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Comparison of Gating Properties and Use-Dependent Block of Nav1.5 and Nav1.7 Channels by Anti-Arrhythmics Mexiletine and Lidocaine.

Wang Y, Mi J, Lu K, Lu Y, Wang K - PLoS ONE (2015)

Bottom Line: The recovery from inactivation of Nav1.5 or Nav1.7 was significantly prolonged by mexiletine compared to lidocaine.Taken together, our findings demonstrate differential responses to blockade by mexiletine and lidocaine that preferentially affect the gating of Nav1.5, as compared to Nav1.7; and mexiletine exhibits stronger use-dependent block of Nav1.5.The differential gating properties of Nav1.5 and Nav1.7 in response to mexiletine and lidocaine may help explain the drug effectiveness and advance in new designs of safe and specific sodium channel blockers for treatment of cardiac arrhythmia or pain.

View Article: PubMed Central - PubMed

Affiliation: Biomedical Research Institute, Shenzhen Peking University-Hong Kong University of Science and Technology Medical Center, Shenzhen 518036, China.

ABSTRACT
Mexiletine and lidocaine are widely used class IB anti-arrhythmic drugs that are considered to act by blocking voltage-gated open sodium currents for treatment of ventricular arrhythmias and relief of pain. To gain mechanistic insights into action of anti-arrhythmics, we characterized biophysical properties of Nav1.5 and Nav1.7 channels stably expressed in HEK293 cells and compared their use-dependent block in response to mexiletine and lidocaine using whole-cell patch clamp recordings. While the voltage-dependent activation of Nav1.5 or Nav1.7 was not affected by mexiletine and lidocaine, the steady-state fast and slow inactivation of Nav1.5 and Nav1.7 were significantly shifted to hyperpolarized direction by either mexiletine or lidocaine in dose-dependent manner. Both mexiletine and lidocaine enhanced the slow component of closed-state inactivation, with mexiletine exerting stronger inhibition on either Nav1.5 or Nav1.7. The recovery from inactivation of Nav1.5 or Nav1.7 was significantly prolonged by mexiletine compared to lidocaine. Furthermore, mexiletine displayed a pronounced and prominent use-dependent inhibition of Nav1.5 than lidocaine, but not Nav1.7 channels. Taken together, our findings demonstrate differential responses to blockade by mexiletine and lidocaine that preferentially affect the gating of Nav1.5, as compared to Nav1.7; and mexiletine exhibits stronger use-dependent block of Nav1.5. The differential gating properties of Nav1.5 and Nav1.7 in response to mexiletine and lidocaine may help explain the drug effectiveness and advance in new designs of safe and specific sodium channel blockers for treatment of cardiac arrhythmia or pain.

No MeSH data available.


Related in: MedlinePlus

Differential use-dependent inhibition of Nav1.5 and Nav1.7 by mexiletine and lidocaine.Cells were held at -120 mV and pulsed at -20 mV for three different frequencies (1, 5 and 10 Hz), with interpulse potential set at -120 mV. The peak currents elicited by each pulse were normalized to the current of first pulse and were plotted against the pulse number. Black symbols represent control condition without drugs, while red and blue symbols represent experiments in the presence of 0.3 mM mexiletine or 0.3 mM lidocaine, respectively. A and B, Nav1.5 and Nav1.7 were stimulated by a train of 60 pulses at 1 Hz and a train of 150 pulses at 5 Hz or 10 Hz in the presence and absence of 0.3 mM mexiletine or lidocaine, respectively. C, Bar graphs represent the relative amplitudes at the last sweep (60th or 150th) of use-dependent protocol for each frequency. Increasing the number of pulses resulted in current reduction for Nav1.5 in a frequency-dependent manner in the presence of mexiletine or lidocaine at 0.3 mM, whereas mexiletine showed a stronger use-dependent inhibition than lidocaine. In contrast, there is no difference in the inhibition of Nav1.7 at 5- and 10-Hz between mexiletine and lidocaine. Besides, the overall current reduction in Nav1.5 is more prominent than that of Nav1.7 due to the drug effects. Asterisk indicates the significance compared to drug-free (control) condition at each frequency by one-way ANOVA, ***p<0.001.
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pone.0128653.g006: Differential use-dependent inhibition of Nav1.5 and Nav1.7 by mexiletine and lidocaine.Cells were held at -120 mV and pulsed at -20 mV for three different frequencies (1, 5 and 10 Hz), with interpulse potential set at -120 mV. The peak currents elicited by each pulse were normalized to the current of first pulse and were plotted against the pulse number. Black symbols represent control condition without drugs, while red and blue symbols represent experiments in the presence of 0.3 mM mexiletine or 0.3 mM lidocaine, respectively. A and B, Nav1.5 and Nav1.7 were stimulated by a train of 60 pulses at 1 Hz and a train of 150 pulses at 5 Hz or 10 Hz in the presence and absence of 0.3 mM mexiletine or lidocaine, respectively. C, Bar graphs represent the relative amplitudes at the last sweep (60th or 150th) of use-dependent protocol for each frequency. Increasing the number of pulses resulted in current reduction for Nav1.5 in a frequency-dependent manner in the presence of mexiletine or lidocaine at 0.3 mM, whereas mexiletine showed a stronger use-dependent inhibition than lidocaine. In contrast, there is no difference in the inhibition of Nav1.7 at 5- and 10-Hz between mexiletine and lidocaine. Besides, the overall current reduction in Nav1.5 is more prominent than that of Nav1.7 due to the drug effects. Asterisk indicates the significance compared to drug-free (control) condition at each frequency by one-way ANOVA, ***p<0.001.

