A Kaposi's sarcoma-associated herpesvirus-encoded cytokine homolog (vIL-6) activates signaling through the shared gp130 receptor subunit

The present studies analyzed the biologic activity of a gene product (vIL-6) encoded by the recently discovered Kaposi's sarcoma-associated herpesvirus (KSHV) bearing 24.8% amino acid identity with human interleukin-6 (huIL-6). Based on this similarity, we hypothesized that this viral homolog might trigger the JAK/STAT pathway, which typically is engaged by IL-6 and other cytokines. Activation of receptor-associated Janus tyrosine kinases (JAKs) results in the subsequent phosphorylation of signal transducers and activators of transcription (STATs) leading to nuclear entry and transcriptional regulation of target genes. Treatment of HepG2 cells with culture medium containing recombinant KSHV-encoded vIL-6 led to rapid induction of JAK1 phosphorylation and a nuclear DNA-binding activity found to contain STAT1 and STAT3. An antibody to the IL-6 receptor (IL-6R) alpha subunit effectively neutralized the response to huIL-6 but failed to block STAT activation by vIL-6. In contrast, an antibody reactive with the gp130 subunit of IL-6R abrogated signaling of both responses. Moreover, a transfected cell line expressing human gp130 without IL-6Ralpha exhibited a robust response to vIL-6 but not to huIL-6. These results demonstrate that KSHV encodes a cytokine that activates specific JAK/STAT signaling via interactions with the gp130 signal transducing subunit independently of the IL-6Ralpha chain. This activity may have an impact on gp130-mediated signaling in response to native cytokines and thereby influence disease pathogenesis upon KSHV infection.

Singlet oxygen generation by novel NIR BODIPY dyes

Five novel near-infrared BODIPY dyes were prepared for improved singlet oxygen generation using thiophene and bromine. Theoretical, optical, photostable, and singlet oxygen generation characteristics of these dyes were assessed. Predicted excitation energies by TDDFT calculations were in good agreement (ΔE ≈ 0.06 eV) with experimental data. All five dyes showed both excitation and emission in the NIR range. In particular, two dyes having sulfur and bromine atoms showed efficient singlet oxygen generation with high photostability.

An antagonist peptide-EPO receptor complex suggests that receptor dimerization is not sufficient for activation

Dimerization of the erythropoietin (EPO) receptor (EPOR), in the presence of either natural (EPO) or synthetic (EPO-mimetic peptides, EMPs) ligands is the principal extracellular event that leads to receptor activation. The crystal structure of the extracellular domain of EPOR bound to an inactive (antagonist) peptide at 2.7 A resolution has unexpectedly revealed that dimerization still occurs, but the orientation between receptor molecules is altered relative to active (agonist) peptide complexes. Comparison of the biological properties of agonist and antagonist EMPs with EPO suggests that the extracellular domain orientation is tightly coupled to the cytoplasmic signaling events and, hence, provides valuable new insights into the design of synthetic ligands for EPOR and other cytokine receptors.

Podophyllotoxin derivatives: current synthetic approaches for new anticancer agents

Podophyllotoxin is an antimitotic natural product. Its inhibitory activity on cell growth led to the development of the clinically valuable anticancer agents, etoposide, teniposide and the water-soluble prodrug, etoposide phosphate. The cytotoxic mechanism of these drugs is the inhibition of topoisomerase II, unlike the lead compound which inhibits mitosis. Through extensive structure-activity relationship studies, several potential drug candidates were synthesized such as GL-331, TOP 53, NK611, and azatoxin. Recently, more complex and diverse analogues have been synthesized either to get more potent compounds or to overcome drug resistance. At the same time, a number of prodrug approaches have been tried to enhance the tumor selectivity or to increase the aqueous solubility. The prodrugs can release cytotoxic etoposide through the actions of hydrolysis, enzymes or catalytic antibodies. More sophisticated prodrug strategies have been applied in etoposide and these produced some interesting results. In this review, the current research trends in the design of new derivatives will be covered with a brief introduction of podophyllotoxin and related analogues.

