• BMB Reports
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• v.49 no.10
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• pp.566-571
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• 2016

Forskolin (FSK), an adenylyl cyclase activator, has recently been shown to enhance nucleotide excision repair (NER) upon UV exposure. However, our study revealed that this effect was detected in human skin epithelial ARPE19 cells only in growing cells, but not in non-cycling cells. When the cells were grown at low density (70% confluence), FSK was capable of stimulating cAMP responsive element binding (CREB) phosphorylation, a marker for FSK-stimulated PKA activation, and resulted in a significant increase of NER activity compared to control treatment. However, cells grown under 100% confluent conditions showed neither FSK-induced CREB phosphorylation nor the resulting NER enhancement. These findings indicate that cellular growth is critical for FSK-induced NER enhancement and suggest that cellular growth conditions should be considered as a variable while evaluating a reagent's pharmacotherapeutic efficacy.

• The Journal of Internal Korean Medicine
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• v.27 no.4
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• pp.855-863
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• 2006

Objectives : This study was performed to evaluate effects of Yangsim-tang extract (YST) on hemodynamics (regional cerebral blood flow (rCBF) and mean arterial blood pressure (MABP) ) in normal rats, and effects of cyclooxygenase and guanylate cyclase under YST. Methods : Laser-Doppler flowmetry (LDF) measured changes of rCBF, and a data acquisition system assembled with MacLab and Macintosh measured changes of MABP. Results : YST significantly increased rCBF, but did not change MABP. Pretreatment with indomethacin significantly inhibited rCBF increased by YST, but pretreatment with methylene blue did not significantly inhibit rCBF increased by YST. Conclusions : YST increases rCBF, and the action of this response is mediated by cyclooxygenase.

• Molecules and Cells
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• v.23 no.2
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• pp.215-219
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• 2007

In mammals light input resets the central clock of the suprachiasmatic nucleus by inducing secretion of pituitary adenylate cyclase-activating polypeptide (PACAP) from retinal ganglion cells (RGCs). We previously showed that thyroid transcription factor 1 (TTF-1), a homeodomain-containing transcription factor, specifically regulates PACAP gene expression in the rat hypothalamus. In the present study we examined the expression of TTF-1 in PACAP-synthesizing retinal cells. Fluorescence in situ hybridization (FISH) showed that it is abundantly expressed in RGCs of the superior region of the retina, but in only a small subset of RGCs in the inferior region. Double FISH experiments revealed that TTF-1 is exclusively expressed in PACAP-producing RGCs. These results suggest that TTF-1 plays a regulatory role in PACAP-expressing retinal ganglion cells.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.1
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• pp.22-28
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• 2001

The induction of enzymes and the accumulation of their end products associated with self-defense mechanism in rice were investigated. When rice leaves were irradiated with UV light, activities of diterpene cyclase, phenylalanine ammonia-lyase (PAL), and cinnamic acid 4-hydroxylase (CA4H) were induced and rice phytoalexin, momilactone A was accumulated. The content of p-coumaric acid in rice leaves was closely correlated with self-defense or allelopathic potential against barnyardgrass. UV-challenged rice leaves gave rise to the inhibition of barnyardgrass growth.

• Tuberculosis and Respiratory Diseases
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• v.43 no.2
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• pp.123-127
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• 1996

Secretion of surfactant phospholipid can be stimulated by a variety of agonists acting via at least three different signal transduction mechanisms. These include the adenylate cyclase system with activation of cAMP-dependent protein kinase; activation of protein kinase C either directly or subsequent to activation of phosphoinositide-specific phospholipase C and generation of diacylglycerols and inositol trisphosphate; and a third mechanism that involves incresed $Ca^{2+}$ levels and a calmodulin-dependent step. ATP stimulates secretion via all three mechanisms. The protein kinase C pathway is also coupled to phopholipase D which, acting on relatively abundant cellular phospholipids, generates diacylglycerols that further activate protein kinase C. Sustained protein kinase C activation can maintain phosphatidylcholine secretion for a prolonged period of time. It is likely that interactions between the different signaling pathways have an important role in the overall physiological regulation of surfactant secretion.

