Increased Monocyte-Derived CD11b+ Macrophage Subpopulations Following Cigarette Smoke Exposure Are Associated With Impaired Bleomycin-Induced Tissue Remodelling.

Anna Dvorkin-Gheva,Fernando M. Botelho,Joshua J. C. McGrath,Matthew F. Fantauzzi,Olivia Mekhael,Aaron I. Hayat,Kjetil Ask,Martin R. Stämpfli,Danya Thayaparan,Peiyao Wang,Christopher S. Stevenson,Steven P. Cass,Spencer D. Revill,Amir Reihani

doi:10.3389/fimmu.2021.740330

Abstract

RationaleThe accumulation of macrophages in the airways and the pulmonary interstitium is a hallmark of cigarette smoke-associated inflammation. Notably, pulmonary macrophages are not a homogenous population but consist of several subpopulations. To date, the manner in which cigarette smoke exposure affects the relative composition and functional capacity of macrophage subpopulations has not been elucidated.MethodsUsing a whole-body cigarette smoke exposure system, we investigated the impact of cigarette smoke on macrophage subpopulations in C57BL/6 mice using flow cytometry-based approaches. Moreover, we used bromodeoxyuridine labelling plus Il1a-/- and Il1r1-/- mice to assess the relative contribution of local proliferation and monocyte recruitment to macrophage accumulation. To assess the functional consequences of altered macrophage subpopulations, we used a model of concurrent bleomycin-induced lung injury and cigarette smoke exposure to examine tissue remodelling processes.Main ResultsCigarette smoke exposure altered the composition of pulmonary macrophages increasing CD11b+ subpopulations including monocyte-derived alveolar macrophages (Mo-AM) as well as interstitial macrophages (IM)1, -2 and -3. The increase in CD11b+ subpopulations was observed at multiple cigarette smoke exposure timepoints. Bromodeoxyuridine labelling and studies in Il1a-/- mice demonstrated that increased Mo-AM and IM3 turnover in the lungs of cigarette smoke-exposed mice was IL-1α dependent. Compositional changes in macrophage subpopulations were associated with impaired induction of fibrogenesis including decreased α-smooth muscle actin positive cells following intratracheal bleomycin treatment. Mechanistically, in vivo and ex vivo assays demonstrated predominant macrophage M1 polarisation and reduced matrix metallopeptidase 9 activity in cigarette smoke-exposed mice.ConclusionCigarette smoke exposure modified the composition of pulmonary macrophage by expanding CD11b+ subpopulations. These compositional changes were associated with attenuated fibrogenesis, as well as predominant M1 polarisation and decreased fibrotic activity. Overall, these data suggest that cigarette smoke exposure altered the composition of pulmonary macrophage subpopulations contributing to impaired tissue remodelling.

Highlights

A strong association has been shown between cigarette smoking and respiratory diseases such as, chronic obstructive pulmonary disease (COPD), lung cancer, and interstitial lung disease
Using the nomenclature proposed by Gibbings et al [17] (Table 1), we demonstrated an expansion of all CD11b+ populations including Mo-alveolar macrophages (AM) and IM1, -2 and – 3 at all cigarette smoke (CS) timepoints (Figure 1A)
CS exposure decreased siglecF expression in resident alveolar macrophages (Res-AM) suggesting a downregulation of cell-cell interactions (Figure S2A)

Summary

Introduction

A strong association has been shown between cigarette smoking and respiratory diseases such as, chronic obstructive pulmonary disease (COPD), lung cancer, and interstitial lung disease. The longevity of primitive AM is unclear; a second developmental wave arises from the foetal liver and enter the lungs by E12-16 [12, 13] These pre-AM enter the lumen postnatally [12, 13] and mature into long-lived tissue resident alveolar macrophages (Res-AM). Mo-AM share 99.9% of genes with Res-AM [15] but contribute to less than 5% of the Abbreviations: a-SMA, alpha-Smooth muscle actin; AM, Alveolar macrophage; BrdU, Bromodeoxyuridine; COPD, Chronic obstructive pulmonary disease; cMoP, Common monocyte progenitor; CS, Cigarette smoke; CSE, Cigarette smoke extract; E, Embryonic day; H&E, Hematoxylin & eosin; IHC, Immunohistochemistry; IM, Interstitial macrophage; LDH, Lactose dehydrogenase; LSK, Lineage negative Sca1+c-Kit+; MMP9, Matrix metallopeptidase 9; Mo-AM, Monocyte-derived alveolar macrophages; MDP, Monocyte-macrophage dendritic cell progenitor; PBS, Phosphate-buffered saline; PCA, Principal component analysis; Res-AM, Resident alveolar macrophage; RA, Room air; TMA, Tissue microarray; TGF-b, 1Transforming growth factor beta 1

Methods

Results

Conclusion