Advances in research on the accumulation, redox behavior, and function of vanadium in ascidians

Abstract

The discovery of high levels of vanadium-containing compounds in ascidian blood cells goes back to 1911. Ascidians, which are also known as tunicates or sea squirts, belong to a subphylum of the Chordata, between the vertebrates and invertebrates. This discovery attracted the attention of an interdisciplinary group of chemists, physiologists, and biochemists, in part because of interest in the possible role of vanadium in oxygen transport as a prosthetic group in respiratory pigments, which was later shown not to be such a role, and in part because of the fact that high levels of vanadium were unknown in other organisms. The intracellular concentration of vanadium in some ascidian species can be as high as 350 mm, which is 107 times that in seawater. Vanadium ions, which are thought to be present in the +5 oxidation state in seawater, are reduced to the +3 oxidation state via the +4 oxidation state and are stored in the vacuoles of vanadium-containing cells called vanadocytes, where high levels of protons and sulfate ions are also found. Recently, many proteins and genes that might be involved in the accumulation and reduction of vanadium have been isolated. In this review, we not only trace the history of vanadium research but also describe recent advances in our understanding of the field from several viewpoints: (i) vanadium-accumulating blood cells, (ii) the energetics of vanadium accumulation, (iii) the redox mechanism of vanadium, (iv) the possible role of sulfate, and (v) the physiological roles of vanadium.

A novel vanadium transporter of the Nramp family expressed at the vacuole of vanadium-accumulating cells of the ascidian Ascidia sydneiensis samea

“…Some ascidians, known as tunicates or sea squirts, belonging to the suborder Phlebobranchia (Chordata, Urochordata, Ascidiacea), accumulate extremely high levels of vanadium in vanadocytes, one of their approximately ten types of blood cell [1][2][3][4]. The vanadium concentration in vanadocytes can reach 350 mM [5,6], corresponding to 10 7 times the level in seawater (35 nM).…”

The First-Row Transition Metals in the Periodic Table of Medicine

“…Although it has been controversial whether vanadium is an essential element for human beings [60], it is known to be essential for some organisms [61]. High levels of V are found in V-accumulating tunicates, and the form in these organisms have been explored and is currentlty believed to be the V-binding proteins (VanaBin) [61,62]. The function and role of vanadium in these organisms are still being investigated [61,62].…”

“…High levels of V are found in V-accumulating tunicates, and the form in these organisms have been explored and is currentlty believed to be the V-binding proteins (VanaBin) [61,62]. The function and role of vanadium in these organisms are still being investigated [61,62]. Other V-containing enzymes were isolated from certain types of algae, seaweed, and fungi, and the class of V-dependent haloperoxidases have been characterized extensively and the X-ray structures of the vanadium-dependent chloroperoxidase and the vanadium-dependent bromoperoxidase have been reported [61].…”

The pharmacological/toxicological effects and rational drug design of vanadium complexes

“…很早就发现钒化合物具有显著的肿瘤预防作用 [9] , 虽然可能是由于上述调节机体能力代谢和抗炎、抗 氧化作用, 但研究亦发现钒化合物可降低DNA的烷基 化 [36,37] , 从而降低DNA突变的发生, 这可能是钒化合物 肿瘤预防的机制之一. 而在钒化合物抗肿瘤方面, 其 作用涉及了调节miRNA表达、调节干细胞分化、抑 制肿瘤生长和肿瘤转移、诱导肿瘤细胞凋亡等多个方 面 [38,39] .…”