Analyses of the onset mechanisms of cardio-stimulatory action by aciclovir

Cardio-stimulatory actions of aciclovir have been considered to primarily depend on the sympathetically-mediated reflex resulting from its hypotensive effect. To further clarify onset mechanisms of the cardio-stimulatory actions, we initially studied them using isoflurane-anesthetized dogs under thorough β1-adrenoceptor blockade with atenolol (1 mg/kg, i.v.) (n = 4). Aciclovir (20 mg/kg/10 min, i.v.) decreased mean arterial blood pressure by 10 mmHg, whereas it increased heart rate by 10 bpm and maximum upstroke velocity of ventricular pressure by 928 mmHg/s, and shortened AH interval by 2 ms, indicating that cardio-stimulatory actions were not totally abolished by β1-adrenoceptor blockade. Then, unknown mechanisms of cardio-stimulatory action were explored. Since aciclovir has a similar chemical structure to theophylline, in silico molecular docking simulation was performed, indicating aciclovir as well as theophylline possesses strong likelihood of interactions with phosphodiesterase 1A, 1C and 3A. Indeed, aciclovir inhibited phosphodiesterase 1A derived from the bovine heart (n = 4), moreover it exerted positive chronotropic action on the atrial tissue preparation of rats along with an increase of tissue cyclic AMP concentration (n = 4). These results indicate that cardio-stimulatory actions of aciclovir could result from not only hypotension-induced, reflex-mediated increase of sympathetic tone but also its inhibitory effects on phosphodiesterase in the heart.

Characterization of cardiovascular profile of anti-influenza drug peramivir: A reverse-translational study using the isoflurane-anesthetized dog

An injectable anti-influenza drug peramivir has been reported to induce QT-interval prolongation in some phase III studies, although its thorough QT/QTc study was negative. We investigated the discrepancy among those clinical studies using isoflurane-anesthetized beagle dogs (n = 4). Peramivir in doses of 1 mg/kg/10 min (sub-therapeutic dose) followed by 10 mg/kg/10 min (clinically-relevant dose) was intravenously administered. Peramivir prolonged QT interval/QTcV and Tpeak-Tend, and tended to delay ventricular repolarization in a reverse-frequency dependent manner, indicating IKr inhibition in vivo. Meanwhile, peramivir did not alter P-wave duration, PR interval or QRS width, indicating a lack of impact on cardiac conduction via Na+ or Ca2+ channel inhibition in vivo. Peramivir prolonged Tpeak-Tend and tended to prolong terminal repolarization period, which would develop substrates for initiating and maintaining spiral reentry, respectively. Meanwhile, peramivir did not prolong J-Tpeakc, which could not induce early afterdepolarization, a trigger inducing torsade de pointes. Thus, our results support that clinical dose exposure of peramivir can delay the ventricular repolarization in influenza patients. Peramivir has only a small potential to induce torsade de pointes in patients with the intact hearts, but caution should be paid on its use for patients formerly having the trigger for torsade de pointes.

INCIDENCE AND CHARACTERISTICS OF NEOVASCULAR AGE-RELATED MACULAR WITH OVER A 12-MONTH REMISSION AFTER THREE MONTHLY AFLIBERCEPT ADMINISTRATION: 60 Months Results of a Pro Re Nata Regimen

PURPOSE

To investigate the characteristics of patients with over a 12-month remission after 3 monthly intravitreal aflibercept injections followed by a pro re nata regimen for exudative age-related macular degeneration (AMD).

METHODS

One hundred forty-four eyes with exudative AMD were included. All patients received 3 monthly intravitreal aflibercept injections as a loading dose, followed by an as-needed regimen for 60 months. Patients were classified into the remission and recurrence groups depending on the presence or absence of a 12-month remission. ARMS2 A69S and CFH I62V were genotyped in all cases.

RESULTS

During the study, 82 eyes (56.9%) showed 12 months or more remission at least once. The cumulative incidence rate of a 12-month remission showed a plateau pattern and converged to 60% (y = -166.26x-2.172 + 0.6, R2 = 0.8168). Patients in the remission group were younger than those in the recurrence group (P < 0.001) and had less risk allele frequency of the ARMS2 gene than the recurrence group (P < 0.001). The longer the remission interval was prolonged, the better visual acuity was achieved at the 60-month visit (P < 0.001).

CONCLUSION

Fifty-seven percent of patients showed a 12-month remission or more at least once during a 60-month follow-up, suggesting that patients with no reactivation can prolong the treatment interval.

Excess heat production of the pair annihilation of ionic vacancies in a copper redox reaction using a double bipolar MHD electrode

Through a copper double bipolar magnetohydrodynamic (MHD) electrode (MHDE) producing twice the amounts of ionic vacancies than a conventional single MHDE, the molar excess heat of the pair annihilation of ionic vacancies, 702 kJ mol-1 at 10 T on average was obtained in a copper redox reaction. It was about twice as large as that of a single MHDE, 387 kJ mol-1 at the same magnetic field. This result strongly suggests that a multi-channel bipolar MHDE will produce much greater excess heat. To conserve the linear momentum and electric charge during electron transfer in an electrode reaction, ionic vacancies are created, storing the solvation energy in the polarized core of the order of 0.1 nm, and the pair annihilation of the vacancies with opposite charges liberates the energy as excess heat. The promoted excess heat by the double bipolar MHDE with a diffuser at 10 T was 710 ± 144 kJ mol-1, whereas as mentioned above, 702 ± 426 kJ mol-1 was obtained by the same electrode without such a diffuser. From the theoretical excess heat of 1140 kJ mol-1, the collision efficiencies in pair annihilation were 0.623 ± 0.126 and 0.616 ± 0.374, respectively. From these results, the reproducibility of the thermal measurement was experimentally validated. At the same time, it was concluded that at magnetic fields beyond 10 T, the concentration of ionic vacancy and the collision efficiency take constant uppermost values.

Characterization of electropharmacological profile of an anti-atrial fibrillatory drug vernakalant along with potential risk toward torsade de pointes: Translational studies using isoflurane-anesthetized dogs and isolated rat aortic preparations

We simultaneously assessed electropharmacological effects of anti-atrial fibrillatory drug vernakalant and its potential risk toward torsade de pointes. Vernakalant hydrochloride in doses of 0.3 and 3 mg/kg/10 min was intravenously administered to isoflurane-anesthetized beagle dogs without (n = 5) and with (n = 4) α-adrenoceptor blockade. Its vascular effect was analyzed using the rat aortae (n = 12). Vernakalant increased total peripheral vascular resistance and preload to left ventricle, leading to transient elevation of mean blood pressure indirectly via non-adrenergic pathway. Vernakalant suppressed sinus automaticity, ventricular contractility and intra-atrial/atrioventricular nodal/intraventricular conductions, and decreased cardiac output. Moreover, vernakalant prolonged atrial/ventricular effective refractory period by 53/55 ms, respectively, whereas it delayed ventricular repolarization in a reverse frequency-dependent manner. The extent of prolongation in early/late ventricular repolarization and electrically vulnerable period was 26/32 and 9 ms, respectively when QT-interval prolongation was the greatest. We compared them with those of known anti-atrial fibrillatory drugs; ranolazine, amiodarone, dronedarone, dl-sotalol and bepridil. The magnitude of vernakalant to alter those variables was the greater among those drugs except that the atrial selectivity was the lesser of those. Thus, vernakalant is expected to be efficacious against atrial fibrillation, but caution should be excised on its use for patients having labile ventricular function and repolarization.

