Neuroprotective effects of enriched environment in MPTP-treated SAMP8 mice

Neuroprotective effects of enriched environment (EE) have been well established. Recent study suggests that exposure to EE can protect dopaminergic neurons against MPTP-induced Parkinsonism. After 64 female SAMP8 mice were reared in EE and standard environment (SE) for 3 months, the effects of EE and SE were compared on behavioural change, tyrosine hydroxylase (TH) immunoreaction positive neuron and dopaminetransporter (DAT) expression in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-treated SAMP8. EE mice showed decreased spontaneous activity compared with SE mice. But EE+MPTP mice showed less decreased spontaneous activity compared with SE+MPTP mice. Otherwise, EE mice showed increased percentage of entries into the open arms and percentage of time spent in the open arms. Furthermore, EE mice demonstrated reduced neurotoxicity, with less decreased TH mRNA and protein expression in Substantia Nigra (SN) after MPTP administration compared with SE mice. SE mice showed a 53.77% loss of TH-positive neurons, whereas EE mice only showed a 42.28% loss. Moreover, EE mice showed decreased DAT mRNA and protein expression compared with SE mice. These data demonstrate that EE can protect dopaminergic neurons against MPTP-induced neuronal damage, which suggest that the probability of developing Parkinson's disease (PD) may be related to life environment.

Roles of cyclins A and E in induction of centrosome amplification in p53-compromised cells

Abnormal amplification of centrosomes, which occurs frequently in cancers, leads to high frequencies of mitotic defect and chromosome segregation error, profoundly affecting the rate of tumor progression. Centrosome amplification results primarily from overduplication of centrosomes, and p53 is involved in the regulation of centrosome duplication partly through controlling the activity of cyclin-dependent kinase (CDK) 2-cyclin E, a kinase complex critical for the initiation of centrosome duplication. Thus, loss or mutational inactivation of p53 leads to an increased frequency of centrosome amplification. Moreover, the status of cyclin E greatly influences the frequency of centrosome amplification in cells lacking functional p53. Here, we dissected the roles of CDK2-associating cyclins, namely cyclins E and A, in centrosome amplification in the p53-negative cells. We found that loss of cyclin E was readily compensated by cyclin A for triggering the initiation of centrosome duplication, and thus the centrosome duplication kinetics was not significantly altered in cyclin E-deficient cells. It has been shown that cells lacking functional p53, when arrested in either early S-phase or late G(2) phase, continue to reduplicate centrosomes, resulting in centrosome amplification. In cells arrested in early S phase, cyclin E, but not cyclin A, is important in centrosome amplification, whereas in the absence of cyclin E, cyclin A is important for centrosome amplification. In late G(2)-arrested cells, cyclin A is important in centrosome amplification irrespective of the cyclin E status. These findings advance our understandings of the mechanisms underlying the numeral abnormality of centrosomes and consequential genomic instability associated with loss of p53 function and aberrant expression of cyclins E and A in cancer cells.

Guanine tetrad and palindromic sequence play critical roles in the RNA dimerization of bovine foamy virus

Retroviruses are unique in having a diploid genome. However, the RNA sequences and structures that link the two RNA molecules are different. To identify the dimer linkage site of bovine foamy virus (BFV), complementary DNAs were used to interfere with RNA dimerization of BFV. We found that two sites, designated SI and SII, within a 53-base RNA fragment, were essential for BFV dimerization in vitro. SI consists of a potential guanine tetrad (GGGGC), which overlaps the primer binding site, while SII contains 15 nucleotides including a palindromic sequence, UCCCUAGGGA. Masking either of the sites completely abolished RNA dimer formation. Furthermore, a deletion of SII was introduced into a BFV infectious DNA clone; we found that deletion of SII significantly increased expression of BFV transactivator Borf-1. Interestingly, we also found that this deletion abolished viral infectivity. These results suggest that dimerization might play a unique role in the BFV life cycle.

Neural precursor cells possess multiple p53-dependent apoptotic pathways

Neural precursor cells (NPCs) are markedly sensitive to apoptotic insults. p53-Dependent transcriptional activation of proapoptotic genes has been hypothesized to regulate NPC death in response to DNA damage. Recent studies of non-NPCs have also indicated that p53 may directly interact with Bcl-2 molecules and thereby regulate death independently of transcription. The contribution of transcription-independent p53 activation in NPC death has not been characterized. In this study, we found that apoptosis caused by chemotherapeutic agents in NPCs required p53 expression and new macromolecular synthesis. In contrast, NPC death induced by staurosporine, a broad kinase inhibitor, is regulated by p53 in the absence of macromolecular synthesis. The apoptosis effector molecules Bax and Bak, Apaf-1, and caspase-9 were shown to be downstream of p53 in both pathways. These findings indicate that p53 is in a unique position to regulate at least two distinct signaling portals that activate the intrinsic apoptotic death pathway in NPCs.

