Morphine-induced delayed pre-conditioning against anoxia/reoxygenation injury in pulmonary artery endothelial cells: The role of mitochondrial KATP channels

Abstract

Opioids produce delayed pre-conditioning (PC) in vivo and in vitro. Our previous research revealed that opioid-induced delayed PC has an antiapoptotic effect on pulmonary artery endothelial cells (PAECs) suffering from anoxia/reoxygenation (A/R) injury. The present study hypothesized that activation of endothelial mitochondrial ATP-sensitive potassium (KATP) channels may result in antiapoptotic effects and against dysfunction in PAECs. Cultured porcine PAECs underwent 16 h anoxia treatment, followed by 1 h reoxygenation, which occurred 24 h following pretreatment with saline (0.9% NaCl; w/v) or morphine (1 μM). To determine the underlying mechanism, a selective mitochondrial KATP inhibitor, 5-hydroxydecanoic acid (5-HD; 100 μM), and an opioid receptor antagonist, naloxone (Nal; 10 μM), were administered 30 min prior to the A/R load. The percentage of apoptotic cells was assessed by Annexin V-fluorescein isothiocyanate staining, using a fluorescence-activated cell sorter. The mRNA expression of intercellular cell adhesion molecule-1 (ICAM-1) was measured by reverse transcription-quantitative polymerase chain reaction. The endothelin-1 (ET-1) content in the supernatant of PAECs cultures was estimated by radioimmunoassay. Compared with the control, A/R caused the apoptosis of PAECs, release of ET-1 and increased mRNA expression of ICAM-1. Morphine-induced delayed PC significantly reduced PAEC apoptosis, increased the release of ET-1 and reduced the mRNA expression of ICAM-1 by ~1.7-times, compared with A/R. The protective effect of morphine was abolished by pretreatment with 5-HD and Nal, however, the two agents themselves failed to aggravate the A/R injury. These results suggested that morphine-induced delayed PC has a protective effect during A/R injury of PAECs. This effect may be mediated by mitochondrial KATP channels and is opioid receptor-dependent.