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Synthesis and characterisation of NS13558: a new important tool for addressing KCa1.1 channel function ex vivo
Bo Hjorth Bentzen1, Rune Wederkinck Andersen, Søren-Peter Olesen
1Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark.
Abstract:
Pharmacological activation of the large-conductance Ca(2+)-activated K(+) channel (KCa1.1) in the cardiac inner mitochondrial membrane has been found to protect the heart against ischemia reperfusion injuries. However, there are concerns about the selectivity of the pharmacological tools used to modulate the channel. Here, we address this issue by synthesising a methylated analogue of the tool KCa1.1 channel activator NS11021. The compound (NS13558) is designed as a structurally closely related and biologically inactive analogue of NS11021. NS13558 did not elicit any significant opening of cloned human KCa1.1 channels, but maintained comparable biological activity towards other cardiac ion channels as compared to NS11021. In isolated perfused rat hearts subjected to ischemia-reperfusion, infarct size was reduced from 29% in control to 7% in NS11021 treated hearts. In comparison, the inactive derivate of NS11021, i.e., NS13558, did not confer any cardioprotection, demonstrated by an infarct size identical to control hearts. This suggests that NS11021 exerts its primary effect through KCa1.1 channels, which indicates an important role of these channels in protection against ischemia-reperfusion injuries. Furthermore, the study demonstrates a novel way of combining an activator of the KCa1.1 channel (NS11021) and its structurally closely related inactive analogue NS13558 to address the functional role of KCa1.1 channels, and we believe these novel tools may constitute a valuable addition to understanding the functional role of KCa1.1 channels under physiological and pathophysiological conditions.
Insights
Pharmacological activation of the large-conductance Ca(2+)-activated K(+) channel (KCa1.1) protects the heart from injury. A new inactive analogue confirms KCa1.1 channels are key to this cardioprotection.
Area of Science:
- Cardiovascular Research
- Pharmacology
- Mitochondrial Physiology
Background:
- The large-conductance Ca(2+)-activated K(+) channel (KCa1.1) in cardiac mitochondria is a target for cardioprotection against ischemia-reperfusion injury.
- Concerns exist regarding the selectivity of pharmacological activators like NS11021.
- Developing selective tools is crucial for understanding KCa1.1 channel function.
Purpose of the Study:
- To synthesize and validate a structurally related, biologically inactive analogue of NS11021 (NS13558) to assess the selectivity of KCa1.1 channel activation.
- To confirm the role of KCa1.1 channels in mediating cardioprotection afforded by NS11021.
- To establish a novel methodological approach for investigating KCa1.1 channel function.
Main Methods:
- Synthesis of NS13558, a methylated analogue of NS11021.
- In vitro electrophysiology to assess KCa1.1 channel activity and off-target effects.
- In vivo studies using isolated perfused rat hearts subjected to ischemia-reperfusion injury.
Main Results:
- NS13558 showed no significant activation of cloned human KCa1.1 channels but retained comparable activity on other cardiac ion channels as NS11021.
- NS11021 significantly reduced infarct size in a rat model of ischemia-reperfusion (from 29% to 7%).
- NS13558 did not provide any cardioprotection, with infarct size remaining similar to controls.
Conclusions:
- NS11021 exerts its cardioprotective effects primarily through the activation of KCa1.1 channels.
- KCa1.1 channels play a critical role in mitigating ischemia-reperfusion injury.
- The combination of NS11021 and its inactive analogue NS13558 provides a valuable tool for studying KCa1.1 channel function in physiological and pathophysiological contexts.
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