Elastocapillary interaction between a long rectangular membrane and a liquid drop.

We report elastocapillary interaction between a long rectangular membrane fixed along its central axis and a liquid drop dispensed at one of its ends. The introduction of the drop results in the elastocapillary-driven wrapping of the membrane along its width and a concomitant flow in the resulting conduit along its length. Depending upon the drop size (d) and capillary length scale (Lc), we identified general criteria for achieving complete wrapping of the membrane in the dry state from energy considerations. For small droplets satisfying d ≲ Lc, we find that the critical membrane length (Wc) required for complete wrapping is proportional to the elastocapillary length scale (Lec). In the case of large droplets with d > Lc, the wrapping behavior depends on the ratio of membrane width to elastocapillary length scale (W/Lec) and the ratio of capillary length scale to the elastocapillary length scale (Lc/Lec). Our study suggests that the critical membrane width for complete wrapping is smaller in the wet state compared to that in the dry state, which can be attributed to the existence of a transmembrane pressure in the wet state. The effect of membrane thickness and width and drop volume on the length and cross-section of the wrapped conduit and attached width of the wrapped membrane is studied. For small droplets, the resulting elastocapillary flow exhibits an inertial regime at small times, followed by a Washburn regime at intermediate times, and finally an inertial regime, and for large droplets, only an inertial regime is observed throughout.

4,4'-(((1E,5E)-pentane-1,5-diylidene)bis(azanylylidene))bis(1-dodecylpyridin-1-ium) bromide as a novel corrosion inhibitor in an acidic solution (part I).

The metal corrosion inhibition efficiency of a novel synthesized cationic gemini surfactant (SCGS), namely, 4,4'-(((1E,5E)-pentane-1,5-diylidene)bis(azanylylidene))bis (1-dodecylpyridin-1-ium) bromide, was studied in acidic medium by three techniques. The achieved results displayed the inhibition efficiency of the metal corrosion that was elevated by increasing both the SCGS's concentration and the applied temperature values. Furthermore, it was noticed that the charge transfer resistance value was elevated; however, the constant phase element was decreased with increasing the SCGS concentrations. The SCGS regards an excellent and mixed-type corrosion inhibitor. The adsorption of SCGS has agreed the Langmuir's adsorption isotherm and was related to physisorption and chemisorption.

Osmolytes modify protein dynamics and function of tetrameric lactate dehydrogenase upon pressurization.

We present a study of the combined effects of natural cosolvents (TMAO, glycine, urea) and pressure on the activity of the tetrameric enzyme lactate dehydrogenase (LDH). To this end, high-pressure stopped-flow methodology in concert with fast UV/Vis spectroscopic detection of product formation was applied. To reveal possible pressure effects on the stability and dynamics of the enzyme, FTIR spectroscopic and neutron scattering measurements were carried out. In neat buffer solution, the catalytic turnover number of the enzyme, kcat, increases up to 1000 bar, the pressure range where dissociation of the tetrameric species to dimers sets in. Accordingly, we obtain a negative activation volume, ΔV# = -45.3 mL mol-1. Further, the enzyme substrate complex has a larger volume compared to the enzyme and substrate in the unbound state. The neutron scattering data show that changes in the fast internal dynamics of the enzyme are not responsible for the increase of kcat upon compression. Whereas the magnitude of kcat is similar in the presence of the osmolytes, the pressure of deactivation is modulated by the addition of cosolvents. TMAO and glycine increase the pressure of deactivation, and in accordance with the observed stabilizing effect both cosolvents exhibit against denaturation and/or dissociation of proteins. While urea does not markedly affect the magnitude of the Michaelis constant, KM, both 1 M TMAO and 1 M glycine exhibit smaller KM values of about 0.07 mM and 0.05 mM below about 1 kbar. Such positive effect on the substrate affinity could be rationalized by the effect the two cosolutes impose on the thermodynamic activities of the reactants, which reflect changes in water-mediated intermolecular interactions. Our data show that the intracellular milieu, i.e., the solution conditions that have evolved, may be sufficient to maintain enzymatic activity under extreme environmental conditions, including the whole pressure range encountered on Earth.

Annexins in Influenza Virus Replication and Pathogenesis.

