Inhibition of hyperpolarization-activated cyclic nucleotide-gated channels by β-blocker carvedilol

BACKGROUND AND PURPOSE

Carvedilol is a clinically effective β-blocker broadly used for treating congestive heart failure (CHF), and several clinical trials have demonstrated that it shows a favourable effect compared with other β-blockers in patients with CHF. The mechanism underlying this beneficial effect of carvedilol compared to other β-blockers is not clearly understood. In addition to β-blockers, inhibitors of hyperpolarization-activated cyclic nucleotide (HCN)-gated channels, which play a critical role in spontaneous rhythmic activity in the heart, have also been proposed to be suitable drugs for reducing heart rate and, therefore, beneficial for treating CHF. In the present study, we investigated the effect of carvedilol on HCN channels.

EXPERIMENTAL APPROACH

Whole-cell patch-clamp recordings were used to assess the effect of carvedilol on currents from wild-type and mutant HCN1, HCN2 and HCN4 channels expressed in CHO cells.

KEY RESULTS

Carvedilol was the only β-blocker tested that showed inhibitory effects on the major sinoatrial HCN channel isoform HCN4. Carvedilol inhibited HCN4 in a concentration-dependent manner with an EC₅₀ of 4.4 μM. In addition, carvedilol also inhibited HCN1 and HCN2 channels. Carvedilol blocked HCN channels by decelerating the rate of channel activation and increasing that of deactivation, and shifted the voltage-dependence of activation leftwards. Our data also showed that carvedilol, unlike other inhibitors of this channel (ivabradine and ZD7288), is not an 'open-channel' inhibitor of HCN4.

CONCLUSIONS AND IMPLICATIONS

Carvedilol is a negative gating modulator of HCN channels. It represents a novel structure for future drug design of HCN channel inhibitors.

Effects of hemocoagulase agkistrodon on the coagulation factors and its procoagulant activities

Objective

Hemocoagulase agkistrodon (HCA), a thrombin-like enzyme (TLE) from the venom of the Chinese moccasin snake (Deinagkistrodon acutus), has been used in clinical practice as a hemostatic compound. The aim of this study was to further investigate the pharmacological properties of HCA.

Materials and methods

Sodium dodecyl sulfate or native polyacrylamide gel electrophoresis (SDS- or N-PAGE) as well as enzyme linked immunosorbent assays (ELISAs) were conducted to study the effects of HCA on the human plasma fibrinogen and prothrombin levels, as well as its in vitro interactions with some coagulation factors. In addition, the bleeding time effects of HCA in the mouse tail-bleeding model as well as its effects on the fibrinogen levels in rabbits were determined in vivo.

Results

In vitro results revealed that HCA exerts its procoagulant activities by hydrolyzing fibrinogen into segments that are easier to be absorbed, reducing the risk of thrombus formation. Besides, HCA could significantly inhibit the activation of prothrombin at the concentration of 0.3 μM. Unexpectedly, we also found that HCA was able to strongly bind to factor X/Xa (in a ratio of 1:1) and thus inhibit the acceleration of active factor X to tissue plasminogen activator-catalyzed plasminogen activation, demonstrating that it could be less likely to lead to thrombus formation. Finally, in vivo results indicated that HCA could significantly shorten the bleeding time in the mouse tail-bleeding model and had no effect on the fibrinogen levels in rabbits.

Conclusion

In summary, HCA, a unique and new family member of TLEs, may become a new clinical drug for the prevention and treatment of hemorrhage due to its unique and complex interactions with the blood system. Clarification of these features will enable us to further understand the mechanism of action of HCA and then promote its further application in clinical practice as a therapeutic drug.

