Proposal of a Network System to Solve the Problem of Small Volume in Liver Transplantation; Catholic Medical Center Network

INTRODUCTION

Liver transplantation (LT) is a complex and demanding procedure associated with significant perioperative challenges and risks. Concerns have arisen regarding LT outcomes in low-volume centers. We implemented an integrated training and surgical team network to address these concerns within the Catholic Medical Center (CMC) network. This study presents a comprehensive review of our 9-year LT experience within the CMC medical network.

METHOD

A retrospective study of LT procedures conducted between January 2013 and August 2021 in 6 CMC-affiliated hospitals was performed. One center was categorized as a high-volume center, conducting over 60 cases annually, and the remaining 5 were considered small-volume centers. The primary endpoints assessed were 1-year and 5-year survival rates.

RESULTS

A total of 793 LTs were performed during the study period. The high-volume center performed 411 living donor LT (LDLT) cases and 127 deceased donor LT (DDLT) cases. Also, 146 LDLT cases and 109 DDLT cases were performed in 5 small-volume centers. One-year and 5-year patient survival for LDLT recipients was 88.3% and 78.8% in the high-volume center and 85.6% and 80.6% in the low-volume center. Five-year survival was not significantly different in small-volume centers (P = .903). For DDLT recipients, 1-year and 5-year patient survival was 80.3% and 70.6% in the high-volume center and 76.1% and 67.6% in the low-volume center. In DDLT cases, 5-year survival was not significantly different in small-volume centers (P = .445).

CONCLUSION

In conclusion, comparable outcomes for liver transplantation can be obtained in a small-volume center with a high level of integrated training systems and networks.

Liver Transplantation at a Small Volume Center-The Role of Network System

BACKGROUND

Liver transplantation (LT) is typically performed at specialized, high-volume centers. However, some smaller centers also offer liver transplantation services, but their outcomes and safety have been a subject of debate. To overcome these difficulties, we tried to build a Catholic Medical Center (CMC) network to share our experiences and overcome the lack of volume. In this study, we reviewed the overall outcome of patients undergoing LT at a small-volume procedure center, with a focus on patient and graft survival rates.

METHODS

Between July 2014 and September 2021, 60 adults underwent LT at Bucheon Saint Mary's Hospital. The overall outcomes were analyzed in terms of perioperative outcomes, complications, and overall survival rate. In addition, the patients were divided into a benign end-stage liver disease (ESLD) group (n = 44) and a hepatocellular carcinoma (HCC) group (n = 16). The baseline characteristics, perioperative outcomes, complications, and overall survival rate were analyzed between the 2 groups.

RESULTS

Of a total of 60 LT, living donor liver transplantation (LDLT) was 26, and deceased donor liver transplantation was 34. LDLT was 14 (31.8%) in the ESLD group and 12 (75.0%) in the HCC group. The overall 1-year, 3-year, and 5-year survival rates were 86.7%, 79.7%, and 77.7%, respectively. The survival difference was not statistically significant (P = .214) between the 2 groups.

CONCLUSION

We suggest that with appropriate patient selection and adequate resources, LT can be safely performed at smaller centers with the assistance of the CMC network, thus expanding access to this life-saving procedure.

Pioneering PGC-1α-boosted secretome: a novel approach to combating liver fibrosis

Purpose

Liver fibrosis is a critical health issue with limited treatment options. This study investigates the potential of PGC-Sec, a secretome derived from peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α)-overexpressing adipose-derived stem cells (ASCs), as a novel therapeutic strategy for liver fibrosis.

Methods

Upon achieving a cellular confluence of 70%-80%, ASCs were transfected with pcDNA-PGC-1α. PGC-Sec, obtained through concentration of conditioned media using ultrafiltration units with a 3-kDa cutoff, was assessed through in vitro assays and in vitro mouse models.

Results

In vitro, PGC-Sec significantly reduced LX2 human hepatic stellate cell proliferation and mitigated mitochondrial oxidative stress compared to the control-secretome. In an in vivo mouse model, PGC-Sec treatment led to notable reductions in hepatic enzyme activity, serum proinflammatory cytokine concentrations, and fibrosis-related marker expression. Histological analysis demonstrated improved liver histology and reduced fibrosis severity in PGC-Sec-treated mice. Immunohistochemical staining confirmed enhanced expression of PGC-1α, optic atrophy 1 (a mitochondrial function marker), and peroxisome proliferator-activated receptor alpha (an antifibrogenic marker) in the PGC-Sec-treated group, along with reduced collagen type 1A expression (a profibrogenic marker).

Conclusion

These findings highlight the therapeutic potential of PGC-Sec in combating liver fibrosis by enhancing mitochondrial biogenesis and function, and promoting antifibrotic processes. PGC-Sec holds promise as a novel treatment strategy for liver fibrosis.

Clinical Analysis of Factors Affecting Hospital Mortality After Liver Transplant in Patients With High Model for End-Stage Liver Disease Score

BACKGROUND

This study was undertaken to identify poor prognostic factors in patients with high Model for End-Stage Liver Disease (MELD) scores.

METHODS

From September 2001 to December 2017, living donor liver transplant and deceased donor liver transplant were performed in 851 (84.4%) and 157 patients (15.6%), respectively, in our center. Eighty-one patients (8.0%) with MELD scores ≥ 35 were classified as patients with high MELD scores.

RESULTS

The overall survival rates in patients with high MELD scores were significantly worse than those in patients with low MELD scores (P = .005). However, no significant difference in survival was found between the 2 groups when in-hospital mortality was excluded. In-hospital mortality occurred in 18 patients (22.2%), and the main cause of death was sepsis (n = 14, 77.8%). On univariate analysis, the risk factors for in-hospital mortality were mean age (P = .028), mean MELD score (P = .045), intubation status (P < .001), culture positivity (P = .042), and encephalopathy grade 3 or 4 (P = .014). On multivariate analysis, age (P = .006), intubation status (P = .042), and culture positivity (P = .036) were significant.

