选择性CDK抑制剂对大鼠局灶性脑缺血后胶质增殖及疤痕形成的抑制作用

目的:探讨选择性周期素依赖性蛋白激酶抑制剂Olomoucine对局灶性脑缺血后星形胶质细胞增殖及胶质疤痕形成的抑制作用。方法:将72只SD大鼠随机分为假手术组12只、模型组27只和干预组33只。3组均手术暴露颅骨,模型组和干预组建立光化学法诱导大鼠局灶性脑缺血模型,之后干预组腹腔注射Olomoucine,分别将3组大鼠于处理后3、7、30 d处死,应用免疫组织化学法检测梗死灶周围胶质纤维酸性蛋白(GFAP)的表达;Western blot法观察损伤侧皮质GFAP、增殖细胞核抗原(PCNA)、周期素蛋白A(CyclinA)和周期素蛋白B1(Cy-clinB1)的表达。结果:缺血后各组梗死灶边缘区GFAP表达明显增强,缺血后7和30 d模型组GFAP表达明显强于干预组(P<0.05),并且7和30 d对照组缺血边缘区可见胶质疤痕形成,尤以30 d最为明显;GFAP、PCNA、Cy-clinA和CyclinB蛋白的表达,模型组明显高于干预组(P<0.05)。结论:Olomoucine可部分抑制胶质细胞的活化增殖及疤痕的形成。该结果提示调控细胞周期可能是治疗脑缺血新的方向。     

Placental passage of olomoucine II,but not purvalanol A,is affected by p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2) and multidrug resistance-associated proteins (ABCCs)

1.?Purine cyclin-dependent kinase inhibitors have recently been recognised as promising candidates for the treatment of various cancers. While pharmacodynamic properties of these compounds are relatively well understood, their pharmacokinetics including possible interactions with placental transport systems have not been characterised to date.

2.?In this study, we investigated transplacental passage of olomoucine II and purvalanol A in rat focusing on possible role of p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2) and/or multidrug resistance-associated proteins (ABCCs). Employing the in situ method of dually perfused rat term placenta, we demonstrate transplacental passage of both olomoucine II and purvalanol A against the concentration gradient in foetus-to-mother direction. Using several ATP-binding cassette (ABC) drug transporter inhibitors, we confirm the participation of ABCB1, ABCG2 and ABCCs transporters in the placental passage of olomoucine II, but not purvalanol A.

3.?Transplacental passage of olomoucine II and purvalanol A from mother to foetus is significantly reduced by active transporters, restricting thereby foetal exposure and providing protection against harmful effects of these xenobiotics. Importantly, we demonstrate that in spite of their considerable structural similarity, the two molecules utilise distinct placental transport systems. These facts should be kept in mind when introducing these prospective anticancer candidates and/or their analogues into the clinical area.     

olomoucine对星形胶质细胞增殖的影响及机制研究

目的:观察细胞周期抑制剂olomoucine对培养星形胶质细胞(AS)机械损伤后增殖的影响,并探讨其作用机制。方法:建立体外培养大鼠纯化的AS物理损伤模型(划痕损伤模型),随机分为对照组、划痕组和干预组,划痕组和干预组均继续培养,干预组给予olomoucine干预。利用免疫荧光细胞化学方法观察损伤后BrdU表达;利用Westernblot印迹分析损伤后PCNA、p27的表达。结果:划痕损伤刺激12h开始出现损伤边缘区AS胞体肥大、数目增加,BrdU阳性细胞比率和PCNA表达水平较对照组增高(P<0.05),p27表达水平较对照组下降(P<0.05);干预组的BrdU阳性细胞比率和PCNA表达水平较划痕组明显减少(P<0.05),p27表达上调(P<0.05)。结论:损伤刺激可促使AS发生反应性胶质增生,CDK选择性细胞周期抑制剂olomoucine可以通过调控细胞周期抑制其反应性增生。     

Effect of Cell Cycle Inhibitor Olomoucine on Astroglial Proliferation and Scar Formation after Focal Cerebral Infarction in Rats

