Ultrasound-activated microbubbles as a novel intracellular drug delivery system for urinary tract infection.

The development of new modalities for high-efficiency intracellular drug delivery is a priority for a number of disease areas. One such area is urinary tract infection (UTI), which is one of the most common infectious diseases globally and which imposes an immense economic and healthcare burden. Common uropathogenic bacteria have been shown to invade the urothelial wall during acute UTI, forming latent intracellular reservoirs that can evade antimicrobials and the immune response. This behaviour likely facilitates the high recurrence rates after oral antibiotic treatments, which are not able to penetrate the bladder wall and accumulate to an effective concentration. Meanwhile, oral antibiotics may also exacerbate antimicrobial resistance and cause systemic side effects. Using a human urothelial organoid model, we tested the ability of novel ultrasound-activated lipid microbubbles to deliver drugs into the cytoplasm of apical cells. The gas-filled lipid microbubbles were decorated with liposomes containing the non-cell-permeant antibiotic gentamicin and a fluorescent marker. The microbubble suspension was added to buffer at the apical surface of the bladder model before being exposed to ultrasound (1.1 MHz, 2.5 Mpa, 5500 cycles at 20 ms pulse duration) for 20 s. Our results show that ultrasound-activated intracellular delivery using microbubbles was over 16 times greater than the control group and twice that achieved by liposomes that were not associated with microbubbles. Moreover, no cell damage was detected. Together, our data show that ultrasound-activated microbubbles can safely deliver high concentrations of drugs into urothelial cells, and have the potential to be a more efficacious alternative to traditional oral antibiotic regimes for UTI. This modality of intracellular drug delivery may prove useful in other clinical indications, such as cancer and gene therapy, where such penetration would aid in treatment.

Physio-chemical and antibacterial characteristics of pressure spun nylon nanofibres embedded with functional silver nanoparticles.

A novel and facile approach to prepare hybrid nanoparticle embedded polymer nanofibers using pressurised gyration is presented. Silver nanoparticles and nylon polymer were used in this work. The polymer solution's physical properties, rotating speed and the working pressure had a significant influence on the fibre diameter and the morphology. Fibres in the range of 60-500nm were spun using 10wt.%, 15wt.% and 20wt.% nylon solutions and these bead-free fibres were processed under 0.2MPa and 0.3MPa working pressure and a rotational speed of 36,000rpm. 1-4wt.% of Ag was added to these nylon solutions and in the case of wt.% fibres in the range 50-150nm were prepared using the same conditions of pressurised gyration. Successful incorporation of the Ag nanoparticles in nylon nanofibres was confirmed by using a combination of advanced microscopical techniques and Raman spectrometry was used to study the bonding characteristics of nylon and the Ag nanoparticles. Inductively coupled plasma mass spectroscopy showed a substantial concentration of Ag ions in the nylon fibre matrix which is essential for producing effective antibacterial properties. Antibacterial activity of the Ag-loaded nanofibres shows higher efficacy than nylon nanofibres for Gram-negative Escherichia coli and Pseudomonas aeruginosa microorganisms, and both Ag nanoparticles and the Ag ions were found to be the reason for enhanced cell death in the bacterial solutions.

The viral death effector Apoptin reveals tumor-specific processes.

