LPS induced macrophage priming effect on O2- production and its signal mechanisms

AIM:To investigate the effect of lipopolysaccharide (LPS) priming on macrophage(MΦ).METHODS:Macrophage cell line RAW264.7 were pretreated with or without LPS for 1 h, then challenged with PMA, or LPS, muramyl dipeptide(MDP), Zymosan, formyl-methionyl-leucyl-phenylalanine(FMLP) for 1 h. O₂^- production in supernatants and intracellular free calcium([Ca²⁺]i) were measured, and changes in [Ca²⁺]i and LPS induced O₂^- production were compared.RESULTS:LPS pretreatment significantly increased O₂^- production in RAW264.7 cells challenged with the stimuli, and in a certain extent, both O₂^- production and increase of resting intracellular [Ca²⁺]i were dose- and time-dependent on LPS pretreatment.Furthermore, the peak [Ca²⁺]i was significantly higher in LPS pretreated groups than that of LPS unpretreated groups when challenged with PMA. Pretreatment with Ca²⁺ inophore A23187 mimicked the LPS priming effects on O₂^- production, but pretreatment with Ca²⁺ chelator BAPTA and EGTA blocked this priming effect.CONCLUSION:LPS-induced MΦ priming effect on O₂^- production is dependent on elevation of resting intracellular [Ca²⁺]i.     

Role of potassium channels in the regulation of intracellular free Ca2+ concentration of pulmonary artery smooth muscle cells in rats

AIM: To investigate the role of potassium channels in the regulation of intracellular free calcium concentration ( [Ca²⁺]_i) of pulmonary artery smooth muscle cells (PASMCs) in rats. METHODS: The fluorescence Ca²⁺ indicator Fura-2/AM was used to observe [Ca²⁺]_i of rat PASMCs in normal and chronic hypoxic condition. The influences of potassium channels on PASMCs proliferation were assessed by MTT assay. RESULTS: 1. In normoxic condition, [Ca²⁺]_i was (156.91±8.60) nmol/L, and in hypoxic condition, [Ca²⁺]_i was (294.01±16.81) nmol/L. 2. In normoxic condition, the voltage-dependent K⁺-channel antagonist 4-aminopyridine (4AP), but not the Ca²⁺-activated K⁺-channel antagonist tetraethylammonium (TEA) and the ATP-sensitive K⁺-channel antagonist glibenclamide (Glib) increased [Ca²⁺]_i. 3. In hypoxic condition, 4AP and TEA caused the rise in [Ca²⁺]_i , but Glib had no effect on [Ca²⁺]_i. 4. MTT assay showed that 4AP increased the value of absorbing light degree (A value) in normoxic and hypoxic condition (0.582±0.062,0.873±0.043,respectively, P＜0.01), TEA increased A value only in hypoxic condition, and Glib had no effect on the proliferation of PASMCs. CONCLUSIONS: K_V plays an important role in the regulation of [Ca²⁺]_i and proliferation of PASMCs. K_Ca serves as distinct responsive roles in the regulation of proliferation of PASMCs in hypoxic condition. K_ATP has no effect on [Ca²⁺]_i and proliferation of PASMCs in normoxic and hypoxic conditions.     

Effect of chronic hypoxia on [Ca2+]iin pulmonary artery endothelial cells and smooth muscle cells under acute hypoxia

AIM AND METHODS: Using Ca²⁺-sensitive fluorescent probe Fura-2,we measured the changes of [Ca²⁺]_iin cultured rat pulmonary artery endothelial cells (PAEC) and porcine pulmonary artery smooth muscle cells (PASMC) from normoxic (NC group) or chronic hypoxic group (CH group) when they were exposed to acute hypoxia. RESULTS: The increase in [Ca²⁺]_iin 6th passage of PASMC caused by acute hypoxia in CH group was significantly lower than that in the same passage of NC group (P<0.05).On the contrary, in PAEC, the acute hypoxia induced increase in _i, which was significantly higher in 5th passage of CH group than that in NC group (P<0.05). CONCLUSION: The decrease of the elevation of [Ca²⁺]_icaused by acute hypoxia in PASMC of CH group indicated that it functioned to lower the constrictive response to hypoxia.The intensive increase in [Ca²⁺]_icaused by acute hypoxia in PAEC of CH group might lead to more relaxing factors derived from PAEC,which results in a decrease in HPV.     