CONCLUSIONS

The main cause of in-hospital mortality was sepsis, and the risk factors for in-hospital mortality of patients with high MELD score were older age, preoperative intubation, and culture positivity. Special attention should be paid to the prevention and treatment of infection in the liver transplant of patient with high MELD scores.

Single-Center Experience with Hepatic Artery Reconstruction During Living Donor Liver Transplantation: Microscope Versus Surgical Loupe

Background

Hepatic artery reconstruction during living donor liver transplantation is a critical step. To perform this risky procedure, a microscope has been used. However, it takes a long time to complete the procedure and it has a long and steep learning curve. Recently, some transplant surgeons have performed the procedure using a surgical loupe. We conducted this study to compare the outcomes after hepatic artery reconstruction using a microscope versus using a surgical loupe.

Material/Methods

We retrospectively reviewed the outcomes of 300 patients at our institution from April 2014 to July 2020. From April 2014 to September 2017 (era 1), hepatic artery reconstruction was performed using a microscope by an experienced plastic surgeon. From September 2017 to the end date (era 2), it was performed using a loupe (×5.0) by an experienced transplantation surgeon.

Results

There was no difference in most perioperative outcomes between the 2 groups, including the major postoperative complications of hepatic artery complications (2/150 versus 2/150, P=1.000), postoperative bleeding (10/150 versus 5/150, P=0.185), and biliary leakage (18/150 versus 13/150, P=0.343). There was a statistically significant difference between the 2 groups in anastomosis time (42.4±11.8 versus 24.2±7.8, P<0.001) and the entire operation time (436.6±83.9 versus 415.3±68.5, P=0.035).

Conclusions

We suggest that when the surgeon is familiar with a loupe and vascular anastomosis, hepatic artery reconstruction using a surgical loupe is a safe and feasible method with a shorter operation time.

PEP27-2, a Potent Antimicrobial Cell-Penetrating Peptide, Reduces Skin Abscess Formation during Staphylococcus aureus Infections in Mouse When Used in Combination with Antibiotics

PEP27, a 27-amino acid (aa) peptide secreted by Streptococcus pneumoniae, is an autolytic peptide that functions as a major virulence factor. To develop a clinically applicable antimicrobial peptide (AMP), we designed PEP27 analogs with Trp substitutions to enhance its antimicrobial activity compared to that of PEP27. Particularly, PEP27-2 showed strong antimicrobial activity against a wide variety of bacteria, including multidrug-resistant (MDR) bacteria. It was found that the antimicrobial activity of PEP27-2 was increased by substituting Trp for the aa at the middle position of PEP27. We found that PEP27-2 acts as an effective cell-penetrating peptide in bacterial and mammalian cells. Here, we proved that subcutaneous infection with MDR Staphylococcus aureus induced skin lesions such as skeletal muscle damage, deep inflammation, and necrosis of the overlaying dermis in mice. Combination treatment with antibiotics revealed synergistic effects, remarkably reducing abscess size and improving the bacteria removal rate from the infection site. Moreover, PEP27-2-antibiotic combination treatment reduced inflammation, lowering levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, inducible NO synthase (iNOS), and cyclooxygenase (COX-2) in skin abscess tissue. The results suggest that the PEP27-2 peptide is a promising therapeutic option for combating MDR bacterial strains by enhancing antibiotic penetration and protecting against MDR bacteria.

Vibration reduction during milling of highly flexible workpieces using active workpiece holder system

The milling of highly flexible workpieces, such as thin-walled structures used in turbine blades, aerospace equipment, and jet engine compressors, requires vibration compensation to improve the quality of the workpiece surface. Vibration can be reduced by selecting appropriate cutting parameters. However, this approach reduces system productivity. This paper presents an active workpiece holder that controls the vibration of general computer numerical control machine tools. The proposed holder, which comprises a flexible guide mechanism, driver, and sensor, measures vibration and actively controls it using piezoactuators. A high-rigidity flexure mechanism was designed for the holder, and finite element method simulation and modal analysis were performed. Finally, the proposed system was fabricated, and experimental verification indicated that the system reduced vibration. The surface quality obtained using the controlled system was ∼50% better than that obtained using the uncontrolled system.

Non-Receptor-Mediated Lipid Membrane Permeabilization by the SARS-CoV-2 Spike Protein S1 Subunit

Due to the pressing need to generate specific drugs or vaccines for COVID-19 and management of its outbreak, detailed knowledge regarding the SARS-CoV-2 entry into host cells and timely, cheap, and easy-to-use detection methods are of critical importance for containing the SARS-CoV-2 epidemic. Through electrophysiology and fluorescence spectroscopy experiments, we show that even in the absence of the angiotensin-converting enzyme 2 receptor, the S1 subunit from SARS-CoV-2 spike protein binding to neutral phospholipid membranes leads to their mechanical destabilization and permeabilization. A similar cytotoxic effect of the protein was seen in human lung epithelial cells. A monoclonal antibody generated toward the S1 subunit alleviates to a considerable extent the destabilizing potential of the protein in such model membranes. Finally, we demonstrate the proof-of-concept capability of an α-hemolysin (α-HL) protein nanopore to detect in aqueous buffer and real time the region-binding domain of the S1 subunit from SARS-CoV-2 spike protein by monitoring its immunological interaction with a target antibody. Our results may offer new perspectives in understanding the pathogenesis of the SARS-CoV-2 infection, its treatment, and real-time detection.

