2-Methoxyestradiol (2-ME) reduces the airway inflammation and remodeling in an experimental mouse model
Introduction
The pathophysiology of asthma involves a number of cell types and mediators. Airway structural changes that occur in patients with asthma in response to persistent inflammation are termed airway remodeling and include airway wall thickening, subepithelial fibrosis, and hyperplasia of mucous glands, myofibroblasts, and smooth muscle vasculature [1]. Chronic airway inflammation plays a key role in asthma. The relationship between inflammation and structural changes is speculative. It is believed that remodeling is a direct result of a switch from acute to chronic inflammation followed by healing [2]. For this reason, anti-inflammatory agents will not necessarily prevent or attenuate the process of remodeling [3]. All current guidelines focus on the treatment of inflammation in asthma although there are differences between the processes of airway wall remodeling for which there is no defined treatment validated [2].
Long-acting β agonists produce bronchial dilation and improve asthma symptoms, effects that are maintained with regular use over time. However, immunotherapy with β agonists has been consistently shown to be inferior to the use of inhaled corticosteroids which can reduce the underlying inflammation associated with asthma. For these reasons, inhaled corticosteroids are recommended as first line maintenance treatment for asthma [4].
2-ME is a naturally occurring derivative of 17β-estradiol and was shown to be a well tolerated small molecule that possesses anti-tumor and anti-angiogenic activities [5]. Studies by Mabjeesh et al. [6] reported that 2-ME destabilizes microtubules and blocks HIF1-α nuclear accumulation and HIF1-α activity by an oxygen- and proteasome-independent pathways. Evidence was provided for a link between the microtubule cytoskeleton and HIF regulation. Destruction of the normal function of the microtubule cytoskeleton is required for HIF1-α-induced inhibition by microtubule-targeted drugs such as Taxol and Vincristine.
Several reports have been published suggesting the use of different strategies for the suppression of antigen-induced asthma in mice. For instance, the oral administration of CpG-ODNs was effective in preventing and reversing antigen-induced eosinophilia airway inflammation [7]. Also, low doses of leukotriene receptor antagonist were an effective therapy in the airway remodeling in the ovalbumin mouse model [8].
Angiogenesis supports the development of many diseases such as cancer, rheumatoid arthritis, psoriasis, macular degeneration, and diabetic retinopathy [9], [10], [11]. VEGF is a major mediator of angiogenesis, whose expression is induced under hypoxic conditions [9], [12]. The induction of VEGF under hypoxic conditions is a multistage process in which the alpha subunit of HIF (HIF-1α) plays a key role [13]. HIF1-α is rapidly degraded by the proteasome under normoxic conditions. Following hypoxic stabilization, HIF-1α is translocated into the nucleus where it heterodimerizes with HIF-1β and activates the transcription of more than forty genes important for adaptation and survival under hypoxia [14]. Hence, the anti-angiogenic activity of 2-ME may regulate the inflammatory process in asthma and reduce cell infiltration. Therefore, we hypothesized that the local intratracheal (IT) administration of 2-ME may inhibit airway inflammation and remodeling. The objective of this study was to test this hypothesis and determine the effect of IT 2-ME administration in the development of airway remodeling using a chronic murine model of allergic airway inflammation with subsequent fibrosis. The findings support our hypothesis and demonstrate that 2-ME significantly inhibited antigen-induced inflammation and airway remodeling in the OVA allergen inflammatory murine model.
Section snippets
Animals
Balb/c mice (males) were obtained and maintained in a pathogen-free environment in the facilities of the Instituto Nacional de Ciencias Medicas y de la Nutricion (INCMN) (Mexico City). The mice were housed in a temperature-controlled room with 12-h dark/light cycles, and allowed food and water ad libitum. All the experiments described below were performed in accordance with the INCMN regulations.
Experimental design
The protocol for sensitization and intratracheal challenge has previously been described by us in
Intratracheal administration of 2-ME reduces OVA-induced atopic response
Three groups of mice (n = 6/group) were examined and were treated with OVA alone (group one), OVA+ 2-ME (group two) and with saline (SS) (group three) as described in Materials and methods. The mice were rendered allergic to OVA with two i.p. injections of OVA-alum suspension at days 0 and 5 and 2 IT challenges at days 12 and 22. Two days after sensitization group two mice were treated three times with 2-ME administered by the intratracheal route every other day. The intensity of allergic
Discussion
The present findings provide for the first time evidence that intratracheal (IT) administration of 2-ME was effective in preventing the pathogenesis of asthma in a murine model of atopic asthma. Administration of 2-ME markedly diminished the inflammatory pulmonary response, eosinophil infiltration in the lung tissue, goblet cell hyperplasia with airway occlusion with mucus and reduction in collagen IV expression. The above findings also correlated with inhibition of circulating level of
Acknowledgments
This work was supported in part by the Fogarty and by the Jonsson Comprehensive Cancer Center at UCLA. The authors also acknowledge the assistance of Erica Keng and Maggie Yang in the preparation of the manuscript.
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