Design and synthesis of a cell-permeable, drug-like small molecule inhibitor targeting the polo-box domain of polo-like kinase 1

BACKGROUND

Polo-like kinase-1 (Plk1) plays a crucial role in cell proliferation and the inhibition of Plk1 has been considered as a potential target for specific inhibitory drugs in anti-cancer therapy. Several research groups have identified peptide-based inhibitors that target the polo-box domain (PBD) of Plk1 and bind to the protein with high affinity in in vitro assays. However, inadequate proteolytic resistance and cell permeability of the peptides hinder the development of these peptide-based inhibitors into novel therapeutic compounds.

METHODOLOGY/PRINCIPAL FINDINGS

In order to overcome the shortcomings of peptide-based inhibitors, we designed and synthesized small molecule inhibitors. Among these molecules, bg-34 exhibited a high binding affinity for Plk1-PBD and it could cross the cell membrane in its unmodified form. Furthermore, bg-34-dependent inhibition of Plk1-PBD was sufficient for inducing apoptosis in HeLa cells. Moreover, modeling studies performed on Plk1-PBD in complex with bg-34 revealed that bg-34 can interact effectively with Plk1-PBD.

CONCLUSION/SIGNIFICANCE

We demonstrated that the molecule bg-34 is a potential drug candidate that exhibits anti-Plk1-PBD activity and possesses the favorable characteristics of high cell permeability and stability. We also determined that bg-34 induced apoptotic cell death by inhibiting Plk1-PBD in HeLa cells at the same concentration as PEGylated 4j peptide, which can inhibit Plk1-PBD activity 1000 times more effectively than bg-34 can in in vitro assays. This study may help to design and develop drug-like small molecule as Plk1-PBD inhibitor for better therapeutic activity.

Total Solution Synthesis of Human Epidermal Growth Factor (h-EGF) by the Assembly of Nine Building Blocks

Human epidermal growth factor (h-EGF) composed of 53 amino acids bearing three intramolecular disulfide bridges was synthesized by the maximum protecting solution method. The synthetic h-EGF coincided with recombinant h-EGF by reverse-phase HPLC, and the sites of three intramolecular disulfide bridges were ascertained by a thermolytic digestion. The synthetic h-EGF possessed m/z 6215.7 in its FAB-MS as expected, and exhibited compatible mitogenic activity.

Integrin α1β1 differentially regulates cytokine-mediated responses in chondrocytes

OBJECTIVE

To elucidate the role of integrin α1β1 in chondrocyte responses to inflammatory interleukin-1α (IL-1) and anabolic transforming growth factor-β1 (TGF-β1) in the knee.

METHODS

Intracellular calcium transient responses to IL-1 and TGF-β1 were measured in wild type and integrin α1-null chondrocytes using real time ex vivo confocal microscopy, and immunohistochemistry was performed to analyze TGF-β1-mediated activation of Smad2/3 in tibial and femoral chondrocytes.

RESULTS

Loss of integrin α1β1 reduces intracellular calcium transient response to IL-1, while it enhances chondrocyte responses to TGF-β1 as measured by intracellular calcium transients and activation of downstream Smad2/3.

CONCLUSIONS

Integrin α1β1 plays a vital role in mediating chondrocyte responses to two contrasting factors that are critical players in the onset and progression of osteoarthritis - inflammatory IL-1 and anabolic TGF-β. Further investigation into the molecular mechanisms by which integrin α1β1 mediates these responses will be an important next step in understanding the influence of increased expression of integrin α1β1 during the early stages of osteoarthritis on disease progression.

De novo design and synthesis of ultra-short peptidomimetic antibiotics having dual antimicrobial and anti-inflammatory activities

BACKGROUND

Much attention has been focused on the design and synthesis of potent, cationic antimicrobial peptides (AMPs) that possess both antimicrobial and anti-inflammatory activities. However, their development into therapeutic agents has been limited mainly due to their large size (12 to 50 residues in length) and poor protease stability.

METHODOLOGY/PRINCIPAL FINDINGS

In an attempt to overcome the issues described above, a set of ultra-short, His-derived antimicrobial peptides (HDAMPs) has been developed for the first time. Through systematic tuning of pendant hydrophobic alkyl tails at the N(π)- and N(τ)-positions on His, and the positive charge of Arg, much higher prokaryotic selectivity was achieved, compared to human AMP LL-37. Additionally, the most potent HDAMPs showed promising dual antimicrobial and anti-inflammatory activities, as well as anti-methicillin-resistant Staphylococcus aureus (MRSA) activity and proteolytic resistance. Our results from transmission electron microscopy, membrane depolarization, confocal laser-scanning microscopy, and calcein-dye leakage experiments propose that HDAMP-1 kills microbial cells via dissipation of the membrane potential by forming pore/ion channels on bacterial cell membranes.

CONCLUSION/SIGNIFICANCE

The combination of the ultra-short size, high-prokaryotic selectivity, potent anti-MRSA activity, anti-inflammatory activity, and proteolytic resistance of the designed HDAMP-1, -3, -5, and -6 makes these molecules promising candidates for future antimicrobial therapeutics.

Exploring the binding nature of pyrrolidine pocket-dependent interactions in the polo-box domain of polo-like kinase 1

BACKGROUND

Over the years, a great deal of effort has been focused on the design and synthesis of potent, linear peptide inhibitors targeting the polo-like kinase 1 (Plk1), which is critically involved in multiple mitotic processes and has been established as an adverse prognostic marker for tumor patients. Plk1 localizes to its intracellular anchoring sites via its polo-box domain, and inhibiting the Plk1 polo-box domain has been considered as an approach to circumvent the specificity problems associated with inhibiting the conserved adenosine triphosphate-binding pocket. The polo-box domain consists of two different binding regions, such as the unique, broader pyrrolidine-binding pocket and the conserved, narrow, Tyr-rich hydrophobic channel, among the three Plk polo-box domains (Plks 1-3), respectively. Therefore, the studies that provide insights into the binding nature of the unique, broader pyrrolidine-binding pocket might lead to the development of selective Plk1-inhibitory compounds.

