Vanadate-induced cell growth regulation and the role of reactive oxygen species

Zhang, Z Huang, CS Li, JX Leonard, SS Lanciotti, R Butterworth, L Shi, XL

Z. Zhang et al., Vanadate-induced cell growth regulation and the role of reactive oxygen species, ARCH BIOCH, 392(2), 2001, pp. 311-320

56

INGLESE

Article

Biochemistry & Biophysics

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS

0003-9861 → ACNP

392

2

2001

311 - 320

ISI

0003-9861(20010815)392:2<311:VCGRAT>2.0.ZU;2-U

While vanadium compounds are known as potent toxicants as well as carcinoge ns, the mechanisms of their toxic and carcinogenic actions remain to be inv estigated. It is believed that an improper cell growth regulation leads to cancer development. The present study examines the effects of vanadate on c ell cycle control and involvement of reactive oxygen species (ROS) in these vanadate-mediated responses in a human lung epithelial cell line, A549. Un der vanadate stimulation, A549 cells generated hydroxyl radical (. OH), as determined by electron spin resonance (ESR), and hydrogen peroxide (H2O2) a nd superoxide anion (O-2(.-)), as detected by flow cytometry using specific dyes. The mechanism of ROS generation involved the reduction of molecular oxygen to O-2(.-) by both a flavoenzyme-containing NADPH complex and the mi tochondria electron transport chain. The O-2(.-) in turn generated H2O2 whi ch reacted with vanadium(IV) to generate . OH radical through a Fenton-type reaction (V(IV) + H2O2 --> V(V) + . OH + OH-). The ROS generated by vanada te induced G(2)/M phase arrest in a time-and dose-dependent manner as deter mined by measuring DNA content. Vanadate also increased p21 and Chk1 levels and reduced Cdc25C expression, leading to phosphorylation of Cdc2 and a sl ight increase in cyclin B-1 expression as analyzed by Western blot. Catalas e, a specific antioxidant for H2O2, decreased vanadate-induced expression o f p21 and Chk1, reduced phosphorylation of Cdc2(Tyr15), and decreased cycli n B-1 levels. Superoxide dismutase, a scavenger of O2(.-), or sodium format e, an inhibitor of . OH, had no significant effects. The results obtained f rom the present study demonstrate that among ROS, H2O2 is the species respo nsible for vanadate-induced G2/M phase arrest. Several regulatory pathways are involved: (1) activation of p21, (2) an increase of Chk1 expression and inhibition of Cdc25C, which results in phosphorylation of Cdc2 and possibl e inactivation of cyclin B-1/Cdc2 complex. (C) 2001 Academic Press.