Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, C014

Oral Communications

Immune modulatory role and cardio stimulatory effect of the adenosine 2b Receptor in a murine model of myocardial infarction

C. Alter1, Z. Ding1, U. Flögel1, J. Schrader1

1. Institute of Molecular Cardiology, Heinrich-Heine-University Düsseldorf, Duesseldorf, Germany.

In previous work we demonstrated that the adenosine A2b receptor (A2bR) was specifically upregulated on cardiomyocytes (CM) three days after MI as well as on immune cell after infiltrating the infarcted myocardium (Borg et al. (2018)). This study therefore aimed to investigate in more detail the anti-inflammatory role of A2bR in the healing processes after MI. A2bR knockout mice, when subjected to 50 min cardiac ischemia by left descending coronary artery ligation (anaesthetized with 1.5% isoflurane in medical respiratory air) followed by four weeks of reperfusion, did not show altered cardiac function in the post MI phase as determined by MRI at 9.4 T. Flow cytometric analysis (n=5), however, revealed that the number of B cells per mg heart tissue was increased in A2bRKO mice (WT: 57 ±15 vs. KO: 99 ±26, p<0.05). Similarly, NK cells (WT: 30 ±4 vs. KO: 61 ±12, p<0.01), CD8 T cells (WT: 28 ±7 vs. KO: 56 ±18, p<0.05) and CD4 T cells (WT: 44 ±18 vs. KO: 80 ±28, p<0.05) including FoxP3+ regulatory T cells (WT: 3±0.9 vs. KO: 8 ±3, p<0.01) were elevated. A2bR deficient T cells isolated from the infarcted heart (n=7) showed elevated mRNA expression of pro-inflammatory IFNγ (WT: 0.09 ±0.05 vs. KO: 0.2± 0.1, p<0.05); IL2 (WT: 0.04 ±0.02 vs. KO: 0.07± 0.02, p<0.05) as well as increased cytokine secretion (n=4-6, pg/ml) of IFNγ (WT: 157±856 vs. KO: 501±284, p<0.05), IL2 (WT: 242±141 vs. KO: 812±361, p<0.05) and TNFα (WT: 2±0.7 vs. KO: 5±2, p<0.05). In contrast relative mRNA levels (n=4) of pro-inflammatory IL1β (WT: 18±6 vs. KO: 5±2, p<0.01) and IL6 (WT: 0.03±0.02 vs. KO: 0.007±0.01, p<0.05) in granulocytes and CM (IL1β: WT: 0.79±0.3 vs. KO: 0.3±0.2, p<0.05; IL6: WT: 0.6±0.2 vs. KO: 0.3±0.07, p<0.01) were significantly reduced when A2bR was lacking. Since the A2bR was shown to be up-regulated after MI on CM we analyzed cardiac ejection (EF) fraction 6 hours after injection of the A2bR agonist BAY60-6583 (80µg/kg BW) in healthy and infarcted WT mice. EF was found to be increased by 16% only in infarcted mice (n=3) (control: 104±6 vs. infarcted: 120±5 % of values pre-injection, p<0.05). Values are means ± SD, all significances were determined by Student's T test. In summary, deletion of the A2bR does not alter post MI cardiac function but increased the pro-inflammatory character of T cells infiltrating the infarcted myocardium. Other compensatory mechanisms include repression of pro-inflammatory signals in granulocytes and CM and increased number of anti-inflammatory regulatory T cells. Pharmacologic stimulation of A2bR, upregulated in the ischemic heart, temporarily increases cardiac function post MI.

Where applicable, experiments conform with Society ethical requirements