Comparison of one-year outcomes between as-needed brolucizumab and aflibercept for polypoidal choroidal vasculopathy

PURPOSE

To compare the one-year visual and anatomic outcomes of an as-needed regimen of brolucizumab and aflibercept for polypoidal choroidal vasculopathy (PCV).

STUDY DESIGN

A retrospective comparative study.

METHODS

A retrospective medical chart review was performed for consecutive 56 eyes from 56 patients with PCV initially treated with thee monthly intravitreal aflibercept (n = 33, 2.0 mg/0.05 ml) or brolucizumab (n = 23, 6.0 mg/0.05 ml) followed by as-needed administration, followed up for at least 12 months. All patients were followed up monthly, and fluorescein and indocyanine green angiography (ICGA) were performed at baseline, 3-month, and 12-month visits.

RESULTS

At the 12-month visit, best-corrected visual acuity significantly improved from 0.30 ± 0.31 to 0.21 ± 0.29 (p = 0.042) in the brolucizumab-treated group and from 0.24 ± 0.25 to 0.14 ± 0.25 (p = 7.7×10^-3) in the aflibercept-treated group, suggesting comparable visual improvement in both groups. Central retinal thickness and subfoveal choroidal thickness decreased by 38.4% and 14.2%, respectively, in the brolucizumab-treated group and by 34.8% and 13.9%, respectively, in the aflibercept-treated group at the 12-month visit. The mean number of additional injections was significantly higher in the aflibercept-treated group (2.9 ± 2.7) than in the brolucizumab-treated group (1.3 ± 1.2, p = 0.045). The complete resolution of polypoidal lesions on ICGA was higher in the brolucizumab-treated group than in the aflibercept-treated group (3-month visit: 56.5% vs 30.3%, 12-month visit: 56.5% vs 30.3%).

CONCLUSIONS

In treatment-naïve eyes with PCV, the as-needed administration regimen of brolucizumab was comparable to aflibercept in terms of visual and anatomical outcomes, with fewer additional injections during the 12-month follow-up.

Electropharmacological Characterization of Licorice Using the Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes Sheets and the Chronic Atrioventricular Block Dogs

Licorice has been traditionally prescribed for palpitation, whereas its overdose has caused lethal arrhythmias including torsade de pointes. Licorice contains glycyrrhizic acid of ≥ 2% (w/w), which is hydrolyzed to glycyrrhetinic acid (GRA) in the intestine. Since their cardiac electropharmacological properties are not fully understood, we assessed them to ask mechanism of licorice-induced torsade de pointes. GRA at 0.1, 1 and 10 μg/mL was cumulatively applied to the human induced pluripotent stem cell-derived cardiomyocytes sheets (n = 6). GRA shortened spontaneous activation interval and repolarization period, and decreased maximum contraction velocity, indicating Ca²⁺ channel blockade. It prolonged effective refractory period and post-repolarization refractoriness with a steep frequency-dependency, whereas it delayed conduction with a modest use-dependency, resembling lidocaine in the mode of Na⁺ channel-blocking action. Meanwhile, Kanzoto containing a decoction of licorice alone in a dose of 2 or 6 g/body/day was orally administered to the conscious chronic atrioventricular block dogs for 3 days (n = 4). Kanzoto prolonged QT interval with increasing its temporal dispersion, suggesting K⁺ channel suppression, and slightly decreased the plasma K⁺ concentration without inducing torsade de pointes. Moreover, it significantly suppressed atrial and idioventricular rates, leading to sinus arrest along with the onset of ventricular fibrillation in one animal, possibly due to Na⁺ channel blockade. These results indicate that electropharmacological profile of licorice can be explained by Na⁺, Ca²⁺ and K⁺ channels blockade, which may be associated with low torsadogenic risk, but might contribute to the onset of other types of lethal ventricular arrhythmias.

A Treat-and-Extend Regimen of Intravitreal Brolucizumab for Exudative Age-Related Macular Degeneration Refractory to Aflibercept: A 12-Month Result

We aimed to investigate whether a treat-and-extend regimen of intravitreal brolucizumab (6.0 mg/0.05 mL) is effective for eyes with exudative age-related macular degeneration (AMD) refractory to aflibercept for 12 months. Sixty eyes from 56 patients receiving brolucizumab for exudative AMD refractory to aflibercept were included. Patients received a mean of 30.1 aflibercept administrations for a mean 67.9-month follow-up. All patients exhibited exudation on optical coherence tomography (OCT) despite regular 4-8 weeks of aflibercept administration. Visit 1 was scheduled at the same interval from the last aflibercept injection to the baseline. The treatment interval was extended or shortened by 1-2 weeks depending on the presence or absence of exudation on OCT. After switching to brolucizumab, the follow-up interval significantly extended at 12 months (before switching: 7.6 ± 3.8 weeks vs. at 12 months: 12.1 ± 6.2 weeks, p = 1.3 × 10^-7). Forty-three percent of the eyes achieved a dry macula at 12 months after switching. However, the best-corrected visual acuity did not improve at any visit. Morphologically, the central retinal thickness and subfoveal choroidal thickness significantly decreased from baseline at 12 months (p = 3.6 × 10^-3 and 1.0 × 10^-3, respectively). Switching to brolucizumab can be considered to extend the treatment interval in eyes with exudative AMD refractory to aflibercept.

Both osmolality-dependent and independent mechanisms are associated with acute hyperglycemia-induced cardiovascular adverse reactions: Analysis of the mutual interactions leading to cardiovascular phenotypes in dogs

Acute hyperglycemia causes various cardiovascular responses; however, the underlying pathophysiology in vivo is myriad and complex, of which mutual interactions remain poorly understood. We analyzed the cardiovascular effects of acute hyperglycemia in comparison with those of hyperosmolality alone. Three g/kg of D-glucose (n = 4) or D-mannitol (n = 4) was intravenously infused to isoflurane-anesthetized intact dogs. Glucose infusion increased plasma glucose level and osmolality, whereas mannitol infusion similarly changed osmolality to glucose infusion but decreased glucose level. Glucose infusion decreased total peripheral vascular resistance, but increased heart rate, left ventricular contraction, left ventricular preload and cardiac output without altering mean blood pressure. Mannitol infusion likewise changed them, but its positive chronotropic and inotropic effects were less potent than those of glucose infusion. Glucose infusion prolonged PR interval, QRS width and QTcV. Mannitol infusion similarly changed them, but its QTcV prolongation was smaller than that of glucose infusion. Glucose infusion-induced cardiovascular responses would be basically attributed to osmolality-dependent mechanisms, whereas its positive chronotropic and inotropic effects along with repolarization delay may be enhanced by osmolality-independent mechanisms, including hyperglycemia by itself and insulin release.

