Mechanical loading opens connexin 43(Cx43)hemichannels(HCs),leading to the release of bone anabolic molecules,such as prostaglandins,from mechanosensitive osteocytes,which is essential for bone formation and remodelin...Mechanical loading opens connexin 43(Cx43)hemichannels(HCs),leading to the release of bone anabolic molecules,such as prostaglandins,from mechanosensitive osteocytes,which is essential for bone formation and remodeling.However,the mechanotransduction mechanism that activates HCs remains elusive.Here,we report a unique pathway by which mechanical signals are effectively transferred between integrin molecules located in different regions of the cell,resulting in HC activation.Both integrinα5 andαV were activated upon mechanical stimulation via either fluid dropping or flow shear stress(FSS).Inhibition of integrinαV activation or ablation of integrinα5 prevented HC opening on the cell body when dendrites were mechanically stimulated,suggesting mechanical transmission from the dendritic integrinαV toα5 in the cell body during HC activation.In addition,HC function was compromised in vivo,as determined by utilizing an antibody blockingαV activation andα5-deficient osteocyte-specific knockout mice.Furthermore,inhibition of integrinαV activation,but not that ofα5,attenuated activation of the phosphoinositide 3-kinase(PI3K)-protein kinase B(AKT)signaling pathway upon mechanical loading,and the inhibition of PI3K/AKT activation blocked integrinα5 activation and HC opening.Moreover,HC opening was blocked only by an anti-integrinαV antibody at low but not high FSS levels,suggesting that dendriticαV is a more sensitive mechanosensor thanα5 for activating HCs.Together,these results reveal a new molecular mechanism of mechanotransduction involving the coordinated actions of integrins and PI3K/AKT in osteocytic dendritic processes and cell bodies that leads to HC opening and the release of key bone anabolic factors.展开更多
Physical mechanical stimulation can maintain and even increase bone mass.Here,we report an important role of osteocytic integrinα5 in regulating the anabolic response of bone to mechanical loading using an Itga5 cond...Physical mechanical stimulation can maintain and even increase bone mass.Here,we report an important role of osteocytic integrinα5 in regulating the anabolic response of bone to mechanical loading using an Itga5 conditional gene knockout(cKO)mouse model.Integrinα5 gene deletion increased apoptotic osteocytes and reduced cortical anabolic responses to tibial compression including decreased endosteal osteoblasts and bone formation,and increased endosteal osteoclasts and bone resorption,contributing to the decreased bone area fraction and biomechanical properties,leading to an enlarged bone marrow area in cKO mice.Similar disruption of anabolic responses to mechanical loading was also detected in cKO trabecular bone.Moreover,integrinα5 deficiency impeded load-induced Cx43 hemichannel opening,and production and release of PGE2,an anabolic factor,resulting in attenuated effects of the loading on catabolic sclerostin(SOST)reduction and anabolicβ-catenin increase.Together,this study shows an indispensable role of integrinα5 in osteocytes in the anabolic action of mechanical loading on skeletal tissue through activation of hemichannels and PGE2-evoked gene expression.Integrinα5 could act as a potential new therapeutic target for bone loss,especially in the elderly population with impeded mechanical sensitivity.展开更多
α-Synuclein accumulation causes synaptic vesicle trafficking defects and may underlie neurodegenerative disorders:Neurodegenerative disorders,such as Parkinson’s disease(PD)and other synucleinopathies,impact the liv...α-Synuclein accumulation causes synaptic vesicle trafficking defects and may underlie neurodegenerative disorders:Neurodegenerative disorders,such as Parkinson’s disease(PD)and other synucleinopathies,impact the lives of millions of patients and their caregivers.Synucleinopathies include PD,dementia with Lewy Bodies(DLB),multiple system atrophy,and several Alzheimer’s Disease variants.They are clinically characterized by intracellular inclusions called Lewy Bodies,which are rich in atypical aggregates of the protein α-synuclein.While dopaminergic neurons in the substantia nigra are particularly susceptible toα-synuclein-induced aggregation and neurodegeneration,glutamatergic neurons in other brain regions(e.g.cortex)are also frequently affected in PD and other synucleinopathies(Schulz-Schaeffer 2010).展开更多
