AIMTo study whether store-operated Ca2+ channel (SOC) is present in rat colonic smooth muscle cells.

METHODSIntracellular Ca2+ ([Ca2+]i) changes induced by thapsigargin- or caffeine-activated SOC channel were measured in enzymatically dissociated rat colonic smooth muscle cells with the fluorescent indicator Fura-2/AM.

RESULTSIn the absence of external Ca2+ , the sarco-endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (1 micromol/L) and ryanodine receptor (RyR) activator caffeine both transiently elevated [Ca2+]i from (68.32 +/- 3.43) nmol/L to (240.85 +/- 12.65 ) nmol/L, (481.25 +/- 34.77) nmol/L. A subsequent reintroduction of Ca2+ into the extracellular solution resulted in [Ca2+]i further elevated to (457.55 +/- 19.80) nmol/L, (1005.93 +/- 54.62) nmol/L; (643.88 +/- 34.65) nmol/L, (920.16 +/- 43.25) nmol/L, respectively. And the elevated response was blocked by lanthanum (1 mmol/L), but was insensitive to L-type voltage calcium channels blocker verapamil and membrane depolarization.

CONCLUSIONSOC activated by store depletion are present in rat colonic smooth muscle cells. And we further prove the existence of such Ca2+ channels in excitable cells.

Animals ; Caffeine ; pharmacology ; Calcium ; metabolism ; Calcium Channels ; physiology ; Colon ; cytology ; Fura-2 ; metabolism ; Myocytes, Smooth Muscle ; drug effects ; metabolism ; Rats ; Rats, Wistar ; Thapsigargin ; pharmacology

OBJECTIVE: Effects of ATP and acetylcholine (ACh) on intracellular Ca2+ concentrations ([Ca2+]i) and possible mechanism of Ca2+-induced Ca2+ release (CICR) of the isolated outer hair cells (OHCs) in the guinea pig cochlea were studied with confocal microscopy. METHOD: OHCs were isolated from guinea pig cochlea by enzymatic and mechanical methods. The effects of ATP, ACh, Ryanodine + ATP (or ACh) and Thapsigargin + ATP (or ACh) in the presence or absence of extracellular Ca2+ on [Ca2+]i in OHCs were examined by confocal microscopy. RESULT: In the presence of ATP, Ryanodine + ATP, Thapsigargin + ATP, ACh, Ryanodine + ACh and Thapsigargin + ACh increased [Ca2+]i and evoked an evident wave, respectively, the relative magnitude of fluorescence were 1.60 +/- 0.01(ATP), 1.644 +/- 0.005 (Ryanodine + ATP), 1.491 +/- 0.005 (Thapsigargin + ATP), 1.43 +/- 0.01 (ACh), 1.58 +/- 0.02 (Ryanodine + ACh), 1.398 +/- 0.003 (Thapsigargin + ACh) in OHCs in the presence of extracellular Ca2+ respectively. In the absence of extracellular Ca2+, ATP and Ryanodine + ATP induced a gradual and small [Ca2+]i wave, the relative magnitude of fluorescence were 1.341 +/- 0.006 and 1.386 +/- 0.008, however, ACh, Ryanodine + ACh, Thapsigargin + ACh and Thapsigargin + ATP can not induce wave but a gradual [Ca2+]i elevation. ACh can not increase [Ca2+]i. CONCLUSION In the presence of extracellular Ca2+, ATP and ACh increased [Ca2+]i in OHCs not only by Ca2+ influx through ion channel on cell membrane but also a release of Ca2+ from IP3-sensitive calcium reservoir and CICR. In the absence of extracellular Ca2+, ATP activated IP3 sensitive calcium reservoir and Ca2+ release through IP3 sensitive calcium reservoir, in turn CICR was induced. ACh can not activate IP3 sensitive calcium reservoir and CICR in the absence of extracellular Ca2+, therefore, the effect of ACh was dependent of extracellular Ca2+.
Acetylcholine ; pharmacology ; Adenosine Triphosphate ; pharmacology ; Animals ; Calcium ; metabolism ; Calcium Channels ; drug effects ; metabolism ; Cells, Cultured ; Cochlea ; cytology ; metabolism ; Guinea Pigs ; Hair Cells, Auditory, Outer ; metabolism ; Microscopy, Confocal ; Ryanodine ; pharmacology ; Thapsigargin ; pharmacology

OBJECTIVETo investigate the effect of Ca(2+) mobilization on release and activation of matrix metalloproteinases (MMPs) in human hepatocellular carcinoma cells.

