孕酮对脑缺氧缺血新生鼠海马葡萄糖转运蛋白表达的影响

目的:观察新生大鼠缺氧缺血后脑内葡萄糖转运蛋白1( GLUT1)和葡萄糖转运蛋白3 (GLUT3)的表达情况以及孕酮对其的影响.方法:新生SD大鼠40只,随机分成4组:正常组、假手术组、缺氧缺血组和孕酮组.建立新生鼠缺氧缺血性脑病模型,免疫组化方法检测新生大鼠海马部位GLUT1及GLUT3的表达.结果:正常组和假手术组新生大鼠海马可见少量GLUT1和GLUT3 的表达,两组间无显著差异( P＞0.05);缺氧缺血组GLUT1和GLUT3表达均明显高于假手术组(P＜0.05);孕酮组GLUT的表达不仅明显高于假手术组(P＜0.01),而且明显高于缺氧缺血组(P＜0.05).结论:孕酮通过上调GLUT1和GLUT3的表达以维持脑组织的能量供给,增强神经元对缺氧缺血的耐受性.     

银杏内酯诱导原代培养神经元低氧诱导因子1α的表达及与ERK通路的关系

目的：研究银杏内酯（Gin）对氯化钴（CoCl2）诱导的化学性缺氧原代培养神经元低氧诱导因子-α（HIF—1α）表达的影响及其与细胞外信号调节激酶（ERK）信号通路之间的关系。方法：以CoCl2（125μmol／L）诱导的原代培养胚胎小鼠大脑皮层神经元为缺氧模型,观察Gin（终浓度37．5mg／L）对神经细胞形态和活力的影响,Western blot HIF—1α和磷酸化ERK（p-ERK）的表达：运用ERK特异性抑制剂PD98059观察HIF-1α表达与ERK通路之间的关系。结果：Gin能明显提高CoCl2处理的神经细胞的活力、在正常培养的皮层神经元中HIF—1α和p-ERK的表达水平较低,CoCl2处理4h后表达水平明显上调;Gin预处理24h其表达强度进一步提高PD98059能部分抑制CoCl2诱导的HIF-1α的表达,显著抑制p-ERK的表达;预加Gin能完全阻止该抑制作用：结论：Gin对CoCl2诱导的化学性缺氧损伤神经元有保护作用,该作用与HIF-1α表达上调、ERK通路的激活有关     

重组人白细胞介素-6对缺氧-复氧后大鼠海马培养神经元Bcl-2、Bax 表达和神经元凋亡的影响

实验在培养的大鼠海马神经元中观察了重组人白细胞介素-6（recombinant human interleukin-6,rhIL-6）对缺氧-复氧后Bcl-2、Bax表达和神经元凋亡的影响。把培养12d的大鼠海马神经元分为对照组和rhIL-6组,同时于缺氧环境（90% N2 10% CO2）中培养2、4h后,再于常氧培养箱内复氧培养24和72h。于不同时间取出,分别用抗Bcl-2和Bax抗血清进行免疫组织化学染色,观察缺氧-复氧后大鼠海马培养神经元Bcl-2和Bax的表达,并用原位末端标记（TUNEL）法和流式细胞术分别检测缺氧-复氧对体外培养海马神经元凋亡的影响。结果可见,与缺氧前相比,缺氧-复氧后24和72h,海马神经元Bal-2表达明显减弱,Bax表达明显增强,凋亡神经元明显增多。经rhIL-6预处理的海马神经元与对照组相比,缺氧-复氧后24和72h,Bcl-2表达明显增强,Bax神经明显减弱,凋亡神经元明显减少。本实验结果提示,rhIL-6对海马神经元缺氧-复氧损伤具有一定的保护作用。     