Influenza A viruses (IAVs) are important human respiratory pathogens which cause seasonal or periodic endemic infections. IAV can result in severe or fatal clinical complications including pneumonia and respiratory distress syndrome. Treatment of IAV infections is complicated because the virus can evade host immunity through antigenic drifts and antigenic shifts, to establish infections making new treatment options desirable. Annexins (ANXs) are a family of calcium and phospholipid binding proteins with immunomodulatory roles in viral infections, lung injury, and inflammation. A current understanding of the role of ANXs in modulating IAV infection and host responses will enable the future development of more effective antiviral therapies. This review presents a comprehensive understanding of the advances made in the field of ANXs, in particular, ANXA1 and IAV research and highlights the importance of ANXs as a suitable target for IAV therapy.

Human neural stem cell transplantation improves cognition in a murine model of Alzheimer's disease.

Stem cell transplantation offers a potentially transformative approach to treating neurodegenerative disorders. The safety of cellular therapies is established in multiple clinical trials, including our own in amyotrophic lateral sclerosis. To initiate similar trials in Alzheimer's disease, efficacious cell lines must be identified. Here, we completed a preclinical proof-of-concept study in the APP/PS1 murine model of Alzheimer's disease. Human neural stem cell transplantation targeted to the fimbria fornix significantly improved cognition in two hippocampal-dependent memory tasks at 4 and 16 weeks post-transplantation. While levels of synapse-related proteins and cholinergic neurons were unaffected, amyloid plaque load was significantly reduced in stem cell transplanted mice and associated with increased recruitment of activated microglia. In vitro, these same neural stem cells induced microglial activation and amyloid phagocytosis, suggesting an immunomodulatory capacity. Although long-term transplantation resulted in significant functional and pathological improvements in APP/PS1 mice, stem cells were not identified by immunohistochemistry or PCR at the study endpoint. These data suggest integration into native tissue or the idea that transient engraftment may be adequate for therapeutic efficacy, reducing the need for continued immunosuppression. Overall, our results support further preclinical development of human neural stem cells as a safe and effective therapy for Alzheimer's disease.

Combined effects of osmotic and hydrostatic pressure on multilamellar lipid membranes in the presence of PEG and trehalose.

We studied the interaction of lipid membranes with the disaccharide trehalose (TRH), which is known to stabilize biomembranes against various environmental stress factors. Generally, stress factors include low/high temperature, shear, osmotic and hydrostatic pressure. Small-angle X-ray-scattering was applied in combination with fluorescence spectroscopy and calorimetric measurements to get insights into the influence of trehalose on the supramolecular structure, hydration level, and elastic and thermodynamic properties as well as phase behavior of the model biomembrane DMPC, covering a large region of the temperature, osmotic and hydrostatic pressure phase space. We observed distinct effects of trehalose on the topology of the lipid's supramolecular structure. Trehalose, unlike osmotic pressure induced by polyethylene glycol, leads to a decrease of lamellar order and a swelling of multilamellar vesicles, which is attributable to direct interactions between the membrane and trehalose. Our results revealed a distinct biphasic concentration dependence of the observed effects of trehalose. While trehalose intercalates between the polar head groups at low concentrations, the effects after saturation are dominated by the exclusion of trehalose from the membrane surface.

The effects of osmolytes and crowding on the pressure-induced dissociation and inactivation of dimeric LADH.

Investigating the correlation between structure and activity of oligomeric enzymes at high pressure is essential for understanding intermolecular interactions and reactivity of proteins in cellulo of organisms thriving at extreme environmental conditions as well as for biotechnological applications, such as high-pressure enzymology. In a combined experimental effort employing small-angle X-ray scattering, FT-IR and fluorescence spectroscopy as well as stopped-flow enzyme kinetics in concert with high-pressure techniques, we reveal the pressure-induced conformational changes of the dimeric enzyme horse liver alcohol dehydrogenase (LADH) on the quaternary, secondary and tertiary structural level. Moreover, the effects of cosolutes and crowding agents, mimicking intracellular conditions, have been addressed. Our results show that beyond an increase of enzymatic activity at low pressures, loss of enzyme activity occurs around 600-800 bar, i.e. in a pressure regime where small conformational changes take place in the coenzyme's binding pocket, only. Whereas higher-order oligomers dissociate at low pressures, subunit dissociation of dimeric LADH takes place, depending on the solution conditions, between 2000 and 4000 bar, only. Oligomerization and subunit dissociation are modulated by cosolvents such as urea or trimethylamine-N-oxide as well as by the crowding agent polyethylene glycol, based on their tendency to bind to the protein's interface or act via their excluded volume effect, respectively.

