Mechanism of cicaprost-induced desensitization in rat pulmonary artery smooth muscle cells involves a PKA-mediated inhibition of adenylyl cyclase

Sobolewski, Anastasia, Jourdan, Karen B., Upton, Paul D., Long, Lu and Morrell, Nicholas W. (2004) Mechanism of cicaprost-induced desensitization in rat pulmonary artery smooth muscle cells involves a PKA-mediated inhibition of adenylyl cyclase. AJP: Lung Cellular and Molecular Physiology, 287 (2). L352-L359. ISSN 1040-0605

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Abstract

Long-term infusion of prostacyclin, or its analogs, is an effective treatment for severe pulmonary arterial hypertension. However, dose escalation is often required to maintain efficacy. The aim of this study was to investigate the mechanisms of prostacyclin receptor desensitization using the prostacyclin analog cicaprost in rat pulmonary artery smooth muscle cells (PASMCs). Desensitization of the cAMP response occurred in 63 nM cicaprost after a 6-h preincubation with agonist. This desensitization was reversed 12 h after agonist removal, and resensitization was inhibited by 10 μg/ml of cycloheximide. Desensitization was heterologous since desensitization to other Gsα-adenylyl cyclase (AC)-coupled agonists, isoproterenol (1 μM), adrenomedullin (100 nM), or bradykinin (1 μM), was also reduced by preincubation with cicaprost. The reduced cAMP response to prolonged cicaprost exposure appeared to be due to inhibition of AC activity since the responses to the directly acting AC agonist forskolin (3 μM) and the selective AC5 activator NKH-477 were similarly reduced. Expression of AC2 and AC5/6 protein levels transiently decreased after 1 h of cicaprost exposure. The PKA inhibitor H-89 (1 μM) added 1 h before cicaprost preincubation (6 h, 63 nM) completely reversed cicaprost-induced desensitization, whereas the PKC inhibitor bisindolylmaleimide (100 nM) was only partly effective. Desensitization was not prevented by the Gi inhibitor pertussis toxin. In conclusion, chronic treatment of PASMCs with cicaprost induced heterologous, reversible desensitization by inhibition of AC activity. Our data suggest that heterologous Gsα desensitization by cicaprost is mediated predominantly by a PKA-inhibitable isoform of AC, most likely AC5/6.

Item Type:	Article
Uncontrolled Keywords:	prostacyclin,cyclic adenosine 5′-monophosphate,heterologous desensitization,camp-dependent protein kinase
Faculty \ School:	Faculty of Science > School of Biological Sciences Faculty of Science > School of Pharmacy (former - to 2024)
UEA Research Groups:	Faculty of Science > Research Groups > Molecular and Tissue Pharmacology
Depositing User:	Pure Connector
Date Deposited:	12 Oct 2016 15:00
Last Modified:	25 Sep 2024 12:17
URI:	https://ueaeprints.uea.ac.uk/id/eprint/60887
DOI:	10.1152/ajplung.00270.2003

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