Relation between esophageal visceral hyperesthesia and expression of acid-sensing ion channel 1 in rats with reflux esophagitis

正Objective To explore the role of the visceral afferent nerve hyperesthesia and acid-sensing ion channel 1(ASIC1)in rats with reflux esophagitis(RE).Methods Sixty male Sprague-Dawley rats were selected and animal model was established.Rats were divided into control group(n=20)and RE group(n=40).The esophageal mocosa biopsy were routinely performed in two groups.The esophageal specific DRG neurons were identified by1,1'-dioctadecy1-3,3',3'-tetramethylindocarbocyanine     

Effects of garlicin on apoptosis in rat model of colitis

AIM:To investigate the effects of garlicin on apoptosis and expression of bcl-2 and bax in lymphocytes in rat model of ulcerative colitis (UC). METHODS:Healthy adult Sprague-Dawley rats of both sexes, weighing 180±30 g, were employed in the present study. The rat model of UC was induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS) enema. The experimental animals were randomly divided into garlicin treatment group (including high and low concentration), model control group, and normal control group. Rats in garlicin treatment group and model control group received intracolic garlicin daily at doses of 10.0 and 30.0 mg/kg and equal amount of saline respectively 24 h after colitis model was induced by alcohol and TNBS co-enema. Rats in normal control group received neither alcohol nor only TNBS but only saline enema in this study. On the 28~(th) d of the experiment, rats were executed, the expression of bd-2 and bax protein was determined immunohistochemically and the apoptotic cells were detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate fluorescence nick end labeling (TUNEL) method. At the same time, the rat colon mucosal damage index (CMDI) was calculated. RESULTS:In garlicin treatment group, the positive expression of bd-2 in lymphocytes decreased and the number of apoptotic cells was more than that in model control group, CMDI was lower than that in model control group. The positive expression of bax in lymphocytes had no significant difference. CONCLUSION:Garlicin can protect colonic mucosa against damage in rat model of UC induced by TNBS enema.     

Effects of drug serum of anti-fibrosis I herbal compound on calcium in hepatic stellate cell and its molecular mechanism

AIM: To investigate the effects of anti-fibrosis I herbal compound on intracellular Ca2+ in activated hepatic stellate cell (HSC) and to try to survey its molecular mechanism in treatment and prevention of hepatic fibrosis and portal hypertension. METHODS: The activated HSC line was plated on small glass cover slips in 24 wells culture dishes at a density of 5×106 /mL, and incubated in RPMI-1640 media for 24 h. After the cells were loaded with Fluo-3/AM, intracellular Ca2+ was measured with laser scanning confocal microscopy (LSCM). The dynamic changes of intracellular Ca2+, stimulated by carbon tetrachloride, TGF-β1 antibody and the drug serum of anti-fibrosis I herbal compound and under orthogonal design were determined by LSCM. The effect of anti-fibrosis I herbal compound on intracellular Ca2+ was observed before and after the addition of TGF-β1 antibody. RESULTS: The intracellular Ca2+ were significantly different in different dosage of carbon tetrachloride anti-fibrosis I formula drug serum, TGF-β1 antibody and different turn of these substance, but their interval time between CCl4 and TGF-β1 antibody, CCl4 and anti-fibrosis I drug serum had no influence on intracellular Ca2+. The result showed intracellular Ca2+ wasn't significantly different between rat serum without anti-fibrosis I and untreated group. After carbon tetrachloride stimulation, intracellular Ca2+ of activated HSC increased significantly when the dosage of CCl4 from 5 to 15 mmol/L, however, decreased significantly after stimulation by 5-20 μg/mL TGF-β1 antibody or 5-20 mL/L drug serum. Moreover, before and after the addition of TGF-β1 antibody, intracellular Ca2+ was significantly different. These results suggested that the molecular mechanism was independent of blocking TGF-β1 effects. CONCLUSION: Anti-fibrosis I herbal compound may treat hepatic fibrosis and decrease portal hypertension by inhibiting activated HSC contractility through decrease of intracellular Ca2+.     

