Indoleamine-2,3-dioxygenase modulation of allergic immune responses

Artemisia argyi essential oil alleviates asthma by regulating 5-LOX-CysLTs and IDO-1-KYN pathways: Insights from metabolomics

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia argyi essential oil (AAEO) is a traditional herbal remedy for asthma. However, the potential effect of AAEO on asthma has not been elucidated.

AIM OF THE STUDY

To investigate the protective properties of AAEO upon asthma and elucidate its mechanism.

MATERIALS AND METHODS

The effects of AAEO in asthma were assessed by histology and biochemical analysis. Then, we integrated real-time reverse transcription-quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, immunohistochemistry and metabolomics analysis to reveal its mechanism.

RESULTS

In vivo, AAEO reduced the counts of white blood cells (WBCs) and cytokines in bronchoalveolar lavage fluid (BALF), ameliorated pathologic alterations in lung tissues, and inhibited secretion of OVA-sIgE and muc5ac. Metabolomics results showed that AAEO can exert therapeutic effects on asthmatic mice by regulating disordered arachidonic acid metabolism and tryptophan metabolism. Further studies shown that AAEO inhibited the expression of 5-LOX and reduced the accumulation of CysLTs in mice. Meanwhile, AAEO promoted the activity of IDO-1, facilitated the conversion of tryptophan to kynurenine, and regulated the imbalance of Treg/Th17 immunity. Immunohistochemical results showed that AAEO promoted the expression of IDO-1. RT-qPCR results showed that AAEO promoted the expression of IL-10 and Foxp3 mRNA, and inhibited the expression of IL-17A and RORγt mRNA, thus regulated the imbalance of Treg/Th17 immunity and exerted its therapeutic effects.

CONCLUSION

AAEO treatment not only attenuates the clinical symptoms of asthma but is also involved in regulating lung tissue metabolism. The anti-asthmatic activity of AAEO may be achieved by reprogramming 5-LOX-CysLTs and IDO-1-KYN pathways.

Trained immunity induced by in vivo peptide-based STAT6 inhibition prevents ragweed allergy in mice

BACKGROUND

Trained immunity is the ability of the innate immune system to form immune memory responses to provide support the formation of appropriate adaptive responses. Allergic airways disease (AAD) is a maladapted immune response to allergens, initiated and maintained by the type 2 (T2) inflammatory pathway. It is predicated by the elaboration of cytokines IL-4 and IL-13 and follows activation of the STAT6 transcription factor.

OBJECTIVE

To investigate the role of trained immunity in mucosal immune responses following neonatal vaccination with the STAT6 inhibitory peptide (STAT6-IP), in preventing the development of ragweed-induced AAD.

METHODS

We demonstrate that transfer of CD4⁺ T cells or dendritic cells (DC) from STAT6-IP vaccinated wild-type BALB/c mice to naïve mice, that were subsequently chronically exposed to sensitizing doses of ragweed allergen, is sufficient to prevent development of T2 responses in recipients.

RESULTS

Our results demonstrate significant reductions in; airways hyperresponsiveness (AHR); ragweed-specific IgE; pulmonary inflammation; T2 cytokines; and inflammatory gene expressions in recipient mice. Expression of IDO, TGFβ and T regulatory cells were all significantly increased. Anti-TGFβ treatment during the ragweed sensitization phase re-constituted the pro-inflammatory T2 immune response. We show that tolerance can be attained via DC trained in the STAT6-IP-mediated tolerant milieu. This effect is not restricted to a particular allergen and does not require antigen-mediated T cell activation prior to transfer.

CONCLUSION

Adoptive transfer experiments suggest that STAT6-IP treatment trains dendritic and cells to mediate tolerant immunity to chronic ragweed exposure in the airways. This indicates that early transient STAT6-inhibition constitutes an effective immunomodulatory airways allergy preventative strategy.