DISTINCT CHARACTERISTICS OF SIMPLE VERSUS COMPLEX CENTRAL SEROUS CHORIORETINOPATHY

PURPOSE

To compare the clinical and genetic characteristics of simple and complex central serous chorioretinopathy using central serous chorioretinopathy international group criteria.

METHODS

Patients with idiopathic central serous chorioretinopathy were included. Depending on the presence or absence of retinal pigment alterations greater than 2-disc areas in either eye, patients were classified into complex or simple types. Demographic factors and clinical findings were compared between groups. CFH variants, including rs800292 and rs1329428, were genotyped using TaqMan technology.

RESULTS

A total of 319 consecutive patients were evaluated at the initial presentation. Of them, 53 (16.6%) had the complex type. The complex type was exclusively seen in men (100% vs. 79.0%, P = 2.0 × 10 -4 ) and demonstrated a significantly higher proportion of bilateral involvement (75.5% vs. 17.7%, P = 6.2 × 10 -18 ) and descending tract(s) (83.0% vs. 0%, P = 1.2 × 10 -57 ) than the simple type. Increased choroidal thickness (425 ± 131 vs. 382 ± 110, P = 0.02) and decreased central retinal thickness (274 ± 151 vs. 337 ± 136, P = 2.9 × 10 -4 ) were observed for the complex versus simple type. The risk allele frequencies of both variants were significantly higher in the complex versus simple type (rs800292: 61.3% vs. 48.7%, P = 0.018; rs1329428: 65.1% vs. 54.3%, P = 0.04).

CONCLUSION

In this new classification system, the complex type has distinct genetic and clinical characteristics compared with the simple type.

Characterization of pathological remodeling in the chronic atrioventricular block cynomolgus monkey heart

We studied time course of pathological remodeling occurring in the cynomolgus monkey hearts against persistent atrioventricular block condition (n = 10). The atrioventricular block induced the ventricular and atrial dilation followed by the ventricular hypertrophy. Interstitial fibrosis in the ventricle was also observed along with gradual increases in the plasma angiotensin II and aldosterone concentrations. These adaptations were associated with the changes in gene expression profiling reflecting fibrosis and hypertrophy. Atrioventricular block reduced the ventricular rate and cardiac output, but the ejection fraction and stroke volume increased, whereas the cardiac output was gradually restored to its basal level. Systolic/diastolic blood pressure after the atrioventricular block was kept equal to or lower than that before the block, according with lack of increase in the plasma catecholamine levels. Chronic atrioventricular block gradually prolonged the QRS width and JT interval, leading to the QT interval prolongation in conscious state. 10 mg/kg of dl-sotalol hydrochloride induced torsade de pointes (TdP) in 6 out of 10 animals by 15 months. Animals showing longer QTcF under anesthesia after the atrioventricular block developed dl-sotalol-induced TdP earlier. No marked difference was observed in pharmacokinetics of dl-sotalol between 1 and 7 months after the atrioventricular block. Each TdP spontaneously terminated, reflecting a monkey's relatively small "effective size of the heart (=∛(left ventricular weight)/wavelength of reentry)". These fundamental knowledge will help better utilize the chronic atrioventricular block monkeys as an in vivo proarrhythmia model for detecting drug-induced TdP.

Cardiovascular safety pharmacology of ivermectin assessed using the isoflurane-anesthetized beagle dogs: ICH S7B follow-up study

Antiparasitic ivermectin has been reported to induce cardiovascular adverse events, including orthostatic hypotension, tachycardia and cardiopulmonary arrest, of which the underlying pathophysiology remains unknown. Since its drug repurposing as an antiviral agent is underway at higher doses than those for antiparasitic, we evaluated the cardiovascular safety pharmacology of ivermectin using isoflurane-anesthetized beagle dogs (n=4). Ivermectin in doses of 0.1 followed by 1 mg/kg was intravenously infused over 10 min with an interval of 20 min, attaining peak plasma concentrations of 0.94 ± 0.04 and 8.82 ± 1.25 μg/mL, which were 29-31 and 276-288 times higher than those observed after its antiparasitic oral dose of 12 mg/body, respectively. The latter peak concentration was > 2 times greater than those inhibiting proliferation of dengue virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and hepatitis B virus in vitro. Ivermectin decreased heart rate without altering mean blood pressure, suggesting that ivermectin does not cause hypotension or tachycardia directly. Ivermectin hardly altered atrioventricular nodal or intraventricular conduction, indicating a lack of inhibitory action on Ca2+ or Na+ channel in vivo. Ivermectin prolonged QT interval/QTcV in a dose-related manner and tended to slow the repolarization speed in a reverse frequency-dependent manner, supporting previously described its IKr inhibition, which would explain Tpeak-Tend prolongation and heart-rate reduction in this study. Meanwhile, ivermectin did not significantly prolong J-Tpeakc or terminal repolarization period, indicating torsadogenic potential of ivermectin leading to the onset of cardiopulmonary arrest would be small. Thus, ivermectin has a broad range of cardiovascular safety profiles, which will help facilitate its drug repurposing.

In vivo analysis of acute eletropharmacological effects of proton pump inhibitors using halothane-anesthetized dogs: a translational study of cardiovascular adverse events

Long-term use of proton pump inhibitors (PPIs) is known to clinically induce hypomagnesemia, increasing the risk toward QT-interval prolongation and lethal ventricular arrhythmias, whereas PPIs can directly modulate cardiac ionic currents in the in vitro experiments. In order to fill the gap between those information, we assessed acute cardiohemodynamic and electrophysiological effects of sub- to supra-therapeutic doses (0.05, 0.5 and 5 mg/kg/10 min) of typical PPIs omeprazole, lansoprazole and rabeprazole, using halothane-anesthetized dogs (n = 6 for each drug). The low and middle doses of omeprazole and lansoprazole increased or tended to increase the heart rate, cardiac output and ventricular contraction, whereas the high dose plateaued and decreased them. Meanwhile, the low and middle doses of omeprazole and lansoprazole decreased the total peripheral vascular resistance, whereas the high dose plateaued and increased it. Rabeprazole decreased the mean blood pressure in a dose-related manner; moreover, its high dose decreased the heart rate and tended to reduce the ventricular contractility. On the other hand, omeprazole prolonged the QRS width. Omeprazole and lansoprazole tended to prolong the QT interval and QTcV, and rabeprazole mildly but significantly prolonged them in a dose-related manner. High dose of each PPI prolonged the ventricular effective refractory period. Omeprazole shortened the terminal repolarization period, whereas lansoprazole and rabeprazole hardly altered it. In effects, PPIs can exert multifarious cardiohemodynamic and electrophysiological actions in vivo, including mild QT-interval prolongation; thus, PPIs should be given with caution to patients with reduced ventricular repolarization reserve.

