scholarly journals Rhynchophylline Protects Cultured Rat Neurons against Methamphetamine Cytotoxicity

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Dan Dan Xu ◽  
Robin Hoeven ◽  
Rong Rong ◽  
William Chi-Shing Cho
Keyword(s):  
Mtt Assay ◽  
Neuronal Death ◽  
Time Course ◽  
Inhibitory Effect ◽  
Neuroprotective Activity ◽  
Free Calcium ◽  
Neuronal Cultures ◽  
Death Time ◽  
Free Calcium Concentration

Rhynchophylline (Rhy) is an active component isolated from species of the genusUncariawhich has been used for the treatment of ailments to the central nervous system in traditional Chinese medicine. Besides acting as a calcium channel blocker, Rhy was also reported to be able to protect against glutamate-induced neuronal death. We thus hypothesize that Rhy may have neuroprotective activity against methamphetamine (MA). The primary neurons were cultured directly from the cerebral cortex of neonatal rats, acting asin vitromodel in the present study. The neurotoxicity of MA and the protective effect of Rhy were evaluated by MTT assay. The effects of MA, Rhy or their combination on intracellular free calcium concentration ([Ca2+]i) were determined in individual neocortical neurons by the Fluo-3/AM tracing method. The MTT assay demonstrated that MA has a dose-dependent neurotoxicity in neuronal cultures. The addition of Rhy prior to the exposure to MA prevented neuronal death. Time course studies with the Fluo-3/AM probe showed that Rhy significantly decreased neuronal [Ca2+]iwhich was elevated by the exposure to MA. Our results suggested that Rhy can protect the neuronal cultures against MA exposure and promptly attenuate intracellular calcium overload triggered by MA challenge. This is the first report demonstrating an inhibitory effect of Rhy against MA impairment in cultured neuronsin vitro.

scholarly journals Bryophyllum pinnatum Compounds Inhibit Oxytocin-Induced Signaling Pathways in Human Myometrial Cells

2021 ◽  
Vol 12 ◽  
Author(s):  
Stefanie Santos ◽  
Leonie Zurfluh ◽  
Mónica Mennet ◽  
Olivier Potterat ◽  
Ursula von Mandach ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Calcium Concentration ◽  
Inhibitory Effect ◽  
Intracellular Free Calcium ◽  
Free Calcium ◽  
Myometrial Cells ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration ◽  
Bryophyllum Pinnatum

Bryophyllum pinnatum has been used in the treatment of premature labor, first in anthroposophic hospitals and, recently, in conventional settings as an add-on medication. In vitro work with hTERT human myometrial cells showed that B. pinnatum leaf press juice inhibits the increase of intracellular free calcium concentration induced by oxytocin, a hormone known to play a role in labor. Our aim was to identify fractions/compounds in B. pinnatum press juice that contribute to this inhibitory effect, and to investigate their effect on oxytocin-driven activation of the MAPK cascade. Several fractions/compounds from B. pinnatum press juice led to a concentration-dependent decrease of oxytocin-induced increase of intracellular free calcium concentration, but none of them was as strong as B. pinnatum press juice. However, the combination of a bufadienolide and a flavonoid-enriched fraction was as effective as B. pinnatum press juice, and their combination had a synergistic effect. B. pinnatum press juice inhibited oxytocin-driven activation of MAPKs SAPK/JNK and ERK1/2, an effect also exerted by the bufadienolide-enriched fraction. The effect of B. pinnatum press juice on oxytocin-induced signaling pathways was comparable to that of the oxytocin-receptor antagonist and tocolytic agent atosiban. Our findings further substantiate the use of B. pinnatum press juice preparations in the treatment of preterm labor.

scholarly journals A Kinetic Analysis of Calcium-Triggered Exocytosis

2001 ◽  
Vol 118 (2) ◽  
pp. 145-156 ◽  
Author(s):  
Paul S. Blank ◽  
Steven S. Vogel ◽  
James D. Malley ◽  
Joshua Zimmerberg
Keyword(s):  
Function Analysis ◽  
Secretory Vesicle ◽  
Free Calcium ◽  
Vesicle Docking ◽  
Calcium Dependence ◽  
Calcium Dependent ◽  
Sea Urchin Egg ◽  
Vesicle Exocytosis ◽  
Free Calcium Concentration

