PhD Scientific Days 2024

Poster Session T - Cardiovascular Medicine and Research 3.

The Effects of 25-hydroxycholesterol on Signaling Events in Vascular Smooth Muscle Cells

Text of the abstract

Cholesterol-25-hydroxylase (CH25H) catalyzes the production of 25-hydroxycholesterol (25-HC). 25-HC is both a cholesterol metabolite and a bioactive molecule. 25-HC was shown to be a mediator of immunological processes and an actor in the pathology of atherosclerosis. Our group found that angiotensin II promotes Ch25h upregulation and 25-HC production in vascular smooth muscle cells (VSMCs).
Our aim is to explore the effects of 25-HC on signalization in VSMCs.
Primary rat VSMCs and A7R5 VSMC line were used during the course of the study. VSMCs were treated with 25-HC and subjected to Western blot procedure to detect phosphorylation of focal adhesion kinase (FAK). Ras activation in A7R5 cells was investigated with bioluminescence resonance energy transfer (BRET).
VSMCs showed a significantly increased FAK phosphorylation on the Y397 residue when treated with 25-HC (50 µM) for 1 hour compared to control group treated with vehicle (ethanol). We found that even at a concentration of 5 µM 25-HC promoted FAK phosphorylation.
To examine Ras activity A7R5 cells recieved 25-HC (50 µM) treatment then were stimulated with epidermal growth factor (EGF). Compared to the ethanol-treated group Ras activation was less sustained after a 6 hour long 25-HC treatment.
Intriguingly, 25-HC induced the activation of FAK in VSMC. Literature data shows that 25-HC activates FAK-related pathways in macrophages by binding integrins. However, there had been no information of such process in VSMCs. Furthermore, we showed that 25-HC treatment was able to interfere with EGF signalization, as indicated by the alteration of Ras activity after 25-HC treatment. The exact mechanism of action cannot be confidently concluded based on our BRET data. Other studies found that 25-HC in the plasma membrane can modify membrane fluidity and thus lipid rafts, which might explain alterations of receptor signalizations.
Our present study showed for the first time that 25-HC promotes FAK phosphorylation in VSMCs, and is able to influence EGF signalization. These findings suggest that 25-HC released by VSMCs has the potential to exert regulatory actions on signaling events in VSMC.
Funds:
Semmelweis 250+ Excellence PhD Scholarship
SUPPORTED BY THE ÚNKP-23-3-II NEW NATIONAL EXCELLENCE PROGRAM OF THE MINISTRY FOR CULTURE AND INNOVATION FROM THE SOURCE OF THE NATIONAL RESEARCH, DEVELOPMENT AND INNOVATION FUND