Research status and prospects on adenosine receptor mechanism of acupuncture for myocardial ischemia / 中国针灸

The relationship between adenosine receptor (AdoR) and myocardial ischemia (MI), effect of acupuncture for MI and action mechanism of acupuncture improving MI by regulating AdoR are summarized. The existing researches have preliminarily reflected that the improvement of MI treated with acupuncture may be achieved by influencing the expression of AdoR. However, there are still some limitations, e.g. most of the research regimens are single-acupoint, the research results are not entirely consistent and the interaction of AdoRs are ignored, all these need to be further verified and supplemented.

Clostridium difficile toxins or infection induce upregulation of adenosine receptors and IL-6 with early pro-inflammatory and late anti-inflammatory pattern

Clostridium difficile causes intestinal inflammation, which increases adenosine. We compared the expression of adenosine receptors (AR) subtypes A1, A2A, A2B, and A3 in HCT-8, IEC-6 cells, and isolated intestinal epithelial cells, challenged or not with Clostridium difficile toxin A and B (TcdA and TcdB) or infection (CDI). In HCT-8, TcdB induced an early A2BR expression at 6 h and a late A2AR expression at 6 and 24 h. In addition, both TcdA and TcdB increased IL-6 expression at all time-points (peak at 6 h) and PSB603, an A2BR antagonist, decreased IL-6 expression and production. In isolated cecum epithelial cells, TcdA induced an early expression of A2BR at 2s and 6 h, followed by a late expression of A2AR at 6 and 24 h and of A1R at 24 h. In CDI, A2AR and A2BR expressions were increased at day 3, but not at day 7. ARs play a role in regulating inflammation during CDI by inducing an early pro-inflammatory and a late anti-inflammatory response. The timing of interventions with AR antagonist or agonists may be of relevance in treatment of CDI.

Amitriptyline inhibits the MAPK/ERK and CREB pathways and proinflammatory cytokines through A3AR activation in rat neuropathic pain models / 대한마취과학회지

BACKGROUND: The pain-relief properties of tricyclic antidepressants can be attributed to several actions. Recent observations suggest that adenosine is involved in the antinociceptive effect of amitriptyline. The A3 adenosine receptor (A3AR) is the only adenosine subtype overexpressed in inflammatory and cancer cells. This study was performed to investigate the role of A3AR in the anti-nociceptive effect of amitriptyline. METHODS: Spinal nerve-ligated neuropathic pain was induced by ligating the L5 and L6 spinal nerves of male Sprague-Dawley rats. The neuropathic rats were randomly assigned to one of the following three groups (8 per group): a neuropathic pain with normal saline group, a neuropathic pain with amitriptyline group, and a neuropathic pain with amitriptyline and 3-ethyl-5-benzyl- 2-methyl-4-phenylethynyl-6-phenyl-1,4-(±)-dihydropyridine-3,5-dicarboxylate (MRS) group. Amitriptyline or saline was administered intraperitoneally and 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(±)-dihydropyridine-3,5-dicarboxylate (MRS-1191), an A3AR antagonist, was injected subcutaneously immediately before amitriptyline administration. The level of extracellular signal-regulated kinase P44/42 (ERK1/2), cyclic AMP response element-binding protein (CREB), and proinflammatory cytokines were assessed using immunoblotting or reverse-transciption polymerase chain reaction. RESULTS: Amitriptyline increased the mechanical withdrawal threshold of the neuropathic rats. The level of phospho-ERK1/2 and phospho-CREB proteins, and proinflammatory cytokines produced by spinal nerve ligation were significantly reduced by amitriptyline administration. However, the use of MRS-1191 before amitriptyline administration not only reduced the threshold of mechanical allodynia, but also increased the signaling protein and proinflammatory cytokine levels, which were reduced by amitriptyline. CONCLUSIONS: The results of this study suggest that the anti-nociceptive effect of amitriptyline involves the suppression of ERK1/2 and CREB signaling proteins, and A3AR activation also affects the alleviation of the inflammatory response.