• Archives of Pharmacal Research
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• v.19 no.6
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• pp.520-528
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• 1996

The involvement of the cyclic AMP (cAMP) effector system in the release of endogenous dopamine and acetylcholine from the rat neostriatum was assessed. Forskolin, an activator of adenylate cyclase, was used to enhance cAMP production, and the consequence of this enhancement on the spontaneous and potassium stimulated release of dopamine and acetylcholine was evaluated. Neostriatal slices were prepared from Fischer 344 rats and after a preincubation period the release of each endogenous neurotransmitter was measured from the same slice preparation. To measure acetylcholine release the slice acetylcholinesterase (AChE) activity was inhibited with physostigmine, but the release from slices with intact AChE activity was also determined (choline, instead of acetylcholine was detected in the medium). Under both conditions forskolin induced a significant dose-dependent increase in the potassium-evoked release of dopamine. In the same tissue preparations the release of neither acetylcholine (AChE inhibited) nor choline (AChE intact) was affected by forskolin. The results indicate that the CAMP second messenger system might be involved in neuronal mechanisms that enhance neostriatal dopamine release, but stimulation of this second messenger by forskolin does not further enhance neostriatal acetylcholine release.

• The Korean Journal of Pharmacology
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• v.32 no.3
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• pp.311-321
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• 1996

Both $M_1$ and $M_2$ muscarinic receptors contain a triplet of amino acid residues consisting of leucine (L), tyrosine (Y) and threonine (T) at C-terminus ends of the second putative transmembrane domains. This triplet is repeated as LYT-LYT in $M_2$ receptors at the interface between the second transmembrane domain and the first extracellular loop. Interestingly, however, it is repeated in a transposed fashion (LYT-TYL) in the sequence of $M_1$ receptors. In this work, we employed site-directed mutagenesis to investigate the possible significance of this unique sequence diversity for determining the distinct differential cellular function at the two receptor subtypes. Mutation of the LYTTYL sequence of $M_1$ receptors to the corresponding $M_2$ receptor LYTLYT sequence did not result in a significant change in the binding affinity of the agonist carbachol. The reverse mutation at the $M_2$ receptor also did not modify agonist affinity. Surprisingly, the LYTLYT $M_1$ receptor mutant demonstrated markedly enhanced coupling to activation of phospholipase C without a change in its coupling to increased cyclic AMP formation. There was also an enhanced receptor sensitivity in transducing elevation of intracellular $Ca^{2+}$. On the other hand, the reverse $LYTLYT{\rightarrow}LYTTYL$ mutation in the $M_2$ receptor did not alter its coupling to inhibition of adenylate cyclase, but slightly enhanced its coupling to stimulation of phosphoinositide (PI) hydrolysis. Our data suggest that the LYTTYL/LYTLYT sequence differences between $M_1$ and $M_2$ muscarinic receptors are not important for specifying ligand binding and coupling of various subtypes of muscarinic receptors to different cellular signaling pathways although they might play a role in the modulation of muscarinic reseptor coupling to PI hydrolysis.

• Animal cells and systems
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• v.3 no.2
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• pp.103-113
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• 1999

Many in-depth reviews related to regulations of prolactin secretion are available. We will, therefore, focus on controversial aspects using personal opinion in this review. The neuroendocrine control of prolactin secretion from the anterior pituitary gland involves multiple factors including prolactin-release inhibiting factor (PIF) and prolactin releasing factor (PRF). The PIF exerts a tonic inhibitory control in the physiological conditions. The PIF should be able to effectively inhibit prolactin release or a lifetime, but the inhibitory action of dopamine cannot be sustained for a long period of time. Perifusion of a high concentration of dopamine (l ,000 nM) could not sustain inhibitory action on prolactin release but when a small amount of ascorbic acid (0.1 mM) is added in a low concentration of dopamine (3 nM) solution, prolactin release was inhibited for a long period. Ascorbate is essential for dopamine action to inhibit prolactin release. We have, therefore, concluded that the PIF is dopamine plus ascorbate. The major transduction system for dopamine to inhibit prolactin release is the adenylyl cyclase system. Dopamine decreases cyclic AMP concentration by inhibiting adenylyl cyclase, and cyclic AMP stimulates prolactin release. However, the inhibitory mechanism of dopamine on prolactin release is much more complex than simple inhibition of CAMP production. The dopamine not only inhibits cyclic AMP synthesis but also inhibits prolactin release by acting on a link(s) after the CAMP event in a chain reaction for inhibiting prolactin release. Low concentrations of dopamine stimulate prolactin release. Lactotropes are made of several different subtypes of cells and several different dopamine receptors are found in pituitary. The inhibitory and stimulatory actions induced by dopamine can be generated by different subtype of receptors. The GH$_4$ZR$_7$ cells express only the short isoform (D$_{2s}$) of the dopamine receptor, as a result of transfecting the D$_{2s}$ receptors into GH$_4$C$_1$ cells which do not express any dopamine receptors. When dopamine stimulates or inhibits prolactin release in GH$_4$ZR$_7$ cells, it is clear that the dopamine should act on dopamine D$_{2s}$ receptors since there is no other dopamine receptor in the GH$_4$ZR$_7$. Dopamine is able to stimulate prolactin release in a relatively low concentration while it inhibits in a high concentration in GH$_4$ZR$_7$. These observations indicate that the dopamine D$_2$ receptor can activate stimulatory and/or inhibitory transduction system depending upon dopamine concentrations.

