Activation of p38 MAPK induced by a multi-cycle ischaemic preconditioning protocol is associated with attenuated p38 MAPK activity during sustained ischaemia and reperfusion

The role of p38 mitogen-activated protein kinase (MAPK) in ischaemic preconditioning remains controversial. Since most previous studies focussed on events only during sustained ischaemia, the aim of this study was to establish the activation pattern of p38 MAPK during a multicycle preconditioning protocol, sustained ischaemia as well as reperfusion and to correlate these events with functional recovery of the isolated perfused rat heart. Isolated perfused rat hearts were preconditioned by 3x5 min global ischaemia followed by 25 min global ischaemia and 30 min reperfusion. Non-preconditioned hearts were subjected to 25 min global ischaemia and 30 min reperfusion. Hearts were freeze-clamped and p38 MAPK activation in tissue lysates was assessed by standard Western blotting techniques, using a dual phospho-p38 MAPK antibody as well as a non-radioactive IP-kinase assay. The results showed that transient dual phosphorylation and activation of p38 MAPK occurs during a 3x5 min preconditioning protocol: the activation was maximal during the first episode, becoming progressively lower during the second and third episodes. p38 MAPK activation was significantly less during both sustained ischaemia and reperfusion in preconditioned hearts, when compared with non-preconditioned hearts. Attenuation of p38 MAPK activity during sustained ischaemia and reperfusion was associated with improved functional recovery. The effect of inhibition of p38 MAPK activation on cardioprotection was further evaluated in adult, isolated cardiomyocytes. Administration of SB 203580 (1-10 microM) before and during the preconditioning protocol, had no effect on cell morphology and viability after 2 h hypoxia, compared to untreated preconditioned cardiomyocytes. When administered to non-preconditioned cells before the onset of 2 h hypoxia, it caused a significant improvement in both morphology and viability. In summary, the results suggest that attenuation of the kinase activity during sustained ischaemia and reperfusion may be an essential element of the preconditioning process.     

Decreased p38 MAPK activity in end-stage failing human myocardium: p38 MAPK alpha is the predominant isoform expressed in human heart.

Short duration exposure to cellular stresses have been shown to activate p38 mitogen-activated protein kinase (MAPK) in cultured rat ventricular cardiomyocytes and isolated perfused hearts; however, effects of chronic stress on p38 MAPK are not well understood. This study determined whether alterations in the p38 MAPK pathway occurred prior to end-stage human heart failure. The p38 MAPK alpha isoform was detectable in human cardiac tissue. However, carefully controlled analysis of protein and message in this study demonstrated an absence of the p38 MAPK beta -isoform. Low levels of message for the non-SB203580 sensitive p38 MAPK gamma and delta isoforms were also detected in both normal and failing human myocardium. Ischemic and idiopathic end-stage failing human hearts were compared to non-failing hearts for both p38 alpha MAPK protein level and total p38 MAPK activity. Western blotting techniques demonstrated no significant changes in total p38 alpha MAPK content. However, approximately 75% decreases in active/phosphorylated p38 MAPK (P<0.005) were observed in both ischemic and idiopathic failing hearts compared to non-failing hearts. In-gel kinase assays confirmed that activated p38 MAPK, detected by Western blotting, phosphorylated its potential downstream targets. When compared to non-failing hearts, approximately 46% decreases in p38 MAPK phosphorylation of mitogen-activated protein kinase-activated protein kinase-2 (MAPKAPK-2) were observed in ischemic and idiopathic failing hearts (P=0.03 and P=0.04 respectively). Active p38 MAPK was localized to sarcomeric structures in the cytosol of myocytes by confocal immunofluorescence microscopy. The correlation between decreased MAPKAPK-2 phosphorylation and loss of active p38 MAPK in failing human myocytes suggests that decreases in the activation of p38 MAPK alpha, the predominant cardiac isoform, occur prior to end-stage heart failure.     

