Corticotropin-releasing factor-like peptides increase cytosolic [Ca2+] in human epidermoid A-431 cells.

Abstract

This study investigated whether sauvagine and urotensin I change [Ca2+]i in human epidermoid A-431 cells and whether these changes are correlated with their anti-edema properties in vivo. A-431 cells were used because they possess the corticotropin-releasing factor (CRF) receptor 2. Treatment with either sauvagine or urotensin I led to an immediate increase in [Ca2+]i, the magnitude of which depended on the concentration of the drug. Sauvagine was more effective than urotensin I, with a median effective concentration (EC50) of 1.4 +/- 0.2 fM, compared to an EC50 of 66 +/- 7 fM for urotensin I. Both were more effective at stimulating increases in [Ca2+]i than CRF (EC50 of 6.8 +/- 0.1 pM). There was a correlation between the EC50 for increasing [Ca2+]i and the median effective dose (ED50) for inhibiting edema induced by heating rat paw (r = 0.99). Removal of extracellular Ca2+ or incubation with La3+ eliminated the increase in [Ca2+]i stimulated by either peptide. Pretreatment with a CRF receptor antagonist reduced the increase in [Ca2+]i by these peptides. This occurred in an antagonist concentration-dependent manner, with median inhibitory concentrations (IC50) of 1.99 +/- 0.04 nM and 0.85 +/- 0.04 nM, respectively. Both pertussis toxin (an inhibitor of G proteins) and U-73122 (an inhibitor for inositol trisphosphate (InsP3) production) partially inhibited the increases. InsP3 was measured to determine whether these peptides mobilized Ca2+ from an InsP3-sensitive store. Both sauvagine and urotensin I increased InsP3. The InsP3 increases were inhibited by U-73 122 and CRF antagonist, but not by removal of external Ca2+. Both peptides elevated protein tyrosine phosphorylation. In summary, these peptides increase [Ca2+]i as a result of Ca2+ influx via CRF receptor-operated Ca2+ channels coupled to pertussis toxin-sensitive G proteins and a Ca2+ mobilization from InsP3-sensitive Ca2+ pools. Their in vivo effectiveness at inhibiting edema is related to their respective capacities to stimulate elevations of [Ca2+]i, supporting a role for intracellular Ca2+ in this process.

• Authors: J G Kiang
• Journal: European journal of pharmacology (Eur J Pharmacol) Vol. 329 Issue 2-3 Pg. 237-44 (Jun 25 1997) ISSN: 0014-2999 [Print] Netherlands
• PMID: 9226418 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Amphibian Proteins
• CRF receptor type 2
• Calcium Channel Blockers
• Peptide Fragments
• Peptide Hormones
• Peptides
• Receptors, Corticotropin-Releasing Hormone
• Urotensins
• Inosine Triphosphate
• Tyrosine
• sauvagine
• Corticotropin-Releasing Hormone
• urotensin I
• corticotropin releasing hormone (9-41)
• Calcium

Topics

• Amphibian Proteins
• Calcium (metabolism)
• Calcium Channel Blockers (pharmacology)
• Corticotropin-Releasing Hormone (pharmacology)
• Humans
• Inosine Triphosphate (metabolism)
• Peptide Fragments (pharmacology)
• Peptide Hormones
• Peptides (pharmacology)
• Phosphorylation (drug effects)
• Receptors, Corticotropin-Releasing Hormone (antagonists & inhibitors, metabolism)
• Tumor Cells, Cultured
• Tyrosine (metabolism)
• Urotensins (pharmacology)