Sensitive detection and quantitation of mouse eosinophils in tissues using an enzymatic eosinophil peroxidase assay: its use to rapidly measure pulmonary eosinophilia during experimental respiratory syncytial virus infection of mice

Correlation between systemic allergen desensitisation and long-term asthma protection in mice following intravenous administration of the live tuberculosis vaccine MTBVAC

BACKGROUND

MTBVAC is a live attenuated tuberculosis vaccine, currently undergoing phase III evaluation for tuberculosis prevention. In previous preclinical studies, we found that local pulmonary administration of MTBVAC via the intranasal route had a strong therapeutic effect against asthma. This effect correlated with the abrogation of allergen-specific Th2 response in the lungs.

METHODS

Using different mouse models of asthma, we investigated the effect of MTBVAC administered by intravenous (IV) route and its potential as immunotherapeutic agent to induce desensitisation of allergen-specific responses at a systemic level. We explored the effects of this process in the efficacy against airway hyperresponsiveness (AHR) induced by exposure to different allergens.

FINDINGS

IV MTBVAC was highly efficient at reducing AHR induced by different allergens. Additionally, IV MTBVAC was found to be well-tolerated, being progressively eliminated from the different organs analysed. From a mechanistic standpoint, we observed that MTBVAC intravenous, but not intranasal, impaired allergen-specific Th2 response in both lungs and spleen. This reduction at a systemic level correlated with long-term therapeutic protection against allergen exposure. Our results also revealed differential immunological mechanisms governing systemic and local pulmonary allergen desensitisation processes. Notably, in a cohort of patients with asthma sensitive to house dust mite (HDM), in vitro incubation of peripheral blood mononuclear cells (PBMCs) with MTBVAC prevented allergen-specific production of Th2 cytokines IL-4 and IL-5.

INTERPRETATION

Altogether, our results suggest that intravenous MTBVAC could be a plausible allergen desensitising approach for treatment of asthma, and could provide long-term protection against allergen exposure.

FUNDING

MCIN/AEI/10.13039/501100011033 [grants number RTI2018-097625-B-I00 and PID2022-138624OB-I00]; Consorcio Centro de Investigación Biomédica en Red- (Groups CB06/06/0020 and CB06/06/0013), Instituto de Salud Carlos III.

Ameliorative effect of two structurally divergent hydrazide derivatives against DSS-induced colitis by targeting Nrf2 and NF-κB signaling in mice

The environmental factors and genetic vulnerability trigger the inflammatory bowel diseases (IBDs) such as ulcerative colitis and Crohn's disease. Furthermore, the oxidative stress and inflammatory cytokines have been implicated in the aggravation of the IBDs. The aim of the present study was to investigate the effect of N-(benzylidene)-2-((2-hydroxynaphthalen-1-yl)diazenyl)benzohydrazides (NCHDH and NTHDH) compounds against the DSS-induced colitis in mice. The colitis was induced by 5% dextran sulfate sodium (DSS) dissolved in normal saline for 5 days. The effect of the NCHDH and NTHDH on the behavioral, biochemical, histological, and immunohistological parameters was assessed. The NCHDH and NTHDH treatment improved the behavioral parameters such as food intake, disease activity index, and diarrhea score significantly compared to DSS control. The NCHDH and NTHDH treatments significantly increased the antioxidant enzymes, whereas oxidative stress markers were markedly reduced. Similarly, the NCHDH and NTHDH treatments significantly suppressed the activity of nitric oxide (NO), myeloperoxidase (MPO), and eosinophil peroxidase (EPO). The histological studies showed a significant reduction in inflammation, immune cell infiltration, and fibrosis in the NCHDH- and NTHDH-treated groups. The immunohistochemical results demonstrated that NCHDH and NTHDH treatments markedly increase the expression level of Nrf2, HO-1 (hemeoxygenase-1), TRX (thioredoxin reductase), and IκB compared to the DSS-induced group. In the same way, the NCHDH and NTHDH significantly reduced the NF-κB and COX-2 (cyclooxygenase-2) expression levels. The NCHDH and NTHDH treatment significantly improved the symptoms associated with colitis via inducing antioxidants and attenuating oxidative stress markers.

