Reconstitution of a minimal ESX-5 type VII secretion system suggests a role for PPE proteins in the outer membrane transport of proteins.

Mycobacteria utilize type VII secretion systems (T7SSs) to secrete proteins across their highly hydrophobic and diderm cell envelope. Pathogenic mycobacteria have up to five different T7SSs, called ESX-1 to ESX-5, which are crucial for growth and virulence. Here, we use a functionally reconstituted ESX-5 system in the avirulent species Mycobacterium smegmatis that lacks ESX-5, to define the role of each esx-5 gene in system functionality. By creating an array of gene deletions and assessing protein levels of components and membrane complex assembly, we observed that only the five components of the inner membrane complex are required for its assembly. However, in addition to these five core components, active secretion also depends on both the Esx and PE/PPE substrates. Tagging the PPE substrates followed by subcellular fractionation, surface labeling and membrane extraction showed that these proteins localize to the mycobacterial outer membrane. This indicates that they could play a role in secretion across this enigmatic outer barrier. These results provide the first full overview of the role of each esx-5 gene in T7SS functionality. IMPORTANCE Pathogenic mycobacteria, such as the notorious Mycobacterium tuberculosis, are highly successful as pathogens, in part due to their specific and diderm cell envelope, with a mycolic acid-containing outer membrane. The architecture of this highly impermeable membrane is little understood and the proteins that populate it even less so. To transport proteins across their cell envelope, mycobacteria employ a specialized transport pathway called type VII secretion. While recent studies have elucidated the type VII secretion membrane channel that mediates transport across the inner membrane, the identity of the outer membrane channel remains a black box. Here, we show evidence that specific substrates of the type VII pathway could form these channels. Elucidating the pathway and mechanism of protein secretion through the mycobacterial outer membrane will allow its exploitation for the development of novel mycobacterial therapeutics.

Cohort profile: the PHARMO Perinatal Research Network (PPRN) in the Netherlands: a population-based mother-child linked cohort.

PURPOSE: Observational population-based research is a very suitable non-invasive method for studies in the vulnerable populations of pregnant women and children. Therefore, the PHARMO Perinatal Research Network (PPRN) was set up as a resource for life course perinatal and paediatric research by linking population-based data from existing registrations. PARTICIPANTS: From 1999 to 2017, the PPRN captures approximately 542 900 pregnancies of 387 100 mothers ('Pregnancy Cohort'). Additionally, mother-child linkage is currently available for a quarter of these pregnancies ('Child Cohort'). The PPRN contains preconceptional information on maternal healthcare, as well as detailed pregnancy and neonatal data, extending into long-term follow-up and outcomes after birth for both mother and child up to nearly 20 years. It includes linked data from different primary and secondary healthcare settings. FINDINGS TO DATE: Through record linkage of the Netherlands Perinatal Registry and the PHARMO Database Network, we have established a large population-based research network including data on demographics, medication use, medical conditions and details concerning labour, birth and neonatal outcomes. Here, we provide an overview of record types available from the PPRN, available database follow-up and pregnancy characteristics of the PPRN cohorts. The PPRN has been used for a number of different pharmacoepidemiological studies, for example, to confirm that preterm-born infants were more likely than full-term infants to be hospitalised or use medication. Similar long-term comparisons showed that children born following spontaneous preterm labour were at increased risk of neurodevelopmental and respiratory conditions. Most recently, the PPRN provided important evidence on the trends in use of potentially harmful medication during pregnancy. FUTURE PLANS: The PPRN provides a unique and rich data set facilitating large-scale observational pharmacoepidemiological perinatal research. The patient-level linkage of many different healthcare data sources allows for long-term follow-up of mother and child, with ongoing annual updates.

Structure and Function of the Mycobacterial Type VII Secretion Systems.