银杏内酯对原代培养神经元缺氧诱导因子-1α基因表达的影响

目的研究银杏内酯(ginkgolides,Gin)对单纯缺氧和模拟缺血神经元的缺氧诱导因子1α(hypoxiainduciblefactor1α,HIF1α)表达的影响。方法用RTPCR法检测原代培养胚胎小鼠皮层神经元经缺氧或剥夺氧和葡萄糖两种损伤处理,以及给予Gin(终浓度为37.5μg/ml)预保护时,HIF1αmRNA表达的变化。结果在培养的皮层神经元中HIF1αmRNA有一定的基础表达,Gin处理24h可明显提高HIF1α的表达水平;经单纯缺氧1h后,HIF1αmRNA表达上调,而预先给予Gin其表达强度进一步提高;但经剥夺氧和葡萄糖处理的神经元,HIF1αmRNA表达较未缺氧对照组明显降低,而预加Gin则能减轻HIF1αmRNA表达的下降。结论Gin对缺氧/缺血损伤神经元的HIF1αmRNA表达有上调作用。     

缺氧对体外培养大鼠海马神经元Bcl—2表达的影响

采用免疫组化方法,观察缺氧对体外培养大鼠海马神经元Bcl-2表达的影响。结果显示,缺氧2h时Bcl-2免疫反应阳性神经元的平均光密度较缺氧前明显增强,但缺氧4h和重新恢复供氧后24—72h时,Bcl-2免疫反应阳性神经元的平均光密度又逐渐减弱。缺氧后Bcl-2免疫反应阳性神经元数和阳性率亦随神经元存活数的下降而逐渐减少。本结果提示,缺氧早期Bcl-2免疫染色阳性神经元的免疫反应增强可能是脑细胞在缺氧条件下的自我保护机制,Bcl-2可能对海马神经元缺氧损伤具有一定调控作用。     

低氧预处理对大鼠海马神经元缺氧耐受性和IL-1β表达的影响

目的:观察低氧预处理对大鼠海马神经元缺氧耐受性和白细胞介素- 1β(IL-1β)表达的影响.方法:取培养12 d的两组(对照组和低氧预处理组)培养神经元,同时置于缺氧环境(0.9L/LN2,0.1L/LCO2)中培养2、4、8和12 h. 分别观察它们的形态变化和神经元存活数,并用抗rhIL-1β单克隆抗体进行免疫组织化学染色,观察缺氧对大鼠海马培养神经元IL-1β表达的影响.结果:经低氧预处理的海马神经元缺氧后IL-1β表达较对照组减弱,神经元损伤程度减轻,神经元存活数明显高于对照组.结论:低氧预处理可使海马培养神经元对缺氧产生耐受 ,其中IL-1β表达降低可能是海马神经元对缺氧的一种适应性变化.     

缺氧对鼠视网膜Müller细胞GLAST和GS表达及功能的影响

研究了缺氧对鼠视网膜Müller细胞谷氨酸转运体(L-glutamate/L-aspartate transporter,GLAST)和谷氨酰胺合成酶(glutamine synthetase,GS)表达的影响,及对谷氨酸摄取的作用.采用出生3～7天的小鼠视网膜组织进行Müller细胞培养,采用125μmol/L的氯化钴(CoCl2)溶液分别进行缺氧干预6、12、24、48和72 h,不加CoCl2溶液培养的Müller细胞为正常对照.采用RT-PCR法、Western blot法和免疫细胞化学染色法检测GLAST和GS的表达,并检测谷氨酸摄取及细胞凋亡情况.结果显示,缺氧早期GLAST表达较正常对照组增强(P<0.001),CoCl2溶液干预12 h后达到最强(P<0.05),之后逐渐降低.CoCl2溶液干预72 h后GLAST表达与正常对照组相比无明显差异(P>0.05).而缺氧也使GS的表达较正常对照组增加(P<0.001),CoCl2溶液干预48 h后GS表达最强(P<0.001),之后开始下降.缺氧促进Müller细胞对谷氨酸的摄取,CoCl2溶液干预48 h后L-[3,4-3H]-谷氨酸的摄取量最大(P<0.005),之后开始下降.CoCl2溶液干预后,Müller细胞死亡数较正常对照组无明显差异(P>0.05).结果表明,在一定时间范围内缺氧能够增强Müller细胞GLAST及GS的表达,增加谷氨酸的摄取.但持续缺氧最终会引起Müller细胞功能失代偿,从而导致谷氨酸的代谢能力降低.     