ROS mediates regulation of intracellular Ca2+ induced by angiotensin II in primarily cultured medullary neurons

AIM: To investigate the role of reactive oxygen species (ROS) in the regulation of intracellular Ca²⁺ induced by angiotensin II (Ang II) in the primarily cultured medullary neurons. METHODS: Primarily cultured medullary neurons were prepared from 14-day-old embryos of Sprague-Dawley rats in the study. The identification of medullary neurons was assessed by double-labeling immunofluorescence. To explore the role of ROS, mainly the superoxide (O₂^·), the O₂^·generation was measured using the fluorogenic probe dihydroethidium (DHE). To determine intracellular free calcium concentration ([Ca²⁺]_i), the neurons were loaded with the Ca²⁺-specific dye Fura-2/AM. The cell viability after adding Ang II was also examined using CCK-8 assay. RESULTS: Most of the cultured cells were medullary neurons, more than 80% of which were glutamate positive neurons. Ang II (5 μmol/L) increased the level of ROS within 10 min in the medullary neurons. Ang II at 5 μmol/L induced a significant[Ca²⁺]_i increase in the medullary neurons, and the effect of Ang II occurred rapidly and reached a peak within 20 min after administration. The level of[Ca²⁺]_i started to decline after washout. The Ca²⁺ elevation induced by Ang II was significantly decreased by apocynin or TEMPOL. No significant difference in the cell viability between control group and 5 μmol/L Ang II treatment group was observed. CONCLUSION: ROS is involved in the regulation of[Ca²⁺]_i induced by Ang II in the primarily cultured medullary neurons, suggesting a potential intracellular signaling mechanism involved in the Ang II-mediated oxidant regulation of central neural control of blood pressure.     

Antagonistic effects of cyproheptadine and anisodamine on [Ca2+]i elevation induced by TNFα in endothelial cell strains

AIM: To study the effects of cyproheptadine (Cyp) and anisodamine (Ani) on the changes of intracellular free Ca²⁺ concentration ([Ca²⁺]_i) induced by tumor necrosis factor (TNFα) in single endothelial cells, and to explore the mechanisms of TNFα mediated shock and antishock actions of Cyp and Ani. METHODS: Human umbilical vein endothelial cell strains (ECV304) were seed in 35 mm tissue culture dish with 2 mL DMEM culture medium. The cultured cells were loaded by Fluo-3/AM. The spatial distribution and the dynamic changes of [Ca²⁺]_i in single endothelial cell was determined by laser scanning confocal microscopy (LSCM). RESULTS: [Ca²⁺]_i in single endothelial cell after stimulation of TNFα rapidly increased in a dose-dependent manner and approached the peak value within 60 seconds, afterwards, decreased and kept above the basal level. The confocal scanning image showed that [Ca²⁺]_i elevation was more obvious in nuclear than in cytoplasma, and decreased slowly. Cyp (3×10^-5, 6×10^-5 mol/L) and Ani (2×10^-5, 4×10^-5 mol·L^-1) markedly inhibited TNFα (1.2×10^-9 mol·L^-1)-induced [Ca²⁺]_i elevation. CONCLUSIONS: TNFα markedly induces elevation of [Ca²⁺]_i in single endothelial cell, it may be an important mechanism of TNFα-induced shock and tissue injury. Cyp and Ani obviously suppress TNFα-induced [Ca²⁺]_i elevation, which probably is one of the mechanisms of their antishock effects.     

