Initial Steps in Methanobactin Biosynthesis: Substrate Binding by the Mixed-Valent Diiron Enzyme MbnBC.

The MbnBC enzyme complex converts cysteine residues in a peptide substrate, MbnA, to oxazolone/thioamide groups during the biosynthesis of copper chelator methanobactin (Mbn). MbnBC belongs to the mixed-valent diiron oxygenase (MVDO) family, of which members use an Fe(II)Fe(III) cofactor to react with dioxygen for substrate modification. Several crystal structures of the inactive Fe(III)Fe(III) form of MbnBC alone and in complex with MbnA have been reported, but a mechanistic understanding requires determination of the oxidation states of the crystallographically observed Fe ions in the catalytically active Fe(II)Fe(III) state, along with the site of MbnA binding. Here, we have used electron nuclear double resonance (ENDOR) spectroscopy to determine such structural and electronic properties of the active site, in particular, the mode of substrate binding to the MV state, information not accessible by X-ray crystallography alone. The oxidation states of the two Fe ions were determined by 15N ENDOR analysis. The presence and locations of both bridging and terminal exogenous solvent ligands were determined using 1H and 2H ENDOR. In addition, 2H ENDOR using an isotopically labeled MbnA substrate indicates that MbnA binds to the Fe(III) ion of the cluster via the sulfur atom of its N-terminal modifiable cysteine residue, with displacement of a coordinated solvent ligand as shown by complementary 1H ENDOR. These results, which underscore the utility of ENDOR in studying MVDOs, provide a molecular picture of the initial steps in Mbn biosynthesis.

Ginseng Oligopeptides Improve the Intestinal Physiology and Promote the Antioxidant Capacity of the Gut-on-a-Chip Model.

During ageing, the permeability of the intestinal barrier increases, the integrity of the intestinal barrier decreases, and the physiology of intestinal cells changes. Furthermore, intestinal inflammation and excessive oxidative stress are both likely to cause systemic diseases. Ginseng oligopeptides have a positive significant effect in terms of improving human health and delaying ageing, but their role in the ageing of the intestine has not been studied much. In our experiment, we constructed a gut-on-a-chip model and induced senescence of the chip with H2O2 so as to explore the effects of ginseng oligopeptides on the senescent intestine. The experimental results showed that ginseng oligopeptides had no obvious effects on the integrity of the intestine, including the TEER value and the expression of tight junction proteins. However, ginseng oligopeptides might have other positive effects, such as inhibiting excessive cell proliferation, promoting mucin secretion, and increasing the antioxidant capacity of the intestine, to improve intestinal health.

Expression of Multicopy Tandem Recombinant Ginseng Hexapeptide in Bacillus subtilis and the Evaluation of Antiaging Activity.

Ginseng oligopeptides are naturally occurring small-molecule peptides extracted from ginseng that exhibit positive effects on health and longevity. However, the current industrial production of ginseng oligopeptides primarily relies on plant extraction and chemical synthesis. In this study, we proposed a novel genetic engineering approach to produce active ginseng peptides through multicopy tandem insertion (5 and 15 times). The recombinant ginseng peptides were successfully produced from engineered Bacillus subtilis with an increasing yield from 356.55 to 2900 mg/L as the repeats multiple. Additionally, an oxidative stress-induced aging model caused by H2O2 was established to evaluate whether the recombinant ginseng peptides, without enzymatic hydrolysis into individual peptides, also have positive effects on antiaging. The results demonstrated that all two kinds of recombinant ginseng peptides could also delay cellular aging through various mechanisms, such as inhibiting cell cycle arrest, suppressing the expression of pro-inflammatory factors, and enhancing cellular antioxidant capacity.

Effects of food-derived oligopeptide iron chelates on liver injury and gut microbiota homeostasis in iron-deficiency anemia female rats: a pilot study.

