A Comparative Analysis of Bupivacaine and Ropivacaine Effects on Human Cardiac SCN5A Channels

Rational design, synthesis, and evaluation of novel polypharmacological compounds targeting NaV1.5, KV1.5, and K2P channels for atrial fibrillation

Atrial fibrillation (AF) involves electrical remodeling of the atria, with ion channels such as NaV1.5, KV1.5, and TASK-1 playing crucial roles. This study investigates acetamide-based compounds designed as multi-target inhibitors of these ion channels to address AF. Compound 6f emerged as the most potent in the series, demonstrating a strong inhibition of TASK-1 (IC50 ∼ 0.3 μM), a moderate inhibition of NaV1.5 (IC50 ∼ 21.2 μM) and a subtle inhibition of KV1.5 (IC50 ∼ 81.5 μM), alongside unexpected activation of TASK-4 (∼ 40% at 100 μM). Functional assays on human atrial cardiomyocytes from sinus rhythm (SR) and patients with AF revealed that 6f reduced action potential amplitude in SR (indicating NaV1.5 block), while in AF it increased action potential duration (APD), reflecting high affinity for TASK-1. Additionally, 6f caused hyperpolarization of the resting membrane potential in AF cardiomyocytes, consistent with the observed TASK-4 activation. Mathematical modeling further validated its efficacy in reducing AF burden. Pharmacokinetic analyses suggest favorable absorption and low toxicity. These findings identify 6f as a promising multi-target therapeutic candidate for AF management.

Optical control of cardiac electrophysiology by the photochromic ligand azobupivacaine 2

BACKGROUND AND PURPOSE

Patients suffering from ischaemic heart disease and heart failure are at high risk of recurrent ventricular arrhythmias (VAs), eventually leading to sudden cardiac death. While high-voltage shocks delivered by an implantable defibrillator may prevent sudden cardiac death, these interventions themselves impair quality of life and raise both morbidity and mortality, which accentuates the need for developing novel defibrillation techniques.

EXPERIMENTAL APPROACH

Photopharmacology allows for reversible control of biological processes by light. When relying on synthetic and externally applied chromophores, it renders genetic modification of target cells dispensable and may hence be advantageous over optogenetic approaches. Here, the photochromic ligand azobupivacaine 2 (AB2) was probed as a modulator of cardiac electrophysiology in an ex vivo intact mouse heart model.

KEY RESULTS

By reversibly blocking voltage-gated Na+ and K+ channels, photoswitching of AB2 modulated both the ventricular effective refractory period and the conduction velocity in native heart tissue. Moreover, photoswitching of AB2 was able to convert VA into sinus rhythm.

CONCLUSION AND IMPLICATIONS

The present study provides the first proof of concept that AB2 enables gradual control of cardiac electrophysiology by light. AB2 may hence open the door to the development of an optical defibrillator based on photopharmacology.

Sodium bicarbonate reverts electrophysiologic cardiotoxicity of ropivacaine faster than lipid emulsions in a porcine model

Ropivacaine has been described as a safer local anaesthetic (LA); however, serious cardiotoxic accidents have been reported. Intravenous-lipid-emulsion (ILE) therapy during LA intoxication seems to act as an antidote. Sodium bicarbonate is the standard treatment for sodium channel blocker drug toxicity. We compared both antidotes on the reversion of electrophysiologic toxicity induced by ropivacaine. Ropivacaine 5 mg kg^-1 was administered in 24 pigs, and 3 min later, the animals received ILE: 1.5 ml kg^-1  + 0.25 ml kg^-1  min^-1 (ILE group); sodium bicarbonate: 2 mEq kg^-1  + 1 mEq kg^-1  h^-1 (NaHCO₃ group); saline solution (CTL group). Electrophysiological parameters were evaluated for 30 min. The area under the curve (AUC) for the first 5 or 30 min was compared between groups. Ropivacaine induced a lengthening of the PR interval by 17% (P = 0.0001), His-ventricle-interval by 58% (P = 0.001), sinus QRS complex by 56% (P = 0.0001), paced QRS at 150 bpm by 257% (P = 0.0001), and at 120 bpm by 143% (P = 0.0001) in all groups. At 5 min after treatment, sinus QRS in the NaHCO₃ group was shorter than that in the CTL group (AUC_QRS5 , P = 0.003) or ILE group (AUC_QRS5 , P = 0.045). During the first minute, seven of the animals in the NaHCO₃ group vs. two in the ILE or 0 in the CTL group recovered more than 30% of the sinus QRS previously lengthened by ropivacaine (P = 0.003). Sodium bicarbonate reversed the electrophysiological toxicity of ropivacaine faster than ILE and control groups.