Mechanism of acupoint selection along meridians to improve adenosine receptor of myocardial ischemia based on acupoint specificity / 中国针灸

OBJECTIVE@#To explore the action mechanism of acupoint selection along meridians to improve adenosine receptor in myocardial ischemia (MI) rats by comparing the effects of acupoint selection along meridians, acupoint selection at other meridians and non-acupoint on expression of adenosine receptor.@*METHODS@#A total of 120 SD rats were randomly divided into a blank group, a sham operation group, a model group, an acupoint-selection-along-meridians (ASAM) group, an acupoint-selection-at-other-meridians (ASAOM) group and a non-acupoint group, 20 rats in each group. The model of MI was not made in the blank group; the left anterior descending coronary artery was not ligated after thoracotomy in the sham operation group; the model of MI was made but acupuncture was not given in the model group. After the model of MI was made, electroacupuncture (EA) was applied at "Neiguan" (PC 6) in the ASAM group, at "Hegu" (LI 4) in the ASAOM group, and at the area between the third and fourth metatarsal bone in the non-acupoint group. EA was given 20 min per treatment, once a day for 5 days. After treatment, the TTC staining was used to detect myocardial infarction, the Tunel method was used to detect cardiomyocyte apoptosis, and the immunohistochemistry was used to detect the expression of adenosine receptors A1, A2a and A2b.@*RESULTS@#Compared with the blank group and the sham operation group, the percentage of myocardial infarction and apoptotic rate of myocardial cells in the model group were increased significantly (<0.01). After EA treatment, compared with the model group, the percentage of myocardial infarction and apoptotic rate of myocardial cells in the ASAM group were decreased significantly (<0.01), and the expression levels of adenosine receptors A1, A2a and A2b were increased significantly (<0.01). The percentage of myocardial infarction and apoptotic rate of myocardial cells in the ASAM group were significantly lower than those in the ASAOM group and the non-acupoint group (<0.01), and the expression levels of adenosine receptors A1, A2a and A2b in the ASAM group were significantly higher than those in the ASAOM group and non-acupoint group (<0.01).@*CONCLUSION@#Compared with acupoint selection at other meridians or non-acupoints, acupoint selection along meridians can effectively regulate the expression of adenosine receptors A1, A2a and A2b, improve the condition of myocardial infarction, inhibit myocardial cell apoptosis, and consequently protect ischemic myocardium.

Mechanisms and therapeutic targets of ischemic acute kidney injury

Acute kidney injury (AKI) due to renal ischemia reperfusion (IR) is a major clinical problem without effective therapy and is a significant and frequent cause of morbidity and mortality during the perioperative period. Although the pathophysiology of ischemic AKI is not completely understood, several important mechanisms of renal IR-induced AKI have been studied. Renal ischemia and subsequent reperfusion injury initiates signaling cascades mediating renal cell necrosis, apoptosis, and inflammation, leading to AKI. Better understanding of the molecular and cellular pathophysiological mechanisms underlying ischemic AKI will provide more targeted approach to prevent and treat renal IR injury. In this review, we summarize important mechanisms of ischemic AKI, including renal cell death pathways and the contribution of endothelial cells, epithelial cells, and leukocytes to the inflammatory response during ischemic AKI. Additionally, we provide some updated potential therapeutic targets for the prevention or treatment of ischemic AKI, including Toll-like receptors, adenosine receptors, and peptidylarginine deiminase 4. Finally, we propose mechanisms of ischemic AKI-induced liver, intestine, and kidney dysfunction and systemic inflammation mainly mediated by Paneth cell degranulation as a potential explanation for the high mortality observed with AKI.

