Epigenetics-Associated Risk Reduction of Hematologic Neoplasms in a Nationwide Cohort Study: The Chemopreventive and Therapeutic Efficacy of Hydralazine.

BACKGROUND: Although several epigenetic drugs have been reported to have therapeutic efficacy for some hematologic neoplasms (HNs) in clinical trials, few achieved disease-free survival benefit. The traditional drug discovery pathway is costly and time-consuming, and thus, more effective strategies are required. We attempted to facilitate epigenetic drug repositioning for therapy of HNs by screening the Human Epigenetic Drug Database (HEDD) in the web, conducting a bench-work cytotoxicity test and a retrospective nationwide cohort study prior to a clinical trial. METHODS: Four FDA-approved epigenetic drugs with antitumor properties and completion of clinical phase II trials were selected from HEDD. Hydralazine (HDZ) and valproate (VAL) among the four were selected with higher cytotoxicity to HN cells, no matter whether carrying the JAK2V617F mutation or not. Both of them were chosen for a cohort study using the Longitudinal Health Insurance Database (LHID) 2000-2015 (N = 1,936,512), a subset of the National Health Insurance Research Database (NHIRD, N= 25.68 millions) in Taiwan. RESULTS: In the initial cohort, HDZ or VAL exposure subjects (11,049) and matching reference subjects (44,196) were enrolled according to maximal daily consumption (300/2,100 mg per day of HDZ/VAL). The HN incidence in HDZ and VAL exposure groups reduced from 4.97% to 3.90% (p <.001) and 4.45% (p = .075), respectively. A further cohort study on HDZ at a lower range of the WHO defined daily dose (<34 mg per day) and HN incidence of HDZ exposure subjects (75,612) reduced from 5.01% to 4.16% (p = 1.725 × 10 -18) compared to the reference subjects (302,448). CONCLUSIONS: An association of a chronically prescribed HDZ, even prescribed low dose, with reduction of overall incidence rate and in most subgroups of HN was observed in our study. Repositioning HDZ for HN management may be feasible. This is the first nationwide cohort study of the epigenetics-associated risk evaluation of overall HN in the existing literature, showing an effective method with a wider scope to inform contemporary clinical trials of epigenetic drugs in the future.

From GWAS to drug screening: repurposing antipsychotics for glioblastoma.

BACKGROUND: Glioblastoma is currently an incurable cancer. Genome-wide association studies have demonstrated that 41 genetic variants are associated with glioblastoma and may provide an option for drug development. METHODS: We investigated FDA-approved antipsychotics for their potential treatment of glioblastoma based on genome-wide association studies data using a 'pathway/gene-set analysis' approach. RESULTS: The in-silico screening led to the discovery of 12 candidate drugs. DepMap portal revealed that 42 glioma cell lines show higher sensitivities to 12 candidate drugs than to Temozolomide, the current standard treatment for glioblastoma. CONCLUSION: In particular, cell lines showed significantly higher sensitivities to Norcyclobenzaprine and Protriptyline which were predicted to bind targets to disrupt a certain molecular function such as DNA repair, response to hormones, or DNA-templated transcription, and may lead to an effect on survival-related pathways including cell cycle arrest, response to ER stress, glucose transport, and regulation of autophagy. However, it is recommended that their mechanism of action and efficacy are further determined.

Erratum: Chen, Y.-R., et al. Improvement of Impaired Motor Functions by Human Dental Exfoliated Deciduous Teeth Stem Cell-Derived Factors in a Rat Model of Parkinson's Disease. Int. J. Mol. Sci. 2020, 21, 3807.

The authors regret to have made a mistake in publishing this paper [...].

Improvement of Impaired Motor Functions by Human Dental Exfoliated Deciduous Teeth Stem Cell-Derived Factors in a Rat Model of Parkinson's Disease.

