Overexpression of Plakophilin2 Mitigates Capillary Leak Syndrome in Severe Acute Pancreatitis by Activating the p38/MAPK Signaling Pathway.

Purpose: Capillary leak syndrome (CLS) is an intermediary phase between severe acute pancreatitis (SAP) and multiple organ failure. As a result, CLS is of clinical importance for enhancing the prognosis of SAP. Plakophilin2 (PKP2), an essential constituent of desmosomes, plays a critical role in promoting connections between epithelial cells. However, the function and mechanism of PKP2 in CLS in SAP are not clear at present. Methods: We detected the expression of PKP2 in mice pancreatic tissue by transcriptome sequencing and bioinformatics analysis. PKP2 was overexpressed and knocked down to assess its influence on cell permeability, the cytoskeleton, tight junction molecules, cell adhesion junction molecules, and associated pathways. Results: PKP2 expression was increased in the pancreatic tissues of SAP mice and human umbilical vein endothelial cells (HUVECs) after lipopolysaccharide (LPS) stimulation. PKP2 overexpression not only reduced endothelial cell permeability but also improved cytoskeleton relaxation in response to acute inflammatory stimulation. PKP2 overexpression increased levels of ZO-1, occludin, claudin1, ß-catenin, and connexin43. The overexpression of PKP2 in LPS-induced HUVECs counteracted the inhibitory effect of SB203580 (a p38/MAPK signaling pathway inhibitor) on the p38/MAPK signaling pathway, thereby restoring the levels of ZO-1, ß-catenin, and claudin1. Additionally, PKP2 suppression eliminated the enhanced levels of ZO-1, ß-catenin, occludin, and claudin1 induced by dehydrocorydaline. We predicted that the upstream transcription factor PPARγregulates PKP2 expression, and our findings demonstrate that the PPARγactivator rosiglitazone significantly upregulates PKP2, whereas its antagonist GW9662 down-regulates PKP2. Administration of rosiglitazone significantly reduced the increase in HUVECs permeability stimulated by LPS. Conversely, PKP2 overexpression counteracted the GW9662-induced reduction in ZO-1, phosphorylated p38/p38, and claudin1. Conclusion: The activation of the p38/MAPK signaling pathway by PKP2 mitigates CLS in SAP. PPARγactivator rosiglitazone can up-regulate PKP2. Overall, directing efforts toward PKP2 could prove to be a feasible treatment approach for effectively managing CLS in SAP.

Cytochrome P450 Enzyme Design by Constraining the Catalytic Pocket in a Diffusion Model.

Although cytochrome P450 enzymes are the most versatile biocatalysts in nature, there is insufficient comprehension of the molecular mechanism underlying their functional innovation process. Here, by combining ancestral sequence reconstruction, reverse mutation assay, and progressive forward accumulation, we identified 5 founder residues in the catalytic pocket of flavone 6-hydroxylase (F6H) and proposed a "3-point fixation" model to elucidate the functional innovation mechanisms of P450s in nature. According to this design principle of catalytic pocket, we further developed a de novo diffusion model (P450Diffusion) to generate artificial P450s. Ultimately, among the 17 non-natural P450s we generated, 10 designs exhibited significant F6H activity and 6 exhibited a 1.3- to 3.5-fold increase in catalytic capacity compared to the natural CYP706X1. This work not only explores the design principle of catalytic pockets of P450s, but also provides an insight into the artificial design of P450 enzymes with desired functions.

Influence of gestational hypertension and maternal air pollutant exposure on birth outcomes.

The relationship between exposure to air pollutants and fetal growth outcomes has shown inconsistency, and only a limited number of studies have explored the impact of air pollution on gestational hypertension and birth outcomes. This study aimed to evaluate how maternal exposure to air pollutants and blood pressure could influence fetal birth outcomes. A total of 55 women with gestational hypertension and 131 healthy pregnant women were enrolled in this study. Data pertaining to personal characteristics, prenatal examinations, outdoor air pollutant exposure, and fetal birth outcomes were collected. The study revealed that fetal birth weight and abdominal circumference exhibited a significant reduction among women with gestational hypertension compared to healthy pregnant women, even after adjustments for body mass index, gestational age, and exposure to air pollutants had been made. Moreover, maternal exposure to outdoor air pollutants displayed a notable correlation with decreased birth length of fetuses. Consequently, the study concluded that maternal blood pressure and exposure to outdoor air pollutants during pregnancy potentially stand as pivotal factors influencing fetal birth outcomes.