NCS-1 en la función neuronal / NCS-1 in neuronal function

NCS-1 es una proteína unidora de calcio, que regula el funcionamiento de otras proteínas, con las cuales interactúa a nivel molecular. Su expresión es amplia y no limitada a neuronas. Sus efectos incluyen la regulación de receptores, canales iónicos y enzimas que intervienen en múltiples funciones neuronales. NCS-1 regula la actividad del receptor D2 de dopamina y del receptor A2A de adenosina, ambos fundamentales en diversos procesos de comunicación que involucran control emocional y control de movimientos en varios circuitos. NCS-1 también regula la actividad del receptor de IP3, un canal de calcio intracelular fundamental en la regulación de la homeostasis de este ion, interactúa con IP kinasas, las cuales a su vez desencadenan cascadas de señalización intracelular y modula la actividad de canales de calcio presinápticos; todos estos efectos redundan en regulación de la liberación de neurotransmisores y por ende, de la plasticidad sináptica, lo cual ha sido probado en diversos modelos experimentales. NCS-1 también parece estar involucrada en la regulación de otros canales iónicos de calcio y de potasio que podrían influir en la homeostasis eléctrica de las neuronas y en la supervivencia neuronal a través de la regulación de vías proapoptóticas. Estos amplios efectos de NCS-1 motivan a profundizar la investigación en los mecanismos involucrados en la regulación que ejerce sobre sus proteínas blanco y en nuevos efectos que ayuden a entender el rol de esta proteína en diversos procesos fisiológicos y fisiopatológicos(AU)

NCS-1 is a calcium-binding protein, which regulates the functioning of diverse proteins, with which interacts to a molecular level. Its expression is widespread and it is not limited to neurons. Its effects include the regulation of receptors, ion channels and enzymes, which intervene in multiple neuronal functions. NCS-1 regulates the functioning of D2 dopamine receptor and adenosine A2A receptor, both fundamental in diverse communication processes that involve emotional and movement control in a variety of neural circuits. NCS-1 also regulates the activity of IP 3 receptor, an intracellular calcium ion channel (which is crucial in the regulation of calcium homeostasis), interacts with the IP kinases, which trigger intracellular signaling cascades, and modulates the activity of presynaptic calcium channels. All these effects lead to the regulation of neurotransmitters release and thus, synaptic plasticity, which had been proved in diverse experimental models. NCS-1 also appears to be involved in the regulation of other calcium and potassium channels, which can influence the neuron electric homeostasis and survival through the modulation of proapoptotic pathways. These broad NCS-1 effects motivates further research of the specific mechanisms that are involved in the regulation that this protein exerts on its target proteins and in new effects that may help to understand the role of this protein in physiological and pathophysiological processes(AU)

Effects of adenosine receptor agonist on the rocuronium-induced neuromuscular block and sugammadex-induced recovery / 대한마취과학회지

BACKGROUND: Several types of receptors are found at neuromuscular presynaptic membranes. Presynaptic inhibitory A1 and facilitatory A2A receptors mediate different modulatory functions on acetylcholine release. This study investigated whether adenosine A1 receptor agonist contributes to the first twitch tension (T1) of train-of-four (TOF) stimulation depression and TOF fade during rocuronium-induced neuromuscular blockade, and sugammadex-induced recovery. METHODS: Phrenic nerve-diaphragm tissues were obtained from 30 adult Sprague-Dawley rats. Each tissue specimen was randomly allocated to either control group or 2-chloroadenosine (CADO, 10 μM) group. One hour of reaction time was allowed before initiating main experimental data collection. Loading and boost doses of rocuronium were sequentially administered until > 95% depression of the T1 was achieved. After confirming that there was no T1 twitch tension response, 15 min of resting time was allowed, after which sugammadex was administered. Recovery profiles (T1, TOF ratio [TOFR], and recovery index) were collected for 1 h and compared between groups. RESULTS: There were statistically significant differences on amount of rocuronium (actually used during experiment), TOFR changes during concentration-response of rocuronium (P = 0.04), and recovery profiles (P < 0.01) of CADO group comparing with the control group. However, at the initial phase of this experiment, dose-response of rocuronium in each group demonstrated no statistically significant differences (P = 0.12). CONCLUSIONS: The adenosine A1 receptor agonist (CADO) influenced the TOFR and the recovery profile. After activating adenosine receptor, sugammadex-induced recovery from rocuronium-induced neuromuscular block was delayed.

Conditioning-induced cardioprotection: Aging as a confounding factor

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-1α) 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.

