BRD4蛋白对B细胞分化的调控及其在B细胞相关自身免疫病发病中的作用

Abnormal differentiation of B cells plays a central role in in the pathogenesis of humoral immune mediated autoimmune disease (AID) such as Systemic lupus erythematosus (SLE) and Sjogren’s syndrome (SS), however, the mechanisms contributing to those abnormal changes of biology are still poorly understood. It has been shown that bromodomain-containingproteins(BRD) participate in modulation of immune responses and growth of tumor cells and immune inflammation recently, but it is still not clear whether BRD is involved in the modulation of B cell differentiation and the pathogenesis of B cell mediated AID. We found that treatment with specific inhibitor of BRD proteins JQ1 suppressed peripheral B-Cell differentiation. We also shown the increased expression of BRD4 proteins in peripheral B-Cell from SLE patients as compared with health control. BRD inhibitors significantly eliminated autoantibody production and reduced renal disease in lupus mice. Therefore, based on our previous studies, this proposal will be aimed at identifying the effect of BRD proteins inhibition on peripheral B-Cell differentiation of health control, SLE ad SS patients and find the evidence for the regulation of B cell differentiation by BRD4 protein and its molecular mechanism by generating B cell–specific Brd4-deficient mice (Brd4flox/floxCD19-Cre+/- mice). We will also observe the therapeutic effect of BRD protein in vivo with murine models of SLE and SS. We propose to clarify the mechanisms underlying B cell differentiation modulated by BRD proteins, providing the scientific basis for establishment of therapeutic target for B cell mediated AID.

B细胞分化异常在系统性红斑狼疮(SLE)、干燥综合征(SS)等体液免疫介导的自身免疫性疾病（AID）发病中起重要作用。包含溴区蛋白(BRD)可能在肿瘤生长和免疫炎症反应中发挥关键作用，但其是否参与调控B细胞分化及B细胞介导的AID发病尚不清楚。我们前期发现BRD抑制剂JQ1可有效抑制外周血来源的健康人B细胞分化成记忆性B细胞、浆母细胞、浆细胞，SLE患者外周血B细胞中BRD4表达显著升高，BRD抑制剂明显减少狼疮小鼠自身抗体产生并减轻肾脏病变。在前期工作基础上本课题拟研究抑制BRD蛋白对健康人和SLE、SS患者外周B细胞体外分化的影响，利用特异性敲除B细胞BRD4的小鼠进一步获得BRD4调控B细胞分化的证据并阐明其分子机制。我们将观察体内抑制BRD蛋白对SLE和SS小鼠模型的治疗作用。从而揭示BRD蛋白对B细胞分化的关键调控作用及其机制，为SLE、SS等B细胞相关AID治疗提供新思路。

B细胞分化异常在系统性红斑狼疮(SLE)、干燥综合征(SS)等体液免疫介导的自身免疫性疾病（AID）发病中起重要作用。包含溴区蛋白(BRD)可能在肿瘤生长和免疫炎症反应中发挥关键作用，但其是否参与调控B细胞分化及B细胞介导的AID发病尚不清楚。本课题运用分子生物学和现代免疫学研究发现：SLE患者外周血B细胞中BRD4的表达量显著高于HC。抑制BRD4蛋白不影响HC外周血活化的B细胞的存活。在HC及SLE患者外周血的研究中，均发现抑制BRD4蛋白可影响外周血B细胞的分化，抑制外周血浆母细胞途径介导的浆细胞分化。体内试验证实BRD4蛋白抑制剂JQ-1、PFI-及利用BRD4flox/floxCD19-Cre+/-小鼠定向敲除B细胞中BRD4基因能明显抑制小鼠体内浆细胞的分化。进一步的机制研究发现，利用BRD4蛋白抑制剂及BRD4flox/floxCD19-Cre+/-小鼠抑制BRD4均明显抑制外周B细胞中STAT3蛋白的磷酸化，并进一步抑制其下游靶基因BLIMP1的表达。利用MRL/lpr小鼠动物模型证实抑制BRD4蛋白表达能改善小鼠的肾小球、肾血管病理损害和临床症状，利用小鼠实验性干燥综合征模型提示条件性敲除B细胞中BRD4基因可提高小鼠唾液流速，改善干燥综合征病情。本研究揭示了BRD蛋白对B细胞分化的关键调控作用，其可能通过STAT3/BLIMP1通路发挥作用，可为SLE、SS等B细胞相关AID提供治疗思路。