Post-conditioning with gradually increased reperfusion provides better cardioprotection in rats / 世界急诊医学杂志（英文）

BACKGROUND:Rapid and complete reperfusion has been widely adopted in the treatment of patients with acute myocardial infarction (AMI), but this process sometimes can cause severe reperfusion injury. This study aimed to investigate different patterns of post-conditioning in acute myocardial ischemia-reperfusion injury, and to detect the role of mitogen activated protein kinase (MAPK) during the injury. METHODS:Rats were randomly divided into five groups:sham group, reperfusion injury (R/I) group, gradually decreased reperfusion group (GDR group, 30/10-25/15-15/25-10/30 seconds of reperfusion/ischemia), equal reperfusion group (ER group, 20/20 seconds reperfusion/ischemia, 4 cycles), and gradually increased reperfusion group (GIR group, 10/30-15/25-25/15-30/10 seconds of reperfusion/ischemia). Acute myocardial infarction and ischemic post-conditioning models were established in the rats. Six hours after reperfusion, 3 rats from each group were sacrificed and myocardial tissues were taken to measure the expressions of phosphorylation of extracellular signal-regulated protein kinase (P-ERK), phosphorylated c-Jun N-terminal kinase (P-JNK), mitogen-activated protein kinase p38 (p38 MAPK), tumor necrosis factor-α (TNF-α), caspases-8 in the myocardial tissue, and cytochrome c in the cytosol using Western blot. Hemodynamics was measured at 24 hours after reperfusion, the blood was drawn for the determination of cardiac enzymes, and the heart tissue was collected for the measurement of apoptosis using TUNEL. One-way analysis of variance and the Q test were employed to determine differences in individual variables between the 5 groups. RESULTS:Three post-conditioning patterns were found to provide cardioprotection (P<0.05) compared with R/I without postconditioning. GIR provided the best cardioprotection effect, followed by ER and then GDR. Apoptotic index and serum marker levels were reduced more significantly in GIR than in ER (P<0.05). The enhanced cardioprotection provided by GIR was accompanied with significantly increased levels of P-ERK 1/2 (1.82±0.22 vs. 1.54±0.32,P<0.05), and lower levels of p-JNK, p38 MAPK, TNF-α, caspase-8, caspase-9 and cytochrome in the cytoplasm (P<0.05), compared with ER. The infarct size was smaller in the GIR group than in the ER group, but this difference was not significant (16.30％±5.22％ vs. 20.57％±6.32％,P<0.05). Allthe measured variables were improved more significantly in the GIR group than in the GDR group (P<0.05). CONCLUSION:Gradually increased reperfusion in post-conditioning could attenuate reperfusion injury more significantly than routine method, thereby the MAPK pathway plays an important role in this process.

Effect of ischemic postconditioning on activation of p38 mitogen activated protein kinase and cardiac myocyte apoptosis in rats / 中国医学科学院学报

<p><b>OBJECTIVE</b>To explore the change of phospho-p38 (P-p38) mitogen activated protein kinase(MAPK) and its influence on myocardial apoptosis in reperfusion injury in postconditioning.</p><p><b>METHODS</b>Totally 60 rats were equally and randomly divided into six groups: Sham group,reperfusion injury (R/I) group, postconditioning (Post) group, SB203580 (I_p38) group, anisomycin plus postconditioning (Ani+post) group,and anisomycin (Ani) group. After the model of acute myocardial infarction was established,placebo solution (DMSO), SB203580 (1 mg/kg), or anisomycin (2 mg/kg) was injected through jugular vein 5 minutes before reperfusion. Six hours later, 3 rats in each group were executed and the hearts were separated to measure the signaling molecules including phospho-p38,tumor necrosis factor-alpha (TNF-α), Caspase-8, Bcl-2/Bax, and cytochrome-c (Cyt-c). Twenty-four hours later,the hemodynamic data were measured in the remaining rats,and then blood was collected to determine the serum markers of cardiac damage. After that,hearts were separated to measure the infarction area and apoptosis.</p><p><b>RESULTS</b>Six hours after reperfusion,the expressions of P-p38 in Post and I_p38 group were significantly lower than those in R/I group (P<0.05), significantly higher in Ani+post and Ani group than in Post group (P<0.05), and significantly lower in Ani+post group than in R/I group (P<0.05). The expressions of TNF-α and Caspase-8 were significantly lower in Post and I_p38 group than in R/I group (P<.05) and significantly higher in Ani+post and Ani group than in Post group (P<0.05). The expression of TNF-α was significantly lower in Ani+post group than in R/I group (P<0.05). The expression of Bcl-2 was significantly higher in Post and I_p38 groups than in R/I group (P<0.05) and significantly lower in Ani+post and Ani groups than in Post group (P<0.05). The expression of Bax was significantly lower in Post and I_p38 groups than in R/I group (P<0.05) and were significantly higher in Ani+post and Ani group than in Post group (P<0.05). The expression of Cyt-c after the removal of the cytoplasm mitochondria was significantly lower in Post and I_p38 group than in R/I group (P<0.05) and was significantly higher in Ani+post and Ani group than in Post group (P<0.05). Twenty-four hours after reperfusion,the values of rate-pressure product and ± delta pressure/delta time max were significantly lower in R/I group than in Post and I_p38 groups (P<0.05) and was significantly higher in Post group than in Ani+post and Ani group (P<0.05). The apoptotic index (AI) was significantly lower in Post and I_p38 groups than in R/I group (P<0.05) and was significantly higher in Ani+post and Ani groups than in Post group (P<0.05). The values of creatine kinase and creatine kinase-MB were significantly lower in Post,Ani+post, and I_p38 groups than in R/I group (P<0.05) and were significantly higher in Ani+post and Ani group than in Post group (P<0.05). The area of necrosis/area at risk ratio was significantly lower in Post and I_p38 groups than in R/I group (P<0.05) and was significantly higher in Ani+post and Ani groups than in Post group (P<0.05).</p><p><b>CONCLUSION</b>Postconditioning can inhibit the phosphorylation of p38 MAPK,through which it can attenuate cardiac myocyte apoptosis by both extrinsic and mitochondria pathways.</p>

