Eosinophil-associated TGF-beta1 mRNA expression and airways fibrosis in bronchial asthma

The histopathology of bronchial asthma is associated with structural changes within the airways, including subepithelial fibrosis, as well as chronic eosinophilic inflammation. The mechanisms responsible for this tissue remodeling, and in particular the role of inflammatory cells, remain to be established. Transforming growth factor-beta (TGF-beta) is a potent profibrotic cytokine which may contribute to the thickening of the reticular lamina by the deposition of collagen fibers. To investigate the molecular mechanisms underlying these structural changes, we have investigated the expression of TGF-beta1 mRNA and immunoreactivity within the bronchial mucosa of mild to severe asthmatic individuals and normal control subjects using the techniques of in situ hybridization and immunocytochemistry. As eosinophils are prominent within the asthmatic airway and are known to synthesize pro-inflammatory cytokines, the presence of TGF-beta1 mRNA and immunoreactive protein in eosinophils was also examined. Asthmatic individuals exhibited a greater expression of TGF-beta1 mRNA and immunoreactivity in the airways submucosa than normal control subjects (P < 0.05), and these increases were directly related to the severity of the disorder. The extent of airways fibrosis, as detected histochemically, was also increased in asthmatics compared with normal control subjects (P < 0.005). In asthmatic subjects, the presence of subepithelial fibrosis was associated with the severity of the disease and correlated with the decline in forced expiratory volume in 1 s (r2 = 0.78; P < 0.05). Within the asthmatic airways, EG2-positive eosinophils represented the major source of TGF-beta1 mRNA and immunoreactivity. These results provide evidence that TGF-beta1 may play a role in the fibrotic changes occurring within asthmatic airways and that activated eosinophils are a major source of this cytokine.

Association of toxic shock syndrome toxin-secreting and exfoliative toxin-secreting Staphylococcus aureus with Kawasaki syndrome complicated by coronary artery disease

Kawasaki syndrome (KS) has been reported to be associated with selective expansion of Vbeta2+ T cells and either staphylococcal toxic shock syndrome toxin-1 or streptococcal pyrogenic exotoxin C in uncomplicated cases. However, there have been no previous studies on the role of superantigens in KS associated with coronary artery disease, the major complication of this illness. The present study characterized bacteria isolated from three acute KS patients who developed coronary artery disease. Staphylococcus aureus secreting either TSST-1 (n = 3) or exfoliative toxin A (n = 1), both known to stimulate expansion of Vbeta2+ T cells, were isolated from all three patients. The percent Vbeta2+ T cells was determined in three patients with coronary artery disease. On presentation, one patient demonstrated reduction, whereas the other two showed expansion, of Vbeta2+ T cells. Repeat analyses of the latter two children showed their percent Vbeta2+ T cells to decrease toward normal. These observations suggest that coronary artery disease in KS may result from superantigenic stimulation of Vbeta2+ T cells. This is also the first demonstration of an association of staphylococcal exfoliative toxin with acute KS. The observation that three different bacterial toxins associated with KS are potent activators of Vbeta2+ T cells suggests an important role for this T cell subset in the pathogenesis of this autoimmune disease.

Glucocorticoid-resistant asthma: pathogenesis and clinical implications for management

At the present time, emphasis is placed on viewing asthma as a manifestation of chronic airway inflammation, possibly secondary to allergen hypersensitivity. Consequently, one aspect of management is to institute measures of environmental control to minimize the inflammatory response related to allergen stimulation, and to administer anti-inflammatory therapy to resolve inflammation and prevent progression of disease. Most patients respond very favourably to conventional therapy, as recommended in recent guidelines for asthma management. Some cases, however, remain very difficult to control despite high-dose inhaled glucocorticoids, even combined with oral glucocorticoid therapy. Management of these patients raises questions about the conditions that alter response to glucocorticoid therapy. The patient with difficult to control asthma not only presents a challenge to clinical management but raises new questions concerning our ability to control the progression of disease. Is difficult to control asthma secondary to overwhelming or ongoing allergen exposure? Do anti-inflammatory medications, specifically inhaled glucocorticoids, really control the progression of the disease? Are these patients destined to become severe asthmatics at birth due to the inherent characteristics of their airways, or is this indeed a consequence of progressive inflammation? This review will summarize present concepts of glucocorticoid-resistant asthma, current knowledge of the mechanisms of persistent inflammation, and the implications for management. The gaps in information will also be addressed in order to stimulate interest in further research that could lead to better understanding of the disease and potential windows for therapeutic intervention.

