• Natural Product Sciences
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• v.3 no.1
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• pp.29-37
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• 1997

Protein Kinase C (PKC) is generally believed to play a central role in signal transduction, cellular growth control, gene expression, and tumor promotion. And it has been suggested that inhibitors of PKC might play important roles for the prevention and treatment of cancer. In order to investigate the possible inhibitors of PKC from natural products, PKC receptor binding assay was performed using bovine brain particulate as a source of PKC and the amount of $[^3H]Phorbol$ 12,13-dibutyrate (PDBu) bound to PKC was measured in the presence of test materials. Total methanol extracts from 100 kinds of natural products were partitioned into 3 fractions (n-hexane, ethyl acetate and aqueous layer) and their binding ability to the regulatory domain of PKC was evaluated. The ethyl acetate fractions of Morus alba $(roots,\;IC_{50}:\;156.6\;{\mu}g/ml)$, Rehmannia glutinosa $(roots,\;IC_{50}:\;134.3\;{\mu}g/ml)$, Lysimachia foenum-graecum $(roots,\;IC_{50}:\;167.8\;{\mu}g/ml)$, Polygonum cuspidata $(roots,\;IC_{50}:\;157.3\;{\mu}g/ml)$, Cnidium officinale $(aerial\;parts,\;IC_{50}:\;145.2\;{\mu}g/ml)$, and the hexane $(IC_{50}:\;179.3\;{\mu}g/ml)$ and the EtOAc fraction of Symplocarpus nipponicus $(roots,\;IC_{50}:\;155.9\;{\mu}g/ml)$ showed inhibitory activity of $[^3H]PDBu$ binding to PKC.

• The Korean Journal of Pharmacology
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• v.23 no.2
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• pp.101-111
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• 1987

We investigated the binding properties of $(^3H)$ QNB and $(^3H)$ NMS to mAchR to elucidate the characterstics of mAchR in rat brain by using two different preparations (homogemates & intact brain cell aggregates). The binding properties of both ligands demonstrated high affinity and saturability in both experiments, however $(^3H)$ QNB showed a significantly higher maximal binding capacity than tha ot $(^3H)$ NMS 1. In rat brain homogenates; Displacement of both lignands with several mAchR antagonists resulted in competition curves in accoradnce with the law of massaction for QNB, atropine & scopolamine in thie preparation, also a similar profile was found for the quaternary ammonium analogs of atropine & scopolamine (methyl atropine & methylscopolamine) when $(^3H)$ NMS was used to label the receptors in rat brain. But when these hydrophillic antagonists were used to displace $(^3H)$ QNB, they showed interaction with high- and low-affinity binding sites in brain homogenates. Pirenzepine, the nonclassical mAchR antagonist, was able to displace both ligands from binding sites in this preparation. 2. In intact rat brain cell aggregates; Intact bain cell aggregates were used to elucidate the binding characteristics of $(^3H)$ NMS to mAchR in rat. The magnitude of binding of this ligand was related linearly to the amount of cell protein in the binding assay with a high ratio of total to nonspecific binding. mAchR antagonists displaced specific $(^3H)$ NMS binding according to the law of mass-action, while it was possible to resolve displacement curves using mAchR agonist into high-& low-affinity component. 3. Our results indicate that more hydrophilic receptor ligand $(^3H)$ QNB, displacement experiments in both tissues demonstrated that the lipid solubility of a particulr mAchR ligand might play an important role in determining its profile of binding to the mAchR, and the concentrations of mAchR in rat brain are both on the cell surface (membrane-bound receptor) and in the intracelluar membrane (intermembrane-bound receptor). 4. The results are discussed in terms of the usefulness of dissociated intact rat brain cells in studying mAchR in central nervous system.

