Oleic acid inhibits the K(ATP) channel subunit Kir6.1 and the K(ATP) current in human umbilical artery smooth muscle cells.

BACKGROUND: The objective of the present study was to determine the effect of various concentrations of oleic acid (OA) on KATP channel expression and the potential relationship to exogenous nitrogen monoxide and protein kinase C levels. METHODS: Human umbilical artery smooth muscle cells (HUASMCs), between the 7th and 10th passages, were divided into control group, OA group (final OA concentration of 0, 50, 100 or 200 µmol/L), nitric oxide (NO) intervention group, protein kinase C inhibitor group or GF-109203X (GFX) intervention group. Western immunoblotting was used to detect the protein expression of the KATP channel subunit Kir6.1. Also, quantitative real-time polymerase chain reaction analysis to determine Kir6.1 messenger RNA levels and whole-cell patch clamping to measure KATP currents were performed. RESULTS: The results suggested that OA inhibited Kir6.1 protein and messenger RNA expression in HUASMCs. Under a high concentration of potassium (140 mmol/L), 100 µmol/L OA significantly reduced ATP-sensitive potassium current density, whereas a low extracellular concentration of potassium (5.4 mmol/L) did not influence KATP density. Pretreatment with either exogenous NO or GFX weakened the OA-induced inhibition of KATP in HUASMCs. CONCLUSIONS: The study demonstrated that OA inhibited Kir6.1, a KATP channel subunit, in HUASMCs, and indirectly inhibited the KATP current. In addition, the results indicated that NO and/or GFX partially reversed OA inhibition in HUASMCs.

Right-sided free wall accessory pathway refractory to conventional catheter ablation: lessons from 3-dimensional electroanatomic mapping.

INTRODUCTION: the aim of this study was to delineate the electroanatomic substrates of right-sided free wall (RFW) accessory pathways (APs) that were refractory to conventional catheter ablation utilizing 3-dimensional (3-D) mapping. METHODS AND RESULTS: eleven patients with RFW APs that failed initial conventional catheter ablation(s) by a mean of 1.9 ± 0.5 attempts were enrolled in the study. Electroanatomic mapping of the right atrium was performed during orthodromic reciprocating tachycardia in 3 patients and right ventricular pacing in 8 patients. The earliest atrial activation site, which represented the atrial insertion of the AP, was separated from the tricuspid annulus by an average of 14.3 ± 3.9 mm, and the local activation time was 27.8 ± 17.0 ms earlier than that of the corresponding annular point. One patient exhibited an AP with wide branching on the atrial side. RF ablation with an irrigated catheter successfully interrupted AP conduction in all patients without complications. CONCLUSIONS: RFW APs resistant to conventional catheter ablation might be due to unique anatomic AP features such as more epicardial course at the annulus level with atrial insertion distant from the tricuspid annulus. Electroanatomic mapping is helpful to accurately localize the atrial insertion sites of these APs and facilitates catheter ablation.

[Expression and function of voltage-gated Na+ channel isoforms in rat sinoatrial node].

OBJECTIVE: To detect the expression of voltage-gated Na(+) channel (NaCh) isoforms in rat sinoatrial node and explore their functions. METHODS: Expressions of NaCh isoforms Nav1.1, Nav1.2, Nav1.3, Nav1.5, Nav1.6 and Nav1.7 in the rat sinoatrial node were detected by immunohistochemistry. The functional roles of the NaChs were tested by observing the effect of tetrodotoxin, a specific blocker of NaChs, on the intrinsic heart rate of isolated rat working heart. RESULTS: The tetrodotoxin- sensitive neuronal isoforms Nav1.1, Nav1.6 and Nav1.7 as well as the tetrodotoxin-resistant cardiac isoform Nav1.5 were present in the rat sinoatrial node, and the neuronal isoforms were more abundant than Nav1.5 (P<0.05). The selective blockade of tetrodotoxin-sensitive isoforms (presumably Nav1.1, Nav1.6 and Nav1.7) by 100 nmol/L tetrodotoxin scarcely affected the intrinsic heart rate (0.5-/+2.9%, P>0.05) while blockade of tetrodotoxin-resistant isoform (presumably Nav1.5) by 2 micromol/L tetrodotoxin resulted in an obvious decline in the intrinsic heart rate (22.1-/+2.1%, P<0.001). CONCLUSIONS: Nav1.1, Nav1.5, Nav1.6 and Nav1.7 are all present in rat sinoatrial node. Although neuronal isoforms are more abundant, Nav1.5 seems to contribute more to activity of the sinoatrial node.

[Inhibition of human macrophage-derived foam cell differentiation by blocking Kv1.3 and Kir2.1 channels].

