Effects of Naturally Occurring Polyols and Urea on Mitochondrial F0F1ATPase

2000 ◽  
Vol 55 (5-6) ◽  
pp. 392-398 ◽  
Author(s):  
Adriana dos Passos Lemos ◽  
Carlos E. Peres-Sampaio ◽  
Horácio Guimarães-Motta ◽  
Jerson L. Silva ◽  
José R. Meyer-Fernandes
Keyword(s):  
Atpase Activity ◽  
Direct Interaction ◽  
Dependent Manner ◽  
Urea Denaturation ◽  
Naturally Occurring ◽  
Activation Level ◽  
Activation Rate ◽  
Initial Activation ◽  
Natural Inhibitor ◽  
Dose Dependent

We show that urea inhibits the ATPase activity of MgATP submitochondrial particles (MgATP-SMP) with Ki = 0.7 м, probably as a result of direct interaction with the structure of F0F1-ATPase. Counteracting compounds (sorbitol, mannitol or inositol), despite slightly (10-20% ) inhibiting the ATPase activity, also protect the F0F1 ATPase against denaturation by urea. However, this protection was only observed at low urea concentrations (less than 1.5 м ) , and in the presence of three polyols, the Ki for urea shift from 0.7 м to 1.2 м. Urea also increases the initial activation rate of latent MgATP-SMP in a dose-dependent-manner. However, when the particles (0.5 mg/ml) were preincubated in the presence of 1 м , 2 м or 3 м urea, a decrease in the activation level occurred after 1 h, 30 and 10 min, respectively. At high MgATP-SMP concentration (3 mg/ml) a decrease in activation was observed after 2 h, 1 h and 20 min, respectively. These data indicate that the effect of urea on the activation of MgATP-SMP depends on time, urea and protein concentrations. It was also observed that polyols suppress the activation of latent MgATP-SMP in a dose-dependent manner, and protect the particles against urea denaturation during activation. We suppose that a decrease in membrane mobility promoted by interactions of polyols with phospholipids around the F0F1 ATPase may also increase the compactation of protein structure, explaining the inhibition of natural inhibitor protein of ATPase (IF1) release and the activation of the enzyme.

scholarly journals Mechanisms of L-Triiodothyronine-Induced Inhibition of Synaptosomal Na+-K+-ATPase Activity in Young Adult Rat Brain Cerebral Cortex

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Pradip K. Sarkar ◽  
Avijit Biswas ◽  
Arun K. Ray ◽  
Joseph V. Martin
Keyword(s):  
Cerebral Cortex ◽  
Atpase Activity ◽  
Adrenergic Receptor ◽  
Receptor Activation ◽  
Mammalian Brain ◽  
Neuronal Membrane ◽  
Dependent Manner ◽  
Adrenergic Agonist ◽  
Adult Rat ◽  
Dose Dependent

The role of thyroid hormones (TH) in the normal functioning of adult mammalian brain is unclear. Our studies have identified synaptosomal Na+-K+-ATPase as a TH-responsive physiological parameter in adult rat cerebral cortex. L-triiodothyronine (T3) and L-thyroxine (T4) both inhibited Na+-K+-ATPase activity (but not Mg2+-ATPase activity) in similar dose-dependent fashions, while other metabolites of TH were less effective. Although both T3and theβ-adrenergic agonist isoproterenol inhibited Na+-K+-ATPase activity in cerebrocortical synaptosomes in similar ways, theβ-adrenergic receptor blocker propranolol did not counteract the effect of T3. Instead, propranolol further inhibited Na+-K+-ATPase activity in a dose-dependent manner, suggesting that the effect of T3on synaptosomal Na+-K+-ATPase activity was independent ofβ-adrenergic receptor activation. The effect of T3on synaptosomal Na+-K+-ATPase activity was inhibited by theα2-adrenergic agonist clonidine and by glutamate. Notably, both clonidine and glutamate activateGi-proteins of the membrane second messenger system, suggesting a potential mechanism for the inhibition of the effects of TH. In this paper, we provide support for a nongenomic mechanism of action of TH in a neuronal membrane-related energy-linked process for signal transduction in the adult condition.

scholarly journals Acetylcholinesterase and Butyrylcholinesterase Inhibitory Compounds from Chelidonium Majus (Papaveraceae)

2010 ◽  
Vol 5 (11) ◽  
pp. 1934578X1000501 ◽  
Author(s):  
Lucie Cahlíková ◽  
Lubomír Opletal ◽  
Milan Kurfürst ◽  
Kateřina Macáková ◽  
Andrea Kulhánková ◽  
...  
Keyword(s):  
Human Plasma ◽  
Human Blood ◽  
Inhibitory Activity ◽  
Dependent Manner ◽  
Isoquinoline Alkaloids ◽  
Chelidonium Majus ◽  
Aerial Parts ◽  
Naturally Occurring ◽  
Inhibitory Compounds ◽  
Dose Dependent

