Metabolic Symbiosis: Lactate as an Epigenetic Regulator and a Biofuel in Age-dependent Intervertebral Disc Degeneration

项目摘要 椎间盘退变（IDD）是许多脊柱疾病的基础，并导致衰弱 背痛残疾和巨大的社会经济负担椎间盘（IVD）是 最大的无血管器官，由低氧髓核（NP）中心组成，周围环绕着 外部，更多氧合的纤维环（AF）。IVD含有大量的乳酸， 其长期以来被视为NP中厌氧糖酵解的有害废物副产物。 然而，我们最近取得了两项重大进展，挑战了这一长期存在的教条。我们 表明AF细胞可以通过氧化吸收和利用乳酸作为碳源， 磷酸化（OXPHOS），从而揭示了NP之间的乳酸依赖性代谢共生 和AF，其中缺氧NP细胞产生乳酸盐以被更需氧AF细胞用作 一种碳生物燃料。我们还发现了高水平的IVD组蛋白乳酸化， 一种新的组蛋白翻译后修饰（PTM）类型，它使用乳酸作为 衬底前体。组蛋白PTM对染色质结构的动态调节至关重要 和基因表达，组蛋白PTM的失调与发展密切相关， 许多疾病。根据我们的初步数据，我们假设椎间盘乳酸盐不是 一种废弃的副产品，而是作为营养贫乏的圆盘的重要生物燃料， 并作为椎间盘基因表达编程的重要代谢调节剂， 乳酰化。我们提出了三个具体目标来检验这一假设：（1）确定是否 乳酸通过组蛋白作为椎间盘基因表达的重要代谢调节剂 使用用酶的化学抑制剂处理的大鼠椎间盘细胞培养模型的乳酰化 （2）确定盘状组蛋白乳酸化和乳酸- 依赖性代谢共生功能障碍与年龄相关的IDD使用 年轻和老年Fischer 344大鼠;和（3）确定是否中断椎间盘乳酸盐依赖性 代谢共生破坏盘组蛋白乳酸化模式，促进IDD使用转基因 AF靶向基因耗竭小鼠模型，以破坏AF乳酸摄取。完成 这些研究将确定组蛋白的乳酸化是否会影响表观遗传转录 调节，控制椎间盘基质稳态和乳酸依赖性代谢共生。 通过年龄相关性碘缺乏病的研究，说明乳酸代谢的影响。 表观遗传基因调控和乳酸盐依赖的代谢共生机制将被 这两个新的和有意义的发现新的治疗靶点，以治疗IDD的可能性更大 在营养不良的环境中取得成功。这将是一种创新的方法， 这是一个超越先前在这种独特组织中取得有限成功的再生努力的进步。

Project Summary Intervertebral disc degeneration (IDD) underlies many spinal disorders and results in debilitating back pain, disability, and tremendous socioeconomic burden. The intervertebral disc (IVD) is the largest avascular organ comprised of a hypoxic nucleus pulposus (NP) center surrounded by an outer, more oxygenated annulus fibrosus (AF). The IVD contains copious amounts of lactic acid, which has long been viewed as a harmful waste byproduct of anaerobic glycolysis in the NP. However, we recently made two major advances that challenge this longstanding dogma. We demonstrated that AF cells can take up and utilize lactate as a carbon source via oxidative phosphorylation (OXPHOS), thus unveiling lactate-dependent metabolic symbiosis between NP and AF whereby the hypoxic NP cells make lactate to be used by the more aerobic AF cells as a carbon biofuel via OXPHOS. We also discovered high levels of IVD histone lactylation, a newly characterized type of histone post-translational modification (PTM) that uses lactate as a substrate precursor. Histone PTMs are critical to the dynamic modulation of chromatin structure and gene expression, and dysregulation of histone PTMs is closely linked with the development of many diseases. Based on our preliminary data, we hypothesize that disc lactate is not as a waste byproduct but rather serves as an important biofuel for the nutrient-poor disc and as a vital metabolic regulator of disc gene expression programming via histone lactylation. We propose three specific aims to test this hypothesis: (1) Determine whether lactate functions as an important metabolic regulator of disc gene expression through histone lactylation using rat disc cell culture models treated with chemical inhibitors of enzymes responsible for histone lactylation; (2) Determine whether disc histone lactylation and lactate- dependent metabolic symbiosis malfunction with age contributing to age-related IDD using young and old Fischer 344 rats; and (3) Determine whether interrupted disc lactate-dependent metabolic symbiosis disrupts disc histone lactylation pattern and promotes IDD using transgenic mouse models with AF-targeted genetic depletion to disrupt AF lactate uptake. Completion of the proposed studies will establish whether histone lactylation exerts epigenetic transcription regulation that controls disc matrix homeostasis and lactate-dependent metabolic symbiosis. Demonstrating the influences of lactate metabolism on age-related IDD through the mechanisms of epigenetic gene regulation and lactate-dependent metabolic symbiosis will be both novel and significant to identify new therapeutic targets to treat IDD with greater likelihood of success in the nutrient poor environment. This will be an innovative approach and significant advance over prior regenerative efforts which have had limited success in this unique tissue.