Therapeutic and prophylactic thalidomide in TNBS-induced colitis： Synergistic effects on TNF-α, IL-12 and VEGF production

AIM： To evaluated the therapeutic and prophylactic effect of thalidomide on 2, 4, 6-trinitrobenzene sulfonic acid （TNBS）-induced colitis. Thalidomide has been reported to downregulate the expression of tumor necrosis factor α （TNF-α）, IL-12, and vascular endothelial growth factor （VEGF）, hallmarks of intestinal inflammation in Crohn＇s disease （CD）.
METHODS： Male Wistar rats were divided in five groups of ten animals each. Four groups received a rectal infusion of TNBS in ethanol. The first group was sacrificed 7 d after colitis induction. The second and third groups received either thalidomide or placebo by gavage and were sacrificed at 14 d. The fourth group received thalidomide 6 h before TNBS administration, and was sacrificed 7 d after induction. The fifth group acted as the control group and colitis was not induced. Histological inflammatory scores of the colon were performed and lamina propria CD4＋ T cells, macrophages, and VEGF＋ cells were detected by immunohistochemistry. TNF-α and IL-12 were quantified in the supernatant of organ cultures by ELISA.
RESULTS： Significant reduction in the inflammatory score and in the percentage of VEGF＋ cells was observed in the group treated with thalidomide compared with animals not treated with thalidomide. Both TNF-α and IL-12 levels were significantly reduced among TNBS induced colitis animals treated with thalidomide compared with animals that did not receive thalidomide. TNF-α levels were also significantly reduced among the animals receiving thalidomide prophylaxis compared with untreated animals with TNBS-induced colitis. Intestinal levels of TNF-α and IL-12 were significantly correlated with the inflammatory score and the number of VEGF＋ cells.
CONCLUSION： Thalidomide significantly attenuates TNBS-induced colitis by inhibiting the intestinal production of TNF-α, IL-12, and VEGF. This effect may support the use of thalidomide as an alternate approach in selected patients with CD.     

Curcumin improves regulatory T cells in gut-associated lymphoid tissue of colitis mice

AIM: To explore the probable pathway by which curcumin(Cur) regulates the function of Treg cells by observing the expression of costimulatory molecules of dendritic cells(DCs).METHODS: Experimental colitis was induced by administering 2, 4, 6-trinitrobenzene sulfonic acid(TNBS)/ethanol solution. Forty male C57BL/6 mice were randomly divided into four groups: normal, TNBS + Cur, TNBS + mesalazine(Mes) and TNBS groups. The mice in the TNBS + Cur and TNBS +Mes groups were treated with Cur and Mes, respectively, while those in the TNBS group were treated with physiological saline for 7 d. After treatment, the curative effect of Cur was evaluated by colonic weight, colonic length, weight index of the colon, and histological observation and score. The levels of CD4+CD25+Foxp3+ T cells(Treg cells) and costimulatory molecules of DCs were measured by flow cytometry. Also, related cytokines were analyzed by enzyme-linked immunosorbent assay. RESULTS: Cur alleviated inflammatory injury of the colonic mucosa, decreased colonic weigh and histological score, and restored colonic length. The number of Treg cells was increased, while the secretion of TNF-α, IL-2, IL-6, IL-12 p40, IL-17 and IL-21 and the expression of costimulatory molecules(CD205, CD54 [ICAM-1], TLR4, CD252[OX40 L], CD256 [RANK] and CD254 [RANK L]) of DCs were notably inhibited in colitis mice treated with Cur.CONCLUSION: Cur potentially modulates activation of DCs to enhance the suppressive functions of Treg cells and promote the recovery of damaged colonic mucosa in inflammatory bowel disease.     

Effect of peroxisome proliferator-activated receptor-gamma ligand on inflammation of human gallbladder epithelial cells

AIM: To investigate the effect of peroxisome proliferatoractivated receptor gamma (PPAR-γ) and its ligand, ciglitazone, on inflammatory regulation of human gallbladder epithelial cells (HGBECs) and to assess the effect of human epithelial growth factor (hEGF) on growth of HGBECs. METHODS: HGBECs were cultured in media containing hEGF or in hEGF-free media. HGBECs were divided into normal control group, inflammatory control group and ciglitazone group (test group). Inflammatory control group and ciglitazone group were treated with 5 μg/L of human interleukin-1β (hIL-1β) to make inflammatory model of HGBECs. The ciglitazone group was treated with various concentrations of ciglitazone, a potent ligand of PPAR-γ. Subsequently, interleukin-8 (IL-8), IL-6, and tumor necrosis factor-α (TNF-α) concentrations in all groups were measured. The data were analyzed statistically. RESULTS: HGBECs were cultured in medium successfully. The longevity of HGBECs in groups containing hEGF was longer than that in hEGF-free groups. So was the number of HGBECs. The longest survival time of HGBEC was 25 d. The inflammatory model of HGBECs was obtained by treating with hIL-lp. The concentrations of IL-6 and IL-8 in ciglitazone group were lower than those in inflammatory control group (P<0.05). The secretion of IL-6 in inflammatory control group was higher (350.31±37.05 μg/L) than that in normal control group (50.0±0.00 μg/L, P<0.001). Compared to normal control group, IL-8 concentration in inflammatory control was higher (P<0.05). CONCLUSION: hEGF improves the growth of HGBECs in vitro. Ciglitazone inhibits the inflammation of HGBECs in vitro and has potential therapeutic effect on cholecystitis in vivo.     

