Electrophysiological evaluation of an anticancer drug gemcitabine on cardiotoxicity revealing down-regulation and modification of the activation gating properties in the human rapid delayed rectifier potassium channel.

Gemcitabine is an antineoplastic drug commonly used in the treatment of several types of cancers including pancreatic cancer and non-small cell lung cancer. Although gemcitabine-induced cardiotoxicity is widely recognized, the exact mechanism of cardiac dysfunction causing arrhythmias remains unclear. The objective of this study was to electrophysiologically evaluate the proarrhythmic cardiotoxicity of gemcitabine focusing on the human rapid delayed rectifier potassium channel, hERG channel. In heterologous hERG expressing HEK293 cells (hERG-HEK cells), hERG channel current (IhERG) was reduced by gemcitabine when applied for 24 h but not immediately after the application. Gemcitabine modified the activation gating properties of the hERG channel toward the hyperpolarization direction, while inactivation, deactivation or reactivation gating properties were unaffected by gemcitabine. When gemcitabine was applied to hERG-HEK cells in combined with tunicamycin, an inhibitor of N-acetylglucosamine phosphotransferase, gemcitabine was unable to reduce IhERG or shift the activation properties toward the hyperpolarization direction. While a mannosidase I inhibitor kifunensine alone reduced IhERG and the reduction was even larger in combined with gemcitabine, kifunensine was without effect on IhERG when hERG-HEK cells were pretreated with gemcitabine for 24 h. In addition, gemcitabine down-regulated fluorescence intensity for hERG potassium channel protein in rat neonatal cardiomyocyte, although hERG mRNA was unchanged. Our results suggest the possible mechanism of arrhythmias caused by gemcitabine revealing a down-regulation of IhERG through the post-translational glycosylation disruption possibly at the early phase of hERG channel glycosylation in the endoplasmic reticulum that alters the electrical excitability of cells.

Effect of Nrf2 on Phenotype Changes of Macrophages in the Anterior Vaginal Wall of Women With Pelvic Organ Prolapse.

OBJECTIVE: The aim of this study was to observe the effect of nuclear factor-erythroid 2-related factor 2 (Nrf2) on the phenotype changes of macrophages in the anterior vaginal wall of patients with pelvic organ prolapse (POP). METHODS: The tissues of the anterior vaginal wall of the control group (n = 30) and POP groups (n = 60) were collected during operation. The expressions of Nrf2, iNOS (representative factor of M1 macrophages), and CD206 (representative factor of M2 macrophages) were determined by immunohistochemical staining and Western blot. Morphological changes and collagen distribution of the anterior vaginal wall were observed by hematoxylin-eosin staining and Masson trichrome staining. RESULTS: Compared with the control group, the expression levels of Nrf2 and CD206 protein in the anterior vaginal wall tissues of the POP groups were significantly decreased ( P < 0.05), and were negatively proportional to the degree of prolapse ( P < 0.05). The expression of iNOS was significantly increased and was directly proportional to the degree of prolapse ( P < 0.05). Hematoxylin-eosin staining and Masson trichrome staining showed that the collagen fibers are more sparsely arranged and disordered in the POP group than the control. CONCLUSIONS: In patients with POP, the expression of antioxidant factor Nrf2 is reduced in the vaginal anterior wall tissues and the antioxidant capacity is weakened, leading to the blocked polarization of macrophages and the accumulation of a large number of M1 macrophages in the tissue, affecting the occurrence and development of POP.

Nitric oxide down-regulates voltage-gated Na+ channel in cardiomyocytes possibly through S-nitrosylation-mediated signaling.

Nitric oxide (NO) is produced from endothelial cells and cardiomyocytes composing the myocardium and benefits cardiac function through both vascular-dependent and-independent effects. This study was purposed to investigate the possible adverse effect of NO focusing on the voltage-gated Na+ channel in cardiomyocytes. We carried out patch-clamp experiments on rat neonatal cardiomyocytes demonstrating that NOC-18, an NO donor, significantly reduced Na+ channel current in a dose-dependent manner by a long-term application for 24 h, accompanied by a reduction of Nav1.5-mRNA and the protein, and an increase of a transcription factor forkhead box protein O1 (FOXO1) in the nucleus. The effect of NOC-18 on the Na+ channel was blocked by an inhibitor of thiol oxidation N-ethylmaleimide, a disulfide reducing agent disulfide 1,4-Dithioerythritol, or a FOXO1 activator paclitaxel, suggesting that NO is a negative regulator of the voltage-gated Na+ channel through thiols in regulatory protein(s) for the channel transcription.