Listeria monocytogenes is a common food-borne pathogen that can disseminate from the intestine and infect multiple organs. Here, we used sequence tag-based analysis of microbial populations (STAMP) to investigate L. monocytogenes population dynamics during infection. We created a genetically barcoded library of murinized L. monocytogenes and then used deep sequencing to track the pathogen's dissemination routes and quantify its founding population (N b ) sizes in different organs. We found that the pathogen disseminates from the gastrointestinal tract to distal sites through multiple independent routes and that N b sizes vary greatly among tissues, indicative of diverse host barriers to infection. Unexpectedly, comparative analyses of sequence tags revealed that fecally excreted organisms are largely derived from the very small number of L. monocytogenes cells that colonize the gallbladder. Immune depletion studies suggest that distinct innate immune cells restrict the pathogen's capacity to establish replicative niches in the spleen and liver. Finally, studies in germ-free mice suggest that the microbiota plays a critical role in the development of the splenic, but not the hepatic, barriers that prevent L. monocytogenes from seeding these organs. Collectively, these observations illustrate the potency of the STAMP approach to decipher the impact of host factors on population dynamics of pathogens during infection.Listeria monocytogenes | STAMP | pathogen dissemination | pathogen transmission | population dynamics S ome pathogens are able to disseminate from their sites of inoculation to reach distant organs and proliferate to high numbers. During dissemination, pathogens must circumvent host defense mechanisms that restrict access to niches permissive for pathogen replication, which constitute "bottlenecks" constraining pathogen establishment. Understanding pathogen dissemination routes and the extent, timing, and nature of host bottlenecks provides valuable understanding of host-pathogen interactions but can be challenging to investigate experimentally (1). Although dissemination routes and population bottlenecks can, in principle, be determined by meticulous counting of the number of organisms at multiple sites over time, obtaining sufficient spatial and temporal resolution for such studies is often not possible.Experimental approaches that rely on inoculation of a population of distinguishable, rather than clonal, organisms have been developed to facilitate quantification of population bottlenecks (2-7). Sequence tag-based analysis of microbial populations (STAMP) (8) uses organisms that can be distinguished based on short-sequence barcodes integrated at a neutral position within their genome [also known as wild-type (wt) isogenic tags]. Barcoded organisms from infected animals are enumerated through deep sequencing, and STAMP combines this information with a mathematical framework from classical population genetics to quantify the founding population (N b ) at each infected site (i.e., the number of organis...

Contrast-induced acute renal injury (CI-AKI) has become a common cause of hospital-acquired renal failure. However, the development of prophylaxis strategies and approved therapies for CI-AKI is limited. Salvianolic acid B (SB) can treat cardiovascular-related diseases. The aim of the present study was to assess the effect of SB on prevention of CI-AKI and explore its underlying mechanisms. We examined its effectiveness of preventing renal injury in a novel CI-AKI rat model. Compared with saline, intravenous SB pretreatment significantly attenuated elevations in serum creatinine and the histological changes of renal tubular injuries, reduced the number of apoptosis-positive tubular cells, activated Nrf2, and lowered the levels of renal oxidative stress induced by iodinated contrast media. The above renoprotection of SB was abolished by the PI3K inhibitor (wortmannin). In HK-2 cells, SB activated Nrf2 and decreased the levels of oxidative stress induced by hydrogen peroxide and subsequently improved cell viability. The above cytoprotection of SB was blocked by the PI3K inhibitor (wortmannin) or siNrf2. Thus, our results demonstrate that, due to its antioxidant properties, SB has the potential to effectively prevent CI-AKI via the PI3K/Akt/Nrf2 pathway.

BackgroundRemote ischemic preconditioning (RIPC) is a promising approach to preventing acute kidney injury (AKI), but its efficacy is controversial.MethodsA systematic review of 30 randomized controlled trials was conducted to investigate the effects of RIPC on the incidence and outcomes of AKI. Random effects model meta-analyses and meta-regressions were used to generate summary estimates and explore sources of heterogeneity. The primary outcome was incidence of AKI and hospital mortality.ResultsThe total pooled incidence of AKI in the RIPC group was 11.5 %, significantly less than the 23.3 % incidence in the control group (P = 0.009). Subgroup analyses indicated that RIPC significantly reduced the incidence of AKI in the contrast-induced AKI (CI-AKI) subgroup from 13.5 % to 6.5 % (P = 0.000), but not in the ischemia/reperfusion-induced AKI (IR-AKI) subgroup (from 29.5 % to 24.7 %, P = 0.173). Random effects meta-regression indicated that RIPC tended to strengthen its renoprotective effect (q = 3.95, df = 1, P = 0.047) in these trials with a higher percentage of diabetes mellitus. RIPC had no significant effect on the incidence of stages 1–3 AKI or renal replacement therapy, change in serum creatinine and estimated glomerular filtration rate (eGFR), hospital or 30-day mortality, or length of hospital stay. But RIPC significantly increased the minimum eGFR in the IR-AKI subgroup (P = 0.006) compared with the control group. In addition, the length of ICU stay in the RIPC group was significantly shorter than in the control group (2.6 vs 2.0 days, P = 0.003).ConclusionsWe found strong evidence to support the application of RIPC to prevent CI-AKI, but not IR-AKI.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1272-y) contains supplementary material, which is available to authorized users.

