Kinetics of apoptosis in the lung of mice with allergic airway inflammation

Niclosamide, but not ivermectin, inhibits anoctamin 1 and 6 and attenuates inflammation of the respiratory tract

Inflammatory airway diseases like cystic fibrosis, asthma and COVID-19 are characterized by high levels of pulmonary cytokines. Two well-established antiparasitic drugs, niclosamide and ivermectin, are intensively discussed for the treatment of viral inflammatory airway infections. Here, we examined these repurposed drugs with respect to their anti-inflammatory effects in airways in vivo and in vitro. Niclosamide reduced mucus content, eosinophilic infiltration and cell death in asthmatic mouse lungs in vivo and inhibited release of interleukins in the two differentiated airway epithelial cell lines CFBE and BCi-NS1.1 in vitro. Cytokine release was also inhibited by the knockdown of the Ca2+-activated Cl- channel anoctamin 1 (ANO1, TMEM16A) and the phospholipid scramblase anoctamin 6 (ANO6, TMEM16F), which have previously been shown to affect intracellular Ca2+ levels near the plasma membrane and to facilitate exocytosis. At concentrations around 200 nM, niclosamide inhibited inflammation, lowered intracellular Ca2+, acidified cytosolic pH and blocked activation of ANO1 and ANO6. It is suggested that niclosamide brings about its anti-inflammatory effects at least in part by inhibiting ANO1 and ANO6, and by lowering intracellular Ca2+ levels. In contrast to niclosamide, 1 µM ivermectin did not exert any of the effects described for niclosamide. The present data suggest niclosamide as an effective anti-inflammatory treatment in CF, asthma, and COVID-19, in addition to its previously reported antiviral effects. It has an advantageous concentration-response relationship and is known to be well tolerated.

Apoptosis of Eosinophil Granulocytes

Simple Summary

Eosinophil granulocytes (eosinophils) belong to the family of white blood cells that play important roles in the development of asthma and various types of allergy. Eosinophils are cells with a diameter of 12–17 µm and they originate from myeloid precursors. They were discovered by Paul Ehrlich in 1879 in the process of staining fixed blood smears with aniline dyes. Apoptosis (programmed cell death) is the process by which cells lose their functionality. Therefore, it is very important to study the apoptosis of eosinophils and their survival factors to understand how to develop new drugs based on the modulation of eosinophil apoptosis for the treatment of asthma and allergic diseases.

Abstract

In the past 10 years, the number of people in the Czech Republic with allergies has doubled to over three million. Allergic pollen catarrh, constitutional dermatitis and asthma are the allergic disorders most often diagnosed. Genuine food allergies today affect 6–8% of nursing infants, 3–5% of small children, and 2–4% of adults. These disorders are connected with eosinophil granulocytes and their apoptosis. Eosinophil granulocytes are postmitotic leukocytes containing a number of histotoxic substances that contribute to the initiation and continuation of allergic inflammatory reactions. Eosinophilia results from the disruption of the standard half-life of eosinophils by the expression of mechanisms that block the apoptosis of eosinophils, leading to the development of chronic inflammation. Glucocorticoids are used as a strong acting anti-inflammatory medicine in the treatment of hypereosinophilia. The removal of eosinophils by the mechanism of apoptosis is the effect of this process. This work sums up the contemporary knowledge concerning the apoptosis of eosinophils, its role in the aforementioned disorders, and the indications for the use of glucocorticoids in their related therapies.

