Search

Microorganisms capable of direct or mediated extracellular electron transfer (EET) have garnered significant attention for their various biotechnological applications, such as bioremediation, metal recovery, wastewater treatment, energy generation in microbial fuel cells, and microbial or enzymatic electrosynthesis. One microorganism of particular interest is the organohalide-respiring bacterium Dehalococcoides mccartyi strain CBDB1, known for its ability to reductively dehalogenate toxic and persistent halogenated organic compounds through organohalide respiration (OHR), using halogenated organics as terminal electron acceptors. A membrane-bound OHR protein complex couples electron transfer to proton translocation across the membrane, generating a proton motive force, which enables metabolism and proliferation. In this study we show that the halogenated compounds can be replaced with redox mediators that can putatively shuttle electrons between the OHR complex and the anode, coupling D. mccartyi cells to an electrode via mediated EET. We identified cobalt-containing metal complexes, referred to as cobalt chelates, as promising mediators using a photometric high throughput methyl viologen-based enzyme activity assay. Through various biochemical approaches, we show that cobalt chelates are specifically reduced by CBDB1 cells, putatively by the reductive dehalogenase subunit (RdhA) of the OHR complex. Using cyclic voltammetry, we also demonstrate that cobalt chelates exchange electrons with a gold electrode, making them promising candidates for bioelectrochemical cultivation. Furthermore, using the AlphaFold 2-calculated RdhA structure and molecular docking, we found that one of the identified cobalt chelates exhibits favorable binding to RdhA, with a binding energy of approximately −28 kJ mol−1. Taken together, our results indicate that bioelectrochemical cultivation of D. mccartyi with cobalt chelates as anode mediators, instead of toxic halogenated compounds, is feasible, which opens new perspectives for bioremediation and other biotechnological applications of strain CBDB1. [ABSTRACT FROM AUTHOR]

Multi-heme cytochromes (MHCs), together with accessory proteins like porins and periplasmic cytochromes, enable microbes to transport electrons between the cytoplasmic membrane and extracellular substrates (e.g., minerals, electrodes, other cells). Extracellular electron transfer (EET) has been described in multiple systems; yet, the broad phylogenetic and mechanistic diversity of these pathways is less clear. One commonality in EET-capable systems is the involvement of MHCs, in the form of porin-cytochrome complexes, pililike cytochrome polymers, and lipid-anchored extracellular cytochromes. Here, we put forth MHCscan—a software tool for identifying MHCs and identifying potential EET capability. Using MHCscan, we scanned ∼60,000 bacterial and 2,000 archaeal assemblies, and identify a diversity of MHCs, many of which represent enzymes with no known function, and many found within organisms not previously known to be electroactive. In total, our scan identified ∼1,400 unique enzymes, each encoding more than 10 heme-binding motifs. In our analysis, we also find evidence for modularity and flexibility in MHC-dependent EET pathways, and suggest that MHCs may be far more common than previously recognized, with many facets yet to be discovered. [ABSTRACT FROM AUTHOR]

The effects of the symbiosis of sulfate-reducing bacteria (SRB) and total general bacteria (TGB) on the microbiologically influenced corrosion (MIC) of carbon steel were investigated in this research. The SRB was the main corrosive bacterium, and TGB induced slightly general MIC. The symbiosis of SRB and TGB induced more severe MIC and pitting corrosion than SRB. The main corrosion products were FeS, Fe2O3, and FeOOH. The presence of TGB facilitates MIC and pitting corrosion by providing a locally anaerobic shelter for SRB. An MIC mechanism of the symbiosis of SRB and TGB was proposed. [ABSTRACT FROM AUTHOR]

Microorganisms capable of direct or mediated extracellular electron transfer (EET) have garnered significant attention for their various biotechnological applications, such as bioremediation, metal recovery, wastewater treatment, energy generation in microbial fuel cells, and microbial or enzymatic electrosynthesis. One microorganism of particular interest is the organohalide-respiring bacterium Dehalococcoides mccartyi strain CBDB1, known for its ability to reductively dehalogenate toxic and persistent halogenated organic compounds through organohalide respiration (OHR), using halogenated organics as terminal electron acceptors. A membrane-bound OHR protein complex couples electron transfer to proton translocation across the membrane, generating a proton motive force, which enables metabolism and proliferation. In this study we show that the halogenated compounds can be replaced with redox mediators that can putatively shuttle electrons between the OHR complex and the anode, coupling D. mccartyi cells to an electrode via mediated EET. We identified cobalt-containing metal complexes, referred to as cobalt chelates, as promising mediators using a photometric high throughput methyl viologen-based enzyme activity assay. Through various biochemical approaches, we show that cobalt chelates are specifically reduced by CBDB1 cells, putatively by the reductive dehalogenase subunit (RdhA) of the OHR complex. Using cyclic voltammetry, we also demonstrate that cobalt chelates exchange electrons with a gold electrode, making them promising candidates for bioelectrochemical cultivation. Furthermore, using the AlphaFold 2-calculated RdhA structure and molecular docking, we found that one of the identified cobalt chelates exhibits favorable binding to RdhA, with a binding energy of approximately −28 kJ mol−1. Taken together, our results indicate that bioelectrochemical cultivation of D. mccartyi with cobalt chelates as anode mediators, instead of toxic halogenated compounds, is feasible, which opens new perspectives for bioremediation and other biotechnological applications of strain CBDB1.

Multi-heme cytochromes (MHCs), together with accessory proteins like porins and periplasmic cytochromes, enable microbes to transport electrons between the cytoplasmic membrane and extracellular substrates (e.g., minerals, electrodes, other cells). Extracellular electron transfer (EET) has been described in multiple systems; yet, the broad phylogenetic and mechanistic diversity of these pathways is less clear. One commonality in EET-capable systems is the involvement of MHCs, in the form of porin-cytochrome complexes, pili-like cytochrome polymers, and lipid-anchored extracellular cytochromes. Here, we put forth MHCscan—a software tool for identifying MHCs and identifying potential EET capability. Using MHCscan, we scanned ~60,000 bacterial and 2,000 archaeal assemblies, and identify a diversity of MHCs, many of which represent enzymes with no known function, and many found within organisms not previously known to be electroactive. In total, our scan identified ~1,400 unique enzymes, each encoding more than 10 heme-binding motifs. In our analysis, we also find evidence for modularity and flexibility in MHC-dependent EET pathways, and suggest that MHCs may be far more common than previously recognized, with many facets yet to be discovered. We present MHCscan as a lightweight and user-friendly software tool that is freely available: https://github.com/Arkadiy-Garber/MHCscan.