METHODSCa(2+) and chemicals which can induce or inhibit Ca(2+) mobilization were added into human SMMC-7721 hepatoma cells in vitro. SDS-PAGE protein electrophoresis and gelatin zymography analysis were carried out to detect the changes of release and activation of MMPs in the cell culture supernatant.

RESULTSAddition of CaCl(2) into culture system resulted in an enhanced secretion and activation of MMP-2 and MMP-9 in a dose-dependent manner. At a dose of 0.8 mmol/L CaCl(2), it maintained a stable high level of MMPs, especially of MMP-2 with (109.71 +/- 27.93)% elevation as compared to the cells without CaCl(2) addition (P < 0.001). SDS-PAGE analysis showed that most secreted proteins were MMPs (MMP-2 and MMP-9) when the cells cultured in media without serum. Thapsigargin (Tg, 4 micromol/L), an inducer of intracellular Ca(2+) stores depletion, significantly enhanced the release and activation of MMP-2 and MMP-9, compared to the control with (58.63 +/- 31.04)% elevation (P < 0.05), while the inducing effect of Tg on MMPs release and activation was significantly inhibited by S-nitro-N-acetylpenicillamine (SNAP, 200 micromol/L), an NO donor.

CONCLUSIONIntracellular Ca(2+) regulation pathways may play an important role in the process of release and activation of MMPs.

Calcium ; metabolism ; Carcinoma, Hepatocellular ; enzymology ; pathology ; Cell Line, Tumor ; Dose-Response Relationship, Drug ; Humans ; Liver Neoplasms ; enzymology ; pathology ; Matrix Metalloproteinase 2 ; metabolism ; secretion ; Matrix Metalloproteinase 9 ; metabolism ; secretion ; Nitric Oxide Donors ; pharmacology ; Penicillamine ; analogs & derivatives ; pharmacology ; Thapsigargin ; pharmacology

To explore the apoptotic effect of simvastatin on K562 cells through endoplasmic reticulum stress, morphological change of apoptotic cells was observed by Hoechst33258 fluorescent staining under fluorescent microscope. Apoptosis rate of cells was determined with annexinV-FITC/PI double staining by flow cytometry; Intracellular calcium concentration ([Ca2+]i) was measured by laser scanning confocal microscope (LSCM); The expression levels of glucose regulated protein 78 (GRP78) and calpain gene mRNA were determined by RT-PCR; The expression levels of caspase-3, -6, -7, -9, -12, calpain and GRP78 proteins were evaluated by Western blotting. In this study, K562 cells treated with simvastatin for 72 h exhibited typical morphological change of apoptosis cells. After 72 h exposed to 10, 20, 30 micromol x L(-1) simvastatin, the apoptotic rates of K562 cells were 12.41%, 19.08% and 23.41%, respectively. Simvastatin induced the increase of [Ca2+]i in K562 cells, fluorescent intensities were 43, 54, and 64, respectively. The expression levels of GRP78 and calpain gene mRNA were up-regulated. The cleavage and activation of caspase-3, -6, -7, -9, -12 and upregulation of GRP78 expression were determined by Western blotting. These findings suggest that endoplasmic reticulum is an important pathway of apoptosis in cells and participates simvastatin-induced apoptosis in K562 cells. It is implied that simvastatin may be suitable for clinical usage in the treatment of myeloma patients.
Apoptosis ; drug effects ; Calcium ; metabolism ; Calpain ; genetics ; metabolism ; Caspases ; metabolism ; Endoplasmic Reticulum ; drug effects ; metabolism ; Enzyme Inhibitors ; pharmacology ; Heat-Shock Proteins ; genetics ; metabolism ; Humans ; K562 Cells ; RNA, Messenger ; metabolism ; Simvastatin ; pharmacology ; Thapsigargin ; pharmacology

OBJECTIVETo determine the activity of endoplasmic reticulum stress (ERS) and its effect on osteogenic differentiation of periodontal ligament stem cells (PDLSC) in inflammatory microenvironment.

