角质细胞生长因子及其辐射防护作用

角质细胞生长因子(KGF)是具有肝素结合特性的成纤维细胞生长因子(FGF)家族中的一员,又称为FGF-7。尽管KGF来源于不同的组织,KGF仅特异性地作用于上皮细胞。KGF可提高辐射后小鼠肠干细胞的存活率,并对辐射引起气道上皮细胞的通透性升高具有拮抗作用。KGF可以加速辐射诱导的DNA损伤的修复,并对维持细胞骨架蛋白F-肌纤蛋白的稳定和保护细胞间连接具有重要作用,其信号转导是通过蛋白激酶C(PKC)途径完成的。因此,不少作者认为,KGF很有希望成为临床上用于胸部、腹部肿瘤放化疗防护的细胞因子。     

辐射生物剂量计的研究现状及发展方向

辐射生物剂量学是放射医学的重要组成部分。近年来,辐射生物剂量研究取得一些新进展,为研发新一代剂量计奠定技术基础。以染色体畸变分析为代表的细胞遗传学方法作为辐射生物剂量估算的金标准方法,正向自动化、网络化分析发展,相关技术已通过国际和国家性的辐射生物剂量实验室网络辐射扩散。γ-H2AX作为DNA损伤的标志性分子,用于放射损伤剂量估算的研究进展较快,其作为放射损伤分子标志物逐步获得国内外的广泛共识。在蛋白分子和表达基因的基础上,代谢物和miRNA作为放射损伤标志物的研究有进一步的新进展。组学技术的发展,推动了利用多分子表达谱评估受照剂量的研究,亦已取得突破。本文从现有辐射生物剂量计的技术特点、国内外的主要发展趋势和今后发展方向展望等3个方面进行综述。     

鼻咽癌细胞辐射抗拒的比较蛋白质组学分析

目的 通过分离并鉴定具有不同辐射抗拒的人鼻咽癌细胞株CNE-2R与CNE-2的差异表达蛋白,探讨与鼻咽癌细胞辐射抗拒相关的分子机制.方法 分别提取鼻咽癌辐射抗拒细胞株CNE-2R及其亲本细胞株CNE-2的总蛋白,采用双向凝胶电泳分离,经软件分析识别差异表达蛋白点,应用基质辅助激光解析电离飞行时间串联质谱技术(MALDI-TOF-MS)鉴定差异蛋白质.结果 两种不同辐射敏感性的鼻咽癌细胞株CNE-2R和CNE-2中,共筛选出差异表达明显的蛋白质点有32个,其中11个蛋白质被鉴定成功,在CNE-2R中上调的蛋白有3个,下调的蛋白有8个.结论 不同辐射敏感性的鼻咽癌细胞的差异表达蛋白,主要涉及调节凋亡、DNA损伤与修复、细胞周期调控、RNA转录、细胞信号转导、细胞骨架组成及辐射应激反应等多个方面.     

肿瘤辐射增敏的分子机制

关于肿瘤辐射增敏的分子机制研究主要包括:DNA损伤的加重及其修复抑制,改变细胞氧合状态,控制细胞周期,转入凋亡相关基因,导入反义物等。不同的辐射增敏剂可通过不同的分子机制提高肿瘤辐射敏感性。分子机制研究将为开发出更高效的辐射增敏剂提供理论依据。     

低水平辐射及有关因子生物效应的生化与分子机制研究

低水平辐射兴奋作用及诱导细胞遗传学适应性反应的分子机制研究,发现细胞内信息传递系统及基因表达和细胞内SOD在转录水平上的变化,是辐射兴奋作用发生的分子基础.细胞内修复蛋白及特异型ADP-核糖多聚体的诱导,促进DNA损伤修复,是细胞遗传学适应性反应发生的分子机制.     

基因芯片技术在辐射生物学领域的应用

辐射能引起机体分子水平的复杂调控,不同组织细胞、同一组织来源不同性状的细胞,其基因对不同剂量的辐射反应各异.不同剂量辐射后可引起细胞或组织多种差异基因表达上调或下调.本文综述了其中某些与细胞凋亡、DNA损伤修复和应激、细胞周期、信号转导、免疫反应和防御等相关的重要基因的最新研究进展.     

