The presence of LPS in OVA inhalations affects airway inflammation and AHR but not remodeling in a rodent model of asthma

Abstract

Tsuchiya K, Siddiqui S, Risse P-A, Hirota N, Martin JG. The presence of LPS in OVA inhalations affects airway inflammation and AHR but not remodeling in a rodent model of asthma. Am J Physiol Lung Cell Mol Physiol 303: L54 -L63, 2012. First published April 20, 2012 doi:10.1152/ajplung.00208.2011 is the most frequently used allergen in animal models of asthma. Lipopolysaccharide (LPS) contaminating commercial OVA may modulate the evoked airway inflammatory response to OVA. However, the effect of LPS in OVA on airway remodeling, especially airway smooth muscle (ASM) has not been evaluated. We hypothesized that LPS in commercial OVA may enhance allergen-induced airway inflammation and remodeling. Brown Norway rats were sensitized with OVA on day 0. PBS, OVA, or endotoxin-free OVA (Ef-OVA) was instilled intratracheally on days 14,19,24. Bronchoalveolar lavage (BAL) fluid, lung, and intrathoracic lymph node tissues were collected 48 h after the last challenge. Immunohistochemistry for ␣-smooth muscle actin, Periodic-Acid-Schiff staining, and real-time qPCR were performed. Airway hyperresponsiveness (AHR) was also measured. BAL fluid macrophages, eosinophils, neutrophils, and lymphocytes were increased in OVA-challenged animals, and macrophages and neutrophils were significantly lower in Ef-OVA-challenged animals. The ASM area in larger airways was significantly increased in both OVA and Ef-OVA compared with PBS-challenged animals. The mRNA expression of IFN-␥ and IL-13 in lung tissues and IL-4 in lymph nodes was significantly increased by both OVA and Ef-OVA compared with PBS and were not significantly different between OVA and Ef-OVA. Monocyte chemoattractant protein (MCP)-1 in BAL fluid and AHR were significantly increased in OVA but not in Ef-OVA. LPS contamination in OVA contributes to the influx of macrophages and MCP-1 increase in the airways and to AHR after OVA challenges but does not affect OVA-induced Th1 and Th2 cytokine expression, goblet cell hyperplasia, and ASM remodeling. animal model; airway hyperresponsiveness; Brown Norway rat; endotoxin; ovalbumin LIPOPOLYSACCHARIDE (LPS) is a cell wall component of Gramnegative bacteria and ubiquitous in the environment and is often present in polluted air as well as in household dust. There has been substantial interest in LPS for its effects on respiratory immunity since the development of the hygiene hypothesis (32, 38). Toll-like receptor 4 (TLR4) is a receptor for LPS, and activation of TLR4 is required to prime dendritic cells and epithelial cells for optimal responses to antigen exposure (12). Stimulation of TLR4 is essential for downstream cellular events that are mediated by mitogen-activated protein kinase p38 and c-Jun NH2-terminal kinase, leading to nuclear translocation of NF-B, resulting in cytokine mRNA transcription and release of proinflammatory cytokines (37).Ovalbumin (OVA) is widely used in animal models of asthma to study mechanisms of airway inflammation, airway hyperresponsiveness (AHR), and airway remodeling. However, commercial OVA has ...

Activated mouse eosinophils protect against lethal respiratory virus infection

“…[15][16][17] Interestingly, and for reasons as yet unclear, eosinophils recruited in response to ova sensitization and challenge do not respond in an analogous fashion to PVM. Although both ova and Af promote eosinophil recruitment when administered via the standard sensitization and challenge protocol, ova is otherwise inert (save for potential contamination with lipopolysaccharide 36 ), whereas Af extract is a complex mix of antigens including those that can signal via Toll-like receptors (TLRs) 2 and 4 expressed on bone marrow dendritic cells, macrophages, lung epithelial cells, [37][38][39] and conceivably eosinophils. 40 Zimmermann et al 41 compared the ova and Af sensitization challenge models directly to one another via DNA microarray; among the 236 transcripts unique to the Af sensitization and challenge model are those encoding several proinflammatory cytokines, including IL-1b, IL-1a, CCL3, and most notably, IL-6, which has already been shown to have an impact on virus-eosinophil interactions.…”

Concomitant Exposure to Ovalbumin and Endotoxin Augments Airway Inflammation but Not Airway Hyperresponsiveness in a Murine Model of Asthma

“…[20] Low dose systemic LPS has similar effects on pulmonary eosinophilia. [30] However, mice lacking lipopolysaccharide binding protein, reportedly mount comparable degrees of eosinophilia in response to OVA challenge to wild type controls, although they do not develop allergen-induced airway hyperresponsiveness. [29] However, the administration of exogenous LPS to OVA challenged C57Bl/6 mice is inhibitory of eosinophilia [20] as is high dose LPS challenge of BALB/c mice [25], indicating that the timing, route of administration, origin and dose of LPS may have important influences on the outcome of the challenge.…”

“…A recent study on the BN rat undergoing repeated challenges with LPS-rich and LPS-free OVA demonstrated comparable airway smooth muscle remodeling in the large airways. [30].…”

Pneumococcal pneumonia suppresses allergy development but preserves respiratory tolerance in mice

“…Nevertheless, the latter ensures a well-controlled and widely accepted model allergen in comparable murine experiments [12,23,33]. In order to exclude any side-effects of any LPS contamination within the employed OVA preparations on S. pneumoniae mediated effects on allergic sensitization, we have used LPS-depleted OVA in our study [34][35][36]. We conclude that in our murine allergy model, an infection with S. pneumoniae near the time of allergen exposure prevents the development of an allergic phenotype in adult mice.…”