Allergen Exposure in Lymphopenic Fas-Deficient Mice Results in Persistent Eosinophilia Due to Defects in Resolution of Inflammation

Asthma is characterized by chronic airway type-2 inflammation and eosinophilia, yet the mechanisms involved in chronic, non-resolving inflammation remain poorly defined. Previously, our group has found that when Rag-deficient mice were reconstituted with Fas-deficient B6 LPR T cells and sensitized and challenged, the mice developed a prolonged type-2-mediated airway inflammation that continued for more than 6 weeks after the last antigen exposure. Surprisingly, no defect in resolution was found when intact B6 LPR mice or T cell specific Fas-conditional knockout mice were sensitized and challenged. We hypothesize that the homeostatic proliferation induced by adoptive transfer of T cells into Rag-deficient mice may be an important mechanism involved in the lack of resolution. To investigate the role of homeostatic proliferation, we induced lymphopenia in the T cell-specific Fas-conditional knockout mice by non-lethal irradiation and sensitized them when T cells began to repopulate. Interestingly, we found that defective Fas signaling on T cells plus antigen exposure during homeostatic proliferation was sufficient to induce prolonged eosinophilic airway inflammation. In conclusion, our data show that the combination of transient lymphopenia, abnormal Fas-signaling, and antigen exposure leads to the development of a prolonged airway eosinophilic inflammatory phase in our mouse model of experimental asthma.

Calcitriol Reduces Eosinophil Necrosis Which Leads to the Diminished Release of Cytotoxic Granules

BACKGROUND

Asthma severity and eosinophilia correlate with a deficiency in vitamin D and its active metabolite calcitriol. Calcitriol modulates numerous leukocyte functions, but its effect on eosinophils is not fully understood. We postulated that calcitriol exerts a direct effect on eosinophil biology by modulating cell survival.

METHODS

Purified peripheral blood eosinophils from atopic donors were incubated in the presence of calcitriol for up to 14 days with or without IL-5. The effect of calcitriol on eosinophil viability was measured using the annexin-V/propidium iodide flow cytometry assay. We also examined the release of eosinophil peroxidase (EPX) in media using a flow cytometry assay with anti-EPX antibodies, and the enzymatic activity of EPX was measured by an OPD-based colorimetric assay.

RESULTS

We observed that calcitriol sustained cell viability in eosinophils with a concurrent reduction of necrotic cells. This effect was amplified by the addition of IL-5. In parallel, we observed that a physiological dose of calcitriol (10 nM) significantly reduced eosinophil necrosis and cytolytic release of EPX in media when coincubated with IL-5.

CONCLUSION

These results suggest that calcitriol may exert a direct effect on eosinophils by reducing necrosis and the cytolytic release of inflammatory mediators like EPX.

JM25-1, a Lidocaine Analog Combining Airway Relaxant and Antiinflammatory Properties: Implications for New Bronchospasm Therapy

BACKGROUND

Inhaled lidocaine antagonized bronchospasm in animal models and patients, but adverse effects limited its efficacy. This study evaluated the antibronchospasm potential of the analog JM25-1, exploring in vitro mechanisms and translation to an animal model.

METHODS

The effectiveness of JM25-1 was assessed in GH3 cells, rat tracheal rings, mouse lymphocytes, and human eosinophil systems in vitro, assessing changes in Na current, contraction, proliferation, and survival, respectively. Lung function and inflammatory changes were studied in ovalbumin-sensitized mice.

RESULTS

The efficacy of JM25-1 was higher than lidocaine in inhibiting carbachol-induced and calcium-induced tracheal contractions (maximum effect inhibition at 1 mM [%]: 67 ± 10 [JM25-1] vs. 41 ± 11 [lidocaine] [P < 0.001] for carbachol; 100 ± 3 [JM25-1] vs. 36 ± 26 [lidocaine] [P < 0.001] for Ca; mean ± SD; n = 9 each) but lower in Na current (50% inhibitory concentration = 151.5, n = 8 vs. 0.2 mM; n = 5; P < 0.001). JM25-1 also inhibited eosinophil survival (dead cells [%]: 65 ± 6; n = 4; P < 0.001 at 1 mM) and lymphocyte proliferation (cells in phase S + G2 [%]: 94 ± 10; n = 6; P < 0.001) at 0.6 mM. Aerosolized JM25-1 (1%) decreased lung eosinophil numbers from 13.2 ± 2.4 to 1.7 ± 0.7 × 10/μm (n = 6; P < 0.001) and neutrophils from 1.9 ± 0.4 to 0.2 ± 0.1 × 10/μm (n = 7; P < 0.001). Other parameters, including airway hyperreactivity, cytokines, mucus, and extracellular matrix deposition, were also sensitive to aerosolized JM25-1.