Mood Worsening on Days with High Pollen Counts is associated with a Summer Pattern of Seasonality

Background:

Summer/spring-type seasonal affective disorder (S-SAD) is the less common subtype of seasonal affective disorder and evidence regarding potential triggers of S-SAD is scarce. Recent reports support association of airborne-pollen with seasonal exacerbation of depression (mood seasonality) and timing of suicidal behavior. Therefore, we hypothesized that Old Order Amish (OOA) with summer/spring pattern of seasonality (abbreviated as summer pattern) and S-SAD will have significant mood worsening on high pollen days.

Methods:

A seasonal pattern of mood worsening and SAD parameters were estimated using Seasonal Pattern Assessment Questionnaire (SPAQ). Age- and gender-adjusted ANCOVAs and post hoc analyses were conducted to compare mood worsening on days with high pollen counts between summer-pattern vs no-summer-pattern of mood worsening, S-SAD vs no-S-SAD, winter-pattern vs no-winter-pattern of mood worsening, and W-SAD vs no-W-SAD groups.

Results:

The prevalence of S-SAD was 0.4%, while 4.5% of individuals had a summer pattern of mood seasonality. A statistically significant difference for mood worsening on high pollen days was observed between summer-pattern vs no-summer-pattern of mood worsening (p = 0.006). The significant association between S-SAD vs no-SAD groups (p = 0.032) for mood worsening on high pollen days did not withstand Bonferroni adjustment for multiple comparisons. No significant association was found for winter-pattern vs no-winter-pattern of mood worsening (p = 0.61) and for W-SAD vs no-W-SAD (p = 0.19) groups.

Conclusion:

Our results are consistent with previous studies implicating links between aeroallergen exposure and summer pattern of seasonality, but not the winter pattern of seasonality.

Deciphering biochemical basis of Qingkailing injection-induced anaphylaxis in a rat model by time-dependent metabolomic profiling based on metabolite polarity-oriented analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Qingkailing injection (QKLI) is prepared from eight traditional Chinese medicinal materials or their extracts, which is widely used in clinical practice to treat the upper respiratory inflammation, pneumonia, high fever and viral encephalitis, nonetheless, suffering from serious anaphylaxis.

AIM OF STUDY

This study aims to develop an integrative metabolomics approach for deciphering the biochemical basis of QKLI induced anaphylaxis (QKLI-IA).

MATERIALS AND METHODS

The accuracy of animal modeling, the coverage of detected metabolites and the timeliness of pathological reaction are three key factors for revealing the biochemical basis of disease with untargeted metabolomics. In this study, firstly, the allergic rats (responders) were first screened by passive cutaneous anaphylaxis experiment and then were utilized for modeling. To cover a wider range of metabolites, a large-scale untargeted metabolomics based on metabolites polarity-oriented analysis was performed using ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Then, to evaluate the timeliness of QKLI-IA, a time-dependent metabolomic profiling including the early, mid and late anaphylaxis stages of QKLI-IA, was performed.

RESULTS

Corresponding to early, mid and late anaphylaxis stages of QKLI-IA, 14, 9 and 4 potential biomarkers were identified, respectively. Metabolism pathway analysis revealed that QKLI-IA resulted in dynamic changes in serum amino acid, fatty acid, glycerolipid, and phospholipid metabolisms. Twenty-four metabolites were found with identical fluctuating trends across the three stages of QKLI-IA. The results indicate that the pathogenesis of QKLI-IA is closely related to arachidonic acid metabolism.

CONCLUSION

This research provides a methodology reference for revealing the biochemical basis of disease using metabolomic profiling and offers a new insight to understand the pathogenesis of QKLI-IA.

Nitrite, neopterin levels and tryptophan degradation in allergic conjunctivitis

PURPOSE

The study aims to evaluate changes in neopterin levels and tryptophan degradation which are induced by Th1-type immune response and nitric oxide metabolism which may be involved in allergic inflammation.

METHODS

Serum nitrite, kynurenine, tryptophan and neopterin levels were evaluated in 36 patients with seasonal allergic conjunctivitis, along with these values in 41 healthy subjects. All these parameters have been compared with symptom and sign scores.

