Impact of Administration Time and Kv7 Subchannels on the Cardioprotective Efficacy of Kv7 Channel Inhibition

Abstract

Purpose

The mechanism of cardioprotection by Kv7.1–5 (KCNQ1-5) channels inhibition by XE991 is unclear. We examined the impact of administration time on the cardioprotective efficacy of XE991, the involvement of key pro-survival kinases, and the importance of the Kv7 subchannels.

Methods

Isolated perfused rat hearts were divided into five groups: 1) vehicle, 2) pre-, 3) post- or 4) pre- and post-ischemic administration of XE991 or 5) chromanol 293B (Kv7.1 inhibitor) followed by infarct size quantification. HL-1 cells undergoing simulated ischemia/reperfusion were exposed to either a) vehicle, b) pre-, c) per-, d) post-ischemic administration of XE991 or pre-, per- and post-ischemic administration of e) XE991, f) Chromanol 293B or g) HMR1556 (Kv7.1 inhibitor). HL-1 cell injury was evaluated by propidium iodide/Hoechst staining. Pro-survival kinase activation of Akt, Erk and STAT3 in XE991-mediated HL-1 cell protection was evaluated using phosphokinase inhibitors. Kv7 subtype expression was examined by RT-PCR and qPCR.

Results

XE991, but not Chromanol 293B, reduced infarct size and improved hemodynamic recovery in all isolated heart groups. XE991 protected HL-1 cells when administered during simulated ischemia. Minor activation of the survival kinases was observed in cells exposed to XE991 but pharmacological inhibition of kinase activation did not reduce XE991-mediated protection. Kv7 subchannels 1–5 were all present in rat hearts but predominately Kv7.1 and Kv7.4 were present in HL-1 cells and selective Kv7.1 did not reduce ischemia/reperfusion injury.

Conclusion

The cardioprotective efficacy of XE991 seems to depend on its presence during ischemia and early reperfusion and do not rely on RISK (p-Akt and p-Erk) and SAFE (p-STAT3) pathway activation. The protective effect of XE991 seems mainly mediated through the Kv7.4 subchannel.

Keywords:

• cardioprotection
• Kv7 channels
• myocardial ischemia reperfusion injury
• myocardial infarction

Acknowledgments

We thank Lisa Maria Røge for excellent technical assistance and dr. William C. Claycomb for kindly providing the HL-1 cells used in this study. Jan Hansen and Jacob Johnsen have shared first authorship, they contributed equally and appear in alphabetical order.

Abbreviations

AAR, area-at-risk; IR, ischemia and reperfusion; IPC, ischemic preconditioning; KH, Krebs–Henseleit; LVDP, left ventricular developed pressure; PI/Hoechst, propidium iodide and Hoechst staining; RT-PCR, reverse transcriptase; TTC, 2,3,5-triphenyltetrazoliumchloride.

Disclosure

The authors report no conflicts of interest in this work.