RESUMO
Epigenetic regulation plays a crucial role in the pathogenesis of autoimmune diseases such as inflammatory arthritis. DNA hypomethylating agents, such as decitabine (DAC), have been shown to dampen inflammation and restore immune homeostasis. In the present study, we demonstrate that DAC elicits potent anti-inflammatory effects and attenuates disease symptoms in several animal models of arthritis. Transcriptomic and epigenomic profiling show that DAC-mediated hypomethylation regulates a wide range of cell types in arthritis, altering the differentiation trajectories of anti-inflammatory macrophage populations, regulatory T cells, and tissue-protective synovial fibroblasts (SFs). Mechanistically, DAC-mediated demethylation of intragenic 5'-Cytosine phosphate Guanine-3' (CpG) islands of the transcription factor Irf8 (interferon regulatory factor 8) induced its re-expression and promoted its repressor activity. As a result, DAC restored joint homeostasis by resetting the transcriptomic signature of negative regulators of inflammation in synovial macrophages (MerTK, Trem2, and Cx3cr1), TREGs (Foxp3), and SFs (Pdpn and Fapα). In conclusion, we found that Irf8 is necessary for the inhibitory effect of DAC in murine arthritis and that direct expression of Irf8 is sufficient to significantly mitigate arthritis.
Assuntos
Artrite , Azacitidina , Camundongos , Animais , Decitabina/farmacologia , Azacitidina/farmacologia , Epigênese Genética , Metilação de DNA , Fatores Reguladores de Interferon/metabolismo , Inflamação/genética , Artrite/genética , Anti-Inflamatórios , Glicoproteínas de Membrana/metabolismo , Receptores Imunológicos/genéticaRESUMO
Hematopoietic stem/progenitor cells (HSPCs) reside in localized microenvironments, or niches, in the bone marrow that provide key signals regulating their activity. A fundamental property of hematopoiesis is the ability to respond to environmental cues such as inflammation. How these cues are transmitted to HSPCs within hematopoietic niches is not well established. Here, we show that perivascular bone marrow dendritic cells (DCs) express a high basal level of Toll-like receptor-1 (TLR1) and TLR2. Systemic treatment with a TLR1/2 agonist induces HSPC expansion and mobilization. It also induces marked alterations in the bone marrow microenvironment, including a decrease in osteoblast activity and sinusoidal endothelial cell numbers. TLR1/2 agonist treatment of mice in which Myd88 is deleted specifically in DCs using Zbtb46-Cre show that the TLR1/2-induced expansion of multipotent HPSCs, but not HSPC mobilization or alterations in the bone marrow microenvironment, is dependent on TLR1/2 signaling in DCs. Interleukin-1ß (IL-1ß) is constitutively expressed in both murine and human DCs and is further induced after TLR1/2 stimulation. Systemic TLR1/2 agonist treatment of Il1r1-/- mice show that TLR1/2-induced HSPC expansion is dependent on IL-1ß signaling. Single-cell RNA-sequencing of low-risk myelodysplastic syndrome bone marrow revealed that IL1B and TLR1 expression is increased in DCs. Collectively, these data suggest a model in which TLR1/2 stimulation of DCs induces secretion of IL-1ß and other inflammatory cytokines into the perivascular niche, which in turn, regulates multipotent HSPCs. Increased DC TLR1/2 signaling may contribute to altered HSPC function in myelodysplastic syndrome by increasing local IL-1ß expression.