CONCLUSION

These findings highlight the potential of JM25-1, emphasizing its putative value in drug development for clinical conditions where there is bronchospasm.

Suppression of heme oxygenase-1 activity reduces airway hyperresponsiveness and inflammation in a mouse model of asthma

OBJECTIVE

Carbon monoxide (CO) levels in expired gas are higher in patients with bronchial asthma than in healthy individuals. Heme oxygenase-1 (HO-1) is a rate-limiting enzyme that catalyzes the degradation of heme to yield biliverdin, CO and free iron. Thus, HO-1 is implicated in the pathogenesis of bronchial asthma. However, whether HO-1 expression and activity in lung tissue are related to allergic airway inflammation remains unclear. We investigated whether expression of HO-1 is related to allergic airway inflammation in lungs and whether HO-1 could influence airway hyperresponsiveness and eosinophilia in mice sensitized to ovalbumin (OVA).

METHODS

C57BL/6 mice immunized with OVA were challenged thrice with an aerosol of OVA every second day for 8 days. HO-1-positive cells were identified by immunostaining in lung tissue, and zinc protoporphyrin (Zn-PP), a competitive inhibitor of HO-1, was administered intraperitoneally to OVA-immunized C57BL/6 mice on day 23 (day before inhalation of OVA) and immediately before inhalation on the subsequent 4 days (total five doses). Mice were analyzed for effects of HO-1 on AHR, inflammatory cell infiltration and cytokine levels in lung tissue. Ethical approval was obtained from the concerned institutional review board.

RESULTS

Number of HO-1-positive cells increased in the subepithelium of the bronchi after OVA challenge, and HO-1 localized to alveolar macrophages. Zn-PP clearly inhibited AHR, pulmonary eosinophilia and IL-5 and IL-13 expression in the lung tissue.

CONCLUSION

Expression of HO-1 is induced in lung tissue during attacks of allergic bronchial asthma, and its activity likely amplifies and prolongs allergic airway inflammation.

Peripheral blood Th9 cells and eosinophil apoptosis in asthma patients

BACKGROUND AND OBJECTIVE

Th9 cells producing interleukin (IL) 9 are novel subset of CD4+ T helper cells, which might contribute to airway inflammation in asthma. Moreover, the effect of IL-9 on eosinophils is still not fully understood. Study aim was to evaluate peripheral blood Th9 cells and eosinophil apoptosis in allergic asthma patients.

MATERIALS AND METHODS

Eighteen patients with allergic asthma and fourteen patients with allergic rhinitis were examined. Control group included sixteen healthy subjects. Allergic asthma and rhinitis patients did not use corticosteroids and antihistamines at least for 1 week. Peripheral blood eosinophils and CD4(+) cells were isolated by high density gradient centrifugation and magnetic separation. Th9 cells and apoptotic eosinophils were estimated by flow cytometer. Serum IL-9 and IL-5 concentration were determined by ELISA.

RESULTS

Peripheral blood Th9 cells percentage was increased in allergic asthma group compared with allergic rhinitis and control group (0.74%±0.32% vs. 0.19%±0.10% and 0.15%±0.08%, respectively, P<0.05). The same tendency was observed for IL-9 (P<0.01). Percentage of peripheral blood apoptotic eosinophils was decreased in allergic asthma and allergic rhinitis groups compared with control group (P<0.05). IL-9 concentration correlated with percentage of Th9 cells (r=0.64, P<0.05) and negatively with percentage of apoptotic eosinophils in allergic asthma group (r=-0.58, P<0.05). Negative correlation was found between apoptotic eosinophils count and IL-5 concentration in allergic asthma group (r=-0.76, P<0.05).

CONCLUSIONS

Patients with allergic asthma demonstrate increased peripheral blood Th9 cells count and serum IL-9, while eosinophil apoptosis is inversely related to IL-9 concentration.

