PI3K抑制剂对肺癌AKT2、MMP9表达的抑制作用的研究及意义

目的探讨PI3K抑制剂LY294002对肺腺癌AKT2及基质金属蛋白酶9(MMP9)表达的作用及意义。方法不同浓度(5μmol/L、10μmol/L、20μmol/L、40μmol/L)LY294002处理肺腺癌A549细胞24h后,分别用免疫细胞化学法和Western blot法检测AKT2、MMP9蛋白表达。人肺癌A549细胞接种于裸鼠皮下,建立肺癌裸鼠移植瘤模型并予LY294002治疗,计算LY294002的抑瘤率,Western blot法测定裸鼠移植瘤组织AKT2、MMP9蛋白的表达。结果肺腺癌细胞株A549细胞中存在AKT2、MMP9蛋白的高表达,应用P13K抑制剂LY294002可抑制该细胞株细胞中AKT2、MMP9蛋白的表达,而且其表达呈浓度依赖型降低。LY294002可有效抑制裸鼠移植瘤的生长,其抑瘤率为40.30%。LY294002治疗组裸鼠移植瘤组织MMP9及VKT2蛋白水平均显著低于对照组(P均<0.01)。结论 LY294002可抑制AKT2活性及下调MMP9蛋白的表达,该作用可能是PI3K抑制剂LY294002发挥抗肿瘤生长及及转移的机制之一。PI3K可能成为肺癌治疗的靶点。     

人参皂苷Rh2调控PI3K/AKT/GSK-3β信号通路诱导人结肠癌细胞凋亡

目的探究人参皂苷Rh2(ginsenoside Rh2,Rh2)诱导人结肠癌细胞SW480凋亡作用机制。方法 CCK-8法检测Rh2对SW480细胞增殖的影响;流式细胞术(Flow cyto Metry,FCM)检测Rh2对SW480细胞凋亡的影响;Hoechst33258染色观察Rh2对SW480细胞凋亡形态学的影响;Western blot检测经Rh2诱导SW480细胞中凋亡相关蛋白Bcl-2、Bax、p53、cleaved caspase-3,PI3K/AKT/GSK-3β信号通路相关蛋白PI3K、AKT、P-AKT、GSK-3β、P-GSK-3β表达量变化;LY294002、Rh2单独及联合诱导SW480细胞后,蛋白PI3K、AKT、P-AKT、GSK-3β、P-GSK-3β表达量变化。结果CCK-8结果显示Rh2呈时间浓度依赖抑制SW480细胞增殖。FCM结果显示细胞早期凋亡率由正常对照组的(0.70±0.09)%增至(11.06±1.04)%(P<0.05)。Hoechst33258结果显示,Rh2诱导SW480细胞48h后呈现典型的凋亡形态学改变。Western blot结果显示,经Rh2诱导的SW480细胞,凋亡相关蛋白Bcl-2表达降低,Bax、p53、激活型胱天蛋白酶3(cleaved caspase-3)蛋白表达增加;PI3K/AKT/GSK-3β信号通路蛋白PI3K、P-AKT、P-GSK-3β表达量与对照组比较明显减少,AKT、GSK-3β表达量无明显变化;LY294002、Rh2和LY294002与Rh2联合诱导SW480细胞后,总AKT蛋白和总GSK-3β蛋白表达量基本一致,LY294002与Rh2联合用药对SW480细胞中PI3K、P-AKT和P-GSK-3β的表达抑制作用较单独用药更加明显。结论Rh2可能是通过抑制PI3K/AKT/GSK-3β通路,激活p53信号通路,激活caspase-3,破坏Bcl-2/Bax比例,诱导结肠癌细胞SW480凋亡。     