Sequence-specific detection of single-stranded DNA with a gold nanoparticle-protein nanopore approach

Fast, cheap and easy to use nucleic acids detection methods are crucial to mitigate adverse impacts caused by various pathogens, and are essential in forensic investigations, food safety monitoring or evolution of infectious diseases. We report here a method based on the α-hemolysin (α-HL) nanopore, working in conjunction to unmodified citrate anion-coated gold nanoparticles (AuNPs), to detect nanomolar concentrations of short single-stranded DNA sequences (ssDNA). The core idea was to use charge neutral peptide nucleic acids (PNA) as hybridization probe for complementary target ssDNAs, and monitor at the single-particle level the PNA-induced aggregation propensity AuNPs during PNA–DNA duplexes formation, by recording ionic current blockades signature of AuNP–α-HL interactions. This approach offers advantages including: (1) a simple to operate platform, producing clear-cut readout signals based on distinct size differences of PNA-induced AuNPs aggregates, in relation to the presence in solution of complementary ssDNAs to the PNA fragments (2) sensitive and selective detection of target ssDNAs (3) specific ssDNA detection in the presence of interference DNA, without sample labeling or signal amplification. The powerful synergy of protein nanopore-based nanoparticle detection and specific PNA–DNA hybridization introduces a new strategy for nucleic acids biosensing with short detection time and label-free operation.

Mechanism of action of antimicrobial peptide P5 truncations against Pseudomonas aeruginosa and Staphylococcus aureus

Rates of microbial drug resistance are increasing worldwide; therefore, antimicrobial peptides (AMPs) are considered promising alternative therapeutic agents to antibiotics. AMPs are essential components of the innate immune system and exhibit broad-spectrum antimicrobial activity. P5 is a Cecropin A-Magainin 2 hybrid analog peptide with antimicrobial activity against Gram-negative and Gram-positive bacteria. In the present study, truncated peptides were designed to reduction length, retainment their antimicrobial activity and low toxicity at high concentrations compared with that of the parent peptide P5. The truncated peptides P5-CT1 and P5-NT1 exhibited antibacterial activities against both Gram-negative and Gram-positive bacteria. In contrast, P5-CT2, P5-CT3, P5-NT2, and P5-NT3 showed higher antibacterial activities against gram-positive bacteria compared to Gram-negative bacteria at low concentration of peptides. The truncated peptides showed lower hemolytic activity and toxic effects against mammalian cells compared with those of the parent peptide P5. The levels of several truncated peptides were maintained in the presence of physiological concentrations of salts, indicating their high stability. The results of flow cytometry, propidium iodide uptake, n-phenyl-1-naphthylamine uptake, and 3,3′-dipropylthiadicarbocyanine iodide assays showed that these truncated peptides killed microbial cells by increasing membrane permeability, thereby causing membrane damage. The results suggested that truncated peptides of P5 have good potential for use as novel antimicrobial agents.

Nonfunctionalized PNAs as Beacons for Nucleic Acid Detection in a Nanopore System

In this work, single-channel current recordings were used to selectively detect individual ssDNA strands in the vestibule of the α-hemolysin (α-HL) protein nanopore. The sensing mechanism was based on the detection of the intrinsic topological change of target ssDNA molecules after the hybridization with complementary PNA fragments. The readily distinguishable current signatures of PNA-DNA duplexes reversible association with the α-HL's vestibule, in terms of blockade amplitudes and kinetic features, allows specific detection of nucleic acid hybridization.

Antimicrobial and Immunomodulatory Properties and Applications of Marine-Derived Proteins and Peptides

Marine organisms provide an abundant source of potential medicines. Many of the marine-derived biomaterials have been shown to act as different mechanisms in immune responses, and in each case they can significantly control the immune system to produce effective reactions. Marine-derived proteins, peptides, and protein hydrolysates exhibit various physiologic functions, such as antimicrobial, anticancer, antioxidant, antihypertensive, and anti-inflammatory activities. Recently, the immunomodulatory properties of several antimicrobial peptides have been demonstrated. Some of these peptides directly kill bacteria and exhibit a variety of immunomodulatory activities that improve the host innate immune response and effectively eliminate infection. The properties of immunomodulatory proteins and peptides correlate with their amino acid composition, sequence, and length. Proteins and peptides with immunomodulatory properties have been tested in vitro and in vivo, and some of them have undergone different clinical and preclinical trials. This review provides a comprehensive overview of marine immunomodulatory proteins, peptides, and protein hydrolysates as well as their production, mechanisms of action, and applications in human therapy.

Single-Molecule, Real-Time Dissecting of Peptide Nucleic Acid-DNA Duplexes with a Protein Nanopore Tweezer

Peptide nucleic acids (PNAs) are artificial, oligonucleotides analogues, where the sugar-phosphate backbone has been substituted with a peptide-like N-(2-aminoethyl)glycine backbone. Because of their inherent benefits, such as increased stability and enhanced binding affinity toward DNA or RNA substrates, PNAs are intensively studied and considered beneficial for the fields of materials and nanotechnology science. Herein, we designed cationic polypeptide-functionalized, 10-mer PNAs, and demonstrated the feasible detection of hybridization with short, complementary DNA substrates, following analytes interaction with the vestibule entry of an α-hemolysin (α-HL) nanopore. The opposite charged state at the polypeptide-functionalized PNA-DNA duplex extremities, facilitated unzipping of a captured duplex at the lumen entry of a voltage-biased nanopore, followed by monomers threading. These processes were resolvable and identifiable in real-time, from the temporal profile of the ionic current through a nanopore accompanying conformational changes of a single PNA-DNA duplex inside the α-HL nanopore. By employing a kinetic description within the discrete Markov chains theory, we proposed a minimalist kinetic model to successfully describe the electric force-induced strand separation in the duplex. The distinct interactions of the duplex at either end of the nanopore present powerful opportunities for introducing new generations of force-spectroscopy nanopore-based platforms, enabling from the same experiment duplex detection and assessment of interstrand base pairing energy.

