Angiotensin II Upregulates the Expression of an Oxysterol Producing Enzyme: Cholesterol-25-Hydroxylase in Vascular Smooth Muscle Cells
Kovács Kinga Bernadett
Molecular Medicine
Dr. Enyedi Péter
SE Élettani Intézet könyvtára
2025-03-03 13:00:00
Cellular and Molecular Physiology
Dr. Hunyady László
Dr. Balla András
Dr. Zákány Róza
Dr. Sipeki Szabolcs
Dr. Ambrus Attila
Dr. Dézsi László
Dr. Oláh Judit
CVD presents major health problems globally. Both the vasoactive hormone AngII and the oxysterol 25-HC contribute to the development of vascular pathologies, thus CVD. In this PhD work, we investigated the relationship between CH25H, the enzyme responsible for 25-HC production, and AngII. We aimed to uncover the AngII-induced gene expression changes and the signaling pathways that lead to them. The major finding of this thesis is the demonstration of AngII-induced Ch25h upregulation in primary rat VSMCs. We determined that Ch25h upregulation depends on AT1R and Gq/11 activation. We examined the role of MAPKs. ERK1/2 inactivity somewhat reduced AngII-induced Ch25h upregulation. Instead, we found p38 MAPK to be the crucial kinase that enables Ch25h upregulation upon the AngII stimulus. Furthermore, we found that p38 MAPK activity is necessary for the AngII-induced phosphorylation of STAT1 transcription factor, which might be the transcription factor responsible for Ch25h upregulation. We further examined whether the ERK1/2 and p38 MAPK mediate AngII-induced Dusp upregulation to assess their role in AngII-induced gene expression changes other than Ch25h. We showed that p38 MAPK is necessary for both Dusp5 and Dusp6 upregulation. However, ERK1/2 is significant only in Dusp6 upregulation. In contrast, Dusp10 expression was not significantly influenced either by p38 MAPK or ERK1/2 inhibition. In addition to signaling pathways, we examined the CH25H protein and its product. Using fluorescently labeled fusion proteins, we determined that CH25H localizes to the ER in VSMCs. Importantly, we identified the increase of 25-HC concentration in the supernatant of AngII-stimulated VSMCs, indicating the functionality of CH25H in this cell type. In this study, we established that AngII upregulates Ch25h expression and that VSMCs can be a source of 25-HC production, which was previously not documented in the literature. We found that the activation of growth-related signaling by AT1R is needed for the AngII-induced Ch25h upregulation. We demonstrated that p38 MAPK orchestrates not only the AngII-induced Ch25h upregulation but the upregulation of other genes affected by the hormone, namely Dusp5 and Dusp6 [37,103]. Furthermore, we showed that AngII stimulus causes 25-HC level elevation in VSMC cultures, which is notable since 25-HC has the potential to act as an autocrine or paracrine mediator in the vessel wall.
