The Proceedings of the American Thoracic Society 1:235-238 (2004)
© 2004 The American Thoracic Society
Nongenomic Actions of Glucocorticosteroids on the Airway Vasculature in Asthma
Adam Wanner,
Gabor Horvath,
Jorge L. Brieva,
Sunil D. Kumar and
Eliana S. Mendes
Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Miami, Miami, Florida
Correspondence and requests for reprints should be addressed to Adam Wanner, M.D., P.O. Box 016960(R-47), Miami, FL 33101. E-mail: awanner{at}miami.edu
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ABSTRACT
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Inhaled glucocorticosteroids (corticosteroids) continue to be the standard treatment for nonexacerbated asthma because of their anti-inflammatory actions. These include effects on the airway vasculature, which participates in the inflammatory process. Corticosteroids are now known to have genomic as well as nongenomic effects that involve different mechanisms of action. The genomic vascular effects of inhaled corticosteroids include a decrease in airway wall hypervascularity (inhibition of angiogenesis), reversal of the increased airway blood flow, and inhibition of vascular hyperpermeability and leukocyte recruitment. In addition, inhaled corticosteroids decrease airway blood flow acutely (within minutes) and reversibly through a nongenomic action that involves noradrenergic neurotransmission. This effect is likely related to the binding of inhaled corticosteroids to the plasma membrane of and the inhibition of the extraneuronal monoamine transporter on airway vascular smooth muscle cells, thereby increasing norepinephrine concentrations at 
1-adrenoceptors and causing airway vascular smooth muscle contraction and a decrease in airway blood flow. Inasmuch as vascular hyperperfusion is a manifestation of airway inflammation, the acute vasoconstriction could also be considered an anti-inflammatory effect of inhaled corticosteroids.
Key Words: angiogenesis • hyperperfusion • hyperpermeability • leukocyte recruitment • vasoconstriction
Glucocorticosteroids (corticosteroids) continue to have an important role in anti-inflammatory therapy. In airway inflammation, notably the inflammation associated with bronchial asthma, corticosteroids have been established as the prototypical agents with which to treat various elements of the inflammatory process in the airway wall (1). Among the features of inflammation, increased blood flow and congestion, edema, and infiltration of the extravascular tissue with bloodborne inflammatory cells can be attributed to vascular changes. Therefore, understanding the effects of corticosteroids on angiogenesis, blood perfusion, tissue edema, and leukocyte recruitment in the airway is of considerable physiologic and clinical importance.
The mechanisms of action of corticosteroids in the inflammatory process are complex, and the corticosteroid-sensitive pathways leading to the vascular manifestations of inflammation have not been completely clarified. Furthermore, corticosteroids have now been shown to have two fundamentally different vascular effects in the airway. The classic corticosteroid action, modification of the transcription of proinflammatory genes, typically requires hours to manifest itself physiologically and seems to be involved in most, if not all, of the vascular elements of inflammation. The other vascular effect is an acute nongenomic action that increases vasomotor tone, thereby reversing inflammation-associated tissue hyperperfusion.
This report focuses on the nongenomic vascular effects of corticosteroids by reviewing recent findings from the author's laboratory on the mechanisms underlying acute corticosteroid-induced vasoconstriction in the airway. This will not only introduce a heretofore unknown effect of corticosteroids in the airway, but will also highlight a new paradigm of catecholamine–corticosteroid interaction. For comparison, the classic genomic effects of corticosteroids on the vascular manifestations of airway inflammation are first summarized.
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GENOMIC VASCULAR CORTICOSTEROID EFFECTS IN AIRWAY INFLAMMATION
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The effects of corticosteroids on the vascular manifestations of airway inflammation involve corticosteroid binding to cytosolic glucocorticoid receptors, translocation of nuclear transcription factors, gene transcription, posttranscriptional mRNA regulation, and protein synthesis. So, the onset of action typically is delayed by hours (Table 1). This mechanism has been extensively studied and reported, with data that have been obtained in animal models and patients with airway disease, especially asthma. Those data reveal that inflammatory angiogenesis, vascular hyperperfusion, vascular hyperpermeability, and leukocyte recruitment are all influenced by corticosteroids (Table 2). The effects include: reversal of airway wall hypervascularity (presumably by modification of angiogenetic factors); a decrease in the asthma-associated hyperperfusion of the airway (presumably by inhibition of inflammatory new vessel formation and vasodilation); reduction in inflammatory microvascular hyperpermeability (presumably by tightening of the endothelial barrier in postcapillary venules); and a decreased influx and activation of inflammatory cells, especially eosinophils, into the airway tissue (presumably by interference with chemokine generation, receptor expression/function, and adhesion molecule expression) (2–6). These observations underscore the notion that corticosteroids are effective anti-inflammatory molecules, in part because they target a wide range of signaling in a process characterized by redundant proinflammatory pathways.
