Influence of Microbiota-Related Metabolites Associated with Inflammation and Sepsis on the Peroxidase Activity of Cyclooxygenase in Healthy Human Monocytes and Acute Monocytic Leukemia Cells

The human microbiota produces metabolites that can enter the bloodstream and exert systemic effects on various functions in both healthy and pathological states. We have studied the participation of microbiota-related metabolites in bacterial infection by examining their influence on the activity of cyclooxygenase (COX) as a key enzyme of inflammation. The influence of aromatic microbial metabolites, derivatives of phenylalanine (phenylpropionic acid, PPA), tyrosine (4-hydroxyphenyllactic acid, HPLA), and tryptophan (indolacetic acids, IAA), the concentrations of which in the blood change notably during sepsis, was evaluated. Also, the effect of itaconic acid (ITA) was studied, which is formed in macrophages under the action of bacterial lipopolysaccharides (LPS) and appears in the blood in the early stages of infection. Metabiotic acetyl phosphate (AcP) as a strong acetylating agent was also tested. The activity of COX was measured via the TMPD oxidation colorimetric assay using the commercial pure enzyme, cultured healthy monocytes, and the human acute monocytic leukemia cell line THP-1. All metabolites in the concentration range of 100-500 μM lowered the activity of COX. The most pronounced inhibition was observed on the commercial pure enzyme, reaching up to 40% in the presence of AcP and 20-30% in the presence of the other metabolites. On cell lysates, the effect of metabolites was preserved, although it significantly decreased, probably due to their interaction with other targets subject to redox-dependent and acetylation processes. The possible contribution of the redox-dependent action of microbial metabolites was confirmed by assessing the activity of the enzyme in the presence of thiol reagents and in model conditions, when the COX-formed peroxy intermediate was replaced with tert-butyl hydroperoxide (TBH). The data show the involvement of the microbial metabolites in the regulation of COX activity, probably due to their influence on the peroxidase activity of the enzyme.

Specific Features of Mitochondrial Dysfunction under Conditions of Ferroptosis Induced by t-Butylhydroperoxide and Iron: Protective Role of the Inhibitors of Lipid Peroxidation and Mitochondrial Permeability Transition Pore Opening

Recent studies have indicated the critical importance of mitochondria in the induction and progression of ferroptosis. There is evidence indicating that tert-butyl hydroperoxide (TBH), a lipid-soluble organic peroxide, is capable of inducing ferroptosis-type cell death. We investigated the effect of TBH on the induction of nonspecific membrane permeability measured by mitochondrial swelling and on oxidative phosphorylation and NADH oxidation assessed by NADH fluo rescence. TBH and iron, as well as their combinations, induced, with a respective decrease in the lag phase, the swelling of mitochondria, inhibited oxidative phosphorylation and stimulated NADH oxidation. The lipid radical scavenger butylhydroxytoluene (BHT), the inhibitor of mitochondrial phospholipase iPLA2γ bromoenol lactone (BEL), and the inhibitor of the mitochondrial permeability transition pore (MPTP) opening cyclosporine A (CsA) were equally effective in protecting these mitochondrial functions. The radical-trapping antioxidant ferrostatin-1, a known indicator of ferroptotic alteration, restricted the swelling but was less effective than BHT. ADP and oligomycin significantly decelerated iron- and TBH-induced swelling, confirming the involvement of MPTP opening in mitochondrial dysfunction. Thus, our data showed the participation of phospholipase activation, lipid peroxidation, and the MPTP opening in the mitochondria-dependent ferroptosis. Presumably, their involvement took place at different stages of membrane damage initiated by ferroptotic stimuli.

Involvement of Multidrug Resistance Modulators in the Regulation of the Mitochondrial Permeability Transition Pore