Mechanisms driving the antibacterial and antibiofilm properties of Hp1404 and its analogue peptides against multidrug-resistant Pseudomonas aeruginosa

Hp1404, identified from the venom of the scorpion Heterometrus petersii, displays antimicrobial activity with cytotoxicity. Several synthetic peptides were designed based on the parent peptide Hp1404 to reduce cytotoxicity and improve activity (deletion of glycine and phenylalanine, substitution with leucine and lysine). The analogue peptides generated comprised 12 amino acids and displayed amphipathic α-helical structures, with higher hydrophobic moments and net positive charge than those of the Hp1404. The analogues showed less hemolytic and toxic effects toward mammalian cells than the Hp1404, especially Hp1404-T1e, which exhibited particularly potent antibacterial and antibiofilm activities against multidrug-resistant Pseudomonas aeruginosa (MRPA) strains. The analogue peptide Hp1404-T1e was more stable against salt and trypsin than the Hp1404. Hp1404's mechanism of action involves binding to lipopolysaccharide (LPS), thereby killing bacteria through membrane disruption. Hp1404-T1e kills bacteria more rapidly than Hp1404 and not only seems to bind more strongly to LPS but may also be able to enter bacterial cells and interact with their DNA. Additionally, Hp1404-T1e can effectively kill bacteria in vivo. The results of this study indicate that Hp1404-T1e not only displays antimicrobial activity, but is also functional in physiological conditions, confirming its potential use as an effective therapeutic agent against MRPA.

Macropis fulvipes Venom component Macropin Exerts its Antibacterial and Anti-Biofilm Properties by Damaging the Plasma Membranes of Drug Resistant Bacteria

The abuse of antibiotics for disease treatment has led to the emergence of multidrug resistant bacteria. Antimicrobial peptides, found naturally in various organisms, have received increasing interest as alternatives to conventional antibiotics because of their broad spectrum antimicrobial activity and low cytotoxicity. In a previous report, Macropin, isolated from bee venom, exhibited antimicrobial activity against both gram-positive and negative bacteria. In the present study, Macropin was synthesized and its antibacterial and anti-biofilm activities were tested against bacterial strains, including gram-positive and negative bacteria, and drug resistant bacteria. Moreover, Macropin did not exhibit hemolytic activity and cytotoxicity to keratinocytes, whereas Melittin, as a positive control, showed very high toxicity. Circular dichroism assays showed that Macropin has an α-helical structure in membrane mimic environments. Macropin binds to peptidoglycan and lipopolysaccharide and kills the bacteria by disrupting their membranes. Moreover, the fractional inhibitory concentration index indicated that Macropin has additive and partially synergistic effects with conventional antibiotics against drug resistant bacteria. Thus, our study suggested that Macropin has potential for use of an antimicrobial agent for infectious bacteria, including drug resistant bacteria.

Prognostic factors after curative resection hepatocellular carcinoma and the surgeon's role

Purpose

Patient, surgical, and tumor factors affect the outcome after surgical resection for hepatocellular carcinoma (HCC). The surgical factors are only modifiable by the surgeon. We reviewed our experience with curative resection for HCC in terms of surgical factors.

Methods

After analyses of the prospectively collected clinical data of 256 consecutive patients undergoing surgical resection for HCC, prognostic factors for disease-free survival (DFS) and overall survival (OS) were identified; all patients were stratified by tumor diameters > or <5 cm and their outcomes were compared.

Results

Multivariate analyses showed that microvascular invasion, estimated blood loss, blood transfusion, and the number of tumors were independent adverse prognostic factors for DFS, whereas microvascular invasion, serum alpha fetoprotein, and tumor diameter were independent adverse prognostic factors for OS. Blood transfusion had borderline significance (P = 0.076). After stratification by tumor diameter, blood transfusion was only associated with poor DFS and OS in patients with tumor diameters > 5 cm.

Conclusion

Tumor recurrence after liver resection for HCC depends on tumor status, bleeding, and transfusions, which subsequently lead to poor patient survival. Surgeons can help improve the prognosis of patients by minimizing blood loss and transfusion, particularly in patients with larger tumors.

Myxinidin2 and myxinidin3 suppress inflammatory responses through STAT3 and MAPKs to promote wound healing

Skin wounds are continuously exposed to bacteria and can easily become infected. Infected wounds require antibiotic treatment, and infections caused by drug-resistant bacteria are an important public health problem. Antimicrobial peptides have broad-spectrum antibacterial activity, induce little or no drug resistance and may be suitable for treating skin infections caused by drug-resistant bacteria. We previously reported the design and function of myxinidin and myxinidin analogues. Here we showed that myxinidin2 and myxinidin3 exhibit antimicrobial and anti-biofilm activities against antibiotic-resistant Staphylococcus aureus, Acinetobacter baumannii, and Pseudomonas aeruginosa in high salt environments and in gelatin. Moreover, these peptides facilitated infected wound healing by decreasing inflammation through suppression of IL-6, IL-8, and TNF-α and regulation of downstream mediators such as STAT3, p38, JNK, and EGFR. In a mouse skin wound model infected with antibiotic-resistant bacteria, myxinidin2 and myxinidin3 eliminated the infection and enhanced wound healing. We therefore propose the use of these peptides for treating infected wounds and burns.

