Immune mechanisms in vulvodynia: key roles for mast cells and fibroblasts

Vulvodynia is a debilitating condition characterized by painful sensitivity to touch and pressure in the vestibular tissue surrounding the vaginal opening. It is often a "diagnosis of exclusion" of idiopathic pain made in the absence of visible inflammation or injury. However, the association between increased vulvodynia risk and a history of yeast infections and skin allergies has led researchers to explore whether immune mechanisms of dysregulated inflammation might underlie the pathophysiology of this chronic pain condition. Here we synthesize epidemiological investigations, clinical biopsies and primary cell culture studies, and mechanistic insights from several pre-clinical models of vulvar pain. Taken together, these findings suggest that altered inflammatory responses of tissue fibroblasts, and other immune changes in the genital tissues, potentially driven by the accumulation of mast cells may be key to the development of chronic vulvar pain. The association of increased numbers and function of mast cells with a wide variety of chronic pain conditions lends credence to their involvement in vulvodynia pathology and underscores their potential as an immune biomarker for chronic pain. Alongside mast cells, neutrophils, macrophages, and numerous inflammatory cytokines and mediators are associated with chronic pain suggesting immune-targeted approaches including the therapeutic administration of endogenous anti-inflammatory compounds could provide much needed new ways to treat, manage, and control the growing global pandemic of chronic pain.

The C-C chemokine receptor 7: An immune molecule that modulates central nervous system function in homeostasis and disease

The interaction between the central nervous system (CNS) and the peripheral immune system is key for brain function in homeostasis and disease. Recent studies have revealed that the C-C chemokine receptor 7 (CCR7) is expressed in both CNS resident cells and peripheral immune cells, and plays an important role in regulating behavior in homeostasis and neuroinflammation in disease. This review integrates studies examining the role of CCR7 in CNS resident and peripheral immune cells in homeostasis and disease, as well as the pathways of peripheral immune cell migration in and out of the brain via CCR7. A special emphasis is placed on the CCR7-dependent migration of peripheral immune cells into the recently discovered meningeal lymphatic vessels surrounding the brain and nasal lymphatics, its migration into cervical lymph nodes, and the implications that this migration might have for CNS function.

Characterizing Differences in Thymic Function in Women With and Without Vulvodynia: A Community-Based Study

OBJECTIVE

The aim of the study was to evaluate the association between vulvodynia and thymic function.

MATERIALS AND METHODS

In this case-control study of 200 clinically confirmed cases of vulvodynia and 205 general population controls residing in the Minneapolis/Saint Paul metropolitan area, we used DNA extracted from whole blood to measure levels of signal joint T-cell receptor excision circles (sjTRECs), a measure of thymic output. We used logistic regression to evaluate the association between vulvodynia and thymic function.

RESULTS

In 405 participants (aged 18-40 years), we observed an association between decreasing thymic function and increasing age. Women with vulvodynia had a steeper decline in sjTREC values across age categories compared with women without vulvodynia. In addition, at younger ages, women with vulvodynia had higher sjTREC values compared with women without vulvodynia. In older women, those with vulvodynia had lower sjTREC than those without vulvodynia. When accounting for recency of vulvar pain onset, women with a shorter time since pain onset had higher thymic function compared with women with a longer time since vulvar pain onset.

CONCLUSIONS

These findings suggest that at younger ages, women with vulvodynia have higher thymic output and a more precipitous decline of thymic function than those without vulvodynia. It also seems that a strong immune inflammatory response is present proximate to the onset of vulvar pain and may wane subsequently over time.

Generating primary murine vaginal fibroblast cell lines

Primary human vulvovaginal fibroblast cell lines are useful for studying biological mechanisms underlying genital pain, pelvic organ prolapse, and the spread of sexually transmitted infections. However, the vaginal biopsies necessary for establishing these cell lines are invasive and relatively difficult to obtain. Primary mouse fibroblast cell lines derived from pre-clinical animal models of these conditions can be used for better controlled experiments that can help us dissect disease mechanisms. To our knowledge, there are no published protocols for establishing primary murine vaginal fibroblast cell lines to date. Here, we describe a protocol for the establishment of murine vaginal fibroblast cell lines via enzymatic digestion of vaginal canal tissue. Cell lines generated using this method can be used for in vitro studies of these important structural cells in a variety of pre-clinical mouse models; such studies are required to identify and characterize relevant regulatory and therapeutic targets in a wide array of diseases of interest. As shown in our representative data, this protocol yields viable cell lines from ND4 Swiss outbred mice. These cells bear surface markers characteristic of fibroblasts and are capable of producing inflammatory cytokines in response to treatment with bacterial and yeast antigens in vitro.

Repeated dermal application of the common preservative methylisothiazolinone triggers local inflammation, T cell influx, and prolonged mast cell-dependent tactile sensitivity in mice

Occupational exposure to toxic chemicals increases the risk of developing localized provoked vulvodynia-a prevalent, yet poorly understood, chronic condition characterized by sensitivity to touch and pressure, and accumulation of mast cells in painful tissues. Here, we topically sensitized female ND4 Swiss mice to the common household and industrial preservative methylisothiazolinone (MI) and subsequently challenged them daily with MI or acetone and olive oil vehicle on the labiar skin. MI-challenged mice developed significant, persistent tactile sensitivity and long-lasting local accumulation of mast cells alongside early, transient increases in CD4+ and CD8+ T cells, eosinophils, neutrophils, and increases in pro-inflammatory cytokines. Therapeutic administration of imatinib, a c-Kit inhibitor known to inhibit mast cell survival, led to reduced mast cell accumulation and alleviated tactile genital pain. We provide the first pre-clinical evidence of dermal MI-induced mast-cell dependent pain and lay the groundwork for detailed understanding of these intersections between MI-driven immunomodulation and chronic pain.

