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1.
Nat Commun ; 11(1): 5777, 2020 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-33188170

RESUMO

Vibrio parahaemolyticus is the leading cause of seafood-borne diarrheal diseases. Experimental overproduction of a type 3 secretion system (T3SS1) in this pathogen leads to decreased intestinal colonization, which suggests that T3SS1 repression is required for maximal virulence. However, the mechanisms by which T3SS1 is repressed in vivo are unclear. Here, we show that host-derived nitrite modifies the activity of a bacterial histidine kinase and mediates T3SS1 repression. More specifically, nitrite activates histidine kinase sensor VbrK through S-nitrosylation on cysteine 86, which results in downregulation of the entire T3SS1 operon through repression of its positive regulator exsC. Replacement of cysteine 86 with a serine (VbrK C86S mutant) leads to increased expression of inflammatory cytokines in infected Caco-2 cells. In an infant rabbit model of infection, the VbrK C86S mutant induces a stronger inflammatory response at the early stage of infection, and displays reduced intestinal colonization and virulence at the later stage of infection, in comparison with the parent strain. Our results indicate that the pathogen V. parahaemolyticus perceives nitrite as a host-derived signal and responds by downregulating a proinflammatory factor (T3SS1), thus enhancing intestinal colonization and virulence.


Assuntos
Proteínas de Bactérias/metabolismo , Histidina Quinase/metabolismo , Sistemas de Secreção Tipo III/metabolismo , Vibrio parahaemolyticus/metabolismo , Vibrio parahaemolyticus/patogenicidade , Anaerobiose , Animais , Sequência de Bases , Sítios de Ligação , Células CACO-2 , Citocinas/metabolismo , Regulação para Baixo/genética , Regulação Bacteriana da Expressão Gênica , Interações Hospedeiro-Patógeno/genética , Humanos , Modelos Biológicos , Nitratos/metabolismo , Nitritos/metabolismo , Nitrosação , Fosforilação , Regiões Promotoras Genéticas/genética , Ligação Proteica , Coelhos , Transcrição Genética , Vibrio parahaemolyticus/genética , Virulência/genética
2.
Chemosphere ; 261: 128172, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33113654

RESUMO

Nitritation is currently known as a bottleneck for mainstream nitrite shunt or partial nitritation/anammox (PN/A). Here we propose a new approach to selectively eliminate nitrite oxidizing bacteria (NOB) for mainstream nitritation by low-dose ultraviolet-A (UVA) irradiation. The results showed that mainstream nitritation was rapidly achieved within 10 days with UVA irradiation at the dose of 0.87 µE L-1 s-1, and nitrite accumulation ratio (NO2--N/(NO2--N + NO3--N) ×100%) stabilized over 80%. Microbial community analysis revealed that two typical NOB populations (Nitrospira and Ca. Nitrotoga) detected in the control reactor were suppressed efficiently in UVA irradiation reactor, whereas the Nitrosomonas genus of ammonium oxidizing bacteria (AOB) remained at similar level. Intracellular reactive oxygen species (ROS) analysis indicated that NOB-dominant sludge tends to generate more intracellular ROS compared with AOB-dominant sludge in the presence of UVA, leading to the inactivation and elimination of NOB. Additionally, amounts of microalgae found in UVA irradiation reactor could help to suppress NOB by generating ROS during photosynthesis. Briefly, the UVA irradiation approach proposed in this study was shown to be promising in NOB suppression for reliable mainstream nitritation.


Assuntos
Bactérias/efeitos da radiação , Reatores Biológicos/microbiologia , Nitritos/metabolismo , Raios Ultravioleta , Eliminação de Resíduos Líquidos/métodos , Compostos de Amônio/metabolismo , Microbiota , Nitrogênio/metabolismo , Nitrosomonas/efeitos da radiação , Oxirredução , Espécies Reativas de Oxigênio/metabolismo , Esgotos/microbiologia , Eliminação de Resíduos Líquidos/instrumentação
3.
Toxicol Appl Pharmacol ; 406: 115242, 2020 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-32931794

RESUMO

Hydraulic fracturing is used to access oil and natural gas reserves. This process involves the high-pressure injection of fluid to fracture shale. Fracking fluid contains approximately 95% water, chemicals and 4.5% fracking sand. Workers may be exposed to fracking sand dust (FSD) during the manipulation of the sand, and negative health consequences could occur if FSD is inhaled. In the absence of any information about its potential toxicity, a comprehensive rat animal model study (see Fedan et al., 2020) was designed to investigate the bioactivities of several FSDs in comparison to MIN-U-SIL® 5, a respirable α-quartz reference dust used in previous animal models of silicosis, in several organ systems. The goal of this study was to assess the effects of inhalation of one FSD, i.e., FSD 8, on factors and tissues that affect cardiovascular function. Male rats were exposed to 10 or 30 mg/m3 FSD (6 h/d for 4 d) by whole body inhalation, with measurements made 1, 7 or 27 d post-exposure. One day following exposure to 10 mg/m3 FSD the sensitivity to phenylephrine-induced vasoconstriction in tail arteries in vitro was increased. FSD exposure at both doses resulted in decreases in heart rate (HR), HR variability, and blood pressure in vivo. FSD induced changes in hydrogen peroxide concentrations and transcript levels for pro-inflammatory factors in heart tissues. In kidney, expression of proteins indicative of injury and remodeling was reduced after FSD exposure. When analyzed using regression analysis, changes in proteins involved in repair and remodeling were correlated. Thus, it appears that inhalation of FSD does have some prolonged effects on cardiovascular, and, possibly, renal function. The findings also provide information regarding potential mechanisms that may lead to these changes, and biomarkers that could be examined to monitor physiological changes that could be indicative of impending cardiovascular dysfunction.