Influence of calcium preconditioning and streptomycin on ventricular dilation-induced arrhythmias in isolated rat hearts

Objective To investigate the mechanism of ventricular dilation-induced arrhythmias by dilating isolated rat hearts. Methods Isolated rat hearts were perfused by Langerdorff method. After equilibration,80 hearts were randomly divided into four groups as follows:(1) control group(n=20) ,(2) Ca2 preconditioning(CPC) group(n=20) ,(3) streptomycin group(n=20) ,and(4) CPC streptomycin group(n=20) . A latex balloon which can be filled with fluid was anchored in the left ventricle through the left atrium and mitral valve. Epicardial ECG of the left ventricle,left ventricular pressure,coronary flow and heart rate were recorded before and during ventricular dilation by injecting fluid into the latex balloon. The rate and duration of ventricular dilation-induced arrhythmias were recorded. Results Under the same increase in ventricular end-diastolic pressure made by inflation of the balloon,the rate of arrhythmias was 100% and duration of arrhythmias was 2. 56±0.46s in the control group. Both the rates of premature ventricular beat(90%) and ventricular tachycardia 70%) were high. Compared with the control group,the total rate(60%) of arrhythmias was lower,and duration(1.67±0.61s) of arrhythmias was shorter in the CPC group. Both the rates of premature ventricular beat(60%) and ventricular tachycardia(40%) were low comparatively. The rate of arrhythmias(45%) was lower and duration(1.64±0.42s) of arrhythmias was shorter,and the rates of premature ventricular beat(30%) or ventricular tachycardia(35%) were lower in the streptomycin group than in the control one. The least ventricular dilation-induced arrhythmias occurred in the CPC streptomycin group. The rate of arrhythmias(10%) was the lowest and duration(1.01±0.37s) of arrhythmias was the shortest;both the rates of premature ventricular beat(5%) and ventricular tachycardia(10%) were the lowest. Conclusions Ventricular dilation may induce arrhythmias in isolated rat hearts. Stretch-activated ion channel and the increase in [Ca2 ]i are supposed to play important roles in the pathological mechanism.     

Effect of Chaiqinchengqi decoction on sarco/endoplasmic reticulum Ca~（2＋）-ATPase mRNA expression of pancreatic tissues in acute pancreatitis rats

AIM： To investigate the effect of Chaiqinchengqi decoction （CQCQD） on sarco/endoplasmic reticulum Ca2＋-ATPase （SERCA） mRNA expression of pancreatic tissues in acute pancreatitis （AP） rats. METHODS： Thirty Sprague-Dawley （SD） rats were randomized into control group, AP group and CQCQD group （n = 3 × 10）. The rats in the CQCQD group were intragastrically administered with CQCQD （10 mL/kg every 2 h） after induction of AP by intraperitoneal injection of caerulein （50 μg/kg.h × 5） within 4 h. At 6 h after the induction of AP model, pancreatic tissues were collected for the pathological observation, mRNA extraction for determination of SERCA1 and SERCA2 mRNA expression or pancreatic acinar cell isolation for measurement of fluorescence intensity （FI） of intracellular calcium ion concentration [Ca2＋ i. RESULTS： There was no expression of pancreatic SERCA1 mRNA in the control group and the AP group. The expression of pancreatic SERCA2 mRNA in the AP group was down-regulated （expression ratio = 0.536; P = 0.001） compared with the control group, while that in the CQCQD group was up-regulated （expression ratio= 2.00; P = 0.012） compared with AP group. The FI of intracellular [Ca2＋ of pancreatic acinar cells in the AP group （138.2 ± 23.1） was higher than the C group （111.0 ± 18.4） and the CQCQD group （118.7 ± 15.2 ） （P 〈 0.05） and the pancreatic pathological score in the CQCQD group was lower than that in the AP group （5.7 ± 1.9 vs 9.2 ± 2.7, P 〈 0.05）.CONCLUSION： CQCQD can up-regulate the expression of SERCA2 mRNA of pancreatic tissues, reduce intracellular calcium overload and relieve pancreatic tissue lesions.     

