Fused hydrophobic elastin-like-peptides (ELP) enhance biological activity of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent with tumor-selective apoptotic activity. Formation of aggregates as trimer is the prerequisite for TRAIL's function as an apoptosis inducer. However the polymerization property of TRAIL has also brought difficulties for its production. RGD-TRAIL is an integrin-targeting TRAIL mutant with enhanced apoptosisinducing activity towards tumor cells both in vitro and in vivo. When expressed in E. coli, TRAIL or its mutant RGDTRAIL usually formed inclusion bodies. Their extreme aggregation propensity for aggregation destabilizes the protein, leading to poor recovery and therefore low yield from the purification process. The low purification efficiency of TRAIL retards its industrial application and large-scale production. To avoid the above problems during RGD-TRAIL production, we employed elastin-like polypeptides (ELPs) for the fusion-expression of recombinant RGD-TRAIL. Recombinant RGD-TRAIL-ELP was expressed in a soluble form and efficiently purified from the clarified cell extracts by three rounds of inverse transition cycling (ITC). SDS-PAGE and Western blotting analyses of purified RGD-TRAIL-ELP showed that RGD-TRAIL-ELP was successfully purified and the yield was up to 10 mg/L of bacterial culture. Apoptosis assay was performed in human colorectal carcinoma cells (COLO-205) and human breast cancer cell line (MDA-MB-231) to assess the potency of the fusion protein. Fusion with hydrophobic ELP effectively enhanced RGD-TRAIL's biological activity. The higher activity and appropriate particle size of RGD-TRAIL-ELP could be used for RGD-TRAIL delivery in tumor therapy.

Hydrogen Sulfide Attenuates Tissue Plasminogen Activator-Induced Cerebral Hemorrhage Following Experimental Stroke

Tissue plasminogen activator (tPA), the only approved drug for the treatment of ischemic stroke, increases the risk of cerebral hemorrhage. Here, we investigated whether the newly identified gaso-transmitter hydrogen sulfide (H2S), when used in combination with tPA, reduced the hemorrhagic transformation following stroke. In a mouse model of middle cerebral artery occlusion (MCAO), intravenous injection of tPA enhanced cerebral hemorrhage, which was significantly attenuated by the co-administration of two structurally unrelated H2S donors, ADT-OH and NaHS. By assessing extravasation of Evans blue into the ischemic hemisphere as well as brain edema following MCAO, we further showed that a tPA-exacerbated BBB disruption was significantly ameliorated by the co-administration of ADT-OH. In the mouse MCAO model, tPA upregulated Akt activation, vascular endothelial growth factor (VEGF) expression, and metalloproteinase 9 (MMP9) activity in the ischemic brain, which was remarkably attenuated by ADT-OH. In the in vitro glucose-oxygen deprivation (OGD) model, ADT-OH markedly attenuated tPA-enhanced Akt activation and VEGF expression in brain microvascular endothelial cells. Finally, ADT-OH improved functional outcomes in mice subjected to MCAO and tPA infusion. In conclusion, H2S donors reduced tPA-induced cerebral hemorrhage by possibly inhibiting the Akt-VEGF-MMP9 cascade. Administration of H2S donors has potential as a novel modality to improve the safety of tPA following stroke.

