hmr-1556 and Disease-Models--Animal

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

The Kv7 family of voltage-gated potassium channels are expressed within the vasculature where they are key regulators of vascular tone and mediate cAMP-linked endogenous vasodilator responses, a pathway that is compromised in hypertension. However, the role of Kv7 channels in non-cAMP-linked vasodilator pathways has not been investigated. Natriuretic peptides are potent vasodilators, which operate primarily through the activation of a cGMP-dependent signaling pathway. This study investigated the putative role of Kv7 channels in natriuretic peptide-dependent relaxations in the vasculature of normal and hypertensive animals. Relaxant responses of rat aorta to both atrial and C-type natriuretic peptides and the nitric oxide donor sodium nitroprusside were impaired by the Kv7 blocker linopirdine (10 μmol/L) but not by the Kv7.1-specific blocker HMR1556 (10 μmol/L) and other K(+) channel blockers. In contrast, only the atrial natriuretic peptide response was sensitive to linopirdine in the renal artery. These Kv7-mediated responses were attenuated in arteries from hypertensive rats. Quantitative polymerase chain reaction showed that A- and B-type natriuretic peptide receptors were expressed at high levels in the aorta and renal artery from normal and spontaneously hypertensive rats. This study provides the first evidence that natriuretic peptide responses are impaired in hypertension and that recruitment of Kv7 channels is a key component of natriuretic peptide-dependent vasodilations.

Topics: Animals; Aorta; Chromans; Cyclic GMP; Disease Models, Animal; Hypertension; Indoles; KCNQ Potassium Channels; KCNQ1 Potassium Channel; Male; Muscle, Smooth, Vascular; Natriuretic Peptides; Nitroprusside; Potassium Channel Blockers; Pyridines; Rats; Rats, Inbred SHR; Rats, Wistar; Renal Artery; Signal Transduction; Sulfonamides; Vasodilation

K(+) recycling at the apical membrane of gastric parietal cells is a prerequisite for gastric acid secretion. Two K(+) channels are currently being considered for this function, namely KCNQ1 and inwardly rectifying K(+) channels (Kir). This study addresses the subcellular localization, trafficking, and potential functional significance of KCNQ1 and Kir4.1 channels during stimulated acid secretion.. The effect of pharmacologic KCNQ1 blockade on acid secretion was studied in cultured rat and rabbit parietal cells and in isolated mouse gastric mucosa. The subcellular localization of KCNQ1 and Kir4.1 was determined in highly purified membrane fractions by Western blot analysis as well as in fixed and living cells by confocal microscopy.. In cultured parietal cells and in isolated gastric mucosa, a robust acid secretory response was seen after complete pharmacologic blockade of KCNQ1. Both biochemical and morphologic data demonstrate that Kir4.1 and KCNQ1 colocalize with the H(+)/K(+)-ATPase but do so in different tubulovesicular pools. All Kir4.1 translocates to the apical membrane after stimulation in contrast to only a fraction of KCNQ1, which mostly remains cytoplasmic.. Acid secretion can be stimulated after complete pharmacologic blockade of KCNQ1 activity, suggesting that additional apical K(+) channels regulate gastric acid secretion. The close association of Kir4.1 channels with H(+)/K(+)-ATPase in the resting and stimulated membrane suggests a possible role for Kir4.1 channels during the acid secretory cycle.

Topics: Animals; Blotting, Western; Cells, Cultured; Chromans; Disease Models, Animal; Gastric Acid; H(+)-K(+)-Exchanging ATPase; Immunohistochemistry; Immunoprecipitation; KCNQ1 Potassium Channel; Male; Mice; Microscopy, Confocal; Parietal Cells, Gastric; Potassium Channels, Inwardly Rectifying; Rabbits; Rats; Rats, Wistar; Sodium-Potassium-Exchanging ATPase; Sulfonamides