Influence of overexpression of SOCS2 on cells of DN rat

Objective: To explore the influence and mechanism of overexpression of SOCS2 on diabetic nephropathy(DN) rats and cells. Methods: STZ was used to induce male SD rats and SOCS2 was injected into left renal vein. Rats were divided into DN group, DN-Ad-null group and DNAd-SOCS2 group. Glucose with high and normal concentration was used to culture HBZY-1 cells and then transfect Ad-SOCS2. HG group, HG-Ad-null group, HG-Ad-SOCS2 group, CG group, CG-Ad-null group, and CG-Ad-SOCS2 group were created. The expression of inflammatory cytokines(MCP-1, TNF-α and IL-6) in kidney tissue of rats, fibrosis related protein(FN, Collagen Ⅳ and TGF-β) in kidney tissue and cells of rats, and JAK/STAT signaling pathway related proteins(p-JAK2 and p-STAT3) were tested by western blot. ELISA was used to test the expression of inflammatory cytokines(TNF-α and IL-6) in cells. Results: The expression of inflammatory cytokines in DN rats(MCP-1, TNF-α and IL-6) and cell(TNF-α and IL-6) were increased(P0.01) significantly. However, SOCS2 could decrease the overexpression of mediated inflammatory cytokines in DN animal models and cell models(P0.01). The expression of fibrosis related protein in DN rats and cells increased while SOCS2 decreased the overexpression of mediated fibrosis related protein in DN model rats and cells(P0.01). The expression of JAK/STAT pathway related protein in both DN rats and cells increased and the JAK/STAT signaling pathway was activated. Yet, SOCS2 obviously suppressed the expression of the JAK/STAT signaling pathway as well as the related proteins(p-JAK2 and p-STAT3) in both DN rats and cells. Conclusions: The overexpression of SOCS2 can decrease the expression of inflammatory cytokines and fibrosis related proteins in DN rats and cells, and meanwhile suppress the activation of JAK/STAT signaling pathway mediated by DN.     

Correlation of restenosis after rabbit carotid endarterectomy and inflammatory cytokines

Objective:To establish rabbit model of restenosis after carotid endartereclomy surgery,and to study tissue inflammatory cytokines(TNF-α,IL-61 involved in restenosis.Methods:A total of 32 rabbits were randomly divided into two groups:model group and control group.The right common carotid artery in rabbits was damaged by carotid endar terectomy in model group.The tissues were harvested at different time points respectively,the pathological changes of the vascular wall after operation were observed at different time points.The changes of expression of tissue vascular wall inflammatory cytokines(TNF-α.IL-6)at different lime points after the surgery was observed by RT-PCR,and the changes of serum inflammatory cytokines(TNT-α,IL-6)were detected by F.I.1SA.Results:The new intima appeared after 7 days of the injury and reached the peak on 28 d which is uneven and significantly thicker than the control group(P0.01).The tissue inflammatory cytokines(TNF-α,IL-6)were significantlv increased after the rabbit common carotid artery injury,which was significant difference compared with normal control group(P0.05).Conclusions:The tissue inflammatory factors significantly increase after the rabbit carotid artery injury,which suggests the mutual concurrent effects of inflammatory cytokines can result in the proliferation of vascular restenosis.     

Thalamic Cav3.1 T-type Ca2+ channel plays a crucial role in stabilizing sleep

It has long been suspected that sensory signal transmission is inhibited in the mammalian brain during sleep. We hypothesized that Cav3.1 T-type Ca2+ channel currents inhibit thalamic sensory transmission to promote sleep. We found that T-type Ca2+ channel activation caused prolonged inhibition (>9 s) of action-potential firing in thalamic projection neurons of WT but not Cav3.1 knockout mice. Inhibition occurred with synaptic transmission blocked and required an increase of intracellular Ca2+. Furthermore, focal deletion of the gene encoding Cav3.1 from the rostral-midline thalamus by using Cre/loxP recombination led to frequent and prolonged arousal, which fragmented and reduced sleep. Interestingly, sleep was not disturbed when Cav3.1 was deleted from cortical pyramidal neurons. These findings support the hypothesis that thalamic T-type Ca2+ channels are required to block transmission of arousal signals through the thalamus and to stabilize sleep.     