Assuntos
Poeira , Fraturamento Hidráulico , Areia , Administração por Inalação , Animais , Pressão Sanguínea , Sistema Cardiovascular , Frequência Cardíaca , Peróxido de Hidrogênio/metabolismo , Rim/metabolismo , Masculino , Microvasos/fisiologia , Miocárdio/metabolismo , Nitratos/metabolismo , Nitritos/metabolismo , Ratos Sprague-Dawley
4.
Appl Environ Microbiol ; 86(22)2020 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-32917751

RESUMO

Nitrite-oxidizing bacteria (NOB) are ubiquitous and abundant microorganisms that play key roles in global nitrogen and carbon biogeochemical cycling. Despite recent advances in understanding NOB physiology and taxonomy, currently very few cultured NOB or representative NOB genome sequences from marine environments exist. In this study, we employed enrichment culturing and genomic approaches to shed light on the phylogeny and metabolic capacity of marine NOB. We successfully enriched two marine NOB (designated MSP and DJ) and obtained a high-quality metagenome-assembled genome (MAG) from each organism. The maximum nitrite oxidation rates of the MSP and DJ enrichment cultures were 13.8 and 30.0 µM nitrite per day, respectively, with these optimum rates occurring at 0.1 mM and 0.3 mM nitrite, respectively. Each enrichment culture exhibited a different tolerance to various nitrite and salt concentrations. Based on phylogenomic position and overall genome relatedness indices, both NOB MAGs were proposed as novel taxa within the Nitrospinota and Nitrospirota phyla. Functional predictions indicated that both NOB MAGs shared many highly conserved metabolic features with other NOB. Both NOB MAGs encoded proteins for hydrogen and organic compound metabolism and defense mechanisms for oxidative stress. Additionally, these organisms may have the genetic potential to produce cobalamin (an essential enzyme cofactor that is limiting in many environments) and, thus, may play an important role in recycling cobalamin in marine sediment. Overall, this study appreciably expands our understanding of the Nitrospinota and Nitrospirota phyla and suggests that these NOB play important biogeochemical roles in marine habitats.IMPORTANCE Nitrification is a key process in the biogeochemical and global nitrogen cycle. Nitrite-oxidizing bacteria (NOB) perform the second step of aerobic nitrification (converting nitrite to nitrate), which is critical for transferring nitrogen to other organisms for assimilation or energy. Despite their ecological importance, there are few cultured or genomic representatives from marine systems. Here, we obtained two NOB (designated MSP and DJ) enriched from marine sediments and estimated the physiological and genomic traits of these marine microbes. Both NOB enrichment cultures exhibit distinct responses to various nitrite and salt concentrations. Genomic analyses suggest that these NOB are metabolically flexible (similar to other previously described NOB) yet also have individual genomic differences that likely support distinct niche distribution. In conclusion, this study provides more insights into the ecological roles of NOB in marine environments.


Assuntos
Bactérias/classificação , Bactérias/metabolismo , Microbiota , Nitritos/metabolismo , Bactérias/isolamento & purificação , Sedimentos Geológicos/microbiologia , Redes e Vias Metabólicas , Oxirredução , República da Coreia , Água do Mar/microbiologia
5.
Sheng Wu Gong Cheng Xue Bao ; 36(8): 1493-1503, 2020 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-32924348

RESUMO

Nitrite is a by-product of the nitrogen cycle. The excessive nitrite not only constrains growth and metabolism of bacteria, but also impairs health of humans and aquatic organisms. On the other hand, the continuous maintaining of nitrite accumulation could achieve the shortcut nitrification process, and reduce energy consumption of biological nitrogen removal to save cost. This article reviews the biological processes and causes of nitrite accumulation in the water environment, and summarizes the factors that affect the accumulation of nitrite, to provide reference for wastewater treatments, including improving the nitrogen removal efficiency, reducing operating costs, decreasing discharge of sewage and nitrite nitrogen in natural water.


Assuntos
Nitritos , Poluentes Químicos da Água , Água , Reatores Biológicos , Nitrificação , Nitritos/metabolismo , Esgotos , Água/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/isolamento & purificação
6.
Appl Environ Microbiol ; 86(20)2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32801185

RESUMO

There is a growing awareness that bacterial interactions follow a highly nonlinear pattern in reality. However, it is challenging to track the varying bacterial interactions using pairwise correlation analysis, which fails to explore their potential effects on the behavior of microbes. Here, we utilized a regularized sequential locally weighted global linear map (S-map) to capture the varying interspecific interactions from the time series data of a bacterial community under exposure to nitrite. Our results show that bacterial interactions are highly variable and that asymmetric interactions dominate the interaction pattern in a community. Furthermore, we propose a Jacobian coefficient-based statistical method to predict the harmony level of a bacterial community at each successive ecosystem state. The results show that the bacterial community exhibits a higher harmony level in nitrite-treated samples than in the control group. We show that the community harmony level is positively associated with the specific endogenous respiration rates and biofilm formation of the culture. In addition, the community tends to process lower diversity and structural stability under zero- and high-nitrite stresses. We demonstrate that the harmony level, rather than structural stability, is a useful index for unveiling the underlying mechanism of bacterial performance. Overall, the regularized S-map can help us to understand bacterial interactions in ecosystems more accurately than previous approaches.IMPORTANCE It has long been acknowledged that bacterial interactions play important roles in community structure and function. Revealing the interaction variability can allow an understanding of how bacteria respond to perturbation and why bacterial community performance changes. Such information should improve our skills in engineering bacterial communities (e.g., in a wastewater treatment plant) and achieve better removal performance and lower energy consumption.


