Spirocyclic Benzopyran-Based Derivatives as New Anti-ischemic Activators of Mitochondrial ATP-Sensitive Potassium Channel

Synthesis and pharmacological characterization of mitochondrial KATP channel openers with enhanced mitochondriotropic effects

Mitochondria play a key role for deciding fate of cells and thus are considered an attractive target for pharmacological interventions focused on containment of myocardial ischemia/reperfusion (I/R) injury. Notably, the activation of mitochondrial potassium (mitoK) channels produces a mild depolarization of mitochondrial membrane, that contributes to reduce the driving force to calcium uptake and prevents the formation of mitochondrial transition membrane pore (MPTP); these events underlie anti-ischemic cardioprotection. However, an ideal mitoK channel opener should possess the fundamental requirement to be delivered at mitochondrial level; therefore, to improve the mitochondrial delivery of a previously characterized spirocyclic benzopyrane F81, new compounds have been developed. The three original triphenylphosphonium (TPP⁺)-derivatives of F81 (1-3), were evaluated for their cardioprotective activity on both isolated cardiac mitochondria and cardiac H9c2 cell line. Compound 1 was further investigated in an in vivo infarct model. This work confirms that the TPP⁺ strategy applied to mitoKATP openers could foster mitochondrial delivery and enhance the cardioprotective effects of mitochondrial activators of potassium channels.

Protective mechanisms of hydrogen sulfide in myocardial ischemia

Hydrogen sulfide (H₂ S), which has been identified as the third gaseous signaling molecule after nitric oxide (NO) and carbon monoxide (CO), plays an important role in maintaining homeostasis in the cardiovascular system. Endogenous H₂ S is produced mainly by three endogenous enzymes: cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfur transferase. Numerous studies have shown that H₂ S has a significant protective role in myocardial ischemia. The mechanisms by which H₂ S affords cardioprotection include the antifibrotic and antiapoptotic effects, regulation of ion channels, protection of mitochondria, reduction of oxidative stress and inflammatory response, regulation of microRNA expression, and promotion of angiogenesis. Amplification of NO- and CO-mediated signaling through crosstalk between H₂ S, NO, and CO may also contribute to the cardioprotective effect. Exogenous H₂ S donors are expected to become effective drugs for the treatment of cardiovascular diseases. This review article focuses on the protective mechanisms and potential therapeutic applications of H₂ S in myocardial ischemia.

Polymer-Supported Syntheses of Heterocycles Bearing Oxazine and Thiazine Scaffolds

In this review, we summarize synthetic approaches to preparing single or fused oxazine and thiazine derivatives using solid-phase synthesis (SPS). The literature survey revealed that diverse compounds bearing variously functionalized 1,2-oxazine, 1,3-oxazine, or 1,4-oxazine scaffolds and the corresponding thiazines are accessible by SPS. The latest contributions involving the stereoselective polymer-supported syntheses of morpholines indicate that the field is continuing to expand.

Synthesis and Functional Evaluation of Novel Aldose Reductase Inhibitors Bearing a Spirobenzopyran Scaffold

Background:

Aldose reductase, the first enzyme of the polyol pathway, is the key determinant for the pathogenesis of long term diabetic complications. Accordingly, its inhibition represents the major therapeutic strategy to treat this kind of pathologies.

Objectives:

In this work we describe the synthesis and the functional evaluation of a number of spiro-oxazolidinone and spiro-morpholinone acetic acid derivatives, and their benzyloxy analogs, developed as aldose reductase inhibitors.

Results:

Most of them proved to inhibit the target enzyme, showing IC₅₀ values in the micromolar/low micromolar range. SARs observed among the three different series allowed to highlight their key pharmacophoric elements, thus creating sound basis for the design of novel and more effective inhibitors.

Conclusion:

Although further substitution patterns are needed, the novel compounds here proposed represent a good starting point for the development of novel and effective ARIs.

