Different effects of low and high dose cardiotonic steroids on cytosolic calcium in spontaneously active hippocampal neurons and in co-cultured glia

1998 ◽  
Vol 795 (1-2) ◽  
pp. 325-340 ◽  
Author(s):  
Gregory R. Monteith ◽  
Mordecai P. Blaustein
2021 ◽  
Author(s):  
Bin Zhang ◽  
Mengshi Yang ◽  
Qiongyu Yan ◽  
Xiaojian Xu ◽  
Fei Niu ◽  
...  

Abstract Background: Our recent studies reported the opposite effects of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) on neuron survival after traumatic brain injury (TBI). However, as a mixed agonist for MR and GR, whether short term use of high-dose endogenous glucocorticoids exerts neurotoxic effects by excessive activation of GR, what is the set-point, and the possible signaling pathways remain unclear. This study examined the dose-dependent dual effects of corticosterone (CORT) on the spatial memory, the survival of hippocampal neurons and the possible receptor-mediated downstream signaling pathways after TBI.Methods: Based on controlled cortical impact (CCI) and CORT treatments, Sprague-Dawley rats (n=168) were randomly divided into the sham, CCI, CCI + CORT1 (0.3 mg/kg), CCI + CORT2 (3 mg/kg), CCI + CORT3 (30 mg/kg), CCI + CORT1 + spirolactone (spirolactone: 50 mg/kg/d), and CCI + CORT3 + RU486 (RU486: 50 mg/kg/d) groups. Brain tissues were collected on postinjury day 3 and processed for histology and western blot analysis.Results: On postinjury day 3, we tested the learning and memory ability, neuronal apoptosis in the hippocampus, activation levels of MR and GR, Bcl-2 family proteins, and apoptosis-related intracellular signaling pathways. We found that different doses of CORT exhibited dual effects on the survival of hippocampal neurons and the spatial memory. Lower doses of CORT (0.3, 3 mg/kg) significantly increased the activation of MR, upregulated the phosphorylation of Akt/CREB/Bad and the Bcl-2 expression, reduced the number of apoptotic neurons, and subsequently improved the spatial memory. In contrast, higher dose of CORT (30 mg/kg) exerted opposite effect by over activating GR, upregulating the expressions of P53/Bax, and inhibiting the Erk/CREB activities. Conclusion: The results suggest that there is a threshold between the neuroprotective and neurotoxic effects of endogenous GC, higher dose of which, even for short-term use, should also be avoided after TBI.


1991 ◽  
Vol 2 (10) ◽  
pp. 827-840 ◽  
Author(s):  
T E Cheyette ◽  
D J Gross

The A431 epidermoid carcinoma cell line responds to epidermal growth factor (EGF) stimulation with a number of rapid changes, including alterations in free cytosolic calcium ion concentration ([Ca2+]i). At the single cell level, these changes in [Ca2+]i are known to proceed after a clear lag phase subsequent to EGF stimulus (Gonzalez et al., 1988). The present study explores the dependence on EGF concentration of this early [Ca2+]i signal. High levels of EGF (9.0-4.3 nM) produce a [Ca2+]i spike followed by an elevation of [Ca2+]i above basal levels. The time of initiation of the spike varies from 5 to 9 s at the high dose and from 8 to 32 s at the low dose in cells that respond. A lower level of EGF (1.5 nM) produces [Ca2+]i oscillations with no prolonged elevation over basal [Ca2+]i. The initiation of response at this [EGF] ranges from 20 to 410 s. Intermediate stimulus levels generate [Ca2+]i responses that are kinetic admixtures of these limiting responses. A simple model based on the enzymatically amplified signal cascade from ligand binding through Ca2+ release or influx is examined. The model predicts a prolonged lag phase followed by a rapid increase in the [CA2+]i signal that compares favorably with the data reported here.


Endocrinology ◽  
2006 ◽  
Vol 147 (11) ◽  
pp. 5303-5313 ◽  
Author(s):  
Shuhua Chen ◽  
Jon Nilsen ◽  
Roberta Diaz Brinton

To address controversies of estrogen therapy, in vitro models of perimenopause and prevention vs. treatment modes of 17β-estradiol (E2) exposure were developed and used to assess the neuroprotective efficacy of E2 against β-amyloid-1–42 (Aβ1–42)-induced neurodegeneration in rat primary hippocampal neurons. Low E2 (10 ng/ml) exposure exerted neuroprotection in each of the perimenopausal temporal patterns, acute, continuous, and intermittent. In contrast, high E2 (200 ng/ml) was ineffective at inducing neuroprotection regardless of temporal pattern of exposure. Although high E2 alone was not toxic, neurons treated with high-dose E2 resulted in greater Aβ1–42-induced neurodegeneration. In prevention vs. treatment simulations, E2 was most effective when present before and during Aβ1–42 insult. In contrast, E2 treatment after Aβ1–42 exposure was ineffective in reversing Aβ-induced degeneration, and exacerbated Aβ1–42-induced cell death when administered after Aβ1–42 insult. We sought to determine the mechanism by which high E2 exacerbated Aβ1–42-induced neurodegeneration by investigating the impact of low vs. high E2 on Aβ1–42-induced dysregulation of calcium homeostasis. Results of these analyses indicated that low E2 significantly prevented Aβ1–42-induced rise in intracellular calcium, whereas high E2 significantly increased intracellular calcium and did not prevent Aβ1–42-induced calcium dysregulation. Therapeutic benefit resulted only from low-dose E2 exposure before, but not after, Aβ1–42-induced neurodegeneration. These data are relevant to impact of perimenopausal E2 exposure on protection against neurodegenerative insults and the use of estrogen therapy to prevent vs. treat Alzheimer’s disease. Furthermore, these data are consistent with a healthy cell bias of estrogen benefit.