Assuntos
Bactérias/classificação , Fenômenos Fisiológicos Bacterianos/efeitos dos fármacos , Microbiota , Nitritos/metabolismo , Águas Residuárias/microbiologia , China , Ecossistema
7.
Appl Environ Microbiol ; 86(20)2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32826214

RESUMO

Complete ammonia-oxidizing (comammox) bacteria play key roles in environmental nitrogen cycling and all belong to the genus Nitrospira, which was originally believed to include only strict nitrite-oxidizing bacteria (sNOB). Thus, differential estimation of sNOB abundance from that of comammox Nitrospira has become problematic, since both contain nitrite oxidoreductase genes that serve as common targets for sNOB detection. Herein, we developed novel comammox Nitrospira clade A- and B-specific primer sets targeting the α-subunit of the ammonia monooxygenase gene (amoA) and a sNOB-specific primer set targeting the cyanase gene (cynS) for quantitative PCR (qPCR). The high coverage and specificity of these primers were checked by use of metagenome and metatranscriptome data sets. Efficient and specific amplification with these primers was demonstrated using various environmental samples. Using the newly designed primers, we successfully estimated the abundances of comammox Nitrospira and sNOB in samples from two chloramination-treated drinking water systems and found that, in most samples, comammox Nitrospira clade A was the dominant type of Nitrospira and also served as the primary ammonia oxidizer. Compared with other ammonia oxidizers, comammox Nitrospira had a higher abundance in process water samples in these two drinking water systems. We also demonstrated that sNOB can be readily misrepresented by an earlier method, calculated by subtracting the comammox Nitrospira abundance from the total Nitrospira abundance, especially when the comammox Nitrospira proportion is relatively high. The new primer sets were successfully applied to comammox Nitrospira and sNOB quantification, which may prove useful in understanding the roles of Nitrospira in nitrification in various ecosystems.IMPORTANCE Nitrospira is a dominant nitrite-oxidizing bacterium in many artificial and natural environments. The discovery of complete ammonia oxidizers in the genus Nitrospira prevents the use of previously identified primers targeting the Nitrospira 16S rRNA gene or nitrite oxidoreductase (nxr) gene for differential determination of strict nitrite-oxidizing bacteria (sNOB) in the genus Nitrospira and among comammox bacteria in this genus. We designed three novel primer sets that enabled quantification of comammox Nitrospira clades A and B and sNOB with high coverage, specificity, and accuracy in various environments. With the designed primer sets, sNOB and comammox Nitrospira were differentially estimated in drinking water systems, and we found that comammox clade A predominated over sNOB and other ammonia oxidizers in process water samples. Accurate quantification of comammox Nitrospira and sNOB by use of the newly designed primers will provide essential information for evaluating the contribution of Nitrospira to nitrification in various ecosystems.


Assuntos
Amônia/metabolismo , Bactérias/classificação , Primers do DNA/análise , Nitritos/metabolismo , Bactérias/genética , Bactérias/metabolismo , Oxirredução
8.
Chemosphere ; 260: 127581, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32758787

RESUMO

Forward osmosis membrane bioreactor (FOMBR) is an integrated physical-biological treatment process that has received increased awareness in treating municipal wastewater for its potential to produce high effluent quality coupled with its low propensity for fouling formation. However, reverse salt diffusion (RSD) is a major issue and so far limited studies have reported long-term FOMBR operation under the elevated salinity conditions induced by RSD. This study investigated the performance of a FOMBR in treating municipal wastewater under a controlled saline environment (6-8 g L-1 NaCl) using two separate sodium chloride draw solution (NaCl DS) concentrations (35 and 70 g L-1) over 243 days. At 35 g L-1 NaCl DS, the water flux performance dropped from 6.75 L m-2 h-1 (LMH) to 2.07 LMH after 72 days of operation in the first experimental stage, when no cleaning procedure was implemented. In the subsequent stage, the DS concentration was increased to 70 g L-1 and a weekly physical cleaning regime introduced. Under stable operation, the water flux performance recovery was 67% after 21 cycles of physical cleaning. For the first time in FOMBR studies, a shortcut nitrogen removal via the nitrite pathway was also achieved under the elevated salinity conditions. At the end of operation (day 243), the ammonia-oxidising bacteria (Nitrosomonas sp.) was the only nitrifier species in the system and no nitrite oxidising bacteria was detected. The above study proves that a FOMBR system is a feasible process for treating municipal wastewater.


