Atlantic salmon post-smolts adapted for a longer time to seawater develop an effective humoral and cellular immune response against Salmonid alphavirus

Salmonid alphavirus (SAV) causes pancreas disease (PD) in Atlantic salmon (Salmo salar L.) and disease outbreaks are mainly detected after seawater transfer. The influence of the smoltification process on the immune responses, specifically the adaptive response of Atlantic salmon after SAV infection, is not fully understood. In this study, Atlantic salmon post-smolts were infected by either bath immersion (BI) or intramuscular injection (IM) with SAV subtype 3, 2 weeks (Phase A) or 9 weeks (Phase B) after seawater transfer. The transcript levels of genes related to cellular, humoral and inflammatory responses were evaluated on head kidney samples collected at 3, 7, 14, 21, and 28 days post-infection (dpi). Corresponding negative control groups (CT) were established accordingly. Significant differences were found between both phases and between the IM and BI groups. The anti-inflammatory cytokine IL-10 was up-regulated in Phase A at a higher level than in Phase B. High mRNA levels of the genes RIG-1, SOCS1 and STAT1 were observed in all groups except the BI-B group (BI-Phase B). Moreover, the IM-B group showed a higher regulation of genes related to cellular responses, such as CD40, MHCII, and IL-15, that indicated the activation of a strong cell-mediated immune response. CD40 mRNA levels were elevated one week earlier in the BI-B group than in the BI-A group (BI-Phase A). A significant up-regulation of IgM and IgT genes was seen in both IM groups, but the presence of neutralizing antibodies to SAV was detected only in Phase B fish at 21 and 28 dpi. In addition, we found differences in the basal levels of some of the analysed genes between non-infected control groups of both phases. Findings suggest that Atlantic salmon post-smolts adapted for a longer time to seawater before they come into contact with SAV, developed a stronger humoral and cell-mediated immune response during a SAV infection.

Atlantic salmon adapted to seawater for 9 weeks develop a robust immune response to salmonid alphavirus upon bath challenge

Pancreas disease (PD) caused by salmonid alphavirus (SAV) is the most serious viral disease in Norwegian aquaculture. Study of the immune response to SAV will aid preventative measures including vaccine development. The innate immune response was studied in Atlantic salmon infected by either bath immersion (BI) or by intra-muscular (i.m.) injection (IM) with SAV subtype 3, two and nine weeks after seawater transfer (Phases A and B respectively). Phase A results have been previously published (Moore et al., 2017) and Phase B results are presented here together with a comparison of results achieved in Phase A. There was a rapid accumulation of infected fish in the IM-B (IM Phase B) group and all fish sampled were SAV RNA positive by 7 dpi (days post infection). In contrast, only a few SAV RNA positive (infected) fish were identified at 14, 21 and 28 dpi in the BI-B (BI Phase B) group. Differences in the transcription of several immune genes were apparent when compared between the infected fish in the IM-B and BI-B groups. Transcription of the analysed genes peaked at 7 dpi in the IM-B group and at 14 dpi in the BI-B group. However, this latter finding was difficult to interpret due to the low prevalence of SAV positive fish in this group. Additionally, fish positive for SAV RNA in the BI-B group showed higher transcription of IL-1β, IFNγ and CXCL11_L1, all genes associated with the inflammatory response, compared to the IM-B group. Histopathological changes in the heart were restricted to the IM-B group, while (immune) cell filtration into the pancreas was observed in both groups. Compared to the Phase A fish that were exposed to SAV3 two weeks after seawater transfer, the Phase B fish in the current paper, showed a higher and more sustained innate immune gene transcription in response to the SAV3 infection. In addition, the basal transcription of several innate immune genes in non-infected control fish in Phase B (CT-B) was also significantly different when compared to Phase A control fish (CT-A).

Abstract 778: Identifying, subtyping and classifying tumor associated circulating endothelial cells in patients with solid tumors

Background: Tumor endothelial cells (ECs) are a population of stromal cells required for tumor growth that cooperate with tumors to form angiogenic structures. In blood, circulating ECs (CECs) are normal constituents of healthy individuals, although a Cancer Associated Vascular Endothelial cell (CAVE) subtype has been observed in cancer patients. The CAVE population has been isolated and identified using their large size or multicellular clustering and a pooled mixture of classical EC markers (i.e. CD31 and CD146). However, there has been no attempt to differentiate CAVEs from the many EC subtypes. This is not surprising as in-depth phenotyping of ECs requires an array of biomarkers that until recently has not been feasible. A multi-phenotypic screening of EC markers was tested on CAVEs from 116 blood samples in 3 types of solid tumors. This data suggests that CAVEs exist as a common and diverse subtype of tumor derived CECs that may express cytokeratin (CK) and various EC biomarkers, correlating to disease stage.

Methods: Peripheral blood samples from 116 cancer patients (stage I-IV) were drawn from 2012-2014 including breast (n=42), lung (n=39) and prostate (n=35), as well as blood from 34 healthy controls. Blood was processed by an established filtration approach, i.e. the CellSieveTM microfiltration technique (Creatv MicroTech), filtering blood by size exclusion and staining cells for CK 8, 18 & 19, EpCAM and CD45. After identification and imaging, the QUAS-R (Quench, Underivatize, Amine-Strip and Restain) technique was used to remove fluorescence signal and restain all cells with CD31, CD146, CD144, & DAPI. After reimaging, QUAS-R was again used to remove fluorescence and restain the cells for CD14, CD105, CD34, & DAPI.

Results: Out of 116 patient samples, we identified CAVEs in 63 patients (54%) based on positivity of CD31, CD144 or CD146, but none were found in healthy controls. CAVEs per 7.5mL sample in patients averaged 5.1 (breast), 5.6 (prostate) and 7.9 (lung). Presence of CAVEs appeared related to stage with 26% in stage 1, 61% in stage 2, 68% in stage 3, and 74% in stage 4 patients. No CAVEs were positive for CD14 or CD45. CD31 was the most present marker, found on 93% of CAVEs, followed by CD144 (85%), CD34 (64%), CD146 (45%), & CD105 (4%). In contrast with the previous study on this topic, CK was found in 67% of CAVEs, but was not a universal marker.

Conclusions: It has been reported that CK+ and CD45- CECs are isolated from the blood of cancer patients in colon and lung cancers, prompting some to classify them as circulating tumor cells. However, subtyping these CECs is incomplete when characterized with only 3-4 biomarkers. A multi-phenotypic subtyping technique was used to properly identify and subtype these CECs in cancer patients. This data suggest that a subset of CECs, e.g. CAVEs, are found in circulation as CK+/CD45-, but exist as a heterogeneous population of cancer specific circulating cells that require further study.

Citation Format: Daniel L. Adams, R. Katherine Alpaugh, Steven H. Lin, Jeffrey R. Marks, Raymond Bergan, Stuart S. Martin, Sarany Chumsri, Massimo Cristofanilli, Cha-Mei Tang, Steingrimur Stefansson. Identifying, subtyping and classifying tumor associated circulating endothelial cells in patients with solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 778. doi:10.1158/1538-7445.AM2017-778

Spiral Countercurrent Chromatography Enrichment, Characterization, and Assays of Carbon Nanotube Chiralities for Use in Biosensors

Single-walled carbon nanotubes (SWCNTs) are synthetic materials that hold great promise for electronics that are smaller and more versatile than the current silica-based technologies. But as-produced SWCNTs are generally a mixture of nanotubes with different structures that have vastly different properties. Separating these SWCNTs from multiwalled and metallic carbon nanotubes is vital to explore their individual properties and commercial utility ranging from optics to semiconductors. Compounding the problem of commercial investigation is that the semiconducting SWCNTs are also a mixture of different diameters and/or chiralities with different properties. Analyzing properties of enriched semiconducting SWCNT chiralities has only recently been possible through separation techniques such as aqueous two-phase solvent systems. Our study illustrates a semipreparative spiral countercurrent chromatography (CCC) separation of a commercial mixture of SWCNTs into distinct enriched fractions. A new mixer-settler spiral disk rotor was applied in this study, in which we compare the enriched SWCNTs for their effectiveness in biosensors with a high-throughput model assay, followed by antibody-mediated detection of Escherichia coli. Our results demonstrate that CCC-enriched responsive SWCNTs for biosensors can be used in our model assay, as well as for the detection of E. coli. To date, we believe that this is the first study along with Liu et al. [Chirality-controlled synthesis of single-wall carbon nanotubes using vapour-phase epitaxy. Nat. Commun.2012, 3, 1199] to demonstrate a specific utility of separated SWCNT species.

