GDC-0879, a BRAFV600E Inhibitor, Protects Kidney Podocytes from Death.

Progressive kidney diseases affect approximately 500 million people worldwide. Podocytes are terminally differentiated cells of the kidney filter, the loss of which leads to disease progression and kidney failure. To date, there are no therapies to promote podocyte survival. Drug repurposing may therefore help accelerate the development of cures in an area of tremendous unmet need. In a newly developed high-throughput screening assay of podocyte viability, we identified the BRAFV600E inhibitor GDC-0879 and the adenylate cyclase agonist forskolin as podocyte-survival-promoting compounds. GDC-0879 protects podocytes from injury through paradoxical activation of the MEK/ERK pathway. Forskolin promotes podocyte survival by attenuating protein biosynthesis. Importantly, GDC-0879 and forskolin are shown to promote podocyte survival against an array of cellular stressors. This work reveals new therapeutic targets for much needed podocyte-protective therapies and provides insights into the use of GDC-0879-like molecules for the treatment of progressive kidney diseases.

Polychlorinated biphenyl 19 blocks the most common form of store-operated Ca2+ entry through Orai.

PCB19, a 2,2',6-trichlorinated biphenyl, is one of many non-dioxin-like polychlorinated biphenyls (NDL-PCBs), which are ubiquitous pollutants. NDL-PCBs affect cytosolic Ca2+ signaling by promoting Ca2+ release from ryanodine receptor-sensitive Ca2+ pools and inhibiting store-operated Ca2+ entry (SOCE) from the extracellular space. However, NDL-PCB-mediated SOCE inhibition has only been demonstrated in PC12 cells, in which SOCE is thought to be mainly mediated by TRPC family channels. Here, we investigated the effect of PCB19 on SOCE using human embryonic kidney 293 (HEK293) cells, human leukemia T cell line Jurkat-T cells and human promyelocytoma HL-60 cells which are the cell lines that are previously demonstrated to mediate the most common form of SOCE solely by the intrinsic Orai channels. PCB19 reduced thapsigargin-induced Ca2+ influx after Ca2+ pool depletion in HEK293 cells. SOCEs in HEK293, Jurkat T, HL-60 and PC12 cells showed distinct sensitivities to SOCE inhibitors such as Gd3+ and ML-9; however, PCB19 also showed a common effect of inhibiting SOCEs in all cell lines. PCB19-mediated SOCE inhibition was confirmed by demonstrating the ability of PCB19 to inhibit the SOCE current but not the TRPM7 current. These results imply that PCB19 inhibits not only TRPC-mediated SOCE as in PC12 cells but also Orai-mediated SOCE as in many other cells including HEK293, Jurkat T and HL-60 cells.

Propofol Decreases Endoplasmic Reticulum Stress-Mediated Apoptosis in Retinal Pigment Epithelial Cells.

Age-related macular degeneration (AMD) is the major cause of loss of sight globally. There is currently no effective treatment available. Retinal pigment epithelial (RPE) cells are an important part of the outer blood-retina barrier and their death is a determinant of AMD. Propofol, a common clinically used intravenous anesthetic agent, has been shown to act as an efficacious neuroprotective agent with antioxidative and anti-inflammatory properties in vivo and in vitro. However, little is known about its effects on RPE cells. The purpose of our research was to investigate whether propofol could protect RPE cells from apoptosis through endoplasmic reticulum (ER) stress-dependent pathways. To this end, prior to stimulation with thapsigargin (TG), ARPE-19 cells were pretreated with varying concentrations of propofol. A protective effect of propofol in TG-treated ARPE-9 was apparent, TUNEL and flow cytometric assays showed decreased apoptosis. We further demonstrated that propofol pretreatment attenuated or inhibited the effects caused by TG, such as upregulation of Bax, BiP, C/EBP homologous protein (CHOP), active caspase 12, and cleaved caspase 3, and downregulation of Bcl2. It also decreased the TG-induced levels of ER stress-related molecules such as p-PERK, p-eIF2α, and ATF4. Furthermore, it downregulated the expression of nuclear factor κB (NF-κB). This study elucidated novel propofol-induced cellular mechanisms for antiapoptotic activities in RPE cells undergoing ER stress and demonstrated the potential value of using propofol in the treatment of AMD.

