Mechanism of Piezo1 channel activation promoting increase in intracellu-lar calcium concentration of rat coronary smooth muscle cells / 中国病理生理杂志

AIM:To investigate the mechanism of Piezo1 channel activation promoting the increase in intra-cellular Ca2+ concentration([Ca2+]i)of rat coronary artery smooth muscle cells(CASMCs).METHODS:The primary CASMCs of SD rats were cultured,and the expression and subcellular localization of Piezo1 in the cells were observed by immunofluorescence staining.The Piezo1 and stromal interaction molecule 1(STIM1)in CASMCs were knocked down by siRNA transfection,and the expression levels of the proteins were detected by Western blot.Utilizing laser confocal mi-croscopy,the change of[Ca2+]i in CASMCs was detected by Fluo-4 AM fluorescent probes.RESULTS:It was confirmed by immunofluorescence staining that the expression of Piezo1 existed in primary rat CASMCs.Immunofluorescence staining also showed that Piezo1 was co-located with sarco-/endoplasmic reticulum Ca2+-ATPase 2(SERCA2),mitochondrial outer membrane protein TOM20 and nuclear membrane protein lamin B1.Western blot results showed that the protein expres-sion levels of STIM1 and Piezo1 were significantly down-regulated by siRNA transfection(P<0.05).Compared with con-trol group,Yoda1,the agonist of Piezo1,could increase the extracellular Ca2+ influx of CASMCs(P<0.01).However,the Ca2+ influx mediated by Yoda1 was not affected by the inhibition of L-type calcium channels.Treatment with Yoda1 in-creased the intracellular Ca2+ release of CASMCs(P<0.01).However,inhibition of calcium channels on endoplasmic re-ticulum,ryanodine receptor and inositol 1,4,5-triphosphate receptor,did not affect intracellular Ca2+ release mediated by Yoda1.After the Ca2+ in endoplasmic reticulum was emptied using thapsigargin(TG),Yoda1 also mediated the Ca2+ re-lease of other organelles in CASMCs(P<0.01).After inhibition of L-type calcium channels,treatment with store-operated calcium channel(SOCC)inhibitor BTP2 or knockdown of STIM1 led to the decrease in extracellular Ca2+ influx of CASMCs mediated by Yoda1(P<0.01).Treatment with TG increased the release of Ca2+ from the endoplasmic reticulum of CASMCs after knockdown of Piezo1(P<0.05),but the extracellular Ca2+ influx mediated by TG was not affected.After inhibition of L-type calcium channels and SOCC,knockdown of Piezo1 led to the decreases in intracellular Ca2+ release and extracellular Ca2+ influx induced by Yoda1(P<0.01).CONCLUSION:The Piezo1 agonist orchestrates the influx of extracellular Ca2+ by activating Piezo1 channels on the cell membrane and inducing the indirect activation of SOCC.More-over,it facilitates the release of Ca2+ from organelles.Consequently,these pathways synergistically elevate the[Ca2+]i of rat CASMCs.

Effect of Fto gene knockout on calcium regulation and aortic smooth muscle contraction in diabetic mice / 中国病理生理杂志

AIM:To investigate the influence of fat mass and obesity-associated(Fto)gene on the aberrant contraction of aortic smooth muscle in diabetes mellitus(DM)mice,and to explore the mechanism of Fto gene underlying the calcium regulation.METHODS:Smooth muscle-specific Fto gene knockout(FtoSMKO)mice were generated using Cre-loxP technology.The experiment involved 3 groups of mice:wild-type(WT)group,DM model group and FtoSMKO-DM group,with 15 mice in each group.In DM group and FtoSMKO-DM group,type 1 DM was induced by intraperitoneal injec-tion of streptozotocin.The mice in WT group were injected with equal volume of citric acid-sodium citrate buffer solution.The influences of different drugs on the contraction responses of aortic smooth muscle in mice were analyzed using a multi-myograph system.The expression level of FTO protein in the aortic tissues was detected by Western blot.RESULTS:(1)Compared with WT mice,the expression levels of FTO protein in the aortic tissues of DM mice were significantly in-creased(P＜0.01).(2)The expression level of FTO protein in smooth muscle was significantly decreased after knockout of Fto gene(P＜0.01).Compared with WT group,the mice in DM group exhibited a significant decrease in body weight and a marked increase in fasting blood glucose level(P＜0.05).There were no noticeable differences in body weight or fasting blood glucose level between FtoSMKO-DM group and DM group(P＞0.05).(3)The contraction responses of aortic smooth muscle in DM group were substantially increased by phenylephrine compared with WT group.Specifically,vaso-constriction responses mediated by non-L-type calcium channels and store-operated calcium channels(SOCC)were signifi-cantly enhanced in DM group.In addition,the responses mediated by inositol 1,4,5-trisphosphate receptors(IP3R),which facilitate calcium release from the sarcoplasmic reticulum,were significantly enhanced.However,the responses mediated by caffeine-activated ryanodine receptors(RyR),which also facilitate calcium release from the sarcoplasmic re-ticulum,were significantly inhibited(P＜0.05).(4)Compared with DM group,the phenylephrine-induced contraction re-sponses of aortic smooth muscle in FtoSMKO-DM group were greatly weakened(P＜0.05).In particular,the vasoconstriction responses mediated by non-L-type calcium channels and SOCC in FtoSMKO-DM group were greatly suppressed(P＜0.05),while those mediated by caffeine-activated RyR were dramatically boosted(P＜0.05).However,IP3R-mediated responses were not affected(P＞0.05).CONCLUSION:Smooth muscle-specific Fto gene knockout suppresses contractile hyperre-sponsiveness in the aortic smooth muscle of DM mice,which may be attributed to involvement of FTO protein in calcium regulation in the vascular smooth muscle.

