Periplasmic Cleavage and Modification of the 1-Phosphate Group of Helicobacter Pylori Lipid A

Pathogenic bacteria modify the lipid A portion of their lipopolysaccharide to help evade the host innate immune response. Modification of the negatively charged phosphate groups of lipid A aids in resistance to cationic antimicrobial peptides targeting the bacterial cell surface. The lipid A of Helicobacter pylori contains a phosphoethanolamine (pEtN) unit directly linked to the 1-position of the disaccharide backbone. This is in contrast to the pEtN units found in other pathogenic Gram-negative bacteria, which are attached to the lipid A phosphate group to form a pyrophosphate linkage. This study describes two enzymes involved in the periplasmic modification of the 1-phosphate group of H. pylori lipid A. By using an in vitro assay system, we demonstrate the presence of lipid A 1-phosphatase activity in membranes of H. pylori. In an attempt to identify genes encoding possible lipid A phosphatases, we cloned four putative orthologs of Escherichia coli pgpB, the phosphatidylglycerol-phosphate phosphatase, from H. pylori 26695. One of these orthologs, Hp0021, is the structural gene for the lipid A 1-phosphatase and is required for removal of the 1-phosphate group from mature lipid A in an in vitro assay system. Heterologous expression of Hp0021 in E. coli resulted in the highly selective removal of the 1-phosphate group from E. coli lipid A, as demonstrated by mass spectrometry. We also identified the structural gene for the H. pylori lipid A pEtN transferase (Hp0022). Mass spectrometric analysis of the lipid A isolated from E. coli expressing Hp0021 and Hp0022 shows the addition of a single pEtN group at the 1-position, confirming that Hp0022 is responsible for the addition of a pEtN unit at the 1-position in H. pylori lipid A. In summary, we demonstrate that modification of the 1-phosphate group of H. pylori lipid A requires two enzymatic steps

Resistance to the Antimicrobial Peptide Polymyxin Requires Myristoylation of Escherichia Coli and Salmonella Typhimurium Lipid A

Attachment of positively charged, amine-containing residues such as 4-amino-4-deoxy-L-arabinose (L-Ara4N) and phosphoethanolamine (pEtN) to Escherichia coli and Salmonella typhimurium lipid A is required for resistance to the cationic antimicrobial peptide, polymyxin. In an attempt to discover additional lipid A modifications important for polymyxin resistance, we generated polymyxin-sensitive mutants of an E. coli pmrAC strain, WD101. A subset of polymyxin-sensitive mutants produced a lipid A that lacked both the 3′-acyloxyacyl-linked myristate (C14) and L-Ara4N, even though the necessary enzymatic machinery required to synthesize L-Ara4N-modified lipid A was present. Inactivation of lpxM in both E. coli and S. typhimurium resulted in the loss of L-Ara4N addition, as well as, increased sensitivity to polymyxin. However, decoration of the lipid A phosphate groups with pEtN residues was not effected in lpxM mutants. In summary, we demonstrate that attachment of L-Ara4N to the phosphate groups of lipid A and the subsequent resistance to polymyxin is dependent upon the presence of the secondary linked myristoyl group

Twelve Years' Experience with Direct-to-Consumer Advertising of Prescription Drugs in Canada: A Cautionary Tale

Direct-to-consumer advertising (DTCA) of prescription drugs is illegal in Canada as a health protection measure, but is permitted in the United States. However, in 2000, Canadian policy was changed to allow 'reminder' advertising of prescription drugs. This is a form of advertising that states the brand name without health claims. 'Reminder' advertising is prohibited in the US for drugs that have 'black box' warnings of serious risks. This study examines spending on DTCA in Canada from 1995 to 2006, 12 years spanning this policy shift. We ask how annual per capita spending compares to that in the US, and whether drugs with Canadian or US regulatory safety warnings are advertised to the Canadian public in reminder advertising.Prescription drug advertising spending data were extracted from a data set on health sector spending in Canada obtained from a market research company, TNS Media Inc. Spending was adjusted for inflation and compared with US spending. Inflation-adjusted spending on branded DTCA in Canada grew from under CAD$2 million per year before 1999 to over$22 million in 2006. The major growth was in broadcast advertising, accounting for 83% of spending in 2006. US annual per capita spending was on average 24 times Canadian levels. Celebrex (celecoxib), which has a US black box and was subject to three safety advisories in Canada, was the most heavily advertised drug on Canadian television in 2005 and 2006. Of 8 brands with >$500,000 spending, which together accounted for 59% of branded DTCA in all media, 6 were subject to Canadian safety advisories, and 4 had US black box warnings.Branded 'reminder' advertising has grown rapidly in Canada since 2000, mainly due to a growth in television advertising. Although DTCA spending per capita is much lower in Canada than in the US, there is no evidence of safer content or product choice; many heavily-advertised drugs in Canada have been subject to safety advisories. For governments searching for compromise solutions to industry pressure for expanded advertising, Canada's experience stands as a stark warning

