Alcohol reduces airway hyperresponsiveness (AHR) and allergic airway inflammation in mice

Abstract

There is very limited knowledge about the effects of alcohol on airway hyperresponsiveness and inflammation in asthma. Historical accounts of alcohol administration to patients with breathing problems suggest that alcohol may have bronchodilating properties. We hypothesized that alcohol exposure will alter airway hyperresponsiveness (AHR) and pulmonary inflammation in a mouse model of allergic asthma. To test this hypothesis, BALB/c mice were fed either 18% alcohol or water and then sensitized and challenged with ovalbumin (OVA). AHR was assessed by means of ventilation or barometric plethysmography and reported as either total lung resistance or enhanced pause, respectively. Airway inflammation was assessed by total and differential cell counts in bronchoalveolar lavage fluid (BALF), cytokine levels in BALF, lung histology, and serum immunoglobulin E (IgE) levels. Alcohol feeding significantly blocked methacholine-induced increases in AHR compared with water-fed controls. Alcohol feeding significantly reduced total cell numbers (64%) as well as the number of eosinophils (84%) recruited to the lungs of these mice. Modest changes in lung pathology were also observed. Alcohol exposure led to a reduction of IgE in the serum of the EtOH OVA mice. These data demonstrate that alcohol exposure blunts AHR and dampens allergic airway inflammation indices in allergic mice and suggest that there may be an important role for alcohol in the modulation of asthma. These data provide an in vivo basis for previous clinical observations in humans substantiating the bronchodilator properties of alcohol and for the first time demonstrates an alcohol-induced reduction of allergic inflammatory cells in a mouse model of allergic asthma.

Fig. 1.

Protocol for the administration of EtOH and ovalbumin (OVA). EtOH was ramped up to 18% beginning on day 0. The OVA sensitization protocol was started at week 6 of EtOH drinking, during which time the mice continued to drink EtOH for the remainder of the experiment. AHR, airway hyperresponsiveness; BALF, bronchoalveolar lavage fluid; ip, intraperitoneal.

Fig. 2.

Ethanol feeding blocks methacholine-induced airway responsiveness. EtOH-drinking OVA-sensitized mice demonstrated a highly significant attenuation in total lung resistance to MCh compared with water-drinking sensitized mice ***P < 0.001. The EtOH-OVA group also had increased responsiveness compared with EtOH-only-consuming mice. No differences were observed between the EtOH-OVA and the water-only groups. n = 8–10 mice per group. Data are presented as means ± SE. R_L, lung resistance.

Fig. 3.

Ethanol attenuates total cell counts in BALF. EtOH consumption resulted in a significant attenuation in total cells (*P < 0.05, **P < 0.01) compared with the water-OVA mice. No differences were observed between the nonsensitized groups. n = 8–12 mice per group.

Fig. 4.

EtOH consumption decreases lung eosinophilia in sensitized mice. EtOH-OVA mice demonstrated a significant attenuation in the total number of eosinophils (**P < 0.01) in the BALF compared with water-OVA mice and a significant potentiation in eosinophils compared with the EtOH only mice (#P < 0.05). The water-only group contained significantly more eosinophils than the water-only and EtOH-only groups of mice (***, ###P < 0.001). No eosinophils were detected in the water-only and EtOH-only groups of mice. No observable differences were observed in the total number of macrophage, lymphocyte, or neutrophil cells present between any groups in the BALF. Both control groups contained primarily all macrophage cells. n = 8–12 mice per group.

Fig. 5.

EtOH activates peroxisome proliferator-activated receptor (PPAR)-γ in Beas-2B cells. Pretreatment of Beas-2B cells with 100 mM EtOH for 6 h results in a significant activation of PPAR-γ (**P < 0.006) compared with media only-treated control cells. No statistical differences were observed with 3-h treatments. Data represent pooled results from at least 3 separate experiments and are reported as means ± SE.

Fig. 6.

EtOH exposure attenuates immunoglobulin E (IgE) levels in OVA-sensitized mouse serum. Effect of EtOH drinking and OVA sensitization on IgE levels in mouse serum. Following the initial serum collection, mice were separated into 4 groups. IgE levels were increased 24 h after the second ip OVA sensitization injection. Following the 1% OVA aerosol challenges, the EtOH-OVA group demonstrated significantly (**P < 0.01) lower IgE levels compared with the water-OVA group. n = 8–12 mice per group.

Fig. 7.

Effect of EtOH on peribronchial and perivascular infiltrates and goblet cell metaplasia following OVA sensitization. Representative hematoxylin and eosin (H&E)-stained (A–D) and periodic acid Schiff (PAS)-stained (E–H) sections of the lungs. EtOH consumption decreases the amount of peribronchial and perivascular inflammation and goblet cell metaplasia in the sensitized mice (D and H, respectively) compared with water-drinking control mice (C and G, respectively). No increased inflammation or goblet cell metaplasia was observed in the control groups of mice (A, B, E, and F). n = 8–10 mice per group, images A–D were taken at ×4, images E–H were taken at ×10. Quantification of PAS staining of mouse lung tissue (I). n = 8–12 mice in each group. *P < 0.05. Results shown here are representative of 3 separate experiments.

Fig. 8.

Effect of EtOH consumption and OVA challenges on calcitonin gene-related peptide (CGRP) in mouse lungs. EtOH consumption decreases the amount of positive stained areas for CGRP in OVA-sensitized mice. Ubiquitous staining was observed in the water-OVA mice. Nonsensitized control mice did not demonstrate any differences in staining. n = 8–10 mice per group, images A–D were taken at ×10. Images are representative of 3 separate experiments. All samples were stained at the same time to avoid experimental artifacts.