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Valsartan Upregulates Kir2.1 in Rats Suffering from Myocardial Infarction via Casein Kinase 2.

Li X, Hu H, Wang Y, Xue M, Li X, Cheng W, Xuan Y, Yin J, Yang N, Yan S - Cardiovasc Drugs Ther (2015)

Bottom Line: In vitro, hypoxia increased CK2 expression and valsartan inhibited CK2 expression.The over-expression of CK2 in cells treated with valsartan abrogated its beneficial effect on KCNJ2/Kir2.1.AT1 receptor antagonist valsartan reduces CK2 activation, increases Kir2.1 expression and thereby ameliorates IK1 remodeling after MI in the rat model.

View Article: PubMed Central - PubMed

Affiliation: School of Medicine, Shandong University, Ji'nan, Shandong, China.

ABSTRACT

Purpose: Myocardial infarction (MI) results in an increased susceptibility to ventricular arrhythmias, due in part to decreased inward-rectifier K+ current (IK1), which is mediated primarily by the Kir2.1 protein. The use of renin-angiotensin-aldosterone system antagonists is associated with a reduced incidence of ventricular arrhythmias. Casein kinase 2 (CK2) binds and phosphorylates SP1, a transcription factor of KCNJ2 that encodes Kir2.1. Whether valsartan represses CK2 activation to ameliorate IK1 remodeling following MI remains unclear.

Methods: Wistar rats suffering from MI received either valsartan or saline for 7 days. The protein levels of CK2 and Kir2.1 were each detected via a Western blot analysis. The mRNA levels of CK2 and Kir2.1 were each examined via quantitative real-time PCR.

Results: CK2 expression was higher at the infarct border; and was accompanied by a depressed IK1/Kir2.1 protein level. Additionally, CK2 overexpression suppressed KCNJ2/Kir2.1 expression. By contrast, CK2 inhibition enhanced KCNJ2/Kir2.1 expression, establishing that CK2 regulates KCNJ2 expression. Among the rats suffering from MI, valsartan reduced CK2 expression and increased Kir2.1 expression compared with the rats that received saline treatment. In vitro, hypoxia increased CK2 expression and valsartan inhibited CK2 expression. The over-expression of CK2 in cells treated with valsartan abrogated its beneficial effect on KCNJ2/Kir2.1.

Conclusions: AT1 receptor antagonist valsartan reduces CK2 activation, increases Kir2.1 expression and thereby ameliorates IK1 remodeling after MI in the rat model.

No MeSH data available.


Related in: MedlinePlus

The regulation of Kir2.1 expression by CK2. a A qPCR analysis and a Western blot analysis demonstrating the CK2 level after transfection (n = 10) and inhibition by TBB (n = 10) and the effects of CK2 (n = 10) and its inhibition (TBB; n = 10) on Kir2.1 protein expression in H9c2 rat ventricular cells. *P < 0.05 vs. control; †P < 0.05 vs. CK2 alone. b IK1 density in cultured neonatal rat ventricular cardiomyocytes. IK1 was elicited by 200-ms pulses at the indicated voltages. *P < 0.05 vs. control; n = 10/group. c Autoradiograms and the EMSA quantification of Sp1 DNA-binding activity in H9c2 rat ventricular cells. The data are the fold values of DNA-binding activity in the CK2 + TBB group compared with the CK2 group. *P < 0.05 vs. control; †P < 0.05 vs. CK2 alone; n = 10/group. Values are means ± SDs
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Fig3: The regulation of Kir2.1 expression by CK2. a A qPCR analysis and a Western blot analysis demonstrating the CK2 level after transfection (n = 10) and inhibition by TBB (n = 10) and the effects of CK2 (n = 10) and its inhibition (TBB; n = 10) on Kir2.1 protein expression in H9c2 rat ventricular cells. *P < 0.05 vs. control; †P < 0.05 vs. CK2 alone. b IK1 density in cultured neonatal rat ventricular cardiomyocytes. IK1 was elicited by 200-ms pulses at the indicated voltages. *P < 0.05 vs. control; n = 10/group. c Autoradiograms and the EMSA quantification of Sp1 DNA-binding activity in H9c2 rat ventricular cells. The data are the fold values of DNA-binding activity in the CK2 + TBB group compared with the CK2 group. *P < 0.05 vs. control; †P < 0.05 vs. CK2 alone; n = 10/group. Values are means ± SDs

Mentions: Adding CK2 inhibitor TBB after the transfection of CK2 into either H9c2 cells or rat primary ventricular cells produced a marked inhibition of CK2 activity (Fig. 3a). Kir2.1 protein expression is significantly downregulated compared with the sham-treated control cells after the transfection of CK2 . And this repression was efficiently rescued by suppressing CK2 activity with TBB (100 μM) (Fig. 3a). KCNJ2 mRNA expression was also decreased by CK2 (Fig. 3a). We subsequently verified the effects of CK2 at the functional level. IK1 was determined in neonatal rat ventricular cells using whole-cell patch-clamp techniques. The cells transfected with CK2 had a lower IK1 density than the control cells, and the difference was eliminated by adding TBB or valsartan (Fig. 3b). The regulation of the KCNJ2 gene by CK2 was confirmed via an EMSA, which indicated that CK2 phosphorylates Sp1 to suppress KCNJ2 expression, and the CK2 inhibitor, TBB, eliminates this effect (Fig. 3c).Fig. 3


Valsartan Upregulates Kir2.1 in Rats Suffering from Myocardial Infarction via Casein Kinase 2.

