Hypodense eosinophils and interleukin 5 activity in the blood of patients with the eosinophilia-myalgia syndrome

Toxicology and safety study of L-tryptophan and its impurities for use in broiler feed

L-tryptophan has been utilized as a feed additive in animal nutrition to improve growth performance, as well as a dietary supplement to alleviate various emotional symptoms in humans. Despite its benefits, concerns regarding its safety arose following the outbreak of eosinophilia-myalgia syndrome (EMS) among individuals who consumed L-tryptophan. The causative material of EMS was determined to be not L-tryptophan itself, but rather L-tryptophan impurities resulting from a specific manufacturing process. To investigate the effect of L-tryptophan and its impurities on humans who consume meat products derived from animals that were fed L-tryptophan and its impurities, an animal study involving broiler chickens was conducted. The animals in test groups were fed diet containing 0.065%-0.073% of L-tryptophan for 27 days. This study aimed to observe the occurrence of toxicological or EMS-related symptoms and analyze the residues of L-tryptophan impurities in meat products. The results indicated that there was no evidence of adverse effects associated with the test substance in the investigated parameters. Furthermore, most of the consumed EMS-causing L-tryptophan impurities did not remain in the meat of broiler chickens. Thus, this study demonstrated the safety of L-tryptophan and some of its impurities as a feed additive.

Safety concerns regarding impurities in L-Tryptophan associated with eosinophilia myalgia syndrome

L-tryptophan is one of the essential amino acids in humans and across the animal kingdom. It has been widely used as a feed additive for domestic animals and is also administered through dietary supplements in humans. Safety concerns have been raised however since a disease known as eosinophilia-myalgia syndrome (EMS) was reported to be related to L-tryptophan supplements. EMS is a rare condition characterized by inflammation in various organ systems including the muscles, skin, and lungs. Through several studies, it has been speculated that the six components generated during the process of L-tryptophan synthesis are related to the induction of EMS. In this review, we discuss the history of EMS and its controversial correlation with L-tryptophan use reported in several studies. Many in vitro and in vivo studies have been conducted to assess the putative correlation between impurities in L-tryptophan preparations and EMS, but no clear and convincing conclusions have been drawn so far.

CCL26/eotaxin-3 is more effective to induce the migration of eosinophils of asthmatics than CCL11/eotaxin-1 and CCL24/eotaxin-2

CCL11, CCL24, and CCL26 are chemokines involved in the recruitment of eosinophils into tissues and mainly activate CCR3. Whereas the genomic or pharmacological inhibition of CCR3 prevents the development of experimental asthma in rodents, it only impairs the recruitment of eosinophils by ∼40% in humans. As humans, but not rodents, express CCL26, we investigated the impact of CCL11, CCL24, and CCL26 on human eosinophils recruitment and evaluated the involvement of CCR3. The migration of eosinophils of healthy volunteers was similar for the three eotaxins. Eosinophils of mild asthmatics had a greater response to CCL11 and a much greater response to CCL26. Whereas all eotaxins induced the migration of eosinophil of asthmatics from 0 to 6 h, CCL26 triggered a second phase of migration between 12 and 18 h. Given that the CCR3 antagonists SB 328437 and SB 297006 inhibited the 5-oxo-eicosatetraenoate-induced migration of eosinophils and that the CCR3 antagonist UCB 35625 was not specific for CCR3, CCR3 blockade was performed with the CCR3 mAb. This antibody completely blocked the effect of all eotaxins on eosinophils of healthy subjects and the effect of CCL24 on the eosinophils of asthmatics. Interestingly, CCR3 blockade did not affect the second migration phase induced by CCL26 on eosinophils of asthmatics. In conclusion, CCL26 is a more effective chemoattractant than CCL11 and CCL24 for eosinophils of asthmatics. The mechanism of this greater efficiency is not yet defined. However, these results suggest that CCL26 may play a unique and important role in the recruitment of eosinophils in persistent asthma.

Mechanisms of eosinophilia in the pathogenesis of hypereosinophilic disorders

The increased numbers of activated eosinophils in the blood and tissues that typically accompany hypereosinophilic disorders result from a variety of mechanisms. Exciting advances in translating discoveries achieved from mouse models and molecular strategies to the clinic have led to a flurry of new therapeutics specifically designed to target eosinophil-associated diseases. So far, this form of hypothesis testing in humans in vivo through pharmacology generally has supported the paradigms generated in vitro and in animal models, raising hopes that a spectrum of novel therapies soon may become available to help those who have eosinophil-associated diseases.

Eosinophilic disorders

Eosinophilic inflammatory responses occur in association with multiple disorders. Although the initial cause and the affected organs vary among the different eosinophilic disorders, there are only 2 major pathways that mediate eosinophilia: (1) cytokine-mediated increased differentiation and survival of eosinophils (extrinsic eosinophilic disorders), and (2) mutation-mediated clonal expansion of eosinophils (intrinsic eosinophilic disorders). Independent from the original trigger, the most common cause of eosinophilia is the increased generation of IL-5-producing T cells. In some cases, tumor cells are the source of eosinophil hematopoietins. The intrinsic eosinophilic disorders are characterized by mutations in pluripotent or multipotent hematopoietic stem cells leading to chronic myeloid leukemias with eosinophils as part of the clone. Here, we propose a new classification of eosinophilic disorders on the basis of these obvious pathogenic differences between the 2 groups of patients. We then discuss many known eosinophilic disorders, which can be further subdivided by differences in T-cell activation mechanisms, origin of the cytokine-producing tumor cell, or potency of the mutated stem cell. Interestingly, many subgroups of patients originally thought to have the idiopathic hypereosinophilic syndrome can be integrated in this classification.