Although the relationship between exocytosis and calcium is fundamental both to synaptic and nonneuronal secretory function, analysis is problematic because of the temporal and spatial properties of calcium, and the fact that vesicle transport, priming, retrieval, and recycling are coupled. By analyzing the kinetics of sea urchin egg secretory vesicle exocytosis in vitro, the final steps of exocytosis are resolved. These steps are modeled as a three-state system: activated, committed, and fused, where interstate transitions are given by the probabilities that an active fusion complex commits (α) and that a committed fusion complex results in fusion, p. The number of committed complexes per vesicle docking site is Poisson distributed with mean n. Experimentally, p and n increase with increasing calcium, whereas α and the pn ratio remain constant, reducing the kinetic description to only one calcium-dependent, controlling variable, n. On average, the calcium dependence of the maximum rate (Rmax) and the time to reach Rmax (Tpeak) are described by the calcium dependence of n. Thus, the nonlinear relationship between the free calcium concentration and the rate of exocytosis can be explained solely by the calcium dependence of the distribution of fusion complexes at vesicle docking sites.

Inhibition of bovine adrenocortical steroidogenesis by benzodiazepines: a direct effect on microsomal hydroxylation or an inhibition of calcium uptake?

1992 ◽  
Vol 135 (2) ◽  
pp. 361-369 ◽  
Author(s):  
I. Thomson ◽  
R. Fraser ◽  
C. J. Kenyon
Keyword(s):  
Direct Effect ◽  
Calcium Metabolism ◽  
Competitive Inhibitor ◽  
Inhibitory Effect ◽  
Zona Glomerulosa ◽  
Free Calcium ◽  
Steroid Hydroxylase ◽  
Drug Concentrations ◽  
Ca Uptake

ABSTRACT We have previously reported that benzodiazepines inhibit microsomal steroid hydroxylases. We have now studied their effects at much lower drug concentrations and have also addressed the suggestion that benzodiazepines alter cellular calcium metabolism. We investigated the in-vitro effects of midazolam on microsomal steroid hydroxylation by measuring basal and ACTH-stimulated cortisol and 17α-hydroxyprogesterone (17-OHP) synthesis. Threshold inhibition of basal cortisol production was achieved by 3·4 μmol midazolam/1 while ACTH-stimulated production required 13·6 μmol/l. This was accompanied by a biphasic response of 17-OHP production, rising to a maximum at 13·6 μmol midazolam/l for basal and 6·8 μmol midazolam/l for ACTH-stimulated synthesis suggesting a preferential inhibitory effect on 21-hydroxylase activity at < 6·8 μmol/l and additonal effects on 17α-hydroxylation at higher drug concentrations. This explains the inhibition of ACTH-stimulated cortisol synthesis by midazolam (50% inhibitor dose (IC50) 22 μmol/l). Using 21-deoxycortisol as substrate, we have demonstrated that midazolam is a competitive inhibitor of 21-hydroxylase (inhibitory constant (KI) 35 μmol/l). Both midazolam and diazepam inhibited K+-stimulated aldosterone synthesis, with IC50 values of 1·2 μmol/l and 0·8 μmol/l respectively, which are far lower than those observed for ACTH-stimulated cortisol synthesis. With 11β-hydroxyprogesterone as substrate, the KI for the inhibition of aldosterone synthesis by midazolam was 54 μmol/l. Potassium stimulates aldosterone biosynthesis at least partly by changing intracellular free calcium levels. To investigate possible antagonistic effects of benzodiazepines on calcium metabolism, we measured 45Ca uptake in the presence of midazolam. Both basal (P < 0·01) and K+-stimulated 45Ca uptake (P < 0·05) were inhibited by the drug although the effects of K+ were not completely abolished. Comparison of the dose-dependent effects of midazolam on basal 45Ca uptake in cell suspensions prepared from different areas of the adrenal cortex indicated that zona glomerulosa cells are more sensitive to midazolam. We confirm that benzodiazepines at low concentrations have a direct effect on microsomal steroid hydroxylase enzymes in vitro and postulate that the greater sensitivity to benzodiazepines of K+-stimulated aldosterone synthesis, when compared with either ACTH-stimulated cortisol synthesis or conversion of 21-deoxycortisol to cortisol, may be explained by additional effects of these drugs on plasma membrane calcium transport. Journal of Endocrinology (1992) 135, 361–369

