No abstract

Proprotein convertase subtilisin/kexin 9 (PCSK9), a member of the protein-converting enzyme family, is highly expressed in adult hepatocytes and small intestinal enterocytes. To our knowledge, in this study, we demonstrate for the first time that PCSK9 is upregulated in a dose-dependent manner via oxidized low-density lipoprotein (oxLDL) stimulation in THP-1-derived macrophages. PCSK9 small interfering RNA (siRNA) suppresses the oxLDL-induced inflammatory cytokine expression in THP-1-derived macrophages. The exposure of macrophages to oxLDL markedly increased the expression of NF-κB protein in the nucleus. However, this effect was significantly attenuated by PCSK9 siRNA. These findings indicate that PCSK9 expression is induced by oxLDL, and that PCSK9 siRNA protects against inflammation via the inhibition of NF-κB activation in oxLDL-stimulated THP-1-derived macrophages. Our results suggest that PCSK9 may be used as a therapeutic target for the treatment of atherosclerosis since PCSK9 siRNA suppresses oxLDL-induced IκB-α degradation and NF-κB nuclear translocation into THP-1-derived macrophages.

No abstract

Purinergic 2X7 receptor (P2X7R) and nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) are expressed in macrophages in atherosclerotic lesions. However, the mechanisms through which P2X7R participates in the inflammatory response in atherosclerosis remain largely unknown. The aim of the present study was to investigate the role of P2X7R in atherosclerosis and the mechanisms of action of the NLRP3 inflammasome following stimulation with oxidized low-density lipoprotein (oxLDL). We observed the expression and distribution of P2X7R in the atherosclerotic plaque in the coronary arteries from an autopsy specimen and in that of the aortic sinuses of apoE−/− mice by immunohistochemistry and immunofluorescence staining. The specificity of short interfering RNA (siRNA) was used to suppress P2X7R and NLRP3 mRNA expression. RT-qPCR and western blot analysis were used to analyze mRNA and protein expression, respectively. Co-immunoprecipitation was used to examine the interaction between protein kinase R (PKR) phosphorylation and NLRP3. P2X7R and NLRP3 were expressed at high levels in the atherosclerotic plaque in the coronary arteries. Stimulation with oxLDL upregulated P2X7R, NLRP3 and interleukin (IL)-1β expression. P2X7R knockdown by siRNA suppressed NLRP3 inflammasome activation by inhibiting the PKR phosphorylation mediated by oxLDL. In the atherosclerotic lesions in the aortic sinuses of apoE−/− mice, P2X7R expression was found at high levels. Moreover, P2X7R siRNA attenuated the development of atherosclerosis in the apoE−/− mice. In conclusion, our results demonstrate that P2X7R plays a significant role in the development of atherosclerosis and regulates NLRP3 inflammasome activation by promoting PKR phosphorylation.

Pyroptosis participates in the formation and development of atherosclerosis (As) by promoting inflammatory factor release and is closely related to the stability of atherosclerotic plaque. MicroRNAs can regulate the expression of target genes at the posttranscriptional level. Previous studies have shown that miR-125a-5p increases in hyperlipidemic-hyperglycemic conditions and is involved in apoptosis, but its specific role in pyroptosis and As remains unclear. We propose that miR-125a-5p may be implicated in oxidized low-density lipoprotein (oxLDL)-induced vascular endothelial cells (VECs) pyroptosis and therefore conducted the current study. We observed that miR-125a-5p can inhibit tet methylcytosine dioxygenase 2 (TET2) expression at the posttranscription level, resulting in abnormal DNA methylation, mitochondrial dysfunction, and increased reactive oxygen species production, activated nuclear factor-κB that induces activation of inflammasome and maturation, release of proinflammatory cytokines interleukin (IL)-1β and IL-18, and pyroptosis. Given the role of VECs in vascular physiology, oxLDL-induced VEC pyroptosis may promote the development of As. Our current study reveals a novel pathway associated with pyroptosis program regulation, which comprises miR-125a-5p and TET2 in VECs.Modulation of their expression levels may serve as a potential target for therapeutic strategies of As. K E Y W O R D Satherosclerosis, miR-125a-5p, pyroptosis, ROS, TET2