Clinical applications of cytokines: new directions in the therapy of atopic diseases

OBJECTIVES

This review will enable the readers to understand the pathogenesis of allergic inflammation, and the role of various cells and cytokines in allergic diseases. Pathogenic cytokines may become key therapeutic targets in the future treatment of allergic diseases.

DATA SOURCES

MEDLINE literature search limited to the English language was performed using the relation between specific cytokines and allergic inflammation as well as therapy of allergic diseases. Relevant articles referenced in retrieved sources and current texts on ctyokines and allergic responses were also utilized.

RESULTS

The mechanism underlying allergic inflammation involves complex interactions between various cells and cytokines. The immediate reaction is caused mainly by mast cells and followed by a cell mediated response that involves eosinophils, mononuclear cells, neutrophils, T lymphocytes and macrophages. The majority of T cells in early allergic reactions are T helper type 2 (TH2)-like producing IL-4, IL-5, IL-13 but not IFN-gamma. These cytokines regulate IgE synthesis, promote eosinophil differentiation and survival, and induce vascular endothelial adhesion molecules, thus contributing to allergic inflammation.

CONCLUSIONS

Although studies of cytokine modulation have utilized animal models of allergic diseases, the increasing availability of recombinant cytokines and cytokine antagonists is likely to lead to more wide scale applications in allergic diseases.

Analysis of CD80 and CD86 expression on peripheral blood B lymphocytes reveals increased expression of CD86 in lupus patients

We screened peripheral blood mononuclear cells from 13 SLE patients, all having quiescent disease at the time of analysis, 12 allergy patients, and 21 normal subjects for the expression of CD80 (B7-1) and CD86 (B7-2, B70) on small (resting) and large (activated) subsets of CD19+ B cells. The percentage of CD86+ cells was significantly higher in all B cell subsets in the SLE patients compared to either normal controls or allergy patients. No differences in the mean percentage CD86+ stained B cells (CD19+) were found when comparing the allergy patients and the normal controls. The percentage of CD80+ cells in the large activated B cell (CD19+) subset of the SLE patient population was significantly higher than in the comparable subset from the normal controls and the allergy patients. Comparison of the small resting B cell subset did not reveal a significant difference in CD80 expression between the normal controls, the allergy patients, and the SLE patients. Our findings suggest that the B7 family of molecules, and CD86 in particular, may reflect immunologic dysregulation in patients with autoimmune disease and may reflect a state facilitating heightened B cell activity and hypergammaglobulinemia that occur in active SLE.

Determinants of functional capacity in chronic mitral regurgitation unassociated with coronary artery disease or left ventricular dysfunction

Impaired functional capacity is common in patients with mitral regurgitation (MR), but the determinants of functional capacity in patients with normal left ventricular (LV) function are unclear. Forty patients with chronic, isolated, nonrheumatic MR with no coronary artery disease underwent exercise echocardiography with continuous expired gas analysis. Cardiac output and regurgitant stroke volume were measured at rest and immediately after exercise by pulsed-wave Doppler echocardiography. For controls, 17 healthy volunteers without MR were also studied. Patients achieved a significantly lower VO2max compared with controls (25.6 +/- 7.7 vs 31.7 +/- 7.7 ml/kg/min, p = 0.008). VO2max showed better correlations with exercise cardiac output than with cardiac output at rest in both patients and controls. Multiple linear regression identified exercise cardiac output (partial r = 0.65), patient age (partial r = -0.56), and gender as independent determinants of VO2max (multiple R = 0.85, p <0.001). Cardiac output at rest, LV ejection fraction, regurgitant stroke volume, and fraction were not significant determinants. With exercise, the regurgitant stroke volume increased in 13 patients and decreased in 27 patients. The former 13 patients had a significantly lower exercise cardiac output (7.4 +/- 2.5 vs 9.4 +/- 2.6 L/min, p = 0.026). Patients who stopped exercise due to dyspnea (n = 7) had a significantly lower exercise cardiac output and VO2max compared with those who stopped due to fatigue (n = 33), with no differences in resting or exercise regurgitant volume. Patients with an increase in LV end-systolic volume with exercise (n = 8) also had a significantly lower exercise cardiac output (6.9 +/- 1.9 vs 9.2 +/- 2.7 L/min, p = 0.037) and showed a trend toward a lower VO2max (21 +/- 7.5 vs 26 +/- 6.4 ml/kg/min, p = 0.07). In patients with chronic MR, exercise cardiac output is the major determinant of VO2max. Regurgitant volume and fraction are not related to functional capacity. Limitations in functional capacity in these patients may be more related to a diminished cardiac reserve than to a large regurgitant volume.