RESULTS

Tryptophan and kynurenine concentrations were not significantly changed, while serum nitrite concentrations were significantly low, and neopterin levels were significantly increased in patients compared to healthy subjects (p < 0.05). There was a significant relationship between symptom scores and serum nitrite levels in patients.

CONCLUSIONS

This preliminary study demonstrates that serum nitric oxide metabolism might have a role in allergic conjunctivitis. Serum neopterin levels but not tryptophan metabolism could serve as a biomarker in patients with seasonal allergic conjunctivitis.

Serum indolamine 2,3 dioxygenase as a marker in the evaluation of allergic rhinitis

BACKGROUND

Allergic rhinitis occurs on exposure to a known allergen and is correlated with a positive skin test and physical examination results. Tryptophan is a substrate of many important proteins, e.g., indolamine 2,3 dioxygenase (IDO). IDO, an immunomodulator, is a metabolic enzyme induced by immune activation. It has a significant role in allergic reactions. T-helper 2 cell is proposed to affect the expression of IDO.

AIM

To evaluate IDO levels in patients with allergic rhinitis compared with controls and its relationship to the severity of allergic rhinitis.

METHODS

This case-control study included 20 patients who were atopic and with allergic rhinitis who attended the allergy clinic of Ain Shams University Hospitals. Twenty age- and sex-matched patients who were not atopic were included as controls. An allergic rhinitis diagnosis was made according to the Allergic Rhinitis and its Impact on Asthma document. Complete history taking, physical examination, skin-prick test, complete blood cell count, erythrocyte sedimentation rate, total serum immunoglobulin E (IgE), IDO concentration, and nasal smear for eosinophils were done for the patients.

RESULTS

There was a significant increase in IDO levels in allergic rhinitis in comparison with subjects without allergy (p < 0.001). IDO was positively correlated with total IgE levels (p < 0.037). There was an insignificant relationship among IDO levels and age, sex, duration of the disease, severity score, nasal and blood eosinophilia, and number of positive allergens.

CONCLUSION

IDO plays an important role in patients with atopic symptomatic allergic rhinitis, especially with increased levels of IgE. There is no relationship between IDO levels and severity of disease.

TGF-β-mediated airway tolerance to allergens induced by peptide-based immunomodulatory mucosal vaccination

We sought to modulate mucosal immune responses using neonatal vaccination to avert the development of allergic airways disease (AAD). Pulmonary pathology in AAD is driven by T helper (TH)2 cytokines, in particular interleukin (IL)4 and IL13, the expression and actions of which are regulated by the transcription factor STAT6. We developed a peptide homolog of STAT6, STAT6-IP. Neonatal mice given, intranasally, STAT6-IP, in an effort to modulate de novo airways immune responses, developed tolerance following subsequent allergen sensitization, with either ovalbumin or ragweed allergens, as demonstrated by reduced TH2 cytokines and specific immunoglobulin (Ig)E and the significant increases in the latency-associated peptide (LAP)(+) T-regulatory (Treg) cell subset and expression of transforming growth factor (TGF)-β. This regulatory phenotype was transferrable by CD4(+) T cells or CD11c(+) dendritic cells (DCs) derived from STAT6-IP-vaccinated mice. Anti-TGF-β treatment during allergen sensitization, however, re-established the pro-inflammatory TH2 response. Thus, neonatal STAT6-IP vaccination induces prospective TGF-β-dependent tolerance to allergen and constitutes a novel highly effective immunomodulatory allergy prevention strategy.

