• The Korean Journal of Physiology
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• v.30 no.1
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• pp.85-96
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• 1996

Adenosine and its analogues are known to possess analgesic effects and to be involved in the opiate-induced antinociception as well. This study was designed to investigate the effects of three adenosine agonists, 5'- (N-cyclopropyl) -carboxamidoadenosine(CPCA), 5'-N-ethylcarboxamidoadeno-sine (NECA) and $N^6-cyclohexyladenosine$ (CHA) on the signal transmission in the spinal cord and also to elucidate mechanisms of their actions in the anesthetized cat. All the tested adenosine agonists(i.v,) exerted inhibitory effects on the responsiveness of the wide dynamic range (WDR) cells, the inhibitory action of CHA, an adenosine $A_1$ receptor agonist, $(80{\mu}g/Kg)$ being most weak. The intravenous CPCA, an adenosine $A_2$ receptor agonist, $(20{\mu}g\;/Kg)$ and NECA, nonspecific adenosine receptor agonist, $(20{\mu}g\;/Kg)$ inhibited the responses of WDR cells to pinch and C fiber stimulation more strongly than those to brush and A fiber stimulation. CPCA (i.v.) also suppressed the responses of WDR cells to thermal stimulus. And all the CPCA-induced inhibitions were caffeine-reversible. When CPCA was directly applied onto the spinal cord or intravenously administered into the spinal cat, on average, about three quarters of the CPCA-induced inhibitory effect was abolished. On the other hand, in the animal with spinal lesions in the ipsilateral dorsolateral area, the CPCA-induced inhibition was comparable to that observed in the spinal cats. In conclusion, this study shows that adenosine agonists strongly suppress the responses of WDR cells to pinch, C fiber stimulation and thermal stimuli mainly through the supraspinal adenosine $A_2-receptors$.

• Korean Journal of Veterinary Research
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• v.47 no.4
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• pp.371-378
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• 2007

To understand the role of $PM_{2X}/P_{2Y}$ receptor in cortex region of kidney and renal artery, molecular and functional analysis of $PM_{2X}/P_{2Y}$ receptor by pharmacophysiological skill in conventional swine tissues were performed. In functional analysis of $P_{2Y}$ receptor for vascular relaxation, 2-methylthio adenosine triphosphate, a strong agonist of $P_{2Y}$ receptor, induced relaxation of noradrenaline (NA)-precontracted renal artery in a dose-dependent manner. Strikingly, relaxative effect of ATP, 2-msATP, agonists of $P_{2Y}$ receptor, abolished by treatment of reactive blue 2, a putative $P_{2Y}$ receptor antagonist. In contrast, no significant differences of gene encoding $PM_{2X}/P_{2Y}$ and protein expression in immortalized suprachiasmatic nucleus from brain, primary isolated vascular smooth muscle cells from renal artery of pigs and HEK293 from human embryonic kidney under with/without adenosine triphosphate were observed. Taken together, the relationship between molecular and functional characteristic of $PM_{2X}/P_{2Y}$ receptors in conventional pig should be considered that they are another important factor which regulate the kidney function in swine. Based on this study, we propose the purinergic receptor as well as adrenergic and cholinergic receptors is an essential component of the renal homeostasis.

• Parasites, Hosts and Diseases
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• v.58 no.4
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• pp.393-402
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• 2020

Toxoplasma gondii is an intracellular parasite that causes severe disease when the infection occurs during pregnancy. Adenosine is a purine nucleoside involved in numerous physiological processes; however, the role of adenosine receptors in T. gondii-induced trophoblast cell function has not been investigated until now. The goal of the present study was to evaluate the intracellular signaling pathways regulated by adenosine receptors using a HTR-8/SVneo trophoblast cell model of T. gondii infection. HTR8/SVneo human extravillous trophoblast cells were infected with or without T. gondii and then evaluated for cell morphology, intracellular proliferation of the parasite, adenosine receptor expression, TNF-α production and mitogen-activated protein (MAP) kinase signaling pathways triggered by adenosine A₃ receptor (A₃AR). HTR8/SVneo cells infected with T. gondii exhibited an altered cytoskeletal changes, an increased infection rate and reduced viability in an infection time-dependent manner. T. gondii significantly promoted increased TNF-α production, A₃AR protein levels and p38, ERK1/2 and JNK phosphorylation compared to those observed in uninfected control cells. Moreover, the inhibition of A₃AR by A₃AR siRNA transfection apparently suppressed the T. gondii infection-mediated upregulation of TNF-α, A₃AR production and MAPK activation. In addition, T. gondii-promoted TNF-α secretion was dramatically attenuated by pretreatment with PD098059 or SP600125. These results indicate that A₃AR-mediated activation of ERK1/2 and JNK positively regulates TNF-α secretion in T. gondii-infected HTR8/SVneo cells.