Effect of interleukin-2 on intracellular calcium levels in rat ventricular myocytes during anoxia and reoxygenation

AIM: To investigate the effect of interleukin-2(IL-2) on the intracellular calcium in electrically stimulated adult rat ventricular myocytes during anoxia and reoxygenation. METHODS: The isolated cardiac ventricular myocytes were exposed to 5 min anoxia followed by 10 min reoxygenation. Chemical anoxia was introduced by Krebs-Henseleit(K-H) solution containing 10^-3 mol/L sodium dithionite. The spectrofluorometric method was used to verify intracellular calcium transient with fura-2/AM as calcium fluorescence probe. RESULTS: It was shown that during anoxia, the amplitude of Ca²⁺ transient was decreased, diastolic [Ca²⁺]_i, time to peak and time to relaxation of Ca²⁺ transient were increased. All the parameters were got back but did not returned to the pre-anoxia level during reoxygenation. IL-2 at 2×10⁵ U/L administrated during anoxia aggravated the effect of rexoxygenation on [Ca²⁺]_i transient. Pretreatment with a specific κ opioid antagonist, nor-BNI(10^-8 mol/L), abolished the effect induced by IL-2 during anoxia on the [Ca²⁺]_i transients, whereas specific δ opioid antagonist, naltrindole(10^-6 mol/L), did not cancel the effect. CONCLUSION: It is concluded that administration of IL-2 during anoxia aggravated the effect of reoxygenation on the [Ca²⁺]_i transients of isolated ventricular myocytes, which was mediated by cardiac κ opioid receptor pathway.     

Role of calcium ion in the cyotoxicity and DNA fragment induction in HL-60 cells by 6F isolated from Pteris semipinnata L.

AIM: To investigate the changes of cytosolic free calcium concentration([Ca²⁺]_i) and expression of Bcl-2 in HL-60 cells treated by 6F isolated from Pteris semipinnata L.(PSL), and to discuss the relations between calcium ion and cytotoxicity and DNA fragment induction effects of 6F. METHODS: HL-60 cells were used as in vitro model. [Ca²⁺]_i was measured on fluorescent spectrophotometry using Fura-2/AM as Ca²⁺ indicator. Bcl-2 expressing level was measured by flow cytometry. Tetrazolium salt(MTT) and diphenylamine staining methods were applied for cytotoxicity assay and DNA fragmentation detection, respectively. RESULTS: [Ca²⁺]_i increased obviously in a dose and time dependent manner after treated HL-60 cells with 6F. 6F decreased the expressing level of Bcl-2. Adding 2 mmol/L Ca²⁺ to the medium, or 1 mmol/L EDTA to chelate Ca²⁺, or 4 μmol/L calcium ionophore A 23187 to increase the concentration of cytosolic Ca²⁺, the DNA fragment induction by 6F was not affected, whereas the cytotoxicity of 6F was enhanced. 250 μmol/L Zn²⁺ attenuated the DNA fragment induction, and the cytotoxicity of 6F against HL-60 cells was enhanced significantly. CONCLUSION: It was speculated that the decreased expressing of Bcl-2 by compound 6F was related to increased [Ca²⁺]_i in HL-60 cells, and DNA fragment induction was possibly catalyzed by Ca²⁺ - independent DNase.     

Effects of tetrandrine and fructose-1, 6-diphosphate on the elevated intrasynaptosomal [Ca2+]i induced by excitatory amino acids

AIM: To study the effects of tetrandrine(Tet) and fructose-1, 6-diphosphate(FDP) on the elevated intrasynaptosomal [Ca²⁺]_i induced by excitatory amino acids(EAA). METHODS: A rapid method for preparing synaptosomes was used, and intrasynaptosomal free calcium([Ca²⁺]_i) was measured by using the fluorescent indicator quin-2. RESULTS: L-glutamate(Glu, 100 μmol/L), aspartate(Asp, 100 μmol·L^-1), N-methy1-D-aspartate(100 μmol/L) and Glu(50 μmol/L) plus Asp(50 μmol/L) all elevated intrasynaptosomal [Ca²⁺]_i in a dose-dependent manner. Pretreatment with Tet(10, 30, 60 μmol/L), FDP(15, 30, 75, 150 μmol/L), MK-801(10, 20 μmol/L) and Tet(15, 30 μmol/L) plus FDP(15, 30 μmol/L) all attenuated the increase in intrasynaptosomal [Ca²⁺]_i induced by EAAs mentioned as above in a dose-dependent manner, and the effect of Tet plus FDP was most significant. CONCLUSION: Both Tet and FDP inhibited a rise in intrasynaptosomal [Ca²⁺]_i induced by EAAs, which may be one of mechanisms that Tet and FDP pretect cerebral tissues against ischemia injury.     