Cardiopulmonary function and dysregulated cardiopulmonary reflexes following acute oleoresin capsicum exposure in rats

Cardiopulmonary functions such as respiratory depression, severe irritation, inflamed respiratory tract, hyperventilation and, tachycardia are the most affected ones when it comes to the riot control agent oleoresin capsicum (OC) exposure. However, no studies have been done to elucidate the mechanism underlying deterioration of the combined cardiopulmonary functions. Parameters such as acute respiratory, cardiac, parameters and ultrasonography (USG) measurements were investigated in an in vivo setup using Wistar rats at 1 h and 24 h post inhalation exposure to 2%, 6% and 10% OC, whereas, cell migration in rat peritoneal mast cells (RPMCs), metabolomics and eosinophil peroxidase (EPO) activity in bronchoalveolar lavage fluid (BALF) were investigated in an in vitro setup. Results obtained from electrophysiological recording indicated that OC exposure produces apnea and decrease in mean arterial pressure (MAP) was obtained from hemodynamic parameters whereas cardiac parameters assessment revealed increase in the level of cardiac output (CO) and decrease in stroke volume (SV) with recovery towards the post-exposure period. A decrease in the percentage area of certain fatty acid pathway metabolites in BALF appropriately linked the lung injury following OC exposure which was further cemented by increasing concentration of EPO. Histopathology and SEM also proved to be favorable techniques for the detection of OC induced physiological cardiac and pulmonary modifications respectively. Furthermore, Boyden chamber experiment established the chemoattractant property of OC. It may be concluded from the above studies that these newly reported facets may be utilized pharmacologically to mitigate cardiopulmonary adverse effects owing to OC exposure.

Selective Monitoring and Imaging of Eosinophil Peroxidase Activity with a J-Aggregating Probe

The specific detection of eosinophil peroxidase (EPO) activity requires the difficult distinction between hypobromous acid generated by EPO and hypochlorous acid generated by other haloperoxidases. Here we report a fluorogenic probe that is halogenated with high kinetic selectivity (≥1200:1) for HOBr over HOCl. Heavy-atom effects do not quench the dibrominated product because of its self-assembly into emissive J-aggregates that provide a turn-on signal. Applications of this fluorogen to EPO activity assays, dipstick sensors, fluorescence imaging of EPO activity, assays of oxidative stress in cancer cells, and immune response detection in live mice are reported.

Reduced expression of granule proteins during extended survival of eosinophils in splenocyte culture with GM-CSF

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a multifaceted hematopoietic cytokine and the culture of mouse bone marrow with GM-CSF produces a variety of myeloid cells including granulocytes, macrophages, and dendritic cells. In the present study, we cultured mouse splenocytes with GM-CSF and examined the changes in hematopoietic cell populations over a week. Most of the splenic hematopoietic cells disappeared significantly from culture within 6days with or without the presence of GM-CSF. Among the splenic granulocyte populations, only eosinophils fully survived throughout the culture with GM-CSF for more than a week. During 10days of culture with GM-CSF, splenic eosinophils maintained their morphology as well as most of their surface molecules at high levels, including CCR3 and Siglec F. Meanwhile, the expression of mRNAs encoding major basic protein-1 (MBP-1) and eosinophil peroxidase (EPO), two major eosinophil-derived granule proteins, was diminished significantly from the cultured eosinophils. EPO assays also revealed that eosinophils in culture for more than 5days retained 30% or less EPO activity compared to those in uncultured splenocytes. In contrast, culture of splenocytes with GM-CSF did not change the capacity of eosinophils to migrate in response to eotaxin-1. Our results indicate that mouse splenic eosinophils are effectively cultured for lengthy periods while their expression of eosinophil-derived granule proteins is specifically suppressed. The relevance of these findings to eosinophilic inflammatory response is discussed.