Potential therapeutic implications of gelsolin in Alzheimer's disease

The presence of amyloid plaques and vascular amyloid deposits is one of the pathological features of Alzheimer's disease (AD). Amyloid plaques and vascular deposits mainly consist of amyloid-β (Aβ), which is a metabolic product of amyloid-β protein precursor cleaved by β- and γ-secretase. Soluble Aβ monomers readily aggregate into oligomers preceding the formation of insoluble fibrils, and Aβ oligomers are more toxic than fibrils. Intensive therapeutic efforts have been attempted in the treatment of AD targeting Aβ, including preventing Aβ generation, inhibiting Aβ aggregation, and promoting Aβ clearance. The results show that amyloid plaque burden is reduced together with improved cognition performance in AD. Gelsolin, a multifunctional actin-binding protein, exists intracellularly as a cytoplasmic form and extracellularly as a secreted form in blood/cerebrospinal fluid. Gelsolin is suggested to be implicated in AD, based on the findings that some changes of gelsolin are correlated with disease progression rate in AD patients. Gelsolin binds Aβ, inhibits its aggregation into fibrils, and protects cells from apoptosis induced by Aβ. More importantly, administration or overexpression of gelsolin results in significant reduction of amyloid load and decrease of Aβ level in AD transgenic mice. In this article, we review the most recent progress of gelsolin as a potential therapeutic strategy for treatment of AD, and discuss the possible mechanism involved in the clearance of amyloid plaques in AD.

Molecular docking to explore the possible binding mode of potential inhibitors of thioredoxin glutathione reductase

Praziquantel (PZQ) is the treatment of choice for schistosomiasis, one of the most important but neglected tropical diseases. Recently, however, Schistosoma have exhibited reduced susceptibility to PZQ, and an urgent need to develop new drugs to treat schistosomiasis has emerged. Thioredoxin glutathione reductase (TGR) plays a crucial role in the redox balance of the parasite, combining glutaredoxin (Grx), glutathione reductase and thioredoxin reductase (TR) activities. Several compounds, including oxadiazole 2-oxides, phosphinic acid amides, isoxazolones and phosphoramidites, have been identified as agents that inhibit TGR from Schistosoma mansoni (smTGR) and exhibit anti-schistosomal activity. 4-Phenyl-1,2,5-oxadiazole-3-carbonitrile-2-oxide has also been shown to be active against TGR from Schistosoma japonicum (sjTGR). The binding sites of these inhibitors, however, remain unclear. To explore the binding interactions of these compounds, we selected six compounds to dock into the NADPH binding site, the active site of the TR domain and the Grx active site of both smTGR and sjTGR using AutoDock 4.2.5.1. The results suggested that the most favoured binding site for all compounds in either sjTGR or smTGR was the oxidised glutathione-binding pocket of the TR domain. Although all of the compounds could fit into the sjTGR site, the inhibition efficiency of these compounds towards sjTGR was marginally lower than it was towards smTGR, suggesting that it would be necessary to design specific inhibitors of TGR for different Schistosoma species. The docking results showed that all compounds docking in smTGR and sjTGR adopted similar binding modes in the TR domain. Two peptide fragments from another subunit, Phe505′–Leu508′ and Pro572′–Thr577′, played a critical role in the interactions with the inhibitors. In conclusion, the present study has revealed binding mechanisms for potential inhibitors of Schistosoma TGRs and could lead to structure-based ligand design and the development of new anti-schistosomiasis drugs.

MicroRNA-31 negatively regulates peripherally derived regulatory T-cell generation by repressing retinoic acid-inducible protein 3

Peripherally derived regulatory T (pT(reg)) cell generation requires T-cell receptor (TCR) signalling and the cytokines TGF-β1 and IL-2. Here we show that TCR signalling induces the microRNA miR-31, which negatively regulates pT(reg)-cell generation. miR-31 conditional deletion results in enhanced induction of pT(reg) cells, and decreased severity of experimental autoimmune encephalomyelitis (EAE). Unexpectedly, we identify Gprc5a as a direct target of miR-31. Gprc5a is known as retinoic acid-inducible protein 3, and its deficiency leads to impaired pT(reg-)cell induction and increased EAE severity. By generating miR-31 and Gprc5a double knockout mice, we show that miR-31 promotes the development of EAE through inhibiting Gprc5a. Thus, our data identify miR-31 and its target Gprc5a as critical regulators for pT(reg)-cell generation, suggesting a previously unrecognized epigenetic mechanism for dysfunctional T(reg) cells in autoimmune diseases.

