The NRF2 activator DH404 attenuates adverse ventricular remodeling post-myocardial infarction by modifying redox signalling.

BACKGROUND: The novel synthetic triterpenoid, bardoxolone methyl, has the ability to upregulate cytoprotective proteins via induction of the nuclear factor erythroid-2-related factor 2 (Nrf2) pathway. This makes it a promising therapeutic agent in disease states characterized by dysregulated oxidative signalling. We have examined the effect of a Nrf2 activator, dihydro-CDDO-trifluoroethyl amide (DH404), a derivative of bardoxolone methyl, on post-infarct cardiac remodeling in rats. METHODS/RESULTS: DH404, administered from day 2 post myocardial infarction (MI: 30min transient ischemia followed by reperfusion) resulted in almost complete protection against adverse ventricular remodeling as assessed at day 28 (left ventricular end-systolic area: sham 0.14±0.01cm2, MI vehicle 0.29±0.04cm2 vs. MI DH404 0.18±0.02cm2, P<0.05); infarct size (21.3±3.4% MI vehicle vs. 10.9±2.3% MI DH404, P<0.05) with associated benefits on systolic function (fractional shortening: sham 71.9±2.6%, MI vehicle 36.2±1.9% vs. MI DH404 58.6±4.0%, P<0.05). These structural and functional benefits were associated with lower myocardial expression of atrial natriuretic peptide (ANP, P<0.01 vs. MI vehicle), and decreased fibronectin (P<0.01 vs. MI vehicle) in DH404-treated MI rats at 28 days. MI increased glutathionylation of endothelial nitric oxide synthase (eNOS) in vitro - a molecular switch that uncouples the enzyme, increasing superoxide production and decreasing nitric oxide (NO) bioavailability. MI-induced eNOS glutathionylation was substantially ameliorated by DH404. An associated increase in glutaredoxin 1 (Grx1) co-immunoprecipitation with eNOS without a change in expression was mechanistically intriguing. Indeed, in parallel in vitro experiments, silencing of Grx1 abolished the protective effect of DH404 against Angiotensin II-induced eNOS uncoupling. CONCLUSION: The bardoxolone derivative DH404 significantly attenuated cardiac remodeling post MI, at least in part, by re-coupling of eNOS and increasing the functional interaction of Grx1 with eNOS. This agent may have clinical benefits protecting against post MI cardiomyopathy.

Oxidative and nitrosative signalling in pulmonary arterial hypertension - Implications for development of novel therapies.

Pulmonary arterial hypertension (PAH) is a syndrome characterised by an increase in pulmonary vascular resistance. This results in elevated resting pulmonary artery pressure and leads to progressive right ventricular (RV) failure, secondary to increased afterload. Although initially thought to be a disease driven primarily by endothelial dysfunction with a resultant vasoconstrictor versus vasodilator imbalance, it has become increasingly apparent that the rise in pulmonary vascular resistance that causes RV failure is also attributable to pulmonary vascular remodelling. This inflammatory, hyper-proliferative and anti-apoptotic phenotype is accompanied by a metabolic switch from physiological mitochondrial oxidative phosphorylation to aerobic glycolysis. The molecular pathways triggering this cellular metabolic shift have been the subject of extensive investigation, as their discovery will inevitably lead to new therapeutic targets. Reactive oxygen/nitrogen species (ROS/RNS) including hydrogen peroxide, superoxide and peroxynitrite are second messenger molecules that are involved in functional oxidative and nitrosative modification of proteins. Dysregulation of oxidative signalling caused by an excess of ROS and RNS relative to antioxidants has been heavily implicated in the underlying pathophysiology of PAH and likely participates in this metabolic reprogramming. This review will focus on the role of oxidative signalling and redox reactions to the molecular pathology of PAH. In addition, promising novel therapeutic agents targeting these pathways will be discussed.

Exploring the anti-cancer activity of novel thiosemicarbazones generated through the combination of retro-fragments: dissection of critical structure-activity relationships.

Thiosemicarbazones (TSCs) are an interesting class of ligands that show a diverse range of biological activity, including anti-fungal, anti-viral and anti-cancer effects. Our previous studies have demonstrated the potent in vivo anti-tumor activity of novel TSCs and their ability to overcome resistance to clinically used chemotherapeutics. In the current study, 35 novel TSCs of 6 different classes were designed using a combination of retro-fragments that appear in other TSCs. Additionally, di-substitution at the terminal N4 atom, which was previously identified to be critical for potent anti-cancer activity, was preserved through the incorporation of an N4-based piperazine or morpholine ring. The anti-proliferative activity of the novel TSCs were examined in a variety of cancer and normal cell-types. In particular, compounds 1d and 3c demonstrated the greatest promise as anti-cancer agents with potent and selective anti-proliferative activity. Structure-activity relationship studies revealed that the chelators that utilized "soft" donor atoms, such as nitrogen and sulfur, resulted in potent anti-cancer activity. Indeed, the N,N,S donor atom set was crucial for the formation of redox active iron complexes that were able to mediate the oxidation of ascorbate. This further highlights the important role of reactive oxygen species generation in mediating potent anti-cancer activity. Significantly, this study identified the potent and selective anti-cancer activity of 1d and 3c that warrants further examination.