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The aim of the present study was to establish a cell model of volume-regulated anion channel subunit LRRC8A and investigate the physiological characteristics of LRRC8A. The eukaryotic expression vectors of LRRC8A and YFP-H148Q/I152L were constructed and transfected into Fischer rat thyroid (FRT) cells by Lipofectamine 2000. The FRT cell lines co-expressing LRRC8A and YFP-H148Q/I152L were obtained by antibiotic screening. The expression of LRRC8A and YFP-H148Q/I152L in FRT cells was detected by the inverted fluorescence microscope. The fluorescence quenching kinetic experiment was done to verify the function and effectiveness of the cell model. Then the cell model was utilized to study the physiological characteristics of LRRC8A, such as the characteristics of anion transport, the opening of LRRC8A by osmotic pressure, the effect of anion transport velocity, and the effect of chloride channel inhibitors on LRRC8A anion channel. The results of the inverted fluorescence microscope showed that LRRC8A was expressed on the cell membrane and YFP-H148Q/I152L was expressed in the cytoplasm. The results of fluorescence quenching kinetic test showed that under the condition of low osmotic state, LRRC8A could transport some kinds of anions, such as iodine and chloride ions. Osmotic pressure played a key role in the regulation of LRRC8A volume-regulated anion channel opening. Chloride channel inhibitors inhibited ion transport of LRRC8A channel in a dose-dependent manner. It is suggested that LRRC8A has the characteristics of classic volume-regulated anion channels by using the cell model of FRT cells co-expressing LRRC8A and YFP-H148Q/I152L.

Objective: To investigate the effect of chloride channel blocker--niflumic acid (NFA) on the pathological process of hypoxia hypercapnia-induced pulmonary vasoconstriction in rats., Methods: We used the model of hypoxia hypercapnia-induced pulmonary vasoconstriction rats, and divided the second, third branch pulmonary artery rings randomly into four groups (n = 8): control group (N group), hypoxia hypercapnia group (H group), DMSO incubation group (HD group), niflumic acid group (NFA group). Under acute hypoxia hypercapnia conditions, we observed the effects of the three stages of hypoxia hypercapnia-induced pulmonary vasoconstriction (HHPV) incubated by NFA in the second, third brach pulmonary artery rings. At the same time, the values of rings' tension changings were recorded via the method of hypoxia hypercapnia conditions reactivity. And investigated the effect of NFA to HHPV., Results: (1) Under the hypoxia hypercapnia condition, we observed a biphasic pulmonary artery contractile (the phase I rapid contraction and vasodilation; the phase II sustained contraction) response in both the second and the third branch pulmonary artery rings compared with the control group (P < 0.05 , P < 0.01); (2) The second and third pulmonary artery rings incubated by NFA which phase II persistent vasoconstriction were significantly attenuated compared with the H group (P < 0.05 , P < 0.01)., Conclusion: The blocker of the chloride channels attenuates the second and third branch pulmonary artery rings constriction in rat, especially the phase II persistent vasoconstriction, so then have an antagonistic effect on HHPV.