Mechanistic studies of the tellurium(II)/tellurium(IV) redox cycle in thiol peroxidase-like reactions of diorganotellurides in methanol

Di-n-hexyl telluride (2), di-p-methoxyphenyl telluride (3), and (S)-2-(1-N,N-dimethylaminoethyl)phenyl phenyl telluride (4) catalyzed the oxidation of PhSH to PhSSPh with H(2)O(2) in MeOH. Telluride 2 displayed greater rate acceleration than the diaryltellurides 3 and 4 as determined by the initial velocities, v(0), for the rate of appearance of PhSSPh determined at 305 nm by stopped-flow spectroscopy. Rate constants for the oxidation of tellurides 2-4 (k(ox)), rate constants for the introduction of PhSH as a ligand to the Te(IV) center (k(PhSH)) of oxidized tellurides 5-7, and thiol-independent (k(1)) and thiol-dependent (k(2)) rate constants for reductive elimination at Te(IV) in oxidized tellurides 5-7 were determined using stopped-flow spectroscopy. Oxidation of the Te atom of the electron-rich dialkyl telluride 2 was more rapid than oxidation of diaryl tellurides 3 and 4. The dimethylaminoethyl substituent of 4, which acts as a chelating ligand to Te(IV), did not affect k(ox). Values of k(PhSH) for the introduction of PhSH to oxidized dialkyl tellurane 5 and oxidized diaryl tellurane 6 were comparable in magnitude, while the chelating dimethylaminoethyl ligand of oxidized telluride 7 diminished k(PhSH) by a fator of 10(3). Reductive elimination by both first-order, thiol-independent (k(1)) and second-order, thiol-dependent (k(2)) pathways was slower from dialkyl Te(IV) species derived from 2 than from diaryl Te(IV) species derived from 3. The chelating dimethylaminoethyl ligand of Te(IV) species derived from 4 diminished k(1) by a factor of 50 and k(2) by a factor of 3 (relative to the 3-derived species).

Far-Red Light-Activatable Prodrug of Paclitaxel for the Combined Effects of Photodynamic Therapy and Site-Specific Paclitaxel Chemotherapy

Paclitaxel (PTX) is one of the most useful chemotherapeutic agents approved for several cancers, including ovarian, breast, pancreatic, and nonsmall cell lung cancer. However, it causes systemic side effects when administered parenterally. Photodynamic therapy (PDT) is a new strategy for treating local cancers using light and photosensitizer. Unfortunately, PDT is often followed by recurrence due to incomplete ablation of tumors. To overcome these problems, we prepared the far-red light-activatable prodrug of PTX by conjugating photosensitizer via singlet oxygen-cleavable aminoacrylate linker. Tubulin polymerization enhancement and cytotoxicity of prodrugs were dramatically reduced. However, once illuminated with far-red light, the prodrug effectively killed SKOV-3 ovarian cancer cells through the combined effects of PDT and locally released PTX. Ours is the first PTX prodrug that can be activated by singlet oxygen using tissue penetrable and clinically useful far-red light, which kills the cancer cells through the combined effects of PDT and site-specific PTX chemotherapy.

Long-term memory and synapse-like dynamics in two-dimensional nanofluidic channels

Fine-tuned ion transport across nanoscale pores is key to many biological processes, including neurotransmission. Recent advances have enabled the confinement of water and ions to two dimensions, unveiling transport properties inaccessible at larger scales and triggering hopes of reproducing the ionic machinery of biological systems. Here we report experiments demonstrating the emergence of memory in the transport of aqueous electrolytes across (sub)nanoscale channels. We unveil two types of nanofluidic memristors depending on channel material and confinement, with memory ranging from minutes to hours. We explain how large time scales could emerge from interfacial processes such as ionic self-assembly or surface adsorption. Such behavior allowed us to implement Hebbian learning with nanofluidic systems. This result lays the foundation for biomimetic computations on aqueous electrolytic chips.

Chromosomal deletion complexes in mice by radiation of embryonic stem cells

Chromosomal deletions ("deficiencies') are powerful tools in the genetic analysis of complex genomes. They have been exploited extensively in Drosophila melanogaster, an organism in which deficiencies can be efficiently induced and selected. Spontaneous deletions in humans have facilitated the dissection of phenotypes in contiguous gene syndromes and led to the positional cloning of critical genes. In mice, deletion complexes created by whole animal irradiation experiments have enabled a systematic characterization of functional units along defined chromosomal regions. However, classical mutagenesis in mice is logistically impractical for generating deletion sets on a genome-wide scale. Here, we report a high-throughput method for generating radiation-induced deletion complexes at defined regions in the genome using ES cells. Dozens of deletions of up to several centiMorgans, encompassing a specific locus, can be created in a single experiment and transmitted through the germline. The ability to rapidly create deletion complexes along chromosomes will facilitate systematic functional analyses of the mammalian genome.