耐辐射奇球菌中多效蛋白PprA功能的研究进展

耐辐射奇球菌(DR)是研究辐射抗性的模式生物,PprA蛋白(pleiotropic protein promoting DNA repair)是DR中一种特有的、促进DNA修复的多效蛋白.笔者对PprA蛋白在DNA损伤修复和维持基因组稳定性等方面的功能进行了综述,另通过运用生物信息学方法预测其结构域及与PprA蛋白相互作用的蛋白,进一步了解其发挥作用的机制和途径.     

组蛋白去乙酰酶阻滞剂的放射增敏作用

放射治疗是肿瘤的重要治疗手段之一,辐射可以导致细胞DNA双链断裂。细胞主要通过同源重组修复和非同源末端连接修复方式修复DNA双链断裂。随着对双链DNA损伤修复机制认识的深化,组蛋白去乙酰酶（HDAC）阻滞剂成为提高放射敏感性的一种新策略。HDAC可分为4类。HDAC阻滞剂可非特异性地或特异性地阻滞这4类HDAC,使组蛋白乙酰化水平提高,染色体解螺旋,核小体结构改变。一方面使DNA更易受到辐射的影响;另一方面通过降低E2F1转录因子活性抑制损伤修复蛋白Ku80、Rad51等的表达,使其不能募集DNA损伤修复蛋白,且不能形成相应的蛋白复合物,使同源重组修复和非同源末端连接修复作用延缓,在伴有或不伴有肿瘤细胞凋亡增加的情况下,提高放射敏感性。现已有一些临床试验在进行中,并取得了初步的结果。     

低剂量辐射诱导适应性反应的分子机制研究现状

低剂量辐射(low dose radiation，LDR)可以增强细胞对随后进行的攻击性剂量(challenge dose)照射的抵抗能力，从而降低攻击性照射引起的染色体畸变和DNA损伤。人们把LDR的这种效应称之为“低剂量辐射诱导的适应性反应”。低剂量辐射诱导适应性反应的分子机制主要涉及细胞信号转导、ROS(活性氧物质)的作用和DNA修复兴奋效应等方面。     

细胞辐射敏感性与DNA双链断裂及修复相关性研究

细胞的辐射敏感性一般由辐照后细胞的存活情况来衡量。细胞的辐射敏感性存在差异，不同个体不同组织来源的细胞对于同种辐射的反应不同，而同种细胞对不同的辐射的反应也存在明显差异。研究表明，DNA是辐射的靶，电离辐射可以引起多种形式的DNA损伤，改变碱基和糖类，引起DNA—DNA和DNA-蛋白之间的交联，同时可以引起DNA单链断裂（single strand break，SSB）和DNA双链断裂（double strand break，DSB）。大量的中性洗脱实验证明DSB是引起细胞死     

Review: ATM: the protein encoded by the gene mutated in the radiosensitive syndrome ataxia-telangiectasia

Purpose: To provide an update on the product of the ATM gene mutated in the human genetic disorder ataxia-telangiectasia (A-T). Summary : The product of the ATM gene mutated in the human genetic disorder A-T is a 350kDa protein that plays a central role in the regulation of a number of cellular processes. It is a member of the phosphatidylinositol 3-kinase superfamily, but is more likely a protein kinase similar to another member of that family, i.e. DNA-dependent protein kinase (DNA-PK). A-T cells and fibroblasts derived from the atm /- mouse are hypersensitive to ionizing radiation and defective in cell cycle checkpoint control. At present the nature of the lesion in damaged DNA recognized by ATM remains uncertain, but it is evident that a small number of residual strand breaks remain unrepaired in A-T cells, which may well account for the radiosensitivity. On the other hand, considerable progress has been achieved in delineating the role of ATM in cell cycle checkpoint control. Defects are observed at all cell cycle checkpoints in A-T cells post-irradiation. At the G1/S interface ATM has been shown to play a central role in radiation-induced activation of the tumour suppressor gene product p53. ATM binds to p53 in a complex fashion and activates the molecule in response to breaks in DNA by phosphorylating it at serine 15 close to the N-terminus and by controlling other phosphorylation and dephosphorylation changes on the molecule. This in turn leads to the induction of p21/WAF1 and other p53 effector proteins before inhibition of cyclin-dependent kinase activity and G1 arrest. Emerging evidence supports a direct role for ATM at other cell cycle checkpoints. Other proteins interacting with ATM include c-Abl a protein tyrosine kinase, beta -adaptin an endosomal protein and p21 a downstream effector of p53. The significance of these interactions is currently being investigated. ATM also plays an important role in the regulation and surveillance of meiotic progression. The localization of ATM to both the nucleus and other subcellular organelles implicates this molecule in a myriad of cellular processes. Conclusion: ATM is involved in DNA damage recognition and cell cycle control in response to ionizing radiation damage. There is evidence that ATM may also have a more general signalling role.     