海马神经元缺血/再灌注后自噬的表达及其作用

目的：研究自噬在大鼠海马神经元缺血缺氧/再灌注过程中的表达及自噬在神经元缺血缺氧/再灌注损伤中的作用。方法：原代培养的大鼠海马神经元经2 h的氧糖剥夺和不同时段的再灌注处理,MTT法检测细胞活性,透射电镜下检测自噬的特异性结构,免疫荧光化学法检测自噬特异性蛋白微管相关蛋白1轻链3（LC3B）的表达。应用自噬抑制剂3-甲基腺嘌呤（3-MA）检测神经元的活性。结果：经氧糖剥夺/再灌注后,海马神经元的活性比未经氧糖剥夺/再灌注组显著地降低。透射电镜和免疫荧光检测,未经氧糖剥夺/再灌注的神经元自噬的发生率极低,氧糖剥夺后和再灌注的不同时间段,均有自噬的发生。应用自噬抑制剂3-MA阻断自噬后,神经元的存活率显著降低。结论：缺血缺氧/再灌注能激活海马神经元的自噬,并可能在缺血缺氧/再灌注过程中起对抗损伤的作用。     

鼠尾草酸对Aβ损伤海马神经元的保护作用研究

采用Aβ诱导建立海马神经元损伤模型,CCK-8检测神经元的活性,RT-PCR检测神经元凋亡相关基因Caspase-3 mRNA的表达,探讨了鼠尾草酸对Aβ所致海马神经元损伤的保护作用及其机制。结果显示,浓度在5~10μmol/L时,鼠尾草酸预处理能显著下调Aβ损伤导致的Caspase-3 mRNA表达的升高,增强神经元活力。表明鼠尾草酸预处理可以保护Aβ所致小鼠海马神经元的损伤,其机制可能与鼠尾草酸调控神经元凋亡相关基因caspase-3 mRNA的表达有关。     

体外培养大鼠海马细胞白细胞介素—1的表达及缺氧的影响

采用免疫组化方法,观察了体外培养大鼠海马细胞对人重组白细胞介素1β（rhIL-βH）抗血清的免疫反应以及缺氧的影响,结果可见,体外培养的大鼠海马神经元和神经胶质细胞对抗rhIL-1β抗血清均呈弱性免疫染色反应,缺氧后免疫染色反应明显增强,经图像分析表明,缺氧后神经元和神经胶质细胞的平均光密度均较缺氧前增加,尤以缺氧2h增加最明显,继续缺氧4－12h,神经元和神经胶质细胞的平均光密度又逐渐减弱,以上结果表明,大鼠海马脑区存在抗rhIL-1β抗血清的免疫反应细胞;缺氧使对抗rhIL-1β抗血清的免疫染色反应增强,提示IL－1β与脑缺氧损伤的调控有关。     

Differential metabolic adaptation to acute and long-term hypoxia in rat primary cortical astrocytes