Mechanisms involved in adenosine pharmacological preconditioning-induced cardioprotection

Adenosine is a naturally occurring breakdown product of adenosine triphosphate and plays an important role in different physiological and pathological conditions. Adenosine also serves as an important trigger in ischemic and remote preconditioning and its release may impart cardioprotection. Exogenous administration of adenosine in the form of adenosine preconditioning may also protect heart from ischemia-reperfusion injury. Endogenous release of adenosine during ischemic/remote preconditioning or exogenous adenosine during pharmacological preconditioning activates adenosine receptors to activate plethora of mechanisms, which either independently or in association with one another may confer cardioprotection during ischemia-reperfusion injury. These mechanisms include activation of K(ATP) channels, an increase in the levels of antioxidant enzymes, functional interaction with opioid receptors; increase in nitric oxide production; decrease in inflammation; activation of transient receptor potential vanilloid (TRPV) channels; activation of kinases such as protein kinase B (Akt), protein kinase C, tyrosine kinase, mitogen activated protein (MAP) kinases such as ERK 1/2, p38 MAP kinases and MAP kinase kinase (MEK 1) MMP. The present review discusses the role and mechanisms involved in adenosine preconditioning-induced cardioprotection.

Renoprotective Effects of a Highly Selective A3 Adenosine Receptor Antagonist in a Mouse Model of Adriamycin-induced Nephropathy

The concentration of adenosine in the normal kidney increases markedly during renal hypoxia, ischemia, and inflammation. A recent study reported that an A3 adenosine receptor (A3AR) antagonist attenuated the progression of renal fibrosis. The adriamycin (ADX)-induced nephropathy model induces podocyte injury, which results in severe proteinuria and progressive glomerulosclerosis. In this study, we investigated the preventive effect of a highly selective A3AR antagonist (LJ1888) in ADX-induced nephropathy. Three groups of six-week-old Balb/c mice were treated with ADX (11 mg/kg) for four weeks and LJ1888 (10 mg/kg) for two weeks as following: 1) control; 2) ADX; and 3) ADX + LJ1888. ADX treatment decreased body weight without a change in water and food intake, but this was ameliorated by LJ1888 treatment. Interestingly, LJ1888 lowered plasma creatinine level, proteinuria, and albuminuria, which had increased during ADX treatment. Furthermore, LJ1888 inhibited urinary nephrin excretion as a podocyte injury marker, and urine 8-isoprostane and kidney lipid peroxide concentration, which are markers of oxidative stress, increased after injection of ADX. ADX also induced the activation of proinflammatory and profibrotic molecules such as TGF-β1, MCP-1, PAI-1, type IV collagen, NF-κB, NOX4, TLR4, TNFα, IL-1β, and IFN-γ, but they were remarkably suppressed after LJ1888 treatment. In conclusion, our results suggest that LJ1888 has a renoprotective effect in ADX-induced nephropathy, which might be associated with podocyte injury through oxidative stress. Therefore, LJ1888, a selective A3AR antagonist, could be considered as a potential therapeutic agent in renal glomerular diseases which include podocyte injury and proteinuria.

In vitro expression and analysis of the 826 human G protein-coupled receptors

G protein-coupled receptors (GPCRs) are involved in all human physiological systems where they are responsible for transducing extracellular signals into cells. GPCRs signal in response to a diverse array of stimuli including light, hormones, and lipids, where these signals affect downstream cascades to impact both health and disease states. Yet, despite their importance as therapeutic targets, detailed molecular structures of only 30 GPCRs have been determined to date. A key challenge to their structure determination is adequate protein expression. Here we report the quantification of protein expression in an insect cell expression system for all 826 human GPCRs using two different fusion constructs. Expression characteristics are analyzed in aggregate and among each of the five distinct subfamilies. These data can be used to identify trends related to GPCR expression between different fusion constructs and between different GPCR families, and to prioritize lead candidates for future structure determination feasibility.