Generally, the collective genomic vascular actions of corticosteroids are assumed to be of therapeutic value in inflammatory airway diseases. The reduction in airway vascularity and vascular congestion might decrease airflow obstruction, especially in the lung periphery, as suggested by animal experiments (7); this has not been experimentally tested in humans. Vascular hyperpermeability leading to tissue edema, on the other hand, is a well recognized mechanism of airway obstruction. The effects of corticosteroids on the recruitment of eosinophils, selected lymphocyte populations, monocytes, and mast cells must be a reflection of their anti-inflammatory actions and, as such, are probably desired outcomes in patients with asthma.
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NONGENOMIC VASCULAR CORTICOSTEROID EFFECTS IN AIRWAY INFLAMMATION
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It is becoming increasingly clear that corticosteroids have biological effects that do not involve gene transcription (8). We have found that inhaled corticosteroids cause acute vasoconstriction in human airways (9, 10); therefore, we have focused our attention on the mechanisms underlying the regulation of human airway vascular smooth muscle tone by corticosteroids. Vasodilation is part of the inflammatory process, and vasoconstriction could be considered an anti-inflammatory corticosteroid action. To date, the experiments have shown that corticosteroids cause acute vasoconstriction by potentiating noradrenergic neurotransmission in the airway vasculature. The effect is transient and has a rapid onset, and the corticosteroid-sensitive extraneuronal monoamine transporter, which is expressed by airway vascular smooth muscle, plays a critical role, probably by regulating norepinephrine concentrations at 1-adrenoceptor sites on airway vascular smooth muscle. The corticosteroid effect is plasma membrane–associated and does not involve the classic cytosolic glucocorticoid receptor. Gene transcription and protein synthesis are not required for this corticosteroid effect. These conclusions are based on a series of in vivo studies conducted in healthy subjects and in subjects with asthma, and on in vitro studies using airway vascular smooth muscle obtained from donor lungs found unsuitable for transplantation (provided by the University of Miami Life Alliance Organ Recovery Agency). The hypothetical basis for the experiments is depicted in Figure 1 and the supporting data are summarized below.
1-Receptor–Mediated Effect of Inhaled Corticosteroids on Airway Blood Flow
As illustrated in Figure 1, corticosteroids have been shown to block uptake2, thereby interfering with the disposal of norepinephrine at 1-receptors on airway vascular smooth muscle. We therefore investigated whether a corticosteroid, fluticasone proprionate, leads to airway vascular smooth muscle contraction, as reflected by a decrease in airway blood flow (
aw).
First, we measured aw before and serially after inhalations of fluticasone propionate (88–1,760 µg) by healthy nonsmokers and corticosteroid-naive patients with mild asthma (9). Fluticasone propionate caused a dose-dependent decrease in aw in both groups; baseline aw was higher; and the absolute and relative decrease after corticosteroid administration was greater in the patients with asthma (Figure 2). Time-course experiments with 880 µg fluticasone proprionate showed a nadir in aw between 30 and 60 minutes and a return to or toward baseline by 90 minutes (9, 10).
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Figure 2. Effect of 880 µg fluticasone proprionate on airway mucosal blood flow (aw) in 10 healthy (normal) subjects and 10 corticosteroid-naive subjects with mild asthma during a 90-minute period. Mean (SE). BSL indicates baseline. Note higher baseline and greater vasoconstrictive response in subjects with asthma. Reprinted by permission from Reference 9.
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Because the main local nervous control of airway vascular smooth muscle tone is provided by the sympathetic nervous system, we examined the effect of 1-receptor blockade on corticosteroid-induced vasoconstriction. Pretreatment with systemic terazosin had no effect on baseline aw but totally prevented the post–fluticasone propionate decrease in aw, which suggested that noradrenergic neurotransmission was involved in the acute vascular effect of fluticasone propionate. This notion was further supported by the finding that a subthreshold dose of fluticasone propionate potentiated the vasoconstrictor effect of inhaled methoxamine, an 1-adrenergic agonist that we have previously shown to decrease aw in a dose-dependent fashion in healthy subjects and subjects with asthma (11). To confirm that the vasoconstrictor effect was not specific for fluticasone propionate, we tested two additional inhaled corticosteroids and found them to also decrease aw (10) (Figure 3). Collectively, these observations strongly suggest that corticosteroids cause vasoconstriction by a mechanism that includes the activation of 1-receptors.
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Figure 3. Comparative vasoconstrictive efficacy of three inhaled corticosteroids in 10 corticosteroid-naive subjects with asthma. Mean (SE). *p < 0.05 versus respective baseline. Noncumulative dose–response curves. Note greater vasoconstrictor efficacy of budesonide and fluticasone than beclomethasone. Reprinted by permission from Reference 10.
