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Forced expression of the cell cycle inhibitor p57Kip2 in cardiomyocytes attenuates ischemia-reperfusion injury in the mouse heart.

Haley SA, Zhao T, Zou L, Klysik JE, Padbury JF, Kochilas LK - BMC Physiol. (2008)

Bottom Line: Therefore, we hypothesized that p57Kip2 has a protective role in cardiomyocytes under hypoxic conditions.The baseline functional parameters, including left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), LVdp/dtmax, heart rate (HR) and rate pressure product (RPR) were not significantly different between the different groups as assessed by the Langendorff perfused heart preparation.However, after subjecting the heart ex vivo to 30 minutes of ischemia-reperfusion injury, the p57Kip2 overexpressing hearts demonstrated preserved cardiac function compared to control mice with higher left ventricular developed pressure (63 +/- 15 vs 30 +/- 6 mmHg, p = 0.05), rate pressure product (22.8 +/- 4.86 vs 10.4 +/- 2.1 x 103bpm x mmHg, p < 0.05) and coronary flow (3.5 +/- 0.5 vs 2.38 +/- 0.24 ml/min, p <0.05).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA. Sheila_Haley@brown.edu

ABSTRACT

Background: Myocardial hypoxic-ischemic injury is the cause of significant morbidity and mortality worldwide. The cardiomyocyte response to hypoxic-ischemic injury is known to include changes in cell cycle regulators. The cyclin-dependent kinase inhibitor p57Kip2 is involved in cell cycle control, differentiation, stress signaling and apoptosis. In contrast to other cyclin-dependent kinase inhibitors, p57Kip2 expression diminishes during postnatal life and is reactivated in the adult heart under conditions of cardiac stress. Overexpression of p57Kip2 has been previously shown to prevent apoptotic cell death in vitro by inhibiting stress-activated kinases. Therefore, we hypothesized that p57Kip2 has a protective role in cardiomyocytes under hypoxic conditions. To investigate this hypothesis, we created a transgenic mouse (R26loxpTA-p57k/+) that expresses p57Kip2 specifically in cardiac tissue under the ventricular cardiomyocyte promoter Mlc2v.

Results: Transgenic mice with cardiac specific overexpression of p57Kip2 are viable, fertile and normally active and their hearts are morphologically indistinguishable from the control hearts and have similar heart weight/body weight ratio. The baseline functional parameters, including left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), LVdp/dtmax, heart rate (HR) and rate pressure product (RPR) were not significantly different between the different groups as assessed by the Langendorff perfused heart preparation. However, after subjecting the heart ex vivo to 30 minutes of ischemia-reperfusion injury, the p57Kip2 overexpressing hearts demonstrated preserved cardiac function compared to control mice with higher left ventricular developed pressure (63 +/- 15 vs 30 +/- 6 mmHg, p = 0.05), rate pressure product (22.8 +/- 4.86 vs 10.4 +/- 2.1 x 103bpm x mmHg, p < 0.05) and coronary flow (3.5 +/- 0.5 vs 2.38 +/- 0.24 ml/min, p <0.05).

Conclusion: These data suggest that forced cardiac expression of p57Kip2 does not affect myocardial growth, differentiation and baseline function but attenuates injury from ischemia-reperfusion in the adult mouse heart.

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Summary of hemodynamic data from the isolated heart perfusion evaluation of control and p57Kip2 overexpressing mice (R26loxpTA-p57k/+;Mlc-2vCrek/+), at baseline and post ischemia/reperfusion (I/R). Left Ventricular Systolic Pressure (LVSP), Left Ventricular End Diastolic Pressure (LVEDP), Left Ventricular Developed Pressure (LVDP), Heart Rate (HR), Rate Pressure Product (RPP), LVdp/dt(max/min) and Coronary Flow (CF). LVDP, RPP and CF were better conserved in the transgenic hearts to a statistical significant degree compared to the hearts of wild type littermates (p < 0.05).
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Figure 5: Summary of hemodynamic data from the isolated heart perfusion evaluation of control and p57Kip2 overexpressing mice (R26loxpTA-p57k/+;Mlc-2vCrek/+), at baseline and post ischemia/reperfusion (I/R). Left Ventricular Systolic Pressure (LVSP), Left Ventricular End Diastolic Pressure (LVEDP), Left Ventricular Developed Pressure (LVDP), Heart Rate (HR), Rate Pressure Product (RPP), LVdp/dt(max/min) and Coronary Flow (CF). LVDP, RPP and CF were better conserved in the transgenic hearts to a statistical significant degree compared to the hearts of wild type littermates (p < 0.05).

