Oxidation of the guanine nucleotide pool underlies cell death by bactericidal antibiotics.

Caesarean section increases the risk of postpartum infection for women and prophylactic antibiotics have been shown to reduce the incidence; however, there are adverse effects. It is important to identify the most effective class of antibiotics to use and those with the least adverse effects. To determine, from the best available evidence, the balance of benefits and harms between different classes of antibiotic given prophylactically to women undergoing caesarean section. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2014) and reference lists of retrieved papers. We included randomised controlled trials comparing different classes of prophylactic antibiotics given to women undergoing caesarean section. We excluded trials that compared drugs with placebo or drugs within a specific class; these are assessed in other Cochrane reviews. Two review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. We included 35 studies of which 31 provided data on 7697 women. For the main comparison between cephalosporins versus penicillins, there were 30 studies of which 27 provided data on 7299 women. There was a lack of good quality data and important outcomes often included only small numbers of women.For the comparison of a single cephalosporin versus a single penicillin (Comparison 1 subgroup 1), we found no significant difference between these classes of antibiotics for our chosen most important seven outcomes namely: maternal sepsis - there were no women with sepsis in the two studies involving 346 women; maternal endometritis (risk ratio (RR) 1.11, 95% confidence interval (CI) 0.81 to 1.52, nine studies, 3130 women, random effects, moderate quality of the evidence); maternal wound infection (RR 0.83, 95% CI 0.38 to 1.81, nine studies, 1497 women, random effects, low quality of the evidence), maternal urinary tract infection (RR 1.48, 95% CI 0.89 to 2.48, seven studies, 1120 women, low quality of the evidence) and maternal composite adverse effects (RR 2.02, 95% CI 0.18 to 21.96, three studies, 1902 women, very low quality of the evidence). None of the included studies looked for infant sepsis nor infant oral thrush.This meant we could only conclude that the current evidence shows no overall difference between the different classes of antibiotics in terms of reducing maternal infections after caesarean sections. However, none of the studies reported on infections diagnosed after the initial postoperative hospital stay. We were unable to assess what impact, if any, the use of different classes of antibiotics might have on bacterial resistance. Based on the best currently available evidence, cephalosporins and penicillins have similar efficacy at caesarean section when considering immediate postoperative infections. We have no data for outcomes on the baby, nor on late infections (up to 30 days) in the mother. Clinicians need to consider bacterial resistance and women's individual circumstances.

Caesarean section increases the risk of postpartum infection for women and prophylactic antibiotics have been shown to reduce the incidence; however, there are adverse effects. It is important to identify the most effective class of antibiotics to use and those with the least adverse effects. To determine, from the best available evidence, the balance of benefits and harms between different classes of antibiotic given prophylactically to women undergoing caesarean section. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (April 2010) and reference lists of retrieved papers. We included randomised controlled trials comparing different classes of prophylactic antibiotics given to women undergoing caesarean section. We excluded trials that compared drugs with placebo or drugs within a specific class; these are assessed in other Cochrane Reviews. Two review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. We included 29 studies of which 25 provided data on 6367 women. There was a lack of good quality data and important outcomes often included only small numbers of women. This meant we could only conclude that the current evidence shows no overall difference between the different classes of antibiotics in terms of reducing maternal infections after caesarean sections. However, none of the studies looked at outcomes on the baby, nor did they report infections diagnosed after the initial postoperative hospital stay. We were unable to assess what impact, if any, the use of different classes of antibiotics might have on bacterial resistance. Based on the best currently available evidence, cephalosporins and penicillins have similar efficacy at caesarean section when considering immediate postoperative infections. We have no data for outcomes on the baby, nor on late infections (up to 30 days) in the mother. Clinicians need to consider bacterial resistance and women's individual circumstances.

Hydroxyl (OH) radical production rates in snowpacks from photolysis of hydrogen peroxide (H 2O 2) and nitrate (NO 3−)

The rising prevalence of antibiotic resistance is rendering certain antibiotics ineffective in treating bacterial infections of public health importance. Deepening our understanding of how these drugs induce bacterial cell death, and whether antibiotics trigger a cell death program compared to direct killing, could help generate novel antibiotics or modify existing therapeutic approaches to improve clinical outcomes. Among the most widely used bactericidal antibiotics (beta-lactams, aminoglycosides, and fluoroquinolones), the primary drug-target interactions, and how they induce cell death, are well characterized. Additionally, there has been a recent debate as to whether a generalized bacterial cell death mechanism exists, shared among bactericidal antibiotics. The hypothesized mechanism, referred to as the common reactive oxygen species (ROS) pathway in this chapter, argues that certain bactericidal antibiotics have off-target effects that increase ROS generation in an iron- and oxygen-dependent manner. Moreover, this spike in ROS is thought to also contribute to induced bacterial cell death. Here we will discuss the target-specific mechanisms of distinct classes of bactericidal antibiotics, how these promote bacterial cell death, and the data that both support and refute the existence of a common cell death pathway.