Correlation of Peripheral Immunity With Rapid Amyotrophic Lateral Sclerosis Progression.

Importance: Amyotrophic lateral sclerosis (ALS) has an immune component, but previous human studies have not examined immune changes over time. Objectives: To assess peripheral inflammatory markers in participants with ALS and healthy control individuals and to track immune changes in ALS and determine whether these changes correlate with disease progression. Design, Setting, and Participants: In this longitudinal cohort study, leukocytes were isolated from peripheral blood samples from 35 controls and 119 participants with ALS at the ALS Clinic of the University of Michigan, Ann Arbor, from June 18, 2014, through May 26, 2016. Follow-up visits occurred every 6 to 12 months. Fifty-one participants with ALS provided samples at multiple points. Immune cell populations were measured and compared between control and ALS groups. Surface marker expression of CD11b+ myeloid cells was also assessed. Changes over time were correlated with disease progression using multivariate regression. Main Outcomes and Measures: The number of immune cells per milliliter of blood and the fold expression of cell surface markers. Multivariate regression models were used to correlate changes in immune metrics with changes on the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R). Results: Thirty-five controls (17 women [48.6%] and 18 men [51.4%]; mean [SD] age, 63.5 [9.9] years) and 119 participants with ALS (50 women [42.0%] and 69 men [68.0%]; mean [SD] age, 61.4 [11.5] years) were enrolled. Compared with controls, participants with ALS had increased mean (SEM) counts ( × 106/mL) of total leukocytes (4.57 [0.29; 95% CI, 3.94-5.11] vs 5.53 [0.16; 95% CI, 5.21-5.84]), neutrophils (2.87 [0.23; 95% CI, 2.40-3.35] vs 3.80 [0.12; 95% CI, 3.56-4.04]), CD16+ monocytes (0.03 [0.003; 95% CI, 0.02-0.04] vs 0.04 [0.002; 95% CI, 0.03-0.04]), CD16- monocytes (0.25 [0.02; 95% CI, 0.21-0.30] vs 0.29 [0.01; 95% CI, 0.27-0.31]), and natural killer cells (0.13 [0.02; 95% CI, 0.10-0.17] vs 0.18 [0.01; 95% CI, 0.16-0.21]). We also observed an acute, transient increase in a population of CD11b+ myeloid cells expressing HLA-DR, CD11c, and CX3CR1. Finally, early changes in immune cell numbers had a significant correlation with disease progression measured by change in ALSFRS-R score, particularly neutrophils (-4.37 [95% CI, -6.60 to -2.14] per 11.47 × 104/mL [SD, 58.04 × 104/mL] per year) and CD4 T cells (-30.47 [95% CI, -46.02 to -14.94] per -3.72 × 104/mL [SD, 26.21 × 104/mL] per year). Conclusions and Relevance: Changes in the immune system occur during ALS and may contribute to the pathologic features of ALS.

Bio-inspired liquid transport via elastocapillary interaction of a thin membrane with a liquid meniscus.

We report bio-inspired (from a hummingbird's tongue) liquid transport via elastocapillary interaction of a thin membrane with a liquid meniscus. A soft wedge-thin rectangular membrane forming a wedge with a rigid substrate and a flat thin rectangular membrane undergo large deformation while interacting with liquid menisci. The membrane deformation leads to the formation of confinement which in turn results in elastocapillary flow along the membrane length. A simple theoretical model based on the Euler Bernoulli law is used to predict the membrane deformation profiles, which compare well with that obtained from experiments. In the wedge case, the membrane surface and liquid are selected such that the Concus-Finn criterion is not satisfied to contrast the present case of elastocapillary flow from the typical corner flow reported in the literature. The meniscus location versus time studies indicated that the flow exhibits the typical Washburn regime with , except for a sudden increase in velocity at the end of the membrane length. The effects of membrane thickness and width, liquids and substrates were studied to determine the expression for the modified Washburn constant Wm in both the wedge and flat membranes. It was found that gravity plays a role for Bo > 0.94 and for Bo = 1.9, the effect of inclination angle on the flow was studied. The elastocapillary flow with thin membranes could open up an opportunity for a new area, namely "membrane microfluidics" or "lab on a membrane", for diagnostics and other applications.