Hepatocellular carcinoma (HCC) is a leading cause of cancer death, and medical treatment options are limited. The multikinase inhibitor sorafenib was the first approved drug widely used for systemic therapy in advanced HCC. Sorafenib might affect polyunsaturated fatty acids (PUFA)-derived epoxygenated metabolite levels, as it is also a potent inhibitor of the soluble epoxide hydrolase (sEH), which catalyzes the conversion of cytochrome-P450 (CYP)-derived epoxide metabolites derived from PUFA, such as omega-6 arachidonic acid (AA) and omega-3 docosahexaenoic acid (DHA), into their corresponding dihydroxy metabolites. Experimental studies with AA-derived epoxyeicosatrienoic acids (EETs) have shown that they can promote tumor growth and metastasis, while DHAderived 19,20-epoxydocosapentaenoic acid (19,20-EDP) was shown to have anti-tumor activity in mice. In this study, we found a significant increase in EET levels in 43 HCC patients treated with sorafenib and a trend towards increased levels of DHA-derived 19,20-EDP. We demonstrate that the effect of sorafenib on CYP-metabolites led to an increase of 19,20-EDP and its dihydroxy metabolite, whereas DHA plasma levels decreased under sorafenib treatment. These data indicate that specific supplementation with DHA could be used to increase levels of the epoxy compound 19,20-EDP with potential anti-tumor activity in HCC patients receiving sorafenib therapy. [ABSTRACT FROM AUTHOR]

Neutrophils are a specialized subset of white blood cells, which have the ability to store pre-formed mediators in their cytoplasmic granules. Neutrophils are wellknown effector cells involved in host protection against pathogens through diverse mechanisms such as phagocytosis, degranulation, extracellular traps, and oxidative burst. In this study, we provide evidence highlighting the significance of the SNARE proteins syntaxin-4 and synaptosomal-associated protein (SNAP) 23 in the release of azurophilic granules, specific granules, and the production of reactive oxygen species in human neutrophils. In contrast, the specific blockade of either syntaxin-4 or SNAP23 did not prevent the release of mitochondrial dsDNA in the process of neutrophil extracellular trap (NET) formation. These findings imply that degranulation and the release of mitochondrial dsDNA involve at least partially distinct molecular pathways in neutrophils. [ABSTRACT FROM AUTHOR]

Neutrophils are a specialized subset of white blood cells, which have the ability to store pre-formed mediators in their cytoplasmic granules. Neutrophils are well-known effector cells involved in host protection against pathogens through diverse mechanisms such as phagocytosis, degranulation, extracellular traps, and oxidative burst. In this study, we provide evidence highlighting the significance of the SNARE proteins syntaxin-4 and synaptosomal-associated protein (SNAP) 23 in the release of azurophilic granules, specific granules, and the production of reactive oxygen species in human neutrophils. In contrast, the specific blockade of either syntaxin-4 or SNAP23 did not prevent the release of mitochondrial dsDNA in the process of neutrophil extracellular trap (NET) formation. These findings imply that degranulation and the release of mitochondrial dsDNA involve at least partially distinct molecular pathways in neutrophils.

The valence electron structure, bond energy and cohesive energy of AlN, AlN doped x%Mg, Mg3N2, Mg3N2 doped x%Al and Mg doped x%Al crystals were calculated using the empirical electron theory of solids and molecules (EET). The calculation results show that AlN consists of two kinds of Al–N bonds and the weak Al–N bond on the outermost surface will break under high temperature in the Mg–Al melt, and liquid Mg atoms are attracted by the exposed N atoms to preferably form a single-layer of Mg3N2 before α-Mg crystallization. Besides, this single Mg layer also has a similar crystal structure to that of the (0001) plane in α-Mg, both of which make AlN an effective heterogeneous nucleant. The increase in the Al content reduces the cohesive energy of Mg3N2; when the Al content exceeds a certain value, the cohesive energy of Mg3N2 is lower than that of α-Mg, resulting in a single Mg layer in Mg3N2 not formed prior to α-Mg. Simultaneously, Al–N bonds might be formed again on AlN surface to increase the Al content, which finally contributes to AlN losing its refining effect. Based on the calculation results, a novel atomic model of AlN heterogeneously nucleated to α-Mg is proposed. [ABSTRACT FROM AUTHOR]

Copyright of Tax & Economic Research is the property of Tax & Economic Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mass spectrometry affords rapid and sensitive analysis of peptides and proteins. Coupling spectroscopy with mass spectrometry allows for the development of new methods to enhance biomolecular structure determination. Herein, we demonstrate two new energy acceptors that can be utilized for action-excitation energy transfer experiments. In the first system, C-S bonds in methionine act as energy acceptors from native chromophores, including tyrosine, tryptophan, and phenylalanine. Comparison among chromophores reveals that tyrosine transfers energy most efficiently at 266 nm, but phenylalanine and tryptophan also transfer energy with comparable efficiencies. Overall, the C-S bond dissociation yields following energy transfer are low for methionine, which led to an investigation of selenomethionine, a common analog that is found in many naturally occurring proteins. Sulfur and selenium are chemically similar, but C-Se bonds are weaker than C-S bonds and have lower lying σ* anti-bonding orbitals. Excitation of peptides containing tyrosine and tryptophan results in efficient energy transfer to selenomethionine and abundant C-Se bond dissociation. A series of helical peptides were examined where the positions of the donor or acceptor were systematically scanned to explore the influence of distance and helix orientation on energy transfer. The distance was found to be the primary factor affecting energy transfer efficiency, suggesting that selenomethionine may be a useful acceptor for probing protein structure in the gas phase.

