Deficient BH4 production via de novo and salvage pathways regulates NO responses to cytokines in adult cardiac myocytes
Deficient BH4 production via de novo and salvage pathways regulates NO responses to cytokines in adult cardiac myocytes
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DOI：
10.1152/ajpheart.00748.2008
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发表时间：
2008-11-01
影响因子：
4.8
通讯作者：
Pieper, Galen M.
中科院分区：
文献类型：
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作者：
Ionova, Irina A.;Vasquez-Vivar, Jeannette;Pieper, Galen M.
Ionova IA，Vasquez-Vivar J，惠特塞特J，Herrnreiter A，Medhora M，Cooley BC，Pieper GM.通过从头和补救途径产生的BH 4缺陷调节成年心肌细胞对细胞因子的NO反应。美国生理学杂志心脏循环生理学295：H2178-H2187，2008年。首次发表于2008年10月3日; doi：10.1152/ajpheart.00748.2008。成年大鼠心肌细胞通常表现出对细胞因子的表型反应，表现为通过诱导型NO合酶（iNOS）产生的一氧化氮（NO）的低增加或不增加，这将它们与其他细胞类型区分开来。为了更好地描述这种反应，我们研究了四氢生物蝶呤（BH 4）合成和精氨酸利用基因在精氨酸刺激的成人心肌细胞的表达。细胞内BH 4和7，8-二氢生物蝶呤（BH 2）和NO的产生进行了定量。细胞因子诱导GTP环化水解酶及其反馈调节蛋白，但BH 4合成水平不足。尽管诱导型一氧化氮合酶的蛋白质，姜黄素刺激的成年心肌细胞产生很少或没有增加NO与未受刺激的细胞。在非还原条件下的Western印迹分析显示iNOS单体的存在。补充sepiapterin（BH 4的前体）增加BH 4以及BH 2，但这并没有提高NO水平或消除iNOS单体。在用sepiapterin治疗大鼠心脏移植受体后，体内证实了类似的发现。结果发现，在成年心肌细胞中未检测到补救途径完全活性所需的二氢叶酸还原酶的表达。因此，成年心肌细胞在细胞因子刺激后合成BH 4的能力有限。其机制涉及翻译后因素损害从头和补救途径。这些条件不能支持NO产生所必需的活性iNOS蛋白二聚体。这些研究结果提出了重要的新问题，关于细胞因子如何通过iNOS在心脏炎性疾病状态期间引起体内心脏功能障碍和损伤的普遍理解，因为心肌细胞不是高NO产生的主要来源。
Ionova IA, Vasquez-Vivar J, Whitsett J, Herrnreiter A, Medhora M, Cooley BC, Pieper GM. Deficient BH4 production via de novo and salvage pathways regulates NO responses to cytokines in adult cardiac myocytes. Am J Physiol Heart Circ Physiol 295: H2178-H2187, 2008. First published October 3, 2008; doi: 10.1152/ajpheart.00748.2008.-Adult rat cardiac myocytes typically display a phenotypic response to cytokines manifested by low or no increases in nitric oxide (NO) production via inducible NO synthase (iNOS) that distinguishes them from other cell types. To better characterize this response, we examined the expression of tetrahydrobiopterin (BH4)- synthesizing and arginine-utilizing genes in cytokine-stimulated adult cardiac myocytes. Intracellular BH4 and 7,8-dihydrobiopterin (BH2) and NO production were quantified. Cytokines induced GTP cyclohydrolase and its feedback regulatory protein but with deficient levels of BH4 synthesis. Despite the induction of iNOS protein, cytokine-stimulated adult cardiac myocytes produced little or no increase in NO versus unstimulated cells. Western blot analysis under nonreducing conditions revealed the presence of iNOS monomers. Supplementation with sepiapterin (a precursor of BH4) increased BH4 as well as BH2, but this did not enhance NO levels or eliminate iNOS monomers. Similar findings were confirmed in vivo after treatment of rat cardiac allograft recipients with sepiapterin. It was found that expression of dihydrofolate reductase, required for full activity of the salvage pathway, was not detected in adult cardiac myocytes. Thus, adult cardiac myocytes have a limited capacity to synthesize BH4 after cytokine stimulation. The mechanisms involve posttranslational factors impairing de novo and salvage pathways. These conditions are unable to support active iNOS protein dimers necessary for NO production. These findings raise significant new questions about the prevailing understanding of how cytokines, via iNOS, cause cardiac dysfunction and injury in vivo during cardiac inflammatory disease states since cardiac myocytes are not a major source of high NO production.