The roots and aerial parts of Chelidonium majus L. were extracted with EtOH and fractionated using CHCl3 and EtOH. Repeated column chromatography, preparative TLC and crystallization led to the isolation of five isoquinoline alkaloids, stylopine (3), chelidonine (4), homochelidonine (5), protopine (6), and allocryptopine (7), along with two isolation artifacts 6-ethoxydihydrosanguinarine (1) and 6-ethoxydihydrochelerythrine (2). All isolated compounds were tested for human blood acetylcholinesterase (HuAChE) and human plasma butyrylcholinesterase (HuBuChE) inhibitory activity. The isolation artifacts exhibited the highest activity against HuAChE and HuBuChE with IC50 values of 0.83 ± 0.04 μM and 4.20 ± 0.19 μM for 6-ethoxydihydrochelerythrine and 3.25 ± 0.24 μM and 4.51 ± 0.31 μM for 6-ethoxydihydrosanguinarine. The most active of the naturally-occurring alkaloids was chelidonine, which inhibited both HuAChE and HuBuChE in a dose-dependent manner with IC50 values of 26.8 ± 1.2 μM and 31.9 ± 1.4 μM, respectively.

The Zinc Finger Protein Gfi1 Controls TLR4-Mediated Inflammatory Response by Directly Antagonizing NF-κB Transcription Factor

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 469-469
Author(s):  
Ehssan Sharif-Askari ◽  
Hui Zeng ◽  
Lothar Vassen ◽  
Christian Kosan ◽  
Cyrus Khandanpour ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Direct Interaction ◽  
Innate Immune ◽  
Dependent Manner ◽  
Negative Regulators ◽  
Tlr Signaling ◽  
Tnf Α ◽  
Dose Dependent ◽  
Lps Treatment ◽  
Stimulation Of

Abstract Inflammatory responses are complex and comprise multiple mediators including cytokines such as TNF-alpha (TNF-α) and IL-1beta. These cytokines are synthesized and secreted in response to signaling by plasma membrane receptors of the Toll-like receptor (TLR) family. A central downstream element of TLR-dependent signaling is the transcription factor NF-kappaB (NF-κB), which plays a pivotal role in controlling the proper sequence of events during an inflammatory response. In unstimulated cells, NF-κB is bound to inhibitory IkappaB (IκB) proteins and remains sequestered in the cytoplasm. Stimulation of TLRs triggers a signaling cascade that leads to phosphorylation and proteasomal degradation of IκB, resulting in the translocation of NF-κB to the nucleus, where it acts as a transcriptional activator of target genes. To keep the innate immune system under control, the TLR signaling cascade is under a tight control of many positive and negative regulators. We have previously shown that the transcription factor Growth Factor Independence 1 (Gfi1) represents a novel factor limiting the inflammatory immune response including TNF-α. Gfi1-deficient (Gfi1−/−) mice show a very strong systemic response to the TLR4 ligand and endotoxin LPS and die rapidly within 36 h with symptoms of septic shock. Here, we investigated the molecular mechanism of this exaggerated TNF-α production in the absence of Gfi1. It is known that endotoxin stimulation results in the activation of the transcription factor NF-κB through TLR4, leading to TNF-α production. This activation also resulted in rapid and de novo expression of Gfi1 in the nucleus in a time- and dose-dependent manner. The expression of Gfi1 was not due to feedback regulation from secreted TNF, since TNF-deficient macrophages were also able to upregulate Gfi1 mRNA following LPS stimulation. As expected, LPS stimulation of Gfi1−/− macrophages resulted in significantly higher levels of TNF-α mRNA, and secreted TNF-α cytokine. Strikingly and in contrast to most known negative regulators of TLRs, Gfi1 did not affect the activity or the expression levels of the cytoplasmic components of TLR signaling pathway. Additionally, NF-κB phosphorylation and nuclear translocation post- LPS treatment were intact in both Gfi1−/− and Gfi1+/+ macrophages. Immunoprecipitation analysis from cells endogenously expressing Gfi1 and NF-κB or over-expressing these two proteins post transfection, clearly revealed a direct interaction between Gfi1 and the p65 subunit of NF-κB. Immunofluorescence staining of macrophages post-LPS treatment confirmed direct interaction of these two proteins in the nucleus at the endogenous level. Gfi1 represses transcription by binding to DNA recognition sequences in target gene promoters. Thus, aiming to investigate the effect of Gfi1 expression on NF-κB nuclear signaling, we found that LPS treatment enhances NF-κB DNA binding activity in Gfi1−/− macrophages as compared to Gfi1+/+ cells. Furthermore, over expression of Gfi1 protein resulted in negative regulation of NF-κB mediated gene activation in a dose-dependent manner. Chromatin immune precipitation with anti-p65 antibodies from LPS stimulated Gfi1+/+ and Gfi1−/− macrophages revealed enhanced NF-κB promoter occupancy at the TNF gene in Gfi1−/− macrophages as compared to Gfi1+/+ cells. In conclusion, our findings reveal a novel function for Gfi1 in the innate immune response by directly antagonizing NF-κB function. This molecular perceptive of TNF-α regulation during inflammation may provide an attractive strategy for therapeutic intervention in chronic inflammatory diseases and certain cancers.