Assuntos
Células da Medula Óssea , Células Dendríticas , Células-Tronco Hematopoéticas , Interleucina-1beta , Síndromes Mielodisplásicas , Animais , Medula Óssea/metabolismo , Células da Medula Óssea/citologia , Citocinas/metabolismo , Células Dendríticas/citologia , Células-Tronco Hematopoéticas/citologia , Humanos , Interleucina-1beta/metabolismo , Camundongos , Síndromes Mielodisplásicas/metabolismo , Fator 88 de Diferenciação Mieloide/metabolismo , RNA/metabolismo , Receptor 1 Toll-Like/metabolismo , Receptor 2 Toll-Like/agonistas , Receptor 2 Toll-Like/metabolismoRESUMO
BACKGROUND: Senescence is a cellular aging-related process triggered by different stresses and characterized by the secretion of various inflammatory factors referred to as senescence-associated secretory phenotype (SASP), some of which are produced by the NLRP3 inflammasome. Here, we present evidence that the NLRP1 inflammasome is a DNA damage sensor and a key mediator of senescence. METHODS: Senescence was induced in fibroblasts in vitro and in mice. Cellular senescence was assessed by Western blot analysis of several proteins, including p16, p21, p53, and SASP factors, released in the culture media or serum. Inflammasome components, including NLRP1, NLRP3 and GSDMD were knocked out or silenced using siRNAs. RESULTS: In vitro and in vivo results suggest that the NLRP1 inflammasome promotes senescence by regulating the expression of p16, p21, p53, and SASP factors in a Gasdermin D (GSDMD)-dependent manner. Mechanistically, the NLRP1 inflammasome is activated in response to genomic damage detected by the cytosolic DNA sensor cGMP-AMP (cGAMP) synthase (cGAS). CONCLUSION: Our findings show that NLRP1 is a cGAS-dependent DNA damage sensor during senescence and a mediator of SASP release through GSDMD. This study advances the knowledge on the biology of the NLRP1 inflammasome and highlights this pathway as a potential pharmcological target to modulate senescence.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal , Senescência Celular , Dano ao DNA , Fibroblastos , Inflamassomos , Peptídeos e Proteínas de Sinalização Intracelular , Camundongos Endogâmicos C57BL , Proteínas de Ligação a Fosfato , Fenótipo Secretor Associado à Senescência , Animais , Inflamassomos/metabolismo , Proteínas de Ligação a Fosfato/metabolismo , Proteínas de Ligação a Fosfato/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Fibroblastos/metabolismo , Proteínas Reguladoras de Apoptose/metabolismo , Proteínas Reguladoras de Apoptose/genética , Proteínas NLR/metabolismo , Proteínas NLR/genética , Nucleotidiltransferases/metabolismo , Nucleotidiltransferases/genética , Camundongos , Proteína Supressora de Tumor p53/metabolismo , Proteína Supressora de Tumor p53/genética , Células Cultivadas , Camundongos Knockout , Humanos , Proteína 3 que Contém Domínio de Pirina da Família NLR , GasderminasRESUMO
Radiotherapy is a commonly used conditioning regimen for bone marrow transplantation (BMT). Cytotoxicity limits the use of this life-saving therapy, but the underlying mechanisms remain poorly defined. Here, we use the syngeneic mouse BMT model to test the hypothesis that lethal radiation damages tissues, thereby unleashing signals that indiscriminately activate the inflammasome pathways in host and transplanted cells. We find that a clinically relevant high dose of radiation causes severe damage to bones and the spleen through mechanisms involving the NLRP3 and AIM2 inflammasomes but not the NLRC4 inflammasome. Downstream, we demonstrate that gasdermin D (GSDMD), the common effector of the inflammasomes, is also activated by radiation. Remarkably, protection against the injury induced by deadly ionizing radiation occurs only when NLRP3, AIM2, or GSDMD is lost simultaneously in both the donor and host cell compartments. Thus, this study reveals a continuum of the actions of lethal radiation relayed by the inflammasome-GSDMD axis, initially affecting recipient cells and ultimately harming transplanted cells as they grow in the severely injured and toxic environment. This study also suggests that therapeutic targeting of inflammasome-GSDMD signaling has the potential to prevent the collateral effects of intense radiation regimens.
Assuntos
Células da Medula Óssea/efeitos da radiação , Transplante de Medula Óssea , Proteínas de Ligação a DNA/genética , Inflamassomos/efeitos da radiação , Peptídeos e Proteínas de Sinalização Intracelular/genética , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Proteínas de Ligação a Fosfato/genética , Animais , Células da Medula Óssea/citologia , Células da Medula Óssea/metabolismo , Proteínas de Ligação a DNA/deficiência , Feminino , Fêmur/citologia , Fêmur/metabolismo , Regulação da Expressão Gênica , Inflamassomos/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/deficiência , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína 3 que Contém Domínio de Pirina da Família NLR/deficiência , Proteínas de Ligação a Fosfato/deficiência , Piroptose/genética , Piroptose/efeitos da radiação , Transdução de Sinais , Baço/metabolismo , Baço/patologia , Baço/efeitos da radiação , Transplante Isogênico , Irradiação Corporal Total , Raios XRESUMO
Overwhelming evidence indicates that excessive stimulation of innate immune receptors of the NOD-like receptor (NLR) family causes significant damage to multiple tissues, yet the role of these proteins in bone metabolism is not well known. Here, we studied the interaction between the NLRP3 and NLRC4 inflammasomes in bone homeostasis and disease. We found that loss of NLRP3 or NLRC4 inflammasome attenuated osteoclast differentiation in vitro. At the tissue level, lack of NLRP3, or NLRC4 to a lesser extent, resulted in higher baseline bone mass compared to wild-type (WT) mice, and conferred protection against LPS-induced inflammatory osteolysis. Bone mass accrual in mutant mice correlated with lower serum IL-1ß levels in vivo. Unexpectedly, the phenotype of Nlrp3-deficient mice was reversed upon loss of NLRC4 as bone mass was comparable between WT mice and Nlrp3;Nlrc4 knockout mice. Thus, although bone homeostasis is perturbed to various degrees by the lack of NLRP3 or NLRC4, this tissue appears to function normally upon compound loss of the inflammasomes assembled by these receptors.