Filamin A mutations cause periventricular heterotopia with Ehlers-Danlos syndrome

OBJECTIVE

To define the clinical, radiologic, and genetic features of periventricular heterotopia (PH) with Ehlers-Danlos syndrome (EDS).

METHODS

Exonic sequencing and single stranded conformational polymorphism (SSCP) analysis was performed on affected individuals. Linkage analysis using microsatellite markers on the X-chromosome was performed on a single pedigree. Western blotting evaluated for loss of filamin A (FLNA) protein and Southern blotting assessed for any potential chromosome rearrangement in this region.

RESULTS

The authors report two familial cases and nine additional sporadic cases of the EDS-variant form of PH, which is characterized by nodular brain heterotopia, joint hypermobility, and development of aortic dilatation in early adulthood. MRI typically demonstrated bilateral nodular PH, indistinguishable from PH due to FLNA mutations. Exonic sequencing or SSCP analyses of FLNA revealed a 2762 delG single base pair deletion in one affected female. Another affected female harbored a C116 single point mutation, resulting in an A39G change. A third affected female had a 4147 delG single base pair deletion. One pedigree with no detectable exonic mutation demonstrated positive linkage to the FLNA locus Xq28, an affected individual in this family also had no detectable FLNA protein, but no chromosomal rearrangement was detected.

CONCLUSION

These results suggest that the Ehlers-Danlos variant of periventricular heterotopia (PH), in part, represents an overlapping syndrome with X-linked dominant PH due to filamin A mutations.

Decreased efficiency of gamma-ray-induced DNA double-strand break rejoining in malignant transformants of human bronchial epithelial cells generated by alpha-particle exposure

PURPOSE

To investigate the cytogenetic changes and DNA double-strand break (DSB) rejoining of transformed cell lines generated from human bronchial epithelial cells by alpha-particle exposure.

MATERIALS AND METHODS

Transformed cell lines were derived from the HPV 18-immortalized human bronchial epithelial cell line BEP2D generated by 1.5 Gy of alpha-particles emitted by a 238Pu source. Two cell lines, BERP35T1 and BERP35T4, were investigated. Karyotypes were analyzed by trypsin/Giemsa banding. Cell survival was estimated by colony assay. PFGE was used to detect the DNA DSB. mRNA expression was analyzed by RT-PCR.

RESULTS

Abnormal chromosomes 2 and 12 with elongated long arm and deletions of chromosomes 2, 12, 13 and 17 were observed in the transformed cell lines. BERP35T4 showed a much higher proportion of polyploid cells (40.5%) compared with parental BEP2D cells and the BERP35TI cell line (5%). BERP35T1 and BERP35T4 showed a markedly lower capacity for rejoining of gamma-ray-induced DNA DSB and increased radiosensitivity compared with parental BEP2D cells. The analysis of mRNA levels revealed a 2.5- to 6.5-fold down-regulated expression of the DNA repair genes XRCC-2, XRCC-3 and Ku80 in BERP35T1 and BERP35T4 cells.

CONCLUSION

The karyotypic changes of chromosomes 2, 12, 13 and 17 and the deficiency of DSB rejoining could be related to the malignant transformation processing of BEP2D cells initiated by alpha-particle exposure.

Identification of a cellular protein that interacts and synergizes with the RTA (ORF50) protein of Kaposi's sarcoma-associated herpesvirus in transcriptional activation

Lytic reactivation of Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8, from latency requires transcriptional transactivation by the viral protein RTA encoded by the ORF50 gene. Very little is known about how RTA functions and the cellular factors that may be involved in its transactivation function. Using the yeast two-hybrid system, we have identified a human cellular protein that can interact with KSHV RTA. The cellular protein, referred to as the human hypothetical protein MGC2663 by GenBank, is encoded by human chromosome 19. This protein is 554 amino acids (aa) in size and displays sequence similarity with members of the Krueppel-associated box-zinc finger proteins (KRAB-ZFPs). MGC2663 expression could be detected in all primate cell lines tested, and its expression level was neither stimulated nor inhibited by RTA. MGC2663 specifically synergizes with RTA to activate viral transcription, and overexpression of MGC2663 in the presence of RTA further enhances RTA transactivation of several viral promoters that were identified as targets for RTA. Coimmunoprecipitation and pull-down assays further demonstrated that MGC2663 interacts with RTA both in vivo and in vitro, and the N-terminal 273 aa of KSHV RTA and the potential zinc finger domain of MGC2663 are required for their interaction. Our results indicate that this novel human cellular protein, MGC2663, named K-RBP (KSHV RTA binding protein) due to its RTA binding feature, specifically interacts with the KSHV RTA protein and functions as a cellular RTA cofactor to activate viral gene expression. Though its normal cellular function needs to be further studied, K-RBP may play a significant role in mediating RTA transactivation in vivo.