Novel insights on the encapsulation mechanism of PLGA terminal groups on ropivacaine

Currently, the influences of free terminal groups (hydroxyl, carboxyl and ester) of PLGA on encapsulating active pharmaceutical ingredient are relatively ambiguous even though PLGA types were defined as critical quality attributes in vast majority of design of experiment process. In this study, emulsion method combined with premix membrane emulsification technique has been used to encapsulate ropivacaine (RVC), a small molecule local anesthetic in clinical. Based on the narrow particle size distribution, the influences and mechanisms of the terminal groups on properties of ropivacaine loaded microspheres have been investigated in detail. It was found that microspheres prepared by PLGA with hydroxyl or ester groups exhibited lower encapsulation efficiency but faster in vitro release rate than that of carboxyl groups. In the meanwhile, on microcosmic level analysis by quartz crystal microbalance with dissipation, atomic force microscope and confocal laser scanning microscopy, we attributed this distinction to the specific interaction between ropivacaine and different terminal groups. Subsequently, the reaction activation centers were verified by density functional simulation calculation and frontier molecular orbital theory at molecular level. Additionally, pharmacokinetics and pharmacodynamic research of infiltration anesthesia model were performed to compare sustained release ability, duration and intensity of the anesthetic effect in vivo. Finally, potential safety and toxicity were evaluated by the biochemical analysis. This study not only provides a novel mechanism of drug encapsulation process but also potential flexible selections in terms of various anesthesia indications in clinical.

In Vitro Negative Inotropic Effect of Low Concentrations of Bupivacaine Relates to Diminished Ca2+ Sensitivity but Not to Ca2+ Handling or β-Adrenoceptor Signaling

BACKGROUND

Systemic toxicity of local anesthetics is predominantly complicated by their myocardial toxicity. Especially long-acting local anesthetics exert a negative inotropic effect that has been described at lower concentrations than defined for blockade of myocardial ion channels. We evaluated the negative inotropic effect of bupivacaine at a concentration described for clinical toxicity testing the hypothesis that negative inotropy is a result of reduced Ca sensitivity rather than blockade of ion channels.

METHODS

We simultaneously measured force development and action potentials in guinea pig right papillary muscles (n = 5 to 7). L-type Ca currents (n = 8 to 16) and Ca transients (n = 10 to 11) were measured in isolated cardiomyocytes. Sensitivity of myofilaments to Ca was assessed in skinned fibers (n = 10). Potential effects of bupivacaine on 3',5'-cyclic adenosine monophosphate concentrations were measured using Förster Resonance Energy Transfer (n = 12 to 14) microscopy.

RESULTS

Bupivacaine reduced force in a concentration-dependent manner from 173 ± 119 µN at baseline to 28 ± 13 µN at 300 µM (mean ± SD). At concentrations giving half-maximum negative inotropic effects (5 µM), the maximum upstroke velocity of action potentials, as a surrogate of sodium channel activity, was unaffected. Maximum positive inotropic effects of isoprenaline were also reduced to 50%. Neither basal nor isoprenaline-induced 3',5'-cyclic adenosine monophosphate accumulation, L-type Ca currents, or Ca transients were affected by 5 µM bupivacaine, but this concentration significantly decreased Ca sensitivity of myofilaments, changing the negative logarithm of the half-maximum effective Ca concentrations from 5.66 to 5.56 -log[M].