METHODOLOGY/PRINCIPAL FINDINGS

In an attempt to retain the monospecificity by targeting the unique, broader pyrrolidine-binding pocket, here, for the first time, a systematic approach was undertaken to examine the structure-activity relationship of N-terminal-truncated PLHSpTM derivatives, to apply a site-directed ligand approach using bulky aromatic and non-aromatic systems, and to characterize the binding nature of these analogues using X-ray crystallographic studies. We have identified a new mode of binding interactions, having improved binding affinity and retaining the Plk1 polo-box domain specificity, at the pyrrolidine-binding pocket. Furthermore, our data revealed that the pyrrolidine-binding pocket was very specific to recognize a short and bulky hydrophobic ligand like adamantane, whereas the Tyr-rich hydrophobic channel was specific with lengthy and small hydrophobic groups.

CONCLUSION/SIGNIFICANCE

The progress made using our site-directed ligands validated this approach to specifically direct the ligand into the unique pyrrolidine-binding region, and it extends the applicability of the strategy for discovering selective protein-protein interaction inhibitors.

Short KR-12 analogs designed from human cathelicidin LL-37 possessing both antimicrobial and antiendotoxic activities without mammalian cell toxicity

KR-12 (residues 18-29 of LL-37) was known to be the smallest peptide of human cathelicidin LL-37 possessing antimicrobial activity. In order to optimize α-helical short antimicrobial peptides having both antimicrobial and antiendotoxic activities without mammalian cell toxicity, we designed and synthesized a series of KR-12 analogs. Highest hydrophobic analogs KR-12-a5 and KR-12-a6 displayed greater inhibition of lipopolysaccharide (LPS)-stimulated tumor necrosis factor-α production and higher LPS-binding activity. We have observed that antimicrobial activity is independent of charge, but LPS neutralization requires a balance of hydrophobicity and net positive charge. Among KR-12 analogs, KR-12-a2, KR-12-a3 and KR-12-a4 showed much higher cell specificity for bacteria over erythrocytes and retained antiendotoxic activity, relative to parental LL-37. KR-12-a5 displayed the strongest antiendotoxic activity but almost similar cell specificity as compared with LL-37. Also, these KR-12 analogs (KR-12-a2, KR-12-a3, KR-12-a4 and KR-12-a5) exhibited potent antimicrobial activity (minimal inhibitory concentration: 4 μM) against methicillin-resistant Staphylococcus aureus. Taken together, these KR-12 analogs have the potential for future development as a novel class of antimicrobial and anti-inflammatory therapeutic agents.

Interleukin 22 polymorphisms and papillary thyroid cancer

BACKGROUND

IL22RA1 (Interleukin 22 receptor-alpha 1), a member of the class II cytokine receptor family, mediates diverse biologic activities and appears to be important in pathogen defense, wound healing, and tissue reorganization. Polymorphisms in genes encoding inflammatory cytokines are associated with increased cancer risk.

AIM

The aim of this study was to evaluate the association between the single nucleotide polymorphisms (SNP) in the IL22 and IL22RA1 and papillary thyroid cancer (PTC), and to assess the relationship between the SNP in the IL22 and IL22RA1 and the clinical parameters of PTC.

MATERIAL AND METHODS

Study enrolled experimental group of 94 PTC patients and 213 controls. PTC patients were grouped and compared for clinical PTC parameters. One promoter SNP of IL22, -429C/T (rs2227485), and one SNP of IL22RA1, Arg518Gly (rs3795299) were analyzed using direct sequencing. Genetic data were analyzed using Helixtree, SNPAnalyzer Pro, SNPStats, and Haploview.

RESULTS

A SNP in IL22 (rs2227485) was significantly associated with PTC (codominant2 model [C/C vs T/T], odds ratio (OR) 2.39, 95% confidence interval (CI) 1.21-4.71, p=0.012; dominant model, OR 1.89, 95% CI 1.08-3.31, p=0.022). The allele T frequency of rs2227485 in IL22 was also associated with PTC (OR 1.59, 95% CI 1.13-2.25, p=0.009). According to clinical parameters, rs2227485 of IL22 was associated with number of cancers (dominant model, OR 3.03, 95% CI 1.02-9.01, p=0.035). By haplotype analysis, TG was associated with PTC (codominant model, OR 1.52, 95% CI 1.07-2.16, p=0.019; dominant model, OR 1.91, 95% CI 1.13- 3.24, p=0.015). Genotype and allele analysis of rs3795299 in IL22RA1 showed no significant differences between PTC patients and controls.

CONCLUSION

The rs2227485 SNP in IL22 might be associated with the risk and the multifocality of PTC.

The inhibitory effects of Escherichia coli maltose binding protein on β-amyloid aggregation and cytotoxicity

The aggregation of β-amyloid (Aβ) peptide from its monomeric to its fibrillar form importantly contributes to the development of Alzheimer's disease. Here, we investigated the effects of Escherichia coli maltose binding protein (MBP), which has been previously used as a fusion protein, on Aβ42 fibrillization, in order to improve understanding of the self-assembly process and the cytotoxic mechanism of Aβ42. MBP, at a sub-stoichiometric ratio with respect to Aβ42, was found to have chaperone-like inhibitory effects on β-sheet fibril formation, due to the accumulation of Aβ42 aggregates by sequestration of active Aβ42 species as Aβ42-MBP complexes. Furthermore, MBP increased the lag time of Aβ42 polymerization, decreased the growth rate of fibril extension, and suppressed Aβ42 mediated toxicity in human neuroblastoma SH-SY5Y cells. It appears that MBP decreases the active concentration of Aβ42 by sequestering it as Aβ42-MBP complex, and that this sequestration suppresses ongoing nucleation and retards the growth rate of Aβ42 species required for fibril formation. We speculate that inhibition of the growth rate of potent Aβ42 species by MBP suppresses Aβ42-mediated toxicity in SH-SY5Y cells.

Keampferol-3-O-rhamnoside abrogates amyloid beta toxicity by modulating monomers and remodeling oligomers and fibrils to non-toxic aggregates

BACKGROUND

Aggregation of soluble, monomeric β- amyloid (Aβ) to oligomeric and then insoluble fibrillar Aβ is a key pathogenic feature in development of Alzheimer's disease (AD). Increasing evidence suggests that toxicity is linked to diffusible Aβ oligomers, rather than to insoluble fibrils. The use of naturally occurring small molecules for inhibition of Aβ aggregation has recently attracted significant interest for development of effective therapeutic strategies against the disease. A natural polyphenolic flavone, Kaempferol-3-O-rhamnoside (K-3-rh), was utilized to investigate its effects on aggregation and cytotoxic effects of Aβ42 peptide. Several biochemical techniques were used to determine the conformational changes and cytotoxic effect of the peptide in the presence and absence of K-3-rh.