Validation of risk-stratification method for the chronic atrioventricular block cynomolgus monkey model and its mechanistic interpretation using 6 drugs with pharmacologically-distinct profile

Validation of risk-stratification method for the chronic atrioventricular block cynomolgus monkey model and its mechanistic interpretation were performed using 6 pharmacologically-distinct drugs. The following drugs were orally administered in conscious state, astemizole: 1, 5 and 10 mg/kg (n = 6); haloperidol: 1, 10 and 30 mg/kg (n = 5); amiodarone: 30 mg/kg (n = 4); famotidine: 10 mg/kg (n = 4); levofloxacin: 100 mg/kg (n = 4); and tolterodine: 0.2, 1 and 4.5 mg/kg (n = 4). Astemizole of 5 and 10 mg/kg significantly prolonged ΔΔQTcF, whereas no significant change was observed by the others. Torsade de pointes (TdP) was induced by astemizole of 5 and 10 mg/kg in 3/6 and 6/6, and by haloperidol of 10 and 30 mg/kg in 1/5 and 1/5, respectively, which was not observed in the others. Torsadogenic risk of the drugs was quantified using the criteria for the monkey model specified in our previous study. Namely, high-risk drugs induced TdP at ≤ 3times of their maximum clinical daily dose. Intermediate-risk drugs did not induce TdP at this dose range, but induced it at higher doses. Low/no-risk drugs never induced TdP at any dose tested. The magnitude of risk was intermediate for astemizole and haloperidol, and low/no risk for the others. The pre-specified, risk-stratification method for the monkey model may solve the issue existing between non-clinical models and patients with labile repolarization, which can reinforce the regulatory decision-making and labelling at time of marketing application of non-double-negative drug candidate (hERG assay positive and/or in vivo QT study positive).

Distinct characteristics of central serous chorioretinopathy according to gender

To investigate the differences in clinical and genetic characteristics between males and females with central serous chorioretinopathy (CSC). Consecutive 302 patients (mean age; 56.3 ± 11.7, male/female: 249/53) with CSC were evaluated on the initial presentation. All CSC patients underwent fluorescein angiography and indocyanine green angiography (FA/ICGA), swept-source or spectral-domain optical coherence tomography (OCT), and fundus autofluorescence (FAF) to confirm a diagnosis. All patients were genotyped for rs800292 and rs1329428 variants of CFH using TaqMan technology. On the initial presentation, female patients were significantly older (p = 2.1 × 10^–4, female 61.6 ± 12.4 vs male 55.1 ± 11.3) and had thinner subfoveal choroidal thickness (p = 3.8 × 10^–5) and higher central retinal thickness (p = 3.0 × 10^–3) compared to males. A descending tract was more frequently seen in males than in females (p = 8.0 × 10^–4, 18.1% vs 0%). Other clinical characteristics were comparable between the sexes. The risk allele frequency of both variants including CFH rs800292 and CFH rs1329428 was comparable between males and females (CFH rs800292 A allele male 51.2% vs female 47.2%, CFH rs1329428 T allele male 56.2% vs 52.8%). On the initial presentation, age, subfoveal choroidal thickness and central retinal thickness differ between males and females in eyes with CSC. A descending tract may be a strong male finding in CSC.

Alteration in peritoneal cells with the chemokine CX3CL1 reverses age-associated impairment of recognition memory

Cognitive function progressively declines with advancing age. The aging process can be promoted by obesity and attenuated by exercise. Both conditions affect levels of the chemokine CX3CL1 in peripheral tissues; however, its role in cognitive aging is unknown. In the current study, we administered CX3CL1 into the peritoneal cavity of aged mice to investigate its impact on the aging process. In the peritoneal cavity, CX3CL1 not only reversed the age-associated accumulation of cells expressing the senescence marker p16^INK4a but also increased peritoneal phagocytic activity, indicating that CX3CL1 affected the phenotypes of peritoneal cells. In the hippocampus of aged mice, intraperitoneal administration of CX3CL1 increased the number of Type-2 neural stem cells and promoted brain-derived neurotrophic factor (BDNF) expression. This treatment, furthermore, improved novel object recognition memory impaired with advancing age. Intraperitoneal transplantation of peritoneal cells from CX3CL1-treated aged mice improved novel object recognition memory in recipient aged mice. It indicates that peritoneal cells have a critical role in the CX3CL1-induced improvement of recognition memory in aged mice. Vagotomy inhibited the CX3CL1-induced increase in BDNF expression, demonstrating that the vagus nerve is involved in the hippocampal BDNF expression induced by intraperitoneal administration of CX3CL1. Thus, our results demonstrate that a novel connection among the peritoneal cells, the vagus nerve, and the hippocampus can reverse the age-associated decline in recognition memory.

Radiographic characteristics of canine subungual keratoacanthoma

Subungual keratoacanthoma (SKA) is a rare benign nail bed tumor in dogs, and its radiographic characteristics have not been reported based on the authors' review of the literature. The purpose of this multicenter, retrospective, observational, descriptive study was to describe the radiographic features of SKA in dogs. Twelve dogs for a total of 12 digits with histologically confirmed SKA met the inclusion criteria. The radiographs of the manus or pes were reviewed by two veterinary radiologists and one veterinarian. The radiology reports were interpreted based on a consensus. In six dogs, there was lysis of both the middle phalanx (P2) and the distal phalanx (P3), whereas in the other six dogs, there was only lysis of P3. In all dogs with osteolysis of P2, the lysis involved the distal articular surface. Osteolysis of P3 was more severe in the ungual process than in the ungual crest in all dogs. The margins of the lytic regions of P2 and P3 were well defined and smoothly marginated in most dogs. Expansile changes in the P3 crest were observed in 83.3% (10/12 dogs), and the nail of the affected digit was enlarged and deformed in 91.6% (11/12 dogs). In summary, the radiographic features of canine SKA include severe pressure resorption of the P3 ungual process, expansile change of the P3 ungual crest, and nail enlargement and deformation. With these radiographic features, SKA should be considered as a differential diagnosis.

Incidence and risk of advanced age-related macular degeneration in eyes with drusenoid pigment epithelial detachment

To investigate the incidence and risk of advanced age-related macular degeneration (AMD), including geographic atrophy (GA) and macular neovascularization (MNV), in eyes with drusenoid pigment epithelial detachment (PED). Eighty-five eyes with drusenoid PED from 85 patients (77.2 ± 7.0 years, male/female: 44/41) were included in this study. Patients were followed up every 1–3 months via spectral-domain optical coherence tomography (SD-OCT) and color fundus photography. If exudation was observed on SD-OCT, fluorescein and indocyanine green angiography were performed to confirm the MNV subtype accordingly. The maximum follow-up period was 60 months. During the study period, GA developed in 8 eyes while MNV also developed in 8 eyes. The Kaplan–Meier estimator revealed that the cumulative incidence for 60 months was 17.9% and 12.2% for GA and MNV, respectively. In eyes developing MNV, retinal angiomatous proliferation was the most common. Cox regression analysis revealed that baseline PED width was the only factor associated with advanced AMD. (p = 0.0026, Cox regression analysis). The 5-year cumulative incidence of advanced AMD, including GA and MNV, was approximately 30% in eyes with drusenoid PED among the Japanese elderly. A larger baseline PED width was the only risk factor for advanced AMD.