Brain astrocytes provide structural and metabolic support to surrounding cells during ischemia. Glucose and oxygen are critical to brain function, and glucose uptake and metabolism by astrocytes are essential to their metabolic coupling to neurons. To examine astrocyte metabolic response to hypoxia, cell survival and metabolic parameters were assessed in rat primary cortical astrocytes cultured for 3 weeks in either normoxia or in either 1 day or 3 weeks sustained hypoxia (5% O2). Although cell survival and proliferation were not affected by the mildly hypoxic environment, substantial differences in glucose consumption and lactate release after either acute or prolonged hypoxia suggest that astrocyte metabolism may contribute to their adaptation. Hypoxia over a period of 1 day increased glucose uptake, lactate release, and glucose transporter 1 (GLUT1) and monocarboxylate transporter 1 (MCT1) expression, whereas hypoxia over a period of 3 weeks resulted in a decrease of all parameters. Furthermore, increased glucose uptake at 1 day of hypoxia was not inhibited by cytochalasin B suggesting the involvement of additional glucose transporters. We uncovered hypoxia-regulated expression of sodium-dependent glucose transporters (SGLT1) in astrocytes indicating a novel adaptive strategy involving both SGLT1 and GLUT1 to regulate glucose intake in response to hypoxia. Overall, these findings suggest that although increased metabolic response is required for the onset of astrocyte adaptation to hypoxia, prolonged hypoxia requires a shift to an energy conservation mode. These findings may contribute to the understanding of the relative tolerance of astrocytes to hypoxia compared with neurons and provide novel therapeutic strategies aimed at maintaining brain function in cerebral pathologies involving hypoxia.     

Differential regulation of the HepG2 and adipocyte/muscle glucose transporters in 3T3L1 adipocytes. Effect of chronic glucose deprivation.

Glucose transport in 3T3L1 adipocytes is mediated by two facilitated diffusion transport systems. We examined the effect of chronic glucose deprivation on transport activity and on the expression of the HepG2 (GLUT 1) and adipocyte/muscle (GLUT 4) glucose transporter gene products in this insulin-sensitive cell line. Glucose deprivation resulted in a maximal increase in 2-deoxyglucose uptake of 3.6-fold by 24 h. Transport activity declined thereafter but was still 2.4-fold greater than the control by 72 h. GLUT 1 mRNA and protein increased progressively during starvation to values respectively 2.4- and 7.0-fold greater than the control by 72 h. Much of the increase in total immunoreactive GLUT 1 protein observed later in starvation was the result of the accumulation of a non-functional or mistargeted 38 kDa polypeptide. Immunofluorescence microscopy indicated that increases in GLUT 1 protein occurred in presumptive plasma membrane (PM) and Golgi-like compartments during prolonged starvation. The steady-state level of GLUT 4 protein did not change during 72 h of glucose deprivation despite a greater than 10-fold decrease in the mRNA. Subcellular fractionation experiments indicated that the increased transport activity observed after 24 h of starvation was principally the result of an increase in the 45-50 kDa GLUT 1 transporter protein in the PM. The level of the GLUT 1 transporter in the PM and low-density microsomes (LDM) was increased by 3.9- and 1.4-fold respectively, and the GLUT 4 transporter content of the PM and LDM was 1.7- and 0.6-fold respectively greater than that of the control after 24 h of glucose deprivation. These data indicate that newly synthesized GLUT 1 transporters are selectively shuttled to the PM and that GLUT 4 transporters undergo translocation from an intracellular compartment to the PM during 24 h of glucose starvation. Thus glucose starvation results in an increase in glucose transport in 3T3L1 adipocytes via a complex series of events involving increased biosynthesis, decreased turnover and subcellular redistribution of transporter proteins.     

Green tea decoction improves glucose tolerance and reduces weight gain of rats fed normal and high-fat diet

Green tea containing polyphenols exerts antidiabetic and antiobesity effects, but the mechanisms involved are not fully understood. In this study, we first analyzed and compared polyphenol compounds [epigallocatechin gallate (EGCG), epigallocatechin (EGC)] in decoction of green tea leaves versus usual green tea extracts. Second, the effects of acute (30 min) or chronic (6 weeks) oral administration of green tea decoction (GTD) on intestinal glucose absorption were studied in vitro in Ussing chamber, ex vivo using isolated jejunal loops and in vivo through glucose tolerance tests. Finally, we explore in rat model fed normal or high-fat diet the effects of GTD on body weight, blood parameters and on the relative expression of glucose transporters SGLT-1, GLUT2 and GLUT4. GTD cooked for 15 min contained the highest amounts of phenolic compounds. In fasted rats, acute administration of GTD inhibited SGLT-1 activity, increased GLUT2 activity and improved glucose tolerance. Similarly to GTD, acute administration of synthetic phenolic compounds (2/3 EGCG+1/3 EGC) inhibited SGLT-1 activity. Chronic administration of GTD in rat fed high-fat diet reduced body weight gain, circulating triglycerides and cholesterol and improved glucose tolerance. GTD-treated rats for 6 weeks display significantly reduced SGLT-1 and increased GLUT2 mRNA levels in the jejunum mucosa. Moreover, adipose tissue GLUT4 mRNA levels were increased. These results indicate that GTD, a traditional beverage rich in EGCG and EGC reduces intestinal SGLT-1/GLUT2 ratio, a hallmark of regulation of glucose absorption in enterocyte, and enhances adipose GLUT4 providing new insights in its possible role in the control of glucose homeostasis.     

