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Prostaglandin endoperoxideHsynthases (PGHSs), also called cyclooxygenases (COXs), convert arachidonic acid (AA) to PGH2. PGHS-1 and PGHS-2 are conformational heterodimers, each composed of an (Eallo) and a catalytic (Ecat) monomer. Previous studies suggested that the binding to Eallo of saturated or monounsaturated fatty acids (FAs) that are not COX substrates differentially regulate PGHS-1 versus PGHS-2. Here, we substantiate and expand this concept to include polyunsaturated FAs known to modulate COX activities. Non-substrate FAs like palmitic acid bind Eallo of PGHSs stimulating human (hu) PGHS-2 but inhibiting huPGHS-1. We find the maximal effects of non-substrate FAs on both huPGHSs occurring at the same physiologically relevant FA/AA ratio of~20. This inverse allosteric regulation likely underlies the ability of PGHS-2 to operate at low AA concentrations, when PGHS-1 is effectively latent. Unlike FAs tested previously, we observe that C-22 FAs, including ω-3 fish oil FAs, have higher affinities for Ecat than Eallo subunits of PGHSs. Curiously, C-20 ω-3 eicosapentaenoate preferentially binds Ecat of huPGHS-1 but Eallo of huPGHS-2. PGE2 production decreases 50% when fish oil consumption produces tissue EPA/AA ratios of≥0.2. However, 50% inhibition of huPGHS-1 itself is only seen with ω-3 FA/AA ratios of ≥5.0. This suggests that fish oil-enriched diets disfavor AA oxygenation by altering the composition of the FA pool in which PGHS-1 functions. The distinctive binding specificities of PGHS subunits permit different combinations of non-esterified FAs, which can be manipulated dietarily, to regulateAAbinding to Eallo and/or Ecat thereby controlling COX activities. [ABSTRACT FROM AUTHOR]

Seed metabolites are the combination of essential compounds required by an organism across various potential environmental conditions. The seed metabolites screening framework based on the network topology approach can capture important biological information of species. This study aims to identify comprehensively the relationship between seed metabolites and pathogenic bacteria. A large-scale data set was compiled, describing the seed metabolite sets and metabolite sets of 124,192 pathogenic strains from 34 genera, by constructing genome-scale metabolic models. The enrichment analysis method was used to screen the specific seed metabolites of each species/genus of pathogenic bacteria. The metabolites of pathogenic microorganisms database (MPMdb) (http://qyzhanglab.hzau.edu.cn/MPMdb/) was established for browsing, searching, predicting, or downloading metabolites and seed metabolites of pathogenic microorganisms. Based on the MPMdb, taxonomic and phylogenetic analyses of pathogenic bacteria were performed according to the function of seed metabolites and metabolites. The results showed that the seed metabolites could be used as a feature for microorganism chemotaxonomy, and they could mirror the phylogeny of pathogenic bacteria. In addition, our screened specific seed metabolites of pathogenic bacteria can be used not only for further tapping the nutritional resources and identifying auxotrophies of pathogenic bacteria but also for designing targeted bactericidal compounds by combining with existing antimicrobial agents.IMPORTANCEMetabolites serve as key communication links between pathogenic microorganisms and hosts, with seed metabolites being crucial for microbial growth, reproduction, external communication, and host infection. However, the large-scale screening of metabolites and the identification of seed metabolites have always been the main technical bottleneck due to the low throughput and costly analysis. Genome-scale metabolic models have become a recognized research paradigm to investigate the metabolic characteristics of species. The developed metabolites of pathogenic microorganisms database in this study is committed to systematically predicting and identifying the metabolites and seed metabolites of pathogenic microorganisms, which could provide a powerful resource platform for pathogenic bacteria research., Competing Interests: The authors declare no conflict of interest.

Legionella is a common intracellular parasitic bacterium that infects humans via the respiratory tract, causing Legionnaires' disease, with fever and pneumonia as the main symptoms. The emergence of highly virulent and azithromycin-resistant Legionella pneumophila is a major challenge in clinical anti-infective therapy. The CRISPR-Cas acquired immune system provides immune defense against foreign nucleic acids and regulates strain biological functions. However, the distribution of the CRISPR-Cas system in Legionella and how it regulates gene expression in L. pneumophila remain unclear. Herein, we assessed 915 Legionella whole-genome sequences to determine the distribution characteristics of the CRISPR-Cas system and constructed gene deletion mutants to explore the regulation of the system based on growth ability in vitro , antibiotic sensitivity, and intracellular proliferation of L. pneumophila . The CRISPR-Cas system in Legionella was predominantly Type II-B and was mainly concentrated in the genome of L. pneumophila ST1 strains. The Type II-B CRISPR-Cas system showed no effect on the strain's growth ability in vitro but significantly reduced resistance to azithromycin and decreased proliferation ability due to regulation of the lpeAB efflux pump and the Dot/Icm type IV secretion system. Thus, the Type II-B CRISPR-Cas system plays a crucial role in regulating the virulence of L. pneumophila . This expands our understanding of drug resistance and pathogenicity in Legionella , provides a scientific basis for the prevention of Legionnaires' disease outbreaks and the rational use of clinical drugs, and facilitates effective treatment of Legionnaires' disease., Competing Interests: The authors declare no conflict of interest.

