活性维生素D3联合LY294002体外抑制大鼠肝星状细胞增殖作用研究*

目的探究维生素D的活性形式—1,25-(OH）2D3联合磷脂酰肌醇-3激酶/蛋白激酶B(PI3K/Akt）信号通路的特异抑制剂LY294002对体外培养大鼠肝星状细胞的抑制作用。方法将HSC-T6细胞分为正常对照、 DMSO组、1,25-(OH）2D3、LY294002组和1,25-(OH）2D3+ LY294002 联合组,采用MTT法检测细胞增殖;在倒置显微镜下观察细胞形态变化;使用流式细胞术检测HSC-T6细胞凋亡;采用Western blotting法检测Phospho-Akt（Ser473）、AKT（PAN）、半胱氨酸天冬氨酸蛋白酶（caspase）-3蛋白表达。结果体外干预肝星状细胞48 h后,两药联合干预组细胞抑制率为87.5%,显著高于1,25-（OH）2D3组的50.3%或LY294002组的40.3%（P<0.05）;联合组细胞凋亡率为92.12%,显著高于1,25-(OH）2D3组的71.0%或LY294002组的34.0%（P<0.05）;在显微镜下观察,两药处理组细胞形状由星形变为不规则形,凋亡数量增多,表现为正常活细胞数目明显减少,胞间隙增宽,细胞体积缩小,胞浆浓缩,胞核固缩,可见空泡及细胞碎片,有的细胞出现数量不等的凋亡小体;与单药干预组比,联合组细胞Bax/Bcl-2比值上升明显（P<0.05）,活化的凋亡蛋白caspase-3表达显著增加（P<0.05）。结论1,25-（OH）2D3可协同LY294002 共同诱导 HSC-T6 细胞凋亡,增强其抗肝纤维化的效果。     

1,25-二羟维生素D3对于哮喘大鼠及其肺泡巨噬细胞中VDUP1/TRX的影响

目的探讨1,25-二羟维生素D3（1,25-dihydroxyvitamin D3,1,25（OH）2D3）对哮喘大鼠支气管肺泡灌洗液（bronchoalveolar lavage fuluid,BALF）中维生素D上调蛋白1（vitamin D up-regulated protein 1,VDUP1）和硫氧还蛋白（thioredoxin,TRX）表达及气道炎症的影响。方法将28只Wistar大鼠随机分为4组,以卵白蛋白（ovalbumin,OVA）诱导哮喘发作,并给予1,25（OH）2D3和地塞米松干预,同时设对照组。测定BALF中IL-4和IL-10水平,细胞总数和肺组织病理变化。同时提取7只哮喘模型大鼠BALF中的巨噬细胞,体外给予1,25（OH）2D3干预。用逆转录-聚合酶链反应检测肺组织及BALF中巨噬细胞表达VDUP1和TRX的水平。结果 1,25（OH）2D3治疗组BALF中细胞总数及嗜酸粒细胞计数和IL-4水平降低,IL-10水平增高。肺组织及肺泡巨噬细胞中VDUP1和TRX表达增加。结论给予哮喘大鼠1,25（OH）2D3可抑制气道炎症,增加TRX和VDUP1的表达,两者可作为哮喘氧化应激的监测指标。     