Immune gene profiles in Atlantic salmon (salmo salar L.) post-smolts infected with SAV3 by bath-challenge show a delayed response and lower levels of gene transcription compared to injected fish

Salmonid alphavirus (SAV) causes pancreatic disease (PD) in salmonids in Northern Europe which results in large economic losses within the aquaculture industry. In order to better understand the underlying immune mechanisms during a SAV3 infection Atlantic salmon post-smolts were infected by either i.m.-injection or bath immersion and their immune responses compared. Analysis of viral loads showed that by 14 dpi i.m.-injected and bath immersion groups had 95.6% and 100% prevalence respectively and that both groups had developed the severe pathology typical of PD. The immune response was evaluated by using RT-qPCR to measure the transcription of innate immune genes involved in the interferon (IFN) response as well as genes associated with inflammation. Our results showed that IFNa transcription was only weakly upregulated, especially in the bath immersion group. Despite this, high levels of the IFN-stimulated genes (ISGs) such as Mx and viperin were observed. The immune response in the i.m.-injected group as measured by immune gene transcription was generally faster, and more pronounced than the response in the bath immersion group, especially at earlier time-points. The response in the bath immersion group started later as expected and appeared to last longer often exceeding the response in the i.m-injected fish at later time-points. High levels of transcription of many genes indicative of an active innate immune response were present in both groups.

Abstract 1550: Multi-biomarker subtyping of circulating tumor cells using sequential fluorescence quenching

Background: Circulating tumor cells (CTCs) are rare but clinically valuable indicators of cancer status. However their clinical utility is limited to 2-3 positive fluorescent markers and 1 negative fluorescent marker. By contrast, tissue biopsies allow for numerous subtyping markers, yielding information about the tumor's biology and predicted treatment response. If CTC analysis is to be more useful, it must move beyond 2-3 identification markers. We describe a simple and inexpensive method to capture and identify CTCs using traditional fluorescence biomarkers with repeated restating of 9 unrelated fluorescent antibodies. In this study, we sought to subtype CTCs with the epithelial to mesenchymal-like phenotype (EMTCTCs) from pancreatic cancer samples first identified using a conventional CTC marker panel: Cytokeratin (CK), EpCAM, and CD45. We further subtyped these EMTCTCs with an immunosuppression therapy panel (PD-L1, CXCR4, PD-1) and then with a mesenchymal marker panel (CD14, CD34, Vimentin) to better interrogate the EMT phenotype. Alternative predictive and prognostic biomarkers may also be utilized. The order of staining does not affect the result. Our data demonstrate the ability to sequentially analyze, subtype and track 9 distinct cancer markers on each individual cell.

Methods: We developed a method of fluorescence quenching using cell lines: A2058, MB231, MCF7, HUVEC, and LnCAP. The technique consists of the steps: quench, underivatize, amine strip and restain (“QUASR”). Cells isolated on CellSieveTM microfilters were stained using the CTC marker panel, after which the QUASR protocol was applied and the cells were stained with a second mesenchymal marker panel. After imaging, QUASR was repeated for a third immunotherapy marker panel, and cells imaged a third time. QUASR was then used on 12 pancreatic cancer patient blood samples previously identified with EMTCTCs provided by Medical College of Wisconsin.

Results: No degradation was observed in cell surface, or intracellular markers for the 3 rounds of QUASR. There were 764 EMTCTCs identified as CK+/CD45- in the cancer patient samples, while EpCAM was positive in only 2% of these EMTCTCs. Post quenching, most EMTCTCs had additional mesenchymal phenotypes, i.e. 97% of cells were vimentin+ and 11% were CD34+. Expression of the immunotherapy markers were highly heterogeneous between patients, ranging from 0% to 100% positivity for PD-L1 and from 0% to 90% positivity for CXCR4. None of the CTCs were PD-1+ nor CD14+.

Conclusions: Our data demonstrates that sequential multi-panel restaining of clinically applicable cancer biomarkers can provide a greater amount and broader variety of information from patient blood samples. The ability to analyze CTCs beyond simple enumeration will greatly enhance the clinical utility of blood based biopsies, as patient samples can now be screened for multiple prognostic and predictive biomarkers.

Citation Format: Daniel L. Adams, Susan Tsai, Cha-Mei Tang, Steingrimur Stefansson. Multi-biomarker subtyping of circulating tumor cells using sequential fluorescence quenching. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1550.

A cell transportation solution that preserves live circulating tumor cells in patient blood samples

Background

Circulating tumor cells (CTCs) are typically collected into CellSave fixative tubes, which kills the cells, but preserves their morphology. Currently, the clinical utility of CTCs is mostly limited to their enumeration. More detailed investigation of CTC biology can be performed on live cells, but obtaining live CTCs is technically challenging, requiring blood collection into biocompatible solutions and rapid isolation which limits transportation options. To overcome the instability of CTCs, we formulated a sugar based cell transportation solution (SBTS) that stabilizes cell viability at ambient temperature. In this study we examined the long term viability of human cancer cell lines, primary cells and CTCs in human blood samples in the SBTS for transportation purposes.

Methods

Four cell lines, 5 primary human cells and purified human PBMCs were tested to determine the viability of cells stored in the transportation solution at ambient temperature for up to 7 days. We then demonstrated viability of MCF-7 cells spiked into normal blood with SBTS and stored for up to 7 days. A pilot study was then run on blood samples from 3 patients with metastatic malignancies stored with or without SBTS for 6 days. CTCs were then purified by Ficoll separation/microfilter isolation and identified using CTC markers. Cell viability was assessed using trypan blue or CellTracker™ live cell stain.

Results

Our results suggest that primary/immortalized cell lines stored in SBTS remain ~90 % viable for > 72 h. Further, MCF-7 cells spiked into whole blood remain viable when stored with SBTS for up to 7 days. Finally, live CTCs were isolated from cancer patient blood samples kept in SBTS at ambient temperature for 6 days. No CTCs were isolated from blood samples stored without SBTS.

Conclusions

In this proof of principle pilot study we show that viability of cell lines is preserved for days using SBTS. Further, this solution can be used to store patient derived blood samples for eventual isolation of viable CTCs after days of storage. Therefore, we suggest an effective and economical transportation of cancer patient blood samples containing live CTCs can be achieved.

Mitosis in circulating tumor cells stratifies highly aggressive breast carcinomas

Background

Enumeration of circulating tumor cells (CTCs) isolated from the peripheral blood of breast cancer patients holds promise as a clinically relevant, minimally invasive diagnostic test. However, CTC utility has been limited as a prognostic indicator of survival by the inability to stratify patients beyond general enumeration. In comparison, histological biopsy examinations remain the standard method for confirming malignancy and grading malignant cells, allowing for cancer identification and then assessing patient cohorts for prognostic and predictive value. Typically, CTC identification relies on immunofluorescent staining assessed as absent/present, which is somewhat subjective and limited in its ability to characterize these cells. In contrast, the physical features used in histological cytology comprise the gold standard method used to identify and preliminarily characterize the cancer cells. Here, we superimpose the methods, cytologically subtyping CTCs labeled with immunohistochemical fluorescence stains to improve their prognostic value in relation to survival.

Methods

In this single-blind prospective pilot study, we tracked 36 patients with late-stage breast cancer over 24 months to compare overall survival between simple CTC enumeration and subtyping mitotic CTCs. A power analysis (1-β = 0. 9, α = 0.05) determined that a pilot size of 30 patients was sufficient to stratify this patient cohort; 36 in total were enrolled.

Results

Our results confirmed that CTC number is a prognostic indicator of patient survival, with a hazard ratio 5.2, p = 0.005 (95 % CI 1.6–16.5). However, by simply subtyping the same population based on CTCs in cytological mitosis, the hazard ratio increased dramatically to 11.1, p < 0.001 (95 % CI 3.1–39.7).