Iron deficiency (ID) is the biggest cause of anemia. This pilot study aimed to investigate the effects of food-derived oligopeptide iron chelates on ameliorating liver injury and restoring gut microbiota homeostasis in iron-deficiency anemia (IDA) female rats. Female Sprague-Dawley rats at 21 days old were selected and randomly divided into a control group (N = 4) and an ID model group (N = 16). The ID model group was fed an iron-deficient diet containing 4 mg kg-1 iron for 28 days to generate the IDA rat model and then randomly subdivided into four groups (N = 4 for each group): ID group, ferrous sulfate group, marine fish oligopeptide iron chelate (MCOP-Fe) group, and whey protein oligopeptide iron chelate (WPP-Fe) group. Iron supplements were given to rats in the three intervention groups once per day via intragastric administration for three weeks. After iron supplementation, the hemoglobin levels in the three intervention groups were significantly improved, with the MCOP-Fe and WPP-Fe groups returning to normal. The ALT and AST levels in the ID group increased significantly, while levels in all intervention groups decreased to normal levels. Liver glutathione in the WPP-Fe group was increased, while the activity of superoxide dismutase also tended to be higher. In addition, 16S rRNA gene sequencing showed that IDA resulted in changes to intestinal microbiota. After intervention, the WPP-Fe group showed increased alpha diversity of intestinal microbes. Therefore, MCOP-Fe and WPP-Fe may improve the iron status of IDA female rats as well as ameliorate liver damage, with WPP-Fe showing a greater potential in improving gut microbiota imbalance.

Extracellular matrix inclusion in immunoisolating alginate-based microcapsules promotes longevity, reduces fibrosis, and supports function of islet allografts in vivo.

Immunoisolation of pancreatic-islets in alginate-microcapsules is applied to treat diabetes. However, long-term islet function is limited, which might be due to damaged and lack of contact with pancreatic extracellular matrix (ECM) components. Herein we investigated the impact of collagen IV combined with laminin sequences, either RGD, LRE, or PDSGR, on graft-survival of microencapsulated bioluminescent islets in vivo. Collagen IV with RGD had the most pronounced effect. It enhanced after 8-week implantation in immune-incompetent mice the bioluminescence of allogeneic islets by 3.2-fold, oxygen consumption rate by 14.3-fold and glucose-induced insulin release by 9.6-fold. Transcriptomics demonstrated that ECM enhanced canonical pathways involving insulin-secretion and that it suppressed pathways related to inflammation and hypoxic stress. Also, 5.8-fold fewer capsules were affected by fibrosis. In a subsequent longevity study in immune-competent mice, microencapsulated allografts containing collagen IV and RGD had a 2.4-fold higher functionality in the first week after implantation and remained at least 2.1-fold higher during the study. Islets in microcapsules containing collagen IV and RGD survived 211 ± 24.1 days while controls survived 125 ± 19.7 days. Our findings provide in vivo evidence for the efficacy of supplementing immunoisolating devices with specific ECM components to enhance functionality and longevity of islet-grafts in vivo. STATEMENT OF SIGNIFICANCE: Limitations in duration of survival of immunoisolated pancreatic islet grafts is a major obstacle for application of the technology to treat diabetes. Accumulating evidence supports that incorporation of extracellular matrix (ECM) molecules in the capsules enhances longevity of pancreatic islets. After selection of the most efficacious laminin sequence in vitro, we show in vivo that inclusion of collagen IV and RGD in alginate-based microcapsules enhances survival, insulin secretion function, and mitochondrial function. It also suppresses fibrosis by lowering proinflammatory cytokines secretion. Moreover, transcriptomic analysis shows that ECM-inclusion promotes insulin-secretion related pathways and attenuates inflammation and hypoxic stress related pathways in islets. We show that inclusion of ECM in immunoisolating devices is a promising strategy to promote long-term survival of islet-grafts.

Dynamic change of oligopeptides and free amino acids composition in five types of tea with different fermentation degree processed from the same batch of fresh tea (Camelilia Sinensis. L.) leaves.

