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Morphine inhibits VEGF expression in myocardial ischemia
S Roy1, S Balasubramanian, Jinghua Wang
1Department of Pharmacology, University of Minnesota, Minneapolis Veterans Affairs Medical Center, Minneapois, MN 55417, USA.
Background:
Vascular endothelial growth factor (VEGF) may contribute to the resolution of myocardial ischemia by stimulating collateral circulation. Morphine analgesia after myocardial ischemia is thought to increase infarct size. We hypothesize that morphine inhibits myocardial VEGF expression by inhibiting hypoxia-induced factor 1alpha (HIF-1alpha) and the signal transduction mechanisms involving Erk-1,2 MAP kinase (p42/p44), and PI3 kinase activity (phospho-Akt).
Methods:
(1) In vitro: primary cultures of rat cardiac myocytes; (2) in vivo: rat coronary ligation model; (3) mRNA measurement: real-time reverse transcriptase-polymerase chain reaction; (4) protein measurements: enzyme-linked immunosorbent assay, Western immunoblot, electromobility shift assay (EMSA), and immunohistochemistry.
Results:
Using rat cardiac myocytes in vitro, we show that morphine: (1) decreases hypoxia-induced VEGF(121) and VEGF(165) mRNA expression and VEGF protein concentration through an opioid receptor mechanism; (2) decreases HIF-1alpha protein expression (immunoblot) and nuclear protein binding to the VEGF HIF-1alpha DNA response element (EMSA); and (3) inhibits phospho-Erk-1,2 MAP kinase (immunoblot) and phospho-Akt kinase activity (immunoblot). Using a rat coronary ligation model, we show that morphine treatment: (1) decreases myocardial VEGF protein expression (immunohistochemistry); (2) decreases HIF-1alpha protein expression (immunoblot); and (3) decreases phospho-Erk-1,2 and phospho-Akt expression.
Conclusions:
(1) Morphine inhibits hypoxia-induced VEGF transcription, in part, through an HIF-1alpha-mediated mechanism and (2) morphine inhibition of hypoxia-induced HIF-1alpha may be mediated by inhibition of ERK 1,2 MAP kinase activity and PI3 kinase activity.
Insights
Morphine reduces vascular endothelial growth factor (VEGF) in myocardial ischemia by inhibiting hypoxia-induced factor 1-alpha (HIF-1alpha) signaling pathways. This suggests morphine may worsen heart attack outcomes by impairing blood vessel growth.
Area of Science:
- Cardiovascular Biology
- Molecular Medicine
- Pharmacology
Background:
- Vascular endothelial growth factor (VEGF) promotes collateral circulation, aiding recovery from myocardial ischemia.
- Morphine analgesia is linked to increased infarct size after myocardial ischemia.
- Hypoxia-induced factor 1-alpha (HIF-1alpha) is a key regulator of VEGF expression.
Purpose of the Study:
- To investigate the effect of morphine on myocardial VEGF expression.
- To determine if morphine inhibits hypoxia-induced factor 1-alpha (HIF-1alpha) and associated signaling pathways.
- To elucidate the role of Erk-1,2 MAP kinase and PI3 kinase in morphine's effect on VEGF.
Main Methods:
- In vitro studies using primary rat cardiac myocytes.
- In vivo studies utilizing a rat coronary ligation model.
- Quantitative mRNA and protein analyses including RT-PCR, ELISA, Western immunoblot, EMSA, and immunohistochemistry.
Main Results:
- Morphine decreased hypoxia-induced VEGF mRNA and protein expression in cardiac myocytes via opioid receptors.
- Morphine reduced HIF-1alpha protein and DNA binding activity, and inhibited Erk-1,2 MAP kinase and PI3 kinase (phospho-Akt) activity.
- In vivo, morphine treatment decreased myocardial VEGF, HIF-1alpha, phospho-Erk-1,2, and phospho-Akt expression.
Conclusions:
- Morphine inhibits hypoxia-induced VEGF transcription partly through an HIF-1alpha-mediated mechanism.
- Morphine's inhibition of HIF-1alpha may involve the suppression of ERK 1,2 MAP kinase and PI3 kinase activities.
- These findings suggest a molecular basis for morphine's potential negative impact on myocardial recovery after ischemia.