Assuntos
Proteínas Reguladoras de Apoptose/metabolismo , Reabsorção Óssea/metabolismo , Osso e Ossos/metabolismo , Proteínas de Ligação ao Cálcio/metabolismo , Inflamassomos/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Animais , Diferenciação Celular/fisiologia , Homeostase/fisiologia , Inflamação/metabolismo , Interleucina-1beta/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Osteoclastos/metabolismo , Osteólise/metabolismoRESUMO
Mutated NLRP3 assembles a hyperactive inflammasome, which causes excessive secretion of interleukin (IL)-1ß and IL-18 and, ultimately, a spectrum of autoinflammatory disorders known as cryopyrinopathies of which neonatal-onset multisystem inflammatory disease (NOMID) is the most severe phenotype. NOMID mice phenocopy several features of the human disease as they develop severe systemic inflammation driven by IL-1ß and IL-18 overproduction associated with damage to multiple organs, including spleen, skin, liver, and skeleton. Secretion of IL-1ß and IL-18 requires gasdermin D (GSDMD), which-upon activation by the inflammasomes-translocates to the plasma membrane where it forms pores through which these cytokines are released. However, excessive pore formation resulting from sustained activation of GSDMD compromises membrane integrity and ultimately causes a pro-inflammatory form of cell death, termed pyroptosis. In this study, we first established a strong correlation between NLRP3 inflammasome activation and GSDMD processing and pyroptosis in vitro. Next, we used NOMID mice to determine the extent to which GSDMD-driven pyroptosis influences the pathogenesis of this disorder. Remarkably, all NOMID-associated inflammatory symptoms are prevented upon ablation of GSDMD. Thus, GSDMD-dependent actions are required for the pathogenesis of NOMID in mice.
Assuntos
Proteínas Reguladoras de Apoptose/fisiologia , Síndromes Periódicas Associadas à Criopirina/metabolismo , Animais , Animais Recém-Nascidos , Proteínas Reguladoras de Apoptose/metabolismo , Membrana Celular/metabolismo , Síndromes Periódicas Associadas à Criopirina/genética , Síndromes Periódicas Associadas à Criopirina/fisiopatologia , Inflamassomos/metabolismo , Inflamação , Interleucina-18/metabolismo , Interleucina-1beta/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Camundongos , Camundongos Endogâmicos C57BL , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Proteínas de Neoplasias/genética , Proteínas de Ligação a Fosfato , Piroptose/fisiologiaRESUMO
The MAP kinase TGFß-activated kinase (TAK1) plays a crucial role in physiologic and pathologic cellular functions including cell survival, differentiation, apoptosis, inflammation, and oncogenesis. However, the entire repertoire of its mechanism of action has not been elucidated. Here, we found that ablation of Tak1 in myeloid cells causes osteopetrosis in mice as a result of defective osteoclastogenesis. Mechanistically, Tak1 deficiency correlated with increased NUMB-like (NUMBL) levels. Accordingly, forced expression of Numbl abrogated osteoclastogenesis whereas its deletion partially restored osteoclastogenesis and reversed the phenotype of Tak1 deficiency. Tak1 deletion also down-regulated Notch intracellular domain (NICD), but increased the levels of the transcription factor recombinant recognition sequence binding protein at Jκ site (RBPJ), consistent with NUMBL regulating notch signaling through degradation of NICD, a modulator of RBPJ. Accordingly, deletion of Rbpj partially corrected osteopetrosis in Tak1-deficient mice. Furthermore, expression of active IKK2 in RBPJ/TAK1-deficient cells significantly restored osteoclastogenesis, indicating that activation of NF-κB is essential for complete rescue of the pathway. Thus, we propose that TAK1 regulates osteoclastogenesis by integrating activation of NF-κB and derepression of NOTCH/RBPJ in myeloid cells through inhibition of NUMBL.