Assuntos
Membranas Artificiais , Nitrogênio/metabolismo , Eliminação de Resíduos Líquidos/instrumentação , Eliminação de Resíduos Líquidos/métodos , Aerobiose , Reatores Biológicos/microbiologia , Desnitrificação , Desenho de Equipamento , Nitrificação , Nitritos/metabolismo , Nitrosomonas/metabolismo , Osmose , Salinidade , Águas Residuárias/química
9.
Sci Rep ; 10(1): 13166, 2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32759980

RESUMO

Nitric oxide (NO) signaling has been studied in the eye, including in the pathophysiology of some eye diseases. While NO production by nitric oxide synthase (NOS) enzymes in the eye has been characterized, the more recently described pathways of NO generation by nitrate (NO3-) and nitrite (NO2-) ions reduction has received much less attention. To elucidate the potential roles of these pathways, we analyzed nitrate and nitrite levels in components of the eye and lacrimal glands, primarily in porcine samples. Nitrate and nitrite levels were higher in cornea than in other eye parts, while lens contained the least amounts. Lacrimal glands exhibited much higher levels of both ions compared to other organs, such as liver and skeletal muscle, and even to salivary glands which are known to concentrate these ions. Western blotting showed expression of sialin, a known nitrate transporter, in the lacrimal glands and other eye components, and also xanthine oxidoreductase, a nitrate and nitrite reductase, in cornea and sclera. Cornea and sclera homogenates possessed a measurable amount of nitrate reduction activity. These results suggest that nitrate ions are concentrated in the lacrimal glands by sialin and can be secreted into eye components via tears and then reduced to nitrite and NO, thereby being an important source of NO in the eye.


Assuntos
Córnea/metabolismo , Aparelho Lacrimal/metabolismo , Nitratos/metabolismo , Nitritos/metabolismo , Esclera/metabolismo , Animais , Feminino , Masculino , Nitrato Redutase/metabolismo , Óxido Nítrico/metabolismo , Nitrito Redutases/metabolismo , Transportadores de Ânions Orgânicos/metabolismo , Transdução de Sinais , Suínos , Simportadores/metabolismo , Xantina Desidrogenase/metabolismo
10.
Appl Environ Microbiol ; 86(20)2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32769185

RESUMO

Veillonella species are among the major anaerobes in the oral cavity and are frequently detected in both caries lesions and healthy oral microbiomes. They possess the ability to utilize lactate and convert nitrate (NO3 -) into nitrite (NO2 -). Recently, interest in NO2 - has increased rapidly because of its beneficial effects on oral and general health; i.e., it inhibits the growth and metabolism of oral pathogenic bacteria, such as Streptococcus mutans, and lowers systemic blood pressure. However, there is only limited information about the biochemical characteristics of NO2 - production by Veillonella species. We found that NO3 - did not inhibit the growth of Veillonella atypica or Veillonella parvula, and it inhibited the growth of Streptococcus mutans only at a high concentration (100 mM). However, NO2 - inhibited the growth of Streptococcus mutans at a low concentration (0.5 mM), while a higher concentration of NO2 - (20 mM) was needed to inhibit the growth of Veillonella species. NO2 - production by Veillonella species was increased by environmental factors (lactate, acidic pH, and anaerobic conditions) and growth conditions (the presence of NO3 - or NO2 -) and was linked to anaerobic lactate metabolism. A stoichiometric evaluation revealed that NO3 - is reduced to NO2 - by accepting reducing power derived from the oxidization of lactate. These findings suggest that the biochemical characteristics of NO2 - production from NO3 - and its linkage with lactate metabolism in oral Veillonella species may play a key role in maintaining good oral and general health.IMPORTANCE The prevalence of dental caries is still high around the world. Dental caries is initiated when the teeth are exposed to acid, such as lactic acid, produced via carbohydrate metabolism by acidogenic microorganisms. Veillonella species, which are among the major oral microorganisms, are considered to be beneficial bacteria due to their ability to convert lactic acid to weaker acids and to produce NO2 - from NO3 -, which is thought to be good for both oral and general health. Therefore, it is clear that there is a need to elucidate the biochemical characteristics of NO2 - production in Veillonella species. The significance of our research is that we have found that lactate metabolism is linked to NO2 - production by Veillonella species in the environment found in the oral cavity. This study suggests that Veillonella species are potential candidates for maintaining oral and general health.


Assuntos
Lactatos/metabolismo , Boca/microbiologia , Nitritos/metabolismo , Streptococcus mutans/crescimento & desenvolvimento , Veillonella/metabolismo , Cárie Dentária/metabolismo , Streptococcus mutans/efeitos dos fármacos , Veillonella/crescimento & desenvolvimento
11.
Toxicol Lett ; 333: 97-104, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32763312

RESUMO

Proton pump inhibitors (PPIs) have wide pleiotropic action in addition to their therapeutic potential in gastroesophageal reflux diseases. Conversely, recent reports revealed a significant incidence of toxic events of PPIs including nephritis, osteoporosis, and cardiac damage. Thus, the study was designed to reconcile the deceptive contraindications. The present investigation targeted to reveal the toxic impact of sub-acute and sub-chronic administration of pantoprazole (PPZ) with different concentrations (low dose 4 mg/kg, medium-dose 8 mg/kg and high dose 16 mg/kg once a day) on normal vascular endothelium and renal tissue of rats. Vascular endothelial dysfunction (VED) was estimated by the contractility of an isolated aortic ring, nitrite/nitrate concentration, oxidative stress, and integrity of the endothelium layer. Moreover, the renal abnormalities were further confirmed by an increased level of serum creatinine, blood urea nitrogen (BUN), the incidence of microproteinuria, and structural alteration. Sub-acute administration of PPZ treatment did not produce any toxicological impact on endothelium and renal tissue. Whereas, sub-chronic administration of PPZ treatment causes moderate VED and renal dysfunction in a dose-dependent manner. Sub-chronic treatment of PPZ also influences the mitigation of NO and elevation of oxidative stress. Collecting all the evidence, it concludes that decreased nitric oxide availability and increased levels of oxidative stress may be a possible underlying mechanism of causing VED and renal abnormalities from high-dose PPZ treatment.


