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TNFα Induces Mitochondrial Fragmentation and Mitochondrial Biogenesis in Human Airway Smooth Muscle Cells
Author(s) -
Kaul Esha Sharika,
Delmotte Philippe,
Sieck Gary C
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.690.3
Subject(s) - mfn2 , microbiology and biotechnology , mitochondrion , mitochondrial fusion , mitochondrial biogenesis , mitochondrial fission , biology , fragmentation (computing) , chemistry , mitochondrial dna , biochemistry , ecology , gene
Airway inflammation is a key aspect of asthma and is associated with airway smooth muscle (ASM) hyperreactivity (airway narrowing due to increased Ca 2+ and force responses to agonist stimulation) as well as airway remodeling (ASM cell proliferation and altering extracellular matrix composition). Proinflammatory cytokines, such as TNF‐α mediate this airway inflammatory response. Previously, we found that the TNF‐α induces an increase ASM force, which is associated with an increase in ATP hydrolysis, imposing a metabolic stress on ASM. Mitochondria play an important role in providing ATP to support contraction in ASM. Mitochondria are dynamically remodelling within ASM cells displaying changing filamentous or fragmented tubular networks. Changing expression of Mitofusin 2 (Mfn2), which is associated with mitochondria fusion, or Dynamin Related Protein 1 (Drp1), which is associated with fission mediate this mitochondrial remodelling. The stressors that induce mitochondrial remodelling in ASM are unknown, but mitochondrial fragmentation may be an initial step in mitochondrial biogenesis to meet increasing energy demand. We hypothesized that human ASM (hASM) cells exposed to TNF‐α will display reduced Mfn2 and increased Drp1 expression resulting in mitochondrial fragmentation and mitochondrial biogenesis. To test our hypothesis, serum‐deprived primary hASM cells were exposed to 20 ng/ml TNF‐α for 24 h after which they were loaded with 500 μM MitoTracker Green to visualize mitochondria and imaged using confocal microscopy. Images were analyzed using MATLAB Image J software to quantify mitochondrial morphometry: form factor and aspect ratio. An increase in form factor and aspect ratio indicates greater mitochondrial filamentous networks. Expression of Mfn2 and Drp1 were determined by Western blot analysis. In hASM exposed to TNF‐α, Mfn2 expression decreased by ~40%, while Drp1 expression increased by ~75% compared to controls. These changes in fusion/fission proteins were associated with mitochondrial fragmentation (reduced form factor and aspect ratio) and an increase in mitochondria number. Our results indicate that hASM cells exposed to TNF‐α display mitochondrial fragmentation due to changes in Mfn2 and Drp1 expression. Mitochondrial fragmentation may be involved in mitochondrial biogenesis in response to increased metabolic demands imposed by airway hyperreactivity. Support or Funding Information APS fellowship (EK) and NIH grant HL126451 (GCS)