| Summary: | 博士 === 國立中山大學 === 生物科學系研究所 === 99 === Depressive disorder is one of the most important diseases influencing human health in the 21st century. Antidepressants can improve some depressive symptoms and signs of depressive disorder in patients. It is thought that neurotransmitters (especially serotonin and/or norepinephrine and/or dopamine) have important roles in antidepression effects, but their pharmacological effects on the intracellular signal transduction pathway remain unclear. The aim of this thesis is to explore the effect of the antidepressants paroxetine (a selective serotonin reuptake inhibitor) and nortriptyline (a tricyclic antidepressant) on the intracellular Ca2+-related signal transduction and apoptosis of human prostate cancer PC3 cells.
By using the fura-2 method, in PC3 cell, we found paroxetine (at concentrations between 10-150 μM) and nortriptyline (at concentrations between 50-500 μM) increased [Ca2+]i of PC3 cells in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+ indicating that Ca2+ entry and release both contributed to the [Ca2+]i rise. In Ca2+-free medium, pretreatment with the endoplasmic reticulum Ca2+ pump inhibitor nearly abolished paroxetine and nortriptyline-induced Ca2+ release. Conversely, pretreatment with nortriptyline greatly reduced the inhibitor-induced [Ca2+]i rise, suggesting that antidepressants released Ca2+ from the endoplasmic reticulum. Inhibition of phospholipase C with U73122 inhibited paroxetine-induced [Ca2+]i rise by 80%, but did not change nortriptyline-induced [Ca2+]i rise. Paroxetine-induced Ca2+ influx was inhibited by the store-operated Ca2+ channel blockers econazole and SK&F96365, the phospholipase A2 inhibitor aristolochic acid, and protein kinase C modulators. Nortriptyline-induced Ca2+ influx was inhibited by activation of protein kinase C. Nortriptyline at a concentration of 10 μM increased the viability of the PC3 cells. At 50 μM, nortriptyline killed 45% of the cells, and induced significant apoptosis, as measured by propidium iodide staining.
Collectively, in PC3 cells, paroxetine induced [Ca2+]i rise is caused by phospholipase C-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ influx via store-operated Ca2+ channels in a manner regulated by protein kinase C and phospholipase A2. Nortriptyline increased [Ca2+]i via phospholipase C-independent Ca2+ release from the endoplasmic reticulum and Ca2+ influx from the protein kinase C-sensitive pathway. Nortriptyline also induced apoptosis at a higher level. The results of this thesis may be helpful for understanding the effects of antidepressants on the intracellular signaling of cultured cells, and might illustrate a new possible mechanism concerning antidepressants’ therapeutic effects or clinical side effects.
|
|---|
