ZFHX3 knockdown increases arrhythmogenesis and dysregulates calcium homeostasis in HL-1 atrial myocytes.

BACKGROUND: ZFHX3 plays an important role in the genesis of atrial fibrillation. However, the atrial electrophysiological effects of ZFHX3 are not clear. This study sought to investigate roles of ZFHX3 in atrial electrophysiology and calcium homeostasis by using HL-1 atrial myocytes knocked-down with ZFHX3. METHODS: Patch clamp, confocal fluorescence microscopy and Western blot were used to study electrical activity, ionic currents, calcium homeostasis and protein expressions in stable ZFHX3 shRNA cells. RESULTS: As compared to control, ZFHX3 shRNA cells with 28% decline of ZFHX3 protein had a larger sarcoplasmic reticulum Ca(2+) content by 62%, Ca(2+) transient by 20%, and calcium leak by 75%. ZFHX3 shRNA cells (n=35) had shorter action potential duration (APD) at 50% (14.7 ± 0.9 versus 20.3 ± 1.4 ms, P<0.005), and 20% (6.1 ± 0.3 versus 8.3 ± 0.8 ms, P<0.005) repolarization than control cells (n=30). ZFHX3 shRNA cells (n=10) had larger amplitudes of isoproterenol (1 µM)-induced delayed after depolarization (14.1 ± 0.9 versus 7.2 ± 0.2 mV, P<0.05) than control cells (n=10). Besides, acetylcholine (3 µM) shortened APD at 90% repolarization to a greater extent (19 ± 4% versus 7 ± 2%, P<0.01) in ZFHX3 shRNA cells (n=11) than in control cells (n=12). In addition, ZFHX3 shRNA cells had increased expressions of SERCA2a, ryanodine receptor, Kv1.4, Kv1.5 and Kir3.4. Moreover, ZFHX3 shRNA cells had a larger SERCA2a activity, ultra-rapid delayed rectifier potassium currents, transient outward currents and acetylcholine-sensitive potassium currents. CONCLUSIONS: ZFHX3 knock-down in atrial myocytes dysregulated calcium homeostasis and increased atrial arrhythmogenesis, which may contribute to the occurrence of AF.

Pardaxin-induced apoptosis enhances antitumor activity in HeLa cells.

Pardaxin, a pore-forming antimicrobial peptide that encodes 33 amino acids was isolated from the Red Sea Moses sole, Pardachirus mamoratus. In this study, we investigated its antitumor activity in human fibrosarcoma (HT-1080) cells and epithelial carcinoma (HeLa) cells. In vitro results showed that the synthetic pardaxin peptide had antitumor activity in these two types of cancer cells and that 15µg/ml pardaxin did not lyse human red blood cells. Moreover, this synthetic pardaxin inhibited the proliferation of HT1080 cells in a dose-dependent manner and induced programmed cell death in HeLa cells. DNA fragmentation and increases in the subG1 phase and caspase 8 activities suggest that pardaxin caused HeLa cell death by inducing apoptosis, but had a different mechanism in HT1080 cells.

Characteristics of the antitumor activities in tumor cells and modulation of the inflammatory response in RAW264.7 cells of a novel antimicrobial peptide, chrysophsin-1, from the red sea bream (Chrysophrys major).

The antimicrobial peptide, chrysophsin-1, exhibits antimicrobial activities with similar efficiencies for both gram-negative and gram-positive bacteria. In this study, we examined the antitumor activity and modulation of the inflammatory response of a synthetic chrysophsin-1 peptide. In vitro results showed that chrysophsin-1 had greater inhibitory effects against human fibrosarcoma (HT-1080), histiocytic lymphoma (U937), and epithelial carcinoma (HeLa) cells. LDH release by HeLa cells was comparable to that of an MTS assay after treatment with 1.5-3 µg/ml chrysophsin-1 for 24h. Under SEM and TEM observations, we found no intact cell membranes after chrysophsin-1 treatment of HeLa cells for 8h. The suggested mechanism of the cytotoxic activity of chrysophsin-1 was disruption of cancer cell membranes. In addition, we also examined caspase-3, -8, and -9 activities by Western blotting; the results excluded the participation of apoptosis in chrysophsin-1's effect on HeLa cells. Stimulation by lipopolysaccharide induced tumor necrosis factor (TNF)-α which was able to modulate chrysophsin-1 treatment of RAW264.7 cells and inhibited endogenous TNF-α release but did not block its secretion. With data from this study, we demonstrate that chrysophsin-1 has antimicrobial and antitumor activities and modulates the inflammatory response in RAW264.7 cells.