P38MAPK磷酸化对HepG2细胞耐药的影响及其意义

目的 探讨p38MAPK磷酸化对HepG2细胞耐药的影响及其意义.方法 采用浓度递增法,建立动态HepG2/顺铂(CDDP)耐药模型,Western blot检测磷酸化p38的表达;予以p38MAPK特异性抑制剂SB203580分别处理24、48、72 h后,流式细胞仪动态分析HepG2/CDDP耐药细胞周期、四甲基偶氮唑盐法检测顺铂对HepG2/CDDP耐药细胞的半数药物抑制浓度(IC50)、Western blot检测HepG2/CDDP耐药细胞凋亡分子Bcl-2、Bax及P-gp蛋白的表达.动态耐药模型磷酸化P38的检测行单因素方差分析; SB203580处理后计量资料行3×3析因设计方差分析,率的比较采用x2检验.结果 成功建立HepG2/CDDP耐药细胞株,其对CDDP的IG50值与对照HepG2细胞差异具有统计学意义(t=99.30,P<0.01);随着HepG2/CDDP耐药细胞株耐药表型的增强,P38MAPK活化水平逐渐增强(F=69.39,P<0.01).P38MAPK特异性抑制剂SB203580可逐渐降低HepG2/CDDP对顺铂的IC50值(F=2350,P<0.01)、G0/Gl期细胞比例(x2=520,P<0.01)、Bcl-2/Bax表达比值(F=83.8,P<0.01)及细胞膜药物转运相关蛋白P-gP的表达(F=107,P<0.01).结论 P38活化水平随着肝癌耐药细胞株耐药表型的增强而逐渐升高;抑制P38的活化可有效逆转肝癌HepG2/CDDP耐药细胞株的耐药性.     

p38 MAPK is activated but not necessary in porcine von Willebrand factor-dependent platelet activation

We have investigated the role of p38 mitogen-activated protein kinase (MAPK) in von Willebrand factor (VWF)-dependent platelet activation. The interaction of platelets with subendothelial VWF, especially under high shear stress, is considered to be the first activation step which primes platelets for subsequent haemostatic events. As a model of VWF-dependent platelet activation, porcine VWF was employed. Porcine VWF induced p38 MAPK activation by 1 min post-addition; assessed by phosphorylation of a recombinant p38 MAPK fusion protein substrate termed glutathione S-transferase-MAPK activated protein kinase-2. To determine if p38 MAPK was necessary for porcine VWF-induced platelet activation, we functionally inhibited p38 MAPK activity with SB203580 before exposure of the platelets to porcine VWF. Inhibition of p38 MAPK had no effect on VWF-induced platelet alpha or lysozomal granule release, expression of activated GPIIb IIIa, modulation of membrane glycoprotein CD41, expression of phosphatidylserine as assessed by annexin V binding, microparticle formation, or platelet agglutination. It was concluded that SB203580-inhibitable p38 MAPK activity induced by porcine VWF is not necessary for platelet activation.     

p38 MAPK信号转导通路参与NO诱导兔关节软骨细胞凋亡

目的探讨p38 MAPK信号转导通路在软骨细胞凋亡中的作用。方法体外培养兔关节软骨细胞,一氧化氮(NO)供体NOC-18和p38 MAPK抑制剂SB203580作用于细胞24 h,用AnnexinV-FITC/PI流式细胞术检测软骨细胞凋亡率,W estern b lot测定p38、磷酸化p38蛋白的表达水平。结果与对照组比较,SB203580显著降低了NOC-18诱导的软骨细胞凋亡率(P<0.05);NOC-18以浓度依赖的方式促进p38 MAPK的磷酸化,而SB203580能抑制其磷酸化(P<0.05)。结论p38 MAPK通路参与了NO诱导的兔关节软骨细胞凋亡的信号转导。     

Ischemic preconditioning activates MAPKAPK2 in the isolated rabbit heart: evidence for involvement of p38 MAPK

