The effect of magnolol on Ca2+ homeostasis and its related physiology in human oral cancer cells

Publication date: Available online 14 February 2018
Source:Archives of Oral Biology
Author(s): Shu-Feng Hsieh, Chiang-Ting Chou, Wei-Zhe Liang, Chun-Chi Kuo, Jue-Long Wang, Lyh-Jyh Hao, Chung-Ren Jan
ObjectiveMagnolol, a polyphenol compound from herbal medicines, was shown to alter physiology in various cell models. However, the effect of magnolol on Ca²⁺ homeostasis and its related physiology in oral cancer cells is unclear. This study examined whether magnolol altered Ca²⁺ signaling and cell viability in OC2 human oral cancer cells.MethodsCytosolic Ca²⁺ concentrations ([Ca²⁺]i) in suspended cells were measured by using the fluorescent Ca²⁺-sensitive dye fura-2. Cell viability was examined by 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] water soluble tetrazolium-1 (WST-1) assay.ResultsMagnolol at concentrations of 20–100 μM induced [Ca²⁺]i rises. Ca²⁺ removal reduced the signal by approximately 50%. Magnolol (100 μM) induced Mn²⁺ influx suggesting of Ca²⁺ entry. Magnolol-induced Ca²⁺ entry was partially suppressed by protein kinase C (PKC) regulators, and inhibitors of store-operated Ca²⁺ channels. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished magnolol-evoked [Ca²⁺]i rises. Conversely, treatment with magnolol abolished BHQ-evoked [Ca²⁺]i rises. Inhibition of phospholipase C (PLC) with U73122 partially inhibited magnolol-induced [Ca²⁺]i rises. Magnolol at 20–100 μM decreased cell viability, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM).ConclusionsTogether, in OC2 cells, magnolol induced [Ca²⁺]i rises by evoking partially PLC-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ entry. Magnolol also caused Ca²⁺-independent cell death. Therefore, magnolol-induced cytotoxicity may not be involved in activation mechanisms associated with intracellular Ca²⁺ mobilization in oral cancer cells.



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