Hepatocellular carcinoma (HCC) is a leading cause of cancer death, and medical treatment options are limited. The multikinase inhibitor sorafenib was the first approved drug widely used for systemic therapy in advanced HCC. Sorafenib might affect polyunsaturated fatty acids (PUFA)-derived epoxygenated metabolite levels, as it is also a potent inhibitor of the soluble epoxide hydrolase (sEH), which catalyzes the conversion of cytochrome-P450 (CYP)-derived epoxide metabolites derived from PUFA, such as omega-6 arachidonic acid (AA) and omega-3 docosahexaenoic acid (DHA), into their corresponding dihydroxy metabolites. Experimental studies with AA-derived epoxyeicosatrienoic acids (EETs) have shown that they can promote tumor growth and metastasis, while DHAderived 19,20-epoxydocosapentaenoic acid (19,20-EDP) was shown to have anti-tumor activity in mice. In this study, we found a significant increase in EET levels in 43 HCC patients treated with sorafenib and a trend towards increased levels of DHA-derived 19,20-EDP. We demonstrate that the effect of sorafenib on CYP- metabolites led to an increase of 19,20-EDP and its dihydroxy metabolite, whereas DHA plasma levels decreased under sorafenib treatment. These data indicate that specific supplementation with DHA could be used to increase levels of the epoxy compound 19,20-EDP with potential anti-tumor activity in HCC patients receiving sorafenib therapy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combined transcriptomic and metabolomic analyses. • 5,6-EET, 8,9-EET, and 11,12-EET, were down-regulated in pulmonary fibrosis lungs. • SSPF regulated arachidonic acid metabolic reprogramming. As a clinical formula derived from Renshen Pingfei San, Shuangshen Pingfei formula (SSPF) has been used to treat pulmonary fibrosis (PF). However, its in-depth mechanism of action remains unknown. In this study, the effect of SSPF was evaluated by applying a rat model of PF caused by intratracheal drip bleomycin. To characterize the molecular changes related to PF and reveal therapeutic targets for SSPF, we performed transcriptomic and metabolomic analyses on rat lung. Finally, western blotting and qPCR experiments were used to validate the multi-omics results. As a result, a significant reduction in inflammation and fibrosis caused by BLM was observed when SSPF was administered. Widespread changes in gene expression and metabolic programming were observed in the lungs of PF rats through RNA-seq and untargeted metabolomic analysis. Combined transcriptomic and metabolomic analyses revealed the involvement of arachidonic acid (AA) metabolism pathways in PF. Further validation of AA metabolite synthase genes and protein levels showed a significant decrease in the levels of epoxyeicosatrienoic acids (EETs) synthases, including Cyp2j2, Cyp2b1, in the PF lungs. SSPF treatment regulated the above changes in gene expression and metabolic programming, particularly the regulation of EETs. This study is the first to investigate the mechanism of action of SSPF in the treatment of PF from the perspective of regulating the synthesis of EETs in AA metabolism. [ABSTRACT FROM AUTHOR]

• Validated assay for arachidonic acid (AA)-underived chiral epoxy-metabolites. • A reliable and reproducible chiral analysis for epoxy-metabolites of AA. • Enantioselective analysis of epoxy-metabolites formed by human liver microsomes. • The assay showed acceptable linearity, precision, and accuracy. Epoxyeicosatrienoic acids (EETs) are increasingly recognized as key metabolites in the arachidonic acid (AA) metabolic pathway. EETs are epoxy derivatives of AA with two chiral centers formed by cytochrome P450 (CYP) enzymes. EETs have reported biological activities as racemates; however, knowledge on specific optical isomers of EET is lacking. A main reason is the absence of practical assay to quantify EETs isomers associated with specific pathological conditions and enzymes. The reported underivatized chiral LC-MS/MS assays utilize different mobile phases and flow rates or required long run times to achieve separation of EET stereoisomers. Others incorporated a derivatization step before the separation of EETs in their assays. Therefore, the objective of this study was to develop and validate a stereoselective assay for the simultaneous quantitation of underivatized EET enantiomers using Liquid Chromatography Mass Spectrometry (LC-MS/MS) with an optimum baseline separation using binary mobile phase and gradient elution. Herein, we report the development and validation of an LC-MS/MS assay, and its application to quantify the formation of EET enantiomers mediated by human liver microsomes. Assay linearity extends over 10–600 ng/mL with r2 > 0.99 for all EETs enantiomers. The inter-run accuracy was within ± 15 %, and precision was ≤ 15 %, and < 20 % for the LLOQ. The matrix effect for the current assay was within ≤ ±20 %, and the mean recovery for quantitative methods was 70–125 %. The assay proved to be reliable and practical for chiral analysis. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) is a leading cause of cancer death, and medical treatment options are limited. The multikinase inhibitor sorafenib was the first approved drug widely used for systemic therapy in advanced HCC. Sorafenib might affect polyunsaturated fatty acids (PUFA)-derived epoxygenated metabolite levels, as it is also a potent inhibitor of the soluble epoxide hydrolase (sEH), which catalyzes the conversion of cytochrome-P450 (CYP)-derived epoxide metabolites derived from PUFA, such as omega-6 arachidonic acid (AA) and omega-3 docosahexaenoic acid (DHA), into their corresponding dihydroxy metabolites. Experimental studies with AA-derived epoxyeicosatrienoic acids (EETs) have shown that they can promote tumor growth and metastasis, while DHA-derived 19,20-epoxydocosapentaenoic acid (19,20-EDP) was shown to have anti-tumor activity in mice. In this study, we found a significant increase in EET levels in 43 HCC patients treated with sorafenib and a trend towards increased levels of DHA-derived 19,20-EDP. We demonstrate that the effect of sorafenib on CYP- metabolites led to an increase of 19,20-EDP and its dihydroxy metabolite, whereas DHA plasma levels decreased under sorafenib treatment. These data indicate that specific supplementation with DHA could be used to increase levels of the epoxy compound 19,20-EDP with potential anti-tumor activity in HCC patients receiving sorafenib therapy.

Inhibition of soluble epoxide hydrolase (sEH, EPHX2) elicits potent cardiovascular protective effects in preclinical models of ischemic cardiovascular disease (CVD), and genetic polymorphisms in EPHX2 have been associated with developing ischemic CVD in humans. However, it remains unknown whether EPHX2 variants are associated with prognosis following an ischemic CVD event. We evaluated the association between EPHX2 p.Lys55Arg and p.Arg287Gln genotype with survival in 667 acute coronary syndrome (ACS) patients. No association with p.Arg287Gln genotype was observed (P = 0.598). Caucasian EPHX2 Arg55 carriers (Lys/Arg or Arg/Arg) had a significantly higher risk of 5-year mortality (adjusted hazard ratio [HR] 1.61, 95% confidence interval [CI] 1.01-2.55, P = 0.045). In an independent population of 2712 ACS patients, this association was not replicated (adjusted HR 0.92, 95% CI 0.70-1.21, P = 0.559). In a secondary analysis, Caucasian homozygous Arg55 allele carriers (Arg/Arg) appeared to exhibit a higher risk of cardiovascular mortality (adjusted HR 2.60, 95% CI 1.09-6.17). These results demonstrate that EPHX2 p.Lys55Arg and p.Arg287Gln polymorphisms do not significantly modify survival after an ACS event. Investigation of other sEH metabolism biomarkers in ischemic CVD appears warranted.