Recent studies suggest that p38 mitogen-activated protein kinase (MAPK) may be involved in ischemic preconditioning (PC). To further test this possibility, the regulation of MAPK-activated protein kinase 2 (MAPKAPK2), a kinase immediately downstream from p38 MAPK, and the activity of c-Jun NH(2)-terminal kinase (JNK), a second MAPK, were examined in preconditioned hearts. Isolated, perfused rabbit hearts were subjected to 20 to 30 minutes of global ischemia. Ventricular biopsies before treatment and after 20 minutes of ischemia were homogenized, and the activities of MAPKAPK2 and JNK were evaluated. For the MAPKAPK2 experiments, 7 groups were studied, as follows: control hearts; preconditioned hearts; hearts treated with 500 nmol/L R(-) N(6)-(2-phenylisopropyl) adenosine (PIA), an A(1)-adenosine receptor agonist; preconditioned hearts pretreated with 100 micromol/L 8-(p-sulfophenyl) theophylline (SPT), an adenosine receptor antagonist; preconditioned hearts also treated with SB 203580, a potent inhibitor of p38 MAPK activation; hearts treated with 50 ng/mL anisomycin (a p38 MAPK/JNK activator); and hearts treated with both anisomycin (50 ng/mL) and the tyrosine kinase inhibitor genistein (50 micromol/L). MAPKAPK2 activity was not altered in control hearts after 20 minutes of global ischemia. By contrast, there was a 3.8-fold increase in activity during ischemia in preconditioned hearts. Activation of MAPKAPK2 in preconditioned hearts was blocked by both SPT and SB 203580. MAPKAPK2 activity during ischemia increased 3.5-fold and 3.3-fold in hearts pretreated with PIA or anisomycin, respectively. MAPKAPK2 activation during ischemia in hearts pretreated with anisomycin was blocked by genistein. In separate hearts, anisomycin mimicked the anti-infarct effect of PC, and that protection was abolished by genistein. JNK activity was measured in control and preconditioned hearts. There was a comparable, modest decline in activity during 30 minutes of global ischemia in both groups. As a positive control, a third group of hearts was treated with anisomycin before global ischemia, and in these, JNK activity increased by 290% above baseline. These results confirm that the p38 MAPK/MAPKAPK2 pathway is activated during ischemia only if the heart is in a preconditioned state. These data further support p38 MAPK as an important signaling component in ischemic PC.     

Gene activity changes in ischemically preconditioned rabbit heart gene: discovery array study

This study tested the hypothesis that classic ischemic preconditioning can cause changes in gene expression patterns in the rabbit heart, assessed by gene array technology. Open-chest rabbits were randomly assigned to sham-operated and ischemically preconditioned groups. The sham-operated group received 5 hours and 20 minutes of no intervention, while the ischemically preconditioned group was subjected to two episodes of preconditioning ischemia (5 minutes each) separated by 5 minutes of reperfusion, followed by an additional 5 hours and 5 minutes of reperfusion. (33)P-labeled cDNA from the sham-operated hearts and the nonischemic and preconditioned areas of the ischemically preconditioned group was hybridized to filters spotted with 18,376 human cDNA clones. Altogether, 35 genes with significantly altered expression patterns were discovered. In the preconditioned area, genes for MAPKAP kinase 3 and cathepsin G were up-regulated. In the nonischemic area, genes for GTP exchange factor, Na(+), K(+)-ATPase, Zn finger protein 35, a representative of the CEA family, cytochrome c oxidase, mitogen-responsive phosphoprotein, and Ran-binding protein were up-regulated. None of the identified genes had been previously reported to be involved in ischemic preconditioning.     

兔颈动脉外膜损伤术后氧化应激中p38 MAPK的表达变化

目的: 探讨p38 MAPK在兔颈动脉外膜损伤致内膜病变氧化应激中的作用。方法: 采用高脂饮食喂养及胶原酶消化＋机械分离的方法,建立兔颈动脉外膜损伤致内膜病变的模型。测定术后不同时间点,对照组和阿托伐他汀组家兔血脂指标（TC,TG,LDL-C和HDL-C）、新生内膜面积（NIA）、活性氧物质（ROS）的产生情况,观察磷酸化p38 MAPK的表达及定位。结果: 从颈动脉外膜损伤术后1 d始,ROS的产生和磷酸化p38 MAPK的表达即增加并持续至少28 d。阿托伐他汀干预后,与对照组比较,各时间点ROS的产生及磷酸化p38的表达均下调（P<0.05）,TC及LDL-C的水平下降（P<0.05）,新生内膜形成减少（P<0.05）。结论: 氧化应激水平的升高和p38 MAPK的持续激活,是血管外膜损伤致新生内膜形成的可能机制之一。     