Objective: To study the effect of chloride channel on proliferation induced by basic-fibroblast growth factor (bFGF) in human lens epithelial cells HLE B-3 (LEC)., Methods: HLE B-3 cells at Logarithmic growth phase were incubated in the 6 or 96 well plate overnight and the proliferation was induced by 10 µg/L bFGF. The cells were divided into bFGF group treated with bFGF and the blank control group with the regular cells culture. LEC were treated with different concentrations of chloride channel inhibitors: 5-nitro-2-[3-phenylpropylamino] benzoic acid (NPPB) at 50, 100, 150 µmol/L and 4 , 4'-2 diisothiocyanostilbene-2, 2' -disulfonic acid (DIDS) at 10, 50, 100 µmol/L with bFGF or without bFGF in 10% serum for 24, 48, 72 hours. The cell viability and the drug toxicity were detected by CCK-8 colorimetric assay. The expression of proliferating cell nuclear antigen (Ki-67) of LEC treated with NPPB or DIDS were observed by immunocytochemistry staining assay. The phase change of cell cycle was examined by flow cytometry. Each experiment group and control group were compared using two-way ANOVA, further pairwise comparisons using LSD-t test or by the Independent-Samples t test., Results: 10 µg/L bFGF induced LEC proliferation and the values of A stage were gradually declined with the increase of chloride channel inhibitors' concentrations and time at 24 hours, 48 hours and 72 hours (bFGF+NPPB group: Ftime = 305.28, Fconcentrations = 18.76, P = 0.000;bFGF+ DIDS group:Ftime = 94.44, Fconcentrations = 24.42, P = 0.000). Different concentrations of chloride channel inhibitor reduced the values of a stage with 10 µg/L bFGF in a dose- and time-dependent manner. The expression of Ki-67 was significantly lowered compared with the bFGF group (bFGF+NPPB group: 18.32% ± 1.23%, F = 580.3, P = 0.000;bFGF+DIDS group: 11.21% ± 1.02%, F = 507.4, P = 0.000), when 150 µmol/L NPPB and 100 µmol/L DIDS with 10 µg/L bFGF were added at 48 hours. After 150 µmol/L NPPB and 100 µmol/L DIDS treatment at the 48th hour, the rate of G1 stage was significantly increased (F = 390.754, P = 0.000), where as that of S stage decreased significantly (F = 166.240, P = 0.000)., Conclusions: These results indicate that chloride channel inhibitors play an important role in modulating the proliferation cycle of LEC treated with bFGF by limiting the cell at cycle S/G1 stage from dividing into S stage.

Objective: To explore the impact of chloride ion channel and its blockers 4, 4'-diisothiocyanostilbene-2, 2'-disulfonic acid (DIDS), cyanato-stilbene-2, 2'-disulfonic acid (SITS) and 5-nitro-2-(3-phenyl-propylamino) benzoic acid (NPPB) on arrhythmias caused by myocardial ischemia reperfusion., Methods: A total of 40 rabbits were divided into control, ischemia reperfusion, DIDS low-dose, DIDS high-dose, SITS low-dose, SITS high-dose, NPPB low-dose and NPPB high-dose groups. Myocardial ischemia reperfusion model was established by ligation of anterior descending coronary artery. And standard limb lead II of electrocardiogram (ECG) was continuously monitored during the experimental process. Then comparisons of heart rate, ECG P wave, R wave, T wave, ST segment changes and arrhythmias score were made between the above groups., Results: During 30-minute ischemia, compared with the control group, all other groups showed significantly decreased heart rate ((199.8 ± 4.0) - (253.6 ± 2.1) vs (267.0 ± 3.4), all P < 0.01), elevated ECG P wave ((0.216 ± 0.019) - (0.356 ± 0.024) vs (0.186 ± 0.019), all P < 0.01), R wave ((0.564 ± 0.017) - (1.138 ± 0.048) vs (0.506 ± 0.018), all P < 0.01), T wave ((0.542 ± 0.013) - (0.856 ± 0.045) vs (0.278 ± 0.015), all P < 0.01) and ST segment ((0.326 ± 0.027) - (0.668 ± 0.054) vs (0.024 ± 0.023), all P < 0.01) and increased arrhythmia score ((1.4 ± 0.5) - (4.6 ± 0.5) vs (0.4 ± 0.5), all P < 0.01). Compared with the ischemia reperfusion group, the above indices significantly improved in the intervention groups (heart rate: (214.8 ± 3.4) - (246.8 ± 4.0) vs (199.8 ± 4.0), all P < 0.01; P wave: (0.216 ± 0.019) - (0.316 ± 0.011) vs (0.356 ± 0.024), all P < 0.01; R wave: (0.564 ± 0.017) - (0.980 ± 0.035) vs (1.138 ± 0.048), all P < 0.01; T wave: (0.542 ± 0.013) - (0.792 ± 0.026) vs (0.856 ± 0.045), all P < 0.01; ST segment: (0.326 ± 0.027) - (0.596 ± 0.018) vs (0.668 ± 0.054), all P < 0.01; arrhythmia score: (1.4 ± 0.5) - (3.8 ± 0.4) vs (4.6 ± 0.5), all P < 0.01). Among which, the DIDS group was the best, followed by the SITS group and then the NPPB group. And the high-dose subgroups were better than those of the low-dose subgroups. During 60-minute reperfusion, the decreased heart rate upswing significantly in each group and the elevated P wave, R wave, T wave and ST segment fell back gradually. The DIDS group showed the most obvious amplitude change, followed by the SITS group and then the NPPB group. And the high-dose subgroups were better than those of the low-dose subgroups. The arrhythmia score during reperfusion showed the same trend., Conclusion: Chloride ion channel is involved in the generation of myocardial ischemia reperfusion arrhythmia.Early application of chloride ion channel blockers DIDS, SITS and NPPB may improve the ECG manifestations and reduce the degree of reperfusion arrhythmia.