Assuntos
Aorta Torácica/efeitos dos fármacos , Endotélio Vascular/efeitos dos fármacos , Rim/efeitos dos fármacos , Pantoprazol/toxicidade , Inibidores da Bomba de Prótons/toxicidade , Administração Oral , Animais , Aorta Torácica/imunologia , Aorta Torácica/metabolismo , Aorta Torácica/patologia , Citocinas/sangue , Relação Dose-Resposta a Droga , Endotélio Vascular/imunologia , Endotélio Vascular/metabolismo , Endotélio Vascular/patologia , Feminino , Rim/imunologia , Rim/metabolismo , Rim/patologia , Peroxidação de Lipídeos/efeitos dos fármacos , Masculino , Nitratos/metabolismo , Nitritos/metabolismo , Ratos , Ratos Wistar , Vasodilatação/efeitos dos fármacos
12.
Am J Physiol Regul Integr Comp Physiol ; 319(4): R401-R411, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32813540

RESUMO

Circulating metabolites of nitric oxide, such as nitrite, iron nitrosyls (FeNO), and nitrosothiols, have vasodilatory bioactivity. In both human and sheep neonates, plasma concentrations of these NO metabolite (NOx) concentrations fall >50% within minutes after birth, raising the possibility that circulating NOx plays a role in maintaining low fetal vascular resistance and in the cardiovascular transition at birth. To test whether the fall in plasma NOx concentrations at birth is due to either ligation of the umbilical cord or oxygenation of the fetus to newborn levels, plasma NOx concentrations were measured during stepwise delivery of near-term fetal lambs. When fetal lambs were intubated and mechanically ventilated with 100% O2 to oxygenate the arterial blood while still in utero with the umbilical circulation still intact, there was no change in plasma NOx levels. In contrast, when the umbilical cord was ligated while fetal lambs were mechanically ventilated with O2 levels that maintained fetal arterial blood gases, plasma NOx levels decreased by nearly 50%. Characterization of the individual NOx species in plasma revealed that the overall fall in NOx at birth was attributable mainly to FeNO compounds. Finally, when the typical fall in NOx after birth was prevented by intravenous nitrite infusion, birth-related changes in blood pressure, heart rate, and carotid flow changes were little affected, suggesting the cardiovascular transition at birth is not dependent on a fall in plasma NOx. In conclusion, this study shows FeNO is released from the placenta and that its decline accounts for most of the measured fall in plasma NOx at birth.


Assuntos
Sangue Fetal/metabolismo , Ferro/sangue , Nitritos/metabolismo , Óxidos de Nitrogênio/sangue , Parto/fisiologia , Placenta/metabolismo , Animais , Sistema Cardiovascular/metabolismo , Feminino , Óxido Nítrico/metabolismo , Gravidez , Ovinos
13.
Nitric Oxide ; 103: 29-30, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32712272

RESUMO

Most outcomes of COVID-19 are associated with dysfunction of the vascular system, particularly in the lung. Inhalation of nitric oxide (NO) gas is currently being investigated as a treatment for patients with moderate to severe COVID-19. In addition to the expected vasodilation effect, it has been also suggested that NO potentially prevents infection by SARS-CoV-2. Since NO is an unstable radical molecule that is easily oxidized by multiple mechanisms in the human body, it is practically difficult to control its concentration at lesions that need NO. Inorganic nitrate and/or nitrite are known as precursors of NO that can be produced through chemical as well enzymatic reduction. It appears that this NO synthase (NOS)-independent mechanism has been overlooked in the current developing of clinical treatments. Here, I suggest the missing link between nitrate and COVID-19 in terms of hypoxic NO generation.


Assuntos
Betacoronavirus/efeitos dos fármacos , Infecções por Coronavirus/tratamento farmacológico , Nitratos/metabolismo , Óxido Nítrico/metabolismo , Nitritos/metabolismo , Pneumonia Viral/tratamento farmacológico , Antivirais/metabolismo , Ácido Ascórbico/química , Ácido Ascórbico/uso terapêutico , Infecções por Coronavirus/metabolismo , Infecções por Coronavirus/prevenção & controle , Fatores Relaxantes Dependentes do Endotélio/metabolismo , Humanos , Nitratos/sangue , Nitritos/sangue , Nitritos/química , Pandemias/prevenção & controle , Pneumonia Viral/metabolismo , Pneumonia Viral/prevenção & controle , Vasodilatação/efeitos dos fármacos
14.
Appl Environ Microbiol ; 86(17)2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32631862