Female sex is associated with increased mortality and morbidity early, but not late, after coronary artery bypass grafting

Objective To describe mortality and morbidity during a periodof 2 years after coronary artery bypass grafting in relationto gender. Design Prospective follow-up study. Setting Two regional cardiothoracic centres which performedall the coronary artery bypass operations in western Swedenat the time. Subjects A total of 2129 (1727 (81%) men and 402 (19%) women)consecutive patients undergoing coronary artery bypass surgerybetween June 1988 and June 1991 without concomitant procedures. Results Females were older and more frequently had a historyof hypertension, diabetes mellitus, congestive heart failure,renal dysfunction and obesity. In a multivariate analysis, takingaccount of age, history of cardiovascular diseases and renaldysfunction, female sex appeared as a significant independentpredictor of mortality during the 30 days after coronary arterybypass grafting (P<0.05), but not thereafter. Various postoperative complications including neurological deficit,hydro- and pneumo-thorax, perioperative myocardial damage andthe need for assist devices and prolonged reperfusion were morecommon in females than males. Conclusion Females run an increased risk of early death andthe development of postoperative complications after coronaryartery bypass surgery as compared with males. Late mortalitydoes not appear to be influenced by gender and the long-termbenefit of the coronary artery bypass graft operation is similarin men and women.     

Evidence that serum potassium is not the etiological agent in ventricular fibrillation following coronary artery occlusion

• 1.1. Elevation of the concentration of potassium in the coronary sinus occurred only in 33 per cent of 69 dogs after ligation of a major coronary artery.
• 2.2. Eighteen of the 23 dogs (78 per cent) with an elevation of the level of potassium in the coronary sinus blood maintained a normal sinus rhythm throughout the experimental period.
• 3.3. Of 12 animals which developed ventricular fibrillation after coronary artery ligation, only 3 showed a significant elevation of the concentration of potassium in the coronary sinus. The other 9 failed to show any increase in the level of potassium in the coronary sinus. None of the 12 showed an increase in the concentration of potassium in the femoral artery.
• 4.4. These results fail to support the thesis that an increase in the levels of serum potassium incites ventricular fibrillation after coronary artery ligation.
     

Phosphorylation state of hsp27 and p38 MAPK during preconditioning and protein phosphatase inhibitor protection of rabbit cardiomyocytes

Small heat shock proteins (hsp) have been implicated in mediation of classic preconditioning in the rabbit, Hsp27 is a terminal substrate of the p38 MAPK cascade. One and 2D gel electrophoresis and immunoblotting of cell fractions was used to determine p38 MAPK and hsp27 phosphorylation levels, respectively, during in vitro ischemia in control, calyculin A (Cal A)-treated (protein phosphatase inhibitor), SB203580-treated (p38MAPK inhibitor) and preconditioned (IPC) isolated adult rabbit cardiomyocytes. The dual phosphorylation of p38 MAPK was increased by early ischemia (30-60 min), after which there was a loss of total cytosolic p38 MAPK. The ischemic increase of p38 MAPK dual phosphorylation was enhanced by IPC. Cal A strongly activated dual phosphorylation of p38 MAPK in oxygenated cells and this was maintained into early ischemia, SB203580 inhibited the dual phosphorylation of p38 MAPK and attenuated the loss of total cytosolic p38 MAPK. In each protocol, ischemia translocated hsp27 from the cytosolic fraction to the cytoskeletal fraction at similar rates and extents, Hsp27 phosphorylation was quantitated as the fraction of diphosphorylated hsp27, based on IEF mobility shifts of hsp27 phosphorylation isoforms. In oxygenated control cells, cytosolic and cytoskeletal hsp27 was highly phosphorylated. After 90 min ischemia, cytoskeletal hsp27 was markedly dephosphorylated. Cal A slightly increased control cytoskeletal hsp27 phosphorylation. During ischemic incubation, Cal A blocked ischemic dephosphorylation, SB203580 accelerated ischemic hsp27 dephosphorylation and injury, IPC insignificantly decreased the initial rate of ischemic dephosphorylation of hsp27, but not the extent of dephosphorylation in later ischemia. Phosphorylation is regulated by both kinase and phosphatase activities. IPC protection was not correlated with a significant increase in cytosolic or cytoskeletal hsp27 phosphorylation levels during prolonged (> 60-90 min) ischemia.     

