Adenosine A2A Receptor Contributes to Ischemic Brain Damage in Newborn Piglet

Pharmacologic inactivation or genetic deletion of adenosine A2A receptors protects ischemic neurons in adult animals, but studies in neonatal hypoxia-ischemia (H-I) are inconclusive. The present study in neonatal piglets examined the hypothesis that A2A receptor signaling after reoxygenation from global H-I contributes to injury in highly vulnerable striatal neurons where A2A receptors are enriched. A2A receptor immunoreactivity was detected in striatopallidal neurons. In nonischemic piglets, direct infusion of the selective A2A receptor agonist CGS 21680 through microdialysis probes into putamen increased phosphorylation of N-methyl-D-aspartic acid (NMDA) receptor NR1 subunit and Na+, K+-ATPase selectively at protein kinase A (PKA)-sensitive sites. In ischemic piglets, posttreatment with SCH 58261, a selective A2A receptor antagonist, improved early neurologic recovery and preferentially protected striatopallidal neurons. SCH 58261 selectively inhibited the ischemia-induced phosphorylation of NR1, Na+, K+-ATPase, and cAMP-regulated phosphoprotein 32 KDa (DARPP32) at PKA-sensitive sites at 3 hours of recovery and improved Na+, K+-ATPase activity. SCH 58261 also suppressed ischemia-induced protein nitration and oxidation. Thus, A2A receptor activation during reoxygenation contributes to the loss of a subpopulation of neonatal putamen neurons after H-I. Its toxic signaling may be related to DARPP32-dependent phosphorylation of PKA-sensitive sites on NR1 and Na+, K+-ATPase, thereby augmenting excitotoxicity-induced oxidative stress after reoxygenation.

Download Full-text

Augmented release of serotonin by adenosine A2a receptor activation and desensitization by CGS 21680 in the rat nucleus tractus solitarius

Brain Research ◽

10.1016/0006-8993(96)00279-x ◽

1996 ◽

Vol 733 (2) ◽

pp. 155-161 ◽

Cited By ~ 25

Author(s):

Robin A Barraco ◽

Carolyn Clough Helfman ◽

Gordon F Anderson

Keyword(s):

Nucleus Tractus Solitarius ◽

Receptor Activation ◽

Adenosine A2a Receptor ◽

Cgs 21680 ◽

A2a Receptor ◽

Adenosine A2a

Download Full-text

The selective adenosine A2A receptor antagonist SCH 58261 discriminates between two different binding sites for [3H]-CGS 21680 in the rat brain

Naunyn-Schmiedeberg s Archives of Pharmacology ◽

10.1007/bf00168448 ◽

1996 ◽

Vol 354 (4) ◽

pp. 539-541 ◽

Cited By ~ 51

Author(s):

Karin Lindstrom ◽

Ennio Ongini ◽

Bertil B. Fredhohn

Keyword(s):

Receptor Antagonist ◽

Rat Brain ◽

Binding Sites ◽

Adenosine A2a Receptor ◽

Cgs 21680 ◽

A2a Receptor ◽

Sch 58261 ◽

Adenosine A2a Receptor Antagonist ◽

Adenosine A2a

Download Full-text

SCH 58261 and ZM 241385 differentially prevent the motor effects of CGS 21680 in mice: evidence for a functional ‘atypical’ adenosine A2A receptor

European Journal of Pharmacology ◽

10.1016/s0014-2999(00)00399-x ◽

2000 ◽

Vol 401 (1) ◽

pp. 63-77 ◽

Cited By ~ 39

Author(s):

Malika El Yacoubi ◽

Catherine Ledent ◽

Marc Parmentier ◽

Jean Costentin ◽

Jean-Marie Vaugeois

Keyword(s):

Adenosine A2a Receptor ◽

Cgs 21680 ◽

A2a Receptor ◽

Sch 58261 ◽

Motor Effects ◽

Adenosine A2a

Download Full-text

Adenosine A2a-receptor activation enhances cardiomyocyte shortening via Ca2+-independent and -dependent mechanisms

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1999.276.5.h1434 ◽

1999 ◽

Vol 276 (5) ◽

pp. H1434-H1441 ◽

Cited By ~ 9

Author(s):