Core-modified porphyrins. Part 4: Steric effects on photophysical and biological properties in vitro

21,23-Dithiaporphyrins (2-10) were designed and prepared as analogues of 5,20-diphenyl-10,15-bis(4-carboxylatomethoxy)phenyl-21,23-dithiaporphyrin (1) to examine the impact of steric bulk at the 5- and 20-meso positions as well as the impact of symmetry. Changes at the meso positions had minimal impact on the UV-vis-near-IR absorption spectra, quantum yields for the generation of singlet oxygen, and quantum yields for fluorescence and some impact on values of the octanol/water partition coefficient. Of the compounds 1-10, 5-phenyl-20-(2-thienyl)-10,15-bis-(4-carboxylatomethoxy-phenyl)-21,23-dithiaporphyrin (3) showed the greatest phototoxicity toward cultured R3230AC cells, with 68% cell kill at 1 x 10(-7)M and irradiation with 5J cm(-2) of 350-750 nm light. Results in this study suggest that smaller substituents on the meso ring and less symmetrical compounds are more effective as photosensitizers than compounds with two bulky substituents at adjoining meso sites and a higher symmetry. The mitochondria appear to be involved in the process of phototoxicity as determined by the inhibition of whole cell cytochrome c oxidase activity in cells treated with 3 and light. No impact upon mitochondrial cytochrome c oxidase activity was observed in cells treated with 3 and no light. Fluorescence microscopy studies suggest that the mitochondria are not initial sites of accumulation of 3.

Regulatory circuit of PKM2/NF-κB/miR-148a/152-modulated tumor angiogenesis and cancer progression

Upregulation of the embryonic M2 isoform of pyruvate kinase (PKM2) emerges as a critical player in the cancer development and metabolism, yet the underlying mechanism of PKM2 overexpression remains to be elucidated. Here we demonstrate that IGF-1/IGF-IR regulates PKM2 expression by enhancing HIF-1α-p65 complex binding to PKM2 promoter. PKM2 expression is regulated by miR-148a/152 suppression. PKM2 directly interacts with NF-κB p65 subunit to promote EGR1 expression for regulating miR-148a/152 feedback circuit in normal cells, but not in cancer cells because of the DNA hypermethylation of miR-148a and miR-152 gene promoters. The silencing of miR-148a/152 contributes to the overexpression of PKM2, NF-κB or/and IGF-IR in some cancer cells. We show that disruption of PKM2/NF-κB/miR-148a/152 feedback loop can regulate cancer cell growth and angiogenesis, and is also associated with triple-negative breast cancer (TNBC) phenotype, which may have clinical implication for providing novel biomarker(s) of TNBC and potential therapeutic target(s) in the future.

Heteromerization of the gammac chain with the interleukin-9 receptor alpha subunit leads to STAT activation and prevention of apoptosis

Interleukin-9 (IL-9) is a cytokine with pleiotropic effects on mast cell and T cell lines. It exerts its effects through the IL-9R complex consisting of IL-9Ralpha and the common gammac subunit. Here we report functional evidence for receptor heteromerization for efficient signal transduction, and we define minimal requirements in the two receptor subunits for IL-9R function. Tyrosine 336 of the IL-9Ralpha and the membrane-proximal segment of gammac are both crucial for signaling. The activated IL-9R complex employs the Janus kinases JAK1 and JAK3 for subsequent activation of the signal transducer and activator transcription (STAT) factors STAT-1, STAT-3, and STAT-5. This process is independent of Tyk2. We demonstrate further that the activated STAT complexes consist of STAT-1 and STAT-5 homodimers and STAT-1-STAT-3 heterodimers. Finally, we show that IL-9R signaling in a T cell line does not result in detectable mitogen-activated protein kinase activation and leads to unsustained proliferation. Nonetheless, these T cells are efficiently protected from dexamethasone-induced apoptosis. These results further define the molecular architecture of the IL-9R and its specific connections to various biologic responses.

Visible Light Controlled Release of Anticancer Drug through Double Activation of Prodrug

We designed and synthesized a novel double activatable prodrug system (drug-linker-deactivated photosensitizer), containing a photocleavable aminoacrylate-linker and a deactivated photosensitizer, to achieve the spatiotemporally controlled release of parent drugs using visible light. Three prodrugs of CA-4, SN-38, and coumarin were prepared to demonstrate the activation of deactivated photosensitizer by cellular esterase and the release of parent drugs by visible light (540 nm) via photounclick chemistry. Among these prodrugs, nontoxic coumarin prodrug was used to quantify the release of parent drug in live cells. About 99% coumarin was released from the coumarin prodrug after 24 h of incubation with MCF-7 cells followed by irradiation with low intensity visible light (8 mW/cm(2)) for 30 min. Less toxic prodrugs of CA-4 and SN-38 killed cancer cells as effectively as free drugs after the double activation.