Amelioration of Cerebral Ischemic Injury by a Synthetic Seco-nucleoside LMT497

Recently, we reported that the A3 adenosine receptor (A3AR) agonist LJ529 (2-chloro-N6-(3-iodobnzyl)-5'-N-methylcarbamoyl-4'-thioadenosine) reduces cerebral ischemic injury via inhibition of recruitment of peripheral inflammatory cells into ischemic brain lesion. A3AR agonists, however, are known to possess anti-platelet activity, which may deter the combination therapy with tissue plasminogen activator for the therapy of cerebral ischemic stroke. Thus, the present study investigates the neuroprotective/anti-ischemic effect of a synthetic seco-nucleoside, LMT497 ((S)-2-((R)-1-(2-chloro-6-(3-iodobenzylamino)-9H-purin-9-yl)-2-hydroxyethoxy)-3-hydroxy-N-methylpropanamide) with little anti-platelet activity. LMT497 neither showed A3AR binding activity nor anti-platelet activity. In our present study LMT497 significantly attenuated the injury/death of cortical neurons exposed to oxygen-glucose deprivation (OGD) followed by re-oxygenation (R). LMT497 significantly reduced the ascending cellular level of reactive oxygen species under ischemic conditions by increasing the superoxide dismutase (SOD) levels. LMT497 also inhibited the migration of microglia which mediates inflammatory responses in ischemia. In rats subjected to middle cerebral artery occlusion (MCAO, 1.5 h) followed by reperfusion, LMT497 largely reduced brain infarction volume, and edema, and improved neurological score. Therapeutic efficacy of LMT497 was obtained by twice treatments even at 10 h and 18 h after the onset of ischemia. Collectively, LMT497 could be a therapeutic drug candidate with a wide therapeutic time window for the treatment of cerebral ischemic stroke.

Roles of adenosine receptors in Alzheimer's disease / 药学学报

As an important neurotransmitter, adenosine displays its functions by acting on the adenosine receptors. Recent studies have shown that the distribution, expression and balance among subtypes of adenosine receptors are closely related with cognitive activities, and changes of adenosine receptors play key roles in neurodegenerative disorders including Alzheimer's disease. It has been pointed out that prolonged activation of adenosine receptors by high level adenosine may lead to the disturbance of balance among adenosine receptor subtypes. This imbalance mainly performed as increased expression of A2a receptor and decreased expression of A1 receptor, and enhancement of the excitatory signals mediated by A2a receptor and weakened inhibitory signals mediated by A1 receptor. Changes of these two subtypes of adenosine receptors may lead to a lot of disorders of neurological activities which developed into dysfunction of cognition to the end. These findings imply that the potential of maintaining the balance among adenosine receptors on the treatment of AD would facilitate both the revealing of the mechanism and the cure of AD.

Antiallodynic effects of intrathecal tianeptine in a neuropathic pain rat

BACKGROUND: Tianeptine is an antidepressant drug which is used for treating depression. Interestingly, the tianeptine has shown antinociceptive effects within a variety of nociceptions. The aim of this study is to investigate the antiallodynic effects of tianeptine in neuropathic pain rats and also determine the involvements of serotonergic, alpha-2 adrenergic and adenosine receptors at the spinal level. METHODS: Neuropathic pain was induced by ligation of left lumbar at 5th and 6th spinal nerves in male Sprague-Dawley rats. PE-10 catheters were placed into the thoracolumbar subarachnoid space for drug injections. Mechanical allodynia was evaluated by measuring the withdrawal threshold to von Frey filament when applying on the plantar surface of rats. The effects of intrathecal tianeptine were observed at 15, 30, 60, 90, 120, 150, 180 minutes after delivery. Antagonists for serotonergic (dihydroergocristine), alpha-2 adrenergic (yohimbine) and adenosine (CGS 15943) receptors were intrathecally administered 10 minutes prior to tianeptine in order to evaluate the involvement of both receptors. RESULTS: Intrathecal tianeptine increased dose-dependently at the withdrawal threshold in the ligated paw. Pretreatment with intrathecal dihydroergocristine, yohimbine and CGS 15943 antagonized the antiallodynic effects of tianeptine. CONCLUSIONS: These results suggested that intrathecal tianeptine attenuates the spinal nerve ligation induced tactile allodynia. Serotonergic, alpha-2 adrenergic and adenosine receptors are all involved in the antiallodynic effects of tianeptine at the spinal level.

