RESUMO
B-cell receptor (BCR)-activated B cells contribute to pathogenesis in chronic graft-versus-host disease (cGVHD), a condition manifested by both B-cell autoreactivity and immune deficiency. We hypothesized that constitutive BCR activation precluded functional B-cell maturation in cGVHD. To address this, we examined BCR-NOTCH2 synergy because NOTCH has been shown to increase BCR responsiveness in normal mouse B cells. We conducted ex vivo activation and signaling assays of 30 primary samples from hematopoietic stem cell transplantation patients with and without cGVHD. Consistent with a molecular link between pathways, we found that BCR-NOTCH activation significantly increased the proximal BCR adapter protein BLNK. BCR-NOTCH activation also enabled persistent NOTCH2 surface expression, suggesting a positive feedback loop. Specific NOTCH2 blockade eliminated NOTCH-BCR activation and significantly altered NOTCH downstream targets and B-cell maturation/effector molecules. Examination of the molecular underpinnings of this "NOTCH2-BCR axis" in cGVHD revealed imbalanced expression of the transcription factors IRF4 and IRF8, each critical to B-cell differentiation and fate. All-trans retinoic acid (ATRA) increased IRF4 expression, restored the IRF4-to-IRF8 ratio, abrogated BCR-NOTCH hyperactivation, and reduced NOTCH2 expression in cGVHD B cells without compromising viability. ATRA-treated cGVHD B cells had elevated TLR9 and PAX5, but not BLIMP1 (a gene-expression pattern associated with mature follicular B cells) and also attained increased cytosine guanine dinucleotide responsiveness. Together, we reveal a mechanistic link between NOTCH2 activation and robust BCR responses to otherwise suboptimal amounts of surrogate antigen. Our findings suggest that peripheral B cells in cGVHD patients can be pharmacologically directed from hyperactivation toward maturity.
Assuntos
Linfócitos B/metabolismo , Doença Enxerto-Hospedeiro/metabolismo , Transplante de Células-Tronco Hematopoéticas , Proteínas de Neoplasias/metabolismo , Receptor Notch2/metabolismo , Receptores de Antígenos de Linfócitos B/metabolismo , Transdução de Sinais , Proteínas Adaptadoras de Transdução de Sinal/biossíntese , Proteínas Adaptadoras de Transdução de Sinal/genética , Adulto , Idoso , Aloenxertos , Linfócitos B/patologia , Doença Crônica , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Doença Enxerto-Hospedeiro/genética , Doença Enxerto-Hospedeiro/patologia , Neoplasias Hematológicas/genética , Neoplasias Hematológicas/metabolismo , Neoplasias Hematológicas/patologia , Humanos , Fatores Reguladores de Interferon/biossíntese , Fatores Reguladores de Interferon/genética , Masculino , Pessoa de Meia-Idade , Proteínas de Neoplasias/genética , Receptor Notch2/genética , Receptores de Antígenos de Linfócitos B/genética , Tretinoína/farmacologiaRESUMO
Although B cells have emerged as important contributors to chronic graft-versus-host-disease (cGVHD) pathogenesis, the mechanisms responsible for their sustained activation remain unknown. We previously showed that patients with cGVHD have significantly increased B cell-activating factor (BAFF) levels and that their B cells are activated and resistant to apoptosis. Exogenous BAFF confers a state of immediate responsiveness to antigen stimulation in normal murine B cells. To address this in cGVHD, we studied B-cell receptor (BCR) responsiveness in 48 patients who were >1 year out from allogeneic hematopoietic stem cell transplantation (HSCT). We found that B cells from cGVHD patients had significantly increased proliferative responses to BCR stimulation along with elevated basal levels of the proximal BCR signaling components B cell linker protein (BLNK) and Syk. After initiation of BCR signaling, cGVHD B cells exhibited increased BLNK and Syk phosphorylation compared with B cells from patients without cGVHD. Blocking Syk kinase activity prevented relative post-HSCT BCR hyper-responsiveness of cGVHD B cells. These data suggest that a lowered BCR signaling threshold in cGVHD associates with increased B-cell proliferation and activation in response to antigen. We reveal a mechanism underpinning aberrant B-cell activation in cGVHD and suggest that therapeutic inhibition of the involved kinases may benefit these patients.
Assuntos
Linfócitos B/metabolismo , Doença Enxerto-Hospedeiro/imunologia , Doença Enxerto-Hospedeiro/metabolismo , Receptores de Antígenos de Linfócitos B/fisiologia , Adulto , Idoso , Fator Ativador de Células B/metabolismo , Linfócitos B/patologia , Proliferação de Células , Células Cultivadas , Doença Crônica , Feminino , Humanos , Ativação Linfocitária/fisiologia , Masculino , Pessoa de Meia-Idade , Cultura Primária de Células , Receptores de Antígenos de Linfócitos B/agonistas , Adulto JovemRESUMO
A new sensitive, precise, rapid and linear RP-HPLC method was developed and validated for the determination of dexrazoxane in formulations and human serum samples. Good chromatographic separation of dexrazoxane was achieved by using Kromasil C18 column. The system was operated at ambient temperature using a mobile phase consisting of methanol, 5% ortho phosphoric acid, 0.01M ammonium dihydrogen phosphate and tetrahydrofuran, pH 4.2 (10:40:30:20, v/v) isocratically at a flow rate of 1 ml/min. The method showed high sensitivity with good linearity (r(2)=0.9998) over the tested concentration range of 0.1 to 0.9 mg/ml. Detection was carried out at 272 nm and retention time was 7.005 min. The accuracy, formulation assay and percentage of RSD were 100.03, 97.48 and 0.03184, respectively with tailing factor (1.84). This method can be used for the routine quality control analysis.
