Fluoxetine-induced Ca2+ signals in Madin-Darby canine kidney cells

Association between selective serotonin reuptake inhibitors and kidney cancer risk: A nationwide population-based cohort study

The association between selective serotonin reuptake inhibitor (SSRI) exposure and cancer incidence has been investigated; however, no epidemiological study has investigated the association between exposure to individual SSRIs and kidney cancer incidence. The aim of this study is to examine whether SSRI use affected the risk of kidney cancer. We conducted a population-based retrospective cohort study using data from Taiwan's National Health Insurance Research Database. After adjusting for sex, age, urbanization level, comorbidity and medication use through propensity score matching, we identified 222 024 SSRI users and 221 361 SSRI nonusers. A robust Cox proportional hazards model was used to examine the associations between use of individual SSRIs and the risk of kidney cancer with 1- and 2-year induction periods. The result showed that SSRI users tended to be associated with a lower risk of kidney cancer with a 2-year induction period than nonusers; however, the association was not statistically significant (adjusted hazards ratio [aHR] = 0.88, 95% confidence interval [CI] = 0.77-1.01). We further examined the effects of individual SSRIs and observed a significantly lower risk of kidney cancer associated with the use of citalopram (aHR = 0.67, 95% CI = 0.47-0.96) and paroxetine (aHR = 0.75, 95% CI = 0.58-0.97) with the 2-year induction period. These findings support that SSRIs are associated with decreased kidney cancer risk and indicate that citalopram and paroxetine have protective effects in depressed patients with kidney cancer.

The Association between Selective Serotonin Reuptake Inhibitors (SSRIs) Use and the Risk of Bladder Cancer: A Nationwide Population-Based Cohort Study

Background: Past studies suggest mixed associations between selective serotonin reuptake inhibitor (SSRI) prescription and carcinogenic risk. There is no epidemiological study reporting on the association between SSRI use and the incidence of bladder cancer. The aim of this study is to determine whether SSRI use influences the risk of bladder cancer. Methods: We conducted a nationwide retrospective cohort study by Taiwan’s National Health Insurance Research Database from January 1, 1997 to December 31, 2013. 192,392 SSRI prescribed individuals were randomly matched 1 to 1 with 191,786 individuals who had never received any SSRIs by propensity scores match. The Cox Proportional Hazard models were conducted to examine the risk of bladder cancer between individuals prescribed SSRIs and individuals not prescribed SSRIs. Results: SSRIs were associated with significant reduced risk of bladder cancer with 0.5, 1, and 2 year induction periods (adjusted hazard ratio (aHR) = 0.86, 95% CI (confidence interval) = 0.76–0.98, aHR = 0.85, 95% CI = 0.75–0.97, and aHR = 0.77, 95% CI = 0.66–0.89). When examining the effect of specific SSRI, there was significantly lower risk of bladder cancer in individuals prescribed fluoxetine (6 month induction period: aHR = 0.78, 95% CI = 0.65–0.93; 1 year induction period: aHR = 0.78, 95% CI = 0.65–0.94; 2 year induction period: aHR = 0.73, 95% CI = 0.60–0.89), paroxetine (6 month induction period: aHR = 0.78, 95% CI = 0.61–0.99; 1 year induction period: aHR = 0.79, 95% CI = 0.61–1.01; 2 year induction period: aHR = 0.72, 95% CI = 0.54–0.95), and citalopram (6 month induction period: aHR = 0.74, 95% CI = 0.53–1.03; 1 year induction period: aHR = 0.70, 95% CI = 0.50–0.99; 2 year induction period: aHR = 0.60, 95% CI = 0.41–0.88). Conclusions: Individuals prescribed fluoxetine, paroxetine, or citalopram had a reduced risk of bladder cancer in this large, cross-national database.