Bacteria have evolved intricate secretion machineries for the successful delivery of large molecules across their cell envelopes. Such specialized secretion systems allow a variety of bacteria to thrive in specific host environments. In mycobacteria, type VII secretion systems (T7SSs) are dedicated protein transport machineries that fulfill diverse and crucial roles, ranging from metabolite uptake to immune evasion and subversion to conjugation. Since the discovery of mycobacterial T7SSs about 15 y ago, genetic, structural, and functional studies have provided insight into the roles and functioning of these secretion machineries. Here, we focus on recent advances in the elucidation of the structure and mechanism of mycobacterial T7SSs in protein secretion. As many of these systems are essential for mycobacterial growth or virulence, they provide opportunities for the development of novel therapies to combat a number of relevant mycobacterial diseases.

Diagnostic performance of seven rapid IgG/IgM antibody tests and the Euroimmun IgA/IgG ELISA in COVID-19 patients.

OBJECTIVES: To evaluate the diagnostic performance of seven rapid IgG/IgM tests and the Euroimmun IgA/IgG ELISA for antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in COVID-19 patients. METHODS: Specificity was evaluated in 103 samples collected before January 2020. Sensitivity and time to seropositivity was evaluated in 167 samples from 94 patients with COVID-19 confirmed with RT-PCR on nasopharyngeal swab. RESULTS: Specificity (confidence interval) of lateral flow assays (LFAs) was ≥91.3% (84.0-95.5) for IgM, ≥90.3% (82.9-94.8) for IgG, and ≥85.4% (77.2-91.1) for the combination IgM OR IgG. Specificity of the ELISA was 96.1% (90.1-98.8) for IgG and only 73.8% (64.5-81.4) for IgA. Sensitivity 14-25 days after the onset of symptoms was between ≥92.1% (78.5-98.0) and 100% (95.7-100) for IgG LFA compared to 89.5% (75.3-96.4) for IgG ELISA. Positivity of IgM OR IgG for LFA resulted in a decrease in specificity compared to IgG alone without a gain in diagnostic performance, except for VivaDiag. The results for IgM varied significantly between the LFAs with an average overall agreement of only 70% compared to 89% for IgG. The average dynamic trend to seropositivity for IgM was not shorter than for IgG. At the time of hospital admission the sensitivity of LFA was <60%. CONCLUSIONS: Sensitivity for the detection of IgG antibodies 14-25 days after the onset of symptoms was ≥92.1% for all seven LFAs compared to 89.5% for the IgG ELISA. The results for IgM varied significantly, and including IgM antibodies in addition to IgG for the interpretation of LFAs did not improve the diagnostic performance.

Trends in mortality, cardiovascular complications, and risk factors in type 2 diabetes.

BACKGROUND: Quality of diabetes care in the Netherlands ranked second in the Euro Diabetes Index 2014, but data on outcomes are lacking. We assessed trends in cardiovascular disease and mortality among type 2 diabetes (T2DM) patients in the context of risk factor control. METHODS: Annual cohorts of adult T2DM patients were constructed from the PHARMO Database Network. Age-standardised mortality rates and incidence rates (IR) of hospitalisations for acute myocardial infarction (AMI), stroke, and congestive heart failure (CHF) were compared with a diabetes-free population matched on age, sex, and general practitioner. Life years lost (LYL) to T2DM or cardiovascular disease were determined by comparing life expectancy between matched groups. Proportions attaining glycated haemoglobin (HbA1c), blood pressure (BP), and low-density lipoprotein cholesterol (LDL-C) goals were assessed annually. RESULTS: Among 53,602 T2DM patients, slight increases in IR between 2008 and 2016 were proportional to those in diabetes-free controls; on average T2DM increased the risk of mortality by 86%, hospitalisation for AMI 69%, stroke 57%, and CHF 185%. At age 55, LYL to T2DM averaged 3.5 years and established CVD added 1.8 years, irrespective of sex. HbA1c goal attainment increased from 58% to 65%, LDL-C from 56% to 65%, and systolic BP from 57% to 72%. CONCLUSION: Despite highly organised diabetes care, excess incident cardiovascular events and mortality due to T2DM did not decrease over the study period. Life expectancy of T2DM patients is significantly reduced and risk factor control is suboptimal. This suggests there is considerable room for improvement of diabetes care in the Netherlands.

Chemotherapy for ovarian cancer in the Netherlands: a population-based study on treatment patterns and outcomes.