Quantification and Clonal Culture of Neural Stem Cells from the Hippocampus of Adult Mouse

Visualizing markers for neural stem cells (NSCs) and morphological analysis are frequently used for identification of NSCs in tissues. However, NSCs are defined as cells with the ability to both self-renew and produce descendants that can differentiate into neurons, astrocytes and oligodendrocytes. The neural colony forming cell (NCFC) assay is a single-step semisolid based assay for the identification of NSCs. In this assay, NSCs generate clonally derived colonies due to their high proliferative potential. The relative comparison of NSC populations between tissues is possible by counting the colonies obtained from the NCSC assay. Furthermore, the colonies can be isolated to establish monolayer cultures of clonal NSCs. Using clonal cultures of NSCs, it is possible to assess differentiation stage and differentiation potential of each NSC. Here, we describe a semi quantitative method for the enumeration of NSCs using the NCFC assay, with slight modification from the original protocol (Louis et al., Stem Cells 26:988-996, 2008). A method to establish monolayer culture of NSCs from a colony derived from NCFC assay is also described.

Simultaneous analyses of hemodynamic and electrophysiological effects of oseltamivir along with its pharmacokinetic profile using the canine paroxysmal atrial fibrillation model

Since information of antiviral drug oseltamivir on the anti-atrial fibrillation (AF) property is still limited, we assessed it using the canine paroxysmal AF model. Oseltamivir in doses of 3 and 30 mg/kg/10 min was intravenously infused to the isoflurane-anesthetized, chronic atrioventricular block dogs (n = 6) with monitoring hemodynamic and electrophysiological variables, in which AF was induced by 10 s of burst pacing on atrial septum. Oseltamivir decreased AF incidence and AF duration, and prolonged AF cycle length in a dose-dependent manner. The low and high doses attained the peak plasma drug concentrations of 9.7 and 96.5 μg/mL, which were approximately 100 and 1000 times greater than those observed in human clinical cases, respectively. The low dose of oseltamivir decreased mean blood pressure without altering sinoatrial or idioventricular rate, whereas its high dose reduced each of them. Oseltamivir delayed inter-atrial conduction in dose- and frequency-dependent manners, whereas it prolonged atrial effective refractory period in dose-dependent but frequency-independent manners. The high dose prolonged ventricular effective refractory period, which was not detected with the low dose. These findings can be used for repurposing oseltamivir as an anti-AF drug candidate.

Effects of Cardiac Massage and β-Blocker Pretreatment on the Success Rate of Cardiopulmonary Resuscitation Assessed by the Canine Ischemia/Reperfusion-Induced Ventricular Fibrillation Model

BACKGROUND

Effects of rapid electrical defibrillation and β-blockade on coronary ischemia/reperfusion-induced ventricular fibrillation (VF) during cardiopulmonary resuscitation (CPR) remain unknown.Methods and Results:After induction of VF by 30 min of ischemia followed by reperfusion, animals were treated with defibrillation alone (Group A, n=13), 2 min of open-chest cardiac massage followed by defibrillation (Group B, n=11), or the same therapy to Group B with propranolol (1 mg/kg, i.v.) treatment before ischemia/reperfusion (Group C, n=11). If return of spontaneous circulation (ROSC) was not attained, each therapy was repeated ≤3 times (Set-1). When ROSC was not obtained within Set-1, cardiac massage was applied to all animals followed by defibrillation, which was repeated ≤3 times (Set-2). ROSC after Set-1 was 8% in Group A, 82% in Group B and 82% in Group C, whereas that after Set-2 was 62% in Group A, 100% in Group B and 82% in Group C. Each animal with ROSC in Groups A (n=8) and B (n=11) showed sinus rhythm, whereas those in Group C (n=9) had sinus rhythm (n=5), atrial fibrillation (n=1), accelerated idioventricular rhythm (n=2) and atrioventricular block (n=1). Post ROSC heart rate and mean arterial pressure were significantly lower in Group C.

CONCLUSIONS

Cardiac massage increased the likelihood of ROSC vs. rapid defibrillation, but β-blocker pretreatment may worsen hemodynamics and electrical stability after ROSC.

Comparison of Outcomes between 3 Monthly Brolucizumab and Aflibercept Injections for Polypoidal Choroidal Vasculopathy

We compared the short-term outcomes between 3-monthly aflibercept and brolucizumab injections for treatment-naïve polypoidal choroidal vasculopathy (PCV). A total of 52 eyes were included. Patients received 3 monthly intravitreal aflibercept (n = 38) or intravitreal brolucizumab (n = 14). Indocyanine green angiography (ICGA) was performed at baseline and at the 3-month visit. Selection of anti-VEGF agents depended on time. In the brolucizumab-treated group, best-corrected visual acuity (BCVA) improved from 0.27 ± 0.34 (log MAR unit) at baseline to 0.20 ± 0.24 at 3-month visit, which is comparable with the aflibercept-treated group (p = 0.87), after adjustment of confounding factors. Central retinal thickness significantly decreased by 43%−44% in both groups. Subfoveal choroidal thickness also significantly decreased by 20.5% during this interval in the brolucizumab-treated group, which was greater than the aflibercept-treated group. The complete resolution rate of polypoidal lesions on ICGA was significantly higher (p = 0.043) in the brolucizumab-treated group (78.6%) than in the aflibercept-treated group (42.1%). Intraocular inflammation was observed in 14.3% (2/14) in the brolucizumab-treated group only. In short-term follow-up, intravitreal injection of 3-monthly brolucizumab was comparable with aflibercept in terms of BCVA and morphological improvement along with higher resolution of polypoidal lesion(s) on ICGA.

Torsadogenic Action of Cisapride, dl-Sotalol, Bepridil, and Verapamil Analyzed by the Chronic Atrioventricular Block Cynomolgus Monkeys: Comparison With That Reported in the CiPA In Silico Mechanistic Model

In order to bridge the gap of information between the in silico model and human subjects, we evaluated torsadogenic risk of cisapride, dl-sotalol, bepridil and verapamil selected from 12 training compounds in the comprehensive in vitro proarrhythmia assay using the chronic atrioventricular block monkeys. Cisapride (0, 1, and 5 mg/kg, n = 5 for each dose), dl-sotalol (0, 1, 3, and 10 mg/kg, n = 5 for each dose), bepridil (0, 10, and 100 mg/kg, n = 4 for each dose), verapamil (0, 1.5, 15, and 75 mg/kg, n = 4 for each dose) were orally administered to the monkeys in conscious state. Five mg/kg of cisapride, 1, 3, and 10 mg/kg of dl-sotalol and 100 mg/kg of bepridil prolonged ΔΔQTcF, which was not observed by verapamil. Torsade de pointes was induced by 5 mg/kg of cisapride in 2 out of 5 animals, by 10 mg/kg of dl-sotalol in 5 out of 5 and by 100 mg/kg of bepridil in 2 out of 4, which was not induced by verapamil. These torsadogenic doses were normalized by their maximum clinical daily ones to estimate torsadogenic risk. The order of risk was dl-sotalol >bepridil ≥cisapride >verapamil in our study. Since the order was bepridil ≥dl-sotalol >cisapride >verapamil in comprehensive in vitro proarrhythmia assay (CiPA) in silico mechanistic model validation, sympathetic regulation on the heart may play a pivotal role in the onset of torsade de pointes in vivo.

Long-term prognosis of polypoidal choroidal vasculopathy with a 5-year remission after an initial combination therapy

PURPOSE

To investigate the visual prognosis of patients with polypoidal choroidal vasculopathy (PCV) with a 5-year remission after an initial combination therapy involving photodynamic therapy (PDT) and intravitreal ranibizumab (IVR) or aflibercept injection (IVA).