Indomethacin inhibits eosinophil migration to prostaglandin D2 : therapeutic potential of CRTH2 desensitization for eosinophilic pustular folliculitis

Indomethacin is a cyclo-oxygenase inhibitor, and shows therapeutic potential for various eosinophilic skin diseases, particularly eosinophilic pustular folliculitis. One of the unique characteristics of indomethacin is that, unlike other non-steroidal anti-inflammatory drugs, it is a potent agonist of chemoattractant receptor-homologous molecule expressed on T helper type 2 cells (CRTH2), a receptor for prostaglandin D2 (PGD2 ). This study investigated the pharmacological actions of indomethacin on eosinophil migration to clarify the actual mechanisms underlying the therapeutic effects of indomethacin on eosinophilic pustular folliculitis. Eosinophils exhibited chemokinetic and chemotactic responses to both PGD2 and indomethacin through CRTH2 receptors. Pre-treatment of eosinophils with indomethacin greatly inhibited eosinophil migration to PGD2 and, to a much lesser extent, to eotaxin (CCL11); these effects could be mediated by homologous and heterologous desensitization of eosinophil CRTH2 and CCR3, respectively, by agonistic effects of indomethacin on CRTH2. Indomethacin also cancelled a priming effect of Δ(12) -PGJ2 , a plasma metabolite of PGD2 , on eosinophil chemotaxis to eotaxin. Indomethacin down-modulated cell surface expression of both CRTH2 and CCR3. Hair follicle epithelium and epidermal keratinocytes around eosinophilic pustules together with the eccrine apparatus of palmoplantar lesions of eosinophilic pustular folliculitis were immunohistochemically positive for lipocalin-type PGD synthase. Indomethacin may exert therapeutic effects against eosinophilic skin diseases in which PGD2 -CRTH2 signals play major roles by reducing eosinophil responses to PGD2 .

Functionally competent eosinophils differentiated ex vivo in high purity from normal mouse bone marrow

We have devised an ex vivo culture system which generates large numbers of eosinophils at high purity (>90%) from unselected mouse bone marrow progenitors. In response to 4 days of culture with recombinant mouse FLT3-L and recombinant mouse stem cell factor followed by recombinant mouse IL-5 alone thereafter, the resulting bone marrow-derived eosinophils (bmEos) express immunoreactive major basic protein, Siglec F, IL-5R alpha-chain, and transcripts encoding mouse eosinophil peroxidase, CCR3, the IL-3/IL-5/GM-CSF receptor common beta-chain, and the transcription factor GATA-1. BmEos are functionally competent: they undergo chemotaxis toward mouse eotaxin-1 and produce characteristic cytokines, including IFN-gamma, IL-4, MIP-1alpha, and IL-6. The rodent pathogen pneumonia virus of mice replicates in bmEos and elevated levels of IL-6 are detected in supernatants of bmEos cultures in response to active infection. Finally, differentiating bmEos are readily transfected with lentiviral vectors, suggesting a means for rapid production of genetically manipulated cells.

High-dose but not low-dose mainstream cigarette smoke suppresses allergic airway inflammation by inhibiting T cell function