Several natural proteins, including the cellular protein TRAIL and the viral proteins E4orf4 and Apoptin, have been found to exert a tumor-preferential apoptotic activity. These molecules are potential anti-cancer agents with direct clinical applications. Also very intriguing is their possible utility as sensors of the tumorigenic phenotype. Here, we focus on Apoptin, discussing recent research that has greatly increased our understanding of its tumor-specific processes. Apoptin, which kills tumor cells in a p53- and Bcl-2-independent, caspase-dependent manner, is biologically active as a highly stable, multimeric complex consisting of 30 to 40 monomers that form distinct superstructures upon binding cooperatively to DNA. In tumor cells, Apoptin is imported into the nucleus prior to the induction of apoptosis; this contrasts with the situation in primary or low-passage normal cell cultures where nuclear translocation of Apoptin is rare and inefficient. Apoptin contains two autonomous death-inducing domains, both of which exhibit a strong correlation between nuclear localization and killing activity. Nevertheless, forced nuclear localization of Apoptin in normal cells is insufficient to allow induction of apoptosis, indicating that another activation step particular to the tumor or transformed state is required. Indeed, a kinase activity present in cancer cells but negligible in normal cells was recently found to regulate the activity of Apoptin by phosphorylation. However, in normal cells, Apoptin can be activated by transient transforming signals conferred by ectopically expressed SV40 LT antigen, which rapidly induces Apoptin's phosphorylation, nuclear accumulation and the ability to induce apoptosis. The region on LT responsible for conferring this effect has been mapped to the N-terminal J domain. In normal cells that do not receive such signals, Apoptin becomes aggregated, epitope-shielded and is eventually degraded in the cytoplasm. Finally, Apoptin interacts with various partners of the human proteome including DEDAF, Nmi and Hippi, which may help to regulate either Apoptin's activation or execution processes. Taken together, these recent advances illustrate that elucidating the mechanism of Apoptin-induced apoptosis can lead to the discovery of novel tumor-specific pathways that may be exploitable as anti-cancer drug targets.

Human death effector domain-associated factor interacts with the viral apoptosis agonist Apoptin and exerts tumor-preferential cell killing.

Apoptin, a protein from chicken anemia virus without an apparent cellular homologue, can induce apoptosis in mammalian cells. Its cytotoxicity is limited to transformed or tumor cells, making Apoptin a highly interesting candidate for cancer therapy. To elucidate Apoptin's mechanism of action, we have searched for binding partners in the human proteome. Here, we report that Apoptin interacts with DEDAF, a protein previously found to associate with death effector domain (DED)-containing pro-apoptotic proteins, and to be involved in regulation of transcription. Like Apoptin, after transient overexpression, DEDAF induced apoptosis in various human tumor cell lines, but not in primary fibroblasts or mesenchymal cells. DEDAF-induced cell death was inhibited by the caspase inhibitor p35. Together with the reported association of DEDAF with a DED-containing DNA-binding protein in the nucleus and the transcription regulatory activity, our findings may provide a clue for the mechanism of Apoptin's actions in mammalian cells.

Apoptin's functional N- and C-termini independently bind DNA.

Apoptin induces apoptosis specifically in tumour cells, where Apoptin is enriched in the DNA-dense heterochromatin and nucleoli. In vitro, Apoptin interacts with dsDNA, forming large nucleoprotein superstructures likely to be relevant for apoptosis induction. Its N- and C-terminal domains also have cell-killing activity, although they are less potent than the full-length protein. Here, we report that both Apoptin's N- and C-terminal halves separately bound DNA, indicating multiple independent binding sites. The reduced cell killing activity of both truncation mutants was mirrored in vitro by a reduced affinity compared to full-length Apoptin. However, none of the truncation mutants cooperatively bound DNA or formed superstructures, which suggests that cooperative DNA binding by Apoptin is required for the formation of nucleoprotein superstructures. As Apoptin's N- and C-terminal fragments not only share apoptotic activity, but also affinity for DNA, we propose that both properties are functionally linked.

Akt mediates insulin rescue from apoptosis in brown adipocytes: effect of ceramide.

We have recently shown that insulin can rescue serum deprived adipocytes from apoptosis in a PI 3 kinase and MAP kinase dependent manner. This study investigated the contribution of Akt and p70S6-kinase in insulin rescue from two different apoptotic triggers, serum deprivation and ceramide treatment. Insulin rescued serum-deprived immortalized brown adipocytes from apoptosis through phosphatidylinositol (PI) 3-kinase and Akt pathways, but independently of p70S6-kinase, as demonstrated by the use of inhibitors such as LY294002 or Rapamycin, and transfection experiments with dominant-negative constructs of Akt or p85 subunit of PI 3-kinase. A constitutively active Akt construct mimicked the insulin survival effect, decreasing the percentage of hypodiploid cells, the percentage of apoptopic cells and precluding the formation of apoptotic nuclei. We propose that the insulin survival effect on immortalized brown adipocytes is mediated through activation of Akt. However, insulin and EGF failed to rescue brown adipocytes from ceramide-induced apoptosis, as determined by DNA laddering, hypodiploid cells and apoptotic nuclei. Ceramide treatment blunted Akt activity but not PI 3-kinase activity, and insulin and EGF were unable to activate Akt. Ceramide also caused apoptosis in cells transfected with a constitutively active Akt construct, since phosphorylation of Akt was impaired under these experimental conditions. This study suggests that activation of Akt may be an absolute requirement for the survival of brown adipocytes.