Our previous studies have confirmed oligopeptides could be meaningful to tea taste and biofunction. As the total content of oligopeptide among different tea types were varied. It is a natural speculation that certain tea processing step could be vital for oligopeptides enrichment. In current study, five types of traditional Chinese tea were produced from the same batch of fresh leaves. Step processing samples were acquired through which to profile the oligopeptides and free amio acids composition change during tea processed. As a result, firstly, withering was the vital step for oligopeptide enrichment, followed by fermentation, yellowing and drying. Secondly, as the enrichment of oligopeptides was often accompanied by the increase of protein amino acids, suggesting certain proteins degradation in fresh leaves could be the main source of oligopeptides. Thirdly, a total of 166 abundant oligopeptides were screened out, through which 14 high degradation protein were also located by protomic approaching.

Icarisid II rescues cognitive dysfunction via activation of Wnt/ß-catenin signaling pathway promoting hippocampal neurogenesis in APP/PS1 transgenic mice.

Restoring the compromised neurogenesis has been served as a potential strategy to rescue cognitive dysfunction of Alzheimer's disease (AD). In this study, we explored whether icarisid II (ICS II), a natural product possessing powerful neuroprotection, could recover the neurogenesis dysfunction of APP/PS1 mice, and investigated its underlying mechanisms. Our results showed that oral administration of ICS II could alleviate cognitive injuries of APP/PS1 mice, promote hippocampal neurogenesis, as well as stimulate Wnt/ß-catenin signal pathway confirmed by upregulated Wnt-3a, phosphorylated glycogen synthase kinase-3ß (p-GSK-3ß), and ß-catenin. ICS II also depressed mitochondrial fission evidenced by upregulated Mitofusin 1 (Mfn 1) and Mitofusin 2 (Mfn 2), and downregulated mitochondrial fission 1 protein (Fis 1), mitochondrial fission factor (Mff), and phosphorylated dynamin-related protein 1 (p-Drp 1). However, these effects of ICS II were blunted by XAV-939, an inhibitor of Wnt/ß-catenin signaling pathway. In summary, our findings revealed that ICS II could improve neurogenesis and inhibit mitochondrial fission via activation of the Wnt/ß-catenin signaling pathway, which contributed to cognitive function restoration of APP/PS1 mice. This study discovered a novel mechanism involving neurogenesis regulation underlying the therapeutic effects of ICS II against AD.

Liujunzi Decoction ameliorated cisplatin-induced anorexia by inhibiting the JAK-STAT signaling pathway and coordinating anorexigenic and orexigenic neuropeptides in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: As a traditional Chinese formula, Liujunzi Decoction (LJZD) originated from the Yi Xue Zheng Zhuan, and has a promising effect in treating chemotherapy-induced anorexia (CIA). AIM OF THE STUDY: The present study aims to investigate whether LJZD acts on interleukin-6 (IL-6)/leptin mediated janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway that regulates hypothalamus anorexigenic and orexigenic peptides to ameliorate CIA, and also elucidates the potential mechanism by metabolomic analysis. MATERIALS AND METHODS: Network pharmacology analyses were conducted to screen out potential targets and pathways. The CIA rat model was established via an intraperitoneal injection of cisplatin. The histological changes of gastric antrum, liver and ileum were observed by HE staining. The serum levels of leptin, ghrelin, IL-6 and growth differentiation factor 15 (GDF15) were measured by ELISA. The JAK1/2 and STAT levels in gastric antrum and hypothalamus were detected by Western blot. The transcriptions of gastric antrum and hypothalamus IL-6R mRNA, and hypothalamus cocaine- and amphetamine-regulated transcript (CART), pro-opiomelanocortin (POMC), thyrotropin-releasing hormone (TRH), upregulated orexigenic peptides neuropeptide Y (NPY), and agouti-related protein (AGRP) mRNA were assessed by RT-qPCR. The blood samples of control, model and high dose LJZD groups were analyzed by metabolomic. RESULTS: Network pharmacology highlighted the IL-6/leptin mediated JAK-STAT signaling pathway, which regulated downstream anorexigenic and orexigenic peptides in hypothalamus. LJZD ameliorated CIA via stimulating food intake and water consumption in rats. Cisplatin-induced gastric antrum, liver, ileum injuries were ameliorated, serum leptin level reduction was elevated, and ghrelin, IL-6, GDF15 level increases were decreased after LJZD treatments. In gastric antrum and hypothalamus, LJZD inhibited cisplatin-induced activation of JAK-STAT signaling pathway, downregulated the transcriptions of downstream anorexigenic peptides CART, POMC, TRH, and upregulated orexigenic peptides NPY, AGRP in hypothalamus. Importantly, the effect of LJZD in treating CIA might partly relate to the improvements of 23 abnormal metabolites. CONCLUSION: This study implies that inhibiting JAK-STAT signaling pathway, regulating the expressions of anorexigenic and orexigenic peptides, and mediating various metabolic pathways might be potential mechanisms of LJZD's effect against CIA.

