Alterations in zinc homeostasis underlie endothelial cell death induced by oxidative stress from acute exposure to hydrogen peroxide

Abstract

Oxidative stress has been associated with multiple pathologies and disease states, including those involving the cardiovascular system. Previously, we showed that pulmonary artery endothelial cells (PAECs) undergo apoptosis after acute exposure to H(2)O(2). However, the underlying mechanisms regulating this process remain unclear. Because of the prevalence of H(2)O(2) in normal physiological processes and apparent loss of regulation in disease states, the purpose of this study was to develop a more complete understanding of H(2)O(2)-mediated adverse effects on endothelial cell survival. Acute exposure of PAECs to H(2)O(2) caused a dose-dependent increase in cellular release of lactate dehydrogenase and a significant increase in production of superoxide ions, which appear to be generated within the mitochondria, as well as a significant loss of mitochondrial membrane potential and activity. Subsequent to the loss of mitochondrial membrane potential, PAECs exhibited significant caspase activation and apoptotic nuclei. We also observed a significant increase in intracellular free Zn(2+) after bolus exposure to H(2)O(2). To determine whether this increase in Zn(2+) was involved in the apoptotic pathway induced by acute H(2)O(2) exposure, we developed an adenoviral construct for overexpression of the Zn(2+)-binding protein metallothionein-1. Our data indicate that chelating Zn(2+), either pharmacologically with N,N,N',N-tetrakis(2-pyridylmethyl)ethylene diamine or by overexpression of the Zn(2+)-binding protein metallothionein-1, in PAECs conferred significant protection from induction of apoptosis and cell death associated with the effects of acute H(2)O(2) exposure. Our results show that the acute toxicity profile of H(2)O(2) can be attributed, at least in part, to liberation of Zn(2+) within PAECs. We speculate that regulation of Zn(2+) levels may represent a potential therapeutic target for cardiovascular disease associated with acute oxidative stress.

UVB radiation induces an increase in intracellular zinc in human epidermal keratinocytes

“…Taken together, these observations are consistent with a model that oxidative processes release zinc from MT by redox regulation (29). Although the mechanism which accounts for the increase in cytoplasmic zinc is still elusive, the available data suggest that zinc release occurs via a ROS-mediated pathway (11,40,41,43). Thus, ROS induced by UVB radiation may attribute to UV-induced rising zinc in HEKa through oxidative stress.…”

“…Though the exact mechanism behind UV-induced toxicity is yet to be elucidated, many studies have suggested oxidative stress playing an important role in UVB elicited DNA damage, cell membrane disruption and subsequent cell death (11)(12)(13)(24)(25)(26). Several lines of evidence indicate that oxidative and nitrosative stress lead to an increase of intracellular zinc and zinc cytotoxicity that may, in turn, stimulate and interfere with signaling pathways (8)(9)(10)40,41). Zinc is normally tightly regulated inasmuch as intracellular concentrations of free zinc have been estimated to be in the pico-or nanomolar concentration range (2,5,6).…”

“…Thus, ROS induced by UVB radiation may attribute to UV-induced rising zinc in HEKa through oxidative stress. Accumulating evidence indicates that zinc is also involved in oxidative cytotoxicity of other pathological conditions, such as ischemia/reperfusion, head trauma, Alzheimer's disease, endothelial cell death of cardiovascular disease, impaired immune responses, and hepatic oxidative stress (7,8,41,45). Interestingly, zinc itself is a strong inducer of oxidative stress by promoting mitochondrial and extra-mitochondrial production of reactive oxygen species (48).…”

Disruption of Endothelial Cell Mitochondrial Bioenergetics in Lambs with Increased Pulmonary Blood Flow

“…Mitochondrial membrane potential was analyzed using the lipophilic cation 5,5¢6,6¢-tetrachloro-1,1¢,3,3¢-tetraethyl benzimidazolyl carbocyanine iodide as previously described (11,57).…”

Sequential Shrinkage and Swelling Underlie P2X7-Stimulated Lymphocyte Phosphatidylserine Exposure and Death

“…Some of these differences in interpretation are likely to be due to the fact that apoptosis and necrosis are not "either/or" alternative death mechanisms, but appear to be the opposite ends of a spectrum of cell death pathways (12). For example, lactate dehydrogenase release has been used to identify necrosis by some researchers, but apoptosis by another (13), whereas unengulfed apoptotic cells may also release lactate dehydrogenase following secondary necrosis (14), suggesting this marker may not efficiently discriminate between the two pathways. Similarly, release of HMGB1 has also been reported to occur during both necrosis and apoptosis (15).…”