Apocynin attenuates angiotensin II-induced vascular smooth muscle cells osteogenic switching via suppressing extracellular signal-regulated kinase 1/2

Abstract

Vascular calcification (VC) is a significant risk factor for cardiovascular morbidity and mortality. We recently reported that apocynin had benefits for preventing cardiovascular diseases. However, whether apocynin could attenuate VC is unknown. Here, we investigated the role of apocynin in VC and its underlying mechanisms. 163 participants with high or normal ankle–brachial index (ABI) were enrolled in this study for analyzing the demographic and biochemical data. In vitro, vascular smooth muscle cells (VSMCs) were exposed to calcification medium containing b-glycerophosphate and angiotensin II (Ang II) for 24 hours. The results showed that serum level of Ang II was significantly increased in patients with high ABI (P<0.05). In cultured VSMCs, Ang II significantly exacerbated osteogenic switching. The expression of osteogenic phenotype markers, including bone morphogenetic protein 2 (BMP2), runt-related transcription factor 2 (Runx2) and osteopontin (OPN), were significantly upregulated, whereas contractile markers expression, including alpha smooth muscle actin (a-SMA) and smooth muscle 22 alpha (SM22a) were simultaneously downregulated. However, these effects were greatly attenuated by apocynin. Apocynin enhanced expression of a-SMA by 5.3%, and reduced expression of BMP2, Runx2, OPN by 3.37%, 0.61% and 3.07%, respectively. Furthermore, extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation was upregulated by Ang II, and this effect was also reversed by apocynin. Intriguingly, pretreatment with U0126, an inhibitor of ERK1/2, had similar effects with apocynin. Apocynin may act as a novel molecular candidate to protect against VSMCs osteogenic switching through suppressing ERK1/2 pathway.

A novel role of cellular interactions in vascular calcification

“…Transduced HASMCs with adenovirus expressing RAGEs induced ALP, calcium deposition and osteogenic differentiation defined by an increase of Msx and BMP2 expression [55]. However, others’ and our findings indicated that administration of different antioxidants like apocynin could significantly ameliorate diabetes-induced calcification [56, 57]. Importantly, the expression of β-catenin was shown to increase with the AGEs concentrations augment in AGEs-induced VSMC calcification, suggesting that there was a cross-talk between AGEs and Wnt/β-catenin signaling pathways [58].…”

Epigallocatechin-3-Gallate Ameliorates Angiotensin II-Induced Oxidative Stress and Apoptosis in Human Umbilical Vein Endothelial Cells through the Activation of Nrf2/Caspase-3 Signaling

“…Consequently, more intracellular ROS production induced cell apoptosis and endothelium dysfunction [7,8]. Therefore, Ang II altered small artery structures and developed atherosclerosis [9,10,11]. …”

The use of apocynin inhibits osteoclastogenesis

“…Another recently published work reported that b-aminoisobutyric acid induces osteoblast lineage (MC3T3-E1) differentiation and, when treated with NAC or APO, b-aminoisobutyric acid completely blocks the differentiation process (Zhu et al, 2018). In a study with rat vascular smooth muscle cell cultures exposed to calcification medium, the authors found that APO treatment (100 mM) blocks osteogenic phenotype markers (Feng et al, 2016). These findings strongly suggest that the role of ROS in bone remodeling is closely related to NOX activity.…”

“…They found that IL-17 blocks RANKL production and reduces TRAP-positive cells number in a NAC-dosedependent manner (Kim et al, 2017). In a study with rat vascular smooth muscle cell cultures exposed to calcification medium, the authors found that APO treatment (100 mM) blocks osteogenic phenotype markers (Feng et al, 2016). One-way ANOVA was used to analyze the statistical differences among groups, followed by the Tukey post hoc test.…”