Repeated exposures to the environmental allergen methylisothiazolinone reduce viability of fibroblasts derived from allergic sites in response to allergen challenge in vitro

Chronic, unexplained vulvar pain or vulvodynia affects 8% of women of reproductive age, and is more common with histories of yeast infections and allergies. We have established mouse models of localized, provoked genital pain driven by repeated labiar and vaginal exposures to allergens such as oxazolone, dinitrofluorobenzene and the common chemical preservative methylisothiazolinone (MI). Pain sensitivity is concomitant with tissue mast cell increases and reduced when mast cells are reduced by chemical degranulation or topical phytocannabinoid treatment. Vulvar fibroblasts from patients show altered inflammatory responses in vitro.to repeated topical application of the allergenic cosmetic preservative methylisothiazolinone (MI) to the murine vaginal canal produces long-lasting contact hypersensitivity. Here, we have optimized methods to grow skin and vaginal canal fibroblasts from outbred Swiss mice that are responsive to lipopolysaccharide and zymosan treatment in vitro. We also show that in vitro MI treatment reduces the viability of derived fibroblasts in a dose-dependent manner, with a more robust effect on cell lines derived from MI-treated skin, indicating that previous exposure to MI in the skin primes fibroblasts to undergo cell death upon future exposures. Our data suggest that fibroblasts may become more sensitive to allergens as a result of previous exposures, which could contribute to the development of chronic allergic and pain sensitivity after repeated low dose chemical exposures.

Ready, Cell, Go! Guided Movement Exercises in an Introductory Cell Biology Course

Cells and dance are each dynamic manifestations of energy, shape, time, and space. Here we present a novel application of movement learning in cell biology education. "Ready, Cell, Go!" is a set of movement exercises for introductory cell biology students designed to teach concepts of fluidity, crowding, and chaos. These aspects of cells are difficult to glean from two-dimensional illustrations in textbooks or animations where necessary simplification abstracts processes from their full cellular context. Forty-four undergraduate biology students were guided to move using three sets of cues in a dance studio setting where each exercise aimed to experientially highlight and deepen understanding of a different aspect of cellular structure and function. Students described their experiences and personal learning outcomes in written reflections. The movement-based exercises we describe provided a means of discovery, inquiry, and interest for introductory cell biology students and serve as a template to teach other central concepts in cell biology.

Tetrahydrocannabinol Reduces Hapten-Driven Mast Cell Accumulation and Persistent Tactile Sensitivity in Mouse Model of Allergen-Provoked Localized Vulvodynia

Vulvodynia is a remarkably prevalent chronic pain condition of unknown etiology. An increase in numbers of vulvar mast cells often accompanies a clinical diagnosis of vulvodynia and a history of allergies amplifies the risk of developing this condition. We previously showed that repeated exposures to oxazolone dissolved in ethanol on the labiar skin of mice led to persistent genital sensitivity to pressure and a sustained increase in labiar mast cells. Here we sensitized female mice to the hapten dinitrofluorobenzene (DNFB) dissolved in saline on their flanks, and subsequently challenged them with the same hapten or saline vehicle alone for ten consecutive days either on labiar skin or in the vaginal canal. We evaluated tactile ano-genital sensitivity, and tissue inflammation at serial timepoints. DNFB-challenged mice developed significant, persistent tactile sensitivity. Allergic sites showed mast cell accumulation, infiltration of resident memory CD8⁺CD103⁺ T cells, early, localized increases in eosinophils and neutrophils, and sustained elevation of serum Immunoglobulin E (IgE). Therapeutic intra-vaginal administration of Δ⁹-tetrahydrocannabinol (THC) reduced mast cell accumulation and tactile sensitivity. Mast cell-targeted therapeutic strategies may therefore provide new ways to manage and treat vulvar pain potentially instigated by repeated allergenic exposures.

Mast cell accumulation drives allergy-driven chronic pain responses in outbred mice

We are building novel outbred mouse models of a poorly understood yet prevalent vulvar pain condition – localized, provoked vulvodynia – that affects a substantial proportion of 18–60 year old women. Epidemiologic studies have shown a surprising and increased risk for developing this condition in women with a history of skin and airway allergies. We show that repeated exposures to low doses of the common contact irritant haptens oxazolone or dinitrofluorobenzene on the genital skin of mice produce sustained painful sensitivity to touch as well as a non-normative accumulation of mast cells and an overgrowth of cutaneous nerves in the affected tissue – changes that are also seen in vulvar biopsies taken from women diagnosed with vulvodynia providing the first evidence of biological plausibility for the immunological underpinnings of this chronic pain condition. In addition to laboratory haptens, we show that the hapten methylisothiazolinone (a common cosmetic preservative found in soaps, shampoos, and feminine hygiene products) can induce these responses suggesting that this ubiquitous environmental exposure might be a possible immunological trigger of hitherto unexplained genital pain conditions that affect many women.

We have further characterized infiltrating T cells at the allergic site to show that FoxP3+ regulatory CD4 T cells and CD103+ resident memory CD8 T accumulate at these sites as well. Our mouse models provide new tools to both dissect allergy driven pain conditions as well as test novel therapies targeting immune cells and mechanisms for the management and treatment of these debilitating disorders.

Recurrent Yeast Infections and Vulvodynia: Can We Believe Associations Based on Self-Reported Data?

OBJECTIVE

We determined whether self-reported new or recurrent yeast infections were a risk factor for and/or consequence of vulvodynia and then determined the extent to which various levels of misclassification of self-reported yeast infections influenced these results.

MATERIALS AND METHODS

In this case-control study we retrospectively assessed self-reported new and recurrent yeast infections prior and subsequent to first vulvar pain onset among 216 clinically confirmed cases and during a similar time period for 224 general population controls.

RESULTS

A history of >10 yeast infections before vulvodynia onset was strongly but imprecisely associated with currently diagnosed vulvodynia after adjustment for age, age at first intercourse, and history of urinary tract infections [adjusted odds ratio = 5.5, 95% confidence interval (CI) 1.7-17.8]. Likewise, a history of vulvodynia was associated with a twofold risk of subsequent new or recurrent onset of yeast infections after adjustment for age, age at first intercourse, and history of yeast infections before vulvodynia onset (comparable time period among controls, 95% CI 1.5-2.9). Bias analyses showed that our observed associations were an underestimation of the true association when nondifferential misclassification of self-reported yeast infections and certain differential misclassification scenarios were present. However, if women with vulvodynia more frequently misreported having them when they truly did not, our observed associations were an overestimate of the truth.

CONCLUSIONS

There appears to be a positive relationship between yeast infections preceding and following the diagnosis of vulvodynia, but this relationship varies from strong to nonexistent depending on the relative accuracy of the recalled diagnosis of yeast infections among cases and controls. To better understand the bidirectional associations between yeast infections and vulvodynia, future validation studies are needed to determine the extent to which misclassification of self-reported yeast infections differs between women with and without vulvodynia.