RESUMO

Dissimilatory nitrate/nitrite reduction to ammonium (DNRA) has recently regained attention as a nitrogen retention pathway that may potentially be harnessed to alleviate nitrogen loss resulting from denitrification. Until recently, the ecophysiology of DNRA bacteria inhabiting agricultural soils has remained largely unexplored, due to the difficulty in targeted enrichment and isolation of DNRA microorganisms. In this study, >100 DNRA bacteria were isolated from NO3 --reducing anoxic enrichment cultures established with rice paddy soils using a newly developed colorimetric screening method. Six of these isolates, each assigned to a different genus, were characterized to improve the understanding of DNRA physiology. All the isolates carried nrfA and/or nirB, and the Bacillus sp. strain possessed a clade II nosZ gene conferring the capacity for N2O reduction. A common prominent physiological feature observed in the isolates was NO2 - accumulation before NH4 + production, which was further examined with Citrobacter sp. strain DNRA3 (possessing nrfA and nirB) and Enterobacter sp. strain DNRA5 (possessing only nirB). Both isolates showed inhibition of NO2 --to-NH4 + reduction at submillimolar NO3 - concentrations and downregulation of nrfA or nirB transcription when NO3 - was being reduced to NO2 - In batch and chemostat experiments, both isolates produced NH4 + from NO3 - reduction when incubated with excess organic electron donors, while incubation with excess NO3 - resulted in NO2 - buildup but no substantial NH4 + production, presumably due to inhibitory NO3 - concentrations. This previously overlooked link between NO3 - repression of NO2 --to-NH4 + reduction and the C-to-N ratio regulation of DNRA activity may be a key mechanism underpinning denitrification-versus-DNRA competition in soil.IMPORTANCE Dissimilatory nitrate/nitrite reduction to ammonium (DNRA) is an anaerobic microbial pathway that competes with denitrification for common substrates NO3 - and NO2 - Unlike denitrification, which leads to nitrogen loss and N2O emission, DNRA reduces NO3 - and NO2 - to NH4 +, a reactive nitrogen compound with a higher tendency to be retained in the soil matrix. Therefore, stimulation of DNRA has often been proposed as a strategy to improve fertilizer efficiency and reduce greenhouse gas emissions. Such attempts have been hampered by lack of insights into soil DNRA bacterial ecophysiology. Here, we have developed a new screening method for isolating DNRA-catalyzing organisms from agricultural soils without apparent DNRA activity. Physiological characteristics of six DNRA isolates were closely examined, disclosing a previously overlooked link between NO3 - repression of NO2 --to-NH4 + reduction and the C-to-N ratio regulation of DNRA activity, which may be a key to understanding why DNRA activity is rarely observed at substantial levels in nitrogen-rich agricultural soils.


Assuntos
Compostos de Amônio/metabolismo , Fenômenos Fisiológicos Bacterianos , Citrobacter/fisiologia , Enterobacter/fisiologia , Nitratos/metabolismo , Nitritos/metabolismo , Colorimetria , Oxirredução , Microbiologia do Solo
15.
J Dairy Sci ; 103(8): 7124-7140, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32600762

RESUMO

Within the rumen, nitrate can serve as an alternative sink for aqueous hydrogen [H2(aq)] accumulating during fermentation, producing nitrite, which ideally is further reduced to ammonium but can accumulate under conditions not yet explained. Defaunation has also been associated with decreased methanogenesis in meta-analyses because protozoa contribute significantly to H2 production. In the present study, we applied a 2 × 2 factorial treatment arrangement in a 4 × 4 Latin square design to dual-flow continuous culture fermentors (n = 4). Treatments were control without nitrate (-NO3-) versus with nitrate (+NO3-; 1.5% of diet dry matter), factorialized with normal protozoa (faunated, FAUN) versus defaunation (DEF) by decreasing the temperature moderately and changing filters over the first 4 d of incubation. We detected no main effects of DEF or interaction of faunation status with +NO3-. The main effect of +NO3- increased H2(aq) by 11.0 µM (+117%) compared with -NO3-. The main effect of +NO3- also decreased daily CH4 production by 8.17 mmol CH4/d (31%) compared with -NO3-. Because there were no treatment effects on neutral detergent fiber digestibility, the main effect of +NO3- also decreased CH4 production by 1.43 mmol of CH4/g of neutral detergent fiber degraded compared with -NO3-. There were no effects of treatment on other nutrient digestibilities, N flow, or microbial N flow per gram of nutrient digested. The spike in H2(aq) after feeding NO3- provides evidence that methanogenesis is inhibited by substrate access rather than concentration, regardless of defaunation, or by direct inhibition of NO2-. Methanogens were not decreased by defaunation, suggesting a compensatory increase in non-protozoa-associated methanogens or an insignificant contribution of protozoa-associated methanogens. Despite adaptive reduction of NO3- to NH4+ and methane inhibition in continuous culture, practical considerations such as potential to depress dry matter intake and on-farm ration variability should be addressed before considering NO3- as an avenue for greater sustainability of greenhouse gas emissions in US dairy production.


Assuntos
Fibras na Dieta/metabolismo , Eucariotos/metabolismo , Hidrogênio/metabolismo , Metano/metabolismo , Microbiota , Nitratos/farmacologia , Compostos de Amônio/metabolismo , Animais , Bactérias/metabolismo , Reatores Biológicos , Técnicas de Cultura , Dieta/veterinária , Ingestão de Alimentos , Ácidos Graxos Voláteis/metabolismo , Fermentação/efeitos dos fármacos , Hidrogênio/análise , Nitritos/metabolismo , Nitrogênio/metabolismo , Rúmen/metabolismo
16.
Phys Med Biol ; 65(19): 195003, 2020 09 25.
Artigo em Inglês | MEDLINE | ID: mdl-32721936

