CD38 modulation of NAD metabolism driving scleroderma pathogenesis

项目摘要/摘要 在系统性硬化症(SSC)中，纤维化会导致多个器官的永久性功能损害。而当 硬化性硬化性硬化症的非消退性纤维化具有致命的后果，其机制尚不清楚，也没有 有效的治疗。基于我们令人兴奋的发现，我们现在提出一个非常新的假设，即纤维化导致 烟酰胺腺嘌呤二核苷酸(NAD)和烟酰胺(NAM)代谢失调 通过CD38酶(将NAD分解为NAM)和烟酰胺N-甲基转移酶(NNMT)，它 将细胞代谢状态与甲基组的变化和细胞重新编程联系起来。此外，我们建议 这种多细胞CD38-NNMT代谢轴代表了SSC治疗的新靶点。我们的初步结果 结果显示：1)CD38和NNMT在SSc患者活检组织中的表达升高，其中这两种NAD- 代谢酶主要定位于免疫细胞(CD38)或基质细胞(NNMT)； CD38的遗传或药物阻断对小鼠的纤维化有保护作用；3)主要的酶类NAM NNMT活性的底物是通过CD38产生的；4)NNMT是转化生长因子诱导的，其 抑制可以消除纤维化反应。我们的新范式建立在这些观察的基础上，蕴含着 CD38和NNMT介导的NAD代谢异常在SSc发病机制中的作用具体来说，我们 认为SSC中CD38活性的升高在产生NAM的同时减少了NAD，这两者随后都会推动 成纤维细胞通过促进NNMT活性和其他机制进行重新编程。这种新陈代谢的相互作用 CD38和NNMT表达的细胞可能是纤维化治疗的选择性靶点。尽管我们 令人信服的观察，关键的NAD代谢酶CD38和NNMT的变化以及它们的 SSC代谢细胞网络中的致病作用、细胞来源和相互作用 被调查过了。因此，我们将使用全面的 部署患者样本、新型工程小鼠和疾病模型的实验策略 药理制剂。在目标1中，我们将定位CD38在SSc患者中的表达，并确定CD38‘S细胞 特定类型在纤维化中的作用和机制。在目标2中，我们将定位NNMT在SSC患者活检组织中的表达 并确定其特定细胞类型的致病作用、机制及其与CD38的相互作用。我们的前提是 极具创新性的建议是通过阐明CD38和CD38之间的致病作用和机制联系 NNMT在SSC中NAD代谢失调的基础上，我们将产生基本的机制 理解以指导发现全新的治疗方法以降低SSC的严重程度或延迟其致命的发病 并发症。

PROJECT SUMMARY/ABSTRACT In systemic sclerosis (SSc), fibrosis causes permanent functional damage in multiple organs. While non-resolving fibrosis in SSc has lethal consequences, its mechanisms are poorly understood and there is no effective treatment. Based on our exciting findings, we now propose the very novel hypothesis that fibrosis results from dysregulation of nicotinamide adenine dinucleotide (NAD) and nicotinamide (NAM) metabolism mediated by the enzymes CD38 (which breaks down NAD to NAM), and nicotinamide N-methyltransferase (NNMT), which couples cellular metabolic states to methylome changes and cellular reprogramming. Moreover, we propose that this multicellular CD38-NNMT metabolic axis represents a novel target for SSc therapy. Our preliminary results show that 1) expression of CD38 and NNMT are elevated in SSc patient biopsies, with these two NAD- metabolizing enzymes mapping predominantly to immune (CD38) or stromal (NNMT) cells, respectively; 2) genetic or pharmacological blockade of CD38 in mice is protective from fibrosis; 3) NAM, the main enzymatic substrate of NNMT that fuels its activity, is generated via CD38; and 4) NNMT is TGF-ß-inducible, and its inhibition abrogates fibrotic responses. Our novel paradigm, built upon these observations, implicates dysregulated NAD metabolism mediated via CD38 and NNMT in the pathogenesis of SSc. Specifically, we propose that elevated CD38 activity in SSc reduces NAD while generating NAM, both of which then drive fibroblast reprogramming via fueling NNMT activity and other mechanisms. This metabolic interplay between CD38-expressing and NNMT-expressing cells might be selectively targeted for fibrosis treatment. Despite our compelling observations, alterations in the key NAD metabolizing enzymes CD38 and NNMT, and their pathogenic roles, cellular sources and reciprocal interaction in a metabolic cellular network in SSc have never been investigated. We will therefore address these critical gaps in this proposal using a comprehensive experimental strategy deploying patient samples, novel engineered mice and disease models and pharmacological agents. In Aim 1 we will map CD38 expression in SSc patients and determine CD38's cell type-specific roles and mechanisms in fibrosis. In Aim 2 we will map NNMT expression in SSc patient biopsies and determine its cell type-specific pathogenic roles, mechanisms and interplay with CD38. The premise of our highly innovative proposal is that by elucidating the pathogenic roles and mechanistic links between CD38 and NNMT underlying dysregulated NAD metabolism in SSc, we will generate fundamental mechanistic understanding to guide discovery of entirely new treatments to reduce severity of SSc or delay onset of its deadly complications.