Assuntos
NF-kappa B/metabolismo , Osteopetrose/enzimologia , Osteopetrose/patologia , Receptores Notch/metabolismo , Transdução de Sinais , Animais , Diferenciação Celular , Deleção de Genes , Proteína de Ligação a Sequências Sinal de Recombinação J de Imunoglobina/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , MAP Quinase Quinase Quinases/deficiência , MAP Quinase Quinase Quinases/metabolismo , Camundongos Endogâmicos C57BL , Células Mieloides/enzimologia , Células Mieloides/patologia , Proteínas do Tecido Nervoso/metabolismo , Osteoclastos/patologia , Osteogênese , Fenótipo , Células-Tronco/metabolismoRESUMO
Activating-mutations in NOD-like receptor (NLR) family, pyrin domain-containing 3 (NLRP3) cause neonatal-onset multisystem inflammatory disease. However, the ontogeny of skeletal anomalies in this disorder is poorly understood. Mice globally expressing the D301N mutation in Nlrp3 (D303N in human) model the human phenotype, including systemic inflammation and skeletal deformities. To gain insights into the skeletal manifestations, we generated mice in which the expression of D301N Nlrp3 (Nlrp3( D301N)) is restricted to myeloid cells. These mice exhibit systemic inflammation and severe osteopenia (â¼ 60% lower bone mass) similar to mice globally expressing the knock-in mutation, consistent with the paradigm of innate immune-driven cryopyrinopathies. Because systemic inflammation may indirectly affect bone homeostasis, we engineered mice in which Nlrp3( D301N) is expressed specifically in osteoclasts, the cells that resorb bone. These mice also develop â¼ 50% lower bone mass due to increased osteolysis, but there is no systemic inflammation and no change in osteoclast number. Mechanistically, aside from its role in IL-1ß maturation, Nlrp3( D301N) expression enhances osteoclast bone resorbing ability through reorganization of actin cytoskeleton while promoting the degradation of poly(ADP-ribose) polymerase 1, an inhibitor of osteoclastogenesis. Thus, NLRP3 inflammasome activation is not restricted to the production of proinflammatory mediators but also leads to cytokine-autonomous responses.
Assuntos
Proteínas de Transporte/metabolismo , Osteólise/etiologia , Animais , Doenças Ósseas Metabólicas/etiologia , Doenças Ósseas Metabólicas/patologia , Doenças Ósseas Metabólicas/fisiopatologia , Proteínas de Transporte/genética , Proteínas de Transporte/imunologia , Diferenciação Celular , Linhagem da Célula , Síndromes Periódicas Associadas à Criopirina/etiologia , Síndromes Periódicas Associadas à Criopirina/patologia , Síndromes Periódicas Associadas à Criopirina/fisiopatologia , Modelos Animais de Doenças , Humanos , Inflamassomos/imunologia , Inflamassomos/metabolismo , Inflamação/etiologia , Inflamação/patologia , Inflamação/fisiopatologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Camundongos Transgênicos , Proteínas Mutantes/genética , Proteínas Mutantes/imunologia , Proteínas Mutantes/metabolismo , Células Mieloides/imunologia , Células Mieloides/metabolismo , Células Mieloides/patologia , Proteína 3 que Contém Domínio de Pirina da Família NLR , Osteoclastos/imunologia , Osteoclastos/metabolismo , Osteoclastos/patologia , Osteólise/patologia , Osteólise/fisiopatologia , Poli(ADP-Ribose) Polimerase-1 , Poli(ADP-Ribose) Polimerases/metabolismo , ProteóliseRESUMO
To examine interactions between bone morphogenic protein (BMP) and canonical Wnt signaling during skeletal growth, we ablated Smad4, a key component of the TGF-ß-BMP pathway, in Osx1(+) cells in mice. We show that loss of Smad4 causes stunted growth, spontaneous fractures and a combination of features seen in osteogenesis imperfecta, cleidocranial dysplasia and Wnt-deficiency syndromes. Bones of Smad4 mutant mice exhibited markers of fully differentiated osteoblasts but lacked multiple collagen-processing enzymes, including lysyl oxidase (Lox), a BMP2-responsive gene regulated by Smad4 and Runx2. Accordingly, the collagen matrix in Smad4 mutants was disorganized, but also hypomineralized. Primary osteoblasts from these mutants did not mineralize in vitro in the presence of BMP2 or Wnt3a, and Smad4 mutant mice failed to accrue new bone following systemic inhibition of the Dickkopf homolog Dkk1. Consistent with impaired biological responses to canonical Wnt, ablation of Smad4 causes cleavage of ß-catenin and depletion of the low density lipoprotein receptor Lrp5, subsequent to increased caspase-3 activity and apoptosis. In summary, Smad4 regulates maturation of skeletal collagen and osteoblast survival, and is required for matrix-forming responses to both BMP2 and canonical Wnt.