Gradual algorithm of postconditioning reduced reperfusion injury through mitochondrion pathway in rats / 中华心血管病杂志

<p><b>OBJECTIVE</b>The effects of various postconditioning algorithm on reperfusion injury and the role of mitochondrion pathway were investigated in a rat model of reperfusion/injury.</p><p><b>METHODS</b>Rats were divided into 5 groups: sham, reperfusion/injury (R/I group), reverse algorithm of postconditioning (R-Post, 30/10-25/15-15/25-10/30 s of reperfusion/re-occlusion), standard algorithm of postconditioning (S-Post, 4 cycles of 20/20 s of reperfusion/re-occlusion), and gradual algorithm of postconditioning (G-Post, 10/30-15/25-25/15-30/10 s of reperfusion/re-occlusion).</p><p><b>RESULTS</b>The levels of Bax, Cytochrome-c, Caspase-9, serum marker of myocardium and apoptosis index were significantly lower while the level of Bcl-2 was significantly higher in the three postconditioning groups than those in R/I group (all P < 0.05). The levels of Bax (0.35 +/- 0.10 vs. 0.50 +/- 0.02, P < 0.05), Cytochrome-c (0.66 +/- 0.16 vs. 1.68 +/- 0.22, P < 0.05), Caspase-9 (0.61 +/- 0.17 vs. 1.66 +/- 0.55, P < 0.05), serum marker of myocardium [CK: (251.00 +/- 45.16) U/L vs. (388.56 +/- 75.01) U/L, P < 0.05; CK-MB: (146.00 +/- 60.12) U/L vs. (291.16 +/- 52.41) U/L, P < 0.05] and apoptosis index [(4.32 +/- 1.16)% vs. (8.58 +/- 1.12)% , P < 0.05] were all significantly lower while Bcl-2 level (2.00 +/- 0.34 vs. 1.40 +/- 0.18, P < 0.05) was significantly higher in G-Post group than those in S-Post group. Moreover, above mentioned cardiac protective effects were significantly stronger in the G-Post group compared to R-Post group (all P < 0.05).</p><p><b>CONCLUSION</b>In conclusion, gradual algorithm of postconditioning could attenuate reperfusion injury more significantly than standard algorithm, and mitochondrion pathway plays an important role in this cardioprotective process.</p>