Trade-offs between cancer and other diseases: do they exist and influence longevity?

Relationships between aging, disease risks, and longevity are not yet well understood. For example, joint increases in cancer risk and total survival observed in many human populations and some experimental aging studies may be linked to a trade-off between cancer and aging as well as to the trade-off(s) between cancer and other diseases, and their relative impact is not clear. While the former trade-off (between cancer and aging) received broad attention in aging research, the latter one lacks respective studies, although its understanding is important for developing optimal strategies of increasing both longevity and healthy life span. In this paper, we explore the possibility of trade-offs between risks of cancer and selected major disorders. First, we review current literature suggesting that the trade-offs between cancer and other diseases may exist and be linked to the differential intensity of apoptosis. Then we select relevant disorders for the analysis (acute coronary heart disease [ACHD], stroke, asthma, and Alzheimer disease [AD]) and calculate the risk of cancer among individuals with each of these disorders, and vice versa, using the Framingham Study (5209 individuals) and the National Long Term Care Survey (NLTCS) (38,214 individuals) data. We found a reduction in cancer risk among old (80+) men with stroke and in risk of ACHD among men (50+) with cancer in the Framingham Study. We also found an increase in ACHD and stroke among individuals with cancer, and a reduction in cancer risk among women with AD in the NLTCS. The manifestation of trade-offs between risks of cancer and other diseases thus depended on sex, age, and study population. We discuss factors modulating the potential trade-offs between major disorders in populations, e.g., disease treatments. Further study is needed to clarify possible impact of such trade-offs on longevity.

Lidocaine-derivative JMF2-1 prevents ovalbumin-induced airway inflammation by regulating the function and survival of T cells

BACKGROUND

Inhalation of the local anaesthetic lidocaine has been suggested to be beneficial for asthmatics, but airway anaesthesia is unpleasant and may exacerbate bronchoconstriction. Our previous study showed that inhalation of the lidocaine analogue JMF2-1 can elicit the anti-inflammatory properties of lidocaine without anaesthesia. This prompted further research on the mechanism of action and putative therapeutic application of JMF2-1.

OBJECTIVE

We tested the hypothesis that JMF2-1 would prevent allergen-induced lung inflammation and airway hyperresponsiveness (AHR) by modulating T cell function in vivo and in vitro. Methods Local and systemic changes in leucocyte levels, cytokine production and lung mechanics were examined in a murine model of lung inflammation. JMF2-1 (0.05-2%) or saline was aerosolized twice a day during the ovalbumin (OVA)-provocation period (19-21 days post-sensitization). Analyses were performed 24 h after the final challenge. Primary cultured lymph node cells were used to assess the effects of JMF2-1 (100-600 μm) at the cellular level.

RESULTS

OVA challenge resulted in lung recruitment of CD4(+) T cells and eosinophils, increased generation of inflammatory cytokines and AHR to inhaled methacholine within 24 h. These changes were prevented by JMF2-1 nebulization, and occurred in parallel with an increase in the number of apoptotic cells in the lung. JMF2-1 treatment did not alter levels of CD4(+) or CD8(+) T cells in the thymus or lymph nodes of naïve mice, although it inhibited OVA-induced IL-13 production and the lymphocyte proliferative response in vitro. It also induced apoptosis of OVA-activated lymphocytes in a mechanism sensitive to z-VAD, indicating that JMF2-1 mediates caspase-dependent apoptosis.

CONCLUSION

Inhalation of JMF2-1 prevents the cardinal features of asthma by reducing T(H) 2 cytokine generation and lung eosinophilic inflammatory infiltrates via local inhibition of T cell function and survival. JMF2-1 may represent a novel therapeutic alternative for asthma control with distinct advantages over local anaesthetics.