METHODSPDLSC were obtained from the primary culture of the human tooth and cloned with limited diluted method. Real-time reverse transcription (RT)-PCR was used to examine the different expression of thapsigargin (TG) treated PDLSC and lipopolysaccharide (LPS) treated PDLSC. Real-time RT-PCR, alizarin red staining and cetyl pyridine chloride quantitative analyze were used to examine the osteogenic differentiation of PDLSC, TG + PDLSC, LPS + PDLSC and LPS + PDLSC + 4-PBA.

RESULTSProtein kinase receptor like endoplasmic reticulum kinase (PERK), glucose regulated protein 78 (GRP78), transcription activation factor 4(ATF4), CCAAT/enhancer-binding protein-homologous protein (CHOP) mRNA expression in group PDLSC + TG in 6 h were respectively 1.49 ± 0.24, 2.77 ± 0.60, 1.75 ± 0.16, 2.16 ± 0.32, which were all greater than that in group PDLSC (P < 0.05). PERK, CHOP mRNA expression reached the peak at 6 h (1.76 ± 0.08, 2.31 ± 0.17) and were greater than group PDLSC (P < 0.05). ERS could suppress osteogenic differentiation of TG + PDLSC and LPS + PDLSC. The runt-related transcription factor-2 (RUNX2), alkaline phosphatase (ALP), osteocalcin (OCN) mRNA expression of group TG + PDLSC was respectively 0.73 ± 0.06, 0.01 ± 0.00, 0.20 ± 0.06 (P < 0.05). The RUNX2, ALP, OCN mRNA expression of group LPS + PDLSC was respectively 0.80 ± 0.06, 0.48 ± 0.05, 0.29 ± 0.04 (P < 0.05). The RUNX2, ALP, OCN mRNA expression of group PDLSC + TG + 4-PBA was respectively 1.10 ± 0.09, 0.74 ± 0.05, 0.67 ± 0.13, which were greater higher than that of group LPS + PDLSC (P < 0.05).

CONCLUSIONSERS was activated in PDLSC and suppressed osteogenic differentiation of PDLSC, which can simulate inflammatory microenvironment in vitro. This effect can be recovered by using ERS inhibitor 4-PBA.

Alkaline Phosphatase ; metabolism ; Butylamines ; pharmacology ; Cell Differentiation ; Cellular Microenvironment ; Core Binding Factor Alpha 1 Subunit ; metabolism ; Endoplasmic Reticulum Stress ; physiology ; Humans ; Osteocalcin ; metabolism ; Osteogenesis ; Periodontal Ligament ; cytology ; metabolism ; Polysaccharides ; pharmacology ; RNA, Messenger ; metabolism ; Stem Cells ; drug effects ; physiology ; Thapsigargin ; pharmacology