The present study aimed to investigate the effects of ursolic acid on the chloride channels and cell volume in nasopharyngeal carcinoma cells (CNE-2Z). The whole-cell patch clamp technique was used to detect the current, and cell imaging technique was applied to measure cell volume. The properties of the currents induced by ursolic acid were investigated by changing the extracellular osmotic pressure, replacing the extracellular anions and applying chloride channel blockers. The results showed that, under isotonic conditions, the background current was weak and stable. When perfusing the cells with ursolic acid (100 nmol/L), a large current (-59.86 pA/pF ± 4.86 pA/pF at -80 mV, 78.92 pA/pF ± 6.39 pA/pF at +80 mV) was induced. The chloride current showed outward rectification and negligible time- and voltage-dependent inactivation. The reversal potential (-4.83 mV ± 0.30 mV) of the current was close to the calculated equilibrium potential for Cl⁻ (-0.9 mV). The permeabilities of the channel to different anions were ranked in order as follows: Cl⁻ = I⁻ > Br⁻ > gluconate. Hypertonic solutions inhibited the current induced by ursolic acid. The chloride channel blockers, tamoxifen (20 μmol/L) and 5-nitro-2-(3-phenylpro-pylamino) benzoic acid (NPPB, 100 μmol/L), suppressed the current. Furthermore, ursolic acid decreased the cell volume by (11.78 ± 1.20)% in 1 h, and the effect was inhibited by NPPB. These results suggest that ursolic acid can activate chloride channels, resulting in outflow of Cl⁻ and decrease of cell volume in nasopharyngeal carcinoma cells.

Objective: To study the effects of silencing CLIC1 gene expression on the proliferation and invasion of Hca-F cells., Methods: The mouse CLIC1 cDNA sequence was retrieved from NCBI. Three shRNA sequences were designed and cloned into pGPU6/GFP/Neo plasmids. The plasmids were transfected into Hca-F cells with Lipofectamine 2000. Cell Counting-8 (CCK-8) kit and transwell chamber were used to study the effects of CLIC1 on the proliferation and invasion of Hca-F cells., Results: The pGPU6/GFP/Neo-shRNA-3 plasmid effectively repressed the expression of CLIC1 mRNA. Inhibition of CLIC1 gene expression led to decreased cell proliferation and reduced invasion., Conclusion: CLIC1 is essential for the proliferation and invasion of Hca-F cells.

Aim: To observe the regulatory volume decrease (RVD) process of human intestine cells and investigate its ion channel mechanism., Methods: Cultured human intestine cells were exposed to hypotonic solution and the cell volume was measured using Coulter Counter System. RT-PCR was explored to detect the mRNA expression of Ca(2+) -activated K+ channel., Results: Human intestine cells showed a RVD process and this process could be blocked by Cl- channel blocker NPPB and K+ channel blocker TEA. Further results demonstrated the subtype of K+ channel involved in RVD was an intermediate-conductance, Ca(2+) -activated K+ channel (IK) because of its high sensitivity to clotrimazole. RT-PCR results also showed the expression of IK in this cell line., Conclusion: The RVD process of intestine cell was dependent on the parallel activation of Cl- channel and K+ channel. The subtype of K+ channel in volved in the RVD process was IK channel.