• Korean Journal of Biological Psychiatry
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• v.3 no.1
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• pp.51-56
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• 1996

The effects of 3 week treatment with haloperidol(2mg/kg/day, i.p.) on dopamine(DA) D2 receptor and DA metabolism in rat striata were studied at various time points after withdrawal from the drug treatment. Striatal DA D2 receptors were characterized with the radioligand 0.5nM [$^3H$]Spiperone. Dopamine(DA), homovanillic acid(HVA), 3,4-dihydroxyphenyl acetic acid(DOPAC) in rat striatum were measured with the high performance liquid chromatography. Drug withdrawal for 1 week induced significant increase in the number of D2 receptor in striatum after withdrawal for 1 week(p<0.05), and then this change was restored to control level during the withdrawal time of 2 and 4 weeks. There was no difference in striatal concentrations of DA and its metabolites among the groups. In conclusion, one-week withdrawal from chronic haloperidol treatment induced DA D2 receptor supersensitivity in the striatum, and that was normalized rapidly. Though this adaptive change in DA receptors, it may not affect the metabolism of DA in striatum.

• Biomolecules & Therapeutics
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• v.22 no.4
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• pp.347-354
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• 2014

Larrea nitida is a plant that belongs to the Zygophyllaceae family and is widely used in South America to treat inflammatory diseases, tumors and menstrual pain. However, its pharmacological activity remains unclear. In this study we evaluated the property of selective estrogen receptor modulator (SERM) of Larrea nitida extracts (LNE) as a phytoestrogen that can mimic, modulate or disrupt the actions of endogenous estrogens, depending on the tissue and relative amount of other SERMs. To investigate the property of SERM of LNE, we performed MCF-7 cell proliferation assays, estrogen response element (ERE)-luciferase reporter gene assay, human estrogen receptor (hER) binding assays and in vivo uterotrophic assay. To gain insight into the active principles, we performed a bioassay-guided analysis of LNE employing solvents of various polarities and using classical column chromatography, which yielded 16 fractions (LNs). LNE showed high binding affinities for $hER{\alpha}$ and $hER{\beta}$ with $IC_{50}$ values of $1.20{\times}10^{-7}$ g/ml and $1.00{\times}10^{-7}$ g/ml, respectively. LNE induced $17{\beta}$-estradiol (E2)-induced MCF-7 cell proliferation, however, it reduced the proliferation in the presence of E2. Furthermore, LNE had an atrophic effect in the uterus of immature rats through reducing the expression level of progesterone receptor (PR) proteins. LN08 and LN10 had more potent affinities for binding on $hER{\alpha}$ and ${\beta}$ than other fractions. Our results indicate that LNE had higher binding affinities for $hER{\beta}$ than $hER{\alpha}$, and showed SERM properties in MCF-7 breast cancer cells and the rat uterus. LNE may be useful for the treatment of estrogen-related conditions, such as female cancers and menopause.

• BMB Reports
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• v.34 no.6
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• pp.573-577
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• 2001

The mammalian heart is known to undergo significant mechanical changes during fetal and neonatal development. The objective of this study was to define the ontogeny of the ryanodine receptor/$Ca^{2+}$ release channel and SERCA that play the major roles in excitation-contraction coupling. Whole ventricular homogenates of fetal (F) (19 and 22 days in gestation), postnatal (N) (1 and 7 days postnatal), and adult (A) (5 weeks postnatal) Sprague-Dawley rat hearts were used to study [$^3H$]ryanodine binding and oxalate-supported $^{45}Ca^{2+}$ uptake. For the ryanodine receptor, the major findings were: (1) The ryanodine receptor density, as determined by maximal [$^3H$]ryanodine binding ($B_{max}$), increased 3 fold between the F22 and A periods ($0.26{\pm}0.1$ vs. $0.73{\pm}0.07$ pmoles/mg protein, p<0.01), whereas there was no significant change during the F22 and N1 development phases ($0.26{\pm}0.1$ vs. $0.34{\pm}0.01$). (2) Affinity of the ryanodine receptor to ryanodine did not significantly change, as suggested by the lack of change in the $K_d$ during the development and maturation. For SERCA, changes started early with an increased rate of $Ca^{2+}$ uptake in the fetal periods (F19: $8.1{\pm}1.1$ vs. F22: $19.3{\pm}2.2$ nmoles/g protein/min; p<0.05) and peaked by 7 days (N7) of the postnatal age ($34.9{\pm}2.1$). Thus, we conclude that the quantitative changes occur in the ryanodine receptor during myocardial development. Also, the maturation of the $Ca^{2+}$ uptake appears to start earlier than that of the $Ca^{2+}$ release.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.455-458
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• 2011