α-Tocopherol supplementation of allergic female mice inhibits development of CD11c+CD11b+ dendritic cells in utero and allergic inflammation in neonates

α-Tocopherol blocks responses to allergen challenge in allergic adult mice, but it is not known whether α-tocopherol regulates the development of allergic disease. Development of allergic disease often occurs early in life. In clinical studies and animal models, offspring of allergic mothers have increased responsiveness to allergen challenge. Therefore, we determined whether α-tocopherol blocked development of allergic responses in offspring of allergic female mice. Allergic female mice were supplemented with α-tocopherol starting at mating. The pups from allergic mothers developed allergic lung responses, whereas pups from saline-treated mothers did not respond to the allergen challenge, and α-tocopherol supplementation of allergic female mice resulted in a dose-dependent reduction in eosinophils in the pup bronchoalveolar lavage and lungs after allergen challenge. There was also a reduction in pup lung CD11b(+) dendritic cell subsets that are critical to development of allergic responses, but there was no change in several CD11b(-) dendritic cell subsets. Furthermore, maternal supplementation with α-tocopherol reduced the number of fetal liver CD11b(+) dendritic cells in utero. In the pups, there was reduced allergen-induced lung mRNA expression of IL-4, IL-33, TSLP, CCL11, and CCL24. Cross-fostering pups at the time of birth demonstrated that α-tocopherol had a regulatory function in utero. In conclusion, maternal supplementation with α-tocopherol reduced fetal development of subsets of dendritic cells that are critical for allergic responses and reduced development of allergic responses in pups from allergic mothers. These results have implications for supplementation of allergic mothers with α-tocopherol.

Indoleamine 2,3 dioxygenase gene polymorphisms correlate with CD8+ Treg impairment in systemic sclerosis

Systemic sclerosis (SSc) is characterized by tissue fibrosis, vasculopathy and autoimmunity. Indoleamine 2,3 dioxygenase (IDO) plays a pivotal role in immunological tolerance modulating regulatory T cell (Treg) generation and function. Single nucleotide polymorphisms (SNPs) of IDO gene could impact on Treg function and predispose to autoimmunity. Here, the existence of an association between specific IDO SNPs and SSc was analyzed. Five specific SNPs in IDO gene were searched in 31 SSc patients and 37 healthy controls by gene sequencing or restriction fragment length polymorphism. The function of both CD4+CD25+ and CD8+ Treg from SSc patients was analyzed by proliferation suppression assay. SNP rs7820268 was statistically more frequent in SSc patients than in controls. Notably, SSc patients bearing the T allelic variant of the rs7820268 SNP showed impaired CD8+ Treg function. Our unprecedented data show that a specific IDO gene SNP is associated with an autoimmune disease such as SSc.

Specific immunotherapy normalizes tryptophan concentrations in patients with allergic rhinitis

BACKGROUND/AIMS

An immune shift towards Th2-type immunity seems to be critical in the pathogenesis of allergic asthma and rhinitis. In a previous study, we found higher serum tryptophan concentrations in patients with seasonal tree or grass pollen rhinoconjunctivitis who underwent specific immunotherapy (SCIT) than in controls, and those with the highest levels at baseline responded less well to SCIT. In the present study, we examined whether 'booster immunotherapy' after cessation of SCIT had any influence on tryptophan metabolism during follow-up.

METHODS

Serum concentrations of tryptophan, kynurenine and neopterin were assayed in 19 patients (mean age: 26.2 years; 6 females) allergic to grass and/or tree pollen before and after they had received a booster immunotherapy with 4 injections of an allergoid vaccine (Pollinex Quattro; Bencard Vienna, Austria) over 8 ± 3 months outside the pollen season.

RESULTS

Serum tryptophan and kynurenine concentrations decreased after booster immunotherapy (mean ± SD, before immunotherapy: 81.1 ± 14.2 µmol/l, after immunotherapy: 61.4 ± 20.9 µmol/l and before immunotherapy: 2.25 ± 0.44, after immunotherapy: 1.69 ± 0.70 µmol/l, respectively; both p < 0.01); this was especially true in those responders who also tended to have lower baseline kynurenine concentrations as compared with nonresponders (p = 0.05). Finally, a correlation between changes in tryptophan metabolism and neopterin concentrations was observed after immunotherapy.

