Mitigating mitochondrial epigenetics in bone remodeling by hydrogen sulfide

 描述(申请人提供)：临床研究报道，出生时患有严重高同型半胱氨酸血症的儿童，由于cbs基因缺失，导致血浆同型半胱氨酸水平升高，导致骨骼畸形，骨质较弱。虽然线粒体功能障碍与骨骼病理有关，但线粒体改变(Mito)的表观遗传学和动力学对脆性骨的作用尚未被研究过。该项目的长期目标是了解遗传性HHcy过程中有丝分裂-表观遗传重塑和骨结构/功能变化的机制。线粒体动力学的改变干扰了骨细胞(破骨细胞/成骨细胞)的分化和基质代谢。研究证实，在HHcy过程中，有机骨基质的主要蛋白质-I型胶原(COIL-1)被同型半胱氨酸化(N-Hcy-COIL-1)。我们的初步数据表明，遗传性HHcy通过改变有丝分裂氧化还原应激、有丝分裂DNA甲基化/羟甲基化、裂变融合而影响有丝分裂表观遗传重构，并导致N-Hcy-Coll-1交联。这些过程累积性地扰乱了骨基质、骨密度、骨血流，并导致有丝分裂伴随着显著的骨丢失。有趣的是，硫化氢(硫化氢，一种抗氧化还原压力和同型半胱氨酸的降低剂)可以减轻骨骼损伤。这一建议的中心假设是，HHcy通过N-Hcy-coll-1，部分通过 增加有丝分裂-表观遗传学重塑和改变线粒体动力学。然而，硫化氢治疗可改善同型半胱氨酸引起的骨异常。我们将通过以下三个具体目标来检验这一假说：具体目标1：确定HHcy是否部分通过改变线粒体的分裂和融合来激发有丝分裂表观遗传学重塑和DNA甲基化，以及硫化氢是否减轻有丝分裂表观遗传学重塑。具体目的#2：确定同型半胱氨酸同型半胱氨酸化骨型胶原，激活基质金属蛋白酶-1，-3，-13，破坏骨基质(基质金属蛋白酶/组织金属蛋白酶；胶原/弹性蛋白比率)，硫化氢改善这些变化。具体目的#3：确定同型半胱氨酸是否改变骨密度、骨矿含量、生物力学承载能力、骨血流和破坏成骨细胞/破骨细胞分化，以及硫化氢是否减轻这些改变。

 DESCRIPTION (provided by applicant): Clinical studies report that children born with severe hyperhomocysteinemia (HHcy), due to deficiency in cystathionine--synthase (CBS) gene, resulting in an elevation in plasma homocysteine (Hcy) levels, develop skeletal malformations with weaker bone. Although mitochondrial dysfunction has been involved in bone pathology, altered mitochondrial (Mito) epigenetics and dynamics contributing to frailer bone have not been studied. The long term goal of this project is to understand the mechanisms of mito-epigenetic remodeling and changes in bone structure/function during genetic HHcy. Alterations in mitochondrial dynamics disturb bone cell (osteoclast/ osteoblast) differentiation and matrix metabolism. Studies have confirmed that type-I collagen (coll-1), a dominant protein of the organic bone matrix, is homocysteinylated (N-Hcy-coll-1) during HHcy. Our preliminary data suggest that genetic HHcy affects mito-epigenetic remodeling by altering mito-redox stress, mito-DNA methylation / hydroxymethylation, fission-fusion and cause N-Hcy-coll-1 cross linking. These processes cumulatively disrupt bone matrix, bone density, bone blood flow and lead to mitophagy accompanying with significant bone loss. Interestingly, hydrogen sulfide (H2S, an anti-redox stress and Hcy lowering agent) mitigates bone damage. The central hypothesis of this proposal is that HHcy contributes to bone-matrix inferiority through N-Hcy-coll-1, in part, by increasing mito- epigenetic remodeling and altering mitochondrial dynamics. However, treatment with H2S ameliorates HHcy-induced bone abnormalities. We will test this hypothesis by following three specific Aims: Specific Aim # 1: To determine whether the HHcy instigates mito-epigenetic remodeling and DNA methylation, in part, by altering mitochondrial fission and fusion, and whether H2S mitigates mito-epigenetic remodeling. Specific Aim # 2: To determine whether the HHcy homocysteinylates bone type-I collagen, activates MMP-1,-3,-13, disrupts bone matrix (MMP/TIMP axis; collagen/elastin ratio) and H2S ameliorates these changes. Specific Aim # 3: To determine whether the HHcy alters bone mineral density, bone mineral content, biomechanical load-bearing capacity, bone blood flow and disrupts osteoblast/osteoclast differentiation and whether H2S alleviates these alterations.