1,25（OH）2D3通过调节miR-146a水平抑制大鼠肝纤维化的体内和体外观察

目的 体内体外观察1,25（OH）₂D₃通过调节miR-146a水平抑制大鼠肝纤维化的作用机制。方法 建立CCl₄诱导的大鼠肝纤维化模型,体外转染肝星状细胞（HSCs）miR-146a 模拟剂/抑制剂,观察1,25（OH）₂D₃处理对动物肝组织变化和HSC增殖和凋亡的影响。采用qPCR法检测肝组织miR-146a水平,采用CCK8法检测细胞增殖,使用流式细胞术检测HSC凋亡。结果 在干预8 w末,1,25（OH）₂D₃干预组大鼠肝纤维化程度明显减轻; 1,25（OH）₂D₃干预组大鼠肝组织miR-146a水平为（0.70± 0.03）,显著高于橄榄油组【（0.33±0.17,P<0.05）】; 1,25（OH）₂D₃组细胞增殖率为58.8%,较DMSO组下降了15.9%,转染miR-146a 模拟剂组大鼠HSC增殖率为46.5%,较对照组下降了53.3%,转染miR-146a 抑制剂组HSC增殖率为132.8%,较对照物组升高了32.8%（P<0.05）,1,25（OH）₂D₃干预组细胞凋亡率为12.6%,较DMSO组增加了5.2%,转染miR-146a 模拟剂组细胞凋亡率为16.8%,较对照组细胞凋亡率增加了8.2%,转染miR-146a 抑制剂组细胞凋亡率为6.3%,较对照组细胞凋亡率减少了2.2%（P<0.05）,提示1,25（OH）₂D₃具有抑制HSC增殖、促进凋亡作用。结论 1,25（OH）₂D₃可能通过调节miR-146a水平抑制HSC活化和抑制大鼠肝纤维化。     

PI3K/Akt/mTOR信号通路对大鼠肾小球系膜细胞增殖的调控作用探讨

目的:探讨磷脂酰肌醇-3(PI3K)/蛋白激酶(Akt)/哺乳动物雷帕霉素靶蛋白(m TOR)信号通路对大鼠肾小球系膜细胞(MC)增殖的调控作用。方法:体外培养大鼠MC,随机分为正常对照组、表皮生长因子(EGF)(10ng/m L)组、PI3K抑制剂LY294002组(2μg/m L)、EGF联合LY294002组。采用四甲基偶氮唑蓝(MTT)法检测4组MC的增殖,流式细胞术检测MC周期,免疫荧光法检测系膜细胞m TOR的表达。结果:与正常对照组相比,EGF组能显著促进大鼠MC增殖,G0/G1期细胞减少,S期及G2/M期细胞增加,且m TOR表达增加;LY294002组大鼠MC增殖受抑制,G0/G1期细胞增加,S期及G2/M期细胞减少,且m TOR表达降低;与EGF组比较,EGF联合LY294002干预组MC增殖受抑制,G0/G1期细胞增多,S期及G2/M期细胞减少,且m TOR表达降低。结论:m TOR信号通路参与了大鼠肾小球MC增殖的调控,抑制该信号通路的活化可显著抑制MC的增殖和MC周期的进程。     

17β-雌二醇和1,25-二羟维生素D3对成骨细胞MC3T3-E1增殖和分化的影响

目的 探讨雌激素和维生素D对成骨细胞MC3T3-E1增殖和分化的协同调节作用及其机制.方法 小鼠成骨细胞系MC3T3-E1细胞用无酚红α-MEM完全培养基培养;用MTT法检测细胞增殖率;用实时荧光定量PCR法检测干预前后MC3T3-E1细胞中细胞周期相关基因[细胞周期素E( cyclin E)、增殖细胞核抗原(PCNA)和细胞周期素依赖性激酶抑制物(Cdkn2b)]和成骨细胞分化标志物[Ⅰ型胶原( COL Ⅰ)、碱性磷酸酶(ALP)和骨桥蛋白(OPN)]基因的表达.ALP活性染色用BCIP/NBT显色法.结果 单用雌激素17β-雌二醇(E2)可促进MC3T3-E1细胞的增殖,尤其在生理浓度时作用最强,单用维生素D活性产物1,25-二羟维生素D3[1,25-(OH) 2D3]对MC3T3-E1细胞的增殖无影响,1,25 - (OH)2 D3不影响E2对MC3T3-E1细胞的促增殖作用.E2上调MC3T3-E1细胞中cyclin E和PCNA的表达,同时下调Cdkn2b基因的表达,1,25-(OH)2D3单独应用不能影响上述基因表达的变化,也不影响E2对上述基因的调节作用.E2可促进MC3T3-E1细胞中分化标志物(COLⅠ、ALP和OPN)基因的表达,加用1,25-(OH)2D3后可增强此作用.结论 雌激素和维生素D作为两种重要的调节骨代谢的激素,在促进成骨细胞增殖方面可能无协同作用,而在促进其分化方面可能有协同作用.     