Parkinson's disease (PD) is a long-term degenerative disease of the central nervous system (CNS) that primarily affects the motor system. So far there is no effective treatment for PD, only some drugs, surgery, and comprehensive treatment can alleviate the symptoms of PD. Stem cells derived from human exfoliated deciduous teeth (SHED), mesenchymal stem cells derived from dental pulp, may have promising potential in regenerative medicine. In this study, we examine the therapeutic effect of SHED-derived conditioned medium (SHED-CM) in a rotenone-induced PD rat model. Intravenous administration of SHED-CM generated by standardized procedures significantly improved the PD symptoms accompanied with increased tyrosine hydroxylase amounts in the striatum, and decreased α-synuclein levels in both the nigra and striatum, from rotenone-treated rats. In addition, this SHED-CM treatment decreased both Iba-1 and CD4 levels in these brain areas. Gene ontology analysis indicated that the biological process of genes affected by SHED-CM was primarily implicated in neurodevelopment and nerve regeneration. The major constituents of SHED-CM included insulin-like growth factor binding protein-6 (IGFBP-6), tissue inhibitor of metalloproteinase (TIMP)-2, TIMP-1, and transforming growth factor 1 (TGF-1). RNA-sequencing (RNA-seq) and Ingenuity Pathway Analysis (IPA) revealed that these factors may ameliorate PD symptoms through modulating the cholinergic synapses, calcium signaling pathways, serotoninergic synapses, and axon guidance. In conclusion, our data indicate that SHED-CM contains active constituents that may have promising efficacy to alleviate PD.

Dental Pulp Stem Cell-Derived Factors Alleviate Subarachnoid Hemorrhage-Induced Neuroinflammation and Ischemic Neurological Deficits.

Aneurysmal subarachnoid hemorrhage (aSAH), characterized by the extravasation of blood into the subarachnoid space caused by an intracranial aneurysm rupture, may lead to neurocognitive impairments and permanent disability and usually carries poor outcome. Dental or gingiva-derived stem cells have been shown to contribute to immune modulation and neuroregeneration, but the underlying mechanisms are unclear. In the present study, we sought to investigate whether dental pulp stem cells (DPSCs) secrete certain factor(s) that can ameliorate the neural damage and other manifestations in a rat aSAH model. Twenty-four hours after the induction of aSAH, microthrombosis, cortical vasoconstriction, and the decrease in microcirculation and tissue oxygen pressure were detected. Intrathecal administration of DPSC-derived conditioned media (DPSC-CM) ameliorated aSAH-induced vasoconstriction, neuroinflammation, and improved the oxygenation in the injured brain. Rotarod test revealed that the aSAH-induced cognitive and motor impairments were significantly improved by this DPSC-CM administration. Cytokine array indicated the major constituent of DPSC-CM was predominantly insulin growth factor-1 (IGF-1). Immunohistochemistry staining of injured brain tissue revealed the robust increase in Iba1-positive cells that were also ameliorated by DPSC-CM administration. Antibody-mediated neutralization of IGF-1 moderately deteriorated the rescuing effect of DPSC-CM on microcirculation, Iba1-positive cells in the injured brain area, and the cognitive/motor impairments. Taken together, the DPSC-derived secretory factors showed prominent therapeutic potential for aSAH. This therapeutic efficacy may include improvement of microcirculation, alleviation of neuroinflammation, and microglial activation; partially through IGF-1-dependent mechanisms.

Melanocyte Differentiation From Induced Pluripotent Stem Cells Derived From Human Adipose-Derived Stem Cells.

The pigment melanin is produced by melanocytes, is primarily responsible for skin color, and protects it against ultraviolet rays that can cause the destruction of genetic material within the keratinocytes. To elucidate the mechanisms of many diseases associated with melanocytes, such as melanoma and albinism, or burns with uneven pigment distribution, the disease model needs to be established first. In this study, we aimed to construct the melanocyte model from patients in a short period.Sandai virus vector containing 4 stemness genes (Oct4, Sox2, Klf4, c-Myc) was transfected into human adipose-derived stem cells to produce induced pluripotent stem cells (iPSCs). Immunofluorescence staining was used to confirm the expression of specific proteins for iPSCs, including Tra-1-60, Tra-1-81, Oct-4, Sox-2, and Nango. polymerase chain reaction results also showed that specific genes of iPSCs with the ability to cause the differentiation of cells into the 3 germ layers were expressed. In our in vivo experiments, iPSCs were subcutaneously injected into nude mice to induce teratoma formation for 2 months. The morphology of the 3 germ layers was confirmed by hematoxylin and eosin staining. Furthermore, melanocytes were purified by serial induction medium, and their presence was confirmed by flow cytometry and the expression of different markers for melanocytes.

Erlotinib-Conjugated Iron Oxide Nanoparticles as a Smart Cancer-Targeted Theranostic Probe for MRI.