scholarly journals Stress hormone masculinizes female morphology and behaviour

2010 ◽  
Vol 7 (1) ◽  
pp. 150-152 ◽  
Author(s):  
Rosemary Knapp ◽  
Edie Marsh-Matthews ◽  
Luanne Vo ◽  
Sarah Rosencrans
Keyword(s):  
Sexual Differentiation ◽  
Sex Steroids ◽  
Full Range ◽  
Reproductive Function ◽  
Morphological Characters ◽  
Sexually Dimorphic ◽  
Dependent Manner ◽  
Stress Hormone ◽  
Naturally Occurring ◽  
Dose Dependent

Sex steroids play major roles in vertebrate sexual differentiation. Unexpectedly, we now find that exposure to elevated levels of the naturally occurring stress hormone cortisol can also masculinize sexually dimorphic morphological characters and behaviour in adult female mosquitofish ( Gambusia affinis ) in a dose-dependent manner. Females masculinized by cortisol developed elongated anal fins with distal tip features similar to those of mature males. Most masculinized females also attempted to copulate when placed with normal females. Although the mechanism of masculinization is currently unknown, we propose a role for an enzyme that both inactivates cortisol and catalyzes the final step in synthesis of a major teleost androgen. This mechanism may also help explain some previously reported effects of stress on sexual development across vertebrate taxa. Our findings underscore the need to understand the full range of chemicals, both naturally occurring hormones and human-produced endocrine disruptors, that can influence sexual differentiation and reproductive function.

Dopamine causes inhibition of Na+-K+-ATPase activity in rat proximal convoluted tubule segments

1987 ◽  
Vol 252 (1) ◽  
pp. F39-F45 ◽  
Author(s):  
A. Aperia ◽  
A. Bertorello ◽  
I. Seri
Keyword(s):  
Atpase Activity ◽  
Sodium Pump ◽  
Maximal Activity ◽  
Proximal Convoluted Tubule ◽  
Decarboxylase Activity ◽  
Dependent Manner ◽  
Site Of Action ◽  
Apparent Reduction ◽  
Ly 171555 ◽  
Dose Dependent

We studied the effect of dopamine (DA) on Na+-K+-ATPase activity in proximal convoluted tubule (PCT) segments dissected from perfused rat kidneys. DA inhibited Na+-K+-ATPase activity in a dose-dependent manner. Inhibition was significant with 10(-7) M DA and maximal with 10(-4) M DA. The inhibition was reversible. Enzyme inhibition occurred in the presence of DA and a DA antagonist, metoclopramide, but not when 10(5) M of the DA1 and DA2 agonists fenoldopam mesylate and LY 171555 were added in the absence of DA. In PCT segments incubated with the DA precursor dopa, Na+-K+-ATPase activity was also inhibited. However, dopa did not inhibit the sodium pump if dopa decarboxylase activity was blocked with benserazide. These findings suggest an intracellular site of action of DA. In tubules incubated in different K concentrations, 10(-5) DA decreased the maximal activity (Vmax) and increased the Km. DA 10(-5) M caused an almost immediate swelling of PCT segments. Swelling did not occur in the presence of both DA and 10(-5) M amiloride. The DA-induced tubular swelling was probably due to inhibition of Na+-K+-ATPase-mediated Na+-transport. We conclude that in rat PCT segments, DA causes a rapid and reversible inhibition of apparent Na+-K+-ATPase activity and an apparent reduction in the affinity for K. The site of action appears to be intracellular.

