Efficient cellular fusion of mononuclear precursors is the prerequisite for the generation of fully functional multinucleated bone-resorbing osteoclasts.However,the exact molecular factors and mechanisms controlling o...Efficient cellular fusion of mononuclear precursors is the prerequisite for the generation of fully functional multinucleated bone-resorbing osteoclasts.However,the exact molecular factors and mechanisms controlling osteoclast fusion remain incompletely understood.Here we identify RANKL-mediated activation of caspase-8 as early key event during osteoclast fusion.展开更多
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 ...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 highthroughput 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 HIF1 A expression in human B cells. In conclusion, HIF-1αsignaling 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.展开更多
Bone mass is maintained by the balance between osteoclast-induced bone resorption and osteoblast-triggered bone formation.In inflammatory arthritis such as rheumatoid arthritis(RA),however,increased osteoclast differe...Bone mass is maintained by the balance between osteoclast-induced bone resorption and osteoblast-triggered bone formation.In inflammatory arthritis such as rheumatoid arthritis(RA),however,increased osteoclast differentiation and activity skew this balance resulting in progressive bone loss.O-GlcNAcylation is a posttranslational modification with attachment of a single O-linkedβ-D-N-acetylglucosamine(O-GlcNAc)residue to serine or threonine residues of target proteins.Although O-GlcNAcylation is one of the most common protein modifications,its role in bone homeostasis has not been systematically investigated.We demonstrate that dynamic changes in O-GlcNAcylation are required for osteoclastogenesis.Increased O-GlcNAcylation promotes osteoclast differentiation during the early stages,whereas its downregulation is required for osteoclast maturation.At the molecular level,O-GlcNAcylation affects several pathways including oxidative phosphorylation and cell-cell fusion.TNFαfosters the dynamic regulation of O-GlcNAcylation to promote osteoclastogenesis in inflammatory arthritis.Targeted pharmaceutical or genetic inhibition of O-GlcNAc transferase(OGT)or O-GlcNAcase(OGA)arrests osteoclast differentiation during early stages of differentiation and during later maturation,respectively,and ameliorates bone loss in experimental arthritis.Knockdown of NUP153,an O-GlcNAcylation target,has similar effects as OGT inhibition and inhibits osteoclastogenesis.These findings highlight an important role of O-GlcNAcylation in osteoclastogenesis and may offer the potential to therapeutically interfere with pathologic bone resorption.展开更多
Osteocytes are the main cells in mineralized bone tissue.Elevated osteocyte apoptosis has been observed in lytic bone lesions of patients with multiple myeloma.However,their precise contribution to bone metastasis rem...Osteocytes are the main cells in mineralized bone tissue.Elevated osteocyte apoptosis has been observed in lytic bone lesions of patients with multiple myeloma.However,their precise contribution to bone metastasis remains unclear.Here,we investigated the pathogenic mechanisms driving melanoma-induced osteocyte death.Both in vivo models and in vitro assays were combined with untargeted RNA sequencing approaches to explore the pathways governing melanoma-induced osteocyte death.We could show that ferroptosis is the primary mechanism behind osteocyte death in the context of melanoma bone metastasis.HMOX1 was identified as a crucial regulatory factor in this process,directly involved in inducing ferroptosis and affecting osteocyte viability.We uncover a non-canonical pathway that involves excessive autophagy-mediated ferritin degradation,highlighting the complex relationship between autophagy and ferroptosis in melanoma-induced osteocyte death.In addition,HIF1αpathway was shown as an upstream regulator,providing a potential target for modulating HMOX1 expression and influencing autophagy-dependent ferroptosis.In conclusion,our study provides insight into the pathogenic mechanisms of osteocyte death induced by melanoma bone metastasis,with a specific focus on ferroptosis and its regulation.This would enhance our comprehension of melanoma-induced osteocyte death.展开更多
基金supported by the Bayerische Forschungsstiftung to B.K.the Deutsche Forschungsgemeinschaft (CRC1181 to G.K.and G.S.+3 种基金SCHE 2062/1-1 to C.S.)funded by the Wellcome Trust Investigator Award (107964/Z/15/Z)the UK Dementia Research Institutefunded by BBSRC Discovery Fellowship (BB/T009543/1)。
文摘Efficient cellular fusion of mononuclear precursors is the prerequisite for the generation of fully functional multinucleated bone-resorbing osteoclasts.However,the exact molecular factors and mechanisms controlling osteoclast fusion remain incompletely understood.Here we identify RANKL-mediated activation of caspase-8 as early key event during osteoclast fusion.
文摘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 highthroughput 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 HIF1 A expression in human B cells. In conclusion, HIF-1αsignaling 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.