褪黑素调控自噬及铁死亡增强胰腺癌细胞PANC-1对吉西他滨的化疗敏感性

目的 探讨褪黑素联合吉西他滨对人胰腺癌细胞株PANC-1化疗敏感性的作用及其潜在的作用机制。方法 单独使用吉西他滨和联合褪黑素处理人胰腺癌细胞株PANC-1,生物因子活性检测(CCK-8)检测细胞活力;克隆形成实验观察褪黑素和吉西他滨单独或联合处理对PANC-1细胞克隆形成能力的影响;采用划痕实验和transwell实验检测细胞迁移能力;细胞活性氧和线粒体膜电位JC-1检测试剂盒测定活性氧的合成和膜电位水平;亚铁离子(Fe²⁺)荧光探针检测细胞内Fe²⁺水平;通过免疫荧光和Western blotting检测不同处理组中LC3、P62、GPX4和SLC7A11的蛋白表达水平。结果 CCK-8结果显示,吉西他滨单独处理48 h及72 h后PANC-1细胞活力受到抑制,呈时间剂量依赖性,吉西他滨联合褪黑素组的细胞活力显著低于吉西他滨组,且细胞活力随着褪黑素的浓度升高而下降;细胞划痕、transwell及平板克隆实验结果显示,吉西他滨联合褪黑素组较吉西他滨组比较,细胞的增殖及迁移能力明显受到抑制;通过荧光显微镜观察并分析得出吉西他滨联合褪黑素组的P...     

PI3K信号通路在LPS诱导RAW264.7细胞表达sTREM-1中的作用

目的：探讨磷脂酰肌醇3-激酶(PI3K)信号通路在脂多糖(LPS)诱导RAW264.7细胞表达可溶性髓样细胞触发受体-1(sTREM-1)中的作用。方法培养小鼠巨噬细胞株RAW264.7,采用相同浓度的LPS在不同时间诱导RAW264.7细胞,应用Western blot法分别检测PI3K蛋白表达水平,RT-PCR法检测PI3K mRNA表达水平,酶联免疫吸附(ELISA)法检测细胞培养血清中sTREM-1表达水平。用不同浓度PI3K特异性抑制剂LY294002处理细胞,观察上述指标变化。结果 LPS可时间依赖性地诱导RAW264.7细胞PI3K蛋白、PI3K mRNA的表达;LY294002可浓度依赖性地抑制PI3K蛋白、PI3K mRNA的表达;LY294002阻断PI3K信号转导通路后,LPS对sTREM-1表达的诱导作用受到显著抑制,并且具有剂量依赖性。结论 LPS通过PI3K信号通路诱导RAW264.7细胞表达sTREM-1。     

莪术醇通过调控PI3K/AKT通路促进人肝癌HepG2细胞凋亡

目的探讨莪术醇促进人肝癌HepG2细胞凋亡的作用是否与PI3K/AKT通路有关。方法采用MTT法检测不同浓度(0、10、25、50、100μmol·L~(-1))莪术醇干预HepG2细胞24、48 h的增殖抑制率,Hoechst 33258染色法观察细胞核凋亡形态,Western blot法检测不同浓度莪术醇及PI3K/AKT通路阻断剂LY294002对HepG2细胞p-PI3K、p-AKT、Caspase-3蛋白表达的影响。结果莪术醇对HepG2细胞的增殖有明显抑制作用,呈浓度依赖性,但干预48 h对比24 h差异无统计学意义;Hoechst 33258染色发现,莪术醇干预后,同一视野下细胞数目明显减少,细胞透亮,部分细胞核碎裂,核固缩,呈现典型的凋亡形态学特征;Western blot结果显示,莪术醇能显著降低细胞p-PI3K、p-AKT蛋白的表达,上调凋亡执行蛋白Caspase-3的表达,与LY294002联用后表现出良好的协同作用,对各蛋白表达的调控较单独用药更加明显。结论莪术醇能通过抑制PI3K/AKT通路诱导人肝癌HepG2细胞凋亡。     