Expression of IL-12 and IL-13 mRNA in asthma and their modulation in response to steroid therapy

Interleukin-12 (IL-12) and IL-13 are two recently characterized cytokines which play an important role in the induction of T helper cell type 1 (Th1-) and Th2-like cells, respectively. Using the technique of in situ hybridization, we have investigated the expression of these cytokines in bronchial biopsies from nine allergic asthmatics and nine normal control subjects. To determine the effect of steroid therapy on the expression of IL-12 and IL-13 in asthma, the numbers of cells expressing these cytokine mRNA before and after a 1-wk course of oral prednisone in six steroid-sensitive (SS) and five steroid-resistant (SR) moderately severe asthmatics were also examined. There was an increased number of IL-13, and a decreased number of IL-12 mRNA positive cells in asthmatic subjects compared with normal control subjects (p < 0.001). After steroid treatment, the increase in FEV1 values observed in SS asthmatics was accompanied by a significant decrease in cells expressing IL-13 mRNA (p < 0.05) and an increase in the numbers of cells expressing IL-12 mRNA (p < 0.05). In contrast, steroid therapy in SR asthmatics was not associated with significant changes in IL-12 and IL-13 mRNA expression. Thus, allergic asthma is associated with a downregulation of IL-12 mRNA expression and an upregulation of IL-13 mRNA expression. These results suggest an in vivo role for IL-12 and IL-13 in modulating allergic responses and support the notion that the clinical effects of glucocorticoids are at least partially mediated through the modulation of cytokine production.

Thromboembolic risks of left atrial thrombus detected by transesophageal echocardiogram

Patients with left atrial thrombus are considered at high risk for thromboembolic events. The actual prognosis of these patients and the features most predictive of future events are unclear. We performed transesophageal echocardiograms in 2,894 patients over a 6 1/2-year period; 94 (age 69 +/- 11 years, 59 men, 83 in atrial fibrillation) were found to have left atrial thrombus. The thrombi were considered mobile in 45 patients and 33 patients had thrombus with a maximum dimension > or = 1.5 cm. Seven of the 94 patients with prosthetic valves were excluded from follow-up analysis. Over a follow-up period of 25.3 +/- 19.2 months, 17 patients had suffered a stroke or embolic event (event rate 10.4% per year) and 27 had died (mortality 15.8% per year). Cox proportional hazard regression analysis identified a maximum thrombus dimension > or = 1.5 cm (RR 19, p = 0.002), history of thromboembolism (RR 4.2, p = 0.038), and mobile thrombus (RR 5.3, p = 0.02) as predictors of subsequent thromboembolism. Moderate or severe left ventricular dysfunction was the only significant predictor of death (RR 2.9, p = 0.04). Gender, age, warfarin therapy at follow-up, atrial fibrillation, location (cavity vs appendage) of thrombus, and spontaneous echocardiographic contrast were not significant. Aggressive antithrombotic therapy may be indicated in these high-risk patients.

Cardioversion guided by transesophageal echocardiography: the ACUTE Pilot Study. A randomized, controlled trial. Assessment of Cardioversion Using Transesophageal Echocardiography

BACKGROUND

Electrical cardioversion in patients with atrial fibrillation is associated with an increased risk for embolic stroke. Screening for atrial thrombi with transesophageal echocardiography (TEE) before cardioversion should, in many patients, safely permit cardioversion to be done earlier than would be possible with prolonged conventional, anticoagulation therapy.

OBJECTIVE

To compare the feasibility and safety of TEE-guided early cardioversion with those of conventional management of cardioversion in patients with atrial fibrillation.

DESIGN

Randomized, multicenter clinical trial.

SETTING

10 hospitals in the United States, Europe, and Australia.

PATIENTS

126 patients who had atrial fibrillation lasting longer than 2 days and were having electrical cardioversion.

INTERVENTION

Conventional therapy or early, TEE-guided cardioversion with short-term anticoagulation therapy.

OUTCOME MEASURES

Feasibility outcome variables were frequency of cardioversion and times to cardioversion and sinus rhythm. Safety outcomes were ischemic stroke, transient ischemic attack, systemic embolization, bleeding, and detected episodes of clinical hemodynamic instability occurring as long as 4 weeks after cardioversion.

