Oxidized phospholipids facilitate calcific aortic valve disease by elevating ATF4 through the PERK/eIF2 & alpha; axis

In this study we sought to analyze the critical role of oxidized phospholipid (OxPL) in the progression of calcific aortic valve disease (CAVD) with the involvement of activating transcription factor 4 (ATF4). Differentially expressed genes related to CAVD were identified using bioinformatics analysis. Expression of ATF4 was examined in mouse models of aortic valve calcification (AVC) induced by the high cholesterol (HC) diet. Valvular interstitial cells (VICs) were then isolated from mouse non-calcified valve tissues, induced by osteogenic induction medium (OIM) and co-cultured with OxPAPC-stimulated macrophages. The effect of OxPLs regulating ATF4 on the macrophage polarization and osteogenic differentiation of VICs was examined with gain- and lossof-function experiments in VICs and in vivo. In aortic valve tissues and OIM-induced VICs, ATF4 was highly expressed. ATF4 knockdown alleviated the osteogenic differentiation of VICs, as evidenced by reduced expression of bone morphogenetic protein-2 (BMP2), osteopontin (OPN), and osteocalcin. In addition, knockdown of ATF4 arrested the AVC in vivo. Meanwhile, OxPL promoted M1 polarization of macrophages and mediated osteogenic differentiation of VICs. Furthermore, OxPL up-regulated ATF4 expression through protein kinase R-like endoplasmic reticulum kinase (PERK)/eukaryotic translation initiation factor 2 subunit alpha (eIF2a) pathway. In conclusion, OxPL can potentially up-regulate the expression of ATF4, inducing macrophages polarized to M1 phenotype, osteogenic differentiation of VICs and AVC, thus accelerating the progression of CAVD.

Automated summary

This study analyzed the crucial role of oxidized phospholipid (OxPL) in the progression of calcific aortic valve disease (CAVD) involving activating transcription factor 4 (ATF4). Differentially expressed genes related to CAVD were identified using bioinformatics analysis. High expression of ATF4 was observed in aortic valve tissues and osteogenic induction medium (OIM)-induced valvular interstitial cells (VICs). Knockdown of ATF4 alleviated osteogenic differentiation of VICs and arrested aortic valve calcification (AVC) in vivo. OxPL promoted M1 polarization of macrophages and mediated osteogenic differentiation of VICs by up-regulating ATF4 expression through the PERK/eIF2a pathway. In conclusion, OxPL potentially up-regulates ATF4 expression, induces M1 polarization of macrophages, osteogenic differentiation of VICs, and accelerates the progression of CAVD.