Effects of two enkephalin analogues, morphine sulphate, dopamine and naloxone on prolactin secretion from rat anterior pituitary glands in vitro

1986 ◽  
Vol 109 (3) ◽  
pp. 313-320 ◽  
Author(s):  
A. M. Bentley ◽  
M. Wallis
Keyword(s):  
Anterior Pituitary ◽  
Time Course ◽  
Opiate Receptors ◽  
Inhibitory Effect ◽  
Antagonistic Effect ◽  
Prolactin Secretion ◽  
Morphine Sulphate ◽  
Low Concentrations ◽  
Pituitary Glands

ABSTRACT Experiments were carried out on the antagonistic effects of opiates on the inhibition by dopamine of prolactin secretion from rat anterior pituitary glands. Dose–response and time-course experiments were carried out using both static incubation of paired hemipituitary glands and perifusion of whole glands. Dopamine (10–1000 nmol/l) was found to have an inhibitory effect on prolactin secretion, but at a lower concentration (0·1 nmol/l) a small stimulation was observed. Against an inhibition established with 100 nmol dopamine/l in static incubation, the three opiates under study, morphine sulphate, Leu5enkephalin and d-Ala2,Met5-enkephalin (DAME), had a maximum antagonistic effect at 50–1000 nmol/l in a 90-min incubation. Morphine and DAME were rather more effective than Leu5-enkephalin, possibly because of degradation of the latter. Naloxone reversed the effect of morphine. All three opiates showed little effect on dopamine-inhibited prolactin secretion in a perifusion system. The data accord with previous suggestions that prolactin secretion may be stimulated both by very low concentrations of dopamine and by opiates acting to reverse the inhibition exerted by higher dopamine concentrations. It should be noted that both morphine and the enkephalins have similar effects on prolactin secretion, despite their normal specificity for different opiate receptors; their actions on the pituitary may thus be rather non-specific. J. Endocr. (1986) 109, 313–320

Toxicity of Industrially Relevant Chlorinated Organic Solvents In Vitro

2013 ◽  
Vol 32 (2) ◽  
pp. 136-145 ◽  
Author(s):  
Catherine McDermott ◽  
James J.A. Heffron
Keyword(s):  
Cell Proliferation ◽  
Organic Solvents ◽  
Caspase 3 ◽  
Free Calcium ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Chlorinated Organic ◽  
Free Calcium Concentration ◽  
Ros Formation

The cytotoxic effects of 4 industrially important chlorinated organic solvents, dichloromethane (DCM), 1,2-dichloroethane (DCE), trichloroethylene (TCE), and tetrachloroethylene (PERC) in vitro, were investigated. Jurkat T cells were exposed to the solvents individually for 72 hours and changes in reactive oxygen species (ROS) formation, cell proliferation, intracellular free calcium concentration ([Ca2+]), and caspase-3 activity were measured. There was a concentration-dependent increase in the ROS formation and intracellular free [Ca2+] following exposure to each of the solvents. This was accompanied by a decrease in the cell proliferation. Solvent potency decreased in the following order: PERC > TCE > DCM > DCE. Caspase-3 activity was increased in a concentration-dependent manner by TCE and PERC but was not significantly altered by DCM or DCE. n-Acetyl-l-cysteine pretreatment showed that changes in the intracellular free [Ca2+] and caspase-3 activity were independent of ROS formation. However, increased ROS formation did play a causal role in the decreased cell proliferation observed.

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