Aminophospholipid Translocase TAT-1 Promotes Phosphatidylserine Exposure during C. elegans Apoptosis

SummaryPhospholipids are distributed asymmetrically across the plasma-membrane bilayer of eukaryotic cells: Phosphatidylserine (PS), phosphatidylethanolamine, and phosphoinositides are predominantly restricted to the inner leaflet, whereas phophatidylcholine and sphingolipids are enriched on the outer leaflet [1, 2]. Exposure of PS on the cell surface is a conserved feature of apoptosis and plays an important role in promoting the clearance of apoptotic cells by phagocytosis [3]. However, the molecular mechanism that drives PS exposure remains mysterious. To address this issue, we studied cell-surface changes during apoptosis in the nematode C. elegans. Here, we show that PS exposure can readily be detected on apoptotic C. elegans cells. We generated a transgenic strain expressing a GFP::Annexin V reporter to screen for genes required for this process. Although none of the known engulfment genes was required, RNAi knockdown of the putative aminophospholipid transporter gene tat-1 abrogated PS exposure on apoptotic cells. tat-1(RNAi) also reduced the efficiency of cell-corpse clearance, suggesting that PS exposure acts as an “eat-me” signal in worms. We propose that tat-1 homologs might also play an important role in PS exposure in mammals

Engulfment of apoptotic cell corpses in the nematode C. elegans

Um zu verhindern, dass der Inhalt einer apoptotischen Zelle in Kontakt mit dem umliegenden Gewebe kommt und dort eventuell Schäden verursacht, werden apoptotische Zellen von anderen Zellen erkannt, umschlossen und eliminiert. Dieser Prozess wird Engulfment oder Phagozytose genannt. Im Nematoden C. elegans führt ein Defekt in einem Phagozytose Gen zu einer verzögerten Elimination der apoptotischen Zellen. Indem die Persistenz apoptotischer Zellen in verschiedenen Phagozytose Mutanten systematisch analysiert wurde, konnte gezeigt werden, dass zusätzliche, bis lang nicht identifizierte, Phagozytose Gene bei der Elimination apoptotischer Zellen eine Rolle spielen. Um neue Phagozytose Gene zu identifizieren, wurde eine genetische Mutagenese in ced-7 defekten Hermaphroditen durchgeführt. Es wurden acht Mutationen isoliert, die sich jedoch als neue Allele von bereits bekannten Phagozytose Genen erwiesen. In Metazoen wird das Vorhandensein von Phosphatidylserin (PS) auf der Zelloberfläche als charakteristischer Marker für apoptotische Zellen angesehen. Es wird angenommen, dass exponiertes PS als Signal für die Phagozytose dient. Bis jetzt war jedoch nicht bekannt, ob PS auch auf der Zelloberfläche von apoptotischen Zellen in C. elegans vorkommt. Mit Hilfe eines Reporterkonstruktes konnte in vivo gezeigt werden, dass PS auch in C. elegans an die Oberfläche von apoptotischen Zellen transportiert wird. Die Analyse von potentiellen Regulatoren dieses Prozesses führte zur Entdeckung von tat-1, dessen Funktion für die Translokation von PS in apoptotischen Zellen benötigt wird. In order to prevent leakage of potentially harmful intracellular contents into the surrounding tissues, apoptotic cells are recognised and rapidly removed by other cells, a process termed engulfment. In the nematode C. elegans mutation of any known engulfment gene results in unengulfed cell corpses that persist for hours, or even days. Kinetic analysis of persistent cell corpse removal in engulfment-defective mutants provided further evidence for the existence of additional, as yet unidentified, engulfment genes. In order to identify novel engulfment genes a genetic screen in a sensitised ced-7 mutant background was performed. Using this approach, eight independent mutations were found that result in defective cell corpse removal. However, all mutations turned out to be novel alleles of already known engulfment genes. In metazoans exposure of phosphatidylserine (PS) has been considered a hallmark of apoptotic cells. However, it was not known so far whether apoptotic cells in C. elegans expose PS as well. By using a novel in vivo approach, it could be shown that dying cells in C. elegans expose PS. Analysis of potential regulators of this process revealed an important function for TAT-1 in the translocation of PS from the inner to the outer plasma membrane of apoptotic cells. Ablating the function of tat-1 impaired PS exposure on apoptotic cells and increased the number of unengulfed apoptotic cell corpses in C. elegans