Production of endothelial progenitor cells obtained from human Wharton's jelly using different culture conditions.

Endothelial progenitor cells (EPC) participate in revascularization and angiogenesis. EPC can be cultured in vitro from mononuclear cells of peripheral blood, umbilical cord blood or bone marrow; they also can be transdifferentiated from mesenchymal stem cells (MSC). We isolated EPCs from Wharton's jelly (WJ) using two methods. The first method was by obtaining MSC from WJ and characterizing them by flow cytometry and their adipogenic and osteogenic differentiation, then applying endothelial growth differentiating media. The second method was by direct culture of cells derived from WJ into endothelial differentiating media. EPCs were characterized by morphology, Dil-LDL uptake/UEA-1 immunostaining and testing the expression of endothelial markers by flow cytometry and RT-PCR. We found that MSC derived from WJ differentiated into endothelial-like cells using simple culture conditions with endothelium induction agents in the medium.

Increased ratio of circulating neutrophils to monocytes in amyotrophic lateral sclerosis.

OBJECTIVE: To elucidate amyotrophic lateral sclerosis (ALS) biomarkers and potential mechanisms of disease, we measured immune cell populations in whole blood from a large cohort of patients with ALS. METHODS: Leukocytes were isolated from the blood of 44 control patients and 90 patients with ALS. The percentages and total numbers of each cell population were analyzed using flow cytometry and matched with patient ALS Functional Rating Scale-Revised (ALSFRS-R) score to correlate leukocyte metrics with disease progression. RESULTS: We show a significant increase in the percentage of neutrophils and a significant decrease in the percentage of CD4 T cells and CD16(-) monocytes in the blood of patients with ALS compared to controls; however, only CD16(-) monocyte levels correlated with disease progression. We also examined the monocyte surface expression of CCRL2 and CCR3; CD16(-) monocytes displayed decreased percentages and total numbers expressing CCR3, but these numbers did not correlate with ALSFRS-R score. We found that combining multiple disease metrics yielded the most accurate predictor of disease progression: the ratio of neutrophils to CD16(-) monocytes (N:M ratio) is significantly increased in patients with ALS and better correlates with disease progression than any other single metric. CONCLUSIONS: These observations implicate neutrophils and monocytes as important factors in late disease progression.

Gene Microarray Analyses of Daboia russelli russelli Daboiatoxin Treatment of THP-1 Human Macrophages Infected with Burkholderia pseudomallei.

Burkholderia pseudomallei is the causative agent of melioidosis and represents a potential bioterrorism threat. In this study, the transcriptomic responses of B. pseudomallei infection of a human macrophage cell model were investigated using whole-genome microarrays. Gene expression profiles were compared between infected THP-1 human monocytic leukemia cells with or without treatment with Daboia russelli russelli daboiatoxin (DRRDbTx) or ceftazidime (antibiotic control). Microarray analyses of infected and treated cells revealed differential upregulation of various inflammatory genes such as interleukin-1 (IL-1), IL-6, tumor necrosis factor-alpha (TNF-α), cyclooxygenase (COX-2), vascular endothelial growth factor (VEGF), chemokine C-X-C motif ligand 4 (CXCL4), transcription factor p65 (NF-kB); and several genes involved in immune and stress responses, cell cycle, and lipid metabolism. Moreover, following DRR-DbTx treatment of infected cells, there was enhanced expression of the tolllike receptor 2 (TLR-2) mediated signaling pathway involved in recognition and initiation of acute inflammatory responses. Importantly, we observed that highly inflammatory cytokine gene responses were similar in infected cells exposed to DRR-DbTx or ceftazidime after 24 h. Additionally, there were increased transcripts associated with cell death by caspase activation that can promote host tissue injury. In summary, the transcriptional responses during B. pseudomallei infection of macrophages highlight a broad range of innate immune mechanisms that are activated within 24 h post-infection. These data provide insights into the transcriptomic kinetics following DRR-DbTx treatment of human macrophages infected with B. pseudomallei.