Quantitative analysis of annexin V-membrane interaction by flow cytometry

We constructed a green fluorescent phosphatidylserine (PS)-binding probe, which was generated by fusing enhanced green fluorescent protein (EGFP) to the C terminus of human annexin V (anxV). With this probe, we investigated anxV-membrane interaction under different calcium and anxV-EGFP concentrations through flow cytometry (FCM). A mathematical description of the binding characteristics is proposed and validated to quantify the relationship concerning the relative concentration of membrane-bound anxV (B), calcium concentration ([C]), and protein concentration ([P]). Further analyses reveal that [Formula: see text] is linear with [Formula: see text] or [Formula: see text] when [P] and [C] are fixed, respectively, which indicates that the anxV-membrane binding reaction may involve sequential multiple steps. Our study provides a reference for application of anxV in apoptosis detection. The mathematical expression facilitates exploration of the possible interactions between calcium, anxV, and membrane. The corresponding mathematical analysis strengthens the interpretation of the interaction data.

Preliminary biological evaluation of ¹⁸F-FBEM-Cys-Annexin V a novel apoptosis imaging agent

A novel annexin V derivative (Cys-Annexin V) with a single cysteine residue at its C-terminal has been developed and successfully labeled site-specifically with ¹⁸F-FBEM. ¹⁸F-FBEM was synthesized by coupling ¹⁸F-fluorobenzoic acid (¹⁸F-FBA) with N-(2-aminoethyl)maleimide using optimized reaction conditions. The yield of ¹⁸F-FBEM-Cys-Annexin V was 71.5% ± 2.0% (n = 4, based on the starting ¹⁸F-FBEM, non-decay corrected). The radiochemical purity of ¹⁸F-FBEM-Cys-Annexin V was >95%. The specific radioactivities of ¹⁸F-FBEM and ¹⁸F-FBEM-Cys-Annexin V were >150 and 3.17 GBq/µmol, respectively. Like the 1st generation ¹⁸F-SFB-Annexin V, the novel ¹⁸F-FBEM-Cys-Annexin V mainly shows renal and to a lesser extent, hepatobiliary excretion in normal mice. In rat hepatic apoptosis models a 3.88 ± 0.05 (n = 4, 1 h) and 10.35 ± 0.08 (n = 4, 2 h) increase in hepatic uptake of ¹⁸F-FBEM-Cys-Annexin V compared to normal rats was observed after injection via the tail vein. The liver uptake ratio (treated/control) at 2 h p.i. as measured via microPET correlated with the ratio of apoptotic nuclei in liver observed using TUNEL histochemistry, indicating that the novel ¹⁸F-FBEM-Cys-Annexin V is a potential apoptosis imaging agent.

PET imaging of apoptosis in tumor-bearing mice and rabbits after paclitaxel treatment with (18)F(-)Labeled recombinant human His10-annexin V

Monitoring response to chemo- or radiotherapy is of great importance in clinical practice. Apoptosis imaging serves as a very useful tool for the early evaluation of tumor response. The goal of this study was PET imaging of apoptosis with (18)F-labeled recombinant human annexin V linked with 10 histidine tag ((18)F-rh-His10-annexin V) in nude mice bearing an A549 tumor and rabbits bearing a VX2 lung cancer after paclitaxel therapy. (18)F-rh-His10-annexin V was prepared by conjugation of rh-His10-annexin V with N-succinimidyl 4-[(18)F]fluorobenzoate. Biodistribution was determined in mice by the dissection method and small-animal PET. Single-dose paclitaxel (175 mg/m(2)) was used to induce apoptosis in A549 and VX2 tumor models. (18)F-rh-His10-annexin V was injected into A549 mice and VX rabbits to acquire dynamic and static PET images 72 h after paclitaxel treatment. The uptake of (18)F-rh-His10-annexin V in apoptotic cells 4 h after induction was 6.45±0.52 fold higher than that in non-induced cells. High focal uptake of (18)F-rh-His10-annexin V was visualized in A549 (SUVmax: 0.35±0.13) and VX2 (0.41±0.23) tumor models after paclitaxel treatment, whereas lower uptake was found in the corresponding tumors before treatment (A549 SUVmax: 0.04±0.02; VX2: 0.009±0.002). The apoptotic index was 75.61±11.56% in the treated VX2 cancer, much higher than that in the untreated VX2 (8.03±2.81%). This study demonstrated the feasibility of (18)F-rh-His10-annexin V for the detection of apoptosis after chemotherapy in A549 and VX2 tumor models.

