Protective effect of cysteinyl leukotriene receptor antagonist montelukast in bleomycin-induced pulmonary fibrosis

Abstract

Background: This study aims to investigate the early- and late-term effects of pharmacological inhibition of cysteinyl leukotriene activity by using montelukast in bleomycin-induced inflammatory and oxidative lung injury in an animal model.

Methods: The study included 48 male Wistar albino rats (weighing 250 g to 300 g). Rats were administered intratracheal bleomycin or saline and assigned into groups to receive montelukast or saline. Bronchoalveolar lavage fluid and lung tissue samples were collected four and 15 days after bleomycin administration.

Results: Bleomycin resulted in significant increases in tumor necrosis factor-alpha levels (4.0±1.4 pg/mL in controls vs. 44.1±14.5 pg/mL in early-term vs. 30.3±5.7 pg/mL in late-term, p<0.001 and p<0.001, respectively), transforming growth factor beta 1 levels (28.6±6.6 pg/mL vs. 82.3±14.1 pg/mL in early-term vs. 60.1±2.9 pg/mL in late-term, p<0.001 and p<0.001, respectively), and fibrosis score (1.85±0.89 in early-term vs. 5.60±1.14 in late-term, p<0.001 and p<0.01, respectively). In bleomycin exposed rats, collagen content increased only in the late-term (15.3±3.0 ?g/mg in controls vs. 29.6±9.1 ?g/mg in late-term, p<0.001). Montelukast treatment reversed all these biochemical indices as well as histopathological alterations induced by bleomycin.

Conclusion: Montelukast attenuates bleomycin-induced inflammatory and oxidative lung injury and prevents lung collagen deposition and fibrotic response. Thus, cysteinyl leukotriene receptor antagonists might be regarded as new therapeutic agents for idiopathic pulmonary fibrosis.

Keywords: Bleomycin; collagen; glutathione; interstitial lung disease; malondialdehyde; myeloperoxidase; transforming growth factor beta 1; tumor necrosis factor-alpha.

Figure 1. Experimental groups. BAL: Bronchoalveolar lavage.

Figure 2. (a) Tumor necrosis factor-alpha and (b) transforming growth factor beta 1 levels in bronchoalveolar lavage fluid. TNF-a: Tumor necrosis factor-alpha; TGF-b1: Transforming growth factor beta 1; B: Bleomycin; * p<0.001 vs C (control group). ‡ p<0.01, § p<0.001 vs B (Bleomycin) + saline groups in same term; † p<0.05 vs late B (Bleomycin) + saline group; ¶ p<0.001 vs late B (Bleomycin) + saline group.

Figure 3. (a) Malondialdehyde and (b) myeloperoxidase levels in lung tissue. MDA: Malondialdehyde, MPO: Myeloperoxidase; * p<0.001, ** p<0.01, *** p<0.05 vs C (control group); † p<0.05 vs B (Bleomycin) + saline group in same term.

Figure 4. (a) Glutathione and (b) collagen levels in lung tissue. GSH: Glutathione; * p<0.001, ** p<0.01, **** p<0.05 vs C (control group); † p<0.001, ‡ p<0.01 vs B (Bleomycin) + saline group in same term; § p<0.05 vs late B (Bleomycin) + saline.

Figure 5. In early bleomycin + saline group. (a) Peribronchiolar and interstitial lymphocytic infil- tration (H-Ex200). (b) Focal interstitial inflammation and fibrosis. Fibrosis score: 3 (x200 Masson’s trichrome). In early bleomycin + montelukast group: (c) Minimal interstitial collagen accumulation. Fibrosis score: 1 (x200 Masson’s trichrome). (d) x400 Masson’s trichrome.

Figure 6. In late bleomycin+saline group: (a) Peribronchiolar dense inflammatory cellular infiltration (H-Ex400). (b) Distortion of lung architecture and severe fibrosis. Fibrosis score: 6 (x400 Masson’s trichrome). (c) Peribronchial and interstitial dense fibrosis. Fibrosis score: 7 (x200 Masson’s trichrome) In late bleomycin+montelukast group: (d) Focal interstitial fibrosis with no architectural distortion. Fibrosis score: 4 (x100 Masson’s trichrome).