RESULTS

62 patients were randomly assigned to receive TEE-guided cardioversion; TEE was done in 56 (90%) of these patients. Atrial thrombi were detected in 7 patients (13%) and led to the postponement of cardioversion. Cardioversion was successful in 38 of 45 patients (84%) who had early cardioversion. No embolization occurred with this strategy. Of the 64 patients receiving conventional therapy, 37 (58%) had cardioversion, which was successful in 28 patients (76%). One patient had a peripheral embolic event. The time to cardioversion was shorter in the TEE group (0.6 weeks [95% CI, 0.3 to 0.9 weeks] compared with 4.8 weeks [CI, 3.8 to 5.7 weeks]; P < 0.01). The incidence of clinical hemodynamic instability and bleeding complications tended to be greater in the conventional therapy group.

CONCLUSIONS

These results suggest that TEE-guided cardioversion with short-term anticoagulation therapy is feasible and safe. The use of TEE may allow cardioversion to be done earlier, may decrease the risk for embolism associated with cardioversion, and may be associated with less clinical instability than conventional therapy. A large, multicenter study to confirm these findings is currently under way.

New insights into the pathogenesis and management of steroid-resistant asthma

A population of difficult-to-control asthmatics exists who, despite high-dose daily GC therapy, continue to display evidence for active disease. This group has been termed steroid resistant since they fail to adequately respond to aggressive courses of high-dose oral and inhaled GC therapy. Persistent immune activation and airway inflammation which to varying degrees is resistant to GC therapy appears to define the immunological abnormality underlying SR asthma. Recent studies utilizing molecular biological techniques have identified both ligand- and DNA-binding defects that could possibly account for steroid resistance at a molecular level. The evaluation of the SR asthmatic must be comprehensive in its scope as several confounding factors can contribute to this symptom complex. Among others, these include poor compliance, improper medication technique, inadequate anti-inflammatory therapy, unrecognized contributing diseases, incorrect diagnoses, environmental factors, and psychosocial disturbances. The management of the SR asthmatic is challenging, and every attempt should be made to maximize conventional therapy in these patients prior to embarking on alternative therapies as all of the alternative anti-inflammatory/immunomodulatory modalities are associated with significant toxicity or cost. Second-generation inhaled GC therapy, methotrexate, cyclosporine, IVIG, and leukotriene antagonists are potential alternative therapies, and although they remain viable options, they have been used in small numbers, and for short periods of time, and fail to result in long-term remissions. Although much insight into the pathogenesis of SR asthma has been gained, several issues remain unresolved. Ongoing airway inflammation is thought to contribute to steroid resistance, but at present, we have no standard method of determining the degree of inflammation. The incorporation of bronchoscopy with transbronchial biopsy has the potential to provide the greatest amount of information regarding the presence or absence of ongoing airway inflammation, but the invasive nature of the procedure precludes its use in pediatric patients and the most severe adult asthmatics. Large multicenter, placebo-controlled studies evaluating the available alternative therapies that incorporate markers of airway inflammation are needed, as are studies that evaluate these therapies over longer periods of time. It is hoped that by better understanding the mechanisms involved and the natural history of the SR asthmatic, specific treatment modalities will be developed for this challenging group of severe asthmatics.

Allergen exposure decreases glucocorticoid receptor binding affinity and steroid responsiveness in atopic asthmatics

Allergen exposure can confound the management of asthma. To understand the potential mechanisms by which allergens increase the steroid requirements in atopic asthmatics, we examined the effects of allergens on glucocorticoid receptor (GCR) binding affinity and glucocorticoid (GC) responsiveness of peripheral blood mononuclear cells (PBMC) from atopic asthmatics. A significant reduction (p < 0.001) in the GCR binding affinity (Kd) was observed in ragweed-allergic asthmatics during ragweed pollen season compared with PBMC obtained before and after ragweed season. In vitro effects of allergen on PBMC GCR Kd were also examined by incubating PBMC from atopic asthmatics with allergen (ragweed and cat) versus Candida albicans. GCR binding affinity was significantly reduced after incubation with ragweed (p < 0.001) or cat allergen (p < 0.001) compared with baseline or C. albicans stimulation. This effect was limited to atopic asthmatics in that in vitro cat allergen incubation for 48 h failed to significantly alter GCR binding affinity in nonasthmatic, atopic individuals. These allergen-induced reductions in GCR binding affinity also rendered the PBMC less sensitive to the inhibitory effects of hydrocortisone and dexamethasone on allergen-induced proliferation (p < 0.01). To test the hypothesis that allergen-induced alterations in GCR binding affinity were cytokine-induced, we examined the effects of interleukin-2 (IL-2)and IL-4 neutralization using anticytokine antibodies. Addition of both anti-lL-2 and anti-lL-4 antibodies resulted in a significant (p < 0.001) inhibition of allergen-induced alterations in GCR binding affinity. Furthermore incubation with cat allergen induced significantly higher concentrations of IL-2 (p = 0.03) and IL-4 (p = 0.02) by PBMC from atopic as compared with nonatopic subjects. Our current observations suggest that allergen exposure may contribute to poor asthma control by reducing GCR binding affinity in mononuclear cells. This appears to be mediated through IL-2 and IL-4. These findings may have important implications for novel approaches to the treatment of poorly controlled asthma.