• Proceedings of the Korean Biophysical Society Conference
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• 1997.07a
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• pp.32-32
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• 1997

The regulatory role of A$\sub$2A/ adenosine receptors in P$_2$ purinoceptor-mediated calcium signaling was investigated in rat pheochromocytoma (PC12) cells. When PC12 cells were treated with 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS21680), a specific agonist of the A$\sub$2A/ adenosine receptor, extracellular ATP-evoked [(CA$\^$2+/)]$\sub$i/ rise was inhibited by 20%.(omitted)

• CELLMED
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• v.2 no.4
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• pp.38.1-38.6
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• 2012

The present study aimed to determine the possible mechanisms of the peripheral antinociception of the aqueous extracts of Dicranopteris linearis (AEDL), Melastoma malabathricum (AEMM) and Bauhinia purpurea (AEBP) leaves in mice. Briefly, the antinociceptive profile of each extract (300, 500, and 1000 mg/kg; subcutaneous (s.c.)), was established using the abdominal constriction test. A single dose (500 mg/kg) of each extract (s.c.) was pre-challenged for 10 min with various pain receptors' antagonists or pain mediators' blockers and 30 min later subjected to the antinociceptive assay to determine the possible mechanism(s) involved. Based on the results obtained, all extracts exerted significant (p < 0.05) antinociceptive activity with dose-dependent activity observed only with the AEMM. Furthermore, the antinociception of AEDL was attenuated by naloxone, atropine, yohimbine and theophylline; AEMM was reversed by yohimbine, theophylline, thioperamide, pindolol, reserpine, and 4-chloro-DL-phenylalanine methyl ester hydrochloride; and of AEBP was inhibited by naloxone, haloperidol, yohimbine and reserpine. In conclusion, the antinociceptive activity of those extracts possibly involved the activation of several pain receptors (i.e. opioids, muscarinic, ${\alpha}_2$-adrenergic and adenosine receptors, adenosine, H3-histaminergic and $5HT_{1A}$, dopaminergic receptors).

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.5
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• pp.311-316
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• 2010

It is well-known that electrical field stimulation (EFS)-induced contraction is mediated by a cholinergic mechanism and other neurotransmitters. NO, ATP, calcitonin gene-related peptide (CGRP), and substance P are released by EFS. To investigate the purinergic mechanism involved in the EFS-induced contraction, purinegic receptors antagonists were used. Suramine, a non-selective P2 receptor antagonist, reduced the contraction induced by EFS. NF023 ($10^{-7}{\sim}10^{-4}M$), a selective P2X antagonist, inhibited the contraction evoked by EFS. Reactive blue ($10^{-6}{\sim}10^{-4}M$), selective P2Y antagonist, also blocked the contraction in a dose-dependent manner. In addition, P2X agonist ${\alpha}$,${\beta}$-methylene 5'-adenosine triphosphate (${\alpha}{\beta}MeATP$, $10^{-7}{\sim}10^{-5}M$) potentiated EFS-induced contraction in a dose-dependent manner. P2Y agonist adenosine 5'-[${\beta}$-thio]diphosphate trilithium salt ($ADP{\beta}S$, $10^{-7}{\sim}10^{-5}M$) also potentiated EFS-induced contractions in a dose-dependent manner. Ecto-ATPase activator apyrase (5 and 10 U/ml) reduced EFS-induced contractions. Inversely, 6-N,$N$-diethyl-D-${\beta}$,${\gamma}$- dibromomethylene 5'-triphosphate triammonium (ARL 67156, $10^{-4}M$) increased EFS-induced contraction. These data suggest that endogenous ATP plays a role in EFS-induced contractions which are mediated through both P2X-receptors and P2Y-receptors stimulation in cat esophageal smooth muscle.