[The efficacy and safety of coil embolization of septal branch in the treatment of patients with obstructive hypertrophic cardiomyopathy]

Objective: To observe the clinical efficacy and safety of coil embolization of septal branch in the treatment of obstructive hypertrophic cardiomyopathy (HOCM). Methods: Eighteen patients with HOCM hospitalized in our department from September 2014 to October 2016 were enrolled in this study. There were 12 males and 6 females in this cohort and the age of patients ranged from 22 to 64 years old. Left ventricular outflow tract gradient (LVOTG) was derived from echocardiographic apical five-chamber view at pre-operation and at 48 hours and 6 months post operation. 24-hour Holter ECG examination was performed to assess the ventricular tachycardia, atrial fibrillation, atrioventricular block at 3 days and 6 months after the interventional operation. Routine ECG and creatine kinase-MB (CK-MB) examination were performed at pre-operation, at 6, 24 and 48 hours post operation. Cardiac troponin T (cTnT) was detected at pre-operation, at 24, 48 hours and 6 days post operation. The clinical symptoms (including chest tightness, chest pain, shortness of breath, syncope) and NYHA classification were assessed at 1, 6 months after the operation by telephone follow-up or outpatient clinic visit. Results: The average preoperative LVOTG detected by cardiac catheter was 103.6 (92.0, 115.0) mmHg (1 mmHg=0.133 kPa) , and the average LVOTG significantly reduced to 44.3 (41.6, 47.2) mmHg immediately after operation (P<0.01). The average ventricular septal thickness at 48 hours (19.2±3.1) mm and 6 months (17.8±2.8) mm after operation tended to be lower than the preoperative ventricular septal thickness ((20.4±3.5) mm, P>0.05). The echocardiographic derived average LVOTG at 48 hours and 6 months after operation was 42.9 (41.1, 45.5) and 39.1 (37.5, 41.0) mmHg, which were significant lower than the preoperative average LVOTG (94.3 (88.5, 101.8) mmHg, both P<0.01). LVOTG at 6 months after operation was significantly lower than that at 48 hours after the operation (P<0.05). The NYHA classification at 6 months after operation was significantly improved compared to pre-operation NYHA classification (P<0.01). During and after the operation, there was no complete atrioventricular block and ventricular tachycardia, no patient developed anterior wall and inferior myocardial infarction. Only one patient experienced transient left bundle branch block. During the 6 months following-up, there was no death, syncope, chest pain, palpitations, shortness of breath, paroxysmal dyspnea and/or lower extremity edema, ventricular tachycardia, atrioventricular block and atrial fibrillation, complete atrioventricular block and ventricular arrhythmia. Conclusion: The coil embolization of septal branch is effective and safe for the treatment of patients with HOCM.

[Value of two left atrium and pulmonary vein stereoscopic imaging reconstruction methods on guiding radiofrequency ablation for atrial fibrillation]

Objective: To compare the value of two 3D imaging reconstruction methods for left atria and pulmonary vein on guiding the catheter ablation for atrial fibrillation (AF). Methods: From January 2014 to January 2017, a total of 100 drug refractory paroxysmal AF patients were divided into left atria direct angiography group (n=50), and indirect angiography group (n=50). 3D CARTO system was applied for mapping and guiding the ablation procedure. Patients assigned to direct angiography group were treated as follows: intraoperative puncture of atrial septum, inject contrast agent directly into the left atrium, conduct left atrial and pulmonary venous rotation angiography, reconstruct three-dimensional image, integrate the image into real-time X-ray system to facilitate circumferential pulmonary vein isolation. Patients assigned into the indirect angiography group were treated as follows: inject contrast agent through the right ventricle, conduct delayed rotation angiography of the left atria and pulmonary vein to guide circumferential pulmonary vein fixation and ablation. The left atrial and pulmonary venous image acquisition, the operation and X-ray exposure time, the success rate and the incidence of complication of the two groups were compared. The patients were followed up for 3-6 months. Results: General clinical characteristics of the two groups were similar(all P>0.05). Ablation was successful in all 100 patients. The operation time[(112.0±21.4)min vs. (134.0±24.3)min]and X-ray exposure time((10.7±4.7)min vs. (15.8±5.2)min)were significantly lower in direct angiography group than in indirect angiography group (both P<0.01). There was no significant difference between the two groups in the immediate (86%(43/50) vs. 82%(41/50), P=0.59) and short-term (76%(38/50) vs. 72%(36/50), P=0.65) success rate and complication rate (1 aneurysm in the direct angiography group, 1 pericardial tamponade in the indirect angiography group). In-hospital mortality was zero percent. Conclusion: It is safe and effective method to guide the radiofrequency catheter ablation of paroxysmal atrial fibrillation by reconstruction 3D image of left atrium and pulmonary vein. Compared with indirect angiography group, direct angiography group can improve the imaging quality of left atrium and pulmonary vein, decrease the X-ray exposure time of the ablation procedure.

