Nitro fatty acids (NFAs) are endogenously generated lipid mediators deriving from reactions of unsaturated electrophilic fatty acids with reactive nitrogen species. Furthermore, Mediterranean diets can be a source of NFA. These highly electrophilic fatty acids can undergo Michael addition reaction with cysteine residues, leading to post-translational modifications (PTM) of selected regulatory proteins. Such modifications are capable of changing target protein function during cell signaling or in biosynthetic pathways. NFA target proteins include the peroxisome proliferator-activated receptor γ (PPAR-γ), the pro-inflammatory and tumorigenic nuclear factor-κB (NF-κB) signaling pathway, the pro-inflammatory 5-lipoxygenases (5-LO) biosynthesis pathway as well as soluble epoxide hydrolase (sEH), which is essentially involved in the regulation of vascular tone. In several animal models of inflammation and cancer, the therapeutic efficacy of well-tolerated NFA has been demonstrated. This has already led to clinical phase II studies investigating possible therapeutic effects of NFA in subjects with pulmonary arterial hypertension. Albeit Michael acceptors feature a broad spectrum of bioactivity, they have for a rather long time been avoided as drug candidates owing to their presumed unselective reactivity and toxicity. However, targeted covalent modification of regulatory proteins by Michael acceptors became recognized as a promising approach to drug discovery with the recent FDA approvals of the cancer therapeutics, afatanib (2013), ibrutinib (2013), and osimertinib (2015). Furthermore, the Michael acceptor, neratinib, a dual inhibitor of the human epidermal growth factor receptor 2 and epidermal growth factor receptor, was recently approved by the FDA (2017) and by the EMA (2018) for the treatment of breast cancer. Finally, a number of further Michael acceptor drug candidates are currently under clinical investigation for pharmacotherapy of inflammation and cancer. In this review, we focus on the pharmacology of NFA and other Michael acceptor drugs, summarizing their potential as an emerging class of future antiphlogistics and adjuvant in tumor therapeutics.

Transglutaminase 2 (TG2) is an enzyme which in the open conformation exerts transamidase activity, leading to protein cross-linking and fibrosis. In the closed conformation, TG2 participates in transmembrane signaling as a G protein. The unspecific transglutaminase inhibitor cystamine causes vasorelaxation in rat resistance arteries. However, the role of TG2 conformation in vascular function is unknown. We investigated the vascular effects of selective TG2 inhibitors by myography in isolated rat mesenteric and human subcutaneous resistance arteries, patch-clamp studies on vascular smooth muscle cells, and blood pressure measurements in rats and mice. LDN 27219 promoted the closed TG2 conformation and inhibited transamidase activity in mesenteric arteries. In contrast to TG2 inhibitors promoting the open conformation (Z-DON, VA5), LDN 27219 concentration-dependently relaxed rat and resistance human arteries by a mechanism dependent on nitric oxide, large-conductance calcium-activated and voltage-gated potassium channels 7, lowering blood pressure. LDN 27219 also potentiated acetylcholine-induced relaxation by opening potassium channels in the smooth muscle; these effects were abolished by membrane-permeable TG2 inhibitors promoting the open conformation. In isolated arteries from 35- to 40-week-old rats, transamidase activity was increased, and LDN 27219 improved acetylcholine-induced relaxation more than in younger rats. Infusion of LDN 27219 decreased blood pressure more effectively in 35- to 40-week than 12- to 14-week-old anesthetized rats. In summary, pharmacological modulation of TG2 to the closed conformation age-dependently lowers blood pressure and, by opening potassium channels, potentiates endothelium-dependent vasorelaxation. Our findings suggest that promoting the closed conformation of TG2 is a potential strategy to treat age-related vascular dysfunction and lowers blood pressure.