Regiodivergent biosynthesis of bridged bicyclononanes.

Medicinal compounds from plants include bicyclo[3.3.1]nonane derivatives, the majority of which are polycyclic polyprenylated acylphloroglucinols (PPAPs). Prototype molecules are hyperforin, the antidepressant constituent of St. John's wort, and garcinol, a potential anticancer compound. Their complex structures have inspired innovative chemical syntheses, however, their biosynthesis in plants is still enigmatic. PPAPs are divided into two subclasses, named type A and B. Here we identify both types in Hypericum sampsonii plants and isolate two enzymes that regiodivergently convert a common precursor to pivotal type A and B products. Molecular modelling and substrate docking studies reveal inverted substrate binding modes in the two active site cavities. We identify amino acids that stabilize these alternative binding scenarios and use reciprocal mutagenesis to interconvert the enzymatic activities. Our studies elucidate the unique biochemistry that yields type A and B bicyclo[3.3.1]nonane cores in plants, thereby providing key building blocks for biotechnological efforts to sustainably produce these complex compounds for preclinical development.

Internal carotid artery injury during endoscopic transsphenoidal pituitary surgery: risk factors, management.

BACKGROUND: Transsphenoidal surgeons should try to avoid internal carotid artery (ICA) injury but also be prepared to manage it. We analyzed our experience with ICA injury during endoscopic transsphenoidal pituitary surgery and present associated risk factors and a management protocol. METHODS: We retrospectively reviewed and analyzed the medical records of 1596 patients who underwent endoscopic transsphenoidal surgery for pituitary tumor resection in our institution from January 2009 to October 2022. RESULTS: Six patients experienced an ICA injury. All received timely and effective hemostasis with immediate direct tamponade followed by endovascular treatment. No serious postoperative complications occurred. CONCLUSIONS: We proposed a treatment plan for ICA injuries encountered during endoscopic transsphenoidal surgery and described our hemostasis process, methods of endovascular treatment, and means of postoperative follow-up in detail.

Etiological Changes and Prognosis of Hospitalized Patients with Acute Pancreatitis Over a 15-Year Period.

BACKGROUND: The worldwide incidence of acute pancreatitis (AP) is increasing, but the dominant etiology of AP may vary by country. Mixed etiologies are involved in the increase in the number of AP patients. AIMS: This study was to analyze the etiological changes and prognosis of AP patients and explore the prognosis of AP patients with mixed etiologies. METHODS: Using a retrospective analysis method, AP patients hospitalized from January 2007 to December 2021 were selected from a pancreatic center in Nanchang, China. Trends in the main etiologies were analyzed, and the severity and prognosis of different etiologies were compared. RESULTS: A total of 10,071 patients were included. Cholelithiasis (56.0%), hyperlipidemia (25.3%), and alcohol (6.5%) were the top three etiologies. The proportion of acute biliary pancreatitis (ABP) showed a decreasing trend, while the proportion of hypertriglyceridemic pancreatitis (HTGP) and alcoholic AP showed an increasing trend (all ptrend < 0.001). The incidence of organ failure and necrotizing pancreatitis was higher in patients with HTGP than in those with AP induced by other etiologies (all p < 0.05). There was no statistically significant difference in mortality among patients with different etiologies. Patients with AP due to a mixed hypertriglyceridemia-alcoholic etiology had higher ICU admission rates and were more severe than those with AP induced by other mixed etiologies. CONCLUSION: In the past 15 years, the proportion of ABP has trended downward, while those of HTGP and alcoholic AP have risen. Among patients with mixed etiologies, those with a mixed hypertriglyceridemia-alcoholic etiology had a worse prognosis.

Gastrointestinal Fistulas in Necrotizing Pancreatitis Receiving a Step-Up Approach Incidence, Risk Factors, Outcomes and Treatment.