丁酸钠和1，25-（OH）2D3对人结肠癌细胞增殖和hTERT表达的影响

背景：端粒酶在肿瘤细胞永生化过程中起重要作用．人端粒酶逆转录酶（hTERT）是调节端粒酶活性的关键因素。有研究发现生物活性制剂丁酸钠和1n,25-二羟维生素D3[1．25-（OH）,D3]具有潜在抗肿瘤效应。目的：观察丁酸钠和1,25-（OH）：D3对人结肠癌细胞增殖的影响及其可能机制。方法：以不同浓度丁酸钠（0．5～2．0mmol／L）、1,25-（0H）2D3（10^-6～10^-6mol/L）或两者联合[1．0mmol／L丁酸钠＋10^-7mol／L1,25-（OH）2D3]诱导人结肠癌细胞株HT29,MTT法检测细胞生长抑制率,流式细胞术检测细胞周期和细胞凋亡,RT—PCR检测hTERTmRNA表达。结果：丁酸钠和1,25-（OH）2D3能剂量和时间依赖性地抑制HT29细胞生长：1．0mmol／L丁酸钠和10^-7mol／L 1．25-（OH）2D3能诱导HT29细胞G0／G1期阻滞和细胞凋亡,抑制hTERTmRNA表达。联合用药组的上述作用较两者单用更为明显（P〈0．05）。结论：丁酸钠和1,25-（OH）2D3抑制人结肠癌细胞增殖的作用与其通过下调hTERT基因表达而抑制端粒酶活性、阻滞细胞周期、诱导细胞凋亡有关：两者联合可产生协同作用．     

1,25-(OH)_2D_3对阿霉素肾病模型大鼠足细胞损伤及podocin表达缺失的影响

目的研究活性维生素D3[1,25-(OH)_2D_3]对阿霉素(ADR)肾病模型大鼠足细胞的作用及对podocin表达的影响。方法 90只雄性SD大鼠随机选取30只作为对照组,其余60只被一次性尾静脉注射ADR 7.5 mg/kg。建模成功后,随机均分为ADR组、治疗组,治疗组每日给予1,25-(OH)_2D_3 0.25μg/kg灌胃,对照组及ADR组每日给予等量的花生油灌胃。于治疗第2、4、6、8、10周末收集24 h尿,进行生化分析;取肾组织进行后续的组织学观察和分子水平检测。结果与对照组相比,ADR组24 h尿蛋白显著增加(P0.05),1,25-(OH)_2D_3显著减少24 h尿蛋白含量(P0.05)。苏木素-伊红(HE)染色结果显示,对照组肾小球形态完好,ADR组肾小球基底膜增厚、肾间质纤维化、大量炎性细胞浸润,1,25-(OH)_2D_3治疗减轻了肾小球损伤。电镜观察显示:与对照组比较,模型组足细胞超微结构发生改变,出现细胞空腔、细胞核畸形,基底膜呈节段性增厚、足突被压扁且融合;1,25-(OH)_2D_3治疗后,足细胞损伤减轻。免疫组织化学检测显示:podocin主要定位于细胞膜,在正常肾小球中高表达,而ADR组表达较低(P0.05);1,25-(OH)_2D_3治疗后,podocin的表达显著增高(P0.05)。荧光定量PCR和Western印迹结果显示:podocin mRNA和蛋白水平具有高度的一致性,与对照组相比,ADR组表达显著降低(P0.05);1,25-(OH)_2D_3治疗后,podocin表达有所恢复。结论 1,25-(OH)_2D_3能够改善ADR肾病模型大鼠肾脏足细胞损伤,逆转podocin蛋白表达缺失,从而减少24 h尿蛋白,发挥重要的肾脏保护作用。     