Mast cells are required for allergy-driven changes in senstivity to touch and pressure in oxazolone challenged skin in sensitized ND4 female mice

Vulvodynia is a chronic vulvar pain condition affecting up to 8–16% of 18–60 year-old women. Epidemiological studies have demonstrated an increased risk of developing vulvodynia for women with histories of seasonal and insect allergies. We show that 10 exposures to the hapten oxazolone on the labiar skin of previously sensitized outbred ND4 female mice provokes increased sensitivity to touch and pressure that lasts for 3 weeks or longer. This persistent sensitivity is accompanied by local labiar mast cell accumulation and overgrowth of cutaneous neurites both of which persist for at least 3 weeks after the final allergen exposure. Oxazolone-challenged mice also show local labiar increases in inflammatory cytokine and neuro-immune signaling transcripts, infiltration of resident memory CD8 cells and CD4+CD25+ regulatory T cells. Local depletion of mast cells via intra-dermal injections of basic secretagogue compound 48/80 reduces the sensitivity to touch and pressure suggesting that persistent accumulation of mast cells in allergen-exposed tissue is necessary for the development of long-lasting painful responses in these mice. Our findings suggest that mast cell-targeted therapies may be a novel area of intervention for the management and treatment of chronic pain conditions associated with allergic and hyper-inflammatory states.

Isolation of Infiltrating Leukocytes from Mouse Skin Using Enzymatic Digest and Gradient Separation

Dissociating murine skin into a single cell suspension is essential for downstream cellular analysis such as the characterization of infiltrating immune cells in rodent models of skin inflammation. Here, we describe a protocol for the digestion of mouse skin in a nutrient-rich solution with collagenase D, followed by separation of hematopoietic cells using a discontinuous density gradient. Cells thus obtained can be used for in vitro studies, in vivo transfer, and other downstream cellular and molecular analyses including flow cytometry. This protocol is an effective and economical alternative to expensive mechanical dissociators, specialized separation columns, and harsher trypsin- and dispase-based digestion methods, which may compromise cellular viability or density of surface proteins relevant for phenotypic characterization or cellular function. As shown here in our representative data, this protocol produced highly viable cells, contained specific immune cell subsets, and had no effect on integrity of common surface marker proteins used in flow cytometric analysis.

Repeated challenge with the hapten oxazolone provokes persistent vulvar mechanical sensitivity, labiar mast cell accumulation and nerve overgrowth in previously sensitized ND4 mice (HUM1P.270)

Vulvodynia is a chronic vulvar pain condition affecting up to 8-16% of 18-60 year-old women. Epidemiological studies have associated an increased risk of developing vulvodynia with a history of seasonal and insect allergies. We have previously demonstrated that acute labiar exposure to the hapten allergen oxazolone provokes increased vulvar mechanical sensitivity in ND4 Swiss mice. Here, we show that repeated oxazolone challenge produces persistent vulvar mechanical sensitivity in sensitized mice for at least12 days after 10 allergen exposures. This persistent sensitivity is accompanied by mast cell accumulation and overgrowth of cutaneous neurites both of which persist for at least 14 days after the final allergen exposure. These changes are accompanied by an early and transient increase in mRNAs encoding CADM1 - an adhesion molecule that facilitates nerve-mast cell synapses - in the skin and mRNAs encoding the inflammatory cytokine IL-6 in the spinal cord. Taken together, these neuroimmune biomarkers may serve as potential diagnostic/therapeutic targets for specific allergy-driven subsets of chronic vulvar pain.

Repeated challenge with the hapten oxazolone provokes persistent vulvar mechanical sensitivity and labiar T cell changes in previously sensitized ND4 mice (HYP7P.258)

Epidemiological evidence suggests a link between environmental allergies and the risk of developing vulvodynia—a chronic provoked vulvar pain condition affecting up to 8-16% of 18-60 year old women. We have previously shown that acute labiar exposure to the hapten allergen oxazolone provokes increased vulvar mechanical sensitivity in ND4 Swiss mice. Here, we show that repeated oxazolone challenge produces persistent vulvar mechanical sensitivity in sensitized mice for at least12 days after final allergen exposure. T cell amplification in the draining iliac lymph nodes resolves within 5 days after final challenge. Persistent sensitivity in the skin is accompanied by sustained changes in skin T cells; CD44+ CD8 and CD4 subsets remain elevated, T cell transcription factors T-bet and FoxP3 continue to be upregulated for up to 17 days after 10 allergen challenges. This is the first characterization of immune infiltrate accompanying sustained allergen-provoked mechanical sensitivity that persists after the resolution of overt inflammatory events following repeated allergen exposures. Our findings can be used to used to elucidate the underlying etiology of allergy-driven subsets of chronic pain conditions.

Clonal differences in IgE antibodies affect cutaneous anaphylaxis-associated thermal sensitivity in mice

Cellular and molecular mediators of immune responses are increasingly implicated in acute and chronic pain pathophysiologies. Here we demonstrate that passive cutaneous IgE/Ag anaphylaxis provokes increased thermal sensitivity in the hind paw tissue of mice. The murine anti-DNP IgE antibodies SPE-7 and ɛ26 are known to induce differential cytokine production in bone marrow cultured mast cells in vitro without antigen challenge. We found a novel, antigen-dependent heterogeneity in the thermal pain responses elicited in the hind paws between SPE-7 and ɛ26 sensitized DNP-challenged mice. Mice experienced pronounced hind paw thermal sensitivity lasting 6h after DNP challenge when sensitized with SPE-7 but not ɛ26 IgE. The two IgE clones induced equivalent hind paw edema, neutrophil influx, cytokine production, and reduction in tissue histamine content in vivo, and bound to the same or overlapping epitopes on the DNP antigen in vitro. Therefore IgE antibodies against the same antigen can induce comparable inflammation, yet contribute to markedly different anaphylaxis-associated pain within an allergic response, suggesting that non-canonical IgE binding partners such as sensory neurons may play a role in allergy-related pain responses.