Purpose: Necrotizing pancreatitis (NP) complicated by gastrointestinal fistula is challenging and understudied. As the treatment of necrotizing pancreatitis changed to a step-up strategy, we attempted to evaluate the incidence, risk factors, clinical outcomes and treatment of gastrointestinal fistulas in patients receiving a step-up approach. Methods: Clinical data from 1274 patients with NP from 2014-2022 were retrospectively analyzed. Multivariable logistic regression analysis was conducted to identify risk factors and propensity score matching (PSM) to explore clinical outcomes in patients with gastrointestinal fistulas. Results: Gastrointestinal fistulas occurred in 8.01% (102/1274) of patients. Of these, 10 were gastric fistulas, 52 were duodenal fistulas, 14 were jejunal or ileal fistulas and 41 were colonic fistulas. Low albumin on admission (OR, 0.936), higher CTSI (OR, 1.143) and invasive intervention prior to diagnosis of gastrointestinal fistula (OR, 5.84) were independent risk factors for the occurrence of gastrointestinal fistula, and early enteral nutrition (OR, 0.191) was a protective factor. Patients who developed a gastrointestinal fistula were in a worse condition on admission and had a poorer clinical outcome (p<0.05). After PSM, both groups of patients had similar baseline information and clinical characteristics at admission. The development of gastrointestinal fistulas resulted in new-onset persistent organ failure, increased open surgery, prolonged parenteral nutrition and hospitalization, but not increased mortality. The majority of patients received only conservative treatment and minimally invasive interventions, with 7 patients (11.3%) receiving surgery for upper gastrointestinal fistulas and 11 patients (26.9%) for colonic fistulas. Conclusion: Gastrointestinal fistulas occurred in 8.01% of NP patients. Independent risk factors were low albumin, high CTSI and early intervention, while early enteral nutrition was a protective factor. After PSM, gastrointestinal fistulas resulted in an increased proportion of NP patients receiving open surgery and prolonged hospitalization. The majority of patients with gastrointestinal fistulas treated with step-up therapy could avoid surgery.

Design, Evaluation, and Implementation of Synthetic Isopentyldiol Pathways in Escherichia coli.

Isopentyldiol (IPDO) is an important raw material in the cosmetic industry. So far, IPDO is exclusively produced through chemical synthesis. Growing interest in natural personal care products has inspired the quest to develop a biobased process. We previously reported a biosynthetic route that produces IPDO via extending the leucine catabolism (route A), the efficiency of which, however, is not satisfactory. To address this issue, we computationally designed a novel non-natural IPDO synthesis pathway (route B) using RetroPath RL, the state-of-the-art tool for bioretrosynthesis based on artificial intelligence methods. We compared this new pathway with route A and two other intuitively designed routes for IPDO biosynthesis from various perspectives. Route B, which exhibits the highest thermodynamic driving force, least non-native reaction steps, and lowest energy requirements, appeared to hold the greatest potential for IPDO production. All three newly designed routes were then implemented in the Escherichia coli BL21(DE3) strain. Results show that the computationally designed route B can produce 2.2 mg/L IPDO from glucose but no IPDO production from routes C and D. These results highlight the importance and usefulness of in silico design and comprehensive evaluation of the potential efficiencies of candidate pathways in constructing novel non-natural pathways for the production of biochemicals.

In silico prediction of mutation sites for anthranilate synthase from Serratia marcesens to deregulate tryptophan feedback inhibition.

Allosteric feedback inhibition of the committed step in amino acid biosynthetic pathways is a major concern for production of amino acids at industrial scale. Anthranilate synthase (AS) catalyzes the first reaction of tryptophan biosynthetic pathway found in microorganisms and is feedback inhibited by its own product i.e. tryptophan. Here, we identified new mutant sites in AS using computational mutagenesis approach. MD simulations (20 ns) followed by MMPBSA and per residue decomposition energy analysis identified seven amino acid residues with best binding affinity for tryptophan. All 19 mutant structures were generated for each identified amino acid residue followed by simulation to evaluate effect of mutation on protein stability. Later, molecular docking studies were employed to generate mutant-tryptophan complex and structures with binding energies (kcal/mol) much higher than wild-type AS were selected. Finally, two mutants i.e., S37W and S37H were identified on the basis of positive binding scores and loss of tryptophan binding inside pocket. Further, MD simulations run for 200 ns were performed over these mutant-tryptophan complexes followed by RMSD, RMSF, radius of gyration , solvent accessible surface area , intra-protein hydrogen bond numbers, principal component analysis, free energy landscape (FEL) and secondary structure analysis to rationale effect of mutations on stability of protein. Cross correlation analysis of mutant site amino acids (S37W) with key residues of catalytic site (G325, T326, H395 and G482) was done to evaluate the effect of mutations on catalytic site conformation. Current computational mutagenesis approach predicted two mutants S37W and S37H with proposed deregulated feedback inhibition by tryptophan and retained catalytic activity.Communicated by Ramaswamy H. Sarma.