Fluoxetine, an antidepressant, suppresses glioblastoma by evoking AMPAR-mediated calcium-dependent apoptosis

The efficacy of glioblastoma chemotherapy is not satisfactory; therefore, a new medication is expected to improve outcomes. As much evidence shows that antidepressants decrease cancer incidence and improve patients' quality of life, we therefore attempted to explore the potential for fluoxetine to be used to treat GBM and its possible underlying mechanism. The expression level of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) was determined using immunohistochemical staining and PCR analysis. The mechanism of fluoxetine-induced apoptosis of gliomas was elucidated. Computer modeling and a binding assay were conducted to investigate the interaction of fluoxetine with the AMPAR. The therapeutic effect of fluoxetine was evaluated using an animal model. We found that fluoxetine directly bound to AMPAR, thus inducing transmembrane Ca²⁺ influx. The rise in the intracellular calcium concentration ([Ca²⁺]_i) causes mitochondrial Ca²⁺ overload, thereby triggering apoptosis. AMPARs are excessively expressed in glioma tissues, suggesting that fluoxetine specifically executes glioma cells. Our in vivo study revealed that fluoxetine suppressed the growth of glioblastomas in brains of Nu/Nu mice, an effect similar to that produced by temozolomide. Our preclinical studies suggest fluoxetine, a commonly used antidepressant, might be selectively toxic to gliomas and could provide a new approach for managing this disease.

Mechanism of paroxetine-induced cell death in renal tubular cells

Paroxetine belongs to the family of selective serotonin reuptake inhibitors. Much research has been performed on the in vitro effect of paroxetine; however, the effect of paroxetine on Madin-Darby canine kidney renal tubular cells is unknown. The present study was aimed at exploring how paroxetine affects viability and to examine the underlying mechanisms. Paroxetine (15-200 microM) was shown to reduce cell viability via inducing apoptosis in a concentration-dependent manner. Paroxetine-induced cytotoxicity and apoptosis were not changed by the p38 mitogen-activated protein kinase inhibitor SB203580 and the c-Jun NH2-terminal kinase inhibitor SP600125, but was potentiated by the extracellular signal-regulated kinase inhibitor PD98059; inhibited by GF 109203X, a protein kinase C inhibitor; and potentiated by phorbol 12-myristate 13-acetate, a protein kinase C activator. Paroxetine induced [Ca2+](i) rises; however, pre-treatment with 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl)ester, a Ca2+ chelator, to prevent 20 microM paroxetine-induced [Ca2+](i) rises did not protect cells from death. H-89 (a protein kinase A inhibitor) and U73122 (a phospholipase C inhibitor) failed to alter paroxetine-induced cell death. The results suggest that in Madin-Darby canine kidney cells, paroxetine caused protein kinase C-dependent, Ca2+-independent apoptosis which was potentiated by inhibition of the extracellular signal-regulated kinase pathway.

Effect of desipramine on Ca2+ levels and growth in renal tubular cells

The in vitro effect of desipramine on renal tubular cell is unknown. In Madin-Darby canine kidney (MDCK) cells, the effect of desipramine on intracellular Ca2+ concentration ([Ca2+]i) was measured by using fura-2. Desipramine (>25 microM) caused a rapid and sustained rise of [Ca2+]i in a concentration-dependent manner (EC50=50 microM). Desipramine-induced [Ca2+]i rise was prevented by 40% by removal of extracellular Ca2+ but was not altered by L-type Ca2+ channel blockers. In Ca2+-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+-ATPase, caused a monophasic [Ca2+]i rise, after which desipramine failed to release more Ca2+; in addition, pretreatment with desipramine partly decreased thapsigargin-induced [Ca2+]i increase. U73122, an inhibitor of phospholipase C, did not change desipramine-induced [Ca2+]i rise. Incubation with 10-100 microM desipramine enhances or inhibits cell proliferation in a concentration- and time-dependent manner. The inhibitory effect of desipramine on proliferation was not extracellular Ca2+-dependent. Apoptosis appears to contribute to desipramine-induced cell death. Together, these findings suggest that desipramine increases baseline [Ca2+]i in renal tubular cells by evoking both extracellular Ca2+ influx and intracellular Ca2+ release, and can cause apoptosis.