[Activated eosinophils: techniques to characterize them]

The deleterious role thought to be played by eosinophils in many situations is linked to their ability to secrete various inflammatory substances, mainly toxic proteins and lipid mediators, in body tissue. This ability is a particular feature of activated eosinophils, which have undergone numerous metabolic, functional, and phenotypic changes from their resting state. Characterizing the properties of these activated cells is an essential step in improving our understanding of their contributions to local inflammatory response, as both regulatory and effector cells. Improvements in existing methods as well as the development of new technical approaches have facilitated the ex vivo and in vitro study of activated eosinophils and their contribution to various disease states.

Eosinophils alter colonic epithelial barrier function: role for major basic protein

Mucosal eosinophils increase in a number of gastrointestinal diseases that are often associated with altered epithelial barrier function, including food allergic enteropathies and inflammatory bowel diseases. Although eosinophils are known to secrete biologically active mediators including granule proteins, their role in gastrointestinal diseases is uncertain. The aim of this study was to determine the impact of eosinophils on intestinal barrier function. Epithelial barrier function was determined in a coculture of eosinophils and T84 epithelial cells and in a murine model of T helper (Th) type 2-mediated colitis. Coculture conditions resulted in decreased transepithelial resistance (TER) and increased transepithelial flux. Cell-free coculture supernatants contained a > or =5-kDa soluble factor that also diminished TER; these supernatants contained the eosinophil-granule proteins major basic protein (MBP) and eosinophil-derived neurotoxin (EDN). T84 barrier function decreased significantly when basolateral surfaces were exposed to native human MBP but not EDN. Additional studies identified downregulation of the tight junctional molecule occludin as at least one mechanism for MBP action. MBP-null mice were protected from inflammation associated with oxazolone colitis compared with wild-type mice. In conclusion, MBP decreases epithelial barrier function and in this manner contributes to the pathogenesis of inflammatory bowel diseases.

Rheumatologic disease with peripheral eosinophilia

Eosinophilia is not common in connective tissue diseases, so the frequency and clinical importance of eosinophilia in rheumatologic disease are not known. The purpose of the present review was to explore its prevalance in rheumatologic disease together with a MEDLINE database search.

L-tryptophan contaminant 'peak E' induces the release of IL-5 and IL-10 by peripheral blood mononuclear cells from patients with functional somatic syndromes

In 1989, the development of eosinophilia myalgia syndrome (EMS) was observed in some patients after the intake of l-tryptophan containing several contaminants, including 1,1'-ethylidenebis[l-tryptophan] ('peak E'). Since l-tryptophan has been taken particularly by individuals suffering from functional somatic syndromes (FSS), such as fibromyalgia syndrome (FMS), we put forward the hypothesis that EMS may have developed preferentially in patients with FSS as an allergic reaction towards the contaminant peak E. We therefore studied the immunological reactivity towards l-tryptophan and peak E in these individuals (n = 12) and compared these data with those obtained in 12 healthy controls and 12 patients with other chronic disorders. Peripheral blood mononuclear cells (PBMC) were cultured for 7 days with pure l-tryptophan and peak E. Supernatant fluids were collected at day 7. The type 2 cytokines IL-4, IL-5 and IL-10, and the type 1 cytokines IL-2 and IFN-gamma, were determined by a double sandwich ELISA. PBMC from seven of the 12 FSS patients, but only three of the 24 controls, produced cytokines after incubation with peak E (P < 0.05). Interestingly, six of the seven FSS patients reacting with peak E produced IL-5 and/or IL-10. In contrast, PBMC from only one patient with other chronic disorders and one healthy control secreted type 2 cytokines in response to peak E. The observed heightened type 2 reactivity towards the more immunogenic contaminant 1,1'-ethylidenebis[l-tryptophan] in FSS patients may therefore be taken as an additional argument for our concept that EMS may have developed as a kind of drug-induced allergic disease.

Systemic activation of basophils and eosinophils: markers and consequences

Basophils and eosinophils are important effector cells in human allergic diseases; they play a significant role in promoting allergic inflammation through the release of proinflammatory mediators (such as histamine, leukotriene C(4), major basic protein, eosinophil cationic protein, IL-4, and IL-13, among others). Notably, in allergic subjects, these cells exist in higher numbers and in a more activated state compared with nonatopic control subjects. Evidence for the greater activation state includes increased expression of intracellular and surface markers and hyperreleasability of allergy mediators. We have been interested in the phenotypic markers of effector-cell activation for many years. There is considerable overlap among activation markers, and few activation markers have been found that define a unique phenotype that is quantifiable in the assessment of the presence and severity of allergic disease. This review summarizes the existing evidence for systemic activation of human basophils and eosinophils in allergic diseases. The potential mechanisms responsible for functional and morphologic alterations in these effector cells and the specificity and utility of surface markers in the assessment of allergic disease activity or severity are also discussed.