RESULTS

K-3-rh showed a dose-dependent effect against Aβ42 mediated cytotoxicity. Anti-amyloidogenic properties of K-3-rh were found to be efficient in inhibiting fibrilogenesis and secondary structural transformation of the peptide. The consequence of these inhibitions was the accumulation of oligomeric structural species. The accumulated aggregates were smaller, soluble, non-β-sheet and non-toxic aggregates, compared to preformed toxic Aβ oligomers. K-3-rh was also found to have the remodeling properties of preformed soluble oligomers and fibrils. Both of these conformers were found to remodel into non-toxic aggregates. The results showed that K-3-rh interacts with different Aβ conformers, which affects fibril formation, oligomeric maturation and fibrillar stabilization.

CONCLUSION

K-3-rh is an efficient molecule to hinder the self assembly and to abrogate the cytotoxic effects of Aβ42 peptide. Hence, K-3-rh and small molecules with similar structure might be considered for therapeutic development against AD.

Linear bactenecin analogs with cell selectivity and anti-endotoxic activity

Bactenecin (Bac) is a 12-residue disulfide-linked antimicrobial peptide isolated from the granules of bovine neutrophils. In this study, to develop novel linear Bac analogs with cell selectivity and anti-endotoxic activity, we designed and synthesized a series of linear Bac analogs with amino acid substitution in Cys3,11 and/or Val6,7 of Bac. Among Bac analogs, some analogs (Bac-W, Bac-KW, Bac-L, Bac-KL, Bac-LW, and Bac-KLW) with higher hydrophobicity showed the amalgamated property of cell selectivity and anti-endotoxic activity. Furthermore, Bac-W, Bac-KW, Bac-LW, and Bac-KLW showed serum stability comparable with that of disulfide-bonded Bac. Therefore, these Bac analogs (Bac-W, Bac-KW, Bac-LW, and Bac-KLW) can serve as promising antibiotics for the development of therapeutic agents for treatment against endotoxic shock and bacterial infection. In addition, our results suggest that a little increase in hydrophobicity may be responsible for the decreased cell selectivity of the multiple Arg-containing peptides (Bac-W, Bac-L, and Bac-LW) over the multiple Lys-containing peptides (Bac-KW, Bac-KL, and Bac-KLW).

Four cases of possible human infections with Delftia lacustris

We report four cases of possible human infections with Delftia lacustris. D. lacustris isolates, which were isolated from blood cultures and bile fluid of patients with underlying diseases such as empyema, renal injury, hepatocellular carcinoma, and renal infarction, were identified using 16S rRNA gene sequencing and biochemical tests. Four D. lacustris isolates did not show the same antimicrobial susceptibility profiles and enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) patterns, indicating their non-clonality.

Application of an immune-magnetic cell sorting method for CD138-positive plasma cells in FISH analysis of multiple myeloma

INTRODUCTION

Interphase fluorescence in situ hybridization (FISH) analysis of multiple myeloma (MM) may indiscriminately count signals of nonplasma cells, thus decreasing specificity and sensitivity. We aimed to evaluate the usefulness of an immune-magnetic sorting method for plasma cells in FISH analysis of MM and define optimal sample preparation conditions.

METHODS

Plasma cells were purified using EasySep(®) CD138 Positive Selection Cocktail and Magnetic Nanoparticles (Invitrogen). We compared FISH results with and without plasma cell purification for three sample preparation methods: direct harvest, 24-h culture, and 96-h culture with interleukin-4 in five newly diagnosed MM patients. Archived fixed bone marrow cells of 17 MM patients were also studied.

RESULTS

The percentage of abnormal cells identified was significantly higher with plasma cell purification than without purification (median, 88.0%; range, 84.0-100.0%vs. 15.0%, 12.5-29.5%, respectively). The three sample preparation methods showed comparable results. Immune-magnetic sorting also significantly increased the percentage of abnormal cells identified in FISH analysis of archived fixed bone marrow cells (P < 0.001).

CONCLUSIONS

Immune-magnetic CD138-positive cell sorting significantly increased the percentage of abnormal cells identified in FISH analysis of MM samples for all sample preparation methods. This method could also be applied for retrospective FISH analysis of archived fixed bone marrow cells.

Prokaryotic selectivity and LPS-neutralizing activity of short antimicrobial peptides designed from the human antimicrobial peptide LL-37

To develop novel antimicrobial peptides (AMPs) with shorter lengths, improved prokaryotic selectivity and retained lipolysaccharide (LPS)-neutralizing activity compared to human cathelicidin AMP, LL-37, a series of amino acid-substituted analogs based on IG-19 (residues 13-31 of LL-37) were synthesized. Among the IG-19 analogs, the analog a4 showed the highest prokaryotic selectivity, but much lower LPS-neutralizing activity compared to parental LL-37. The analogs, a5, a6, a7 and a8 with higher hydrophobicity displayed LPS-neutralizing activity comparable to that of LL-37, but much lesser prokaryotic selectivity. These results indicate that the proper hydrophobicity of the peptides is crucial to exert the amalgamated property of LPS-neutralizing activity and prokaryotic selectivity. Furthermore, to increase LPS-neutralizing activity of the analog a4 without a remarkable decrease in prokaryotic selectivity, we synthesized Trp-substituted analogs (a4-W1 and a4-W2), in which Phe(5) or Phe(15) of a4 is replaced by Trp. Despite their same prokaryotic selectivity, a4-W2 displayed much higher LPS-neutralizing activity compared to a4-W1. When compared with parental LL-37, a4-W2 showed retained LPS-neutralizing activity and 2.8-fold enhanced prokaryotic selectivity. These results suggest that the effective site for Trp-substitution when designing novel AMPs with higher LPS-neutralizing activity, without a remarkable reduction in prokaryotic selectivity, is the amphipathic interface between the end of the hydrophilic side and the start of the hydrophobic side rather than the central position of the hydrophobic side in their α-helical wheel projection. Taken together, the analog a4-W2 can serve as a promising template for the development of therapeutic agents for the treatment of endotoxic shock and bacterial infection.