Conclusions

Our data suggest that (1) mitotic CTCs are relativity common in aggressive late-stage breast cancer, (2) mitotic CTCs may significantly correlate with shortened overall survival, and (3) larger and more defined patient cohort studies are clearly called for based on this initial pilot study.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-016-0706-4) contains supplementary material, which is available to authorized users.

Atlantic salmon (Salmo salar L.) post-smolts challenged two or nine weeks after seawater-transfer show differences in their susceptibility to salmonid alphavirus subtype 3 (SAV3)

Background

Pancreas disease (PD), caused by salmonid alphavirus (SAV), is an important disease affecting salmonid aquaculture. It has been speculated that Atlantic salmon post-smolts are more prone to infections in the first few weeks following seawater- transfer. After this period of seawater acclimatization, the post-smolts are more robust and better able to resist infection by pathogens. Here we describe how we established a bath immersion (BI) model for SAV subtype 3 (SAV3) in seawater. We also report how this challenge model was used to study the susceptibility of post-smolts to SAV3 infection in two groups of post-smolts two weeks or nine weeks after seawater - transfer.

Methods

Post-smolts, two weeks (Phase-A) or nine weeks (Phase-B) after seawater- transfer, were infected with SAV3 by BI or intramuscular injection (IM) to evaluate their susceptibility to infection. A RT-qPCR assay targeting the non-structural protein (nsP1) gene was performed to detect SAV3-RNA in blood, heart tissue and electropositive-filtered tank-water. Histopathological changes were examined by light microscope, and the presence of SAV3 antigen in pancreas tissue was confirmed using immuno-histochemistry.

Results

Virus shedding from the Phase-B fish injected with SAV3 (IM Phase-B) was markedly lower than that from IM Phase-A fish. A lower percentage of viraemia in Phase-B fish compared with Phase-A fish was also observed. Viral RNA in hearts from IM Phase-A fish was higher than in IM Phase-B fish at all sampling points (p < 0.05) and a similar trend was also seen in the BI groups. Necrosis of exocrine pancreatic cells was observed in all infected groups. Extensive histopathological changes were found in Phase-A fish whereas milder PD-related histopathological lesions were seen in Phase-B fish. The presence of SAV3 in pancreas tissue from all infected groups was also confirmed by immuno-histochemical staining.

Conclusion

Our results suggest that post-smolts are more susceptible to SAV3 infection two weeks after seawater-transfer than nine weeks after transfer. In addition, the BI challenge model described here offers an alternative SAV3 infection model when better control of the time-of-infection is essential for studying basic immunological mechanisms and disease progression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0520-8) contains supplementary material, which is available to authorized users.

Precision Microfilters as an all in one System for Multiplex Analysis of Circulating Tumor Cells

Enumeration of circulating tumor cells (CTCs) from cancer patient blood is an established diagnostic assay used to evaluate patient status as a singleplex test. However, in the coming age of personalized medicine, multiplex analysis of patient CTCs, including proteomic and genomic techniques, will have to be integrated with CTC isolation platform technologies. Advancements in microfabrication have demonstrated that CTCs can be isolated and analyzed using microfluidic lab-on-a-chip devices. However, to date, most microfluidic devices are either still in the development phase, not applicable to all clinical tests, or are not commercially available. To overcome these discrepancies, we describe an all-in-one device for the isolation and multiplexing of clinically applicable CTC assays. Microfilters present an ideal lab-on-a-chip platform for analysis of CTCs as non-toxic and inert materials allow for a multitude of tests from cell growth through clinical staining techniques, all without background interference. Lithographically fabricated microfilters, can be made with high porosity, precise pore dimensions, arrayed pore distribution, and optimized for CTC size-based isolation. In this study we describe microfilter use in isolation and in situ analysis of CTCs using multiple sequential techniques including culture, FISH, histopathological analysis, H&E staining, photobleaching and re-staining. Further, as a proof of principle, we then describe the ability to quantitatively release patient derived CTCS from the microfilters for potential use in downstream genomic/proteomic analysis.

Cytometric characterization of circulating tumor cells captured by microfiltration and their correlation to the CellSearch(®) CTC test

Recent studies reporting hundreds, to thousands, of circulating tumor cells (CTCs) in the blood of cancer patients have raised questions regarding the prevalence of CTCs, as enumerated by the CellSearch(®) CTC Test. Although CellSearch has been shown to consistently detect clinically relevant CTCs; the ability to only capture EpCAM positive cells has led to speculation that it captures limited subsets of CTCs. In contrast, alternative approaches to CTC isolation are often cited as capturing large numbers of CTCs from patient blood. Not surprisingly the number of cells isolated by alternative approaches show poor correlations when compared to CellSearch, even when accounting for EpCAM presence or absence. In an effort to address this discrepancy, we ran an exploratory method comparison study to characterize and compare the CTC subgroups captured from duplicate blood samples from 30 breast and prostate cancer patients using a microfiltration system (CellSieve™) and CellSearch. We then categorized the CellSieve Cytokeratin(CK)+/CD45-/DAPI+ cells into five morphologically distinct subpopulations for correlative analysis. Like other filtration techniques, CellSieve isolated greater numbers of CK+/CD45- cells than CellSearch. Furthermore, analysis showed low correlation between the total CK+/CD45- cells captured by these two assays, regardless of EpCAM presence. However, subgrouping of CK+/CD45-/DAPI+ cells based on distinct cytokeratin staining patterns and nuclear morphologies elucidated a subpopulation correlative to CellSearch. Using method comparison analyses, we identified a specific CTC morphology which is highly correlative between two distinct capture methods. These data suggests that although various morphologic CTCs with similar phenotypic expressions are present in the blood of cancer patients, the clinically relevant cells isolated by CellSearch can potentially be identified using non-EpCAM dependent isolation. © 2014 The Authors. Published by Wiley Periodicals, Inc.

Comparison of radioimmuno and carbon nanotube field-effect transistor assays for measuring insulin-like growth factor-1 in a preclinical model of human breast cancer

Background

To realize the promise of personalized medicine, diagnostic instruments used for detecting and measuring biomarkers must become smaller, faster and less expensive. Although most techniques used currently to detect biomarkers are sensitive and specific, many suffer from several disadvantages including their complexity, high cost and long turnaround time. One strategy to overcome these problems is to exploit carbon nanotube (CNT) based biosensors, which are sensitive, use inexpensive disposable components and can be easily adapted to current assay protocols. In this study we investigated the applicability of using a CNT field-effect transistor (CNT-FET) as a diagnostic instrument for measuring cancer biomarkers in serum using a mouse model of Breast Cancer Susceptibility 1-related breast cancer. Insulin like growth factor-1 (IGF-1) was chosen because it is highly relevant in breast cancer and because measuring serum IGF-1 levels by conventional methods is complicated due to specific IGF-1 serum binding proteins.

Findings

Our results show that there is good correlation between the two platforms with respect to detecting serum IGF-1. In fact, the CNT-FETs required only one antibody, gave real-time results and required approximately 100-fold less mouse serum than the radioimmunoassay.

Conclusions

Both IGF-1 radioimmuno and CNT-FET assays gave comparable results. Indeed, the CNT-FET assay was simpler and faster than the radioimmunoassay. Additionally, the low serum sample required by CNT-FETs can be especially advantageous for studies constricted by limited amount of human clinical samples and for mouse studies, since animals often need to be sacrificed to obtain enough serum for biomarker evaluation.