The activity of medicinal plants and secondary metabolites on eosinophilic inflammation

Eosinophils are leukocytes that are present in several body compartments and in the blood at relatively low numbers under normal conditions. However, an increase in the number of eosinophils, in the blood or in the tissues, is observed in allergic or parasitic disorders. Although some progress has been made in understanding the development of eosinophil-mediated inflammation in allergic and parasitic diseases, the discovery of new compounds to control eosinophilia has lagged behind other advances. Plant-derived secondary metabolites are the basis for many drugs currently used to treat pathologic conditions, including eosinophilic diseases. Several studies, including our own, have demonstrated that plant extracts and secondary metabolites can reduce eosinophilia and eosinophil recruitment in different experimental animal models. In this review, we summarize these studies and describe the anti-eosinophilic activity of various plant extracts, such as Ginkgo biloba, Allium cepa, and Lafoensia pacari, as well as those of secondary metabolites (compounds isolated from plant extracts), such as quercetin and ellagic acid. In addition, we highlight the medical potential of these plant-derived compounds for treating eosinophil-mediated inflammation, such as asthma and allergy.

A role for Bid in eosinophil apoptosis and in allergic airway reaction

Bid, a proapoptotic member of Bcl-2 family, is involved in Fas receptor signaling. Fas activation promotes human eosinophil cell death and is believed to accelerate the resolution of pulmonary Th2-driven allergic reaction in mice. We hypothesized that Bid would regulate eosinophil apoptosis and Ag-induced airway inflammation, particularly eosinophilia. C57BL/6 Bid(-/-) and wild-type mice were immunized and repeatedly challenged with OVA, and bronchoalveolar lavage (BAL) fluid, lung, and spleen were collected 4-240 h after the final challenge. Cultured BAL eosinophils from Bid-deficient mice showed resistance to Fas-mediated apoptotic DNA fragmentation, phosphatidylserine exposure, mitochondria depolarization, and caspase-3 activity. In addition, OVA-challenged Bid(-/-) mice had higher BAL eosinophilia and a lower proportion of BAL apoptotic eosinophils than Bid(+/+) mice. This was accompanied by augmented BAL levels of the eosinophilotactic cytokine, IL-5, and of the eosinophil-associated mediators, TGF-beta1 and fibronectin. Finally, cultured OVA-stimulated lung mononuclear cells and splenocytes from Bid-deficient mice showed increased release of the Th2-type cytokines, IL-4 and IL-5, but no change in cell number. We conclude that Bid modulates BAL eosinophilia by regulating both eosinophil apoptosis and Th2-type cytokine production.

Strain-dependent resistance to allergen-induced lung pathophysiology in mice correlates with rate of apoptosis of lung-derived eosinophils

Although exposed to similar allergic and environmental stimuli, not all humans develop asthma. Similarly, mouse strains vary in the degree of pathophysiology seen following induction of experimental asthma. Three mouse strains (CBA/Ca, BALB/c, and C57BL/6) were used to determine if the extent and duration of inflammation influenced the degree of lung tissue damage in an OVA-induced allergic asthma model. Airways obstruction, leukocyte infiltration, edema, eosinophil accumulation, and degranulation were less severe in wild-type (wt) CBA/Ca mice than wt BALB/c and C57BL/6 mice. F1 hybrids of CBA/Ca mice crossed with BALB/c or C57BL/6 mice had bronchoalveolar lavage leukocyte (BAL) and cell-free protein profiles similar to those of the respective disease-susceptible parental strain. IL-5 transgene expression on each of the three genetic backgrounds accentuated the difference between CBA/Ca and the other two strains. Importantly, even when overexpressing IL-5, CBA/Ca mice did not develop substantial airways obstruction. Eosinophils recovered from the airways of allergic wt and IL-5 transgenic (Tg) CBA/Ca mice entered apoptosis at a faster rate than eosinophils from the other parental strains and F1 hybrids. In contrast, eosinophils harvested from the peritoneal cavities of untreated CBA/Ca IL-5 Tg mice had a relatively low rate of apoptosis in vitro. The CBA/Ca mouse strain is therefore relatively resistant to experimental asthma, and this may be a consequence of a propensity for apoptosis of eosinophils recruited into the allergic lung. Restricting survival of a key effector cell may thus limit pathogenesis in this experimental model and in humans.