Salidroside increases release of intracellular free Ca2+ from sarcoplasmic reticulum in cultured rat cardiomyocytes

AIM: To observe the effects of salidroside on intracellular free Ca²⁺ concentration in cultured rat cardiomyocytes. METHODS: Primarily cultured cardiomyocytes of neonatal rats were divided into control group, different concentrations of salidroside groups and verapamil pretreatment+different concentrations of salidroside groups. The fluorescent intensity of intercellular free calcium concentration ([Ca²⁺]_i) in cultured cardiomyocytes of newborn rats loaded with fluo-3/AM(5 μmol/L) was measured by laser scanning confocal microscopy. RESULTS: Salidroside at concentrations of 15 mg/L, 30 mg/L and 60 mg/L elevated [Ca²⁺]_i in cultured rat cardiomyocytes with the peak values of 574.08±4.65, 591.86±3.64 and 618.66±4.27, respectively (all P<0.01), indicating that the effect of salidroside on the level of [Ca²⁺]_i was dose-dependent. In the presence of verapamil in D-Hanks solution, salidroside also elevated the fluorescent intensity of [Ca²⁺]_i in cardiomyocytes from 357.74±3.13, 387.17±2.37 and 391.43±1.34 to 480.86±3.98, 496.70±3.08 and 522.18±3.19, respectively (all P<0.01). CONCLUSION: Salidroside increases the release of [Ca²⁺]_i from sarcoplasmic reticulum in cultured rat cardiomyocytes.     

Effects of levcromakalim on pulmonary arterial endothelial cells and smooth muscle cells exposed to hypoxia

AIM:To explore the effects of levcromakalim(Lev) on pulmonary arterial endothelial cells (PAEC) and smooth muscle cells (PASMC) exposed to hypoxia and the mechanisms involved.METHODS:The effects of Lev on [Ca²⁺]_i, and expression of PKC_α, eNOS, iNOS and PDGF-B mRNA and protein levels were observed. The nitrite (NO₂^-) and entothelin-1(ET-1) concentrations in supernatant in cultured PAEC and PASMC were measured. The proliferation and apoptosis of PASMC was also detected.RESULTS:When PASMC were exposed to hypoxia, Lev reduced concentration of ET-1 in cultured cell supernatant, lowed the expression of PKC_α, iNOS and PDGF-B both at mRNA and protein levels, decreased [Ca²⁺]_i concentration, increased proliferation and promoted the apoptosis in PASMC. However, in the presence of Lev, the [Ca²⁺]_i concentration was not changed in the hypoxic PAEC. The NO₂^- concentration in cultured cell supernant and expression of eNOS at mRNA and protein levels in hypoxic PASMC and PAEC were also unchanged. The downregulated ET-1 activity in PASMC and PAEC and proliferation in PASMC involved in the inhibition of PKC_α signaling pathway.CONCLUSIONS:Lev reduce some disadvatage effect of hypoxia on PASMC and PAEC. The mechanism of Lev action may partly involve in the downregulation of PKC_α signaling functions.     

Sodium Ferulate protects human aortic smooth muscle cells against oxidized Lipoprotein(a)