Epidemiological studies have identified childhood exposure to environmental tobacco smoke as a significant risk factor for the onset and exacerbation of asthma, but studies of smoking in adults are less conclusive, and mainstream cigarette smoke (MCS) has been reported to both enhance and attenuate allergic airway inflammation in animal models. We sensitized mice to ovalbumin (OVA) and exposed them to MCS in a well-characterized exposure system. Exposure to MCS (600 mg/m(3) total suspended particulates, TSP) for 1 h/day suppresses the allergic airway response, with reductions in eosinophilia, tissue inflammation, goblet cell metaplasia, IL-4 and IL-5 in bronchoalveolar lavage (BAL) fluid, and OVA-specific antibodies. Suppression is associated with a loss of antigen-specific proliferation and cytokine production by T cells. However, exposure to a lower dose of MCS (77 mg/m(3) TSP) had no effect on the number of BAL eosinophils or OVA-specific antibodies. This is the first report to demonstrate, using identical smoking methodologies, that MCS inhibits immune responses in a dose-dependent manner and may explain the observation that, although smoking provokes a systemic inflammatory response, it also inhibits T cell-mediated responses involved in a number of diseases.

Modulation of the epithelial inflammatory response to rhinovirus in an atopic environment

BACKGROUND

Immune responses to rhinovirus (RV) as well as direct effects of RV on respiratory epithelium may contribute to the induction of asthma exacerbations.

OBJECTIVE

To evaluate the effect of the environment resulting from an atopic immune response on RV-induced epithelial inflammation, replication and cytotoxicity.

METHODS

Peripheral blood mononuclear cells (PBMC) from atopic asthmatic subjects and matched controls (12 pairs) were isolated and stimulated by RVs. Human bronchial epithelial (BEAS-2B) cells were infected with RV in the presence of conditioned media from RV-stimulated PBMC cultures. IL-6, IL-8, RANTES and TGF-beta1 levels were measured by ELISA, RV-induced cytotoxicity by a colorimetric method and RV titres on Ohio-HeLa cells.

RESULTS

RV-induced epithelial production of IL-6, IL-8 and RANTES was significantly lower, while TGF-beta1 was higher when cells were exposed to conditioned media from atopic asthmatic subjects compared with those from normal controls. Exposure to the 'atopic' environment also resulted in elevated RV titres and increased RV-induced cytotoxicity.

CONCLUSIONS

Under the influence of an atopic environment, the epithelial inflammatory response to RV is down-regulated, associated with increased viral proliferation and augmented cell damage, while TGF is up-regulated. These changes may help explain the propensity of atopic asthmatic individuals to develop lower airway symptoms after respiratory infections and indicate a mechanism through which viral infections may promote airway remodelling.

Mesenteric adipose tissue alterations resulting from experimental reactivated colitis

BACKGROUND

Adipose tissue secretes a large number of hormones that act either locally or at distant sites, modulating immune responses, inflammation, and many endocrine and metabolic functions. Abnormalities of fat in the mesentery have been long recognized in surgical specimens as characteristic features of Crohn's disease; however, the importance of this in chronic inflammatory disease is unknown. Additionally, adipocytes in depots that enclose lymph nodes or other dense masses of lymphoid tissue have many site-specific physiological properties.

METHODS

In this study, the alterations of mesenteric and perinodal mesenteric adipose tissue during experimental colitis, induced by repeated intracolonic trinitrobenzene sulfonic acid instillations, were evaluated, focusing on morphological and activity alterations and the adipocytokine production profile.

RESULTS

After a 35-day protocol, the colitis animals presented greater mesenteric fat masses despite their lower body weights. Another adipose tissue depot, epididymal adipose tissue, was also evaluated and no change in mass was observed. The mesenteric adipocyte from colitis animals had a reduced diameter, normal PPAR-gamma-2 expression, and higher basal lipolysis and TNF-alpha production when compared to normal rats. Perinodal mesenteric adipocytes present normal diameters, downregulated levels of PPAR-gamma-2, higher basal lipolysis and TNF-alpha, and leptin and adiponectin production.

CONCLUSIONS

The findings suggest that mesenteric adipose tissue has a site-specific response during experimental inflammation, where perinodal adipose tissue retains the ability to produce different adipocytokines. These substances may interfere in many lymph node aspects, while mesenteric adipose tissue produces substances that could contribute directly to aggravate the inflammatory process.