Involvement of Orai1 in tunicamycin-induced endothelial dysfunction

Endoplasmic reticulum (ER) stress is mediated by disturbance of Ca²⁺ homeostasis. The store-operated calcium (SOC) channel is the primary Ca²⁺ channel in non-excitable cells, but its participation in agent-induced ER stress is not clear. In this study, the effects of tunicamycin on Ca²⁺ influx in human umbilical vein endothelial cells (HUVECs) were observed with the fluorescent probe Fluo-4 AM. The effect of tunicamycin on the expression of the unfolded protein response (UPR)-related proteins BiP and CHOP was assayed by western blotting with or without inhibition of Orai1. Tunicamycin induced endothelial dysfunction by activating ER stress. Orai1 expression and the influx of extracellular Ca²⁺ in HUVECs were both upregulated during ER stress. The SOC channel inhibitor SKF96365 reversed tunicamycin-induced endothelial cell dysfunction by inhibiting ER stress. Regulation of tunicamycin-induced ER stress by Orai1 indicates that modification of Orai1 activity may have therapeutic value for conditions with ER stress-induced endothelial dysfunction.

MicroRNA-199a-3p enhances expressions of fibrosis-associated genes through targeting Smad1 in mouse cardiac fibroblasts / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the role of miR-199a-3p in cardiac fibrosis and the potential target of miR-199a-3p.</p><p><b>METHODS</b>Cardiac fibroblasts were isolated from C57BL/6 mice and cultured. The miR-199a-3p mimic and Smad1 siRNA were transiently transfected into the cardiac fibroblasts via liposome. Dual luciferase reporter assay was performed to confirm the interaction between miR-199a-3p and the 3'-UTR of Smad1. The expressions of Smad1 and fibrosis-related genes at the mRNA and protein levels in the cells after miR-199a-3p mimic transfection were determined using RT-qPCR and Western blotting, respectively. The expressions of Smad1, Smad3 and fibrosis-related genes at the protein level in cells transfected with miR-199a-3p mimic and Smad1 siRNA were detected using Western blotting.</p><p><b>RESULTS</b>Over-expression of miR-199a-3p significantly increased the expression of cardiac fibrosis-related genes in cultured mouse cardiac fibroblasts. Dual luciferase reporter assay revealed the interaction of miR-199a-3p with the 3'-UTR of Smad1. The results of RT-qPCR and Western blotting confirmed that miR-199a-3p inhibited Smad1 expression at the post- transcriptional level. Transfection with miR-199a-3p mimic and siRNA-mediated Smad1 silencing consistently activated the Smad3 signaling pathway and enhanced the expressions of cardiac fibrosis-related genes in the cardiac fibroblasts.</p><p><b>CONCLUSIONS</b>As the target gene of miR-199a-3p, Smad1 mediates the pro-fibrotic effect of miR-199a-3p by activating the Smad3 signaling in cultured mouse cardiac fibroblasts.</p>

The bifunctional effect of propofol on thromboxane agonist (U46619)-induced vasoconstriction in isolated human pulmonary artery