OBJECTIVE: To investigate the expression of Kv1.3 and Kir2.1 during human monocyte-derived macrophages differentiation into foam cells and their function in foam cells formation. METHODS: The human macrophage-derived foam cells were obtained by incubating macrophages with ox-LDL (30 mg/L) for 60 h. The expression of Kv1.3 and Kir2.1 channels were examined by immunocytochemistry, RT-PCR and Western blot. Effects of channel blockers (rMargatoxin and BaCl2) on the cellular cholesterol metabolism were studied by measuring the cellular contents of total cholesterol (TC), free cholesterol (FC), and cholesterol ester (CE) in the presence or absence of the channel blockers. RESULTS: After incubating macrophages with 30 mg/L ox-LDL for 60 h, the cellular contents of TC, FC and CE were markedly increased and the ratio of CE/TC was raised from (14.4+/-6.8)% to (57.9+/-3.5)% (P<0.05), which indicated that the cells had differentiated into foam cells. The expression of Kv1.3 and Kir2.1 channels appeared no obvious difference when differentiating into foam cells (P>0.05); After being blocked specifically (rMargatoxin: 0.1, 10 nmol/L; BaC(12): 75, 125 micromol/L), the cellular contents of TC and CE were markedly reduced without exception and the ratios of CE/TC were all less than 50% (P<0.05). CONCLUSION: Both Kv1.3 and Kir2.1 channels play a critical role in differentiation of macrophages into foam cells and blockage of corresponding potassium channels would prevent the formation of the foam cells.

Inhibitory effects of blocking voltage-dependent potassium channel 1.3 on human monocyte-derived macrophage differentiation into foam cells.

OBJECTIVE: To investigate the expression of voltage-dependent potassium channel 1.3 (Kv1.3) mRNA and protein during human monocyte-derived macrophage differentiation into foam cells and its function in foam cell formation. METHODS: Human peripheral blood monocytes were isolated from healthy male volunteers by density gradient centrifugation and then by adherent method. The obtained monocytes were cultured for 5 days to differentiate into macrophages. Based on establishment of the human macrophage-derived foam cell model, the expression of Kv1.3 channel was investigated by immunocytochemical staining, reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. Furthermore, the effects of rMargatoxin, a Kv 1.3 channel-specific inhibitor, on cholesterol metabolism in macrophages incepting oxidized low density lipoprotein (OxLDL) were studied. RESULTS: After the macrophages co-incubated with 30 mg/L OxLDL at 37 degrees C for 60 hours, the cellular volume obviously enlarged and many red lipid granules were deposited in cytoplasm. The total amount of cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) in cells markedly increased and the ratio of CE/TC rose from (14.4+/-6.8)% to (57.9+/-3.5)% (n=7, P<0.05). However, the expression of Kv1.3 channel had no significant change. rMargatoxin (0.1 nmol/L and 10 nmol/L) markedly reduced the contents of TC, FC and CE in macrophages and the ratios of CE/TC decreased to (42.8+/-11.6)% and (22.6+/-8.0)%, respectively (n=7, P<0.05). Meanwhile, the red lipid granules deposited in the cytoplasm of macrophages also decreased. CONCLUSION: These data clearly show that the expression of Kv1.3 channel does not change obviously during human monocyte-derived macrophage differentiation into foam cells and the blocking of it would prevent foam cell formation.

The expression of maxiK channel alpha--subunit during human macrophages differentiating into foam cells.

OBJECTIVE: To investigate the expression of MaxiK channel alpha-subunit during human monocyte-derived macrophages differentiating into foam cells. METHODS: Human peripheral blood monocytes were isolated from male healthy volunteers by density gradient centrifugation, which, by culture, differentiated further into macrophages as a homogeneous monocyte population. The foam cell model originated from human macrophage was established by incubating macrophages with oxidized low density lipoprotein (OxLDL). The expression of MaxiK channel alpha-subunit was investigated by RT-PCR techniques, Western blotting and immunocytochemistry. RESULTS: After incubating macrophages with 30 mg/L OxLDL for 60 hours, the cellular contents of total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) were markedly increased and the ratio of CE/TC was further raised from (14.437 +/- 6.781) % to (57.946 +/- 3.507) %. Although the expression of MaxiK channel alpha-subunit was downregulated during human monocyte-derived macrophages differentiating into foam cells, there was no significant difference between macrophages and foam cells (P > 0.05). CONCLUSION: That 30 mg/L OxLDL can lead the monocyte-derived macrophage cultured for 60 hours to differentiate into foam cell, but the expression of MaxiK channel alpha-subunit does not change obviously.

[Inhibitory effect of blocking MaxiK channel on human monocyte-derived macrophages differentiation into foam cells].