In previous report, with the aid of receptor-oriented pharmacophore-based in silico screening, we characterized three novel hPNMT inhibitors (YPN010, YPN016, and YPN017) and proposed that the hydrogen bonding interaction between inhibitors and side chain of Lys57 is very important to inhibitory activity of hPNMT. To confirm the importance of Lys57, mutant with substitution of Lys57 with Ala was cloned and binding study was performed for a K57A mutant of hPNMT using STD-NMR and fluorescence experiments. The binding constants for three novel inhibitors with mutant hPNMT were dramatically decreased compared to those with wild-type protein. K57A mutant-induced conversion of noradrenaline to adrenaline was suppressed about 95 % compared to wild-type hPNMT. Mutagenic analysis using a K57A mutant confirmed the importance of the Lys57 residue in binding of the inhibitor candidate to hPNMT as well as enzymatic activity of hPNMT, implying that these results are consistent with our binding model.

• The Korean Journal of Physiology and Pharmacology
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• v.5 no.5
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• pp.397-405
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• 2001

The ryanodine receptor, a $Ca^{2+}$ release channel of the sarcoplasmic reticulum (SR), is responsible for the rapid release of $Ca^{2+}$ that activates cardiac muscle contraction. In the excitation-contraction coupling cascade, activation of SR $Ca^{2+}$ release channel is initiated by the activity of sarcolemmal $Ca^{2+}$ channels, the dihydropyridine receptors. Previous study showed that the relaxation defect of diabetic heart was due to the changes of the expressional levels of SR $Ca^{2+}$ATPase and phospholamban. In the diabetic heart contractile abnormalities were also observed, and one of the mechanisms for these changes could include alterations in the expression and/or activity levels of various $Ca^{2+}$ regulatory proteins involving cardiac contraction. In the present study, underlying mechanisms for the functional derangement of the diabetic cardiomyopathy were investigated with respect to ryanodine receptor, and dihydropyridine receptor at the transcriptional and translational levels. Quantitative changes of ryanodine receptors and the dihydropyridine receptors, and the functional consequences of those changes in diabetic heart were investigated. The levels of protein and mRNA of the ryanodine receptor in diabetic rats were comparable to these of the control. However, the binding capacity of ryanodine was significantly decreased in diabetic rat hearts. Furthermore, the reduction in the binding capacity of ryanodine receptor was completely restored by insulin. This result suggests that there were no transcriptional and translational changes but functional changes, such as conformational changes of the $Ca^{2+}$ release channel, which might be regulated by insulin. The protein level of the dihydropyridine receptor and the binding capacity of nitrendipine in the sarcolemmal membranes of diabetic rats were not different as compared to these of the control. In conclusion, in diabetic hearts, $Ca^{2+}$ release processes are impaired, which are likely to lead to functional derangement of contraction of heart. This dysregulation of intracellular $Ca^{2+}$ concentration could explain for clinical findings of diabetic cardiomyopathy and provide the scientific basis for more effective treatments of diabetic patients. In view of these results, insulin may be involved in the control of intracellular $Ca^{2+}$ in the cardiomyocyte via unknown mechanism, which needs further study.