METHODS

Medical records of 69 consecutive patients with PCV treated with PDT with IVR/IVA were retrospectively reviewed, and 17 eyes were identified with a 5-year remission after the initial combination therapy. The eyes that did not require additional treatment during the 1^st-5^th year were assigned to the remission group and the eyes requiring additional treatment during the 1^st-5^th year were assigned to the recurrence group.

RESULTS

During the 7-year follow-up, the mean logarithm of the minimal angle resolution best-corrected visual acuity (logMAR BCVA) significantly improved from 0.39±0.27 to 0.17±0.38 (p=2.9 × 10^-4) in the remission group, whereas the mean logMAR BCVA was maintained throughout the follow-up period (0.58±0.27 to 0.60±0.48) in the recurrence group. In the remission group, only two (11.8%) of the 17 eyes experienced recurrence during the 5^th-7^th year. Comparison of baseline characteristics between the two groups revealed that a higher proportion of female (p=0.012), better baseline BCVA (p=3.1 × 10^-3), and lower risk allele frequency in ARMS2 A69S (p=0.029) were observed in the remission group.

CONCLUSIONS

The combination therapy showed a favourable outcome for PCV over a 7-year follow-up, especially in the eyes without recurrence during the 1^st-5^th year. Physicians should be careful of recurrent exudation in the eyes without recurrence during the 1^st-5^th years, although the recurrence rate was low.

Effects of mechanical ventilation with expiratory negative airway pressure on porcine pulmonary and systemic circulation: mechano-physiology and potential application

We studied the impact of mechanically regulated, expiratory negative airway pressure (ENAP) ventilation on pulmonary and systemic circulation including its mechanisms and potential applications. Microminipigs weighing about 10 kg were anesthetized (n = 5). First, hemodynamic variables were evaluated without and with ENAP to approximately -16 cmH2O. ENAP significantly increased heart rate and cardiac output, but decreased right atrial, pulmonary arterial and pulmonary capillary wedge pressures. Second, the evaluation was repeated following pharmacological adrenergic blockade, modestly blunting ENAP effects. Third, fluvoxamine (10 mg/kg) was intravenously administered to intentionally induce cardiovascular collapse in the presence of adrenergic blockade. ENAP was started when systolic pressure was < 40 mmHg in the animals assigned to ENAP treatment-group. Fluvoxamine induced cardiovascular collapse within 4 out of 5 animals. ENAP increased systolic pressure to > 50 mmHg (n = 2): both animals fully recovered without neurological deficit, whereas without ENAP both animals died of cardiac arrest (n = 2). ENAP may become an innovative treatment for drug-induced cardiovascular collapse.

Translational Studies on Anti-Atrial Fibrillatory Action of Oseltamivir by its in vivo and in vitro Electropharmacological Analyses

Oseltamivir has been shown to prolong the atrial conduction time and effective refractory period, and to suppress the onset of burst pacing-induced atrial fibrillation in vitro. To better predict its potential clinical benefit as an anti-atrial fibrillatory drug, we performed translational studies by assessing in vivo anti-atrial fibrillatory effect along with in vivo and in vitro electropharmacological analyses. Oseltamivir in intravenous doses of 3 (n = 6) and 30 mg/kg (n = 7) was administered in conscious state to the persistent atrial fibrillation model dogs to confirm its anti-atrial fibrillatory action. The model was prepared by tachypacing to the atria of chronic atrioventricular block dogs for > 6 weeks. Next, oseltamivir in doses of 0.3, 3 and 30 mg/kg was intravenously administered to the halothane-anesthetized intact dogs to analyze its in vivo electrophysiological actions (n = 4). Finally, its in vitro effects of 10–1,000 μM on I_K,ACh, I_Kur, I_Kr, I_Na and I_CaL were analyzed by using cell lines stably expressing Kir3.1/3.4, K_V1.5, hERG, Na_V1.5 or Ca_V1.2, respectively (n = 3 for I_K,ACh and I_Kr or n = 6 for I_Kr, I_Na and I_CaL). Oseltamivir in doses of 3 and 30 mg/kg terminated the atrial fibrillation in 1 out of 6 and in 6 out of 7 atrial fibrillation model dogs, respectively without inducing any lethal ventricular arrhythmia. Its 3 and 30 mg/kg delayed inter-atrial conduction in a frequency-dependent manner, whereas they prolonged atrial effective refractory period in a reverse frequency-dependent manner in the intact dogs. The current assay indicated that IC₅₀ values for I_K,ACh and I_Kr were 160 and 231 μM, respectively, but 1,000 µM inhibited I_Na, I_CaL and I_Kur by 22, 19 and 13%, respectively. The extent of I_Na blockade was enhanced at faster beating rate and more depolarized resting membrane potential. Oseltamivir effectively terminated the persistent atrial fibrillation, which may be largely due to the prolongation of the atrial effective refractory period and inter-atrial conduction time induced by I_K,ACh and I_Kr inhibitions along with I_Na suppression. Thus, oseltamivir can exert a powerful anti-atrial fibrillatory action through its ideal multi-channel blocking property; and oseltamivir would become a promising seed compound for developing efficacious and safe anti-atrial fibrillatory drugs.

CT and MRI characteristics of presumptive hypervitaminosis A in a cat

Case summary

A rescued stray cat with an unknown history was examined for non-ambulatory paraparesis in the hindlimbs. Survey radiographs revealed typical findings of hypervitaminosis A, characterised by vertebral exostoses and extensive osteophytes, mainly in the cervicothoracic spine. CT findings were consistent with the radiographic findings, and CT-based volume rendering and virtual endoscopy into the vertebral canal were created for three-dimensional visualisation of the lesion. MRI revealed a focal and mild dilation of the central canal of the spinal cord. Although the clinical diagnosis of hypervitaminosis A is based on an unusual dietary history and characteristic radiographic findings, the history of this cat was unknown and serum concentrations of vitamin A were unremarkable, when measured >1 month after rescue. However, other possible differential diagnoses were thought to be unlikely and clinical signs never worsened, and thus, hypervitaminosis A was presumed.

Relevance and novel information

To our knowledge, this is the first report to present the CT and MRI characteristics of a cat with suspected hypervitaminosis A.