Background:Astrocytes become reactive following many types of CNS injuries.Excessive astrogliosis is detrimental and contributes to neuronal damage.We sought to determine whether inhibition of cell cycle could decrease the proliferation of astroglial cells and therefore reduce excessive gliosis and glial scar formation after focal ischemia.Methods:Cerebral infarction model was induced by photothrombosis method.Rats were examined using MRI,and lesion volumes were estimated on day 3 post-infarction.The expression of glial fibrillary acidic protein(GFAP) and proliferating cell nuclear antigen(PCNA) was observed by immunofluorescence staining.Protein levels for GFAP,PCNA,Cyclin A and Cyclin B1 were determined by Western blot analysis from the ischemic and sham animals sacrificed at 3,7,30 days after operation.Results:Cell cycle inhibitor olomoucine significantly suppressed GFAP and PCNA expression and reduced lesion volume after cerebral ischemia.In parallel studies,we found dense astroglial scar in boundary zone of vehicle-treated rats at 7 and 30 days.Olomoucine can markedly attenuate astroglial scar formation.Western blot analysis showed increased protein levels of GFAP,PCNA,Cyclin A and Cyclin B1 after ischemia,which was reduced by olomoucine treatment.Conclusion: Our results suggested that astroglial activation,proliferation and subsequently astroglial scar formation could be partially inhibited by regulation of cell cycle.Cell cycle modulation thereby provides a potential promising strategy to treat cerebral ischemia.     

Pleiotropic effects of selective CDK inhibitors on human normal and cancer cells

Escape from the proper control of the cell cycle by up-regulation of cyclins or aberrant activation of cyclin-dependent kinases (CDKs) as well as by inactivation of cellular inhibitors of CDKs (CKI) leads to malignant transformation. Loss of cellular CKIs in cancers provided a rationale for development of pharmacological inhibitors of CDKs. Recently synthesized CKIs, e.g., purine derivatives such as olomoucine (OLO) and roscovitine (ROSC) are non-genotoxic and exhibit increased selectivity towards CDK2 and CDK7/9. Interestingly, both drugs induce additional effects. Recently, a new, unexpected action of OLO on normal human cells was observed. OLO strongly up-regulates CLIMP-63, a 65 kD protein that mediates the anchoring of the ER to microtubules. Moreover, ROSC induces in human MCF-7 cells phosphorylation of p53 protein at Ser-46 which in turn initiates caspase-independent apoptosis.In the present contribution we raised the question whether both CKIs would be able to block cell cycle progression and to reactivate p53 protein in human HPV-positive HeLa cervix carcinoma cells. We also addressed the question whether exponentially growing cancer cells are more susceptible to the inhibitory action of CKIs than normal cells. Our results show that HeLa cells are much more sensitive to ROSC than normal fibroblasts. ROSC induces G₂ arrest and apoptosis in HeLa cells. It also reactivates and stabilizes wt p53 protein. The increase of p53 protein coincides with down-regulation of E6 oncoprotein.Thus, the biological action of substituted purines is not restricted to the inhibition of CDKs and open new perspectives for their therapeutic applications.     

Suppression of astroglial scar formation and enhanced axonal regeneration associated with functional recovery in a spinal cord injury rat model by the cell cycle inhibitor olomoucine

It is well established that axons of the adult mammalian CNS are capable of regrowing only a limited amount after injury. Astrocytes are believed to play a crucial role in the failure to regenerate, producing multiple inhibitory proteoglycans, such as chondroitin sulphate proteoglycans (CSPGs). After spinal cord injury (SCI), astrocytes become hypertrophic and proliferative and form a dense network of astroglial processes at the site of lesion constituting a physical and biochemical barrier. Down-regulations of astroglial proliferation and inhibitory CSPG production might facilitate axonal regeneration. Recent reports indicated that aberrant activation of cell cycle machinery contributed to overproliferation and apoptosis of cells in various insults. In the present study, we sought to determine whether a cell cycle inhibitior, olomoucine, would decrease neuronal cell death, limit astroglial proliferation and production of inhibitory CSPGs, and eventually enhance the functional compensation after SCI in rats. Our results showed that up-regulations of cell cycle components were closely associated with neuronal cell death and astroglial proliferation as well as the production of CSPGs after SCI. Meanwhile, administration of olomoucine, a selective cell cycle kinase (CDK) inhibitor, has remarkably reduced the up-regulated cell cycle proteins and then decreased neuronal cell death, astroglial proliferation, and accumulation of CSPGs. More importantly, the treatment with olomoucine has also increased expression of growth-associated proteins-43, reduced cavity formation, and improved functional deficits. We consider that suppressing astroglial cell cycle in acute SCIs is beneficial to axonal growth. In the future, therapeutic strategies can be designed to achieve efficient axonal regeneration and functional compensation after traumatic CNS injury.     