拮抗或激活促肾上腺皮质激素释放因子受体对肠易激综合征大鼠内脏敏感性及结肠动力的影响

目的 探讨促肾上腺皮质激素释放因子(CRF)及其受体对肠易激综合征大鼠内脏敏感性及结肠动力的影响.方法 SD大鼠60只,随机平均分入空白组(不做处理)、模型组(特殊气味条件刺激和肢体束缚直肠刺激非条件刺激轮替致敏)、干预对照组(造模前侧脑室注射0.9%NaC1)、干预一组(造模前侧脑室注射CRF-R1拮抗剂)和干预二组(造模前侧腑室注射CRF-R2激动剂).采用腹部收缩反射(AWR)评分标准评估各组大鼠肠道敏感性,记录各组大鼠结肠快、慢波波动率、最大振幅、收缩波数及振幅指数等电生理活动改变.采用SPSS16.0统计软件分析,计量资料采用方差分析,等级资料采用秩和检验.结果 以AWR=3分时所需的直肠注水量作为评价指标,模型组大鼠[(0.90±0.11)ml]较空白组[(1.23±0.07)ml]内脏敏感性增高(F＝82.586,P＜0.01);结肠电生理活动增强,造模成功.干预对照组直肠注水量为(0.81±0.11)ml,与模型组[(0.90±0.11)ml]差异无统计学意义(F＝3.734,P＞0.05),干预一组[(1.28±0.07)ml,F＝161.878,P＜0.01]和干预二组[(1.22±0.05)ml,F＝121.564,P＜0.01]较干预对照组内脏敏感性降低.干预对照组大鼠结肠快、慢波波动率、最大振幅、收缩波数及振幅指数等电生理活动与模型组无明显差异(P均＞0.05);干预一组和干预二组大鼠结肠电生理活动均较干预对照组明显减弱(均P＜0.05).结论 CRF在IBS发病中起重要作用,抑制CRF-R1或激活CRF-R2可降低1BS大鼠内脏敏感性并抑制结肠运动.

Abstract：

Objective To explore the effect of corticotropin releasing factor (CRF) and its receptor on visceral sensitivity and colon motility of irritable bowel syndrome (IBS) rats. Methods sixty SD rats were divided randomly and equally into control group (without treatment),model group (sensitized in turn with camphor odor as conditional stimulation and physical restraint in combination with rectal distention pressure as non-conditional stimulation),treatment control group (injected physiological saline into lateral ventricles before treatment),treatment group 1 (injected CRF-R1antagonist into lateral ventricles before treatment),treatment group 2 (injected CRF-R2 agonist into lateral ventricles before treatment). Then the rats' visceral sensitivity were assessed by AWR,and colonic electricity activities such as volatility,maximum amplitude of fast wave and slow wave,interdigestive number of contraction wave and index of contraction were recorded. The data was analyzed with SPSS 16. 0 software. Results By the amount of ractal water injection to reach AWR=3 as the evaluation index,model group [(0. 90±0. 11) ml] showed higher visceral sensitivity than that of control group [(1. 23±0. 07) ml,F=82. 586,P＜0. 01],and colonic electricity activity increased (P＜0. 05),model was successfully set up. There was no significant difference of the amount of ractal water injection between model group [(0. 90±0. 11) ml] and treatment control group [(0. 81±0. 11) ml,F=3. 734,P＞0. 05]. Compared with treatment control group,the visceral sensitivity decreased in treatment group 1 [(1. 28±0. 07) ml,F=161. 878,P＜0. 01] and treatment group 2 [(1. 22±0.05) ml,F=121. 564,P＜0. 01]. There was no significant difference between treatment control group and model group in electricity activities such as volatility,maximum amplitude of fast wave and slow wave,interdigestive number of contraction wave and index of contraction (all P＞0. 05). While the electricity activities was weakened in treatment group 1 and 2 compared with the treatment control group (all P＜0. 05). Conclusions CRF plays an important role in the pathogenesis of IBS. Inhibition of CRF-R1 or activation of CRF-R2 may lower visceral hypersensitivity and decrease colon motility of rats.     

