In silico modelling of stroke volume, cardiac output and systemic vascular resistance in cardiovascular safety pharmacology studies by telemetry.

The principle of proportionality of the systolic area of the central aortic pressure to stroke volume (SV) has been long known. The aim of the present work was to evaluate an in silico solution derived from this principle for modelling SV (iSV model) in cardiovascular safety pharmacology studies by telemetry. Blood pressure was measured in the abdominal aorta in accordance with standard practice. Central aortic pressure was modelled from the abdominal aortic pressure waveform using the N-point moving average (NPMA) method for beat-to-beat estimation of SV. First, the iSV was compared to the SV measured by ultrasonic flowmetry in the ascending aorta (uSV) after various pharmacological challenges in beagle dogs anaesthetised with etomidate/fentanyl. The iSV showed minimal bias (0.2 mL i.e. 2%) and excellent agreement with uSV. Then, previous telemetry studies including reference vasoactive and inotropic compounds were retrospectively reanalysed to model drug effects on stroke volume (iSV), cardiac output (iCO) and systemic vascular resistance (iSVR). Among them, the examples of nicardipine and isoprenaline highlight risks of erroneous or biased estimation of drug effects from the abdominal aortic pressure due to pulse pressure amplification. Furthermore, the examples of verapamil, quinidine and moxifloxacin show that iSV, iCO and iSVR are earlier biomarkers than blood pressure itself for predicting drug effect on blood pressure. This in silico modelling approach included in vivo telemetry safety pharmacology studies can be considered as a New Approach Methodology (NAM) that provides valuable additional information and contribute to improving non-clinical translational research to the clinic.

Contribution of haemodynamic side effects and associated autonomic reflexes to ventricular arrhythmias triggering by torsadogenic hERG blocking drugs.

BACKGROUND AND PURPOSE: HERG blocking drugs known for their propensity to trigger Torsades de Pointes (TdP) were reported to induce a sympatho-vagal coactivation and to enhance High Frequency heart rate (HFHR) and QT oscillations (HFQT) in telemetric data. The present work aimed to characterize the underlying mechanism(s) leading to these autonomic changes. EXPERIMENTAL APPROACH: Effects of 15 torsadogenic hERG blocking drugs (astemizole, chlorpromazine, cisapride, droperidol, ibutilide, dofetilide, haloperidol, moxifloxacin, pimozide, quinidine, risperidone, sotalol, sertindole, terfenadine, and thioridazine) were assessed by telemetry in beagle dogs. Haemodynamic effects on diastolic and systolic arterial pressure were analysed from the first doses causing QTc prolongation and/or HFQT oscillations enhancement. Autonomic control changes were analysed using the high frequency autonomic modulation (HFAM) model. KEY RESULTS: Except for moxifloxacin and quinidine, all torsadogenic hERG blockers induced parasympathetic activation or sympatho-vagal coactivation combined with enhancement of HFQT oscillations. These autonomic effects result from reflex compensatory mechanisms in response to mild haemodynamic side effects. These haemodynamic mechanisms were characterized by transient HR acceleration during HF oscillations. A phenomenon of concealed QT prolongation was unmasked for several torsadogenic hERG blockers under ß-adrenoceptor blockade with atenolol. Resulting enhancement of HFQT oscillations was shown to contribute directly to triggering dofetilide-induced ventricular arrhythmias. CONCLUSION AND IMPLICATIONS: This work supports for the first time a contribution of haemodynamic side properties to ventricular arrhythmias triggered by torsadogenic hERG blocking drugs. These haemodynamic side effects may constitute a second component of their arrhythmic profile, acting as a trigger alongside their intrinsic arrhythmogenic electrophysiological properties.

Relevance of electroencephalogram assessment in amyloid and tau pathology in rat.