叶酸受体在食管癌细胞中的表达及其与食管癌生物学行为的关系

目的研究PI3K/AKT信号通路靶向抑制剂LY294002对食管癌细胞EC109中FR的表达的影响,从而了解食管癌生物学行为与叶酸受体的关系。方法将LY294002作用于食管癌细胞株EC109,四甲基偶氮唑蓝（MTT）法测定细胞增殖抑制率,流式细胞术检测食管癌细胞FR的表达。结果随LY294002浓度的增加及作用时间（12h、24h）的延长,实验组EC109细胞的增殖抑制率逐渐增大,LY294002抑制作用与浓度及作用时间呈正相关。LY294002干预食管癌细胞24小时后,实验组叶酸受体表达的表达较对照组明显降低。结论阻断PI3K/AKT信号通路可以改变食管癌细胞株EC109中FR的表达,并能明显抑制细胞增殖,其机制可能与其抑制AKT磷酸化,从而改变食管癌细胞的生物学行为有关。     

生长抑素联合人转录因子叉头框蛋白 D1通过磷脂酰肌醇 3激酶 /蛋白激酶 B通路调控胰腺癌细胞增殖、迁移和侵袭的机制研究

目的探讨生长抑素联合人转录因子叉头框蛋白 D1(FOXD1)通过磷脂酰肌醇 3激酶 /蛋白激酶 B(PI3K/AKT)通路调控胰腺癌细胞增殖、迁移和侵袭的机制研究。方法研究于 2018年 12月至 2019年 12月进行,通过体外培养 PANC-1细胞,过不同浓度( 0 mg/L、100 mg/L、200 mg/L、400 mg/L)的生长抑素( SST)处理细胞,记为生长抑素各剂量组,其中 0 mg/L和 400 mg/经L的生长抑素作为对照组( Control)和生长抑素组( SST);将过表达载体( pcDNA)和过表达 FOXD1(FOXD1)转染至 PANC-1细胞,经过 400 mg/L的生长抑素及 20 mol/L的 PI3K抑制剂 LY294002处理细胞,记为 SST+pcDNA组、 SST+FOXD1组和 SST+ FOXD1+LY294002组。四甲基偶氮唑盐微量酶反应比色法( MTT)检测细胞增殖; Transwell检测细胞迁移和侵袭;蛋白质印迹法( Western blotting)检测增殖细胞核抗原( PCNA)、基质金属蛋白酶 -2(MMP-2)、基质金属蛋白酶 -9(MMP-9)、 FOXD1和 PI3K/ AKT相关蛋白的表达;实时荧光定量逆转录聚合酶链反应( qRT-PCR)检测 FOXD1 mRNA的表达。结果与 Control组相比, SST组可以抑制 FOXD1 mRNA(0.47±0.03)及蛋白表达( 0.42±0.04)、增殖( 0.52±0.05)、迁移( 66.8±7.2)和侵袭( 63.7±6.5)能力,下调 p-PI3K(0.43±0.04)、 p-AKT(0.39±0.03)蛋白表达;与 SST+pcDNA组相比, SST+FOXD1组可以促进以抑制 FOXD1 mRNA(0.67±0.05)及蛋白表达( 0.64±0.06)、增殖( 0.71±0.07)、迁移( 86.9±8.5)和侵袭( 81.5±7.3)能力,上调 p-PI3K(0.62±0.05)、 p-AKT(0.65±0.06)蛋白表达。与 SST+FOXD1组相比, SST+FOXD1+LY294002组可以抑制 FOXD1 mRNA(0.37±0.04)及蛋白表达(0.35±0.03)、增殖( 0.53±0.05)迁移(67.2±6.5)和侵袭( 62.5±5.2)。结论生长抑素通过调控 FOXD1的表达抑制胰腺癌细胞增殖、迁移和侵袭,其作用机制可能与抑制 PI3K/AKT通路有关。     