Effect of Adenosine on Melanogenesis in B16 Cells and Zebrafish

BACKGROUND: Adenosine is a nucleoside, in which an adenine molecule is attached to a ribofuranose sugar moiety. It can be released into the microenvironment by metabolically active cells, and then fulfills a multitude of functions in regulation of cell proliferation, by activating four subtypes of G protein-coupled adenosine receptors. OBJECTIVE: In this study, we investigated the effect of adenosine on melanogenesis, using B16 melanoma cells. METHODS: The toxic effects of adenosine on B16 melanoma cells were assessed. To understand the mechanism of the effect of adenosine on melanogenesis in B16 cells, melanin content and tyrosinase activity were measured. Tyrosinase, tyrosinase-related protein-1, and dopachrome tautomerase were monitored by Western blotting. Finally, adenosine was applied to zebrafish embryos, and its in vivo effect on pigmentation investigated. RESULTS: At a low concentration, adenosine increased melanin content and tyrosinase activity, while a high dose of adenosine resulted in inhibition of tyrosinase activity. Western blotting showed that adenosine increased tyrosinase protein levels slightly, while high-dose adenosine decreased the expression of tyrosinase. In zebrafish tests, adenosine slightly inhibited body pigmentation. CONCLUSION: In this study, we investigated the effect of adenosine on melanogenesis, using the well-established B16 melanoma cell and zebrafish models. The results suggest that adenosine may inhibit pigmentation, through negative regulation of tyrosinase.

Molecular Vibration-Activity Relationship in the Agonism of Adenosine Receptors

The molecular vibration-activity relationship in the receptor-ligand interaction of adenosine receptors was investigated by structure similarity, molecular vibration, and hierarchical clustering in a dataset of 46 ligands of adenosine receptors. The resulting dendrogram was compared with those of another kind of fingerprint or descriptor. The dendrogram result produced by corralled intensity of molecular vibrational frequency outperformed four other analyses in the current study of adenosine receptor agonism and antagonism. The tree that was produced by clustering analysis of molecular vibration patterns showed its potential for the functional classification of adenosine receptor ligands.

Caffeine-induced endothelial cell death and the inhibition of angiogenesis / 대한해부학회지

Numerous studies have shown that adenosine or adenosine agonists can stimulate angiogenesis. However, the effect of caffeine (a known adenosine receptor antagonist) on angiogenesis has not been previously studied. Accordingly, this study was undertaken to examine the effect of caffeine on angiogenesis and to clarify the mechanism involved. Chick chorioallantoic membrane assays were used to investigate the effect of caffeine on angiogenesis and proliferation assays using human umbilical vein endothelial cells (HUVECs), were used to study its effects on specific aspects of angiogenesis. The expressions of caspase-3 and Bcl-2 were examined by western blotting, immunofluorescence staining was used to identify HUVEC morphological changes, and fluorescence activated cell sorting (FACS) and DAPI staining were used to detect HUVEC apoptosis. Caffeine was found to inhibit blood vessel formation dose-dependently and to inhibit the proliferation of HUVECs time- and dose-dependently. FACS analysis and DAPI staining showed that inhibitory effect of caffeine on HUVEC proliferation was the result of apoptosis and the up-regulation of thrombospondin-1 (TSP-1). Furthermore, TSP-1 levels were down-regulated by NECA but were unaffected by CGS21680, indicating that caffeine regulated TSP-1 expression via adenosine A2B receptor. In addition, caffeine up-regulated caspase-3 and down-regulated Bcl-2 at the protein level. These results suggest that the inhibitory effect of caffeine on angiogenesis is associated, at least in part, with its induction of endothelial cell apoptosis, probably mediated by a caspase-3 dependent mechanism.