Single cell analysis of voltage-gated potassium channels that determines neuronal types of rat hypothalamic paraventricular nucleus neurons

The hypothalamic paraventricular nucleus (PVN), a site for the integration of both the neuroendocrine and autonomic systems, has heterogeneous cell composition. These neurons are classified into type I and type II neurons based on their electrophysiological properties. In the present study, we investigated the molecular identification of voltage-gated K+ (Kv) channels, which determines a distinctive characteristic of type I PVN neurons, by means of single-cell reverse transcription-polymerase chain reaction (RT-PCR) along with slice patch clamp recordings. In order to determine the mRNA expression profiles, firstly, the PVN neurons of male rats were classified into type I and type II neurons, and then, single-cell RT-PCR and single-cell real-time RT-PCR analysis were performed using the identical cell. The single-cell RT-PCR analysis revealed that Kv1.2, Kv1.3, Kv1.4, Kv4.1, Kv4.2, and Kv4.3 were expressed both in type I and in type II neurons, and several Kv channels were co-expressed in a single PVN neuron. However, we found that the expression densities of Kv4.2 and Kv4.3 were significantly higher in type I neurons than in type II neurons. Taken together, several Kv channels encoding A-type K+ currents are present both in type I and in type II neurons, and among those, Kv4.2 and Kv4.3 are the major Kv subunits responsible for determining the distinct electrophysiological properties. Thus these 2 Kv subunits may play important roles in determining PVN cell types and regulating PVN neuronal excitability. This study further provides key molecular mechanisms for differentiating type I and type II PVN neurons.

Blood donors on teratogenic drugs and donor deferral periods in a clinical situation

Deferral of blood donors taking teratogenic drugs is critical. From March 2008 to January 2009, we analysed stored blood specimens from donors who had taken teratogenic drugs and whose blood was transfused to women of childbearing age to determine the plasma concentration at the time of donation using high-performance liquid chromatography. In total, 167 specimens were examined. The numbers of specimens exceeding the quantification limit were 7, 39, 4, 2 and 1 for finasteride, isotretinoin, acitretin, etretinate and dutasteride, respectively. Finasteride was beyond the recommended drug deferral period in one specimen. These results may help create practical deferral policies.

A rare case of Lennert's type peripheral T-cell lymphoma with t(14;19)(q11.2;q13.3)

Although most patients with peripheral T-cell lymphoma (PTCL) show clonal rearrangement of T-cell receptor genes, few PTCLs show recurrent chromosomal abnormalities. We describe here a rare chromosomal rearrangement, t(14;19)(q11.2;q13.3), in a Lennert's lymphoma, a variant of PTCL, not otherwise specified. Sequential fluorescence in situ hybridization assays showed that the breakpoint in 19q13.3 was located distal to the BCL3 and PVRL2 genes, both of which may be candidate proto-oncogenes. These findings suggest that another gene is involved in the pathogenic characteristics observed in this patient with Lennert's lymphoma.

Antimicrobial activity, bactericidal mechanism and LPS-neutralizing activity of the cell-penetrating peptide pVEC and its analogs

pVEC is a cell-penetrating peptide derived from the murine vascular endothelial-cadherin protein. To evaluate the potential of pVEC as antimicrobial peptide (AMP), we synthesized pVEC and its analogs with Trp and Arg/Lys substitution, and their antimicrobial and lipopolysaccharide (LPS)-neutralizing activities were investigated. pVEC and its analogs displayed a potent antimicrobial activity (minimal inhibitory concentration: 4-16 μM) against Gram-positive and Gram-negative bacteria but no or less hemolytic activity (less than 10% hemolysis) even at a concentration of 200 μM. These peptides induced a near-complete membrane depolarization (more than 80%) at 4 μM against Staphylococcus aureus and a significant dye leakage (35-70%) from bacterial membrane-mimicking liposome at a concentration as low as 1 μM. The fluorescence profiles of pVEC and its analogs in dye leakage from liposome and membrane depolarization were similar to those of a frog-derived AMP, magainin 2. These results suggest that pVEC and its analogs kill bacteria by forming a pore or ion channel in the cytoplasmic membrane. pVEC and its analogs significantly inhibited nitric oxide production or tumor necrosis factor-α release in LPS-stimulated mouse macrophage RAW264.7 cells at 10 to 50 μM, in which RAW264.7 were not damaged. Taken together, our results suggest that pVEC and its analogs with potent antimicrobial and LPS-neutralizing activities can serve as AMPs for the treatment of microbial infection and sepsis.

Plk1-targeted small molecule inhibitors: molecular basis for their potency and specificity

Members of polo-like kinases (collectively, Plks) have been identified in various eukaryotic organisms and play pivotal roles in cell proliferation. They are characterized by the presence of a distinct region of homology in the C-terminal noncatalytic domain, called polo-box domain (PBD). Among them, Plk1 and its functional homologs in other organisms have been best characterized because of its strong association with tumorigenesis. Plk1 is overexpressed in a wide spectrum of cancers in humans, and is thought to be an attractive anti-cancer drug target. Plk1 offers, within one molecule, two functionally different drug targets with distinct properties-the N-terminal catalytic domain and the C-terminal PBD essential for targeting the catalytic activity of Plk1 to specific subcellular locations. In this review, we focused on discussing the recent development of small-molecule and phosphopeptide inhibitors for their potency and specificity against Plk1. Our effort in understanding the binding mode of various inhibitors to Plk1 PBD are also presented.