Active management of the third stage of labour without controlled cord traction: a randomized non-inferiority controlled trial

BACKGROUND: The third stage of labour refers to the period between birth of the baby and complete expulsion of the placenta. Some degree of blood loss occurs after the birth of the baby due to separation of the placenta. This period is a risky period because uterus may not contract well after birth and heavy blood loss can endanger the life of the mother. Active management of the third stage of labour (AMTSL) reduces the occurrence of severe postpartum haemorrhage by approximately 60-70%. Active management consists of several interventions packaged together and the relative contribution of each of the components is unknown. Controlled cord traction is one of those components that require training in manual skill for it to be performed appropriately. If it is possible to dispense with controlled cord traction without losing efficacy it would have major implications for effective management of the third stage of labour at peripheral levels of health care. OBJECTIVE: The primary objective is to determine whether the simplified package of oxytocin 10 IU IM/IV is not less effective than the full AMTSL package. METHODS: A hospital-based, multicentre, individually randomized controlled trial is proposed. The hypothesis tested will be a non-inferiority hypothesis. The aim will be to determine whether the simplified package without CCT, with the advantage of not requiring training to acquire the manual skill to perform this task, is not less effective than the full AMTSL package with regard to reducing blood loss in the third stage of labour.The simplified package will include uterotonic (oxytocin 10 IU IM) injection after delivery of the baby and cord clamping and cutting at approximately 3 minutes after birth. The full package will include the uterotonic injection (oxytocin 10 IU IM), controlled cord traction following observation of uterine contraction and cord clamping and cutting at approximately 3 minutes after birth. The primary outcome measure is blood loss of 1000 ml or more at one hour and up to two hours for women who continue to bleed after one hour. The secondary outcomes are blood transfusion, the use of additional uterotonics and measure of severe morbidity and maternal death.We aim to recruit 25,000 women delivering vaginally in health facilities in eight countries within a 12 month recruitment period. MANAGEMENT: Overall trial management will be from HRP/RHR in Geneva. There will be eight centres located in Argentina, Egypt, India, Kenya, Philippines, South Africa, Thailand and Uganda. There will be an online data entry system managed from HRP/RHR. The trial protocol was developed following a technical consultation with international organizations and leading researchers in the field. EXPECTED OUTCOMES: The main objective of this trial is to investigate whether a simplified package of third stage management can be recommended without increasing the risk of PPH. By avoiding the need for a manual procedure that requires training, the third stage management can be implemented in a more widespread and cost-effective way around the world even at the most peripheral levels of the health care system. This trial forms part of the programme of work to reduce maternal deaths due to postpartum haemorrhage within the RHR department in collaboration with other research groups and organizations active in the field. TRIAL REGISTRATION: ACTRN12608000434392

Docking and molecular dynamics simulations of the ternary complex nisin2:lipid II

Lanthionine antibiotics are an important class of naturally-occurring antimicrobial peptides. The best-known, nisin, is a commercial food preservative. However, structural and mechanistic details on nisin/lipid II membrane complexes are currently lacking. Recently, we have developed empirical force-field parameters to model lantibiotics. Docking and molecular dynamics (MD) simulations have been used to study the nisin2:lipid II complex in bacterial membranes, which has been put forward as the building block of nisin/lipid II binary membrane pores. A Ile1Trp mutation of the N-terminus of nisin has been modelled and docked onto lipid II models; the computed binding affinity increased compared to wildtype. Wild-type nisin was also docked onto three different lipid II structures and a stable 2:1 nisin:lipid II complex formed. This complex was inserted into a membrane. Six independent MD simulations revealed key interactions in the complex, specifically the N terminal engagement of nisin with lipid II at the pyrophosphate and C-terminus of the pentapeptide chain. Nisin2 inserts into the membrane and we propose this is the first step in pore formation, mediated by the nisin N-terminus–lipid II pentapeptide hydrogen bond. The lipid II undecaprenyl chain adopted different conformations in the presence of nisin, which may also have implications for pore formation

