Vagotomy attenuates bleomycin-induced pulmonary fibrosis in mice

Abstract

The progression of pulmonary fibrosis (PF) entails a complex network of interactions between multiple classes of molecules and cells, which are closely related to the vagus nerve. Stimulation of the vagus nerve increases fibrogenic cytokines in humans, therefore, activation of the nerve may promote PF. The hypothesis was tested by comparing the extent and severity of fibrosis in lungs with and without vagal innervation in unilaterally vagotomized mice. The results show that in vagotomized lungs, there were less collagen staining, less severe fibrotic foci (subpleural, peri-vascular and peri-bronchiolar lesions) and destruction of alveolar architecture; decreased collagen deposition (denervated vs intact: COL1α1, 19.1 ± 2.2 vs 22.0 ± 2.6 ng/mg protein; COL1α2, 4.5 ± 0.3 vs 5.7 ± 0.5 ng/mg protein; p < 0.01, n = 21) and protein levels of transforming growth factor beta and interleukin 4; and fewer myofibroblast infiltration (denervated vs intact: 1.2 ± 0.2 vs 3.2 ± 0.6 cells/visual field; p < 0.05, n = 6) and M2 macrophages [though the infiltration of macrophages was increased (denervated vs intact: 112 ± 8 vs 76 ± 9 cells/visual field; p < 0.01, n = 6), the percentage of M2 macrophages was decreased (denervated vs intact: 31 ± 4 vs 57 ± 9%; p < 0.05, n = 5)]. It indicated that the vagus nerve may influence PF by enhancing fibrogenic factors and fibrogenic cells.

Deficiency of α7 Nicotinic Acetylcholine Receptor Attenuates Bleomycin-Induced Lung Fibrosis in Mice

“…Vagotomy reduced BLM-induced lung fibrosis (16), suggesting that acetylcholine acting on its receptor is required for the development of lung fibrosis. Here, for the first time we uncovered the mechanism that activation of acetylcholine receptor-α7 nAChR upregulates TGF-β signaling, enhances transcription of profibrotic genes and promotes fibrogenesis in human fibroblasts.…”

“…Nicotine may directly interact with α7 nAChR to increase collagen accumulation in the airway and alveolar walls following nicotine exposure in utero (27). Unilateral vagotomy was shown to attenuate deposition of collagen by decreasing numbers of fibrogenic cells and cytokines (TGF-β and IL-4) in a BLM-induced lung fibrosis mouse model (16).…”

Perinatal nicotine with or without early life influenza infection leads to lung dysfunction with age.

“…After staining tissue sections were dehydrated using standard procedures and then mounted with Vectamount mounting medium (Vector Laboratories #H5000 Burlingame, California). Quantification of collagen was conducted using ImageJ (Version 1.51k) software as previously described (139,140). For our analysis, we applied a minimum threshold level of 37 and a maximum threshold level of 190 for our Masson's trichrome stained slides (collagen).…”

“…After staining tissue sections were dehydrated using standard procedures and then mounted with Vectamount mounting medium (Vector Laboratories #H5000). Quantification of collagen was conducted using ImageJ (Version 1.51k) software as previously described (139,140).…”

“…Quantification of collagen and fibronectin was conducted using ImageJ (Version 1.51k) software. Individual lung images were imported into ImageJ software in .tiff format and analyzed as previously described (139,140). For our analysis, we applied a minimum threshold level of 37 and a maximum threshold level of 150 or 190 (14-or 30-day old mice) for our Masson's trichrome stained slides (collagen) and a minimum threshold level of 150 and a maximum threshold level of 220 was applied for our fibronectin stained slides.…”