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AIM:To investigate whether ellagic acid (EA) attenuates hypoxic-ischemic encephalopathy (HIE) by down-regulating autophagy.METHODS:In vivo, Sprague-Dawley rats (n=17) were randomly divided into 3groups:5 rats for sham group, 6 rats for HIE group and 6 rats for HIE+EA pretreatment group.The rats in HIE+EA pretreatment group were treated with EA (10 mg/kg, 10 m L/kg, suspended in corn oil, ig).After 24 h of operation, the rats from each group were sacrificed and their brains were collected.TTC staining and HE staining were used to define the infarct areas and brain structure.The autophagy-related proteins beclin-1, P62, LC3-II/-I and Atg5 in the cortex in each group were compared by Western blot.In vitro, PC12 cells were divided into 3 groups:control group, Coand CoEA pretreatment group.Co800μmol/L was added to the PC12 cells to induce an anoxic environment.The PC12 cells were pretreated with EA at 8μmol/L and the cell viability was measured by CCK-8 assay.The production of reactive oxidative species (ROS) in the cells was detected by flow cytometry with DCFH-DA staining.MDC staining and TM-RE staining were applied to reflect the extent of autophagy and the state of apoptosis, respectively.The autophagy-related proteins in PC12 cells were also investigated.RESULTS:In HIE group, 7-day-old rats were given the operations and the their large infarct areas in the hemisphere were observed by TTC staining.HE staining displayed the injured hemispheres which contained few neurons, and exhibited edema status and serious structural damage.EA pretreatment decreased the infarct area and alleviated the damage to hemisphere with more visible neurons, compared with HIE group.Compared with sham group, the levels of autophagy-related proteins Atg5, beclin-1 and LC3-II/-I in the cortex were increased (P<0.01) , and P62 protein expression was decreased (P<0.01) in HIE group.Compared with HIE group, the protein expression of Atg5, beclin-1 and LC3-II/-I was decreased (P<0.01) and P62 protein expression was increased in HIE+EA pretreatment group (P<0.01).In vitro, compared with CoPC12 cells in CoEA pretreatment group showed a lower ROS level.Moreover, the cells in CoEA pretreatment group exhibited higher mitochondrial membrane potential than that in CoMDC staining in Coshowed high value of fluorescence and increased number of autophagosomes.EA pretreatment reduced the number of autophagosomes and the extent of autophagy to protect PC12cells.Furthermore, the protein levels of Atg5, beclin-1 and LC3-II/-I in Cowere higher (P<0.01) , and the protein expression of P62 was lower (P<0.01) than those in control group.In CoEA pretreatment group, the protein levels of Atg5, beclin-1 and LC3-II/-I were decreased (P<0.01) and the protein expression of P62 was increased as compared with Co (P<0.01).CONCLUSION:EA pretreatment attenuates autophagy to protect the neurons against HIE injury.
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Cystatin, which widely distributed in both tissues and body fluids of animal and plant, was a superfamily of cysteine proteinase inhibitors. It could form activity-inhibitor complexes with cysteine proteinases to inhibit the hydrolytic activity of proteinases. Cystatin played important roles not only in the inhibition of the proteolytic degradation of fish muscle, but also in biological defense systems against invaders. To explore the functions of fish cystatin and the potential values in fish disease prevention and cure, as well as seafood processing, the recombinant yeast strains which could express Chinese sturgeon cystatin were constructed. First, the cystatin cDNA of Chinese sturgeon, which had been PCR modified, was subcloned into yeast integrated vector pPICZaA. After extracted and purified, the recombinant plasmids were linearized by Sac I. The yeast Pichia pastoris GS115 strain was transformed by use of the Lithium Chloride transformation method, and the recombinant cystatin yeast strains got. After 0.5% methanol induction, SDS-PAGE analysis of the culture supernatant indicated that the yield of recombinant cystatin was about 215mg x L(-1) with the percentage about 73.6%. The recombinant cystatin was purified through Q-Sepharose anion-exchange chromatography, and the purity reached about 94.2%. The inhibitory activity of recombinant cystatin was measured by inhibiting the proteinase activity of papain. The results showed that about 1 microg recombinant cystatin could inhibit the activity of 15 microg papain. Heat stability assay results showed that there was a decrease in inhibitory activity of cystatin with the increasing of temperature. When solution of recombinant cystatin was kept at 70 degrees C for 5min, the inhibitory activity reduced fast. While the recombinant cystatin was heated to 90 degrees C for 5min, the inhibitory activity of recombinant cystatin was undetected. The inhibitory activity for recombinant Chinese sturgeon cystatin was higher than that of CPI (cysteine proteinase inhibitor) from seeds of corn, that about 1 microg purified CIP could inhibited the activity of 0.278 microg papain. But the heat stability of recombinant cystatin is lower than that of the corn CPI. The expression level and the activity of recombinant cystatin from yeast Pichia pastoris were higher than those from E. coli. Moreover, recombinant cystatin from Pichia pastoris was easier to separate and purify. This paper reported that recombinant fish cystatin was produced in a highly efficient expression system based on the methylotrophic yeast, further work will focus on the function of recombinant Chinese sturgeon cystatin to resist fish disease and explore the value of cystatin as a food additive to inhibit cysteine proteinases during surimi processing.