Suppression of Astroglial Scar Formation and Enhanced Axonal Regeneration Associated with Functional Recovery in a Spinal Cord Injury Rat Model by the Cell Cycle Inhibitor Olomoucine

Objective：To determine if a cell cycle inhibitior, olomoucine, would decrease neuronal cell death, limit astroglial proliferation and production of inhibitory CSPGs, and eventually enhance the functional compensation after SCI in rats. Methods： Three were used as un-operated controls and twelve as sham operated controls. Follow- ing spinal cord injury, 48 rats were randomly and blindly assigned to either olomoucine （n=24） or vehicle treatment （n=24） groups. Results： Up-regulations of cell cycle components were closely associated with neuronal ceil death and astroglial proliferation as well as the production of CSPGs after SCI. Meanwhile, administration of olomoucine, a selective cell cycle kinase （CDK） inhibitor, has remarkably reduced the up-regulated cell cycle proteins and then decreased neuronal cell death, astroglial proliferation as well as accumulation of CSPGs. More importantly, the treatment with olomoucine has also increased expression of growth-associated proteins-43 （GAP-43）, reduced the cavity formation, and improved functional deficits. Conclusion： Suppressing astroglial cell cycle in acute spinal cord injuries is beneficial to axonal growth, in turn, the future therapeutic strategies can be designed to achieve efficient axonal regeneration and functional compensation after traumatic CNS injury.     

Synergistic actions of olomoucine and bone morphogenetic protein-4 in axonal repair after acute spinal cord contusion

To determine whether olomoucine acts synergistically with bone morphogenetic protein-4 in the treatment of spinal cord injury, we established a rat model of acute spinal cord contusion by impacting the spinal cord at the T8 vertebra. We injected a suspension of astrocytes derived from glial-restricted precursor cells exposed to bone morphogenetic protein-4 （GDAsBMP） into the spinal cord around the site of the injury, and/or olomoucine intraperitoneally. Olomoucine effectively inhibited astrocyte proliferation and the formation of scar tissue at the injury site, but did not prevent proliferation of GDAsBMP or inhibit their effects in reducing the spinal cord lesion cavity. Furthermore, while GDAsBMP and olomoucine independently resulted in small improve- ments in locomotor function in injured rats, combined administration of both treatments had a significantly greater effect on the restoration of motor function. These data indicate that the combined use of olomoucine and GDAsBMP creates a better environment for nerve regeneration than the use of either treatment alone, and contributes to spinal cord repair after injury.     

CDK抑制剂olomoucine对星形胶质细胞增殖活化的影响

目的 观察体外培养的星形胶质细胞(astrocyte，AS)对物理损伤的反应，探讨细胞周期调控对AS活化及增殖的影响。方法 建立体外培养大鼠纯化的AS机械损伤模型，利用免疫细胞化学方法观察损伤区的细胞增殖细胞核抗原(PCNA)、5-溴脱氧尿苷(BrdU)的动态变化；以及周期素依赖的蛋白激酶(CDK)选择性抑制剂olomoucine干预后PCNA、BrdU表达的变化。结果 物理损伤后24h，损伤边缘区AS明显活化，细胞数目增加、胞体肥大，且交织成网状；PCNA表达增强，BrdU阳性细胞比率增加，大量AS进入增殖期。特异性细胞周期抑制剂olomoucine干预后，AS的PCNA表达增强被抑制，胞体肥大程度减轻，BrdU阳性细胞比率减少。结论 损伤刺激可促使胶质细胞细胞周期(cell cycle)启动、反心性增殖活化：olomoucine可以通过抑制CDK调控反应性AS的肥大、增殖。     

细胞周期蛋白依赖性激酶抑制剂

目的：系统介绍细胞周期蛋白依赖性激酶(CDK)抑制剂的抗肿瘤作用。方法：对近几年国外有关CDK抑剂的发现、构效研究及临床试验等文献进行检索和综述。结果：olomoucine，roscovitine等三取代嘌呤类化合物，flavopiridol及butyrolactone三类化合物具有明显的CDK抑制活性，对多种人类肿瘤均有疗效，且不良反应小。结论细胞周期蛋白依赖性漱酶(CDK)抑制剂有望成为新一代抗肿瘤药。