PhD Scientific Days 2023

Molecular Sciences - Posters B

The Substantial Role of p38-MAP Kinase in Angiotensin II-induced Cholesterol-25-hydroxylase Upregulation and 25-hydroxycholesterol Effects in Vascular Smooth Muscle Cells

Text of the abstract

The renin-angiotensin-aldosterone system exerts crucial effects on the vasculature mainly due to the hormone angiotensin II (AngII). Excessive AngII signaling events contribute to cardiovascular disease development and progression. Our group established the role of AngII in the upregulation of cholesterol-25-hydroxylase (CH25H) in vascular smooth muscle cells (VSMCs), a type 1 AngII receptor (AT1R) dependent effect. The oxysterol product of the enzyme, 25-hydroxycholesterol (25-HC), has been implicated in various VSMC related pathological processes.
This study aims to explore the signal transduction leading to the Ch25h upregulation and subsequent actions of 25-HC on VSMCs.
The study was conducted using primary rat VSMCs. VSMCs that received inhibitor treatments and AngII stimulus were analyzed with qRT-PCR to assess Ch25h mRNA levels, and protein phosphorylation was observed with Western blot. To find out the effects of 25-HC on integrin signaling VSMCs were treated with 25-HC and FAK phosphorylation was measured.
Our results show that the AngII-induced Ch25h expression is abolished in the groups treated with Gq/11 or p38 MAPK inhibitors. The inhibitors caused a reduced phosphorylation of the p38 MAPK. Furthermore, the impaired activity of p38 MAPK led to a decrease in STAT1 phosphorylation at the 727 serine residue. In cells treated with 25-HC, we observed an increase of FAK phosphorylation on the 397 tyrosine residue.
Our data show that the activation of p38 MAPK by the AT1R signalization is crucial to the upregulation of Ch25h expression in VSMCs. This conclusion is in line with previous studies investigating Ch25h expression in immune cells. The downstream targets of p38 MAPK include transcription factors (TF). There is evidence in the literature that STAT1 TF activity is necessary for Ch25h expression. In our experiments the reduction of STAT1 phosphorylation due to p38 MAPK inhibition suggests that p38 MAPK contributes to Ch25h expression via STAT1 activation. However, to further confirm the role of STAT1 in Ch25h expression additional investigations are needed. A notable finding of our work is the 25-HC induced increase of FAK phosphorylation. This piece of data shows that 25-HC can activate FAK signalization in VSMCs. FAK signaling effects VSMC proliferation, and proinflammatory events, thus it has implications in the physiological and pathological processes of the vasculature.
In conclusion our study demonstrated the importance of p38 MAPK activity in AngII induced Ch25h upregulation in VSMCs, and the possible role of STAT1 transcription factor. The observation of 25-HC induced FAK activity suggests a potential way in which 25-HC released by VSMCs affects surrounding cells in the vessel wall.
Funding: EFOP-3.6.3-VEKOP-16-2017-00009