Antisense approaches for investigating mechanisms of abnormal development

MiR-125b protects against ethanol-induced apoptosis in neural crest cells and mouse embryos by targeting Bak 1 and PUMA

MicroRNAs are a class of small noncoding RNAs that have been implicated in regulation of a broad range of cellular and physiologic processes, including apoptosis. The objective of this study is to elucidate the roles of miR-125b in modulating ethanol-induced apoptosis in neural crest cells (NCCs) and mouse embryos. We found that treatment with ethanol resulted in a significant decrease in miR-125b expression in NCCs and in mouse embryos. We also validated that Bcl-2 antagonist killer 1 (Bak1) and p53-upregulated modulator of apoptosis (PUMA) are the direct targets of miR-125b in NCCs. In addition, over-expression of miR-125b significantly reduced ethanol-induced increase in Bak1 and PUMA protein expression, caspase-3 activation, and apoptosis in NCCs, indicating that miR-125b can modulate ethanol-induced apoptosis by the regulation of Bcl-2 and p53 pathways. Furthermore, microinjection of miR-125b mimic resulted in a significant increase in miR-125b expression and a decrease in the protein expression of Bak1 and PUMA in ethanol-exposed mouse embryos. Up-regulation of miR-125b also significantly reduced ethanol-induced caspase-3 activation and diminished ethanol-induced growth retardation in mouse embryos. This is the first demonstration that miR-125b can prevent ethanol-induced apoptosis and that microinjection of miRNA mimic can prevent ethanol-induced embryotoxicity.

Polymer nanocarriers for the delivery of small fragments of nucleic acids: oligonucleotides and siRNA

The success of the application of new therapeutic methods based on RNA interfering strategies requires the in vivo delivery of active ODN or siRNA down to the intracellular compartment of the target cells. This article aims to review the studies related to the formulation of RNA interfering agents in polymer nanocarriers. It will present the different types of polymer nanocarriers used as well as the biological activity of the resulting ODN and siRNA loaded nanocarriers. As will be explained, the part of the in vitro studies provided useful data about the intracellular delivery of the formulated RNA interfering agents. Investigations performed in vivo have considered animal models of different relevant diseases. Results from these investigations have clearly demonstrated the interest of several polymer nanocarriers tested so far to deliver active RNA interfering effectors in vivo making possible their administration by the intravenous route.

Phenotyping renal leukocyte subsets by four-color flow cytometry: characterization of chemokine receptor expression

To investigate mechanisms of cell-mediated injury in renal inflammatory disease it is critical to determine the surface phenotype of infiltrating renal leukocyte subsets. However, the cell-specific expression of many leukocyte receptors is difficult to characterize in vivo. Here, we report a protocol based on flow cytometry that allows simultaneous characterization of surface receptor expression on different subsets of infiltrating renal leukocytes. The described technique combines an adapted method to prepare single cell suspensions from whole kidneys with subsequent four-color flow cytometry. We recently applied this technique to determine the differential expression of murine chemokine receptors CCR2 and CCR5 on infiltrating renal leukocyte subsets. In this article, we summarize our current findings on the validity of the method as compared with immunohistology and in situ hybridization in two murine models of nonimmune (obstructive nephropathy) and immune-mediated (lupus nephritis) inflammatory renal disease. Flow cytometry analysis revealed an accumulation of CCR5-, but not CCR2-positive lymphocytes in inflamed kidneys, compared to the peripheral blood. Particularly renal CD8+ cells expressed CCR5 (79% in obstructed kidneys, 90% in lupus nephritis). In both models, infiltrating renal macrophages were positive for CCR2 and CCR5. These data corresponded to immunohistological and in situ hybridization results. They demonstrate that flow cytometric analysis of single cell suspensions prepared from inflamed kidneys is a rapid and reliable technique to characterize and quantify surface receptor expression on infiltrating renal leukocyte subsets.

DNA topoisomerase II is essential for preimplantation mouse development

Topoisomerase II (topo II) is an essential enzyme that alters DNA topology. This activity is important for a variety of chromosome functions including DNA replication, transcription, recombination, and chromosome condensation and segregation. Previously we localized topo II in mouse gametes and preimplantation embryos using isoform-specific antibodies demonstrating the presence of the enzyme in oocytes and embryos, but not sperm. To probe functions of topo II during preimplantation development, we treated mouse zygotes with 100 nM teniposide, and assessed embryo morphology and DNA replication. Teniposide blocked cleavage in 69% embryos; the remainder cleaved once but had abnormal nuclei. Teniposide-treated embryos were devoid of topo II immunofluorescence. Teniposide also prevented DNA replication, implicating topo II in this process. Embryos treated with a 2 hr pulse of teniposide recovered and developed to the blastocyst stage, indicating 100 nM teniposide did not induce apoptosis. To more specifically analyze topo IIalpha function, we treated zygotes with topo IIalpha-targeted antisense oligodeoxynucleotides. Most zygotes arrested at the 2-cell stage while controls developed into blastocysts indicating topo IIalpha is essential for preimplantation development. The absence of topo IIalpha, but not beta immunofluorescence in antisense-treated embryos confirms the specificity and impact of the treatment. In addition, topo IIalpha is newly synthesized at the 2-cell stage. These results establish an essential function for topo II in mouse preimplantation embryonic development.