Nanoscale Investigation of Generation 1 PAMAM Dendrimers Interaction with a Protein Nanopore

Herein, we describe at uni-molecular level the interactions between poly(amidoamine) (PAMAM) dendrimers of generation 1 and the α-hemolysin protein nanopore, at acidic and neutral pH, and ionic strengths of 0.5 M and 1 M KCl, via single-molecule electrical recordings. The results indicate that kinetics of dendrimer-α-hemolysin reversible interactions is faster at neutral as compared to acidic pH, and we propose as a putative explanation the fine interplay among conformational and rigidity changes on the dendrimer structure, and the ionization state of the dendrimer and the α-hemolysin. From the analysis of the dendrimer's residence time inside the nanopore, we posit that the pH- and salt-dependent, long-range electrostatic interactions experienced by the dendrimer inside the ion-selective α-hemolysin, induce a non-Stokesian diffusive behavior of the analyte inside the nanopore. We also show that the ability of dendrimer molecules to adapt their structure to nanoscopic spaces, and control the flow of matter through the α-hemolysin nanopore, depends non-trivially on the pH- and salt-induced conformational changes of the dendrimer.

The therapeutic applications of antimicrobial peptides (AMPs): a patent review

Antimicrobial peptides (AMPs) are small molecules with a broad spectrum of antibiotic activities against bacteria, yeasts, fungi, and viruses and cytotoxic activity on cancer cells, in addition to anti-inflammatory and immunomodulatory activities. Therefore, AMPs have garnered interest as novel therapeutic agents. Because of the rapid increase in drug-resistant pathogenic microorganisms, AMPs from synthetic and natural sources have been developed using alternative antimicrobial strategies. This article presents a broad analysis of patents referring to the therapeutic applications of AMPs since 2009. The review focuses on the universal trends in the effective design, mechanism, and biological evolution of AMPs.

A Protein Nanopore-Based Approach for Bacteria Sensing

We present herein a first proof of concept demonstrating the potential of a protein nanopore-based technique for real-time detection of selected Gram-negative bacteria (Pseudomonas aeruginosa or Escherichia coli) at a concentration of 1.2 × 108 cfu/mL. The anionic charge on the bacterial outer membrane promotes the electrophoretically driven migration of bacteria towards a single α-hemolysin nanopore isolated in a lipid bilayer, clamped at a negative electric potential, and followed by capture at the nanopore's mouth, which we found to be described according to the classical Kramers' theory. By using a specific antimicrobial peptide as a putative molecular biorecognition element for the bacteria used herein, we suggest that the detection system can combine the natural sensitivity of the nanopore-based sensing techniques with selective biological recognition, in aqueous samples, and highlight the feasibility of the nanopore-based platform to provide portable, sensitive analysis and monitoring of bacterial pathogens.

Electroosmotic Trap Against the Electrophoretic Force Near a Protein Nanopore Reveals Peptide Dynamics During Capture and Translocation

We report on the ability to control the dynamics of a single peptide capture and passage across a voltage-biased, α-hemolysin nanopore (α-HL), under conditions that the electroosmotic force exerted on the analyte dominates the electrophoretic transport. We demonstrate that by extending outside the nanopore, the electroosmotic force is able to capture a peptide at either the lumen or vestibule entry of the nanopore, and transiently traps it inside the nanopore, against the electrophoretic force. Statistical analysis of the resolvable dwell-times of a metastable trapped peptide, as it occupies either the β-barrel or vestibule domain of the α-HL nanopore, reveals rich kinetic details regarding the direction and rates of stochastic movement of a peptide inside the nanopore. The presented approach demonstrates the ability to shuttle and study molecules along the passage pathway inside the nanopore, allows to identify the mesoscopic trajectory of a peptide exiting the nanopore through either the vestibule or β-barrel moiety, thus providing convincing proof of a molecule translocating the pore. The kinetic analysis of a peptide fluctuating between various microstates inside the nanopore, enabled a detailed picture of the free energy description of its interaction with the α-HL nanopore. When studied at the limit of vanishingly low transmembrane potentials, this provided a thermodynamic description of peptide reversible binding to and within the α-HL nanopore, under equilibrium conditions devoid of electric and electroosmotic contributions.

Role of antimicrobial peptides expressed by host cells upon infection by Helicobacter pylori

Colonization of the stomach by Helicobacter pylori can result in such gastrointestinal illnesses as chronic gastritis, peptic ulcer and gastric cancer. Antimicrobial peptides (AMPs) are expressed in the stomach and play a key role in the innate immune responses to H. pylori in humans. During H. pylori infections, AMP expression mediated by NOD-1, NF-kB and/or ERK, functions to eradicate the bacteria, thereby preventing the gastritis and gastric cancer. This suggests that the use of synthetic AMPs could be one component of an effective therapeutic strategy to combat H. pylori. In addition, it appears that some peptides, and combinations of peptides, act synergistically with conventional drugs, thereby enhancing therapeutic efficacy. Our aim in this article was to review what is currently known about gastric AMP expression in response to H. pylori infection, and to briefly discuss the potential use of AMPs, either alone or in combination with conventional antibiotics, for the treatment of H. pylori infection.

Antagonistic Activities of Novel Peptides from Bacillus amyloliquefaciens PT14 against Fusarium solani and Fusarium oxysporum

Bacillus species have recently drawn attention due to their potential use in the biological control of fungal diseases. This paper reports on the antifungal activity of novel peptides isolated from Bacillus amyloliquefaciens PT14. Reverse-phase high-performance liquid chromatography revealed that B. amyloliquefaciens PT14 produces five peptides (PT14-1, -2, -3, -4a, and -4b) that exhibit antifungal activity but are inactive against bacterial strains. In particular, PT14-3 and PT14-4a showed broad-spectrum antifungal activity against Fusarium solani and Fusarium oxysporum. The PT14-4a N-terminal amino acid sequence was identified through Edman degradation, and a BLAST homology analysis showed it not to be identical to any other protein or peptide. PT14-4a displayed strong fungicidal activity with minimal inhibitory concentrations of 3.12 mg/L (F. solani) and 6.25 mg/L (F. oxysporum), inducing severe morphological deformation in the conidia and hyphae. On the other hand, PT14-4a had no detectable hemolytic activity. This suggests PT14-4a has the potential to serve as an antifungal agent in clinical therapeutic and crop-protection applications.

