TVP1022: A Novel Cardioprotective Drug Attenuates Left Ventricular Remodeling After Ischemia/Reperfusion in Pigs.

BACKGROUND: The current cornerstone treatment of myocardial infarction (MI) is restoration of coronary blood flow by means of thrombolytic therapy or primary percutaneous coronary intervention. However, reperfusion of ischemic myocardium can actually provoke tissue damage, defined as "ischemia-reperfusion (I/R) injury." TVP1022 [the S-isomer of rasagiline (Azilect), FDA-approved anti-Parkinson's drug] was found to exert cardioprotective activities against various cardiac insults, such as chronic heart failure and I/R, in rat models. Therefore, we tested the hypothesis that TVP1022 will provide cardioprotection against I/R injury and post-MI remodeling in a pig model. METHODS: For inducing MI, we used an I/R model of midleft anterior descending artery occlusion for 90 minutes followed by follow-up for 8 weeks in 18 farm pigs (9 pigs in each group, MI + TVP1022 or MI + Vehicle). Echocardiographic measurements were performed and cardiac scar size was calculated using histopathological methods. For fibrosis evaluation, we measured the interstitial collagen volume fraction in the remote noninfarcted tissue. RESULTS: TVP1022 administration significantly decreased cardiac scar size, attenuated left ventricular dilation, and improved cardiac function assessed by segmental circumferential strain analysis. Furthermore, TVP1022 significantly reduced myocardial fibrosis 8 weeks post-MI. CONCLUSIONS: Collectively, these findings indicate that TVP1022 provides prominent cardioprotection against I/R injury and post-MI remodeling in this I/R pig model.

Combating diabetes complications by 1-Fe, a corrole-based catalytic antioxidant.

The potent corrole-based ROS/RNS decomposition catalyst 1-Fe was examined regarding its effect on the development of diabetes complications, in parallel with studies that addressed safety and toxicity issues that are crucial for forwarding the compound towards clinical trials. Cardiotoxicity and mutagenic potential were addressed by applying the hERG and AMES tests on 1-Fe, revealing that it is safe enough for further development. General toxicity studies in rats disclosed the appearance of mild adverse effect only at a dose of 300 mg/kg/day. In the streptozotocin-induced rat model of diabetes, 20 mg/kg/day 1-Fe prevented cataract incidents and reduced its severity, displayed a favorable effect on kidney function, and also decreased serum cholesterol and triglyceride levels. Comparisons with alpha lipoic acid, a compound with reported benefits in the same mouse model, indicate that the benefits of 1-Fe are due to the combination of its ability to disarm ROS/RNS and its positive effect on lipid profile.

I1 imidazoline receptor: novel potential cytoprotective target of TVP1022, the S-enantiomer of rasagiline.

TVP1022, the S-enantiomer of rasagiline (Azilect®) (N-propargyl-1R-aminoindan), exerts cyto/cardio-protective effects in a variety of experimental cardiac and neuronal models. Previous studies have demonstrated that the protective activity of TVP1022 and other propargyl derivatives involve the activation of p42/44 mitogen-activated protein kinase (MAPK) signaling pathway. In the current study, we further investigated the molecular mechanism of action and signaling pathways of TVP1022 which may account for the cyto/cardio-protective efficacy of the drug. Using specific receptor binding and enzyme assays, we demonstrated that the imidazoline 1 and 2 binding sites (I(1) & I(2)) are potential targets for TVP1022 (IC(50) =9.5E-08 M and IC(50) =1.4E-07 M, respectively). Western blotting analysis showed that TVP1022 (1-20 µM) dose-dependently increased the immunoreactivity of phosphorylated p42 and p44 MAPK in rat pheochromocytoma PC12 cells and in neonatal rat ventricular myocytes (NRVM). This effect of TVP1022 was significantly attenuated by efaroxan, a selective I(1) imidazoline receptor antagonist. In addition, the cytoprotective effect of TVP1022 demonstrated in NRVM against serum deprivation-induced toxicity was markedly inhibited by efaroxan, thus suggesting the importance of I(1)imidazoline receptor in mediating the cardioprotective activity of the drug. Our findings suggest that the I(1)imidazoline receptor represents a novel site of action for the cyto/cardio-protective efficacy of TVP1022.