• BMB Reports
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• v.28 no.5
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• pp.437-442
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• 1995

The potency of yeast-derived methionyl-free human growth hormone (rhGH), which was obtained by removal of the N-terminal Met from methionyl-hGH, was estimated by in vitro and in vivo assays. In radio-receptor assay where the binding affinity of growth hormone to the receptor was estimated, the recombinant hGH showed 2.9 international units (IU) per mg of specific activity. In contrast, pitUitary-derived human growth hormone had a slightly lower receptor binding activity (2.5 IU/mg) compared with recombinant growth hormone. For the in vivo assay, efficacy of rhGH was tested by use of hypophysectomized rats, in which pituitary organs were surgically removed, resulting in the termination of growth hormone secretion. The weight-increase in rats by the injection of rhGH was almost identical to the result obtained by the injection of the same amount of pituitary-derived (international standard) hGH. A comparision of the secondary structures of rhGH and rMet-hGH by circular dichroism spectrophotometer demonstrated that the removal of the methionyl residue from rMet-hGH did not exert any effect on the structure of the growth hormone. In conclusion, methionyl-free human growth hormone produced from yeast was highly potent in biological activity and maintained a legitimate three dimensional structure.

• Journal of Plant Biotechnology
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• v.48 no.4
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• pp.289-303
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• 2021

Covid-19 is an ongoing pandemic as we speak in 2022. This infectious disease is caused by the SARS-CoV-2 virus, which infects cells by binding to the angiotensin-converting enzyme 2 (ACE2) receptor on the cell surface. Thus, strategies that inhibit the binding of SARS-CoV-2 to the ACE2 receptor can stop this contagion. Hanjeli (Coix lacryma-jobi) essential oil contains many bioactive compounds, including dodecanoic acid; tetradecanoic acid; 7-Amino-8-imino-2-(2-imino-2H-chromen-3-yl); and 1,5,7,10-tetraaza-phen-9-one. These compounds suppress viral replication and may prevent Covid-19. Accordingly, this study assessed whether, these four limonoid compounds can block the ACE2 receptor. To this end, their physicochemical properties were predicted using Lipinski's "rule of five" on the SwissADME website, and their toxicity was assessed using the online tools ProTox and pkCSM. Additionally, their interactions with the ACE2 receptor were predicted via molecular docking using Autodock Vina. All the four compounds satisfied the "rule of five" and tetradecanoic acid was predicted to have a higher affinity than the comparison compound remdesivir and the original ligand of ACE2. Molecular docking results suggested that the compounds from hanjeli essential oil interact with the active site of the ACE2 receptor similarly as the original ligand and remdesivir. In conclusion, hanjeli essential oil contains compounds predicted hinder the interaction of SARS-CoV-2 with the ACE2 receptor. Accordingly, our data may facilitate the development of a phytomedical strategy against SARS-CoV-2 infection.

• Biomolecules & Therapeutics
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• v.20 no.2
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• pp.183-188
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• 2012

In this study, we examined the estrogenic activity of bavachin, a component of Psoralea corylifolia that has been used as a traditional medicine in Asia. Bavachin was purified from ethanolic extract of Psoralea corylifolia and characterized its estrogenic activity by ligand binding, reporter gene activation, and endogenous estrogen receptor (ER) target gene regulation. Bavachin showed ER ligand binding activity in competitive displacement of [$^3H$] $E_2$ from recombinant ER. The estrogenic activity of bavachin was characterized in a transient transfection system using $ER{\alpha}$ or $ER{\beta}$ and estrogen-responsive luciferase plasmids in CV-1 cells with an $EC_{50}$ of 320 nM and 680 nM, respectively. Bavachin increased the mRNA levels of estrogen-responsive genes such as pS2 and PR, and decreased the protein level of $ER{\alpha}$ by proteasomal pathway. However, bavachin failed to activate the androgen receptor in CV-1 cells transiently transfected with the corresponding receptor and hormone responsive reporter plasmid. These data indicate that bavachin acts as a weak phytoestrogen by binding and activating the ER.