Transient modulation of gene expression in the neurulation staged mouse embryo

Transient modulation of gene expression in the embryo during early organogenesis will allow studies to be conducted that determine tissue- and stage-specific function(s) of genes. To achieve this goal, viral vectors and antisense oligodeoxynucleotides have been used to produce gain-of-function and loss-of-function models. Adenoviral transduction of whole embryos, embryonic heart and vasculature, and primary neural crest cell culture has been reported. The morphological consequences of overexpression or decreasing expression of selected genes have been evaluated using these tools. Gene-teratogen interaction studies have also been performed. The viral vectors appear to be important tools for modulating gene expression and hold great promise for future research.

Expression and role of Bcl-2 in rat blastocysts exposed to high D-glucose

Bcl-2 mRNA expression was detected in rat blastocysts by in situ hybridization. The distribution of mRNA expression was rather heterogenous, with approximately 2% of high-expressing cells. In vitro exposure to 28 mmol/l D-glucose for 24 h resulted in a significant increase in the proportion of these cells compared with control embryos in either 6 mmol/l D-glucose or 28 mmol/l D+L-glucose. Heterogeneity in the expression of Bcl-2 was also observed at the protein level by immunocytochemistry. Exposure to 28 mmol/l D-glucose significantly increased the incidence of chromatin degradation (karyolysis) and nuclear fragmentation (karyorhexis), two nuclear markers of apoptosis in rat blastocysts. When two different antisense oligodeoxynucleotides designed to block Bcl-2 expression were added to 28 mmol/1 D-glucose, the incidence of karyolysis (but not karyorhexis) was increased compared with embryos in 28 mmol/l D-glucose alone. These data suggest that Bcl-2 is involved in the protective response against the induction of karyolysis in blastocysts on their exposure to high concentrations of D-glucose in vitro, whereas karyorhexis appears to result from the activation of an intracellular pathway that is independent of Bcl-2.

Differentiation induction subtraction hybridization (DISH): a strategy for cloning genes displaying differential expression during growth arrest and terminal differentiation

Human cancers often display aberrant patterns of differentiation. By appropriate chemical manipulation, specific human cancers, such as human melanoma, leukemia and neuroblastoma, can be induced to lose growth potential irreversibly and terminally differentiate. Treatment of HO-1 human melanoma cells with a combination of recombinant human fibroblast interferon (IFN-beta) and the antileukemic compound mezerein (MEZ) results in irreversible growth arrest, a suppression in tumorigenic properties and terminal cell differentiation. A potential mechanism underlying these profound changes in cancer cell physiology is the activation of genes that can suppress the cancer phenotype and/or the inactivation of genes that promote the cancer state. To define the repertoire of genes modulated as a consequence of induction of growth arrest and terminal differentiation in human melanoma cells, we are using a differentiation induction subtraction hybridization (DISH) approach. A subtracted cDNA library, differentiation inducer treated cDNAs minus uninduced cDNAs, was constructed that uses temporally spaced mRNAs isolated from HO-1 cells treated with IFN-beta+MEZ. Approximately 400 random clones were isolated from the subtracted DISH library and analyzed by reverse Northern and Northern blotting approaches. These strategies resulted in the identification and cloning of both 30 known and 26 novel cDNAs displaying elevated expression in human melanoma cells induced to growth arrest and terminally differentiate by treatment with IFN-beta+MEZ. The DISH scheme and the genes presently identified using this approach should provide a framework for delineating the molecular basis of growth regulation, expression of the transformed phenotype and differentiation in melanoma and other cancers.

Beta1 integrin antisense oligodeoxynucleotides: utility in controlling osteoclast function

The involvement of beta1 integrins in osteoclast function has been investigated by utilising an antisense oligodeoxynucleotide (ODN) approach. 18-mer antisense and control phosphorothioate ODNs were made to a conserved internal region of beta1 integrin sequence (nucleotide positions 1634-1651 of the human beta1 fibronectin receptor). These were tested on rabbit osteoclasts for anti-adhesive and resorptive effects mediated by alphaVbeta3 and alpha2beta1, the major integrins of osteoclasts. Antisense, but not control, beta1 ODNs inhibited osteoclast adhesion to collagen-coated glass (by up to 70%), but not to glass coated with vitronectin, fibronectin or fibrinogen. Adhesion to dentine and subsequent resorption were also inhibited (up to 60%) in a sequence-specific manner. The mechanism of action was verified using both a melanoma cell line, DX3, which expresses multiple integrins at high level including alphaVbeta3 and alpha2beta1, and in a rabbit osteoclast marrow culture (BMC) system. Exposure of DX3 cells to antisense ODN for up to 48 hours reduced adhesion to FCS- and collagen-coated glass, and concomitantly inhibited beta1 protein expression assessed by FACS and Western blot analysis; expression of other integrin subunits, alphaV and beta3, was unaffected. Similarly, the beta1 protein levels in the BMC were reduced by > 75% without any effect on actin expression. These data reveal the utility of antisense ODNs in exploring osteoclast biology and further define the functional role of osteoclastic beta1 integrin(s).