Dual Functioning Thieno-Pyrrole Fused BODIPY Dyes for NIR Optical Imaging and Photodynamic Therapy: Singlet Oxygen Generation without Heavy Halogen Atom Assistance

We discovered a rare phenomenon wherein a thieno-pyrrole fused BODIPY dye (SBDPiR690) generates singlet oxygen without heavy halogen atom substituents. SBDPiR690 generates both singlet oxygen and fluorescence. To our knowledge, this is the first example of such a finding. To establish a structure-photophysical property relationship, we prepared SBDPiR analogs with electron-withdrawing groups at the para-position of the phenyl groups. The electron-withdrawing groups increased the HOMO-LUMO energy gap and singlet oxygen generation. Among the analogs, SBDPiR688, a CF3 analog, had an excellent dual functionality of brightness (82290 m(-1)  cm(-1) ) and phototoxic power (99170 m(-1)  cm(-1) ) comparable to those of Pc 4, due to a high extinction coefficient (211 000 m(-1)  cm(-1) ) and balanced decay (Φflu =0.39 and ΦΔ =0.47). The dual functionality of the lead compound SBDPiR690 was successfully applied to preclinical optical imaging and for PDT to effectively control a subcutaneous tumor.

Effects of paramyxoviral infection on airway epithelial cell Foxj1 expression, ciliogenesis, and mucociliary function

To elucidate molecular mechanisms underlying the association between respiratory viral infection and predisposition to subsequent bacterial infection, we used in vivo and in vitro models and human samples to characterize respiratory virus-induced changes in airway epithelial cell morphology, gene expression, and mucociliary function. Mouse paramyxoviral bronchitis resulted in airway epithelial cell infection and a distinct pattern of epithelial cell morphology changes and altered expression of the differentiation markers beta-tubulin-IV, Clara cell secretory protein, and Foxj1. Furthermore, changes in gene expression were recapitulated using an in vitro epithelial cell culture system and progressed independent of the host inflammatory response. Restoration of mature airway epithelium occurred in a pattern similar to epithelial cell differentiation and ciliogenesis in embryonic lung development characterized by sequential proliferation of undifferentiated cells, basal body production, Foxj1 expression, and beta-tubulin-IV expression. The effects of virus-induced alterations in morphology and gene expression on epithelial cell function were illustrated by decreased airway mucociliary velocity and impaired bacterial clearance. Similar changes in epithelial cell Foxj1 expression were also observed in human paramyxoviral respiratory infection. Taken together, these model systems of paramyxoviral respiratory infection mimic human pathology and identify epithelial cell Foxj1 expression as an early marker of epithelial cell differentiation, recovery, and function.

Far-red light activatable, multifunctional prodrug for fluorescence optical imaging and combinational treatment

We recently developed “photo-unclick chemistry”, a novel chemical tool involving the cleavage of aminoacrylate by singlet oxygen, and demonstrated its application to visible light-activatable prodrugs. In this study, we prepared an advanced multifunctional prodrug, Pc-(L-CA4)₂, composed of the fluorescent photosensitizer phthalocyanine (Pc), an SO-labile aminoacrylate linker (L), and a cytotoxic drug combretastatin A-4 (CA4). Pc-(L-CA4)₂ had reduced dark toxicity compared with CA4. However, once illuminated, it showed improved toxicity similar to CA4 and displayed bystander effects in vitro. We monitored the time-dependent distribution of Pc-(L-CA4)₂ using optical imaging with live mice. We also effectively ablated tumors by the illumination with far-red light to the mice, presumably through the combined effects of photodynamic therapy (PDT) and released chemotherapy drug, without any sign of acute systemic toxicity.