Role of interleukin-12 in the regulation of CD4+ T cell apoptosis in a mouse model of asthma

Allergic asthma, a chronic inflammatory disease of the airways, is characterized by the presence of T helper 2 cells and eosinophils in sputum, bronchoalveolar lavage, and mucosal biopsy specimens. Although the T helper 1-promoting cytokine, interleukin-12, is capable of inhibiting the T helper 2-driven asthma symptoms and bronchial responsiveness, the specific mechanisms underlying these interleukin-12 actions are unclear. The anti-allergic response to interleukin-12 is only partially dependent on interferon-gamma, which induces apoptosis by enhancing expression of Fas antigen. We therefore investigated in vivo whether the anti-allergic action of interleukin-12 is mediated through induction of apoptosis. C57BL/6 mice immunized to ovalbumin by intraperitoneal injection were challenged three times with an ovalbumin aerosol every second day for 7 days. Recombinant interleukin-12 was administered intravenously after the final challenge. After the last ovalbumin challenge, mice were examined for effects of interleukin-12 on inflammatory cell infiltration and apoptosis in the lung as detected by terminal deoxynucleotidyl transferase-mediated deoxyribonucleoside triphosphate nick end-labelling. Administration of interleukin-12 reduced ovalbumin-induced pulmonary eosinophilia (P < 0.01) and CD4+ T cell infiltration (P < 0.01). Moreover, treatment with interleukin-12 shortly after ovalbumin inhalation resulted in both increased interferon-gamma production (P < 0.01) and enhanced apoptosis of CD4+ T cells in allergic airway infiltrates (P < 0.05). These results suggest that the beneficial effects of interleukin-12 in asthma may include enhancement of apoptosis of CD4+ T cells in airways.

Effects of post-inhalation treatment with interleukin-12 on airway hyper-reactivity, eosinophilia and interleukin-18 receptor expression in a mouse model of asthma

BACKGROUND

Correcting Th1/Th2 imbalance with administration of IL-12 before and during antigen challenge holds therapeutic promise in asthma. However, the effects of IL-12 on the established asthmatic responses have not fully been examined.

OBJECTIVE

We investigated whether IL-12 administered after antigen challenge could diminish airway hyper-reactivity (AHR) and eosinophilia in mice actively sensitized to ovalbumin. We also have investigated the ability of administered IL-12 to induce IL-18 receptor (IL-18R) expression that may lead possible synergic action of IL-12 with endogenous IL-18.

METHODS

C57BL/6 mice immunized to ovalbumin (OVA) by intraperitoneal (i.p.) injection, were challenged three times with an aerosol of OVA every second day for 8 days. Recombinant IL-12 (500 ng) was intravenously administered on a single occasion 1 h after the final challenge of mice. Mice were analysed for effects of IL-12 on AHR, inflammatory cell infiltration and cytokine levels in lung tissue as well as serum immunoglobulin (Ig) E levels. Immunohistochemistry for IL-18R was performed using rat monoclonal antibody specific for murine IL-18Ralpha (IL-1 receptor related protein; IL-1Rrp).

RESULTS

An intravenous IL-12 administration diminished AHR, pulmonary eosinophilia and T lymphocyte infiltration, serum IgE, IL-4 and IL-13 in lung tissue. Expression of IL-18R was induced in the mononuclear cells in the lung of mice exposed to OVA. IL-12 administration enhanced the IL-18R expression compared with the control.

CONCLUSION

These data indicate that IL-12 can attenuate established antigen-induced AHR and inflammation. In this mechanism it would be interpreted as follows: IL-12 administration in OVA-challenged mice decreased IL-4 production and IgE production thereafter through direct effect on inhibiting the activation of established Th2 cells response and also combined effect with up-regulation of IL-18R expression by inflammatory cells in the lung.