Poly(ADP-ribose) polymerase, a major determinant of early cell response to ionizing radiation

PURPOSE: To determine whether DNA-dependent protein kinase (DNA-PK) and poly(ADP-ribose) polymerase (PARP-1) are involved in eliciting the rapid fluctuations of radiosensitivity that have been observed when cells are exposed to short pulses of ionizing radiation. MATERIALS AND METHODS: The effect of DNA-PK and PARP-1 inhibitors on the survival of cells to split-dose irradiation was investigated using Chinese hamster V79 fibroblasts and human carcinoma SQ-20B cells. The responses of PARP-1 proficient and PARP-1 knockout mouse 3T3 fibroblasts were compared in a similar split-dose assay. RESULTS: Inactivation of DNA-PK by wortmannin potentiated radiation-induced cell kill but it did not alter the oscillatory, W-shaped pattern of early radiation response. In contrast, oscillatory radiation response was abolished by 3-aminobenzamide, a reversible inhibitor of enzymes containing a PARP catalytic domain. The oscillatory response was also lacking in PARP-1 knockout mouse 3T3 fibroblasts. CONCLUSION: The results show that PARP-1 plays a key role in the earliest steps of cell response to ionizing radiation with clonogenic ability or growth as endpoint. It is hypothesized that rapid poly(ADP-ribosylation) of target proteins, or recruitment of repair proteins by activated PARP-1 at the sites of DNA damage, bring about rapid chromatin remodelling that may affect the incidence of chromosomal damage upon re-irradiation.     

Poly(ADP-ribose) polymerase,a major determinant of early cell response to ionizing radiation

Purpose : To determine whether DNA-dependent protein kinase (DNA-PK) and poly(ADP-ribose) polymerase (PARP-1) are involved in eliciting the rapid fluctuations of radiosensitivity that have been observed when cells are exposed to short pulses of ionizing radiation. Materials and methods : The effect of DNA-PK and PARP-1 inhibitors on the survival of cells to split-dose irradiation was investigated using Chinese hamster V79 fibroblasts and human carcinoma SQ-20B cells. The responses of PARP-1 proficient and PARP-1 knockout mouse 3T3 fibroblasts were compared in a similar split-dose assay. Results : Inactivation of DNA-PK by wortmannin potentiated radiation-induced cell kill but it did not alter the oscillatory, W-shaped pattern of early radiation response. In contrast, oscillatory radiation response was abolished by 3-aminobenzamide, a reversible inhibitor of enzymes containing a PARP catalytic domain. The oscillatory response was also lacking in PARP-1 knockout mouse 3T3 fibroblasts. Conclusion : The results show that PARP-1 plays a key role in the earliest steps of cell response to ionizing radiation with clonogenic ability or growth as endpoint. It is hypothesized that rapid poly(ADP-ribosylation) of target proteins, or recruitment of repair proteins by activated PARP-1 at the sites of DNA damage, bring about rapid chromatin remodelling that may affect the incidence of chromosomal damage upon re-irradiation.     

ATM: the protein encoded by the gene mutated in the radiosensitive syndrome ataxia-telangiectasia.