Effective mentoring of undergraduates in an immunology research laboratory (EDU1P.252)

Rapid turnover, limited time availability, steep learning curve for bench skills, need for close supervision are challenges in the effective engagement of undergraduate students in active research laboratories. We have met this challenge in our immunology research group with early recruitment of first and second year students, year-round research activity and weekly lab meetings, scaffolded transition to independent bench work, peer-to-peer mentoring, an integrated majors’ research methods course, and a “5th year internship” for a selected student to work full-time for a year after graduation. Early recruitment allows motivated students to spend up to 3-4 years in the lab. Year-round journal clubs and lab meetings support a culture of productivity and accountability. Students collaborate, as appropriate, in the entire arc of research from generating preliminary data for grants to submitting manuscripts. In the past 7 years, 30% of 40 students trained have earned co-authorship on five peer-reviewed, published manuscripts to date. A critical outcome of this approach is an authentic ownership of research problems and motivation to contribute to the broader scientific community that is rare among undergraduates. This experience prepares them to pursue their own research careers after college. Of my 26 research students who have graduated, ten (38%) are currently enrolled in PhD programs in the biomedical sciences and 12 (46%) have worked in biomedical research.

SPE-7 but not Epsilon-26 anti-dinitrophenyl-Immunoglobulin E induces antigen-dependent thermal hyperalgesia accompanying equivalent inflammatory responses during passive cutaneous anaphylaxis reactions in mice (HYP3P.405)

Sensitization of mast cells with SPE-7 anti-DNP-IgE alone initiates inflammatory cytokine production in vitro. In contrast, ε26 anti-DNP IgE does not induce inflammatory cytokines independent of antigen-stimulation. We tested these two anti-DNP IgE clones in our model of murine thermal hyperalgesia. We found pronounced hind paw hyperalgesic responses lasting to at least 6 hours following antigen challenge 24 hours after sensitization with SPE-7 but not ε26. SPE-7/DNP did not induce greater levels of mast cell degranulation in the hind paw. Differential hyperalgesic responses were accompanied by otherwise equivalent inflammatory changes measured including histamine release, neutrophil influx, expression of TNF-α, IL-1β, and IL-6 genes and changes in levels of TNF-α, IL-1, and IL-6 proteins. Inflammatory responses and hyperalgesia were dependent on antigen challenge and were not detected in sham-challenged mice. Hyperalgesia responses or other inflammatory changes were not detected in the hind paw tissue post-sensitization in the 24 hours prior to antigen challenge. We demonstrate a novel behavioral, antigen-dependent difference between reactions mediated by these IgE antibody clones in vivo in mice. We are currently further investigating the inflammatory cytokine milieu and measuring changes in mRNA and protein levels of nociceptive signaling molecules provoked by IgE/Ag-induced cutaneous anaphylaxis to elucidate the mechanisms underlying this differential pain outcome.

Repeated allergen challenge provokes mechanical sensitivity, hyper-innervation and mast cell accumulation in the vulvar tissue of mice (HYP7P.319)

Epidemiological evidence suggests a link between a history of environmental allergies and the risk of developing vulvodynia - a chronic provoked vulvar pain condition affecting up to 20% of women in populates assessed. We have previously shown that acute labiar exposure to a hapten allergen provokes increased mechanical sensitivity in the vulvar tissue of sensitized mice. Here, we show repeated challenge with contact hypersensitivity allergen oxazolone produces sustained mechanical hyperalgesia in the vulvar region of previously sensitized female mice for 10-14 days after final allergen exposure. Acute inflammatory responses including labiar neutrophil influx, T and B cell amplification in the draining iliac lymph nodes, labiar expression of inflammatory cytokine genes (IL-6, IL-1β and Cxcl-2) are all resolved within 5 days after final allergen exposure while increased densities of both peptidergic nerve fibers and mast cells in the labiar tissue are observed. Our findings provide the first evidence of the induction of measurable and sustained pain persisting after the resolution of overt inflammatory events following an allergic response in the labiar/vulvar tissue in mice. We have established the first model of chronic allergy-provoked vulvar pain in mice that can be used to elucidate the underlying etiology of subsets of vulvar pain that present without accompanying inflammation and are associated with histories of allergic skin responses.

Mast cells: versatile gatekeepers of pain

Mast cells are important first responders in protective pain responses that provoke withdrawal from intense, noxious environmental stimuli, in part because of their sentinel location in tissue-environment interfaces. In chronic pain disorders, the proximity of mast cells to nerves potentiates critical molecular cross-talk between these two cell types that results in their synergistic contribution to the initiation and propagation of long-term changes in pain responses via intricate signal networks of neurotransmitters, cytokines and adhesion molecules. Both in rodent models of inflammatory pain and chronic pain disorders, as well as in increasing evidence from the clinic, it is abundantly clear that understanding the mast cell-mediated mechanisms underlying protective and maladaptive pain cascades will lead to improved understanding of mast cell biology as well as the development of novel, targeted therapies for the treatment and management of debilitating pain conditions.

Measuring changes in tactile sensitivity in the hind paw of mice using an electronic von Frey apparatus

Measuring inflammation-induced changes in thresholds of hind paw withdrawal from mechanical pressure is a useful technique to assess changes in pain perception in rodents. Withdrawal thresholds can be measured first at baseline and then following drug, venom, injury, allergen, or otherwise evoked inflammation by applying an accurate force on very specific areas of the skin. An electronic von Frey apparatus allows precise assessment of mouse hind paw withdrawal thresholds that are not limited by the available filament sizes in contrast to classical von Frey measurements. The ease and rapidity of measurements allow for incorporation of assessment of tactile sensitivity outcomes in diverse models of rapid-onset inflammatory and neuropathic pain as multiple measurements can be taken within a short time period. Experimental measurements for individual rodent subjects can be internally controlled against individual baseline responses and exclusion criteria easily established to standardize baseline responses within and across experimental groups. Thus, measurements using an electronic von Frey apparatus represent a useful modification of the well-established classical von Frey filament-based assays for rodent mechanical allodynia that may also be applied to other nonhuman mammalian models.

TNF-alpha neutralizing antibody blocks thermal sensitivity induced by compound 48/80-provoked mast cell degranulation

Background: Neuro-inflammatory circuits in the tissue regulate the complex pathophysiology of pain. Protective nociceptive pain serves as an early warning system against noxious environmental stimuli. Tissue-resident mast cells orchestrate the increased thermal sensitivity following injection of basic secretagogue compound 48/80 in the hind paw tissues of ND4 mice. Here we investigated the effects of pre-treatment with TNF-α neutralizing antibody on compound 48/80-provoked thermal hyperalgesia.