In order to contribute to a better knowledge on the relationship between amyloid and tau pathology, and electroencephalography (EEG) disturbances, the aim of this study was to evaluate the effects of injection of beta amyloid Abeta(1-42) peptide, tau (a recombinant AAV (Adeno-Associated Virus) containing the human transgene tau with the P301 L mutation on rats and the combination of both, on the power of brain's rhythm (delta, theta, alpha, beta and gamma waves) during the different sleep/wake states of animals by EEG recording. Currently, no preclinical studies explore the effect of the tau pathology on EEG. The experimentations were performed 3 weeks and 3 months post injections. Beta amyloid deposits and hyperphosphorylated Tau are observed by immunohistofluorescence, only in the hippocampus. Furthermore, using a radial arm water maze, the main effect was observed on working memory which was significantly impaired in Abeta-Tau group only 3 months post injections. However, on EEG, as early as the 3rd week, an overall decrease of the EEG bands power was observed in the treated groups, particularly the theta waves during the rapid eye movement (REM) sleep. Beta amyloid was mainly involved in these perturbations. Obviously, EEG seems to be an interesting tool in the early diagnostic of amyloid and tau pathologies, with a good sensitivity and the possibility to perform a follow up during a large period.

High-frequency autonomic modulation: a new model for analysis of autonomic cardiac control.

BACKGROUND AND PURPOSE: Increase in high-frequency beat-to-beat heart rate oscillations by torsadogenic hERG blockers appears to be associated with signs of parasympathetic and sympathetic co-activation which cannot be assessed directly using classic methods of heart rate variability analysis. The present work aimed to find a translational model that would allow this particular state of the autonomic control of heart rate to be assessed. EXPERIMENTAL APPROACH: High-frequency heart rate and heart period oscillations were analysed within discrete 10 s intervals in a cohort of 200 healthy human subjects. Results were compared to data collected in non-human primates and beagle dogs during pharmacological challenges and torsadogenic hERG blockers exposure, in 127 genotyped LQT1 patients on/off ß-blocker treatment and in subgroups of smoking and non-smoking subjects. KEY RESULTS: Three states of autonomic modulation, S1 (parasympathetic predominance) to S3 (reciprocal parasympathetic withdrawal/sympathetic activation), were differentiated to build a new model of heart rate variability referred to as high-frequency autonomic modulation. The S2 state corresponded to a specific state during which both parasympathetic and sympathetic systems were coexisting or co-activated. S2 oscillations were proportionally increased by torsadogenic hERG-blocking drugs, whereas smoking caused an increase in S3 oscillations. CONCLUSIONS AND IMPLICATIONS: The combined analysis of the magnitude of high-frequency heart rate and high-frequency heart period oscillations allows a refined assessment of heart rate autonomic modulation applicable to long-term ECG recordings and offers new approaches to assessment of the risk of sudden death both in terms of underlying mechanisms and sensitivity.

Comparison of high-definition oscillometry -- a non-invasive technology for arterial blood pressure measurement -- with a direct invasive method using radio-telemetry in awake healthy cats.

This study compared indirect blood pressure measurements using a non-invasive method, high-definition oscillometry (HDO), with direct measurements using a radio-telemetry device in awake cats. Paired measurements partitioned to five sub-ranges were collected in six cats using both methods. The results were analysed for assessment of correlation and agreement between the two methods, taking into account all pressure ranges, and with data separated in three sub-groups, low, normal and high ranges of systolic (SBP) and diastolic (DBP) blood pressure. SBP data displayed a mean correlation coefficient of 0.92 ± 0.02 that was reduced for low SBP. The agreement level evaluated from the whole data set was high and slightly reduced for low SBP values. The mean correlation coefficient of DBP was lower than for SBP (ie, 0.81 ± 0.02). The bias for DBP between the two methods was 22.3 ± 1.6 mmHg, suggesting that HDO produced lower values than telemetry. These results suggest that HDO met the validation criteria defined by the American College of Veterinary Internal Medicine consensus panel and provided a faithful measurement of SBP in conscious cats. For DBP, results suggest that HDO tended to underestimate DBP. This finding is clearly inconsistent with the good agreement reported in dogs, but is similar to outcomes achieved in marmosets and cynomolgus monkeys, suggesting that this is not related to HDO but is species related. The data support that the HDO is the first and only validated non-invasive blood pressure device and, as such, it is the only non-invasive reference technique that should be used in future validation studies.