Z-没药甾酮通过激活PI3K/AKT/eNOS通路发挥脑微血管内皮细胞保护作用

摘要：目的:探讨Z-没药甾酮（Z-GS）对大鼠脑微血管内皮细胞的保护作用及药理机制。方法:脑微血管内皮细胞制作氧糖剥夺模型体外模拟缺血性脑卒中,培养的脑微血管内皮细胞分为对照组、模型组、 Z-GS低、中、高(12.5,25,50μmol·L-1)剂量组。给药组细胞在OGD造模前分别给予不同剂量的Z-GS处理。在机制研究中,50μmol·L-1?Z-GS+抑制剂组在造模给药前加入PI3K抑制剂LY294002。试剂盒检测细胞活力、乳酸脱氢酶（LDH）释放和血管活性物质水平;免疫印迹分析磷脂酰肌醇3-激酶（PI3K）、蛋白激酶B（AKT）和内皮型一氧化氮合酶（eNOS）蛋白表达及磷酸化水平;LY294002用于特异性抑制PI3K表达。结果:Z-GS给药可提高细胞活力、降低LDH释放。同时Z-GS可通过降低内皮素-1和血栓素B2水平、升高血栓调节蛋白和6-酮-前列环素1α水平缓解血瘀。机制研究表明,Z-GS给药可激活PI3K/AKT/eNOS通路,增加一氧化氮（NO）的生成。而在LY294002特异性抑制PI3K后,Z-GS对该通路的调控作用消失。结论:Z-GS可通过调控血管活性物质发挥血管内皮保护作用,其机制与激活PI3K/AKT/eNOS通路,进而促进NO的生成有关。     

PD-1免疫检查点与膀胱癌灌注药物疗效的研究

目的:探讨PD-1免疫检查点在膀胱癌灌注药物疗效中的作用。方法:常规传代培养人膀胱癌T24细胞,取处于生长对数期的细胞,将其分为对照组、吉西他滨组、吉西他滨+Durvalumab组。采用定量聚合酶链式反应(Q-PCR)检测Caspase-3基因的表达。采用蛋白质印迹法(Western Blot)检测Caspase-3蛋白的表达。采用膜联蛋白V调往检测试剂(AnnexinV-FITC/PI)双染法检测细胞凋亡。采用细胞代谢活性比色法(MTT)检测细胞增殖能力。结果:吉西他滨+Durvalumab组Caspase-3基因的表达水平明显高于吉西他滨组和对照组,且对照组最低;吉西他滨+Durvalumab组Caspase-3蛋白的表达水平明显高于吉西他滨组和对照组,且吉西他滨组与对照组相近;吉西他滨组和吉西他滨+Durvalumab组与对照组相比细胞增殖水平明显降低,且吉西他滨+Durvalumab组为最低;吉西他滨+Durvalumab组凋亡表达水平明显高于吉西他滨组和对照组,而对照组与吉西他滨组比较差异无统计学意义。结论:PD-1主要在各种水平的活化T细胞表面表达,对提升膀胱癌治疗效果具有重要意义。     

siRNA沉默Twist1增强吉西他滨诱导胰腺癌细胞凋亡的研究

目的通过抑制Twist1来观察胰腺癌细胞对吉西他滨化疗敏感性的变化。方法通过靶向人Twist1基因小干扰RNA(siRNA)抑制Twist1的表达;用Western法检测Twist1的表达、Annexin V/PI染色和流式细胞术检测吉西他滨诱导的细胞凋亡;通过Western blot检测caspase及可能的丝裂原活化蛋白激酶(MAPK)和线粒体途径;用激光扫描共聚焦显微镜检测细胞内活性氧和线粒体膜的电位。结果 Twist1沉默显著增加了Panc-1细胞对吉西他滨的敏感性,JNK/线粒体的途径被激活,Twist1 siRNA诱导线粒体膜去极化同时显著上调线粒体分裂相关蛋白Fis1并降低融合相关蛋白Mfn1的表达。Twist1 siRNA提高了细胞内活性氧(ROS)的水平,与吉西他滨联合治疗进一步增加ROS。结论 siRNA介导的Twist1沉默在PANC-1细胞对吉西他滨化疗耐受中扮演了关键角色,Twist1沉默可能作为胰腺癌治疗的一种有效方法。     