A pilot test of the new Swiss regulatory procedure for categorizing clinical trials by risk: A randomized controlled trial

BACKGROUND/AIMS Several countries are working to adapt clinical trial regulations to align the approval process to the level of risk for trial participants. The optimal framework to categorize clinical trials according to risk remains unclear, however. Switzerland is the first European country to adopt a risk-based categorization procedure in January 2014. We assessed how accurately and consistently clinical trials are categorized using two different approaches: an approach using criteria set forth in the new law (concept) or an intuitive approach (ad hoc). METHODS This was a randomized controlled trial with a method-comparison study nested in each arm. We used clinical trial protocols from eight Swiss ethics committees approved between 2010 and 2011. Protocols were randomly assigned to be categorized in one of three risk categories using the concept or the ad hoc approach. Each protocol was independently categorized by the trial's sponsor, a group of experts and the approving ethics committee. The primary outcome was the difference in categorization agreement between the expert group and sponsors across arms. Linear weighted kappa was used to quantify agreements, with the difference between kappas being the primary effect measure. RESULTS We included 142 of 231 protocols in the final analysis (concept = 78; ad hoc = 64). Raw agreement between the expert group and sponsors was 0.74 in the concept and 0.78 in the ad hoc arm. Chance-corrected agreement was higher in the ad hoc (kappa: 0.34 (95% confidence interval = 0.10-0.58)) than in the concept arm (0.27 (0.06-0.50)), but the difference was not significant (p = 0.67). LIMITATIONS The main limitation was the large number of protocols excluded from the analysis mostly because they did not fit with the clinical trial definition of the new law. CONCLUSION A structured risk categorization approach was not better than an ad hoc approach. Laws introducing risk-based approaches should provide guidelines, examples and templates to ensure correct application

Nurses' and Physicians' Perceptions of Indwelling Urinary Catheter Practices and Culture in Their Institutions.

OBJECTIVES Indwelling urinary catheters (IUCs) are commonly used devices in acute care that may lead to catheter-associated urinary tract infections or noninfectious complications. Responsibilities for IUC are usually shared between nurses and physicians, and a common mental model among the two professional groups is thus essential for a successful reduction in catheter use. The aim of this study was to determine variation in the perceptions of current practices and culture regarding IUC use between these two groups. METHODS Nurses and physicians (N = 1579) from seven Swiss hospitals completed a written survey on safe IUC use in their institution. The survey assessed participant's perceptions of current practices and culture in their institution, and their perceived responsibilities related to IUC care. t tests and logistic regression were used to examine differences in responses between physicians and nurses. RESULTS Nurses and physicians each have their own tasks but also share responsibilities for catheter placement, care, and removal. Overall, nurses were more positive than physicians about current practices and culture regarding IUC use within their institution (mean scale scores = 5.4 for nurses versus 5.1 for physicians, P < 0.001). Perceptions of the two professional groups diverged most strongly on practices to avoid unnecessary placement of IUCs, the presence of shared values and attitudes in support of restrictive catheter use, and the other group's leadership commitment. CONCLUSIONS Indwelling urinary catheter management is a strong interprofessional domain and a shared responsibility. It is crucial that measures to raise awareness and to communicate new standards target both nurses and physicians and are discussed in interprofessional formats.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal

Impact of an evidence-based intervention on urinary catheter utilization, associated process indicators, and infectious and non-infectious outcomes.

BACKGROUND Multicentre intervention studies tackling urinary catheterization and its infections and non-infectious complications are lacking. AIM To decrease urinary catheterization and consequently catheter-associated urinary tract infections (CAUTI) and non-infectious complications. METHODS Before/after non-randomized multicenter intervention study in seven hospitals in Switzerland. Intervention bundle consisting of 1) a concise list of indications for urinary catheterization, 2) daily evaluation of the need for ongoing catheterization, and 3) education on proper insertion and maintenance of urinary catheters. The primary outcome was urinary catheter utilization. Secondary outcomes were CAUTI, non-infectious complications, and process indicators such as proportion of indicated catheters and frequency of catheter evaluation. FINDINGS We included 25,880 patients [13,171 before the intervention (August-October 2016) and 12,709 after the intervention (August-October 2017)]. Catheter utilization dropped from 23.7% to 21.0% (p=0.001), and catheter-days per 100 patient-days from 17.4 to 13.5 (p=0.167). CAUTI remained stable on a low level with 0.02 infections per 100 patient-days (before) and 0.02 infections (after), (p=0.98). Measuring infections per 1,000 catheter-days, the rate was 1.02 (before) and 1.33 (after), (p=0.60). Non-infectious complications dropped significantly, from 0.79 to 0.56 events per 100 patient-days (p<0.001), and from 39.4 to 35.4 events per 1,000 catheter-days (p=0.23). Indicated catheters increased from 74.5% to 90.0% (p<0.001). Reevaluations increased from 168 to 624 per 1,000 catheter-days (p<0.001). CONCLUSION A straightforward bundle of three evidence-based measures reduced catheter utilization and non-infectious complications, whereas the proportion of indicated urinary catheters and daily evaluations increased. The CAUTI rate remained unchanged, albeit on a very low level

