Vanadium compounds have been regarded as promising in therapeutic treatment of diabetes and in
cancer prevention. In the present work, we studied the effects of
vanadium compounds on mitochondria to investigate the mechanisms of toxicity. Mitochondria were isolated from rat liver and incubated with a variety of
vanadium compounds, i.e. VOSO(4), NaVO(3), and
vanadyl complexes with organic
ligands. Our studies indicated that VO(2+), VO(3)(-),
VO(acac)(2) and VOcit (1-100microM) could induce mitochondrial swelling in a concentration dependent manner and disrupt mitochondrial membrane potential (Deltapsi(m)) in a time dependent manner, which is quite different from the rapid Deltapsi(m) collapse caused by Ca(2+) or
CCCP (
carbonyl cyanide m-chlorophenylhydrazone, a mitochondrial uncoupling
reagent). Release of
cytochrome c (Cyt c) was observed and could be inhibited by
cyclosporin A (CsA), an inhibitor of the
mitochondrial permeability transition pore (PTP). Interestingly, VOdipic caused release of Cyt c without mitochondrial swelling and Deltapsi(m) disruption, an action previously only observed on the
Bax protein, suggesting a potentially role of VOdipic in regulating PTP opening. In addition, all the
vanadium compounds tested stimulated mitochondrial production of
reactive oxygen species (ROS).
Antioxidants, i.e.
vitamin C and E, significantly delayed the Deltapsi(m) disruption. Overall, our experimental evidence indicated
vanadium compounds exhibited multiple actions on mitochondria.
Vanadium compounds did induce oxidative stress on mitochondrial and thus caused PTP opening, which led to collapse of Deltapsi(m) and Cyt c release as the initiation of cell apoptosis.