Erythromycin inhibits the differentiation of NCR-ILC3s activated by lung dendritic cells in mice exposed to cigarette smoke.

BACKGROUND

Both dendritic cells (DCs) and nature cytotoxicity receptor-negative 3-type innate lymphoid cells (NCR-ILC3s) have been implicated in chronic lung inflammation in mice with cigarette smoke (CS)-induced chronic obstructive pulmonary disease (COPD). Our study aims to investigate whether erythromycin (EM) can suppress the differentiation of ILC3s into NCR-ILC3s through restraining DCs activation and therefore attenuate CS-related lung injuries in COPD mice.

METHODS

Our study comprised both in vivo and in vitro experiments. In the former, lung samples were collected from non-smokers, smokers, patients with stable COPD, as well as mice exposed to air, CS, and CS combined with EM, respectively. In the latter, lung DCs sifted by CD11c magnetic beads from mice exposed to either air or CS were co-cultured with lung CD45+Lin-CD127+ILCs sorted from air-exposed mice. EM was added to the co-culture involving DCs from CS-exposed mice. Flow cytometry and other assays were used to examine the quantities of NCR-ILC3s, DCs, relevant costimulatory molecules and cytokines in human tissues, mice lungs, and cell cultures.

RESULTS

Compared to non-smokers, lung NCR-ILC3s frequencies significantly increased in both smokers and COPD patients, and inversely correlated with forced expiratory volume in 1 second percent predicted (FEV1% pred) and diffusing capacity for carbon monoxide (P<0.05). CS-exposed mice showed evident emphysema and elevated frequencies of lung NCR-ILC3s and DCs. In contrast, mice receiving CS and EM displayed attenuated emphysema and reduced levels of NCR-ILC3s and DCs (P<0.05). In co-culture experiments, NCR-ILC3s frequencies were markedly higher when DCs were derived from CS-exposed mice than from air-exposed mice. This increase was substantially reversed by the addition of EM (P<0.05).

CONCLUSIONS

Lung NCR-ILC3s frequencies escalate consistently in smokers, COPD patients, and CS-exposed mice. In CS-exposed mice, EM can inhibit DC-mediated NCR-ILC3s activation in the lungs, alleviate CS-related chronic lung inflammation, and ameliorate emphysema.