Antimicrobial agent triclosan is a proton ionophore uncoupler of mitochondria in living rat and human mast cells and in primary human keratinocytes.

Triclosan (TCS) is an antimicrobial used widely in hospitals and personal care products, at ~10 mm. Human skin efficiently absorbs TCS. Mast cells are ubiquitous key players both in physiological processes and in disease, including asthma, cancer and autism. We previously showed that non-cytotoxic levels of TCS inhibit degranulation, the release of histamine and other mediators, from rat basophilic leukemia mast cells (RBL-2H3), and in this study, we replicate this finding in human mast cells (HMC-1.2). Our investigation into the molecular mechanisms underlying this effect led to the discovery that TCS disrupts adenosine triphosphate (ATP) production in RBL-2H3 cells in glucose-free, galactose-containing media (95% confidence interval EC50 = 7.5-9.7 µm), without causing cytotoxicity. Using these same glucose-free conditions, 15 µm TCS dampens RBL-2H3 degranulation by 40%. The same ATP disruption was found with human HMC-1.2 cells (EC50 4.2-13.7 µm), NIH-3 T3 mouse fibroblasts (EC50 4.8-7.4 µm) and primary human keratinocytes (EC50 3.0-4.1 µm) all with no cytotoxicity. TCS increases oxygen consumption rate in RBL-2H3 cells. Known mitochondrial uncouplers (e.g., carbonyl cyanide 3-chlorophenylhydrazone) previously were found to inhibit mast cell function. TCS-methyl, which has a methyl group in place of the TCS ionizable proton, affects neither degranulation nor ATP production at non-cytotoxic doses. Thus, the effects of TCS on mast cell function are due to its proton ionophore structure. In addition, 5 µm TCS inhibits thapsigargin-stimulated degranulation of RBL-2H3 cells: further evidence that TCS disrupts mast cell signaling. Our data indicate that TCS is a mitochondrial uncoupler, and TCS may affect numerous cell types and functions via this mechanism. Copyright © 2015 John Wiley & Sons, Ltd.

Pharmacological dimerization and activation of the exchange factor eIF2B antagonizes the integrated stress response.

The general translation initiation factor eIF2 is a major translational control point. Multiple signaling pathways in the integrated stress response phosphorylate eIF2 serine-51, inhibiting nucleotide exchange by eIF2B. ISRIB, a potent drug-like small molecule, renders cells insensitive to eIF2α phosphorylation and enhances cognitive function in rodents by blocking long-term depression. ISRIB was identified in a phenotypic cell-based screen, and its mechanism of action remained unknown. We now report that ISRIB is an activator of eIF2B. Our reporter-based shRNA screen revealed an eIF2B requirement for ISRIB activity. Our results define ISRIB as a symmetric molecule, show ISRIB-mediated stabilization of activated eIF2B dimers, and suggest that eIF2B4 (δ-subunit) contributes to the ISRIB binding site. We also developed new ISRIB analogs, improving its EC50 to 600 pM in cell culture. By modulating eIF2B function, ISRIB promises to be an invaluable tool in proof-of-principle studies aiming to ameliorate cognitive defects resulting from neurodegenerative diseases.

Zonisamide suppresses endoplasmic reticulum stress-induced neuronal cell damage in vitro and in vivo.

