The phenolic compound 2,5-dimethylphenol is a natural product. 2,5-Dimethylphenol has been shown to affect rat hepatic and pulmonary microsomal metabolism. However, the effect of 2,5-dimethylphenol on Ca(2+ )signaling and cyotoxicity has never been explored in any culture cells. This study explored the effect of 2,5-dimethylphenol on cytosolic free Ca(2+ )levels ([Ca(2+)]i) and cell viability in PC3 human prostate cancer cells. 2,5-Dimethylphenol at concentrations between 500 μM and 1000 μM evoked [Ca(2+)]i rises in a concentration-dependent manner. This Ca(2+ )signal was inhibited by approximately half by the removal of extracellular Ca(2+). 2,5-Dimethylphenol-induced Ca(2+ )influx was confirmed by Mn(2+)-induced quench of fura-2 fluorescence. Pretreatment with the protein kinase C (PKC) inhibitor GF109203X, nifedipine or the store-operated Ca(2+ )entry inhibitors (econazole or SKF96365) inhibited 2,5-dimethylphenol-induced Ca(2+ )signal in Ca(2+)-containing medium by ∼30%. Treatment with the endoplasmic reticulum Ca(2+ )pump inhibitor thapsigargin in Ca(2+)-free medium abolished 2,5-dimethylphenol-induced [Ca(2+)]i rises. Conversely, treatment with 2,5-dimethylphenol abolished thapsigargin-induced [Ca(2+)]i rises. Inhibition of phospholipase C (PLC) with U73122 reduced 2,5-dimethylphenol-evoked [Ca(2+)]i rises by ∼80%. 2,5-Dimethylphenol killed cells at concentrations of 350-1000 μM in a concentration-dependent fashion. Chelation of cytosolic Ca(2+ )with 1,2-bis(2-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid/AM (BAPTA/AM) did not prevent 2,5-dimethylphenol's cytotoxicity. Together, in PC3 cells, 2,5-dimethylphenol induced [Ca(2+)]i rises that involved Ca(2+ )entry through PKC-regulated store-operated Ca(2+ )channels and PLC-dependent Ca(2+ )release from the endoplasmic reticulum. 2,5-Dimethylphenol induced cytotoxicity in a Ca(2+)-independent manner.
Toxicology mechanisms and methods. 2016 Jun 16 [Epub ahead of print]
Jue-Long Wang, Chiang-Ting Chou, Wei-Zhe Liang, Jeng-Hsien Yeh, Chun-Chi Kuo, Chao-Ying Lee, Pochuen Shieh, Daih-Huang Kuo, Fu-An Chen, Chung-Ren Jan
a Department of Rehabilitation , Kaohsiung Veterans General Hospital Tainan Branch , Tainan , Taiwan , ROC ., b Department of Nursing , Division of Basic Medical Sciences, Chang Gung Institute of Technology , Chia-Yi, Taiwan , ROC ., d Department of Medical Education and Research , Kaohsiung Veterans General Hospital , Kaohsiung , Taiwan , ROC ., e Department of Pathology and Laboratory Medicine , Kaohsiung Veterans General Hospital , Kaohsiung , Taiwan , ROC ., f Department of Nursing , Tzu Hui Institute of Technology , Pingtung , Taiwan , ROC ., g School of Pharmacy, China Medical University , Taichung , Taiwan , ROC ., h Department of Pharmacy , Tajen University , Pingtung , Taiwan , ROC., h Department of Pharmacy , Tajen University , Pingtung , Taiwan , ROC., h Department of Pharmacy , Tajen University , Pingtung , Taiwan , ROC., d Department of Medical Education and Research , Kaohsiung Veterans General Hospital , Kaohsiung , Taiwan , ROC .