Molecular basis of R-type calcium channels in central amygdala neurons of the mouse

R-type Ca2+ channels play a critical role in coupling excitability to dendritic Ca2+ influx and neuronal secretion. Unlike other types of voltage-sensitive Ca2+ channels (L, N, P/Q, and T type), the molecular basis for the R-type Ca2+ channel is still unclear, thereby limiting further detailed analyses of R-type Ca2+ channel physiology. The prevailing hypothesis is that alpha(1E) (Ca(V)2.3) gene encodes for R-type Ca2+ channels, but the dearth of critical evidence has rendered this hypothesis controversial. Here we generated alpha1E-deficient mice (alpha1E-/-) and examined the status of voltage-sensitive Ca2+ currents in central amygdala (CeA) neurons that exhibit abundant alpha1E expression and R-type Ca2+ currents. The majority of R-type currents in CeA neurons were eliminated in alpha1E-/- mice whereas other Ca2+ channel types were unaffected. These data clearly indicate that the expression of alpha1E gene underlies R-type Ca2+ channels in CeA neurons. Furthermore, the alpha1E-/- sign mice exhibited signs of enhanced fear as evidenced by their vigorous escaping behavior and aversion to open-field conditions. These latter findings imply a possible role of alpha1E-based R-type Ca2+ currents in amygdala physiology associated with fear.     

内脏高敏感大鼠白细胞介素-1β、肿瘤坏死因子α与5-羟色胺转运体的表达

目的 研究内脏高敏感大鼠结肠细胞因子和5-羟色胺(5-HT)转运体(SERT)的表达,为细胞因子和5-HT系统在内脏高敏感性产生机制中的作用提供依据.方法 16只胎龄小于8 d的新生SD大鼠被随机分为2组,每组8只.采用乳鼠醋酸灌肠法建立大鼠慢性内脏高敏感动物模型,以盐水灌肠作为对照组.待乳鼠成年后应用直肠内球囊扩张检测腹碓收缩阈值和弓背抬起阈值的方法评估其内脏敏感性;通过检测髓过氧化物酶(MPO)评价肠道黏膜炎症程度;采用免疫组化的方法检测大鼠结肠组织中IL-1β和TNFα的水平;采用Western blot方法检测大鼠结肠组织SERT的表达水平.结果 两组大鼠体重增长趋势基本一致,HE染色显示结肠黏膜未见明显急、慢性炎症改变;两组大鼠结肠组织MPO水平相比,差异无统计学意义[(0.497±0.570)U/g湿片比(0.623±0.739)U/g湿片,P=0.724];实验组大鼠腹壁收缩阈值和弓背抬起阈值分别为(0.19±0.06)ml和(0.47±0.13)ml,较对照组大鼠[(0.40±0.14)ml和(0.91±0.26)ml]显著减低,P＜0.01;实验组大鼠结肠IL-1β、TNFα的表达水平(0.196±0.002和0.194±0.001)均显著高于对照组(0.185±0.001和0.182±0.001),P＜0.01;实验组大鼠SERT蛋白相对表达水平(0.298±0.038)较对照组(0.634±0.200)显著减低,P＜0.05.结论 内脏高敏感大鼠IL-1β和TNFα的表达升高,SERT的表达水平减低,细胞因子与SERT可相互影响,IL-1β、TNFα和SERT可能在大鼠内脏高敏感性的发生机制中具有一定的作用.     

Insulin-like growth factor-1 increases intracellular calcium concentration in human primary neuroendocrine pancreatic tumor cells and a pancreatic neuroendocrine tumor cell line (BON-1) via R-type Ca2+ channels and regulates chromogranin a secretion in BON-1 cells

Insulin-like growth factor 1 (IGF-1) is a potent mitogenic and secretory factor that acts on voltage operated Ca(2+) channels (VOCCs). VOCCs are categorized into L-type channels (Ca(V)1.1-1.4), P/Q-type channels (Ca(V)2.1), N-type channels (Ca(V)2.2), R-type channels (Ca(V)2.3), and T-type channels (Ca(V)3.1-3.3). Aside from regulating membrane excitability, VOCCs influence chromogranin A (CgA) secretion in neuroendocrine tumor (NET) cells. It is not known, whether VOCCs play a role in the IGF-1-dependent regulation of CgA secretion in NET cells. We therefore studied the effects of IGF-1 on individual VOCC subtypes and characterized their role in mediating IGF-1-dependent regulation of CgA secretion in NET cells. Using specific modulators of VOCC subtypes, we identified the functional expression of L-, N-, P/Q- and R-type channels in primary as well as permanent models of NET. The IGF-1-induced intracellular Ca(2+) increase in NET cells was mainly due to the activation of R-type channel activity. The effects on intracellular calcium, observed in whole-cell patch-clamp recordings and fluorescence imaging, were partially blocked by the specific R-type channel blocker SNX-482 and antisense oligonucleotides against the alpha(1) subunit of this channel. IGF-1 potently induced CgA secretion. The effect of IGF-1 was reduced by both, inhibition of R-type channel activity and a reduction of R-type channel expression using antisense oligonucleotides. Since R-type channels exist in NET cells and couple to both, IGF-1 receptor signaling as well as CgA secretion, pharmacological interference with R-type channels may represent a new therapeutic option by blocking Ca(2+) signaling thereby abrogating IGF-1-dependent hypersecretion in NET disease.     

