Tc17 cells are associated with cigarette smoke-induced lung inflammation and emphysema

Abstract

Some types of T lymphocytes, especially cytotoxic T-cells (Tc1) and T-helper (Th17) cells, play a pivotal role in cigarette smoke-induced lung diseases. However, whether Tc17 cells are involved remains largely unknown. We investigated Tc17 involvement using a cigarette smoke-exposure model.Groups of mice were exposed to cigarette smoke or filtered air. At weeks 2, 8, 12 and 24, mice were sacrificed to observe histological changes by HE stain and/or immunohistochemical staining. The frequency of T cell subsets in the lung and spleen were detected by flow cytometry. In addition, the expression levels of T cell-related factors were measured by real-time polymerase chain reaction or enzyme-linked immunosorbent assay.Cigarette smoke caused substantial inflammatory cell infiltration and led to emphysema. Cigarette smoke exposure promoted the expression of interferon-gamma (IFN)-γ and interleukin (IL)-17A at the messenger ribonucleic acid and protein levels. In addition to Tc1 and Th17 cells, pulmonary and splenic Tc17 cells increased, which was accompanied by the upregulation of cytokines IL-6, transforming growth factor beta (TGF)-β) and transcriptional factors Stat3 and RAR-related orphan receptor gamma. Compared with untreated mice, γH2AX-positive cells were more frequently observed in mice exposed to cigarette smoke.Long-term cigarette smoke exposure induced Tc17 cell expansion both locally and distally, which was associated with emphysema and deoxyribonucleic acid damage. As an important source of IL-17A, this T cell subset may be a potential target for chronic obstructive pulmonary disease therapy.