In light of the importance of epoxyeicosatrienoic acids (EETs) in mammalian pathophysiology, a nonenzymatic route that might form these monoepoxides in cells is of significant interest. In the late 1970s, a simple system of arranging linoleic acid molecules on a monolayer on silica was devised and shown to yield monoepoxides as the main autoxidation products. Here, we investigated this system with arachidonic acid and characterized the primary products. By the early stages of autoxidation (∼10% conversion of arachidonic acid), the major products detected by LC-MS and HPLC-UV were the 14,15-, 11,12-, and 8,9-EETs, with the 5,6-EET mainly represented as the 5-δ-lactone-6-hydroxyeicosatrienoate as established by 1H-NMR. The EETs were mainly the cis epoxides as expected, with minor trans configuration EETs among the products. 1H-NMR analysis in four deuterated solvents helped clarify the epoxide configurations. EET formation in monolayers involves intermolecular reaction with a fatty acid peroxyl radical, producing the EET and leaving an incipient and more reactive alkoxyl radical, which in turn gives rise to epoxy-hydro(pero)xides and other polar products. The monolayer alignment of fatty acid molecules resembles the arrangements of fatty acids in cell membranes and, under conditions of lipid peroxidation, this intermolecular mechanism might contribute to EET formation in biological membranes.

The low efficiency of extracellular electron transfer (EET) is a major bottleneck for Shewanella oneidensis MR-1 acting as an electroactive biocatalyst in bioelectrochemical systems. Although it is well established that a periplasmic c -type cytochrome (c -Cyt) network plays a critical role in regulating EET efficiency, the understanding of the network in terms of structure and electron transfer activity is obscure and partial. In this work, we attempted to systematically investigate the impacts of the network components on EET in their absence and overproduction individually in microbial fuel cell (MFC). We found that overexpression of c -Cyt CctA leads to accelerated electron transfer between CymA and the Mtr system, which function as the primary quinol oxidase and the outer-membrane (OM) electron hub in EET. In contrast, NapB, FccA, and TsdB in excess severely impaired EET, reducing EET capacity in MFC by more than 50%. Based on the results from both strategies, a series of engineered strains lacking FccA, NapB, and TsdB in combination while overproducing CctA were tested for a maximally optimized c -Cyt network. A strain depleted of all NapB, FccA, and TsdB with CctA overproduction achieved the highest maximum power density in MFCs (436.5 mW/m2), ∼3.62-fold higher than that of wild type (WT). By revealing that optimization of periplasmic c -Cyt composition is a practical strategy for improving EET efficiency, our work underscores the importance in understanding physiological and electrochemical characteristics of c -Cyts involved in EET. [ABSTRACT FROM AUTHOR]

The low efficiency of extracellular electron transfer (EET) is a major bottleneck for Shewanella oneidensis MR-1 acting as an electroactive biocatalyst in bioelectrochemical systems. Although it is well established that a periplasmic c-type cytochrome (c-Cyt) network plays a critical role in regulating EET efficiency, the understanding of the network in terms of structure and electron transfer activity is obscure and partial. In this work, we attempted to systematically investigate the impacts of the network components on EET in their absence and overproduction individually in microbial fuel cell (MFC). We found that overexpression of c-Cyt CctA leads to accelerated electron transfer between CymA and the Mtr system, which function as the primary quinol oxidase and the outer-membrane (OM) electron hub in EET. In contrast, NapB, FccA, and TsdB in excess severely impaired EET, reducing EET capacity in MFC by more than 50%. Based on the results from both strategies, a series of engineered strains lacking FccA, NapB, and TsdB in combination while overproducing CctA were tested for a maximally optimized c-Cyt network. A strain depleted of all NapB, FccA, and TsdB with CctA overproduction achieved the highest maximum power density in MFCs (436.5 mW/m2), ∼3.62-fold higher than that of wild type (WT). By revealing that optimization of periplasmic c-Cyt composition is a practical strategy for improving EET efficiency, our work underscores the importance in understanding physiological and electrochemical characteristics of c-Cyts involved in EET.

[Display omitted] • A simultaneous bioelectricity generation and complete DNRA strain was isolated. • Genome and q-PCR analysis explain the mechanism of DNRA and outward EET pathway. • The presence of NH 4 + significantly enhances output voltage and the DNRA performance. • Bioelectricity promotes the up-regulated expression of NarG and NirB related to DNRA. • The bacterial community of cathode biofilms was affected by the bioelectricity. The synchronous bioelectricity generation and dissimilatory nitrate reduction to ammonium (DNRA) pathway in Klebsiella variicola C1 was investigated. The presence of bioelectricity facilitated cell growth on the anodic biofilms, consequently enhancing the nitrate removal efficiency decreasing total nitrogen levels and causing a negligible accumulation of NO 2 – in the supernatant. Genomic analysis revealed that K. variicola C1 possessed a complete DNRA pathway and largely annotated electron shuttles. The up-regulated expression of genes narG and nirB , encoding nitrite oxidoreductase and nitrite reductase respectively, was closely associated with increased extracellular electron transfer (EET). High-throughput sequencing analysis was employed to investigate the impact of bioelectricity on microbial community composition within cathodic biofilms. Results indicated that Halomonas , Marinobacter and Prolixibacteraceae were enriched at the cathode electrodes. In conclusion, the integration of a DNRA strain with MFC facilitated the efficient removal of wastewater containing high concentrations of NO 3 – and enabled the environmentally friendly recovery of NH 4 +. [ABSTRACT FROM AUTHOR]

Microbial fuel cell (MFC) is a promising technology that utilizes exoelectrogens cultivated in the form of biofilm to generate power from various types of sources supplied. A metal-reducing pathway is utilized by these organisms to transfer electrons obtained from the metabolism of substrate from anaerobic respiration extracellularly. A widely established model organism that is capable of extracellular electron transfer (EET) is Shewanella oneidensis. This review highlights the strategies used in the transformation of S. oneidensis and the recent development of MFC in terms of intervention through genetic modifications. S. oneidensis was genetically engineered for several aims including the study on the underlying mechanisms of EET, and the enhancement of power generation and wastewater treating potential when used in an MFC. Through engineering S. oneidensis, genes responsible for EET are identified and strategies on enhancing the EET efficiency are studied. Overexpressing genes related to EET to enhance biofilm formation, mediator biosynthesis, and respiration appears as one of the common approaches. [ABSTRACT FROM AUTHOR]

Epoxyeicosatrienoic acids (EETs) are metabolites of arachidonic acid by cytochrome P450 (CYP) epoxygenases, which include four regioisomers: 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET. Each of them possesses beneficial effects against inflammation, fibrosis, and apoptosis, which could combat cardiovascular diseases. Numerous studies have demonstrated that elevation of EETs by overexpression of CYP2J2, inhibition of sEH, or treatment with EET analogs showed protective effects in various cardiovascular diseases, including hypertension, myocardial infarction, and heart failure. As is known to all, cardiac remodeling is the major pathogenesis of cardiovascular diseases. This review will begin with the introduction of EETs and their protective effects in cardiovascular diseases. In the following, the roles of EETs in cardiac remodeling, with a particular emphasis on myocardial hypertrophy, apoptosis, fibrosis, inflammation, and angiogenesis, will be summarized. Finally, it is suggested that upregulation of EETs is a potential therapeutic strategy for cardiovascular diseases. The EET-related drug development against cardiac remodeling is also discussed, including the overexpression of CYP2J2, inhibition of sEH, and the analogs of EET.