Information on treatment patterns for ovarian cancer (OC) is limited. The aim of this study was to describe current patterns of chemotherapy and other systemic treatments for OC in the Netherlands and evaluate survival outcomes following subsequent lines of treatment. Data from the Eindhoven Cancer Registry, including on newly diagnosed cancer patients, were linked to the PHARMO Database Network, including information on in- and out-patient drug use. Patients diagnosed with OC between January 2000 and December 2010 were selected. An algorithm was used to identify separate lines of treatment. Data were studied descriptively. Detailed data on systemic drug use were available for 261 patients (17%) with OC. In first-line treatment, 87% of the patients (227/261) received platinum-based chemotherapy. Of the 161 patients receiving second-line treatment, 101 patients (63%) received platinum-based chemotherapy. In third line, this was 51% (53/103). The median number of treatment lines received by patients was two (interquartile range 1-3), and eight or more lines of chemotherapy were identified for 12 patients. Median survival from diagnosis onwards was 47 months from the end of first-line treatment, median survival was 32 months, and from the end of second-line treatment, it was 14 months. Predominantly beyond second-line treatment, there is much variety in treatment patterns with chemotherapy for OC. Although uncertainty remains regarding the desirability of this observed treatment variation, there seems a need for detailed clinical guidance, assuring that physicians can properly choose the most suitable treatment for each patient.

Screening for renal involvement in ANCA-associated vasculitis: room for improvement?

BACKGROUND: Renal involvement in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) requires prompt and aggressive immunosuppressive therapy. The aim of this study was to evaluate screening practice for renal involvement in AAV and its potential effect on renal outcomes. METHODS: Between 2005 and 2015, ANCA-positive AAV patients in a teaching hospital in the Netherlands were retrospectively included. Complete screening for renal involvement was defined as: assessment of erythrocyturia, proteinuria and serum creatinine within two weeks of the diagnosis of AAV. Characteristics at presentation and at 12 months were compared between patients with and without complete screening. RESULTS: A total of 109 AAV patients (63% male) were identified with a mean age of 62 ±; 14 years. Complete screening for renal involvement was performed in 90 of the 109 patients (83%). Patients with incomplete screening had a lower serum creatinine (86 ±; 53 vs. 190 ±; 185 µmol/l, p < 0.001) and were more often diagnosed outside the renal department (100% vs. 78%, p = 0.02). Three patients with incomplete screening had a rise in serum creatinine of ≥ 30% at 12 months. Incomplete screening was not associated with the development of end-stage renal disease. Urine analysis of patients with renal biopsy-proven AAV (n = 31) showed erythrocyturia in 58% after one sample and in 94% after three samples. CONCLUSION: Screening for renal involvement in AAV was suboptimal, primarily in patients who presented outside the renal department. A higher sensitivity for erythrocyturia is achieved if urine analysis is repeated. Incomplete screening may lead to renal impairment if renal involvement is not treated appropriately.

The influence of phosphate, calcium and magnesium on matrix Gla-protein and vascular calcification: a systematic review.

Vitamin K-dependent matrix Gla protein (MGP) is a key inhibitor of vascular calcification (VC). MGP is synthesized by chondrocytes and vascular smooth muscle cells (VSMC) and the absence or inactivity of MGP results in excessive calcification of both growth plate and vasculature. Apart from its vitamin K dependency little is known about other factors that influence MGP metabolism. Phosphate, calcium and magnesium are involved in bone mineralization and play an important role in VC. In this review we provide a summary of the effect of phosphate, calcium, and magnesium on MGP metabolism. Elevated phosphate and calcium levels promote VC, in part by increasing the release of matrix vesicles (MV) that under the influence of calcium and phosphate become calcification competent. Phosphate and calcium simultaneously induce an upregulation of MGP protein and gene expression, which possibly inhibits calcification. Elevated phosphate levels did not change MGP protein levels in MV. On the contrary, elevated calcium concentrations caused a decrease of MGPloading in MV, which might in part explainthe calcifying effects of MV. Magnesium is a known inhibitor of VC. However, magnesium has been shown to have an inhibitory effect on MGP synthesis induced through downregulation of the calcium-sensing receptor and hereby causing a decrease in calcium induced MGP upregulation. There might also be stimulatory effect of magnesium on MGP in which the TRPM7 channel is involved. In conclusion there is a clear interaction between MGP and phosphate, calcium and magnesium. The upregulation of MGP by phosphate and calcium might be a cellular response that possibly results in the mitigation of VC.