Cell selectivity, mechanism of action and LPS-neutralizing activity of bovine myeloid antimicrobial peptide-18 (BMAP-18) and its analogs

To develop novel antimicrobial peptides (AMPs) with improved cell selectivity and potent LPS-neutralizing activity, we synthesized an 18 N-terminal residues peptide (BAMP-18) of bovine myeloid antimicrobial peptide-27 (BMAP-27) and its analogs (BMAP-18-W, BMAP-18-L, BMAP-18-I and BMAP-18-f). BMAP-18 and its analogs displayed much higher cell selectivity (about 4-97-fold increased) as compared to parental BMAP-27 because of their decreased hemolytic activity and retained antimicrobial activity. BMAP-27 caused near-complete dye leakage from bacterial-membrane-mimicking vesicles even at very low concentration of 0.5μM, whereas BMAP-18 and its analogs induced very little dye leakage (less than 40%) even at 16μM. These peptides induced near-complete membrane depolarization of Staphylococcus aureus cells under their MIC (4μM). These results suggests that BMAP-18 and its analogs exhibit lethality toward microbes due to their ability to form small channels that permit the transit of ions or protons, but not molecules as large as calcein, and not by the membrane-disruption/perturbation mode. BMAP-18 and its analogs significantly inhibited nitric oxide (NO) production or tumor necrosis factor-α (TNF-α) release in LPS-stimulated mouse macrophage RAW264.7 cells at 10μM. In particular, BMAP-18-W showed LPS-neutralizing activity comparable to that of BMAP-27. There was a significant linear correlation between the increase in the hydrophobicity of peptides and LPS-neutralizing activity. Although BMAP-18-W has lower hydrophobicity than BMAP-18-L, it showed higher LPS-neutralizing activity as compared to BMAP-18-L. This result suggests other important parameters of AMPs may be involved in their LPS-neutralizing activity, as well as positive charge and hydrophobicity.

Biflavonoids are superior to monoflavonoids in inhibiting amyloid-β toxicity and fibrillogenesis via accumulation of nontoxic oligomer-like structures

Polymerization of monomeric amyloid-β peptides (Aβ) into soluble oligomers and insoluble fibrils is one of the major pathways triggering the pathogenesis of Alzheimer's disease (AD). Using small molecules to prevent the polymerization of Aβ peptides can, therefore, be an effective therapeutic strategy for AD. In this study, we investigate the effects of mono- and biflavonoids in Aβ42-induced toxicity and fibrillogenesis and find that the biflavonoid taiwaniaflavone (TF) effectively and specifically inhibits Aβ toxicity and fibrillogenesis. Compared to TF, the monoflavonoid apigenin (AP) is less effective and less specific. Our data show that differential effects of the mono- and biflavonoids in Aβ fibrillogenesis correlate with their varying cytoprotective efficacies. We also find that other biflavonoids, namely, 2',8''-biapigenin, amentoflavone, and sumaflavone, can also effectively inhibit Aβ toxicity and fibrillogenesis, implying that the participation of two monoflavonoids in a single biflavonoid molecule enhances their activity. Biflavonoids, while strongly inhibiting Aβ fibrillogenesis, accumulate nontoxic Aβ oligomeric structures, suggesting that these are off-pathway oligomers. Moreover, TF abrogates the toxicity of preformed Aβ oligomers and fibrils, indicating that TF and other biflavonoids may also reduce the toxicity of toxic Aβ species. Altogether, our data clearly show that biflavonoids, possibly because of the possession of two Aβ binders separated by an appropriate size linker, are likely to be promising therapeutics for suppressing Aβ toxicity.

Candidacidal mechanism of a Leu/Lys-rich α-helical amphipathic model antimicrobial peptide and its diastereomer composed of D,L-amino acids

We investigated the mechanism of candidacidal action of a Lys/Leu-rich α-helical model antimicrobial peptide (K(9)L(8)W) and its diastereomeric peptide (D(9)-K(9)L(8)W) composed of D,L-amino acids. K(9)L(8)W killed completely Candida albicans within 30 min, but D(9)-K(9)L(8)W killed only 72% of C. albicans even after 100 min. Tryptophan fluorescence spectroscopy indicated that the fungal cell selectivity of D(9)-K(9)L(8)W is closely correlated with a selective interaction with the negatively charged PC/PE/PI/ergosterol (5:2.5:2.5:1, w/w/w/w) phospholipids, which mimic the outer leaflet of the plasma membrane of C. albicans. K(9)L(8)W was able to induce almost 100% calcein leakage from PC/PE/PI/ergosterol (5:2.5:2.5:1, w/w/w/w) liposomes at a peptide:lipid molar ratio of 1:16, whereas D(9)-K(9)L(8)W caused only 25% dye leakage even at a peptide:lipid molar ratio of 1:2. Confocal laser-scanning microscopy revealed that FITC-labeled D(9)-K(9)L(8)W penetrated the cell wall and cell membrane and accumulated inside the cells, whereas FITC-labeled K(9)L(8)W did not penetrate but associated with the membranes. Collectively, our results demonstrated that the candidacidal activity of K(9)L(8) W and D(9)-K(9)L(8)W may be due to the transmembrane pore/channel formation or perturbation of the fungal cytoplasmic membranes and the inhibition of intracellular functions, respectively. Finally, D(9)-K(9)L(8)W with potent anti-Candida activity but no hemolytic activity may be potentially a useful lead compound for the development of novel antifungal agents.

CT characteristics of a uterus-like mass in the sigmoid mesocolon

A uterus-like mass is a rare, benign extra-uterine tumour composed of smooth muscle and endometrium. The majority of uterus-like masses occur in the ovary. Rarely, uterus-like masses occur in the broad ligament, small bowel, small bowel mesentery or uterine cervix. Here, we report a case of a uterus-like mass in the sigmoid mesocolon. A well-defined, markedly enhanced soft-tissue mass with central cystic change and haemorrhage was observed on CT. The current report describes the CT characteristics of this sigmoid mesocolon uterus-like mass together with the differential diagnoses.

The thin line between cell-penetrating and antimicrobial peptides: the case of Pep-1 and Pep-1-K

Cell-penetrating peptides (CPPs) are cationic oligopeptides able to translocate across biological membranes without perturbing them, while antimicrobial peptides (AMPs) kill bacteria mainly by disrupting their membranes. The two peptide classes share several characteristics (charge, amphipathicity, helicity, and length), and therefore the molecular properties discriminating between the two different bioactivities are not clear. Pep-1-K (KKTWWKTWWTKWSQPKKKRKV) is a new AMP derived from the widely studied CPP Pep-1 (KETWWETWWTEWSQPKKKRKV), or 'Chariot', known for its ability to carry large cargoes across biological membranes. Pep-1-K was obtained from Pep-1 by substituting the three Glu residues with Lys, to increase its cationic character. Previous studies showed that these modifications endow Pep-1-K with a potent antimicrobial activity, with MICs in the low micromolar range. Here, we characterized the interaction of Pep-1 and Pep-1-K with model membranes to understand the reason for the antimicrobial activity of Pep-1-K. The data show that this peptide causes vesicle aggregation, perturbs membrane order, and induces the leakage of ions, but not of larger solutes, while these effects were not observed for Pep-1. These differences are likely due, at least in part, to the higher affinity of Pep-1-K toward anionic bilayers, which mimick the composition of bacterial membranes.

