Hypoxia-inducible factor (HIF) activation promotes osteogenic transition of valve interstitial cells and accelerates heart valve calcification in chronic kidney disease (CKD)

Abstract

Objective: Valve calcification (VC) is a widespread complication in chronic kidney disease (CKD) patients on hemodialysis. VC is an active process with the involvement of in situ osteogenic transition of valve interstitial cells (VICs). VC is accompanied by the activation of hypoxia inducible factor (HIF) pathway, but the role of HIF activation in the calcification process remains undiscovered. Approach and Results: Using in vitro and in vivo approaches we addressed the role of HIF activation in osteogenic transition of VICs and CKD-associated VC. Elevation of osteogenic (Runx2, Sox9) and HIF activation markers (HIF-1α and HIF-2α) and VC occurred in adenine-induced CKD mice. High phosphate (Pi) induced upregulation of osteogenic (Runx2, alkaline-phosphatase, Sox9, osteocalcin) and hypoxia markers (HIF-1α, HIF-2α, Glut-1), and calcification in VICs. Down-regulation of HIF-1α and HIF-2α inhibited, whereas further activation of HIF pathway by hypoxic exposure (1% O2) or hypoxia mimetics (desferrioxamine, CoCl2, Daprodustat (DPD)) promoted Pi-induced calcification of VICs. Pi augmented the formation of reactive oxygen species (ROS) and decreased viability of VICs, whose effects were further exacerbated by hypoxia. N-acetyl cysteine inhibited Pi-induced ROS production, cell death and calcification under both normoxic and hypoxic conditions. DPD treatment corrected anemia but promoted VC in the CKD mice model. Conclusion: HIF activation plays a fundamental role in Pi-induced osteogenic transition of VICs and CKD-induced VC. The cellular mechanism involves stabilization of HIF-1α and HIF-2α, increased ROS production and cell death. Targeting the HIF pathways may thus be investigated as a therapeutic approach to attenuate VC. Translational perspective: One in four hemodialysis-dependent CKD patients on DPD treatment experience a major cardiovascular event during a 2.5-year follow-up period. This work provides a possible explanation for this phenomenon and should initiate further studies to address whether DPD-mediated acceleration of valve calcification triggers the unbeneficial effect of DPD.

High glucose promotes osteogenic differentiation of human lens epithelial cells through hypoxia‐inducible factor (HIF) activation

“…A previous study showed that HG induces HIF‐1α stabilisation in LECs (Han et al, 2015) and because HIF pathway activation was shown to be associated with the promotion of vascular and valve calcification (Balogh et al, 2019; Csiki et al, 2023; Mokas et al, 2016), we next investigated whether this mechanism is involved in the HG‐induced promotion of calcification in HuLECs. To address this, we treated HuLECs with OM (2.5 mmol/L Pi, 0.3 mmol/L Ca, 48 h) under NG and HG conditions.…”

“…It is increasingly clear that hypoxia and HIF‐1 activation are involved in the osteogenic phenotype switch and calcification of VSMCs and VICs (Balogh et al, 2019; Csiki et al, 2023; Mokas et al, 2016; Tóth et al, 2022). In accordance with that here, we showed that calcification of HuLECs is attenuated in the absence of HIF‐1α or HIF‐2α, suggesting that hyperglycaemia‐induced stabilisation of HIF‐1α and HIF‐2α and subsequent activation of the HIF‐1 pathway plays a critical role in HG‐induced promotion of calcification (Figure 4).…”

“…Recent findings have suggested that activation of the hypoxia‐inducible factor (HIF) pathway promotes osteogenic differentiation of VSMCs as well as valve interstitial cells (VICs) (Balogh et al, 2019; Csiki et al, 2023; Mokas et al, 2016; Tóth et al, 2022). Hyperglycaemia has been associated with HIF‐1α stabilisation and subsequent HIF pathway activation in diverse cell types including LECs (Han et al, 2015).…”

Anemia and Hypoxia Impact on Chronic Kidney Disease Onset and Progression: Review and Updates

“…Hypoxia promotes the macrophages' disposition to the kidney, which produces profibrotic cytokines (as a transforming growth factor) and activates renal fibroblasts by inducing pro-inflammatory adhesion molecules and chemokines [99,262]. Hypoxia also directly activates fibroblasts to increase extracellular matrix deposition due to increasing collagen and tissue-metalloproteinase-I production inhibitors while diminishing collagenase expression [101,263]. The activated fibroblasts, inflammatory cell enrollment, and injury to tubule epithelial cells contribute to tubulointerstitial fibrosis development.…”