Methods: We treated ND4 Swiss male mice with intravenous anti-TNF-α antibody or vehicle 30 minutes prior to bilateral, intra-plantar compound 48/80 administration and measured changes in the timing of hind paw withdrawal observed subsequent to mice being placed on a 51oC hotplate. We also assessed changes in tissue swelling, TNF-α gene expression and protein abundance, mast cell degranulation, and neutrophil influx in the hind paw tissue.

Findings: We found that TNF-α neutralization significantly blocked thermal hyperalgesia, and reduced early tissue swelling. TNF-α neutralization had no significant effect on mast cell degranulation or neutrophil influx into the tissue, however. Moreover, no changes in TNF-α protein or mRNA levels were detected within 3 hours of administration of compound 48/80.

Interpretation:  The neutralizing antibodies likely target pre-formed TNF-α including that stored in the granules of tissue-resident mast cells. Pre-formed TNF-α, released upon degranulation, has immediate effects on nociceptive signaling prior to the induction of neutrophil influx. These early effects on nociceptors are abrogated by TNF-α blockade, resulting in compromised nociceptive withdrawal responses to acute, harmful environmental stimuli.

TNF-alpha neutralizing antibody blocks thermal sensitivity induced by compound 48/80-provoked mast cell degranulation

BACKGROUND

Neuro-inflammatory circuits in the tissue regulate the complex pathophysiology of pain. Protective nociceptive pain serves as an early warning system against noxious environmental stimuli. Tissue-resident mast cells orchestrate the increased thermal sensitivity following injection of basic secretagogue compound 48/80 in the hind paw tissues of ND4 mice. Here we investigated the effects of pre-treatment with TNF-α neutralizing antibody on compound 48/80-provoked thermal hyperalgesia.

METHODS

We treated ND4 Swiss male mice with intravenous anti-TNF-α antibody or vehicle 30 minutes prior to bilateral, intra-plantar compound 48/80 administration and measured changes in the timing of hind paw withdrawal observed subsequent to mice being placed on a 51oC hotplate. We also assessed changes in tissue swelling, TNF-α gene expression and protein abundance, mast cell degranulation, and neutrophil influx in the hind paw tissue.

FINDINGS

We found that TNF-α neutralization significantly blocked thermal hyperalgesia, and reduced early tissue swelling. TNF-α neutralization had no significant effect on mast cell degranulation or neutrophil influx into the tissue, however. Moreover, no changes in TNF-α protein or mRNA levels were detected within 3 hours of administration of compound 48/80.

INTERPRETATION

  The neutralizing antibodies likely target pre-formed TNF-α including that stored in the granules of tissue-resident mast cells. Pre-formed TNF-α, released upon degranulation, has immediate effects on nociceptive signaling prior to the induction of neutrophil influx. These early effects on nociceptors are abrogated by TNF-α blockade, resulting in compromised nociceptive withdrawal responses to acute, harmful environmental stimuli.

An immunology course focused on faculty research interest provides key inputs for research productivity at a primarily undergraduate institution (P4529)

Rapid turnover of trained undergraduate student researchers and limited time faculty and students can devote to research activities during the academic year are some of the roadblocks to maintaining a productive research program at a primarily undergraduate institution. At Macalester College, a highly selective liberal arts institution, we have addressed these issues, in part, through the design and implementation of a “Research in Immunology” course that is open by application to a group of eight second- or third-year students each spring. The course consists of a journal club with reading, writing and presentation activities that immerse students in the primary literature around the faculty member’s research question, and a laboratory component that emphasizes intensive skill building while fully exposing students to novel, unanswered questions. A subset of these students then enter the lab the following summer with a high level of intellectual and technical preparation and many are highly productive in the laboratory for 2+ years providing continuity of trained personnel, critical peer mentoring and a degree of involvement in and ownership of the research problems that is rare among undergraduates. In the past 6 years, I have trained 40 students in my laboratory most of whom have taken this course. Of these, 30% have completed honors research projects and earned co-authorship on manuscripts, and 6 have gone on to PhD programs in immunology/biomedicine.

Contact hypersensitivity to oxazolone provokes vulvar mechanical hyperalgesia in mice (P6028)

Vulvodynia can affect ~20% of women of child-bearing age. Activities such as contact with tight clothing or sexual intercourse provoke burning pain sensations whose etiology and underlying mechanisms are poorly understood. Epidemiological evidence suggests a link between a history of environmental allergies and the risk of developing vulvodynia. Clinicians find increased mast cell numbers, hyperinnervation and up-regulation of inflammatory cytokines in biopsies from vulvodynia patients vs. controls. An allergy-based mast cell focused mouse model of vulvodynia is needed to elucidate the mechanisms underlying this pathology. We show that challenge with contact hypersensitivity allergen oxazolone produces acute mechanical hyperalgesia in the vulvar region of previously sensitized female mice. Acute pain is localized to the challenge site, lasts up to 24 hours post-challenge and is accompanied by influx of neutrophils into the labiar tissue and up-regulation of several inflammatory cytokine genes including IL-6, Cxcl-1 and Cxcl-2. Pre-challenge administration of H1R-antagonist pyrilamine, tricyclic antidepressant amitryptiline, and sodium cromoglycate all abrogate the hyperalgesic response. Our findings provide the first evidence of the induction of measurable pain following an allergic response in the labiar/vulvar tissue in mice thus establishing a model that can be adapted to chronic challenges and long-term assessment of pain with and without ongoing inflammation.