Exploring the performance of the National Early Warning Score (NEWS) in a European emergency department.

BACKGROUND: Several triage systems have been developed for use in the emergency department (ED), however they are not designed to detect deterioration in patients. Deteriorating patients may be at risk of going undetected during their ED stay and are therefore vulnerable to develop serious adverse events (SAEs). The national early warning score (NEWS) has a good ability to discriminate ward patients at risk of SAEs. The utility of NEWS had not yet been studied in an ED. OBJECTIVE: To explore the performance of the NEWS in an ED with regard to predicting adverse outcomes. DESIGN: A prospective observational study. Patients Eligible patients were those presenting to the ED during the 6 week study period with an Emergency Severity Index (ESI) of 2 and 3 not triaged to the resuscitation room. INTERVENTION: NEWS was documented at three time points: on arrival (T0), hour after arrival (T1) and at transfer to the general ward/ICU (T2). The outcomes of interest were: hospital admission, ICU admission, length of stay and 30 day mortality. RESULTS: A total of 300 patients were assessed for eligibility. Complete data was able to be collected for 274 patients on arrival at the ED. NEWS was significantly correlated with patient outcomes, including 30 day mortality, hospital admission, and length of stay at all-time points. CONCLUSION: The NEWS measured at different time points was a good predictor of patient outcomes and can be of additional value in the ED to longitudinally monitor patients throughout their stay in the ED and in the hospital.

Analysis of the urinary glucose-[¹5N, ¹5N]-ureide content in the study of the lactose-[¹5N, ¹5N]-ureide metabolism in healthy humans.

BACKGROUND/OBJECTIVES: Lactose-[(15)N, (15)N]-ureide is used to study the fate of the colonic urea-nitrogen metabolism. During the passage through the gastrointestinal tract, lactose ureide is hydrolysed to glucose ureide, which is absorbed to a limited extent from the small intestine and is excreted urinarily. In the present study, a procedure has been developed to quantify the urinary excretion of glucose-[(15)N, (15)N]-ureide. In addition, urine and faecal samples obtained during a dietary intervention study with the prebiotic lactulose were retrospectively analysed. SUBJECTS/METHODS: The glucose ureide and lactose ureide content was measured by GC-MS in 19 healthy volunteers. After consumption of a standard test meal containing 75 mg lactose-[(15)N, (15)N]-ureide, six healthy volunteers performed a fractionated 24 h urine collection to investigate the urinary excretion of glucose-[(15)N, (15)N]-ureide. In 13 volunteers, the effect of lactulose administration on the urinary excretion of glucose-[(15)N, (15)N]-ureide was analysed. RESULTS: The urinary excretion of glucose-[(15)N, (15)N]-ureide reached its maximum level in the 3-6 h urine collection and decreased in the 6-9 h urine. The label was still detectable in the 9-24 h urine collection. The cumulative excretion of (15)N-labelled glucose ureide after 24 h amounted 12.91%. No significant differences in glucose-[(15)N, (15)N]-ureide excretion were found in either of the urine fractions after administration of lactulose, compared with baseline. In none of the urine samples lactose-[(15)N, (15)N]-ureide was detected. CONCLUSIONS: In conclusion, the results obtained in the present study indicated that the percentage dose glucose-[(15)N, (15)N]-ureide recovered in urine is rather constant and not influenced by the presence of lactulose.

Seasonal effects on the nasolabial skin condition.

In the present work, nasolabial skin condition and the influence of seasonal changes during autumn and winter were studied in 16 healthy female volunteers. Apart from visual scoring of erythema and skin scaliness, transepidermal water loss (TEWL), skin hydration, apparent skin pH, skin colour and skin desquamation were biophysically measured. The study results showed that nasolabial TEWL was significantly higher during wintertime than in autumn. Also skin colour measurements and squamometry scorings revealed higher values, indicating a more reddish and scaly nasolabial skin during winter compared to autumn. Results from tape stripping and skin surface lipid analysis by high-performance thin-layer chromatography demonstrated significant differences for triglycerides and cholesterol esters, indicating a functionally inferior hydrolipidic layer during the winter season.