Effect of p-chloroamphetamine on calcium movement and viability in renal tubular cells

In Madin-Darby canine kidney (MDCK) cells, the effect of p-chloroamphetamine, a neurotoxin that depletes intracellular serotonin, on intracellular Ca2+ concentration ([Ca2+]i) and viability was measured by using the Ca2+-sensitive fluorescent dye fura-2 and the viability detecting fluorescent dye tetrazolium. p-Chloroamphetamine (> or = 10 microM) caused a rapid rise of [Ca2+]i in a concentration-dependent manner. p-Chloroamphetamine-induced [Ca2+]i rise was partly reduced by removal of extracellular Ca2+. p-Chloroamphetamine-induced extracellular Ca2+ influx was also suggested by Mn2+ influx-induced fura-2 fluorescence quench. In Ca2+-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+-ATPase, caused a monophasic [Ca2+]i rise, after which p-chloroamphetamine failed to increase [Ca2+]i; also, pretreatment with p-chloroamphetamine reduced 50% of thapsigargin-sensitive Ca2+ stores. U73122, an inhibitor of phospholipase C, abolished ATP (but not p-chloroamphetamine)-induced [Ca2+]i rise. Overnight incubation with 1-500 microM p-chloroamphetamine decreased cell viability. These findings suggest that p-chloroamphetamine evokes a rapid increase in [Ca2+]i in renal tubular cells by stimulating both extracellular Ca2+ influx and intracellular Ca2+ release, and is cytotoxic.

Effect of methylglyoxal on intracellular calcium levels and viability in renal tubular cells

Methylglyoxal (2-oxopropanal), a physiological glucose metabolite, is a highly reactive dicarbonyl compound that can induce stress in cells and cause apoptotic cell death. This study examines the early signaling effects of methylglyxal on renal cells. It was found that methylglyoxal caused a slow and sustained rise of intracellular Ca2+ concentration ([Ca2+]i) in a concentration-dependent manner (EC50=1.8 mM). Methylglyoxal also induced a [Ca2+]i rise when extracellular Ca2+ was removed, but the magnitude was reduced by 80%. Depletion of intracellular Ca2+ stores with thapsigargin (TG), an endoplasmic reticulum (ER) Ca2+ pump inhibitor, did not affect methylglyoxal's effect. In Ca2+-free medium, the methylglyoxal-induced [Ca2+]i rise was abolished by depleting stored Ca2+ with carbonylcyanide m-chlorophenylhydrazone (CCCP; a mitochondrial uncoupler). Methylglyoxal-caused [Ca2+]i rise in the Ca2+-containing medium was not affected by modulation of protein kinase C activity, presence of voltage-gated Ca2+ channel blockers, or preincubation with thiol-containing antioxidants. U73122, an inhibitor of phospholipase C, abolished ATP (but not methylglyoxal)-induced [Ca2+]i rise. Furthermore, the [Ca2+]i-elevating effect of methylglyoxal was cell type-dependent, because methylglyoxal failed to cause [Ca2+]i rises in CHO-K1, neutrophils, or platelets. Pretreatment with methylglyoxal for 0-24 h decreased cell viability in a concentration- and time-dependent manner. Meanwhile, methylglyoxal-induced cell death involved apoptotic and necrotic events, the former being the dominant. These findings suggest that methylglyoxal induced a significant rise in [Ca2+]i in Madin-Darby canine kidney (MDCK) renal tubular cells by stimulating both extracellular Ca2+ influx and CCCP-sensitive intracellular Ca2+ release via as yet unidentified mechanisms. The cell type-specific Ca2+ signaling may play an important role in the early process of cytotoxic action of methylglyoxal.