Assuntos
Doenças do Desenvolvimento Ósseo/metabolismo , Matriz Óssea/embriologia , Matriz Óssea/metabolismo , Osteoblastos/metabolismo , Osteogênese , Transdução de Sinais , Proteína Smad4/metabolismo , Proteínas Wnt/metabolismo , Animais , Doenças do Desenvolvimento Ósseo/congênito , Doenças do Desenvolvimento Ósseo/genética , Doenças do Desenvolvimento Ósseo/fisiopatologia , Matriz Óssea/anormalidades , Proteína Morfogenética Óssea 2/metabolismo , Colágeno/metabolismo , Feminino , Humanos , Masculino , Camundongos , Osteoblastos/citologia , Proteína Smad4/genética , Fator de Crescimento Transformador beta/metabolismo , Proteínas Wnt/genética , beta Catenina/metabolismoRESUMO
Canonical Wnt (cWnt) signaling through ß-catenin regulates osteoblast proliferation and differentiation to enhance bone formation. We previously reported that osteogenic action of ß-catenin is dependent on BMP signaling. Here, we further examined interactions between cWnt and BMP in bone. In osteoprogenitors stimulated with BMP2, ß-catenin localizes to the nucleus, physically interacts with Smad4, and is recruited to DNA-binding transcription complexes containing Smad4, R-Smad1/5 and TCF4. Furthermore, Tcf/Lef-dependent transcription, Ccnd1 expression and proliferation all increase when Smad4, 1 or 5 levels are low, whereas TCF/Lef activities decrease when Smad4 expression is high. The ability of Smad4 to antagonize transcription of Ccnd1 is dependent on DNA-binding activity but Smad4-dependent transcription is not required. In mice, conditional deletion of Smad4 in osterix(+) cells increases mitosis of cells on trabecular bone surfaces as well as in primary osteoblast cultures from adult bone marrow and neonatal calvaria. By contrast, ablation of Smad4 delays differentiation and matrix mineralization by primary osteoblasts in response to Wnt3a, indicating that loss of Smad4 perturbs the balance between proliferation and differentiation in osteoprogenitors. We propose that Smad4 and Tcf/Lef transcription complexes compete for ß-catenin, thus restraining cWnt-dependent proliferative signals while favoring the matrix synthesizing activity of osteoblasts.
Assuntos
Proliferação de Células , Osteoblastos/metabolismo , Proteína Smad4/metabolismo , Via de Sinalização Wnt , beta Catenina/metabolismo , Animais , Sítios de Ligação , Proteína Morfogenética Óssea 2/fisiologia , Calcificação Fisiológica , Linhagem Celular , Ciclina D1/genética , Ciclina D1/metabolismo , Regulação da Expressão Gênica , Técnicas de Inativação de Genes , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Mitose , Regiões Promotoras Genéticas , Ligação Proteica , Proteína Smad4/genética , Transcrição GênicaRESUMO
The importance of membrane-bound PGE synthase 1 (mPGES1) in the regulation of renal function has been examined in mPGES1-deficient mice or by evaluating changes in its expression. However, it is unknown whether prolonged mPGES1 inhibition induces significant changes of renal function when Na(+) intake is normal or low. This study examined the renal effects elicited by a selective mPGES1 inhibitor (PF-458) during 7 days in conscious chronically instrumented dogs with normal Na(+) intake (NSI) or low Na(+) intake (LSI). Results obtained in both in vitro and in vivo studies have strongly suggested that PF-458 is a selective mPGES1 inhibitor. The administration of 2.4 mg·kg(-1)·day(-1) PF-458 to dogs with LSI did not induce significant changes in renal blood flow (RBF) and glomerular filtration rate (GFR). A larger dose of PF-458 (9.6 mg·kg(-1)·day(-1)) reduced RBF (P < 0.05) but not GFR in dogs with LSI and did not induce changes of renal hemodynamic in dogs with NSI. Both doses of PF-458 elicited a decrease (P < 0.05) in PGE2 and an increase (P < 0.05) in 6-keto-PGF1α. The administration of PF-458 did not induce significant changes in renal excretory function, plasma renin activity, and plasma aldosterone and thromboxane B2 concentrations in dogs with LSI or NSI. The results obtained suggest that mPGES1 is involved in the regulation of RBF when Na(+) intake is low and that the renal effects elicited by mPGES1 inhibition are modulated by a compensatory increment in PGI2. These results may have some therapeutical implications since it has been shown that prolonged mPGES1 inhibition has lower renal effects than those elicited by nonsteroidal anti-inflammatory drugs or selective cyclooxygenase-2 inhibitors.
Assuntos
Oxirredutases Intramoleculares/antagonistas & inibidores , Oxirredutases Intramoleculares/metabolismo , Rim/fisiologia , Circulação Renal/fisiologia , Sódio/farmacologia , Aldosterona/sangue , Animais , Benzoxazóis/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Cães , Inibidores Enzimáticos/farmacologia , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Oxirredutases Intramoleculares/genética , Rim/efeitos dos fármacos , Piperidinas/farmacologia , Potássio/urina , Prostaglandina-E Sintases , Circulação Renal/efeitos dos fármacos , Sódio/administração & dosagem , Sódio/urina , Tromboxano B2/sangueRESUMO
Direct cell-to-cell interactions via cell adhesion molecules, in particular cadherins, are critical for morphogenesis, tissue architecture, and cell sorting and differentiation. Partially overlapping, yet distinct roles of N-cadherin (cadherin-2) and cadherin-11 in the skeletal system have emerged from mouse genetics and in vitro studies. Both cadherins are important for precursor commitment to the osteogenic lineage, and genetic ablation of Cdh2 and Cdh11 results in skeletal growth defects and impaired bone formation. While Cdh11 defines the osteogenic lineage, persistence of Cdh2 in osteoblasts in vivo actually inhibits their terminal differentiation and impairs bone formation. The action of cadherins involves both cell-cell adhesion and interference with intracellular signaling, and in particular the Wnt/ß-catenin pathway. Both cadherin-2 and cadherin-11 bind to ß-catenin, thus modulating its cytoplasmic pools and transcriptional activity. Recent data demonstrate that cadherin-2 also interferes with Lrp5/6 signaling by sequestering these receptors in inactive pools via axin binding. These data extend the biologic action of cadherins in bone forming cells, and provide novel mechanisms for development of therapeutic strategies aimed at enhancing bone formation.