Influence of sea temperature and initial marine feeding on survival of Atlantic salmon Salmo salar post-smolts from the Rivers Orkla and Hals, Norway

The abundance of returning adult Atlantic salmon Salmo salar, in the River Orkla in mid-norway (1 sea-winter, SW, fish) and River Hals in north Norway (1-3 SW fish), was tested against the early marine feeding and the seawater temperature experienced by their corresponding year classes of post-smolts immediately after entry into the Trondheimsfjord (Orkla smolts, 22 years of data) and Altafjord (Hals smolts, 17 years of data). In both river-fjord systems, there was a significant positive correlation between the abundance of returning S. salar and the mean seawater temperature at the time of smolts descending to the sea. The number of 1SW fish reported caught in River Orkla was positively correlated to the proportion of fish larvae in the post-smolt stomachs in Trondheimsfjord. The abundance of returning S.salar was, however, neither correlated to forage ratio (R(F)) nor other prey groups in post-smolt stomachs in the two fjord systems. In the Altafjord, the post-smolts fed mainly on pelagic fish larva (70-98%) and had a stable R(F) (0.009-0.023) over the 6 years analysed. In the Trondheimsfjord, however, there was a higher variation in R(F) (0.003-0.036), and pelagic fish larvae were dominant prey in only two (50 and 91%) of the 8 years analysed. These 2 years also showed the highest return rates of S. salar in River Orkla. These results demonstrate that the thermal conditions experienced by post-smolts during their early sea migration may be crucial for the subsequent return rate of adults after 1-3 years at sea. Pelagic marine fish larvae seem to be the preferred initial prey for S. salar post-smolts. As the annual variation in abundance of fish larvae is related to seawater temperature, it is proposed that seawater temperature at sea entry and the subsequent abundance of returning adult S. salar may be indirectly linked through variation in annual availability of pelagic fish larvae or other suitable food items in the early post-smolt phase.

The Contributions of Integrin Affinity and Integrin-Cytoskeletal Engagement in Endothelial and Smooth Muscle Cell Adhesion to Vitronectin

The serine proteinase inhibitor, plasminogen activator inhibitor type-1 (PAI-1), binds to the adhesion protein vitronectin with high affinity at a site that is located directly adjacent to the vitronectin RGD integrin binding sequence. The binding of PAI-1 to vitronectin sterically blocks integrin access to this site and completely inhibits the binding of purified integrins to vitronectin; however, its inhibition of endothelial and smooth muscle cell adhesion to vitronectin is at most 50-75%. Because PAI-1 binds vitronectin with approximately 10-100-fold higher affinity than purified integrins, we have analyzed the mechanism whereby these cells are able to overcome this obstacle. Our studies exclude proteolytic removal of PAI-1 from vitronectin as the mechanism, and show instead that cell adhesion in the presence of PAI-1 is dependent on integrin-cytoskeleton engagement. Disrupting endothelial or smooth muscle cell actin polymerization and/or focal adhesion assembly reduces cell adhesion to vitronectin in the presence of PAI-1 to levels similar to that observed for the binding of purified integrins to vitronectin. Furthermore, endothelial cell, but not smooth muscle cell adhesion to vitronectin in the presence of PAI-1 requires both polymerized microtubules and actin, further demonstrating the importance of the cytoskeleton for integrin-mediated adhesion. Finally, we show that cell adhesion in the presence of PAI-1 leads to colocalization of PAI-1 with the integrins alphavbeta3 and alphavbeta5 at the cell-matrix interface.

Mutants of plasminogen activator inhibitor-1 designed to inhibit neutrophil elastase and cathepsin G are more effective in vivo than their endogenous inhibitors

Neutrophil elastase and cathepsin G are abundant intracellular neutrophil proteinases that have an important role in destroying ingested particles. However, when neutrophils degranulate, these proteinases are released and can cause irreparable damage by degrading host connective tissue proteins. Despite abundant endogenous inhibitors, these proteinases are protected from inhibition because of their ability to bind to anionic surfaces. Plasminogen activator inhibitor type-1 (PAI-1), which is not an inhibitor of these proteinases, possesses properties that could make it an effective inhibitor of neutrophil proteinases if its specificity could be redirected. PAI-1 efficiently inhibits surface-sequestered proteinases, and it efficiently mediates rapid cellular clearance of PAI-1-proteinase complexes. Therefore, we examined whether PAI-1 could be engineered to inhibit and clear neutrophil elastase and cathepsin G. By introducing specific mutations in the reactive center loop of wild-type PAI-1, we generated PAI-1 mutants that are effective inhibitors of both proteinases. Kinetic analysis shows that the inhibition of neutrophil proteinases by these PAI-1 mutants is not affected by the sequestration of neutrophil elastase and cathepsin G onto surfaces. In addition, complexes of these proteinases and PAI-1 mutants are endocytosed and degraded by lung epithelial cells more efficiently than either the neutrophil proteinases alone or in complex with their physiological inhibitors, alpha1-proteinase inhibitor and alpha1-antichymotrypsin. Finally, the PAI-1 mutants were more effective in reducing the neutrophil elastase and cathepsin G activities in an in vivo model of lung inflammation than were their physiological inhibitors.

Plasminogen activator inhibitor-1 in tumor growth, angiogenesis and vascular remodeling

Plasminogen activator inhibitor-1 (PAI-1) is the principal inhibitor of urokinase type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA), and as such is thought to play an important role in the regulation of extracellular matrix remodeling. In blood, PAI-1 is bound to the adhesion protein vitronectin and is associated with vitronectin in fibrin clots and the provisional matrix. Elevated levels of PAI-1 are associated with atherosclerosis and an increased thrombotic tendency, while PAI-1 deficiency leads to increased fibrinolysis and bleeding. PAI-1 is also elevated in many solid tumors and is associated with a poor prognosis in cancer. PAI-1 has been shown to be a potent regulator of both vascular cell migration in vitro and of angiogenesis and tumor growth in vivo. PAI-1 can both promote and inhibit tumor growth and angiogenesis. Low concentrations of PAI-1 can stimulate tumor angiogenesis while treatment of animals with high doses of PAI-1 inhibits angiogenesis and tumor growth. Hence, PAI-1 appears to have a multifunctional role in regulating the migratory and fibrinolytic activity of vascular cells, and this, in turn, may help to explain the many varied actions of PAI-1.

Old dogs and new tricks: proteases, inhibitors, and cell migration

A new model for the actions of plasminogen activator inhibitors (PAIs) on cell migration may resolve the conflicting research data on these proteins in metastasis and angiogenesis. Results from two groups reveal a role for PAI-1 in promoting cycles of attachment and detachment of the cell from the extracellular matrix that is independent of its role as an enzymatic inhibitor of urokinase-type plasminogen activator (uPA). Through the formation of a complex of integrins, uPA and its receptor, and the clearance receptors of the low-density lipoprotein family, PAI-1 may promote endocytosis and recycling of these adhesion-controlling proteins, allowing cycling of cellular attachment and detachment.

Gene therapy vector-mediated expression of insulin-like growth factors protects cardiomyocytes from apoptosis and enhances neovascularization

IGF-I and IGF-II are single-chain polypeptide growth factors that regulate pleiotropic cellular responses. We have characterized the effect of recombinant IGF proteins, as well as third-generation adenoviral vectors encoding either IGF-I or IGF-II genes, on cardiomyocyte apoptosis and on angiogenesis. We found that endothelial cells cultured in the presence of the extracellular protein laminin exhibit a robust response to IGF-I and -II proteins via enhanced cell migration and angiogenic outgrowth. Furthermore, IGF vectors greatly enhanced neovascularization in an in vivo Matrigel model. Transduction of cardiomyocytes with the IGF adenoviral vectors resulted in a dose- and time-dependent increase in the expression of IGF-I or IGF-II protein. This correlated with abrogation of apoptosis induced by ischemia-reoxygenation, ceramide, or heat shock with optimal inhibition of approximately 80%. We conclude that gene transfer of IGF-I and IGF-II is a plausible strategy for the local delivery of IGFs to treat ischemic heart disease and heart failure by stimulating angiogenesis and protecting cardiomyocytes from cell death.