Combination therapy with hepatocyte growth factor and oseltamivir confers enhanced protection against influenza viral pneumonia.

Frequent outbreaks caused by influenza viruses pose considerable public health threats worldwide. Virus-inflicted alveolar damage represents a major contributor of acute lung injury in influenza. We have previously demonstrated that hepatocyte growth factor (HGF) produced by macrophages enhances alveolar epithelial proliferation during influenza infection. Here, we investigated the therapeutic efficacy of recombinant human HGF (rhHGF) and an antiviral agent (oseltamivir) alone or in combination to treat influenza viral pneumonia in macrophage-depleted BALB/c mice. Combination therapy of infected mice significantly reduced lung pathology and mortality compared to other animal groups that received either treatment alone. Combination treatment with rhHGF induced alveolar type II (AT2) epithelial hyperplasia more prominently in the distal airways, evident by increased cells with double-positive staining for surfactant protein-C and proliferating cell nuclear antigen within the alveolar epithelial lining. Similarly, rhHGF supplementation also induced stem cell antigen-1 (SCA-1) transcriptional expression at 5 days post-infection (dpi), but mRNA levels of both SCA-1 and its receptor c-KIT were decreased by 10 dpi. Microarray and pathway analyses indicated that rhHGF administration may act by accelerating tissue repair and suppressing inflammatory processes to minimize damage by infection and to restore lung function by earlier repair. These results reveal that transient administration of rhHGF may confer synergistic effects in enhancing pulmonary repair by promoting AT2 cell proliferation. Thus, the combination of rhHGF and oseltamivir may represent a promising therapeutic option against influenza pneumonia to improve existing antiviral treatment regimens.

Snake venom phospholipases A(2): a novel tool against bacterial diseases.

The majority of snake venom phospholipases A(2) (svPLA(2)s) are toxic and induce a wide spectrum of biological effects. They are cysteine-rich proteins that contain 119-134 amino acids and share similar structures and functions. About 50% of the residues are incorporated into α-helices, whereas only 10% are in ß-sheets. Fourteen conserved cysteines form a network of seven disulfide bridges that stabilize the tertiary structure. They show a high degree of sequence and structural similarity, and are believed to have a common calcium- dependent catalytic mechanism. Additionally, svPLA(2)s display an array of biological actions that are either dependent or independent of catalysis. The PLA(2)s of mammalian origin also exert potent bactericidal activity by binding to anionic surfaces and enzymatic degradation of phospholipids in the target membranes, preferentially of Gram-positive species. The bactericidal activity against Gram-negatives by svPLA(2) requires a synergistic action with bactericidal/permeability-increasing protein (BPI), but is equally dependent on enzymatic- based membrane degradation. Several hypotheses account for the bactericidal properties of svPLA(2)s, which include "fatal depolarization" of the bacterial membrane, creation of physical holes in the membrane, scrambling of normal distribution of lipids between the bilayer leaflets, and damage of critical intracellular targets after internalization of the peptide. The present review discusses several svPLA(2)s and derived peptides that exhibit strong bactericidal activity. The reports demonstrate that svPLA(2)-derived peptides have the potential to counteract microbial infections. In fact, the C-terminal cationic/hydrophobic segment (residues 115-129) of svPLA(2)s is bactericidal. Thus identification of the bactericidal sites in svPLA(2)s has potential for developing novel antimicrobials.

Antimicrobial proteins from snake venoms: direct bacterial damage and activation of innate immunity against Staphylococcus aureus skin infection.