Assuntos
Osso e Ossos/citologia , Osso e Ossos/metabolismo , Caderinas/metabolismo , Adesão Celular/fisiologia , Comunicação Celular/fisiologia , Transdução de Sinais/fisiologia , Animais , Humanos , Osteoblastos/metabolismoRESUMO
Chemotherapy is a widely used treatment for a variety of solid and hematological malignancies. Despite its success in improving the survival rate of cancer patients, chemotherapy causes significant toxicity to multiple organs, including the skeleton, but the underlying mechanisms have yet to be elucidated. Using tumor-free mouse models, which are commonly used to assess direct off-target effects of anti-neoplastic therapies, we found that doxorubicin caused massive bone loss in wild-type mice, a phenotype associated with increased number of osteoclasts, leukopenia, elevated serum levels of danger-associated molecular patterns (DAMPs; e.g. cell-free DNA and ATP) and cytokines (e.g. IL-1ß and IL-18). Accordingly, doxorubicin activated the absent in melanoma (AIM2) and NLR family pyrin domain containing 3 (NLRP3) inflammasomes in macrophages and neutrophils, causing inflammatory cell death pyroptosis and NETosis, which correlated with its leukopenic effects. Moreover, the effects of this chemotherapeutic agent on cytokine secretion, cell demise, and bone loss were attenuated to various extent in conditions of AIM2 and/or NLRP3 insufficiency. Thus, we found that inflammasomes are key players in bone loss caused by doxorubicin, a finding that may inspire the development of a tailored adjuvant therapy that preserves the quality of this tissue in patients treated with this class of drugs.
Assuntos
Inflamassomos , Melanoma , Humanos , Animais , Camundongos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Alarminas , Doxorrubicina/efeitos adversos , InflamaçãoRESUMO
OBJECTIVE: Inflammasomes modulate the release of bioactive interleukin (IL)-1ß. Excessive IL-1ß levels are detected in patients with systemic juvenile idiopathic arthritis (sJIA) and cytokine storm syndrome (CSS) with mutated and unmutated inflammasome components, raising questions on the mechanisms of IL-1ß regulation in these disorders. METHODS: To investigate how the NLRP3 inflammasome is modulated in sJIA, we focused on Transmembrane protein 178 (Tmem178), a negative regulator of calcium levels in macrophages, and measured IL-1ß and caspase-1 activation in wild-type (WT) and Tmem178-/- macrophages after calcium chelators, silencing of Stim1, a component of store-operated calcium entry (SOCE), or by expressing a Tmem178 mutant lacking the Stromal Interaction Molecule 1 (Stim1) binding site. Mitochondrial function in both genotypes was assessed by measuring oxidative respiration, mitochondrial reactive oxygen species (mtROS), and mitochondrial damage. CSS development was analyzed in Perforin-/- /Tmem178-/- mice infected with lymphocytic choriomeningitis virus (LCMV) in which inflammasome or IL-1ß signaling was pharmacologically inhibited. Human TMEM178 and IL1B transcripts were analyzed in data sets of whole blood and peripheral blood monocytes from healthy controls and patients with active sJIA. RESULTS: TMEM178 levels are reduced in whole blood and monocytes from patients with sJIA while IL1B levels are increased. Accordingly, Tmem178-/- macrophages produce elevated IL-1ß compared with WT cells. The elevated intracellular calcium levels after SOCE activation in Tmem178-/- macrophages induce mitochondrial damage, release mtROS, and ultimately promote NLRP3 inflammasome activation. In vivo, inhibition of inflammasome or IL-1ß neutralization prolongs Tmem178-/- mouse survival in LCMV-induced CSS. CONCLUSION: Down-regulation of TMEM178 levels may represent a marker of disease activity and help identify patients who could benefit from inflammasome targeting.