New Findings r What is the central question of this study?Oxidative stress is known to play an important role in the development and progression of diabetic nephropathy. However, the mechanism of overproduction of reactive oxygen species (ROS) in high-glucose conditions is not completely clear. r What is the main finding and its importance?We demonstrated that high-glucose concentrations induced excessive production of ROS and stimulated the phosphoinositide 3-kinase-Akt-FoxO3a signalling pathway via the upregulation of transforming growth factor-β1, resulting in phosphorylation and inactivation of FoxO3a and a reduction in the expression of its target gene, FoxO3a-dependent manganese superoxide dismutase, and then further excessive production of ROS.Oxidative stress has been shown to play an important role in the development and progression of diabetic nephropathy, and the formation of reactive oxygen species (ROS) is a direct consequence of hyperglycaemia. We hypothesized that hyperglycaemia-induced ROS can activate the transforming growth factor-β1 (TGF-β1)-phosphoinositide 3-kinase (PI3K)-AktFoxO3a signalling pathway, negatively regulating expression of manganese superoxide dismutase (MnSOD), which promotes excessive ROS generation and accelerates the pathological process of diabetic nephropathy. In vitro, in rat mesangial cells, high glucose (30 mmol l −1 ), but not equimolar mannitol, stimulated ROS production, upregulated the levels of TGF-β1, increased the phosphorylated Akt/total Akt and phosphorylated FoxO3a/total FoxO3a protein ratios, altered the subcellular localization of FoxO3a and reduced the levels of MnSOD expression. These highglucose-induced changes further promoted the generation of ROS. In vivo, in db/db mice treated with an inhibitor of TGF-β1 (SB431542) or PI3K (LY294002), the levels of phosphorylated Akt and phosphorylated FoxO3a in the kidney cortices were decreased, the level of MnSOD expression was increased and the level of the lipid peroxidation end-product, malondialdehyde, was reduced. We conclude that overproduction of ROS induced by a high glucose concentration decreases the expression of MnSOD via the PI3K-Akt-FoxO3a pathway and further aggravates oxidative stress in diabetic nephropathy.Q.L. and Y.Z. contributed equally to this work.

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BackgroundParthenocarpy is an important trait for yield and quality in many plants. But due to its complex interactions with genetic and physiological factors, it has not been adequately understood and applied to breeding and production. Finding novel and effective quantitative trait loci (QTLs) is a critical step towards understanding its genetic mechanism. Cucumber (Cucumis sativus L.) is a typical parthenocarpic plant but the QTLs controlling parthenocarpy in cucumber were not mapped on chromosomes, and the linked markers were neither user-friendly nor confirmed by previous studies. Hence, we conducted a two-season QTL study of parthenocarpy based on the cucumber genome with 145 F2:3 families derived from a cross between EC1 (a parthenocarpic inbred line) and 8419 s-1 (a non-parthenocarpic inbred line) in order to map novel QTLs. Whole genome re-sequencing was also performed both to develop effective linked markers and to predict candidate genes.ResultsA genetic linkage map, employing 133 Simple Sequence Repeats (SSR) markers and nine Insertion/Deletion (InDel) markers spanning 808.1 cM on seven chromosomes, was constructed from an F2 population. Seven novel QTLs were identified on chromosomes 1, 2, 3, 5 and 7. Parthenocarpy 2.1 (Parth2.1), a QTL on chromosome 2, was a major-effect QTL with a logarithm of odds (LOD) score of 9.0 and phenotypic variance explained (PVE) of 17.0 % in the spring season and with a LOD score of 6.2 and PVE of 10.2 % in the fall season. We confirmed this QTL using a residual heterozygous line97-5 (RHL97-5). Effectiveness of linked markers of the Parth2.1 was validated in F3:4 population and in 21 inbred lines. Within this region, there were 57 genes with nonsynonymous SNPs/InDels in the coding sequence. Based on further combined analysis with transcriptome data between two parents, CsARF19, CsWD40, CsEIN1, CsPPR, CsHEXO3, CsMDL, CsDJC77 and CsSMAX1 were predicted as potential candidate genes controlling parthenocarpy.ConclusionsA major-effect QTL Parth2.1 and six minor-effect QTLs mainly contribute to the genetic architecture of parthenocarpy in cucumber. SSR16226 and Indel-T-39 can be used in marker-assisted selection (MAS) of cucumber breeding. Whole genome re-sequencing enhances the efficiency of polymorphic marker development and prediction of candidate genes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0873-6) contains supplementary material, which is available to authorized users.

Listeria monocytogenes maintains capabilities for free-living growth in the environment and for intracellular replication in a wide range of hosts, including livestock and humans. Here, we characterized an enterocolitis model of foodborne L. monocytogenes infection. This work highlights a multiorgan trafficking circuit and reveals a fitness advantage for bacteria that successfully complete this cycle. Because virulence factors play critical roles in systemic dissemination and multiple bottlenecks occur as the bacterial population colonizes different tissue sites, this multiorgan trafficking circuit likely provides purifying selection of virulence genes. This study also serves as a foundation for future work using the L. monocytogenes-induced enterocolitis model to investigate the biology of L. monocytogenes in the intestinal environment.

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