Different classes of antibiotics given to women routinely for preventing infection at caesarean section.

We investigated hydroxyl radical (OH) production by human natural killer (NK) cells, using electron spin resonance (ESR) spectroscopy and 5.5 dimethyl-1-pyrroline-N-oxide (DMPO), a spin trap specific for OH. production. We confirmed that hydroxyl radical scavengers, n-propyl gallate and catechin, inhibited NK cell-mediated cytotoxicity (NK-CMC) in a dose-dependent manner and demonstrated that DMPO also inhibited NK-CMC. Polymorphonuclear leukocytes (PMNL) activated by opsonized zymosan (2.4 mg/ml) and mixed with DMPO (0.14 M) showed an early increase in hydroxyl radical production, leading to a net production of free radical of almost 400 pMol/10(6) cells. We then mixed NK cells with K562, an NK-sensitive tumor cell, at a 1:1 ratio and added DMPO (0.14 M). We pelleted the cells to increase EC to TC binding before taking the sample readings. Activated NK cells showed no increase in OH. production, leading to a net production of free radicals less than 1% that of activated PMNL. These data strongly suggest that hydroxyl radical production does not play a role in the early events of NK cell activation; they indicate a need to reevaluate the mechanism of inhibition of NK-CMC by OH. scavengers.

Hydroxyl radicals cause fluctuation in intracellular ferrous ion levels upon light exposure during photoreceptor cell death

It was recently proposed that bactericidal antibiotics, besides through specific drug-target interactions, kill bacteria by a common mechanism involving the production of reactive oxygen species (ROS). However, this mechanism involving the production of hydroxyl radicals has become the subject of a lot of debate. Since the contribution of ROS to antibiotic mediated killing most likely depends on the conditions, differences in experimental procedures are expected to be at the basis of the conflicting results. In the present study different methods (ROS specific stainings, gene-expression analyses, electron paramagnetic resonance, genetic and phenotypic experiments, detection of protein carbonylation and DNA oxidation) to measure the production of ROS upon antibiotic treatment in Burkholderia cepacia complex (Bcc) bacteria were compared. Different classes of antibiotics (tobramycin, ciprofloxacin, meropenem) were included, and both planktonic and biofilm cultures were studied. Our results indicate that some of the methods investigated were not sensitive enough to measure antibiotic induced production of ROS, including the spectrophotometric detection of protein carbonylation. Secondly, other methods were found to be useful only in specific conditions. For example, an increase in the expression of OxyR was measured in Burkholderia cenocepacia K56-2 after treatment with ciprofloxacin or meropenem (both in biofilms and planktonic cultures) but not after treatment with tobramycin. In addition results vary with the experimental conditions and the species tested. Nevertheless our data strongly suggest that ROS contribute to antibiotic mediated killing in Bcc species and that enhancing ROS production or interfering with the protection against ROS may form a novel strategy to improve antibiotic treatment.

Cytochrome P-450-dependent oxidase activity and hydroxyl radical production in micellar and membranous types of reconstituted systems

A Common Mechanism of Cellular Death Induced by Bactericidal Antibiotics

Terephthalate dianion (TA) has been used in this study as a hydroxyl radical probe to quantitatively measure the production of hydroxyl radicals from irradiated melanin, human hair, autoxidation of ascorbic acid, and the Fenton reaction. The production of radicals from irradiated human hair melanin under UVA-Visible light has been studied by the combination of two techniques: Electron spin resonance and fluorescence spectrometry. As a comparison, sepia melanin which is pure natural eumelanin has also been studied. The fluorescent probe for hydroxyl radicals has allowed us to compare the amount of radicals from different types of melanin under UVA-Visible irradiation $(\\rm \\lambda > 320nm).$ The ESR experiments show the superoxide is the initial product from irradiated melanin, and undergoes further dismutation to form hydrogen peroxide and produce hydroxyl radicals either through the Fenton reaction or the photolysis of hydrogen peroxide. Hydroxyl radical production is proportional to the irradiation time. Red hair melanin produces more radicals than both sepia and brown hair melanin. The effects of hydroxyl radical scavengers and other additives have also studied. ESR spin trapping experiments show that hydroxyl radicals are produced when solid human hair is irradiated at wavelengths above 320 nm. Fluorescent results show that red hair and bleached hair produce more radicals than brown and blond hair. Ammonium thioglycolate extraction shows that bleached hair contains much more extractable iron than brown hair and white hair presumably due to the presence of more negative charges on the surface of bleached hair. 2-hydroxyterephthalate (HTA) is produced from TA when ascorbic acid undergoes autoxidation in the presence of trace amounts of transition metals. Reverse-phase HPLC was used to monitor the concentration of ascorbic acid. During this process, hydroxyl radicals are produced via the Fenton cycle. In the presence of trace amounts of melanin, the oxidation of ascorbic acid is largely inhibited. When the concentration of melanin increases to a certain value, the inhibition starts to decrease because melanin is also a radical producer. More melanin is needed to obtain the same percentage of inhibition when iron is added to the ascorbic acid solution. Melanin inhibits the oxidation of ascorbic acid by acting as a metal chelator. For comparison, the effect of deferoxamine was also studied. The inhibition increases with the deferoxamine concentration. The decomposition of hydrogen peroxide is inhibited in the presence of melanin. Melanin competes with EDTA for iron ions. DOPA melanin is a weaker chelator than natural melanins.