Assuntos
Inflamassomos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Animais , Humanos , Camundongos , Cálcio/metabolismo , Caspase 1/metabolismo , Inflamassomos/metabolismo , Interleucina-1beta/metabolismo , Macrófagos/metabolismo , Monócitos/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismoRESUMO
OBJECTIVE: The mechanistic link between Janus kinase (JAK) signaling and structural damage to arthritic joints in rheumatoid arthritis (RA) is poorly understood. This study was undertaken to investigate how selective inhibition of JAK with tofacitinib (CP-690,550) affects osteoclast-mediated bone resorption in a rat adjuvant-induced arthritis (AIA) model, as well as human T lymphocyte RANKL production and human osteoclast differentiation and function. METHODS: Hind paw edema, inflammatory cell infiltration, and osteoclast-mediated bone resorption in rat AIA were assessed using plethysmography, histopathologic analysis, and immunohistochemistry; plasma and hind paw tissue levels of cytokines and chemokines (including RANKL) were also assessed. In vitro RANKL production by activated human T lymphocytes was evaluated by immunoassay, while human osteoclast differentiation and function were assessed via quantitative tartrate-resistant acid phosphatase staining and degradation of human bone collagen, respectively. RESULTS: Edema, inflammation, and osteoclast-mediated bone resorption in rats with AIA were dramatically reduced after 7 days of treatment with the JAK inhibitor, which correlated with reduced numbers of CD68/ED-1+, CD3+, and RANKL+ cells in the paws; interleukin-6 (transcript and protein) levels were rapidly reduced in paw tissue within 4 hours of the first dose, whereas it took 4-7 days of therapy for RANKL levels to decrease. Tofacitinib did not impact human osteoclast differentiation or function, but did decrease human T lymphocyte RANKL production in a concentration-dependent manner. CONCLUSION: These results suggest that the JAK inhibitor tofacitinib suppresses osteoclast-mediated structural damage to arthritic joints, and this effect is secondary to decreased RANKL production.
Assuntos
Artrite Experimental/tratamento farmacológico , Artrite Experimental/metabolismo , Janus Quinases/antagonistas & inibidores , Inibidores de Proteínas Quinases/farmacologia , Pirimidinas/farmacologia , Pirróis/farmacologia , Ligante RANK/metabolismo , Animais , Artrite Experimental/imunologia , Reabsorção Óssea/tratamento farmacológico , Reabsorção Óssea/imunologia , Reabsorção Óssea/metabolismo , Diferenciação Celular/efeitos dos fármacos , Células Cultivadas , Modelos Animais de Doenças , Feminino , Humanos , Janus Quinases/metabolismo , Macrófagos/citologia , Macrófagos/efeitos dos fármacos , Monócitos/citologia , Monócitos/efeitos dos fármacos , Osteoclastos/citologia , Osteoclastos/efeitos dos fármacos , Osteoclastos/enzimologia , Piperidinas , Ratos , Ratos Endogâmicos Lew , Transdução de Sinais/efeitos dos fármacos , Linfócitos T/citologia , Linfócitos T/efeitos dos fármacos , Linfócitos T/enzimologiaRESUMO
Objective: Inflammasomes modulate the release of bioactive IL-1ß. Excessive IL-1ß levels are detected in patients with systemic juvenile idiopathic arthritis (sJIA) and cytokine storm syndrome (CSS) with mutated and unmutated inflammasome components, raising questions on the mechanisms of IL-1ß regulation in these disorders. Methods: To investigate how the NLRP3 inflammasome is modulated in sJIA, we focused on Tmem178, a negative regulator of calcium levels in macrophages, and measured IL-1ß and caspase-1 activation in wild-type (WT) and Tmem178 -/- macrophages following calcium chelators, silencing of Stim1, a component of store-operated calcium entry (SOCE), or by expressing a Tmem178 mutant lacking Stim1 binding site. Mitochondrial function in both genotypes was assessed by measuring oxidative respiration, mitochondrial reactive oxygen species (mtROS), and mitochondrial damage. CSS development was analyzed in Perforin -/- /Tmem178 -/- mice infected with LCMV in which inflammasome or IL-1 signaling was pharmacologically inhibited. Human TMEM178 and IL-1B transcripts were analyzed in a dataset of peripheral blood monocytes from healthy controls and active sJIA patients. Results: TMEM178 levels are reduced in monocytes from sJIA patients while IL-1B show increased levels. Accordingly, Tmem178 -/- macrophages produce elevated IL-1ß compared to WT cells. The elevated intracellular calcium levels following SOCE activation in Tmem178 -/- macrophages induce mitochondrial damage, release mtROS, and ultimately, promote NLRP3 inflammasome activation. In vivo , inhibition of inflammasome or IL-1 neutralization prolongs Tmem178 -/- mouse survival to LCMV-induced CSS. Conclusion: Downregulation of Tmem178 levels may represent a new biomarker to identify sJIA/CSS patients that could benefit from receiving drugs targeting inflammasome signaling.
RESUMO
Senescence is a cellular aging-related process triggered by different stresses and characterized by the secretion of various inflammatory factors referred to as the senescence-associated secretory phenotype (SASP). Here, we present evidence that the inflammasome sensor, NLRP1, is a key mediator of senescence induced by irradiation both in vitro and in vivo. The NLRP1 inflammasome promotes senescence by regulating the expression of p16, p21, p53, and SASP in Gasdermin D (GSDMD)-dependent manner as these responses are reduced in conditions of NLRP1 insufficiency or GSDMD inhibition. Mechanistically, the NLRP1 inflammasome is activated downstream of the cytosolic DNA sensor cGMP-AMP (cGAMP) synthase (cGAS) in response to genomic damage. These findings provide a rationale for inhibiting the NLRP1 inflammasome-GSDMD axis to treat senescence-driven disorders.