Switching off calcium-dependent inactivation in L-type calcium channels by an autoinhibitory domain

The retinal L-type Ca2+ channel Cav1.4 is distinguished from all other members of the high voltage-activated (HVA) Ca2+ channel family by lacking Ca2+-calmodulin-dependent inactivation. In synaptic terminals of photoreceptors and bipolar cells, this feature is essential to translate graded membrane depolarizations into sustained Ca2+ influx and tonic glutamate release. The sequences conferring Ca2+-dependent inactivation (CDI) are conserved throughout the HVA calcium channel family, raising the question of how Cav1.4 manages to switch off CDI. Here, we identify an autoinhibitory domain in the distal C terminus of Cav1.4 that serves to abolish CDI. We show that this domain (ICDI, inhibitor of CDI) uncouples the molecular machinery conferring CDI from the inactivation gate by binding to the EF hand motif in the proximal C terminus. Deletion of ICDI completely restores Ca2+-calmodulin-mediated CDI in Cav1.4. CDI can be switched off again in the truncated Cav1.4 channel by coexpression of ICDI, indicating that ICDI works as an autonomous unit. Furthermore, we show that in the Cav1.2 l-type Ca2+-channel replacement of the distal C terminus by the corresponding sequence of Cav1.4 is sufficient to block CDI. This finding suggests that autoinhibition of CDI can be introduced principally into other Ca2+ channel types. Our data provide a previously undescribed perspective on the regulation of HVA calcium channels by Ca2+.     

Intracellular Ca- and PKC-dependent upregulation of T-type Ca channels in LPC-stimulated cardiomyocytes

Lysophosphatidylcholine (LPC) accumulation in intracellular and/or interstitial space in cardiomyocytes may underlie as a mechanism for tachycardia and various arrhythmias during cardiac ischemia, which is usually accompanied by elevation of intracellular Ca²⁺ concentration ([Ca²⁺]_i). The present study was therefore designed to investigate possible mechanisms responsible for [Ca²⁺]_i elevation by LPC focusing on T-type Ca²⁺ channel current (I_Ca.T). LPC as well as phorbol 12-myristate 13-acetate (PMA) significantly accelerated the beating rates of neonatal rat cardiomyocytes. Augmentation of I_Ca.T by LPC was dependent on the intracellular Ca²⁺ concentration: an increase of I_Ca.T was significantly larger in high [Ca²⁺]_i condition (pCa = 7) than those in low [Ca²⁺]_i condition (pCa = 11). In heterologous expression system by use of human cardiac Ca_V3.1 and Ca_V3.2 channels expressed in HEK293 cells, LPC augmented Ca_V3.2 channel current (I_Cav3.2) in a concentration-dependent manner but not Ca_V3.1 channel current (I_Cav3.1). Augmentation of I_Cav3.2 by LPC was highly [Ca²⁺]_i dependent: I_Cav3.2 was unchanged when pCa was 11 but was markedly increased when [Ca²⁺]_i was higher than 10⁻¹⁰ M (pCa ≤ 10) by LPC application (10-50 μM). A specific inhibitor of protein kinase Cα (Ro-32-0432) attenuated the increase of I_Cav3.2 by LPC. LPC stimulates I_Ca.T in a [Ca²⁺]_i-dependent manner via PKCα activation, which may play a role in triggering arrhythmias in pathophysiological conditions of the heart.     

Subtype switching of L-Type Ca 2+ channel from Cav1.3 to Cav1.2 in embryonic murine ventricle.

