ryanodine and Prostatic-Neoplasms

Very little is known about the functional expression and the physiological role of ryanodine receptors in nonexcitable cells, and in prostate cancer cells in particular. Nonetheless, different studies have demonstrated that calcium is a major factor involved in apoptosis. Therefore, the calcium-regulatory mechanisms, such as ryanodine-mediated calcium release, may play a substantial role in the regulation of apoptosis.. We assessed the presence of such functional receptors in LNCaP prostate cancer cells, using fluorimetric measurements of intracellular calcium and expression assays of mRNA encoding ryanodine receptors.. We show here that LNCaP cells responded to caffeine, a ryanodine receptor agonist, by mobilizing calcium. Another ryanodine receptor agonist, 4-chloro-m-cresol, had a similar effect and promoted calcium release. These effects were inhibited by pretreatment with ryanodine or thapsigargin. In addition to a calcium release, caffeine was able to produce a calcium entry blocked by nickel. We used a reverse transcription-polymerase chain reaction assay to investigate the expression of ryanodine receptors in LNCaP cells. Two types of ryanodine receptor mRNAs were expressed in LNCaP cells: RyR1 and RyR2 mRNAs. Finally, we show that ryanodine receptor activation by caffeine slightly stimulates apoptosis of prostate cancer cells, and that the inhibition of these receptors by ryanodine protects the cells against apoptosis.. The combination of results showed that LNCaP cells, derived from a human prostate cancer, express functional RyRs able to mobilize Ca(2+) from intracellular stores and which might control apoptosis.

Topics: Apoptosis; Caffeine; Calcium; Flow Cytometry; Humans; Male; Prostatic Neoplasms; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Ryanodine; Ryanodine Receptor Calcium Release Channel; Tumor Cells, Cultured

Calcium seems to be a major second messenger involved in the regulation of prostatic cell functions, but the mechanisms underlying its control are poorly understood. We investigated spatiotemporal aspects of Ca2+ signals in the LNCaP cell line, a model of androgen-dependent prostatic cells, by using non-invasive external electric field pulses that hyperpolarize the anode facing membrane and depolarize the membrane facing the cathode. Using high-speed fluo-3 confocal imaging, we found that an electric field pulse (10-15 V/cm, 1-5 mA, 5 ms) initiated rapidly, at the hyperpolarized end of the cell, a propagated [Ca2+]i wave which spread through the cell with a constant amplitude and an average velocity of about 20 microns/s. As evidenced by the total wave inhibition either by the block of Ca2+ entry or the depletion of Ca2+ stores by thapsigargin, a specific Ca(2+)-ATPase inhibitor, the [Ca2+]i wave initiation may imply a localized Ca2+ influx linked to a focal auto-regenerative process of Ca2+ release. Using different external Ca2+ and Ca2+ entry blockers concentrations, Mn2+ quenching of fluo-3 and fura-2 fluorescence and inhibitors of InsP3 production, we found evidence that the [Ca2+]i wave progression required, in the presence of basal levels of InsP3, an interplay between Ca2+ release from InsP3-sensitive Ca2+ stores and Ca2+ influx through channels possibly activated by the [Ca2+]i rise.

Topics: Calcium; Calcium Channel Blockers; Calcium Signaling; Cell Polarity; Electric Stimulation; Enzyme Inhibitors; Fura-2; Gadolinium; Humans; Lanthanum; Male; Manganese; Microscopy, Confocal; Nimodipine; Prostatic Neoplasms; Ryanodine; Thapsigargin; Tumor Cells, Cultured