Antiarrhythmic activity of a new spiro-cyclic benzopyran activator of the cardiac mitochondrial ATP dependent potassium channels

'Compound A' (4(ı)-(N-(4-acetamidobenzyl))-2,2-dimethyl-2,3-dihydro-5(ı)H-spiro[chromene-4,2(ı)-[1,4]oxazinan]-5(ı)-one) is a new spiro-cyclic benzopyran activator of the mitochondrial ATP-dependent potassium channels (mitoKATP). We researched the effect of compound A on ischemia/reperfusion (I/R)-induced ventricular arrhythmias. We also tested the hypothesis that the application of the activation of mitoKATP in combination with the inhibition of sarcolemmal ATP-dependent potassium channels (sarcKATP) may produce a stronger antiarrhythmic effect. In anesthetized rats, myocardial ischemia was performed by ligating the left main coronary artery followed by reperfusion. At a dose of 10 mg/kg, compound A significantly decreased arrhythmia scores and the total length of arrhythmias, whereas this was found to be ineffective at a dose of 3 mg/kg. Pre-treatment with 5-HD, a selective mitoKATP blocker, abolished the antiarrhythmic effect of compound A. Both diazoxide, a selective mitoKATP opener and HMR 1098, a selective sarcKATP blocker, significantly decreased the total length of arrhythmias. However, the combination of neither diazoxide nor compound A with HMR 1098 showed no additional therapeutic benefit. These results reveal that compound A may have a dose-dependent antiarrythmic effect, which is more pronounced than the antiarrhythmic effect of diazoxide. The antiarrhythmic effect of compound A may possibly depend on mitoKATP activation.

Anti-Diastereoselective Synthesis of CF3-Containing Spirooxazolines and Spirooxazines via Regiospecific Trifluoromethylative Spirocyclization by Photoredox Catalysis

A novel synthesis of CF3-containing spirooxazolines and spirooxazines has been developed. Regiospecific trifluoromethylative spirocyclization (CF3-spirocyclization) of cyclic alkenes bearing an amide pendant mediated by photoredox catalysis is a useful strategy for construction of a C(sp(3))-CF3 bond and an spirooxazoline or spirooxazine ring onto C═C bonds via a single step. The key intermediate is α-CF3-substituted carbocationic species smoothly generated from single-electron-transfer (SET) photoredox processes, which results in diastereoselective spirocyclization. This is the first example of synthesis of CF3-containing spirooxazolines and spirooxazines in anti-fashion with respect to the CF3 group and the oxygen atom of the spirocycles.

Different patterns of H2S/NO activity and cross-talk in the control of the coronary vascular bed under normotensive or hypertensive conditions

Hydrogen sulfide (H2S) and nitric oxide (NO) play pivotal roles in the cardiovascular system. Conflicting results have been reported about their cross-talk. This study investigated their interplays in coronary bed of normotensive (NTRs) and spontaneously hypertensive rats (SHRs). The effects of H2S- (NaHS) and NO-donors (sodium nitroprusside, SNP) on coronary flow (CF) were measured in Langendorff-perfused hearts of NTRs and SHRs, in the absence or in the presence of propargylglycine (PAG, inhibitor of H2S biosynthesis), L-NAME (inhibitor of NO biosynthesis), ODQ (inhibitor of guanylate cyclase), L-Cysteine (substrate for H2S biosynthesis) or L-Arginine (substrate for NO biosynthesis). In NTRs, NaHS and SNP increased CF; their effects were particularly evident in Angiotensin II (AngII)-contracted coronary arteries. The dilatory effects of NaHS were abolished by L-NAME and ODQ; conversely, PAG abolished the effects of SNP. In SHRs, high levels of myocardial ROS production were observed. NaHS and SNP did not reduce the oxidative stress, but produced clear increases of the basal CF. In contrast, in AngII-contracted coronary arteries of SHRs, significant hyporeactivity to NaHS and SNP was observed. In SHRs, the vasodilatory effects of NaHS were only modestly affected by L-NAME and ODQ; PAG poorly influenced the effects of SNP. Then, in NTRs, the vascular actions of H2S required NO and vice versa. By contrast, in SHRs, the H2S-induced actions scarcely depend on NO release; as well, the NO effects are largely H2S-independent. These results represent the first step for understanding pathophysiological mechanisms of NO/H2S interplays under both normotensive and hypertensive conditions.

Direct access to functionalized 4-nitromethyl-chromenes via a domino reaction under catalyst-free conditions

A simple and practical tandem reaction has been established to synthesize functionalized 4-(nitromethyl)-4H-chromenes. Most products were obtained in medium to good yields. Further, chromeno[4,3-b]chromene, an important structure, was easily obtained via this strategy.