Zonisamide has been reported to have protective effects on epilepsy and Parkinson׳s disease and to work via various mechanisms of action, such as inhibition of monoamine oxidase-B and enhancement of tyrosine hydroxylase. Recently, it has been suggested that zonisamide itself shows neuroprotective actions. Therefore, in the present study we investigated the neuroprotective effects of zonisamide against endoplasmic reticulum (ER) stress. We used human neuroblastoma (SH-SY5Y) cells and investigated the protective effects of zonisamide against tunicamycin- and thapsigargin-induced neuronal cell death. In addition, we investigated the effect of zonisamide against 1-methyl-4-phenylpyridinium (MPP⁺)-induced cell death and the mechanism of protection against ER stress. In vivo, we investigated the effect of zonisamide (20 mg/kg, p.o.) in the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of Parkinson׳s disease. Zonisamide not only suppressed MPP⁺-induced cell death, but also inhibited ER stress-induced cell death and suppressed the expression of ER stress-related factors such as C/EBO homologous protein (CHOP) in vivo. Furthermore, zonisamide inhibited the activation of caspase-3 in vitro. These results suggest that zonisamide affected ER stress via caspase-3. We think that ER stress, particularly the mechanism via caspase-3, is involved in part of the neuroprotective effect of zonisamide against the experimental models of Parkinson׳s disease.

FOXO3-mediated up-regulation of Bim contributes to rhein-induced cancer cell apoptosis.

The anthraquinone compound rhein is a natural agent in the traditional Chinese medicine rhubarb. Preclinical studies demonstrate that rhein has anticancer activity. Treatment of a variety of cancer cells with rhein may induce apoptosis. Here, we report that rhein induces atypical unfolded protein response in breast cancer MCF-7 cells and hepatoma HepG2 cells. Rhein induces CHOP expression, eIF2α phosphorylation and caspase cleavage, while it does not induce glucose-regulated protein 78 (GRP78) expression in both MCF-7 and HepG2 cells. Meanwhile, rhein inhibits thapsigargin-induced GRP78 expression and X box-binding protein 1 splicing. In addition, rhein inhibits Akt phosphorylation and stimulates FOXO transactivation activity. Rhein induces Bim expression in MCF-7 and HepG2 cells, which can be abrogated by FOXO3a knockdown. Knockdown of FOXO3a or Bim abrogates rhein-induced caspase cleavage and apoptosis. The chemical chaperone 4-phenylbutyrate acid antagonizes the induction of FOXO activation, Bim expression and caspase cleavage by rhein, indicating that protein misfolding may be involved in triggering these deleterious effects. We conclude that FOXO3a-mediated up-regulation of Bim is a key mechanism underlying rhein-induced cancer cells apoptosis.

Effects of aegeline, a main alkaloid of Aegle Marmelos Correa leaves, on the histamine release from mast cells.

Aegeline or N-[2-hydroxy-2(4-methoxyphenyl) ethyl]-3-phenyl-2-propenamide is a main alkaloid isolated from Aegle marmelos Correa collected in Yogyakarta Indonesia. In our study, we investigated the effects of aegeline on the histamine release from mast cell. The study was performed by using (1) rat basophilic leukemia (RBL-2H3) cell line, and (2) rat peritoneal mast cells (RPMCs). DNP(24)-BSA, thapsigargin, ionomycin, compound 48/80 and PMA were used as inducers for histamine release from mast cell. In our study, aegeline inhibited the histamine release from RBL-2H3 cells induced by DNP(24)-BSA. Indeed, aegeline showed strong inhibition when RBL-2H3 cells induced by Ca(2+) stimulants such as thapsigargin and ionomycin. Aegeline is suggested to influence the intracellular Ca(2+) pool only since could not inhibit the (45)Ca(2+) influx into RBL-2H3 cells. Aegeline showed weak inhibitory effects on the histamine release from RPMCs, even though still succeed to inhibit when the histamine release induced by thapsigargin. These findings indicate that aegeline altered the signaling pathway related to the intracellular Ca(2+) pool in which thapsigargin acts. Based on the results, the inhibitory effects of aegeline on the histamine release from mast cells depended on the type of mast cell and also involved some mechanisms related to intracellular Ca(2+) signaling events via the same target of the action of thapsigargin or downstream process of intracellular Ca(2+) signaling in mast cells.

A novel imidazo[1,5-b]isoquinolinone derivative, U63A05, inhibits Syk activation in mast cells to suppress IgE-mediated anaphylaxis in mice.