We designed and synthesized novel theranostic nanoparticles that showed the considerable potential for clinical use in targeted therapy, and non-invasive real-time monitoring of tumors by MRI. Our nanoparticles were ultra-small with superparamagnetic iron oxide cores, conjugated to erlotinib (FeDC-E NPs). Such smart targeted nanoparticles have the preference to release the drug intracellularly rather than into the bloodstream, and specifically recognize and kill cancer cells that overexpress EGFR while being non-toxic to EGFR-negative cells. MRI, transmission electron microscopy and Prussian blue staining results indicated that cellular uptake and intracellular accumulation of FeDC-E NPs in the EGFR overexpressing cells was significantly higher than those of the non-erlotinib-conjugated nanoparticles. FeDC-E NPs inhibited the EGFR-ERK-NF-κB signaling pathways, and subsequently suppressed the migration and invasion capabilities of the highly invasive and migrative CL1-5-F4 cancer cells. In vivo tumor xenograft experiments using BALB/c nude mice showed that FeDC-E NPs could effectively inhibit the growth of tumors. T2-weighted MRI images of the mice showed significant decrease in the normalized signal within the tumor post-treatment with FeDC-E NPs compared to the non-targeted control iron oxide nanoparticles. This is the first study to use erlotinib as a small-molecule targeting agent for nanoparticles.

Genome-wide analysis of HIF-2α chromatin binding sites under normoxia in human bronchial epithelial cells (BEAS-2B) suggests its diverse functions.

Constitutive functional HIF-2α was recently identified in cancer and stem cell lines under normoxia. In this study, BEAS-2B, a bronchial epithelial cell line, was shown to constitutively express active HIF-2α under normoxia and exhibit markers of pluripotency including Oct-4, Nanog, and sphere formation. Oct-4 expression was reduced after knockdown of HIF-2α under normoxia. Global enrichment analysis of HIF-2α demonstrated the diverse functions of HIF-2α under normoxia. Bioinformatics analysis of the enriched loci revealed an enhancer role of HIF-2α binding sites, involvement of HIF-2α interacting proteins, and enriched de novo motifs which suggest the diverse role of HIF-2α in pseudohypoxia. The low ratio of the discovered loci overlapping with those revealed in cancer cell lines 786-O (16.1%) and MCF-7 (15.9%) under hypoxia indicated a prevailing non-canonical mechanism. Hypoxia had positive, marginal or adverse effects on the enrichment of the selected loci in ChIP-PCR assays. Deletion of the N-terminal activation domain (N-TAD) of HIF-2α disrupted the reporting activity of two of the loci annotated to ELN and ANKRD31. Hypoxia incurring abundance variation of HIF-2α may misrepresent the N-TAD functions as canonical hypoxia inducible features via C-TAD activation. Elucidation of the pseudohypoxia functions of constitutive HIF-2α is useful for resolving its role in malignancy and pluripotency.

Novel Anthra[1,2-c][1,2,5]Thiadiazole-6,11-Diones as Promising Anticancer Lead Compounds: Biological Evaluation, Characterization & Molecular Targets Determination.

The novel compounds NSC745885 and NSC757963 developed at our laboratory were tested against a panel of 60 cancer cell lines at the National Cancer Institute, USA, and a panel of 39 cancer cell lines at the Japanese Foundation of Cancer Research. Both compounds demonstrated selective unique multi-log differential patterns of activity, with GI50 values in the sub-micro molar range against cancer cells rather than normal cardiac cells. NSC757963 showed high selectivity towards the leukemia subpanel. Activities of both compounds strongly correlated to expression of NFKB1 and CSNK2B genes, implying that they may inhibit the NF-κB pathway. Immunocytochemical microscopy of OVCAR-3 cells showed clear cytosolic accumulation of the NF-κB p65 subunit following treatment. Western blotting showed dose dependent inhibition of the nuclear expression of the NF-κB p65 subunit with subsequent accumulation in the cytosol following treatment. Docking experiments showed binding of both compounds to the NF-κB activator IKKß subunit preventing its translocation to the nucleus. Collectively, these results confirm the ability of our compounds to inhibit the constitutively active NF-κB pathway of OVCAR-3 cells. Furthermore, COMPARE analysis indicated that the activity of NSC757963 is similar to the antituberculosis agent rifamycin SV, this was confirmed by testing the antimycobacterial activity of NSC757963 against Mycobacterium tuberculosis, results revealed potent activity suitable for use in clinical practice. Molecular properties and Lipinski's parameters predicted acceptable bioavailability properties with no indication of mutagenicity, tumorigenicity, irritability and reproductive effects. Oral absorption experiments using the human Caco-2 model showed high intestinal absorption of NSC745885 by passive transport mechanism with no intestinal efflux or active transport mechanisms. The unique molecular characterization as well as the illustrated anticancer spectra of activity and bioavailability properties warrant further development of our compounds and present a foundation brick in the pre-clinical investigations to implement such compounds in clinical practice.