Dormancy within Staphylococcus epidermidis biofilms : a transcriptomic analysis by RNA-seq

The proportion of dormant bacteria within Staphylococcus epidermidis biofilms may determine its inflammatory profile. Previously, we have shown that S. epidermidis biofilms with higher proportions of dormant bacteria have reduced activation of murine macrophages. RNA-sequencing was used to identify the major transcriptomic differences between S. epidermidis biofilms with different proportions of dormant bacteria. To accomplish this goal, we used an in vitro model where magnesium allowed modulation of the proportion of dormant bacteria within S. epidermidis biofilms. Significant differences were found in the expression of 147 genes. A detailed analysis of the results was performed based on direct and functional gene interactions. Biological processes among the differentially expressed genes were mainly related to oxidation-reduction processes and acetyl-CoA metabolic processes. Gene set enrichment revealed that the translation process is related to the proportion of dormant bacteria. Transcription of mRNAs involved in oxidation-reduction processes was associated with higher proportions of dormant bacteria within S. epidermidis biofilm. Moreover, the pH of the culture medium did not change after the addition of magnesium, and genes related to magnesium transport did not seem to impact entrance of bacterial cells into dormancy.The authors thank Stephen Lorry at Harvard Medical School for providing CLC Genomics software. This work was funded by Fundacao para a Ciencia e a Tecnologia (FCT) and COMPETE grants PTDC/BIA-MIC/113450/2009, FCOMP-01-0124-FEDER-014309, FCOMP-01-0124-FEDER-022718 (FCT PEst-C/SAU/LA0002/2011), QOPNA research unit (project PEst-C/QUI/UI0062/2011), and CENTRO-07-ST24-FEDER-002034. The following authors had an individual FCT fellowship: VC (SFRH/BD/78235/2011) and AF (2SFRH/BD/62359/2009)

Insight into the Mechanisms of Adenovirus Capsid Disassembly from Studies of Defensin Neutralization

Defensins are effectors of the innate immune response with potent antibacterial activity. Their role in antiviral immunity, particularly for non-enveloped viruses, is poorly understood. We recently found that human alpha-defensins inhibit human adenovirus (HAdV) by preventing virus uncoating and release of the endosomalytic protein VI during cell entry. Consequently, AdV remains trapped in the endosomal/lysosomal pathway rather than trafficking to the nucleus. To gain insight into the mechanism of defensin-mediated neutralization, we analyzed the specificity of the AdV-defensin interaction. Sensitivity to alpha-defensin neutralization is a common feature of HAdV species A, B1, B2, C, and E, whereas species D and F are resistant. Thousands of defensin molecules bind with low micromolar affinity to a sensitive serotype, but only a low level of binding is observed to resistant serotypes. Neutralization is dependent upon a correctly folded defensin molecule, suggesting that specific molecular interactions occur with the virion. CryoEM structural studies and protein sequence analysis led to a hypothesis that neutralization determinants are located in a region spanning the fiber and penton base proteins. This model was supported by infectivity studies using virus chimeras comprised of capsid proteins from sensitive and resistant serotypes. These findings suggest a mechanism in which defensin binding to critical sites on the AdV capsid prevents vertex removal and thereby blocks subsequent steps in uncoating that are required for release of protein VI and endosomalysis during infection. In addition to informing the mechanism of defensin-mediated neutralization of a non-enveloped virus, these studies provide insight into the mechanism of AdV uncoating and suggest new strategies to disrupt this process and inhibit infection

Precancerous Stem Cells Have the Potential for both Benign and Malignant Differentiation

Cancer stem cells (CSCs) have been identified in hematopoietic and solid tumors. However, their precursors—namely, precancerous stem cells (pCSCs) —have not been characterized. Here we experimentally define the pCSCs that have the potential for both benign and malignant differentiation, depending on environmental cues. While clonal pCSCs can develop into various types of tissue cells in immunocompetent mice without developing into cancer, they often develop, however, into leukemic or solid cancers composed of various types of cancer cells in immunodeficient mice. The progress of the pCSCs to cancers is associated with the up-regulation of c-kit and Sca-1, as well as with lineage markers. Mechanistically, the pCSCs are regulated by the PIWI/AGO family gene called piwil2. Our results provide clear evidence that a single clone of pCSCs has the potential for both benign and malignant differentiation, depending on the environmental cues. We anticipate pCSCs to be a novel target for the early detection, prevention, and therapy of cancers