RESUMO

The efficacy of dose-enhancing gold nanoparticles (AuNPs) is negatively impacted by low tumor uptake, low cell membrane penetration, limited diffusion distance, and short lifetime of radiation-induced secondary particles. To overcome these limitations, we have developed a novel AuNP system capable of radiation-triggered release of nitrite, a precursor of reactive nitrogen species, and report here on the in vivo characterization of this system. AuNPs were functionalized through PEGylation, cell-penetrating peptides (CPP; AuNP@CPP), and nitroimidazole (nIm; AuNP@nIm-CPP). Mice with subcutaneous 4T1 tumors received either AuNP@nIm-CPP or AuNP@CPP intraperitoneally. Tumor and normal tissue uptake were evaluated 24 h post AuNP administration. A separate cohort of mice was injected and irradiated to a single-fraction dose of 18 Gy in a 225 kVp small animal irradiator 24 h post NP administration. The mice were followed for two weeks to evaluate tumor response. The mean physical and hydrodynamic size of both NP systems were 5 and 13 nm, respectively. NP nIm-loading of 1 wt% was determined. Tumor accumulation of AuNP@nIm-CPP was significantly lower than that of AuNP@CPP (0.2% vs 1.2%, respectively). In contrast, AuNP@nIm-CPP showed higher accumulation compared to AuNP@CPP in liver (16.5% vs 6.6%, respectively) and spleen (10.8% vs 3.1%, respectively). With respect to tumor response, no differential response was found between non-irradiated mice receiving either saline or AuNP@nIm-CPP alone. The combination of AuNP@CPP+ radiation showed no differential response from radiation alone. In contrast, a significant delay in tumor regrowth was observed in mice receiving AuNP@nIm-CPP+ radiation compared to radiation alone. AuNP functionalized with both CPP and nIm exhibited an order of magnitude less tumor accumulation compared to the NP system without nIm yet resulted in a significantly higher therapeutic response. Our data suggest that by improving the biokinetics of AuNP@nIm-CPP, this novel NP system could be a promising radiosensitizer for enhanced therapeutic response following radiation therapy.


Assuntos
Neoplasias da Mama/terapia , Raios gama , Ouro/química , Nanopartículas Metálicas/administração & dosagem , Nitritos/metabolismo , Radiossensibilizantes/administração & dosagem , Espécies Reativas de Nitrogênio/metabolismo , Animais , Apoptose , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Proliferação de Células , Terapia Combinada , Feminino , Humanos , Nanopartículas Metálicas/química , Camundongos , Camundongos Nus , Radiossensibilizantes/química , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de Xenoenxerto
17.
Huan Jing Ke Xue ; 41(2): 831-838, 2020 Feb 08.
Artigo em Chinês | MEDLINE | ID: mdl-32608744

RESUMO

Because of the massive discharge of nitrogenous wastewater, the eutrophication of a water body is becoming increasingly serious, and how to effectively remove nitrogen from this wastewater remains an urgent problem to be solved. In this study, due to disadvantages in the traditional biological nitrogen removal process, such as complex and long procedures, high energy consumption, weak impact resistance, and N2O release, the nitrogen removal theory by heterotrophic nitrification was further analyzed by discussing the physiological-biochemical, heterotrophic nitrification-aerobic denitrification, and N2O production characteristics of a high-efficiency heterotrophic nitrifying bacteria Pseudomonas aeruginosa YL. Results show that the strain YL had an eminent heterotrophic nitrification and aerobic denitrification ability, and NH4+-N, NO2--N, and NO3--N with concentration of 100 mg·L-1 could be completely removed during the 24-hour incubation period. There was almost no intermediate product in the process of heterotrophic nitrification, however when NO3--N was used as nitrogen source, the accumulation of NO2--N reached 25.55 mg·L-1. Meanwhile, the successful expression of denitrification genes napA, nirK, and nosZ further confirmed the aerobic denitrification ability of strain YL. Gaseous nitrogen products accounted for about 30%-40% of removed TN in the heterotrophic nitrification-aerobic denitrification process by strain YL, and N2 was the main denitrification product. When NH4+-N, NO2--N, and NO3--N were used as the sole nitrogen source, N2 production amounted to 3.46, 3.49, and 3.36 mg, respectively. In contrast, only small amounts of N2O were produced in the denitrification process by strain YL, and the total amount was 6.63 µg when NH4+-N was the nitrogen source, which was much lower than in the cases of NO2--N and NO3--N as the sole nitrogen source. In addition, high C/N, low pH, high temperature, high NH4+-N, and high NO2--N conditions could result in more N2O generation. Nevertheless, most environmental factors had little effect on N2O production of strain YL, and the maximum N2O production was significantly lower than that of short-cut nitrification system and autotrophic nitrification system. These results demonstrated that strain YL exhibited excellent abilities of nitrogen removal, N2O emission control, and tolerance to environmental conditions, and could be an effective candidate for treating wastewater without secondary air pollution.


Assuntos
Desnitrificação , Processos Heterotróficos , Nitritos/metabolismo , Pseudomonas aeruginosa/fisiologia , Aerobiose , Genes Bacterianos , Nitrificação , Nitrogênio/metabolismo
18.
Nitric Oxide ; 102: 21-27, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32535185

