Estrogen-mediated downregulation of HIF-1α signaling in B lymphocytes influences postmenopausal bone loss

Xianyi Meng,Shan Cao,Iga Janowska,Knab Katharina,Darja Andreev,Marta Rizzi,Gerhard Krönke,Aline Bozec,Michael Sean Wiesener,Karl Xaver Knaup,Georg Schett,Zhen Lin,Jinming Wen,Koshiro Sonomoto

doi:10.1038/s41413-022-00189-x

Abstract

In the bone marrow, B cells and bone-resorbing osteoclasts colocalize and form a specific microenvironment. How B cells functionally influence osteoclasts and bone architecture is poorly understood. Using genetically modified mice and high-throughput analyses, we demonstrate that prolonged HIF-1α signaling in B cells leads to enhanced RANKL production and osteoclast formation. In addition, deletion of HIF-1α in B cells prevents estrogen deficiency-induced bone loss in mice. Mechanistically, estrogen controls HIF-1α protein stabilization through HSP70-mediated degradation in bone marrow B cells. The stabilization of HIF-1α protein in HSP70-deficient bone marrow B cells promotes RANKL production and osteoclastogenesis. Induction of HSP70 expression by geranylgeranylacetone (GGA) administration alleviates ovariectomy-induced osteoporosis. Moreover, RANKL gene expression has a positive correlation with HIF1A expression in human B cells. In conclusion, HIF-1α signaling in B cells is crucial for the control of osteoclastogenesis, and the HSP70/HIF-1α axis may serve as a new therapeutic target for osteoporosis.

Highlights

The balance between bone formation by osteoblasts and bone resorption by osteoclasts regulates bone homeostasis.[1,2] Osteoclast activation is a hallmark of many forms of bone loss
We showed that hypoxia-inducible factor (HIF)-1α bound to the hypoxia-responsive element (HRE) II region under hypoxic receptor α (ERα) protein expression levels were found in bone conditions using a chromatin immunoprecipitation (ChIP) assay marrow B cells, especially in the Pro-B and Pre-B subpopulations (Fig. 2i)
Since HSP70 expression is regulated by heat shock factors (HSFs),[33] we examined Hsf[1] and Hsf[2] mRNA induction and receptor activator of nuclear factor kappa-Β ligand (RANKL) gene expression correlates with HIF1A gene expression in human B cells found increased Hsf[1] gene transcription in estrogen-treated B cells (Fig. S4a)

Summary

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The balance between bone formation by osteoblasts and bone resorption by osteoclasts regulates bone homeostasis.[1,2] Osteoclast activation is a hallmark of many forms of bone loss. Osteoclast activation is a hallmark of many forms of bone loss These multinucleated cells are differentiated from the monocyte/ macrophage lineage, and their differentiation essentially depends on macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor kappa-Β ligand (RANKL).[3,4]. HIF-1a signaling in B cell controls bone homeostasis X Meng et al. a lack of Hif1a in B cells restricts estrogen deficiency- HIF-1α directly regulates Rankl gene expression induced bone loss. HIF-1α expression levels in B cells To understand how HIF-1α signaling modulates B cells during are controlled by estrogen-induced HSP70 expression through the estrogen deficiency-induced bone loss, RNA sequencing (RNA-seq) ubiquitin–proteasome degradation system. Genetic analysis and HIF-1α ChIP-sequencing (ChIP-seq) analysis were deletion of HSP70 in B cells markedly exacerbated HIF-1α signaling performed on bone marrow B cells from mice that received sham activation and RANKL-mediated osteoclastogenesis. Identified 22 genes (Tnfsf[11], Jup, Ust, Gnaz, Kitl, Aif[1], Kalm, Mylk, Parvb, Cpt1a, Fgf[1], Fgf[13], Dlg[2], Shank[2], Dgki, Igf2bp[3], Mmrn[1], Ccdc[148], Nr1h3, Fbn[1], Cndb[2], Scn4b), including Rankl (Tnfsf11), that

RESULTS

12 NS NS 9 6 3 0

DISCUSSION

B CLP Pro- B Imm Pre-B ature

Findings

MATERIALS AND METHODS