Metabolic Epoxidation Is a Critical Step for the Development of Benzbromarone-Induced Hepatotoxicity

Benzbromarone (BBR) is effective in the treatment of gout; however, clinical findings have shown it can also cause fatal hepatic failure. Our early studies demonstrated that CYP3A catalyzed the biotransformation of BBR to epoxide intermediate(s) that reacted with sulfur nucleophiles of protein to form protein covalent binding both in vitro and in vivo. The present study attempted to define the correlation between metabolic epoxidation and hepatotoxicity of BBR by manipulating the structure of BBR. We rationally designed and synthesized three halogenated BBR derivatives, fluorinated BBR (6-F-BBR), chlorinated BBR (6-Cl-BBR), and brominated BBR (6-Br-BBR), to decrease the potential for cytochrome P450-mediated metabolic activation. Both in vitro and in vivo uricosuric activity assays showed that 6-F-BBR achieved favorable uricosuric effect, while 6-Cl-BBR and 6-Br-BBR showed weak uricosuric efficacy. Additionally, 6-F-BBR elicited much lower hepatotoxicity in mice. Fluorination of BBR offered advantage to metabolic stability in liver microsomes, almost completely blocked the formation of epoxide metabolite(s) and protein covalent binding, and attenuated hepatic and plasma glutathione depletion. Moreover, the structural manipulation did not alter the efficacy of BBR. This work provided solid evidence that the formation of the epoxide(s) is a key step in the development of BBR-induced hepatotoxicity.

Significant positive association of endotoxemia with histological severity in 237 patients with non-alcoholic fatty liver disease

BACKGROUND

Patients with nonalcoholic steatohepatitis (NASH) have gut dysbiosis and intestinal bacterial overgrowth.

AIM

To test the hypothesis that endotoxemia is associated with the histological severity of nonalcoholic fatty liver disease (NAFLD) and determine factors associated with endotoxemia.

METHODS

The endotoxemia markers lipopolysaccharide-binding protein (LBP) and endotoxin levels were measured in 237 NAFLD patients 1 day before liver biopsy. Biomarkers of liver injury and transient elastography were performed as additional markers of disease severity.

RESULTS

A total of 114/237 (48%) patients had NASH and 80/237 (34%) had F2-4 fibrosis. LBP was correlated with lobular inflammation (P=.001), while both LBP (P=.0004) and endotoxin levels (P=0.008) were correlated with fibrosis. LBP was also correlated with cytokeratin-18 fragments (P=.002) and aspartate aminotransferase-to-alanine aminotransferase ratio (P=.006), and both LBP (P=.019) and endotoxin (P=.006) were correlated with liver stiffness measurement by transient elastography. LBP was increased in patients with NASH (15.3±4.6 vs 13.8±3.3 μg/mL; P=.005) and F2-4 fibrosis (15.4±4.4 vs 14.0±3.7 μg/mL; P=.008). Interestingly, patients harbouring the TM6SF2 rs58542926 T allele that predispose to NAFLD/NASH had higher LBP level. By multivariate analysis, gender, higher body mass index and glycated haemoglobin, and TM6SF2 variants were independent factors associated with increased LBP level.

CONCLUSIONS

Endotoxemia is positively associated with NASH and significant fibrosis. The association between TM6SF2 and endotoxemia warrants further investigations. The findings may shed light on the pathogenesis of NASH and inform a novel treatment target.