Magnolol Inhibits LPS-induced NF-κB/Rel Activation by Blocking p38 Kinase in Murine Macrophages

This study demonstrates the ability of magnolol, a hydroxylated biphenyl compound isolated from Magnolia officinalis, to inhibit LPS-induced expression of iNOS gene and activation of NF-κB/Rel in RAW 264.7 cells. Immunohisto-chemical staining of iNOS and Western blot analysis showed magnolol to inhibit iNOS gene expression. Reporter gene assay and electrophoretic mobility shift assay showed that magnolol inhibited NF-κB/Rel transcriptional activation and DNA binding, respectively. Since p38 is important in the regulation of iNOS gene expression, we investigated the possibility that magnolol to target p38 for its anti-inflammatory effects. A molecular modeling study proposed a binding position for magnolol that targets the ATP binding site of p38 kinase (3GC7). Direct interaction of magnolol and p38 was further confirmed by pull down assay using magnolol conjugated to Sepharose 4B beads. The specific p38 inhibitor SB203580 abrogated the LPS-induced NF-κB/Rel activation, whereas the selective MEK-1 inhibitor PD98059 did not affect the NF-κB/Rel. Collectively, the results of the series of experiments indicate that magnolol inhibits iNOS gene expression by blocking NF-κB/Rel and p38 kinase signaling.

Mammalian cell toxicity and candidacidal mechanism of Arg- or Lys-containing Trp-rich model antimicrobial peptides and their d-enantiomeric peptides

In this study, we investigated the mammalian cell toxicity and candidacidal mechanism of Arg- or Lys-containing Trp-rich model antimicrobial peptides (K(6)L(2)W(3) and R(6)L(2)W(3)) and their d-enantiomeric peptides (K(6)L(2)W(3)-d and R(6)L(2)W(3)-d). Arg-containing peptides were more toxic to human erythrocytes and mammalian cells as compared to Lys-containing peptides. Arg-containing peptides is slightly more hydrophobic than Lys-containing counterparts, as judged from their reverse phase-high performance liquid chromatography (RP-HPLC) retention time. These results suggested that a little difference in hydrophobicity of these peptides affect their hemolytic activity and mammalian cell toxicity. Interestingly, K(6)L(2)W(3) and K(6)L(2)W(3)-d almost similar mammalian cell cytotoxicity, whereas R(6)L(2)W(3)-d showed much higher cytotoxicity as compared to R(6)L(2)W(3). A low ability to facilitate fluorescent marker escape from Candida albicans membrane-mimicking vesicles suggested that the major target site of Lys-containing peptides may be not the cell membrane but the cytoplasm of C. albicans. Confocal laser-scanning microscopy revealed that FITC-labeled Lys-containing peptides penetrated the cell wall and cell membrane and accumulated inside the cells, whereas FITC-labeled Arg-containing peptides did not penetrate but associated with the membranes. Collectively, our results suggested that the ultimate target site of action of Arg-containing peptides and Lys-containing peptides may be the membrane and the cytoplasm of C. albicans, respectively.

Analysis of the solution structure of the human antibiotic peptide dermcidin and its interaction with phospholipid vesicles

Dermcidin is a human antibiotic peptide that is secreted by the sweat glands and has no homology to other known antimicrobial peptides. As an initial step toward understanding dermcidin's mode of action at bacterial membranes, we used homonuclear and heteronuclear NMR to determine the conformation of the peptide in 50% trifluoroethanol solution. We found that dermcidin adopts a flexible amphipathic alpha-helical structure with a helix-hinge-helix motif, which is a common molecular fold among antimicrobial peptides. Spin-down assays of dermcidin and several related peptides revealed that the affinity with which dermcidin binds to bacterial-mimetic membranes is primarily dependent on its amphipathic alpha-helical structure and its length (>30 residues); its negative net charge and acidic pI have little effect on binding. These findings suggest that the mode of action of dermcidin is similar to that of other membrane-targeting antimicrobial peptides, though the details of its antimicrobial action remain to be determined.

Purification of catalytically active caspase-12 and its biochemical characterization

Caspase-12, mainly detected in endoplasmic reticulum (ER), has been suggested to play a role in ER-mediated apoptosis and inflammatory caspase activation pathway. Cleavage of the prodomain by caspase-3/-7 at the carboxyl terminus of Asp94 or m-calpain at the carboxyl terminus of Lys158 was reported to be a part of caspase-12-involved apoptosis. We biochemically characterized the prodomain-free forms of caspase-12 and the equivalent enzymes; Deltapro1(G95-D419), rev-Deltapro1[(T319-N419)-(G95-D318), a reverse form of Deltapro1] and rev-Deltapro2[(T319-N419)-(T159-D318)]. The three variants showed comparable activities which were dependent on salt concentration and pH. Auto-proteolytic cleavage was observed at two sites (carboxyl termini of Asp318 and Asp320) in Deltapro1. Constitutively active forms of caspase-12 (rev-Deltapro1 and rev-Deltapro2) could induce cell death in cells transfected with the corresponding expression vectors, but no cleavage of caspase-3, DFF45 or Bid was observed, indicating caspase-12 may mediate a distinct apoptotic pathway rather than caspase-8 or -9-mediated cell death.