1,25-二羟维生素D3对支气管哮喘小鼠气道重塑及基质金属蛋白酶9表达的影响

目的观察1,25-二羟维生素D3[1,25-(OH)2D3]对支气管哮喘(简称哮喘)小鼠气道重塑及其肺组织中基质金属蛋白酶9(matrix metalloprotease-9,MMP-9)表达的影响,探讨1,25-(OH)2D3在哮喘治疗中的作用。方法BALB/c小鼠随机分为对照组、哮喘组及1,25-(OH)2D3组。卵白蛋白致敏和激发建立慢性哮喘小鼠模型;HE染色观察各组气道结构改变情况;采用计算机图像分析系统评价各组气道重塑情况;采用RT-PCR法检测各组的MMP-9mRNA表达水平。结果①HE染色提示哮喘组与对照组相比出现炎性细胞浸润增多、上皮细胞脱落及平滑肌细胞层增厚等气道重塑改变,而1,25-(OH)2D3组可部分逆转上述病理改变;②1,25-(OH)2D3组的支气管内壁厚度、平滑肌层厚度和平滑肌细胞核数显著低于哮喘组,但仍高于对照组(P<0.05);③1,25-(OH)2D3组肺组织MMP-9mRNA表达水平均明显低于哮喘组,但仍高于对照组(P<0.05)。结论1,25-(OH)2D3干预可显著减轻慢性哮喘气道重塑的病理改变;并可通过部分抑制肺内MMP-9的表达来延缓气道重塑进程。     

活性维生素D3联合LY294002体外抑制大鼠肝星状细胞增殖作用研究

目的探究维生素D的活性形式—1,25-(OH)2D3联合磷脂酰肌醇-3激酶/蛋白激酶B(PI3K/Akt)信号通路的特异抑制剂LY294002对体外培养大鼠肝星状细胞的抑制作用。方法将HSC-T6细胞分为正常对照、DMSO组、1,25-(OH)2D3、LY294002组和1,25-(OH)2D3+LY294002联合组,采用MTT法检测细胞增殖;在倒置显微镜下观察细胞形态变化;使用流式细胞术检测HSC-T6细胞凋亡;采用Western blotting法检测Phospho-Akt(Ser473)、AKT(PAN)、半胱氨酸天冬氨酸蛋白酶(caspase)-3蛋白表达。结果体外干预肝星状细胞48 h后,两药联合干预组细胞抑制率为87.5%,显著高于1,25-(OH)2D3组的50.3%或LY294002组的40.3%(P0.05);联合组细胞凋亡率为92.12%,显著高于1,25-(OH)2D3组的71.0%或LY294002组的34.0%(P0.05);在显微镜下观察,两药处理组细胞形状由星形变为不规则形,凋亡数量增多,表现为正常活细胞数目明显减少,胞间隙增宽,细胞体积缩小,胞浆浓缩,胞核固缩,可见空泡及细胞碎片,有的细胞出现数量不等的凋亡小体;与单药干预组比,联合组细胞Bax/Bcl-2比值上升明显(P0.05),活化的凋亡蛋白caspase-3表达显著增加(P0.05)。结论 1,25-(OH)2D3可协同LY294002共同诱导HSC-T6细胞凋亡,增强其抗肝纤维化的效果。     

