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Updated: Aug 6, 2026
Quantification of Vascular Parameters in Whole Mount Retinas of Mice with Non-Proliferative and Proliferative Retinopathies
Published on: March 12, 2022
Morphine stimulates vascular endothelial growth factor-like signaling in mouse retinal endothelial cells
Chunsheng Chen1, Mariya Farooqui, Kalpna Gupta
1Vascular Biology Center, Division of Hematology, Oncology and Transplantation, University of Minnesota Medical School, Mayo Mail Code 480, Minneapolis, Minnesota 55455, USA.
Abstract:
Go/Gi coupled G-protein receptor mediated transactivation is critical in the activation of receptor tyrosine kinases (RTK). Here we show that mu opioid receptor (MOR) transactivates Flk1 and platelet-derived growth factor-beta (PDGF-beta) receptors and its agonist morphine stimulates pro-angiogenic and survival-promoting signaling in mouse retinal endothelial cells (mREC). Morphine stimulates mREC proliferation in a dose dependent fashion and promotes survival to the same extent as vascular endothelial growth factor164 (VEGF164). Morphine stimulates mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and Akt phosphorylation in a time dependent manner like VEGF in mREC. Moreover, analogous to VEGF, morphine stimulates oncogenic signal transducer and activator of transcription 3 (STAT3) signaling. Morphine as well as VEGF-induced phospho-STAT3 and phospho-Flk1 immunoprecipitated with MOR-associated proteins. In addition morphine also stimulated MOR associated PDGF-beta receptor phosphorylation. Consistent with the relationship between VEGF and MOR we found that VEGF upregulates MOR protein and RNA expression in mREC. These data suggest that MOR associates and transactivates RTKs for Flk1 and PDGF-beta, which may have a compounding effect on angiogenic signaling in endothelium. Therefore, G-Protein coupled receptors including MOR provide novel targets to develop anti-angiogenic agents.
Insights
The mu opioid receptor (MOR) activates key signaling pathways involved in cell growth and survival. This discovery reveals MOR as a potential target for developing new anti-angiogenic therapies.
Area of Science:
- Endothelial cell biology
- Molecular signaling pathways
- G-protein coupled receptor research
Background:
- G-protein coupled receptor (GPCR) transactivation of receptor tyrosine kinases (RTKs) is crucial for cellular signaling.
- The mu opioid receptor (MOR) is a GPCR involved in various physiological processes.
Purpose of the Study:
- To investigate the role of MOR in transactivating RTKs.
- To determine the effects of morphine on angiogenic and survival signaling in mouse retinal endothelial cells (mRECs).
Main Methods:
- Western blotting to assess protein phosphorylation (MAPK/ERK, Akt, STAT3, Flk1, PDGF-beta).
- Immunoprecipitation to identify protein-protein interactions.
- Cell proliferation and survival assays.
- Quantitative RT-PCR and Western blotting to measure MOR expression.
Main Results:
- Morphine, an agonist of MOR, stimulates mREC proliferation and survival, comparable to VEGF164.
- Morphine activates MAPK/ERK, Akt, and STAT3 signaling pathways in mRECs, similar to VEGF.
- MOR physically associates with and transactivates Flk1 and PDGF-beta receptors.
- VEGF upregulates MOR expression in mRECs.
Conclusions:
- MOR transactivates Flk1 and PDGF-beta receptors, contributing to pro-angiogenic signaling in endothelial cells.
- GPCRs, including MOR, represent novel therapeutic targets for anti-angiogenic drug development.