Extracellular export of sphingosine kinase-1 enzyme. Sphingosine 1-phosphate generation and the induction of angiogenic vascular maturation

The enzyme sphingosine kinase (SK) catalyzes the formation of sphingosine 1-phosphate (S1P), a bioactive lipid that acts extracellularly on G protein-coupled receptors of the S1P(1)/EDG-1 subfamily. Although S1P is formed in the cytosol of various cells, S1P release is not understood and is controversial because this lipid mediator is also regarded as a second messenger. In this report, we describe the existence of an extracellular S1P-generating system in vascular endothelial cells. Endothelial cells release SK constitutively and form S1P in the range of receptor stimulation. Levels of sphingosine but not ATP in the extracellular environment are rate-limiting. Treatment of endothelial cells with small interfering RNA for SK-1 transcript specifically inhibited SK export, and SK-1-transfected human embryonic kidney 293 cells exhibited enhanced release of SK-1. The export of SK-1 is constitutive and is inhibited by cytochalasin D and treatment at 4 degrees C but not by brefeldin A or nocodazole, suggesting that a nonclassical secretory pathway that requires the actin cytoskeleton dynamics is involved. Because S1P regulates angiogenesis and vascular maturation, we overexpressed SK-1 using an adenoviral vector in vivo in the Matrigel system of angiogenesis. Overexpression of SK-1 resulted in enhanced release of SK activity and induced angiogenesis and vascular maturation. These findings suggest that S1P is made in the extracellular milieu and that extracellular export of SK contributes to the action of S1P in the vascular system.

Plasminogen activator inhibitor-1 regulates tumor growth and angiogenesis

Elevated expression of plasminogen activator inhibitor-1 (PAI-1) in tumors is associated with a poor prognosis in many cancers. Reduced tumor growth and angiogenesis have also been reported in mice deficient in PAI-1. These results suggest that PAI-1 may be required for efficient angiogenesis and tumor growth. In the present study, we demonstrate that PAI-1 can both enhance and inhibit the growth of M21 human melanoma tumors in nude mice and that this appears to be due to PAI-1 regulation of angiogenesis. Quantitative analysis of angiogenesis in a Matrigel implant assay indicated that in PAI-1 null mice angiogenesis was reduced approximately 60% compared with wild-type mice, while in mice overexpressing PAI-1, angiogenesis was increased nearly 3-fold. Furthermore, addition of PAI-1 to implants in wild-type mice enhanced angiogenesis up to 3-fold at low concentrations but inhibited angiogenesis nearly completely at high concentrations. Together, these data demonstrate that PAI-1 is a potent regulator of angiogenesis and hence of tumor growth and suggest that understanding the mechanism of this activity may lead to the development of important new therapeutic agents for controlling pathologic angiogenesis.

Inhibition of angiogenesis in vivo by plasminogen activator inhibitor-1

The process of angiogenesis is important in both normal and pathologic physiology. However, the mechanisms whereby factors such as basic fibroblast growth factor promote the formation of new blood vessels are not known. In the present study, we demonstrate that exogenously added plasminogen activator inhibitor-1 (PAI-1) at therapeutic concentrations is a potent inhibitor of basic fibroblast growth factor-induced angiogenesis in the chicken chorioallantoic membrane. By using specific PAI-1 mutants with either their vitronectin binding or proteinase inhibitor activities ablated, we show that the inhibition of angiogenesis appears to occur via two distinct but apparently overlapping pathways. The first is dependent on PAI-1 inhibition of proteinase activity, most likely chicken plasmin, while the second is independent of PAI-1's anti-proteinase activity and instead appears to act through PAI-1 binding to vitronectin. Together, these data suggest that PAI-1 may be an important factor regulating angiogenesis in vivo.

Endothelial cells inhibit flow-induced smooth muscle cell migration: role of plasminogen activator inhibitor-1

BACKGROUND

The endothelium may play a pivotal role in hemodynamic force-induced vascular remodeling. We investigated the role of endothelial cell (EC) plasminogen activator inhibitor-1 (PAI-1) in modulating flow-induced smooth muscle cell (SMC) migration.

METHODS AND RESULTS

Human SMCs cocultured with or without human ECs were exposed to static (0 mL/min) or flow (26 mL/min; shear stress 23 dyne/cm(2)) conditions for 24 hours in a perfused capillary culture system. SMC migration was then assessed with a Transwell migration assay. In the absence but not in the presence of ECs, pulsatile flow significantly increased the migration of SMCs (264+/-26%) compared with SMCs under static conditions, concomitant with a 3- and 4-fold increase in PAI-1 mRNA and protein, respectively, in cocultured ECs. In the presence of PAI-1-/- ECs, flow increased wild-type SMC migration (226+/-25%), an effect that was reversed by exogenous PAI-1. To determine whether the antimigratory activity of PAI-1 was dependent primarily on inhibition of PAs or its association with vitronectin, experiments were conducted with PAI-1R (a mutant PAI-1 that binds to vitronectin but does not inhibit PA) and PAI-1K (a mutant that inhibits PA but has reduced affinity for vitronectin). PAI-1R inhibited both basal and flow-induced migration, whereas PAI-1K inhibited flow-induced migration in the absence of any effect on baseline migration.

CONCLUSIONS

Flow-induced EC PAI-1 inhibits flow-induced SMC migration in vitro. EC PAI-1 expression may be one of the predominant mechanisms responsible for controlling the process of vascular remodeling.

Type 1 plasminogen activator inhibitor binds to fibrin via vitronectin

Type 1 plasminogen activator inhibitor (PAI-1), the primary inhibitor of tissue-type plasminogen activator (t-PA), circulates as a complex with the abundant plasma glycoprotein, vitronectin. This interaction stabilizes the inhibitor in its active conformation In this report, the effects of vitronectin on the interactions of PAI-1 with fibrin clots were studied. Confocal microscopic imaging of platelet-poor plasma clots reveals that essentially all fibrin-associated PAI-1 colocalizes with fibrin-bound vitronectin. Moreover, formation of platelet-poor plasma clots in the presence of polyclonal antibodies specific for vitronectin attenuated the inhibitory effects of PAI-1 on t-PA-mediated fibrinolysis. Addition of vitronectin during clot formation markedly potentiates PAI-1-mediated inhibition of lysis of (125)I-labeled fibrin clots by t-PA. This effect is dependent on direct binding interactions of vitronectin with fibrin. There is no significant effect of fibrin-associated vitronectin on fibrinolysis in the absence of PAI-1. The binding of PAI-1 to fibrin clots formed in the absence of vitronectin was characterized by a low affinity (K(d) approximately 3.5 micrometer) and rapid loss of PAI-1 inhibitory activity over time. In contrast, a high affinity and stabilization of PAI-1 activity characterized the cooperative binding of PAI-1 to fibrin formed in the presence of vitronectin. These findings indicate that plasma PAI-1.vitronectin complexes can be localized to the surface of fibrin clots; by this localization, they may modulate fibrinolysis and clot reorganization.

Targeting of venom phospholipases: the strongly anticoagulant phospholipase A(2) from Naja nigricollis venom binds to coagulation factor Xa to inhibit the prothrombinase complex

The strongly anticoagulant basic phospholipase A(2) (CM-IV) from Naja nigricollis venom has previously been shown to inhibit the prothrombinase complex of the coagulation cascade by a novel nonenzymatic mechanism (S. Stefansson, R. M. Kini, and H. J. Evans Biochemistry 29, 7742-7746, 1990). That work indicated that CM-IV is a noncompetitive inhibitor and thus it interacts with either factor Va or factor Xa, or both. We further examined the interaction of CM-IV and the protein components of the prothrombinase complex. Isothermal calorimetry studies indicate that CM-IV does not bind to prothrombin or factor Va, but only to factor Xa. CM-IV has no effect on the cleavage of prothrombin by factor Xa in the absence of factor Va. However, in the presence of factor Va, CM-IV inhibits thrombin formation by factor Xa. With a constant amount of CM-IV, raising the concentration of factor Va relieved the inhibition. The phospholipase A(2) enzyme inhibits by competing with factor Va for binding to factor Xa and thus prevents formation of the normal Xa-Va complex or replaces bound factor Va from the complex. Thus factor Xa is the target protein of this anticoagulant phospholipase A(2), which exerts its anticoagulant effect by protein-protein rather than protein-phospholipid interactions.