Reducing endothelial NOS activation and interstitial fluid pressure with n-3 PUFA offset tumor chemoresistance.

The aim of this study was to determine how n-3 polyunsaturated fatty acid (PUFAs) counteracted tumor chemoresistance by restoring a functional vascularization. Rats with chemically induced mammary tumors were divided into two nutritional groups: a control group and a group fed with an n-3 PUFA-enriched diet. Both groups were treated with docetaxel. Functional vascular parameters (ultrasounds, interstitial fluid pressure) were determined for both nutritional groups before (W(0)) and during docetaxel treatment [every 2 h up to 1 week (W(+1)) for interstitial fluid pressure, at W(+1) for Evans blue extravasation and at W(+2) and W(+6) for ultrasounds]. In vitro n-3 PUFA-induced changes in endothelial cell migration, permeability and phosphorylation of endothelial nitric oxide synthase were evaluated using human umbilical vein endothelial cells. Whereas docetaxel stabilized tumor growth in the rat control group, it induced a 50% tumor regression in the n-3 PUFA group. Ultrasounds parameters were consistently lower in the n-3 PUFA group at all time points measured, down to ∼50% at W(+6). A single dose of docetaxel in the n-3 PUFA group markedly reduced interstitial fluid pressure from 2 h after injection up to W(+1) when Evans blue extravasation was increased by 3-fold. A decreased activation of endothelial nitric oxide synthase in tumors of the n-3 PUFA group, and in human umbilical vein endothelial cell cultured with n-3 PUFA, points toward a PUFA-induced disruption of nitric oxide signaling pathway. This normalization of tumor vasculature functions under n-3 PUFA diet indicates that such a supplementation, by improving drug delivery in mammary tumors, could be a complementary clinical strategy to decrease anticancer drug resistance.

Electrophysiological profile of propiverine--relationship to cardiac risk.

Drugs that prolong the QT interval by blocking human ether-a-go-go (HERG) channels may enhance the risk of ventricular arrhythmia. The spasmolytic drug propiverine is widely used for the therapy of overactive bladder (OAB). Here, we have investigated the effects of propiverine on cardiac ion channels and action potentials as well as on contractile properties of cardiac tissue, in order to estimate its cardiac safety profile, because other drugs used in this indication had to be withdrawn due to safety reasons. Whole-cell patch clamp technique was used to record the following cardiac ion currents: rapidly and slowly activating delayed rectifier K+ current (I(Kr), I(Ks)), ultra rapidly activating delayed rectifier K+ current (I(Kur)), inwardly rectifying K+ current I(K1), transient outward K+ current (I(to)), and L-type Ca2+ current (I(Ca,L)). Action potentials in cardiac tissue biopsies were recorded with conventional microelectrodes. The torsade de pointes screening assay (TDPScreen) was used for drug scoring. Propiverine blocked in a concentration-dependent manner HERG channels expressed in HEK293 cells, as well as native I(Kr) current in ventricular myocytes of guinea pig (IC50 values: 10 microM and 1.8 microM respectively). At high concentrations (100 microM), propiverine suppressed I(Ks). I(K1) and the transient outward current I(to) and I(Kur) were not affected. In guinea-pig ventricular and human atrial myocytes, propiverine also blocked I(Ca,L) (IC50 values: 34.7 microM and 41.7 microM, respectively) and reduced force of contraction. Despite block of I(Kr), action potential duration was not prolonged in guinea-pig and human ventricular tissue, but decreased progressively until excitation failed altogether. Similar effects were observed in dog Purkinje fibers. Propiverine obtained a low score in the TDPScreen. In conclusion, in vitro and in vivo studies of propiverine do not provide evidence for an enhanced cardiovascular safety risk. We propose that lack of torsadogenic risk of propiverine is related to enhancement of repolarization reserve by block of I(Ca,L).