Feline leukemia virus envelope sequences that affect T-cell tropism and syncytium formation are not part of known receptor-binding domains.

The envelope protein is a primary pathogenic determinant for T-cell-tropic feline leukemia virus (FeLV) variants, the best studied of which is the immunodeficiency-inducing virus, 61C. We have previously demonstrated that T-cell-tropic, cytopathic, and syncytium-inducing viruses evolve in cats infected with a relatively avirulent, transmissible form of FeLV, 61E. The envelope gene of an 81T variant, which encoded scattered single-amino-acid changes throughout the envelope as well as a 4-amino-acid insertion in the C-terminal half of the surface unit (SU) of envelope, was sufficient to confer the T-cell-tropic, cytopathic phenotype (J. L. Rohn, M. S. Moser, S. R. Gwynn, D. N. Baldwin, and J. Overbaugh, J. Virol. 72:2686-2696, 1998). In the present study, we examined the role of the 4-amino-acid insertion in determining viral replication and tropism of FeLV-81T. The 4-amino-acid insertion was found to be functionally equivalent to a 6-amino-acid insertion at an identical location in the 61C variant. However, viruses expressing a chimeric 61E/81T SU, containing the insertion together with the N terminus of 61E SU, were found to be replication defective and were impaired in the processing of the envelope precursor into the functional SU and transmembrane (TM) proteins. In approximately 10% of cultured feline T cells (3201) transfected with the 61E/81T envelope chimeras and maintained over time, replication-competent tissue culture-adapted variants were isolated. Compensatory mutations in the SU of the tissue culture-adapted viruses were identified at positions 7 and 375, and each was shown to restore envelope protein processing when combined with the C-terminal 81T insertion. Unexpectedly, these viruses displayed different phenotypes in feline T cells: the virus with a change from glutamine to proline at position 7 acquired a T-cell-tropic, cytopathic phenotype, whereas the virus with a change from valine to leucine at position 375 had slower replication kinetics and caused no cytopathic effects. Given the differences in the replication properties of these viruses, it is noteworthy that the insertion as well as the two single-amino-acid changes all occur outside of predicted FeLV receptor-binding domains.

Lymphokines modulate the growth and survival of thymic tumor cells containing a novel feline leukemia virus/Notch2 variant.

Tumorigenesis occurs through a multistep process initiated by genetic lesions and facilitated by endogenous and external growth/survival signals. In many malignancies, specific oncogenic mutations correlate with phenotypic characteristics, inferring lineage-specific pathogenic mechanisms. To characterize these relationships in a unique feline tumor, we studied primary cells and two-cell lines independently-derived from a thymic lymphoma that contained and actively expressed a novel feline leukemia virus (FeLV) recombinant with transduced host Notch2 sequences. All three tumor cell populations contained similar FeLV/Notch2 proviral variants and phenotypically resembled mature thymocytes. Multiple Notch2 transcripts were expressed in the cell lines, including species that correspond to viral genomes and spliced subgenomic viral mRNA. Tumor cell line FeLV/Notch2 virus was packaged into virions; however, the variant was not efficiently transmitted to feline cells in vitro. Primary tumor cells constitutively expressed mRNA for interleukin-4 (IL-4), IL-6 and the p40 subunit of IL-12. Lymphokine mRNA was not detected in established tumor cell lines nor was T-cell growth-promoting activity found in culture supernatants. Exogenous IL-4 enhanced primary tumor cell survival, but inhibited proliferation of the cell lines. Interleukin-4 abrogated hydrocortisone-induced apoptosis in all three populations and had divergent effects on cell line clonogenic colony formation. Exogenous IL-7 and, to a lesser degree, IL-6 also had variable positive effects on the growth and viability of the tumor cell populations. Collectively, these data suggest that thymocytes are susceptible to the transforming potential of dysregulated Notch2 and that thymopoietic factors could, through overlapping and distinct mechanisms, promote the survival and outgrowth of FeLV/Notch2-containing neoplastic cells.