Different clinical prognostic factors are associated with improved glycaemic control: findings from MARCH randomized trial

AIMS

Metformin and acarbose have comparable efficacy as initial therapy for HbA_1c reduction in Chinese patients with newly diagnosed Type 2 diabetes. However, not all participants achieved glycaemic control. Our aim was to discover a monotherapy predictor for therapeutic response in Type 2 diabetes on the basis of baseline features.

METHODS

Data from the MARCH trial were collected, resulting in 698 individuals being available for longitudinal analyses. All participants were divided into subgroups based on successful and unsuccessful achievement of the glycaemic target according to primary endpoints at week 24 (HbA_1c < 53 mmol/mol; 7.0%). Logistic regression analysis with stepwise variable selection was performed to assess the independent risk factors for good glycaemic control of monotherapy with metformin or acarbose.

RESULTS

Median HbA_1c was 66 ± 1 mmol/mol (8.2 ± 0.07%) in the metformin group at baseline, and 66 ± 1 mmol/mol (8.2 ± 0.07%) in the acarbose group. After 24 weeks of monotherapy, 79.8% of participants in the metformin group achieved glycaemic targets compared with 78.7% of those in the acarbose group. Multivariate regression analysis showed that BMI and fasting blood glucose were significant independent predictors for the maintenance of good glycaemic control in the metformin group, whereas phase I insulin secretion (Insulin/Glucose at 30 min, I30/G30) and duration of diabetes were associated with good glycaemic control in the acarbose group.

CONCLUSIONS

For newly diagnosed Type 2 diabetes, some clinical features and laboratory parameters are important prognostic factors for predicting drug responsiveness. Participants with a higher BMI and lower fasting blood glucose achieved good glycaemic control when metformin was selected as the initial treatment. Acarbose was best for participants with higher phase I insulin secretion (I30/G30) and shorter duration of Type 2 diabetes.

HCN Channel as Therapeutic Targets for Heart Failure and Pain

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels play important roles both in the control of heart rate and neuronal excitability. HCN channels open on hyperpolarization voltage, permeate to potassium and sodium, and generate an inward current, which is modulated by intracellular cAMP. HCN channels have been reported to involve in various human diseases, including heart failure, pain and epilepsy with datas from mutagenesis, transgenic mice and pharmacological studies. As a result, HCN channels may offer excellent drug development opportunities for novel analgestic, bradycardic and anticonvulsant drugs. Ivabradine is the first HCN channel inhibitor being clinically approved in 2005 for the treatment of chronic stable angina pectoris and heart failure. This review will summarize the structure and function of HCN channels. Further, we will discuss recent advances concerning the identification and action mechanism of reported HCN channel inhibitors.

The efficacy of proanthocyanidins and secnidazole in the treatment of chronic periodontitis after scaling and root planing therapy

The aim of this study is to evaluate the clinical and microbiological effect of the systemic antibiotic therapy of proanthocyanidins and secnidazole on periodontitis. Seventy-five subjects with chronic periodontitis were randomly divided into two treatment groups (secnidazole or proanthocyanidins) and one placebo control group (25 cases each). Plaque index (PI), gingival index (GI), gingival bleeding index (BI), probing pocket depth (PPD), and clinical attachment level (CAL) were carried out at baseline, post-treatment and 3 months after treatment. Microbial analysis was performed at baseline and post-treatment. The results show that the two treatment groups had greater mean reduction in BI, GI, and PPD evaluated at both post-treatment and 3 months after treatment compared to the control group (p less than 0.05), but there were no significant differences in those of PI and CAL (except CAL evaluated at post-treatment, p 0.05). After treatment, culturable bacteria counts significantly decreased. In conclusion, the adjunctive use of proanthocyanidins or secnidazole in combination with scaling and root planing in adults with periodontitis is effective in reducing the pathogenic flora and achieves significantly better clinical results to a certain degree.