The Fibrinogen γ Chain Dodecapeptide Inhibits Agonist-induced Aggregation of Rabbit Platelets and Fibrinogen Binding to Rabbit Glycoprotein IIb-IIIa

1999 ◽  
Vol 82 (12) ◽  
pp. 1680-1686 ◽  
Author(s):  
Marian Packham ◽  
Desirée Taylor ◽  
Erik Yeo ◽  
Cynthia Gemmell ◽  
Sonali Patil ◽  
...  
Keyword(s):  
Direct Interaction ◽  
Human Platelets ◽  
Rabbit Platelet ◽  
Dependent Manner ◽  
Affinity Matrix ◽  
Human Fibrinogen ◽  
Fibrinogen Binding ◽  
Rabbit Platelets ◽  
Induced Aggregation ◽  
Dose Dependent

SummaryThe HHLGGAKQAGDV (H12) sequence at the carboxyl termini of the γ chains and the RGD sequences in the Aα chains of human fibrinogen are potential recognition sites for the binding of soluble fibrinogen to glycoprotein IIb-IIIa (GPIIb-IIIa) on activated human platelets. Thus, addition of either H12 or RGD-containing peptides inhibits aggregation of and fibrinogen binding to human platelets. In contrast, we reported previously that RGDS had relatively little inhibitory effect on these functions of rabbit platelets. In the present study, we found that H12 inhibited ADP- and thrombin-induced aggregation of rabbit platelets in a dose-dependent manner. Specificity was demonstrated by the failure of the variant HHLGGAKQAGEV peptide to inhibit ADP-induced aggregation. Furthermore, flow cytometric analyses demonstrated that H12 inhibited the binding of FITC-fibrinogen to ADP-activated rabbit platelets in a dose-dependent manner. To examine the direct interaction of H12 with rabbit GPIIb-IIIa, we performed affinity chromatography by applying an octylglucoside extract of rabbit platelet proteins onto an affinity matrix containing the fibrinogen γ chain sequence. Proteins of ∼135 kDa and ∼95 kDa were specifically eluted by soluble H12, and the 95 kDa protein band was immunoblotted by anti-LIBS1, a monoclonal antibody against human GPIIIa. In control samples, no detectable protein from rabbit platelet lysates was eluted from an RGD affinity matrix by GRGDSP. Collectively, our results demonstrated that H12 inhibits aggregation of and fibrinogen binding to rabbit platelets by directly interacting with rabbit GPIIb-IIIa. These findings suggest that rabbit platelets would serve as a suitable thrombosis model for testing the efficacy of peptide mimetics derived from H12.

scholarly journals Naturally occurring human anti-band 3 autoantibodies accelerate clearance of erythrocytes in guinea pigs

Blood ◽  
1995 ◽  
Vol 85 (7) ◽  
pp. 1920-1928 ◽  
Author(s):  
U Giger ◽  
B Sticher ◽  
R Naef ◽  
R Burger ◽  
HU Lutz
Keyword(s):  
Guinea Pigs ◽  
Band 3 ◽  
Complement C3 ◽  
Erythrocyte Membranes ◽  
Dependent Manner ◽  
Band 3 Protein ◽  
Naturally Occurring ◽  
Dose Dependent

A variety of naturally occurring autoantibodies (NOAs) have been found in sera of animals and humans. Although their specific homeostatic role in the clearance of altered or senescent cells has been proposed and in vitro studies support such functions, in vivo evidence has been lacking. We studied the effect of affinity-purified human anti-band 3 NOA on the survival of untreated and diamide-treated erythrocytes in normal and complement C3-deficient guinea pigs. In vitro exposure to diamide, an oxidative agent, severely reduced the erythrocyte deformability and increased the amount of high-molecular-weight forms of band 3 protein and band 3-hemoglobin adducts in erythrocyte membranes, thereby markedly shortening the survival of these cells in vivo. Human anti-band 3 NOA bound in a dose-dependent manner to erythrocytes, and binding increased with exposure to diamide. In normal guinea pigs anti-band 3 NOA significantly accelerated the clearance of erythrocytes that were mildly damaged by iodine surface labeling and of those that were further oxidized by diamide. However, the anti-band 3 effect was transient and small. In contrast, anti-band 3 NOA did not significantly alter erythrocyte survival in functionally C3-deficient guinea pigs, thereby supporting the C3b requirement for anti-band 3 NOA activity. On the other hand, a pretreatment of animals with purified human band 3 protein slowed down the clearance of erythrocytes incubated with IgG depleted of anti-band 3 NOA. These results provide the first in vivo evidence of a role for anti-band 3 NOA in the clearance of erythrocytes.

scholarly journals Lysophosphatidic Acid Stimulates MCP-1 Secretion from C2C12 Myoblast