Highly cytokinergic SPE-7 anti-dinitrophenyl-immunoglobulin E induces antigen-dependent thermal hyperalgesia and inflammatory cytokine production in the mouse hindpaw (P6000)

SPE-7 anti-DNP-IgE initiates inflammatory cytokine production without antigen stimulation in vitro. In contrast, ϵ2624 anti-DNP IgE does not induce inflammatory cytokines independent of antigen-stimulation. However, their effects in vivo have not been described. We tested two well-characterized anti-mouse IgE antibody clones in our model of murine thermal hyperalgesia. We found pronounced hindpaw hyperalgesic responses lasting to at least 6 hours following antigen challenge after sensitization with SPE-7. These responses were accompanied by histamine release and neutrophil influx as we have previously shown in c48/80-mediated thermal hyperalgesia. In contrast, we found that antigen challenge following sensitization with clone ϵ2624 produced slight hyperalgesia at 1 hr that was resolved by 3 hours. We demonstrate a novel functional, behavioral difference between reactions mediated by these IgE antibody clones in vivo in mice. Also, SPE-7 does not lead to antigen-independent cytokine production in the mouse hind paw. After antigen challenge, both IgEs produce equivalent levels of TNF-α, IL-1, and IL-6, and cause equivalent histamine release and neutrophil influx. Thus tissue-resident sentinel mast cells may be critical initiators of allergen-evoked hyperalgesia in mice and differences in the nature and repertoire of IgE antibodies produced during an allergic response likely have pathophysiological implications for various health outcomes including pain.

Semaphorin 4A is dynamically regulated during thymocyte development in mice

Semaphorins are important regulators of peripheral T and B-cell mediated immune responses in mice and humans. Modulatory roles of semaphorins in T cell development are also being characterized. We carefully analyzed the gene expression and protein levels of semaphorins 4A, 4D, and 7A at various developmental stages of T cell maturation in the thymus of C57BL/6 mice. Sema7a was expressed at very low levels, while Sema4d was abundant at all developmental stages of mouse thymocytes. We found the most interesting pattern of gene regulation and protein localization for semaphorin 4A. Both semaphorin 4A mRNA and protein were clearly detected on the earliest progenitors and were downregulated through thymic development. SEMA4A protein also showed a distinct cortico-medullary pattern of localization. Our findings contribute to an understanding of the complex roles played by semaphorins in the network of spatially and temporally regulated cues underpinning T cell development in the thymus.

Mast cell degranulation mediates compound 48/80-induced hyperalgesia in mice

Mast cells mediate allergies, hypersensitivities, host defense, and venom neutralization. An area of recent interest is the contribution of mast cells to inflammatory pain. Here we found that specific, local activation of mast cells produced plantar hyperalgesia in mice. Basic secretagogue compound 48/80 induced plantar mast cell degranulation accompanied by thermal hyperalgesia, tissue edema, and neutrophil influx in the hindpaws of ND4 Swiss mice. Blocking mast cell degranulation, neutrophil extravasation, and histamine signaling abrogated these responses. Compound 48/80 also produced edema, pain, and neutrophil influx in WT C57BL/6 but not in genetically mast cell-deficient C57BL/6-Kit(W-sh)(/)(W-sh) mice. These responses were restored following plantar reconstitution with bone marrow-derived cultured mast cells.

IgE antibody-mediated degranulation of cutaneous mast cells induces thermal pain in mice (118.8)

Pain is a key component of inflammation and a public health issue of significance. Mast cell activity has been implicated in pain responses associated with irritable bowel syndrome, migraine headaches, interstitial cystitis, postoperative pain, and endometriosis, but the mechanisms underlying mast cell involvement in pain pathologies are not clear. We show that degranulation of plantar mast cells caused by passive local antibody (IgE anti-DNP/HSA) sensitization and systemic antigen (DNP/HSA) challenge, induces thermal hyperalgesia as well as significant edema, neutrophil influx, and upregulation of IL-1beta and IL-6 proteins in the plantar tissue. Pre-treatment with histamine receptor H2 and H3/4 antagonists significantly abrogates pain, but not edema, associated with IgE/antigen-mediated mast cell degranulation This suggests that while pain has a multifactorial pathophysiology, tissue-resident sentinel mast cells may be a critical initiators of allergen-invoked hyperalgesia in mice.

Building a toolkit: An undergraduate teaching laboratory sequence in immunology (50.1)

We have designed a laboratory curriculum in immunology where students build and use a toolkit of basic techniques. In the first 10 weeks, students learn how to isolate human and mouse immune cells, label cells with antibodies, perform magnetic enrichment, flow cytometry analysis, T cell proliferation, and ELISA assays. We emphasize keen observation, excellent record keeping, and protocol development. We ensure that each team has at least two opportunities to perform each new technique. Students survey the published literature and formulate a novel question about effects of a dietary supplement of choice on in vitro T cell stimulation. Teams develop experimental designs that are critiqued in a group workshop. Independent experiments are carried out, data collected and analyzed by teams, and a detailed, reflective lab notebook entry compiled by each student. Teams present their findings in a culminating mini-symposium. Our iterative emphasis on skill building, critical record-keeping, application of newly learned skills, and teamwork closely simulates the learning that happens in authentic research laboratories. Students encounter and comprehend these basic procedures in classroom discussions, research seminars, and journal articles. According to students surveyed, this plays a critical role in the productive integration of classroom and laboratory learning, and gives students a strong sense of engagement with the professional world of immunology research.

Neutrophils: key players in mast cell-mediated thermal pain in mice (67.4)

Mast cells are involved in a range of physiologies and pathologies including allergic disease, defense against pathogens, and neutralization of venoms. Recently, these cells have been shown to play significant roles in inflammatory pain. Acute inflammation is a beneficial mechanism designed to prevent further tissue damage; however, it can also lead to a decreased quality of life and, as such, is a pervasive health concern. The involvement of mast cells in this process has not been fully characterized. We show, in a mast cell-dependent model of thermal pain that degranulation of peripheral mast cells in the plantar tissue of mice is accompanied by neutrophil influx as well as edema and upregulation of pro-inflammatory cytokines. When mast cells are stabilized with sodium cromoglycate, pain, edema and neutrophil influx are abrogated. Additionally, when neutrophil influx is blocked with pre-administration of the selectin blocker fucoidan, pain and edema are also abrogated. This suggests neutrophil influx is a key event in the development of mast cell-initiated inflammatory pain.