In vivo characterization of anti-atrial fibrillatory potential and pharmacological safety profile of INa,L plus IKr inhibitor ranolazine using the halothane-anesthetized dogs

To characterize in vivo anti-atrial fibrillatory potential and pharmacological safety profile of ranolazine having I_Na,L plus I_Kr inhibitory actions in comparison with those of clinically available anti-atrial fibrillatory drugs; namely, dronedarone, amiodarone, bepridil and dl-sotalol in our previous studies, ranolazine dihydrochloride in sub-therapeutic (0.3 mg/kg) and supra-therapeutic (3 mg/kg) doses was intravenously infused over 10 min to the halothane-anesthetized dogs (n = 5). The low dose increased the heart rate, cardiac output and atrioventricular conduction velocity possibly via vasodilator action-induced, reflex-mediated increase of adrenergic tone. Meanwhile, the high dose decreased the heart rate, ventricular contraction, cardiac output and mean blood pressure, indicating that drug-induced direct actions may exceed the reflex-mediated compensation. In addition, it prolonged the atrial and ventricular effective refractory periods, of which potency and selectivity for the former were less great compared with those of the clinically-available drugs. Moreover, it did not alter the ventricular early repolarization period in vivo, but prolonged the late repolarization with minimal risk for re-entrant arrhythmias. These in vivo findings of ranolazine suggest that I_Na,L suppression may attenuate I_Kr inhibition-associated prolongation of early repolarization in the presence of reflex-mediated increase of adrenergic tone. Thus, ranolazine alone may be less promising as an anti-atrial fibrillatory drug, but its potential risk for inducing torsade de pointes will be small. These information can be used as a guide to predict the utility and adverse effects of anti-atrial fibrillatory drugs having multi-channel modulatory action.

Five-Year Outcome of Aflibercept Monotherapy for Exudative Age-Related Macular Degeneration with Good Baseline Visual Acuity

We investigated the long-term visual and anatomical outcomes of aflibercept monotherapy for exudative age-related macular degeneration (AMD) with good baseline best-corrected visual acuity (BCVA). A medical chart review was performed for 40 consecutive patients with baseline decimal BCVA ≥ 0.6 secondary to exudative AMD. Three monthly injections were administrated, and thereafter additional injection was performed if needed over 5 years. In total, 13 eyes with neovascular AMD (nAMD) and 27 eyes with polypoidal choroidal vasculopathy (PCV) were enrolled. In both groups, the mean BCVA significantly improved at the 12-month visit (p < 0.05). However, the significant improvement in BCVA disappeared at the 24-month visit, and the final mean BCVA was equivalent to that at baseline (p = 0.17 in the nAMD group and p = 0.15 in the PCV group). The median number of injections required after the loading dose was 15.0 during the 5-year follow-up (nAMD:15.0 vs. PCV:15). During the study period, 37 (92.5%) eyes required retreatment(s). Cox regression analysis demonstrated that the protective allele of ARMS2 A69S was associated with a retreatment-free period from the initial injection (p = 0.041, repeated forward selection method). As-needed aflibercept monotherapy is a preferable treatment option for exudative AMD with good initial visual acuity regardless of nAMD or PCV during the 5-year study period.

An exploratory analysis of effects of poyendarone, a deuterated analogue of dronedarone, on the canine model of paroxysmal atrial fibrillation

Poyendarone, a deuterated analogue of dronedarone, is expected to reduce the onset of cardiovascular adverse events of dronedarone, including congestive heart failure and excessive QT-interval prolongation. Since information is still lacking on the anti-atrial fibrillatory property of poyendarone, we assessed it along with effects on the inter-atrial conduction time (IACT) and atrial effective refractory period (AERP) using the canine paroxysmal atrial fibrillation model. Poyendarone hydrochloride (n = 4) and dronedarone hydrochloride (n = 4) in intravenous doses of 0.3 and 3 mg/kg/30 s were cumulatively administered. Poyendarone hardly altered sinoatrial rate, but dronedarone decreased it in a dose-related manner, whereas both drugs slightly but significantly reduced idioventricular rate. Poyendarone shortened duration of burst pacing-induced atrial fibrillation, whereas such abbreviation was not observed by dronedarone. Poyendarone and dronedarone similarly prolonged IACT in a frequency-dependent manner, indicating that their I_Na inhibitory actions may be similar. The high dose of poyendarone prolonged AERP in a reverse frequency-dependent manner, extent of which at basic pacing cycle lengths of 300 and 400 ms was comparable to that of dronedarone. However, the extent at a basic pacing cycle length of 200 ms was tended to be greater in poyendarone than in dronedarone, suggesting greater I_Ks inhibitory action of poyendarone. The deuteration of dronedarone attenuated the inhibition of sinus automaticity and prolonged the AERP with keeping the blood pressure and ventricular rate stable. Thus, poyendarone may have both more potent anti-atrial fibrillatory action and wider cardiovascular safety margin than dronedarone.

In vivo analysis of concentration-dependent effects of halothane or isoflurane inhalation on the electrocardiographic and hemodynamic variables in dogs

We assessed concentration-dependent effects of halothane or isoflurane inhalation on the electrocardiographic and hemodynamic variables using a cross-over design in intact beagle dogs (n = 4). Elevation of inhaled halothane from 1.0% to 2.0% or isoflurane from 1.5% to 2.5% decreased the mean blood pressure and prolonged the QRS width without significantly altering the heart rate, PR interval or QT interval. However, the observed changes disappeared after regressions of both anesthetic conditions to their initial settings. These results indicate that hypotension-induced, reflex-mediated increase of sympathetic tone may have counterbalanced the direct negative chronotropic, dromotropic and repolarization slowing effects of the anesthetics.

Assessment of Contractility in Human iPS Cell-Derived Cardiomyocytes Using Motion Vector Analysis

Human-induced pluripotent stem cell (iPSC) technology paves the way for next-generation drug-safety assessment. In particular, human iPSC-derived cardiomyocytes, which exhibit electrical activity, are useful as a human cell model for assessing QT-interval prolongation and the risk of the lethal arrhythmia Torsade de Pointes (TdP). In addition to proarrhythmia assay, contractile behavior has received increased attention in drug development. In this study, we developed a novel high-throughput in vitro assay system using motion vectors to evaluate the contractile activity of iPSC-derived cardiomyocytes as a physiologically relevant human platform. The methods presented here highlight the use of commercially available iPSC-derived cardiomyocytes, iCell cardiomyocytes, for contractility evaluation recorded by the motion vector system.

Long-Term Electrodeposition under a Uniform Parallel Magnetic Field. 1. Instability of Two-Dimensional Nucleation in an Electric Double Layer

Under a parallel magnetic field, after long-term copper deposition from an acidic copper sulfate solution, numerous spherical secondary nodules of 10 to 100 μm diameters were formed one upon another in dendritic mode. This is a new type of micro-magnetohydrodynamic (MHD) effect arising from the unstable growth of three-dimensional (3D) and two-dimensional (2D) nuclei by specific adsorption of hydrogen ions (second micro-MHD effect). From the viewpoint of instability in electrodeposition, though 3D nucleation in the diffusion layer is always unstable, with ionic specific adsorption such as hydrogen ions, stable 2D nucleation turns unstable after long-term deposition. The resultant competitive growth of 3D and 2D nuclei produces spherical nodules as their composite, leading to their dendritic growth. Furthermore, though negligibly small, nonequilibrium fluctuations occurring in 2D nucleation migrate with the laminar solution flow caused by Lorentz force (MHD flow). Depending on whether the ionic adsorption is specific or nonspecific, the traveling asymmetrical fluctuation changes the direction to the upstream or downstream side, respectively.