Inhibition of antigen-induced eosinophilia and late phase airway hyperresponsiveness by an IL-5 antisense oligonucleotide in mouse models of asthma

Chronic airway eosinophilia is associated with allergic asthma and is mediated in part by secretion of IL-5 from allergen-specific Th2 lymphocytes. IL-5 is a known maturation and antiapoptotic factor for eosinophils and stimulates release of nascent eosinophils from bone marrow into the peripheral circulation. An antisense oligonucleotide found to specifically inhibit IL-5 expression in vitro was observed to significantly reduce experimentally induced eosinophilia in vivo, in both the murine OVA lung challenge and allergic peritonitis models. Intravenous administration resulted in sequence-dependent inhibition of eosinophilia coincident with reduction of IL-5 protein levels, supporting an antisense mechanism of action. Potent suppression of lung eosinophilia was observed up to 17 days after cessation of oligonucleotide dosing, indicating achievement of prolonged protection with this strategy. Furthermore, sequence-specific, antisense oligonucleotide-mediated inhibition of Ag-mediated late phase airway hyperresponsiveness was also observed. These data underscore the potential utility of an antisense approach targeting IL-5 for the treatment of asthma and eosinophilic diseases.

Alternative testing systems for evaluating noncarcinogenic, hematologic toxicity

Hematopoietic tissues are the targets of numerous xenobiotics. Clinical hematotoxicity is either a decrease or an increase in peripheral blood cell counts in one or more cell lineages--a cytopenia or a cytosis, respectively--that carries a risk of an adverse clinical event. The purpose of in vitro hematotoxicology is the prediction of these adverse hematologic effects from the effects of the toxicants on human hematopoietic targets under controlled experimental conditions in the laboratory. Building on its important foundations in experimental hematology and the wealth of hematotoxicology data found in experimental oncology, this field of alternative toxicology has developed rapidly during the past decade. Although the colony-forming unit-granulocyte/monocyte neutrophil progenitor is most frequently evaluated, other defined progenitors and stem cells as well as cell types found in the marrow stroma can be evaluated in vitro. End points have been proposed for predicting toxicant exposure levels at the maximum tolerated dose and the no observable adverse effect level for the neutrophil lineage, and several clinical prediction models for neutropenia have developed to the point that they are ready for prospective evaluation and validation in both preclinical species and humans. Known predictive end points are the key to successful comparisons across species or across chemical structures when in vitro dose-response curves are nonparallel. Analytical chemistry support is critical for accurate interpretation of in vitro data and for relating the in vitro pharmacodynamics to the in vivo pharmacokinetics. In contrast to acute neutropenia, anemia and acute thrombocytopenia, as well as adverse effects from chronic toxicant exposure, are much more difficult to predict from in vitro data. Pharmacologic principles critical for clinical predictions from in vitro data very likely will apply to toxicities to other proliferative tissues, such as mucositis.

Type 1 and type 2 cytokine dysregulation in human infectious, neoplastic, and inflammatory diseases

In the mid-1980s, Mosmann, Coffman, and their colleagues discovered that murine CD4+ helper T-cell clones could be distinguished by the cytokines they synthesized. The isolation of human Th1 and Th2 clones by Romagnani and coworkers in the early 1990s has led to a large number of reports on the effects of Th1 and Th2 on the human immune system. More recently, cells other than CD4+ T cells, including CD8+ T cells, monocytes, NK cells, B cells, eosinophils, mast cells, basophils, and other cells, have been shown to be capable of producing "Th1" and "Th2" cytokines. In this review, we examine the literature on human diseases, using the nomenclature of type 1 (Th1-like) and type 2 (Th2-like) cytokines, which includes all cell types producing these cytokines rather than only CD4+ T cells. Type 1 cytokines include interleukin-2 (IL-2), gamma interferon, IL-12 and tumor necrosis factor beta, while type 2 cytokines include IL-4, IL-5, IL-6, IL-10, and IL-13. In general, type 1 cytokines favor the development of a strong cellular immune response whereas type 2 cytokines favor a strong humoral immune response. Some of these type 1 and type 2 cytokines are cross-regulatory. For example, gamma interferon and IL-12 decrease the levels of type 2 cytokines whereas IL-4 and IL-10 decrease the levels of type 1 cytokines. We use this cytokine perspective to examine human diseases including infections due to viruses, bacteria, parasites, and fungi, as well as selected neoplastic, atopic, rheumatologic, autoimmune, and idiopathic-inflammatory conditions. Clinically, type 1 cytokine-predominant responses should be suspected in any delayed-type hypersensitivity-like granulomatous reactions and in infections with intracellular pathogens, whereas conditions involving hypergammaglobulinemia, increased immunoglobulin E levels, and/or eosinophilia are suggestive of type 2 cytokine-predominant conditions. If this immunologic concept is relevant to human diseases, the potential exists for novel cytokine-based therapies and novel cytokine-directed preventive vaccines for such diseases.