1,25(OH)_2D_3对脂多糖诱导下肾小管上皮细胞增殖与凋亡的影响

目的探讨1,25(OH)_2D_3对脂多糖诱导下人肾小管上皮细胞(HK-2细胞)增殖与凋亡的影响。方法体外培养HK-2细胞,随机分为正常对照组、脂多糖(1μg/ml)组、1,25(OH)_2D_3(10~(-8)mol/L)组、脂多糖联合1,25(OH)_2D_3组,干预培养48 h,采用细胞计数试剂盒(CCK)-8法检测各组HK-2细胞的增殖,流式细胞术分别检测各组HK-2细胞的细胞周期与细胞凋亡。结果与正常对照组比较,脂多糖组HK-2细胞增殖明显被促进,G0/G1期细胞明显减少,S期及G2/M期细胞明显增加,且细胞凋亡率明显下降;1,25(OH)_2D_3组HK-2细胞增殖明显被抑制,G0/G1期细胞明显增加,S期及G2/M期细胞明显减少,且细胞凋亡率明显增加。与脂多糖组比较,脂多糖联合1,25(OH)_2D_3组HK-2细胞增殖明显被抑制,G0/G1期细胞明显增加,S期及G2/M期细胞明显减少,且细胞凋亡率明显增加。结论 1,25(OH)_2D_3可抑制HK-2细胞的增殖,诱导其凋亡,且1,25(OH)2D3可逆转脂多糖对HK-2细胞的促增殖、抑制凋亡的作用。     

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] increases insulin-like growth factor I (IGF-I) receptors in clonal osteoblastic cells. Study on interaction of IGF-I and 1,25-(OH)2D3

We previously reported a cooperative effect between insulin-like growth factor I (IGF-I) and 1,25-dihydroxy-vitamin D3 [1,25-(OH)2D3] in murine clonal osteoblastic cells, MCT3T3-E1. In the present study, the possible mechanism of interaction between these hormones was investigated. The effect of IGF-I on 1,25-(OH)2D3 receptors in MC3T3-E1 cells was examined. The affinity and hormone binding capacity of 1,25-(OH)2D3 receptors were not altered by IGF-I. Immunoblot analysis showed about 54 kilodaltons (kDa) 1,25-(OH)2D3 receptors, similar to that observed for mouse fibroblasts. The synthesis of IGF-I by the cells under a serum-free condition was determined by RIA. The assay revealed immunoreactive IGF-I secreted by MC3T3-E1 cells (1.79 +/- 0.04 x 10(-9) M, mean +/- SE, n = 5). Rat GH significantly increased the concentration of IGF-I, but 1,25-(OH)2D3 did not. IGF-I radioligand-receptor assay revealed specific binding of IGF-I to MC3T3-E1 cells. The relative potency of IGF-I-related peptides to bind with the cells was in the order of IGF-I much greater than multiplication-stimulating activity (the rat homologue of IGF-II) greater than insulin, and the receptor protein migrated as a 130-kDa band in autoradiography. Scatchard analysis showed a significant increase in IGF-I binding sites by 50% after 3-day treatment with 5 x 10(-11) M 1,25-(OH)2D3, without any change in affinity. These results indicate that the interaction of IGF-I and 1,25-(OH)2D3 in the culture of MC3T3-E1 cells may be mediated by the effect of 1,25-(OH)2D3 on IGF-I receptors.     

Effects of 1,25-dihydroxyvitamin D3 on osteoblastic MC3T3-E1 cells

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] was examined for a possible stimulative effect on osteoblastic MC3T3-E1 cells. During the early period of culture, 1,25-(OH)2D3 had a stimulative effect. During the growth phase, however, the steroid had little effect on either the protein or DNA content of the cultures. 1,25-(OH)2D3 increased bone-liver-kidney-type alkaline phosphatase activity in a dose-related manner up to a concentration of 5 pg/ml; the increase was 2.2-fold over the control value. Studies on the effect of actinomycin D or cycloheximide treatment indicated that the vitamin may enhance de novo synthesis of ALP. The steroid also stimulated type I collagen production dose dependently via an increase in collagen synthesis rather than by inhibition of collagen degradation. MC3T3-E1 cells have a specific receptor for 1,25-(OH)2D3 which has a dissociation constant of 4.17 X 10(-11) M and a sedimentation coefficient of 3.67S. The receptor concentration varied with the period of culture, being higher during the growth phase and lower at confluence, but its affinity did not change. The results indicate that 1,25-(OH)2D3 has a direct specific anabolic effect on osteoblastic cells in vitro during the growth phase and that this effect is related to receptor concentration.     