AIM: To investigate the influences of native and oxidized lipoprotein(a) on human arterial smooth muscle cell (SMC) proliferation, change of intracellular free calcium concentration ( [Ca²⁺]_i) and the protective effect of sodium ferulate(SF). METHODS: Lp(a) was oxidized by Cu²⁺ and the extent of oxidation was assessed by the MDA content.Human SMC were incubated in culture media with SF for 12 h, then exposed to Lp(a) and oxidized-Lp(a) , respectively. MTT colorimetry and flow cytometry were used to evaluated the proliferation of SMC and flurorescent indicator Fura-2/AM was used to determined [Ca²⁺]_i. RESULTS: ox-Lp(a) significantly promoted proliferation of SMC and increased [Ca²⁺]_i compared with Lp(a). SF(40,80 mg/L) remarkedly inhibited SMC proliferation and decreased the rising of [Ca²⁺]_i induced by ox-Lp(a) in a dose-dependent manner, but no effect on SMC proliferation and the increase in [Ca²⁺]_i induced by Lp(a).CONCLUSION: ox-Lp(a) induces the strong growth-promoting effect in SMC through increasing in [Ca²⁺]_i, which might be one of the cellular mechanisms responsible for the higher atherogenic potential of ox-Lp(a) compared with Lp(a), and this process can be prevented by inhibiting of oxidation by SF.     

Effects of glucose and Mg2+ in the neurons damaged by glutamate

AIM and METHODS: To observe the effects of glucose-free and Mg²⁺-free in the extracellular fluid on the changes of [Ca ²⁺]_i in the cerebro-cortical neurons damaged by 1mmol/L glutamate using laser confocal scanning microscope. RESULTS: Both frequency and amplitude of neuronal calcium oscillation induced by glutamate were lowered in glucose-free and Mg²⁺-free buffers. The basic [Ca²⁺]_i concentration was lowered in the former case , but it was elevated in the latter case. CONCLUSION: Mg²⁺-free aggravates [Ca²⁺]_i overload induced by 1mmol/L glutamate ,under certain conditions the glucose-free might resist damage role of glutamate and Mg²⁺-free.     

Salvia miltiorrhiza antagonized the alterations of contraction and intracellular calcium of rat ventricular cardiomyocytes induced by anoxia and reoxygenation

AIM:To study the effect of salvia miltiorrhiza (SM) on cell contraction and intracellular calcium of enzymatically isolated rat ventricular myocytes during normoxia and anoxia/reoxygenation.METHODS:Contraction and intracel ular calcium were determined with video tracking system and spectrofluorometric method,and the chemical anoxic method was employed. RESULTS:The ±dL/dt_max, dL of cell contraction and the amplitude of [Ca²⁺]_i in the cardiomyocytes following SM treatment were decreased in a dose-dependent manner. During anoxia, the ±dL/dt_max, dL and amplitude of [Ca²⁺]_i were decreased, while the diastolic Ca²⁺ level was elevated compared with control group. All the contractile parameters and the diastolic Ca²⁺ level were back toward pretreatment values during reoxygenation, but could not return to control level. After the treatment with SM (3 g/L), ±dL/dt_max and dL of cell contraction and the amplitude of [Ca²⁺]_i were higher and the diastolic Ca²⁺ level was lower than those in anoxia/reoxygenation group. CONCLUSION:SM antagonized effects of anoxia and reoxygenation on cell contraction and intracellular calcium in isolated ventricular myocytes.     

Calcium-sensing receptor modulates pulmonary artery tension through G-protein-PLC-IP3 pathways

AIM: To observe the role of calcium-sensing receptor (CaSR) in the regulation of pulmonary artery tension. METHODS: The intracellular calcium concentration ([Ca²⁺]_i) was detected by laser-scanning confocal microscopy, and the pulmonary artery tension was determined by the pulmonary arterial ring technique. RESULTS: Increased levels of [Ca²⁺]_o or Gd³⁺ (an agonist of CaSR) induced the increase in [Ca²⁺]_i and pulmonary artery constriction in a concentration-dependent manner. Additionally, the effects of Ca²⁺ and Gd³⁺ were inhibited by U73122 and D609 (specific inhibitor of PLC), and 2-APB and heparin (specific antagonist of IP₃ receptor). However, U73343 (U73122 inactive analogue) did not take effect. CONCLUSION: CaSR may be involved in the regulation of pulmonary artery tension by increasing [Ca²⁺]_i through G-protein-PLC-IP₃ pathway.     