Endoplasmic reticulum (ER) stress occurs in macrophage-rich areas of advanced atherosclerotic lesions and contributes to macrophage apoptosis and subsequent plaque necrosis. The purpose of the present study was to investigate the effects of caveolin-1 (Cav-1) on ER stress-induced apoptosis in cultured macrophages and the underlying mechanisms. RAW264.7 cells were incubated with thapsigargin (TG) to establish ER stress model. And Cav-1 expression was detected by Western blot. After being pretreated with filipin(III), a caveolae inhibitor, RAW264.7 cells were assayed with flow cytometry and confocal laser scanning microscopy to detect cell apoptosis. Moreover, p38 mitogen-activated protein kinase (MAPK) phosphorylation and C/EBP homologous protein (CHOP) expression were detected with Western blot. The results showed that Cav-1 expression was markedly increased at early stage of TG treatment (P < 0.05) and then decreased with prolonged or high dose TG treatments. The increasing of Cav-1 expression induced by TG in RAW264.7 cells was abolished under inhibition of caveolae by filipin(III) (P < 0.05). The effect of TG on apoptosis of RAW264.7 cells was further augmented after pretreatment with filipin(III) (P < 0.05). Western blotting showed that MAPK phosphorylation induced by TG was inhibited by filipin(III) in RAW264.7 cells (P < 0.05), whereas CHOP remained unchanged (P > 0.05). These results suggest that Cav-1 may play a critical role in suppressing ER stress-induced macrophages apoptosis in vitro, and one of the mechanisms may be correlated with the activation of p38 MAPK prosurvival pathway.
Animals ; Apoptosis ; drug effects ; Caveolin 1 ; genetics ; metabolism ; Cell Line ; Endoplasmic Reticulum Stress ; physiology ; Filipin ; pharmacology ; MAP Kinase Signaling System ; Macrophages ; cytology ; drug effects ; Mice ; Thapsigargin ; pharmacology ; Transcription Factor CHOP ; metabolism ; p38 Mitogen-Activated Protein Kinases ; metabolism

Effect of strophanthidin (Str) on intracellular calcium concentration ([Ca2+]i) was investigated on isolated ventricular myocytes of guinea pig. Single ventricular myocytes were obtained by enzymatic dissociation technique. Fluorescent signal of [Ca2+]i was detected with confocal microscopy after incubation of cardiomycytes in Tyrode' s solution with Fluo3-AM. The result showed that Str increased [Ca2+]i in a concentration-dependent manner. The ventricular myocytes began to round-up into a contracture state once the peak level of [Ca2+]i was achieved in the presence of Str (10 micromol L(- 1)), but remained no change in the presence of Str (1 and 100 nmol L(-1)). Tetrodotoxin (TTX), nisodipine, and high concentration of extracellular Ca2+ changed the response of cardiomycytes to Str (1 and 100 nmol L(-1)) , but had no obvious effects on the action of Str (10 micromol L(-1)). The elevation of [Ca2+]i caused by Str at all of the detected concentrations was partially antagonized by rynodine (10 micromol L(-1)) or the removal of Ca2+ from Tyrode's solution. In Na+, K+ -free Tyrode' s solution, the response of cardiomycytes in [Ca2+]i elevation to Str (10 micromol L(-1)) was attenuated, while remained no change to Str (1 and 100 nmol L(-1)). TTX, nisodipine, and high concentration of extracellular Ca2+ changed the response of cardiomycytes to Str at all of the detected concentrations in Na+, K+ -free Tyrode's solution. The study suggests that the elevation of [Ca2+]i by Str at the low (nomomolar) concentrations is partially mediated by the extracellular calcium influx through Ca2+ channel or a "slip mode conductance" of TTX sensitive Na+ channel. While the effect of Str at high (micromolar) concentrations was mainly due to the inhibition of Na+, K+ -ATPase. Directly triggering the release of intracellular Ca2+ from sarcoplasmic reticulum (SR) by Str may be also involved in the mechanism of [Ca2+]i elevation.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; pharmacology ; Aequorin ; pharmacology ; Animals ; Calcium ; metabolism ; Calcium Channel Blockers ; pharmacology ; Calcium Channels ; metabolism ; Fura-2 ; pharmacology ; supply & distribution ; Guinea Pigs ; Myocardium ; pathology ; Nifedipine ; pharmacology ; Ryanodine ; pharmacology ; Sarcolemma ; metabolism ; pathology ; Sarcoplasmic Reticulum ; drug effects ; metabolism ; Sodium-Calcium Exchanger ; Sodium-Potassium-Exchanging ATPase ; antagonists & inhibitors ; Strophanthidin ; pharmacology ; Tetrodotoxin ; pharmacology ; Thapsigargin ; pharmacology