The discipline of lipidomics, as coined in 2003, has made profound advances and been rapidly expanded. Direct infusion-based shotgun lipidomics contributes a major part of the research in this discipline. However, des...The discipline of lipidomics, as coined in 2003, has made profound advances and been rapidly expanded. Direct infusion-based shotgun lipidomics contributes a major part of the research in this discipline. However, despite of its numerous advantages over other lipidomics platforms, the classical shotgun lipidomics approach suffers ion suppression and has the difficulties to assess low abundance lipid classes, particularly those less ionizable or that do not yield sensitive and specific fragments. To overcome this obstacle and broaden coverage, strategies have been developed based on unique chemistry and/or physics of lipid classes of interest to enhance shotgun lipidomics. This article overviews the recent enhancements of shotgun lipidomics, including prefractionation, acid/base hydrolysis, derivatization, charge feature utilization. We believe that, by this versatile platform, comprehensive coverage of cellular lipidomes would be achieved in more accurate and effective manner. Therefore, application of the enhanced shotgun lipidomics would greatly accelerate lipidomics research to substantiate the aberrant lipid metabolism, signaling, trafficking, and homeostasis under pathological conditions and their underpinning biochemical mechanisms. It would also facilitate precision medicine studies.展开更多
Estrogen deficiency in postmenopausal women is a major cause of bone loss,resulting in osteopenia,osteoporosis,and a high risk for bone fracture.Connexin 43 (Cx43) hemichannels (HCs) in osteocytes play an important ro...Estrogen deficiency in postmenopausal women is a major cause of bone loss,resulting in osteopenia,osteoporosis,and a high risk for bone fracture.Connexin 43 (Cx43) hemichannels (HCs) in osteocytes play an important role in osteocyte viability,bone formation,and remodeling.We showed here that estrogen deficiency reduced Cx43 expression and HC function.To determine if functional HCs protect osteocytes and bone loss during estrogen deficiency,we adopted an ovariectomy model in wild-type (WT) and two transgenic Cx43 mice:R76W (dominant-negative mutant inhibiting only gap junction channels) and Cx43 Δ130–136 (dominant-negative mutant compromising both gap junction channels and HCs).The bone mineral density (BMD),bone structure,and histomorphometric changes of cortical and trabecular bones after ovariectomy were investigated.Our results showed that the Δ130–136 transgenic cohort had greatly decreased vertebral trabecular bone mass compared to WT and R76W mice,associated with a significant increase in the number of apoptotic osteocyte and empty lacunae.Moreover,osteoclast surfaces in trabecular and cortical bones were increased after ovariectomy in the R76W and WT mice,respectively,but not in Δ130–136 mice.These data demonstrate that impairment of Cx43 HCs in osteocytes accelerates vertebral trabecular bone loss and increase in osteocyte apoptosis,and further suggest that Cx43 HCs in osteocytes protect trabecular bone against catabolic effects due to estrogen deficiency.展开更多
A thorough understanding of how proteins induce nanoparticle (NP) aggregation is crucial when designing in vitro and in vivo assays and interpreting experimental results. This knowledge is also crucial when developi...A thorough understanding of how proteins induce nanoparticle (NP) aggregation is crucial when designing in vitro and in vivo assays and interpreting experimental results. This knowledge is also crucial when developing nano-applications and formulation for drug delivery systems. In this study, we found that extraction of immunoglobulin G (IgG) from cow serum results in lower polystyrene NPs aggregation. Moreover, addition of isolated IgG or fibrinogen to fetal cow serum enhanced this aggregation, thus demonstrating that these factors are major drivers of NP aggregation in serum. Counter-intuitively, NP aggregation was inversely dependent on protein concentration; i.e., low protein concentrations induced large aggregates, whereas high protein concentrations induced small aggregates. Protein-induced NP aggregation and aggregate size were monitored by absorbance at 400 nm and dynamic light scattering, respectively. Here, we propose a mechanism behind the protein concentration dependent aggregation; this mechanism involves the effects of multiple protein interactions on the NP surface, surface area limitations, aggregation kinetics, and the influence of other serum proteins.展开更多
Dear Editor,Pancreatic cancer*is one of the deadliest cancers,with an overall 5-year survival rate of less than 10%unchanged over the last 40 years.Approximately 80-85%of patients are diagnosed as advanced stage,which...Dear Editor,Pancreatic cancer*is one of the deadliest cancers,with an overall 5-year survival rate of less than 10%unchanged over the last 40 years.Approximately 80-85%of patients are diagnosed as advanced stage,which are not eligible for curative surgery.1 Therapeutic options for advanced pancreatic cancer patients are still chemotherapy drugs with limited outcomes to improve patient survival and life quality.展开更多
基金the National Institutes of Health(NIH)grant AR072072(to J.X.J.)the Welch Foundation grant AQ-1507(to J.X.J.).We also thank the UTHSCSA CMMI and the UTHSCSA Optical Imaging Facility supported by the Cancer Therapy and Research Center for the support provided from the NIH-National Cancer Institute P30 award CA054174 and Texas state funds.