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Norepinephrine Uptake by Airway Vascular Smooth Muscle Cells
After release from sympathetic nerves, norepinephrine must be taken up by postsynaptic cells for inactivation by intracellular enzymes, notably monoamino oxidase and catecholamine-O-methyltransferase. Because uptake2 of norepinephrine is corticosteroid sensitive, corticosteroids could increase norepinephrine concentrations near 1-receptors on airway vascular smooth muscle, causing vasoconstriction. We therefore determined norepinephrine uptake into freshly dissociated human airway vascular smooth muscle cells using a fluorimetric technique (12). This revealed that norepinephrine uptake was time-dependent (within minutes) and concentration-dependent. Corticosterone and O-methyl-isoprenaline (an uptake2 inhibitor), but not desipramine (an uptake1 inhibitor), interfered with norepinephrine uptake. The effect of corticosterone was reversible and not sensitive to a glucocorticoid receptor antagonist, a transcription inhibitor, or a protein synthesis inhibitor. Corticosterone that was made membrane-impermeant by coupling to bovine serum albumin (BSA) also blocked norepinephrine uptake. These results are consistent with the idea that corticosteroids inhibit norepinephrine uptake into postsynaptic cells through a plasma membrane effect that is seen within minutes, is reversible, and does not involve classic corticosteroid receptors, transcription, or protein synthesis, i.e., a genomic mode of action.
Role of the Extraneuronal Monoamine Transporter
Because the uptake2 experiments showed that norepinephrine uptake into airway vascular smooth muscle cells is a regulated process, we evaluated mRNA expression of different norepinephrine transporters in human airway vascular smooth muscle (13). Reverse transcriptase/polymerase chain reaction analysis demonstrated mRNA expression of the organic cation transporter extraneuronal monamine transporter (EMT) (OCT-3) and, to a lesser extent, OCT-1. It has been reported that EMT function is corticosteroid-sensitive (14), so we hypothesized that corticosteroids inhibit norepinephrine uptake into airway vascular smooth muscle cells by interfering with the transport function of EMT. Although we have thus far not demonstrated EMT protein expression in airway vascular smooth muscle, the above-mentioned pharmacologic inhibition profile was typical for EMT, thereby supporting its involvement in norepinephrine uptake.
Methoxamine-induced vasoconstriction is enhanced in the airways of patients with asthma (11). One possible mechanism for this observation is decreased norepinephrine uptake by postsynaptic cells. Although this has not been tested in humans, we have found that in rabbits, systemic ovalbumin sensitization downregulates the expression of EMT mRNA in the aorta and decreases norepinephrine uptake by freshly dissociated rabbit aortic smooth muscle cells (14). A similar phenomenon could exist in patients with asthma and lead to 1-adrenergic hyperresponsiveness of the airway vascular smooth muscle.
Interestingly, EMT and OCT-1 are also expressed by cultured airway epithelial cells, suggesting that steroid-sensitive organic cation transport could play a physiologic role in airway cells other than airway vascular smooth muscle cells.
The mechanism whereby corticosteroids inhibit EMT is unknown. Having shown that the corticosteroid effect is also observed with impermeant corticosteroid, we expected to find that corticosteroids can bind to an as yet unidentified plasma membrane receptor. We therefore used immunohistochemistry as a first approach, with a BSA-coupled corticosterone and an antibody to BSA to show that there is a specific membrane binding site for the corticosteroid (Figure 4) (12). It can only be speculated how the plasma membrane–bound corticosteroid might interfere with EMT function and exert its nongenomic effect. Regulation of ion channels, signaling through G proteins, direct binding to the EMT, or changing plasma membrane fluidity are all possibilities that deserve to be explored. For example, it has been reported that estradiol binds to and acutely activates maxi-K channels (15), and this could involve second messenger systems that regulate EMT function (16).
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Figure 4. Immunochemical demonstration of a specific plasma membrane binding site for corticosterone in human bronchial arterial smooth muscle cells. Cells were incubated with bovine serum albumin (BSA) (A and B), corticosterone-BSA (C and D), or corticosterone-BSA with excess corticosterone (E and F). Immunochemistry used a rabbit anti-BSA primary antibody and a goat anti-rabbit IgG secondary antibody labeled with tetramethyl rhodamine isothiocyanate (TRITC). A, C, and E: differential interference contrast microscopy; B, D, and F: fluorescence (TRITC) microscopy. Reprinted by permission from Reference 12.