Propofol is known to cause vasorelaxation of several systemic vascular beds. However, its effect on the pulmonary vasculature remains controversial. In the present study, we investigated the effects of propofol on human pulmonary arteries obtained from patients who had undergone surgery. Arterial rings were mounted in a Multi-Myograph system for measurement of isometric forces. U46619 was used to induce sustained contraction of the intrapulmonary arteries, and propofol was then applied (in increments from 10–300 µM). Arteries denuded of endothelium, preincubated or not with indomethacin, were used to investigate the effects of propofol on isolated arteries. Propofol exhibited a bifunctional effect on isolated human pulmonary arteries contracted by U46619, evoking constriction at low concentrations (10–100 µM) followed by secondary relaxation (at 100–300 µM). The extent of constriction induced by propofol was higher in an endothelium-denuded group than in an endothelium-intact group. Preincubation with indomethacin abolished constriction and potentiated relaxation. The maximal relaxation was greater in the endothelium-intact than the endothelium-denuded group. Propofol also suppressed CaCl₂-induced constriction in the 60 mM K⁺-containing Ca²⁺-free solution in a dose-dependent manner. Fluorescent imaging of Ca²⁺ using fluo-4 showed that a 10 min incubation with propofol (10–300 µM) inhibited the Ca²⁺ influx into human pulmonary arterial smooth muscle cells induced by a 60 mM K⁺-containing Ca²⁺-free solution. In conclusion, propofol-induced arterial constriction appears to involve prostaglandin production by cyclooxygenase in pulmonary artery smooth muscle cells and the relaxation depends in part on endothelial function, principally on the inhibition of calcium influx through L-type voltage-operated calcium channels.

Model construction of rat coronary artery smooth muscle cell endoplas-mic reticulum stress induced by thapsigargin / 中国病理生理杂志

AIM: To investigate the primary culture method for coronary artery smooth muscle cells (CASMCs), and to establish the endoplasmic reticulum stress ( ERS) model in CASMCs of SD rats.METHODS:CASMCs were cultured by tissue explant method .The morphological characteristics were observed under optical micro-scope.The marker proteins of CASMCs , including α-SMA and SM-MHC, were identified by immunofluorescence tech-nique.The protein expression levels of BiP and CHOP , the marker molecules of ERS, were determined by Western blot . RESULTS:The spindle-shaped CASMCs climbed out from the edge of coronary artery tissues after 6 d, and formed the typical hill and valleygrowth pattern of CASMCs at 9~10 d.The result of immunofluorescence technique showed that α-SMA and SM-MHC were positively expressed .The results of Western blot showed that the protein expression of BiP and CHOP in TG ( 1 and 2 μmol/L ) treatment groups was increased compared with control group .Compared with control group, the protein expression of BiP and CHOP was significantly increased after 1 μmol/L TG treatment for 24 and 48 h. CONCLUSION:CASMCs can be successfully cultured by tissue explant method .ERS model of CASMCs was established by 1 μmol/L TG treatment for 24 h.

Role of tumor necrosis factor-αin the regulation of T-type calcium channel current in HL-1 cells / 中国病理生理杂志

AIM:Increasing evidence indicates that inflammation contributes to the initiation and perpetuation of atrial fibrillation ( AF) .Al-though tumor necrosis factor ( TNF)-αlevels are increased in patients with AF , the role of TNF-αin the pathogenesis of AF remains unclear.Recent research has revealed that T-type Ca2+currents ( ICa,T ) play an important role in the pathogenesis of AF .METH-ODS:In this study , we used the whole-cell voltage-clamp technique and biochemical assays to explore the role of TNF-αin the regula-tion of ICa,T in atrial myocytes.RESULTS:We found that compared with sinus rhythm (SR) controls, T-type calcium channel (TCC) subunit mRNA levels were decreased , while TNF-αexpression levels were increased , in human atrial tissue from patients with AF .In murine atrial myocyte HL-1 cells, after cultured for 24 h, 12.5, 25 and 50 μg/L TNF-αsignificantly reduced the protein expression levels of the TCC α1G subunit in a concentration-dependent manner .The peak current was reduced by the application of 12.5 or 25μg/L TNF-αin a concentration-dependent manner [from ( -15.08 ±1.11) pA/pF in controls to ( -11.89 ±0.83) pA/pF and (-8.54 ±1.55) pA/pF in 12.5 and 25 μg/L TNF-αgroups, respectively].TNF-αapplication also inhibited voltage-dependent inactivation of ICa,T shifted the inactivation curve to the left .CONCLUSION:These results suggest that TNF-αis involved in the path-ogenesis of AF, probably via decreasing ICa,T function in atrium-derived myocytes through impaired channel function and down -regula-tion of channel protein expression .This pathway thus represents a potential pathogenic mechanism in AF .

