Triiodothyronine Potentiates Vasorelaxation via PKG/VASP Signaling in Vascular Smooth Muscle Cells

Abstract

Background/Aims: Vascular relaxation caused by Triiodothyronine (T3) involves direct activation of endothelial cells (EC) and vascular smooth muscle cells (VSMC). Activation of protein kinase G (PKG) has risen as a novel contributor to the vasorelaxation mechanism triggered by numerous stimuli. We hypothesize that T3-induced vasorelaxation involves PKG/vasodilator-stimulated phosphoprotein (VASP) signaling pathway in VSMC. Methods: Human aortic endothelial cells (HAEC) and VSMC were treated with T3 for short (2 to 60 minutes) and long term (24 hours). Nitric oxide (NO) production was measured using DAF-FM. Expression of protein targets was determined using western blot. For functional studies, rat aortas were isolated and treated with T3 for 20 minutes and mounted in a wire myograph. Relaxation was measured by a concentration-dependent response to acetylcholine (ACh) and sodium nitroprusside (SNP). Results: Aortas stimulated with T3 exhibited augmented sensitivity to ACh and SNP-induced relaxation, endothelium-dependent and endothelium-independent responses, respectively. T3 directly increased vasorelaxation, which was abolished in the presence of a PKG inhibitor. T3 markedly induced phosphorylation of Akt, eNOS and consequently increased NO production in EC. Likewise, T3 induced phosphorylation of VASP at serine 239 via the PKG pathway in VSMC. Conclusion: Our findings have uncovered a PKG/VASP signaling pathway in VSMC as a key molecular mechanism underlying T3-induced vascular relaxation.

Triiodothyronine Reduces Vascular Dysfunction Associated with Hypertension by Attenuating Protein Kinase G/Vasodilator-Stimulated Phosphoprotein Signaling

“…T3 Activates PKG/VASP Signaling in the Aortas of HS-Treated Rats. Based on our previous study showing that T3 promotes vascular relaxation via a PKG/VASP signaling pathway in cultured vascular smooth muscle cells (VSMC) (Samuel et al, 2017), we examined whether improvement of function in hypertensive aortas caused by short-term treatment with T3 is associated with activation of PKG/VASP signaling. The immunoblot analysis revealed that expression of PKG in aortas from the HS group was significantly reduced in comparison with the LS group (Fig.…”

“…The aortas were treated with 0.1 mM T3 (Sigma-Aldrich) for 30 minutes. The concentration of T3 was chosen based on results from a previous study (Samuel et al, 2017). A stock solution of T3 was made by dissolving T3 in DMSO (ATCC) and further diluted in Krebs solution.…”

“…Total protein was extracted from the aortas of HS and LS rats after treatment with 0.1 mM T3 for 30 minutes. Equivalent amounts of protein (40 mg) were loaded and separated by 10% SDS-PAGE, and transferred to polyvinylidene fluoride membranes (Thermo Fisher Scientific, Rockfold, IL) as previously described elsewhere (Samuel et al, 2017). The membranes were blocked for 1 hour with 5% nonfat milk solution in Tris-buffered saline with 0.1% Tween-20 (TBST), then incubated overnight at 4°C with the following specific primary antibodies: PKG (1:1000, catalog no.3248; Cell Signaling Techonology, Danvers, MA), total and phosphorylated VASP (1:1000, catalog no.…”

“…known to cause rapid vascular relaxation and likely plays a crucial role in vascular homeostasis (Samuel et al, 2017). Our group has recently identified that T3 improves vascular function via a nongenomic mechanism involving the protein kinase G/vasodilator-stimulated phosphoprotein (PKG/VASP) signaling pathway (Samuel et al, 2017). In the current study, we determined whether T3 can improve vascular function in Dahl SS rats.…”

Alzheimer's Disease and Type 2 Diabetes: A Critical Assessment of the Shared Pathological Traits

“…Mass spectrometry on STZ-induced diabetic rats showed high levels of lysine-acetylated proteins in their kidney cells compared to control animals (Kosanam et al, 2014 ). Also, treatment of murine aorta cells with high glucose or FFA to induce short term diabetes causes increased levels of lysine acetylation (Samuel et al, 2017 ). Although, there are very few reports, aberrant acetylation of tau in T2DM may interfere with the physiological functions of microtubule binding and assembly predisposing cytoplasmic tau toward the formation of aggregates (Irwin et al, 2013 ; Trzeciakiewicz et al, 2017 ).…”