In vivo evolution of a novel, syncytium-inducing and cytopathic feline leukemia virus variant.

Studies of feline leukemia virus (FeLV) have illustrated the importance of the genotype of the infecting virus in determining disease outcome. In FeLV infections, as in other retroviral infections, it is less clear how virus variants that evolve from the transmitted virus affect pathogenesis. We previously reported an analysis of the genotypic changes that occur in the viral envelope gene (env) in cats infected with a prototype transmissible FeLV clone, 61E (J. Rohn, M. Linenberger, E. Hoover, and J. Overbaugh, J. Virol. 68:2458-2467, 1994). In one cat, each variant (81T) had evolved, in addition to scattered amino acid changes, a four-amino-acid insertion with respect to 61E. This insertion was located at the same site in the extracellular envelope glycoprotein where the immunodeficiency-inducing molecular clone 61C possesses a six-amino-acid insertion critical for its pathogenic phenotype, although the sequences of the insertions were distinct. To determine whether acquisition of the four-amino-acid insertion was associated with a change in the replication or cytopathic properties of the virus, we constructed chimeras encoding 81T env genes in a 61E background. One representative chimeric virus, EET(TE)-109, was highly cytopathic despite the fact that it replicated with delayed kinetics in the feline T-cell line 3201 compared to the parental 61E virus. The phenotype of this virus was also novel compared to other FeLVs, including both the parental virus 61E and the immunodeficiency-inducing variant 61C, because infection of T cells was associated with syncytium formation. Moreover, in single-cycle infection assays, the 81T-109 envelope demonstrated receptor usage properties distinct from those of both 61E and 61C envelope. Thus, these studies demonstrate the evolution of a novel T-cell cytopathic and syncytium-inducing FeLV in the host. The 81T virus will be valuable for dissecting the mechanism of T-cell killing by cytopathic variants in the FeLV model.

The opposing roles of the Akt and c-Myc signalling pathways in survival from CD95-mediated apoptosis.

Expression of the proto-oncogene c-myc stimulates cell proliferation in the presence of the appropriate survival factors and triggers apoptosis in their absence; this dual capacity ensures that cell growth is restricted to the correct paracrine environment and is thereby strictly controlled. Recently our laboratory demonstrated that c-Myc-induced apoptosis requires the CD95 death receptor pathway and that insulin-like growth factor (IGF-1) signalling suppresses this killing. To investigate further the links between c-Myc and IGF-1 pathways in CD95-induced apoptosis, we examined the effects of c-Myc and a downstream IGF-1 survival kinase, Akt, on killing mediated by CD95 and its recruited effector proteins (FADD and caspase-8). Here, we show that c-Myc activation does not exacerbate killing induced by FADD or pro-caspase-8, which narrows the point at which c-Myc exerts its action downstream of the interaction of CD95 with its ligand and upstream of FADD. We show further that activated Akt suppresses CD95-induced apoptosis and that Akt exerts its activity at a point downstream of FADD but upstream of caspase-8. These results restrict the possible mechanisms by which CD95-induced apoptosis is modulated by death signals and survival factors.

Viral genetic variation, AIDS, and the multistep nature of carcinogenesis: the feline leukemia virus model.