Mast cells play a pivotal role in IgE-mediated allergic responses. Development of specific inhibitors against FcεRI-associated proximal signaling molecules in mast cells may represent a promising therapeutic strategy for allergic diseases. We examined whether a novel synthetic compound, 3-butyl-1-chloro-8-(2-methoxycarbonyl)phenyl-5H-imidazo[1,5-b]isoquinolin-10-one (U63A05), could suppress antigen-stimulated degranulation and cytokine secretion in mast cells and IgE-mediated passive cutaneous anaphylaxis (PCA) in mice. U63A05 reversibly and dose-dependently inhibited degranulation of rat basophilic leukemia (RBL)-2H3 mast cells and bone marrow-derived mast cells (BMMCs) stimulated by antigen (IC(50) values for RBL-2H3 and BMMCs were 4.1 and 4.8 µM, respectively). The secretion of inflammatory cytokines was also suppressed in antigen-stimulated mast cells. However, degranulation by thapsigargin, a typical calcium inducer, was not inhibited by U63A05. U63A05 exerts its inhibitory effect, to the same extent as in degranulation, on the activating phosphorylation of Syk and downstream signaling molecules, including LAT and SLP-76. Further downstream, the activating phosphorylations of Akt, Erk1/2, p38, and JNK were also inhibited. Finally, antigen-stimulated PCA was dose-dependently suppressed in mice (ED(50), 26.3 mg/kg). Taken together, the results suggest that U63A05 suppresses the activation of mast cells and the mast cell-mediated allergic response through the inhibition of Syk activation in mast cells.

LiCl attenuates thapsigargin-induced tau hyperphosphorylation by inhibiting GSK-3ß in vivo and in vitro.

Abnormal hyperphosphorylation of microtubule-associated protein tau is involved in the pathogenesis of several neurodegenerative diseases, including Alzheimer's disease (AD). Endoplasmic reticulum (ER) stress is indicated to play an important role in neurodegeneration and activation of glycogen synthase kinase-3ß (GSK-3ß), an integral kinase in tau phosphorylation. To explore the effect of ER stress on tau phosphorylation, we treated cultured cells (HEK293 and SH-SY5Y cells) and rat brain with thapsigargin, an ER stress inducer. We found that the phosphorylation level of tau was significantly increased after thapsigargin treatment. By using a cell-free reconstitution system, we also observed that co-culture of the thapsigargin-treated ER fraction from HEK293/wt (without tau) with cytoplasm prepared from HEK293/tau induced an increased tau phosphorylation. Concurrently, activation of GSK-3ß as evidenced by an increased phospho-GSK-3ß at Tyr-216 and decreased phospho-GSK-3ß at Ser-9 both in vitro and in vivo was detected. Application of lithium chloride, a GSK-3ß inhibitor, could efficiently attenuate the thapsigargin-induced tau hyperphosphorylation with suppressed activation of GSK-3ß in cell cultures and rat brains. Our data provide further evidence supporting the role of ER stress in tau hyperphosphorylation and the protective role of lithium.

The genome-wide expression profile of Scrophularia ningpoensis-treated thapsigargin-stimulated U-87MG cells.

The endoplasmic reticulum (ER) is a principal site for protein synthesis, protein folding, calcium storage, and calcium signaling. Thapsigargin (TG), an inducer of ER stress, inhibits ER-associated Ca(2+)-ATPase and disrupts Ca(2+) homeostasis. ER stress plays an important pathogenetic role in Alzheimer's disease, Parkinson's disease, Huntington's disease, Lou Gehrig's disease, and prion protein diseases. This study was conducted to evaluate the protective mechanisms of Scrophularia ningpoensis (SN) extracts and chemicals on TG-stimulated U-87MG cells. In this study, the recovery activities of E-harpagoside (EHA), harpagide (HA), 8-O-E-p-methoxycinnamoylharpagide (MH), aucubin (AB), cinnamic acid (CA), p-coumaric acid (pCA), p-methoxycinnamic acid methyl ester (MME), caffeic acid (CFA), ferulic acid (FA), and (E)-p-methoxycinnamic acid (MA) on TG-stimulated U-87MG cells were evaluated. The results revealed that SN, MME, CFA, and MH showed considerable recovery effects. Therefore, SN, MME, CFA, and MH were selected to evaluate the gene expression profile of U-87MG cells by using microarray analysis and real-time RT-PCR. The results of this analysis revealed that cell cycle, proliferation, protein folding, and anti-apoptosis-related genes were up-regulated in SN, MME, CFA, and MH-treated U-87MG cells. In addition, significant decreases in apoptosis, the MAPK signaling pathway, and mitochondria-related gene expressions were observed in SN-, MME-, CFA-, and MH-treated U-87MG cells. Thus, SN, MME, CFA, and MH might affect neurodegenerative diseases.