Interleukin-5 receptor alpha subunit gene regulation in human eosinophil development: identification of a unique cis-element that acts lie an enhancer in regulating activity of the IL-5R alpha promoter

Further functional and biochemical characterization of the nuclear factor(s) which interacts with the EOS1 enhancer-like element in the IL-5R alpha promoter is currently in progress. Since different transcription factors recognize and interact with DNA in distinct fashions and with distinct structural motifs, we have modeled potential binding of the EOS1 factor to its cis-element based upon its methylation interference pattern (Fig. 2), using a cylindrical DNA helical projection (Fig. 6). Over a length of two helical turns, all nuclear protein contacts indicated by methylation interference map to one side of the DNA helix, suggesting that EOS1 binds in the major groove, across the minor groove, and on only one side of the helix. Further review of the model also reveals a potential diad symmetry for the binding site, suggestive of binding by a homodimer and consistent with the formation of the two DNA-protein complexes in our electrophoretic mobility shift experiments that could represent interactions with monomer versus dimer. Comparison of the EOS1 binding motif to similar models for the binding of other transcription factor families for which structural crystallographic and/or binding data is available suggests a similarity of the EOS1 complex to that of the bacterial helix-turn-helix phage lambda and 434 repressor-operator complexes, and the Cys4 zinc finger glucocorticoid response element (GRE) DNA-binding motifs, all of which show similar diad symmetry and binding in the major groove on one side of the DNA. The possibility that EOS1 functions as a GRE is being investigated, especially since there is a consensus AP-1 site at bp -440 to -432 of the IL-5R alpha promoter, immediately adjacent to the EOS1 binding site (see Fig. 5 in reference [36]) and AP-1/GRE interactions have been identified for composite response elements in the regulation of a number of different genes. The identification or cloning of EOS1, a potentially novel and eosinophil lineage-active transcription factor, should enhance our understanding of the processes involved in eosinophil development in particular and myeloid lineage commitment and differentiation in general.

Identification and characterization of a functional promoter region in the human eosinophil IL-5 receptor alpha subunit gene

The molecular basis for the commitment of multipotential myeloid progenitors to the eosinophil lineage, and the transcriptional mechanisms by which eosinophil-specific genes are subsequently expressed and regulated during eosinophil development are currently unknown. Interleukin-5 (IL-5) is a T cell and mast cell-derived cytokine with actions restricted to the eosinophil and closely related basophil lineages in humans. The high affinity receptor for IL-5 (IL-5R) is composed of an alpha subunit (IL-5R alpha) expressed by the eosinophil lineage, that associates with a beta c subunit shared with the receptors for IL-3 and granulocyte-macrophage colony stimulating factor (GM-CSF). As a prerequisite to studies of the transcriptional regulation of the IL-5R alpha subunit gene, we used three different methods, including primer extension, RNase protection, and 5'-RACE to precisely map the transcriptional start site to a position 15 base pairs (bp) upstream of the 5' end of the published sequence of IL-5R alpha exon 1. To initially identify the IL-5R alpha promoter, 3.5 kilobases (kb) and 561 bp of the 5' sequence flanking the transcriptional start site were subcloned into the promoterless pXP2-luciferase vector. Transient transfection of these constructs into an eosinophil-committed HL-60 subline, clone HL-60-C15, induced the expression of approximately 240-fold greater luciferase activity than the promoterless vector, identifying a strong functionally active promoter region within the 561 bp of sequence proximal to the transcriptional start site and with activity equivalent to pXP2 constructs containing the entire 3.5 kb of upstream sequence. To more precisely localize the cis-acting regulatory elements in this region important for promoter activity, a series of 5' deletion mutants of the 561-bp region were generated in the pXP2-luciferase vector. Deletion of the region between bp -432 and -398 reduced promoter activity by more than 80% in the HL-60-C15 cell line. Further analyses of the activity of the IL-5R alpha promoter constructs in various other eosinophil, myeloid, and non-myeloid cell lines indicated that the promoter was relatively myeloid and eosinophil lineage-specific in its expression. Consensus sequences for known transcription factor binding sites were not present in the 34-bp region of the promoter required for maximal activity, suggesting unique myeloid- and possibly eosinophil-specific regulatory elements.(ABSTRACT TRUNCATED AT 400 WORDS)

Pulmonary vasculitis with hypereosinophilia and episodic pulmonary hypertension: report of three siblings

Three siblings with eosinophilia who developed pulmonary hypertension are reported. They consisted of a 3 year old boy (case 1), a 9 year old boy (case 2) and a 13 year old girl (case 3), all of whom died within an 18 month period of severe episodic attacks of pulmonary hypertension and the resultant low cardiac output. Marked peripheral eosinophilia was found in cases 1 and 2, and mild eosinophilia in case 3. Open lung biopsy of case 1 revealed pulmonary arteritis with massive eosinophilic infiltration and intimal thickening of muscular arteries of 300-1500 microns in diameter. At autopsy, cases 2 and 3 showed almost similar findings, comprising widespread obliteration of the pulmonary arteries by concentric intimal thickening, medial hypertrophy and recanalized thrombi of arterioles. Rarely, there were foci of granulomas in the thickened intima surrounding birefringent foreign bodies. There were small areas of infarction in the lungs and heart due to arterial thrombi. Vascular lesions other than those in the lungs were mild and almost limited to the branches of the coronary arteries. Therefore, the present cases appear to be a single disease of pulmonary hypertension secondary to endothelial injury and the resultant intimal fibrosis probably evoked by toxic substances, although such agents were not confirmed.

