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，目的是研究催化血红素降解的诱导酶--血红素加氧酶-1(HO-1)在线粒体生物发生调节中的新功能。所提出的机理是基于HO(HO/CO)内源产生CO。一氧化碳和一氧化氮(NO)一样，是一种气体信号分子，在健康和疾病中发挥调节作用。我们发现，在生理浓度的CO上调核转录因子，核呼吸因子(NRF)-1和-2，以及中央共激活因子，PGC-11，调节线粒体的生物发生。我们的初步数据显示，在线粒体生物发生过程中，CO促进了mtDNA的复制，并增加了小鼠心脏中mtDNA的拷贝数。后者是核控制下的一个基本过程，需要线粒体融合、分裂和呼吸蛋白合成，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不清楚，但我们有新的初步数据表明，CO-细胞色素C氧化酶A3-血红素结合在线粒体上，导致H_2O_2介导的促生存激酶Akt/PKB的激活和氧化还原敏感的Nrf2转录因子的核转位。我们的假设是，HO产生的生理性(内源性)CO通过氧化还原激活线粒体生物发生来产生抗氧化和抗凋亡的线粒体表型，从而发挥细胞生存功能。我们提出了三个特定的目标：目的1：验证外源性和内源性CO通过Akt依赖的PGC-11磷酸化来激活心肌线粒体生物发生的假设。目的：验证线粒体HO/CO信号通路及其通过Nrf2转录因子调控HO-1和NRF-1基因表达的假说，从而实现线粒体生物发生的转录调控。目的：验证一氧化碳心肌保护作用依赖于内源性HO-1活性和阿霉素心肌病抗凋亡线粒体表型的假说。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，该机制可能适用于通过一系列独特和新颖的策略进行治疗干预。与公共健康相关：这是一项研究血红素加氧酶-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)的两种主要同工酶之一。我们的初步数据表明，HO-1通过产生一氧化碳，作为线粒体生物发生的调节因子。我们在小鼠心脏和心肌细胞中的工作表明，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在健康和疾病中的不同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.