Epidermal ceramidase activity regulates epidermal desquamation via stratum corneum acidification.

The acidic pH of the outer surface of the mammalian skin plays several important roles in the epidermal barrier function. The 2 endogenous pathways that are currently known to elicit this acidic pH are the generation of free fatty acids from phospholipids and the exchange of protons for sodium ions by non-energy-dependent sodium-proton exchangers. In this study, we propose a third endogenous pathway, i.e. epidermal ceramidase activity, generating free fatty acids from ceramides. By topical application of N-oleylethanolamine, a well-known ceramidase inhibitor, we could demonstrate a significant increase in the stratum corneum pH and a corresponding decrease in the epidermal free fatty acid content. Moreover, we could show that the resulting change in the apparent skin pH also provoked a delay in early barrier recovery and an increased epidermal desquamation, corresponding to earlier observations made for the already known endogenous mechanisms.

Effect of dietary intervention with different pre- and probiotics on intestinal bacterial enzyme activities.

OBJECTIVE: To investigate the influence of different pre- and probiotics on faecal beta-glucuronidase and beta-glucosidase activity, as one of the claimed beneficial effects of pre- and probiotics is the hypothesis that these substrates are able to reduce the production of toxic and carcinogenic metabolites by suppressing specific enzyme activities in the colon. SETTING: Department of Gastrointestinal Research, University Hospital Gasthuisberg, KU Leuven, Belgium. DESIGN AND SUBJECTS: The effect was evaluated in a randomized, crossover study in 53 healthy volunteers who were randomly assigned to one of five treatment groups. INTERVENTIONS: At the start and after a 4-week treatment period, the healthy volunteers collected faeces during 72 h. Lactulose and oligofructose-enriched inulin (OF-IN) were chosen as prebiotics, whereas Lactobacillus casei Shirota, Bifidobacterium breve and Saccharomyces boulardii were selected as probiotics. Two synbiotic combinations were evaluated as well. The enzyme activity was assessed spectrophotometricly. RESULTS: Lactulose and OF-IN significantly decreased beta-glucuronidase activity, whereas a tendency to a decreased beta-glucuronidase activity was observed after L. casei Shirota and B. breve intake. To the contrary, B. breve increased beta-glucosidase levels. Supplementation with the synbiotic did not appear to be more beneficial than either compound alone. No influence of S. boulardii was noted. CONCLUSIONS: Administration of lactulose, OF-IN, L. casei Shirota or B. breve resulted in a decrease of the beta-glucuronidase activity, which is considered beneficial for the host.

Kinetic characteristics of acidic and alkaline ceramidase in human epidermis.

It has recently become evident that at least five ceramidase (CDase) isoforms are present in human epidermis, and that specifically acidic CDase (aCDase) and alkaline CDase (alkCDase) activities increase during keratinocyte differentiation, and thus might play a pivotal role(s) in permeability barrier function. Prior to investigating their possible roles in the epidermal barrier function, it is necessary to characterize basic kinetic parameters for these enzymes, as well as to determine the effects of the established CDase inhibitors and their activities. In this study, assays for both aCDase and alkCDase activities in fully differentiated human epidermis were optimized using a radiolabeled substrate. These studies revealed that aCDase activity is substantially higher than alkCDase activity, and that both isoenzymes are inhibited by a CDase inhibitor N-oleylethanolamine. These findings were also confirmed using an in situ enzyme assay.

A keratinocyte's course of life.

An adequate permeability barrier function of the mammalian epidermis is guaranteed by the characteristic architecture of the stratum corneum. This uppermost layer consists of a highly organized extracellular lipid compartment which is tightly joined to the corneocytes. The generation of the extracellular lipid compartment and the transformation of the keratinocytes into corneocytes are the main features of epidermal differentiation. However, equally important is the continuous renewal of the stratum corneum, which is insured by a careful balance between the replenishment of new keratinocytes from the proliferating basal layer, and the well-orchestrated loss of the most superficial cells after the so-called 'epidermal programmed cell death'. In this overview, the complete life of keratinocytes is described, from the proliferative organization to the process of desquamation.