Low-Dose Radiation Induces Cell Proliferation in Human Embryonic Lung Fibroblasts but not in Lung Cancer Cells: Importance of ERK1/2 and AKT Signaling Pathways

Hormesis and adaptive responses are 2 important biological effects of low-dose ionizing radiation (LDR). In normal tissue, LDR induces hormesis as evinced by increased cell proliferation; however, whether LDR also increases tumor cell proliferation needs to be investigated. In this study, cell proliferation was assayed by total cell numbers and the Cell Counting Kit 8 assay. Mitogen-activated protein kinases (MAPK)/extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3′ -kinase(PI3K)-Akt (PI3K/AKT) phosphorylation were determined by Western blot analysis. Human embryonic lung fibroblast 2BS and lung cancer NCI-H446 cell lines were irradiated with LDR at different doses (20-100 mGy). In response to 20 to 75 mGy X-rays, cell proliferation was significantly increased in 2BS but not in NCI-H446 cells. In 2BS cells, LDR at 20 to 75 mGy also stimulated phosphorylation of MAPK/ERK pathway proteins including ERK, MEK, and Raf and of the PI3K/AKT pathway protein AKT. To test whether ERK1/2 and AKT pathway activation was involved in the stimulation of cell proliferation in 2BS cells, the MAPK/ERK and PI3K/AKT pathways were inhibited using their specific inhibitors, U0126 and {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002. U0126 decreased the phosphorylation of ERK1/2, and {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 decreased the phosphorylation of AKT; each could significantly inhibit LDR-induced 2BS cell proliferation. However, LDR did not stimulate these kinases, and kinase inhibitors also did not affect cell proliferation in the NCI-H446 cells. These results suggest that LDR stimulates cell proliferation via the activation of both MAPK/ERK and PI3K/AKT signaling pathways in 2BS but not in NCI-H446 cells. This finding implies the potential for applying LDR to protect normal tissues from radiotherapy without diminishing the efficacy of tumor therapy.     

人参皂苷Rh2与P13K/AKT信号通路抑制剂LY294002对乳腺癌细胞转移和侵袭的影响

目的：研究人参皂苷Rh2（GensenosideRh。）与磷脂酰肌醇-3-激酶／丝苏氨酸蛋白激酶（P13K／AKT）信号通路抑制剂LY294002对乳腺癌细胞转移和侵袭的影响。方法：试验分为对照（空白培养液）组、人参皂苷Rh2（80μmol／L）组、LY294002（50gmol／L）组与人参皂苷Rh2（80gmol／L）＋LY294002（50gmol／L）组。人参皂苷Rh：与LY294002体外作用于人乳腺癌细胞MCF7／Adr,Westernblot法检测细胞基质金属蛋白酶（MMP）2、P-糖蛋白（P-gP）、丝苏氨酸蛋白激酶（AKT）、磷酸化丝苏氨酸蛋白激酶（p-AKT）蛋白表达;黏附试验观察细胞与基底膜的黏附力,Transwell法观察细胞侵袭能力和迁移能力。结果：与对照纽比较,人参皂苷Rh2组、LY294002组与人参皂苷Rh2＋LY294002组p—AKT、P—gP、MMP．2蛋白表达显著减弱,细胞与基底膜的黏附力、细胞迁移能力与侵袭能力显著减弱（P〈0．05）;人参皂苷Rh2＋LY294002组与人参皂苷Rh2组、LY294002组比较以上指标差异具有统计学意义（P〈0．05）。结论：抑制P13K／AKT信号通路可有效降低MCF7／Adr侵袭迁移能力,P13K／AKT通路是调控乳腺癌侵袭迁移的重要信号通路之一。     

