The most toxic and mobile form of vanadium (V) is V(V). Thus, the oxidation of V is a subject of considerable importance since the process may increase environmental risks of V. V(IV) is known to be stable when pH < 4.5. However, in this study, stable V(IV) was oxidized almost completely in goethite suspension within 60 min at pH 2.0 and pH 4.0, correspondingly, only 25%–30% and 15%–20% of V(IV) were oxidized in equimolar Fe 3+ solution and the blank solution, respectively. The promoted oxidation of V(IV) by FeOOH is attributed to the formation of the complex, VO(OFe<) + or VO(OFe<) 2 . On the one hand, the formation of the complex caused higher pH in the interface of solid FeOOH and corresponding lower conditional potential of V(V)/V(IV) than those in bulk solutions, which facilitates the oxidation of V(IV). On the other hand, the surface group OFe < may serve as a medium that facilitating the electron transfer from V(IV) ions to dissolved oxygen molecules, also favoring the oxidation of V(IV). This study not only deepens our understanding of the transfer, transformation, and risk of V in environments, but also provides a reference to speculate the fate of similar elements in environments.
Alzheimer's disease (AD) is a major type of dementia in the elderly. Clinical medication at present can only relieve symptoms but has no therapeutical effect. Thus, it is urgent to develop an effective drug for the treatment of AD. In this study, 2-month-old triple transgenic AD model mice (3 × Tg-AD) was treated with 0.2 and 1.0 mM bis(ethylmaltolato) oxidovanadium IV (BEOV) in drinking water for 2 months respectively. The results of open field test, elevated plus-maze test and Y maze test showed that BEOV could significantly improve the exploratory ability, memory capacity and exercise ability and relieve the anxiety of 4-month-old 3 × Tg-AD mice. The dendritic spines of pyramidal neuron in neocortex were detected by in vivo two-photon imaging of YFP and AD-YFP mice (the offspring of 3 × Tg-AD and YFP mice). The numbers of dendritic spines increased in YFP mice but decreased in AD-YFP mice from 2.5-month-old to 3.5-month-old. Treatment with BEOV (1.0 mM) in the AD-YFP mice significantly increased the numbers of total dendritic spines, mushroom spines and thin spines, which suggested that BEOV could protect cortical neurons and reduce the loss of dendritic spines. The contents of metal ions in the brain of mice were further measured by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that BEOV (1.0 mM) could significantly increase the contents of V and Se and decrease the contents of Fe, Zn, Hg, Pb, Bi and Ni in AD brains, implying that vanadium might synergize with selenium to regulate the contents of metal ions in AD mice. Summarily, BEOV could mediate the homeostasis of multiple metal ions in AD brain and protect cortical neurons by reducing the loss of dendritic spines, thus to interfere with the pathological process of AD.
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