PURPOSE: In non-excitable cells, which include parotid and pancreatic acinar cells, Ca(2+) entry is triggered via a mechanism known as capacitative Ca(2+) entry, or store-operated Ca(2+) entry. This process is initiated by the perception of the filling state of endoplasmic reticulum (ER) and the depletion of internal Ca(2+) stores, which acts as an important factor triggering Ca(2+) entry. However, both the mechanism of store-mediated Ca(2+) entry and the molecular identity of store-operated Ca(2+) channel (SOCC) remain uncertain. MATERIALS AND METHODS: In the present study we investigated the Ca(2+) entry initiation site evoked by depletion of ER to identify the localization of SOCC in mouse parotid and pancreatic acinar cells with microfluorometeric imaging system. RESULTS: Treatment with thapsigargin (Tg), an inhibitor of sarco/endoplasmic reticulum Ca(2+)-ATPase, in an extracellular Ca(2+) free state, and subsequent exposure to a high external calcium state evoked Ca(2+) entry, while treatment with lanthanum, a non-specific blocker of plasma Ca(2+) channel, completely blocked Tg-induced Ca(2+) entry. Microfluorometric imaging showed that Tg-induced Ca(2+) entry started at a basal membrane, not a apical membrane. CONCLUSION: These results suggest that Ca2+ entry by depletion of the ER initiates at the basal pole in polarized exocrine cells and may help to characterize the nature of SOCC.
Animals ; Calcium/*metabolism ; Calcium Channels/drug effects/metabolism ; Cells, Cultured ; Endoplasmic Reticulum/drug effects/*metabolism ; Mice ; Mice, Inbred ICR ; Microscopy, Fluorescence ; Pancreas/cytology/drug effects/*metabolism ; Parotid Gland/cytology/drug effects/*metabolism ; Thapsigargin/pharmacology

OBJECTIVEThe release of intracellular stores of Ca(2+) occurs virtually in all types of cells by a means of amplifying external signals that modulate intracellular signaling events. In cardiac myocytes, type 2 ryanodine receptor (RyR(2)) is activated during excitation-contraction (E-C) coupling by Ca(2+)-induced Ca(2+) release (CICR) triggered by Ca(2+) influx across the sarcolemma. The hyperadrenergic state of heart failure results in leaky RyR(2) channels attributable to PKA hyperphosphorylation and depletion of the stabilizing FK506 binding protein, FKBP12.6. Dysregulation of sarcoplasmic reticulum (SR) Ca(2+) release via RyR(2) could contribute to defects in Ca(2+) signaling in failing hearts. Researchers tested the hypothesis that improved cardiac muscle function attributable to beta-AR blockade is associated with restoration of normal RyR(2) channel function in patients with heart failure. The authors aimed to observe change of RyR in junior mouse with HF and the effect of beta-adrenoreceptor blocker on RyR in HF in this experiment.

METHODSThe animal model of congestive heart failure was established by constriction of abdominal aorta. Five weeks old mice were randomly divided into 3 groups: (1) HF group without treatment (n = 20); (2) HF group treated with carvedilol (n = 20); (3) Sham-operated group (n = 20). Carvedilol was administered through direct gastric gavage. After 4 weeks of treatment the high frequency ultrasound was performed. Myocardial SR was fractionated with velocity centrifugation. The time courses of Ca(2+) uptake and leak were determined by fluorescent spectrophotometr.

