreens, and other cosmetic products. However, it remains unclear whether exposure to nano-TiO2 results in immunosuppressive effects or induces a contact hypersensitivity response. To address these data gaps, studies were conducted with the hypothesis that nano-TiO2 exposure could alter immune responses. After 28 days of oral gavage, nano-TiO2 (1.25–250 mg/kg in 0.5% methylcellulose) produced no significant effects on innate, humoral, or cell-mediated immune functions in female B6C3F1 mice. Furthermore, there were no effects on the weights of selected organs (spleen, thymus, liver, lung, and kidneys with adrenals). Following dermal exposure on the ears for 3 days, nano-TiO2 (2.5–10% w/v in 4:1 acetone:olive oil) did not affect auricular lymph node cell proliferation, although an irritancy response was observed following treatment with 5% and 10% nano-TiO2. Dermal sensitization (2.5–10%) on the back and subsequent challenge (10%) on the right ear with nano-TiO2 produced no significant effects on percentage ear swelling in the Mouse Ear Swelling Test (MEST). However, when nano-TiO2 was injected subcutaneously along the mid-line on top of the head at 125–250 mg/kg (in 0.5% methylcellulose), significant increases in auricular lymph node cell proliferation resulted. These results demonstrate that immune effects of nano-TiO2 exposure are route-of-exposure dependent, and they suggest that irritancy and/or potential hypersensitivity responses may occur following parenteral exposure or dermal administration of nano-TiO2 to compromised skin.