Cubilin, the endocytic receptor for intrinsic factor-vitamin B(12) complex, mediates high-density lipoprotein holoparticle endocytosis

Receptors that endocytose high-density lipoproteins (HDL) have been elusive. Here yolk-sac endoderm-like cells were used to identify an endocytic receptor for HDL. The receptor was isolated by HDL affinity chromatography and identified as cubilin, the recently described endocytic receptor for intrinsic factor-vitamin B(12). Cubilin antibodies inhibit HDL endocytosis by the endoderm-like cells and in mouse embryo yolk-sac endoderm, a prominent site of cubilin expression. Cubilin-mediated HDL endocytosis is inhibitable by HDL(2), HDL(3), apolipoprotein (apo)A-I, apoA-II, apoE, and RAP, but not by low-density lipoprotein (LDL), oxidized LDL, VLDL, apoC-I, apoC-III, or heparin. These findings, coupled with the fact that cubilin is expressed in kidney proximal tubules, suggest a role for this receptor in embryonic acquisition of maternal HDL and renal catabolism of filterable forms of HDL.

[Disability in Iceland 1996: size and characteristics.]

OBJECTIVE

To determine the size and main medical and social characteristics of the group of individuals receiving disability benefits in Iceland and compare those with figures from the other Nordic countries.

MATERIAL AND METHODS

The study includes all those receiving disability benefits on the 1st of December 1996 as ascertained by the disability register at the State Social Security Institute of Iceland.

RESULTS

On the prevalence day 8714 individuals were receiving disability benefits. Of those there were 7315 individuals who had disability assessed as being more than 75% (4.2% of the total population between 16 and 66 years of age); women: 4286 (58.6%), men: 3029 (41.4%). Disability was assessed as being 50% or 65% for 1399 individuals (0.7% of the total population between 16 and 66 years of age); women: 914 (65.3%), men: 485 (34.7%). Of those receiving disability benefits there is thus a significant excess of women (p<0.0001). Individuals with >75% disability are in excess in the capital region as compared with other areas (p<0.001 for men, p=0.03 for women). When different age groups within the population are compared there is a steady increase with age of the ratio of individuals with >75% disability. Disability is most commonly associated with mental disorders or diseases of the musculoskeletal system.

CONCLUSION

The percentage of the total population receiving disability benefits in Iceland, is similar to that in Denmark but considerably lower than in Finland, Norway and Sweden. When different age groups are compared it emerges that there are more individuals below 30 years of age receiving disability benefits in Iceland than in the other Nordic countries. In the older age groups this ratio is reversed and gets more marked with increasing age. The following main explanations for this difference are suggested: the level of allowance and organization of the social security system is different in Iceland compared with the other Nordic countries; the Icelandic unemployment level is lower and work participation higher, especially in the upper age groups in Iceland.

Plasminogen activator inhibitor-1 contains a cryptic high affinity binding site for the low density lipoprotein receptor-related protein

Much of the controversy surrounding the binding of plasminogen activator inhibitor-1 (PAI-1) to the low density lipoprotein receptor-related protein (LRP) may be due to the labile structure of PAI-1 and the distinct conformations that it can adopt. To examine this possibility and to test the hypothesis that PAI-1 contains a specific high affinity binding site for LRP, a sensitive and quantitative assay for PAI-1 binding to LRP was developed. This assay utilizes a unique PAI-1 mutant that was constructed with a hexapeptide tag at the NH2 terminus, which is recognized by the protein kinase, heart muscle kinase and can be specifically labeled with 32P. Our results show that only 32P-PAI-1 in complex with a proteinase binds LRP with high affinity and is efficiently endocytosed by cells, indicating that a high affinity site for LRP is generated on PAI-1 only when in complex with a proteinase. In addition, PAI-1 in complex with different proteinases is shown to cross-compete for LRP binding, demonstrating that the binding site is independent of the proteinase and therefore must reside on the PAI-1 portion of the complex. Finally, mutagenesis of PAI-1 results in loss of LRP binding, confirming that the high affinity binding site is located on PAI-1 and suggesting that the LRP binding site lays within a region of PAI-1 previously shown to contain the heparin binding domain.

[Peak bone mass of Icelandic women and associated factors.]

OBJECTIVE

The aim of this study was to evaluate at which age peak bone mass is reached among Icelandic women. Previous studies on this subject have been conflicting indicating that this might be reached sometime between the age of 16 and 35 years. We have also analyzed associated nutritional and physical factors which might be of use for preventive measures against osteoporosis.

MATERIAL AND METHODS

A random sample of 16, 18, 20 and 25 years old women in Reykjavik were invited, altogether 335 women participated. Bone mineral density (BMD) was analyzed by Dual Energy X-ray Absorptiometry (DEXA) in the lumbar spine, hip, forearm and total skeleton. Calcium, protein and vitamin D intake was assessed by a semiquantitative food frequency questionnaire. The level of 25-OH-vitamin D in serum was measured by a radioimmunoassay. Physical activity was assessed by a questionnaire. Multivariate analysis was performed by multiple linear regression.

RESULTS

Maximal bone mineral density was reached for total skeleton, hip and forearm at the age of 20 years, BMD for the lumbar spine was 1% higher at the age of 25 than at 20 years but this was not statistically significant. No significant association was found between the calcium intake and BMD except in the subgroup of 18 years old women with calcium intake below 1000 mg/day. 25-OH-vitamin D levels were low (<25 nmol/L) in 15-18.5% of the groups but still no significant relationship was found with the bone mineral density. The strongest correlation was found between total BMD and the lean mass (0.38-0.53, p<0.01) but physical activity was also a significant factor in the age groups 16-20 years. About 25-30% of BMD variability can be attributed to these modifiable factors.

CONCLUSION

Peak bone mass seems to be reached at the age of 20 and measures to increase it should therefore be emphasized before that age. Our results indicate that modifiable factors, especially lean mass and physical activity, are of considerable importance in the attainment of peak bone mass in women.

Neuroserpin, a brain-associated inhibitor of tissue plasminogen activator is localized primarily in neurons. Implications for the regulation of motor learning and neuronal survival

A cDNA clone for the serine proteinase inhibitor (serpin), neuroserpin, was isolated from a human whole brain cDNA library, and recombinant protein was expressed in insect cells. The purified protein is an efficient inhibitor of tissue type plasminogen activator (tPA), having an apparent second-order rate constant of 6. 2 x 10(5) M-1 s-1 for the two-chain form. However, unlike other known plasminogen activator inhibitors, neuroserpin is a more effective inactivator of tPA than of urokinase-type plasminogen activator. Neuroserpin also effectively inhibited trypsin and nerve growth factor-gamma but reacted only slowly with plasmin and thrombin. Northern blot analysis showed a 1.8 kilobase messenger RNA expressed predominantly in adult human brain and spinal cord, and immunohistochemical studies of normal mouse tissue detected strong staining primarily in neuronal cells with occasionally positive microglial cells. Staining was most prominent in the ependymal cells of the choroid plexus, Purkinje cells of the cerebellum, select neurons of the hypothalamus and hippocampus, and in the myelinated axons of the commissura. Expression of tPA within these regions is reported to be high and has previously been correlated with both motor learning and neuronal survival. Taken together, these data suggest that neuroserpin is likely to be a critical regulator of tPA activity in the central nervous system, and as such may play an important role in neuronal plasticity and/or maintenance.

Characterization of the binding of different conformational forms of plasminogen activator inhibitor-1 to vitronectin. Implications for the regulation of pericellular proteolysis

Plasminogen activator inhibitor type 1 (PAI-1), the primary physiologic inhibitor of plasminogen activation, is associated with the adhesive glycoprotein vitronectin (Vn) in plasma and the extracellular matrix. In this study we examined the binding of different conformational forms of PAI-1 to both native and urea-purified vitronectin using a solid-phase binding assay. These results demonstrate that active PAI-1 binds to urea-purified Vn with approximately 6-fold higher affinity than to native Vn. In contrast, inactive forms of PAI-1 (latent, elastase-cleaved, synthetic reactive center loop peptide-annealed, or complexed to plasminogen activators) display greatly reduced affinities for both forms of adsorbed Vn, with relative affinities reduced by more than 2 orders of magnitude. Structurally, these inactive conformations all differ from active PAI-1 by insertion of an additional strand into beta-sheet A, suggesting that it is the rearrangement of sheet A that results in reduced Vn affinity. This is supported by the observation that PAI-1 associated with beta-anhydrotrypsin, which does not undergo rearrangement of beta-sheet A, shows no such decrease in affinity, whereas PAI-1 complexed to beta-trypsin, which does undergo sheet A rearrangement, displays reduced affinity for Vn similar to PAI-1.plasminogen activator complexes. Together these data demonstrate that the interaction between PAI-1 and Vn depends on the conformational state of both proteins and suggest that the Vn binding site on PAI-1 is sensitive to structural changes associated with loss of inhibitory activity.