Cx43 is involved in electrical remodeling of atrial myocytes through regu-lating L-type calcium current / 中国病理生理杂志

AIM:To investigate whether the association of connexin 43 ( Cx43 ) and L-type calcium channel involved in the pathogenesis of atrial fibrillation ( AF) .METHODS:The biochemical assays and whole-cell patch-clamp technique were used to study the expression of Cx43 in human atrial tissue.The co-localization of Cx43 and L-type calcium channel, and the regulation of L-type calcium current in atrial myocytes were investigated.RESULTS:The expression of Cx43 at mRNA and protein levels was decreased in human atrial tissues of AF patients.In cultured atrium-derived myocytes ( HL-1 cells) , knockdown of Cx43 significantly inhibited the mRNA expression of L-type calcium channelα1c subunit, as well as L-type calcium current.Co-localization of Cx43 with L-type calcium channel α1c subunit in mouse atrial myocytes was observed.CONCLUSION:The decrease in Cx43 is involved in the pathogenesis of AF, probably through reducing the L-type calcium current in atrial myoctyes by co-localization with L-type calcium channel, thus representing the potential pathogenesis in atrial fibrillation.

Dexmedetomidine inhibits 5-HT-induced intrapulmonary artery vasoconstriction / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of dexmedetomidine on 5-HT-induced constrictions of isolated human intrapulmonary arteries and explore the mechanisms.</p><p><b>METHODS</b>Lung tissue was obtained from patients undergoing surgery for lung carcinoma. Intrapulmonary arteries were dissected and cut into rings, which were mounted in a Multi Myograph system to determine the effect of dexmedetomidine (0.3-3 nmol/L) on 5-HT-induced vasoconstrictions. The influences of the endothelium removal and various drugs including L-NAME, yohimbine and indomethacin were tested on the effects of dexmedetomidine.</p><p><b>RESULTS</b>Dexmedetomidine (0.1-100 nmol/L) did not obviously affect the resting tension of endothelium-intact human intrapulmonary arteries. 5-HT induced concentration-dependent contraction in endothelium-intact intrapulmonary arteries [pD2: 6.11∓0.05, Emax: (102.10∓1.96)%]. In the rings with intact endothelium, dexmedetomidine (0.3-3 nmol/L) significantly attenuated the Emax and pD2 of 5-HT-induced vasoconstriction [pD2: 5.94∓0.03, Emax: (79.96∓1.31)%]. 5-HT also induced concentration-dependent contraction in endothelium-denuded intrapulmonary arteries [pD2: 6.10∓0.07, Emax: (107.40∓3.20)%]. Dexmedetomidine produced no significant effects on the rings with denuded endothelium. The effects of dexmedetomidine on 5-HT-induced vasoconstriction was suppressed by L-NAME and yohimbine, but not by indomethacin.</p><p><b>CONCLUSION</b>Dexmedetomidine can inhibit 5-HT-induced vasoconstriction of isolated human intrapulmonary arteries probably through α2-adrenergic acceptor and NO released from the endothelium.</p>

Reactivity of intrapulmonary arterial rings to thromboxane A2 and endothelin-1 is reduced in patients with chronic obstructive pulmonary disease / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the reactivity of intrapulmonary arterial rings to vasoactive substances as thromboxane A2 and endothelin-1 in patients with chronic obstructive pulmonary disease (COPD).</p><p><b>METHODS</b>Intrapulmonary arterial rings isolated from patients with normal lung function and COPD were mounted in a Multi Myograph system to determine the reactivity of the intrapulmonary arterial rings to 60 mmol/L KCl, thromboxane A2 analogue U46619 and endothelin-1 before and after preconditioning with the COX synthase inhibitor indomethacin.</p><p><b>RESULTS</b>The reactivity of intrapulmonary arterial rings to U46619 and endothelin-1 was significantly decreased in patients with COPD. The reactivity to U46619 was dramatically decreased in patients with normal lung function after application of indomethacin.</p><p><b>CONCLUSION</b>The reactivity of intrapulmonary arterial rings is significantly decreased in patients with COPD.</p>

Effect of ketamine on transient outward potassium current of isolated human atrial myocytes / 药学学报

The effects of ketamine on transient outward potassium current (I(to)) of isolated human atrial myocytes were investigated to understand the mechanism of part of its effects by whole-cell patch-clamp. Atrial myocytes were enzymatically isolated from specimens of human atrial appendage obtained from patients under going cardiac valve displacing. Ito is recorded in voltage-clamp modes using the patch-clamp technique at room temperature. Currents signals were recorded by an Axopatch 200B amplifier with the Digidata 1322A-pClamp 9.0 data acquisition system. Ketamine decreased I(to) of human atrial myocytes in a dose-dependent manner. The current-voltage curve was significantly lowered, 30, 100, 300, and 1000 micromol x L(-1) ketamine decreased respectively I(to) current density about (13.62 +/- 0.04)%, (38.92 +/- 0.05)%, (72.24 +/- 0.10)% and (83.84 +/- 0.05)% at the potential of 50 mV, with an IC50 of 121 micromol x L(-1). The I(to) activation curve, inactivation curve and the recovery curve were not altered by ketamine. So, ketamine concentration-dependently decreased I(to) of human atrial myocytes.