The soluble tumor necrosis factor-alpha receptor suppresses airway inflammation in a murine model of acute asthma

Abstract

Purpose: Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine that has been implicated in many aspects of the airway pathology in asthma. TNF-alpha blocking strategies are now being tried in asthma patients. This study investigated whether TNF-alpha blocking therapy inhibits airway inflammation and airway hyperresponsiveness (AHR) in a mouse model of asthma. We also evaluated the effect of TNF-alpha blocking therapy on cytokine production and adhesion molecule expression.

Materials and methods: Ovalbumin (OVA) sensitized BALB/c female mice were exposed to intranasal OVA administration on days 31, 33, 35, and 37. Mice were treated intraperitoneally with soluble TNF-alpha receptor (sTNFR) during the OVA challenge.

Results: There were statistically significant decreases in the numbers of total cell and eosinophil in bronchoalveolar lavage fluid (BALF) in the sTNFR treated group compared with the OVA group. However, sTNFR-treatment did not significantly decrease AHR. Anti-inflammatory effect of sTNFR was accompanied with reduction of T helper 2 cytokine levels including interleukin (IL)-4, IL-5 and IL-13 in BALF and vascular cell adhesion molecule 1 expression in lung tissue.

Conclusion: These results suggest that sTNFR treatment can suppress the airway inflammation via regulation of Th2 cytokine production and adhesion molecule expression in bronchial asthma.

Keywords: Asthma; airway inflammation; soluble TNF-α receptor.

Fig. 1

Effect of sTNFR treatment on airway hyperresponsiveness (AHR) to inhaled methacholine (Mch). AHR was measured 24 hours after the final ovalbumin (OVA) challenge using a Allmedicus system by which mice were exposed to increasing concentrations of methacholine (3.125 - 50 mg/mL). Values are expressed as mean, n = 16 mice/group in three separated experiments. sTNFR, solubel tumor necrosis factor-alpha receptor.

Fig. 2

Effect of sTNFR on IL-4 (A), IL-5 (B), IL-13 (C) and IL-10 (D) levels in bronchoalveolar lavage fluid (BALF). Mice were sacrified 24 hours after the final ovalbumin (OVA) challenge, and BALF were separated and cytokines levels were measured with ELISA, as described in Material and Methods. Values are expressed as mean ± SEM, n = 16 mice/group in three separated experiments, and ^*p < 0.05, ^**p < 0.01 in comparison with the OVA group. IL, interleukin; sTNFR, solubel tumor necrosis factor-alpha receptor.

Fig. 3

Effect of sTNFR on VCAM-1. Mice were sacrificed 24 hours after the final ovalbumin challenge. (A) Expression of VCAM-1 in lung tissue was determined by Western blotting. (B) Densimometric analyses are presented as the ratio of VCAM-1 relative to actin, and ^*p < 0.05 in comparison with the OVA group. OVA, ovalbumin; sTNFR, solubel tumor necrosis factor-alpha receptor; VCAM-1, vascular cell adhesion molecule 1.

Fig. 4

Photomicrographs showing staining of lung tissue with antibodies to VCAM-1. Mice were sacrificed 24 hours after the final ovalbumin challenge. Paraffin-embeded lung tissue sections were stained with specific antibody to VCAM-1. Immunohistochemical detection of VCAM-1 was measured with monoclonal antibody, as described in Material and Methods. Positive staining is depicted in pink. (A) Control group. (B) OVA group. (C) sTNFR treated group (×200). VCAM-1, vascular cell adhesion molecule 1; OVA, ovalbumin; sTNFR, solubel tumor necrosis factor-alpha receptor.