Newby, A. C. | bioRxiv Science

bioRxiv2023

Extracellular Matrix Stiffness Promotes Vascular Smooth Muscle Cell Calcification by Reducing The Levels of Nuclear Actin Monomers

1.0BackgroundVascular calcification (VC) is a prevalent independent risk factor for adverse cardiovascular events and is associated with diabetes, hypertension, chronic kidney disease, and atherosclerosis. However, the mechanisms regulating the osteogenic differentiation of vascular smooth muscle cells (VSMC) are not fully understood. MethodsUsing hydrogels of tuneable stiffness and lysyl oxidase-mediated stiffening of human saphenous vein ex vivo,we investigated the role of extracellular matrix (ECM) stiffness in the regulation of VSMC calcification ResultsWe demonstrate that increased ECM stiffness enhances VSMC osteogenic differentiation and VSMC calcification. We show that the effects of ECM stiffness are mediated via a reduction in the level of actin monomer within the nucleus. We show that in cells interacting with soft ECM, elevated levels of nuclear actin monomer repress osteogenic differentiation and calcification by repressing YAP-mediated activation of both TEA Domain transcription factor (TEAD) and RUNX Family Transcription factor 2 (RUNX2). ConclusionThis work highlights for the first time the role of nuclear actin in mediating ECM stiffness-dependent VSMC calcification and the dual role of YAP-TEAD and YAP-RUNX2 transcriptional complexes. 2.0 GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/545506v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@132edd1org.highwire.dtl.DTLVardef@9b59e2org.highwire.dtl.DTLVardef@12a1c55org.highwire.dtl.DTLVardef@1aa3e2e_HPS_FORMAT_FIGEXP M_FIG C_FIG 9.0 HIGHLIGHTSO_LIIncreased ECM stiffness promotes VSMC calcification. C_LIO_LIIncreased ECM stiffness reduces levels of nuclear actin monomer. C_LIO_LIOn physiological soft ECM, high levels of nuclear actin monomer inhibits calcification by repressing YAP activation. C_LIO_LIYAP activation promotes calcification by stimulating the activity of TEAD and RUNX2. C_LI

cell biology↗

bioRxiv2019

A pivotal role for Nrf2 in endothelial detachment- implications for endothelial erosion of stenotic plaques

Endothelial erosion of atherosclerotic plaques and resulting thrombosis causes approximately 30% of acute coronary syndromes (ACS). As changes in the haemodynamic environment strongly influence endothelial function and contribute to plaque development, we reconstructed the coronary artery geometries of plaques with thrombi overlying intact fibrous caps from 17 ACS patients and performed computational fluid dynamic analysis. The results demonstrated that erosions frequently occur within areas of stenosis exposed to elevated flow. We recapitulated this flow environment in vitro, exposing human coronary artery endothelial cells to elevated flow and modelled smoking (a risk factor for erosion) by exposure to a combination of aqueous cigarette smoke extract and TNF. This treatment induced endothelial detachment, which increased with pharmacological activation of the antioxidant system controlled by transcription factor Nrf2 (encoded by NFE2L2). The expression of Oxidative Stress Growth INhibitor genes OSGIN1 and OSGIN2 increased under these conditions and also in the aortas of mice exposed to cigarette smoke. Sustained high level expression of OSGIN1+2 resulted in cell cycle arrest, induction of senescence, loss of focal adhesions and actin stress fibres, and dysregulation of autophagy. Overexpression of either Nrf2 or OSGIN1+2 induced cell detachment, which did not depend on apoptosis, and could be partially rescued by inhibition of HSP70 using VER-155008, or AMP kinase activation using metformin. These findings demonstrate that under elevated flow, smoking-induced hyperactivation of Nrf2 can trigger endothelial cell detachment, highlighting a novel mechanism that could contribute to ACS involving endothelial erosion overlying stenotic plaques.

cell biology↗