2021 ◽  
Vol 22 (24) ◽  
pp. 13590
Author(s):  
Katarina Ilic ◽  
Xiao Lin ◽  
Ayse Malci ◽  
Mario Stojanović ◽  
Borna Puljko ◽  
...  

The recent identification of plasma membrane (Ca2+)-ATPase (PMCA)-Neuroplastin (Np) complexes has renewed attention on cell regulation of cytosolic calcium extrusion, which is of particular relevance in neurons. Here, we tested the hypothesis that PMCA-Neuroplastin complexes exist in specific ganglioside-containing rafts, which could affect calcium homeostasis. We analyzed the abundance of all four PMCA paralogs (PMCA1-4) and Neuroplastin isoforms (Np65 and Np55) in lipid rafts and bulk membrane fractions from GM2/GD2 synthase-deficient mouse brains. In these fractions, we found altered distribution of Np65/Np55 and selected PMCA isoforms, namely PMCA1 and 2. Cell surface staining and confocal microscopy identified GM1 as the main complex ganglioside co-localizing with Neuroplastin in cultured hippocampal neurons. Furthermore, blocking GM1 with a specific antibody resulted in delayed calcium restoration of electrically evoked calcium transients in the soma of hippocampal neurons. The content and composition of all ganglioside species were unchanged in Neuroplastin-deficient mouse brains. Therefore, we conclude that altered composition or disorganization of ganglioside-containing rafts results in changed regulation of calcium signals in neurons. We propose that GM1 could be a key sphingolipid for ensuring proper location of the PMCA-Neuroplastin complexes into rafts in order to participate in the regulation of neuronal calcium homeostasis.


2004 ◽  
Vol 286 (5) ◽  
pp. F866-F874 ◽  
Author(s):  
Max Salomonsson ◽  
William J. Arendshorst

We used genistein (Gen) and tyrphostin 23 (Tyr-23) to evaluate the importance of tyrosine phosphorylation in norepinephrine (NE)-induced changes in intracellular free calcium concentration ([Ca2+]i) in rat afferent arterioles. [Ca2+]i was measured in microdissected arterioles using ratiometric photometry of fura 2 fluorescence. The control [Ca2+]i response to NE (1 μM) consisted of a rapid initial peak followed by a plateau phase sustained above baseline. Pretreatment with the tyrosine kinase inhibitor Tyr-23 (50 μM, 10 min) caused a slow 40% increase in baseline [Ca2+]i. Tyr-23 attenuated peak and plateau responses to NE, both by ∼70%. In the absence of extracellular Ca2+ (0 Ca), Tyr-23 reduced the immediate [Ca2+]i response to NE by ∼60%, indicative of mobilization of internal stores, and abolished the plateau phase. In other arterioles, the [Ca2+]i response to depolarization induced by KCl (50 mM) was not attenuated by Tyr-23, indicating no direct effect on L-type Ca+ channels activated by depolarization. The Ca2+ channel blocker nifedipine (1 μM) inhibited the NE response by ∼50%; the effects of nifedipine and Tyr-23 were not additive. Nifedipine had no inhibitory effect after Tyr-23 pretreatment, indicating Tyr-23 inhibition of Ca2+ entry. Another tyrosine kinase inhibitor, Gen (5 and 50 μM), did not affect baseline [Ca2+]i. High-dose Gen inhibited the peak and plateau response to NE by 87 and 75%, respectively; low-dose Gen attenuated both responses by ∼20%. In 0 Ca, Gen (50 μM) abolished the immediate [Ca2+]i mobilization response. Combined nifedipine and Gen (50 μM) inhibited the rapid NE response by ∼90% in the presence of extracellular Ca2+. Gen (50 μM) also inhibited by 60% the [Ca2+]i response to 50 mM KCl, indicating a direct interaction with voltage-sensitive, L-type Ca2+ entry channels. These results indicate that tyrosine phosphorylation is an important link in the chain of events leading to α-adrenoceptor-induced Ca2+ recruitment (both entry and release) in afferent arteriolar smooth muscle cells. Furthermore, different blockers of tyrosine kinase appear to have different modes of action in renal microvessels.


2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Lina Liu ◽  
Fei Ge ◽  
Haoran Yang ◽  
Huilian Shi ◽  
Weiting Lu ◽  
...  

