Abnormal Ribosome Biogenesis Partly Induced p53-Dependent Aortic Medial Smooth Muscle Cell Apoptosis and Oxidative Stress

Abstract

Ribosome biogenesis is a crucial biological process related to cell proliferation, redox balance, and muscle contractility. Aortic smooth muscle cells (ASMCs) show inhibition of proliferation and apoptosis, along with high levels of oxidative stress in aortic dissection (AD). Theoretically, ribosome biogenesis should be enhanced in the ASMCs at its proliferative state but suppressed during apoptosis and oxidative stress. However, the exact status and role of ribosome biogenesis in AD are unknown. We therefore analyzed the expression levels of BOP1, a component of the PeBoW complex which is crucial to ribosome biogenesis, in AD patients and a murine AD model and its influence on the ASMCs. BOP1 was downregulated in the aortic tissues of AD patients compared to healthy donors. In addition, overexpression of BOP1 in human aortic smooth muscle cells (HASMCs) inhibited apoptosis and accumulation of p53 under hypoxic conditions, while knockdown of BOP1 decreased the protein synthesis rate and motility of HASMCs. The RNA polymerase I inhibitor cx-5461 induced apoptosis, ROS production, and proliferative inhibition in the HASMCs, which was partly attenuated by p53 knockout. Furthermore, cx-5461 aggravated the severity of AD in vivo, but a p53-/- background extended the life-span and lowered AD incidence in the mice. Taken together, decreased ribosome biogenesis in ASMCs resulting in p53-dependent proliferative inhibition, oxidative stress, and apoptosis is one of the underlying mechanisms of AD.

BOP1 Knockdown Attenuates Neointimal Hyperplasia by Activating p53 and Inhibiting Nascent Protein Synthesis

“…The immunofluorescence revealed that p53-positive cells in the media and neointimal significantly increased after BOP1 knockdown in the ligated mouse carotid artery, compared with the LV-SCR group ( Figure 2(j) ). Our previous study depicted that overexpression of BOP1 attenuated ROS production and cell apoptosis under serum-free and hypoxic conditions of HVSMCs in a p53-dependent way [ 13 ]. We therefore detected 8-hydroxy-2-deoxyguanosine (8-OHdG), a biomarker indicated the DNA damage induced by ROS, in the ligated carotid artery.…”

“…Our previous study revealed that the BOP1 knockdown may induce AMD through the upregulation of p53 [ 13 ]. As BOP1 is highly conserved in mammalian cells, and ribosome biogenesis also plays critical functions within normal cells, we tested the local intervention approach to avoid system side effects, in line with the practice of the clinical stent system.…”

“…To study the role of p53 on migration capacity change, HVSMCs were pretreated with 10 μ M PFT- α or DMSO followed by resuspended and cotreated with 20 ng/ml platelet-derived growth factor-BB (PDGF-BB; MedChemExpress, # HY-P7055, China). The ability of cell migration was evaluated via wound healing assay as our previous described [ 13 ].…”

“…Cell doublets were excluded by gating on the fluorescence width versus area plot, and the proportion of cells in each phase of the cell cycle was determined by flow cytometry. The cytometric analysis of cell apoptosis and detection of reactive oxygen species (ROS) by flow cytometry were conducted, as previously described [ 13 ]. Data acquisition was executed using CytoFLEX (BC43326, Beckman, USA) and further analyzed with FlowJo software.…”

“…The repressing BOP1 function may alter the chromosome segregation or inhibit the cell migration ability via inhibiting RhoA and the actin stress fiber assembly [ 11 ], while overexpressing BOP1 increases the production of multipolar spindles in cells, which contributes to the progression of colorectal tumorigenesis [ 12 ]. The previous research conducted by the investigators revealed that BOP1 induces aortic media degeneration (AMD) in the process of aortic aneurysm/dissection (AA/AD) through accelerating p53-dependent VSMC apoptosis and oxidative stress [ 13 ]. Hence, it was assumed that BOP1 may be closely correlated to vascular homeostasis and play a vital role in neointimal hyperplasia.…”