Epoxyeicosatrienoic acids (EETs) are metabolites of arachidonic acid by cytochrome P450 (CYP) epoxygenases, which include four regioisomers: 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET. Each of them possesses beneficial effects against inflammation, fibrosis, and apoptosis, which could combat cardiovascular diseases. Numerous studies have demonstrated that elevation of EETs by overexpression of CYP2J2, inhibition of sEH, or treatment with EET analogs showed protective effects in various cardiovascular diseases, including hypertension, myocardial infarction, and heart failure. As is known to all, cardiac remodeling is the major pathogenesis of cardiovascular diseases. This review will begin with the introduction of EETs and their protective effects in cardiovascular diseases. In the following, the roles of EETs in cardiac remodeling, with a particular emphasis on myocardial hypertrophy, apoptosis, fibrosis, inflammation, and angiogenesis, will be summarized. Finally, it is suggested that upregulation of EETs is a potential therapeutic strategy for cardiovascular diseases. The EET-related drug development against cardiac remodeling is also discussed, including the overexpression of CYP2J2, inhibition of sEH, and the analogs of EET. [ABSTRACT FROM AUTHOR]

Pyrene-perylene (Py-Pery) doped 2-naphthol (2-NP) luminophors (Py-Pery/2-NP) were prepared by conventional solid state reaction method. Excitation energy transfer and electrical properties were studied by fluorimetry and cyclic voltametric (CV) analysis respectively.2-NP acts as an good light emitting matrix. The effect of the donor emission was perceived by changing the dopant and dopant concentrations; this showed that Py-Pery in 2-NP matrix exhibits green emission in the wavelength region 480–550 nm, peaking at 510 nm. Structural properties and thermal stability was studied by XRD, SEM and TGA-DSC. The HOMO and LUMO energy levels were in the range from 5.46–5.48 eV and 2.76–2.77 eV, respectively. An electrochemical band gap estimated was within the range of 2.68–2.72 eV. This study reveals that 2-NP luminophors can be used as a hole-transporting materials used in optoelectronics. [ABSTRACT FROM AUTHOR]

Shipin Chen,1,* Meixiu Luo,1,* Liang Ma,2 Wenjun Lin1 1College of Forestry, Fujian Agriculture and Forestry University, Fuzhou City, Fujian Province 350001, China; 2Institute of Art of Landscape, Fujian Agriculture and Forestry University, Fuzhou City, Fujian Province 350001, China *These authors contributed equally to this work Purpose: This study aimed to investigate the effect of ethylacetate extract from Tetrastigma hemsleyanum (EET) on the proliferation and apoptosis of HepG2 and SMMC-7721 cells and determine the underlying mechanisms. Materials and methods: HepG2 and SMMC-7721 cells were cultured in vitro until the exponential growth phase and then treated with different concentrations of EET for 24 h. We performed a colony forming assay to determine colony forming ability, CCK8 assay to detect cell proliferation, Annexin V–FITC/PI double staining to analyze cell apoptosis, and Western blot to measure the protein expression of Caspase-3, Bcl-2, and Bax. Results: EET significantly inhibited the proliferation of HepG2 and SMMC-7721 cells in a concentration- and time-dependent manner (P

Like many eicosanoids, epoxyeicosatrienoic acids (EETs) have multiple biological functions, including reduction of blood pressure, inflammation, and atherosclerosis in multiple species. Hydration of EETs by the soluble epoxide hydrolase (sEH) is the major route of their degradation to the less bioactive diols. Inhibition of the sEH stabilizes EETs, thus, enhancing the beneficial effects of EETs. Human data show an association of sEH (Ephx2) gene polymorphisms with increased risk of atherosclerosis and cardiovascular diseases. These data suggest a potential therapeutic effect of sEH inhibitors (sEHI) in the treatment of atherosclerosis. Indeed, two laboratories reported independently that using different sEHIs in apolipoprotein E–deficient mice significantly attenuated atherosclerosis development and aneurysm formation. The antiatherosclerotic effects of sEHI are correlated with elevation in EET levels and associated with reduction of low-density lipoprotein and elevation of high-density lipoprotein cholesterols, as well as attenuation of expression of proinflammatory genes and proteins. In addition, the antihypertensive effects and improvement of endothelial function also contribute to the mechanism of the antiatherosclerotic effects of sEHI. The broad spectrum of biological action of EETs and sEHIs with multiple biological beneficial actions provides a promising new class of therapeutics for atherosclerosis and other cardiovascular diseases.

Endoscopic treatment is recommended for patients with Barrett's esophagus (BE) with high-grade dysplasia, yet clinical management recommendations are inconsistent for patients with BE without dysplasia (NDBE) or with low-grade dysplasia (LGD). We used a comparative modeling analysis to identify optimal management strategies for these patients. We used 3 independent population-based models to simulate cohorts of 60-year-old individuals with BE in the United States. We followed up each cohort until death without surveillance and treatment (natural disease progression), compared with 78 different strategies of management for patients with NDBE or LGD. We determined the optimal strategy using cost-effectiveness analyses, at a willingness-to-pay threshold of $100,000 per quality-adjusted life-year (QALY). In the 3 models, the average cumulative incidence of esophageal adenocarcinoma was 111 cases, with costs totaling $5.7 million per 1000 men with BE. Surveillance and treatment of men with BE prevented 23% to 75% of cases of esophageal adenocarcinoma, but increased costs to $6.2 to $17.3 million per 1000 men with BE. The optimal strategy was surveillance every 3 years for men with NDBE and treatment of LGD after confirmation by repeat endoscopy (incremental cost-effectiveness ratio, $53,044/QALY). The average results for women were consistent with the results for men for LGD management, but the optimal surveillance interval for women with NDBE was 5 years (incremental cost-effectiveness ratio, $36,045/QALY). Based on analyses from 3 population-based models, the optimal management strategy for patient with BE and LGD is endoscopic eradication, but only after LGD is confirmed by a repeat endoscopy. The optimal strategy for patients with NDBE is endoscopic surveillance, using a 3-year interval for men and a 5-year interval for women. [ABSTRACT FROM AUTHOR]