CONCLUSIONS

The decrease in tryptophan and kynurenine concentrations following booster immunotherapy in hay fever patients strengthens the hypothesis that tryptophan metabolism might be involved in the course of allergic responses. However, it is still unclear whether the abnormal tryptophan metabolism in pollinosis patients is related to indoleamine 2,3-dioxygenase and/or to a specific cytokine background.

Pathophysiology of allergic inflammation

Allergic inflammation is due to a complex interplay between several inflammatory cells, including mast cells, basophils, lymphocytes, dendritic cells, eosinophils, and sometimes neutrophils. These cells produce multiple inflammatory mediators, including lipids, purines, cytokines, chemokines, and reactive oxygen species. Allergic inflammation affects target cells, such as epithelial cells, fibroblasts, vascular cells, and airway smooth muscle cells, which become an important source of inflammatory mediators. Sensory nerves are sensitized and activated during allergic inflammation and produce symptoms. Allergic inflammatory responses are orchestrated by several transcription factors, particularly NF-κB and GATA3. Inflammatory genes are also regulated by epigenetic mechanisms, including DNA methylation and histone modifications. There are several endogenous anti-inflammatory mechanisms, including anti-inflammatory lipids and cytokines, which may be defective in allergic disease, thus amplifying and perpetuating the inflammation. Better understanding of the pathophysiology of allergic inflammation has identified new therapeutic targets but developing effective novel therapies has been challenging. Corticosteroids are highly effective with a broad spectrum of anti-inflammatory effects, including epigenetic modulation of the inflammatory response and suppression of GATA3.

Local expression of indoleamine 2,3 dioxygenase in syngeneic fibroblasts significantly prolongs survival of an engineered three-dimensional islet allograft

OBJECTIVE

The requirement of systemic immunosuppression after islet transplantation is of significant concern and a major drawback to clinical islet transplantation. Here, we introduce a novel composite three-dimensional islet graft equipped with a local immunosuppressive system that prevents islet allograft rejection without systemic antirejection agents. In this composite graft, expression of indoleamine 2,3 dioxygenase (IDO), a tryptophan-degrading enzyme, in syngeneic fibroblasts provides a low-tryptophan microenvironment within which T-cells cannot proliferate and infiltrate islets.

RESEARCH DESIGN AND METHODS

Composite three-dimensional islet grafts were engineered by embedding allogeneic mouse islets and adenoviral-transduced IDO-expressing syngeneic fibroblasts within collagen gel matrix. These grafts were then transplanted into renal subcapsular space of streptozotocin diabetic immunocompetent mice. The viability, function, and criteria for graft take were then determined in the graft recipient mice.

RESULTS

IDO-expressing grafts survived significantly longer than controls (41.2 +/- 1.64 vs. 12.9 +/- 0.73 days; P < 0.001) without administration of systemic immunesuppressive agents. Local expression of IDO suppressed effector T-cells at the graft site, induced a Th2 immune response shift, generated an anti-inflammatory cytokine profile, delayed alloantibody production, and increased number of regulatory T-cells in draining lymph nodes, which resulted in antigen-specific impairment of T-cell priming.

CONCLUSIONS

Local IDO expression prevents cellular and humoral alloimmune responses against islets and significantly prolongs islet allograft survival without systemic antirejection treatments. This promising finding proves the potent local immunosuppressive activity of IDO in islet allografts and sets the stage for development of a long-lasting nonrejectable islet allograft using stable IDO induction in bystander fibroblasts.

Airway epithelial indoleamine 2,3-dioxygenase inhibits CD4+ T cells during Aspergillus fumigatus antigen exposure