Congenital loss of function and drug-induced inhibition of the slowly-activating delayed-rectifier K(+) current (I(Ks)) cause impaired cardiac repolarization. beta-Adrenergic-receptor stimulation contributes to sympathetically-induced torsades de pointes (TdP). An in vivo model of long-QT1 (LQT1) syndrome and TdP in a species with I(Ks) characteristics relevant to man is lacking. We investigated the in vivo mechanisms of TdP in a novel canine model of drug-induced LQT1 syndrome.. Adult beagle dogs (n=30; F/M) were anesthetized with lofentanil (0.075 mg/kg i.v.) and etomidate (1.5 mg/kg/hour). ECGs, left- (LV) and right-ventricular (RV) monophasic action potentials (MAPs), and intracavitary pressures were recorded simultaneously. Infusion of the I(Ks) blocker HMR1556 (0.025-0.050 mg/kg/min) mimicked LQT1, and bolus injections of isoproterenol (1.25-5 microg/kg) reproducibly triggered TdP in 94% of dogs (defibrillated if necessary).. Isoproterenol evoked paradoxical repolarization prolongation during heart rate accelerations. Beat-to-beat variability [QT, LV MAP duration (MAPD(90))] and spatial dispersion of repolarization (T(peak)-T(end) interval, endo-minus epicardial MAPD(90), LV-RVMAPD(90)) were significantly increased. Early afterdepolarizations occurred predominantly in the endocardium and not the epicardium. During isoproterenol, secondary systolic contractions (aftercontractions; peak 25+/-6 mm Hg) arose in the LV (not RV) when TdP ensued. Prevention of TdP by esmolol (1.25 mg/kg), verapamil (0.4 mg/kg) or mexiletine (5 mg/kg) was only successful when repolarization prolongation was contained and aftercontractions remained absent.. beta-Adrenergic challenges trigger TdP in a reproducible manner in this model of drug-induced LQT1. Paradoxical prolongation and increased temporal and spatial dispersion of repolarization precipitate TdP. Incremental LV systolic aftercontractions precede TdP, suggesting abnormal cellular Ca(2+) handling contributes to the arrhythmogenic mechanism.

Topics: Action Potentials; Animals; Anti-Arrhythmia Agents; Calcium; Chromans; Disease Models, Animal; Dogs; Female; Isoproterenol; Long QT Syndrome; Male; Reproducibility of Results; Sulfonamides; Torsades de Pointes

Antiarrhythmic drugs for treatment of atrial fibrillation in patients with heart failure are limited by proarrhythmia and low efficacy. Experimental studies indicate that the pure I(Ks) blocking agents chromanol 293b and HMR 1556 prolong repolarization more markedly at fast than at slow heart rates and during beta-adrenergic stimulation. These properties may overcome some of the above quoted limitations.. Ten domestic swine underwent pacemaker implantation (PM) and atrial burst pacing to induce persistent AF. Four days after onset of persistent AF, pigs were randomized to HMR 1556 (30 mg/kg, p.o., 10 days) or placebo. All animals receiving HMR 1556 converted to SR (5.2 +/- 1.9 days), whereas placebo pigs remained in AF. Pigs treated with placebo developed high ventricular rates (297 +/- 5 bpm) and severe heart failure, whereas pigs treated with HMR 1556 remained hemodynamically stable. Left ventricular ejection fraction on the day of euthanization was significantly lower in the placebo compared to the HMR 1556 group (30 +/- 4% vs. 69 +/- 5%, p < 0.005). Similar results were seen with epinephrine levels (placebo 1563 +/- 193 pmol/l vs. HMR 613 +/-196 pmol/l, p < 0.05). Right atrial monophasic action potentials were significantly longer in the HMR 1556 compared to the placebo group (230 +/- 7 ms vs. 174 +/- 13 ms, p < 0.05).. The new I(Ks) blocker HMR 1556 efficiently and safely restores SR and prevents CHF in a model of persistent AF. Restoration of SR is most likely linked to a marked prolongation of atrial repolarization even at high heart rates.

Topics: Action Potentials; Animals; Anti-Arrhythmia Agents; Atrial Fibrillation; Chromans; Disease Models, Animal; Heart Conduction System; Pacemaker, Artificial; Potassium Channels, Voltage-Gated; Sinoatrial Node; Sulfonamides; Sus scrofa