Effect of 1,25-dihydroxyvitamin D3 on rat pituitary prolactin release

The effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on PRL secretion from rat pituitary in vivo and in vitro was investigated. Treating the rats for three days with 0.05 microgram/kg per day had no effect on basal PRL secretion, whereas the TRH-induced PRL secretion was increased (P less than 0.001). The enhancing effect of 1,25(OH)2D3 was blunted by verapamil. Incubating dispersed anterior pituitary cells with 10(-8) mol/l 1,25(OH)2D3 induced a significant increase in PRL secretion after 96 h (364 +/- 30 ng/well vs 481 +/- 33 ng/well, P less than 0.001; mean +/- SEM) compared with control cells. The TRH-induced PRL secretion was increased in cells incubated with 1,25(OH)2D3 for 144 h (0.766 +/- 0.061 vs 1.024 +/- 0.076 microgram/well, P less than 0.05; mean +/- SEM) compared with control cells. Neither 25-hydroxyvitamin D3 (25OH-D3) nor 24,25-dihydroxyvitamin D3 had any effects on the PRL secretion. However, when the cells were incubated with both 10(-8) mol/l 1,25(OH)2D3 and 10(-6) mol/l 25OHD3, the enhancing effect of 1,25(OH)2D3 on the basal PRL secretion was blunted. The results suggest that 1,25(OH)2D3 possibly affects the regulation of PRL release from the rat pituitary and that this effect is specific for 1,25(OH)2D3.     

Effect of 1,25-(OH)2-vitamin D3 on growth, homologous receptor and c-myc regulation in C3H/10T1/2 cells

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) receptor concentration, cell proliferation, and the steady-state level of c-myc mRNA were examined in the C3H/10T1/2 mouse embryo fibroblasts, before and after exposing the cells to 1,25-(OH)2D3. The non-transformed, logarithmically growing C3H/10T1/2 Cl 8 cells contained a high concentration of 1,25-(OH)2D3 receptor (164 fmol/mg of protein). An up-regulation of the 1,25-(OH)2D3 receptor and a potent inhibition of cell growth were observed by exposing the cells to 10 nM 1,25-(OH)2D3. The concentration of 1,25-(OH)2D3 receptor in the two chemically transformed, tumorigenic cell lines. C3H/10T1/2 Cl 16 and C3H/10T1/2 TPA 482, was 218 and 63 fmol/mg of protein, respectively. In the two transformed cell lines, 10 nM 1,25-(OH)2D3 had only negligible effect on cell growth. In the Cl 16 cells, an up-regulation of the 1,25-(OH)2D3 receptor was demonstrated, but only a weak up-regulation was found in the TPA 482 cells by the 1,25-(OH)2D3 treatment. No major changes were found in c-myc mRNA levels by the 1,25-(OH)2D3 treatment. Despite inhibition of cell growth, the steady-state level of c-myc mRNA was slightly induced (35%, mean) in the Cl 8 cells compared to control cells. In the transformed cells, no consistent change of the c-myc level was found. In contrast to earlier reports, we did not find any correlation between the 1,25-(OH)2D3 receptor and c-myc level, nor did we find any decrease of c-myc mRNA by 1,25-(OH)2D3 treatment in the C3H/10T1/2 fibroblasts.     

Effect of 1,25-dihydroxyvitamin D3 on TSH secretion from rat pituitary cells in culture

The effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on TSH secretion from rat pituitary cells was studied. When incubating cells with 1,25(OH)2D3 even at 100 X the physiological concentrations (10(-8)), no effect on basal TSH secretion was observed. The TRH-induced TSH secretion increased after a 24-h incubation with 10(-8) mol/l 1,25(OH)2D3 (2.9 +/- 0.2 ng/well vs 4.3 +/- 0.5 ng/well, mean +/- SD; P less than 0.05). When serum was omitted from the incubation medium, the potentiating effect of 1,25(OH)2D3 on the TRH-induced TSH release was blunted. No effect on cellular protein content was observed after incubating the cells with 10(-8) mol/l 1,25(OH)2D3. The results indicate that at unphysiological concentrations, 1,25(OH)2D3 affects the TRH-induced TSH secretion from pituitary cells. The physiological significance remains unclear.     