Risk factors and long-term outcomes of delayed graft function in deceased donor renal transplantation

Purpose

The purpose of this study was to analyze the risk factors for delayed graft function (DGF) and determine its impact on the outcomes of deceased donor (DD) kidney transplantation (KT).

Methods

Between January 2000 and December 2011, we performed 195 DD renal transplants. After the exclusion of primary nonfunctional grafts (n = 4), the study recipients were divided into two groups-group I, DGF (n = 31, 16.2%); group II, non-DGF (n = 160, 83.8%). The following variables were compared: donor and recipient characteristics, patient and graft survival, postoperative renal function, acute rejection (AR) episodes, and the rates of surgical and infectious complications.

Results

Donor-related variables that showed significant differences included hypertension (P = 0.042), diabetes (P = 0.025), and prerecovery serum creatinine levels (P < 0.001). However, there were no significant differences in recipient-related factors. One significantly different transplant-related factor was positive panel reactive antibody (PRA > 20%, P = 0.008). On multivariate analysis, only the prerecovery serum creatinine level (P < 0.001; hazard ratio [HR], 1.814) was an independent risk factor for the development of DGF. A Cox multivariate analysis of risk factors for graft survival identified these independent risk factors for graft survival: nephron mass (donor kidney weight to recipient body weight ratio) index (P = 0.026; HR, 2.328), CMV infection (P = 0.038; HR, 0.114), and AR episode (P = 0.038; HR, 0.166).

Conclusion

In DD KT, an independent risk factor for DGF was the prerecovery serum creatinine level. Although there was a significant difference in graft survival between the DGF and non-DGF groups, DGF was not an independent risk factor for graft failure in this study.

Acidity-Mediated, Electrostatic Tuning of Asymmetrically Charged Peptides Interactions with Protein Nanopores

Despite success in probing chemical reactions and dynamics of macromolecules on submillisecond time and nanometer length scales, a major impasse faced by nanopore technology is the need to cheaply and controllably modulate macromolecule capture and trafficking across the nanopore. We demonstrate herein that tunable charge separation engineered at the both ends of a macromolecule very efficiently modulates the dynamics of macromolecules capture and traffic through a nanometer-size pore. In the proof-of-principle approach, we employed a 36 amino acids long peptide containing at the N- and C-termini uniform patches of glutamic acids and arginines, flanking a central segment of asparagines, and we studied its capture by the α-hemolysin (α-HL) and the mean residence time inside the pore in the presence of a pH gradient across the protein. We propose a solution to effectively control the dynamics of peptide interaction with the nanopore, with both association and dissociation reaction rates of peptide-α-HL interactions spanning orders of magnitude depending upon solution acidity on the peptide addition side and the transmembrane electric potential, while preserving the amplitude of the blockade current signature.

The effects of marine carbohydrates and glycosylated compounds on human health

Marine organisms have been recognized as a valuable source of bioactive compounds with industrial and nutraceutical potential. Recently, marine-derived carbohydrates, including polysaccharides and low molecular weight glycosylated oligosaccharides, have attracted much attention because of their numerous health benefits. Moreover, several studies have reported that marine carbohydrates exhibit various biological activities, including antioxidant, anti-infection, anticoagulant, anti-inflammatory, and anti-diabetic effects. The present review discusses the potential industrial applications of bioactive marine carbohydrates for health maintenance and disease prevention. Furthermore, the use of marine carbohydrates in food, cosmetics, agriculture, and environmental protection is discussed.

Marine peptides and their anti-infective activities

Marine bioresources are a valuable source of bioactive compounds with industrial and nutraceutical potential. Numerous clinical trials evaluating novel chemotherapeutic agents derived from marine sources have revealed novel mechanisms of action. Recently, marine-derived bioactive peptides have attracted attention owing to their numerous beneficial effects. Moreover, several studies have reported that marine peptides exhibit various anti-infective activities, such as antimicrobial, antifungal, antimalarial, antiprotozoal, anti-tuberculosis, and antiviral activities. In the last several decades, studies of marine plants, animals, and microbes have revealed tremendous number of structurally diverse and bioactive secondary metabolites. However, the treatments available for many infectious diseases caused by bacteria, fungi, and viruses are limited. Thus, the identification of novel antimicrobial peptides should be continued, and all possible strategies should be explored. In this review, we will present the structures and anti-infective activity of peptides isolated from marine sources (sponges, algae, bacteria, fungi and fish) from 2006 to the present.

Quantitative understanding of pH- and salt-mediated conformational folding of histidine-containing, β-hairpin-like peptides, through single-molecule probing with protein nanopores

Inter-amino acid residues electrostatic interactions contribute to the conformational stability of peptides and proteins, influence their folding pathways, and are critically important to a multitude of problems in biology including the onset of misfolding diseases. By varying the pH and ionic strength, the inter-amino acid residues electrostatic interactions of histidine-containing, β-hairpin-like peptides alter their folding behavior, and we studied this through quantifying, at the unimolecular level, the frequency, dwell-times of translocation events, and amplitude of blockades associated with interactions between such peptides and the α-hemolysin (α-HL) protein. Acidic buffers were shown to dramatically decrease the rate of peptide capture by the α-HL protein, through the interplay of enthalpic and entropic contributions brought about on the free energy barrier, which controls the peptides-α-HL association rate. We found that in acidic buffers, the amplitude of the blockage induced by an α-HL, β-barrel-residing peptide is smaller than the value seen at neutral pH, and this supports our interpretation of the pH-induced change in the conformation of the peptide, which behaves as a less-stable hairpin at acidic pH values that obstructs, to a lesser extent, the protein pore. This is also confirmed by the fact that the dissociation rate of such model peptide from the α-HL's β-barrel is higher at acidic, as compared to neutral, pH values. Experiments performed in low-salt buffers revealed the dramatic decrease of the peptide capture rate by the α-HL protein, most likely caused by the increase in the radius of counterions cloud around the peptide that hinders peptide partition into the α-barrel, and histidines protonation at low pH bolsters this effect. Reduced electrostatic screening in low-salt buffers, at neutral pH, leads to a decrease in peptides effective cross-sectional areas and an increase of their mobility inside the α-HL pore, due most likely to the chain stretching augmentation, via increased inter-residues electrostatic interactions.