Attenuation of endothelin-1 induced vasoconstriction by 17beta estradiol is not sustained during long-term therapy in postmenopausal women with coronary heart disease

OBJECTIVES: The goal of this study was to determine the long-term effects of estrogen replacement therapy on the response to endothelin-1 (ET-1) in postmenopausal women with coronary heart disease. BACKGROUND: It is thought that the vasoconstrictor ET-1 is involved in the development and progression of atherosclerosis. Estrogen replacement may slow the development of atherosclerosis in postmenopausal women. METHODS: Nineteen of 20 postmenopausal women randomized to either three months of 2 mg oral estradiol or placebo completed the double-blind placebo-controlled protocol. Change in forearm blood flow (FBF) in response to a 60 min brachial arterial infusion of ET-1 (5 pmol/min) was measured before randomization, after one month of randomized therapy and after three months of therapy using venous occlusion plethysmography. RESULTS: Estrogen treatment had no effect on baseline FBF. Systolic and diastolic blood pressure and heart rate did not change in response to estrogen therapy or ET-1. Before randomization, in response to ET-1, FBF was reduced by -21.9% (mean response over 60 min) in the placebo group and -19.0% in the estradiol group (p = 0.67). After one month of therapy, the response was attenuated in the estrogen group, -10.0%, compared with the placebo group, -23.6 (difference in means 13.6%, 95% confidence interval [0.7%, 26.6%], p = 0.041). After three months of therapy, there was no difference in response between the placebo group, -27.0%, and estrogen group, -30.2% (p = 0.65). CONCLUSIONS: In postmenopausal women with coronary heart disease, estrogen therapy inhibits the vasoconstrictor response to ET-1 after one month of therapy. This effect is lost after three months of therapy, suggesting that tachyphylaxis to one potentially beneficial action of estradiol develops during chronic treatment.     

Red blood cell level is increased in obese but not in non-obese patients with coronary heart disease

Objective To examine the changes of red blood cell levels in the obese and non-obese patients with coronary heart disease （CHD） and its clinical significance. Methods 230 cases of coronary heart disease were selected and divided into the obese group and the non- obese group. Obesity and non-obesity were defined based on the body mass index （BMI if 28.0kg/m2）, or waist-hip ratio （men〉 0.9, women〉 0.85）. In addition, 130 healthy subjects were recruited as controls. The pathological status of coronary lesions was quantita- tively analyzed according to the Coronary Vascular Image Segmentation Evaluation Criteria （American Heart Association 1984） and the Gensini scoring system. Results of the changes of both the hemoglobin levels and the red blood cell count in the obese group, the non- obese group with CHD and the control group were compared. Besides, Multivariant Logistic Regression Analysis was applied to assess the correlation between the red blood cells and the coronary artery disease. Results The red blood cell count and the level of hemoglobin in the obese group with CHD was higher than that in the non-obese group with CHD [（4.35 ± 0,55） and （4.13 ± 0.56） 10^9/L; （136.71± 15.87） and （129.96 ±16.23） g/L, P 〈 0.05 in both]; the proportion of acute coronary syndrome in the obese group with CHD was higher in the obese group with CI-/D than that in the non-obese group with CHD （P〈0.05）; Multivariant logistic regression analysis also showed that the red blood cell count was positively correlated with obesity with CHD.Conclusion The red blood cell count and the level of hemoglobin in the obese group were higher than those in the non-obese group; the increase of red blood cell count and hemoglobin level is one of the independent risk factors for the obese patients with CHD.     