• Korean journal of applied entomology
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• v.43 no.2
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• pp.155-162
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• 2004

Serotonin receptor binds to serotonin (5-HT) and activates effector proteins such as adenylyl cyclase, phospholipase C, cyclic GMP phosphodiesterase or ion channel through G protein on the cell membrane, resulting in various physiological responses like diuresis, memory and development. To examine the comparative expression of the 5-HT$\_$7/ receptor of Aedes aegypti, the Aedes 5-HT$\_$7/ receptor gene was transfected into Drosophila Schneider2 (S2) cells and mammalian Chinese hamster ovary (CHO)-Kl cells. The expression of the Aedes 5-HT$\_$7/ receptor gene in selected cell lines, Tr-CHO and Tr-S2, was confirmed with reverse transcription-PCR, Western blot and immunocytochemistry. Compared with the induced intracellular cAMP level of Tr-S2 cell line to 5-HT, the induced cAMP in the Tr-CHO cell line was over 9 times higher and was dose-dependent. These results suggest that the functionality of Aedes 5-HT$\_$7/ receptor is much more effective in mammalian CHO-K 1 cells and that the Tr-CHO cell line expressing Aedes 5-HT$\_$7/ receptor can be used for synthetic agonist or antagonist candidate screening.

• The Korean Journal of Physiology
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• v.28 no.2
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• pp.181-190
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• 1994

Endothelium-derived relaxing factor (EDRF) activates guanylate cyclase which mediates the formation of cGMP from GTP in vascular smooth muscle. It is well known that endothelium-dependent relaxation is impaired in spontaneously hypertensive rats (SHR). However, it is still unknown whether the impaired endothelium-dependent relaxation in SHR results from the reduced release of EDRF or from the decrease of vascular response to EDRF. We investigated the effects of cGMP on the contractility and Ca movement in the aorta of SHR and Wistar-Kyoto rats (WKY). The amplitude of the endothelium-dependent relaxation to actylcholine (ACh) was significantly less in SHR than in WKY. L-arginine $(10^{-3}M)$ did not increase endothelium-dependent relaxation in both strains. Sodium nitroprusside (SNP), an activator of guanylate cyclase, relaxed the 40 mM $K^+-induced$ contraction in a dose-dependent manner $(10^{-10}{\sim}10^{-6}\;M)$ in the endothelium-rubbed aortic strips of both strains. However, there was no significant difference in these relaxations between WKY and SHR. 8-bromo-cyclic guanosine monophosphate (8-Br-cGMP), a cell membrane-permeable derivative of cGMP relaxed the 40 mM $K^+-induced$ contraction in a dose-dependent manner $(10^{-6}{\sim}10^{-4}\;M)$ in the endothelium-rubbed aortic strips of both strains. Also norepinephrine $(10^{-6}\;M)-induced$ contractions in normal and Ca-free Tyrode's solution were suppressed by the pretreatment with 8-Br-cGMP $(10^{-4}\;M)$ in either strain. However, the amplitudes of suppression induced by 8-Br-cGMP were greater in SHR than that in WKY. Basal $^{45}Ca$ uptake and 40mM $K^+-stimulated\;^{45}Ca$ uptake were not suppressed by pretreatment with 8-Br-cGMP $(10^{-4}\;M)$ in single aortic smooth muscle cells of both SHR and WKY. From the above results, it is suggested that cGMP decreases Ca sensitivity in vascular smooth muscle cells and that the impaired endothelium-dependent relaxation in the aortic strips of SHR is not the result of a reduced vascular response to EDRF.