RESULTSCompared with the sham-operated group, left ventricular diastolic dimension (LVEDD) (P < 0.05), left ventricular systolic dimension (LVESD), interventricular septal thickness at end-diastole (IVSTd), interventricular septal thickness at end-systole (IVSTs), left ventricular posterior wall thickness at end-diastole (LVPWTd), and left ventricular posterior wall thickness at end-systole (LVPWTs) were all significantly increased (P < 0.01). Ejection fraction (EF) and fractional shortening (FS) were decreased (P < 0.01) in HF group without treatment. LVEDD (P < 0.05), LVESD, IVSTd, IVSTs, LVPWTd and LVPWTs were all prominently decresed (P < 0.01). EF and FS were increased (P < 0.01) in cases of HF treated with carvedilol when compared with HF group without treatment. After adding thapsigargin to the buffer including SR of three groups, there were fewer Ca(2+) leak in sham-operated group and HF group treated with carvedilol than that of HF group without treatment (P < 0.01), while after adding FK506 and thapsigargin together to the buffer including SR of three groups, there were marked Ca(2+) leak in sham-operated group and HF group treated with carvedilol (P < 0.01). However, there was no additional increase in Ca(2+) leak in HF group compared with that of the group where only thapsigargin was added (P > 0.05).

CONCLUSIONThere is more cardiac Ca(2+) leak in HF. Carvedilol can inhibite Ca(2+) leak by restoring the contactation of FKBP12.6 back to RyR in HF to improve cardiac function and prevent left ventricle from remodeling.

Adrenergic beta-Antagonists ; pharmacology ; Animals ; Animals, Newborn ; Calcium ; metabolism ; Calcium Signaling ; drug effects ; Calcium-Transporting ATPases ; antagonists & inhibitors ; Carbazoles ; pharmacology ; Disease Models, Animal ; Heart Failure ; diagnostic imaging ; drug therapy ; metabolism ; Myocardial Contraction ; drug effects ; Myocytes, Cardiac ; drug effects ; metabolism ; Propanolamines ; pharmacology ; Rats ; Rats, Wistar ; Ryanodine Receptor Calcium Release Channel ; metabolism ; Sarcoplasmic Reticulum ; drug effects ; metabolism ; Spectrometry, Fluorescence ; Thapsigargin ; pharmacology ; Ultrasonography

To interact with the egg, the spermatozoon must undergo several biochemical and motility modifications in the female reproductive tract, collectively called capacitation. Only capacitated sperm can undergo acrosomal exocytosis, near or on the egg, a process that allows the sperm to penetrate and fertilize the egg. In the present study, we investigated the involvement of cyclic adenosine monophosphate (cAMP)-dependent processes on acrosomal exocytosis. Inhibition of protein kinase A (PKA) at the end of capacitation induced acrosomal exocytosis. This process is cAMP-dependent; however, the addition of relatively high concentration of the membrane-permeable 8-bromo-cAMP (8Br-cAMP, 0.1 mmol l^-1) analog induced significant inhibition of the acrosomal exocytosis. The induction of acrosomal exocytosis by PKA inhibition was significantly inhibited by an exchange protein directly activated by cAMP (EPAC) ESI09 inhibitor. The EPAC selective substrate activated AE at relatively low concentrations (0.02-0.1 μmol l^-1), whereas higher concentrations (>5 μmol l^-1) were inhibitory to the AE induced by PKA inhibition. Inhibition of PKA revealed about 50% increase in intracellular cAMP levels, conditions under which EPAC can be activated to induce the AE. Induction of AE by activating the actin severing-protein, gelsolin, which causes F-actin dispersion, was inhibited by the EPAC inhibitor. The AE induced by PKA inhibition was mediated by phospholipase C activity but not by the Ca²⁺-channel, CatSper. Thus, inhibition of PKA at the end of the capacitation process induced EPAC/phospholipase C-dependent acrosomal exocytosis. EPAC mediates F-actin depolymerization and/or activation of effectors downstream to F-actin breakdown that lead to acrosomal exocytosis.
8-Bromo Cyclic Adenosine Monophosphate/pharmacology* ; Acrosome/metabolism* ; Acrosome Reaction/drug effects* ; Calcimycin/pharmacology* ; Cyclic AMP/metabolism* ; Cyclic AMP-Dependent Protein Kinases/antagonists & inhibitors* ; Exocytosis/drug effects* ; Guanine Nucleotide Exchange Factors/metabolism* ; Humans ; Male ; Protein Kinase Inhibitors/pharmacology* ; Signal Transduction/drug effects* ; Spermatozoa/metabolism* ; Thapsigargin/pharmacology*