Mentions: The significant increase of slow inactivation in the presence of either mexiletine or lidocaine shows that some channels enter into a slow inactivated state during depolarization, thus resulting in accumulation of channels in a drug-modified state and leading to use/frequency-dependent inhibition. To test use-dependent inhibition of Nav1.5 or Nav1.7 by mexiletine and lidocaine, we applied a series of 60- or 150–50 ms short depolarizing pulses at -20 mV with different frequencies (1 Hz, 5 Hz and 10 Hz). In the absence of drugs, there was no discernable block of channel isoforms when stimulated at 1 Hz and also the currents at 5- and 10-Hz remained above 95% of their initial values (Fig 6A and 6B), indicating that tested channels were able to effectively cycle through the processes of the closed, open and inactivated conformations without obvious reduction in current amplitude.


Comparison of Gating Properties and Use-Dependent Block of Nav1.5 and Nav1.7 Channels by Anti-Arrhythmics Mexiletine and Lidocaine.

Wang Y, Mi J, Lu K, Lu Y, Wang K - PLoS ONE (2015)

Differential use-dependent inhibition of Nav1.5 and Nav1.7 by mexiletine and lidocaine.Cells were held at -120 mV and pulsed at -20 mV for three different frequencies (1, 5 and 10 Hz), with interpulse potential set at -120 mV. The peak currents elicited by each pulse were normalized to the current of first pulse and were plotted against the pulse number. Black symbols represent control condition without drugs, while red and blue symbols represent experiments in the presence of 0.3 mM mexiletine or 0.3 mM lidocaine, respectively. A and B, Nav1.5 and Nav1.7 were stimulated by a train of 60 pulses at 1 Hz and a train of 150 pulses at 5 Hz or 10 Hz in the presence and absence of 0.3 mM mexiletine or lidocaine, respectively. C, Bar graphs represent the relative amplitudes at the last sweep (60th or 150th) of use-dependent protocol for each frequency. Increasing the number of pulses resulted in current reduction for Nav1.5 in a frequency-dependent manner in the presence of mexiletine or lidocaine at 0.3 mM, whereas mexiletine showed a stronger use-dependent inhibition than lidocaine. In contrast, there is no difference in the inhibition of Nav1.7 at 5- and 10-Hz between mexiletine and lidocaine. Besides, the overall current reduction in Nav1.5 is more prominent than that of Nav1.7 due to the drug effects. Asterisk indicates the significance compared to drug-free (control) condition at each frequency by one-way ANOVA, ***p<0.001.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4465899&req=5