基金financial support provided by the following grants and institutions:Grants DI 1537/7-1, DI 1537/8-1, DI 1537/9-1, DI 1537/9-2, DI 1537/11-1,DI 1537/12-1, DI 1537/13-1, DI 1537/14-1, DI 1537/17-1, DI 1537/20-1, DI 1537/22-1,MA 9219/2-1, RA 2506/3-1 and ZH 809/2-1 of the Deutsche Forschungsgemeinschaft(DFG, German Research Foundation)SFB CRC1181 (project C01)+10 种基金SFB TR221/project number 324392634 (B04) and project number 52732026 of the DFGgrants J40, J82,A79 and A64 of the IZKF in Erlangengrant 2013.056.1 of the Wilhelm-SanderFoundationgrants 2014_A47 and 2014_A184 of the Else-Kr?ner-Fresenius-Foundationgrant 14-12-17-1-Bergmann, 21-07-23-1-Gy?rfi19-12-06-1-Matei of the ELAN-Foundation Erlangen,MASCARA program/TP2 (01EC1903A) of Federal Ministry of Education and Research (BMBF)China Scholarship Councilresearch Award of the German Scleroderma Foundation (Deutsche Stiftung Sklerodermie)Edith Busch Stiftunga Career Support Award of Medicine of the Ernst Jung FoundationOpen Access funding enabled and organized by Projekt DEAL。
文摘Bone mass is maintained by the balance between osteoclast-induced bone resorption and osteoblast-triggered bone formation.In inflammatory arthritis such as rheumatoid arthritis(RA),however,increased osteoclast differentiation and activity skew this balance resulting in progressive bone loss.O-GlcNAcylation is a posttranslational modification with attachment of a single O-linkedβ-D-N-acetylglucosamine(O-GlcNAc)residue to serine or threonine residues of target proteins.Although O-GlcNAcylation is one of the most common protein modifications,its role in bone homeostasis has not been systematically investigated.We demonstrate that dynamic changes in O-GlcNAcylation are required for osteoclastogenesis.Increased O-GlcNAcylation promotes osteoclast differentiation during the early stages,whereas its downregulation is required for osteoclast maturation.At the molecular level,O-GlcNAcylation affects several pathways including oxidative phosphorylation and cell-cell fusion.TNFαfosters the dynamic regulation of O-GlcNAcylation to promote osteoclastogenesis in inflammatory arthritis.Targeted pharmaceutical or genetic inhibition of O-GlcNAc transferase(OGT)or O-GlcNAcase(OGA)arrests osteoclast differentiation during early stages of differentiation and during later maturation,respectively,and ameliorates bone loss in experimental arthritis.Knockdown of NUP153,an O-GlcNAcylation target,has similar effects as OGT inhibition and inhibits osteoclastogenesis.These findings highlight an important role of O-GlcNAcylation in osteoclastogenesis and may offer the potential to therapeutically interfere with pathologic bone resorption.
基金funding from the European Research Council(ERC)under the european union Horizon 2020 research and innovation program(grant agreement ERC co-LS4 ODE(AB)and ERC Synergy Grant 4D Nanoscope(GS))Deutsche Forschungsgemeinschaft DFG-Project number 501752319-TRR369-DIONE-Project No A02 and B05,FOR 2886(TP02),CRC1181(TPA01)DFG funding(450993414)Thunder Imager and the Leibniz Award(GS)。
文摘Osteocytes are the main cells in mineralized bone tissue.Elevated osteocyte apoptosis has been observed in lytic bone lesions of patients with multiple myeloma.However,their precise contribution to bone metastasis remains unclear.Here,we investigated the pathogenic mechanisms driving melanoma-induced osteocyte death.Both in vivo models and in vitro assays were combined with untargeted RNA sequencing approaches to explore the pathways governing melanoma-induced osteocyte death.We could show that ferroptosis is the primary mechanism behind osteocyte death in the context of melanoma bone metastasis.HMOX1 was identified as a crucial regulatory factor in this process,directly involved in inducing ferroptosis and affecting osteocyte viability.We uncover a non-canonical pathway that involves excessive autophagy-mediated ferritin degradation,highlighting the complex relationship between autophagy and ferroptosis in melanoma-induced osteocyte death.In addition,HIF1αpathway was shown as an upstream regulator,providing a potential target for modulating HMOX1 expression and influencing autophagy-dependent ferroptosis.In conclusion,our study provides insight into the pathogenic mechanisms of osteocyte death induced by melanoma bone metastasis,with a specific focus on ferroptosis and its regulation.This would enhance our comprehension of melanoma-induced osteocyte death.