Respiratory syncytial virus synergizes with Th2 cytokines to induce optimal levels of TARC/CCL17

Respiratory syncytial virus (RSV) is a ubiquitous virus that preferentially infects airway epithelial cells, causing asthma exacerbations and severe disease in immunocompromised hosts. Acute RSV infection induces inflammation in the lung. Thymus- and activation-regulated chemokine (TARC) recruits Th2 cells to sites of inflammation. We found that acute RSV infection of BALB/c mice increased TARC production in the lung. Immunization of BALB/c mice with individual RSV proteins can lead to the development of Th1- or Th2-biased T cell responses in the lung after RSV infection. We primed animals with a recombinant vaccinia virus expressing either the RSV fusion (F) protein or the RSV attachment (G) protein, inducing Th1- and Th2-biased pulmonary memory T cell responses, respectively. After RSV infection, TARC production significantly increased in the vaccinia virus G-primed animals only. These data suggest a positive feedback loop for TARC production between RSV infection and Th2 cytokines. RSV-infected lung epithelial cells cultured with IL-4 or IL-13 demonstrated a marked increase in the production of TARC. The synergistic effect of RSV and IL-4/IL-13 on TARC production reflected differential induction of NF kappa B and STAT6 by the two stimuli (both are in the TARC promoter). These findings demonstrate that RSV induces a chemokine TARC that has the potential to recruit Th2 cells to the lung.

Mast cell-derived TNF contributes to airway hyperreactivity, inflammation, and TH2 cytokine production in an asthma model in mice

BACKGROUND

Mast cells, IgE, and TNF, which have been implicated in human atopic asthma, contribute significantly to the allergic airway inflammation induced by ovalbumin (OVA) challenge in mice sensitized with OVA without alum. However, it is not clear to what extent mast cells represent a significant source of TNF in this mouse model.

OBJECTIVE

We investigated the importance of mast cell-derived TNF in a mast cell-dependent model of OVA-induced airway hyperreactivity (AHR) and allergic airway inflammation.

METHODS

Features of this model of airway inflammation were analyzed in C57BL/6J-wild-type mice, mast cell-deficient C57BL/6J-Kit(W-sh)(/W-sh) mice, and C57BL/6J Kit(W-sh/W-sh) mice that had been systemically engrafted with bone marrow-derived cultured mast cells from C57BL/6J-wild-type or C57BL/6J-TNF(-/-) mice.

RESULTS

Ovalbumin-induced AHR and airway inflammation were significantly reduced in mast cell-deficient Kit(W-sh/W-sh) mice versus wild-type mice. By contrast, Kit(W-sh/W-sh) mice that had been engrafted with wild-type but not with TNF(-/-) bone marrow-derived cultured mast cells exhibited responses very similar to those observed in wild-type mice. Mast cells and mast cell-derived TNF were not required for induction of OVA-specific memory T cells in the sensitization phase, but significantly enhanced lymphocyte recruitment and T(H)2 cytokine production in the challenge phase.

CONCLUSION

Mast cell-derived TNF contributes significantly to the pathogenesis of mast cell-dependent and IgE-dependent, OVA-induced allergic inflammation and AHR in mice, perhaps in part by enhancing lymphocyte recruitment and T(H)2 cytokine production.

CLINICAL IMPLICATIONS

Our findings in mice support the hypothesis that mast cell-derived TNF can promote allergic inflammation and AHR in asthma.