Insight into de-regulation of amino acid feedback inhibition: a focus on structure analysis method.

Regulation of amino acid's biosynthetic pathway is of significant importance to maintain homeostasis and cell functions. Amino acids regulate their biosynthetic pathway by end-product feedback inhibition of enzymes catalyzing committed steps of a pathway. Discovery of new feedback resistant enzyme variants to enhance industrial production of amino acids is a key objective in industrial biotechnology. Deregulation of feedback inhibition has been achieved for various enzymes using in vitro and in silico mutagenesis techniques. As enzyme's function, its substrate binding capacity, catalysis activity, regulation and stability are dependent on its structural characteristics, here, we provide detailed structural analysis of all feedback sensitive enzyme targets in amino acid biosynthetic pathways. Current review summarizes information regarding structural characteristics of various enzyme targets and effect of mutations on their structures and functions especially in terms of deregulation of feedback inhibition. Furthermore, applicability of various experimental as well as computational mutagenesis techniques to accomplish feedback resistance has also been discussed in detail to have an insight into various aspects of research work reported in this particular field of study.

Protein engineering and iterative multimodule optimization for vitamin B6 production in Escherichia coli.

Vitamin B6 is an essential nutrient with extensive applications in the medicine, food, animal feed, and cosmetics industries. Pyridoxine (PN), the most common commercial form of vitamin B6, is currently chemically synthesized using expensive and toxic chemicals. However, the low catalytic efficiencies of natural enzymes and the tight regulation of the metabolic pathway have hindered PN production by the microbial fermentation process. Here, we report an engineered Escherichia coli strain for PN production. Parallel pathway engineering is performed to decouple PN production and cell growth. Further, protein engineering is rationally designed including the inefficient enzymes PdxA, PdxJ, and the initial enzymes Epd and Dxs. By the iterative multimodule optimization strategy, the final strain produces 1.4 g/L of PN with productivity of 29.16 mg/L/h by fed-batch fermentation. The strategies reported here will be useful for developing microbial strains for the production of vitamins and other bioproducts having inherently low metabolic fluxes.

GPR35-mediated kynurenic acid sensing contributes to maintenance of gut microbiota homeostasis in ulcerative colitis.

Ulcerative colitis (UC) is a recurrent inflammatory disease related to gut microbiota disorder. Metabolites and their sensors play an important role in the communication between gut microbes and their host. Our previous study revealed that G protein-coupled receptor 35 (GPR35) is a key guardian of kynurenic acid (KA) and a core element of the defense responses against gut damage. However, the mechanism remains unknown. In this study, a DSS-induced rat colitis model was established and 16S rRNA sequencing was applied to explore the influence of GPR35-mediated KA sensing on gut microbiota homeostasis. Our results demonstrated that GPR35-mediated KA sensing is a necessary component in maintaining gut barrier integrity against DSS-induced damage. Furthermore, we provide compelling evidence suggesting that GPR35-mediated KA sensing plays a crucial role in maintaining gut microbiota homeostasis, which contributes to alleviation of DSS-induced colitis. In addition, five classes (Actinobacteria, Beta-/Gamma-proteobacteria, Erysipelotrichi, and Coriobacteriia) and six genera (Corynebacterium, Allobaculum, Parabacteroides, Sutterella, Shigella, and Xenorhabdus) were identified as the marked bacterial taxa that characterized the progression and outcome of colitis and are regulated by GPR35-mediated KA sensing. Our findings highlight that GPR35-mediated KA sensing is an essential defense mechanism against disorder of gut microbiota in UC. The results provide insights into the key role of specific metabolites and their monitor in maintaining gut homeostasis.

Hepatic Krüppel-like factor 14 regulates lipid metabolism in nonalcoholic steatohepatitis mice.

