Mitochondrial reactive oxygen species and glycolysis in airway smooth muscle cell proliferation in COPD

Abstract

Background: Airway smooth muscle (ASM) thickening in COPD results from ASM cell (ASMC) hyperplasia and hypertrophy. Transforming growth factor (TGF)-β, which is up-regulated in COPD, is a key driver of ASMC hyperplasia. The balance between mitochondrial respiration and glycolysis, and mitochondrial reactive oxygen species (ROS) levels are major determinants of cell survival. We hypothesised that TGF-β drives ASMC hyperplasia in COPD by skewing the balance between mitochondrial and glycolytic function. Aims and Objectives: Determine the effect of TGF-β on the proliferation, mitochondrial ROS production and metabolic gene expression of COPD and healthy smoker and non-smoker ASMCs. Methods: ASMCs were cultured from bronchoscopic biopsies of patients with COPD and healthy smokers and non-smokers. mRNA was measured by real-time PCR, and cell proliferation by BrdU incorporation. Mitochondrial ROS were detected by MitoSOX staining. Results: TGF-β (1ng/ml) with FBS (2.5%) increased ASMC proliferation and this effect was stronger in ASMCs from COPD patients (n=9) compared to healthy non-smokers (n=4; p<0.05). TGF-β/FBS increased mitochondrial ROS in ASMCs from healthy non-smokers (n=5; p<0.05) but not in healthy smokers (n=4) and COPD patients (n=7). TGF-β/FBS increased glucose transporter (GLUT)-1, hexokinase (HK)-2, pyruvate dehydrogenase kinase (PDK)-1 and lactate dehydrogenase (LDHA) mRNA levels (n=3-5/group), and 2-deoxy-D-glucose, an inhibitor of glycolysis, inhibited TGF-β/FBS-mediated proliferation of ASMCs of all groups (n=4-7/group). Conclusions: Modulation of mitochondrial ROS levels and glycolysis by TGF-β may be involved in ASMC hyperplasia in COPD.