Chloride channels have been identified in vascular smooth muscle cells (SMCs). It has been shown that these channels are involved in myogenic tone regulation and neuromuscular transmission in various vascular beds. However, whether the chloride channels are responsible for the formation of excitatory junction potentials (EJPs) of SMCs in the spiral modiolar artery (SMA) remains unelucidated. In the present study, the effects of chloride channel blockers (niflumic acid, NFA; indanyloxyacetic acid 94, IAA-94; disodium 4, 4'-diisothiocyanatostilbene-2, 2'-disulfonate, DIDS) on EJP were explored in guinea pigs, using intracellular recording techniques on acutely isolated SMA. It was found that EJP was evoked in the majority of the SMCs (75%, n=49) with an adequate electronic stimulation. The amplitude of the EJP was partially blocked (30% approximately 80%) by combined application of alpha(1) receptor antagonist (prazosin) and alpha(2) receptor antagonist (idazoxan) at concentration of up to 1 micromol/L, and P(2x) receptor antagonist (PPADS, 10 approximately 100 micromol/L). NFA (100 micromol/L) could further inhibit the residual EJP in the presence of alpha(1), alpha(2)-adrenergic and P(2x) receptor antagonists. IAA-94 or DIDS not only inhibited the amplitude but also shortened the duration of EJP. Decrease of extracellular chloride concentration from 135.6 mmol/L to 60 mmol/L would enhance EJP. Moreover, IAA-94 (100 micromol/L) and DIDS (200 mumol/L) could reverse the enhancement of EJP by low extracellular Cl(-). NFA (100 micromol/L) could also block the residual depolarizations evoked by norepinephrine (NE, 1 approximately 50 micromol/L). Based on these results, it is inferred that NE could activate a novel adrenoceptor to open the chloride channel on the membrane of the SMCs, leading to a transmembrane Cl(-) current. This current is involved, at least partially, in the formation of EJP.

Activation of N-methyl-d-aspartic acid (NMDA) receptor plays an important role in neuronal apoptosis induced by cerebral ischemia but the underlying mechanisms are still unclear. The present study examined the neuroprotection of three chloride blockers in an in vitro cell model of cerebral ischemia established by treatment of cultured rat hippocampal neurons with NMDA. Hoechst 33258 staining and MTT assay were used to detect neuronal apoptosis and cell viability, respectively. The neuroprotective effects of chloride channel blockers on the cell viability and neuronal apoptosis were only observed when the blockers were applied before NMDA exposure. In comparison with DIDS, SITS showed more potent protective effect in a dose-dependent manner, whereas NPPB showed no significant neuroprotective effect. The results demonstrate that pretreatment with both SITS and DIDS have protective effect against neuronal apoptosis, which is achieved by blocking both NMDA receptor and chloride channel.

To investigate regulatory volume decrease (RVD) and its mechanism in primary-culturing fetal human nasopharyngeal epithelial cells, living cell imaging technique was employed to detect the volume changes following exposure to hypotonic solution, and blockage of Cl- channels was used to clarify the role of Cl- channels in RVD. The results showed that extracellular hypotonic treatment swelled the cells and induced RVD. 47% hypotonic solution (160 mOsmol/L) swelled the cell by 144.7% and induced 38.7% recovery of cell volume within 20 min. RVD was correlated negatively to the extracellular osmolarity (r=-0.99, P<0.05) and positively to the swelling volume(r=0.99, P<0.05) in "S" shape, respectively. Chloride channel blockers, tamoxfen (20 micromol/ L), ATP (10 mmol/L) and NPPB (100 micromol/L), inhibited RVD by 100%, 76.3% and 62.7% (P< 0.01), respectively. The results indicated that primary-culturing fetal human nasopharyngeal epithelial cells are capable of RVD. Cl- efflux through Cl- channels is the key mechanism of RVD.

Aim: To investigate the effects of NPPB, a chloride channel blocker, on proliferation of mesangial cells., Methods: Cell proliferation was determined by measuring cell number and 3H-thymidine incorporation. The LDH activity released from these cells was measured as evaluation of cell viability. The phase of cell cycle was detected by flow cytometry., Results: Cell proliferation assays showed that treatment with both NPPB (50 and 25 micromol x L(-1)) and in hypertonic media (100% increased osmolarity with D-mannitol ) significantly reduced the number of human MC and 3H-thymidine incorporation in a dose-dependent manner. But the LDH activity was not significantly altered in the treatment with 50 micromol x L(-1) NPPB. Flow cytometry experiments showed that 50 and 25 micromol x L(-1) NPPB arrested (84.2 +/- 2.4) % and (80.8 +/- 2.9) % of cells at G0/G1 stage, versus (70.5 +/- 1.4) % of control cells. Conclusion NPPB suppresses cell proliferation and produces growth arrest at G0/G1 phase in human MC by a mechanism probably associated with changes in cell volume.