Efficient downregulation of VEGF in retinal pigment epithelial cells by integrin ligand-labeled liposome-mediated siRNA delivery.

BACKGROUND: The purpose of this study was to demonstrate the effectiveness of an integrin peptide ligand-labeled liposomal delivery system loaded with vascular endothelial growth factor (VEGF)-siRNA in a model study of gene therapy for retinopathy using human retinal pigment epithelial cells. METHODS: Arg(R)-Gly(G)-Asp(D) motif peptide conjugating polyethylene glycol modified (RGD-PEGylated) liposomes were prepared using a thin-film hydration method and optimized for surface charge, particle size, small interfering RNA (siRNA) load, and entrapment efficiency. Reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assays were used to determine VEGF levels in retinal pigment epithelial cells. Cytotoxicity was determined using the 3-[4, 5-dimethylthiazol-2-yl]-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and flow cytometry. RESULTS: Physicochemical properties, including particle size, zeta potential, and siRNA load, of the prepared RGD-PEGylated liposomes and their entrapment efficiency were determined to be within the following ranges: 123.8-234.1 nm, 17.31-40.09 m V, 5.27%-6.33%, and >97%, respectively. RGD-PEGylated liposome-mediated fluorescent-labeled siRNA delivery demonstrated significantly enhanced cellular uptake, and 3 mol% RGD-PEGylated liposomes (having 3ß-[N-(N', N'-dimethylaminoethane) carbamoyl] cholesterol (DC-cholesterol) DSPE and DSPE-PEG(2000)-RGD with molar ratio of 50/47/3) were shown to have better efficacy with regard to specificity for retinal pigment epithelial cells, reduced cytotoxicity, and knockdown of the target molecule. CONCLUSION: By integrin receptor-mediated endocytosis, 3 mol% RGD-PEGylated liposomes were shown to be a suitable vector when loaded with VEGF-siRNA for efficient downregulation of VEGF in retinal pigment epithelial cells at both the protein and gene levels. This integrin ligand-modified liposomal delivery system has therapeutic potential for ocular gene therapy.

Different sham procedures for rats in traumatic brain injury experiments induce corresponding increases in levels of trauma markers.

BACKGROUND: In traumatic brain injury animal models, sham or naïve control groups are often used for the analysis of injured animals; however, the existence and/or significance of differences in the control groups has yet to be studied. In addition, recent controversies regarding the decompressive craniectomy trial in which decompressive craniectomies in patients with severe traumatic brain injury and refractory increased intracranial pressure remains unsettled. Although the report demonstrated that the procedure may result in less favorable long-term outcomes despite the decrease in intracranial pressure and shorter length of intensive care unit stay, the study has been criticized, and the debate is still inconclusive partly because of a lack of mechanistic explanation. We have recently discovered epithelial and endothelial tyrosine kinase (Etk) to exhibit upregulation after traumatic neural injury and will compare the effects of craniectomy procedure with those of other procedures inducing different levels of severity. MATERIALS AND METHODS: Four groups of rats receiving different procedures (controlled cortical impact, craniectomy, bicortical drilling, and unicortical drilling [UD]) were compared. Polymerase chain reaction, Western blot analysis, and immunoflorescence staining of Etk, S100, and glial fibrillary acidic protein levels were used to analyze the results and compare the different groups. RESULTS: Etk upregulation was statistically significant between craniectomy and UD groups. The level of change for glial fibrillary acidic protein and S100 was only significant when cortex was impacted. CONCLUSIONS: UD may be preferable as a sham control procedure over craniectomy or bicortical drilling. Increases in the expression of Etk in the craniectomy group suggest a possible mechanism by which unfavorable outcome occurs in patients receiving craniectomy procedures.