CONCLUSIONS

We provide evidence that the negative inotropic effect of bupivacaine may be caused mainly by a reduction in myofilament sensitivity to Ca.

Potent Inactivation-Dependent Inhibition of Adult and Neonatal NaV1.5 Channels by Lidocaine and Levobupivacaine

BACKGROUND

Cardiotoxic effects of local anesthetics (LAs) involve inhibition of NaV1.5 voltage-gated Na channels. Metastatic breast and colon cancer cells also express NaV1.5, predominantly the neonatal splice variant (nNaV1.5) and their inhibition by LAs reduces invasion and migration. It may be advantageous to target cancer cells while sparing cardiac function through selective blockade of nNaV1.5 and/or by preferentially affecting inactivated NaV1.5, which predominate in cancer cells. We tested the hypotheses that lidocaine and levobupivacaine differentially affect (1) adult (aNaV1.5) and nNaV1.5 and (2) the resting and inactivated states of NaV1.5.

METHODS

The whole-cell voltage-clamp technique was used to evaluate the actions of lidocaine and levobupivacaine on recombinant NaV1.5 channels expressed in HEK-293 cells. Cells were transiently transfected with cDNAs encoding either aNaV1.5 or nNaV1.5. Voltage protocols were applied to determine depolarizing potentials that either activated or inactivated 50% of maximum conductance (V½ activation and V½ inactivation, respectively).

RESULTS

Lidocaine and levobupivacaine potently inhibited aNaV1.5 (IC50 mean [SD]: 20 [22] and 1 [0.6] μM, respectively) and nNaV1.5 (IC50 mean [SD]: 17 [10] and 3 [1.6] μM, respectively) at a holding potential of -80 mV. IC50s differed significantly between lidocaine and levobupivacaine with no influence of splice variant. Levobupivacaine induced a statistically significant depolarizing shift in the V½ activation for aNaV1.5 (mean [SD] from -32 [4.6] mV to -26 [8.1] mV) but had no effect on the voltage dependence of activation of nNaV1.5. Lidocaine had no effect on V½ activation of either variant but caused a significantly greater depression of maximum current mediated by nNaV1.5 compared to aNaV1.5. Similar statistically significant shifts in the V½ inactivation (approximately -10 mV) occurred for both LAs and NaV1.5 variants. Levobupivacaine (1 μM) caused a significantly greater slowing of recovery from inactivation of both variants than did lidocaine (10 μM). Both LAs caused approximately 50% tonic inhibition of aNaV1.5 or nNaV1.5 when holding at -80 mV. Neither LA caused tonic block at a holding potential of either -90 or -120 mV, voltages at which there was little steady-state inactivation. Higher concentrations of either lidocaine (300 μM) or levobupivacaine (100 μM) caused significantly more tonic block at -120 mV.

CONCLUSIONS

These data demonstrate that low concentrations of the LAs exhibit inactivation-dependent block of NaV1.5, which may provide a rationale for their use to safely inhibit migration and invasion by metastatic cancer cells without cardiotoxicity.

Anaesthetic management of C-section in Brugada syndrome: When less is more

Brugada Syndrome (BrS) is a rare and high risk condition, seldom encountered in the delivery room. Pregnant patients with BrS benefit from the lowest possible doses of arrhythmogenic drugs such as local anesthetics. Based on this premise, the following case report exposes how a subarachnoid approach might be a desirable technique in C-section procedures for BrS patients. Pain and anxiety management are priorities in this specific population. Peri-partum planning, with a previous anesthesiology appointment and mutidisciplinary care in tertiary hospital facilities are crucial to avoid complications.