(99m)Tc-3P-RGD2 micro-single-photon emission computed tomography/computed tomography provides a rational basis for integrin αvβ3-targeted therapy

PURPOSE

This study was to demonstrate the utility of (99m)Tc-3P-RGD2 micro-single-photon emission computed tomography/computed tomography (SPECT/CT) for the integrin αvβ3 expression quantification in NCI-H446 and A549 lung cancer xenografts.

MATERIALS AND METHODS

(99m)Tc-3P-RGD2 was prepared with high radiochemical purity (97%±2%) and showing high in vitro stability. The in vitro affinities of (99m)Tc-3P-RGD2 to NCI-H446 and A549 tumor cells were analyzed with γ-counter, while the in vivo uptakes in NCI-H446 and A549 xenografts were evaluated with micro-SPECT/CT. The region of interest was drawn over the tumor site and contralateral muscle on the SPECT/CT image, and the tumor to nontumor (T/NT) ratio was calculated to estimate αvβ3 expression and tumor uptake. The expressions of integrin αvβ3 in vitro and in vivo were analyzed using a flow cytometer and immunofluorescence.

RESULTS

Micro-SPECT/CT demonstrated focal uptake in the tumors. T/NT ratio in NCI-H446 xenografts was significantly higher compared with the A549 tumor model, as 5.92±0.82 and 3.62±0.91, respectively, with p<0.05. In addition, integrin αvβ3 expression in NCI-H446 cells was significantly higher compared with the A549 cells, which was consistent with the imaging data. A linear relationship was observed between (99m)Tc-3P-RGD2 uptake and αvβ3 expression (R(2)=0.7667, p<0.001).

CONCLUSION

(99m)Tc-3P-RGD2 SPECT/CT could be used to quantify integrin αvβ3 expression within tumors, providing a rational basis for integrin αvβ3-targeted cancer therapy.

The CpxR/CpxA two-component regulatory system up-regulates the multidrug resistance cascade to facilitate Escherichia coli resistance to a model antimicrobial peptide

A genome-wide susceptibility assay was used to identify specific CpxR-dependent genes that facilitate Escherichia coli resistance to a model cationic antimicrobial peptide, protamine. A total of 115 strains from the Keio Collection, each of which contained a deletion at a demonstrated or predicted CpxR/CpxA-dependent locus, were tested for protamine susceptibility. One strain that exhibited high susceptibility carried a deletion of tolC, a gene that encodes the outer membrane component of multiple tripartite multidrug transporters. Concomitantly, two of these efflux systems, AcrAB/TolC and EmrAB/TolC, play major roles in protamine resistance. Activation of the CpxR/CpxA system stimulates mar transcription, suggesting a new regulatory circuit that enhances the multidrug resistance cascade. Tripartite multidrug efflux systems contribute to bacterial resistance to protamine differently from the Tat system. DNase I footprinting analysis demonstrated that the CpxR protein binds to a sequence located in the -35 and -10 regions of mar promoter. This sequence resembles the consensus CpxR binding site, however, on the opposite strand. aroK, a CpxR-dependent gene that encodes a shikimate kinase in the tryptophan biosynthesis pathway, was also found to facilitate protamine resistance. Specific aromatic metabolites from this pathway, such as indole, can stimulate expression of well studied CpxR-dependent genes degP and cpxP, which are not components of the tripartite multidrug transporters. Thus, we propose a novel mechanism for E. coli to modulate resistance to protamine and likely other cationic antimicrobial peptides in which the CpxR/CpxA system up-regulates mar transcription in response to specific aromatic metabolites, subsequently stimulating the multidrug resistance cascade.