Location and level of Etk expression in neurons are associated with varied severity of traumatic brain injury.

BACKGROUND: Much recent research effort in traumatic brain injury (TBI) has been devoted to the discovery of a reliable biomarker correlating with severity of injury. Currently, no consensus has been reached regarding a representative marker for traumatic brain injury. In this study, we explored the potential of epithelial/endothelial tyrosine kinase (Etk) as a novel marker for TBI. METHODOLOGY/PRINCIPAL FINDINGS: TBI was induced in Sprague Dawley (SD) rats by controlled cortical impact. Brain tissue samples were analyzed by Western blot, Q-PCR, and immunofluorescence staining using various markers including glial fibrillary acidic protein, and epithelial/endothelial tyrosine kinase (Etk). Results show increased Etk expression with increased number and severity of impacts. Expression increased 2.36 to 7-fold relative to trauma severity. Significant upregulation of Etk appeared at 1 hour after injury. The expression level of Etk was inversely correlated with distance from injury site. Etk and trauma/inflammation related markers increased post-TBI, while other tyrosine kinases did not. CONCLUSION/SIGNIFICANCE: The observed correlation between Etk level and the number of impacts, the severity of impact, and the time course after impact, as well as its inverse correlation with distance away from injury site, support the potential of Etk as a possible indicator of trauma severity.

Novel RGD-lipid conjugate-modified liposomes for enhancing siRNA delivery in human retinal pigment epithelial cells.

BACKGROUND: Human retinal pigment epithelial cells are promising target sites for small interfering RNA (siRNA) that might be used for the prevention and/or treatment of choroidal neovascularization by inhibiting the expression of angiogenic factor; for example, by downregulating expression of the vascular endothelial growth factor gene. METHODS: A novel functional lipid, DSPE-PEG-RGD, a Arg(R)-Gly(G)-Asp(D) motif peptide conjugated to 1, 2-distearoyl-sn-glycero-3-phosphoethanolamine- N-[maleimide (polyethylene glycol)-2000], was synthesized for the preparation of siRNA-loaded RGD-PEGylated liposomes to enhance uptake of encapsulated siRNA in retinal pigment epithelial cells. Various liposomes, with 1 mol% and 5 mol% PEGylated lipid or 1 mol% and 5 mol% RGD-PEGylated lipid, were fabricated. RESULTS: Characterization of the liposomes, including siRNA entrapment efficiency, average particle size and ζ-potential, were determined to be as follows: >96%, 129.7 ± 51 to 230.7 ± 60.7 nm, and 17.3 ± 0.6 to 32 ± 1.3 mV, respectively. For the in vitro retinal pigment epithelial cell studies, the RGD-PEGylated liposomes had high delivery efficiency with siRNA delivery, about a four-fold increase compared with the PEGylated liposomes. Comparison of the various liposomes showed that the 1 mol% RGD-modified liposome had less cytotoxicity and higher siRNA delivery efficiency than the other liposomes. The antibody blocking assay confirmed that uptake of the 1 mol% RGD-PEGylated liposome was via integrin receptor- mediated endocytosis in retinal pigment epithelial cells. CONCLUSION: The results of this study suggest that RGD-PEGylated liposomes might be useful for siRNA delivery into retinal pigment epithelial cells by integrin receptor-medicated endocytosis.

Simvastatin inhibits pro-inflammatory mediators through induction of heme oxygenase-1 expression in lipopolysaccharide-stimulated RAW264.7 macrophages.

It has been reported that the anti-inflammatory activity of 3-hydroxy-3-methyl-glutary coenzyme A (HMG-CoA) reductase inhibitors (statins) is independent of their hypocholesterolemic effect. Previous studies indicated that induction of heme oxygenase-1 (HO-1) exerts a cytoprotective activity in several inflammatory diseases. Here, the possibility that HO-1 is involved in the anti-inflammatory action of simvastatin, using lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages as a model system has been specifically addressed. Our results demonstrated that in the presence of LPS, simvastatin significantly increased HO-1 expression and activity in a dose-dependent manner compared to that of LPS-stimulated alone macrophages. Moreover, simvastatin significantly inhibited LPS-induced inducible nitric oxide synthase (NOS) expression, and formation of pro-inflammatory mediators, including tumor necrosis factor-α (TNF-α), nitrite and free radicals, but enhanced interleukin-10 (IL-10) production. Similarly, the IκB-α degradation and nuclear transcription factor-κB translocation and activation caused by LPS were significantly suppressed by simvastatin. However, these anti-inflammatory activities of simvastatin were markedly reversed by addition of a HO-1 inhibitor zinc protoporphyrin (ZnPP). Accordingly, the present results indicate that the anti-inflammatory activity of simvastatin could, at least in part, be regulated by induction of HO-1-mediated processes.