Relaxation effect of isoliensinine on isolated mouse airway smooth muscle

AIM: To study the relaxation effect of isoliensinine on high K⁺-induced isolated mouse airway smooth muscle (ASM) and the underlying mechanism. METHODS: The muscle tension transducer was used to detect the effects of isoliensinine on high K⁺-induced precontraction and Ca²⁺ influx in ASM. The technique of patch-clamp and calcium imaging system were respectively used to examine the effects of isoliensinine on LVDCC currents and[Ca²⁺]_i of the ASM cells (ASMCs). RESULTS: Isoliensinine significantly relaxed precontracted ASM induced by high K⁺ in a concentration-dependent manner. The maximum relaxation ratio was(95.3±3.9)% by isoliensinine at 100 μmol/L. In addition, LVDCC currents were measured using the whole-cell patch-clamp technique, which were abolished by isoliensinine. High K⁺-induced 340/380 nm fluorescence ratio of Fura-2 was 0.63±0.10 in ASMCs, while it decreased to 0.36±0.05 after the addition of isoliensinine (P<0.01). When isoliensinine was added at the peak point of[Ca²⁺]_i, the ratio rapidly decreased from 0.74±0.02 to 0.42±0.05 (P<0.01). Moreover, isoliensinine inhibited high K⁺-induced Ca²⁺ influx-mediated contraction of ASM. CONCLUSION: Isoliensinine inhibits LVDCC currents, terminates Ca²⁺ influx and reduces[Ca²⁺]_i, eventually resulting in relaxation of the ASM, indicating isoliensinine might be a potential bronchodilator.     

Different concentrations of intracellular calcium in uterine myometrial cells at term and non-term

AIM:To investigate different intracellular concentration of Ca²⁺ in uterine myometrial cells at term and non-term.METHODS:The living cells suspensions were made to measure intracellular Ca²⁺ concentrations after stainned by calcium fluorescent indicator Fluo-3 AM, then examined by laser scanning confocal microscope (LSCM).RESULTS:Intracelluar Ca²⁺ showed very stronger red positive signal in myometrial cells at term than that in non-term cells. [Ca²⁺]i were (35±8.1) nmol/L at non term and (75±7.3) nmol/L at term, which had significant difference compared with each other (P＜0.05).CONCLUSION:Increase in [Ca²⁺]i in myometrial cells might play a very important role labor.     

Protective effect of hydrogen sulfide on PC12 cells injured by ATP

AIM: To prove the purinergic signaling mechanism of the neuroprotective action of hydrogen sulfide by observing the effects of sodium hydrosulfide (NaHS), a donor of hydrogen sulfide, on the cell viability, intracellular Ca²⁺ concentration ([Ca²⁺]_i) and the change of membrane permeability in the PC12 cells injured by adenosine triphosphate (ATP). METHODS: PC12 cells in logarithmic growth phase were randomly divided into 4 groups. In control group, the cells were cultured without ATP treatment. In ATP group, the cells were treated with ATP after cultured for 24 h. In NaHS+ATP group, the cells were incubated with NaHS for 30 min before treated with ATP, and NaHS always existed in the reaction system. In KN-62+ATP group, the cells were pretreated with KN-62 for 30 min, and the other treatments were as the same as those in NaHS+ATP group. The cell viability was assessed by MTT assay. The [Ca²⁺]_i was detected by Fura-2/AM staining. The membrane permeability was observed by staining with fluorescent dye YO-PRO-1.RESULTS: ATP at concentration of 0.3 mmol/L showed no injury effect on the cells. However, the cell viability was dropped gradually in a dose-dependent manner as the ATP at doses of 1, 3, 5 and 10 mmol/L. The decline of cell viability by ATP was obviously reversed by 200 μmol/L of NaHS in the PC12 cells (P<0.05), but exasperated by 800 μmol/L of NaHS (P<0.05). At the same time, ATP evoked the increase in [Ca²⁺]_i in a dose-dependent manner, which was inhibited by NaHS (P<0.05). Furthermore, the YO-PRO-1 uptake induced by ATP in a dose-dependent and time-dependent manner was also reduced by NaHS (P<0.05). CONCLUSION: Hydrogen sulfide has protective effect on the PC12 cells injured by ATP. The mechanism may be related to the reverse of the increased [Ca²⁺]_i and YO-PRO-1 uptake.     