Long-Term Electrodeposition under a Uniform Parallel Magnetic Field. 2. Flow-Mode Transition from Laminar MHD Flow to Convection Cells with Two-Dimensional (2D) Nucleation

Following the analysis of the self-organization of two-dimensional (2D) nuclei in Part 1, the flow-mode transition from laminar magnetohydrodynamics (MHD) flow to convection cells accompanied by 2D nucleation under a uniform parallel magnetic field was theoretically examined using the statistical mechanics of nonequilibrium fluctuation. As a result, it was clarified that secondary nodules of 2D nuclei develop with multiple nucleations during the transition, forming a one-upon-another structure. Then, the evolution of the convection cells as well as the secondary nodules requires unstable growth of the asymmetrical fluctuations by the specific adsorption of an ion. As predicted by the theory, the electrolytic current in copper deposition with specific adsorption of hydrogen ions under a parallel magnetic field developed with time, resulting in a nonlinear steplike curve in a 1200 s deposition time.

Reverse translational analysis of clinically reported, lamotrigine-induced cardiovascular adverse events using the halothane-anesthetized dogs

Lamotrigine has been used for patients with epilepsy and/or bipolar disorder, overdose of which induced the hypotension, elevation of the atrial pacing threshold, cardiac conduction delay, wide complex tachycardia, cardiac arrest and Brugada-like electrocardiographic pattern. To clarify how lamotrigine induces those cardiovascular adverse events, we simultaneously assessed its cardiohemodynamic and electrophysiological effects using the halothane-anesthetized dogs (n = 4). Lamotrigine was intravenously administered in doses of 0.1, 1 and 10 mg/kg/10 min under the monitoring of cardiovascular variables, possibly providing subtherapeutic to supratherapeutic plasma concentrations. The low or middle dose of lamotrigine did not alter any of the variables. The high dose significantly delayed the intra-atrial and intra-ventricular conductions in addition to the prolongation of ventricular effective refractory period, whereas no significant change was detected in the other variables. Lamotrigine by itself has relatively wide safety margin for cardiohemodynamics, indicating that clinically reported hypotension may not be induced through its direct action on the resistance arterioles or capacitance venules. The electrophysiological effects suggested that lamotrigine can inhibit Na⁺ channel in the in situ hearts. This finding may partly explain the onset mechanism of lamotrigine-associated cardiac adverse events in the clinical cases. In addition, elevation of J wave was induced in half of the animals, suggesting that lamotrigine may have some potential to unmask Brugada electrocardiographic genotype in susceptible patients.

Cardiohemodynamic and Arrhythmogenic Effects of the Anti-Atrial Fibrillatory Compound Vanoxerine in Halothane-Anesthetized Dogs

While vanoxerine (GBR-12909) is a synaptosomal dopamine uptake inhibitor, it also suppresses I_Kr, I_Na and I_Ca,L in vitro. Based on these profiles on ionic currents, vanoxerine has been developed as a candidate compound for treating atrial fibrillation. To investigate electropharmacological profiles, vanoxerine dihydrochloride was intravenously administered at 0.03 and 0.3 mg/kg to halothane-anesthetized dogs (n = 4), possibly providing subtherapeutic and therapeutic concentrations, respectively. The low dose increased the heart rate and cardiac output, whereas it prolonged the ventricular refractoriness. The high dose decreased the heart rate but increased the total peripheral vascular resistance, whereas it delayed the ventricular repolarization and increased the atrial refractoriness in addition to further enhancing the ventricular refractoriness. The extent of increase in the refractoriness in the atrium was 0.8 times of that in the ventricle. The high dose also prolonged the early and late repolarization periods of the ventricle as well as the terminal repolarization period. Meanwhile, no significant change was detected in the mean blood pressure, ventricular contraction, preload to the left ventricle, or the intra-atrial, intra-ventricular or atrioventricular conductions. The high dose can be considered to inhibit I_Kr, but it may not suppress I_Na or I_Ca in the in situ heart, partly explaining its poor atrial selectivity for increasing refractoriness. The prolongation of early repolarization period may reflect enhancement of net inward current, providing potential risk for intracellular Ca²⁺ overload. Thus, vanoxerine may provide both trigger and substrate toward torsade de pointes, which would make the drug less promising as an anti-atrial fibrillatory drug.

Dasatinib can Impair Left Ventricular Mechanical Function But May Lack Proarrhythmic Effect: A Proposal of Non-clinical Guidance for Predicting Clinical Cardiovascular Adverse Events of Tyrosine Kinase Inhibitors

Tyrosine kinase inhibitors are known to clinically induce various types of cardiovascular adverse events; however, it is still difficult to predict them at preclinical stage. In order to explore how to better predict such drug-induced cardiovascular adverse events, we tried to develop a new protocol by assessing acute electrophysiological, cardiohemodynamic, and cytotoxic effects of dasatinib in vivo and in vitro. Dasatinib at 0.03 and 0.3 mg/kg was intravenously administered to the halothane-anesthetized dogs for 10 min with an interval of 20 min between the dosing (n = 4). Meanwhile, that at 0.1, 0.3, and 1 μM was cumulatively applied to the human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) (n = 7). In the dogs, the low and high doses provided peak plasma concentrations of 40 ± 5 (0.08) and 615 ± 38 ng/mL (1.26 μM), respectively. The low dose decreased the heart rate, impaired the left ventricular mechanical function, and prolonged the ventricular effective refractory period. The high dose prolonged the repolarization period, induced hemorrhagic tendency, and increased plasma cardiac troponin I level in addition to enhancement of the changes observed after the low dose, whereas it neither affected the cardiac conduction nor induced ventricular arrhythmias. In the hiPSC-CMs, dasatinib prolonged the repolarization and refractory periods like in dogs, while it did not induce apoptotic or necrotic process, but that it increased the conduction speed. Clinically observed major cardiovascular adverse events of dasatinib were observed qualitatively by currently proposed assay protocol, which may become a useful guide for predicting the cardiotoxicity of new tyrosine kinase inhibitors.

In vivo comparison of dl-sotalol-induced electrocardiographic responses among halothane anesthesia, isoflurane anesthesia with nitrous oxide, and conscious state

We compared dl-sotalol-induced electrocardiographic responses in intact dogs using a repeated-measures design among 1% halothane anesthesia, 1.5% isoflurane anesthesia with nitrous oxide (N₂O), and conscious state to clarify influences of the anesthetics (n = 4). Basal PR interval was longer in halothane than either in isoflurane with N₂O or in conscious state, reflecting sympathetic nerve suppression for the atrioventricular node by halothane. Both anesthetics exhibited longer basal QRS width than conscious state, suggesting their ventricular I_Na inhibition. Also, both anesthetics showed longer basal QT interval, QTcF and T_peak-T_end than conscious state, indicating their ventricular I_Kr inhibition. Meanwhile, dl-sotalol prolonged PR interval similarly in isoflurane with N₂O and in conscious state, which was less great in halothane, suggesting further sympathetic nerve suppression for the atrioventricular node might be limited in halothane. dl-Sotalol prolonged QT interval and QTcF >3 times greater in either of the anesthetics than in conscious state; moreover, dl-sotalol prolonged T_peak-T_end similarly in both anesthetics, but hardly altered it in conscious state; indicating isoflurane with N₂O as well as halothane may have reduced the repolarization reserve to increase the sensitivity of ventricle toward I_Kr suppression. Thus, isoflurane with nitrous oxide could be useful for in vivo I_Kr assay like halothane.