Effects of corticosteroid, montelukast and iNOS inhibition on distal lung with chronic inflammation

Abstract

We evaluated the effects of anti-iNOS (1400W – W) associated with leukotriene antagonist (montelukast – M) or corticosteroid (dexamethasone – D) on distal lung of guinea pigs (GP) with chronic pulmonary inflammation.

Methods

GP were inhaled with ovalbumin (OVA-2×/week/4 weeks), treated with M (OVAM), D (OVAD) and/or W (OVAW, OVADW, OVAMW) and distal lungs were evaluated by morphometry.

Results

Isolated treatments were not sufficient to reduce all parameters. In OVADW, all parameters were reduced with greater reduction in elastic fibers, TIMP-1, IL-4, IL-5, IFN-gamma and PGF2-alpha compared with OVAD (p < 0.05). OVAMW potentiated the reduction of actin, elastic fibers, TIMP-1, IL-4, IL-5, TGF-beta, IFN-gamma, iNOS, and PGF2-alpha to a greater extent than OVAM (p < 0.05). A reduction of TIMP-1, IL-4, IL-5, TGF-beta, IFN-gamma and iNOS was observed in OVADW compared with OVAMW (p < 0.05).

Conclusions

Although anti-iNOS paired with montelukast or dexamethasone yields better results than isolated treatments, the most effective pairing for controlling inflammation, oxidative stress and remodeling in this asthma model was found to be corticosteroids and anti-iNOS.

Introduction

Asthma is a complex disease caused by multiple environmental factors in combination with more than 100 major and minor susceptibility genes with several different phenotypes (GINA, 2011). Several authors have shown that the peripheral lung parenchyma of asthmatic patients exhibited eosinophilic inflammation, overexpression of IL-5 and extracellular matrix remodeling (Holgate et al., 2003, Ramos-Barbón and Parra-Arrondo, 2011). The importance of distal lung responses to global pulmonary alterations, particularly in patients with partially controlled or uncontrolled asthma, has also been recently emphasized (De Magalhães et al., 2005, GINA, 2011).

We have previously shown that in the ovalbumin-induced severe asthma model, repeated allergen exposures lead to chronic allergic airway and distal lung parenchyma inflammation. The latter is characterized by an influx of eosinophils, mast cells and allergen-specific T cells (Th2-type cytokine pattern), leading to airway and extracellular tissue remodeling in the distal lung (Lanças et al., 2006, Angeli et al., 2008, Nakashima et al., 2008, Starling et al., 2009).

Among the different drug classes used to control asthma, corticosteroids are the most important (GINA, 2011). Corticosteroids have significant anti-inflammatory effects, such as decreasing the airway infiltration of activated T-cells and eosinophils, which play an important role in the development of the late asthmatic reaction (GINA, 2011). Antagonists of cysteinyl leukotrienes, however, may also be used to control asthma, as cysLTs play an important role in bronchoconstriction and airway inflammation (Offer et al., 2003, Amlani et al., 2011).

Cysteinyl leukotrienes (cysLTs) are synthesized from arachidonic acid, and most of their effects are mediated by the CysLT1 receptor, which is a G protein-coupled receptor. CysLTs have many pulmonary effects, including airway smooth muscle contraction, chemotaxis, mucous secretion, smooth muscle proliferation and vascular permeability increases (Barnes, 2011, Amlani et al., 2011).

Clinical trials with cysteinyl leukotrienes receptors antagonists in uncontrolled asthma have shown improvements in pulmonary function and symptoms, with less need for rescue medication and fewer asthma exacerbations (Stelmach et al., 2002, Joos et al., 2008). It has also been shown that leukotriene antagonists reduce sputum and mucosal eosinophils in subjects with asthma (McMillan et al., 2005). However, recent long-term trials have shown that spirometry, symptoms, and quality of life were more greatly improved and that β₂-agonist use was more significantly reduced with glucocorticoids than with CysLT receptor antagonists (Bonsignore et al., 2008, Jartti, 2008). Nonetheless, Price et al. (2011) showed that 2 months of treatment with leukotriene receptor antagonist was equivalent to an inhaled glucocorticoid as first-line controller therapy and to long-acting β₂-agonist as add-on therapy for diverse primary care patients. Nevertheless, this equivalence was not demonstrated for 2 years.

Increased levels of exhaled nitric oxide are a marker of the pulmonary inflammatory response. In addition, there is evidence that iNOS inhibition reduces lung hyper-responsiveness and inflammation as well as airway and lung tissue remodeling (Prado et al., 2005a, Prado et al., 2005b, Prado et al., 2006, Starling et al., 2009). Sugiura et al. (2008) showed the importance of nitrative stress in refractory and severe asthma, demonstrating the correlation of several response markers with the decline of FEV1.

Although some asthma cases are controlled with the current therapies, severe asthma (5–10% of all cases) is particularly difficult to treat with these drugs. In addition, functional, inflammatory and remodeling alterations in the distal lung tissue could contribute to the poor control of disease in these patients (GINA, 2011).

We evaluated the effects of a new therapeutic approach in which an anti-iNOS is paired with standardized treatments (corticosteroids or leukotriene antagonist) to better control the inflammatory response and extracellular matrix remodeling, as well as to manage activation of the oxidative stress pathway. We used a guinea pig model of severe allergic inflammation and focused our analyses on alterations in the distal lung.