Excessive lipid accumulation is a critical characteristic in the development of nonalcoholic steatohepatitis (NASH). The underlying molecular mechanism, however, is unclear. In this study, we explored whether and how Krüppel-like factor 14 (KLF14) affects hepatic lipid metabolism in NASH. KLF14 expression was detected in NASH patients and mice fed a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD). Adeno-associated viruses and adenoviruses were used to alter hepatic KLF14 expression in vivo or in vitro to investigate how KLF14 functions in lipid regulation. The molecular mechanisms were explored using RNA-seq, luciferase reporter, and ChIP assays. The fatty liver phenotype was analyzed histopathologically, and serum and hepatocyte biochemical parameters were measured. The NASH mouse model developed quickly in C57BL/6J mice fed a CDAHFD for 8 weeks. We found that KLF14 expression was decreased in NASH patients and CDAHFD mice. Oleic acid and palmitic acid treatment also reduced KLF14 levels in hepatocytes. KLF14 knockdown downregulated the genes involved in fatty acid oxidation, promoting the progression of hepatic steatosis. In contrast, hepatic KLF14 overexpression alleviated lipid accumulation and oxidative stress in CDAHFD mice. These effects resulted from direct activation of the PPARα signaling pathway. PPARα inhibition diminished the KLF14 overexpression-reduced protective effects against steatosis in OA&PA-treated MPHs and AAV-KLF14-infected CDAHFD mice. These data reveal that hepatic KLF14 regulates lipid accumulation and oxidative stress through the KLF14-PPARα pathway as NASH progresses. KLF14 may be a novel therapeutic target for hepatic steatosis.

Albumin infusion may decrease the mortality of hypoalbuminemia patients with severe acute pancreatitis: a retrospective cohort study.

BACKGROUND: At present, the relationship between severe acute pancreatitis (SAP) and albumin infusion is not clear. We aimed to identify the impact of serum albumin on the prognosis of SAP and the association between albumin infusions and mortality for hypoalbuminemia patients. METHODS: This was a retrospective cohort study that analyzed 1000 patients with SAP who were admitted to the First Affiliated Hospital of Nanchang University between January 2010 and December 2021 using data from a prospectively maintained database. Multivariate logistic regression analysis was conducted to reveal the relationship between serum albumin within 1 week after admission and poor prognosis of SAP. Propensity score matching (PSM) analysis was adopted to evaluate the effect of albumin infusion for hypoalbuminemia patients with SAP. RESULTS: The prevalence of hypoalbuminemia (≤ 30 g/L) was 56.9% within 1 week after admission. Multivariate logistic regression identified that age (OR: 1.02; 95% CI: 1.00-1.04; P = 0.012), serum urea (OR: 1.08; 95% CI: 1.04-1.12; P < 0.001), serum calcium (OR: 0.27; 95% CI: 0.14-0.50; P < 0.001), lowest albumin level within 1 week after admission (OR: 0.93; 95% CI: 0.89-0.97; P = 0.002), and APACHE II score ≥ 15 (OR: 1.73; 95% CI: 1.19-2.51; P = 0.004) were independently associated with mortality. The PSM analysis demonstrated that mortality (OR: 0.52, 95% CI: 0.29-0.92, P = 0.023) was less common in albumin-infused than non-albumin-infused hypoalbuminemia patients. In subgroup analyses, doses > 100 g within 1 week after admission for hypoalbuminemia patients with albumin infusions was associated with lower mortality than doses ≤ 100 g (OR: 0.51, 95% CI: 0.28-0.90, P = 0.020). CONCLUSIONS: Hypoalbuminemia in early-stage SAP is significantly related to poor prognosis. However, albumin infusions could significantly decrease mortality in hypoalbuminemia patients with SAP. Additionally, infusing sufficient albumin within a week after admission may decrease mortality in hypoalbuminemia patients.

Defined, low threshold for caesarean section and multidisciplinary team management improves fetal outcome from acute pancreatitis in pregnancy.