Indoleamine 2,3-dioxygenase (IDO) suppresses the functions of CD4(+) T cells through its ability to metabolize the essential amino acid tryptophan. Although the activity of IDO is required for the immunosuppression of allergic airway disease by the Toll-Like-Receptor 9 (TLR9) agonist, oligonucleotides comprised of cytosine and guanine nucleotides linked by phosphodiester bonds (CpG) DNA, it is unclear whether IDO expression by resident lung epithelial cells is sufficient to elicit these effects. Therefore, we created a transgenic mouse inducibly overexpressing IDO within nonciliated airway epithelial cells. Upon inhalation of formalin-fixed Aspergillus fumigatus hyphal antigens, the overexpression of IDO from airway epithelial cells of these mice reduced the number of CD4(+) T cells within the inflamed lung and impaired the capacity of antigen-specific splenic CD4(+) effector T cells to secrete the cytokines IL-4, IL-5, IL-13, and IFN-γ. Despite these effects, allergic airway disease pathology was largely unaffected in mice expressing IDO in airway epithelium. In support of the concept that dendritic cells are the major cell type contributing to the IDO-inducing effects of CpG DNA, mice expressing TLR9 only in the airway epithelium did not augment IDO expression subsequent to the administration of CpG DNA. Furthermore, the systemic depletion of CD11c(+) cells rendered mice incapable of CpG DNA-induced IDO expression. Our results demonstrate that an overexpression of IDO within the airway epithelium represents a novel mechanism by which the number of CD4(+) T cells recruited to the lung and their capacity to produce cytokines can be diminished in a model of allergic airway disease, and these results also highlight the critical role of dendritic cells in the antiasthmatic effects of IDO induction by CpG DNA.

Interferon-gamma-responsive nonhematopoietic cells regulate the immune response to Mycobacterium tuberculosis

Immunity to Mycobacterium tuberculosis in humans and in mice requires interferon gamma (IFN-gamma). Whereas IFN-gamma has been studied extensively for its effects on macrophages in tuberculosis, we determined that protective immunity to tuberculosis also requires IFN-gamma-responsive nonhematopoietic cells. Bone marrow chimeric mice with IFN-gamma-unresponsive lung epithelial and endothelial cells exhibited earlier mortality and higher bacterial burdens than control mice, underexpressed indoleamine-2,3-dioxygenase (Ido1) in lung endothelium and epithelium, and overexpressed interleukin-17 (IL-17) with massive neutrophilic inflammation in the lungs. We also found that the products of IDO catabolism of tryptophan selectively inhibit IL-17 production by Th17 cells, by inhibiting the action of IL-23. These results reveal a previously unsuspected role for IFN-gamma responsiveness in nonhematopoietic cells in regulation of immunity to M. tuberculosis and illustrate the role of IDO in the inhibition of Th17 cell responses.

Inhibition of indoleamine 2, 3-dioxygenase-mediated tryptophan catabolism accelerates crescentic glomerulonephritis

Immunomodulatory enzyme indoleamine 2, 3-dioxygenase (IDO) is one of the initial and rate-limiting enzymes involved in the catabolism of the essential amino acid tryptophan. Via catalysing tryptophan degradation, IDO suppresses adaptive T cell-mediated immunity and plays an important role in various forms of immune tolerance. Its role in T helper type 1 (Th1)-directed, cell-mediated crescentic glomerulonephritis (GN) is still unclear. Therefore, we investigated the activity and role of IDO in crescentic GN using a model of nephrotoxic serum nephritis (NTN), and IDO activity was inhibited by 1-methyl-tryptophan (1-MT) in vivo. Our results showed that activity of IDO, as determined by high performance liquid chromatography analysis of the kynurenine/tryptophan ratio, was increased markedly in the serum and renal tissue of NTN mice, and immunohistochemistry revealed that expression of IDO was up-regulated significantly in glomeruli and renal tubular epithelial cells during NTN. Treatment with 1-MT resulted in significantly exacerbated kidney disease with increased glomerular crescent formation, accumulation of CD4(+)T cells and macrophages in renal tissue, and augmented renal injury compared with phosphate-buffered saline-treated NTN mice, which was associated with enhanced Th1 responses and intrarenal cellular proliferation. These findings suggest that the development of NTN was regulated negatively by increased IDO activity, and IDO might play an important role in the pathogenesis of crescentic GN.