Eosinophils in the 1990s: new perspectives on their role in health and disease

Eosinophils are characterized by their unique crystalloid granules that contain four basic proteins--MBP, ECP, EDN and EPO. The cell has many common features with neutrophils but, unlike that cell type, eosinophils utilize VLA-4/VCAM-1 as an adherence pathway and have a number of other receptors not shared by neutrophils. These include recognition units for IgE (distinct from CD23), and receptors for IL-5, IL-3 and RANTES. Following stimulation with a variety of agents, eosinophils preferentially elaborate LTC4 as the major 5-lipoxygenase product of arachidonic acid and produce substantial amounts of PAF. Of particular interest is the ability of eosinophils to synthesize a number of cytokines. Thus eosinophils have marked pro-inflammatory potential. There is now convincing evidence that eosinophilia is T-cell dependent. The Th2-type cell, which selectively secretes IL-5 and IL-4, seems particularly involved. IL-5, IL-3 and GM-CSF are required for eosinophil maturation, and cause activation and prolonged survival of the mature cell. IL-5 is unique in that it promotes terminal differentiation of the committed eosinophil precursor and in vivo in mice appears to be sufficient on its own for eosinophil growth from uncommited stem cells. IL-4 selectively upregulates VCAM-1 expression on endothelial cells thus augmenting VLA-4-dependent eosinophil adhesion. The role of eosinophils in disease is complex but in general their numbers are increased in helminthic parasitic disease and atopic allergy and asthma. Eosinophil products can produce many of the pathological features of asthma, and helminthic larvae coated with immunoglobulin or complement are particularly susceptible to eosinophil-mediated cytotoxicity. Eosinopenia is often related to acute inflammation or stress.

A comparative study on antibodies to nucleoli and 5-hydroxytryptamine in patients with fibromyalgia syndrome and tryptophan-induced eosinophilia-myalgia syndrome

Eosinophilia myalgia syndrome (EMS) has been related to intake of "contaminated" L-tryptophan, and an alteration in tryptophan 5-hydroxytryptamine (5-HT, serotonin) metabolism has been reported in EMS patients. Recently we found that a defined autoantibody pattern consisting of antibodies to nucleoli, gangliosides, and phospholipids is closely related to the fibromyalgia syndrome (FS) which clinically resembles the EMS. We were therefore interested to see whether these antibodies can also be detected in patients with EMS. Studied were 27 patients with acute EMS (13 of whom were also examined 2 years after acute onset), 100 patients with FS, and 40 patients with progressive systemic sclerosis (PSS). As controls, sera from 100 blood donors were analyzed. Antibodies to nucleoli were demonstrated by immunofluorescence test on cell cultures in 52% of patients with acute EMS, 62% of patients with chronic EMS, and 37% of FS patients. Western blotting with a nuclear extract from HeLa cells revealed in both diseases the same epitopes at 63, 57, and 53 kDa. Antibodies to 5-HT, gangliosides (Gm1), and phospholipids were determined by enzyme-linked immunosorbent assay. Among patients with FS 73% had antibodies to 5-HT, in contrast to only 19% of patients with acute EMS. However, 77% of the 13 EMS patients analyzed 2 years later had become anti-5-HT antibody positive during that time. Also the incidence of antibodies to Gm1 increased from 37% at acute onset to 69% in patients with chronic EMS (30%). The various antibodies were detected in only 18% of healthy controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Releasability of human hypereosinophilic eosinophils is related to the density of the cells

The activity of eosinophils and neutrophils with respect to the release of granule proteins was studied in 11 patients with the hypereosinophilic syndrome (HES). Granulocytes or purified eosinophils were stimulated with serumopsonized Sephadex particles (C3b-induced release), and the released amounts of eosinophil cationic protein (ECP), eosinophils protein-X (EPX) and myeloperoxidase (MPO) were measured by means of specific radioimmunoassays (RIA). Eosinophils obtained from patients with HES released significantly more ECP (P < 0.002) and EPX (P < 0.01) after 20 min of incubation than cells from the control group. The cellular content of ECP and EPX in eosinophils obtained from the patients with HES was significantly reduced to 50% and 62%, respectively, of the content of these granule proteins of eosinophils from the control group. In separated eosinophils light-density eosinophils released more of both ECP and EPX than normal density eosinophils. There was no difference in MPO release between the patients and the control group. We conclude that the eosinophils from patients with HES have an increased propensity to release their granule proteins and the releasability seems to be related to the density of the cells.

1,1'-Ethylidenebis(tryptophan) (Peak E) induces functional activation of human eosinophils and interleukin 5 production from T lymphocytes: association of eosinophilia-myalgia syndrome with a L-tryptophan contaminant

This study was designed to clarify the important association between eosinophilia-myalgia syndrome (EMS) and the L-tryptophan contaminant, "Peak E." To determine the functional activation of eosinophils induced by Peak E, eosinophil cationic protein (ECP) release was examined. Peak E augumented the release of ECP from peripheral blood normodense eosinophils by degranulation. Proliferative analysis using the human eosinophilic leukemia cell line EoL-3 showed prominent cellular replication in the presence of Peak E. Moreover, Peak E upregulated interleukin 5 (IL-5) receptor levels on normodense eosinophils. Of particular interest, Peak E-stimulated human splenic T cells produced bioactive and immunoreactive IL-5. Marked induction of IL-5 mRNA in Peak E-stimulated T cells was also shown by reverse-transcriptase polymerase chain reaction (RT-PCR). In contrast, L-tryptophan without the contaminant showed none of these effects. Thus, these data suggest that Peak E might be involved in the pathogenesis of EMS through bimodal mechanism including IL-5 generation by T cells and potentiation of eosinophil functional activation.