Significant Reduction of the GLUT3 Level,but not GLUT1 Level,Was Observed in the Brain Tissues of Several Scrapie Experimental Animals and Scrapie-Infected Cell Lines

Glucose transporters 1 (GLUT1) and 3 (GLUT3) belong to the solute carrier family 2 (SLC2, facilitated glucose transporter) and are the two most important glucose transporters (GLUTs) in brain tissue, and between them, GLUT3 is the primary one for neurons, which is responsible for glucose uptake. To obtain insights into the possible alterations of GLUT1 and GLUT3 in transmissible spongiform encephalopathies (TSEs), the protein levels of GLUT1 and GLUT3 in the brain tissues of agents 263K- and 139A-infected hamsters, as well as agents 139A- and ME7-infected mice, were evaluated. Western blots, immunofluorescent assay (IFA), and immunohistochemical (IHC) assays revealed that at the terminal stages of the infection, GLUT3 level in the brain tissues of scrapie-infected rodents was significantly downregulated, while GLUT1 level remained almost unchanged. The decline of GLUT3 level was closely related with prolonged incubation time. In line with these results in vivo, the GLUT3 level in a prion persistently infected cell line SMB-S15 was also lower than that of its normal cell line SMB-PS. Moreover, the level of hypoxia-inducible factor-1 alpha (HIF-1α), which positively regulated the expressions of GLUTs, was also markedly downregulated in the brains of several scrapie-infected animals. In vitro glucose uptake assays illustrated a markedly decreased 2-[N-(7-nitrobenze-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose uptake activity in SMB-S15 cells. Our data indicate that the reduction of GLUT3 is a common phenomenon in prion diseases, which occurs much earlier than the appearance of clinical symptoms. Defect in glucose uptake and metabolism of neurons, like in other neurodegenerative diseases, for example, Alzheimer’s disease (AD), may be one of the essential processes in the pathogenesis of prion diseases.     

Weekly intra-amniotic IGF-1 treatment increases growth of growth-restricted ovine fetuses and up-regulates placental amino acid transporters

Frequent treatment of the growth-restricted (IUGR) ovine fetus with intra-amniotic IGF-1 increases fetal growth. We aimed to determine whether increased growth was maintained with an extended dosing interval and to examine possible mechanisms. Pregnant ewes were allocated to three groups: Control, and two IUGR groups (induced by placental embolization) treated with weekly intra-amniotic injections of either saline (IUGR) or 360 μg IGF-1 (IGF1). IUGR fetuses were hypoxic, hyperuremic, hypoglycemic, and grew more slowly than controls. Placental glucose uptake and SLC2A1 (GLUT2) mRNA levels decreased in IUGR fetuses, but SLC2A3 (GLUT3) and SLC2A4 (GLUT4) levels were unaffected. IGF-1 treatment increased fetal growth rate, did not alter uterine blood flow or placental glucose uptake, and increased placental SLC2A1 and SLC2A4 (but not SLC2A3) mRNA levels compared with saline-treated IUGR animals. Following IGF-1 treatment, placental mRNA levels of isoforms of the system A, y(+), and L amino acid transporters increased 1.3 to 5.0 fold, while the ratio of phosphorylated-mTOR to total mTOR also tended to increase. Weekly intra-amniotic IGF-1 treatment provides a promising avenue for intra-uterine treatment of IUGR babies, and may act via increased fetal substrate supply, up-regulating placental transporters for neutral, cationic, and branched-chain amino acids, possibly via increased activation of the mTOR pathway.     