Structural flexibility and the positive charges are the key factors in bacterial cell selectivity and membrane penetration of peptoid-substituted analog of Piscidin 1

Piscidin 1 (Pis-1) is a novel cytotoxic peptide with a cationic alpha-helical structure isolated from the mast cells of hybrid striped bass. In our previous study, we showed that Pis-1[PG] with a substitution of Pro(8) for Gly(8) in Pis-1 had higher bacterial cell selectivity than Pis-1. We designed peptoid residue-substituted peptide, Pis-1[NkG], in which Gly(8) of Pis-1 was replaced with Nlys (Lys peptoid residue). Pis-1[NkG] had higher antibacterial activity and lower cytotoxicity against mammalian cells than Pis-1 and Pis-1[PG]. We determined the tertiary structure of Pis-1[PG] and Pis-1[NkG] in the presence of DPC micelles by NMR spectroscopy. Both peptides had a three-turn helix in the C-terminal region and a bent structure in the center. Pis-1[PG] has a rigid bent structure at Pro(8) whereas Pis-1[NkG] existed as a dynamic equilibrium of two conformers with a flexible hinge structure at Nlys(8). Depolarization of the membrane potential of Staphylococcus aureus and confocal laser-scanning microscopy study revealed that Pis-1[NkG] effectively penetrated the bacterial cell membrane and accumulated in the cytoplasm, whereas Pis-1[PG] did not penetrate the membrane but remained outside or on the cell surface. Introduction of a lysine peptoid at position 8 of Pis-1 provided conformational flexibility and increased the positive charge at the hinge region; both factors facilitated penetration of the bacterial cell membrane and conferred bacterial cell selectivity on Pis-1[NkG].

Cell selectivity and anti-inflammatory activity of a Leu/Lys-rich alpha-helical model antimicrobial peptide and its diastereomeric peptides

To investigate the effect of the number and distribution of d-amino acids introduced into non-cell-selective alpha-helical antimicrobial peptides on the cell selectivity, protease stability and anti-inflammatory activity, we synthesized an 18-meric Leu/Lys-rich alpha-helical model peptide (K(9)L(8)W) and d-amino acid-containing diastereomeric peptides. Increasing in cell selectivity of the peptides was increased in parallel with increasing in the number of d-amino acids introduced. Despite having the same number of d-amino acids, D(9)-K(9)L(8)W-1 had better cell selectivity than D(9)-K(9)L(8)W-2, indicating that a dispersed distribution of d-amino acids in diastereomeric peptides is more effective for cell selectivity than their segregated distribution. D(3)-K(9)L(8)W-2, D(6)-K(9)L(8)W, D(9)-K(9)L(8)W-1 and D(9)-K(9)L(8)W-2 showed complete resistance to tryptic digestion. Furthermore, K(9)L(8)W and all of its diastereomeric peptides significantly inhibited nitric oxide (NO) production, inducible nitric oxide synthase (iNOS) mRNA expression and tumor necrosis factor-alpha (TNF-alpha) release in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells at a lower concentration than bactericidal concentration. The order of anti-inflammatory activity for the peptides was K(9)L(8)W approximately D(3)-K(9)L(8)W-1 approximately D(3)-K(9)L(8)W-2 approximately D(6)-K(9)L(8)W approximately D(9)-K(9)L(8)W-2>D(4)-K(9)L(8)W>D(9)-K(9)L(8)W-1. Increasing in hydrophobicity or alpha-helicity of the peptides was more closely correlated with increasing in hemolytic activity and anti-inflammatory activity than antimicrobial and LPS-disaggregation activities. Collectively, we successfully developed several d-amino acid-containing antimicrobial peptides (D(4)-K(9)L(8)W, D(6)-K(9)L(8)W and D(9)-K(9)L(8)W-1) with good cell selectivity, protease stability and potent anti-inflammatory activity. These antimicrobial peptides could serve as templates for the development of peptide antibiotics for the treatment of sepsis, as well as microbial infection.

Antimicrobial specificity and mechanism of action of disulfide-removed linear analogs of the plant-derived Cys-rich antimicrobial peptide Ib-AMP1

Ib-AMP1 is a 20-residue disulfide-linked beta-sheet antimicrobial peptide found in the seeds of Impatiens balsamina. In order to investigate the effects of the 2 disulfide bonds on the antimicrobial specificity, to determine the mechanism of antimicrobial action of Ib-AMP1 and to develop novel cell-selective antimicrobial peptides with improved antimicrobial specificity as compared to wild-type Ib-AMP1, we synthesized a disulfide-removed linear analog of Ib-AMP1 with L-Pro, D-Pro or peptoid residues (Nala and Nlys) at the central position of the molecule. All linear analogs displayed a 3.7-4.8-fold higher antimicrobial specificity than wild-type Ib-AMP1, indicating that the disulfide bonds of Ib-AMP1 analogs are not essential for its antimicrobial specificity. Circular dichroism spectra revealed that the peptoid residues, as well as the proline at the central position of disulfide bond-removed Ib-AMP1 analogs, induce a beta-turn structure in a negatively charged bacterial membrane-mimicking environment. Ib-AMP1 was not effective in depolarizing the cytoplasmic membranes of Staphylococcus aureus and showed almost no leakage of calcein from negatively charged bacterial membranes mimicking lipid vesicles. In contrast, all linear analogs caused very weak dye leakage from negatively charged vesicles, but they almost completely depolarized the membrane potential of S. aureus cells. Collectively, our results suggest that the target of Ib-AMP1 may not be the cytoplasmic membranes of bacteria but their intracellular components. All linear analogs exhibit lethality due to their ability to form small channels that permit the transit of ions or protons and not molecules as large as calcein, and not by disrupting membranes.

Different modes of antibiotic action of homodimeric and monomeric bactenecin, a cathelicidin-derived antibacterial peptide

The bactenecin is an antibacterial peptide with an intramolecular disulfide bond. We recently found that homodimeric bactenecin exhibits more potent antibacterial activity than the monomeric form and retains its activity at physiological conditions. Here we assess the difference in the modes of antibiotic action of homodimeric and monomeric bactenecins. Both monomeric and dimeric bactenecins almost completely killed both Staphylococcus aureus and E. coli within 10-30 min at concentrations of 8-16 muM. However, exposure to liposomes elicited an increase in the fluorescence quantum yield from a tryptophan-containing monomeric analog, while the homodimeric analog showed a significant reduction in fluorescence intensity. Moreover, unlike the monomer, the homodimer displayed apparent membrane-lytic activity enabling release of various sized dyes from liposomes, and rapidly and fully depolarized the S. aureus membrane. Together, our results suggest that homodimeric bactenecin forms pores in the bacterial membrane, while monomeric one penetrates through the membrane to target intracellular molecules/organelles. [BMB reports 2009; 42(9): 586-592].

