The mechanism of protriptyline-induced Ca2+ movement and non-Ca2+-triggered cell death in PC3 human prostate cancer cells

Protriptyline, a tricyclic anti-depressant, is used primarily to treat the combination of symptoms of anxiety and depression. However, the effect of protriptyline on prostate caner is unknown. This study examined whether the anti-depressant protriptyline altered CA(2+) movement and cell viability in PC3 human prostate Cancer cells. The CA(2+)-sensitive Fluorescent Dye fura-2 was used to measure [CA(2+)](i). Protriptyline evoked [CA(2+)](i) rises concentration-dependently. The response was reduced by removing extracellular CA(2+). Protriptyline-evoked CA(2+) entry was inhibited by store-operated channel inhibitors (nifedipine, econazole and SKF96365), protein kinase C activator (phorbol 12-myristate 13 acetate, PMA) and protein kinase C inhibitor (GF109203X). Treatment with the endoplasmic reticulum CA(2+) pump inhibitor 2,5-di-tert-butylhydr-oquinone (BHQ) in CA(2+)-free medium inhibited 60% of protriptyline-evoked [CA(2+)](i) rises. Conversely, treatment with protriptyline abolished BHQ-evoked [CA(2+)](i) rises. Inhibition of Phospholipase C with U73122 suppressed 50% of protriptyline-evoked [CA(2+)](i) rises. At concentrations of 50-70 µM, protriptyline decreased cell viability in a concentration-dependent manner; which were not reversed by chelating cytosolic CA(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Collectively, in PC3 cells, protriptyline evoked [CA(2+)](i) rises by inducing Phospholipase C-associated CA(2+) release from the endoplasmic reticulum and Other stores, and CA(2+) influx via protein kinase C-sensitive store-operated CA(2+) channels. Protriptyline caused cell death that was independent of [CA(2+)](i) rises.