The E3 ubiquitin-ligase Bmi1/Ring1A controls the proteasomal degradation of Top2alpha cleavage complex - a potentially new drug target.

BACKGROUND: The topoisomerases Top1, Top2alpha and Top2beta are important molecular targets for antitumor drugs, which specifically poison Top1 or Top2 isomers. While it was previously demonstrated that poisoned Top1 and Top2beta are subject to proteasomal degradation, this phenomena was not demonstrated for Top2alpha. METHODOLOGY/PRINCIPAL FINDINGS: We show here that Top2alpha is subject to drug induced proteasomal degradation as well, although at a lower rate than Top2beta. Using an siRNA screen we identified Bmi1 and Ring1A as subunits of an E3 ubiquitin ligase involved in this process. We show that silencing of Bmi1 inhibits drug-induced Top2alpha degradation, increases the persistence of Top2alpha-DNA cleavage complex, and increases Top2 drug efficacy. The Bmi1/Ring1A ligase ubiquitinates Top2alpha in-vitro and cellular overexpression of Bmi1 increases drug induced Top2alpha ubiquitination. A small-molecular weight compound, identified in a screen for inhibitors of Bmi1/Ring1A ubiquitination activity, also prevents Top2alpha ubiquitination and drug-induced Top2alpha degradation. This ubiquitination inhibitor increases the efficacy of topoisomerase 2 poisons in a synergistic manner. CONCLUSIONS/SIGNIFICANCE: The discovery that poisoned Top2alpha is undergoing proteasomal degradation combined with the involvement of Bmi1/Ring1A, allowed us to identify a small molecule that inhibits the degradation process. The Bmi1/Ring1A inhibitor sensitizes cells to Top2 drugs, suggesting that this type of drug combination will have a beneficial therapeutic outcome. As Bmi1 is also a known oncogene, elevated in numerous types of cancer, the identified Bmi1/Ring1A ubiquitin ligase inhibitors can also be potentially used to directly target the oncogenic properties of Bmi1.

Membrane interactions and metal ion effects on bilayer permeation of the lipophilic ion modulator DP-109.

DP-109, a lipophilic bivalent metal ion modulator currently under preclinical development for neurodegenerative disorders, was designed to have membrane-associated activity, thereby restricting its action to the vicinity of cell membranes. We describe the application of a colorimetric phospholipid/polydiacetylene (PDA) biomimetic membrane assay in elucidating DP-109 membrane interactions and penetration into lipid bilayers. In this membrane model, visible quantifiable color changes were monitored in studying membrane interactions. The colorimetric data identified a biphasic concentration-dependent interaction, with a break point around the critical micelle concentration (CMC) of DP-109. The kinetics and colorimetric dose-response profile of DP-109 indicate that the compound inserts into the lipid bilayers rather than being localized at the bilayer surface. Analysis of interactions of DP-109 with phospholipid/PDA vesicles in which ionic gradients were imposed indicates that membrane activity of DP-109 is strongly affected by electrochemical gradients imposed by K+ and Zn2+. The ionic gradient effects suggest that the insertion of DP-109 into the membrane may depend on the membrane potential.

Clinical pharmacology of DP-b99 in healthy volunteers: first administration to humans.