Atopic dermatitis: immunobiology and treatment with immune modulators

Atopic dermatitis (AD), a chronic inflammatory skin disease, is frequently seen in patients with a personal or family history of asthma and allergic rhinitis. Population studies suggest an increasing prevalence of AD in children since World War II, with 10-15% of the population being affected by AD at some time during childhood. In patients with moderate to severe AD, involvement can be life-long, causing significant interference with school, work and social interactions. The term atopic dermatitis was introduced to reflect the close association between AD and respiratory allergy. During the past decade, extraordinary progress has been made in our understanding of the immunopathogenesis of allergic diseases. In particular, this constellation of inherited illnesses has now been demonstrated to be associated with activation of a specific group of cytokine genes encompassing IL-3, IL-4, IL-5, IL-13 and granulocyte-macrophage colony-stimulating factor (GM-CSF). The molecular basis for selective activation of this cytokine gene cluster and the immunological consequences are now being pursued actively by many laboratories. However, it is clear that allergic diseases result from a polygenic inheritance pattern which involves not only cytokine gene activation but also activation of other less well defined gene products. Furthermore, the clinical expression of allergic diseases is highly dependent on a complex interaction between the host and its environment, e.g. allergen exposure. The genetic predisposition to develop allergic responses may be similar in patients with AD and other allergic diseases, such as asthma. However, targeting of the allergic immune response may relate to the organ in which allergen sensitization first occurs; the capacity of immune effector cells, e.g. T lymphocytes, to home preferentially to the skin versus the respiratory mucosa; and the programmed response of resident cells, e.g. epithelial cells, to injury and inflammation. This review examines the cellular and immunological mechanisms that are thought to play an important role in the pathogenesis of chronic AD. An understanding of the immunological basis of AD is likely to have important clinical implications in our approach to the management of this common illness, and the development of immunomodulators for its treatment.

Effects of glucocorticoids on lymphocyte activation in patients with steroid-sensitive and steroid-resistant asthma

BACKGROUND

Glucocorticoids are important medications used to control the airway inflammation associated with asthma. Synthetic glucocorticoids vary in their binding affinity for the glucocorticoid receptor (GCR).

METHODS

We compared hydrocortisone, beclomethasone dipropionate, triamcinolone acetonide, flunisolide, and budesonide with regard to their capacity to inhibit phytohemagglutinin-induced peripheral blood mononuclear cell proliferation from six patients with steroid-sensitive asthma and seven patients with steroid-resistant asthma. Peripheral blood mononuclear cell GCR binding affinities for dexamethasone and budesonide were also determined for both patient groups by using a radioligand binding assay and Scatchard analysis.

RESULTS

Dose-dependent inhibition was demonstrated for all glucocorticoids in both patient groups, with the steroid-resistant group requiring approximately 2 log-fold more glucocorticoids for an equivalent degree of inhibition. The mean concentrations necessary to cause 50% inhibition of lymphocyte proliferation (IC50s) for the steroid-sensitive group ranged from 2 x 10(-10) mol/L for budesonide to 7 x 10(-8) mol/L for hydrocortisone, whereas the mean IC50s for the steroid-resistant group ranged from approximately 2 x 10(-8) mol/L for budesonide to greater than 10(-6) mol/L for hydrocortisone. In addition, a significant correlation was noted between the degree of inhibition of lymphocyte proliferation (IC50) and the binding affinity of dexamethasone to the GCR. Patients with steroid-resistant asthma have been shown to have a reduced GCR binding affinity. The GCR binding affinity for budesonide was significantly higher in both groups (i.e., lower dissociation constant) than that obtained for dexamethasone.