Polyphenol (-)-epigallocatechin gallate-induced cardioprotection may attenuate ischemia-reperfusion injury through adenosine receptor activation: a preliminary study / 대한마취과학회지

BACKGROUND: The activation of guanine nucleotide binding protein-coupled receptors, such as adenosine receptor (ADR) and opioid receptor (OPR), protects the heart against ischemia and reperfusion injury. We hypothesized that ADR or OPR might be involved in polyphenol (-)-epigallocatechin gallate (EGCG)-induced cardioprotection. METHODS: Langendorff perfused rat hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Hearts were treated with 10 microM of EGCG, with or without the ADR or OPR antagonist at early reperfusion. Infarct size measured with 2,3,5-triphenyltetrazolium chloride staining was chosen as end-point. RESULTS: EGCG significantly reduced infarct volume as a percentage of ischemic volume (33.5 +/- 4.1%) compared to control hearts (14.4 +/- 1.1%, P 0.05 vs. EGCG) blocked the anti-infarct effect by EGCG. The infarct reducing effect of EGCG was significantly reversed by 200 nM of the A1 ADR antagonist DPCPX (25.9 +/- 1.1%, P 0.05 vs. EGCG) and 100 nM of the A3 ADR antagonist MRS1334 (24.1 +/- 1.8%, P > 0.05). CONCLUSIONS: The infarct reducing effect of EGCG appears to involve activation of ADR, especially A1 and A2B ADR, but not OPR.

role of the A2A receptor in cell apoptosis caused by MDMA

Ecstasy, also known as 3, 4-methylenedioxymethamphetamine [MDMA], is a psychoactive recreational hallucinogenic substance and a major worldwide recreational drug. There are neurotoxic effects observed in laboratory animals and humans following MDMA use. MDMA causes apoptosis in neurons of the central nervous system [CNS]. Withdrawal signs are attenuated by treatment with the adenosine receptor [A2A receptor]. This study reports the effects of glutamyl cysteine synthetase [GCS], as an A2A receptor agonist, and succinylcholine [SCH], as an A2A receptor antagonist, on Sprague Dawley rats, both in the presence and absence of MDMA. In this experimental study, we used seven groups of Sprague Dawley rats [200-250 g each]. Each group was treated with daily intraperitoneal [IP] injections for a period of one week, as follows: i. MDMA [10 mg/kg]; ii. GCS [0.3 mg/kg]; iii. SCH [0.3 mg/kg]; iv. GCS + SCH [0.3 mg/kg each]; v. MDMA [10 mg/kg] + GCS [0.3 mg/kg]; vi. MDMA [10 mg/kg] + SCH [0.3 mg/kg]; and vi. normal saline [1 cc/kg] as the sham group. Bax [apoptotic protein] and Bcl-2 [anti-apoptotic protein] expressions were evaluated by striatum using RT-PCR and Western blot analysis. There was a significant increase in Bax protein expression in the MDMA+SCH group and a significant decrease in Bcl-2 protein expression in the MDMA+SCH group [p<0.05]. A2A receptors have a role in the apoptotic effects of MDMA via the Bax and Bcl-2 pathways. An agonist of this receptor [GCS] decreases the cytotoxcity of MDMA, while the antagonist of this receptor [SCH] increases its cytotoxcity

Expression of adenosine receptors in human retinal pigment epithelium cells in vitro / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Adenosine receptors (ADORs) have been reported to play a role in experimental myopia. This study aimed to determine the distribution of ADORs in human retinal pigment epithelium (RPE) cells cultured in vitro.</p><p><b>METHODS</b>Human RPE cells (cell line D407) were cultured in vitro. ADOR mRNA in RPE was detected by reverse transcription polymerase chain reaction. ADOR protein expression in RPE was confirmed by Western blotting analysis of cell lysates. Confocal fluorescence microscopy was used to study the subcellular distribution of ADORs.</p><p><b>RESULTS</b>All four subtypes of ADORs mRNA and protein were expressed in human RPE. This was confirmed by Western blotting analysis. The ADOR subtypes were differently distributed within the cells. ADORA1 was expressed in nucleus, perinucleus and cytoplasm of RPE. ADORA2A was concentrated mainly in one side of the perinucleus and cytoplasm of RPE. ADORA2B was strongly expressed in the nucleus, perinucleus and the cytoplasm, and ADORA3 was expressed weakly in the cytoplasm of RPE.</p><p><b>CONCLUSIONS</b>ADORs are expressed in human RPE. The different distribution at the subcellular level suggests different functions of ADOR subtypes.</p>