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Partial agonist behaviour depends upon the level of nociceptin/orphanin FQ receptor expression: studies using the ecdysone‐inducible mammalian expression system

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Zeitschriftentitel: British Journal of Pharmacology
Personen und Körperschaften: McDonald, J, Barnes, T A, Okawa, H, Williams, J, Calo', G, Rowbotham, D J, Lambert, D G
In: British Journal of Pharmacology, 140, 2003, 1, S. 61-70
Format: E-Article
Sprache: Englisch
veröffentlicht:
Wiley
Schlagwörter:
Pharmacology
Details
Zusammenfassung: <jats:p> <jats:list list-type="explicit-label"> <jats:list-item><jats:p>Partial agonism is primarily dependent upon receptor density and coupling efficiency. As these parameters are tissue/model dependent, intrinsic activity in different tissues can vary. We have utilised the ecdysone‐inducible expression system containing the human nociceptin/orphanin FQ (N/OFQ) peptide receptor (hNOP) expressed in Chinese hamster ovary cells (CHO<jats:sub>INDhNOP</jats:sub>) to examine the activity of a range of partial agonists in receptor binding, GTP<jats:italic>γ</jats:italic><jats:sup>35</jats:sup>S binding and inhibition of adenylyl cyclase studies.</jats:p></jats:list-item> <jats:list-item><jats:p>Incubation of CHO<jats:sub>INDhNOP</jats:sub> cells with ponasterone A (PON) induced hNOP expression ([leucyl‐<jats:sup>3</jats:sup>H]N/OFQ binding) of 24, 68, 191 and 1101 fmol mg<jats:sup>−1</jats:sup> protein at 1, 2, 5 and 10 <jats:italic>μ</jats:italic><jats:sc>M</jats:sc> PON, respectively. At 191 fmol mg<jats:sup>−1</jats:sup>, protein hNOP pharmacology was identical to that reported for other traditional expression systems.</jats:p></jats:list-item> <jats:list-item><jats:p>pEC<jats:sub>50</jats:sub> values for GTP<jats:italic>γ</jats:italic><jats:sup>35</jats:sup>S binding ranged from 7.23 to 7.72 (2–10 <jats:italic>μ</jats:italic><jats:sc>M</jats:sc> PON) for the partial agonist [Phe<jats:sup>1</jats:sup><jats:italic>ψ</jats:italic>(CH<jats:sub>2</jats:sub>–NH)Gly<jats:sup>2</jats:sup>]N/OFQ(1–13)–NH<jats:sub>2</jats:sub> ([F/G]N/OFQ(1–13)–NH<jats:sub>2</jats:sub>) and 8.12–8.60 (1–10 <jats:italic>μ</jats:italic><jats:sc>M</jats:sc> PON) for N/OFQ(1–13)–NH<jats:sub>2</jats:sub> and <jats:italic>E</jats:italic><jats:sub>max</jats:sub> values (stimulation factor relative to basal) ranged from 1.51 to 3.21 (2–10 <jats:italic>μ</jats:italic><jats:sc>M</jats:sc> PON) for [F/G]N/OFQ(1–13)–NH<jats:sub>2</jats:sub> and 1.28–6.95 (1–10 <jats:italic>μ</jats:italic><jats:sc>M</jats:sc>) for N/OFQ(1–13)–NH<jats:sub>2</jats:sub>. Intrinsic activity of [F/G]N/OFQ(1–13)–NH<jats:sub>2</jats:sub> relative to N/OFQ(1–13)–NH<jats:sub>2</jats:sub> was 0.3–0.5. [F/G]N/OFQ(1–13)–NH<jats:sub>2</jats:sub> did not stimulate GTP<jats:italic>γ</jats:italic><jats:sup>35</jats:sup>S binding at 1 <jats:italic>μ</jats:italic><jats:sc>M</jats:sc> PON, but competitively antagonised the effects of N/OFQ(1–13)–NH<jats:sub>2</jats:sub> with a p<jats:italic>K</jats:italic><jats:sub>B</jats:sub>=7.62.</jats:p></jats:list-item> <jats:list-item><jats:p>pEC<jats:sub>50</jats:sub> values for cAMP inhibition ranged from 8.26 to 8.32 (2–10 <jats:italic>μ</jats:italic><jats:sc>M</jats:sc> PON) for [F/G]N/OFQ(1–13)–NH<jats:sub>2</jats:sub> and 9.42–10.35 for N/OFQ(1–13)–NH<jats:sub>2</jats:sub> and <jats:italic>E</jats:italic><jats:sub>max</jats:sub> values (% inhibition) ranged from 19.6 to 83.2 for [F/G]N/OFQ(1–13)–NH<jats:sub>2</jats:sub> and 40.9–86.0 for N/OFQ(1–13)–NH<jats:sub>2</jats:sub>. The intrinsic activity of [F/G]N/OFQ(1–13)–NH<jats:sub>2</jats:sub> relative to N/OFQ(1–13)–NH<jats:sub>2</jats:sub> was 0.48–0.97.</jats:p></jats:list-item> <jats:list-item><jats:p>In the same cellular environment with receptor density as the only variable, we show that the profile of [F/G]N/OFQ(1–13)–NH<jats:sub>2</jats:sub> can be manipulated to encompass full and partial agonism along with antagonism.</jats:p></jats:list-item> </jats:list> </jats:p><jats:p><jats:italic>British Journal of Pharmacology</jats:italic> (2003) <jats:bold>140</jats:bold>, 61–70. doi:<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" xlink:href="10.1038/sj.bjp.0705401">10.1038/sj.bjp.0705401</jats:ext-link></jats:p>
Umfang: 61-70
ISSN: 0007-1188
1476-5381
DOI: 10.1038/sj.bjp.0705401