CONCLUSION

These data suggest that glucocorticoids such as budesonide, by virtue of their high GCR binding affinities and greater ability to suppress lymphocyte proliferation, may therefore be beneficial in the management of difficult-to-control asthma.

Left ventricular function after valve repair for chronic mitral regurgitation: predictive value of preoperative assessment of contractile reserve by exercise echocardiography

OBJECTIVES

We evaluated the value of preoperative assessment of left ventricular contractile reserve in predicting ventricular function after valve repair for minimally symptomatic mitral regurgitation.

BACKGROUND

The optimal timing for operation in minimally symptomatic patients with significant mitral regurgitation is controversial. Accurate preoperative assessment of left ventricular function is difficult, and the ability to predict postoperative function is limited. Previous studies in patients undergoing mitral valve replacement may not be applicable in the present era of valve repair.

METHODS

We performed exercise echocardiography in 139 patients with isolated mitral regurgitation and no coronary disease, 74 of whom subsequently underwent uncomplicated valve repair. We measured rest left ventricular end-systolic dimension, end-systolic wall stress and positive first derivative of left ventricular pressure (dP/dt). End-diastolic and end-systolic volumes and ejection fraction were measured preoperatively at rest, immediately after exercise and postoperatively.

RESULTS

Ejection fraction decreased postoperatively to 55 +/- 10% from a rest preoperative value of 64 +/- 9% (p < 0.001). Compared with patients with a postoperative ejection fraction > or = (n = 56), patients with postoperative ejection fraction < 50% (n = 18) had a significantly lower preoperative exercise ejection fraction (57 +/- 11% vs. 73 +/- 9%, p < 0.0005), a larger exercise end-systolic volume index (32 +/- 8 vs. 18 +/- 7 cm3/m2, p < 0.0005) and a lower change in ejection fraction with exercise (-4 +/- 8% vs. 9 +/- 10%, p < 0.005). Preoperative rest indexes, including dP/dt, end-systolic wall stress and end-systolic volume index were less predictive, whereas exercise capacity, rest ejection fraction and end-systolic dimension were not predictive of post-repair ejection fraction. An exercise end-systolic volume index > 25 cm3/m2 was the best predictor of postoperative dysfunction, with a sensitivity and specificity of 83%.

CONCLUSIONS

In minimally symptomatic patients with mitral regurgitation, latent ventricular dysfunction may be indicated by a limited contractile reserve, manifest at exercise as an inadequate increase in ejection fraction and a larger end-systolic volume. These variables may also be used to predict left ventricular function after repair.

The potential role of gastroesophageal reflux in the pathogenesis of food-induced wheezing

Severe reactive airways disease (RAD) in children is frequently associated with gastroesophageal reflux or food allergy. However a relationship between these two confounding factors has yet to be investigated. We postulate that, in certain patients with micro-aspiration of gastric contents into the airways, food allergens sensitize T cells in the peribronchial lymphoid tissue and induce the production of food-specific IgE antibodies that sensitize airway cells. Subsequent exposure to these food allergens might then induce IgE dependent mediator release from mast cells as well as T cell and eosinophil activation, thus contributing to airway inflammation and RAD. In the current report, we describe the case of a patient with severe asthma who had food allergy and gastroesophageal reflux whose clinical findings support this hypothesis. We also provide additional evidence for a high rate of food sensitization in patients with bronchopulmonary dysplasia (BPD), RAD and GER. We conclude that additional studies are warranted to examine the possibility that patients who have RAD and GER require an evaluation for food allergy.

The role of glucocorticoids in the management of asthma

Glucocorticoids (GCs) are a highly effective class of medication used in the treatment of airway inflammation associated with chronic asthma. Nevertheless, there remain concerns regarding potential adverse effects accompanying the use of systemic and high-dose inhaled GC therapy. Recent studies also suggest that there is high variability in airway response to GCs. Indeed, the immunopathogenesis of a subset of asthmatics poorly responsive to glucocorticoid therapy have been studied and may provide new insights into mechanisms by which glucocorticoids act in chronic asthma. The current review will examine a number of these issues, particularly mechanisms by which GCs act in asthma, the immunology of steroid resistance, and adverse effects associated with GC treatment.

Steroid-resistant asthma: evaluation and management

LEARNING OBJECTIVES

Reading this article will reinforce the reader's knowledge of the definition, pathophysiology, differential diagnosis, and treatment of the steroid-resistant asthmatic patient.