AMP-activated protein kinase activates p38 mitogen-activated protein kinase by increasing recruitment of p38 MAPK to TAB1 in the ischemic heart

AMP-activated protein kinase (AMPK) promotes glucose transport, maintains ATP stores, and prevents injury and apoptosis during ischemia. AMPK has several direct molecular targets in the heart but also may interact with other stress-signaling pathways. This study examined the role of AMPK in the activation of the p38 mitogen-activated protein kinase (MAPK). In isolated heart muscles, the AMPK activator 5-aminoimidazole-4-carboxy-amide-1-beta-D-ribofuranoside (AICAR) increased p38 MAPK activation. In AMPK-deficient mouse hearts, expressing a kinase-dead (KD) alpha2 catalytic subunit, p38 MAPK activation was markedly reduced during low-flow ischemia (2.3- versus 7-fold in wild-type hearts, P<0.01) and was similarly reduced during severe no-flow ischemia in KD hearts (P<0.01 versus ischemic wild type). Knockout of the p38 MAPK upstream kinase, MAPK kinase 3 (MKK3), did not affect ischemic activation of either AMPK or p38 MAPK in transgenic mkk3(-/-) mouse hearts. Ischemia increased p38 MAPK recruitment to transforming growth factor-beta-activated protein kinase 1-binding protein 1 (TAB1), a scaffold protein that promotes p38 MAPK autophosphorylation. Moreover, TAB1 was associated with the alpha2 catalytic subunit of AMPK. p38 MAPK recruitment to TAB1/AMPK complexes required AMPK activation and was reduced in ischemic AMPK-deficient transgenic mouse hearts. The potential role of p38 MAPK in mediating the downstream action of AMPK to promote glucose transport was also assessed. The p38 MAPK inhibitor SB203580 partially inhibited both AICAR- and hypoxia-stimulated glucose uptake and GLUT4 translocation. Activation of p38 MAPK by anisomycin also increased glucose transport in heart muscles. Thus, AMPK has an important role in promoting p38 MAPK activation in the ischemic heart by inducing p38 MAPK autophosphorylation through interaction with the scaffold protein TAB1.     

Effect of coronary occlusion on left ventricular function with and without collateral supply during beating heart coronary artery surgery

OBJECTIVE: To study the effects of coronary occlusion and collateral supply on left ventricular (LV) function during beating heart coronary artery surgery. DESIGN: Prospective intraoperative study, performed at baseline, during wall stabilisation, coronary artery occlusion, and 2 and 10 minutes after reperfusion. Transoesophageal M mode echocardiograms, simultaneous high fidelity LV pressure, and thermodilution cardiac output were measured. LV anterior wall thickening, thinning velocities, thickening fraction, regional work, and power production were derived. Asynchrony during the isovolumic periods was quantified as cycle efficiency. SETTING: Tertiary referral cardiac centre. PATIENTS: 14 patients with stable angina, mean (SD) age 62 (7) years, undergoing left anterior descending artery grafting using the "Octopus" device. RESULTS: Collaterals were absent in nine patients and present in five. Epicardial stabilisation did not affect LV function. Results are expressed as mean (SD). Coronary occlusion (15.6 (2) minutes) depressed anterior wall thickening (1.4 (0.6) v 2.6 (0.6) cm/s) and thinning velocities (1.4 (0.5) v 3.0 (0.6) cm/s), regional work (2.2 (0.8) v 4.6 (0.6) mJ/cm2), and power (21 (4) v 33 (5) mW/cm2) in patients without collaterals (p < 0.05 for all), but only wall thinning (3.5 (0.5) v 4.8 (0.5) cm/s, p < 0.05) in patients with collaterals. All returned to baseline within 10 minutes of reperfusion. Cycle efficiency and regional work were impaired at baseline and fell during occlusion, regardless of collaterals. Within 10 minutes of reperfusion both had increased above baseline. CONCLUSIONS: Coronary occlusion for up to 15 minutes during beating heart coronary artery surgery depressed standard measurements of systolic and diastolic anterior wall function in patients without collaterals, but only those of diastolic function in patients with collaterals. Regional synchrony decreased in both groups. All disturbances regressed within 10 minutes of reperfusion.