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Tamotsu Tsukahara ◽  
Hisao Haniu
Keyword(s):  
Lysophosphatidic Acid ◽  
Cell Types ◽  
C2c12 Cells ◽  
C2c12 Myoblast ◽  
Dependent Manner ◽  
Naturally Occurring ◽  
Chemotactic Protein ◽  
Cyclic Phosphatidic Acid ◽  
Cell Migration And Proliferation ◽  
Dose Dependent

Chemokines are regulatory proteins that play an important role in muscle cell migration and proliferation. In this study, C2C12 cells treated with lysophosphatidic acid (LPA) showed an increase in endogenous monocyte chemotactic protein-1 (MCP-1) expression and secretion. LPA is a naturally occurring bioactive lysophospholipid with hormone- and growth-factor-like activities. LPA is produced by activated platelets, cytokine-stimulated leukocytes, and possibly by other cell types. However, the LPA analog cyclic phosphatidic acid (cPA) had no effect on the expression and secretion of MCP-1. LPA, although similar in structure to cPA, had potent inducing effects on MCP-1 expression in C2C12 cells. In this study, we showed that LPA enhanced MCP-1 mRNA expression and protein secretion in a dose-dependent manner. Taken together, these results suggest that LPA enhances MCP-1 secretion in C2C12 cells and thus may play an important role in cell proliferation.

scholarly journals TGF-β Signaling Cooperates with AT Motif-Binding Factor-1 for Repression of the α-Fetoprotein Promoter

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Nobuo Sakata ◽  
Satoshi Kaneko ◽  
Souichi Ikeno ◽  
Yutaka Miura ◽  
Hidekazu Nakabayashi ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Inhibitory Action ◽  
Fetal Liver ◽  
Direct Interaction ◽  
Detectable Level ◽  
Dependent Manner ◽  
Reporter System ◽  
Adult Liver ◽  
Binding Factor ◽  
Dose Dependent

α-Fetoprotein (AFP) is known to be highly produced in fetal liver despite its barely detectable level in normal adult liver. On the other hand, hepatocellular carcinoma often shows high expression of AFP. Thus, AFP seems to be an oncogenic marker. In our present study, we investigated how TGF-β signaling cooperates with AT motif-binding factor-1 (ATBF1) to inhibit AFP transcription. Indeed, the expression of AFP mRNA in HuH-7 cells was negatively regulated by TGF-β signaling. To further understand how TGF-β suppresses the transcription of the AFP gene, we analyzed the activity of the AFP promoter in the presence of TGF-β. We found that the TGF-β signaling and ATBF1 suppressed AFP transcription through two ATBF1 binding elements (AT-motifs). Using a heterologous reporter system, both AT-motifs were required for transcriptional repression upon TGF-β stimulation. Furthermore, Smads were found to interact with ATBF1 at both its N-terminal and C-terminal regions. Since the N-terminal (ATBF1N) and C-terminal regions of ATBF1 (ATBF1C) lack the ability of DNA binding, both truncated mutants rescued the cooperative inhibitory action by the TGF-β signaling and ATBF1 in a dose-dependent manner. Taken together, these findings indicate that TGF-β signaling can act in concert with ATBF1 to suppress the activity of the AFP promoter through direct interaction of ATBF1 with Smads.

Evaluation of Dose and Route Effects of Platelet Activating Factor-Induced Extravasation in the Guinea Pig

1984 ◽  
Vol 52 (01) ◽  
pp. 034-036 ◽  
Author(s):  
Dean A Handley ◽  
Ronald G Van Valen ◽  
Mary Kay Melden ◽  
Robert N Saunders
Keyword(s):  
Guinea Pig ◽  
Platelet Activating Factor ◽  
The Other ◽  
Plasma Extravasation ◽  
Dependent Manner ◽  
Naturally Occurring ◽  
Protein Rich ◽  
Dose Dependent

SummaryPlatelet-activating factor (PAF) is a naturally occurring lipid that is reported to induce vessel hyperpermeability leading to loss of protein-rich plasma (extravasation). We have quantitated the systemic extravasation effects of synthetic PAF in the guinea pig by monitoring increases in hematocrit. When given intravenously (10-170 ng/kg), PAF produced dose-dependent increases in hematocrit, with maximal hemoconcentration developing in 5-7 min. In leukopenic animals the expected hematocrit increase was reduced by 57%. PAF given intra-arterially produced the dose-dependent changes in hematocrit similar to the intravenous effects of PAF. However, PAF given intraperitoneally (10-2500 μg/kg) was 800-1100-fold less effective than the other routes and hemoconcentration continued for 30-45 min until a maximal hematocrit was observed. These results show that PAF may markedly influence extravasation of plasma in a dose and route-dependent manner.

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