BACKGROUND: Acute pancreatitis in pregnancy (APIP) is associated with increased maternal and fetal mortality. OBJECTIVES: We sought to determine whether a low threshold for cesarean section (C-section) in severe acute pancreatitis (SAP) or Predict SAP improves maternal and fetal outcomes in patients with APIP. METHODS: We identified patients with APIP at a single institution from a prospective database and studied fetal and maternal health in APIP before (2005-2014) and after (2015-2019) introduction of multidisciplinary team management with a defined, lowered threshold for C-section. The primary end point was fetal mortality comprising abortion and perinatal death. Risk factors associated with fetal mortality were analyzed by univariable and multivariable logistic regression analysis. RESULTS: A total of 165 patients with APIP were eligible for analysis. There was a highly significant increase in patients undergoing C-section from 37 (30.8%) of 120 during 2005-2014 to 27 (60%) of 45 in 2015-2019 (P = 0.001), with a highly significant fall in fetal mortality from 37 (30.8%) of 120 to 3 (6.7%) of 45 between the same periods (P = 0.001), when maternal mortality fell from 6 to zero (P = 0.19). Maternal early systemic inflammatory response syndrome (SIRS) (odds ratio [OR] 6.98, 95% confidence interval [CI] 1.53, 30.80, P = 0.01) and SAP (OR 3.64, 95%CI 1.25, 10.60, P = 0.02) were two independent risk factors associated with fetal mortality. CONCLUSIONS: Multidisciplinary collaboration and a defined, low threshold for C-section improve fetal outcomes in patients with APIP.

The severity and infection of acute pancreatitis may increase the risk of bleeding in patients undergoing EUS-guided drainage and endoscopic necrosectomy: a large retrospective cohort.

BACKGROUND: There has been great progress in the use of endoscopic ultrasound (EUS)-guided drainage in acute pancreatitis patients using a novel lumen-apposing metal stent (LAMS) in the last decade, but some patients experience bleeding. Our research analyzed the preprocedural risk factors for bleeding. METHODS: From July 13, 2016 to June 23, 2021, we retrospectively analyzed all patients who received endoscopic drainage by the LAMS in our hospital. Univariate and multivariate statistical analyses were used to identify the independent risk factors. We plotted ROC curves based on the independent risk factors. RESULTS: A total of 205 patients were analyzed and 5 patients were excluded. A total of 200 patients were included in our research. Thirty (15%) patients presented with bleeding. In the multivariate analysis, computed tomography severity index score (CTSI) score [odds ratio (OR), 2.66; 95% CI: 1.31-5.38; P = 0.007], positive blood cultures [odds ratio (OR), 5.35; 95% CI: 1.31-21.9; P = 0.02], and Acute Physiology and Chronic Health Evaluation II (APACHE II) score [odds ratio (OR), 1.14; 95% CI: 1. 01-1.29; P = 0.045] were associated with bleeding. The area under the ROC curve of the combined predictive indicator was 0.79. CONCLUSION: Bleeding in endoscopic drainage by the LAMS is significantly associated with the CTSI score, positive blood cultures, and APACHE II score. This result could help clinicians make more appropriate choices.

Why comply? Risk and efficacy perceptions drive compliance in mass marketing scams.

Using a mix-method design, we examined participants' willingness to respond to mass marketing scams (MMS). In Experiment 1, we examined the effect of age (young versus older) and letter style ("hot" versus "cold") on the intention to respond. The intention of responding was negatively associated with risk (p < .001) and having at least a high school education was positively associated with perception of benefits (b = .684, p < .001). In Experiment 2, we examined reward sensitivity on the intention to respond by manipulating reward amounts (low versus high) and the presence of an activation fee. The presence of an activation fee decreased intent to contact, but percentages remained high (25.75%). Analyses of qualitative data indicated that risk and benefit were both predicted by perceived self-efficacy. The results indicate that consumers' beliefs about their ability to control the outcomes of future interactions affected how they behaved when provided with MMS materials.

Identification and engineering efflux transporters for improved L-homoserine production in Escherichia coli.