The innate immune system is the first line of defense against microbial diseases. Antimicrobial proteins produced by snake venoms have recently attracted significant attention due to their relevance to bacterial infection and potential development into new therapeutic agents. Staphylococcus aureus is one of the major human pathogens causing a variety of infections involving pneumonia, toxic shock syndrome, and skin lesions. With the recent emergence of methicillin (MRSA) and vancomycin (VRSA) resistance, S. aureus infection is a serious clinical problem that will have a grave socio-economic impact in the near future. Although S. aureus susceptibility to innate antimicrobial peptides has been reported recently, the protective effect of snake venom phospholipase A2 (svPLA2) proteins on the skin from S. aureus infection has been understudied. This review details the protective function of svPLA2s derived from venoms against skin infections caused by S. aureus. We have demonstrated in vivo that local application of svPLA2 provides complete clearance of S. aureus within 2 weeks after treatment compared to fusidic acid ointment (FAO). In vitro experiments also demonstrate that svPLA2 proteins have inhibitory (bacteriostatic) and killing (bactericidal) effects on S. aureus in a dose-dependant manner. The mechanism of bacterial membrane damage and perturbation was clearly evidenced by electron microscopic studies. In summary, svPLA2s from Viperidae and Elapidae snakes are novel molecules that can activate important mechanisms of innate immunity in animals to endow them with protection against skin infection caused by S. aureus.

Purification, characterization and bactericidal activities of basic phospholipase A2 from the venom of Agkistrodon halys (Chinese pallas).

Agkistrodon snake venoms contain a variety of phospholipases (PLA2), some of which are myotoxic. In this study, we used reverse-phase HPLC to purify PLA2 from the venom of Agkistrodon halys. The enzyme named as AgkTx-II, a basic Asp49 PLA2, has a molecular masses of 13,869.05. The amino acid sequence and molecular mass of AgkTx-II was identical to those of an Asp49 basic myotoxic PLA2 previously isolated from this venom. Antibacterial activities were tested by susceptibility and broth-dilution assays. AgkTx-II exerted a potent antibacterial activity against Staphylococcus aureus, Proteus vulgaris, Proteus mirabilis, and Burkholderia pseudomallei. The MIC values of AgkTx-II ranged between 85 and 2.76microM and was most effective against S. aureus, P. vulgaris, P. mirabilis (MIC of 21.25microM) and B. pseudomallei (MIC of 10.25microM). This AgkTx-II rapidly killed S. aureus, P. vulgaris and B. pseudomallei in a dose-dependent manner. The effect of the AgkTx-II on bacterial membranes was evaluated by scanning and transmission electron microscopy. AgkTx-II caused morphological alterations apparent on their cellular surfaces, suggesting a killing mechanism based on membrane permeabilization and damage. Cytotoxicity was measured by XTT tetrazolium (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) and lactate dehydrogenase (LDH) assays using U-937 cells (monocytes). The AgkTx-II did not affect cell viability up to 500microM concentrations but cell death was evident at 1000microM concentration after 24 and 48h. Furthermore, the repeated exposure of AgkTx-II (2-14microM) treated mice showed different tissue alterations, mainly at the brain and kidney; the toxicological potential of AgkTx-II remains to be elucidated. The AgkTx-II exhibits no hemolytic action even at high doses (10-100microM) in human erythrocytes. However, the AgkTx-II is believed to exert its bactericidal effect by permeabilizing the bacterial membrane by forming pores. In addition, the basic PLA2 AgkTx-II displays a bactericidal effect, which may be either dependent or independent of catalysis.

Understanding the colonic complications of pancreatitis.

BACKGROUND: Colonic necrosis, fistula and stricture are infrequent but potentially lethal complications of pancreatitis. As any individual unit will have only limited experience, this study aims to provide a structured, systematic appraisal of published experience to identify any consistent trends and disease patterns that may help in practical management. METHODS: A computerized search of the MEDLINE databases for the period January 1950 through January 2006 yielded 43 articles. Pooled extracted data were examined for type of pancreatitis and colonic complications, method and time of diagnosis, treatment and outcome. RESULTS: 43 reports provided pooled data on 97 patients. Colonic complications were more frequent in severe disease, occurring in 15%. The principal presentations were necrosis, fistula and stricture. All episodes of colonic necrosis complicated severe acute pancreatitis, were diagnosed operatively, presented at a median of 25 (1-55) days into the episode and were associated with a mortality of 54%. In contrast, stricture presented at a median of 50 (10-270) days. Surgical resection without anastomosis is the mainstay of management of necrosis. Trial of conservative management in a stable patient with a fistula may facilitate spontaneous closure. CONCLUSIONS: This study highlights several consistent trends: preoperative diagnosis is difficult, colonic necrosis and fistula are rare complications principally of severe acute pancreatitis and they present either as ongoing abdominal sepsis or rectal bleeding. Surgical resection remains the mainstay of management. A high index of suspicion should be maintained in patients with severe acute pancreatitis, with ongoing sepsis and evidence of gastrointestinal blood loss.