Synthesis and biological evaluation of 2'-oxo-2,3-dihydro-3'H- spiro[chromene-4,5'-[1,3]oxazolidin]-3'yl]acetic acid derivatives as aldose reductase inhibitors

Aldose reductase (ARL2) is the first enzyme in the polyol pathway which catalyzes the NADPH-dependent reduction of glucose to sorbitol. Its involvement on diabetic complications makes this enzyme a challenge therapeutic target widely investigated to limit and/or prevent them. On this basis, a limited series of 4-spiro-oxazolidinone-benzopyran derivatives (1-7) were synthesized to evaluate them as potential ARL2 inhibitors. The activity was determined spectrophotometrically by monitoring the oxidation of NADPH catalyzed by ALR2. Within the series of compounds, the 4-methoxy derivative 1b showed to be the most active compound, exhibiting inhibitory levels in the submicromolar range. In addition, the activity against the aldehyde reductase isoform (ARL1) was also evaluated. Unlike sorbinil (reference drug) that lack of selectivity towards the two enzyme all the tested compounds resulted to be devoid of ARL1 inhibitory activity (IC(50) > 10 µM), thus proving to be selective.

Novel adenosine 5'-triphosphate-sensitive potassium channel ligands: a patent overview (2005-2010)

INTRODUCTION

ATP-sensitive potassium channels are important metabolic regulators that link cellular metabolism to excitability. Their wide distribution in various tissues and organs makes them significant and topical targets in a large number of diseases.

AREAS COVERED

This review summarizes the current understanding of the molecular biology and pharmacology of K(ATP) channels, and the pathological states that result from aberrant expression or function of these proteins. In particular, relevant research, patents and patent applications of the past 5 years are discussed.

EXPERT OPINION

The tissue-specific K(ATP) channel modulation reflects an early discovery stage in drug design. The wide distribution of K(ATP) channels lets us consider them as valid targets for several pathologies, but on other hand the ubiquitous nature is a relevant drawback in developing an effective therapy because of the onset of side effects related to the lack of selectivity. On this basis, further investigations on both the structures and the localization of each receptor subtype should be carried out either exploring the structure-activity relationship of the already existing K(ATP) ligands or developing new selective fluorescent probes. To date, this research area still strives to design new tissue-targeted ligands that could pave the way to the development of innovative and effective drugs for clinical use.

Hydrogen sulphide: novel opportunity for drug discovery

Hydrogen sulphide (H(2)S) is emerging as an important endogenous modulator, which exhibits the beneficial effects of nitric oxide (NO) on the cardiovascular (CV) system, without producing toxic metabolites. H(2)S is biosynthesized in mammalian tissues by cystathionine-β-synthase and cystathionine-γ-lyase. H(2)S exhibits the antioxidant properties of inorganic and organic sulphites, behaving as a scavenger of reactive oxygen species. There is also clear evidence that H(2)S triggers other important effects, mainly mediated by the activation of ATP-sensitive potassium channels (K(ATP)). This mechanism accounts for the vasorelaxing and cardioprotective effects of H(2)S. Furthermore, H(2)S inhibits smooth muscle proliferation and platelet aggregation. In non-CV systems, H(2)S regulates the functions of the central nervous system, as well as respiratory, gastroenteric, and endocrine systems. Conversely, H(2)S deficiency contributes to the pathogenesis of hypertension. Likewise, impairment of H(2)S biosynthesis is involved in CV complications associated with diabetes mellitus. There is also evidence of a cross-talk between the H(2)S and the endothelial NO pathways. In particular, recent observations indicate a possible pathogenic link between deficiencies of H(2 S activity and the progress of endothelial dysfunction. These biological aspects of endogenous H(2)S have led several authors to look at this mediator as "the new NO" that has given attractive opportunities to develop innovative classes of drugs. In this review, the main biological actions of H(2)S are discussed. Moreover, some examples of H(2)S-donors are shown, as well as some hybrids, in which H(2)S-releasing moieties are added to well-known drugs, for improving their pharmacodynamic profile or reducing the potential for adverse effects, are reported.

Design, synthesis and biological evaluation of new ionone derivatives as potential neuroprotective agents in cerebral ischemia

A new series of ionone derived allylic alcohols have been evaluated for anti-ischemic activity. Out of them, 12f and 13b decreased infarct volume to 23.98+/-4.7 mm3 and 93.98+/-24.8 mm3 as compared to ischemic group.