RESUMO
The chloride-proton antiporter ClC-7 has been speculated to be involved in acidification of the lysosomes and the resorption lacunae in osteoclasts; however, neither direct measurements of chloride transport nor acidification have been performed. Human osteoclasts harboring a dominant negative mutation in ClC-7 (G215R) were isolated, and used these to investigate bone resorption measured by CTX-I, calcium release and pit scoring. The actin cytoskeleton of the osteoclasts was also investigated. ClC-7 enriched membranes from the osteoclasts were isolated, and used to test acidification rates in the presence of a V-ATPase and a chloride channel inhibitor, using a H(+) and Cl(-) driven approach. Finally, acidification rates in ClC-7 enriched membranes from ADOII osteoclasts and their corresponding controls were compared. Resorption by the G215R osteoclasts was reduced by 60% when measured by both CTX-I, calcium release, and pit area when comparing to age and sex matched controls. In addition, the ADOII osteoclasts showed no differences in actin ring formation. Finally, V-ATPase and chloride channel inhibitors completely abrogated the H(+) and Cl(-) driven acidification. Finally, the acid influx was reduced by maximally 50% in the ClC-7 deficient membrane fractions when comparing to controls. These data demonstrate that ClC-7 is essential for bone resorption, via its role in acidification of the lysosomes and resorption lacunae in osteoclasts.
Assuntos
Reabsorção Óssea/metabolismo , Canais de Cloreto/fisiologia , Lisossomos/metabolismo , Osteoclastos/metabolismo , Ácidos/metabolismo , Arginina/genética , Reabsorção Óssea/genética , Cálcio/metabolismo , Canais de Cloreto/antagonistas & inibidores , Canais de Cloreto/genética , Genes Dominantes , Glicina/genética , Humanos , Concentração de Íons de Hidrogênio , Mutação , Osteoclastos/ultraestrutura , ATPases Vacuolares Próton-Translocadoras/antagonistas & inibidores , ATPases Vacuolares Próton-Translocadoras/metabolismoRESUMO
T helper 9 (TH9) cells are important for the development of inflammatory and allergic diseases. The TH9 transcriptional network converges signals from cytokines and antigen presentation but is incompletely understood. Here, we identified TL1A, a member of the TNF superfamily, as a strong inducer of mouse and human TH9 differentiation. Mechanistically, TL1A induced the expression of the transcription factors BATF and BATF3 and facilitated their binding to the Il9 promoter leading to enhanced secretion of IL-9. BATF- and BATF3-deficiencies impaired IL-9 secretion under TH9 and TH9-TL1A-polarizing conditions. In vivo, using a T-cell transfer model, we demonstrated that TL1A promoted IL-9-dependent, TH9 cell-induced intestinal and lung inflammation. Neutralizing IL-9 antibodies attenuated TL1A-driven mucosal inflammation. Batf3-/- TH9-TL1A cells induced reduced inflammation and cytokine expression in vivo compared to WT cells. Our results demonstrate that TL1A promotes TH9 cell differentiation and function and define a role for BATF3 in T-cell-driven mucosal inflammation.
Assuntos
Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Inflamação/imunologia , Doenças Inflamatórias Intestinais/imunologia , Interleucina-9/metabolismo , Proteínas Repressoras/metabolismo , Linfócitos T Auxiliares-Indutores/imunologia , Animais , Anticorpos Neutralizantes/metabolismo , Fatores de Transcrição de Zíper de Leucina Básica/genética , Diferenciação Celular , Células Cultivadas , Humanos , Interleucina-9/genética , Interleucina-9/imunologia , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Regiões Promotoras Genéticas/genética , Ligação Proteica , Proteínas Repressoras/genética , Transdução de Sinais , Membro 15 da Superfamília de Ligantes de Fatores de Necrose Tumoral/metabolismoRESUMO
Mice deficient in the chloride channel ClC-7, which is likely involved in acidification of the resorption lacuna, display severe osteopetrosis. To fully characterize the osteopetrotic phenotype, the phenotypes of osteoclasts and osteoblasts were evaluated. ClC-7(-/-) mice and their corresponding wild-type littermates were killed at 4-5 weeks of age. Biochemical markers of bone resorption (CTX-I), osteoclast number (TRAP5b), and osteoblast activity (ALP) were evaluated in serum. Splenocytes were differentiated into osteoclasts using M-CSF and RANKL. Mature osteoclasts were seeded on calcified or decalcified bone slices, and CTX-I, Ca(2+), and TRAP were measured. Acidification rates in membrane vesicles from bone cells were measured using acridine orange. Osteoblastogenesis and nodule formation in vitro were investigated using calvarial osteoblasts. ClC-7(-/-) osteoclasts were unable to resorb calcified bone in vitro. However, osteoclasts were able to degrade decalcified bone. Acid influx in bone membrane vesicles was reduced by 70% in ClC-7(-/-) mice. Serum ALP was increased by 30% and TRAP5b was increased by 250% in ClC-7(-/-) mice, whereas the CTX/TRAP5b ratio was reduced to 50% of the wild-type level. Finally, evaluation of calvarial ClC-7(-/-) osteoblasts showed normal osteoblastogenesis. In summary, we present evidence supporting a pivotal role for ClC-7 in acidification of the resorption lacuna and evidence indicating that bone formation and bone resorption are no longer balanced in ClC-7(-/-) mice.