Xiao-Yao-San (XYS) decoction is a traditional Chinese medicine formula. This study aimed to investigate the effect of XYS on cognitive abilities and its underlying mechanism in ovariectomized rats. Female Sprague-Dawley rats were ovariectomized and treated with XYS (3 g/kg or 9 g/kg) by gavage, with subcutaneous injection of 17-β estradiol (E2, 2 μg/kg) as a positive drug control and gavage of 1 ml saline (0.9%) as a placebo control. After 6 weeks of treatment, rats were examined using the Morris water maze test. The estradiol level in the serum and hippocampus was measured by ELISA. Golgi staining was performed to observe neuronal morphology in the hippocampus. Apoptosis of hippocampal cells was observed by TUNEL staining. The protein content of N-methyl-D-aspartate receptor (NMDAR) 2A and 2B in the hippocampal CA1 region was determined by Western blot and immunohistochemistry. Expression of estrogen receptor (ER) and PI3K signaling was detected by Western blot. Compared with the sham group, both learning and memory were impaired in ovariectomized rats. Rats treated with E2 or high-dose XYS showed better learning and memory compared with the saline-treated rats. High-dose XYS significantly reduced escape latency in the spatial acquisition trial; meanwhile, the cross times and duration in the probe quadrant were increased in the spatial probe trial. High-dose XYS promoted the de novo synthesis of E2 content in the hippocampus but had no significant effect on the serum E2 level. Golgi staining indicated that high-dose XYS could increase the branch number and density of dendritic spines in the hippocampal CA1 area. TUNEL staining showed that high-dose XYS alleviated ovariectomy-induced neuronal apoptosis. The expression level of NMDAR2A and NMDAR2B in hippocampal CA1 was upregulated by XYS treatment. The beneficial effect of XYS was through activating ERα-PI3K signaling. In conclusion, high-dose XYS treatment can improve the cognitive abilities of ovariectomized rats by protecting the hippocampal neurons and restoring the hippocampal E2 level.


2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A749-A749
Author(s):  
Celeste M Sheftel ◽  
Luma C Sartori ◽  
Robbie S J Manuel ◽  
Hannah P Fricke ◽  
Julia F Charles ◽  
...  

Abstract Lactation taxes mothers’ bone health, causing them to lose up to 10% of their bone mass for milk calcium. Selective serotonin reuptake inhibitor antidepressants (SSRIs) are commonly used during pregnancy and lactation but independently decrease bone mass. We previously demonstrated that both maternal and offspring bone densities were compromised by maternal treatment with the SSRI fluoxetine throughout pregnancy and lactation. In this study, we examined whether sertraline similarly affect maternal and offspring bone. Female C57BL/6 dams (n=23/group) were treated with sertraline (10 mg/kg/d) or a vehicle (DMSO) for 41 d (E0-lactation(L) 21). Pups were euthanized at weaning (L21). Dams were euthanized at peak lactation (L10, n=4/group), weaning (L21, n=9/group) or 3 mo post-weaning (n=10/group) for analysis. Sertraline treatment did not affect dams’ weight gain during pregnancy or lactation and did not impact milk production/consumption, measured by weigh-suckle-weigh. Unlike fluoxetine, which increases circulating calcium, sertraline treatment reduced serum calcium concentration at L21 compared with control (p<0.05). Mammary calcium genes were not altered at L10, but at L21 we observed decreased mammary expression of the calcium transporters Orai1, Spca1, Spca2, and Serca2 (p<0.05), and a tendency for decreased Pthlh (a calcium-regulating peptide; p=0.08). In the intestinal duodenum, Calb1 (a cytosolic calcium trafficking protein) expression was increased at L10 and L21 (p<0.05), and the calcium transporters Trpv6, Pmca1 and Spca2 were increased by L21 (p<0.05). Sertraline treatment did not affect L21 calcium concentration in either tissue, although the mammary gland calcium was 3.5 times that of the duodenum. Previously, we reported that circulating markers of bone formation (P1NP) or bone resorption (CTX) were unchanged in sertraline-treated dams at L21. This is unlike fluoxetine, which decreased P1NP without altering CTX. Furthermore, compared with control, sertraline treatment did not alter expression of bone resorption or formation genes (e.g. Trap, Rank/RankL, Alp, Runx2) in maternal femoral bone at L21 or 3 mo post-weaning. Interestingly, in utero exposure to sertraline reduced litter size (5.4 vs 6.8 pups/dam, p<0.01) and increased pup mortality (20% vs 5% dead pups/litter, p<0.01) during the first 24 hours postpartum compared with controls, but did not affect length of gestation or live birth rate. Exposure to sertraline during lactation did not alter weight gain in the surviving offspring, nor did it alter circulating calcium in the pups at weaning, suggesting an adequate supply of calcium in the milk from the dam. These data suggest that, compared with high-dose fluoxetine, low-dose peripartal sertraline has a milder impact on maternal bone and may reduce mammary calcium but could induce a failure to thrive in the offspring.


2021 ◽  
Vol Volume 15 ◽  
pp. 2433-2444
Author(s):  
Qiufeng Wei ◽  
Jing Chen ◽  
Fei Xiao ◽  
Youbing Tu ◽  
Yu Zhong ◽  
...  

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