pone.0128653.g006: Differential use-dependent inhibition of Nav1.5 and Nav1.7 by mexiletine and lidocaine.Cells were held at -120 mV and pulsed at -20 mV for three different frequencies (1, 5 and 10 Hz), with interpulse potential set at -120 mV. The peak currents elicited by each pulse were normalized to the current of first pulse and were plotted against the pulse number. Black symbols represent control condition without drugs, while red and blue symbols represent experiments in the presence of 0.3 mM mexiletine or 0.3 mM lidocaine, respectively. A and B, Nav1.5 and Nav1.7 were stimulated by a train of 60 pulses at 1 Hz and a train of 150 pulses at 5 Hz or 10 Hz in the presence and absence of 0.3 mM mexiletine or lidocaine, respectively. C, Bar graphs represent the relative amplitudes at the last sweep (60th or 150th) of use-dependent protocol for each frequency. Increasing the number of pulses resulted in current reduction for Nav1.5 in a frequency-dependent manner in the presence of mexiletine or lidocaine at 0.3 mM, whereas mexiletine showed a stronger use-dependent inhibition than lidocaine. In contrast, there is no difference in the inhibition of Nav1.7 at 5- and 10-Hz between mexiletine and lidocaine. Besides, the overall current reduction in Nav1.5 is more prominent than that of Nav1.7 due to the drug effects. Asterisk indicates the significance compared to drug-free (control) condition at each frequency by one-way ANOVA, ***p<0.001.
Mentions: The significant increase of slow inactivation in the presence of either mexiletine or lidocaine shows that some channels enter into a slow inactivated state during depolarization, thus resulting in accumulation of channels in a drug-modified state and leading to use/frequency-dependent inhibition. To test use-dependent inhibition of Nav1.5 or Nav1.7 by mexiletine and lidocaine, we applied a series of 60- or 150–50 ms short depolarizing pulses at -20 mV with different frequencies (1 Hz, 5 Hz and 10 Hz). In the absence of drugs, there was no discernable block of channel isoforms when stimulated at 1 Hz and also the currents at 5- and 10-Hz remained above 95% of their initial values (Fig 6A and 6B), indicating that tested channels were able to effectively cycle through the processes of the closed, open and inactivated conformations without obvious reduction in current amplitude.

Bottom Line: The recovery from inactivation of Nav1.5 or Nav1.7 was significantly prolonged by mexiletine compared to lidocaine.Taken together, our findings demonstrate differential responses to blockade by mexiletine and lidocaine that preferentially affect the gating of Nav1.5, as compared to Nav1.7; and mexiletine exhibits stronger use-dependent block of Nav1.5.The differential gating properties of Nav1.5 and Nav1.7 in response to mexiletine and lidocaine may help explain the drug effectiveness and advance in new designs of safe and specific sodium channel blockers for treatment of cardiac arrhythmia or pain.

View Article: PubMed Central - PubMed

Affiliation: Biomedical Research Institute, Shenzhen Peking University-Hong Kong University of Science and Technology Medical Center, Shenzhen 518036, China.

ABSTRACT
Mexiletine and lidocaine are widely used class IB anti-arrhythmic drugs that are considered to act by blocking voltage-gated open sodium currents for treatment of ventricular arrhythmias and relief of pain. To gain mechanistic insights into action of anti-arrhythmics, we characterized biophysical properties of Nav1.5 and Nav1.7 channels stably expressed in HEK293 cells and compared their use-dependent block in response to mexiletine and lidocaine using whole-cell patch clamp recordings. While the voltage-dependent activation of Nav1.5 or Nav1.7 was not affected by mexiletine and lidocaine, the steady-state fast and slow inactivation of Nav1.5 and Nav1.7 were significantly shifted to hyperpolarized direction by either mexiletine or lidocaine in dose-dependent manner. Both mexiletine and lidocaine enhanced the slow component of closed-state inactivation, with mexiletine exerting stronger inhibition on either Nav1.5 or Nav1.7. The recovery from inactivation of Nav1.5 or Nav1.7 was significantly prolonged by mexiletine compared to lidocaine. Furthermore, mexiletine displayed a pronounced and prominent use-dependent inhibition of Nav1.5 than lidocaine, but not Nav1.7 channels. Taken together, our findings demonstrate differential responses to blockade by mexiletine and lidocaine that preferentially affect the gating of Nav1.5, as compared to Nav1.7; and mexiletine exhibits stronger use-dependent block of Nav1.5. The differential gating properties of Nav1.5 and Nav1.7 in response to mexiletine and lidocaine may help explain the drug effectiveness and advance in new designs of safe and specific sodium channel blockers for treatment of cardiac arrhythmia or pain.

No MeSH data available.


Related in: MedlinePlus