Cigarette smoke-induced mitochondrial fragmentation and dysfunction in human airway smooth muscle

Abstract

The balance between mitochondrial fission and fusion is crucial for mitochondria to perform its normal cellular functions. We hypothesized that cigarette smoke (CS) disrupts this balance and enhances mitochondrial dysfunction in the airway. In nonasthmatic human airway smooth muscle (ASM) cells, CS extract (CSE) induced mitochondrial fragmentation and damages their networked morphology in a concentration-dependent fashion, via increased expression of mitochondrial fission protein dynamin-related protein 1 (Drp1) and decreased fusion protein mitofusin (Mfn) 2. CSE effects on Drp1 vs. Mfn2 and mitochondrial network morphology involved reactive oxygen species (ROS), activation of extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), protein kinase C (PKC) and proteasome pathways, as well as transcriptional regulation via factors such as NF-κB and nuclear erythroid 2-related factor 2. Inhibiting Drp1 prevented CSE effects on mitochondrial networks and ROS generation, whereas blocking Mfn2 had the opposite, detrimental effect. In ASM from asmatic patients, mitochondria exhibited substantial morphological defects at baseline and showed increased Drp1 but decreased Mfn2 expression, with exacerbating effects of CSE. Overall, these results highlight the importance of mitochondrial networks and their regulation in the context of cellular changes induced by insults such as inflammation (as in asthma) or CS. Altered mitochondrial fission/fusion proteins have a further potential to influence parameters such as ROS and cell proliferation and apoptosis relevant to airway diseases.

Mechanisms of BDNF regulation in asthmatic airway smooth muscle

“…ASM cells were transfected with 200 pM siRNA [against TRPC1, TRPC3, TRPC6, or cAMP response element binding protein (CREB)] under serum-and antibiotic-free conditions using Lipofectamine (Invitrogen, Carlsbad, CA) (6,44). Vehicle-alone treatment and transfection with scrambled nontargeting RNA served as controls.…”

Mitochondria in lung disease

“…35 and Figure 2). Hyperfusion has been documented in COPD and in lung cancer (17,18,37,38), whereas loss of fusion, specifically loss of MFN2, has been associated with lung cancer (38) and PH (39). The role of mitochondrial fission and fusion in lung cancer may be microenvironment specific; increased fission may allow cancer cells to proliferate rapidly and invade the surrounding tissue, while increased fusion may allow for cell survival during times of stress or drug toxicity (27).…”

1α,25-Dihydroxyvitamin D3 Regulates Mitochondrial Oxygen Consumption and Dynamics in Human Skeletal Muscle Cells

“…To assess the extent of filamentous versus fragmented morphometry, the form factor (an index of mitochondrial branching) and aspect ratio (an index of mitochondrial branch length) were calculated for each cell using a custom-written MATLAB (The MathWorks)-based program (36,37). A decrease in aspect ratio and/or form factor indicates mitochondrial fragmentation (33)(34)(35)(36)(37).…”