Activation of hERG3 channel stimulates autophagy and promotes cellular senescence in melanoma.

Ion channels play a major factor in maintaining cellular homeostasis but very little is known about the role of these proteins in cancer biology. In this work we have discovered that, the Kv11.3 (hERG3) a plasma-membrane potassium channel plays a critical role in the regulation of autophagy in a cancer cell model. We have found that pharmacologic stimulation of the Kv11.3 channel with a small molecule activator, NS1643 induced autophagy via activation of an AMPK-dependent signaling pathway in melanoma cell line. In addition, we have found that NS1643 produced a strong inhibition of cell proliferation by activating a cellular senescence program. Furthermore, inhibition of autophagy via siRNA targeting AMPK or treatment with hydroxychloroquine an autophagy inhibitor activates apoptosis in NS1643-treated cells. Thus, we propose that, Kv11.3 is a novel mediator of autophagy, autophagy can be a survival mechanism contributing to cellular senescence, and that use of a combinatorial pharmacologic approach of Kv11.3 activator with inhibitors of autophagy represents a novel therapeutic approach against melanoma.

Azelastine desensitization of transient receptor potential vanilloid 1: a potential mechanism explaining its therapeutic effect in nonallergic rhinitis.

BACKGROUND: Capsaicin, a prototypic transient receptor potential vanilloid 1 (TRPV1) agonist, has been shown to be more clinically effective in the treatment of nonallergic rhinitis (NAR) compared with other rhinitis subtypes. Azelastine has also been found to be clinically effective in the treatment of NAR but its mechanism(s) of action is still poorly elucidated. This study was designed to determine, using in vitro cell lines, whether topical therapies including azelastine have activity on TRPV1 ion channels similar to capsaicin. METHODS: The effects of capsaicin (1 µM), azelastine (30 µM), bepotastine (10 µM), olopatadine (10 µM), and fluticasone (200 µM) on TRPV1 channels using mice neuronal cells (Cath.a), as surrogates for submucosal sensory neurons, and human nasal epithelial cells (hNEC) were determined and compared. For azelastine, bepotastine, and capsaicin, which elicited an agonist effect on TRPV1, live cell [Ca(2+)] signaling in Cath.a cells and hNECs expressing TRPV1 were performed in the absence and presence of capsazepine at 10 µM (a TRPV1 antagonist) or using wild-type mouse embryonic fibroblasts (wtMEFs) that express TRPV1 ion channels and TRPV1 homozygous null mutant (TRPV1-/-) knockout MEF cells as controls to establish TRPV1 channel selectivity. As azelastine has previously been found clinically effective in NAR, additional experiments were performed to determine its ability to desensitize TRPV1 ion channels and its effect on regulating intracellular calcium homeostasis. RESULTS: Cath.a cells treated with azelastine, bepotastine, or capsaicin showed a significant increase in TRPV1-dependant (Ca(2+)) specific cytosolic fluorescence. Continuous treatment with azelastine or capsaicin resulted in desensitization of TRPV1 channels. In hNECs, azelastine stimulation resulted in Ca(2+) shifts from the cytosol to mitochondria and overexpression of hematopoietic cell-specific Lyn substrate 1-associated protein X1, which may thus be effective in cytosolic Ca(2+) homeostasis. CONCLUSION: Azelastine, similar to capsaicin, exhibits direct activity on TRPV1 ion channels that may represent a novel mechanistic pathway explaining its clinical efficacy in NAR.