ABSTRACT Humic lakes and ponds receive large amounts of terrestrial carbon and are important components of the global carbon cycle, yet how their redox cycling influences the carbon budget is not fully understood. Here we compared metagenomes obtained from a humic bog and a clear-water eutrophic lake and found a much larger number of genes that might be involved in extracellular electron transfer (EET) for iron redox reactions and humic substance (HS) reduction in the bog than in the clear-water lake, consistent with the much higher iron and HS levels in the bog. These genes were particularly rich in the bog’s anoxic hypolimnion and were found in diverse bacterial lineages, some of which are relatives of known iron oxidizers or iron-HS reducers. We hypothesize that HS may be a previously overlooked electron acceptor and that EET-enabled redox cycling may be important in pelagic respiration and greenhouse gas budget in humic-rich freshwater lakes.

Abstract Biochar widely applied to soil can influence microbial community composition and participate in extracellular electron transfer (EET). However, little is known about the cotransport behaviors of bacteria and biochar in aquifer and soil-water environments, which can affect the fate and application performance of biochar. In this study, we found that in comparison to their individual transport behaviors, the mobilities of cotransporting Shewanella oneidensis MR-1 and biochar colloid (BC) were significantly inhibited. The decreasing colloidal mobilities at higher ionic strengths signified the importance of electrostatic interaction between cell and BC in cotransport. Moreover, the less suppressed cotransport of BC and mutants defective of EET and the elevated inhibition effects on cotransport by adding exogenous electron donor suggested the importance of EET. Difference in cotransport behavior was also observed with BC having different redox states. Compared with oxidized BC, reduced BC with higher hydrophobicity led to easier aggregation with cell and higher retention in column. More importantly, MR-1 exhibited EET-dependent taxis towards biochar, which also contributed to the enhanced heteroaggregation and decreased mobilities of cell and biochar. Our results highlight that metabolic activities of microbes towards abiotic colloids cannot be neglected when assessing their transport behaviors, especially in subsurface environments abounded with redox-active inorganic particles and microbes performing extracellular respiration. Graphical abstract Unlabelled Image Highlights • Heteroaggregation of biochar and cell retards their cotransport. • Mobilities of biochar and cell decrease with increasing ionic strength. • Reduction increases biochar's hydrophobicity and inhibits cotransport. • EET-dependent taxis of cell towards biochar inhibits cotransport. [ABSTRACT FROM AUTHOR]

Highlights • Dietary n-3 LC-PUFA supplementation modulates hippocampal oxylipins profile. • Dietary n-3 LC-PUFA supplementation decreases hippocampal pro-inflammatory cytokines induced by LPS. • Oxylipin profile depending on dietary intake could orchestrate inflammatory response to LPS. Abstract The brain is highly enriched in long chain polyunsaturated fatty acids (LC-PUFAs) that display immunomodulatory properties in the brain. At the periphery, the modulation of inflammation by LC-PUFAs occurs through lipid mediators called oxylipins which have anti-inflammatory and pro-resolving activities when derived from n-3 LC-PUFAs and pro-inflammatory activities when derived from n-6 LC-PUFAs. However, whether a diet rich in LC-PUFAs modulates oxylipins and neuroinflammation in the brain has been poorly investigated. In this study, the effect of a dietary n-3 LC-PUFA supplementation on oxylipin profile and neuroinflammation in the brain was analyzed. Mice were given diets deficient or supplemented in n-3 LC-PUFAs for a 2-month period starting at post-natal day 21, followed by a peripheral administration of lipopolysaccharide (LPS) at adulthood. We first showed that dietary n-3 LC-PUFA supplementation induced n-3 LC-PUFA enrichment in the hippocampus and subsequently an increase in n-3 PUFA-derived oxylipins and a decrease in n-6 PUFA-derived oxylipins. In response to LPS, n-3 LC-PUFA deficient mice presented a pro-inflammatory oxylipin profile whereas n-3 LC-PUFA supplemented mice displayed an anti-inflammatory oxylipin profile in the hippocampus. Accordingly, the expression of cyclooxygenase-2 and 5-lipoxygenase, the enzymes implicated in pro- and anti-inflammatory oxylipin synthesis, was induced by LPS in both diets. In addition, LPS-induced pro-inflammatory cytokine increase was reduced by dietary n-3 LC-PUFA supplementation. These results indicate that brain n-3 LC-PUFAs increase by dietary means and promote the synthesis of anti-inflammatory derived bioactive oxylipins. As neuroinflammation plays a key role in all brain injuries and many neurodegenerative disorders, the present data suggest that dietary habits may be an important regulator of brain cytokine production in these contexts. [ABSTRACT FROM AUTHOR]

Abstract Excited state intramolecular proton transfer (ESIPT) meso flanked BODIPY dyad are synthesized and investigated by using spectroscopic, fluorescence lifetime decay, electrochemical and DFT method. Excitation (λ exc = 290 nm) of the Bn-OH-BDY dyad leads to emission (λ emi = 545 nm) totally directed by the BODIPY subunits pointing to excitation energy transfer (EET) from the ESIPT to BODIPY core. A large shift of 255 nm has been observed between excitation and emitted light. Attachment of ESIPT unit does not cause any perturbation in the low-energy absorption band of the Bn-OH-BDY dyad. The electrochemical study shows an irreversible peak of single-electron oxidation of ESIPT core at 0.38 eV and reduction of BODIPY core at 1.023 eV. DFT calculation studies show the existence of charge transfer (CT) state from ESIPT to BODIPY core. The results obtained from photophysics, electrochemical study and DFT support EET from excited ESIPT core to BODIPY subunits. The DFT results show dominating electronic contribution to the linear polarizability (α) and first hyperpolarizability (β). NLO response was measured using Z scan technique. The values obtained for nonlinear absorption coefficient (β) in DMSO is −5.95 × 10−12 (m/W) and for third-order susceptibility (χ)3 it is 14.19 × 10−13 (e.s.u). The geometries of the dyad were optimized by using B3LYP/6–311++ G (d,p) level of theory. Graphical abstract Image 1 Highlights • meso fused Excitation Energy Transfer (EET) BODIPY dyad is synthesized. • A shift of 255 nm observed between excitation light and emitted light. • Dyad shows irreversible single-electron redox peak. • Electronic contribution to the linear polarizability (α) and first hyperpolarizability (β). • β = −5.95 × 10−12 m/W and χ3 = 14.19 × 10−13 e. s.u are Z-scan value. [ABSTRACT FROM AUTHOR]