The permeability transition pore in mitochondria (MPTP) and the ATP-binding cassette transporters (АВС transporters) in cell membranes provide the efflux of low-molecular compounds across mitochondrial and cell membranes, respectively. The inhibition of ABC transporters, especially of those related to multi drug resistance (MDR) proteins, is an actively explored approach to enhance intracellular drug accumulation and increase thereby the efficiency of anticancer therapy. Although there is evidence showing the simultaneous effect of some inhibitors on both MDR-related proteins and mitochondrial functions, their influence on MPTP has not been previously studied. We examined the participation of verapamil and quinidine, classified now as the first generation of MDR modulators, and avermectin, which has recently been actively studied as an MDR inhibitor, in the regulation of the MPTP opening. In experiments on rat liver mitochondria, we found that quinidine lowered and verapamil increased the threshold concentrations of calcium ions required for MPTP opening, and that they both decreased the rate of calcium-induced swelling of mitochondria. These effects may be associated with the positive charge of the drugs and their aliphatic properties. Avermectin not only decreased the threshold concentration of calcium ions, but also by itself induced the opening of MPTP and the mitochondrial swelling inhibited by ADP and activated by carboxyatractyloside, the substrate and inhibitor of adenine nucleotide translocase (ANT), which suggests the involvement of ANT in the process. Thus, these data indicate an additional opportunity to evaluate the effectiveness of MDR modulators in the context of their influence on the mitochondrial-dependent apoptosis.

Influence of Microbial Metabolites on the Nonspecific Permeability of Mitochondrial Membranes under Conditions of Acidosis and Loading with Calcium and Iron Ions

Mitochondrial dysfunction is currently considered one of the main causes of multiple organ failure in chronic inflammation and sepsis. The participation of microbial metabolites in disorders of bioenergetic processes in mitochondria has been revealed, but their influence on the mitochondrial membrane permeability has not yet been studied. We tested the influence of various groups of microbial metabolites, including indolic and phenolic acids, trimethylamine-N-oxide (TMAO) and acetyl phosphate (AcP), on the nonspecific permeability of mitochondrial membranes under conditions of acidosis, imbalance of calcium ions and excess free iron, which are inherent in sepsis. Changes in the parameters of the calcium-induced opening of the mitochondrial permeability transition pore (MPTP) and iron-activated swelling of rat liver mitochondria were evaluated. The most active metabolites were indole-3-carboxylic acid (ICA) and benzoic acid (BA), which activated MPTP opening and swelling under all conditions. AcP showed the opposite effect on the induction of MPTP opening, increasing the threshold concentration of calcium by 1.5 times, while TMAO activated swelling only under acidification. All the redox-dependent effects of metabolites were suppressed by the lipid radical scavenger butyl-hydroxytoluene (BHT), which indicates the participation of these microbial metabolites in the activation of membrane lipid peroxidation. Thus, microbial metabolites can directly affect the nonspecific permeability of mitochondrial membranes, if conditions of acidosis, an imbalance of calcium ions and an excess of free iron are created in the pathological state.

Sepsis 2016 Agra, India

P1 D-Dimer in adult patients with presumed sepsis and their clinical outcomes

Surinder Kumar Sharma, Anurag Rohatgi, Mansi Bajaj

P2 Diagnosis of infection utilizing Acellix CD64

Charles L. Sprung, Ricardo Calderon Morales, Harvey Kasdan, Allon Reiter, Tobias Volker, Julien Meissonnier

P3 High levels of phenylcarboxylic acids reflect the severity in ICU patients and affect phagocytic activity of neutrophils

Natalia Beloborodova, Viktor Moroz, Aleksandra Bedova, Yulia Sarshor, Artem Osipov, Katerina Chernevskaya

P4 The role of bacterial phenolic metabolites in mitochondrial dysfunction

Nadezhda Fedotcheva, Ekaterina Chernevskaya, Natalia Beloborodova

P5 The early diagnosis of severe sepsis and judgment of rapid transport to critical care center: better prognostic factor

Hisashi Imahase, Kosuke C Yamada, Yuichiro Sakamoto, Miho Ohta, Ryota Sakurai, Mayuko Yahata, Mitsuru Umeka, Toru Miike, Hiroyuki Koami, Futoshi Nagashima, Takashi Iwamura, Satoshi Inoue

P6 Translational neuromodulation of the immune system

Zhifeng Li, Dennis Grech, Patrick Morcillo, Alex Bekker, Luis Ulloa

P7 Pathway-level meta-analysis reveals transcriptional signature of septic shock

Samanwoy Mukhopadhyay, Abhay D Pandey, Samsiddhi Bhattacharjee, Saroj K Mohapatra

P8 Antibiotic dosing in septic patients on the critical care unit - a literature review

Julie K Wilson

P9 Pandemic of Escherichia coli clone O25: H4-ST131 producing CTX-M-15 extended spectrum- β- lactamase- as serious cause of multidrug resistance extraintestinal pathogenic E. coli infections in India

Savita Jadhav, Rabindra Nath Misra, Nageswari Gandham, Kalpana Angadi, Chanda Vywahare, Neetu Gupta, Deepali Desai

P10 Detection and characterization of meningitis using a DDA-based mass spectrometry approach

Anahita Bakochi, Tirthankar Mohanty, Adam Linder, Johan Malmström

P11 Diagnostic usefulness of lipid profile and procalcitonin in sepsis and trauma patients

Dimple Anand, Seema Bhargava, Lalit Mohan Srivastava, Sumit Ray

P12 Heparin – a novel therapeutic in sepsis?