A critical role of Fas-associated protein with death domain phosphorylation in intracellular reactive oxygen species homeostasis and aging

AIM

Reactive oxygen species (ROS) plays important roles in aging. However, the specific mechanisms for intracellular ROS accumulation, especially during aging, remain elusive.

RESULTS

We have reported that Fas-associated protein with death domain (FADD) phosphorylation abolishes the recruitment of phosphatase type 2A C subunit (PP2Ac) to protein kinase C (PKC)βII, which specifically regulates mitochondrial ROS generation by p66shc. Here, we have studied the role of FADD phosphorylation in an FADD constitutive-phosphorylation mutation (FADD-D) mouse model. In FADD-D mice, the constitutive FADD phosphorylation led to ROS accumulation (hydrogen peroxide [H₂O₂]), in a process that was dependent on PKCβ and accompanied by increased PKCβ and p66shc phosphorylation, impaired mitochondrial integrity, and enhanced sensitivity to oxidative stress-mediated apoptosis. Moreover, FADD-D mice exhibited premature aging-like phenotypes, including DNA damage, cellular senescence, and shortened lifespan. In addition, we demonstrate that FADD phosphorylation and the recruitment of PP2A and FADD to PKCβ are induced responses to oxidative stress, and that the extent of FADD phosphorylation in wild-type mice was augmented during aging, accompanied by impairment of the interaction between PKCβ and PP2A.

INNOVATION

The present study first addresses the role of FADD phosphorylation in aging through controlling mitochondrial ROS specifically generated by PKCβ.

CONCLUSION

These data identify that FADD phosphorylation is critical for the PKCβ-p66shc signaling route to generate H₂O₂ and to implicate enhanced FADD phosphorylation as a primary cause of ROS accumulation during aging.

Constraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension Gμ below 10(-8) in some regions of the cosmic string parameter space.

Adenosine 5'-monophosphate ameliorates D-galactosamine/lipopolysaccharide-induced liver injury through an adenosine receptor-independent mechanism in mice

D-galactosamine (GalN)/lipopolysaccharide (LPS)-induced lethality and acute liver failure is dependent on endogenously produced inflammatory cytokines. Adenosine has been proven to be a central role in the regulation of inflammatory response. It is not entirely clear that which adenosine action is actually crucial to limiting inflammatory tissue destruction. Here we showed that GalN/LPS challenge elevated hepatic adenosine and induced lethality in adenosine receptor-deficient mice with equal efficiency as wild-type mice. In GalN/LPS-treated mice, pretreatment with adenosine 5'-monophosphate (5'-AMP) significantly elevated hepatic adenosine level and reduced mortality through decreasing cytokine and chemokine production. In RAW264.7 cells, 5'-AMP treatment inhibited the production of inflammatory cytokines, which is not mediated through adenosine receptors. 5'-AMP failed to attenuate LPS-induced nuclear factor-κB (NF-κB) p65 nuclear translocation, but reduced LPS-induced recruitment of NF-κB p65 to inflammatory gene promoters and decreased LPS-induced enrichment of H3K4 dimethylation at the tumor necrosis factor-α (TNF-α) promoter, which was involved in 5'-AMP-induced elevation of cellular adenosine and a decline of methylation potential. In vitro biochemical analysis revealed that adenosine directly attenuated recruitment of NF-κB to the TNF-α and interleukin-6 promoters. Our findings demonstrate that 5'-AMP-inhibiting inflammatory response is not mediated by adenosine receptors and it may represent a potential protective agent for amelioration of LPS-induced liver injury.