Antibacterial activity of snake, scorpion and bee venoms: a comparison with purified venom phospholipase A2 enzymes.

AIMS: Venoms of snakes, scorpions, bees and purified venom phospholipase A(2) (PLA(2)) enzymes were examined to evaluate the antibacterial activity of purified venom enzymes as compared with that of the crude venoms. METHODS AND RESULTS: Thirty-four crude venoms, nine purified PLA(2)s and two L-amino acid oxidases (LAAO) were studied for antibacterial activity by disc-diffusion assay (100 microg ml(-1)). Several snake venoms (Daboia russelli russelli, Crotalus adamanteus, Naja sumatrana, Pseudechis guttata, Agkistrodon halys, Acanthophis praelongus and Daboia russelli siamensis) showed activity against two to four different pathogenic bacteria. Daboia russelli russelli and Pseudechis australis venoms exhibited the most potent activity against Staphylococcus aureus, while the rest showed only a moderate activity against one or more bacteria. The order of susceptibility of the bacteria against viperidae venoms was -S. aureus > Proteus mirabilis > Proteus vulgaris > Enterobacter aerogenes > Pseudomonas aeruginosa and Escherichia coli. The minimum inhibitory concentrations (MIC) against S. aureus was studied by dilution method (160-1.25 microg ml(-1)). A stronger effect was noted with the viperidae venoms (20 microg ml(-11)) as compared with elapidae venoms (40 microg ml(-1)). The MIC were comparable with those of the standard drugs (chloramphenicol, streptomycin and penicillin). CONCLUSION: The present findings indicate that viperidae (D. russelli russelli) and elapidae (P. australis) venoms have significant antibacterial effects against gram (+) and gram (-) bacteria, which may be the result of the primary antibacterial components of laao, and in particular, the PLA(2) enzymes. The results would be useful for further purification and characterization of antibacterial agents from snake venoms. SIGNIFICANCE AND IMPACT OF THE STUDY: The activity of LAAO and PLA(2) enzymes may be associated with the antibacterial activity of snake venoms.

In vitro antimicrobial activity of natural toxins and animal venoms tested against Burkholderia pseudomallei.

BACKGROUND: Burkholderia pseudomallei are the causative agent of melioidosis. Increasing resistance of the disease to antibiotics is a severe problem in treatment regime and has led to intensification of the search for new drugs. Antimicrobial peptides are the most ubiquitous in nature as part of the innate immune system and host defense mechanism. METHODS: Here, we investigated a group of venoms (snakes, scorpions and honey bee venoms) for antimicrobial properties against two strains of Gram-negative bacteria Burkholderia pseudomallei by using disc-diffusion assay for in vitro susceptibility testing. The antibacterial activities of the venoms were compared with that of the isolated L-amino acid oxidase (LAAO) and phospholipase A2 (PLA2s) enzymes. MICs were determined using broth dilution method. Bacterial growth was assessed by measurement of optical density at the lowest dilutions (MIC 0.25 mg/ml). The cell viability was measured using tetrazolium salts (XTT) based cytotoxic assay. RESULTS: The studied venoms showed high antimicrobial activity. The venoms of C. adamanteus, Daboia russelli russelli, A. halys, P. australis, B. candidus and P. guttata were equally as effective as Chloramphenicol and Ceftazidime (30 microg/disc). Among those tested, phospholipase A2 enzymes (crotoxin B and daboiatoxin) showed the most potent antibacterial activity against Gram-negative (TES) bacteria. Naturally occurring venom peptides and phospholipase A2 proved to possess highly potent antimicrobial activity against Burkholderia pseudomallei. The XTT-assay results showed that the cell survival decreased with increasing concentrations (0.05-10 mg/mL) of Crotalus adamanteus venom, with no effect on the cell viability evident at 0.5 mg/mL. CONCLUSION: This antibacterial profile of snake venoms reported herein will be useful in the search for potential antibacterial agents against drug resistant microorganisms like B. pseudomallei.