PURPOSE: To provide an update on the product of the ATM gene mutated in the human genetic disorder ataxia-telangiectasia (A-T). SUMMARY: The product of the ATM gene mutated in the human genetic disorder A-T is a 350 kDa protein that plays a central role in the regulation of a number of cellular processes. It is a member of the phosphatidylinositol 3-kinase superfamily, but is more likely a protein kinase similar to another member of that family, i.e. DNA-dependent protein kinase (DNA-PK). A-T cells and fibroblasts derived from the atm -/- mouse are hypersensitive to ionizing radiation and defective in cell cycle checkpoint control. At present the nature of the lesion in damaged DNA recognized by ATM remains uncertain, but it is evident that a small number of residual strand breaks remain unrepaired in A-T cells, which may well account for the radiosensitivity. On the other hand, considerable progress has been achieved in delineating the role of ATM in cell cycle checkpoint control. Defects are observed at all cell cycle checkpoints in A-T cells post-irradiation. At the G1 /S interface ATM has been shown to play a central role in radiation-induced activation of the tumour suppressor gene product p53. ATM binds to p53 in a complex fashion and activates the molecule in response to breaks in DNA by phosphorylating it at serine 15 close to the N-terminus and by controlling other phosphorylation and dephosphorylation changes on the molecule. This in turn leads to the induction of p21/WAF1 and other p53 effector proteins before inhibition of cyclin-dependent kinase activity and G1 arrest. Emerging evidence supports a direct role for ATM at other cell cycle checkpoints. Other proteins interacting with ATM include c-Abl a protein tyrosine kinase, beta-adaptin an endosomal protein and p21 a downstream effector of p53. The significance of these interactions is currently being investigated. ATM also plays an important role in the regulation and surveillance of meiotic progression. The localization of ATM to both the nucleus and other subcellular organelles implicates this molecule in a myriad of cellular processes. CONCLUSION: ATM is involved in DNA damage recognition and cell cycle control in response to ionizing radiation damage. There is evidence that ATM may also have a more general signalling role.     

Adaptive response and the influence of ageing: effects of low-dose irradiation on cell growth of cultured glial cells

Purpose : To examine the molecular mechanism of radiation adaptive response (RAR) for the growth of cultured glial cells and to investigate the influence of ageing on the response. Materials and methods : Glial cells were cultured from young and older rats (1 and 24 months). RAR for the growth of glial cells conditioned with a low dose of X-rays and subsequently exposed to a high dose of X-rays was examined for cell number and BrdU incorporation. Involvement of the subcellular signalling pathway factors in RAR was investigated using their inhibitors, activators, and mutated and knockout glial cells. Results : RAR was observed in cells cultured from young rats but was not in cells from older animals. The inhibitors of protein kinase C (PKC) and DNA-dependent protein kinase (DNA-PK) or phosphatidylinositol 3-kinase (P13K) suppressed RAR. The activators of PKC instead of low-dose irradiation also caused RAR. Moreover, glial cells cultured from severe combined immunodeficiency (scid) mice (CB-17 scid) and ataxiatelangiectasia mutated (Atm) knockout mice showed no RAR. Conclusion : The results indicated that PKC, ATM, DNAPK and/or P13K were involved in RAR for growth and BrdU incorporation of cultured glial cells and RAR decreased with ageing.     

Adaptive response and the influence of ageing: effects of low-dose irradiation on cell growth of cultured glial cells

PURPOSE: To examine the molecular mechanism of radiation adaptive response (RAR) for the growth of cultured glial cells and to investigate the influence of ageing on the response. MATERIALS AND METHODS: Glial cells were cultured from young and older rats (1 and 24 months). RAR for the growth of glial cells conditioned with a low dose of X-rays and subsequently exposed to a high dose of X-rays was examined for cell number and BrdU incorporation. Involvement of the subcellular signalling pathway factors in RAR was investigated using their inhibitors, activators, and mutated and knockout glial cells. RESULTS: RAR was observed in cells cultured from young rats but was not in cells from older animals. The inhibitors of protein kinase C (PKC) and DNA-dependent protein kinase (DNA-PK) or phosphatidylinositol 3-kinase (PI3K) suppressed RAR. The activators of PKC instead of low-dose irradiation also caused RAR. Moreover, glial cells cultured from severe combined immunodeficiency (scid) mice (CB-17 scid) and ataxia-telangiectasia mutated (Atm) knockout mice showed no RAR. CONCLUSION: The results indicated that PKC, ATM, DNAPK and/or PI3K were involved in RAR for growth and BrdU incorporation of cultured glial cells and RAR decreased with ageing.     

Radiation-induced surface IgG modulation: protein kinase C involvement.

Although radiation-induced loss of surface IgG (s-IgG) expression on murine B cells is known to be dependent on intact energy metabolism and integrity of the cytoskeleton, the exact mechanism of this radiation effect is not known. Evidence reported here shows that inhibition of protein kinase C (PKC) by H-7 impairs the radiation-induced s-IgG modulation, whereas addition of HA-1004, which preferently inhibits c-AMP-dependent protein kinase, shows only minor effects. On the other hand PMA, a PKC activator, mimics the radiation effect, and H-7 but not HA-1004 inhibits the PMA-induced loss of s-IgG expression. Therefore it is suggested that PKC is involved in the modulation of s-IgG induced by irradiation on B cells. The possibility of membrane participation in this event is discussed.