Design of novel indolicidin-derived antimicrobial peptides with enhanced cell specificity and potent anti-inflammatory activity

Indolicidin (IN) is a 13-residue Trp-rich antimicrobial peptide isolated from bovine neutrophils. To develop novel IN-derived antimicrobial peptides with enhanced cell specificity (therapeutic index) and potent anti-inflammatory activity, several IN analogs were synthesized by Pro-->Lys substitution. All IN analogs displayed an increase in therapeutic index by 3- to 15-fold relative to parental IN. IN and its analogs induced a significant membrane depolarization against intact Staphylococcus aureus in a dose-dependent manner and depolarized membrane potential at 5 microg/ml (MIC for S. aureus) almost completely. However, these peptides caused less than 40% calcein leakage from negatively charged EYPG/EYPE liposomes mimicking bacterial membranes at 10 microg/ml. Based on these results, we hypothesize that IN and its analogs kill microorganisms via the formation of small ion channels that permit transit of ions or protons, but not molecules as large as calcein. Furthermore, IN and its analogs induced a remarkable suppression in nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) mRNA expression in LPS-stimulated mouse macrophage RAW264.7 cells. All IN analogs showed LPS-binding activity comparable to that of IN. Taken together, their potent antimicrobial, anti-inflammatory and LPS-neutralizing activities similar to those of IN, coupled with their no cytotoxicity, our designed IN analogs make excellent candidates for novel antimicrobial and anti-sepsis agents.

Antimicrobial and cytolytic activities and plausible mode of bactericidal action of the cell penetrating peptide penetratin and its lys-linked two-stranded peptide

The cell penetrating peptide, penetratin (RQIKIWFQNRRMKWKK-NH2) showed potent antimicrobial activity (MIC: 0.5-4 microM) without any cytotoxicity against mammalian cells. This study investigated the effect of linking together two peptide chains of penetratin on antimicrobial and cytolytic activities and plausible mode of bactericidal action. Two-stranded penetratin was prepared by a simultaneous solid-phase synthesis of the two strands of a single lysine residue attached to the solid support. Two-stranded penetratin markedly increased cytolytic activity against human erythrocytes and NIH-3T3 mouse fibroblast cells without a significant effect on antimicrobial activity. This finding suggested that penetratin is active as a monomer to bacterial cells but as an oligomer to mammalian cells. Circular dichroism analysis revealed that the alpha-helical content of the membrane-bound penetratin was unaffected by two-stranded Lys-linkage. Penetratin had very weak ability in the depolarization of membrane potential of intact Staphylococcus aureus cells and the fluorescent dye leakage of calcein-entrapped negatively charged bacterial membrane-mimicking vesicles. In contrast, two-stranded penetratin significantly caused membrane depolarization and dye leakage. These results suggest that the two-stranded penetratin induces a significant change in its mode of bactericidal action from the intracellular-target mechanism to the membrane-targeting mechanism.

Screening of flavonoids as candidate antibiotics against Enterococcus faecalis

beta-Ketoacyl acyl carrier protein synthase (KAS) III, the most divergent member of the condensing enzyme family, is a key catalyst in bacterial fatty acid biosynthesis and, thus, an attractive target for novel antibiotics. Here, we perform docking studies between Enterococcus faecalis KAS III (efKAS III) and one flavanone and 11 hydroxyflavanones with hydroxy groups at various positions. The MIC values of these flavanones for E. faecalis and vancomycin-resistant E. faecalis (VREF) were measured, and binding affinities to efKAS III were determined. Naringenin (9), eriodictyol (10), and taxifolin (12), with high-scoring functions and good binding affinities, docked well with efKAS III, resulting in MIC values in the range 128-512 microg/mL. Our results indicate that hydrogen bonds between the 5- and 4'-hydroxy groups and the side-chain of Arg38 and the backbone carbonyl of Phe308 are the key interactions for efKAS III inhibition. These flavanones are good candidate KAS III inhibitors and may be utilized as effective antimicrobials.

Cell specificity, anti-inflammatory activity, and plausible bactericidal mechanism of designed Trp-rich model antimicrobial peptides

To develop novel short Trp-rich antimicrobial peptides (AMPs) with potent cell specificity (targeting bacteria but not eukaryotic cells) and anti-inflammatory activity, a series of 11-meric Trp-rich model peptides with different ratios of Leu and Lys/Arg residues, XXWXXWXXWXX-NH(2) (X indicates Leu or Lys/Arg), was synthesized. K(6)L(2)W(3) displayed an approximately 40-fold increase in cell specificity, compared with the natural Trp-rich AMP indolicidin (IN). Lys-containing peptides (K(8)W(3), K(7)LW(3) and K(6)L(2)W(3)) showed approximately 2- to 4-fold higher cell specificities than did their counterparts, the Arg-containing peptides (R(8)W(3), R(7)LW(3) and R(6)L(2)W(3)), indicating that multiple Lys residues are more important than multiple Arg residues in the design of AMPs with good cell specificity. The excellent resistance of d-enantiomers (K(6)L(2)W(3)-D and R(6)L(2)W(3)-D) and Orn/Nle-containing peptides (O(6)L(2)W(3) and O(6)L(2)W(3)) to trypsin digestion compared with the rapid breakdown of the l-enantiomers (K(6)L(2)W(3) and R(6)L(2)W(3)), highlights the clinical potential of such peptides. K(6)L(2)W(3), R(6)L(2)W(3), K(6)L(2)W(3)-D and R(6)L(2)W(3)-D caused weak dye leakage from bacterial membrane-mimicking negatively charged EYPG/EYPE (7:3, v/v) liposomes. Confocal microscopy showed that these peptides penetrated the cell membrane of Escherichia coli and accumulated in the cytoplasm, as observed for buforin-2. Gel retardation studies revealed that the peptides bound more strongly to DNA than did IN. These results suggested that one possible peptide bactericidal mechanism may relate to the inhibition of intracellular functions via interference with DNA/RNA synthesis. Furthermore, some model peptides, containing K(6)L(2)W(3), K(5)L(3)W(3), R(6)L(2)W(3), O(6)L(2)W(3), O(6)L(2)W(3), and K(6)L(2)W(3)-D inhibited LPS-induced inducible nitric oxide synthase (iNOS) mRNA expression, the release of nitric oxide (NO) following LPS stimulation in RAW264.7 cells and had powerful LPS binding activities at bactericidal concentrations. Collectively, our results indicated that these peptides have potential for future development as novel antimicrobial and anti-inflammatory agents.