SummaryConditions that impair protein folding in the Gramnegative bacterial envelope cause stress. The destabilizing effects of stress in this compartment are recognized and countered by a number of signal transduction mechanisms. Data presented here reveal another facet of the complex bacterial stress response, release of outer membrane vesicles. Native vesicles are composed of outer membrane and periplasmic material, and they are released from the bacterial surface without loss of membrane integrity. Here we demonstrate that the quantity of vesicle release correlates directly with the level of protein accumulation in the cell envelope. Accumulation of material occurs under stress, and is exacerbated upon impairment of the normal housekeeping and stress-responsive mechanisms of the cell. Mutations that cause increased vesiculation enhance bacterial survival upon challenge with stressing agents or accumulation of toxic misfolded proteins. Preferential packaging of a misfolded protein mimic into vesicles for removal indicates that the vesiculation process can act to selectively eliminate unwanted material. Our results demonstrate that production of bacterial outer membrane vesicles is a fully independent, general envelope stress response. In addition to identifying a novel mechanism for alleviating stress, this work provides physiological relevance for vesicle production as a protective mechanism.

It has been long noted that gram-negative bacteria produce outer membrane vesicles, and recent data demonstrate that vesicles released by pathogenic strains can transmit virulence factors to host cells. However, the mechanism of vesicle release has remained undetermined. This genetic study addresses whether these structures are merely a result of membrane instability or are formed by a more directed process. To elucidate the regulatory mechanisms and physiological basis of vesiculation, we conducted a screen in Escherichia coli to identify gene disruptions that caused vesicle over-or underproduction. Only a few low-vesiculation mutants and no null mutants were recovered, suggesting that vesiculation may be a fundamental characteristic of gram-negative bacterial growth. Gene disruptions were identified that caused differences in vesicle production ranging from a 5-fold decrease to a 200-fold increase relative to wild-type levels. These disruptions included loci governing outer membrane components and peptidoglycan synthesis as well as the E cell envelope stress response. Mutations causing vesicle overproduction did not result in upregulation of the ompC gene encoding a major outer membrane protein. Detergent sensitivity, leakiness, and growth characteristics of the novel vesiculation mutant strains did not correlate with vesiculation levels, demonstrating that vesicle production is not predictive of envelope instability.Release of outer membrane (OM) vesicles has been observed for all gram-negative bacteria studied to date (reviewed in references 5, 15, and 16). Native vesicles are rounded structures with lumenal periplasmic components bounded by an outer layer of outer membrane proteins (Omps) and lipids (16). For Escherichia coli, our laboratory has reported that strain DH5␣ releases 0.23% of Omps F and C and 0.14% of OmpA into vesicles (12); other investigators have found vesicles to account for 0.2 to 0.5% of bacterial culture material (9,20). Electron microscopy studies reveal bulging of the OM and subsequent fission of vesicles containing electron-dense material (16). These biochemical and microscopic observations suggest that OM vesicles are formed from protrusions that are pinched off from the OM in a manner that leads to the inclusion of periplasmic material.The wide variety of strains and diversity of environments for which vesiculation has been observed suggest an important role for vesicle production in gram-negative bacterial growth and survival (5,15,16). Vesicle production varies with growth phase and nutrient availability, and vesicle-associated enzymes may aid in nutrient scavenging. Vesicle-mediated transfer of toxic components to other bacteria can eliminate competing species. In addition, interactions between eukaryotic cells and vesicles from pathogenic bacteria suggest a role for vesicles in pathogenesis (13).We have conducted a screen to generate and identify mutants in E. coli that exhibit altered vesiculation levels. Both vesicle-overproducing and -underproducing mutants are of interest, ...

Significant duration-dependent reductions in ovarian cancer incidence in the general population are associated with OCP use.

Oral contraceptives may influence the risk of certain cancers. As part of the AHRQ Evidence Report, Oral Contraceptive Use for the Primary Prevention of Ovarian Cancer, we conducted a systematic review to estimate associations between oral contraceptive use and breast, cervical, colorectal, and endometrial cancer incidence. We searched PubMed, Embase, and Cochrane Database of Systematic Reviews. Study inclusion criteria were women taking oral contraceptives for contraception or ovarian cancer prevention; includes comparison group with no oral contraceptive use; study reports quantitative associations between oral contraceptive exposure and relevant cancers; controlled study or pooled patient-level meta-analyses; sample size for nonrandomized studies !100; peer-reviewed, English-language; published from January 1, 2000 forward. Random-effects meta-analyses were conducted by estimating pooled ORs with 95% confidence intervals (CIs). We included 44 breast, 12 cervical, 11 colorectal, and 9 endometrial cancers studies. Breast cancer incidence was slightly but significantly increased in users (OR, 1.08; CI, 1.00-1.17); results show a higher risk associated with more recent use of oral contraceptives. Risk of cervical cancer was increased with duration of oral contraceptive use in women with human papillomavirus infection; heterogeneity prevented meta-analysis. Colorectal cancer (OR, 0.86; CI, 0.79-0.95) and endometrial cancer incidences (OR, 0.57; CI, 0.43-0.77) were significantly reduced by oral contraceptive use. Compared with never use, ever use of oral contraceptives is significantly associated with decreases in colorectal and endometrial cancers and increases in breast cancers. Although elevated breast cancer risk was small, relatively high incidence of breast cancers means that oral contraceptives may contribute to a substantial number of cases. Cancer Epidemiol Biomarkers Prev; 22(11); 1931-43. Ó2013 AACR.

Our analyses suggest that associations between ever use of OCs and ovarian and breast cancer among women who are BRCA1 or BRCA2 mutation carriers are similar to those reported for the general population.

Current use of combined OCPs is associated with increased odds of venous thromboembolism and ischemic stroke but not hemorrhagic stroke or MI.

Few studies have evaluated interventions addressing 1 or more CVD risk factors in people with serious mental illness. Glucose- and lipid-related results were mainly reported as secondary outcome assessments in studies of weight-management interventions. Comparative effectiveness studies are needed to test multimodal strategies, agents known to be effective in nonserious mental illness populations, and antipsychotic-management strategies.

Outer membrane vesicles (blebs) are produced by Escherichia coli, Salmonella, and all other gram-negative bacteria both in vitro and in vivo. Most of the research in the field has focused on the properties of vesicles derived from pathogenic bacteria and their interactions with eukaryotic cells. These data indicate that vesicles are able to contribute to pathogenesis. Thus, it appears that pathogenic gram-negative bacteria have co-opted vesicles for the dissemination of virulence determinants. However, the role of vesicle production by nonpathogenic bacteria is less obvious. This section reviews the data demonstrating the mechanistic and physiological basis of outer membrane vesicle production by bacteria. Vesiculation can be seen as a mechanism for cells to react to conditions in the surrounding environment by carrying away unnecessary components and allowing rapid modification of the outer membrane composition. In addition, vesicles can transmit biological activities distant from the originating cell. Vesicles could act to bind and deplete host immune factors at the site of infection that would otherwise attack the bacteria. Vesicles in the area surrounding the cell may also provide the cell protection inside a human or animal host. The concept of vesicles as virulence factors has received considerable attention, and they are likely to play a significant role in the pathogenesis of gram-negative bacteria. By analysis of their composition, mechanism of formation, regulation, and physiological function, progress is being made in understanding the ubiquitous nature of outer membrane vesicles produced by gram-negative bacteria.