AIM: To investigate the expression of high-conductance Ca2+-activated potassium channel (MaxiK channel) mRNA and protein during human monocyte-derived macrophage differentiation into foam cells and to study its function in foam cell formation. METHODS: Human peripheral blood monocytes were isolated from healthy male volunteers by density gradient centrifugation and then by adherent method. The obtained monocytes were cultured for 5 days to differentiate into macrophages. Based on establishment of human macrophage-derived foam cells model, the expression of MaxiK channel alpha-subunit was investigated by immunocytochemical staining, RT-PCR and Western blot. Furthermore, the effect of Paxilline, a MaxiK channel-specific inhibitor, on cholesterol metabolism in macrophages incepting oxidized low density lipoprotein (OxLDL) was studied. RESULTS: After the macrophages were co-incubated with 30 mg/L OxLDL at 37 degrees C for 60 hours, the cellular volume obviously enlarged and many red lipid granules were deposited in cytoplasm. The total amount of cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) in cells markedly increased and the ratio of CE/TC rose from (14.437+/-6.781)% to (57.946+/-3.507)% (n=7, P<0.05). However, the expression of MaxiK channel alpha-subunit had no significant change (P<0.05). Paxilline (5 micromol/L and 10 micromol/L) markedly reduced the content of TC, FC and CE in macrophages and the ratio of CE/TC decreased to (41.217+/-5.584)% (5 micromol/L Paxilline) and (18.017+/-11.559)% (10 micromol/L Paxilline), respectively (n=7, P<0.05). Meanwhile, the red lipid granules deposited in the cytoplasm of macrophages also decreased. CONCLUSION: Blocking MaxiK channel can inhibit human monocyte-derived macrophage to be differentiated into foam cells.

Expression of Kir2.1 channel during differentiation of human macrophages into foam cells.

OBJECTIVE: Detected in non-transformed bone marrow-derived macrophages (BMDM) and identified as one of the key channels in modulating macrophage proliferation, activation and apoptosis, Kir2.1 channel is also characterized to play a crucial role in cell differentiation. The purpose of this study was to investigate the expression of Kir2.1 channel mRNA and protein during human monocyte-derived macrophage differentiation into foam cells. METHODS: Human peripheral blood monocytes were isolated from healthy male volunteers by density gradient centrifugation and then by adherence method. The macrophages identified as a homogeneous population of adherent cells were obtained after 5 days of culture. Expression of Kir2.1 channel during human macrophage differentiation into foam cells was investigated by RT-PCR, Western blotting and immunocytochemistry, respectively. RESULTS: After incubation of the macrophages with 30 mg/L OxLDL at 37 degrees C for 60 h, the cells were obviously enlarged in size and numerous red lipid granules observed under optical microscope. The cellular contents of the total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) were markedly increased from 54.79+/-28.304 mg/g, 47.968+/-26.787 mg/g and 6.822+/-3.437 mg/g to 229.775+/-57.453 mg/g, 96.241+/-24.003 mg/g and 133.535+/-36.292 mg/g, respectively; the CE/TC ratio rose from (14.437+/-6.781)% to (57.946+/-3.507)% (n=7, P<0.05), suggesting the phenotype of foam cells. However, there was no significant difference in the relative expression of Kir2.1 channel mRNA between the macrophages and foam cells [(59.074+/-10.566)% vs (46.98+/-12.527)%, n=5, P>0.05], nor was there significant difference in the relative expression of Kir2.1 channel protein between them [(60.527+/-18.621)% vs (50.243+/-11.583)%, n=6, P>0.05]. CONCLUSION: Incubation of human monocyte-derived macrophages with 30 mg/L OxLDL for 60 h induces the differentiation of the cells into foam cells, but the expression of Kir2.1 channel does not change obviously.

Centrifugal force stretcher a new of in vitro mechanical cell stimulator.

A number of mechanical cell stimulators have been used to study the effect of mechanical stimulation on cells in vitro. But the efficiency of these devices is not fully desirable. We recently developed a new device for mechanical cell stimulation, the centrifugal force stretcher, and compared its efficacy with that of the traditional Flexercell Strain Unit. When the mechanical stretcher circumrotates with certain speed, cardiac myocytes attached on the plate are stretched and elongated by centrifugal force. Neonatal rat cardiac myocytes were isolated by enzymatic dissociation from the hearts of 3~5 d old Sprague Dawley rats, and were mechanically stimulated by traditional 20% stretch and 180 r/min centrifugal force for 12 and 24 h. The effects of mechanical stimulation on the hypertrophic response of neonatal rat cardiac myocytes and production of angiotensin II (Ang II) were examined. Compared with the non-stretch group, the radioactivity of (3)H-leucine incorporated into the stretch-stimulated cardiac myocytes in the centrifugal force stretch group was significantly higher [(1295.17+/-51.19) vs (1122.67+/-51.63) in 12 h; (1447.5+/-35.96) vs (1210.67+/-90.92) in 24 h, P<0.05]. Ang II was also dramatically increased by 128% in 12 h (P<0.05) and 139% in 24 h (P<0.01). After the myocytes was stretched for 24 h, the LDH level in the medium in the Flexercell Strain Unit group was significantly higher than that in the centrifugal force group [(14.5+/-8.7) U/L vs (7.8+/-4.3) U/L, P<0.05]. The centrifugal force stretcher is a new and improved mechanical cell stimulator with the same effects on the protein synthesis and Ang II secretion of the cardiac myocytes, and the damage to the cells bronght by this stimulator is relatively slighter in comparison with the Flexercell Strain Unit.