Distinct regulation of glucose transport and GLUT1/GLUT3 transporters by glucose deprivation and IGF-I in chromaffin cells

Effects of prolonged metabolic (glucose deprivation) and hormonal [insulin-like growth factor I (IGF-I)] challenge on regulation of glucose transporter (GLUT) expression, glucose transport rate and possible signaling pathways involved were studied in the neuroendocrine chromaffin cell. The results show that bovine chromaffin cells express both GLUT1 and GLUT3. Glucose deprivation and IGF-I activation led to an elevation of GLUT1 and GLUT3 mRNA, the strongest effect being that of IGF-I on GLUT3 mRNA. Both types of stimulus increased the GLUT1 protein content in a cycloheximide (CHX)-sensitive manner, and the glucose transport rate was elevated by 3- to 4-fold after 48 h under both experimental conditions. IGF-I-induced glucose uptake was totally suppressed by CHX. In contrast, only approximately 50% of transport activation in glucose-deprived cells was sensitive to the protein synthesis inhibitor. Specific inhibitors of mTOR/FRAP and p38 MAPK each partially blocked IGF-I-stimulated glucose transport, but had no effect on transport rate in glucose-deprived cells. The results are consistent with IGF-I-activated transport being completely dependent on new GLUT protein synthesis while the enhanced transport in glucose-deprived cells was partially achieved independent of new synthesis of proteins, suggesting a mechanism relying on preexisting transporters.     

Comparative expression of hexose transporters (SGLT1, GLUT1, GLUT2 and GLUT5) throughout the mouse gastrointestinal tract

Hexose transporters play a pivotal role in the absorption of food-derived monosaccharides in the gastrointestinal tract. Although a basic knowledge of the hexose transporters has already been gained, their detailed distribution and comparative intensities of expression throughout the gastrointestinal tract have not been fully elucidated. In this study, we quantitatively evaluated the expression of SGLT1, GLUT1, GLUT2, and GLUT5 by in situ hybridization and real-time PCR techniques using a total of 28 segments from the gastrointestinal tract of 9-week-old mice. GLUT2 and GLUT5 mRNA expressions were detected predominantly from the proximal to middle parts of the small intestine, showing identical expression profiles, while SGLT1 mRNA was expressed not only in the small intestine but also in the large intestine. Notably, GLUT1 mRNA was expressed at a considerable level in both the stomach and large intestine but was negligible in the small intestine. Immunohistochemistry demonstrated the polarized localization of hexose transporters in the large intestine: SGLT1 on the luminal surface and GLUT1 on the basal side of epithelial cells. The present study provided more elaborate information concerning the localization of hexose transporters in the small intestine. Furthermore, this study revealed the significant expression of glucose transporters in the large intestine, suggesting the existence of the physiological uptake of glucose in that location in mice.     

Increases in mRNA levels of glucose transporters types 1 and 3 in Ehrlich ascites tumor cells during tumor development

A common feature of many tumors is an increase in glucose catabolism during tumor growth. We studied the mechanism of this phenomenon by using Ehrlich ascites tumor bearing mice as the animal model. We found that Ehrlich ascites tumor cells possess only glucose transporter 1 (GLUT1) and GLUT3 but no GLUT2, GLUT4, or GLUT5. The mRNA levels of GLUT1 and GLUT3 increased progressively in the tumour during development; however, there were no changes observable in mRNA levels of glucose transporters of all types in brain, liver, and heart of the host mice. These findings suggest that Ehrlich ascites tumor augments its glucose transport mechanism relative to other tissues in response to its unique growth needs. J. Cell. Biochem. 67:131–135, 1997. © 1997 Wiley-Liss, Inc.