Change of JNK MAPK and its influence on cardiocyte apoptosis in ischemic postconditioning / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To test whether postconditioning could inhibit the expression of phospho-JNK (P-JNK) mitogen activated protein kinase (MAPK) and study its relation to apoptosis of cardiocyte.</p><p><b>METHODS</b>Sixty rats were randomly divided into six groups: sham, reperfusion injury (R/I), postconditioning (Post), SP600125 (I_JNK), anisomycin and postconditioning (Ani+Post) and anisomycin (Ani) groups. After acute myocardial infarction was induced in rats, placebo solution (DMSO), SP600125 (6 mg/kg) or anisomycin (2 mg/kg) was injected through jugular vein 5 min before reperfusion; 6 h later 3 rats of each group were executed and the hearts were separated to measure the signaling molecules (phospho-JNK, TNF alpha, Caspase-8, Bcl-2/Bax, cytochrome-c). Twenty-two hours later hemodynamic data were measured in the left rats, and then blood samples were taken to determine serum markers of cardiac damage, and hearts were separated to measure the infarction area and cardiocyte apoptosis.</p><p><b>RESULT</b>Postconditioning improved +/-DP/DTmax of left ventricle, limited infarct area, relieved apoptosis and necrosis of cardiocytes, and inhibited the expression of P-JNK (1.12 +/-0.21 Compared with 1.90 +/-0.32, P<0.05). At the same time the levels of TNFalpha Caspase-8, Bax and Cyt-c were lower in Post group than those in R/I group, but Bcl-2 expression levels were higher. I_JNK group presented the similar protection effect of postconditioning [TUNEL index: (6.23 +/-2.43)% Compared with (18.22 +/-5.10)%, P<0.05; Infarct area: (23.44 +/-6.34)% Compared with (42.31 +/-8.21)%, P<0.05]. On the other hand, Ani+Post group partially lost cardioprotection effect [TUNEL index: (14.12 +/-2.00)% Compared with (18.22 +/-5.10)%,P>0.05; Infarct area: (35.27 +/-5.28)% Compared with (42.31+/-8.21)%,P>0.05], because of the activation of JNK MAPK.</p><p><b>CONCLUSION</b>Postconditioning can inhibit phosphorylation of JNK MAPK, which attenuates cardiocyte apoptosis by both extrinsic and mitochondria pathway.</p>

Chronic effects of spironolactone in conjunction with an angiotensin-converting enzyme inhibitor enalapril on circulating procollagen marker P III NP and vascular resistance in patients with essential hypertension / 中华心血管病杂志

<p><b>OBJECTIVE</b>Disturbances of the synthesis and breakdown of the extracellular matrix of arterial walls have emerged as key features of the atherosclerotic process. We observed the changes of circulating procollagen marker for type III collagen turnover rate, the N-terminal propeptide P III NP and vascular resistance in hypertensive patients treated with various antihypertensive regimens.</p><p><b>METHOD</b>A total of 130 light to moderate hypertensive patients were randomly assigned to receive enalapril (group B, n = 43), enalapril + spirolactone (20 mg/d, group A, n = 44) and anti-hypertensive drugs not directly affecting RAAS (calcium antagonist, beta-blocker, group C, n = 43) for 1 year. Target blood pressure is < 130/80 mm Hg.</p><p><b>RESULTS</b>Target blood pressure was reached in all treated patients and was similar among various groups. Under the same blood pressure controlling precondition, serum P III NP were similar at baseline among various groups and remained unchanged in group B [(3.4 +/- 0.3) microg/L vs. (3.7 +/- 0.3) microg/L, P > 0.05] and significantly decreased in group A [(2.3 +/- 0.2) microg/L vs. (3.8 +/- 0.2) microg/L, P < 0.05] while significantly increased in group C [(3.9 +/- 2.0) microg/L vs. (3.2 +/- 1.5) microg/L, P < 0.05]. Vascular resistance was similar among groups before therapy and all significantly decreased after 1 year antihypertensive therapy and the decrease was more significant in group A [(1064.3 +/- 158.6) dyn.s(-1).cm(-5)] than that in group B [(1200.8 +/- 298.7) dyn.s(-1).cm(-5)] and group C [(1205.1 +/- 206.4) dyn.s(-1).cm(-5)].</p><p><b>CONCLUSION</b>Spironolactone in conjunction with enalapril is a more favorable antihypertensive regimen in decreasing P III NP and improving vascular resistance than enalapril alone or antihypertensive drug regimens not directly affecting RAAS.</p>

Effect of glycosylation at Asn302 of pro-urokinase on its stability in culture supernatant / 中国医学科学杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the effect of glycosylation at Asn302 of pro-urokinase (pro-UK) on the stability in culture supernatant.</p><p><b>METHODS</b>Nonglycosylated pro-UK was constructed by site-directed mutagenesis of Asn302 to Ala302. The pro-UK mutant and native pro-UK were transfected into dhfr(-)-CHO cells, and serum-free culture supernatant was harvested and incubated at 4 degrees C and 37 degrees C, respectively. The pro-UK activity in culture supernatant was measured by the optical density (OD) increase with time (12 hours) at 405 nm. Without thermolysin activation, the percentage of single chain pro-UK was measured.</p><p><b>RESULTS</b>After 48 hours of incubation at 4 degrees C, the activities of pro-UK mutant and native pro-UK decreased 3.7% and 2.9% respectively, and at 37 degrees C decreased 37.9% and 23.5%, respectively. The total activity of native pro-UK was significantly higher than that of nonglycosylated mutant at 37 degrees C. The single-chain percentage of native pro-UK was higher than that of nonglycosylated mutant at both 4 degrees C and 37 degrees C.</p><p><b>CONCLUSION</b>Higher temperature increases the proteolysis of pro-UK. The glycosylation site on Asn302 is beneficial to pro-UK stability in culture supernatant.</p>

