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Identification and characterization of functional angiotensin II receptors in human neuroblastoma cells
Abstract:
The presence of specific AII receptors in 6 different human neuroblastoma cell lines was investigated using binding, cAMP and [Ca2+]i studies. We found high affinity (0.1 nM), low capacity ((1-2).10(3) sites/cell) binding sites for [125I](Sar-1,Ile-8)AII in one half of the cell lines studied. In the positive cell lines mathematical modeling of multiple competition curves among AII and analogs strongly indicated the presence of a homogenous class of sites, i.e., AT1 receptors. The presence of AT1 receptors was further substantiated by AII-induced inhibition of VIP-stimulated cAMP levels and by AII-evoked [Ca2+]i transient. The density of AT1 receptors in neuroblastoma cells was not affected by treatment with pertussis toxin and retinoic acid but was significantly increased by subacute treatment with VIP. In neuroblastoma cells, AII does not stimulate DNA synthesis, suggesting other roles rather than mitogenesis. Neuroblastoma cells represents an interesting model to investigate the function of AII in neural crest derived tissues.
Insights
Angiotensin II (AII) AT1 receptors were identified in human neuroblastoma cells using binding and signaling studies. These findings suggest AII plays a role in neural crest-derived tissues beyond cell growth.
Area of Science:
- Neuroscience
- Endocrinology
- Molecular Biology
Background:
- Neuroblastoma cells, derived from neural crest, are a significant area of research.
- Angiotensin II (AII) is a peptide hormone with diverse physiological roles, including in the nervous system.
- Understanding AII receptor expression in neuroblastoma is crucial for elucidating its function in neural development and disease.
Purpose of the Study:
- To investigate the presence and characteristics of AII receptors in human neuroblastoma cell lines.
- To determine the functional implications of AII receptor expression in these cells.
- To explore the potential role of AII in neuroblastoma biology.
Main Methods:
- Radioligand binding assays using [125I](Sar-1,Ile-8)AII.
- Cyclic adenosine monophosphate (cAMP) assays to assess G-protein coupled receptor activity.
- Intracellular calcium ([Ca2+]i) mobilization studies.
- Mathematical modeling of competition binding curves.
- Treatment with pertussis toxin, retinoic acid, and vasoactive intestinal peptide (VIP).
Main Results:
- High-affinity, low-capacity AII binding sites, identified as AT1 receptors, were found in approximately half of the studied neuroblastoma cell lines.
- AII binding correlated with AII-induced inhibition of VIP-stimulated cAMP levels and AII-evoked [Ca2+]i transients.
- AT1 receptor density was not altered by pertussis toxin or retinoic acid but was increased by VIP.
- AII did not stimulate DNA synthesis in neuroblastoma cells.
Conclusions:
- Human neuroblastoma cells express functional AT1 receptors.
- AII signaling in neuroblastoma cells does not appear to be primarily mitogenic.
- Neuroblastoma cells provide a valuable model for studying AII function in neural crest-derived tissues.