文摘Mechanical loading opens connexin 43(Cx43)hemichannels(HCs),leading to the release of bone anabolic molecules,such as prostaglandins,from mechanosensitive osteocytes,which is essential for bone formation and remodeling.However,the mechanotransduction mechanism that activates HCs remains elusive.Here,we report a unique pathway by which mechanical signals are effectively transferred between integrin molecules located in different regions of the cell,resulting in HC activation.Both integrinα5 andαV were activated upon mechanical stimulation via either fluid dropping or flow shear stress(FSS).Inhibition of integrinαV activation or ablation of integrinα5 prevented HC opening on the cell body when dendrites were mechanically stimulated,suggesting mechanical transmission from the dendritic integrinαV toα5 in the cell body during HC activation.In addition,HC function was compromised in vivo,as determined by utilizing an antibody blockingαV activation andα5-deficient osteocyte-specific knockout mice.Furthermore,inhibition of integrinαV activation,but not that ofα5,attenuated activation of the phosphoinositide 3-kinase(PI3K)-protein kinase B(AKT)signaling pathway upon mechanical loading,and the inhibition of PI3K/AKT activation blocked integrinα5 activation and HC opening.Moreover,HC opening was blocked only by an anti-integrinαV antibody at low but not high FSS levels,suggesting that dendriticαV is a more sensitive mechanosensor thanα5 for activating HCs.Together,these results reveal a new molecular mechanism of mechanotransduction involving the coordinated actions of integrins and PI3K/AKT in osteocytic dendritic processes and cell bodies that leads to HC opening and the release of key bone anabolic factors.
基金supported by the National Institutes of Health(NIH)Grants:AR072020(to J.X.J.)Welch Foundation grant:AQ-1507(to J.X.J.).
文摘Physical mechanical stimulation can maintain and even increase bone mass.Here,we report an important role of osteocytic integrinα5 in regulating the anabolic response of bone to mechanical loading using an Itga5 conditional gene knockout(cKO)mouse model.Integrinα5 gene deletion increased apoptotic osteocytes and reduced cortical anabolic responses to tibial compression including decreased endosteal osteoblasts and bone formation,and increased endosteal osteoclasts and bone resorption,contributing to the decreased bone area fraction and biomechanical properties,leading to an enlarged bone marrow area in cKO mice.Similar disruption of anabolic responses to mechanical loading was also detected in cKO trabecular bone.Moreover,integrinα5 deficiency impeded load-induced Cx43 hemichannel opening,and production and release of PGE2,an anabolic factor,resulting in attenuated effects of the loading on catabolic sclerostin(SOST)reduction and anabolicβ-catenin increase.Together,this study shows an indispensable role of integrinα5 in osteocytes in the anabolic action of mechanical loading on skeletal tissue through activation of hemichannels and PGE2-evoked gene expression.Integrinα5 could act as a potential new therapeutic target for bone loss,especially in the elderly population with impeded mechanical sensitivity.
基金supported by a grant from the National Institutes of Health National Institute of Neurological Disorders and Stroke/National Institute on Aging(NIH NINDS/NIA R01NS078165 to JRM)National Institute of General Medical Sciences(NIH/NIGMS Grant R01GM118933 to EML and RS).
文摘α-Synuclein accumulation causes synaptic vesicle trafficking defects and may underlie neurodegenerative disorders:Neurodegenerative disorders,such as Parkinson’s disease(PD)and other synucleinopathies,impact the lives of millions of patients and their caregivers.Synucleinopathies include PD,dementia with Lewy Bodies(DLB),multiple system atrophy,and several Alzheimer’s Disease variants.They are clinically characterized by intracellular inclusions called Lewy Bodies,which are rich in atypical aggregates of the protein α-synuclein.While dopaminergic neurons in the substantia nigra are particularly susceptible toα-synuclein-induced aggregation and neurodegeneration,glutamatergic neurons in other brain regions(e.g.cortex)are also frequently affected in PD and other synucleinopathies(Schulz-Schaeffer 2010).