Mast cell-deficient mice show attenuated thermal pain responses (163.18)

Pain is a cardinal component of inflammation and a significant public health issue. Inflammatory cytokines such as TNF-alpha, IL-1beta, CXCL1/IL-8, as well as neutrophil influx have been implicated in the potentiation of peripheral inflammatory pain in models of thermal and mechanical hindpaw hypernociception in rodents.. Degranulation of mast cells has been shown to be important for phosphorylation of Erk in nociceptive neurons in a rat model of migraine-like stimulation. Mechanical bladder pain in a model of interstitial cystitis was abrogated in mast cell deficient mice. We show that degranulation of plantar mast cells caused by direct secretagogue treatment or passive antibody sensitization and challenge, causes reduction in paw withdrawal latencies as well as significant edema, neutrophil influx, and upregulation of local TNF-alpha and IL-1beta levels, as well as histamine release in the hindpaws of mice in a model of thermal pain. Mast cell-deficient C57BL/6 Wsh/Wsh mice show no edema, histamine release or pain response indicated by reduction in paw withdrawal latencies. This suggests that while pain is a complex and multifactorial physiology, tissue sentinel mast cells may be a critical initiator of inflammatory pain in both protective and allergic/pathological contexts.

Immunology and the liberal arts: constructing a multi-level immunology curriculum at an undergraduate institution (51.2)

At a liberal arts college, immunology is not restricted to a specialized biology course. Its relevance to global public health attracts biology majors and non-majors. Its inherent evolutionary scaffolding and broad focus on cellular/molecular physiology makes it suitable for all levels of the majors’ curriculum. With sophisticated technology and model systems, and translational significance, it appeals to senior biology majors undertaking collaborative research with faculty, participating in journal club-style seminar courses and writing independent capstone papers. At Macalester College, we offer a multi-level immunology curriculum ranging from non-majors global and community health seminars on pandemics and vaccine development, an introductory immunology course, with laboratory and civic engagement components, for juniors, and senior-level seminar and research courses and honors research projects. Our flow cytometry core supports labs across the biology curriculum. With its inherent focus on integrative thinking and application of concepts to solving problems, relevance to global health and lastly, but importantly, room for concepts of identity, organization and collective action, immunology is a perfect liberal art. We present examples of course and laboratory innovations, strategies for funding a research laboratory at a liberal arts college, and ways of getting students across campus engaged in studying the immune system.

Mast cells are initiators of inflammatory pain in thermal pain in mice. (86.2)

Pain is a cardinal component of inflammation and a significant public health issue. Cytokines such as TNF-alpha, IL-1beta, IL-15 and CXCL1/IL-8, as well as neutrophil influx have been implicated in the potentiation of peripheral inflammatory pain in models of thermal and mechanical hindpaw hypernociception in rodents. These lines of evidence point to sentinel mast cells in the tissues as possible regulators of these pain responses. Degranulation of mast cells has been shown to be important for phosphorylation of Erk in nociceptive neurons in a rat model of migraine-like stimulation. Mechanical bladder pain in a model of interstitial cystitis was abrogated in mast cell deficient mice. We show that c4880-mediated degranulation of mast cells causes pain as well as significant edema and upregulation of local TNF-alpha and IL-1beta levels in the hindpaws of mice in a model of thermal pain. Mast cell-deficient Wsh mice show abrogation of this pain response. IgE/Ag mediated degranulation of mast cells in the paws of WT mice also causes pain and edema but it is not accompanied by detectable upregulation of TNF-alpha in the paws. This suggests that mast cells may be necessary for the initiation of inflammatory pain but that the underlying mechanisms of potentially protective inflammatory pain vs. potentially pathological allergic pain may be different.

Arrested bone marrow resident T cell committed progenitors in athymic nu/nu mice can give rise to alpha-beta T cells in an OP9DL1 co-culture system. (36.34)

Bone marrow-resident committed T cell progenitors (CTP) are arrested at a Thy1.2hiLin-CD2- stage in athymic nu/nu mice. In WT mice, CTP progress to a Thy1.2hiLin-CD2+ intermediate stage that then can produce mature, function single positive T cells through thymic and extrathymic maturation pathways. The nu/nu bone marrow microenvironment, therefore, likely disrupts the T cell competence of these precursors during the transition from hematopoietic stem cell (HSC) to CTP prior to these cells leaving the bone marrow for the thymus or periphery. This defect is currently not characterized. We investigated the developmental potential of the arrested CTP from nu/nu bone marrow in a hyper-Notch signal environment induced by the OP9DL1 co-culture system that is able to support the development of mature single-positive T cells from HSCs, embryonic stem cells (ESC) and double negative thymocytes. We found that the OP9DL1 co-culture microenvironment allows the arrested nu/nu CTP to progress to the Thy1.2+Lin-CD2+ intermediate stage as well as to double positive CD4+CD8+ and single positive CD4 and CD8 αβ T cells. It is likely therefore that Notch signaling is compromised in the bone marrow of nu/nu mice and this dysregulated signaling results in the absence of acquisition of T cell competence by early hematopoietic precursors in the bone marrow of these congenitally athymic mice.

The expression of semaphorins 4A, 4D and 7A in early hematopoietic T progenitors in the bone marrow of C57BL/6 mice. (36.65)

Semaphorins are a group of transmembrane, secreted, and GPI-linked proteins that have been thoroughly studied in the nervous system where they function as ‘traffic’ enzymes in guiding axonal growth. Although most exhaustively characterized in this realm, they are also expressed in several other physiological systems. We have characterized the expression and localization of T cell semaphorins 4A, 4D and 7A in developing thymocytes. We show here that hematopoietic T cell progenitor cells (CD90+) enriched from the Bone Marrow have high levels of sema4A and 4D expression, but no sema7A. PlexinD1 and C1 (the receptors for sema4A and 7A) were also expressed in this subset, but there was no PlexinB1 or CD72 (the receptors for sema4A and 4D respectively). This provides further evidence of the dynamic expression and regulation of sema4A, 4D and 7A in early T cell development.

Characterization of Sema4D and Sema7A mRNA Expression in Developing C57BL/6 Mouse Thymocytes (138.24)

Semaphorins are a family of membrane-bound and secreted signaling molecules with active roles in nearly every organ system in processes ranging from heart morphogenesis to tumor development. We are investigating the potential roles of these molecules during T cell development in the thymus. Using Real Time PCR, we have characterized the mRNA expression of Sema4D and Sema7A, semaphorins with known peripheral immune system activity, in subsets of developing thymocytes. While Sema4D and Sema7A mRNA is expressed by all subsets of thymocytes, there appears to be no differential expression of these transcripts between CD4-CD8-, CD4+CD8+, CD4+, and CD8+ populations. While Sema7A expression has previously been described in the human thymus, this is the first time Sema4D and Sema7A mRNA expression has been reported in the murine thymus.