AIMS: To investigate the safety, tolerability and pharmacokinetics of DP-b99 in healthy volunteers. DP-b99 is a newly developed lipophilic, cell permeable derivative of BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid), which selectively modulates the distribution of metal ions in hydrophobic milieu, and is in clinical development as a neuroprotectant for cerebral ischaemic stroke. To our knowledge no BAPTA derivative has ever been administered to man. Here we report the first human administration of DP-b99 in a phase I, two-part, double-blind, randomized placebo controlled study, with single IV doses of 0.003-1.0 mg kg(-1) day(-1) DP-b99 (part 1) or multiple ascending doses of 0.03-1.0 mg kg(-1) day(-1) DP-b99 over 4 days (part 2). METHODS: A double-blind, dose escalating tolerability study of DP-b99 in normal (young - aged between 18 and 40 years and elderly - aged between 65 and 85 years) healthy adult male volunteers was conducted. Part 1 of the study investigated single administration of ascending intravenous doses, and part 2 examined the effects of ascending doses given repeatedly over 4 days. Twenty-four young volunteers in part 1 received single dose administrations and 26 young volunteers in part 2 received repeated ascending dose administrations of either intravenous DP-b99 or placebo. Subsequently, 10 elderly volunteers received repeated intravenous DP-b99 (1 mg kg(-1)) or placebo in part 2 over 4 days. Adverse events were identified by either subject self reporting or based upon laboratory parameters (blood chemistry, complete blood cell count, prothrombin time (PT), activated partial thromboplastin (PTT), physical examination, vital signs (blood pressure, pulse rate, respiratory rate, body temperature) and urinalysis. A comprehensive set of cardiovascular parameters was assessed as well (blood pressure, 12 lead-ECG recordings and continuous bedside cardiac monitoring for 6 h on day 1). RESULTS: The administration of DP-b99 up to the highest dose of 1.0 mg kg(-1) was well tolerated and had an acceptable safety profile up to the highest dose of 1.0 mg kg(-1) tested in both study parts. No serious or severe adverse events were encountered. Eight mild to moderate adverse events were observed in six of the seven young subjects treated with four repeated doses of 1.0 mg kg(-1), with reversible phlebitis being the most frequently reported adverse event. The drug was tolerated better at the injection site by the elderly group compared with the younger subjects. No adverse effects were observed in cardiovascular parameters sensitive to trans-membranous calcium concentrations. The pharmacokinetic parameters were derived by noncompartmental analysis. On day 1 following administration of 1 mg kg(-1) the mean half-life of DP-b99 in young volunteers was 3.47 +/- 0.90 h and in the elderly was 2.11 +/- 0.09 h. On day 4 following the same administration of DP-b99 the mean half-life was 4.36 +/- 1.49 and 2.10 +/- 1.14 h in the young and elderly, respectively. There was higher systemic exposure in the elderly, for example C(max), had a mean 1.6-fold higher exposure on day 1 (95% CI Lower 0.90, Upper 2.74) and 2.5-fold on day 4 (95%CI 1.70, 3.68). This increase is in line with the presumed central role of hepatic blood flow in the elimination of DP-b99. No accumulation was observed after repeated dosing with 1 mg kg(-1) (mean accumulation calculated by AUC(0, 24 h) (day 4) : AUC(0, 24 h) (day 1) and was observed to be between 0.9 and 1.3 (young, elderly). CONCLUSIONS: This study suggests that DP-b99 is well tolerated in healthy young and elderly volunteers within the dose range evaluated. Studies to investigate further the efficacy of the compound are in progress.

The lipophilic metal chelator DP-109 reduces amyloid pathology in brains of human beta-amyloid precursor protein transgenic mice.

Metals such as zinc, copper and iron contribute to aggregation of amyloid-beta (Abeta) protein and deposition of amyloid plaques in Alzheimer's disease (AD). We examined whether the lipophilic metal chelator DP-109 inhibited these events in aged female hAbetaPP-transgenic Tg2576 mice. Daily gavage administration of DP-109 for 3 months markedly reduced the burden of amyloid plaques and the degree of cerebral amyloid angiopathy in brains, compared to animals receiving vehicle treatment. Moreover, DP-109 treatment appeared to facilitate the transition of Abeta from insoluble to soluble forms in the cerebrum. These results further support the hypothesis that endogenous metals are involved in the deposition of aggregated Abeta in brains of AD patients, and that metal chelators may be useful therapeutic agents in the treatment of AD.

Bioactive lipids and their receptors.

Recent studies show that several, if not all, degradative products of glycerol- and sphingosine-based lipids are active molecules that play important roles in different signal transduction pathways. The functions and actions of lysophosphatidic acid and sphingosine 1-phosphate, the degradation products of phospholipids and sphingolipids, respectively, have received a great deal of attention during the past few years. These lipid mediators are active through several abundant G protein-coupled receptors that were recently identified and characterized. This review will discuss recent achievements in the area of bioactive lipids.