Introduction: We previously showed that a "10-hour daytime on-site" and "nighttime (NT) on-call" staffing strategy was associated with higher mortality for intensive care unit (ICU) patients admitted during NT than it was for patients admitted during office hours (OH). In here, we evaluated the clinical effects of a 24-hour intensivist staffing model., Methods: We formed an intervention group of 3034 consecutive ICU patients hospitalized from January 2013 to December 2015, and a control group of 2891 patients from our previous study (2009-2011). We applied propensity score matching (PSM) for whole and subgroup analyses adjusting for confounding factors. We compared clinical outcomes of patients under the 2 staffing models using multivariate logistic regression and survival analyses., Results: After PSM, we balanced the clinical data between the complete cohorts and the subgroups. Comparison of ICU survivals between the intervention and control cohorts yielded no significant differences. However, the intervention was significantly associated with a higher ICU survival in the NT (5:30 pm-07:30 am) admission patients ( P = .049) than in those admitted during OH (07:30 am to 5:30 pm; P = .456). Additionally, the intervention shortened the LOS HOS ( P = .001) and/or LOS ICU ( P < .001), reduced the hospital ( P = .672) and/or ICU ( P = .004) expenses, and resulted in earlier mechanical ventilation extubation ( P = .442) as compared to the same variables in the control group, especially for NT admissions., Conclusions: The 24-hour intensivists staffing could significantly improve ICU outcomes, especially for NT-admission patients in high-acuity, high-volume ICUs with frequent NT admissions.

The balance of putative pro- and antiinflammatory lipoxygenase (LOX)-derived S-hydroxyeicosatetraenoic acids (S-HETEs) in colon mucosa is a potential target for modulating colon cancer risk and progression. The biological effects of S-HETEs and R-hydroxyeicosatetraenoic acids (produced by distinct pathways) may differ, but levels of these compounds in the colon are unknown. The objective of this study was to develop chiral methods to characterize hydroxyeicosatetraenoic (HETE) enantiomers in colonic mucosa and evaluate the effects of fish oil on HETE formation. C57BL/6 mice (COX-1 null, COX-2 null, wild-type) were fed a diet supplemented with either olive oil or menhaden oil for 11 wk, and R-/S-HETEs in colonic mucosa were quantified by chiral LC-MS/MS. The R-enantiomer comprised 60-72% of 5-HETE, 18-58% of 15-HETE, and 1-16% of 12-HETE in colonic mucosa, suggesting that non-LOX sources contribute to HETE profiles. Fish oil reduced levels of both R- and S-HETEs, and increased the preponderance of the R-enantiomers (particularly 12- and 15-HETEs). There was apparent shunting of arachidonic acid to 12-/15-LOX in the COX-1 null animals. This is the first report of the enantiomeric composition of HETEs in the colon in vivo and shows large effects of fish oil in the normal colon.

This experiment was conducted to investigate the effects of zinc sulfate and zinc methionine (Zn-Met) and their levels on apoptosis induced by glucocorticoid of thymocytes and the possible mechanism. Dexamethasone was used to make the apoptosis model of thymocytes; zinc sulfate and zinc methionine were supplemented to the medium at levels of 0, 50, 100, 500, and 1000 microM. The activity of cells, Cu,Zn superoxide dismutase (Cu,Zn-SOD), DNA ladder pattern, intracellular calcium concentration, and the percentage of apoptosis nuclei were determined. Both ZnSO4 and Zn-Met could modulate apoptosis; they inhibited apoptosis and decreased DNA fragmentation. The regulation was concentration dependent. At levels of 50 and 100 microM, the effect of Zn-Met on inhibiting apoptosis was less efficient than that of ZnSO4 (p<0.05), but the activity of the cells cultured with Zn-Met was higher than those cultured with ZnSO4; they showed no difference in modulating apoptosis when added at levels of 500 and 1000 microM to the medium (p>0.05). Intracellular calcium concentrations of cells cultured with Zn-Met were higher than those cultured with ZnSO4 at the same levels. Zinc supplementation decreased the concentration of intracellular calcium significantly (p<0.05) and increased the activity of Cu,Zn-SOD in the extract of the cells (p<0.05). Both zinc sulfate and Zn-Met could modulate apoptosis of thymocytes induced by glucocorticoid; the mechanism might involve the exchange of intracellular calcium, the redox of cells, and the two forms of zinc might go different ways in the regulations.