Selective serotonin reuptake inhibitors directly signal for apoptosis in biopsy-like Burkitt lymphoma cells

Selective serotonin reuptake inhibitors (SSRIs) are the treatment of choice for clinical depression and a range of anxiety-related disorders. They are well tolerated over extended periods with more than 50 million people worldwide benefiting from their use. Here we show that 3 structurally distinct SSRIs--fluoxetine, paroxetine, and citalopram--act directly on Burkitt lymphoma (BL) cells to trigger rapid and extensive programmed cell death. SSRIs unexpectedly stimulated calcium flux, tyrosine phosphorylation, and down-regulation of the c-myc and nm23 genes in Burkitt lymphoma cells remaining faithful to the biopsy phenotype. Resultant SSRI-induced apoptosis was preceded by caspase activation, poly(ADP-ribose) polymerase-1 (PARP-1) cleavage, DNA fragmentation, a loss of mitochondrial membrane potential, and the externalization of phosphatidylserine, and reversed by the overexpression of bcl-2. Normal peripheral blood mononuclear cells and tonsil B cells, whether resting or stimulated into cycle, were largely resistant to SSRI-induced death as were 5 non-BL lymphoid cell lines tested. We discuss these findings within the context of whether the SSRI class of antidepressants could find future application as potential therapeutics for the highly aggressive and-because of its association with AIDS-increasingly more common Burkitt lymphoma.

Novel effect of carvedilol on Ca2+ movement in renal tubular cells

The effect of carvedilol on intracellular free Ca(2+) levels ([Ca(2+)](i)) has not been explored previously. This study was aimed to examine the effect of carvedilol on Ca(2+) handling in renal tubular cells. Madin-Darby canine kidney cells were used as a model for renal tubular cells and fura-2 was used as a fluorescent Ca(2+) probe. Carvedilol increased [Ca(2+)](i) in a concentration-dependent manner with an EC(50) value of 5 microM. Extracellular Ca(2+) removal partly inhibited the [Ca(2+)](i) signals. Carvedilol-induced Ca(2+) influx was verified by measuring Mn(2+)-induced quench of fura-2 fluorescence. Carvedilol-induced store Ca(2+) release was reduced by pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor) but not with 5 microM ryanodine or 2 microM carbonylcyanide m-chlorophenylhydrazone (a mitochondrial uncoupler). Carvedilol (30 microM)-induced Ca(2+) release was not affected by inhibiting phospholipase C with 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-l)amino)hexyl)-1H-pyrrole-2,5-dione (U73122; 2 microM), but was potentiated by increasing cAMP levels or inhibiting protein kinase C. The carvedilol-induced Ca(2+) mobilization was not significantly sequestered by the endoplasmic reticulum or mitochondria. This study shows that carvedilol increased [Ca(2+)](i) in renal tubular cells by causing Ca(2+) release from the endoplasmic reticulum and other unknown stores in an inositol-1,4,5-trisphosphate-independent manner, and by inducing Ca(2+) influx. The Ca(2+) release was modulated by cAMP and protein kinase C.

Effect of clomiphene on Ca(2+) movement in human prostate cancer cells

The effect of clomiphene, an ovulation-inducing agent, on cytosolic free Ca(2+) levels ([Ca(2+)](i)) in populations of PC3 human prostate cancer cells was explored by using fura-2 as a Ca(2+) indicator. Clomiphene at concentrations between 10-50 microM increased [Ca(2+)](i) in a concentration-dependent manner. The [Ca(2+)](i) signal was biphasic with an initial rise and a slow decay. Ca(2+) removal inhibited the Ca(2+) signal by 41%. Adding 3 mM Ca(2+) increased [Ca(2+)](i) in cells pretreated with clomiphene in Ca(2+)-free medium, confirming that clomiphene induced Ca(2+) entry. In Ca(2+)-free medium, pretreatment with 50 microM brefeldin A (to permeabilize the Golgi complex), 1 microM thapsigargin (to inhibit the endoplasmic reticulum Ca(2+) pump), and 2 microM carbonylcyanide m-chlorophenylhydrazone (to uncouple mitochondria) inhibited 25% of 50 microM clomiphene-induced store Ca(2+) release. Conversely, pretreatment with 50 microM clomiphene in Ca(2+)-free medium abolished the [Ca(2+)](i) increase induced by brefeldin A, thapsigargin or carbonylcyanide m-chlorophenylhydrazone. The 50 microM clomiphene-induced Ca(2+)release was unaltered by inhibiting phospholipase C with 2 microM 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). Trypan blue exclusion assay suggested that incubation with clomiphene (50 microM) for 2-15 min induced time-dependent decrease in cell viability by 10-50%. Collectively, the results suggest that clomiphene induced [Ca(2+)](i) increases in PC3 cells by releasing store Ca(2+) from multiple stores in an phospholipase C-independent manner, and by activating Ca(2+) influx; and clomiphene was of mild cytotoxicity.

