The novel compound liguzinediol exerts positive inotropic effects in isolated rat heart via sarcoplasmic reticulum Ca2+ ATPase-dependent mechanism

C=C-Ene-Reductases Reduce the C=N Bond of Oximes

Although enzymes have been found for many reactions, there are still transformations for which no enzyme is known. For instance, not a single defined enzyme has been described for the reduction of the C=N bond of an oxime, only whole organisms. Such an enzymatic reduction of an oxime may give access to (chiral) amines. By serendipity, we found that the oxime moiety adjacent to a ketone as well as an ester group can be reduced by ene-reductases (ERs) to an intermediate amino group. ERs are well-known enzymes for the reduction of activated alkenes, as of α,β-unsaturated ketones. For the specific substrate used here, the amine intermediate spontaneously reacts further to tetrasubstituted pyrazines. This reduction reaction represents an unexpected promiscuous activity of ERs expanding the toolkit of transformations using enzymes.

The protective effects of liguzinediol on congestive heart failure induced by myocardial infarction and its relative mechanism

Background

Heart failure (HF) is one of the most common causes of cardiovascular diseases in the world. Currently, the drugs used to treat HF in the clinic may cause serious side effects. Liguzinediol, 2, 5-dimethyl-3, 6-dimethyl-pyrazine, is a compound synthesized after the structural modification of ligustrazine (one active ingredient of Szechwan Lovage Rhizome). We aimed to observe the effects of liguzinediol on preventing HF and explore the related mechanisms.

Methods

The ligation of left anterior descending coronary artery was operated to established the myocardial infarction (MI) model in Sprague–Dawley rats. Cardiac functions were recorded by echocardiography and hemodynamics. The changes in the Renin–Angiotensin–Aldosterone System (RAAS), inflammation, and oxidative stress were detected by radioimmunoassay and Elisa kits. Western blot and real-time PCR were applied to determine the expressions of the TGF-β1/Smads pathway.

Results

Firstly, liguzinediol enhanced the systolic and diastolic functions of the heart in MI rats. Liguzinediol improved ventricular remodeling by reducing myocardial cell necrosis, as well as reducing collagen deposition and myocardial fibrosis. Then, liguzinediol suppressed the activation of RAAS, inhibited the synthesis of pro-inflammation factors, and reduced oxidative stress. In the end, liguzinediol also down-regulated the expressions of the TGF-β1/Smads pathway.

Conclusions

Liguzinediol could alleviate HF caused by MI in rats, and the protective effect was associated with the regulation of the TGF-β1/Smads pathway.

Hydrogen Sulfide Targets the Cys320/Cys529 Motif in Kv4.2 to Inhibit the Ito Potassium Channels in Cardiomyocytes and Regularizes Fatal Arrhythmia in Myocardial Infarction

AIMS

The mechanisms underlying numerous biological roles of hydrogen sulfide (H2S) remain largely unknown. We have previously reported an inhibitory role of H2S in the L-type calcium channels in cardiomyocytes. This prompts us to examine the mechanisms underlying the potential regulation of H2S on the ion channels.

RESULTS

H2S showed a novel inhibitory effect on Ito potassium channels, and this effect was blocked by mutation at the Cys320 and/or Cys529 residues of the Kv4.2 subunit. H2S broke the disulfide bridge between a pair of oxidized cysteine residues; however, it did not modify single cysteine residues. H2S extended action potential duration in epicardial myocytes and regularized fatal arrhythmia in a rat model of myocardial infarction. H2S treatment significantly increased survival by ∼1.4-fold in the critical 2-h time window after myocardial infarction with a protection against ventricular premature beats and fatal arrhythmia. However, H2S did not change the function of other ion channels, including IK1 and INa.

INNOVATION AND CONCLUSION

H2S targets the Cys320/Cys529 motif in Kv4.2 to regulate the Ito potassium channels. H2S also shows a potent regularizing effect against fatal arrhythmia in a rat model of myocardial infarction. The study provides the first piece of evidence for the role of H2S in regulating Ito potassium channels and also the specific motif in an ion channel labile for H2S regulation.

