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A4634 - Macrophage Migration Inhibitory Factor Protects Against Cigarette Smoke-Induced Senescence
Author Block: S. Kim1, I. S. Bazan1, P. Shan1, M. Sauler1, L. Leng2, R. Bucala2, P. Lee1; 1Section of Pulmonary, Critical Care and Sleep Medicine, Yale University School of Medicine, New Haven, CT, United States, 2Section of Rheumatology, Yale University School of Medicine, New Haven, CT, United States.
RATIONALE: Chronic obstructive pulmonary disease (COPD) is characterized by gradual destruction of alveolar architecture and subsequent airflow obstruction. Advancing age and significant exposures to cigarette smoke (CS) are the most common risk factors. Cellular senescence and apoptosis have been implicated as important mechanisms for COPD. However, crucial executors of these underlying mechanisms remain unknown. Macrophage migration inhibitory factor (MIF) is an important regulator of innate immunity, cellular homeostasis and survival. We reported that circulating MIF was lower in smokers with COPD compared with smokers without COPD. Others have confirmed these findings and correlated decreased MIF protein with greater radiologic/functional evidence of emphysema in people. Reports have also found MIF to be released by senescent cells, thus identifying MIF as a senescence-associated secretory phenotype. Therefore, we investigated the effect of MIF on CS-induced senescence.
METHODS: CS extract (CSE) was prepared by bubbling smoke from one research grade cigarette into media, and sterile filtered before use. Human umbilical vein endothelial cells (HUVECs) were cultured in 1% fetal bovine serum-contained M199 media and incubated respectively with 0, 3 and 5% CSE for 24 h. To determine the effect of MIF on CSE-induced senescence, HUVECs were incubated with MIF020 (100 nM), a MIF agonist, or MIF098 (5 μM), a MIF antagonist, for 24 h with 3% CSE, and senescence-associated beta-galactosidase (SA-β-gal) staining was performed. HUVECs were incubated with 100 ng/mL human recombinant-MIF (rMIF) for 0, 30, 60 and 90 min and the protein expressions were measured by western blot.
RESULTS: CSE significantly induced senescence in HUVECs, indicated by increased SA-β-gal positive cells by 2.9- (3% CSE) and 1.9-fold (5% CSE), respectively, compared with the control group. This increase was attenuated by MIF020, while it was augmented by MIF098. Incubation
of HUVECs with rMIF induced phosphorylated (p)-ERK1/2 and p-Akt in a time-dependent manner.
CONCLUSIONS: Senescence was induced in endothelial cells by CS, an important causative factor for COPD. MIF020 attenuated this increased senescence in endothelial cells, whereas MIF098 had the opposite effect. Furthermore, activation of MIF signaling with rMIF induced ERK and Akt signaling pathway, which are known to support cell survival and proliferation. These data suggest that therapeutic manipulation of MIF targeting lung endothelial cells may be a novel strategy to protect against senescence-induced COPD. Further studies will define the range of anti-senescence effects of MIF agonists and elucidate the precise molecular mechanisms, as well as test the impact of MIF020 in vivo.