Verteporfin-photoinduced apoptosis in HepG2 cells mediated by reactive oxygen and nitrogen species intermediates.

Photodynamic therapy (PDT) is a rapidly evolving treatment modality with diverse usages in the field of cancer therapy. Most of PDT is based on free radical-mediated photo-killing of cancer cells. This study aimed to elucidate the detailed cascade of events that lead to apoptotic cell death of HepG2 cells resulting from the photodynamic effect (PDE) of verteporfin. PDE of verteporfin could rapidly provoke hyper-oxidative stress and caspase activity. Glutathione (GSH) depletion and lipid peroxidation phenomena could simultaneously be evoked. The membrane integrity was decreased and permeability as reflected by the depolarization of the mitochondrial membrane potential (Deltapsi(m)) increased, resulting in a sudden influx of cytosolic calcium into the mitochondria. Altogether, it is suggested that these events serve as the final arbitrator to initiate the lethal apoptotic process of HepG2 cells under PDE. In addition, the data are consistent with the notion that GSH depletion is an effective strategy to sensitize cancer cells to undergo apoptosis.

Sorafenib induces preferential apoptotic killing of a drug- and radio-resistant Hep G2 cells through a mitochondria-dependent oxidative stress mechanism.

Sorafenib (Nexavar, BAY43-9006), a bi-arylurea, is a newly established anti-cancer drug and its functional attribute of cytotoxicity is based on the multi-kinase inhibitory action. Here, we report yet another novel pathway in which sorafenib can induce apoptotic cell death preferentially and efficaciously on an experimentally proven drug- and radio-resistant human Hep G2 cells via a mitochondria-dependent oxidative stress mechanism. A real time confocal imaging assay revealed that sorafenib could rapidly provoke the production of ROS plethorically, mainly concentrating in the mitochondria, albeit substantial amounts of ROS could also be detected in cytosol and nucleus. The rapid production of ROS could simultaneously induce intracellular glutathione (iGSH) depletion. A nearly 90% of iGSH was found to be depleted in 1h period after the cells received the drug treatment. Besides mitochondria, iGSH depletion could also be detected in other cellular compartment including cytoplasm and nucleus. Interestingly, we also demonstrated that sorafenib could trigger mitochondrial Ca(2+) overload. All these events compoundedly serve as the final arbitrator to initiate lethal apoptotic process through the release of cytochrome c and caspase 3/7 activation. Collectively, we provide first evidence here that sorafenib can provoke an alternative pathway for apoptosis induction of Hep G2 cells through a mitochondria-dependent oxidative stress mechanism which is independent of original kinase inhibitory attribute of the drug action. Most importantly, we also demonstrate that sorafenib can effectively eradicate a highly drug- and radio-resistant HCC cells. Thus, our data can provide the basis for a potential applicability of sorafenib in a combined treatment modality.

Staphylokinase-annexin XI chimera exhibited efficient in vitro thrombolytic activities.

Annexins (ANXs) are a family of calcium dependent phospholipid binding proteins. Phospholipids such as phosphatidylserine are rapidly exposed on the surfaces of injured endothelial cells, activated platelets, and apoptotic cells in a large number of disorders. In this study, annexin V and XI (ANXV and ANXXI) were individually fused to the C-terminal of staphylokinase (SAK), a fibrin-selective thrombolytic protein, to form chimeras for evaluation of their in-vitro thrombolytic activities. The two chimeras were found to have plasminogen activation activity of comparable efficiency. When the chimeras were challenged under higher concentrations of plasmin for 1 h, hydrolysis of them into moieties was not seen on SDS-PAGE. In two thrombolytic assays, SAK-ANXXI was found to resolve both platelet rich plasma (PRP) clots and platelet poor plasma (PPP) clots with an efficiency similar to that of SAK. However, SAK-ANXV showed significantly reduced efficiency. With regard to anticoagulation ability, SAK-ANXXI was also found to have a stronger effect on dose-dependent extension of clotting time among the four tested proteins. The unique long N-terminal tail of ANXXI, composed of 202 residues, in contrast to the 16 residues of ANXV, probably served successfully to dispatch two moieties to function properly in a complicated microenvironment. Hence, a new option other than the most committed ANXV for the ANX based chimera without elaboration of linker construction is presented.