文摘The discipline of lipidomics, as coined in 2003, has made profound advances and been rapidly expanded. Direct infusion-based shotgun lipidomics contributes a major part of the research in this discipline. However, despite of its numerous advantages over other lipidomics platforms, the classical shotgun lipidomics approach suffers ion suppression and has the difficulties to assess low abundance lipid classes, particularly those less ionizable or that do not yield sensitive and specific fragments. To overcome this obstacle and broaden coverage, strategies have been developed based on unique chemistry and/or physics of lipid classes of interest to enhance shotgun lipidomics. This article overviews the recent enhancements of shotgun lipidomics, including prefractionation, acid/base hydrolysis, derivatization, charge feature utilization. We believe that, by this versatile platform, comprehensive coverage of cellular lipidomes would be achieved in more accurate and effective manner. Therefore, application of the enhanced shotgun lipidomics would greatly accelerate lipidomics research to substantiate the aberrant lipid metabolism, signaling, trafficking, and homeostasis under pathological conditions and their underpinning biochemical mechanisms. It would also facilitate precision medicine studies.
基金supported by NIH grants,AR072020 and CA196214Welch Foundation grant AQ-1507 to J.X.J.+1 种基金China Scholarship Council funding to L.M.Micro-CT imaging was completed at RAYO,the Daniel Carlisle Center for Bone and Mineral Imaging at the University of Texas Health Science Center at San AntonioRAYO is supported by an equipment grant.R.J.F. was supported by NIH grant RR025687
文摘Estrogen deficiency in postmenopausal women is a major cause of bone loss,resulting in osteopenia,osteoporosis,and a high risk for bone fracture.Connexin 43 (Cx43) hemichannels (HCs) in osteocytes play an important role in osteocyte viability,bone formation,and remodeling.We showed here that estrogen deficiency reduced Cx43 expression and HC function.To determine if functional HCs protect osteocytes and bone loss during estrogen deficiency,we adopted an ovariectomy model in wild-type (WT) and two transgenic Cx43 mice:R76W (dominant-negative mutant inhibiting only gap junction channels) and Cx43 Δ130–136 (dominant-negative mutant compromising both gap junction channels and HCs).The bone mineral density (BMD),bone structure,and histomorphometric changes of cortical and trabecular bones after ovariectomy were investigated.Our results showed that the Δ130–136 transgenic cohort had greatly decreased vertebral trabecular bone mass compared to WT and R76W mice,associated with a significant increase in the number of apoptotic osteocyte and empty lacunae.Moreover,osteoclast surfaces in trabecular and cortical bones were increased after ovariectomy in the R76W and WT mice,respectively,but not in Δ130–136 mice.These data demonstrate that impairment of Cx43 HCs in osteocytes accelerates vertebral trabecular bone loss and increase in osteocyte apoptosis,and further suggest that Cx43 HCs in osteocytes protect trabecular bone against catabolic effects due to estrogen deficiency.
文摘A thorough understanding of how proteins induce nanoparticle (NP) aggregation is crucial when designing in vitro and in vivo assays and interpreting experimental results. This knowledge is also crucial when developing nano-applications and formulation for drug delivery systems. In this study, we found that extraction of immunoglobulin G (IgG) from cow serum results in lower polystyrene NPs aggregation. Moreover, addition of isolated IgG or fibrinogen to fetal cow serum enhanced this aggregation, thus demonstrating that these factors are major drivers of NP aggregation in serum. Counter-intuitively, NP aggregation was inversely dependent on protein concentration; i.e., low protein concentrations induced large aggregates, whereas high protein concentrations induced small aggregates. Protein-induced NP aggregation and aggregate size were monitored by absorbance at 400 nm and dynamic light scattering, respectively. Here, we propose a mechanism behind the protein concentration dependent aggregation; this mechanism involves the effects of multiple protein interactions on the NP surface, surface area limitations, aggregation kinetics, and the influence of other serum proteins.
基金This work was supported by the grant from the National Natural Science Foundation of China(Grant No.81903108 to S.H.)the Key Project of Zhejiang Ministry of Science and Technology(Grant No.2021C03087 to T.X.)the Key Project of Hangzhou Ministry of Science and Technology(Grant No.20212013B03 to T.X.).We thank Pierre Baillargeon and Lina Deluca at Scripps for their help with compound management,and Shujuan Zhao at Hangzhou Normal University for proteomics analysis.
文摘Dear Editor,Pancreatic cancer*is one of the deadliest cancers,with an overall 5-year survival rate of less than 10%unchanged over the last 40 years.Approximately 80-85%of patients are diagnosed as advanced stage,which are not eligible for curative surgery.1 Therapeutic options for advanced pancreatic cancer patients are still chemotherapy drugs with limited outcomes to improve patient survival and life quality.