Inhibition of phosphatidylinositol-3-kinase synergizes with gemcitabine in low-passage tumor cell lines correlating with Bax translocation to the mitochondria

Apoptotic pathways, including the phosphatidylinositol-3-kinase (PI3K)/AKT survival pathway, are altered in most cancer cells in relation to their normal counterparts and these differences may present an excellent therapeutic window. To gain insight into the relevance of the PI3K pathway as a target for drug discovery we generated tumor cell lines from different tumor samples that we maintained at low passage. The characterization of these cell lines indicates that all of them have constitutively activated the PI3K pathway through different mechanisms. All cell lines were differentially sensitive to the PI3K inhibitor LY294002. Our data also support previous work indicating that PI3K inhibition might help classical chemotherapeutic treatments such as gemcitabine and strengthen suboptimal doses that might be effective for these purposes in decreasing the risk of side-effects. Finally, the analysis of the molecular markers that might be implicated in the synergism between LY294002 and gemcitabine suggests that PI3K inhibition might aid chemotherapeutic treatment, leading to changes in the balance between anti- and pro-apoptotic molecules of the Bcl-2 family, Bcl-XL and Bax. These results facilitate the exploration of potential synergism between chemotherapeutic treatment and the search for others that can account for similar molecular mechanisms of cooperation.     

Differential effects of LY294002 and wortmannin on neurons and vascular endothelial cells in the rat retina

BackgroundNeuronal damage leads to capillary degeneration in an N-methyl-D-aspartate (NMDA)-induced retinal degeneration model; however, the mechanisms underlying this phenomenon are not fully understood. The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway has been recognized as an intracellular pro-survival signaling system. Therefore, we used the PI3K inhibitors LY294002 and wortmannin to investigate the role of this pathway in neuronal and blood vessel injury in the rat retina treated with NMDA.MethodsMale Sprague-Dawley rats weighing 220–240 g were used in this study. NMDA combined with LY294002, wortmannin, or vehicle was administered intravitreally, and histological evaluation was performed at 2 and 7 days after injection. The effects of LY294002 or wortmannin alone were also evaluated.ResultsThe number of cells in the ganglion cell layer (GCL) was significantly reduced at 2 and 7 days after intravitreal injection of NMDA, whereas enhanced capillary degeneration was observed at 7 days. Simultaneous injection of LY294002 with NMDA significantly attenuatedNMDA-induced retinal cell loss and capillary degeneration at 7 days. However, simultaneous injection of wortmannin with NMDA did not affect cell loss, but enhanced capillary degeneration. Treatment with LY294002 alone showed no effect on neuronal or vascular cells, whereas wortmannin induced capillary degeneration without significantly affecting the cell number in the GCL.ConclusionsAlthough both LY294002 and wortmannin are known as PI3K inhibitors, they exhibit differential effects on neurons and vascular endothelial cells in the rat retina. Therefore, the results obtained using these inhibitors should be carefully interpreted. However, our finding that LY294002 was protective against NMDA-induced retinal damage suggests that this compound may be an effective candidate for preventing the development of retinal diseases associated with glutamate-induced excitotoxicity.     

3-Methyladenine can depress drug efflux transporters via blocking the PI3K–AKT–mTOR pathway thus sensitizing MDR cancer to chemotherapy

Abstract

Multi-drug resistance (MDR) cancer is an intractable problem. Over-expression of drug efflux transporters such as ABCB1, ABCC1 and ABCG2 contributes to it, by which they pump drugs out of cells, and result in the decrease in the efficacy of chemotherapy. To reverse the cancer MDR, we used 3-methyladenine (3-MA) treatment on taxol or doxorubicin stressed MDR cell lines A2780DX5 and SGC7091R and xeno-tumor implanted mice. The results indicate that ABCB1, ABCC1 and ABCG2 were depressed, and the PI3K–AKT–mTOR pathway was blocked. Moreover, using FITC-labeled taxol as the indicator, we observed that the drug accumulation was enhanced in MDR cells and more cells were killed after 3-MA administration. Thus suggesting that 3-MA can reverse cancer MDR via depressing agent-efflux transporters.     