U-rich sequence-binding proteins (URBPs) interacting with a 20-nucleotide U-rich sequence in the 3' untranslated region of c-fos mRNA may be involved in the first step of c-fos mRNA degradation

Rapid decay of the c-fos transcript plays a critical role in controlling transforming potential of the c-fos proto-oncogene. One of the mRNA instability determinants is a 75-nucleotide AU-rich element (ARE) present in the 3' untranslated region of the c-fos transcript. It appears to control two steps in the process of c-fos mRNA degradation: removal of the poly(A) tail, which does not require the AUUUA motifs, and subsequent degradation of deadenylated mRNA, which appears to be dependent on the AUUUA motifs. In this study, we report the identification of four U-rich sequence binding proteins (URBPs) that specifically interact with a 20-nucleotide U-rich sequence within the c-fos ARE. Gel mobility shift assay and competition experiments showed that these protein factors form three specific band-shifted complexes with the c-fos ARE. Binding activity of one of the protein factors, a 37-kDa protein, is significantly affected by serum induction and by pretreatment of cells with drugs known to stabilize many of the immediate-early gene mRNAs. Combining UV cross-linking with a new approach, designated sequential RNase digestion, we were able to better determine the molecular masses of these cellular proteins. The binding sites for the four proteins were all mapped to a 20-nucleotide U-rich sequence located at the 3' half of the c-fos ARE, which contains no AUUUA pentanucleotides but stretches of uridylate residues. Single U-to-A point mutations in each of the three AUUUA motifs within the c-fos ARE have little effect on formation of the mobility-shifted complexes. Our data indicate c-fos ARE-protein interaction involves recognition of U stretches rather than recognition of the AUUUA motifs. We propose that UTBP binding may be involved in the first step, removal of the Poly(A) tail, in the c-fos ARE-mediated decay pathway.

Water soluble, core-modified porphyrins. 3. Synthesis, photophysical properties, and in vitro studies of photosensitization, uptake, and localization with carboxylic acid-substituted derivatives

Water soluble, core-modified porphyrins 1-5 bearing 1-4 carboxylic acid groups were prepared and evaluated in vitro as photosensitizers for photodynamic therapy. The 21,23-core-modified porphyrins 1-5 gave band I absorption maxima with lambda(max) of 695-701 nm. The number of carboxylic acid groups in the dithiaporphyrins 1-4 had little effect on either absorption maxima (lambda(max) of 696-701 nm for band I) or quantum yields of singlet oxygen generation [phi((1)O(2)) of 0.74-0.80]. Substituting two Se atoms for S gave a shorter band I absorption maximum (lambda(max) of 695 nm) and a smaller value for the quantum yield for generation of singlet oxygen [phi((1)O(2)) of 0.30]. The phototoxicity of 1-5 was evaluated against R3230AC cells. The phototoxicities of dithiaporphyrin 2, sulfonated thiaporphyrin 30, HPPH, and Photofrin were also evaluated against Colo-26 cells in culture using 4 J cm(-2) of 570-800 nm light. Compound 2 was significantly more phototoxic than sulfonated dithiaporphyrin 30, HPPH, or Photofrin. Cellular uptake was much greater for compounds 1, 2, and 5 relative to compounds 3 and 4. Confocal scanning laser microscopy and double labeling experiments with rhodamine 123 suggested that the mitochondria were an important target for dithiaporphyrins 1 and 2. Inhibition of mitochondrial cytochrome c oxidase activity in whole R3230AC cells was observed in the dark with compounds 1 and 30 and both in the dark and in the light with core-modified porphyrin 2.

Folate receptor-mediated enhanced and specific delivery of far-red light-activatable prodrugs of combretastatin A-4 to FR-positive tumor

We examined the concept of a novel prodrug strategy in which anticancer drug can be locally released by visible/near IR light, taking advantage of the photodynamic process and photo-unclick chemistry. Our most recently formulated prodrug of combretastatin A-4, Pc-(L-CA4)₂, showed multifunctionality for fluorescence imaging, light-activated drug release, and the combined effects of PDT and local chemotherapy. In this formulation, L is a singlet oxygen cleavable linker. Here, we advanced this multifunctional prodrug by adding a tumor-targeting group, folic acid (FA). We designed and prepared four FA-conjugated prodrugs 1–4 (CA4-L-Pc-PEG_n-FA: n = 0, 2, 18, ∼45) and one non-FA-conjugated prodrug 5 (CA4-L-Pc-PEG₁₈-boc). Prodrugs 3 and 4 had a longer PEG spacer and showed higher hydrophilicity, enhanced uptake to colon 26 cells via FR-mediated mechanisms, and more specific localization to SC colon 26 tumors in Balb/c mice than prodrugs 1 and 2. Prodrug 4 also showed higher and more specific uptake to tumors, resulting in selective tumor damage and more effective antitumor efficacy than non-FA-conjugated prodrug 5. FR-mediated targeting seemed to be an effective strategy to spare normal tissues surrounding tumors in the illuminated area during treatment with this prodrug.

On the mechanism of gas adsorption for pristine, defective and functionalized graphene

Defects are no longer deemed an adverse aspect of graphene.