Assessment of Alamandine in Pulmonary Fibrosis and Respiratory Mechanics in Rodents

Abstract

Introduction: Pulmonary fibrosis (PF) is characterized by an accelerated decline in pulmonary function and has limited treatment options. Alamandine (ALA) is a recently described protective peptide of the renin-angiotensin system (RAS) with essential tasks in several conditions. Our group previously demonstrated that ALA is reduced by 365% in the plasma of patients with idiopathic PF, and thus, it is plausible to believe that stimulation of this peptide could represent an important therapeutic target. In this sense, this study investigates the effects of ALA in an experimental model of PF.

Materials and methods: Bleomycin (BLM) was administrated in Wistar rats, and these fibrotic animals were treated with ALA for 14 days. Body weight, histology, respiratory, and hemodynamic parameters were analyzed to study the effects of ALA.

Results: ALA treatment attenuated the development of fibrosis (P < 0.0001), reduced respiratory system elastance (P < 0.0001), and preserved weight gain (P < 0.0001) in fibrotic animals without affecting the autonomic control of blood pressure and heart rate.

Conclusion: The data from this study demonstrate the potential of ALA to alleviate pulmonary fibrosis and improve respiratory system mechanics in vivo. The promising results encourage more detailed investigations of the potential of ALA as a future and efficient antifibrotic.

Figure 1

Effect of alamandine on development of pulmonary fibrosis. (a) Bodyweight variation (%) analyzed by two-way analysis of variance (ANOVA) followed by Tukey's multiple comparison posttest. (b) Ashcroft modified score (F = 33.10) and collagen area quantification in the lungs (F = 8.285). (c) Representative images of effects at two weeks after alamandine treatment on histological findings and collagen deposition in the lungs. Hematoxylin and eosin (HE) and Masson's trichrome (TM) staining. Magnification at 400x. CO: animals that received only saline; ALA: saline intratracheally and alamandine in the osmotic minipumps; BLM: bleomycin intratracheally and saline in the osmotic minipumps; BLM+ALA: bleomycin intratracheally and alamandine in the osmotic minipumps. Arrows: alveolar septa; asterisks: fibrous bands or fibrous masses; arrowhead: inflammatory cells. Tissue changes were analyzed by one-way ANOVA, followed by Tukey's multiple comparison posttest. All data represent mean ± SEM; n = 7 − 9. P < 0.05 was considered statistically significant. ^∗P < 0.05; ^∗∗∗P < 0.001; ^∗∗∗∗P < 0.0001.

Figure 2

Lung mechanics on day 14. (a) Elastance, F = 11.28. (b) Compliance, F = 20.50. (c) Resistance: level of constriction, F = 8.672. CO: animals that received only saline; ALA: saline intratracheally and alamandine in the osmotic minipumps; BLM: bleomycin intratracheally and saline in the osmotic minipumps; BLM+ALA: bleomycin intratracheally and alamandine in the osmotic minipumps. One-way ANOVA followed by Tukey's multiple comparison test was used. Data represent mean ± SEM; n = 6 − 7; P < 0.05 was considered statistically significant. ^∗∗P < 0.01; ^∗∗∗P < 0.001; ^∗∗∗∗P < 0.0001.

Figure 3

Pearson's correlation between Ashcroft score and pulmonary elastance. (a) BLM and BLM+ALA groups (R² = 0.7143). (b) BLM group (R² = 0.8640). (c) BLM+ALA group (R² = 0.1347). BLM: bleomycin intratracheally and saline in the osmotic minipumps; BLM+ALA: bleomycin intratracheally and alamandine in the osmotic minipumps; N = 7. •: BLM group. °: BLM+ALA group.