Beta-adrenergic activation induces cardiac collapse by aggravating cardiomyocyte contractile dysfunction in bupivacaine intoxication

In order to determine the role of the adrenergic system in bupivacaine-induced cardiotoxicity, a series of experiments were performed. In an animal experiment, male Sprague-Dawley (SD) rats under chloral hydrate anesthesia received intravenous bupivacaine, followed by an intravenous injection of adrenalin or isoprenalin, and the electrocardiogram (ECG), left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), the maximum rate of rise of left ventricular pressure (+dP/dtmax) and the maximum rate of pressure decrease (-dP/dtmax) were continually monitored. In a cellular experiment, freshly isolated adult SD rat ventricular myocytes were perfused with bupivacaine at different concentrations in the presence or absence of isoprenalin, with or without esmolol. The percentage of the sarcomere shortening (bl% peak h), departure velocity (dep v) of sarcomere shortening and time to 50% of the peak speed of myocyte contraction (Tp50) was assessed by a video-based edge-detection system. In an additional experiment, Swiss mice pretreated with saline, isoprenalin, esmolol or dexmedetomidine received bupivacaine to determine the 50% lethal dose (LD50) of bupivacaine. Electron microscopy of myocardial mitochondria was performed to assess damage of these structures. To test mitochondrial reactive oxygen species (ROS) production, freshly isolated SD rat ventricular myocytes were incubated with bupivacaine in the presence of isoprenalin, with or without esmolol. First, our results showed that bupivacaine significantly reduced the LVSP and +dP/dtmax, as well as enhanced the LVEDP and -dP/dtmax (P < 0.05, vs. control, and vs. baseline). Adrenalin and isoprenalin induced a further reduction of LVSP and +dP/dtmax (P < 0.05, vs. before adrenalin or isoprenalin delivery, and vs. control). Second, bupivacaine induced a dose-dependent cardiomyocyte contractile depression. While 5.9 μmol/L or 8.9 μmol/L of bupivacaine resulted in no change, 30.0 μmol/L of bupivacaine prolonged the Tp50 and reduced the bl% peak h and dep v (P < 0.05, vs. control and vs. baseline). Isoprenalin aggravated the bupivacaine-induced cardiomyocyte contractile depression, significantly prolonging the Tp50 (P < 0.05, vs. bupivacaine alone) and reducing the dep v (P < 0.05, vs. bupivacaine alone). Third, esmolol and dexmedetomidine significantly enhanced, while isoprenalin significantly reduced, the LD50 of bupivacaine in mice. Fourth, bupivacaine led to significant mitochondrial swelling, and the extent of myocardial mitochondrial swelling in isoprenalin-pretreated mice was significantly higher than that compared with mice pretreated with saline, as reflected by the higher mitochondrial damage score (P < 0.01). Meanwhile, esmolol pretreatment significantly reduced the mitochondrial damage score (P < 0.01). Fifth, bupivacaine significantly increased the ROS in freshly isolated cardiomyocytes, and added isoprenalin induced a further enhancement of ROS production (P < 0.05, vs. bupivacaine alone). Added esmolol significantly decreased ROS production (P < 0.05, vs. bupivacaine + isoprenalin). Our results suggest that bupivacaine depressed cardiac automaticity, conductivity and contractility, but the predominant effect was contractile dysfunction which resulted from the disruption of mitochondrial energy metabolism. β-adrenergic activation aggravated the cellular metabolism disorder and therefore contractile dysfunction.

Cardiotoxic Antiemetics Metoclopramide and Domperidone Block Cardiac Voltage-Gated Na+ Channels

BACKGROUND

Metoclopramide and domperidone are prokinetic and antiemetic substances often used in clinical practice. Although domperidone has a more favorable side effect profile and is considered the first-line agent, severe cardiac side effects were reported during the administration of both substances. Cardiac Na channels are common targets of therapeutics inducing cardiotoxicity. Therefore, the aim of this study was to investigate whether the differential cardiotoxicities of metoclopramide and domperidone correlate with the block of Na channels.

