RESUMO
Rheumatoid arthritis (RA) is an inflammatory autoimmune disease characterized by joint destruction and severe morbidity. Methotrexate (MTX) is the standard first-line therapy of RA. However, about 40% of RA patients are unresponsive to MTX treatment. Regulatory T cells (Tregs, CD4(+)CD25(+)FoxP3(+)) are thought to play an important role in attenuating RA. To investigate the role of Tregs in MTX resistance, we recruited 122 RA patients (53 responsive, R-MTX; 69 unresponsive, UR-MTX) and 33 healthy controls. Three months after MTX treatment, R-MTX but not UR-MTX showed higher frequency of peripheral blood CD39(+)CD4(+)CD25(+)FoxP3(+) Tregs than the healthy controls. Tregs produce adenosine (ADO) through ATP degradation by sequential actions of two cell surface ectonucleotidases: CD39 and CD73. Tregs from UR-MTX expressed a lower density of CD39, produced less ADO, and had reduced suppressive activity than Tregs from R-MTX. In a prospective study, before MTX treatment, UR-MTX expressed a lower density of CD39 on Tregs than those of R-MTX or control (P < 0.01). In a murine model of arthritis, CD39 blockade reversed the antiarthritic effects of MTX treatment. Our results demonstrate that MTX unresponsiveness in RA is associated with low expression of CD39 on Tregs and the decreased suppressive activity of these cells through reduced ADO production. Our findings thus provide hitherto unrecognized mechanism of immune regulation in RA and on mode of action of MTX. Furthermore, our data suggest that low expression of CD39 on Tregs could be a noninvasive biomarker for identifying MTX-resistant RA patients.
Assuntos
Antígenos CD/metabolismo , Apirase/metabolismo , Artrite Reumatoide/tratamento farmacológico , Artrite Reumatoide/imunologia , Resistência a Medicamentos/imunologia , Metotrexato/uso terapêutico , Linfócitos T Reguladores/imunologia , 5'-Nucleotidase/metabolismo , Adenosina/metabolismo , Animais , Artrite Experimental/tratamento farmacológico , Artrite Experimental/imunologia , Artrite Experimental/patologia , Artrite Reumatoide/patologia , Biomarcadores/metabolismo , Resistência a Medicamentos/efeitos dos fármacos , Humanos , Contagem de Linfócitos , Metotrexato/farmacologia , Camundongos Endogâmicos C57BL , Linfócitos T Reguladores/efeitos dos fármacos , Células Th1/imunologia , Células Th17/imunologiaRESUMO
Recent studies have demonstrated the role of adenosine (ADO) in sickle-cell anemia (SCA). ADO is produced by CD39 and CD73 and converted to inosine by adenosine deaminase (ADA). We evaluated the effects of hydroxycarbamide (HU) treatment on the modulation of adenosine levels in SCA patients. The expressions of CD39, CD73, and CD26 were evaluated by flow cytometry on blood cells in 15 HU-treated and 17 untreated patients and 10 healthy individuals. RNA was extracted from monocytes, and ADA gene expression was quantified by real-time PCR. ADA activity was also evaluated. We found that ADA transcripts were two times higher in monocytes of HU-treated patients, compared with untreated (P = 0.039). Monocytes of HU-treated patients expressed CD26, while monocytes of controls and untreated patients did not (P = 0.023). In treated patients, a lower percentage of T lymphocytes expressed CD39 compared with untreated (P = 0.003), and the percentage of T regulatory (Treg) cells was reduced in the treated group compared with untreated (P = 0.017) and controls (P = 0.0009). Besides, HU-treated patients displayed increased ADA activity, compared with untreated. Our results indicate a novel mechanism of action of HU mediated by the reduction of adenosine levels and its effects on pathophysiological processes in SCA.
Assuntos
Adenosina/metabolismo , Anemia Falciforme/metabolismo , Antidrepanocíticos/farmacologia , Células Sanguíneas/efeitos dos fármacos , Células Sanguíneas/metabolismo , Hidroxiureia/farmacologia , 5'-Nucleotidase/genética , 5'-Nucleotidase/metabolismo , Adenosina Desaminase/genética , Adenosina Desaminase/metabolismo , Adolescente , Adulto , Anemia Falciforme/tratamento farmacológico , Anemia Falciforme/genética , Antígenos CD/genética , Antígenos CD/metabolismo , Antidrepanocíticos/uso terapêutico , Apirase/genética , Apirase/metabolismo , Células Sanguíneas/patologia , Estudos de Casos e Controles , Criança , Dipeptidil Peptidase 4/genética , Dipeptidil Peptidase 4/metabolismo , Proteínas Ligadas por GPI/genética , Proteínas Ligadas por GPI/metabolismo , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Humanos , Hidroxiureia/uso terapêutico , Redes e Vias Metabólicas/efeitos dos fármacos , Redes e Vias Metabólicas/genética , Pessoa de Meia-Idade , Adulto JovemRESUMO
Mesenchymal stromal cells (MSCs) suppress T cell responses through mechanisms not completely understood. Adenosine is a strong immunosuppressant that acts mainly through its receptor A(2a) (ADORA2A). Extracellular adenosine levels are a net result of its production (mediated by CD39 and CD73), and of its conversion into inosine by Adenosine Deaminase (ADA). Here we investigated the involvement of ADO in the immunomodulation promoted by MSCs. Human T lymphocytes were activated and cultured with or without MSCs. Compared to lymphocytes cultured without MSCs, co-cultured lymphocytes were suppressed and expressed higher levels of ADORA2A and lower levels of ADA. In co-cultures, the percentage of MSCs expressing CD39, and of T lymphocytes expressing CD73, increased significantly and adenosine levels were higher. Incubation of MSCs with media conditioned by activated T lymphocytes induced the production of adenosine to levels similar to those observed in co-cultures, indicating that adenosine production was mainly derived from MSCs. Finally, blocking ADORA2A signaling raised lymphocyte proliferation significantly. Our results suggest that some of the immunomodulatory properties of MSCs may, in part, be mediated through the modulation of components related to adenosine signaling. These findings may open new avenues for the development of new treatments for GVHD and other inflammatory diseases.
