Zinc-alkaline phosphatase at sites of aortic calcification

IF 2.9 4区生物学 Q3 CELL BIOLOGY

Journal of Molecular Histology Pub Date : 2024-06-08 DOI:10.1007/s10735-024-10207-3

Santiago Gomez, José Luis Millán

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Abstract

Zinc (Zn) is a normal trace element in mineralizing tissues, but it is unclear whether it is primarily bound to the mineral phase or to organic molecules involved in the mineralization process, or both. Tissue-nonspecific alkaline phosphatase (TNAP) is a Zn metalloenzyme with two Zn ions bound to the M1 and M2 catalytic sites that functions to control the phosphate/pyrophosphate ratio during biomineralization. Here, we studied aortas from Tagln-Cre ^+/−; Hprt^ALP/Y TNAP overexpressor (TNAP-OE) mice that develop severe calcification. Zn histochemistry was performed using the sulfide-silver staining method in combination with a Zn partial extraction procedure to localize mineral-bound (mineral Zn) and TNAP-bound Zn (tenacious Zn), since soluble Zn (loose Zn) is extracted during fixation of the specimens. Two synthetic bone mineral composites with different Zn content, bone ash, and rat epiphyseal growth plate cartilage were used as controls for Zn staining. In order to correlate the distribution of mineral and tenacious Zn with the presence of mineral deposits, the aortas were examined histologically in unstained and stained thin sections using various light microscopy techniques. Our results show that 14 and 30 dpn, TNAP is concentrated in the calcifying matrix and loses Zn as Ca²⁺ progressively displaces Zn²⁺ at the M1 and M2 metal sites. Thus, in addition to its catalytic role TNAP has an additional function at calcifying sites as a Ca-binding protein.

Graphical Abstract

Abstract Image

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主动脉钙化部位的锌碱性磷酸酶

锌（Zn）是矿化组织中的一种正常微量元素，但目前还不清楚锌是主要与矿化相结合，还是与参与矿化过程的有机分子结合，或者两者兼而有之。组织非特异性碱性磷酸酶（TNAP）是一种锌金属酶，其 M1 和 M2 催化位点结合了两个锌离子，在生物矿化过程中起着控制磷酸盐/焦磷酸比例的作用。在这里，我们研究了出现严重钙化的 Tagln-Cre +/-; HprtALP/Y TNAP 过度表达者（TNAP-OE）小鼠的主动脉。由于可溶性锌（松散锌）会在标本固定过程中被提取出来，因此我们使用硫化银染色法结合锌部分提取程序对矿物结合锌（矿物质锌）和 TNAP 结合锌（顽固锌）进行了锌组织化学定位。两种不同锌含量的合成骨矿物复合材料、骨灰和大鼠骺生长板软骨被用作锌染色的对照组。为了将矿物质和韧性锌的分布与矿物质沉积的存在联系起来，我们使用各种光镜技术对主动脉未染色和染色的薄切片进行了组织学检查。我们的结果表明，在 14 和 30 dpn，TNAP 集中在钙化基质中，并随着 Ca2+ 逐渐取代 M1 和 M2 金属位点上的 Zn2+ 而失去 Zn。因此，除了催化作用外，TNAP 在钙化位点还具有钙结合蛋白的功能。

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来源期刊

Journal of Molecular Histology 生物-细胞生物学

CiteScore

5.90

自引率

0.00%

发文量

审稿时长

1 months

期刊介绍： The Journal of Molecular Histology publishes results of original research on the localization and expression of molecules in animal cells, tissues and organs. Coverage includes studies describing novel cellular or ultrastructural distributions of molecules which provide insight into biochemical or physiological function, development, histologic structure and disease processes. Major research themes of particular interest include: - Cell-Cell and Cell-Matrix Interactions; - Connective Tissues; - Development and Disease; - Neuroscience. Please note that the Journal of Molecular Histology does not consider manuscripts dealing with the application of immunological or other probes on non-standard laboratory animal models unless the results are clearly of significant and general biological importance. The Journal of Molecular Histology publishes full-length original research papers, review articles, short communications and letters to the editors. All manuscripts are typically reviewed by two independent referees. The Journal of Molecular Histology is a continuation of The Histochemical Journal.