Tunicamycin desensitizes store-operated Ca2+ entry to ATP and mitochondrial potential.

Tunicamycin effect on thapsigargin-induced store-operated calcium entry was investigated. Ca2+ influx was stimulated by 50% upon exposure of Jurkat cells to tunicamycin. Moreover, tunicamycin efficiently prevented the inhibition of store-operated calcium entry caused by dissipation of mitochondrial membrane potential. Protective action of tunicamycin on store-operated Ca2+ entry was also partially preserved in Jurkat cells depleted of ATP, while Ca2+ entry into ATP-deprived cells grown in tunicamycin-free medium was almost completely inhibited. Tunicamycin-evoked changes in cellular Ca2+ fluxes coincided with decreased glycosylation of STIM1 protein. Although the latter observation is correlative and needs additional confirmation it may suggest that deglycosylation of STIM1 protein deprives store-operated calcium entry system of an important regulatory mechanism. This study suggests a novel mechanism of modulation of the activity of store-operated calcium channels in lymphoidal cells.

Cytoprotective roles of senescence marker protein 30 against intracellular calcium elevation and oxidative stress.

Senescence marker protein 30 (SMP30) is identified as an important aging marker molecule and known to play multifunctional roles as an intracellular calcium regulatory protein in the signaling process. To elucidate the functional significance of SMP30, we established the stably transfected P19 cell line with SMP30 expression vector. Overexpression of SMP30 slightly suppressed the proliferation of P19 cells. However, SMP30 overexpression was cytoprotective against calcium-mediated stress such as calcium ionophore (A23187), and thapsigargin. We found that SMP30 overexpression reduced the elevated intracellular calcium levels induced by A23187, but not by thapsigargin. In addition, SMP30 transfected P19 cells were more protective to tert-butylhydroperoxide induced cytotoxicity, indicating the antioxidative properties of SMP30. Taken together, our results suggest that external calcium regulation and antioxidant properties are involved in the cytoprotective mechanism of SMP30.

Effects of antrodia camphorata on viability, apoptosis, and [Ca2+]i in PC3 human prostate cancer cells.

Antrodia camphorata (AC) has been used as a health supplement in Asia to control different cancers; however, the cellular mechanisms of its effects are unclear. The effect of AC on cultured human prostate cancer cells (PC3) has not been explored. This study examined the effect of AC on viability, apoptosis, mitogen-activated protein kinases (MAPKs) phosphorylation and Ca2+ handling in PC3 cells. AC at concentrations of 5-50 microg/ml did not affect cell viability, but at 100-200 microg/ml decreased viability and induced apoptosis in a concentration-dependent manner. AC at concentrations of 25-200 microg/ml did not alter basal [Ca2+]i, but at a concentration of 25 microg/ml decreased the [Ca2+]i increases induced by ATP, bradykinin, histamine and thapsigargin. ATP, bradykinin and histamine increased cell viability whereas thapsigargin decreased it. AC (25 microg/ml) pretreatment inhibited ATP-, bradykinin-, and histamine-induced enhancement on viability, but reversed thapsigargin-induced cytotoxicity. Immunoblotting showed that AC (200 microg/ml) did not induce the phosphorylation of ERK, JNK, and p38 MAPKs. Collectively, in PC3 cells, AC exerted multiple effects on viability and [Ca2+]i, caused apoptosis via pathways unrelated to [Ca2+]i signal and phosphorylation of ERK, JNK and p38 MAPKs.