UBE2M-mediated p27 degradation in gemcitabine cytotoxicity

Gemcitabine (2′-deoxy-2′, 2′-difluorocytidine; Gem) is a nucleoside anti-metabolite and is commonly used for treating various human cancers including human bladder carcinoma. Gemcitabine not only functions as a suicide nucleoside analog but also inhibits DNA polymerase activity and results in the termination of chain elongation. Using 2-dimensional gel electrophoresis analysis, a Gem-induced protein was identified as UBE2M (a.k.a. UBC12), a NEDD8 conjugation E2 enzyme which contributes to protein degradation. Gem induced UBE2M expression at both RNA and protein levels in several human cancer cell lines. The induction of UBE2M by Gem was accompanied by a reduction in p27^Kip1 protein levels, which could be restored by silencing UBE2M expression with siRNA or by treating cells with the proteasome inhibitor MG132, indicating that UBE2M mediates Gem-induced p27^Kip1 protein degradation. The induction of UBE2M and reduction of p27^Kip1 by Gem were prevented by the PI3K inhibitor LY294002. These results indicate that PI3K activity is necessary for Gem-induced UBE2M expression and that UBE2M facilitates degradation of p27^Kip1. Notably, silencing of UBE2M expression reduced Gem sensitivity in NTUB1 cells, suggesting that UBE2M mediates in part cell sensitivity to Gem, possibly by degradation of p27^Kip1. Analysis of Gem-resistant sub lines also showed that loss of UBE2M and increased p27^Kip1 expression were associated with the acquisition of drug resistance. In conclusion, our results demonstrate a role for UBE2M in mediating cytotoxicity of gemcitabine in human urothelial carcinoma cells while also suggesting a potential function of p27^Kip1 in drug resistance.     

LY294002 inhibits glucocorticoid-induced COX-2 gene expression in cardiomyocytes through a phosphatidylinositol 3 kinase-independent mechanism

Glucocorticoids induce COX-2 expression in rat cardiomyocytes. While investigating whether phosphatidylinositol 3 kinase (PI3K) plays a role in corticosterone (CT)-induced COX-2, we found that LY294002 (LY29) but not wortmannin (WM) attenuates CT from inducing COX-2 gene expression. Expression of a dominant-negative mutant of p85 subunit of PI3K failed to inhibit CT from inducing COX-2 expression. CT did not activate PI3K/AKT signaling pathway whereas LY29 and WM decreased the activity of PI3K. LY303511 (LY30), a structural analogue and a negative control for PI3K inhibitory activity of LY29, also suppressed COX-2 induction. These data suggest PI3K-independent mechanisms in regulating CT-induced COX-2 expression. LY29 and LY30 do not inhibit glucocorticoid receptor transactivity. Both compounds have been reported to inhibit Casein Kinase 2 activity and modulate potassium and calcium levels independent of PI3K, while LY29 has been reported to inhibit mammalian Target of Rapamycin (mTOR), and DNA-dependent Protein Kinase (DNA-PK). Inhibitor of Casein Kinase 2 (CK2), mTOR or DNA-PK failed to prevent CT from inducing COX-2 expression. Tetraethylammonium (TEA), a potassium channel blocker, and nimodipine, a calcium channel blocker, both attenuated CT from inducing COX-2 gene expression. CT was found to increase intracellular Ca²⁺ concentration, which can be inhibited by LY29, TEA or nimodipine. These data suggest a possible role of calcium instead of PI3K in CT-induced COX-2 expression in cardiomyocytes.