To characterize the background current in fetal human nasopharyngeal epithelial cells and clarify its relationship with volume activated Cl(-) currents (I(Cl,vol)), whole-cell patch clamp and cell imaging techniques were employed. Under isotonic conditions, a background current [(5.9+/-2.1) pA/pF at +80 mV, n=21] was detected. The current presented a weak outward rectification and a negligible time-dependent inactivation. The current-voltage relationship showed that the reversal potential of the background current [(-0.73+/-1.7) mV, n=21] was close to the calculated equilibrium potential for Cl(-)(-0.9 mV). Application of extracellular hypertonic stimulation (440 mOsmol/L) suppressed the current by (59.6+/-7.1)% and the inhibition was reversible after returned to isotonic conditions. Bathing the cells in hypotonic solution (160 mOsmol/L) induced a volume-sensitive Cl(-) current. The Cl(-) channel blockers, tamoxifen (20 micromol/L) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) (100 micromol/L), inhibited the background current by (74.0+/-5.2)% (P<0.01, n=5) and (60.9+/-8.9)% (P<0.01, n=6) at +80 mV and increased basal cell volume by (107.7+/-2.9)% (P<0.01, n=25) and (104.4+/-2.4)% (P<0.01, n=19), respectively. The data indicate that Cl(-) current is an important component of the background current in fetal human nasopharyngeal epithelial cells. The background Cl(-) current is involved in volume activated Cl(-) current and basal cell volume regulation.

Objective: To explore the effects of chloride channels on the regulation of platelet cytoplasmic free calcium concentration ([Ca2+]i) and platelet aggregation (PAG)., Methods: Freshly separated platelets were activated by thrombin. Chloride channel blockers DIDS or NFA and calcium channel blockers SK&F96365 or nifedipine were added to study the effects on platelet [Ca2+]i and PAG by a single reagent or the combination of reagents and find out the interactions among DIDS, NFA, SK&F96365 and nifedipine., Results: Both DIDS and NFA could inhibit the thrombin (1 U/ml) induced PAG in a dose-dependent manner, whereas had little effect on resting [Ca2+]i. As compared with the control group, DIDS, SK&F96365 and Nifedipine could significantly reduce the PAG, Ca2+ release and Ca2+ influx in thrombin activated platelet (P < 0.05). The combination of DIDS and SK&F96365 had greater effects in reducing the PAG, Ca2+ release and Ca2+ influx than either reagent alone (P < 0.05). The combination of DIDS and nifedipine also had greater effect than each alone in reducing Ca2+ release (P < 0.05). The combination of NFA and SK&F96365 weakened each other's effect on Ca2+ release (P < 0.05), while NFA and nifedipine weakened each other's effects on PAG, Ca2+ release and Ca2+ influx in thrombin activated platelet (P < 0.05)., Conclusion: DIDS and NFA have no effect on the resting [Ca2+]i and the leak calcium influx of platelet. DIDS can inhibit the Ca2+ release, Ca2+ influx and PAG of platelet induced by thrombin, while NFA can only inhibit the Ca2+ release. The chloride channel and calcium channel blockers have interactions in affecting resting [Ca2+]i and PAG of platelet. The opening of chloride channel can influence the cellular calcium movement of platelet.

The purpose of this work was to investigate the effects of niflumic acid (NFA), a chloride channel blocker, on the proliferation of human hepatoma cell line (HHCC). Cell proliferation was analyzed by cell count and MTT assay. Cell cycle analysis was carried out by flow cytometry. [Ca(2+)](i) was determined by laser scanning confocal system. It was found that NFA decreased significantly the cell number and the MTT optical density (OD) of HHCC cells, and that the OD value was reversed after washout of NFA. Compared with control, NFA blocked cell cycle progression in G(1) phase. Extracellular application of NFA (100 micromol/L) induced a rapid decrease in [Ca(2+)](i). These findings demonstrate that blockage of chloride channels by NFA induces growth arrest of HHCC in G(1) phase, which may be due to the inhibition of Ca(2+)/CaM-dependent signaling pathways.