Reducing ischaemia/reperfusion injury through delta-opioid-regulated intrinsic cardiac adrenergic cells: adrenopeptidergic co-signalling.
OBJECTIVE
The purpose of this study was to determine whether intrinsic cardiac adrenergic (ICA) cells release calcitonin gene-related peptide (CGRP), exerting synergistic adrenopeptidergic cardioprotection.


RESULTS
In situ hybridization coupled with immunostaining demonstrated that ICA cells exclusively expressed CGRP mRNA and co-expressed CGRP and delta-opioid receptor in human and rat left ventricular (LV) myocardium. Radioimmunoassay detected constitutive CGRP release from ICA cells in human and rat hearts. The delta-opioid agonist [D-Pen(25)]-enkephalin (DPDPE) increased CGRP release from ICA cells in denervated rat heart. In an ischaemia/reperfusion rat model, pre-ischaemic treatment with DPDPE reduced infarct size (IS) by 51 +/- 16% (P < 0.01). Co-infusion of beta(2)-adrenergic receptor (beta(2)-AR) and CGRP receptor (CGRP-R) antagonists increased IS by 62 +/- 23% (P < 0.01) compared with saline and abolished DPDPE-initiated IS reduction. Pre-treatment of ICA cell-myocyte co-culture with the beta(2)-AR/CGRP-R antagonists increased myocyte death rate by 24 +/- 4% (P < 0.01) and abolished DPDPE-initiated myocyte protection against hypoxia/reoxygenation (re-O(2)). In the ICA cell-depleted myocyte culture, DPDPE did not confer myocyte protection. Supplementing ICA cell-depleted myocyte culture with beta(2)-AR/CGRP-R agonists reduced hypoxia/re-O(2)-induced myocyte death by 24 +/- 5% (P < 0.01), simulating endogenous neurohormonal effects of ICA cells. Western blot analysis showed that DPDPE markedly increased phosphorylated myocardial Akt levels. This effect was abolished in the presence of beta(2)-AR/CGRP-R blockade. Terminal dUTP nick-end labelling staining analysis of the LV infarct zone demonstrated that DPDPE reduced myocyte apoptosis by 58 +/- 19% (P < 0.05), an effect that was eliminated in the presence of beta(2)-AR/CGRP-R blockade. Finally, echocardiography showed that DPDPE increased LV contractility in a manner dependent on beta-AR/CGRP-R stimulation.


CONCLUSIONS
ICA cells constitute a delta-opioid-regulated adrenopeptidergic paracrine system conferring robust cardioprotection through beta(2)-AR/CGRP-R co-signalling, resulting in the activation of an anti-apoptotic pathway during ischaemia/reperfusion.
Huang
Ming-He
MH
Cardiology Division, Department of Internal Medicine, University of Texas Medical Branch, 5.106 John Sealy Annex, Galveston, TX 77555-0553, USA. mihuang@utmb.edu
Nguyen
Vincent
V
Wu
Yewen
Y
Rastogi
Saurabh
S
Lui
Charles Y
CY
Birnbaum
Yochai
Y
Wang
Hui-Qun
HQ
Ware
David L
DL
Chauhan
Madhu
M
Garg
Nisha
N
Poh
Kian-Keong
KK
Ye
Lei
L
Omar
Abdul Razakjr
AR
Tan
Huay-Cheem
HC
Uretsky
Barry F
BF
Fujise
Kenichi
K
D058666:Adrenergic beta-2 Receptor Agonists; D058672:Adrenergic beta-2 Receptor Antagonists; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D004195:Disease Models, Animal; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000494:pharmacology; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D009200:Myocardial Contraction / Q000502:physiology; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000819:agonists / Q000378:metabolism*; D017465:Receptors, Opioid, delta / Q000819:agonists / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
D058666:Adrenergic beta-2 Receptor Agonists; D058672:Adrenergic beta-2 Receptor Antagonists; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D018343:Receptors, Adrenergic, beta-2; D018015:Receptors, Calcitonin Gene-Related Peptide; D017465:Receptors, Opioid, delta; D020881:Enkephalin, D-Penicillamine (2,5)-; D051057:Proto-Oncogene Proteins c-akt; D015740:Calcitonin Gene-Related Peptide