AIMS: This study aimed to functionally identify the potential L-homoserine transporters in Escherichia coli, and to generate the promising beneficial mutants by targeted directed evolution for improving the robustness and efficiency of microbial cell factories. METHODS AND RESULTS: By constructing a series of gene deletion and overexpression strains, L-homoserine tolerance assays revealed that RhtA was an efficient and major L-homoserine exporter in E. coli, whereas RhtB and RhtC exhibited relatively weak transport activities for L-homoserine. Real-time RT-PCR analysis suggested that the expression levels of these three target mRNAs were generally variably enhanced when cells were subjected to L-homoserine stress. Based on in vivo continuous directed evolution and growth-couple selections, three beneficial mutations of RhtA exporter (A22V, P119L, and T235I) with clearly increased tolerance against L-homoserine stress were quickly obtained after two rounds of mutagenesis-selection cycles. L-homoserine export assay revealed that the RhtA mutants exhibited different degrees of improvement in L-homoserine export capacity. Further studies suggested that a combination of these beneficial sites led to synergistic effects on conferring L-homoserine-resistance phenotypes. Moreover, the introduction of RhtA beneficial mutants into the L-homoserine-producing strains could facilitate increased amounts of L-homoserine in the shake-flask fermentation. CONCLUSIONS: In this study, we provided further evidence that RhtA serves as a major L-homoserine exporter in E. coli, and obtained several RhtA beneficial mutants, including A22V, P119L, and T235I that contributed to improving the L-homoserine resistance phenotypes and the production efficiency in microbial chassis.

Timing of minimally invasive step-up intervention for symptomatic pancreatic necrotic fluid collections: A systematic review and meta-analysis.

BACKGROUND AND AIMS: Minimally invasive step-up interventions are now the standard treatment recommended by current guidelines for symptomatic pancreatic necrotic fluid collections (PNFC); however, it is controversial whether delayed treatment after four weeks should always be used in patients who have failed conservative treatment and whose condition has not improved or worsened. The aim of this meta-analysis was to evaluate the impacts of the different timing of interventions on the clinical outcomes and prognosis of patients with symptomatic PNEC requiring intervention. METHODS: We searched Embase, Cochrane Library, PubMed and Web of Science databases to identify comparative studies assessing the safety and efficacy of early and postponed interventions in treating symptomatic PNFC. PRIMARY OUTCOME: Mortality. Secondary outcomes included some major complications, need for further minimally invasive necrosectomy and length of hospital stay. RESULTS: This meta-analysis included ten studies (2 RCTs and 8 observational studies) with a total of 1178 symptomatic PNFC patients who required intervention. Pooled results showed that there was no significant difference between early minimally invasive intervention and postponed intervention in mortality(OR 1.41, 95%CI 0.93-2.12;p = 0.10) and the incidence of early and late complications, but the early intervention group had a significantly increased need for further minimally invasive necrosectomy compared with postponed intervention (OR 2.04,95%CI 1.04-4.03; p = 0.04). There was no increase in length of stay for patients who received early intervention compared to postponed drainage (MD 3.53, 95% CI -4.20, 11.27; p = 0.37). CONCLUSION: Intervention before four weeks should be considered for patients with PNFC complicated by persistent organ failure or infections, who have been treated conservatively to the maximum extent possible.

Organic ultraviolet filter mixture promotes bleaching of reef corals upon the threat of elevated seawater temperature.

Global reef degradation is a critical environmental health issue that has triggered intensive research on ocean warming, but the implications of emerging contaminants in coral habitats are largely overlooked. Laboratory experiments assessing organic ultraviolet (UV) filter exposure have shown that these chemicals negatively affect coral health; their ubiquitous occurrence in association with ocean warming may pose great challenges to coral health. We investigated both short- (10-day) and long-term (60-day) single and co-exposures of coral nubbins to environmentally relevant organic UV filter mixtures (200 ng/L of 12 compounds) and elevated water temperatures (30 °C) to investigate their effects and potential mechanisms of action. The initial 10-day exposure of Seriatopora caliendrum resulted in bleaching only under co-exposure conditions (compounds + temperature). The 60-day mesocosm study entailed the same exposure settings with nubbins of three species (S. caliendrum, Pocillopora acuta and Montipora aequituberculata). Bleaching (37.5 %) and mortality (12.5 %) of S. caliendrum were observed under UV filter mixture exposure. In the co-exposure treatment, 100 % S. caliendrum and P. acuta bleached associating with 100 % and 50 % mortality, respectively, and significant increase of catalase activities in P. acuta and M. aequituberculata nubbins were found. Biochemical and molecular analyses indicated significant alteration of oxidative stress and metabolic enzymes. The results suggest that upon the adverse effects of thermal stress, organic UV filter mixture at environmental concentrations can cause bleaching in corals by inducing a significant oxidative stress and detoxification burden, suggesting that emerging contaminants may play a unique role in global reef degradation.