Analysis of epidermal lipids of the healthy human skin: factors affecting the design of a control population.

The intervariability of studies on the lipids of human epidermis and stratum corneum is high because of the different origin of the skin samples and the variety of extraction methods used. In the present work, a high-performance thin-layer chromatographic technique has been used to study the parameters age, sex, and anatomical site for their effects on the lipid profiles recovered from healthy epidermal skin biopsy specimens. It was found that sex-related differences were seen at the level of the total ceramide concentration. Observed decreases in lipid concentration, due to ageing, depended on the anatomical site. Therefore, these variables should be controlled in a reproducible and standardized way in order to be able to study the direct relationship between skin condition and barrier lipid composition. Only when this relation is established, results of topical treatment can be scientifically evaluated.

Reconstitution of Sec-dependent membrane protein insertion: nascent FtsQ interacts with YidC in a SecYEG-dependent manner.

The inner membrane protein YidC is associated with the preprotein translocase of Escherichia coli and contacts transmembrane segments of nascent inner membrane proteins during membrane insertion. YidC was purified to homogeneity and co-reconstituted with the SecYEG complex. YidC had no effect on the SecA/SecYEG-mediated translocation of the secretory protein proOmpA; however, using a crosslinking approach, the transmembrane segment of nascent FtsQ was found to gain access to YidC via SecY. These data indicate the functional reconstitution of the initial stages of YidC-dependent membrane protein insertion via the SecYEG complex.

Nascent Lep inserts into the Escherichia coli inner membrane in the vicinity of YidC, SecY and SecA.

Targeting and assembly of the Escherichia coli inner membrane protein leader peptidase (Lep) was studied using a homologous in vitro targeting/translocation assay. Assembly of full-length Lep was efficient in the co-translational presence of membrane vesicles and hardly occurred when membranes were added post-translationally. This is consistent with the signal recognition particle-dependent targeting of Lep. Crosslinking experiments showed that the hydrophilic region P1 of nascent membrane-inserted Lep 100-mer was in the vicinity of SecA and SecY, whereas the first transmembrane domain H1 was in the vicinity of YidC. These results suggested that YidC, together with the Sec translocase, functions in the assembly of Lep. YidC might be a more generic component in the assembly of inner membrane proteins.

Transcription regulation of the nir gene cluster encoding nitrite reductase of Paracoccus denitrificans involves NNR and NirI, a novel type of membrane protein.

The nirIX gene cluster of Paracoccus denitrificans is located between the nir and nor gene clusters encoding nitrite and nitric oxide reductases respectively. The NirI sequence corresponds to that of a membrane-bound protein with six transmembrane helices, a large periplasmic domain and cysteine-rich cytoplasmic domains that resemble the binding sites of [4Fe-4S] clusters in many ferredoxin-like proteins. NirX is soluble and apparently located in the periplasm, as judged by the predicted signal sequence. NirI and NirX are homologues of NosR and NosX, proteins involved in regulation of the expression of the nos gene cluster encoding nitrous oxide reductase in Pseudomonas stutzeri and Sinorhizobium meliloti. Analysis of a NirI-deficient mutant strain revealed that NirI is involved in transcription activation of the nir gene cluster in response to oxygen limitation and the presence of N-oxides. The NirX-deficient mutant transiently accumulated nitrite in the growth medium, but it had a final growth yield similar to that of the wild type. Transcription of the nirIX gene cluster itself was controlled by NNR, a member of the family of FNR-like transcriptional activators. An NNR binding sequence is located in the middle of the intergenic region between the nirI and nirS genes with its centre located at position -41.5 relative to the transcription start sites of both genes. Attempts to complement the NirI mutation via cloning of the nirIX gene cluster on a broad-host-range vector were unsuccessful, the ability to express nitrite reductase being restored only when the nirIX gene cluster was reintegrated into the chromosome of the NirI-deficient mutant via homologous recombination in such a way that the wild-type nirI gene was present directly upstream of the nir operon.