Inflammatory conditions increase cardiovascular (CV) risk. Some nonsteroidal anti-inflammatory drugs (NSAIDs) that are used to treat pain and inflammation are also associated with CV complications. Inflammation, but not NSAIDs, disrupts the balance of vasodilator and vasoconstrictor components of the renin-angiotensin system within the heart. Herein, we report the effect of both inflammation and NSAIDs (rofecoxib, celecoxib, and meloxicam) on the physiologically active cytochrome P450 metabolites of arachidonic acid (ArA) in the rat with adjuvant arthritis. After oral administration of 7 daily therapeutically equivalent doses of NSAIDs or vehicle, the anti-inflammatory response, as well as the ArA metabolites and drug concentrations in plasma, heart and kidneys were assessed. Inflammation in the form of adjuvant arthritis caused a significant tissue-dependent imbalance of ArA metabolites by elevating the ratio of cardiotoxic 20-hydroxyeicosatetraenoic acid over cardioprotective epoxyeicosatrienoic acids in the heart, and reducing the ratio in the kidney. The observed imbalance was augmented by cardiotoxic rofecoxib but not by other examined NSAIDs with known milder cardiotoxicity. The cardio-renal toxicity of NSAIDs with known severe CV side effects may be due to altered cytochrome P450–mediated ArA acid metabolism. The ArA metabolism profile may be a marker of NSAIDs safety and toxicity. [ABSTRACT FROM AUTHOR]

Inflammation is the body's reaction to pathogenic (biological or chemical) stimuli and covers a burgeoning list of compounds and pathways that act in concert to maintain the health of the organism. Eicosanoids and related fatty acid derivatives can be formed from arachidonic acid and other polyenoic fatty acids via the cyclooxygenase and lipoxygenase pathways generating a variety of pro- and anti-inflammatory mediators, such as prostaglandins, leukotrienes, lipoxins, resolvins and others. The cytochrome P450 pathway leads to the formation of hydroxy fatty acids, such as 20-hydroxyeicosatetraenoic acid, and epoxy eicosanoids. Free radical reactions induced by reactive oxygen and/or nitrogen free radical species lead to oxygenated lipids such as isoprostanes or isolevuglandins which also exhibit pro-inflammatory activities. Eicosanoids and their metabolites play fundamental endocrine, autocrine and paracrine roles in both physiological and pathological signaling in various diseases. These molecules induce various unsaturated fatty acid dependent signaling pathways that influence crosstalk, alter cell–cell interactions, and result in a wide spectrum of cellular dysfunctions including those of the tissue microenvironment. Although the complete role of eicosanoids, including that of the recently elucidated anti-inflammatory specialized pro-resolving lipid mediators (SPMs), e.g. lipoxins, resolvins, protectins and maresins, is not completely understood, the result of unremitting chronic inflammation is fostering early stages of carcinogenesis. Chronic inflammation facilitates the transition from a normal cell to a cancerous one. The disruption of homeostasis across a wide, but identifiable, swath of diverse molecular pathways creates a micromilieu which constitutes an early and necessary step in the 6-step sequence of carcinogenesis for the vast majority of cancers, termed “sporadic cancers”.

Microsomal and soluble epoxide hydrolase (mEH and sEH) fulfill apparently distinct roles: Whereas mEH detoxifies xenobiotics, sEH hydrolyzes fatty acid (FA) signaling molecules and is thus implicated in a variety of physiological functions. These epoxy FAs comprise epoxyeicosatrienoic acids (EETs) and epoxy-octadecenoic acids (EpOMEs), which are formed by CYP epoxygenases from arachidonic acid (AA) and linoleic acid, respectively, and then are hydrolyzed to their respective diols, the so-called DHETs and DiHOMEs. Although EETs and EpOMEs are also substrates for mEH, its role in lipid signaling is considered minor due to lower abundance and activity relative to sEH. Surprisingly, we found that in plasma from mEH KO mice, hydrolysis rates for 8,9-EET and 9,10-EpOME were reduced by 50% compared to WT plasma. This strongly suggests that mEH contributes substantially to the turnover of these FA epoxides-despite kinetic parameters being in favor of sEH. Given the crucial role of liver in controlling plasma diol levels, we next studied the capacity of sEH and mEH KO liver microsomes to synthesize DHETs with varying concentrations of AA (1-30 μM) and NADPH. mEH-generated DHET levels were similar to the ones generated by sEH, when AA concentrations were low (1 μM) or epoxygenase activity was curbed by modulating NADPH. With increasing AA concentrations sEH became more dominant and with 30 μM AA produced twice the level of DHETs compared to mEH. Immunohistochemistry of C57BL/6 liver slices further revealed that mEH expression was more widespread than sEH expression. mEH immunoreactivity was detected in hepatocytes, Kupffer cells, endothelial cells, and bile duct epithelial cells, while sEH immunoreactivity was confined to hepatocytes and bile duct epithelial cells. Finally, transcriptome analysis of WT, mEH KO, and sEH KO liver was carried out to discern transcriptional changes associated with the loss of EH genes along the CYP-epoxygenase-EH axis. We found several prominent dysregulations occurring in a parallel manner in both KO livers: (a) gene expression of Ephx1 (encoding for mEH protein) was increased 1.35-fold in sEH KO, while expression of Ephx2 (encoding for sEH protein) was increased 1.4-fold in mEH KO liver; (b) Cyp2c genes, encoding for the predominant epoxygenases in mouse liver, were mostly dysregulated in the same manner in both sEH and mEH KO mice, showing that loss of either EH has a similar impact. Taken together, mEH appears to play a leading role in the hydrolysis of 8,9-EET and 9,10-EpOME and also contributes to the hydrolysis of other FA epoxides. It probably profits from its high affinity for FA epoxides under non-saturating conditions and its close physical proximity to CYP epoxygenases, and compensates its lower abundance by a more widespread expression, being the only EH present in several sEH-lacking cell types. [ABSTRACT FROM AUTHOR]

