mTOR contributes to endothelium-dependent vasorelaxation by promoting eNOS expression and preventing eNOS uncoupling

Area of Science:

• Vascular Biology
• Molecular Medicine
• Cell Signaling

Background:

• Clinically used mammalian target of rapamycin (mTOR) inhibitors negatively impact endothelial-dependent vasodilatation (EDD).
• The precise mechanisms underlying this impairment remain unidentified.
• Endothelial dysfunction contributes to various cardiovascular diseases.

Purpose of the Study:

• To elucidate the mechanisms by which mTOR inhibition affects endothelial function and nitric oxide (NO) production.
• To differentiate the roles of mTORC1 and mTORC2 in regulating endothelial-dependent vasodilatation.
• To identify potential therapeutic targets for restoring EDD in mTOR-inhibited conditions.

Main Methods:

• Endothelium-specific deletion of Mtor in mice to inhibit both mTOR complexes.
• Depletion of Raptor or Rictor to selectively disrupt mTORC1 or mTORC2.
• Measurement of NO levels in mouse serum and endothelial cells (EC).
• Analysis of eNOS gene expression, KLF2 regulation, MAPK activation, and reactive oxygen species (ROS) generation.

Main Results:

• Endothelium-specific Mtor inhibition, or disruption of mTORC1/mTORC2, impaired EDD and reduced serum NO.
• mTORC1 inhibition suppressed eNOS gene expression via impaired p70S6K-mediated KLF2 regulation.
• mTORC2 inhibition led to excessive ROS generation, eNOS uncoupling, and decreased NO bioavailability through MAPK activation and Nox2 upregulation.
• Adeno-associated virus-mediated KLF2 overexpression or Nox2 suppression restored EDD in inhibited mice.

Conclusions:

• mTORC1 and mTORC2 regulate EDD through distinct molecular pathways involving NO production.
• mTORC1 affects EDD by modulating eNOS expression via KLF2.
• mTORC2 impacts EDD by promoting oxidative stress and eNOS uncoupling.
• Targeting KLF2 or Nox2 may offer therapeutic strategies to counteract mTOR inhibitor-induced endothelial dysfunction.