Nerve growth factor blocks thapsigargin-induced apoptosis at the level of the mitochondrion via regulation of Bim.

This study examined how the neurotrophin, nerve growth factor (NGF), protects PC12 cells against endoplasmic reticulum (ER) stress-induced apoptosis. ER stress was induced using thapsigargin (TG) that inhibits the sarcoplasmic/ER Ca2+-ATPase pump (SERCA) and depletes ER Ca2+ stores. NGF pre-treatment inhibited translocation of Bax to the mitochondria, loss of mitochondrial transmembrane potential, cytochrome c release, activation of caspases (-3, -7 and -9) and apoptosis induction by TG. Notably, TG also caused a marked induction of BimEL mRNA and protein, and knockdown of Bim with siRNA protected cells against TG-induced apoptosis. NGF delayed the induction and increased the phosphorylation of BimEL. NGF-mediated protection was dependent on phosphatidylinositol-3 kinase (PI3K) signalling since all above apoptotic events, including expression and phosphorylation status of BimEL protein, could be reverted by the PI3K inhibitor LY294002. In contrast, NGF had no effect on the TG-mediated induction of the unfolded protein response (increased expression of Grp78, GADD34, splicing of XBP1 mRNA) or ER stress-associated pro-apoptotic responses (induction of C/EBP homologous protein [CHOP], induction and processing of caspase-12). These data indicate that NGF-mediated protection against ER stress-induced apoptosis occurs at the level of the mitochondria by regulating induction and activation of Bim and mitochondrial translocation of Bax.

Dual role of tubulin-cytoskeleton in store-operated calcium entry in human platelets.

Two mechanisms for store-operated Ca(2+) entry (SOCE) regulated by two independent Ca(2+) stores, the dense tubular system (DTS) and the acidic stores, have been described in platelets. We have previously suggested that coupling between the type II IP(3) receptor (IP(3)RII) and hTRPC1, involving reorganization of the actin microfilaments, play an important role in SOCE. However, the involvement of the tubulin microtubules, located beneath the plasma membrane, remains unclear. Here we show that the microtubule disrupting agent colchicine reduced Ca(2+) entry stimulated by low concentrations (0.1 U/mL) of thrombin, which activates SOCE mostly by depleting acidic Ca(2+)-store. Consistently, colchicine reduced SOCE activated by 2,5 di-(tertbutyl)-1,4-hydroquinone (TBHQ), which selectively depletes the acidic Ca(2+) stores. In contrast, colchicine enhanced SOCE mediated by depletion of the DTS, induced by high concentrations of thapsigargin (TG), which depletes both the acidic Ca(2+) stores and the DTS, the major releasable Ca(2+) store in platelets. These findings were confirmed by using Sr(2+) as a surrogate for Ca(2+) entry. Colchicine attenuated the coupling between IP(3)RII and hTRPC1 stimulated by thrombin while it enhanced that evoked by TG. Paclitaxel, which induces microtubular stabilization and polymerization, exerted the opposite effects on thrombin- and TG-evoked SOCE and coupling between IP(3)RII and hTRPC1 compared with colchicine. Neither colchicine nor paclitaxel altered the ability of platelets to extrude Ca(2+). These findings suggest that tubulin microtubules play a dual role in SOCE, acting as a barrier that prevents constitutive SOCE regulated by DTS, but also supporting SOCE mediated by the acidic Ca(2+) stores.

[Mechanism of serum containing SSTG on calcium overload in cardiomyocytes injuryed by hypoxia and reoxygenation].

