TET1 Regulates Nestin Expression and Human Airway Smooth Muscle Proliferation

Area of Science:

• Biochemistry
• Molecular Biology
• Pulmonology

Background:

• Asthma involves abnormal airway smooth muscle (ASM) proliferation, thickening the airway wall and worsening obstruction.
• The precise mechanisms driving ASM proliferation in asthma remain unclear.
• Ten-eleven translocation methylcytosine dioxygenase (TET) enzymes regulate DNA methylation by converting 5-methylcytosine to 5-hydroxymethylcytosine, impacting gene expression.

Purpose of the Study:

• To investigate the role of TET enzymes, specifically TET1, in regulating ASM proliferation in asthma.
• To explore the molecular mechanisms by which TET1 influences ASM cell growth.

Main Methods:

• Assessed TET1 activity and protein levels in human asthmatic ASM cells.
• Measured 5-hydroxymethylcytosine levels in asthmatic and non-asthmatic ASM cells.
• Utilized TET1 knockdown (KD) to assess its impact on 5-hydroxymethylcytosine, nestin expression, and the mTOR pathway.
• Examined the effect of TET1 inhibition on platelet-derived growth factor-induced signaling and ASM cell proliferation.

Main Results:

• TET1 activity and protein were elevated in asthmatic ASM cells, correlating with higher 5-hydroxymethylcytosine concentrations.
• TET1 KD, but not TET2 KD, decreased 5-hydroxymethylcytosine levels in asthmatic cells.
• TET1 KD reduced nestin expression and inhibited the mTOR pathway (including phosphorylation of p70S6K, 4E-BP, S6, and Akt).
• Inhibition of TET1 attenuated ASM cell proliferation.

Conclusions:

• TET1 plays a significant role in driving ASM proliferation in asthma.
• The TET1-mediated proliferation appears to occur through the nestin-mTOR signaling axis.
• TET1 represents a potential therapeutic target for managing asthma-related airway remodeling.