Protective effect of quercetin on ER stress-related apoptosis induced by thapsigargin in macrophages

AIM: To investigate the effects and possible mechanisms of quercetin (Que) on endoplasmic reti-culum stress (ERS)-related apoptosis induced by thapsigargin (TG) in RAW264.7 cells. METHODS: ER stress of RAW264.7 cells were induced by TG at concentration of 1 μmol/L for 24 h. After treated with different concentrations of Que (80, 120 and 160 μmol/L), the cell viability was determined by MTT assay.The apoptotic rate and the changes of intracellular Ca²⁺ concentration ([Ca²⁺]_i) were determined by flow cytometry, and the cell apoptotic morphology was observed under laser scanning confocal microscope.The protein levels of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) were detected by Western blotting. The effect of Que on GRP78 and CHOP induced by TG with phosphatidylinositol 3-kinase (PI3K) inihibitor LY294002 at concentration of 15 nmol/L was measured by Western blotting. RESULTS: Que suppressed ER stress-related injury induced by TG in RAW264.7 cells. Compared with TG group, the cell viability increased (P<0.05), apoptotic rate and [Ca²⁺]_i decreased (P<0.05) and the changes of apoptotic morphology were alleviated. The increase in GRP78 and CHOP induced by TG as an ER stress marker was suppressed by Que (P<0.05). The suppressive effect of Que on GRP78 and CHOP was reproduced by LY294002 (P<0.05), but they failed to exhibit additive suppression. CONCLUSION: Que suppresses the ER stress induced by TG in RAW264.7 cells. The protective effect may be related to its suppression on PI3K signaling pathway.     

Erythropoietin inhibits eryptosis induced by reactive oxygen species

AIM: To observe the influence of erythropoietin (EPO) on eryptosis and production of reactive oxygen species (ROS) in erythrocytes under stimulation of hydrogen peroxide (H₂O₂),and to explore its related mechanism. METHODS: The erythrocyte suspension (1%) was cultured in vitro and divided into 3 groups:control group (C group, the culture medium was PBS), H₂O₂ group (H group, the culture medium was PBS containing H₂O₂ at final concentration of 100 μmol/L) and EPO group (E group, the culture medium was PBS containing H₂O₂ at final concentration of 100 μmol/L and EPO at final concentration of 2×10⁴ U/L). The erythrocytes were collected at 24 h and 60 h. The eryptosis was detected by flow cytometry with Annexin V staining. The production of ROS and intracellular calcium ion concentration ([Ca²⁺]_i) were also analyzed by flow cytometry. RESULTS: The eryptosis in C group was increased as the incubating time extended. The eryptosis in H group was higher than that in C group (P<0.01), while that in E group was lower than that in H group (P<0.01). Meanwhile, ROS production and[Ca²⁺]_i were higher in H group than those in C group (P<0.01), but those were lower in E group than those in H group (P<0.05 or P<0.01). CONCLUSION: EPO inhibits eryptosis induced by H₂O₂ and its mechanism may be related to antioxidant effect and change of[Ca²⁺]_i.     

Effects of cimetidine on platelet function and thrombosis

AIM:To observe the effects of cimetidine(Cim) on platelet function and thrombosis. METHODS:After incubated with Cimin vitro, rat platelets were activated with ADP or thrombin. The platelet aggregation, platelet malondialdehyde(MDA) formation, platelet intracellular free calcium( [Ca²⁺]_i), and thromboxane B₂ (TXB₂) were measured. The effects of Cim on electric-induced thrombosis in rat carotid artery were examined. RESULTS:Cim potentiated ADP induced platelet aggregation, increased the thrombin induced [Ca²⁺]_i and MDA formation, decreased TXB₂. Also, Cim shortened the duration of electric-stimulated occlution time in rat carotid artery. CONCLUSION:Cim increased platelet function and accelerated thrombosis.