A review of candidate pathways underlying the association between asthma and major depressive disorder

OBJECTIVE

To consider the mechanisms that may link asthma and major depressive disorder (MDD). Asthma and MDD co-occur at higher rates than expected, but whether this reflects shared underlying pathophysiological mechanisms is not known.

METHODS

A review of the epidemiological data linking asthma and MDD was conducted and the possible biological mechanisms that could account for the high rate of this comorbidity were reviewed.

RESULTS

MDD occurs in almost half of patients with asthma assessed in tertiary care centers. Dysregulation of the hypothalamic pituitary adrenal axis may predispose people to both MDD and asthma, and similar alterations in the immune, autonomic nervous, and other key systems are apparent and may contribute to this increased risk of co-occurrence.

CONCLUSIONS

High rates of MDD in asthma may result from the stress of chronic illness, the medications used to treat it, or a combination of the two. The high level of co-occurrence may also reflect dysregulation of certain stress-sensitive biological processes that contribute to the pathophysiology of both conditions.

Potential role of tryptophan derivatives in stress responses characterized by the generation of reactive oxygen and nitrogen species

To face physicochemical and biological stresses, living organisms evolved endogenous chemical responses based on gas exchange with the atmosphere and on formation of nitric oxide (NO(*)) and oxygen derivatives. The combination of these species generates a complex network of variable extension in space and time, characterized by the nature and level of the reactive oxygen (ROS) and nitrogen species (RNS) and of their organic and inorganic scavengers. Among the latter, this review focusses on natural 3-substituted indolic structures. Tryptophan-derived indoles are unsensitive to NO(*), oxygen and superoxide anion (O(2)(*-)), but react directly with other ROS/RNS giving various derivatives, most of which have been characterized. Though the detection of some products like kynurenine and nitroderivatives can be performed in vitro and in vivo, it is more difficult for others, e.g., 1-nitroso-indolic compounds. In vitro chemical studies only reveal the strong likelihood of their in vivo generation and biological effects can be a sign of their transient formation. Knowing that 1-nitrosoindoles are NO donors and nitrosating agents indicating they can thus act both as mutagens and protectors, the necessity for a thorough evaluation of indole-containing drugs in accordance with the level of the oxidative stress in a given pathology is highlighted.

High serum tryptophan concentration in pollinosis patients is associated with unresponsiveness to pollen extract therapy

BACKGROUND/AIMS

The immunologic background of allergic asthma and rhinitis includes a preponderance of Th2-type immunity. In parallel, Th1-type immune response is suppressed by Th2-type cytokines. As a consequence, biochemical pathways triggered by Th1-type cytokine interferon-gamma, such as tryptophan degradation by indoleamine 2,3-dioxygenase and neopterin production, might be altered. We examined whether they are related to the outcome of hyposensitization therapy in atopic patients.

METHODS

In serum specimens of 44 atopic patients (18 women, 26 men) before any specific immunotherapy, tryptophan and kynurenine concentrations were measured by HPLC, and the kynurenine to tryptophan ratio (kyn/trp) was calculated. Neopterin concentrations were measured by ELISA. Results were compared with concentrations in 38 serum specimens from healthy blood donors and with the outcome of specific subcutaneous immunotherapy in atopics: on clinical grounds, 27 patients were classified as responders, and 17 patients as non-responders.

RESULTS

Serum tryptophan concentrations were higher in atopics (84.3 +/- 24.4 microM) than in blood donors (57.9 +/- 7.46 microM; p < 0.001), kynurenine and kyn/trp were not different between the 2 groups. All of the neopterin concentrations measured in patients were <8.7 nM, the upper limit of the normal. Non-responders to subcutaneous immunotherapy had significantly higher tryptophan concentrations (95.7 +/- 27.0 microM) than responders (77.1 +/- 19.9 microM; p = 0.01). No other marker concentrations differed between the groups.

CONCLUSIONS

The measurement of serum tryptophan may present an option to predict the outcome of pollen extract therapy. Higher tryptophan levels may result from lower indoleamine 2,3-dioxygenase activity in atopics. However, this possible relationship needs to be confirmed in further studies.