Nitrooleate mediates nitric oxide synthase activation in endothelial cells

Area of Science:

• Cardiovascular Biology
• Lipid Biochemistry
• Molecular Pharmacology

Background:

• Nitrated lipids, such as nitrooleate (OLA-NO2), are endogenous peroxisome proliferator-activated receptor gamma (PPARγ) ligands with known vascular protective effects.
• The precise molecular mechanisms by which OLA-NO2 influences nitric oxide (NO) production and endothelial nitric oxide synthase (eNOS) regulation in the vasculature remain incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying OLA-NO2-mediated nitric oxide (NO) production and endothelial nitric oxide synthase (eNOS) activation in endothelial cells.
• To investigate the role of protein-protein interactions and post-translational modifications of eNOS in response to OLA-NO2 treatment.

Main Methods:

• Endothelial cells were treated with OLA-NO2 (3 μM) to assess NO release, protein expression (eNOS, caveolin-1, Hsp90), and eNOS activity.
• Immunoprecipitation assays were performed to analyze the interaction between eNOS, caveolin-1 (Cav-1), and heat shock protein 90 (Hsp90).
• Western blotting was used to detect eNOS phosphorylation and dephosphorylation at specific sites (Ser633, Ser1177, Ser113, Thr495), as well as the phosphorylation of Akt and extracellular signal-regulated protein kinase (ERK1/2).

Main Results:

• OLA-NO2 treatment increased NO release in a time-dependent manner.
• Protein expression analysis revealed decreased levels of eNOS and Cav-1, alongside increased Hsp90 expression.
• Immunoprecipitation confirmed a shift from eNOS/Cav-1 to eNOS/Hsp90 interaction, enhancing eNOS activity. OLA-NO2 also induced specific eNOS phosphorylation/dephosphorylation patterns and activated Akt and ERK1/2 signaling pathways.

Conclusions:

• Nitrated fatty acid OLA-NO2 exerts vascular protective effects by significantly increasing NO bioavailability.
• This protective effect is mediated by modulating eNOS activity through altered protein interactions (eNOS/Hsp90 complex formation) and specific phosphorylation/dephosphorylation events.
• The findings reveal a novel mechanism for OLA-NO2 in regulating vascular function, highlighting its potential therapeutic relevance.