Angela J. Woodiwiss ◽

Thomas W. Honeyman ◽

Richard A. Fenton ◽

James G. Dobson

Keyword(s):

Ventricular Myocytes ◽

Receptor Activation ◽

Adrenergic Stimulation ◽

Cgs 21680 ◽

A2a Receptor ◽

Intracellular Ca ◽

Inhibitory G Protein ◽

Adenosine A2a ◽

Myocyte Contractility ◽

Adrenergic Receptor Agonist

Adenosine A2a receptor (A2aR) stimulation enhances the shortening of ventricular myocytes. Whether the A2aR-mediated increase in myocyte contractility is associated with alterations in the amplitude of intracellular Ca2+ transients was investigated in isolated, contracting rat ventricular myocytes using the Ca2+-sensitive fluorescent dye fura 2-AM. In the presence of intact inhibitory G protein pathways, 10−4 M 2- p-(2-carboxyethyl)phenethyl-amino-5′- N-ethylcarboxamidoadenosine (CGS-21680), an A2aR agonist, insignificantly increased Ca2+transients by 8 ± 5%, whereas myocyte shortening increased by 54 ± 1%. In contrast, 2 × 10−7 M isoproterenol, a β-adrenergic receptor agonist, increased Ca2+ transients by 104 ± 15% and increased myocyte shortening by 61 ± 6%. When A2aR were stimulated in myocytes that had the antiadrenergic actions of adenosine (Ado) abolished by either treatment with pertussis toxin (PTx) or the presence of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), an adenosine A1-receptor antagonist, the maximum increases in Ca2+transients were similarly nominal (with PTx: 10−4 M CGS-21680, 14 ± 6% and 10−4 M Ado, 15 ± 4%; without PTx: 10−5 M Ado + 2 × 10−7 M DPCPX, 19 ± 1%). These results indicate that compared with β-adrenergic stimulation, which markedly increases myocyte Ca2+ transients and shortening, A2aR-mediated increases in myocyte shortening are accompanied by only modest increases in Ca2+ transients. These observations suggest that the A2aR-induced contractile effects are mediated predominantly by Ca2+-independent inotropic mechanisms.

Download Full-text

A Cellular Assay for the Identification and Characterization of Connexin Gap Junction Modulators

International Journal of Molecular Sciences ◽

10.3390/ijms22031417 ◽

2021 ◽

Vol 22 (3) ◽

pp. 1417

Author(s):

Azeem Danish ◽

Robin Gedschold ◽

Sonja Hinz ◽

Anke C. Schiedel ◽

Dominik Thimm ◽

...

Keyword(s):

Gap Junctions ◽

Small Molecules ◽

High Throughput Screening ◽

Cell Communication ◽

Receptor Activation ◽

Adenosine A2a Receptor ◽

Intracellular Camp ◽

Donor Cells ◽

A2a Receptor ◽

Adenosine A2a

Connexin gap junctions (Cx GJs) enable the passage of small molecules and ions between cells and are therefore important for cell-to-cell communication. Their dysfunction is associated with diseases, and small molecules acting as modulators of GJs may therefore be useful as therapeutic drugs. To identify GJ modulators, suitable assays are needed that allow compound screening. In the present study, we established a novel assay utilizing HeLa cells recombinantly expressing Cx43. Donor cells additionally expressing the Gs protein-coupled adenosine A2A receptor, and biosensor cells expressing a cAMP-sensitive GloSensor luciferase were established. Adenosine A2A receptor activation in the donor cells using a selective agonist results in intracellular cAMP production. The negatively charged cAMP migrates via the Cx43 gap junctions to the biosensor cells and can there be measured by the cAMP-dependent luminescence signal. Cx43 GJ modulators can be expected to impact the transfer of cAMP from the donor to the biosensor cells, since cAMP transit is only possible via GJs. The new assay was validated by testing the standard GJ inhibitor carbenoxolon, which showed a concentration-dependent inhibition of the signal and an IC50 value that was consistent with previously reported values. The assay was demonstrated to be suitable for high-throughput screening.

Download Full-text