Change in staff perspectives on indwelling urinary catheter use after implementation of an intervention bundle in seven Swiss acute care hospitals: results of a before/after survey study

OBJECTIVE To evaluate changes in staff perspectives towards indwelling urinary catheter (IUC) use after implementation of a 1-year quality improvement project. DESIGN Repeated cross-sectional survey at baseline (October 2016) and 12-month follow-up (October 2017). SETTING Seven acute care hospitals in Switzerland. PARTICIPANTS The survey was targeted at all nursing and medical staff members working at the participating hospitals at the time of survey distribution. A total of 1579 staff members participated in the baseline survey (T) (49% response rate) and 1527 participated in the follow-up survey (T) (47% response rate). INTERVENTION A multimodal intervention bundle, consisting of an evidence-based indication list, daily re-evaluation of ongoing catheter need and staff training, was implemented over the course of 9 months. MAIN OUTCOME MEASURES Staff knowledge (15 items), perception of current practices and culture (scale 1-7), self-reported responsibilities (multiple-response question) and determinants of behaviour (scale 1-7) before and after implementation of the intervention bundle. RESULTS The mean number of correctly answered knowledge questions increased significantly between the two survey periods (T: 10.4, T: 11.0; p<0.001). Self-reported responsibilities with regard to IUC management by nurses and physicians changed only slightly over time. Perception of current practices and culture in regard to safe urinary catheter use increased significantly (T: 5.3, T: 5.5; p<0.001). Significant changes were also observed for determinants of behaviour (T: 5.3, T: 5.6; p<0.001). CONCLUSION We found small but significant changes in staff perceptions after implementation of an evidence-based intervention bundle. Efforts now need to be targeted at sustaining and reinforcing these changes, so that restrictive use of IUCs becomes an integral part of the hospital culture

Change in staff perspectives on indwelling urinary catheter use after implementation of an intervention bundle in seven Swiss acute care hospitals: results of a before/after survey study.

OBJECTIVE To evaluate changes in staff perspectives towards indwelling urinary catheter (IUC) use after implementation of a 1-year quality improvement project. DESIGN Repeated cross-sectional survey at baseline (October 2016) and 12-month follow-up (October 2017). SETTING Seven acute care hospitals in Switzerland. PARTICIPANTS The survey was targeted at all nursing and medical staff members working at the participating hospitals at the time of survey distribution. A total of 1579 staff members participated in the baseline survey (T0) (49% response rate) and 1527 participated in the follow-up survey (T1) (47% response rate). INTERVENTION A multimodal intervention bundle, consisting of an evidence-based indication list, daily re-evaluation of ongoing catheter need and staff training, was implemented over the course of 9 months. MAIN OUTCOME MEASURES Staff knowledge (15 items), perception of current practices and culture (scale 1-7), self-reported responsibilities (multiple-response question) and determinants of behaviour (scale 1-7) before and after implementation of the intervention bundle. RESULTS The mean number of correctly answered knowledge questions increased significantly between the two survey periods (T0: 10.4, T1: 11.0; p<0.001). Self-reported responsibilities with regard to IUC management by nurses and physicians changed only slightly over time. Perception of current practices and culture in regard to safe urinary catheter use increased significantly (T0: 5.3, T1: 5.5; p<0.001). Significant changes were also observed for determinants of behaviour (T0: 5.3, T1: 5.6; p<0.001). CONCLUSION We found small but significant changes in staff perceptions after implementation of an evidence-based intervention bundle. Efforts now need to be targeted at sustaining and reinforcing these changes, so that restrictive use of IUCs becomes an integral part of the hospital culture