RESUMO
We have previously shown that targeted expression of a dominant-negative truncated form of N-cadherin (Cdh2) delays acquisition of peak bone mass in mice and retards osteoblast differentiation; whereas deletion of cadherin 11 (Cdh11), another osteoblast cadherin, leads to only modest osteopenia. To determine the specific roles of these two cadherins in the adult skeleton, we generated mice with an osteoblast/osteocyte specific Cdh2 ablation (cKO) and double Cdh2(+/-);Cdh11(-/-) germline mutant mice. Age-dependent osteopenia and smaller diaphyses with decreased bone strength characterize cKO bones. By contrast, Cdh2(+/-);Cdh11(-/-) exhibit severely reduced trabecular bone mass, decreased in vivo bone formation rate, smaller diaphyses and impaired bone strength relative to single Cdh11 null mice. The number of bone marrow immature precursors and osteoprogenitor cells is reduced in both cKO and Cdh2(+/-);Cdh11(-/-) mice, suggesting that N-cadherin is involved in maintenance of the stromal cell precursor pool via the osteoblast. Although Cdh11 is dispensable for postnatal skeletal growth, it favors osteogenesis over adipogenesis. Deletion of either cadherin reduces ß-catenin abundance and ß-catenin-dependent gene expression, whereas N-cadherin loss disrupts cell-cell adhesion more severely than loss of cadherin 11. Thus, Cdh2 and Cdh11 are crucial regulators of postnatal skeletal growth and bone mass maintenance, serving overlapping, yet distinct, functions in the osteogenic lineage.
Assuntos
Osso e Ossos/citologia , Osso e Ossos/metabolismo , Caderinas/metabolismo , Osteoblastos/citologia , Osteoblastos/metabolismo , Animais , Fenômenos Biomecânicos , Densidade Óssea , Caderinas/genética , Adesão Celular , Diferenciação Celular/genética , Diferenciação Celular/fisiologia , Células Cultivadas , Immunoblotting , Camundongos , Camundongos Knockout , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Osteoarthritis is a joint disease characterized by a poorly-defined inflammatory response that does not encompass a massive immune cell infiltration yet contributes to cartilage degradation and loss of joint mobility, suggesting a chondrocyte intrinsic inflammatory response. Using primary chondrocytes from joints of osteoarthritic mice and patients, we first show that these cells express ample pro-inflammatory markers and RANKL in an NF-κB dependent manner. The inflammatory phenotype of chondrocytes was recapitulated by exposure of chondrocytes to IL-1ß and bone particles, which were used to model bone matrix breakdown products revealed to be present in synovial fluid of OA patients, albeit their role was not defined. We further show that bone particles and IL-1ß can promote senescent and apoptotic changes in primary chondrocytes due to oxidative stress from various cellular sources such as the mitochondria. Finally, we provide evidence that inflammation, oxidative stress and senescence converge upon IκB-ζ, the principal mediator downstream of NF-κB, which regulates expression of RANKL, inflammatory, catabolic, and SASP genes. Overall, this work highlights the capacity and mechanisms by which inflammatory cues, primarily joint degradation products, i.e., bone matrix particles in concert with IL-1ß in the joint microenvironment, program chondrocytes into an "inflammatory phenotype" which inflects local tissue damage.
RESUMO
Autophagy is a highly evolutionarily conserved process in the eukaryotic cellular system by which dysfunctional organelles are selectively degraded through a series of processes of lysosomal activity and then returned to the cytoplasm for reuse. All cells require this process to maintain cellular homeostasis and promote cell survival during stress responses such as deprivation and hypoxia. Osteoblasts and osteoclasts are two cellular phenotypes in the bone that mediate bone homeostasis. However, an imbalance between osteoblastic bone formation and osteoclastic bone resorption contributes to the onset of bone diseases. Recent studies suggest that autophagy, mitophagy, and selective mitochondrial autophagy may play an essential role in regulating osteoblast differentiation and osteoclast maturation. Autophagic activity dysregulation alters the equilibrium between osteoblastic bone creation and osteoclastic bone resorption, allowing bone disorders like osteoporosis to develop more easily. The current review emphasizes the role of autophagy and mitophagy and their related molecular mechanisms in bone metabolic disorders. In the current review, we emphasize the role of autophagy and mitophagy as well as their related molecular mechanism in bone metabolic disorders. Furthermore, we will discuss autophagy as a target for the treatment of metabolic bone disease and future application in therapeutic translational research.