Micropit surfaces designed for accelerating osteogenic differentiation of murine mesenchymal stem cells via enhancing focal adhesion and actin polymerization

Recent reports demonstrate that enhanced focal adhesion (FA) between cells and the extracellular matrix (ECM) and intracellular actin polymerization (AP) upregulates cellular functions such as proliferation, stem-cell fate and differentiation. Purposed to accelerate osteogenic differentiation, enhancement of FAs and AP of cells was induced by adding a tailor-made micropit (tMP, 3 × 3 μm(2)) with different heights (2 or 4 μm). The tMP surface was examined for its differentiation efficiency using mouse mesenchymal stem cells, C3H10T1/2. Though the cell spreading area was not affected by the surface topography, cells on the tMP substrates had enhanced FAs which were significantly confined inside the micropits, increased actin polymerization and traction forces, and osteogenic differentiation. Further experiments with Y-27632 and Blebbistatin, which specifically regulate FA or AP functions, demonstrated that the tMP-induced acceleration of osteogenic differentiation was caused by the rho-associated, coiled-coil containing protein kinase (ROCK) and nonmuscle myosin II (NM II), which are key molecules of the RhoA/ROCK signaling pathway. The tMP is applicable as an osteo-active substrate for the instructive bone cell differentiation and population.

PG-2, a Potent AMP against Pathogenic Microbial Strains, from Potato (Solanum tuberosum L cv. Gogu Valley) Tubers Not Cytotoxic against Human Cells

In an earlier study, we isolated potamin-1 (PT-1), a 5.6-kDa trypsin-chymotrypsin protease inhibitor, from the tubers of a potato strain (Solanum tuberosum L cv. Gogu Valley). We established that PT-1 strongly inhibits pathogenic microbial strains, but not human bacterial strains, and that its sequence shows 62% homology with a serine protease inhibitor. In the present study, we isolated an antifungal and antibacterial peptide with no cytotoxicity from tubers of the same potato strain. The peptide (peptide-G2, PG-2) was isolated using salt-extraction, ultrafiltration and reverse-phase high performance liquid chromatography (RP-HPLC). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) showed the protein to have a molecular mass of 3228.5 Da, while automated Edman degradation showed the N-terminal sequence of PG-2 to be LVKDNPLDISPKQVQALCTDLVIRCMCCC-. PG-2 exhibited antimicrobial activity against Candida albicans, a human pathogenic yeast strain, and Clavibacter michiganensis subsp. michiganensis, a plant late blight strain. PG-2 also showed antibacterial activity against Staphylococcus aureus, but did not lyse human red blood cells and was thermostable. Overall, these results suggest PG-2 may be a good candidate to serve as a natural antimicrobial agent, agricultural pesticide and/or food additive.

Effect of repetitive lysine-tryptophan motifs on the eukaryotic membrane

In a previous study, we synthesized a series of peptides containing simple sequence repeats, (KW)_n–NH₂ (n = 2,3,4 and 5) and determined their antimicrobial and hemolytic activities, as well as their mechanism of antimicrobial action. However, (KW)₅ showed undesirable cytotoxicity against RBC cells. In order to identify the mechanisms behind the hemolytic and cytotoxic activities of (KW)₅, we measured the ability of these peptides to induce aggregation of liposomes. In addition, their binding and permeation activities were assessed by Trp fluorescence, calcein leakage and circular dichrorism using artificial phospholipids that mimic eukaryotic liposomes, including phosphatidylcholine (PC), PC/sphingomyelin (SM) (2:1, w/w) and PC/cholesterol (CH) (2:1, w/w). Experiments confirmed that only (KW)₅ induced aggregation of all liposomes; it formed much larger aggregates with PC:CH (2:1, w/w) than with PC or PC:SM (2:1, w/w). Longer peptide (KW)₅, but not (KW)₃ or (KW)₄, strongly bound and partially inserted into PC:CH compared to PC or PC:SM (2:1, w/w). Calcein release experiments showed that (KW)₅ induced calcein leakage from the eukaryotic membrane. Greater calcein leakage was induced by (KW)₅ from PC:CH than from PC:SM (2:1, w/w) or PC, whereas (KW)₄ did not induce calcein leakage from any of the liposomes. Circular dichroism measurements indicated that (KW)₅ showed higher conformational transition compared to (KW)₄ due to peptide-liposome interactions. Taken together, our results suggest that (KW)₅ reasonably mediates the aggregation and permeabilization of eukaryotic membranes, which could in turn explain why (KW)₅ displays efficient hemolytic activity.

