Regulation of mitochondrial biogenesis by heme oxygenase-1

描述（由申请人提供）：这是一份修改后的申请，旨在研究催化血红素降解的诱导酶的新功能，血红素加氧酶-1 (HO-1)，在线粒体生物发生调节中的作用。提出的机制是基于内源性的CO由HO （HO/CO）产生。一氧化碳，像一氧化氮（NO）一样，越来越被认为是一种气体信号分子，在健康和疾病中起调节作用。我们发现，在生理浓度下，CO上调核转录因子、核呼吸因子(NRF) -1和-2，以及调节线粒体生物发生的中心共激活因子PGC-11。我们的初步数据表明，在线粒体生物发生过程中，CO促进了小鼠心脏mtDNA的复制，增加了mtDNA拷贝数。后者是核控制下的重要过程，需要线粒体融合、裂变和呼吸蛋白合成，以满足器官对有氧ATP合成的持续需求，以实现收缩功能。HO/CO促进生物发生的途径尚未明确，但我们有新的初步数据表明，CO-细胞色素c氧化酶a3-血红素在线粒体中的结合机制，导致h2o2介导的促生存激酶、Akt/PKB的激活和氧化还原敏感的Nrf2转录因子的核易位。我们的假设是，HO产生的生理性（内源性）CO通过线粒体生物发生的氧化还原激活来产生抗氧化和抗凋亡的线粒体表型，从而发挥细胞存活功能。目的1：验证外源性和内源性CO通过akt依赖性PGC-11磷酸化激活心脏线粒体生物发生的假设。目的2：验证HO/CO介导的线粒体H2O2信号传导及其通过Nrf2转录因子的相互作用调控HO-1和NRF-1基因的表达，从而通过转录调控线粒体生物发生的假说。目的3：验证在阿霉素心肌病中，CO的心肌保护作用取决于内源性HO-1活性和细胞抵抗线粒体表型的产生的假设。这些目标的完成将扩大和发展我们对CO作为细胞信号分子在线粒体健康和疾病中的作用的理解。这意味着HO/ co调节的线粒体生物发生是维持正常心血管功能以及适应氧化应激和致病性炎症的基础。这将为HO- 1的保护作用提供一个统一的机制，可以通过一系列独特和新颖的策略进行治疗干预。公共卫生相关性：这是研究血红素加氧酶-1 （HO-1）新功能的新建议，HO-1是将血红素转化为胆绿素、铁和一氧化碳（CO）的酶的两种主要亚型之一。我们的初步数据表明，HO-1通过CO的产生，作为线粒体生物发生的调节剂。我们在小鼠心脏和心肌细胞中的研究表明，HO/ co调节的线粒体生物发生是适应氧化和炎症应激的基础。对我们的假设的成功测试将为HO-1在健康和疾病中的多种保护作用建立一个统一的机制。

DESCRIPTION (provided by applicant): This is an amended application to study a novel function for the inducible enzyme that catalyzes heme degradation, heme oxygenase-1 (HO-1), in the regulation of mitochondrial biogenesis. The proposed mechanism is based on the endogenous production of CO by HO (HO/CO). CO, like nitric oxide (NO), is increasingly recognized as a gaseous signaling molecule serving regulatory roles in health and disease. We have discovered that CO at physiological concentrations up-regulates the nuclear transcription factors, nuclear respiratory factors (NRF) -1 and -2, and the central co-activator, PGC-11, which regulate , mitochondrial biogenesis. Our preliminary data show that CO promotes mtDNA replication and increases mtDNA copy number in the mouse heart during mitochondrial biogenesis. The latter is an essential process under nuclear control that requires mitochondrial fusion, fission, and respiratory protein synthesis in order to meet the organ's continuous demand for aerobic ATP synthesis for contractile function. The pathways by which HO/CO promotes biogenesis are not yet well defined but we have new preliminary data implicating CO-cytochrome c oxidase a3-heme binding in mitochondria in the mechanism, leading to H2O2-mediated activation of the pro-survival kinase, Akt/PKB and nuclear translocation of the redox-sensitive Nrf2 transcription factor. Our hypothesis is that physiological (endogenous) CO produced by HO serves a cell survival function by redox activation of mitochondrial biogenesis to produce an anti-oxidant and anti- apoptotic mitochondrial phenotype. We propose three Specific Aims: Aim 1: Test the hypothesis that exogenous and endogenous CO activates cardiac mitochondrial biogenesis through Akt-dependent phosphorylation of PGC-11. Aim 2: Test the hypothesis that mitochondrial H2O2 signaling by HO/CO and its interplay through the Nrf2 transcription factor regulate HO-1 and NRF-1 gene expression for the transcriptional regulation of mitochondrial biogenesis. Aim 3: Test the hypothesis that the myocardial protective effect of CO depends on endogenous HO-1 activity and the generation of an apoptosis-resistent mitochondrial phenotype in doxorubicin cardiomyopathy. The completion of these Aims will expand and develop our understanding of the role of CO as a cell-signaling molecule in mitochondrial health and disease. The implication is that HO/CO-regulated mitochondrial biogenesis is fundamental to the maintenance of normal cardiovascular function as well as to adaptation to oxidative stress and pathogenic inflammation. This would provide a unifying mechanism for the protective role of HO- 1 that may be amenable to therapeutic intervention by a range of unique and novel strategies. PUBLIC HEALTH RELEVANCE: This is new proposal to study a novel function for heme oxygenase-1 (HO-1), one of two main isoforms of the enzyme that converts heme into biliverdin, Fe, and carbon monoxide (CO). Our preliminary data implicate HO-1, through the production of CO, as a regulator of mitochondrial biogenesis. Our work in the mouse heart and in cardiomyocytes suggests the hypothesis that HO/CO-regulated mitochondrial biogenesis is fundamental for adaptation to oxidative and inflammatory stress. A successful test of our hypothesis would establish a unifying mechanism for the diverse protective roles of HO-1 in health and disease.