Regulation of Rhcg, an ammonia transporter, by aldosterone in the kidney.

Rhesus C glycoprotein (Rhcg), an ammonia transporter, is a key molecule in urinary acid excretion and is expressed mainly in the intercalated cells (ICs) of the renal collecting duct. In the present study we investigated the role of aldosterone in the regulation of Rhcg expression. In in vivo experiments using C57BL/6J mice, Western blot analysis showed that continuous subcutaneous administration of aldosterone increased the expression of Rhcg in membrane fraction of the kidney. Supplementation of potassium inhibited the effect of aldosterone on the Rhcg. Next, mice were subjected to adrenalectomy with or without administration of aldosterone, and then ad libitum 0.14 M NH4Cl containing water was given. NH4Cl load increased the expression of Rhcg in membrane fraction. Adrenalectomy decreased NH4Cl-induced Rhcg expression, which was restored by administration of aldosterone. Immunohistochemical studies revealed that NH4Cl load induced the localization of Rhcg at the apical membrane of ICs in the outer medullary collecting duct. Adrenalectomy decreased NH4Cl-induced membrane localization of Rhcg, which was restored by administration of aldosterone. For in vitro experiments, IN-IC cells, an immortalized cell line stably expressing Flag-tagged Rhcg (Rhcg-Flag), were used. Western blot analysis showed that aldosterone increased the expression of Rhcg-Flag in membrane fraction, while the increase in extracellular potassium level inhibited the effect of aldosterone. Both spironolactone and GÓ§6983, a PKC inhibitor, inhibited the expression of Rhcg-Flag in the membrane fraction. These results suggest that aldosterone regulates the membrane expression of Rhcg through the mineralocorticoid receptor and PKC pathways, which is modulated by extracellular potassium level.

Potent Cyclic Tetrapeptide for Lead Detoxification.

Lead (Pb) is a ubiquitous poisonous metal, affecting the health of vast populations worldwide. Medications to treat Pb poisoning suffer from various limitations and are often toxic owing to insufficient metal selectivity. Here, we report a cyclic tetrapeptide that selectively binds Pb and eradicates its toxic effect on the cellular level, with superior potency than state-of-the-art drugs. The Pb-peptide complex is remarkably strong and was characterized experimentally and computationally. Accompanied by the lack of toxicity and enhanced stability of this peptide, these qualities indicate its merit as a potential remedy for Pb poisoning.

Cyclopropyl Scaffold: A Generalist for Marketed Drugs.