Epoxyeicosatrienoic acids (EETs) are potent vasodilators that play important roles in cardiovascular physiology and disease, yet the molecular mechanisms underlying the biological actions of EETs are not fully understood. Multiple lines of evidence suggest that the actions of EETs are in part mediated via G protein-coupled receptor (GPCR) signaling, but the identity of such a receptor has remained elusive. We sought to identify 14,15-EET-responsive GPCRs. A set of 105 clones were expressed in Xenopus oocyte and screened for their ability to activate cAMP-dependent chloride current. Several receptors responded to micromolar concentrations of 14,15-EET, with the top five being prostaglandin receptor subtypes (PTGER 2 , PTGER 4 , PTGFR, PTGDR, PTGER 3 IV). Overall, our results indicate that multiple low-affinity 14,15-EET GPCRs are capable of increasing cAMP levels following 14,15-EET stimulation, highlighting the potential for cross-talk between prostanoid and other ecosanoid GPCRs. Our data also indicate that none of the 105 GPCRs screened met our criteria for a high-affinity receptor for 14,15-EET. [ABSTRACT FROM AUTHOR]

The valence electron structures (VES) of Mo 2 FeB 2 -based cermets were constructed based on the empirical electron theory of solids and molecules (EET). The formation mechanism of grains and the influence of grain morphologies on the mechanical properties of the materials were explained in accordance with the calculated phase structure formation factors (S') and the interface electron structure (σ N : the number of atom state groups, ∆ρ': electron density difference, and ρ': electron density), respectively. The results indicated that the morphologies of the Mo 2 FeB 2 hard phase grains were reflected by the S' value of the distinct crystal planes. The progressive decrease in the Mo/B atomic ratio aggravated the differences between the S (210) ' and S (001) ' values and promoted the preferential growth of the hard phase grains along the [001] direction. This resulted in an increase in the (210)/(100) interface area, with the grains gradually forming an elongated structure. However, it was noticed that as the ratio of Mo to B increased, the value of |S (210) ' − S (001) '| gradually tended toward 0, which allowed the elongated hard phase grains to transform into quasi-equiaxial grains. In addition, the maximum decrease in the σ N value recorded was over 2500 when the Mo to B ratio increased continuously, indicating that the bonding strength at the (210)/(100) interface between the hard and binder phases was better at low Mo/B atomic ratios than at high Mo/B atomic ratios. This helped improve the fracture toughness and transverse rupture strength of the Mo 2 FeB 2 -based cermets. • Applying EET theory to the study of hard phase grain formation in Mo 2 FeB 2 -based cermets for the first time. • From the level of electrons, the formation mechanism of Mo 2 FeB 2 hard phase grains was explicated for the first time. • The influence of grain morphologies on the mechanical properties was explained using electron structure parameters. [ABSTRACT FROM AUTHOR]

Epoxygenase-dependent metabolites of arachidonc acid, EETs and the heme-oxygenase (HO)-1/carbon monoxide/bilverdin system share similarities in their activity and mediators. They control endothelial function, dilating small arterial vessels, decrease blood pressure, protect the heart from ischemic and hypertensive cardiopathy, control renal circulation and function, promote angiogenesis and organ regeneration, oppose oxidative stress and inflammation, improve diabetes and obesity, have protective effects on the liver, and participate in portal hypertension. Furthermore, EETs induce HO-1, and inhibition of HO-1 abolishes most of the effects of EETs. Thus, a close interaction between the two systems exists, and is relevant in view of their therapeutic potential. [ABSTRACT FROM AUTHOR]

The cytochrome P450 (CYP) soluble epoxide hydrolase (sEH) pathway generates a large number of biologically active epoxides and diols from a range of ω-3 and ω-6 polyunsaturated fatty acids (PUFAs). While epoxides of arachidonic acid or epoxyeicosatrienoic acids are probably the best studied of these mediators, epoxides of linoleic acid as well as the fish oils; docosahexaenoic acid and eicosapentaenoic acid have also been attributed signaling actions. Cell and tissue levels of the PUFA epoxides are largely determined by the sEH and in many cases inflammation and chronic diseases, e.g., cardiovascular disease, diabetes and Alzheimer's disease, have been associated with increased sEH expression and the accelerated conversion of PUFA epoxides to their corresponding diols. In low concentrations, the diols act to influence stem and progenitor cells as well as brown adipose tissue but in high concentrations, they tend to have pro-inflammatory and cytotoxic effects that promote disease progression. This review outlines some of the actions to the PUFA epoxides and diols in physiology and pathophysiology as well as the beneficial effects associates with sEH inhibition., Competing Interests: Conflict of interest There are no conflicts of interest to report., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Adenosine A2A receptors and ATP-activated K+ (KATP) channels contribute to part of the cerebral vasodilatory response to systemic hypoxia, but other mediators are likely involved. Epoxyeicosatrienoic acids (EETs) are cerebral vasodilators and are released from astrocytes exposed to hypoxia. Moreover, stimulation of metabotropic glutamate receptors (mGluR) produces vasodilation by an EET-dependent mechanism. Here, we tested the hypothesis that EET signaling and mGluR activation contribute to hypoxic vasodilation. Laser-Doppler flow was measured over cerebral cortex of anesthetized rats subjected to stepwise reductions in arterial oxygen saturation to 50-70%. Hypoxic reactivity was calculated as the slope of the change in laser-Doppler flow vs. the reciprocal of arterial oxygen content. Hypoxic reactivity significantly decreased from 9.2 ± 1.9 (±95% confidence interval) in controls with vehicle treatment to 2.6 ± 1.4 with the EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid, to 3.0 ± 1.5 with the EET synthesis inhibitor MS-PPOH, to 1.9 ± 2.3 with the combined mGluR subtype 1 and 5 antagonists 2-methyl-6-(phenylethynyl)pyridine and LY367385, to 5.6 ± 1.2 with the KATP channel inhibitor glibenclamide, and to 5.8 ± 2.3 with the A2A receptor antagonist SCH58261. However, reactivity was not significantly altered by the A2B receptor antagonist MRS1754 (6.7 ± 1.8; P = 0.28 Dunnett's test) or by the 20-hydroxyeicosatetraenoic acid synthesis inhibitor HET0016 (7.5 ± 2.3; P = 0.6). These data indicate that, in addition to the known contributions of A2A receptors and KATP channels to the increase in cerebral blood flow during hypoxia, EETs and mGluRs make a major contribution, possibly by mGluR stimulation and hypoxia-induced release of EETs. In contrast, A2B receptors do not make a major contribution, and 20-hydroxyeicosatetraenoic acid does not significantly limit hypoxic vasodilation. [ABSTRACT FROM AUTHOR]