Lack of eosinophil peroxidase or major basic protein impairs defense against murine filarial infection

Eosinophils are a hallmark of allergic diseases and helminth infection, yet direct evidence for killing of helminth parasites by their toxic granule products exists only in vitro. We investigated the in vivo roles of the eosinophil granule proteins eosinophil peroxidase (EPO) and major basic protein 1 (MBP) during infection with the rodent filaria Litomosoides sigmodontis. Mice deficient for either EPO or MBP on the 129/SvJ background developed significantly higher worm burdens than wild-type mice. Furthermore, the data indicate that EPO or MBP is involved in modulating the immune response leading to altered cytokine production during infection. Thus, in the absence of MBP, mice showed increased interleukin-10 (IL-10) production after stimulation of macrophages from the thoracic cavity where the worms reside. In addition to elevated IL-10 levels, EPO(-/-) mice displayed strongly increased amounts of the Th2 cytokine IL-5 by CD4 T cells as well as a significantly higher eosinophilia. Interestingly, a reduced ability to produce IL-4 in the knockout strains could even be seen in noninfected mice, arguing for different innate propensities to react with a Th2 response in the absence of either EPO or MBP. In conclusion, both of the eosinophil granule products MBP and EPO are part of the defense mechanism against filarial parasites. These data suggest a hitherto unknown interaction between eosinophil granule proteins, defense against filarial nematodes, and cytokine responses of macrophages and CD4 T cells.

Eotaxin-1-regulated eosinophils have a critical role in innate immunity against experimental Brugia malayi infection

Using two models of filarial infection in which Brugia malayi microfilariae (Mf) are contained in distinct anatomical compartments, in blood or tissue sites, we have demonstrated a critical role for eotaxin-1 in parasite clearance. In the first model, implantation of adult B. malayi into the peritoneal cavity of eotaxin-1(-/-) mice resulted in increased Mf survival associated with a dramatic reduction in peritoneal cavity eosinophilic infiltration. In the second model Mf were injected intravenously into eotaxin-1(-/-) mice; Mf clearance from the blood was more rapid than in wild-type mice and was associated with a pronounced blood eosinophilia, resulting from the inability of eosinophils to migrate to tissue sites in the absence of eotaxin-1. (Eotaxin-1 + IL-5)(-/-) mice had extended Mf survival in the blood and significantly reduced blood eosinophil levels. Interestingly, rapid clearance of a secondary Mf infection following immunization was unaltered in either eotaxin-1(-/-) mice or (eotaxin-1 + IL-5)(-/-) mice. Eosinophil peroxidase levels were high during primary, but not secondary infection, suggesting that eosinophil degranulation is important during primary Mf clearance. Thus, our data show that the presence of eosinophils is critical for innate clearance of B. malayi Mf infection, whereas rapid clearance of secondary infections is independent of both eotaxin-1 and IL-5.

Development and functional analysis of eosinophils from murine embryonic stem cells

We have established a culture system for the development of eosinophils from murine embryonic stem (ES) cells. After transferring ES cells from embryonic fibroblast cells onto macrophage colony-stimulating factor-deficient stromal cells, OP9, ES cells were cultured in the presence of interleukin (IL)-5 with either IL-3 or granulocyte-macrophage colony stimulating factor (GM-CSF) for 20 d to obtain approximately 50% eosinophils. Electron microscopy confirmed the presence of crystallized major basic protein (MBP) in the granules of some of these cells. Neither IL-5, IL-3, GM-CSF nor eotaxin alone could induce eosinophils as efficiently as the conditions described above. Eotaxin induced eosinophil development in combination with either IL-3 or IL-5. Levels of GATA-1, Friend of GATA (FOG)-1, PU.1, CCAAT/enhancer binding protein (C/EBP)alpha, C/EBPbeta, IL-3 receptor alpha (IL-3Ralpha), GM-CSF receptor alpha (GM-CSFRalpha), and MBP mRNAs were increased in ES cells 10 d after transfer onto OP9 cells. In contrast, C/EBPepsilon, IL-5Ralpha, and eosinophil peroxidase mRNAs were induced in response to IL-3 and IL-5 after transfer onto OP9 cells. Eosinophils that developed in this system expressed Gr-1, F4/80, B220, CCR3, IL-3Ralpha, IL-5Ralpha, and DX5. Finally, eosinophils developed from ES cells produced reactive oxygen species in response to Leishmania as do peripheral blood eosinophils.