Cytochrome P450 2J3/epoxyeicosatrienoic acids mediate the cardioprotection induced by ischaemic post-conditioning, but not preconditioning, in the rat.

1. Cytochrome P450 (CYP) epoxygenases and their arachidonic acid metabolites play a protective role against ischaemia-reperfusion injury. In the present study, we investigated whether endogenous CYP2J3/epoxyeicosatrienoic acid (EET) mediates the cardioprotective effects of ischaemic preconditioning (IPC) and ischaemic post-conditioning (IPost). 2. Male Wistar rats were subjected to two cycles of IPC, consisting of 5 min ischaemia and 5 min reperfusion, followed by 45 min occlusion and 2 h reperfusion; IPost consisted of three cycles of 30 s reperfusion and 30 s re-occlusion at the onset of reperfusion. The selective CYP epoxygenase inhibitor N-methylsulphonyl-6-(2-propargyloxyphenyl)hexanamide (MS-PPOH; 3 mg/kg) was administered 10 min before ischaemia or during ischaemia 10 min before reperfusion started. Cardiac function was measured continuously with a angiocatheter connected to a fluid-filled pressure transducer and myocardial infarct size was assessed by triphenyl tetrazolium chloride staining at the end of the experiment. 3. Subjecting rats to IPC and IPost similarly improved cardiac function and reduced myocardial infarct size. Interestingly, IPost, but not IPC, significantly increased CYP2J3 mRNA (1.75 ± 0.22 vs 1.0; P < 0.05) and protein (1.62 ± 0.22 vs 1.0; P < 0.05), as well as 11,12-EET synthesis compared to I/R (6.2 ± 0.2 vs 2.9 ± 0.2 ng/mg wet weight, respectively; P < 0.01). Administration of MS-PPOH before ischaemia significantly decreased 11,12-EET synthesis in both IPC and IPost compared with I/R rats (2.1 ± 0.2, 3.2 ± 0.3 and 2.9 ± 0.2 ng/mg wet weight, respectively; P < 0.01), but decreased the cardioprotective effects, as evidenced by cardiac function and myocardial infarct size, of IPost only. 4. These data indicate that endogenous activation of CYP2J3/EET may be an essential trigger leading to the protective effects of IPost, but not IPC, in the rat heart.

Apelin protects heart against ischemia/reperfusion injury in rat.

Apelin, the endogenous ligand of the G protein-coupled APJ receptor, is a peptide mediator with emerging regulatory actions in the heart. We aimed to determine whether the endogenous apelin/APJ system is an intrinsic protective pathway in ischemic/reperfusion injury. A Langendorff model of perfused isolated rat hearts and primary cultured myocardial cells from neonatal rats were used. Cardiac function was monitored and apelin/APJ expression was determined by real-time PCR and Western blot analysis. In rats under I/R, cardiac function was significantly decreased as compared with controls, and APJ was over-expressed at both the mRNA and protein levels (by 7-fold and 35%, respectively, both p<0.01). However, pre-administration of apelin (30pmol/L) greatly ameliorated the reduced heart function. To gain mechanistic insight into the cardio-protective effects of apelin/APJ, cultured cardiomyocytes were treated with apelin (30 pmol/L), and those under hypoxia/re-oxygenation showed H/R-induced apoptosis and up-regulated apelin/APJ mRNA expression by 6-fold and 7-fold, respectively (both p<0.01). And lactate dehydrogenase leakage was greatly increased as well. Meanwhile, apoptosis, the generation of reactive oxygen species and malonaldehyde content as well as lactate dehydrogenase leakage were inhibited by apelin. Furthermore, apelin enhanced superoxide dismutase activity and phosphorylation of extracellular signal-regulated kinase 1/2 and Akt after hypoxia/re-oxygenation. In conclusion, apelin/APJ has protective effects in ischemic heart disease and might constitute an important therapy target.

[Effects of 11, 12-epoxyeicosatrienoic acid preconditioning and postconditioning on Ca(2+)- handling proteins in myocardial ischemia/reperfusion injury in rats].

