Enzastaurin cardiotoxicity: QT interval prolongation, negative inotropic responses and negative chronotropic action

Several clinical trials observed that enzastaurin prolonged QT interval in cancer patients. However, the mechanism of enzastaurin-induced QT interval prolongation is unclear. Therefore, this study aimed to assess the effect and mechanism of enzastaurin on QT interval and cardiac function. The Langendorff and Ion-Optix MyoCam systems were used to assess the effects of enzastaurin on QT interval, cardiac systolic function and intracellular Ca²⁺ transient in guinea pig hearts and ventricular myocytes. The effects of enzastaurin on the rapid delayed rectifier (I_Kr), the slow delayed rectifier K⁺ current (I_Ks), transient outward potassium current (I_to), action potentials, Ryanodine Receptor 2 (RyR2) and the sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2a (SERCA2a) expression and activity in HEK 293 cell system and primary cardiomyocytes were investigated using whole-cell recording technique and western blotting. We found that enzastaurin significantly prolonged QT interval in guinea pig hearts and increased the action potential duration (APD) in guinea pig cardiomyocytes in a dose-dependent manner. Enzastaurin potently inhibited I_Kr by binding to the human Ether-à-go-go-Related gene (hERG) channel in both open and closed states, and hERG mutant channels, including S636A, S631A, and F656V attenuated the inhibitory effect of enzastaurin. Enzastaurin also moderately decreased I_Ks. Additionally, enzastaurin also induced negative chronotropic action. Moreover, enzastaurin impaired cardiac systolic function and reduced intracellular Ca²⁺ transient via inhibition of RyR2 phosphorylation. Taken together, we found that enzastaurin prolongs QT, reduces heart rate and impairs cardiac systolic function. Therefore, we recommend that electrocardiogram (ECG) and cardiac function should be continuously monitored when enzastaurin is administered to cancer patients.

[The application of next-generation sequencing in the diagnosis of Pneumocystis pneumonia in non-HIV infected patients]

Objective: To evaluate the clinical value of next-generation sequencing in the diagnosis of Pneumocystis pneumonia in non-HIV infected patients. Methods: A retrospective study was conducted on the diagnosis and treatment of Pneumocystis pneumonia in 5 non-HIV patients in the Fourth Medical Center of the General Hospital of the PLA from September 1, 2017 to September 1, 2018. Next-generation sequencing of BALF were compared with the traditional laboratory microbiological test, and the advantages of the next-generation sequencing in the diagnosis of Pneumocystis pneumonia in non-HIV infected patients were analyzed. Results: There were 3 males and 2 females, with a mean age (48±6) years. Three patients had membranous nephropathy, a patient had tuberculous meningitis, and a patient had esophageal cancer after radiotherapy and chemotherapy. All patients had glucocorticoid medication history before. The clinical manifestations were fever, cough and dyspnea. The chest CT mainly showed bilateral lung ground glass shadows. All the results of 1, 3-β-D-glucan test were more than 1 000 ng/L. Bronchoalveolar lavage was performed in the 5 cases, and Pneumocystis cysts were found in 1 BALF by Gomori's methenamine silver nitrate staining, and the DNAs of Pneumocystis and human herpesvirus were detected in 5 BALFs by next-generation sequencing. All patients were treated with sulfamethoxazole/trimethoprim (orally, 1.44 g, q8 h) for 23 to 72 days (median 33 days), and with ganciclovir(Ⅳ, 250 mg q12 h) for 6 to 22 days (median 15 days). The chest CT manifestations and symptoms were improved after treatment, without death. Conclusions: The next-generation sequencing of BALF is more specific and sensitive in the diagnosis of Pneumocystis pneumoniae in non-HIV patients. It is faster, more comprehensive and more accurate than the traditional laboratory test, and could be widely used as a PCP diagnosis technique.

Effect of antisense oligonucleotide against mouse dentine matrix protein 1 on mineralization ability and calcium ions metabolism in odontoblast-like cell line MDPC-23

AIM

To study the mineralization ability and the dynamic changes of intracellular and extracellular concentrations of calcium ions in the odontoblast-like cell line MDPC-23 affected by antisense oligonucleotide (AS-ODN) against mouse dentine matrix protein 1 (DMP1).

METHODOLOGY

The expression of DMP1 in MDPC-23 cells was detected by an immunohistochemical method and its blocking outcome by the Western blot method. The alkaline phosphatase (ALP) activity, size and number of mineralized nodules, and the intracellular free ([Ca2+]if), total ([Ca2+]it) and the extracellular ([Ca2+]e) calcium ion concentrations in MDPC-23 cells in the experimental group affected with AS-ODN were compared with those in the control group (paired-samples t-test).

RESULTS

Dentine matrix protein 1 was stably expressed in a stable way in MDPC-23 cells; the expression was only just detectable at 12 h and became negative after 24 h affected by AS-ODN. Compared with the control groups, ALP activity of MDPC-23 cells in the AS-ODN group was decreased (P < 0.05), and both the number and size of mineralized nodules were smaller than those in the control group. [Ca2+]if in the AS-ODN group increased and then decreased after 24 h. [Ca2+]it dropped substantially to the lowest point at 24 h (P < 0.01). [Ca2+]e increased before treatment for 24 h and then dropped, however, it was still higher than that of the control group.

CONCLUSIONS

Antisense oligonucleotide against DMP1 could decrease mineralization ability and affect the intracellular and extracellular concentrations of calcium ions in MDPC-23 cells. This would indicate that DMP1 regulates the metabolism and transportation of calcium ions in odontoblasts, and thus boosts dentine mineralization.