Search results for "thapsigargin"
showing 8 items of 28 documents
Protective effect of paraoxonase-2 against endoplasmic reticulum stress-induced apoptosis is lost upon disturbance of calcium homoeostasis
2008
PON2 (paraoxonase-2) is a ubiquitously expressed antioxidative protein which is largely found in the ER (endoplasmic reticulum). Addressing the cytoprotective functions of PON2, we observed that PON2 overexpression provided significant resistance to ER-stress-induced caspase 3 activation when the ER stress was induced by interference with protein modification (by tunicamycin or dithiothreitol), but not when ER stress was induced by disturbance of Ca2+ homoeostasis (by thapsigargin or A23187). When analysing the underlying molecular events, we found an activation of the PON2 promoter in response to all tested ER-stress-inducing stimuli. However, only tunicamycin and dithiothreitol resulted i…
Modulation of intracellular calcium concentrations and T cell activation by prickly pear polyphenols.
2004
Opuntia ficus indica (prickly pear) polyphenolic compounds (OFPC) triggered an increase in [Ca2+]i in human Jurkat T-cell lines. Furthermore, OFPC-induced rise in [Ca2+]i was significantly curtailed in calcium-free buffer (0% Ca2+) as compared to that in 100% Ca2+ medium. Preincubation of cells with tyrphostin A9, an inhibitor of Ca2+ release-activated Ca2+ (CRAC) channels, significantly diminished the OFPC-induced sustained response on the increases in [Ca2+]i. Lanthanum and nifedipine, the respective inhibitors of voltage-dependent and L-type calcium channels, failed to curtail significantly the OFPC-induced calcium response. As OFPC still stimulated increases in [Ca2+]i in 0% Ca2+ medium…
Regulation of calcium signalling by docosahexaenoic acid in human T-cells: implication of CRAC channels
2000
Abstract We elucidated the role of docosahexaenoic acid (DHA) on the increases in free intracellular calcium concentrations, [Ca2+]i, in human (Jurkat) T-cell lines. DHA evoked an increase in [Ca2+]i in a dose-dependent manner in these cells. Anti-CD3 antibody, known to stimulate increases in Ca2+ from endoplasmic reticulum (ER) via the production of inositol trisphosphate, also evoked increases in [Ca2+]i in Jurkat T-cells. We also used thapsigargin which inhibits Ca2+-ATPase of the ER and, therefore, increases Ca2+ in the cytosol. Interestingly, addition of DHA during the thapsigargin-induced peak response exerted an additive effect on the increases in [Ca2+]i in human T-cells, indicating…
Role of three isoforms of phospholipase A2in capacitative calcium influx in human T-cells
2002
The present study was conducted on human Jurkat T-cell lines in order to elucidate the role of phospholipase A2 in capacitative calcium entry. We have employed thapsigargin (TG) that induces increases in [Ca2+]i by emptying the calcium pool of endoplasmic reticulum, followed by capacitative calcium entry. We designed a Ca2+ free/Ca2+ reintroduction (CFCR) protocol for the experiments, conducted in Ca2+-free medium. By employing CFCR protocol, we observed that addition of exogenous arachidonic acid (AA) stimulated TG-induced capacitative calcium influx. The liberation of endogenous AA and its autocrine action seems to be implicated during TG-induced capacitative calcium influx: TG potentiate…
n-3 Fatty Acids Modulate T-Cell Calcium Signaling in Obese Macrosomic Rats
2004
Objective: We investigated the effects of a diet containing EPAX-7010, rich in PUFAs such as eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)], i.e., a PUFA/EPAX regimen, on T-cell activation in diabetic pregnant rats and their obese pups. Research Methods and Procedures: Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin on Day 5 of gestation. T-cell blastogenesis was assayed by using 3H-thymidine, whereas intracellular free calcium concentrations ([Ca2+]i) were measured by using Fura-2 in diabetic pregnant rats and their obese offspring. Results: Concavalin-A-stimulated T-cell proliferation was decreased in both pregnant dia…
Regulation of the human bradykinin B2 receptor expressed in sf21 insect cells: A possible role for tyrosine kinases
2000
The functional regulation of the human bradykinin B2 receptor expressed in sf21 cells was studied. Human bradykinin B2 receptors were immunodetected as a band of 75–80 kDa in membranes from recombinant baculovirus-infected cells and visualized at the plasma membrane, by confocal microscopy, using an antibody against an epitope from its second extracellular loop. B2 receptors, detected in membranes by [3H-bradykinin] binding, showed a Kd of 0.66 nmol/L and an expression level of 2.57 pmol/mg of protein at 54 h postinfection. In these cells, bradykinin induced a transient increase of intracellular calcium ([Ca2+]i) in fura 2-AM loaded sf21 cells, and promoted [35S]-GTPγS binding to membranes.…
Calcium inhibits ovarian steroidogenesis in the blowfly Phormia regina.
2002
1479-6805 0022-0795; Calcium is frequently involved in the stimulation of steroidogenesis in gonads and endocrine glands, generally in association with cAMP. However, our present observations show that it has the opposite effect in the ovary of the blowfly Phormia regina. Our in vitro experiments first showed that extracellular calcium does not play a role during the stimulation of steroidogenesis in fly ovaries; indeed steroidogenesis was activated in vitro as efficiently in a medium with or without calcium, either by pharmacological compounds mimicking cAMP signaling or by active brain extracts. When calcium was experimentally introduced into biosynthetic cells by ionophores or liberated …
Regulation of motility of cells from marine sponges by calcium ions
1996
Sponges are known not to contain muscle and nerve cells. Since sponge cells are characterized by high motility we determined the effect of intracellular calcium ion concentration ([Ca2+]i) on their motility. Addition of the Ca2+ ionophore ionomycin to dissociated cells from the marine sponge Suberites domuncula caused in Ca(2+)-containing artificial seawater (ASW) an increase in motility from 0.2 micron/min (absence of the ionophore) to 3.7 microns/min (presence of ionomycin). When the experiments were performed in Ca(2+)-free medium, no effect of ionomycin could be observed. In parallel experiments the changes of [Ca2+]i using the dye Fura-2 were measured. The experiments revealed that ion…