OBJECTIVE: To investigate the effects of 11, 12-epoxyeicosatrienoic acid (11, 12-EET) preconditioning and postconditioning on Ca(2+)-handling proteins in myocardial ischemia/reperfusion (IR) injury in rats and reveal the effects and mechanism of 11, 12-EET on cardioprotection. METHODS The IR injury model was built by stopping perfusion for 40 minutes followed by reperfusion for 30 minutes. The isolated Langendorff-perfused rat hearts were divided into 4 groups: control group, IR group, EET preconditioning (Pre-EET) group and EET postconditioning (Post-EET) group. The computer-based electrophysiological recorder system was used to measure the changes of the maximal rate of pressure increased in the contraction phase (+dp/dt(max)), the maximal rate of pressure decreased in the diastole phase (-dp/dt(max)), the left ventricular end diastolic pressure (LVEDP) and the difference of left ventricular pressure (delta LVP). The activity of Ca(2+)-ATPase in sarcoplasmic reticulum was measured with colorimetric method. Reverse transcription-polymerase chain reaction was used to assess the gene expression of C(a2+)-handling protein [sarcoplasic reticulum Ca(2+)-ATPase (SERCA), phospholamban (PLB), ryanodine receptor type 2 (RyR,), and 1, 4, 5-trisphosphate inositol receptor type 2 (IP3 R2) ] mRNAs level. RESULTS: Compared with IR group, the myocardial functions, the value of Ca(2+)-ATPase, and the expressions of IP3 R2 mRNA were significantly increased and the expression of PLB mRNA was significantly decreased in both Pre-EET group and Post-EET group (P < 0.05, P < 0.01). And the expression of SERCA mRNA was significantly increased in Pre-EET group (P < 0. 05). However, no significant differences were detected between Pre-EET and Post-EET groups. Moreover, the expression of RyR2 mRNA was not significantly different among all groups. CONCLUSIONS: 11, 12-EET preconditioning and post-conditioning can protect myocardium from IR injury by elevating the activity of Ca(2+)-ATPase in sarcoplasmic reticulum, up-regulating the expression of IP3 R2 mRNA, and down-regulating the expression of PLB mRNA. Moreover, up-regulating the expression of SERCA mRNA maybe one of mechanisms of 11, 12-EET preconditioning on cardio protection against IR injury.

[Effect of 11, 12-epoxyeicosatrienoic acids on hypoxia/reoxygenation injury in the human umbilical vein endothelial cells].

OBJECTIVE: To investigate the effects of 11, 12-epoxyeicosatrienoic acids (11, 12-EET) on the degree of hypoxia/reoxygenation injury in human umbilical vein endothelial cells ( HUVECs), and reveal the possible pathway of EET on protection. METHODS: Primary cultured HUVECs were randomly divided into control group, hypoxia/reoxygenation group, 11, 12-EET control group, 11, 12- EET hypoxia/reoxygenation group, inhibition of extracellular signal-regulated kinase (ERKI/2) group, and inhibition of nitric oxide synthase (NOS) group. Hypoxia/reoxygenation injury model in HUVECs was established by exposure to hypoxia (2% O2, 5% CO2 and 93% N2) for 3 hours, followed by reoxygenation (95% air and 5% CO2) for 1 hour. The evaluation of the endothelial cells were made by immunohistochemistry. The cell viability was monitored by MTT assay. Colorimetry method was used to assay the lactate dehydrogenase (LDH) , malondialdehyde (MDA) and activity of superoxide dismutase (SOD) in culture medium. Western blot was used to detect the expressions of endothelial nitric oxide synthase (eNOS) and phosphorylated ERK1/2 in HUVECs. RESULTS: 11, 12-EET caused minor injury in normal oxygen incubated HUVECs; however, in hypoxia/reoxygenation HUVECs, it raised the cell viability markedly, decreased the LDH release and MDA content, and increased the activity of SOD and the expressions of eNOS and phosphorylated ERK1/2. CONCLUSIONS: 11, 12-EET may prevent against endothelial cell hypoxia/reoxygenation injury. The mechanism may be related to the increased activity of SOD, elimination of oxygen-derived free radicals, and reduction of eNOS and phosphorylated ERK1/2 lesion caused by hypoxia/reoxygenation.