In recent decades, much attention has been given to cyclopropyl scaffolds, which commonly exist in natural products and synthetic organic molecules. Clinical drug molecules with cyclopropyl rings are an area of focus in therapeutic research due to their interesting chemical properties and unique pharmacology activity. These molecular drugs against different targets are applicable in some therapeutic treatment fields including cancer, infection, respiratory disorder, cardiovascular and cerebrovascular diseases, dysphrenia, nervous system disorders, endocrine and metabolic disorders, skin disease, digestive disorders, urogenital diseases, otolaryngological and dental diseases, and eye diseases. This review is a guide for pharmacologists who are in search of valid preclinical/clinical drug compounds where the progress, from 1961 to the present day, of approved marketed drugs containing cyclopropyl scaffold is examined.

SARS-CoV-2 attachment to host cells is possibly mediated via RGD-integrin interaction in a calcium-dependent manner and suggests pulmonary EDTA chelation therapy as a novel treatment for COVID 19.

SARS-CoV-2 is a highly contagious virus that has caused serious health crisis world-wide resulting into a pandemic situation. As per the literature, the SARS-CoV-2 is known to exploit humanACE2 receptors (similar toprevious SARS-CoV-1) for gaining entry into the host cell for invasion, infection, multiplication and pathogenesis. However, considering the higher infectivity of SARS-CoV-2 along with the complex etiology and pathophysiological outcomes seen in COVID-19 patients, it seems that there may be an alternate receptor for SARS-CoV-2. I performed comparative protein sequence analysis, database based gene expression profiling, bioinformatics based molecular docking using authentic tools and techniques for unveiling the molecular basis of high infectivity of SARS-CoV-2 as compared to previous known coronaviruses. My study revealed that SARS-CoV-2 (previously known as 2019-nCoV) harbors a RGD motif in its receptor binding domain (RBD) and the motif is absent in all other previously known SARS-CoVs. The RGD motif is well known for its role in cell-attachment and cell-adhesion. My hypothesis is that the SARS-CoV-2 may be (via RGD) exploiting integrins, that have high expression in lungs and all other vital organs, for invading host cells. However, an experimental verification is required. The expression of ACE2, which is a known receptor for SARS-CoV-2, was found to be negligible in lungs. I assume that higher infectivity of SARS-CoV-2 could be due to this RGD-integrin mediated acquired cell-adhesive property. Gene expression profiling revealed that expression of integrins is significantly high in lung cells, in particular αvß6, α5ß1, αvß8 and an ECM protein, ICAM1. The molecular docking experiment showed the RBD of spike protein binds with integrins precisely at RGD motif in a similar manner as a synthetic RGD peptide binds to integrins as found by other researchers. SARS-CoV-2 spike protein has a number of phosphorylation sites that can induce cAMP, PKC, Tyr signaling pathways. These pathways either activate calcium ion channels or get activated by calcium. In fact, integrins have calcium & metal binding sites that were predicted around and in vicinity of RGD-integrin docking site in our analysis which suggests that RGD-integrins interaction possibly occurs in calcium-dependent manner. The higher expression of integrins in lungs along with their previously known high binding affinity (~KD = 4.0 nM) for virus RGD motif could serve as a possible explanation for high infectivity of SARS-CoV-2. On the contrary, human ACE2 has lower expression in lungs and its high binding affinity (~KD = 15 nM) for spike RBD alone could not manifest significant virus-host attachment. This suggests that besides human ACE2, an additional or alternate receptor for SARS-CoV-2 is likely to exist. A highly relevant evidence never reported earlier which corroborate in favor of RGD-integrins mediated virus-host attachment is an unleashed cytokine storm which causes due to activation of TNF-α and IL-6 activation; and integrins role in their activation is also well established. Altogether, the current study has highlighted possible role of calcium and other divalent ions in RGD-integrins interaction for virus invasion into host cells and suggested that lowering divalent ion in lungs could avert virus-host cells attachment.

Ghrelin antagonist overrides the mRNA expression of NPY in hypothalamus in feed restricted ewes.