Antifungal activity of (KW)n or (RW)n peptide against Fusarium solani and Fusarium oxysporum

The presence of lysine (Lys) or arginine (Arg) and tryptophan (Trp) are important for the antimicrobial effects of cationic peptides. Therefore, we designed and synthesized a series of antimicrobial peptides with various numbers of Lys (or Arg) and Trp repeats [(KW and RW)(n)-NH(2), where n equals 2, 3, 4, or 5]. Antifungal activities of these peptides increased with chain length. Light microscopy demonstrated that longer peptides (n = 4, 5) strongly inhibited in vitro growth of Fusarium solani, and Fusarium oxysporum, at 4-32 μM. Furthermore, longer peptides displayed potent fungicidal activities against a variety of agronomical important filamentous fungi, including F. solani and F. oxysporum, at their minimal inhibitory concentrations (MICs). However, RW series peptides showed slightly higher fungicidal activities than KW peptides against the two strains. Taken together, the results of this study indicate that these short peptides would be good candidates for use as synthetic or transgenic antifungal agents.

Effect of repetitive lysine-tryptophan motifs on the bactericidal activity of antimicrobial peptides

Previous studies identified lysine- and tryptophan-rich sequences within various cationic antimicrobial peptides. In the present study, we synthesized a series of peptides composed of lysine (K)-tryptophan (W) repeats (KW)_n (where n equals 2, 3, 4 or 5) with amidation of the C-terminal to increase cationicity. We found that increases in chain length up to (KW)₄ enhanced the peptides’ antibacterial activity; (KW)₅ exhibited somewhat less bactericidal activity than (KW)₄. Cytotoxicity, measured as lysis of human red blood cells, also increased with increasing chain length. With (KW)₅, reduced antibacterial activity and increased cytotoxicity correlated with greater hydrophobicity and self-aggregation in the aqueous environment. The peptides acted by inducing rapid collapse of the bacterial transmembrane potential and induction of membrane permeability. The mode of interaction of the peptides and the phosphate groups of lipopolysaccharide was dependent upon the peptides’ ability to permeate the membrane. Longer peptides [(KW)₄ and (KW)₅] but not shorter peptides [(KW)₂ and (KW)₃] strongly bound and partially inserted into negatively charged, anionic lipid bilayers. These longer peptides also induced membrane permeabilization and aggregation of lipid vesicles. The peptides had a disordered structure in aqueous solution, and only (KW)₄ and (KW)₅ displayed a folded conformation on lipid membranes. Moreover, (KW)₄ destroyed and agglutinated bacterial cells, demonstrating its potential as an antimicrobial agent. Collectively, the results show (KW)₄ to be the most efficacious peptide in the (KW)_n series, exhibiting strong antibacterial activity with little cytotoxicity.

Isolation and purification of a novel deca-antifungal peptide from potato (Solanum tuberosum L. cv. Jopung) against Candida albicans

In a previous study, an antifungal protein, AFP-J, was purified from tubers of the potato (Solanum tuberosum cv. L Jopung) and by gel filtration and HPLC. In this study, the functional peptide was characterized by partial acid digestion using HCl and HPLC. We obtained three peaks from the AFP-J, the first and third peaks were not active in the tested fungal strain. However, the second peak, which was named Potide-J, was active (MIC; 6.25 μg/mL) against Candida albicans. The amino acid sequences were analyzed by automated Edman degradation, and the amino acid sequence of Potide-J was determined to be Ala-Val-Cys-Glu-Asn-Asp-Leu-Asn-Cys-Cys. Mass spectrometry showed that its molecular mass was 1083.1 Da. Finally, we confirmed that a disulfide bond was present between Cys(3) and Cys(9) or Cys(10). Using this structure, Potide-J was synthesized via solid-phase methods. In these experiments, only the linear sequence was shown to display strong activity against Candida albicans. These results suggest that Potide-J may be an excellent candidate compound for the development of commercially applicable antibiotic agents.

The effect of substrate microtopography on focal adhesion maturation and actin organization via the RhoA/ROCK pathway

Recently, a growing number of reports have reported that micro- or nanoscale topography enhances cellular functions such as cell adhesion and stem cell differentiation, but the mechanisms responsible for this topography-mediated cell behavior are not fully understood. In this study, we examine the underlying processes and mechanisms behind specific topography-mediated cellular functions. Formation of focal adhesions (FA) was studied by culturing cells on different kinds of topographies, including a flat surface and surfaces with a micropatterned topography (2 μm lattice pattern with 3 μm intervals). We found that the formation and maturation of focal adhesions were highly dependent on the topography of the substrate although the shape, morphology and spreading of cells on the different substrates were not significantly affected. Focal adhesion maturation and actin polymerization were also promoted in cells cultured on the micropatterned substrate. These differences in cell adhesion led us to focus on the Rho GTPases, RhoA and downstream pathways since a number of reports have demonstrated that RhoA-activated cells have highly enhanced focal adhesions and actin activation such as polymerization. By inhibiting the Rho-associated kinase (ROCK) and downstream myosin II, we found that the FA formation, actin organization, and FAK phosphorylation were dramatically decreased. The topographical dependency of FA formation was also highly decreased. These results show that the FA formation and actin cytoskeleton organization of cells on the microtopography is regulated by the RhoA/ROCK pathway.

A simplified fabrication process of Fresnel zone plates with controlling proximity effect correction

Fresnel zone plates (FZPs) for soft X-ray microscopy with an energy range of 284 eV to 540 eV are designed and fabricated in a simple method. An adequate aspect ratio of the resist mold for electroplating was obtained by the proximity effect correction technology for an incident electron beam on a single thick layer resist. Without additional complicated reactive ion etching, a sufficient electro plating mold for nickel structures was fabricated. The overall fabrication procedures which involve a mix-and-match overlay technique for electron beam lithography and an optic exposure system that centers the membrane on the nanostructures, and hybrid silicon etching technology in junction with deep anisotropy and a KOH wet method in order to release the backside Si substrates of the Si3N4 membranes with no deformation of FZPs are introduced. High quality nanostructures with minimum outermost zone widths of 50 nm and diameters of 120 microm were fabricated with simplified fabrication process and with cost-effective.