Biomedical subjects

Yang V Li

Publications and source records attributed to Yang V Li.

5 recordsLinked to original sources

PubMed2006

Intracellular zinc elevation measured with a "calcium-specific" indicator during ischemia and reperfusion in rat hippocampus: a question on calcium overload.

Much of our current evidence concerning of the role of calcium (Ca2+) as a second messenger comes from its interaction with fluorescent probes; however, many Ca2+ probes also have a higher affinity for another divalent cation: zinc (Zn2+). In this study, using a selective Zn2+ probe (Newport Green), we investigated the accumulation of intracellular Zn2+ transients in acute rat hippocampal slices during ischemia, simulated by oxygen and glucose deprivation (OGD). Subsequent reperfusion with glucose-containing oxygenated medium resulted in an additional increase in intracellular Zn2+. Such observations compelled us to investigate the contribution of Zn2+ to the alleged intracellular Ca2+ overload occurring in ischemia and reperfusion. Using confocal fluorescent microscopy of Calcium Green-1, a widely used Ca2+ indicator, we detected increases in fluorescence intensity during OGD and reperfusion. However, application of a Zn2+ chelator, at the peak of the fluorescence elevation (interpreted as Ca2+ overload), resulted in a significant drop in intensity, suggesting that rising Zn2+ is the primary source of the increasing Calcium Green-1 fluorescence. Finally, staining with the cell viability indicator propidium iodide revealed that Zn2+ is responsible for the ischemic neuronal cell death, because Zn2+ chelation prevented cells from sustaining ischemic damage. Current cellular models of ischemic injury center on Ca2+-mediated excitotoxicity. Our results indicate that Zn2+ elevation contributes to conventionally recognized Ca2+ overload and also suggest that the role of Ca2+ in neurotoxicity described previously using Ca2+ probes may need to be re-examined to determine whether effect previously attributed to Ca2+ could, in part, be attributable to Zn2+.

Animals↗

PubMed2006

Determining zinc with commonly used calcium and zinc fluorescent indicators, a question on calcium signals.

Investigations into the roles of Ca(2+) and Zn(2+) in cell biology have been facilitated by the development of sensitive fluorometric probes that have enabled the measurement of Ca(2+) or Zn(2+) in both extracellular and intracellular environments. It is critical to be aware of the specificity and relative selectivity of a probe for the targeted ion. Here, we investigated metal-ion responses by screening nominally Zn(2+)- or Ca(2+)-selective fluorophores in solutions containing various concentrations of Ca(2+), as a potential interferent for Zn(2+), or Zn(2+), as a potential interferent for Ca(2+). The results suggested that Zn(2+)-sensitive dyes were more specific for their targeted ion than dyes that targeted Ca(2+). Ca(2+)-sensitive dyes such as Calcium Green-1, Fura-2, and Fluo-3 showed a wide range of interaction with Zn(2+), even responding to Zn(2+) in the presence of high concentrations of Ca(2+). We demonstrate that these Ca(2+) indicators can effectively measure dynamic changes of cytosolic Zn(2+). Our results appeal for a new generation of Ca(2+) fluorophores that are more specific for Ca(2+) over Zn(2+). One implication of these results is that data obtained using Ca(2+)-sensitive dyes may need to be re-examined to determine if results previously attributed to Ca(2+) could, in part, be due to Zn(2+).

Animals↗

PubMed2006

Measuring cell viability with membrane impermeable zinc fluorescent indicator.

Recent findings suggest that the accumulation of cytoplasmic zinc [Zn2+]i is a ubiquitous component in the cell death cascade. Zn2+ can be liberated from intracellular stores following oxidative stress and contribute to cell death processes. Here we show that the membrane/cell impermeable Zn2+ fluorescent indicator Newport Green (NG), which is non-toxic and impermeable to the membranes of healthy cells, can label unhealthy cells in tissue slices in a manner comparable to the traditional viability indicator propidium iodide (PI). Using confocal microscopy, we detected PI labeled nuclei colocalized with NG fluorescence. Our results indicate that cells which absorbed PI into their nuclei also allowed cell-impermeable Zn2+ dye to penetrate their plasma membranes, subsequently exhibiting cytosolic and nuclear fluorescence. As in PI staining, we observed marked increases in NG fluorescence in damaged/dead cells of tissue slices. Two other cell impermeable fluorescent Zn2+ dyes, Fluozin-3 and Zinpyr-4, also stained cytosolic Zn2+ in PI labeled cells. Our data indicates that the application of a Zn2+ fluorescent indicator is a fast, simple, non-toxic and reliable method for visualizing cell viability within in vitro tissue preparations. Accordingly, we demonstrate that intracellular accumulation of Zn2+ correlates with neuronal death.

Animals↗

PubMed2003

Do we need zinc to think?

Chelatable Zn(2+), which is found in the synaptic vesicles of certain glutamatergic neurons in several regions of the forebrain, is released during neuronal activity. Zn(2+) exhibits numerous effects on ligand-gated and voltage-dependent ion channels, and released Zn(2+) is therefore likely able to modulate synaptic transmission. The physiologically relevant actions of Zn(2+), however, have remained unclear. Recent research exploiting improved Zn(2+)-sensitive optical probes has suggested some intriguing effects for synaptically released Zn(2+), including heterosynaptic regulation of N-methyl-D-aspartate (NMDA) receptor function, and a novel role as a trans-synaptic second messenger that may enter postsynaptic neurons to modulate various signal transduction pathways.

Animals↗

PubMed2003

MEK/ERK pathway is aberrantly active in Hodgkin disease: a signaling pathway shared by CD30, CD40, and RANK that regulates cell proliferation and survival.

The mitogen-activated protein kinase (MAPK) (also called extracellular signal-regulated kinase [ERK]) pathway has been implicated in malignant transformation and in the regulation of cellular growth and proliferation of several tumor types, but its expression and function in Hodgkin disease (HD) are unknown. We report here that the active phosphorylated form of MAPK/ERK is aberrantly expressed in cultured and primary HD cells. Inhibition of the upstream MAPK kinase (also called MEK) by the small molecule UO126 inhibited the phosphorylation of ERK and demonstrated a dose- and time-dependent antiproliferative activity in HD cell lines. UO126 modulated the levels of several intracellular proteins including B-cell lymphoma protein 2 (Bcl-2), myeloid cell leukemia-1 (Mcl-1) and caspase 8 homolog FLICE-inhibitory protein (cFLIP), and induced G2M cell-cycle arrest or apoptosis. Furthermore, UO126 potentiated the activity of apoliprotein 2/tumor necrosis factor-related apoptosis-inducing ligand (APO2L/TRAIL) and chemotherapy-induced cell death. Activation of CD30, CD40, and receptor activator of nuclear kappabeta (RANK) receptors in HD cells by their respective ligands increased ERK phosphorylation above the basal level and promoted HD cell survival. UO126 inhibited basal and ligand-induced ERK phosphorylation, and inhibited ligand-induced cell survival of HD cell lines. These findings provide a proof-of-principle that inhibition of the MEK/ERK pathway may have therapeutic value in HD.

Antineoplastic Agents↗