Myeloid progenitors from the bone marrow of patients with vitamin D resistant rickets (type II) fail to respond to 1,25(OH)2D3

The active metabolite of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), has been shown to enhance the growth of human granulocyte/macrophage haemopoietic progenitors in vitro and to induce these cells to differentiate along the monocyte/macrophage pathway. In order to evaluate the relationship between specific receptors for 1,25(OH)2D3 and the role of 1,25(OH2D3 in the regulation of haemopoietic cell differentiation, we examined the effect of haemopoietic cell differentiation, we examined the effect of 1,25(OH)2D3 on the in vitro growth and differentiation patterns of marrow myeloid progenitor cells from two patients with 1,25(OH)2D3 resistant rickets, resulting from defective receptors to vitamin D. A significant rise in the frequency of myeloid colonies in control marrow cell cultures was induced by 2 X 10(-9) to 2 X 10(-7)M 1,25(OH)2D3. This rise reached a plateau at 2 X 10(-9)_2 X 10(-8) M 1,25(OH)2D3, resulting in a maximal 54 +/- 9% increase in colony numbers. In contrast, no stimulatory effect could be detected when 1,25(OH)2D3 was added to cultured marrow cells from the patients with 1,25(OH)2D3 resistance. Analysis of colony composition revealed that 2 X 10(-8) and 2 X 10(-7) M, 1,25(OH)2D3 induced a 50 +/- 26% increase in the frequency of colonies composed only of monocytes/macrophages in control, but not in the patients' marrow cell cultures. The effect of 2 X 10(-8) and 2 X 10(-7) M 1,25(OH)2D3 on progenitor cell differentiation towards monocytes/macrophages was also observed in marrow cell suspension cultures. Whereas 1,25(OH)2D3 induced a 81-136% increase in the frequency of monocytes in control marrow cells, no effect could be detected on the generation of mature monocytes in marrow cells of the 1,25(OH)2D3 resistant patients. Our results show that marrow granulocyte/macrophage progenitor cells from patients with 1,25(OH)2D3 resistance fail to respond to 1,25(OH)2D3. We thus demonstrate that the effect of 1,25(OH)2D3 on the proliferation and differentiation of haemopoietic progenitor cells is mediated through its binding to specific cytoplasmic receptors.     

1,25-Dihydroxyvitamin D3 prevented allergic asthma in a rat model by suppressing the expression of inducible nitric oxide synthase

The active form of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] regulates calcium homeostasis, immunity, and other physiological processes while its effect in T-helper lymphocyte type 2 models is not very clear. The prevention effect of 1,25(OH)2D3 for allergic asthma in a rat asthma model was investigated. Healthy Wistar rats were randomly divided into four groups: control group, asthma group, drug prevention group, and treatment group. Asthma was induced in rats by sensitization and challenges with ovalbumin (OVA). The drug prevention group and treatment group were given 1,25(OH)2D3 or vitamin D3 on different schedules. The effects of 1,25(OH)2D3 on the development of asthma were analyzed. The airway hyperresponsiveness, the inflammatory cell infiltration in bronchoalveolar lavage (BAL) fluid, and histological changes of lung cells were examined. Nitric oxide production and the expression and activity of induced nitric oxide synthase (iNOS) in the lungs were examined also. Our study showed that 1,25(OH)2D3 reduced the airway inflammatory response in BAL. The concentration of NO and the activity and expression of iNOS in the lungs were decreased in the 1,25(OH)2D3 prevention and treatment groups. The expression of iNOS mRNA and protein levels were dose-dependently attenuated in the presence of 10(-13)-10(-8) mol/L of 1,25(OH)2D3 in alveolar macrophage culture. These findings collectively indicated that 1,25(OH)2D3 lowered many symptoms of inflammatory responses and decreased the expression of iNOS in OVA-induced experimental asthma. 1,25(OH)2D3 could be used as a new therapeutic agent in the treatment of asthma.     

