Functional and morphologic dysfunctions in the airways of rats submitted to an experimental model of obesity-exacerbated asthma

Abstract

The obesity-exacerbated asthma phenotype is characterized by more severe asthma symptoms and glucocorticoid resistance. The aim of this study was to standardize an obesity-exacerbated asthma model by a high glycemic level index (HGLI) diet and ovalbumin (OVA) sensitization and challenges in Wistar rats. Animals were divided into groups: control (Ctrl), obese (Ob), asthmatic (Asth), obese asthmatic (Ob + Asth) and obese asthmatic treated with dexamethasone (Ob + Asth + Dexa), and in vivo and in vitro functional and morphological parameters were measured. After HGLI consumption, there was an increase in body weight, fasting blood glucose, abdominal circumferences, body mass index and adiposity index. Respiratory function showed a reduction in pulmonary tidal volume and ventilation. In isolated tracheas, carbachol showed an increase in contractile efficacy in the Ob, Ob + Asth and Ob + Asth + Dexa, but mostly on Ob + Asth. Histological analysis of lungs showed peribronchovascular inflammation and smooth muscle hypertrophy and extracellular remodeling on Ob + Asth and Ob + Asth + Dexa. An obesity-exacerbated asthma model was successfully established. Therefore, this model allows further molecular investigations and the search for new therapies for the treatment and relief of symptoms of patients with obesity-induced resistant asthma.

Figure 1

Final body mass values of rats from the Ctrl, Ob, Asth, Ob + Asth and Ob + Asth + Dexa. One-way ANOVA followed by Tukey's posttest (n = 4–6). *p < 0.05 (Ctrl vs. Ob, Ob + Asth), ^bp < 0.05 (Asth vs. Ob + Asth).

Figure 2

Fasting blood glucose of rats from the Ctrl, Ob, Asth and Ob + Asth. One-way ANOVA followed by Tukey's posttest (n = 6). *p < 0.05 (Ctrl vs. Ob + Asth), ^bp < 0.05 (Asth vs. Ob + Asth), ^&p < 0.05 (Ob + Asth day 0 vs. Ob + Asth after 16 weeks).

Figure 3

Evaluation of body mass index of rats from Ctrl, Ob, Asth, Ob + Asth and Ob + Asth + Dexa. One-way ANOVA followed by Tukey's posttest (n = 6). *p < 0.05 (Ctrl vs. Ob, Ob + Asth); ^bp < 0.05 (Asth vs. Ob + Asth).

Figure 4

Adiposity index of rats from the Ctrl, Ob, Asth, Ob + Asth and Ob + Asth + Dexa. One-way ANOVA followed by Tukey's posttest (n = 4–6). *p < 0.05 (Ctrl vs. Ob, Ob + Asth, and Ob + Asth + Dexa), ^bp < 0.05 (Asth vs. Ob + Asth).

Figure 5

Evaluation of (A) tidal volume (VT), (B) respiratory frequency (RF), and (C) ventilation (VE) on days 1, 12 and 21 of asthma induction. Symbols and vertical bars represent the mean and the e.p.m., respectively. One-way ANOVA followed by Tukey's posttest (n = 6). *p < 0.05 (Ctrl vs. Asth, Ob + Asth and Ob + Asth + Dexa).

Figure 6

Effect of stimulation of rat trachea with 100 µg/ml OVA. Symbols and vertical bars represent the mean and the e.p.m., respectively. One-way ANOVA followed by Tukey's posttest (n = 3–5). *p < 0.05 (Ctrl vs. Asth, Ob + Asth, and Ob + Asth + Dexa); ^ap < 0,05 (Ob vs. Ob + Asth); ^bp < 0,05 (Asth vs. Ob + Asth).

Figure 7

Cumulative concentration–response curves to potassium chloride (KCl) in the presence of functional epithelium in rat trachea. Symbols and vertical bars represent the mean and the e.p.m., respectively. One-way ANOVA followed by Tukey's posttest (n = 5).

Figure 8

Cumulative concentration–response curves to carbachol (CCh) in the presence of functional epithelium in rat trachea. Symbols and vertical bars represent the mean and the e.p.m., respectively. One-way ANOVA followed by Tukey's posttest (n = 5). *p < 0.05 (Ctrl vs. Asth, Ob, Ob + Asth and Ob + Asth + Dexa); ^bp < 0,05 (Asth vs. Ob + Asth).

Figure 9

Cumulative concentration–response curves to nifedipine (A), isoprenaline (B) and aminophylline (C) in precontracted rat trachea with 10^–5 M CCh in the presence of functional epithelium. The symbols and vertical bars represent the mean and the e.p.m., respectively. One-way ANOVA followed by Tukey's posttest (n = 5). *p < 0.05 (Ctrl vs. Ob, Asth and Ob + Asth).

Figure 10

Photomicrograph of the lungs of rats from the Ctrl (A,F), Ob (B,G), Asth (C,H), Ob + Asth (D,I) and Ob + Asth + Dexa (E,J) stained with HE and Masson's trichrome, respectively. Cell infiltrate (black arrows).

Figure 11

Measurements of inflammatory area (A), smooth muscle thickness (B) and remodeling through the extracellular matrix (C) in the lungs of animals in the Ctrl, Ob, Asth, Ob + Asth and Ob + Asth + Dexa. Symbols and vertical bars represent the mean and the e.p.m., respectively (n = 6). One-way ANOVA followed by Tukey's posttest. *p < 0.05 (Ctrl vs. Ob, Asth and Ob + Asth), ^ap < 0.05 (Ob vs. Ob + Asth), ^b p < 0.05 (Asth vs. Ob + Asth), ^#p < 0.05 (Ob + Asth vs. Ob + Asth + Dexa).

Figure 12

Photomicrograph of smooth muscle of terminal bronchioles of rats from the Ctrl (A), Ob (B), Asth (C), Ob + Asth (D) and Ob + Asth + Dexa (E) stained with HE. Smooth muscle (asterisk).

Figure 13

Flowchart and timeline of the study design for asthma. OVA ovalbumin, Al(OH)₃ aluminum hydroxide, ip intraperitoneally.