DATA SOURCES

Prospective and retrospective data from the authors' experience were evaluated. In addition, a Medline database was searched from 1981, using the key words "asthma," "glucocorticoids," and "glucocorticoid resistance" with the restrictions of English language and human subjects. Relevant articles referenced in retrieved sources and current texts on severe asthma were also utilized.

STUDY SELECTION

Data source abstracts, pertinent articles, and book chapters meeting the objectives were critically reviewed.

RESULTS

Although rare, individuals with steroid-resistant asthma are often the most difficult-to-manage asthmatic patients in that they have severe disease yet fail to respond to glucocorticoids. To make the diagnosis of steroid-resistant asthma, the patient must fail to respond to a 7 to 14-day course of daily prednisone as measured by less than a 15% improvement in morning prebronchodilator FEV1 following the glucocorticoid course. Ongoing inflammation is thought to play a major role in the pathogenesis of steroid-resistant asthma, and recent studies have demonstrated diminished glucocorticoid receptor to glucocorticoid, or diminished glucocorticoid receptor to DNA binding as possible mechanisms for diminished glucocorticoid responsiveness. Alternative asthma therapies such as methotrexate, cyclosporine, and intravenous gammaglobulin are often used in this group of asthmatic patients.

CONCLUSIONS

The patient with steroid-resistant asthma presents several challenges. These individuals often display many of the sequelae of long-term systemic glucocorticoid use while achieving little therapeutic benefit. Prior to making the diagnosis of steroid-resistant asthma, diseases that can contribute to poor control of asthma must be ruled out, and noncompliance issues addressed. Alternative asthma therapies are often used; however, they also carry the potential for adverse effects, and have not been thoroughly studied in this population of asthmatic patients.

Staphylococcal toxins and protein A differentially induce cytotoxicity and release of tumor necrosis factor-alpha from human keratinocytes

It has been proposed that toxins and other bacterial protein products of Staphylococcus aureus can act as triggers or persistence factors in several inflammatory skin diseases. In this study, we examined the S. aureus isolates from the skin of patients with atopic dermatitis and psoriasis. We found that the bacterial isolates from these patients exhibited either characteristic superantigenic toxins or thermolabile toxins believed to be staphylococcal alpha-toxin. All of these staphylococcal strains also secreted extracellular staphylococcal protein A. We found significant differences in the action of these toxins on human keratinocytes and keratinocyte cell lines. The superantigenic toxins toxic shock syndrome toxin-1, staphylococcal enterotoxins A and B, and exfoliative toxin-A, as well as staphylococcal protein A, did not induce significant cytotoxic damage in the keratinocyte cell line HaCaT, whereas the staphylococcal alpha-toxin produced profound cytotoxicity. Keratinocyte cytotoxicity induced by staphylococcal alpha-toxin was time and concentration dependent and demonstrated the morphologic and functional characteristics of necrosis, not apoptosis. Addition of alpha-toxin to keratinocytes simultaneously induced cell lysis and tumor necrosis factor-alpha release into the medium within 30 min; apparently, it was constitutive tumor necrosis factor-alpha. On the other hand, superantigenic toxins and, in particular, protein A showed stimulation of tumor necrosis factor-alpha secretion in keratinocytes and release of this cytokine after 6-12 h of incubation. Thus, staphylococcal protein A, alpha-toxin, and superantigenic toxins found in S. aureus isolates from patients with psoriasis and atopic dermatitis can produce direct pro-inflammatory effects on keratinocytes through the release of tumor necrosis factor-alpha. We propose that these effects may be relevant to the induction and persistence of lesions in these two diseases.

Eosinophil infiltration in nonallergic chronic hyperplastic sinusitis with nasal polyposis (CHS/NP) is associated with endothelial VCAM-1 upregulation and expression of TNF-alpha