RESUMO

BACKGROUND: To maintain vascular tone and blood flow when tissue oxygenation is reduced, nitrite anions are reduced to nitric oxide (NO). From a practical perspective, it is unclear how the application of a tourniquet during blood collection might influence measurement of NO metabolites. Accordingly, this study evaluated the effect of venous occlusion on plasma nitrite and nitrate during venous blood collection. METHODS: Fifteen healthy participants completed two trials that were preceded by the ingestion of nitrate-rich beetroot juice (BRJ; total of ~8.4 mmol nitrate) or no supplementation (control). In both trials, blood was collected using a venepuncture needle while a tourniquet was applied to the upper arm and using an indwelling intravenous cannula, from the opposing arm. The venepuncture samples were collected at 35 s post occlusion. Changes in the oxygenation of forearm flexor muscles were assessed using near-infrared spectroscopy. Plasma nitrite and nitrate were analysed using gas-phase chemiluminescence. RESULTS: In the control trial, plasma nitrite was significantly elevated when collected via the cannula (179 ± 67 nM) compared to venepuncture (112 ± 51 nM, P = 0.03). The ingestion of BRJ increased plasma nitrite and values remained higher when sampled from the cannula (473 ± 164 nM) compared to venepuncture (387 ± 136 nM, P < 0.001). Plasma nitrate did not differ between collection methods in either trial (all P > 0.05). The delta changes in total-, deoxy-, and oxy-haemoglobin were all significantly greater during venepuncture sample compared to the cannula sample at the point of blood collection (all P < 0.05). CONCLUSIONS: Venous occlusion during venepuncture blood collection lowers plasma nitrite concentration, potentially due to localised changes in haemoglobin concentration and/or a suppression of endogenous NO synthesis. Accordingly, the method of blood collection to enable measurements of NO metabolites should be carefully considered and consistently reported by researchers.


Assuntos
Coleta de Amostras Sanguíneas , Nitratos/sangue , Nitritos/sangue , Adulto , Feminino , Voluntários Saudáveis , Humanos , Medições Luminescentes , Masculino , Nitratos/metabolismo , Nitritos/metabolismo
19.
Chemosphere ; 258: 127228, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32535438

RESUMO

Urea hydrolysis in partial nitritation process forming nitrite and ammonia is advantageous to subsequent treatment with ANAMMOX for total nitrogen removal. In this study, stable partial nitritation for urea wastewater with urea increasing from 250 to 2000 mg L-1 were achieved in an aerobic SBR. Urea removal efficiency and nitrite accumulation percentage both kept above 98%, with nitrite production rate about 0.985 kg N·m-3·d-1. Urea hydrolysis mechanism in this aerobic system was described as, (1) massive urea in the bulk was absorbed into cell, (2) urea was hydrolyzed by intracellular urease inside cell, (3) produced ammonia then slowly diffused into the bulk through membrane, which is later converted by ammonia-oxidizing bacteria (AOB) into nitrite. Due to this mechanism, the activity of AOB could not be inhibited by high FA (free ammonia) value under high urea concentration condition while nitrite-oxidizing bacteria (NOB) remained to be inhibited. An uncultured genus belonging to poorly characterized phylum Gemmatimonadetes was found enriched in this process and became dominant genus. This genus was speculated to have same energy pathway like ureaplasma, by absorbing excessive urea from environment and utilize urea hydrolysis to generate energy. So it was believed to be responsible for urea hydrolysis mechanism mentioned above. This SBR showed stable partial nitritation and high urea removal efficiency for treating urea wastewater, which was obviously feasible as the pretreatment process for subsequent ANAMMOX.


Assuntos
Amônia/análise , Reatores Biológicos/microbiologia , Nitritos/análise , Ureia/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Aerobiose , Amônia/metabolismo , Bactérias/metabolismo , Hidrólise , Nitritos/metabolismo , Nitrogênio/análise , Nitrogênio/metabolismo , Oxirredução , Ureia/metabolismo , Águas Residuárias/química , Poluentes Químicos da Água/metabolismo
20.
Arch Biochem Biophys ; 689: 108453, 2020 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-32524996

RESUMO

Nitric oxide (NO) deficiency and NADPH oxidase plays key roles in endothelial dysfunction and atherosclerotic plaque formation. Recent evidence demonstrates that nitrate-nitrite-NO pathway in vivo exerts beneficial effects upon the cardiovascular system. We aimed to investigate the effects of dietary nitrate on endothelial function and atherosclerosis in apolipoprotein E knockout (ApoE-/-) mice fed a high-fat diet. It was shown that dietary nitrate significantly attenuated aortic endothelial dysfunction and atherosclerosis in ApoE-/- mice. Mechanistic studies revealed that dietary nitrate significantly improved plasma nitrate/nitrite, inhibited vascular NADPH oxidase activity and oxidative stress in ApoE-/- mice, while xanthine oxidoreductase (XOR) expression and activity was enhanced in ApoE-/- mice in comparison with wide type animals. These beneficial effects of nitrate in ApoE-/- mice were abolished by PTIO (NO scavenger) and significantly prevented by febuxostat (XOR inhibitor). In the presence of nitrate, no further effect of apocynin (NADPH oxidase inhibitor) was observed, suggesting NADPH oxidase as a possible target. In vitro, NO donor significantly inhibited NADPH oxidase activity in vascular endothelial cells via the induction of heme oxygenase-1. Altogether, boosting this nitrate-nitrite-NO signaling pathway resulted in the decreases of vascular NADPH oxidase-derived oxidative stress and endothelial dysfunction, and consequently protected ApoE-/- mice against atherosclerosis. These findings may have novel nutritional implications for the preventive and therapeutic strategies against vascular endothelial dysfunction in atherosclerotic disease.


Assuntos
Aterosclerose/terapia , Endotélio Vascular/patologia , NADPH Oxidases/metabolismo , Nitratos/uso terapêutico , Animais , Apolipoproteínas E/genética , Aterosclerose/genética , Aterosclerose/metabolismo , Aterosclerose/patologia , Dieta Hiperlipídica/efeitos adversos , Suplementos Nutricionais , Modelos Animais de Doenças , Endotélio Vascular/metabolismo , Masculino , Camundongos , Camundongos Knockout , Nitratos/metabolismo , Nitritos/metabolismo , Estresse Oxidativo
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