The serpin PAI-1 inhibits cell migration by blocking integrin alpha V beta 3 binding to vitronectin

During wound healing, migrating cells increase expression of both the vitronectin receptor (VNR) integrins and plasminogen activators. Here we report that vitronectin significantly enhances the migration of smooth muscle cells (SMCs), and that the specific VNR alpha V beta 3 is required for cell motility. We also show that the alpha V beta 3 attachment site on vitronectin overlaps with the binding site for plasminogen activator inhibitor (PAI)-1, and that the active conformation of PAI-1 blocks SMC migration. This effect requires high-affinity binding to vitronectin, and is not dependent on the ability of PAI-1 to inhibit plasminogen activators. Formation of a complex between PAI-1 and plasminogen activators results in loss of PAI-1 affinity for vitronectin and restores cell migration. These data demonstrate a direct link between plasminogen activators and integrin-mediated cell migration, and show that PAI-1 can control cell-matrix interactions by regulating the accessibility of specific cell-attachment sites. This indicates that the localization of plasminogen activators at sites of focal contact does not initiate a proteolytic cascade leading to generalized matrix destruction, but instead is required to expose cryptic cell-attachment sites necessary for SMC migration.

Plasminogen activator inhibitor-1 and vitronectin promote the cellular clearance of thrombin by low density lipoprotein receptor-related proteins 1 and 2

Thrombin is a multifunctional protein that has both proteinase and growth factor-like activities. Its regulation is largely mediated by interaction with a host of inhibitors including antithrombin III (ATIII), heparin cofactor II (HCII), alpha2-macroglobulin (alpha2-M), protease nexin I, and plasminogen activator inhibitor-1 (PAI-1). ATIII, HCII, and alpha2-M are all abundant in blood and can inactivate blood-borne thrombin leading to rapid hepatic clearance of the thrombin-inhibitor complex. PAI-1 alone, a poor solution phase inhibitor of thrombin, can efficiently inhibit thrombin in the presence of native vitronectin (VN). In this study, active thrombin was found to be efficiently endocytosed and degraded by cultured pre-type II pneumocyte cells, and both processes could be blocked by polyclonal antibodies to PAI-1. When the relative efficiency of cellular endocytosis of thrombin in complex with a number of inhibitors was examined, 125I-thrombin-PAI-1 complexes were most efficiently cleared compared to 125I-thrombin in complex with the serpins ATIII, HCII, alpha1-proteinase inhibitor, or d-phenylalanyl-l-prolyl-l-arginine chloromethyl ketone. Low density lipoprotein receptor-related proteins 1 (LRP) and 2 (gp330/megalin) mediate the endocytosis of thrombin-PAI-1, since antagonists of receptor function such as LRP-1 and LRP-2 antibodies and the 39-kDa receptor-associated protein blocked 125I-thrombin-PAI-1 endocytosis and degradation. The LRP-mediated clearance of exogenously added 125I-thrombin by cultured cells was found to be enhanced 5-fold by inclusion of wild-type PAI-1 but by only 2-fold when a mutant form of PAI-1 that is unable to bind VN was included. This wild-type PAI-1 enhancement of 125I-thrombin clearance was found to occur only in the presence of native VN and not with its conformationally altered form. The results highlight a novel mechanism for cellular clearance of thrombin involving native VN promoting the interaction of thrombin and PAI-1 and the subsequent endocytosis of the complex by LRP-1 or LRP-2. This pathway is potentially important for the regulation of the potent biological activities of thrombin, particularly at sites of vascular injury.

Glycoprotein 330/low density lipoprotein receptor-related protein-2 mediates endocytosis of low density lipoproteins via interaction with apolipoprotein B100

The ability of glycoprotein 330/low density lipoprotein receptor-related protein-2 (LRP-2) to function as a lipoprotein receptor was investigated using cultured mouse F9 teratocarcinoma cells. Treatment with retinoic acid and dibutyryl cyclic AMP, which induces F9 cells to differentiate into endoderm-like cells, produced a 50-fold increase in the expression of LRP-2. Levels of the other members of the low density lipoprotein (LDL) receptor (LDLR) family, including LDLR, the very low density lipoprotein receptor, and LRP-1, were reduced. When LDL catabolism was examined in these cells, it was found that the treated cells endocytosed and degraded at 10-fold higher levels than untreated cells. The increased LDL uptake coincided with increased LRP-2 activity of the treated cells, as measured by uptake of both 125I-labeled monoclonal LRP-2 antibody and the LRP-2 ligand prourokinase. The ability of LDL to bind to LRP-2 was demonstrated by solid-phase binding assays. This binding was inhibitable by LRP-2 antibodies, receptor-associated protein (the antagonist of ligand binding for all members of the LDLR family), or antibodies to apoB100, the major apolipoprotein component of LDL. In cell assays, LRP-2 antibodies blocked the elevated 125I-LDL internalization and degradation observed in the retinoic acid/dibutyryl cyclic AMP-treated F9 cells. A low level of LDL endocytosis existed that was likely mediated by LDLR since it could not be inhibited by LRP-2 antibodies, but was inhibited by excess LDL, receptor-associated protein, or apoB100 antibody. The results indicate that LRP-2 can function to mediate cellular endocytosis of LDL, leading to its degradation. LRP-2 represents the second member of the LDLR family identified as functioning in the catabolism of LDL.

Identification of glycoprotein 330 as an endocytic receptor for apolipoprotein J/clusterin

Glycoprotein 330 (gp330) is a member of a family of endocytic receptors related to the low density lipoprotein receptor. gp330 has previously been shown to bind a number of ligands in common with its family member, the low density lipoprotein receptor-related protein (LRP). To identify ligands specific for gp330 and relevant to its localization on epithelia such as in the mammary gland, gp330-Sepharose affinity chromatography was performed. As a result, a 70-kDa protein was selected from human milk and identified by protein sequencing to be apolipoprotein J/clusterin (apoJ). Solid-phase binding assays confirmed that gp330 bound to apoJ with high affinity (Kd = 14.2 nM). Similarly, gp330 bound to apoJ transferred to nitrocellulose after SDS-polyacrylamide gel electrophoresis. LRP, however, showed no binding to apoJ in either type of assay. The binding of gp330 to apoJ could be competitively inhibited with excess apoJ as well as with the gp330 ligands apolipoprotein E, lipoprotein lipase, and the receptor-associated protein, a 39-kDa protein that acts to antagonize binding of all known ligands for gp330 and LRP. Several cultured cell lines that express gp330 and ones that do not express the receptor were examined for their ability to bind and internalize 125I-apoJ. Only cells that expressed gp330 endocytosed and degraded radiolabeled apoJ. Furthermore, F9 cells treated with retinoic acid and dibutyryl cyclic AMP to increase expression levels of gp330 displayed an increased capacity to internalize and degrade apoJ. Cellular internalization and degradation of radiolabeled apoJ could be inhibited with unlabeled apoJ, receptor-associated protein, and gp330 antibodies. The results indicate that gp330 but not LRP can bind to apoJ in vitro and that gp330 expressed by cells can mediate apoJ endocytosis leading to lysosomal degradation.