We studied potential mechanisms of eosinophil accumulation in nonallergic chronic hyperplastic sinusitis with nasal polyposis (CHS/NP). We measured expression of endothelial vascular cell adhesion molecule-1 (VCAM-1), which mediates selective eosinophil transendothelial migration, the cytokines interleukin (IL)-1 beta, TNF-alpha and IL-13 which upregulate VCAM-1 expression, and the chemokine RANTES which mediates lymphocyte, monocyte, and eosinophil chemotaxis in chronic hyperplastic sinusitis with nasal polyposis (CHS/NP) nasal polyps (nonallergic versus allergic) and middle turbinate biopsies from normal controls. By immunohistochemical staining, the density of EG2+ eosinophils was increased in both the nonallergic and allergic CHS/NP subgroups compared to normal controls. VCAM-1 expression was significantly increased in CHS/NP subjects compared to normal controls (P = 0.0005), with the highest intensity seen in nonallergic CHS/NP. By in situ hybridization, the densities of IL-1 beta, TNF-alpha, IL-13, and RANTES mRNA+ cells were all increased in nonallergic CHS/NP compared to normal controls (P = 0.009, 0.0005, 0.0005, and 0.001, respectively). In comparison to allergic CHS/NP, nonallergic CHS/NP had a significantly higher tissue density of TNF-alpha (P = 0.04) and a lower density of IL-13 (P = 0.005) mRNA+ cells. In general, VCAM-1 expression correlated strongly in CHS/NP with the density of TNF-alpha (R = .91, P = 0.0005) but not the density of IL-1 beta, IL-13, or RANTES mRNA+ cells. We conclude that upregulation of VCAM-1 and elaboration of RANTES may contribute to the marked accumulation of eosinophils in nonallergic CHS/NP. TNF-alpha may play a critical role in VCAM-1 upregulation in this nonallergic eosinophilic disorder.

A novel action of IL-13: induction of diminished monocyte glucocorticoid receptor-binding affinity

We have recently demonstrated that the combination of IL-2 and IL-4 blunts T cell responses to glucocorticoids in steroid resistant (SR) asthma by reducing glucocorticoid receptor (GCR)-binding affinity. Since immune activation appears to be involved in the acquisition of steroid resistance, we sought to identify whether other cytokines could also induce diminished GCR-binding affinity. In the current report, utilizing a [3H]dexamethasone radioligand-binding assay and Scatchard analysis, we found that IL-13, a cytokine with similar actions as IL-4, could induce diminished GCR binding-affinity (GCR Kd = 34.4 +/- 2.3 nM with IL-13 vs Kd = 8.8 +/- 0.7 nM for unstimulated control cells; p < 0.001) in PBMC from normal subjects. In contrast, PBMC incubated with IL-1, IL-3, IL-5, IL-7, IL-8, IL-12, or granulocyte-macrophage-CSF had no effect on GCR-binding affinity; and no additive effect to the decreased GCR-binding affinity was noted when IL-13 was cocultured with IL-2 or IL-4. The cell target of IL-13-induced GCR effects was studied and found to reside in the non-T cell population; specifically, the monocyte fraction. To determine the functional significance of the decreased GCR-binding affinity, monocytes were pretreated with and without IL-1 3 prior to stimulation with LPS and hydrocortisone. IL-13 pretreatment of monocytes significantly diminished (p = 0.005) the suppressive effects of hydrocortisone on LPS-induced IL-6 production. IL-13, by virtue of its ability to induce diminished GCR-binding affinity, may contribute to impaired GC responsiveness during inflammatory illnesses.

A novel action of IL-13: induction of diminished monocyte glucocorticoid receptor-binding affinity

We have recently demonstrated that the combination of IL-2 and IL-4 blunts T cell responses to glucocorticoids in steroid resistant (SR) asthma by reducing glucocorticoid receptor (GCR)-binding affinity. Since immune activation appears to be involved in the acquisition of steroid resistance, we sought to identify whether other cytokines could also induce diminished GCR-binding affinity. In the current report, utilizing a [3H]dexamethasone radioligand-binding assay and Scatchard analysis, we found that IL-13, a cytokine with similar actions as IL-4, could induce diminished GCR binding-affinity (GCR Kd = 34.4 +/- 2.3 nM with IL-13 vs Kd = 8.8 +/- 0.7 nM for unstimulated control cells; p &lt; 0.001) in PBMC from normal subjects. In contrast, PBMC incubated with IL-1, IL-3, IL-5, IL-7, IL-8, IL-12, or granulocyte-macrophage-CSF had no effect on GCR-binding affinity; and no additive effect to the decreased GCR-binding affinity was noted when IL-13 was cocultured with IL-2 or IL-4. The cell target of IL-13-induced GCR effects was studied and found to reside in the non-T cell population; specifically, the monocyte fraction. To determine the functional significance of the decreased GCR-binding affinity, monocytes were pretreated with and without IL-1 3 prior to stimulation with LPS and hydrocortisone. IL-13 pretreatment of monocytes significantly diminished (p = 0.005) the suppressive effects of hydrocortisone on LPS-induced IL-6 production. IL-13, by virtue of its ability to induce diminished GCR-binding affinity, may contribute to impaired GC responsiveness during inflammatory illnesses.