title: Chronic opioids regulate KATP channel subunit Kir6.2 and carbonic anhydrase I and II expression in rat adrenal chromaffin cells via HIF-2α and protein kinase A.
abstract: At birth, asphyxial stressors such as hypoxia and hypercapnia are important physiological stimuli for adrenal catecholamine release that is critical for the proper transition to extrauterine life. We recently showed that chronic opioids blunt chemosensitivity of neonatal rat adrenomedullary chromaffin cells (AMCs) to hypoxia and hypercapnia. This blunting was attributable to increased ATP-sensitive K(+) (KATP) channel and decreased carbonic anhydrase (CA) I and II expression, respectively, and involved μ- and δ-opioid receptor signaling pathways. To address underlying molecular mechanisms, we first exposed an O2- and CO2-sensitive, immortalized rat chromaffin cell line (MAH cells) to combined μ {[d-Arg(2),Ly(4)]dermorphin-(1-4)-amide}- and δ ([d-Pen(2),5,P-Cl-Phe(4)]enkephalin)-opioid agonists (2 μM) for ∼7 days. Western blot and quantitative real-time PCR analysis revealed that chronic opioids increased KATP channel subunit Kir6.2 and decreased CAII expression; both effects were blocked by naloxone and were absent in hypoxia-inducible factor (HIF)-2α-deficient MAH cells. Chronic opioids also stimulated HIF-2α accumulation along a time course similar to Kir6.2. Chromatin immunoprecipitation assays on opioid-treated cells revealed the binding of HIF-2α to a hypoxia response element in the promoter region of the Kir6.2 gene. The opioid-induced regulation of Kir6.2 and CAII was dependent on protein kinase A, but not protein kinase C or calmodulin kinase, activity. Interestingly, a similar pattern of HIF-2α, Kir6.2, and CAII regulation (including downregulation of CAI) was replicated in chromaffin tissue obtained from rat pups born to dams exposed to morphine throughout gestation. Collectively, these data reveal novel mechanisms by which chronic opioids blunt asphyxial chemosensitivity in AMCs, thereby contributing to abnormal arousal responses in the offspring of opiate-addicted mothers.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada; and.
authors.forename: Shaima
authors.initials: S
authors.lastname: Salman
authors.affiliation: Division of Reproductive Biology, Department of Obstetrics and Gynecology Division of Reproductive Biology, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Alison C
authors.initials: AC
authors.lastname: Holloway
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada; and nursec@mcmaster.ca.
authors.forename: Colin A
authors.initials: CA
authors.lastname: Nurse
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D000302:Adrenal Cortex / Q000166:cytology / Q000378:metabolism; D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D024401:Carbonic Anhydrase I / Q000096:biosynthesis; D024402:Carbonic Anhydrase II / Q000096:biosynthesis; D015687:Cell Hypoxia; D002460:Cell Line; D019439:Chromaffin Cells / Q000166:cytology / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006935:Hypercapnia; D007211:Indoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D054086:KATP Channels / Q000096:biosynthesis* / Q000235:genetics; D008301:Maleimides / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000096:biosynthesis* / Q000235:genetics; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017465:Receptors, Opioid, delta / Q000819:agonists*; D017450:Receptors, Opioid, mu / Q000819:agonists*; D013449:Sulfonamides / Q000494:pharmacology; D000099162:Endothelial PAS Domain-Containing Protein 1; D000099161:Kcnj11 Channel
chemical_list: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000701:Analgesics, Opioid; D051792:Basic Helix-Loop-Helix Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D024401:Carbonic Anhydrase I; D024402:Carbonic Anhydrase II; D017868:Cyclic AMP-Dependent Protein Kinases; D004298:Dopamine; D020881:Enkephalin, D-Penicillamine (2,5)-; D004791:Enzyme Inhibitors; D007211:Indoles; D007546:Isoquinolines; D054086:KATP Channels; D008301:Maleimides; D009020:Morphine; D009270:Naloxone; D009292:Narcotic Antagonists; D009638:Norepinephrine; D009842:Oligopeptides; D024661:Potassium Channels, Inwardly Rectifying; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D013449:Sulfonamides; D000099162:Endothelial PAS Domain-Containing Protein 1; D000099161:Kcnj11 Channel; C063076:tyrosyl-arginyl-phenylalanyl-lysinamide; C063302:KN 62; C070515:bisindolylmaleimide I; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide
keywords: adenosine 5′-triphosphate-sensitive potassium channels; carbonic anhydrase; hypoxia-inducible factor-2α; opioid