METHODS

Effects of metoclopramide and domperidone on the human α-subunit Nav1.5 expressed in human embryonic kidney 293 cells and on Na currents in neonatal rat cardiomyocytes were investigated by means of whole-cell patch clamp recordings.

RESULTS

Tonic block of resting Nav1.5 channels was more potent for domperidone (IC50 85 ± 25 μM; 95% confidence interval [CI], 36-134) compared with metoclopramide (IC50 458 ± 28 μM; 95% CI, 403-513). Both agents induced use-dependent block at 10 and 1 Hz, stabilized fast and slow inactivation, and delayed recovery from inactivation. However, metoclopramide induced considerably smaller effects compared with domperidone. Na currents in rat cardiomyocytes displayed tonic and use-dependent block by both substances, and in this system, domperidone (IC50 312 ± 15 μM; 95% CI, 22-602) and metoclopramide (IC50 250 ± 30 μM; 95% CI, 191-309) induced a similar degree of tonic block.

CONCLUSIONS

Our data demonstrate that the clinically relevant cardiotoxicity of domperidone and metoclopramide corresponds to a rather potent and local anesthetic-like inhibition of cardiac Na channels including Nav1.5. These data suggest that Nav1.5 might be a hitherto unrecognized molecular mechanism of some cardiovascular side effects, for example, malignant arrhythmias of prokinetic and antiemetic agents.

Bupivacaine effectively relieves inflammation-induced pain by suppressing activation of the NF-κB signalling pathway and inhibiting the activation of spinal microglia and astrocytes

The pain induced by local acute inflammation results in mild to severe discomfort, in addition to the possibility of physiological dysfunction and psychiatric disorders, such as sleep disorders and depression. However, the pathogenesis of pain is yet to be fully elucidated. In the present study, the effects of bupivacaine were explored in rat models inflammatory pain in order to investigate the anti-pain mechanism of bupivacaine. Complete Freund's adjuvant (CFA) was injected into the right rear foot of the rats to establish a model of transient inflammation-induced pain. Rats were randomly divided into four groups (n=8): CFA, CFA plus bupivacaine, CFA plus saline and untreated. The mechanical withdrawal threshold (MWT) of the rats was detected prior to and following CFA injection, and the results demonstrated that the MWT in the right rear foot significantly decreased from the 1st day of CFA injection (P<0.01; n=8), as compared with the untreated controls. Bupivacaine treatment was demonstrated to significantly increase the MWT of rats treated with CFA stimulation, as compared with the CFA group (P<0.01). Rotarod testing was performed to assess the motor activity of the rats, and the results demonstrated no significant differences among the four groups (P>0.05). Furthermore, the respective body weights of the rats were determined every two days before and after CFA injection, and no significant differences were detected among the four groups (P>0.05). Western blot analysis was performed to analyze expression levels of IκB and nuclear factor (NF)-κB, and the results demonstrated that bupivacaine increased the expression of IκB and decreased the expression levels of NF-κB, as compared with the rats with CFA-induced inflammatory responses, suggesting that bupivacaine inhibited NF-κB activation in the dorsal horn of the lumbar spinal cord of the model rats. Furthermore, reverse transcription-quantitative polymerase chain reaction analysis was performed to analyze the expression levels of inflammatory cytokines, which demonstrated that bupivacaine significantly inhibited the expression of TNF-α, IL-1β and IL-6, as compared with the untreated group (P<0.01). Moreover, bupivacaine treatment significantly decreased the expression of spinal microglial marker OX42 and astrocyte marker-glial fibrillary acidic protein, as compared with the rats in the CFA group (P<0.01). The present findings demonstrated that treatment with bupivacaine significantly decreased the activation of microglia and astrocytes in rat models of inflammatory pain. Therefore, the present results may provide clarification of the pathogenesis and mechanism of inflammation-induced pain and may provide novel therapeutic strategies for the clinical treatment of pain.