The manifestations and mechanisms of myocardial cell injury and cell death in response to impaired coronary perfusion and thrombosis continue to be the collective subject of ongoing investigation because of intrinsic scientific interest and relevance for the diagnosis and treatment of patients with ischemic heart disease. An extensive body of evidence has documented the cellular and subcellular alterations that accompany the progressive reduction in high-energy ATP in response to oxygen and substrate deprivation affecting all cell types, including cardiac myocytes.1 2 3 The characteristic pattern of ischemic cell injury involves fluid and electrolyte alterations, with loss of K+ and Mg2+ and accumulation of water, Na+, Cl−, H+ (acidosis), and Ca2+; cytoplasmic, organellar, and cellular swelling with plasma membrane blebbing; and margination and clumping of nuclear chromatin. These cellular changes are due to progressive impairment of membrane composition, structure, and function.1 The transition from reversible to irreversible injury is characterized by the development of a severe membrane permeability defect that allows the unregulated influx of divalent and trivalent cations, including calcium.1 Subsequently, the swollen cells develop physical defects (holes) in their cell membranes and rupture. These features of cell injury with cell swelling have been shown to involve cardiac myocytes subjected to hypoxia in vitro and cardiac muscle during the evolution of myocardial infarction in vivo.1 3 Myocardium undergoing ischemic death ultimately exhibits some variant of coagulation necrosis and elicits an inflammatory response with an initial influx of neutrophils.3 The underlying membrane damage to ischemic myocytes is the basis for the diagnosis of myocardial infarction by pathology laboratory and nuclear cardiology methods. Recently, considerable attention has been directed to another form of cell death, referred to as apoptosis.1 2 Although apoptosis was initially characterized as a …

Fundamental research has been carried out to define optimal "green" synthesis conditions for the production of titania (TiO(2)) and silver (Ag) nanocomposites (TANCs) ranging from 12.7-22.8 nm in diameter. A bottom-up colloidal approach was employed to accurately control TANC monodispersity and composition. TANCs were found to be effective at inactivating Escherichia coli (E. coli) in water. The presence of Ag in the nanocomposites induced a decrease in TiO(2) band gap energy, which favoured valence to conduction band electron transfer and allowed for electron excitation using visible light. Aggregation of ultra-fine particles was prevented through the use of a long-chain polymer as evidenced by electrophoretic mobility studies. The TANCs catalyzed oxidation of bacterial membranes and cell death or disinfection. Theoretically, the TANC mode of E. coli disinfection is via water photolysis, which results in production of hydroxyl radicals and hydrogen peroxide. These interact with the outer membrane polysaccharides and lipids, leading to lipid peroxidation, membrane weakening and resulted in cell death. Our overarching goals were to optimize the variables involved in TANC "green" synthesis and to characterize its nanostructure. High resolution (HR) transmission and scanning electron microscopic (TEM and SEM) studies demonstrated that TANCs were highly crystalline and mono-dispersive. Elemental composition of Ag and Ti, as measured by X-ray energy dispersive (EDS) and X-ray photoelectron spectroscopy (XPS) confirmed sample purity. Ultraviolet-visible (UV-VIS) spectroscopy showed that the energy band-gap of Ag modified TiO(2) was in the visible range.

Production of hydroxyl radicals by copper-containing metallothionein: Roles as prooxidant

ABSTRACTFor this article, the authors tested various commercially available materials, such as activated carbon of vegetable origin, kaolin, vermiculite, Portland cement, magnetite and Earth´s Fuller to identify which is the best catalyst in the production of hydroxyl radical. The researchers used oxalic acid as a test compound to quantify the production of hydroxyl radical, taking advantage of the rapid reaction hydroxyl radical (.OH)-oxalic acid, and the very slow reaction ozone-oxalic acid. The best catalyst defined in terms of higher degradation of the oxalic acid (higher production of hydroxyl radical and oxidizing-species) was fixed it to glass spheres using a polymer film technique. The combination activated carbon and Portland cement (in a 1:1 ratio w/w) showed it the best performance in the oxalic acid elimination in a ratio catalyst-compound/ozone 900 (w/w), this condition produced a removal of 56% of the mass of oxalic acid initial (1000 mg) in the water treated with ozone over a period of 5 minutes. The main contribution of this article was to discover between some commercial materials, a compound capable to produce hydroxyl radical to manner efficient with the ozone. The synergistic effect of Portland cement in the system activated carbon-ozone increased the production of hydroxyl radicals. Besides their affordability and accessibility, the combined use of activated carbon and Portland cement lead to greater efficiency in the technical implementation of advanced oxidation processes.