On-demand phosphodiesterase type 5 inhibitor (PDE5i) monotherapy is a first-line treatment for erectile dysfunction (ED), but 30%-40% of patients exhibit little or no response. The success rate of alprostadil therapy is high in these patients, but this treatment requires painful intracavernosal injection. To systematically review the efficacy and safety of second-line oral pharmacologic combination therapies of ED when PDE5i monotherapy fails. PubMed and Embase were searched to identify reports providing quantitative data on the treatment of ED in patients failing PDE5i monotherapy. The measures of erectile function were the International Index of Erectile Function (IIEF) and the Erectile Function Domain (EFD). Chronic treatment with the PDE5i tadalafil alone or in combination with sildenafil on demand showed similar IIEF-5 score improvements. None of the 3 randomized controlled trials (RCTs) in patients who had failed PDE5i monotherapy found a superior effect on IIEF scores from the combination of androgen plus PDE5i compared with PDE5i monotherapy. Combination therapy with androgen supplementation and PDE5i appears safe. In 1 RCT, combination therapy with PDE5i and an α₁-adrenoceptor antagonist was not superior to PDE5i monotherapy. Six other studies, each with a different combination of PDE5i and another drug (eg, metformin, folic acid, 5-alpha-reductase inhibitors), were identified, but further research is required to investigate their efficacy in treating ED. For ED, chronic treatment with low-dose PDE5i can be attempted when standard on-demand regimens fail. Combination therapy with androgen supplementation and a PDE5i appears to be safe. The combination of an α₁-adrenoceptor antagonist and PDE5i shows no advantageous effect on ED compared with PDE5i monotherapy. The efficacy of combining PDE5i with metformin, folic acid, or 5-alpha-reductase inhibitors is uncertain and requires further research. There is an unmet need for oral treatment of ED in nonresponders to PDE5i treatment. Munk NE, Knudsen JS, Comerma-Steffensen S, et al. Systematic Review of Oral Combination Therapy for Erectile Dysfunction When Phosphodiesterase Type 5 Inhibitor Monotherapy Fails. Sex Med Rev 2019;7:430-441.

The prevalence of obesity increases and is associated with increases in co-morbidities e.g. type 2 diabetes, hyperlipidemia, hypertension, obstructive sleep apnea, heart disease, stroke, asthma, several forms of cancer, depression, and may result in reduction of expected remaining lifespan. We have reviewed the adverse effects on the cardiovascular system of anti-obesity drugs now retracted from the market as well as the cardiovascular profile of current drugs and potential pathways which are considered for treatment of obesity. Fenfluramine, and sibutramine were withdrawn due to increased cardiovascular risk, while an inverse agonist at cannabinoid type 1 (CB₁) receptors, rimonobant was withdrawn due to serious psychiatric problems. At present there are only few treatments available including orlistat and, phentermine alone or in combination with topiramate and lorcaserin, although cardiovascular side effects need to be clarified regarding phentermine and lorcaserin. Drugs approved for type 2 diabetes including glucagon like peptide (GLP-1) analogues and metformin also cause moderate weight losses and have a favourable cardiovascular profile, while the anti-obesity potential of nebivolol remains unexplored. Pathways with anti-obesity potential include sirtuin activation, blockade of transient receptor potential (TRPV1) channels, acetyl-CoA carboxylase 1 and 2 inhibitors, uncoupling protein activators, bile acids, crotonins, CB₁ antagonists, but the cardiovascular profile remains to be investigated. For type 2 diabetes, new drug classes with possible advantageous cardiovascular profiles, e.g. GLP-1 analogues and sodium-glucose co-transport type 2 inhibitors, are associated with weight loss and are currently being evaluated as anti-obesity drugs.

Proline-rich oligopeptides (PROs) are a large family which comprises the bradykinin-potentiating peptides (BPPs). They inhibit the activity of the angiotensin I-converting enzyme (ACE) and have a typical pyroglutamyl (Pyr)/proline-rich structure at the N- and C-terminus, respectively. Furthermore, PROs decrease blood pressure in animals. In the present study, the isolation and biological characterization of a novel vasoactive BPP isolated from the skin secretion of the frog Brachycephalus ephippium is described. This new PRO, termed BPP-Brachy, has the primary structure WPPPKVSP and the amidated form termed BPP-BrachyNH₂ inhibits efficiently ACE in rat serum. In silico molecular modeling and docking studies suggest that BPP-BrachyNH₂ is capable of forming a hydrogen bond network as well as multiple van der Waals interactions with the rat ACE, which blocks the access of the substrate to the C-domain active site. Moreover, in rat thoracic aorta BPP-BrachyNH₂ induces potent endothelium-dependent vasodilatation with similar magnitude as captopril. In DAF-FM DA-loaded aortic cross sections examined by confocal microscopy, BPP-BrachyNH₂ was found to increase the release of nitric oxide (NO). Moreover, BPP-BrachyNH₂ was devoid of toxicity in endothelial and smooth muscle cell cultures. In conclusion, the peptide BPP-BrachyNH₂ has a novel sequence being the first BPP isolated from the skin secretion of the Brachycephalidae family. This opens for exploring amphibians as a source of new biomolecules. The BPP-BrachyNH₂ is devoid of cytotoxicity and elicits endothelium-dependent vasodilatation mediated by NO. These findings open for the possibility of potential application of these peptides in the treatment of endothelial dysfunction and cardiovascular diseases.