Feline leukemia virus (FeLV) infection in cats serves as a valuable animal model system for understanding the mechanisms of human diseases such as cancer and immunodeficiency. We have used experimental infection with molecularly cloned viruses to isolate and characterize novel FeLV variants that evolved in vivo and that were associated with the development of thymic lymphoma. One variant, FeLV-81T, contained a mutated envelope gene that conferred cytopathicity, enhanced replication rate, and syncytium induction in feline T cells, and is reminiscent of immunodeficiency-inducing strains of FeLV. Another variant transduced a portion of the feline Notch2 gene, which was expressed as a novel truncated protein in the cell nucleus and which we believe functioned as an oncogene in the development of T cell malignancy. Understanding how FeLV variants that either stimulate or destroy lymphocytes evolve and interrelate during disease progression will help elucidate the mechanisms of retroviral pathogenicity.

Transduction of Notch2 in feline leukemia virus-induced thymic lymphoma.

Feline leukemia virus (FeLV) is thought to induce neoplastic diseases in infected cats by a variety of mechanisms, including the transduction of host proto-oncogenes. While FeLV recombinants that encode cellular sequences have been isolated from tumors of naturally infected animals, the acquisition of an unrelated host gene has never been documented in an experimental FeLV infection. We isolated recombinant FeLV proviruses encoding feline Notch2 sequences from thymic lymphoma DNA of two cats inoculated with the molecularly cloned virus FeLV-61E. Four recombinant genomes were identified, three in one cat and one in the other. Each had similar but distinct transduction junctions, and in all cases, the insertions replaced most of the envelope gene with a region of Notch2 that included the intracellular ankyrin repeat functional domain. The product of the FeLV/Notch2 recombinant provirus was a novel, truncated 65- to 70-kD Notch2 protein that was targeted to the cell nucleus. This virally encoded Notch2 protein, which resembles previously constructed, constitutively activated forms of Notch, was apparently expressed from a subgenomic transcript spliced at the normal envelope donor and acceptor sequences. The data reported here implicate a nuclear, activated Notch2 protein in FeLV-induced leukemogenesis.

In vivo selection of long terminal repeat alterations in feline leukemia virus-induced thymic lymphomas.

To determine what genetic changes are selected in the enhancer sequences of the feline leukemia virus (FeLV) long terminal repeat in cats that develop T cell tumors, we cloned proviral U3 sequences in cats that died with thymic lymphoma following infection with molecularly cloned FeLV. Analysis of the U3 enhancer region revealed single base changes, including point mutations in the core and FLV-1 sequences. Additionally, in clones from two of four cat tumors, portions of the enhancer including Lvb and core were duplicated with respect to the single enhancer unit of the inoculating virus. In contrast, a PCR survey of necropsy DNA samples derived from five cats that did not develop tumors revealed that all retained the single enhancer unit of the infecting virus. These results demonstrate that viruses with duplicated enhancers can be generated and selected after only a single passage in cats, and furthermore, that such viruses may be particularly selected in tumors.

Evolution of feline leukemia virus variant genomes with insertions, deletions, and defective envelope genes in infected cats with tumors.

In order to study retroviral variation, selection, and viral correlates of in vivo pathogenicity, we documented the evolution of feline leukemia virus (FeLV) variants in cats that died with thymic lymphoma after infection with molecularly cloned subgroup A FeLV. Using genomic DNA from cat necropsy samples, we employed PCR to amplify and clone the envelope gene, which is a major determinant of the specific pathogenicity of different FeLV variants. In the envelope gene, mutations encoded scattered amino acid changes that did not cluster into clearly definable variable regions; however, characterization of these terminal variant sequences revealed a predominance of G-to-A and A-to-G nucleotide substitutions. Additionally, some cats harbored variants with recombinant subgroup B-like envelope genes, while the major variant from one cat had a 12-bp insertion in a region previously characterized as an immunodeficiency-inducing determinant. Finally, proviruses from tumor DNA frequently possessed envelope genes predicted to encode a protein truncated in the N-terminal half because of either premature termination codons or deletions ranging from 29 to 1,666 bp. In contrast, all envelope genes cloned from the bone marrow of one cat were predicted to encode full-length envelope product, and only a minority of proviral clones from a cat that did not develop a tumor had defective envelope genes. Thus, in the cat, viruses evolved from subgroup A FeLV that had point mutations, insertions, deletions, or recombinant envelope genes. Furthermore, defective variants were particularly prominent in T-cell tumors.