Sensitization by dietary docosahexaenoic acid of rat mammary carcinoma to anthracycline: a role for tumor vascularization.

PURPOSE: To investigate whether dietary docosahexaenoic acid (DHA), a peroxidizable polyunsaturated omega-3 fatty acids, sensitizes rat mammary tumors to anthracyclines and whether its action interferes with tumor vascularization, a critical determinant of tumor growth. EXPERIMENTAL DESIGN: Female Sprague-Dawley rats were initiated by N-methylnitrosourea to develop mammary tumors and then assigned to a control group (n = 18), receiving a supplementation of palm oil, or to a DHA group (n = 54), supplemented with a microalgae-produced oil (DHASCO, 1.5 g/d). The DHA group was equally subdivided into three subgroups with addition of different amounts of alpha-tocopherol. Epirubicin was injected weekly during 6 weeks after the largest tumor reached 1.5 cm(2), and subsequent changes in the tumor surface were evaluated. Tumor vascularization was assessed by power Doppler sonography before and during chemotherapy. RESULTS: DHA and alpha-tocopherol were readily absorbed and incorporated into rat tissues. Epirubicin induced a 45% mammary tumor regression in the DHA-supplemented group, whereas no tumor regression was observed in the control group. In the DHA group, before chemotherapy was initiated, tumor vascular density was 43% lower than in the control group and remained lower during chemotherapy. Enhancement of epirubicin efficacy by DHA was abolished in a dose-dependent manner by alpha-tocopherol, and the same trend was observed for DHA-induced reduction in tumor vascular density. CONCLUSIONS: Dietary DHA supplementation led to a reduction in tumor vascularization before the enhancement of any response to anthracyclines, suggesting that DHA chemosensitizes mammary tumors through an inhibition of the host vascular response to the tumor.

Dietary long-chain omega-3 fatty acids of marine origin: a comparison of their protective effects on coronary heart disease and breast cancers.

The relationship between high fish consumption and low mortality following coronary heart disease (CHD) and low incidence of breast cancer was first mentioned 3 decades ago. The fishes of interest are rich in omega-3 long-chain polyunsaturated fatty acids (omega-3 LC-PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which could be the active nutrients. The current consensus about cardioprotection is that omega-3 LC-PUFAs would mainly exert antiarrhythmic effects. One of the proposed mechanisms is that circulating non-esterified LC-PUFAs partition into cardiac cells membrane phospholipids and exert a direct effect on ionic channels and/or modify intracellular calcium homeostasis. In another hypothesis, changes in the metabolism of phosphoinositides would be involved and lead to the differential activation of PKC isoforms. As compared to the mechanisms proposed for the cardioprotective effects of omega-3 LC-PUFAs, less is known about the molecular mechanisms involved in breast cancers prevention. Some proposed mechanisms such as the modulation of phosphoinositides metabolism and/or modulation of intracellular calcium homeostasis, are common to both pathologies. Other hypotheses involve the alteration of the cellular redox status induced by highly peroxidizable polyunsaturated fatty acids (FA), or the modulation of gene expression, both phenomena being tightly linked to apoptosis. In this review, we report and compare some proposed mechanisms for the involvement of omega-3 LC-PUFAs in both cardiac and breast cancer protection. Deliberately, we chose to discuss only the mechanisms, which are less described in other reviews such as ionic channels in cancer, calcium homeostasis, PKC activation or matrix metalloproteinases in both cancer and cardiac models. The leitmotiv along this review is that cardio- and cancero-protective effects use common pathways. Comparison of the cellular effects might therefore help to highlight the "protective" pathways.