Expression of cyclins E1 and E2 during mouse development and in neoplasia

Cyclin E1 (formerly called cyclin E) and the recently described cyclin E2 belong to the family of E-type cyclins that operate during the G(1)/S phase progression in mammalian cells. The two E-cyclins share a catalytic partner, cyclin-dependent kinase 2 (CDK2), and activate their associated kinase activities at similar times during cell cycle progression. Despite these similarities, it is unknown whether the two proteins perform distinct functions, or, alternatively, they control S-phase entry of different cell types in a tissue-specific fashion. To start addressing in vivo functions of E-cyclins, we determined the expression pattern of cyclins E1 and E2 during normal mouse development. We found that the two E-cyclins showed very similar patterns of expression; both were expressed within the proliferating compartment during embryo development. Analyses of cells and tissues lacking members of the retinoblastoma (pRB) family of proteins revealed that the expression of both cyclins is controlled in a pRB-dependent, but p107- and p130-independent fashion, likely through the pRB-dependent E2F transcription factors. We also found that cyclins E1 and E2 are expressed at high levels in mouse breast tumors driven by the Myc oncogene. Last, we found that cyclin E2 is overexpressed in approximately 24% of analyzed human mammary carcinomas. Collectively these findings suggest that the expression of cyclins E1 and E2 is governed by similar molecular circuitry.

Chlamydia pneumoniae exacerbates aortic inflammatory foci caused by murine cytomegalovirus infection in normocholesterolemic mice

Inflammatory foci induced by murine cytomegalovirus infection in normocholesterolemic mice were present temporarily in the aortic wall, but some of these foci developed into advanced lesions that persisted late after infection. The early foci induced by virus infection were significantly exacerbated following a single inoculation with Chlamydia pneumoniae.

The influence of human single chain inteleukin-12 gene transduction on the biological behavior of hepatoma 7721 cells

OBJECTIVE

To investigate the anti-tumor effects of human single chain interleukin-12 (hscIL-12).

METHOD

pcDNA/hscIL-12 recombinant was transfected into human hepatic carcinoma cells (7721 cells) by lipofectin method. The 7721/hscIL-12 cells which secrete hscIL-12 stably, were obtained via G418 selection, and in vitro the influence of hscIL-12 gene transduction on the growth of tumor cells was evaluated by cell cycle analysis. In vivo, genetically engineered 7721 cells (7721/hscIL-12, 7721/pcDNA) and parental cells were implanted into BALB/c nude mice, respectively. 7721/pcDNA and 7721/hscIL-12 groups were divided into two sub-groups on day 8: one was administered with hPBL twice, 6 days at interval; the other was given equal volume of PBS. Mice were sacrificed on day 26, and spleens and tumors were taken out for histologic assay.

RESULTS

hscIL-12 produced stably by 7721/hscIL-12 cells had bioactivity, and it was proved by Western blot, immunocytochemistry, and in situ hybridization. In vitro, compared with 7721 and 7721/pcDNA, the 7721/hscIL-12 grew much more slowly. FACS assay showed apparent G1 arrest of 7721/hscIL-12 cells. In animal experiment, on day 8 after inoculation, the tumors of 7721 and 7721/pcDNA group were up to 5 approximately 7 mm, while those of 7721/hscIL-12 group were 2 approximately 4 mm. When treated with hPBL, the tumor of 7721/hscIL-12 group disappeared completely. Histologically, the tumors from 7721/hscIL-12 without hPBL treatment had numerous lymphocyte infiltration, the tumor cells displayed depression looking, atrophy, focal necrosis and apoptosis, whereas the tumors of 7721 and 7721/pcDNA groups grew thrivingly.

CONCLUSION

hscIL-12 transduced 7721 cells could induced significant antitumor immune response which resulted in tumor regression totally when the hPBL was inoculated, and also hscIL-12 has certain effects on mice immune system. These findings suggest that hscIL-12 and hscIL-12 gene therapy might have promising prospects in clinical application.

Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8 ORF50 gene product contains a potent C-terminal activation domain which activates gene expression via a specific target sequence

The ART (Activator of Replication and Transcription) protein of Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus-8 (HHV-8), is encoded by the ORF50 gene. It is expressed as an immediate-early gene and plays a crucial role in the transition between latency and productive infection. HHV-8 ART is a transcriptional transactivator which can up-regulate viral gene expression. Transient expression assays showed that ART strongly activated ORF57 and K8 promoter-directed gene expression in both CV-1 and BJAB cells. The ART target site was mapped to a 40-bp region compassing nt 81904 to 81943 on the ORF57 promoter. When linked upstream to a heterologous SV40 promoter, this region by itself was able to confer ART responsiveness. This 40-bp segment contains a 16-bp consensus sequence which is also found in the K8 promoter region located between nt 74769 to 74784. Deletion of the fragment including this 16-bp consensus abrogated the ART responsiveness of the K8 promoter. The role of this 16-bp consensus in ART transactivation was further supported by site-directed mutagenesis. Mutations of the conserved nucleotides within the 16-bp consensus in the ORF57 promoter dramatically impaired its responsiveness to ART. Fusion protein analysis with chimeric proteins containing the DNA binding domain of yeast transactivator Gal4 (residues 1 to 147) and different ART segments defined an acidic C-terminal region (amino acids [aa] 527 to 634) as a potent activator. Deletions of this activation domain in the ART protein resulted in a decrease or loss of its ability to activate ORF57 and K8 promoters containing the ART responsive element in transfected cells. How the ART activation domain activates ORF57 and K8 gene expression through the 16-bp consensus sequence remains to be determined.

Dysregulation of lymphocyte interleukin-12 receptor expression in Sézary syndrome

Initial phase I and II clinical trials with recombinant human interleukin-12 have demonstrated the therapeutic efficacy of this cytokine in early stage cutaneous T cell lymphoma as compared with more advanced stages such as the leukemic Sézary syndrome. In an effort to optimize the use of recombinant human interleukin-12, using flow cytometry we studied the regulation of the interleukin-12 receptor beta1 (high affinity chain) and beta2 (chain necessary for interleukin-12 signal transduction) on normal volunteer CD4+ and CD8+ T cells and CD4+ and CD8+ cells from eight patients with different degrees of leukemic involvement with Sézary syndrome. The beta1 chain was not readily detectable on resting normal and T cells from Sézary patients, but expression was induced following T cell activation with phytohemagglutinin. Similarly, the beta2 chain was not detectable on resting normal volunteer T cells, but could be induced following phytohemagglutinin stimulation. Moreover, the beta2 chain on normal volunteer T cells was markedly upregulated following short-term culture with interferon-gamma or recombinant human interleukin-12. CD8+ T cells routinely exhibited a greater expression of beta2 than did CD4+ T cells. In marked contrast, both CD4+ and CD8+ T cells from patients with Sézary syndrome and a high tumor cell burden (> 50% circulating atypical Sézary T cells) failed to express the beta2 chain under any culture conditions. Although, culture with anti-interleukin-10 also markedly increased beta2 expression on normal volunteer T cells, this failed to induce expression on either CD4+ or CD8+ T cells from Sézary patients and a high tumor burden. Investigation of patients with Sézary syndrome and a low tumor cell burden (< 15% circulating Sézary T cells) revealed a pattern of beta2 expression that was intermediate between advanced Sézary syndrome and normal volunteers. Both CD4+ and CD8+ peripheral blood T cells from these earlier stage patients were induced to express the beta2 chain, although at a lower frequency of positivity than T cells from normals, following culture with phytohemagglutinin, interferon-gamma, recombinant human interleukin-12, or anti-interleukin-10. These results indicate that short-term culture with interferon-gamma and recombinant human interleukin-12 potently upregulates beta2 chain expression on T cells from normal volunteers, whereas a similar, but less marked effect occurs on T cells from Sézary syndrome patients and a low circulating tumor cell burden. In contrast, the beta2 chain appears to be suppressed on both CD4+ and CD8+ T cells from Sézary patients with a heavy circulating tumor cell burden and it is not induced by interferon-gamma or recombinant human interleukin-12. Therefore, recombinant human interleukin-12 is likely to be most effective for early stage cutaneous T cell lymphoma due to a greater display of beta2 receptors on responding CD8+ anti-tumor cytotoxic T cells.