Jane Fisher, Peter Bentzer, Adam Linder

P13 Hypothalamic impairment is associated with vasopressin deficiency during sepsis

Luis Henrique Angenendt da Costa, Nilton Nascimentos dos Santos Júnior Carlos Henrique Rocha Catalão, Maria José Alves da Rocha

P14 Presepsin (soluble CD14 subtype) is a dependable prognostic marker in critical septic patients

Alfredo Focà, Cinzia Peronace, Giovanni Matera, Aida Giancotti, Giorgio Settimo Barreca, Angela Quirino, Maria Teresa Loria, Pio Settembre, Maria Carla Liberto, Bruno Amantea

P15 Safety and efficacy of gelatin-containing solutions versus crystalloids and albumin - a systematic review with quantitative and qualitative summaries

Christiane Hartog, Christiane Hartog, Claudia Moeller, Carolin Fleischmann, Daniel Thomas-Rueddel, Vlasislav Vlasakov, Bram Rochwerg, Philip Theurer, Konrad Reinhart

P16 Immunomodulatory properties of peripheral blood mesenchymal stem cells following endotoxin stimulation in an equine model

Anna E. Smith, Sandra D. Taylor

P17 Frequency and outcome of early sepsis-associated coagulopathy

Christopher Da Costa, Amanda Radford, Terry Lee, Joel Singer, John Boyd, David Fineberg, Mark Williams, James A Russell

Effect of phenolic acids of microbial origin on production of reactive oxygen species in mitochondria and neutrophils

BACKGROUND

Several low-molecular-weight phenolic acids are present in the blood of septic patients at high levels. The microbial origin of the most of phenolic acids in the human body was shown previously, but pathophysiological role of the phenolic acids is not clear. Sepsis is associated with the excessive production of reactive oxygen species (ROS) in both the circulation and the affected organs. In this work the influence of phenolic acids on ROS production in mitochondria and neutrophils was investigated.

METHODS

ROS production in mitochondria and neutrophils was determined by MCLA- and luminol-dependent chemiluminescence. The rate of oxygen consumption by mitochondria was determined polarographically. The difference of electric potentials on the inner mitochondrial membrane was registered using a TPP+-selective electrode. The formation of phenolic metabolites in monocultures by the members of the main groups of the anaerobic human microflora and aerobic pathogenic bacteria was investigated by the method of gas chromatography-mass spectrometry.

RESULTS

All phenolic acids had impact on mitochondria and neutrophils, the main producers of ROS in tissues and circulation. Phenolic acids (benzoic and cinnamic acids) producing the pro-oxidant effect on mitochondria inhibited ROS formation in neutrophils. Their effect on mitochondria was abolished by dithiothreitol (DTT). Phenyllactate and p-hydroxyphenyllactate decreased ROS production in both mitochondria and neutrophils. Bifidobacteria and lactobacilli produced in vitro considerable amounts of phenyllactic and p-hydroxyphenyllactic acids, Clostridia s. produced great quantities of phenylpropionic and p-hydroxyphenylpropionic acids, p-hydroxyphenylacetic acid was produced by Pseudomonas aeruginosa and Acinetobacter baumanii; and benzoic acid, by Serratia marcescens.

CONCLUSIONS

The most potent activators of ROS production in mitochondria are phenolic acids whose effect is mediated via the interaction with thiol groups. Among these are benzoic and cinnamic acids. Some phenolic acids, in particular phenyllactate and p-hydroxyphenyllactate, which decrease ROS production in mitochondria and neutrophils, can play a role of natural antioxidants. The results indicate that low-molecular weight phenolic acids of microbial origin participate in the regulation of the ROS production in both the circulation and tissues, thereby affecting the level of oxidative stress in sepsis.