Background: Vascular calcification is a prevalent complication in chronic kidney disease and contributes to increased cardiovascular morbidity and mortality. XBP1 (X-box binding protein 1), existing as the unspliced (XBP1u) and spliced (XBP1s) forms, is a key component of the endoplasmic reticulum stress involved in vascular diseases. However, whether XBP1u participates in the development of vascular calcification remains unclear. Methods: We aim to investigate the role of XBP1u in vascular calcification.XBP1u protein levels were reduced in high phosphate (Pi)-induced calcified vascular smooth muscle cells (VSMCs), calcified aortas from mice with adenine diet-induced chronic renal failure (CRF) and calcified radial arteries from CRF patients. Results: Inhibition of XBP1u rather than XBP1s upregulated in the expression of the osteogenic markers runt-related transcription factor 2 (Runx2) and msh homeobox2 (Msx2), and exacerbated high Pi-induced VSMC calcification, as verified by calcium deposition and Alizarin red S staining. In contrast, XBP1u overexpression in high Pi-induced VSMCs significantly inhibited osteogenic differentiation and calcification. Consistently, SMC-specific XBP1 deficiency in mice markedly aggravated the adenine diet- and 5/6 nephrectomy-induced vascular calcification compared with that in the control littermates. Further interactome analysis revealed that XBP1u bound directly to β-catenin, a key regulator of vascular calcification, via aa 205-230 in its C-terminal degradation domain. XBP1u interacted with β-catenin to promote its ubiquitin-proteasomal degradation and thus inhibited β-catenin/T-cell factor (TCF)-mediated Runx2 and Msx2 transcription. Knockdown of β-catenin abolished the effect of XBP1u deficiency on VSMC calcification, suggesting a β-catenin-mediated mechanism. Moreover, the degradation of β-catenin promoted by XBP1u was independent of glycogen synthase kinase 3β (GSK-3β)-involved destruction complex. Conclusions: Our study identified XBP1u as a novel endogenous inhibitor of vascular calcification by counteracting β-catenin and promoting its ubiquitin-proteasomal degradation, which represents a new regulatory pathway of β-catenin and a promising target for vascular calcification treatment.

Danggui Buxue Tang (DBT) is a classic Chinese herbal formula which consists of Astragali mongholici Radix and Angelica sinensis Radix (ASR). For chemical ingredients, HPLC were performed. Results showed compared with single herbs, DBT decoction could promote the dissolution of ingredients such as ferulic acid and calycosin. Furthermore, when ratio of AMR to ASR was 5 to 1, synthetic score was the best. For angiogenesis, normal and injured zebrafish model were applied. Results showed DBT and its ingredients had angiogenesis effects on Sub Intestinal vessels (SIVs) of normal zebrafish. Meanwhile, DBT and its single herbs could also recover Inter-Segmental Vessels (ISVs) injured by VRI. Angiogenesis effects of DBT on ISVs were better than single herbs. AMR extract, Total Saponins of AMR, Polysaccharide of ASR, ferulic acid, calycosin and calycosin-7-glucoside could be effective ingredients for angiogenisis. For endothelium functions, Lysoph-Osphatidyl choline was used to damage rat endothelial function of thoracic aorta. The results showed DBT and its single herbs could improve endothelial dysfunctions in dose-dependence. Both ferulic acid and calycosin-7-glucoside could also improve endothelium dysfunction in dose dependence. Therefore, compatibility of DBT was reasonable. Compared with single herbs, DBT could promote dissolution of effective ingredients, enhance angiogenesis and relieve endothelial dysfunction.

No abstract

No abstract