A negative energy balance (NEB) is detrimental to reproduction in animals. A suggested link between NEB and reproductive failure is the gastrointestinal hormone ghrelin, because of the association between ghrelin and the hypothalamo-pituitary-gonadal axis. The [D-Lys3]-Growth Hormone Releasing Peptide-6 ([D-Lys3]-GHRP-6) is a ghrelin antagonist that acts on ghrelin receptors (GHS-R1). The objective of this study was to evaluate the effect of [D-Lys3]-GHRP-6 on reproduction variables in feed restricted ewes. Two experiments were conducted. Experiment I was conducted for 30 days; and Experiment II for 13 days. In both experiments the ewes (n = 18) were randomly assigned to: Control (CO): fed to meet maintenance requirements; Feed restriction (FR): 80% of maintenance restriction; or Ghrelin antagonist (GA): feed restricted and daily subcutaneous of 7.5µg/kg of [D-Lys3]-GHRP-6. Plasma was collected to measure hormones and metabolite concentration. In Experiment II, the hypothalamus and ovaries were collected on day 13. In both Experiments, sheep allocated to the FR and GA treatments decreased their body weight compared with sheep in the CO group (P < 0.06); progesterone however, did not differ between treatments (P > 0.10). Experiment I: Plasma ghrelin concentration was greater (P < 0.01) in FR and GA compared with CO ewes. Plasma non-esterified fatty acids concentration was greater (P < 0.01) in GA and FR than CO. Experiment II: Kisspeptin1-Receptor (Kiss1-R) mRNA expression was greater in FR (P < 0.01) and tended to be greater in GA (P = 0.10) compared with CO ewes. The neuro peptide-Y (NPY) mRNA expression was greater (P = 0.03) in FR than CO; and tended to be greater (P = 0.06) compared with GA ewes. Growth hormone releasing hormone (GhRH) mRNA expression was greater in GA (P = 0.04) and tended to be greater in FR (P = 0.07) compared with CO ewes. Feed restriction increased GhRH, NPY, and Kiss-R mRNA expression in hypothalamus without affecting reproductive variables.Ghrelin antagonist may prevent an increase inNPY expression in ewes.

Puerarin Rebuilding the Mucus Layer and Regulating Mucin-Utilizing Bacteria to Relieve Ulcerative Colitis.

The colonic mucus barrier serves as a primary defense against enteric pathogens; destruction of this mucus layer has been observed in ulcerative colitis patients. This study aims to investigate the possibility of rebuilding the colon mucus layer through puerarin supplementation, which can stimulate mucin secretion and goblet cells differentiation. After puerarin supplementation, the thickness of colon mucus layer was increased and the permeability was reduced. The erosion of intestinal epithelium by bacteria was blocked, and the loss of epithelial integrity was alleviated. Puerarin also altered the composition of mucin-utilizing bacteria, which influenced the mucus permeability. Levels of short-chain fatty acids (SCFAs) were increased after puerarin supplementation, which as a direct source of energy for the proliferation of epithelia and goblet cells. This study demonstrated that enhancement of mucin secretion to relieve ulcerative colitis (UC) by puerarin supplementation is feasible, and the regulation of mucin-utilizing bacteria and the increased levels of SCFAs may be the main reasons.

Evaluation inhibitory activity of catechins on trypsin by capillary electrophoresis-based immobilized enzyme microreactor with chromogenic substrate.