Chronic immune activation in the eosinophilia-myalgia syndrome

Eosinophilia-myalgia syndrome (EMS) is a multisystem illness of uncertain pathogenesis that occurred in an epidemic related to the ingestion of contaminated L-tryptophan. To investigate the role of immune dysfunction in EMS we prospectively measured a serologic index of T-cell activation, the soluble interleukin-2 receptor (sIL-2R), in 7 patients followed into the late stages of the illness. As a group, EMS patients had significantly elevated sIL-2R levels throughout the study. Five patients suffered chronic symptoms of myalgia, arthralgia, muscle cramps, fatigue, or subjective memory impairment and all had persistently elevated sIL-2R levels. Two patients had near-resolution of EMS and normal sIL-2R levels. We conclude that chronic symptoms are common in EMS and are associated with persistent T-cell activation as measured by serum sIL-2R levels. These findings suggest that immunosuppressive treatment may be beneficial in EMS.

IL-5 in post-traumatic eosinophilic pleural effusion

Thoracic trauma or pneumothorax can result in pleural fluid eosinophilia. In this study we investigated the role of the eosinophilopoietic cytokine IL-5 in three cases of post-traumatic eosinophilic pleural effusions (EPE). Using a specific immunoenzymatic assay, significant levels of IL-5 were found in EPE (range 100-3000 pg/ml), while IL-5 was undetectable (< 25 pg/ml) in corresponding serum samples and in non-eosinophilic pleural fluids. IL-5 present in pleural fluids was found bioactive in a proliferative assay using a mouse CTLL-2 cell line transfected with the cDNA corresponding to the alpha chain of the human IL-5 receptor. Using a reverse polymerase chain reaction (PCR) method, we found IL-5 mRNA expression within pleural mononuclear cells from patients with EPE, but not in corresponding peripheral blood mononuclear cells (PBMC), confirming that IL-5 is synthesized locally in the pleural cavity. In the two cases in which pleural CD4+ cells were purified, these cells were identified as the major source of IL-5. Taken together, these data indicate that the development of post-traumatic EPE is related to a local secretion of IL-5 by CD4+ cells present in the pleural cavity.

The biology of interleukin-5 and its receptor

IL-5 is primarily a T-cell-derived cytokine that has multiple regulatory functions on eosinophils and (in the mouse) on antibody-secreting B cells. A complex network of cytokines appear to control transcription of the gene for IL-5 and its production. Abnormally high levels of this cytokine are associated with infections with tissue-dwelling parasites and a diverse group of hypereosinophilic conditions of no known etiology. Our understanding of the biological role of IL-5 in the regulation of Ig production and the development of immunity to parasites is far from complete, but basic knowledge of its action at the cellular level is accumulating and will be critical for the intelligent application of immunotherapy with IL-5 or antibodies to IL-5 in infectious, neoplastic, and possibly other diseases.

L-tryptophan and the eosinophilia-myalgia syndrome: current understanding of the etiology and pathogenesis

The eosinophilia-myalgia syndrome (EMS) is a newly recognized illness that occurred in an epidemic form during the summer of 1989. The illness was characterized in the acute phase by myalgia and eosinophilia, followed in many patients by chronic cutaneous lesions, progressive neuropathy, and myopathy. EMS was associated with ingestion of L-tryptophan, an essential amino acid marketed as a nutritional supplement but widely used as a therapeutic agent. Evidence of abnormal L-tryptophan metabolism has been described in patients with EMS, and most likely reflects increased activity of indoleamine 2,3-dioxygenase, the rate-limiting enzyme of tryptophan metabolism. A contaminant identified in EMS-associated L-tryptophan preparations has been isolated and characterized, but its biologic effects and role as the etiologic agent in EMS remain to be established. Pathologic observations and experimental studies indicate that eosinophils, mononuclear inflammatory cells, and fibroblasts are potential effector cells, and interleukin-5 and transforming growth factor-beta are important mediators in the pathogenesis of the syndrome. Although few new cases of EMS occurred following the withdrawal of L-tryptophan, affected patients continue to manifest late sequelae of the disease, including dermal fibrotic conditions. This tragic outbreak of a newly recognized illness has focused interest on the role of chemical and environmental agents in the pathogenesis of various idiopathic illness characterized by tissue inflammation and fibrosis.

Mapping of the interleukin 5 receptor gene to human chromosome 3 p25-p26 and to mouse chromosome 6 close to the Raf-1 locus with polymorphic tandem repeat sequences

Simple-sequence tandem repeat sequences in the 3' UTR of interleukin 5 (IL5)-receptor gene of human and mouse are polymorphic in their length among humans and different strains of mice. In 20 different human Epstein-Barr virus (EBV)-transformed cell lines, six alleles of IL5R could be distinguished. In the mouse, three different alleles are found. With the human-specific IL5R tandem repeat marker in human-rodent somatic cell hybrids, the IL5R gene was mapped to human Chromosome (Chr) 3 p25-p26. With the mouse-specific IL5R tandem repeat sequence in recombinant inbred strains of mice, the Il5r gene was mapped to the distal part of mouse Chr 6 close to the Raf-1 locus.

Tryptophan metabolism via the kynurenine pathway in patients with the eosinophilia-myalgia syndrome

OBJECTIVE

To investigate the metabolism of L-tryptophan (LT) via the kynurenine pathway in patients with the eosinophilia-myalgia syndrome (EMS).