Mechanism of bradykinin-induced Ca(2+) mobilization in MG63 human osteosarcoma cells

BACKGROUND

The effect of bradykinin on intracellular free Ca(2+) levels ([Ca(2+)](i)) in MG63 human osteosarcoma cells was explored using fura-2 as a Ca(2+) dye.

METHODS/RESULTS

Bradykinin (0.1 nM-1 microM) increased [Ca(2+)](i) in a concentration-dependent manner with an EC(50) value of 0.5 nM. The [Ca(2+)](i) signal comprised an initial peak and a fast decay which returned to baseline in 2 min. Extracellular Ca(2+) removal inhibited the peak [Ca(2+)](i )signals by 35 +/- 3%. Bradykinin (1 nM) failed to increase [Ca(2+)](i) in the absence of extracellular Ca(2+ )after cells were pretreated with thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor; 1 microM). Bradykinin (1 nM)-induced intracellular Ca(2+) release was nearly abolished by inhibiting phospholipase C with 2 microM 1-(6-((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). The [Ca(2+)](i )increase induced by 1 nM bradykinin in Ca(2+)- free medium was abolished by 1 nM HOE 140 (a B2 bradykinin receptor antagonist) but was not altered by 100 nM Des-Arg-HOE 140 (a B1 bradykinin receptor antagonist). Pretreatment with 1 pM pertussis toxin for 5 h in Ca(2+) medium inhibited 30 +/- 3% of 1 nM bradykinin-induced peak [Ca(2+)](i) increase.

CONCLUSIONS

Together, this study shows that bradykinin induced [Ca(2+)](i) increases in a concentration-dependent manner, by stimulating B2 bradykinin receptors leading to mobilization of Ca(2+) from the thapsigargin-sensitive stores in a manner dependent on inositol-1,4,5-trisphosphate, and also by inducing extracellular Ca(2+) influx. The bradykinin response was partly coupled to a pertussis toxin-sensitive G protein pathway.

Up-regulation of 5-HT2B receptor density and receptor-mediated glycogenolysis in mouse astrocytes by long-term fluoxetine administration

The effects were studied of short-term (1 week) versus long-term (2-3 weeks) fluoxetine treatment of primary cultures of mouse astrocytes, differentiated by treatment with dibutyryl cyclic AMP. From previous experiments it is known that acute treatment with fluoxetine stimulates glycogenolysis and increases free cytosolic Ca2+ concentration ([Ca2+]i]) in these cultures, whereas short-term (one week) treatment with 10 microM down-regulates the effects on glycogen and [Ca2+]i, when fluoxetine administration is renewed (or when serotonin is administered). Moreover, antagonist studies have shown that these responses are evoked by activation of a 5-HT2, receptor that is different from the 5-HT2A receptor and therefore at that time tentatively were interpreted as being exerted on 5-HT2C receptors. In the present study the cultures were found by RT-PCR to express mRNA for 5-HT2A and 5-HT2B receptors, but not for the 5-HT2C receptor, identifying the 5-HT2 receptor activated by fluoxetine as the 5-HT2B receptor, the most recently cloned 5-Ht2 receptor and a 5-HT receptor known to be more abundant in human, than in rodent, brain. Both short-term and long-term treatment with fluoxetine increased the specific binding of [3H]mesulergine, a ligand for alL three 5-HT2 receptors. Long-term treatment with fluoxetine caused an agonist-induced up-regulation of the glycogenolytic response to renewed administration of fluoxetine, whereas short-term treatment abolished the fluoxetine-induced hydrolysis of glycogen. Thus, during a treatment period similar to that required for fluoxetine's clinical response to occur, 5-HT2B-mediated effects are initially down-regulated and subsequently up-regulated.