OBJECTIVE: To explore the effects and mechanism of Shuangshen Tongguan (SSTG) serum, a formula composed of the active fractions of Chinese medicine, on calcium overload in cultured cardiomyocytes injured by hypoxia and reoxygenation. METHOD: The cardiomyocytes were deprived of oxygen and glucose to producl hypoxia reoxygenation injuried models. The changes of intracellular calcium fluorescence intensity induced by K+ and Thapsigargin were measured by fluorospectrophotometry and laster scanning confocal microscope respectively. RESULT: Intracellular calcium concentration was low in normal cardiomyocytes and was enhanced after hypoxia/reoxygenation (P < 0.05); SSTC drug serum reduced the intracellular calcium concentration and depressed the increase of calcium fluorescence intensity in singular cardiomyocyte due to K+ and Thapsigargin stimulation. CONCLUSION: Hypoxia/reoxygenation injury, K+ and Thapsigargin could induce calcium overload in cardiomyocytes. The effects of calcium antagonism of SSTG drug serum were achieved by inhibiting calcium inflow, promoting calcium re-absorption of calcium.

SAMMA induces premature human acrosomal loss by Ca2+ signaling dysregulation.

SAMMA is licensed for development as a contraceptive microbicide. Understanding mechanisms of its biological activity is prerequisite to designing more active second generation products. This study examined Ca(2+) involvement in SAMMA-induced premature acrosomal loss (SAL) in noncapacitated human spermatozoa. SAMMA causes acrosomal loss (AL) in a dose-dependent manner (ED(50) = 0.25 microg/mL). SAL requires extracellular Ca(2+) (ED(50) = 85 microM). SAL is inhibited by verapamil (nonspecific voltage-dependent Ca(2+) channel blocker; IC(50) = 0.4 microM), diphenylhydantoin and NiCl(2) (T-type [Ca(v)3.x] channel blockers; IC(50) 210 microM and 75 microM, respectively). Verapamil blockade of L-type (Ca(v)1.x) channels is use-dependent; activated channels are more sensitive to inhibition. However, verapamil inhibition of SAL does not increase after repeated SAMMA stimulation. SAL is unaffected by 10 microM nifedipine (selective L-type channel blocker). This contrasts to 40% inhibition (P < .001) of AL induced by 1 microM thapsigargin (Ca(2+)-ATPase inhibitor; releases intracellular Ca(2+) stores, promotes capacitative Ca(2+) entry). SAL is unaffected by 1 microM BAPTA-AM (intracellular Ca(2+) chelator), and 50 microM 2-APB (blocks InsP3 receptors and store-operated channels). This contrasts with thapsigargin-induced AL, inhibited nearly 65% by BAPTA-AM (P < .005) and 91% by 2-APB (P, .001). The results suggest that SAL is mediated by Ca(2+) entry through channels pharmacologically similar to the T-type (Ca(v)3.2) class. This process appears distinct from that caused by physiological stimuli such as progesterone or zona pellucida-derived proteins. SAMMA's contraceptive activity may be caused by induction of premature AL through dysregulation of Ca(2+) signaling.

MicroRNA modulation of megakaryoblast fate involves cholinergic signaling.

MicroRNAs (miRNAs) are abundant small regulatory RNAs with multiple roles in cell fate determination. The processes regulating cellular miRNA levels are still unclear and experimental oligonucleotide tools to readily mimic their effects are not yet available. Here, we report that thapsigargin-induced intracellular Ca(++) release suppressed pre-miR-181a levels in human promegakaryotic Meg-01 cells, induced differentiation-associated nuclear endoreduplication and caspase-3 activation and replaced the acetylcholinesterase 3' splice variant AChE-S with AChE-R. AChE, PKC and PKA inhibitors all attenuated the pre-miR-181a decline and the induced differentiation. AChmiON, a synthetic 23-mer 2'-oxymethylated oligonucleotide mimicking the miR-181a sequence, blocked the calcium-induced differentiation while elevating cellular pre-miR-181a levels and inducing DNA fragmentation and cell death. Moreover, when added to RW 264.7 macrophages, AChmiON at 100 nM induced nitric oxide production with efficiency close to that of bacterial endotoxin, demonstrating physiologically relevant activities also in blood-born monocytes/macrophages. The stress-induced modulation of hematopoietic miR-181a levels through AChE, PKC and PKA cascade(s) suggests using miRNA mimics for diverting the fate of hematopoietic tumor cells towards differentiation and/or apoptosis.