Mechanisms of antiplatelet activity of PC-09, a newly synthesized pyridazinone derivative.

In this study, we examined whether PC-09, a new pyridazinone derivative, has antiplatelet activity in vitro and further investigated the possible mechanisms involved. Pretreatment with PC-09 resulted in an inhibition on rabbit platelet aggregation and ATP release induced by arachidonic acid, collagen or thrombin, with the IC(50) values of 5.4 to 76.8 muM. The thromboxane B(2) formation caused by collagen or thrombin was markedly inhibited by PC-09, but there was no alteration in that caused by arachidonic acid. The rise of platelet intracellular calcium level stimulated by aggregation agonists and collagen-induced platelet membrane surface glycoprotein IIb/IIIa expression was also reduced by PC-09. In addition, PC-09 itself significantly increased the cyclic AMP level through inhibiting cyclic AMP phosphodiesterase activity. These findings demonstrate that PC-09 is an inhibitor of platelet aggregation, which may be associated with mechanisms including inhibition of thromboxane A(2) formation, intracellular calcium mobilization and platelet surface GPIIb/IIIa expression accompanied by increasing cyclic AMP level.

Effect of melanin produced by a recombinant Escherichia coli on antibacterial activity of antibiotics.

A recombinant plasmid, pYL-1, containing a tyrosinase gene whose expression is under the control of a phage T5 promoter and 2 lac operators, was constructed. Escherichia coli JM109 harboring pYL-1 was used for production of bacterial melanin. A simple procedure for the isolation and purification of melanin was developed. The ultraviolet (UV)-visible light absorption spectra of melanin prepared by chemical synthesis and derived from different organisms, including bacteria, a plant and an animal source, were determined. Melanins produced by both bacteria and chemical synthesis showed a steady increase of absorption at wavelengths of UV light ranging from approximately 200-400 nm, while melanin derived either from plant or animal sources showed an additional discrete absorption peak at wavelength 280 nm upon a similar steady increase of absorption. This additional absorption peak could be due to the presence of protein-bound melanins in animal and plant sources while a free form of melanin was obtained from bacteria and chemical synthesis. Analysis of the effect of bacterial melanin on the activity of antibiotics against E. coli revealed that the activities of polymyxin B, kanamycin, tetracycline, and ampicillin were markedly reduced in the presence of melanin, whereas the activity of norfloxacin was not affected. The reduction of the antibacterial activity may result directly from the interaction of antibiotics with melanin. However, the mechanism of this interaction remains to be demonstrated.

Purification and characterization of inducible cephalexin synthesizing enzyme in Gluconobacter oxydans.

Cephalexin synthesizing enzyme (CSE) of Gluconobacter oxydans ATCC 9324 was purified up to about 940-fold at a yield of 12%. CSE biosynthesis in G. oxydans was found inducible in the presence of D-phenylglycine but not its substrate phenylglycine methyl ester. The purified enzyme was shown homogeneous on SDS-PAGE and exhibited a specific activity of 440 U per mg protein. The apparent molecular mass of the native enzyme was estimated to be 70 kDa over a Superdex 200 gel filtration column and 68 kDa on SDS-PAGE, indicating that the native enzyme is a monomer. Its isoelectric focusing point is 7.1, indicating a neutral character. The enzyme had maximal activity around pH 6.0 to 6.5, and this activity was thermally stable up to 40 degrees C. Synthesis of cephalexin from D-phenylglycine methyl ester and 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) by the purified CSE was demonstrated. Its L-enantiomer was not accepted by CSE. Apart from cephalexin, ampicillin was also synthesized by the purified CSE from its acyl precursors and 6-aminopenicillanic acid (6-APA). Substrate specificity studies indicated that the enzyme required a free alpha amino group and an activated carboxyl group as a methyl ester of D-form phenylglycine. Interestingly, the purified enzyme did not catalyze hydrolysis of its products, e.g., cephalexin, cephradine, and ampicillin, in contrast to enzymes from other strains of Pseudomonadaceae.