The calcitriol analogue EB1089 impairs alveolarization and induces localized regions of increased fibroblast density in neonatal rat lung

The active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3, or calcitriol), is a potent mitogen for fibroblasts cultured from rat lungs at postnatal day 4 (P4), during the peak of septation (P3 to P7). In light of the key role of fibroblasts in alveolar septation, the authors conducted studies to measure the extent to which 1,25-(OH)2D3 affects lung maturation in vivo, as well as its ability to influence the stimulatory activity of all-trans retinoic acid (RA). To identify a calcitriol analogue with maximal mitogenic activity and low systemic toxicity, two compounds with reduced calcemic activity (EB1089 and CB1093) and a superagonist (MC1288) were evaluated in neonatal rat lung fibroblast cultures. All 3 analogues were more potent mitogens than 1,25-(OH)(2)D3 itself (MC1288 approximately CB1093 > EB1089 > 1,25-(OH)2D3). In addition, each was more effective than 1,25-(OH)2D3(EB1089 > CB1093 > MC1288 > 1,25-(OH)2D3) in the activation of a vitamin D response element from the platelet-derived growth factor (PDGF)-A gene, whose expression is essential for normal alveolarization. Daily administration of EB1089 to rats 4 to 12 days of age caused an increase in mean alveolar chord length (P < .0001), and also elicited prominent regions of fibroblast hypercellularity, as defined in terms of a vimentin-positive, factor VIII-negative phenotype. EB1089 and RA each induced the expression of 2 important lung structural proteins, collagen and elastin. Regions of fibroblast hypercellularity induced by EB1089 were strongly positive for expression of the alveolarization-relevant growth factors, PDGF-AA and vascular endothelial growth factor (VEGF). These studies demonstrate that 1,25-(OH)2D3 disrupts the overall alveolarization process in the neonatal lung, although it stimulates expression of some proteins associated with lung morphogenesis.     

Pretreatment with 1,25-dihydroxycholecalciferol enhances thyrotropin-releasing hormone- and inositol 1,4,5-trisphosphate-induced release of sequestered Ca2+ in permeabilized GH4C1 pituitary cells.

In GH4C1 cells 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] has been shown to enhance the TRH- and bombesin-induced increase in intracellular Ca2+ ([Ca2+]i). The aim of the present study was to investigate whether this increase in [Ca2+]i could be due to enhanced release of sequestered Ca2+ in cells pretreated with 1,25-(OH)2D3. In digitonin-permeabilized cells, the addition of 10 microM inositol 1,4,5-trisphosphate (IP3) rapidly increased free Ca2+ ([Ca2+]) to 50 +/- 10 nM (mean +/- SE) in cells pretreated with 1 nM 1,25-(OH)2D3 for 24 h, compared with 25 +/- 5 in control cells (P < 0.05). Furthermore, stimulating permeabilized cells with TRH increased [Ca2+]. The increase in control cells was 20 +/- 2, compared with 55 +/- 11 in cells pretreated with 1,25-(OH)2D3 (P < 0.05). Repeated additions of IP3 resulted in an attenuation of the response of [Ca2+] in both control cells and cells pretreated with 1,25-(OH)2D3. However, only the first addition of IP3 resulted in an enhanced increase in [Ca2+] in cells pretreated with 1,25-(OH)2D3 compared with control cells. If the cells were stimulated first with TRH and then with IP3, no difference in the [Ca2+] response was observed between control cells and cells pretreated with 1,25-(OH)2D3. Furthermore, if cells were stimulated with IP3 and then with TRH, no difference in the [Ca2+] response was observed between control cells and cells pretreated with 1,25-(OH)2D3. Stimulating the permeabilized cells with thapsigargin resulted in an increase in [Ca2+]. However, no difference in the response was observed between control cells and cells pretreated with 1,25-(OH)2D3. Addition of GTP or the nonhydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) had no effect on [Ca2+]. The results suggest that 1,25-(OH)2D3 has a modulatory effect on an IP3-sensitive intracellular Ca2+ pool in GH4C1 cells.