Self-renewal and differentiation of muscle satellite cells are regulated by the Fas-associated death domain

Making the decision between self-renewal and differentiation of adult stem cells is critical for tissue repair and homeostasis. Here we show that the apoptotic adaptor Fas-associated death domain (FADD) regulates the fate decisions of muscle satellite cells (SCs). FADD phosphorylation was specifically induced in cycling SCs, which was high in metaphase and declined in later anaphase. Furthermore, phosphorylated FADD at Ser-191 accumulated in the uncommitted cycling SCs and was asymmetrically localized in the self-renewing daughter SCs. SCs containing a phosphoryl-mimicking mutation at Ser-191 of FADD (FADD-D) expressed higher levels of stem-like markers and reduced commitment-associated markers. Moreover, a phosphoryl-mimicking mutation at Ser-191 of FADD suppressed SC activation and differentiation, which promoted the cycling SCs into a reversible quiescent state. Therefore, these data indicate that FADD regulates the fate determination of cycling SCs.

Molecular cloning of the alpha subunit of complement component C8 (CpC8α) of whitespotted bamboo shark (Chiloscyllium plagiosum)

Complement-mediated cytolysis is the important effect of immune response, which results from the assembly of terminal complement components (C5b-9). Among them, α subunit of C8 (C8α) is the first protein that traverses the lipid bilayer, and then initiates the recruitment of C9 molecules to form pore on target membranes. In this article, a full-length cDNA of C8α (CpC8α) is identified from the whitespotted bamboo shark (Chiloscyllium plagiosum) by RACE. The CpC8α cDNA is 2183 bp in length, encoding a protein of 591 amino acids. The deduced CpC8α exhibits 89%, 49% and 44% identity with nurse shark, frog and human orthologs, respectively. Sequence alignment indicates that the C8α is well conserved during the evolution process from sharks to mammals, with the same modular architecture as well as the identical cysteine composition in the mature protein. Phylogenetic analysis places CpC8α and nurse shark C8α in cartilaginous fish clade, in parallel with the teleost taxa, to form the C8α cluster with higher vertebrates. Hydrophobicity analysis also indicates a similar hydrophobicity of CpC8α to mammals. Finally, expression analysis revealed CpC8α transcripts were constitutively highly expressed in shark liver, with much less expression in other tissues. The well conserved structure and properties suggests an analogous function of CpC8α to mammalian C8α, though it remains to be confirmed by further study.

Molecular characterization and expression analysis of complement component C9 gene in the whitespotted bambooshark, Chiloscyllium plagiosum

Complement system is known as highly sophisticated immune defense mechanism for antigen recognition as well as effector functions. Activation of the terminal pathway of the complement system leads to the assembly of terminal complement complexes (C5b-9), which induces the characteristic complement-mediated cytolysis. The lytic activity of shark complement involves functional analogues of mammalian C8 and C9. In this article, a full-length cDNA of C9 (CpC9) is identified from cartilaginous species, the whitespotted bambooshark, Chiloscyllium plagiosum by RACE. The CpC9 cDNA is 2263 bp in length, encoding a protein of 603 amino acids, which shares 42% and 43% identity with human and Xenopus C9 respectively. Through sequence alignment and comparative analysis, the CpC9 protein was found well conserved, with the typical modular architecture in TCCs and nearly unanimous cysteine composition from fish to mammal. Phylogenetic analysis places it in a clade with C9 orthologs in higher vertebrate and as a sister taxa to the Xenopus. Expression analysis revealed that CpC9 is constitutively highly expressed in shark liver, with much less or even undetectable expression in other tissues; demonstrating liver is the primary tissue for C9synthesis. To sum up, the structural conservation and distinctive phylogenetics might indicate the potentially vital role of CpC9 in shark immune response, though it remains to be confirmed by further study.