Mentions: After we characterized histologically the adult transgenic mice and demonstrated no differences in 3 months of age, we proceeded with the analysis of cardiovascular function. We studied age matched adult mice from the same cohort that covered the adult lifespan from 14–30 weeks, when the excitation-coupling mechanisms are known to remain constant [25]. To assess the contractile function of p57Kip2 overexpressing transgenic hearts, we utilized the Langendorff isolated perfused mouse heart preparation as previously described [26-28]. After 30 minutes of stabilization baseline functional data were obtained and the hearts were then subjected to a protocol of 30 minutes global ischemia followed by 30 minutes reperfusion. This protocol is based on our experience from previous studies [26-28]. In one of the experiments we assessed the myocardial necrotic area after staining with 10% 2,3,5-triphenyltetrazolium chloride (TTC) and we found that the area of necrotic tissue was reduced (20% vs. 37%) in the double transgenic heart compared with the control (Figure 4). The baseline functional parameters, including left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), LVdp/dt, rate pressure product (RPP) and heart rate (HR) were not significantly different between the different groups. However, after subjecting the hearts to 30 minutes of ischemia, the reperfused p57Kip2 expressing hearts exhibited significantly better preservation of cardiac function than the WT hearts. More specifically the transgenic hearts demonstrated higher left ventricular developed pressure (LVDP), rate pressure product (RPP) and coronary flow (CF) as assessed at the end of the reperfusion period (p ≤ 0.05, Figure 5; Table 2). The hemodynamic benefits were apparent from the onset of the reperfusion stage and were maintained throughout the 30 min period, suggesting that the protective effect of the p57Kip2 transgene may be manifest during the acute hypoxic phase and not restricted to the reperfusion phase of the injury.


Forced expression of the cell cycle inhibitor p57Kip2 in cardiomyocytes attenuates ischemia-reperfusion injury in the mouse heart.

Haley SA, Zhao T, Zou L, Klysik JE, Padbury JF, Kochilas LK - BMC Physiol. (2008)

Summary of hemodynamic data from the isolated heart perfusion evaluation of control and p57Kip2 overexpressing mice (R26loxpTA-p57k/+;Mlc-2vCrek/+), at baseline and post ischemia/reperfusion (I/R). Left Ventricular Systolic Pressure (LVSP), Left Ventricular End Diastolic Pressure (LVEDP), Left Ventricular Developed Pressure (LVDP), Heart Rate (HR), Rate Pressure Product (RPP), LVdp/dt(max/min) and Coronary Flow (CF). LVDP, RPP and CF were better conserved in the transgenic hearts to a statistical significant degree compared to the hearts of wild type littermates (p < 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2268709&req=5