Changes in levels of Sema4A mRNA in developing thymocyte subsets in C57 mice (81.5)

Since their discovery in 1993, the semaphorin family has expanded to include over twenty different types of the proteins with known guidance and developmental roles ranging from heart morphogenesis and vertebrate growth to immuno-regulation. These functions of semaphorins as adaptors of peripheral immune responses in vertebrates have led us to ask whether these molecules may be important for developing T cells in the mouse thymus. We previously showed by RT-PCR that Sema4A mRNA is expressed in the thymus of 4 wk-old C57BL/6 mice. Our immuno-histochemistry studies showed that Sema4A protein is expressed in the thymus of these mice and appears localized to the medullary region. Our current findings show that by quantitative real time PCR analysis, CD4-CD8- (DN) cells as well as CD4+ and CD8+ (SP ) cells express Sema4A mRNA at 2-2.5 fold higher levels compared to CD4+CD8+ (DP) cells in the thymus of C57BL/6 mice. Taken together, our results show that levels of Sema4A mRNA fluctuate during the staged development of thymocytes. In particular, the expression pattern on DN and SP but not DP cells suggests that Sema4A may be used as an adaptor molecule in the expansion of DP cells during positive selection and naïve SP cells once again express Sema4A mRNA prior to their exit from the thymus upon which this molecule serves its known accessory role in antigen-mediated peripheral activation and maturation.

IL-3 is required for increases in blood basophils in nematode infection in mice and can enhance IgE-dependent IL-4 production by basophils in vitro

Basophils represent potential effector and immunoregulatory cells, as well as a potential source of IL-4, during the immune response elicited by infection with the nematode Nippostrongylus brasiliensis (N.b.), and in other settings. However, the factors which regulate the numbers of blood basophils in mice, or the ability of these cells to produce IL-4, are not fully understood. We found that infection of mice with the nematodes N.b. or Strongyloides venezuelensis (S.v.) induced substantial increases in the numbers of blood basophils (to as high as 18% of circulating blood leukocytes). Experiments in IL-3-/- vs IL-3+/+ mice, and in IL-3-treated IL-3-/- mice, showed that essentially all of the increases in blood or bone marrow basophils during N.b. or S.v. infection were IL-3 dependent. Many of the blood, bone marrow or liver-derived basophils from IL-3-/- or IL-3+/+ mice expressed intracellular IL-4 upon stimulation with anti-IgE in vitro. However, after incubation of the cells with exogenous IgE in vitro, blood- or liver-derived basophils from IL-3+/+ mice exhibited higher levels of intracellular IL-4 after stimulation with anti-IgE than did basophils derived from IL-3-/- mice. Thus, IL-3 is a major regulator of the marked increases in blood basophil levels observed during infection of mice with N.b. or S.v. and also can enhance levels of intracellular IL-4 upon activation of basophils with anti-IgE in vitro.

Adoptive transfer of mast cells does not enhance the impaired survival of Kit(W)/Kit(W-v) mice in a model of low dose intraperitoneal infection with bioluminescent Salmonella typhimurium

Mast cells are important effector cells in IgE-associated immune responses, but also can contribute to host defense in certain examples of bacterial infection. We found that genetically mast cell-deficient WBB6F1-Kit(W)/Kit(W-v) mice exhibited more bacterial CFUs per spleen by 6 days after intraperitoneal injection of bioluminescent Salmonella typhimurium, and died more rapidly after infection, than did the congenic WBB6F1-Kit(+/+) wild type mice. Adoptive transfer of bone marrow-derived cultured mast cells of Kit(+/+) origin to the peritoneal cavity of Kit(W)/Kit(W-v) mice resulted in engraftment of mast cells in the peritoneal cavity and mesentery of the recipient mice, and the development of large numbers of mast cells in the spleen. However, such mast cell-engrafted Kit(W)/Kit(W-v) mice appeared sicker after intraperitoneal injection with S. typhimurium than did mast cell-deficient Kit(W)/Kit(W-v) mice, and exhibited numbers of CFUs of bacteria per spleen, and a survival curve, that were not significantly different than those of Kit(W)/Kit(W-v) mice. These results, when taken together with prior studies investigating the roles of mast cells in innate immunity, strongly suggest that whether mast cells can be shown to have a significant role in enhancing survival during bacterial infections may depend critically on the details of the particular experimental systems examined.

Mast cells promote homeostasis by limiting endothelin-1-induced toxicity

Endothelin-1 (ET-1) is a 21-amino-acid peptide, derived from vascular endothelial cells, with potent vasoconstrictor activity. ET-1 has been implicated in diverse physiological or pathological processes, including the vascular changes associated with sepsis. However, the factors that regulate ET-1-associated toxicity during bacterial infections, or in other settings, are not fully understood. Both the pathology associated with certain allergic and autoimmune disorders, and optimal host defence against bacterial and parasitic infections are mediated by mast cells. In vitro, mast cells can produce ET-1 (ref. 11), undergo ET-1-dependent and endothelin-A receptor (ET(A))-dependent activation, and release proteases that degrade ET-1 (ref. 14). Although the potential relationships between mast cells and the ET-1 system thus may be complex, the importance of interactions between ET-1 and mast cells in vivo is obscure. Here we show that ET(A)-dependent mast-cell activation can diminish both ET-1 levels and ET-1-induced pathology in vivo, and also can contribute to optimal survival during acute bacterial peritonitis. These findings identify a new biological function for mast cells: promotion of homeostasis by limiting the toxicity associated with an endogenous mediator.

RabGEF1 is a negative regulator of mast cell activation and skin inflammation

Mast cell activation induced by aggregation of Fc epsilon RI receptors with immunoglobulin E and antigen is mediated through the activation of multiple protein kinase cascades. Here we report that the regulatory protein RabGEF1 bound to Ras and negatively regulated Ras activation and its 'downstream' effector pathways in Fc epsilon RI-dependent mast cell activation. RabGEF1-deficient mast cells showed enhanced degranulation and release of lipid mediators and cytokines in response to Fc epsilon RI aggregation. RabGEF1-deficient mice developed severe skin inflammation and had increased numbers of mast cells. Thus, RabGEF1 is a negative regulator of Fc epsilon RI-dependent mast cell activation, and a lack of RabGEF1 results in the development of skin inflammation in vivo.