Lung tissue eosinophils may be cleared through luminal entry rather than apoptosis: effects of steroid treatment

Spontaneous or steroid-induced eosinophil apoptosis occurring in vitro has not been demonstrated in lung tissues in vivo. This study examines cell apoptosis in rat lungs using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) technique and transmission electron microscopy (TEM). After establishing sustained lung edema and eosinophilia by challenge with Sephadex beads intratracheally, budesonide treatment was started intratracheally. Sephadex alone increased the total number of apoptotic cells, which were not efficiently engulfed by macrophages or other cells, in vivo. Yet apoptotic tissue eosinophils were exceedingly rare (1 of 360 TEM-analyzed eosinophils). By contrast, approximately 20% of eosinophils in the airway lumen were apoptotic, and unengulfed. Budesonide promptly inhibited edema but 3 d of steroid treatment were required to reduce the established tissue eosinophilia. Not at any time point did budesonide induce eosinophil apoptosis (0 of 318 TEM-analyzed tissue eosinophils). We conclude that (1) eosinophil apoptosis can occur but is a rare event in vivo in respiratory tract tissues; (2) airway tissue eosinophils, rather than undergoing apoptosis, are eliminated by migration into airway lumen followed by apoptosis and mucociliary clearance; (3) anti-inflammatory steroid treatment may not increase eosinophil apoptosis in vivo nor may it affect the luminal entry of eosinophils; (4) steroids permit elimination of eosinophils into airway lumen and slowly resolve established lung eosinophilia.

Fas deficiency delays the resolution of airway hyperresponsiveness after allergen sensitization and challenge

BACKGROUND

In asthma, persistent inflammation might be the result of (1) an impaired ability to clear inflammatory cells from the airways and/or (2) impaired apoptotic responses.

OBJECTIVE

In a mouse model, we investigated the regulatory role of Fas (CD95)-induced apoptosis in the development and resolution of airway inflammation and airway hyperresponsiveness (AHR).

METHODS

Mice that were either Fas-sufficient (wild-type; WT) or Fas-deficient (lpr ) were sensitized by intraperitoneal injections of ovalbumin (OVA) and challenged once intranasally with OVA (IP-IN mice). Control (IN) mice were challenged only.

RESULTS

IP-IN WT mice developed AHR at 48 hours; changes in airway resistance resolved by 96 hours. Airway responsiveness at 48 hours in IP-IN lpr mice was similar to that in IP-IN WT mice. However, in contrast to WT mice, IP-IN lpr mice sustained significant AHR at 96 hours in comparison with IN lpr mice; the AHR resolved by 6 days. Bronchoalveolar lavage fluid cell composition was similar in all of the different groups at 48 hours and 96 hours. Both IP-IN WT mice and lpr mice exhibited similar tissue eosinophilia, whereas IP-IN lpr mice had significantly lower numbers of TdT-mediated dUTP nick end labeling (TUNEL)-positive cells in comparison with IP-IN WT mice at 48 hours. Anti-IL-5 antibody given to IP-IN lpr mice 48 hours and 72 hours after the challenge significantly decreased AHR and eosinophilic inflammation and increased TUNEL-positive cell numbers at 96 hours.

CONCLUSION

These results suggest that Fas expression can regulate the onset and resolution of AHR through an increase in eosinophil apoptosis.

Eosinophilic apoptosis in sinus mucosa: relationship to tissue eosinophilia and its resolution in allergic sinusitis

BACKGROUND

Apoptosis, which is regulated by both cell survival and death signals, is important for the swift clearance of unwanted cells.

OBJECTIVE

We sought to elucidate whether eosinophilic apoptosis is associated with tissue eosinophilia and to determine its resolution in allergic sinusitis (AS).

METHODS

Numbers of eosinophils, numbers of IL-5(+) cells, and the apoptosis index of eosinophils were calculated in the submucosa (both superficial and deep layers) of patients with AS by using histochemical methods before and after prednisolone treatment. Patients without AS were used for control groups. Anti-EG2 antibody was used to identify eosinophils. IL-5, Fas, or Bax expression of eosinophils was evaluated to elucidate the role of the factors affecting eosinophilic apoptosis.