Identification, Characterization, Synthesis and Quantification of Related Impurities of Liguzinediol

An HPLC method was employed to create an impurity profile for liguzinediol as an active pharmaceutical ingredient (API), which resulted in the identification of two related impurities. Therefore, in order to improve the quality control of the liguzinediol-API, we identified and then developed a method for quantifying the two impurities (impurity-1 and impurity-2) by LC-TOF-MS-MS and then chemically synthesized them for further studies. Based on spectral data from IR, MS, (1)H and (13)C NMR, the structures of impurity-1 and impurity-2 were characterized as 2-hydroxymethyl-3,6-dimethylpyrazine and 2-hydroxymethyl-3,5,6-trimethylpyrazine, respectively. We further validated the method according to the International Conference on Harmonization guidelines to demonstrate the sensitivity, precision, linearity, accuracy and stability of the method described. In addition, the potential mechanisms underlying formation of impurity-1 and impurity-2 in the liguzinediol-API are discussed in detail.

Synthesis and biological evaluation of liguzinediol mono- and dual ester prodrugs as promising inotropic agents

The potent positive inotropic effect, together with the relatively low safety risk of liguzinediol (LZDO), relative to currently available inotropic drugs, has prompted us to intensively research and develop LZDO as a potent positive inotropic agent. In this study, to obtain LZDO alternatives for oral chronic administration, a series of long-chain fatty carboxylic mono- and dual-esters of LZDO were synthesized, and preliminarily evaluated for physicochemical properties and bioconversion. Enhanced lipophilic properties and decreased solubility of the prodrugs were observed as the side chain length increased. All esters showed conspicuous chemical stability in phosphate buffer (pH 7.4). Moreover, the enzymatic hydrolysis of esters in human plasma and human liver microsomes confirmed that the majority of esters were converted to LZDO, with release profiles that varied due to the size and structure of the side chain. In vivo pharmacokinetic studies following oral administration of monopivaloyl (M5), monodecyl (M10) and monododecyl (M12) esters demonstrated the evidently extended half-lives relative to LZDO dosed alone. In particular the monopivaloyl ester M5 exhibited an optimal pharmacokinetic profile with appropriate physiochemical characteristics.

Liguzinediol improved the heart function and inhibited myocardial cell apoptosis in rats with heart failure

AIM

Liguzinediol is a novel derivative of ligustrazine isolated from the traditional Chinese medicine Chuanxiong (Ligusticum wallichii Franch), and produces significant positive inotropic effect in isolated rat hearts. In this study we investigated the effects of liguzinediol on a rat model of heart failure.

METHODS

To induce heart failure, male SD rats were injected with doxorubicin (DOX, 2 mg/kg, ip) once a week for 4 weeks. Then the rats were administered with liguzinediol (5, 10, 20 mg·kg(-1)·d(-1), po) for 2 weeks. Hemodynamic examination was conducted to evaluate heart function. Myocardial cell apoptosis was examined morphologically. The expression of related genes and proteins were analyzed using immunohistochemical staining and Western blot assays, respectively.

RESULTS

Oral administration of liguzinediol dose-dependently improved the heart function in DOX-treated rats. Electron microscopy revealed that liguzinediol (10 mg·kg(-1)·d(-1)) markedly attenuated DOX-induced injury of cardiomyocytes, and decreased the number of apoptotic bodies in cardiomyocytes. Furthermore, liguzinediol significantly decreased Bax protein level, and increased Bcl-2 protein level in cardiomyocytes of DOX-treated rats, led to an increase in the ratio of Bcl-2/Bax. Moreover, liguzinediol significantly decreased the expression of both cleaved caspase-3 and NF-κB in cardiomyocytes of DOX-treated rats. Administration of digitalis (0.0225 mg·kg(-1)·d(-1)) also markedly improved the heart function and the morphology of cardiomyocytes in DOX-treated rats.

CONCLUSION

Liguzinediol improves the heart function and inhibits myocardial cell apoptosis in the rat model of heart failure, which is associated with regulating Bcl-2, Bax, caspase-3 and NF-κB expression.

Synthesis, biological evaluation, and pharmacokinetic study of novel liguzinediol prodrugs

Liguzinediol (LZDO) ester prodrugs 3-5 were synthesized and evaluated in vitro and in vivo for their potential use in prolonging the half-life of the parent drug LZDO (1a) in vivo. Prodrugs 3-5 were found to display a potent positive inotropic effect on the myocardium, without the risk of arrhythmia. Prodrugs 3-5 rapidly underwent enzymatic hydrolysis to release the parent compound LZDO in 1-3 h in rat liver microsomes and rat plasma. The half-life of the parent compound was prolonged after intragastric administration of prodrug 3, which was found to be a superior prodrug candidate for increasing myocardial contractility.