In this study, a capillary electrophoresis-based online immobilized enzyme microreactor was developed for evaluating the inhibitory activity of green tea catechins and tea polyphenol extracts on trypsin. The immobilized trypsin activity and other kinetic parameters were evaluated by measuring the peak area of the hydrolyzate of chromogenic substrate S-2765. The results indicated that the activity of the immobilized trypsin remained approximately 90.0% of the initial immobilized enzyme activity after 30 runs. The value of Michaelis-Menten constant (Km ) was (0.47 ± 0.08) mM, and the half-maximal inhibitory concentration (IC50 ) and inhibition constant (Ki ) of benzamidine were measured as 3.34 and 3.00 mM, respectively. Then, the inhibitory activity of four main catechins (epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate) and three tea polyphenol extracts (green tea, white tea, and black tea) on trypsin were investigated. The results showed that four catechins and three tea polyphenol extracts had potential trypsin inhibitory activity. In addition, molecular docking results illustrated that epigallocatechin gallate, epicatechin gallate, epicatechin, and epigallocatechin were all located not only in the catalytic cavity, but also in the substrate-binding pocket of trypsin. These results indicated that the developed method is an effective tool for evaluating inhibitory activity of catechins on trypsin.

Metalloid Reductase Activity Modified by a Fused Se0 Binding Peptide.

A selenium nanoparticle binding peptide was isolated from a phage display library and genetically fused to a metalloid reductase that reduces selenite (SeO32-) to a Se0 nanoparticle (SeNP) form. The fusion of the Se binding peptide to the metalloid reductase regulates the size of the resulting SeNP to ∼35 nm average diameter, where without the peptide, SeNPs grow to micron sized polydisperse precipitates. The SeNP product remains associated with the enzyme/peptide fusion. The Se binding peptide fusion to the enzyme increases the enzyme's SeO32- reductase activity. Size control of particles was diminished if the Se binding peptide was only added exogenously to the reaction mixture. The enzyme-peptide construct shows preference for binding smaller SeNPs. The peptide-SeNP interaction is attributed to His based ligation that results in a peptide conformational change on the basis of Raman spectroscopy.

Assessment of polymyxin B-doxycycline in combination against Pseudomonas aeruginosa in vitro and in a mouse model of acute pneumonia.

The increasing prevalence of antibiotic resistance in Pseudomonas aeruginosa has created an urgent need for suitable therapy. This study explored the pairing of doxycycline with other antipseudomonal antibiotics, and found that polymyxin B in combination with doxycycline had a synergistic effect against clinical strains of P. aeruginosa. This synergistic combination was studied by checkerboard assays and time-kill curve analysis. Further, in-vitro biofilm disruption, pyoverdine inhibition assays were performed. The efficacy of polymyxin B-doxycycline in combination, administered by inhalation, was evaluated using a mouse model of acute pneumonia. The combination was found to have a synergistic effect in both in-vitro and in-vivo studies. The combination decreased biofilms of P. aeruginosa and reduced the level of pyoverdine, an important siderophore of P. aeruginosa. In addition, the combination decreased the P. aeruginosa population by 3 log10 (P<0.01) in the mouse model of acute pneumonia, and showed an improvement in lung function by inhalation. To the best of the authors' knowledge, this is the first in-vivo study to evaluate the efficacy of polymyxin B in combination with doxycycline against P. aeruginosa, showing a possible promising option for acute pneumonia due to multi-drug-resistant P. aeruginosa.

The Effects of Cyanobacterial Bloom Extracts on the Biomass, Chl-a, MC and Other Oligopeptides Contents in a Natural Planktothrix agardhii Population.

Blooms of the cyanobacterium Planktothrix agardhii are common in shallow, eutrophic freshwaters. P. agardhii may produce hepatotoxic microcystins (MCs) and many other bioactive secondary metabolites belonging mostly to non-ribosomal oligopeptides. The aim of this work was to study the effects of two extracts (Pa-A and Pa-B) of P. agardhii-predominated bloom samples with different oligopeptide profiles and high concentration of biogenic compounds on another natural P. agardhii population. We hypothesised that the P. agardhii biomass and content of oligopeptides in P. agardhii is shaped in a different manner by diverse mixtures of metabolites of different P. agardhii-dominated cyanobacterial assemblages. For this purpose, the biomass, chlorophyll a and oligopeptides content in the treated P. agardhii were measured. Seven-day microcosm experiments with four concentrations of the extracts Pa-A and Pa-B were carried out. Generally, aeruginosins (AERs), cyanopeptolins (CPs) and anabaenopeptins (APs) were the most numerous peptides; however, only 16% of them were common for both extracts. The addition of the extracts resulted in similar effects on P. agardhii: an increase in biomass, Chl-a and MC content in the exposed P. agardhii as well as changes in its oligopeptide profile were observed. MCs present in the extracts did not inhibit accumulation of P. agardhii biomass, and did not have any negative effect on MC and Chl-a content. No evidence for bioaccumulation of dissolved peptides in the P. agardhii exposed was found. As the two tested extracts differed considerably in oligopeptide composition, but contained similar high concentrations of nutrients, it seems that biogenic compounds, not oligopeptides themselves, positively influenced the mixed natural P. agardhii population.