RESULTS

EG2 and IL-5(+) cells were abundant in the submucosa of patients with AS, especially in the superficial layer. About 50% to 60% of the IL-5-producing cells were eosinophils. Apoptotic eosinophils were less numerous in the superficial layer than the deep layer in these diseases. After prednisolone treatment, an induction of eosinophilic apoptosis was accompanied by a significant decrease in the number of EG2(+) and IL-5(+) cells. No remarkable difference was observed in the Fas or Bax expression of eosinophils after prednisolone treatment.

CONCLUSION

Autocrine secretion of IL-5 from eosinophils may be one reason why eosinophilic disease is difficult to manage. Induction of eosinophilic apoptosis is critical for reversing tissue eosinophilia in patients with AS.

IL-18 deficiency selectively enhances allergen-induced eosinophilia in mice

BACKGROUND

T(H2) cytokines are associated with airway inflammation and hyperreactivity in bronchial asthma, and restoration of the T(H1)/T(H2) imbalance is a potential avenue for novel therapies. IL-18 is a cytokine secreted by activated macrophages, and it shares some of its biologic activities with IL-12, a typical T(H1)-type cytokine. Although IL-18 and IL-12 act on T cells synergistically to induce IFN-gamma production, the contribution of IL-18 T(H1)/T(H2) imbalance and to subsequent asthmatic response has not been elucidated in vivo.

OBJECTIVE

We studied a model of allergic asthma in IL-18-deficient mice to investigate the modulatory role of IL-18 on induction and maintenance of T(H2) mucosal immunity. We also have investigated the ability of intraperitoneal instilled IL-18 to reduce T(H2) mucosal immunity in IL-18-deficient mice.

METHODS

IL-18-deficient mice immunized to ovalbumin by means of intraperitoneal injection were challenged 3 times with an aerosol of ovalbumin every second day for 8 days. Recombinant (r)IL-18 was intraperitoneally administered in mice before every first challenge. Mice were analyzed for effects on lung eosinophilia, cytokines, and serum IgE levels.

RESULTS

In IL-18-deficient mice, levels of eosinophilia and lung damage were significantly higher than in wild-type C57/BL6 litter mates. Intraperitoneal administration of rIL-18 in deficient mice reduced these antigen-induced changes to levels seen in wild-type mice in association with a decrease in IL-4 in bronchoalveolar lavage fluid and lung tissue. However, administration of rIL-18 did not affect the IFN-gamma level and somewhat enhanced the production of IL-5. Notably, reconstitution with rIL-18 increased the numbers of cells staining for Fas ligand, as well as apoptotic cells stained by nick end-labeling in bronchial submucosa infiltrates.

CONCLUSION

These findings indicate that in vivo IL-18 not only inhibited antigen-specific T(H2) development but also affected apoptosis through Fas-Fas ligand interactions. These data support a role for IL-18 in the complex pathogenesis of allergic inflammation in which IL-18 limited the development of the local inflammatory response to antigen.

Advances in the immunobiology of eosinophils and their role in disease

Eosinophils play a protective role in host immunity to infections by parasitic worms and, detrimentally, are involved in the pathophysiology of asthma and other allergic diseases. Airway inflammation is central to the pathology of asthma and is characterized by infiltration of the bronchial mucosa by large numbers of proinflammatory cells, amongst which the eosinophil is prominent despite being a minority constituent of circulating leukocytes. Crucial steps in eosinophilic inflammation include augmented production of eosinophils in the bone marrow, their increased release into the circulation, and their selective accumulation in the conducting airways. The eosinophil has a potent armory of proinflammatory mediators, including cytotoxic granule proteins, cytokines and lipid mediators with considerable potential to initiate and sustain an inflammatory response. Thus there is much interest in the elucidation of the mechanisms responsible for eosinophil accumulation, persistence, activation and ultimate fate. This article reviews our current understanding of the role of the eosinophil in human disease and the immunobiology of this important proinflammatory cell.