• BMB Reports
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• v.44 no.5
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• pp.335-340
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• 2011

In this study, we attempted to isolate novel mast cell-stimulating molecules from Staphylococcus aureus. Water-soluble extract of S. aureus cell lysate strongly induced human interleukin-8 in human mast cell line-1 and mouse interleukin-6 in mouse bone marrow-derived mast cells. The active molecule was purified to homogeneity through a $C_{18}$ reverse phase HPLC column. By determination of its structure by MALDITOF and $^1H$- and $^{13}C$-NMR, adenosine was revealed to be responsible for the observed cytokine induction activities. Further studies using 8-sulfophenyl theophylline, a selective adenosine receptor blocker, verified that purified adenosine can induce interleukin-8 production via adenosine receptors on mast cells. Moreover, adenosine was purified from S. aureus-engulfed RAW264.7 cells, a murine macrophage cell line, used to induce phagocytosis of S. aureus. These results show a novel view of the source of exogenous adenosine in vivo and provide a mechanistic link between inflammatory disease and bacterial infection.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.5
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• pp.467-479
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• 2018

The aging process induces a plethora of changes in the body including alterations in hormonal regulation and metabolism in various organs including the heart. Aging is associated with marked increase in the vulnerability of the heart to ischemia-reperfusion injury. Furthermore, it significantly hampers the development of adaptive response to various forms of conditioning stimuli (pre/post/remote conditioning). Aging significantly impairs the activation of signaling pathways that mediate preconditioning-induced cardioprotection. It possibly impairs the uptake and release of adenosine, decreases the number of adenosine transporter sites and down-regulates the transcription of adenosine receptors in the myocardium to attenuate adenosine-mediated cardioprotection. Furthermore, aging decreases the expression of peroxisome proliferator-activated receptor gamma co-activator 1-alpha ($PGC-1{\alpha}$) and subsequent transcription of catalase enzyme which subsequently increases the oxidative stress and decreases the responsiveness to preconditioning stimuli in the senescent diabetic hearts. In addition, in the aged rat hearts, the conditioning stimulus fails to phosphorylate Akt kinase that is required for mediating cardioprotective signaling in the heart. Moreover, aging increases the concentration of $Na^+$ and $K^+$, connexin expression and caveolin abundance in the myocardium and increases the susceptibility to ischemia-reperfusion injury. In addition, aging also reduces the responsiveness to conditioning stimuli possibly due to reduced kinase signaling and reduced STAT-3 phosphorylation. However, aging is associated with an increase in MKP-1 phosphorylation, which dephosphorylates (deactivates) mitogen activated protein kinase that is involved in cardioprotective signaling. The present review describes aging as one of the major confounding factors in attenuating remote ischemic preconditioning-induced cardioprotection along with the possible mechanisms.

• The Korean Journal of Pharmacology
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• v.32 no.1
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• pp.23-29
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• 1996

According to the traditional receptor model, competitive antagonists share with agonists the ability to bind to a common site on receptors, but they are different from agonist in that they cannot trigger the biological response-i.e., they lack intrinsic efficacy. Recent findings extend the model by indicating that not all antagonists display an intrinsic efficacy of zero but that some display 'inverse agonism'. In the present study we studied the inverse agonism at $A_1$ adenosine receptors in membranes prepared from rat cerebral cortex. Eight commercially available $A_1$ adenosine receptor antagonists (CGS-15943, ADPX, CPT, DPCPX, DPX, N-0840, PACPX and 8-PT) were screened for inverse agonism by measuring the extent of $[^{35}S]guanosine-5'-({\gamma}-thio)$ triphosphate $([^{35}S]GTP_{\gamma}S)$ binding to G proteins. The agonist-induced stimulation of $[^{35}S]GTP_{\gamma}S$ bindings was completely blocked in the presence of $A_1$ adenosine receptor antagonists. Under optimal conditions, two types of antagonists could be distinguished. Seven antagonists including DPCPX decreased the basal $[^{35}S]GTP_{\gamma}S$ binding in the absence of agonist, displaying inverse agonist activity. One (CGS-15943) had no effect on the basal bindings. N-ethylmaleimide treatment reduced the basal bindings as well as agonist-mediated stimulation of $[^{35}S]GTP_{\gamma}S$ bindings, indicating that a substantial amount of this binding reflects an activated state of the C proteins. In good agreement with these findings, 0.1 mM GTP decreased the apparent affinity of the receptors for the agonist PIA, increased that for DPCPX, and had no effect on that for CGS-15943.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.178.3-178.3
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• 2003

P2X receptors are ligand gated cation channels activated by the binding of extracellular adenosine 5'-triphosphate (ATP) and classified into 7 subtype families. $P2X_1$ receptors are abundantly expressed in smooth muscle mediates blood vessel and mediate constriction upon binding of neuronal ATP. The activation of $P2X_3$ receptor by ATP has been known to initiate the pain signaling in the peripheral nervous system, which is involved in chronic inflammatory nociception and neuropathic pain by nerve injury. (omitted)