Insulin resistance and carotid atherosclerosis in 221 patients with potential hyperglycemia / 中国医学科学杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the relationship between insulin resistance and carotid atherosclerosis in patients with potential hyperglycemia.</p><p><b>METHODS</b>A total of 221 patients were recruited among those with potential hyperglycemia. All participants underwent physical examination, medical history interview, and 75 g oral glucose tolerance test. Venous blood was sampled for measurement of insulin and cholesterol levels. The intima-media thickness (IMT) in bilateral common carotid arteries was observed by B-mode ultrasound. Insulin resistance index was calculated by homeostasis model assessment (HOMA-IR). Subjects were stratified in quintiles according to HOMA-IR values. Risk factors and atherosclerotic parameters were analyzed.</p><p><b>RESULTS</b>With HOMA-IR value increase, incidence of impaired glucose tolerance, diabetes mellitus, hypertension, and coronary artery disease increased, the levels of triglyceride (TG), low density lipoprotein cholesterol (LDL-C), fasting plasma glucose, 2 hour plasma glucose, and fasting insulin increased as well, while the level of high density lipoprotein cholesterol (HDL-C) decreased. Meanwhile, all atherosclerotic parameters increased. Multivariate regression analysis showed that TG, total cholesterol, HDL-C, LDL-C levels, and ln(HOMA-IR) were related to IMT, hence were risk factors for IMT increase.</p><p><b>CONCLUSION</b>Insulin resistance is implicated in atherogenesis.</p>

Effects of atrial excitable period on the stability of atrial fibrillation in goats / 中华心血管病杂志

<p><b>OBJECTIVE</b>To investigate the effects of atrial excitable period (EP) on the stability of atrial fibrillation (AF) in goats.</p><p><b>METHODS</b>Ten female goats were instrumented with epicardial electrodes patches on the left atrium (LA) free wall. AF was induced and maintained by a home-made stimulator with frequency of 50 Hz at a 1-second duration and a 2-seconds interval. The stimulator was disconnected regularly. AF-induced duration, average AF cycle length (AFCL), and atrial effective refractory period during AF (ERP(AF)) were measured; EP was calculated by AFCL-ERP(AF).</p><p><b>RESULTS</b>Eight goats were studied. Persistent AF (> 24 h) could be induced in all the 8 goats within 6-16 days. When the induced AF lasted for 3-10 min or 24 h, the AFCL was 98.3 ms +/- 11.0 ms and 84.9 ms +/- 5.2 ms (P < 0.05), respectively, ERP(AF) was 90.5 ms +/- 13.2 ms and 63.0 ms +/- 4.8 ms (P < 0.05), respectively, and EP was 7.8 ms +/- 2.4 ms and 21.9 ms +/- 3.5 ms (P < 0.05), respectively.</p><p><b>CONCLUSION</b>The decrease in ERP(AF) is more significant than the shortening in AFCL, resulting in the gradually widening of EP which may contribute to the perpetuation of AF.</p>

Relationship between the expression of Fas, bcl-2 and apoptosis of cardiomyocytes in experimental myocardial ischemia in rats / 中华病理学杂志

<p><b>OBJECTIVE</b>To explore the relationship between expression of Fas, bcl-2 and apoptosis of cardiomyocytes in myocardial ischemia in rats.</p><p><b>METHODS</b>Myocardial ischemia was experimentally induced by ligating the left coronary artery. The rate were killed from 10 minutes to 7 days after the operation. Apoptotic myocardial cells were detected by TUNEL method. The expression of Fas and bcl-2 was studied by ABC immunohistochemistry.</p><p><b>RESULTS</b>Cardiomyocytic apoptosis appeared from 3 to 36 hours after ischemia. This phenomenon however could not be detected by TUNEL method 7 days after ischemia. The expression of Fas could be detected by ABC immunohistochemistry from 3 hours to 7 days after ischemia, and the expression of bcl-2 from 10 minutes to 7 days. Cardiomyocytic apoptosis and Fas / bcl-2 expression appeared in different regions of myocardium: apoptosis in the ischemic regions, while Fas and bcl-2 expression in regions without obvious ischemia.</p><p><b>CONCLUSION</b>In rats, Fas and bcl-2 may not directly regulate apoptosis of cardiomyocytes in case of myocardial ischemia.</p>