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CONCLUSIONS
This review of the genomic and nongenomic vascular effects of corticosteroid and their role in airway inflammation suggests that angiogenesis, vascular hyperperfusion and hyperpermeability, and leukocyte recruitment are all altered through genomic corticosteroid actions in ways that can be assumed to be anti-inflammatory. The recently demonstrated nongenomic acute vascular action of corticosteroid, thus far explored in airway vascular smooth muscle, opens new avenues for therapeutic interventions with corticosteroids. Furthermore, the corticosteroid–noradrenergic neurotransmission interaction introduces another paradigm of catecholamine–corticosteroid interplay that could be extended to other airway cells and organic cations, including ß-agonists.
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ACKNOWLEDGMENTS
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A.W. received an academic research grant in 2002 from GSK in the amount of $49,000; G.H. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript; J.L.B. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript; S.D.K. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript; E.S.M. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript.
(Received in original form February 18, 2004; accepted in final form April 6, 2004)
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REFERENCES
|
|---|
- Djukanovic R, Wilson JW, Britten KM, Wilson SJ, Walls AF, Roche WR, Howarth PH, Holgate ST. Effect of an inhaled corticosteroid on airway inflammation and symptoms in asthma. Am Rev Respir Dis 1992;145:669–674.[Medline]
- Chetta A, Zanini A, Foresi A, DelDonno M, Castagnaro A, DiIppolito R, Baraldo S, Testi R, Saetta M, Oliveri D. Vascular component of airway remodeling in asthma is reduced by high dose fluticasone. Am J Respir Crit Care Med 2003;167:751–757.[Abstract/Free Full Text]
- Brieva JL, Danta I, Wanner A. Effect of an inhaled glucocorticosteroid on airway mucosal blood flow in subjects with mild asthma. Am J Respir Crit Care Med 2000;161:293–296.[Abstract/Free Full Text]
- Persson CG. The action of beta-receptors on microvascular endothelium or: is airway plasma exudation inhibited by beta-agonists? Life Sci 1993;52:2111–2121.[CrossRef][Medline]
- Fornhem C, Peterso CG, Dahlback M, Scheynius A, Alving K. Granulocyte function in the airways of antigen-challenged pigs: effects of inhaled and systemic budesonide. Clin Exp Allergy 1996;26:1436–1448.[Medline]
- Blease K, Lukacs NW, Hogaboam CM, Kunkel SL. Chemokines and their role in airway hyperreactivity. Respir Res 2000;1:54–61.[CrossRef][Medline]
- Csete ME, Abraham WM, Wanner A. Vasomotion influences airflow in peripheral airways. Am Rev Respir Dis 1990;141:1409–1413.[Medline]
- Losel R, Wehling M. Non-genomic actions of steroid hormones. Nat Rev Mol Cell Biol 2003;1:4–47.
- Kumar SD, Brieva JL, Danta I, Wanner A. Transient effect of inhaled fluticasone on airway mucosal blood flow in subjects with and without asthma. Am J Respir Crit Care Med 2000;161:918–921.[Abstract/Free Full Text]
- Mendes ES, Pereira A, Danta I, Duncan RC, Wanner A. Comparative bronchial vasoconstrictive efficacy of inhaled glucocorticosteroids. Eur Respir J 2003;21:989–993.[Abstract/Free Full Text]
- Brieva JL, Wanner A. Adrenergic airway vascular smooth muscle responsiveness in healthy and asthmatic subjects. J Appl Physiol 2001;90:665–669.[Abstract/Free Full Text]
- Horvath G, Sutto Z, Torbati A, Conner GE, Salathe M, Wanner A. Norepinephrine transported by the extraneuronal monoamine transporter in human bronchial arterial smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2003;10:1152–1158.
- Grundemann D, Schechinger B, Rappold GA, Schomig E. Molecular identification of the corticosterone-sensitive extraneuronal catecholamine transporter. Nat Neurosci 1998;1:349–351.[CrossRef][Medline]
- Horvath G, Torbati A, Conner GE, Salathe M, Wanner A. Systemic ovalbumin sensitization downregulates norepinephrine uptake by rabbit aortic smooth muscle cells. Am J Respir Cell Mol Biol 2002;27:746–751.[Abstract/Free Full Text]
- Valverde MA, Rojas P, Amigo J, Cosnelli D, Orio P, Bahamonde MI, Mann GE, Vergara C, Latorre R. Acute activation of maxi-K channels (hSlo) by estradiol binding to the ß-subunit. Science 1999;285:1929–1931.[Abstract/Free Full Text]
- Martel F, Keating E, Calhau C, Grundemann D, Schomig E, Azevedo I. Regulation of human extraneuronal monoamine transporter (hEMT) expressed in HEK293 cells by intracellular second messenger systems. Naunyn Schmiedebergs Arch Pharmacol 2001;364:487–495.[CrossRef][Medline]
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ABSTRACT
GENOMIC VASCULAR CORTICOSTEROID...