Luminescent silicon nanoparticles for distinctive tracking of cellular targeting and trafficking.

Developing therapeutic nanoparticles that actively target disease cells or tissues by exploiting the binding specificity of receptors presented on the cell surface has extensively opened up biomedical applications for drug delivery and imaging. An ideal nanoparticle for biomedical applications is required to report confirmation of relevant targeting and the ultimate fate in a physiological environment for further verification, e.g. to adapt dosage or predict response. Herein, we demonstrate tracking of silicon nanoparticles through intrinsic photoluminescence (PL) during the course of cellular targeting and uptake. Time-resolved analysis of PL characteristics in cellular microenvironments provides dynamic information on the physiological conditions where the silicon nanoparticles are exposed. In particular, the PL lifetime of the silicon nanoparticles is in the order of microseconds, which is significantly longer than the nanosecond lifetimes exhibited by fluorescent molecules naturally presented in cells, thus allowing discrimination of the nanoparticles from the cellular background autofluorescence in time-gated imaging. The PL lifetime is a physically intensive property that reports the inherent characteristics of the nanoparticles regardless of surrounding noise. Furthermore, we investigate a unique means to inform the lifespan of the biodegradable silicon nanoparticles responsive to local microenvironment in the course of endocytosis. A multivalent strategy of nanoparticles for enhanced cell targeting is also demonstrated with complementary analysis of time-resolved PL emission imaging and fluorescence correlation spectroscopy. The result presents the promising potential of the photoluminescent silicon nanoparticles toward advanced cell targeting systems that simultaneously enable tracking of cellular trafficking and tissue microenvironment monitoring.

Gastrointestinal Interaction between Dietary Amino Acids and Gut Microbiota: With Special Emphasis on Host Nutrition.

The gastrointestinal tract (GIT) of humans and animals is host to a complex community of different microorganisms whose activities significantly influence host nutrition and health through enhanced metabolic capabilities, protection against pathogens, and regulation of the gastrointestinal development and immune system. New molecular technologies and concepts have revealed distinct interactions between the gut microbiota and dietary amino acids (AAs) especially in relation to AA metabolism and utilization in resident bacteria in the digestive tract, and these interactions may play significant roles in host nutrition and health as well as the efficiency of dietary AA supplementation. After the protein is digested and AAs and peptides are absorbed in the small intestine, significant levels of endogenous and exogenous nitrogenous compounds enter the large intestine through the ileocaecal junction. Once they move in the colonic lumen, these compounds are not markedly absorbed by the large intestinal mucosa, but undergo intense proteolysis by colonic microbiota leading to the release of peptides and AAs and result in the production of numerous bacterial metabolites such as ammonia, amines, short-chain fatty acids (SCFAs), branched-chain fatty acids (BCFAs), hydrogen sulfide, organic acids, and phenols. These metabolites influence various signaling pathways in epithelial cells, regulate the mucosal immune system in the host, and modulate gene expression of bacteria which results in the synthesis of enzymes associated with AA metabolism. This review aims to summarize the current literature relating to how the interactions between dietary amino acids and gut microbiota may promote host nutrition and health.