METHODS

Measurement of LT, L-kynurenine, and quinolinic acid in plasma and cerebrospinal fluid (CSF) from subjects with EMS, from asymptomatic users of LT, and from normal subjects.

RESULTS

Plasma LT concentrations were lower in untreated EMS patients (n = 5) than in corticosteroid-treated EMS patients (n = 5; P less than 0.05) and in asymptomatic users of LT (n = 5; P less than 0.05). Untreated EMS patients, who had discontinued LT weeks to months prior to study, had significantly higher plasma levels of L-kynurenine and quinolinic acid than did corticosteroid-treated EMS patients (P less than 0.05), normal subjects (P less than 0.02), and asymptomatic users of LT (P less than 0.05). EMS patients also had significantly elevated levels of L-kynurenine (P less than 0.05) and quinolinic acid (P less than 0.001) in CSF compared with normal subjects. After a 1-gm oral dose of LT, untreated EMS patients (n = 4) showed lower peak levels of LT and accentuated synthesis of L-kynurenine and quinolinic acid, compared with these values in corticosteroid-treated EMS patients (n = 2), who responded like normal subjects (n = 5).

CONCLUSION

These data demonstrate that during the active phase of EMS, LT metabolism via the kynurenine pathway was accentuated, probably secondary to induction of the enzyme indoleamine-2,3-dioxygenase. Ingestion of large amounts of LT (median daily dose 1.5 gm) resulted in high concentrations of kynurenine-pathway metabolites in blood and extrahepatic tissues, which was accentuated in EMS patients and which may have played a significant role in the pathogenesis of the disease.

Interleukin-5 in eosinophilic gastroenteritis

During a 4-year period a 28-year-old female had 4 episodes of eosinophilia of over 10,000/mu 1; these episodes were associated with nausea, vomiting, diarrhea, and abdominal pain. On one occasion, she had ascites and pleural effusion which contained numerous mature eosinophils. On each occasion, these attacks disappeared within several weeks without any specific treatment. A diagnosis of eosinophilic gastroenteritis was made. A plasma sample obtained during the eosinophilia generated in vitro eosinophilic colonies when added to granulocyte/macrophage-progenitor (CFU-GM) cultures without exogenous growth factors. Colony formation was inhibited by anti-interleukin-5 (IL-5) antibody but not by antibodies toward IL-3, granulocyte colony-stimulating factor (G-CSF) or GM-CSF. A high plasma interleukin-5 (IL-5) level was noted when measured by enzyme-linked immunosorbent assay, while IL-3, G-CSF, and GM-CSF were undetectable. During remission the plasma gave negative results both for colony formation and IL-5 level. These results indicate that the eosinophilia of this disease is mediated by IL-5.

Gastrointestinal involvement in L-tryptophan (L-Trp) associated eosinophilia-myalgia syndrome (EMS)

We report a 45-year-old female who had symptomatic gastrointestinal involvement, eosinophils in the cellular infiltrate, and who proved to have L-tryptophan-associated eosinophilia-myalgia syndrome. This case illustrates that gastrointestinal disease can be a major, seemingly primary clinical presentation in this syndrome, and that a drug history, specifically L-tryptophan, needs to be included in the differential diagnosis of "eosinophilic gastroenteritis."

Platelet-activating factor primes human eosinophil generation of superoxide

Platelet-activating factor (PAF) is a potent inflammatory mediator that can cause airway obstruction and hyperresponsiveness; these processes are also associated with pulmonary eosinophilia, suggesting a link between these two events. Thus, PAF's interaction with eosinophils may provide a mechanism for airway damage. However, direct in vitro activation of eosinophils by PAF requires concentrations that are likely higher than those achieved in vivo. As a result, we investigated whether lower, more physiologic concentrations of PAF could prime eosinophils for subsequent activation to another receptor-stimulated factor, in this case formylmethionylleucylphenylalanine (FMLP). To test this hypothesis, eosinophils were preincubated (1 and 15 min) with low concentrations of PAF (1 x 10(-8) and 1 x 10(-10) M); this exposure to PAF resulted in enhanced generation of superoxide anion to FMLP stimulation. Moreover, similar concentrations of PAF decreased eosinophil density and increased expression of cell surface CR3 receptors. Finally, low, nonactivating concentrations of PAF (1 x 10(-10) to 1 x 10(-8) M) caused transient increases in eosinophil cytosolic free Ca2+ concentrations. Collectively, these responses are consistent with the hypothesis that short-term exposure to low concentrations of PAF primes eosinophils to cause an enhanced inflammatory response upon subsequent activation to another receptor agonist. The consequences of this PAF-associated phenomenon can produce an enhanced inflammatory response and airway injury.