BACKGROUND: Embryonic hearts exhibit spontaneous electrical activity, which depends on Ca2+ influx through L-type Ca2+ channels. In this study the expression of the L-type Ca2+ channel alpha1 subunit gene in the developing mouse heart was investigated. METHODS AND RESULTS: Mouse cardiac ventricles 9.5 days post coitum (dpc), 18 dpc and adult were used. At 9.5 dpc the level of Cav1.3 mRNA was higher than that of Cav1.2 mRNA. With development, Cav1.2 mRNA increased and Cav1.3 mRNA decreased. Analysis of Cav1.3 splicing variants showed that Cav1.3(1b) mRNA was expressed at a higher density than Cav1.3(1a) mRNA. Cav1.3 protein was detected only at 9.5 dpc, whereas Cav1.2 protein was expressed from 9.5 dpc and its expression increased with development. L-type Ca2+ currents were prominent at 9.5 dpc. The Ca2+ current amplitude at 9.5 dpc was comparable to that at 18 dpc, and was larger in adults than at the embryonic stage. L-type Ca2+ current at 9.5 dpc was activated and/or inactivated at more negative membrane potentials than at 18 dpc or adult. L-type Ca2+ channels at 9.5 dpc were less sensitive to inhibition by nisoldipine than at adult. CONCLUSIONS: The Cav1.3 channel is functionally expressed in early embryonic mouse ventricular myocytes and potentially underlies ventricular automaticity.     

Melatonin‐mediated inhibition of Cav3.2 T‐type Ca2+ channels induces sensory neuronal hypoexcitability through the novel protein kinase C‐eta isoform

Recent studies implicate melatonin in the antinociceptive activity of sensory neurons. However, the underlying mechanisms are still largely unknown. Here, we identify a critical role of melatonin in functionally regulating Cav3.2 T‐type Ca²⁺ channels (T‐type channel) in trigeminal ganglion (TG) neurons. Melatonin inhibited T‐type channels in small TG neurons via the melatonin receptor 2 (MT₂ receptor) and a pertussis toxin‐sensitive G‐protein pathway. Immunoprecipitation analyses revealed that the intracellular subunit of the MT₂ receptor coprecipitated with Gα_o. Both shRNA‐mediated knockdown of Gα_o and intracellular application of QEHA peptide abolished the inhibitory effects of melatonin. Protein kinase C (PKC) antagonists abolished the melatonin‐induced T‐type channel response, whereas inhibition of conventional PKC isoforms elicited no effect. Furthermore, application of melatonin increased membrane abundance of PKC‐eta (PKC_η) while antagonism of PKC_η or shRNA targeting PKC_η prevented the melatonin‐mediated effects. In a heterologous expression system, activation of MT₂ receptor strongly inhibited Cav3.2 T‐type channel currents but had no effect on Cav3.1 and Cav3.3 current amplitudes. The selective Cav3.2 response was PKC_η dependent and was accompanied by a negative shift in the steady‐state inactivation curve. Furthermore, melatonin decreased the action potential firing rate of small TG neurons and attenuated the mechanical hypersensitivity in a mouse model of complete Freund's adjuvant‐induced inflammatory pain. These actions were inhibited by T‐type channel blockade. Together, our results demonstrated that melatonin inhibits Cav3.2 T‐type channel activity through the MT₂ receptor coupled to novel G_βγ‐mediated PKC_η signaling, subsequently decreasing the membrane excitability of TG neurons and pain hypersensitivity in mice.     

Antihypertensive effects of the putative T-type calcium channel antagonist mibefradil are mediated by the L-type calcium channel Cav1.2

The role of T-type Ca2+ channels for cardiovascular physiology, in particular blood pressure regulation, is controversial. Selective blockade of T-type Ca2+ channels in resistance arteries has been proposed to explain the effect of the antihypertensive drug mibefradil. In the present study, we used a third generation, time- and tissue-specific conditional knockout model of the L-type Ca2+ channel Cav1.2 (Cav1.2SMAKO mice) to genetically dissect the effects of mibefradil on T- and L-type Ca2+ channels. Myogenic tone and phenylephrine-induced contraction in hindlimb perfusion experiments were sensitive to mibefradil in control mice, whereas the drug showed no effect in Cav1.2-deficient animals. Mean arterial blood pressure in awake, freely moving control mice was reduced by 38+/-2.5 mm Hg at a dose of 1.25 mg/kg bodyweight mibefradil, but not changed in Cav1.2SMAKO mice. These results demonstrate that the effect of the putative T-type Ca2+ channel-selective blocker mibefradil on blood pressure and small vessel myogenic tone is mediated by the Cav1.2 L-type Ca2+ channel.