Li X, Hu H, Wang Y, Xue M, Li X, Cheng W, Xuan Y, Yin J, Yang N, Yan S - Cardiovasc Drugs Ther (2015)

The regulation of Kir2.1 expression by CK2. a A qPCR analysis and a Western blot analysis demonstrating the CK2 level after transfection (n = 10) and inhibition by TBB (n = 10) and the effects of CK2 (n = 10) and its inhibition (TBB; n = 10) on Kir2.1 protein expression in H9c2 rat ventricular cells. *P < 0.05 vs. control; †P < 0.05 vs. CK2 alone. b IK1 density in cultured neonatal rat ventricular cardiomyocytes. IK1 was elicited by 200-ms pulses at the indicated voltages. *P < 0.05 vs. control; n = 10/group. c Autoradiograms and the EMSA quantification of Sp1 DNA-binding activity in H9c2 rat ventricular cells. The data are the fold values of DNA-binding activity in the CK2 + TBB group compared with the CK2 group. *P < 0.05 vs. control; †P < 0.05 vs. CK2 alone; n = 10/group. Values are means ± SDs
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Related In: Results  -  Collection

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Fig3: The regulation of Kir2.1 expression by CK2. a A qPCR analysis and a Western blot analysis demonstrating the CK2 level after transfection (n = 10) and inhibition by TBB (n = 10) and the effects of CK2 (n = 10) and its inhibition (TBB; n = 10) on Kir2.1 protein expression in H9c2 rat ventricular cells. *P < 0.05 vs. control; †P < 0.05 vs. CK2 alone. b IK1 density in cultured neonatal rat ventricular cardiomyocytes. IK1 was elicited by 200-ms pulses at the indicated voltages. *P < 0.05 vs. control; n = 10/group. c Autoradiograms and the EMSA quantification of Sp1 DNA-binding activity in H9c2 rat ventricular cells. The data are the fold values of DNA-binding activity in the CK2 + TBB group compared with the CK2 group. *P < 0.05 vs. control; †P < 0.05 vs. CK2 alone; n = 10/group. Values are means ± SDs
Mentions: Adding CK2 inhibitor TBB after the transfection of CK2 into either H9c2 cells or rat primary ventricular cells produced a marked inhibition of CK2 activity (Fig. 3a). Kir2.1 protein expression is significantly downregulated compared with the sham-treated control cells after the transfection of CK2 . And this repression was efficiently rescued by suppressing CK2 activity with TBB (100 μM) (Fig. 3a). KCNJ2 mRNA expression was also decreased by CK2 (Fig. 3a). We subsequently verified the effects of CK2 at the functional level. IK1 was determined in neonatal rat ventricular cells using whole-cell patch-clamp techniques. The cells transfected with CK2 had a lower IK1 density than the control cells, and the difference was eliminated by adding TBB or valsartan (Fig. 3b). The regulation of the KCNJ2 gene by CK2 was confirmed via an EMSA, which indicated that CK2 phosphorylates Sp1 to suppress KCNJ2 expression, and the CK2 inhibitor, TBB, eliminates this effect (Fig. 3c).Fig. 3

Bottom Line: In vitro, hypoxia increased CK2 expression and valsartan inhibited CK2 expression.The over-expression of CK2 in cells treated with valsartan abrogated its beneficial effect on KCNJ2/Kir2.1.AT1 receptor antagonist valsartan reduces CK2 activation, increases Kir2.1 expression and thereby ameliorates IK1 remodeling after MI in the rat model.

View Article: PubMed Central - PubMed

Affiliation: School of Medicine, Shandong University, Ji'nan, Shandong, China.

ABSTRACT

Purpose: Myocardial infarction (MI) results in an increased susceptibility to ventricular arrhythmias, due in part to decreased inward-rectifier K+ current (IK1), which is mediated primarily by the Kir2.1 protein. The use of renin-angiotensin-aldosterone system antagonists is associated with a reduced incidence of ventricular arrhythmias. Casein kinase 2 (CK2) binds and phosphorylates SP1, a transcription factor of KCNJ2 that encodes Kir2.1. Whether valsartan represses CK2 activation to ameliorate IK1 remodeling following MI remains unclear.

Methods: Wistar rats suffering from MI received either valsartan or saline for 7 days. The protein levels of CK2 and Kir2.1 were each detected via a Western blot analysis. The mRNA levels of CK2 and Kir2.1 were each examined via quantitative real-time PCR.

Results: CK2 expression was higher at the infarct border; and was accompanied by a depressed IK1/Kir2.1 protein level. Additionally, CK2 overexpression suppressed KCNJ2/Kir2.1 expression. By contrast, CK2 inhibition enhanced KCNJ2/Kir2.1 expression, establishing that CK2 regulates KCNJ2 expression. Among the rats suffering from MI, valsartan reduced CK2 expression and increased Kir2.1 expression compared with the rats that received saline treatment. In vitro, hypoxia increased CK2 expression and valsartan inhibited CK2 expression. The over-expression of CK2 in cells treated with valsartan abrogated its beneficial effect on KCNJ2/Kir2.1.

Conclusions: AT1 receptor antagonist valsartan reduces CK2 activation, increases Kir2.1 expression and thereby ameliorates IK1 remodeling after MI in the rat model.

No MeSH data available.


Related in: MedlinePlus