Eosinophil hematopoietins antagonize the programmed cell death of eosinophils. Cytokine and glucocorticoid effects on eosinophils maintained by endothelial cell-conditioned medium

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was established as the constitutive and elicited human umbilical vein endothelial cell-derived eosinophil viability-sustaining factor. Stimulation of endothelium cell monolayers with IL-1 alpha (5 U/ml) increased the 48-h elaboration of GM-CSF from a mean of 3.2 to a mean of 8.2 pM (P less than 0.05). Dexamethasone (100 nM) decreased the constitutive GM-CSF elaboration by 49% (P less than 0.001) but did not diminish production by IL-1 alpha-stimulated endothelium. However, eosinophil viability decreased by 21% in dexamethasone-pretreated IL-1 alpha-stimulated endothelial cell-conditioned medium (P less than 0.05), which suggested viability antagonism by glucocorticoids. After 24 h of culture, eosinophil viability for replicate cells in enriched medium alone or with 1 pM GM-CSF decreased from means of 43 and 75% to means of 21 and 54%, respectively, when dexamethasone was included (P less than 0.05). However, 10 pM GM-CSF, IL-3, or IL-5 protected the cells against dexamethasone and against endonuclease-specific DNA fragmentation. In this model system of eosinophil-tissue interactions, dexamethasone prevents the endothelial cells from inducing a pathobiologic phenotypic change in the eosinophil by suppression of GM-CSF elaboration to concentrations that are not cytoprotective. Cytokine priming by GM-CSF, IL-3, or IL-5 may account for the differential responsiveness of select eosinophilic disorders to glucocorticoids.

Interleukin-5 and the posttreatment eosinophilia in patients with onchocerciasis

To understand the role of the eosinophilopoietic cytokine IL-5 in humans, the posttreatment eosinophilic response in a group of microfilaria (mf)-positive patients with onchocerciasis (n = 10) was examined before and after treatment with diethylcarbamazine (6 mg/kg for 7 d). Sequential blood samples were assessed at 24 and 1 h before treatment (baseline values), then at frequent intervals over the next 14 d. Symptom scores, skin microfilariae (mf), and peripheral blood eosinophil counts were recorded as a function of time after treatment, and serum levels of IL-5 were quantitated by a highly sensitive (sensitivity greater than or equal to 20 pg/ml) monoclonal-based ELISA. Pretreatment eosinophil counts ranged from 240 to 1,186 eosinophils/microliter (geometric mean, 675), and the mf counts from 10 to 218 per mg skin (geometric mean, 79). After an initial decline in the peripheral eosinophil count to 28 +/- 8% of pretreatment levels at 8 h after beginning treatment, the eosinophil counts steadily increased over the next 2 wk, reaching a maximum at 14 d (257 +/- 38% of pretreatment levels). Serum levels of IL-5 rose sharply from pretreatment levels to a peak of 70.5 +/- 11 pg/ml by 24 h after treatment. Serum IL-5 remained elevated over the next 2-3 d and declined toward baseline by approximately 6 d after treatment, at which time the eosinophil levels were steadily increasing. IL-3 and granulocyte macrophage colony-stimulating factor, two other cytokines implicated in eosinophilopoeisis, were not detectable in the serum at any time before or after treatment. The rise in serum IL-5 before the posttreatment eosinophilia seen in this group of patients with onchocerciasis demonstrates a temporal relationship between IL-5 and the subsequent development of eosinophilia and implicates IL-5 as an important mediator of eosinophilia in humans.

Effects of IL-5, granulocyte/macrophage colony-stimulating factor (GM-CSF) and IL-3 on the survival of human blood eosinophils in vitro

The mechanisms that could affect the lifespan of eosinophils after they have left the bone marrow, and their capacity to respond to activation factors were studied by examining the effects of IL-5, GM-CSF and IL-3 on purified human blood eosinophils in culture. All three cytokines prolonged the lifespan of the majority of blood eosinophils. This effect was dose-dependent: IL-5 greater than GM-CSF greater than IL-3. Light density eosinophils from most patients had a longer lifespan in culture than did normal density eosinophils, with or without the three cytokines. Eosinophil death in the absence of these cytokines occurred by apoptosis. Eosinophils from two patients did not survive when cultured with IL-5, although they survived in the presence of IL-3 or GM-CSF. IL-5, GM-CSF and IL-3 induced the expression of the activation epitope on the eosinophil ribonucleases recognized by monoclonal antibody EG2. We conclude that small amounts of IL-5, GM-CSF and IL-3 prevented programmed cell death in human blood eosinophils and induced the expression of the activation forms of eosinophil ribonucleases. We suggest that differences in the capacity of normal and light density eosinophils to survive in culture, and in the ability of eosinophils from some patients to respond to IL-5 could account for variations in the severity of disease seen in patients with persistent eosinophilia.

The role of eosinophils in the pathophysiology of asthma

From current information, a number of conclusions can be drawn. Antigen activation of the allergic reaction in the airways is associated with an immediate rise in mast cell derived mediators, including histamine and tryptase. Associated with antigen activation of the allergic reaction is recruitment of eosinophils to the airways. This can best be seen in the airway lavage 48 hours after challenge with antigen. An increased presence of eosinophils suggests that they are an important contributor to the late allergic reaction and may be one of the major constituents in the development of bronchial inflammation. Although many factors participate in the late allergic inflammatory response, eosinophil-derived proteins are known to cause airway injury. Regulation of eosinophils in this process is not clearly established; however, our findings of increased IL-5 in relationship to the presence of eosinophils and their granular proteins suggests that this cytokine may be an important modulator of eosinophil function and activation following allergen challenge. However, much remains unknown in understanding bronchial inflammation and the eosinophil's role in the process. In conclusion, the eosinophil is a major cellular participant in late phase allergic airway disease. Its presence and known functions suggest that the eosinophil is a significant cellular factor in the development of allergic airways disease in asthma. Further advances in this area will follow continued studies, particularly those which involve biopsy and correlation with airway physiology.