Figure 5: Summary of hemodynamic data from the isolated heart perfusion evaluation of control and p57Kip2 overexpressing mice (R26loxpTA-p57k/+;Mlc-2vCrek/+), at baseline and post ischemia/reperfusion (I/R). Left Ventricular Systolic Pressure (LVSP), Left Ventricular End Diastolic Pressure (LVEDP), Left Ventricular Developed Pressure (LVDP), Heart Rate (HR), Rate Pressure Product (RPP), LVdp/dt(max/min) and Coronary Flow (CF). LVDP, RPP and CF were better conserved in the transgenic hearts to a statistical significant degree compared to the hearts of wild type littermates (p < 0.05).
Mentions: After we characterized histologically the adult transgenic mice and demonstrated no differences in 3 months of age, we proceeded with the analysis of cardiovascular function. We studied age matched adult mice from the same cohort that covered the adult lifespan from 14–30 weeks, when the excitation-coupling mechanisms are known to remain constant [25]. To assess the contractile function of p57Kip2 overexpressing transgenic hearts, we utilized the Langendorff isolated perfused mouse heart preparation as previously described [26-28]. After 30 minutes of stabilization baseline functional data were obtained and the hearts were then subjected to a protocol of 30 minutes global ischemia followed by 30 minutes reperfusion. This protocol is based on our experience from previous studies [26-28]. In one of the experiments we assessed the myocardial necrotic area after staining with 10% 2,3,5-triphenyltetrazolium chloride (TTC) and we found that the area of necrotic tissue was reduced (20% vs. 37%) in the double transgenic heart compared with the control (Figure 4). The baseline functional parameters, including left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), LVdp/dt, rate pressure product (RPP) and heart rate (HR) were not significantly different between the different groups. However, after subjecting the hearts to 30 minutes of ischemia, the reperfused p57Kip2 expressing hearts exhibited significantly better preservation of cardiac function than the WT hearts. More specifically the transgenic hearts demonstrated higher left ventricular developed pressure (LVDP), rate pressure product (RPP) and coronary flow (CF) as assessed at the end of the reperfusion period (p ≤ 0.05, Figure 5; Table 2). The hemodynamic benefits were apparent from the onset of the reperfusion stage and were maintained throughout the 30 min period, suggesting that the protective effect of the p57Kip2 transgene may be manifest during the acute hypoxic phase and not restricted to the reperfusion phase of the injury.

Bottom Line: Therefore, we hypothesized that p57Kip2 has a protective role in cardiomyocytes under hypoxic conditions.The baseline functional parameters, including left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), LVdp/dtmax, heart rate (HR) and rate pressure product (RPR) were not significantly different between the different groups as assessed by the Langendorff perfused heart preparation.However, after subjecting the heart ex vivo to 30 minutes of ischemia-reperfusion injury, the p57Kip2 overexpressing hearts demonstrated preserved cardiac function compared to control mice with higher left ventricular developed pressure (63 +/- 15 vs 30 +/- 6 mmHg, p = 0.05), rate pressure product (22.8 +/- 4.86 vs 10.4 +/- 2.1 x 103bpm x mmHg, p < 0.05) and coronary flow (3.5 +/- 0.5 vs 2.38 +/- 0.24 ml/min, p <0.05).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA. Sheila_Haley@brown.edu

ABSTRACT

Background: Myocardial hypoxic-ischemic injury is the cause of significant morbidity and mortality worldwide. The cardiomyocyte response to hypoxic-ischemic injury is known to include changes in cell cycle regulators. The cyclin-dependent kinase inhibitor p57Kip2 is involved in cell cycle control, differentiation, stress signaling and apoptosis. In contrast to other cyclin-dependent kinase inhibitors, p57Kip2 expression diminishes during postnatal life and is reactivated in the adult heart under conditions of cardiac stress. Overexpression of p57Kip2 has been previously shown to prevent apoptotic cell death in vitro by inhibiting stress-activated kinases. Therefore, we hypothesized that p57Kip2 has a protective role in cardiomyocytes under hypoxic conditions. To investigate this hypothesis, we created a transgenic mouse (R26loxpTA-p57k/+) that expresses p57Kip2 specifically in cardiac tissue under the ventricular cardiomyocyte promoter Mlc2v.

Results: Transgenic mice with cardiac specific overexpression of p57Kip2 are viable, fertile and normally active and their hearts are morphologically indistinguishable from the control hearts and have similar heart weight/body weight ratio. The baseline functional parameters, including left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), LVdp/dtmax, heart rate (HR) and rate pressure product (RPR) were not significantly different between the different groups as assessed by the Langendorff perfused heart preparation. However, after subjecting the heart ex vivo to 30 minutes of ischemia-reperfusion injury, the p57Kip2 overexpressing hearts demonstrated preserved cardiac function compared to control mice with higher left ventricular developed pressure (63 +/- 15 vs 30 +/- 6 mmHg, p = 0.05), rate pressure product (22.8 +/- 4.86 vs 10.4 +/- 2.1 x 103bpm x mmHg, p < 0.05) and coronary flow (3.5 +/- 0.5 vs 2.38 +/- 0.24 ml/min, p <0.05).

Conclusion: These data suggest that forced cardiac expression of p57Kip2 does not affect myocardial growth, differentiation and baseline function but attenuates injury from ischemia-reperfusion in the adult mouse heart.

Show MeSH
Related in: MedlinePlus