No abstract

The activation of the transcription factor NF-E2-related factor 2 (Nrf2) maintains cellular homeostasis in response to oxidative stress by the regulation of multiple cytoprotective genes. Without stressors, the activity of Nrf2 is inhibited by its interaction with the Keap1 (kelch-like ECH-associated protein 1). Here, we describe (3S)-1-[4-[(2,3,5,6-tetramethylphenyl) sulfonylamino]-1-naphthyl]pyrrolidine-3-carboxylic acid (RA839), a small molecule that binds noncovalently to the Nrf2-interacting kelch domain of Keap1 with a K d of ϳ6 M, as demonstrated by x-ray co-crystallization and isothermal titration calorimetry. Whole genome DNA arrays showed that at 10 M RA839 significantly regulated 105 probe sets in bone marrow-derived macrophages. Canonical pathway mapping of these probe sets revealed an activation of pathways linked with Nrf2 signaling. These pathways were also activated after the activation of Nrf2 by the silencing of Keap1 expression. RA839 regulated only two genes in Nrf2 knock-out macrophages. Similar to the activation of Nrf2 by either silencing of Keap1 expression or by the reactive compound 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid methyl ester (CDDO-Me), RA839 prevented the induction of both inducible nitric-oxide synthase expression and nitric oxide release in response to lipopolysaccharides in macrophages. In mice, RA839 acutely induced Nrf2 target gene expression in liver. RA839 is a selective inhibitor of the Keap1/Nrf2 interaction and a useful tool compound to study the biology of Nrf2.The transcription factor NF-E2-related factor 2 (Nrf2) 2 is a promising target for the treatment of oxidative and inflammatory stress-related disorders, such as neurodegenerative and microvascular diseases (1-5). Nrf2 regulates the expression of several cytoprotective anti-oxidative and anti-inflammatory proteins by binding to the cis-acting antioxidant response element (ARE) within gene promoters. Nrf2 itself is regulated by the kelch-like ECH-associated protein 1 (Keap1), which is a substrate recognition subunit for a cullin3-based ubiquitin E3 ligase and functions as a sensor for oxidative and electrophilic stress. Structural elements of the Keap1 protein include the C-terminal Nrf2-binding kelch domain, the intervening region, and the broad complex-Tramtrack-Bric-a-Brac domain. Keap1 binds as a dimer via its two Kelch domains to one molecule of Nrf2, specifically to the high affinity ETGE and the low affinity DLG motives at the N terminus of Nrf2. Without stressors, this leads to the ubiquitinylation and subsequent proteolytic degradation of the transcription factor. In the presence of oxidative or electrophilic stress, cysteine residues within the intervening region and broad complex-Tramtrack-Bric-a-Brac domain of Keap1 become modified. According to the hinge and latch model, this weakens the interaction between Keap1 and the DLG motif of Nrf2 but does not lead to a release of Nrf2 (6, 7). The conformation cycling model postulates a stabilization of the Keap1/Nrf2 interaction by the Keap1 modifica...

Nicotinamide N-methyltransferase (NNMT) is a cytosolic enzyme that catalyzes the transfer of a methyl group from the co-factor S-adenosyl-L-methionine (SAM) onto the substrate, nicotinamide (NA) to form 1-methyl-nicotinamide (MNA). Higher NNMT expression and MNA concentrations have been associated with obesity and type-2 diabetes. Here we report a small molecule analog of NA, JBSNF-000088, that inhibits NNMT activity, reduces MNA levels and drives insulin sensitization, glucose modulation and body weight reduction in animal models of metabolic disease. In mice with high fat diet (HFD)-induced obesity, JBSNF-000088 treatment caused a reduction in body weight, improved insulin sensitivity and normalized glucose tolerance to the level of lean control mice. These effects were not seen in NNMT knockout mice on HFD, confirming specificity of JBSNF-000088. The compound also improved glucose handling in ob/ob and db/db mice albeit to a lesser extent and in the absence of weight loss. Co-crystal structure analysis revealed the presence of the N-methylated product of JBSNF-000088 bound to the NNMT protein. The N-methylated product was also detected in the plasma of mice treated with JBSNF-000088. Hence, JBSNF-000088 may act as a slow-turnover substrate analog, driving the observed metabolic benefits.

AimsType 2 diabetes mellitus (DM) leads to cardiac dysfunction irrespective of hypertension and coronary artery disease; this is called diabetic cardiomyopathy. Here, we investigated the severity of diabetic cardiomyopathy and myocardial remodelling in aged Zucker diabetic fatty (ZDF) rats. Methods and resultsBody weight, blood glucose and glycated haemoglobin (Hb A1c ) levels, and urinary albumin excretion were monitored regularly in ZDF rats (n ¼ 19) and control littermates (n ¼ 19) up to age 45 weeks. ZDF rats were severely diabetic during the entire study period and demonstrated decreased body and heart weights at sacrifice. Left ventricular (LV) function was determined using magnetic resonance imaging (MRI) at age 44 weeks and revealed similar LV ejection fraction and cardiac output index in control and ZDF rats, indicating preserved systolic function. LV pressure characteristics assessed at age 45 weeks showed significant, but mild elevations of LV end-diastolic pressure (+45%) and relaxation time constant Tau (+54%) in ZDF rats, indicating diastolic dysfunction. Histological analyses revealed a significantly increased LV collagen content (+50%), but no cardiomyocyte hypertrophy in ZDF rats. ConclusionThe present study clearly shows that long term, severe DM in 45-week-old ZDF rats resulted in relatively mild impairment of diastolic LV function, whereas systolic function was well preserved. These data do not support the notion that diabetes per se is a critical factor in the induction of a clinically relevant degree of cardiac dysfunction. Co-morbidities such as hypertension and coronary artery disease probably have larger impacts on myocardial function in diabetic individuals.--

Cathepsin A (CatA) is a serine carboxypeptidase distributed between lysosomes, cell membrane, and extracellular space. Several peptide hormones including bradykinin and angiotensin I have been described as substrates. Therefore, the inhibition of CatA has the potential for beneficial effects in cardiovascular diseases. Pharmacological inhibition of CatA by the natural product ebelactone B increased renal bradykinin levels and prevented the development of salt-induced hypertension. However, so far no small molecule inhibitors of CatA with oral bioavailability have been described to allow further pharmacological profiling. In our work we identified novel β-amino acid derivatives as inhibitors of CatA after a HTS analysis based on a project adapted fragment approach. The new inhibitors showed beneficial ADME and pharmacokinetic profiles, and their binding modes were established by X-ray crystallography. Further investigations led to the identification of a hitherto unknown pathophysiological role of CatA in cardiac hypertrophy. One of our inhibitors is currently undergoing phase I clinical trials.