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

Helicobacter pylori versus the Host: Remodeling of the Bacterial Outer Membrane Is Required for Survival in the Gastric Mucosa

Modification of bacterial surface structures, such as the lipid A portion of lipopolysaccharide (LPS), is used by many pathogenic bacteria to help evade the host innate immune response. Helicobacter pylori, a gram-negative bacterium capable of chronic colonization of the human stomach, modifies its lipid A by removal of phosphate groups from the 1- and 4′-positions of the lipid A backbone. In this study, we identify the enzyme responsible for dephosphorylation of the lipid A 4′-phosphate group in H. pylori, Jhp1487 (LpxF). To ascertain the role these modifications play in the pathogenesis of H. pylori, we created mutants in lpxE (1-phosphatase), lpxF (4′-phosphatase) and a double lpxE/F mutant. Analysis of lipid A isolated from lpxE and lpxF mutants revealed lipid A species with a 1 or 4′-phosphate group, respectively while the double lpxE/F mutant revealed a bis-phosphorylated lipid A. Mutants lacking lpxE, lpxF, or lpxE/F show a 16, 360 and 1020 fold increase in sensitivity to the cationic antimicrobial peptide polymyxin B, respectively. Moreover, a similar loss of resistance is seen against a variety of CAMPs found in the human body including LL37, β-defensin 2, and P-113. Using a fluorescent derivative of polymyxin we demonstrate that, unlike wild type bacteria, polymyxin readily associates with the lpxE/F mutant. Presumably, the increase in the negative charge of H. pylori LPS allows for binding of the peptide to the bacterial surface. Interestingly, the action of LpxE and LpxF was shown to decrease recognition of Helicobacter LPS by the innate immune receptor, Toll-like Receptor 4. Furthermore, lpxE/F mutants were unable to colonize the gastric mucosa of C57BL/6J and C57BL/6J tlr4 -/- mice when compared to wild type H. pylori. Our results demonstrate that dephosphorylation of the lipid A domain of H. pylori LPS by LpxE and LpxF is key to its ability to colonize a mammalian host

The Sources and Environmental Influence of Free Radicals

Wolne rodniki odgrywają istotną rolę w funkcjonowaniu żywych organizmów. Biorą one udział w regulowaniu metabolizmu, oczyszczaniu, przekazywaniu sygnałów i wspomaganiu systemu odpornościowego. Mogą być także przyczyną wielu schorzeń, takich jak nowotwory, miażdżyca czy różnego rodzaju stany zapalne. Wolne rodniki powstają w wyniku procesów metabolicznych, ale również pod wpływem czynników zewnętrznych, np. pożarów. W artykule zostały omówione zewnętrzne źródła powstawania wolnych rodników i sposoby ochrony przed ich szkodliwym działaniem.The article describes the sources of reactive forms of oxygen and nitrogen, especially considering the external sources. The special attention has been paid to their influence on firefighters health who, because of their profession, are especially exposed to so called oxidative stress. Further, the author presents ways of fighting the reactive forms of oxygen and nitrogen using antioxidative compounds

Bioactive compounds in wine

Wines are the subject of an increasing number of investigations. The benefits of red wine became widely recognized after the observation of “French paradox” [8–10]. It has been found that there is a low mortality rate from ischemic heart disease among French people despite their high consumption of saturated fatty acids and the prevalence of other risk factors. The health-protective properties of wine are attributed to their antioxidant activity, i.e. the capability to scavenge reactive oxygen species, ROS . An imbalance between antioxidants and oxygen species results in oxidative stress leading to cellular damage. The phenolic compounds present in wine show beneficial physiological properties including protection against coronary heart disease, as well as anti-inflammatory and anti-carcinogenic activity. Most of the beneficial effects of wine are attributed to the presence of flavonoids, resveratrol, phenolic acids and other antioxidants. This paper reviews the significance of different compounds present in wine and their effect on human health. Chapter 1 focuses on flavonoids: flavonols, flavan-3-ols and anthocyanidins (Fig. 1) [14–29]. This class of compounds can exist both in a simple form, as aglycones, and bounded with sugars, as glycosides. The presence of phenolic hydroxyl group in these compounds is essential for their antioxidant activity and enables to scavenge free radicals in vivo. Chapter 2 describes chemical and physicochemical properties of resveratrol (Fig. 2) [30-41] which is the main antioxidant in wine. Moreover, this compound has been shown to inhibit the oxidation of low density lipoproteins and the aggregation of platelets [44-47]. Resveratrol also exhibits anti-inflammatory and anticancer properties [48, 49]. Chapter 3 reveals that wines are also a good source of other antioxidants [50–55] as phenolic acids (Fig. 3), tyrosol and hydroxytyrosol (Fig. 4), and also melatonin (Fig. 5). Unfortunately, some wines can include mycotoxins, mainly ochratoxin A [59, 60] (Fig. 6), which is produced by the phytopatogenic fungi, Aspergillus carbonarius. All types of red wine contain different amounts of ethanol and phenolic antioxidants, and therefore it is probable that the cardioprotective effect of red wine is caused by both these kinds of components [57–58]. Epidemiological observations, clinical and experimental in vitro research prove that regular and moderate intake of wine, particularly red wine, reduces cardiovascular morbidity and mortality [66–70]

The Evaluation of Contact Work Failures Using the Fire Resistant Paint

W artykule przedstawiono koncepcję wykorzystania zmodyfikowanej farby ogniochronnej jako indykatora temperatury. Pokazano również wynik badań eksperymentalnych na modelach zestyków pokrytych powłokami wytworzonej mieszaniny.The article presents the test results of thermoindicator made on the base of fire resistant paint. The proposed thermoindicator has got many advantages proved by the test results

The Phase Transitions of Environmental Flexible Polymeric Hydrogels. Part 2: The Application of Polymeric Hydrogels Properties

Żele polimerowe można zdefiniować jako jedną makrocząsteczkę w postaci sieci polimerowej wypełnioną rozpuszczalnikiem. Zawartość wody w hydrożelach jest zazwyczaj wyższa niż 95%, niemniej jednak materiały te mają właściwości charakterystyczne dla cieczy i ciał stałych. Dzięki swojej specyficznej budowie i wrażliwości na czynniki środowiskowe żele znalazły wiele zastosowań w różnych dziedzinach. W poniższym artykule przedstawiono niektóre z tych zastosowań.Thanks to their properties the polymeric hydrogels are very useful in both, various industrial branches as well as in every day life. Many research teams aim at finding new hydrogels which will have bigger and other applications. They also aim at the synthesis of new hydrogels with strictly defined properties. Those materials should show big sorbing capacity comparing to water solutions and to specified chemical substances. Hydrogels, which undergo phase transition in specified environmental and which are sensitive to other and new environmental factors, have been searched

Phase Transitions of Environmental Susceptible Polymer Gels. Part one: General Characteristics, Divisions and Methods of Gels Preparation

W artykule przedstawiono ogólną charakterystykę, podział oraz metody otrzymywania żeli ze szczególnym uwzględnieniem żeli podlegających zjawisku objętościowego przejścia fazowego. Następnie bardziej szczegółowo omówiono zjawisko objętościowego przejścia fazowego żeli. Wspomniano także o praktycznych możliwościach jego zastosowania.The article presents general characteristics and the methods of preparation of gels. Particular attention is given to the gels undergoing the volume phase transition. This transition is illustrated in detail. Possible applications are discussed too