Identification of the low density lipoprotein receptor-related protein (LRP) as an endocytic receptor for thrombospondin-1

Thrombospondin-1 (TSP1) has potent biological effects on vasculature smooth muscle cells (SMCs) and endothelial cells. The regulation of extracellular accumulation of TSP1 is mediated by a previously obscure process of endocytosis which leads to its lysosomal degradation. Since members of the low density lipoprotein receptor (LDLR) family have been found to mediate endocytosis which leads to degradation of a diverse array of ligands, we evaluated their possible role in the uptake and degradation of TSP1 by vascular SMCs, endothelial-cells and fibroblasts. 125I-TSP1 was found to be internalized and degraded lysosomally by all these cell types. Both the internalization and degradation of 125I-TSP1 could be inhibited by a specific antagonist of the LDLR family, the 39-kD receptor-associated protein (RAP). Antibodies to the LDLR-related protein (LRP) completely blocked the uptake and degradation of 125I-TSP1 in SMCs and fibroblasts but not endothelial cells. Solid-phase binding assays confirmed that LRP bound to TSP1 and that the interaction was of high affinity (Kd = 5 nM). Neither RAP nor LRP antibodies inhibited the binding of 125I-TSP1 to surfaces of SMCs. However, cell surface binding, as well as, endocytosis and degradation could be blocked by heparin or by pre-treatment of the cells with either heparitinase, chondroitinase or beta-D-xyloside. The data indicates that cell surface proteoglycans are involved in the LRP-mediated clearance of TSP1. A model for the clearance of TSP1 by these cells is that TSP1 bound to proteoglycans is presented to LRP for endocytosis. In endothelial cells, however, the internalization of TSP1 was not mediated by LRP but since RAP inhibited TSP1 uptake and degradation, we postulate that another member of the LDLR family is likely to be involved.

gp330 on type II pneumocytes mediates endocytosis leading to degradation of pro-urokinase, plasminogen activator inhibitor-1 and urokinase-plasminogen activator inhibitor-1 complex

Glycoprotein 330 (gp330) is a member of a family of receptors related to the low density lipoprotein receptor (LDLR). Although several ligands have been shown to bind gp330 in solid-phase assays, the ability of gp330 to mediate ligand endocytosis has not been demonstrated. To develop a cellular model for gp330 function we screened a variety of cultured cell lines and identified several that expressed this protein, including immortalized rat type II pneumocytes and a human and two rodent tumor cell lines. Using type II pneumocytes, endocytosis of a previously described gp330 ligand, urokinase (uPA) complexed with plasminogen activator inhibitor-1 (uPA:PAI-1) and two new ligands, PAI-1 and pro-uPA, was demonstrated. RAP, the 39 kDa receptor-associated protein known to antagonize ligand binding to gp330 in solid-phase binding assays, completely inhibited both internalization and degradation of the radiolabeled ligands by type II pneumocytes. This suggested that the clearance of these ligands was dependent on either gp330 or the LDLR-related protein (LRP), which shares several ligand-binding characteristics with gp330. By using polyclonal antibodies to gp330, the cellular internalization and degradation of the ligands were inhibited by 30–50%; remaining ligand internalization and degradation activity could be partially inhibited by polyclonal antibodies against LRP. These findings indicate that gp330, like other LDLR family members, mediates endocytosis of its ligands. In addition, gp330 acts in concert with LRP in type II pneumocytes to mediate clearance of a variety of proteins involved in plasminogen activation, including uPA:PAI-1 complexes PAI-1 and pro-uPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Native TIMP-free 70 kDa progelatinase (MMP-2) secreted at elevated levels by RSV transformed fibroblasts

Rous sarcoma virus-transformed cultures of chicken embryo fibroblasts (RSVCEF) secrete elevated levels of a 70 kDa progelatinase, an avian form of the 72 kDa matrix metalloproteinase-2 (MMP-2). Affinity-purified preparations of secreted 70 kDa progelatinase are composed of two distinct populations of zymogen: a 70 kDa progelatinase tightly complexed with an avian form of TIMP-2 and a native 70 kDa progelatinase free of any detectable TIMP-2. These two forms of the progelatinase can be separated by Mono Q FPLC in the absence of denaturing agents. The homogeneity of the two separated forms is demonstrated by both SDS-PAGE and nondenaturing, native gel electrophoresis. The purified TIMP-free 70 kDa progelatinase is stable in aqueous conditions and does not spontaneously autoactivate. Treatment of the TIMP-free progelatinase with the organomercurial, p-aminophenylmercuric acetate (APMA), results in rapid (5-60 minutes) autolytic conversion of the 70 kDa progelatinase to 67 kDa, 62 kDa and lower molecular weight forms of the enzyme. APMA treatment of the TIMP-free progelatinase yields a preparation that is enzymatically active with a high specific activity towards a peptide substrate. Identical treatment of TIMP-complexed progelatinase with APMA results in a significantly slower conversion process in which the 70 kDa progelatinase is only 50% converted after 6-24 hours and the specific enzyme activity of the preparation is 8 to 18-fold lower. Purified avian TIMP-2 added to the TIMP-free progelatinase forms a complex with the progelatinase and prevents the rapid autolytic conversion induced by APMA. Comparative analysis of parallel cultures of transformed RSVCEF and normal CEF demonstrates that the transformed cultures contain threefold higher levels of the TIMP-free progelatinase than the normal CEF cultures which produce predominantly TIMP-complexed progelatinase. The presence in transformed cultures of elevated levels of a more readily activated TIMP-free progelatinase, the suppression of its rapid activation by TIMP-2, and the potential effect of the altered balance between TIMP-free and TIMP-complexed 70 kDa progelatinase on the invasive, malignant phenotype, are discussed.

Incidence and clinical significance of hemidiaphragmatic paresis in patients undergoing carotid endarterectomy during cervical plexus block anesthesia

This study was designed to investigate the incidence and clinical consequences of hemidiaphragmatic paresis in patients undergoing carotid endarterectomy using cervical plexus block anesthesia. In 28 patients, diaphragmatic motion was evaluated by fluoroscopy 20 min after cervical plexus block with 1% mepivacaine. In 61% of the patients abnormalities of diaphragmatic motion were detected. These motion anomalies were associated with a statistically significant elevation of PaCO2. Gender, age, and whether the block was on the left or right side did not appear to affect the incidence of motion abnormalities after cervical plexus block anesthesia.

Tolerance to sodium nitroprusside. Studies in cultured porcine vascular smooth muscle cells

BACKGROUND

Tolerance to nitrovasodilators, including sodium nitroprusside (SNP), is a clinical problem. SNP causes vasodilatation by releasing nitric oxide, which stimulates intracellular guanosine 3':5'-cyclic monophosphate (cGMP) accumulation in smooth muscle cells. This study examined tolerance to SNP in coronary smooth muscle cells by measuring intracellular cGMP formation.

METHODS

Smooth muscle cells were isolated from pig coronary vessels. Intracellular cGMP formation in response to SNP, nitroglycerine, and atrial natriuretic peptide (ANP) was quantitated by radioimmunoassay before and after chronic pretreatment.

RESULTS

The detection of tolerance of cells rechallenged with SNP required exposure to a minimum concentration of 1 microM for SNP for at least 60 min. In untreated cells, acutely applied 100 microM SNP increased the cGMP concentration to 300 +/- 8.6 pmol/mg protein (mean +/- SEM). The cGMP concentration in cells pretreated with 1 microM SNP for 60 min increased to 213 +/- 11 pmol/mg in response to 100 microM SNP (P < 0.01, compared to untreated cells). The pretreatment of cells for 60 min with increasing concentrations of SNP caused a sequential reduction in the acute concentration-response curves of cGMP to SNP. After a 6 h washout period, cGMP accumulation in response to a rechallenge with SNP returned to control levels. The acute concentration-response curve of cGMP to SNP in cells pretreated with 100 microM nitroglycerine for 60 min was reduced significantly. Pretreatment with 100 microM SNP for 60 min did not change the response of cAMP accumulation to isoproterenol or forskolin. However, the response of cGMP formation to ANP was potentiated after pretreatment. In addition, elevation of basal cAMP or cGMP concentrations, induced with isoproterenol or ANP, respectively, did not alter the response of cGMP formation to SNP.

CONCLUSION

The study yielded the following findings: (1) reversible tolerance to SNP was induced in cultured vascular smooth muscle cells; (2) chronic exposure to nitroglycerine induced cross-tolerance to SNP; (3) cells that were tolerant to SNP showed a potentiated response to ANP.

Double-blind comparison of cefixime and cefaclor in the treatment of acute otitis media in children

In a double-blind study cefixime, an oral cephalosporin of the third generation, was compared to cefaclor in the treatment of acute otitis media in 397 children aged 6 months to 12 years. Clinical evaluation was carried out at the beginning, at day 10-12 and day 28-35 after the start of the treatment. Specimens for bacterial culture and sensitivity testings were taken from the nasopharynx at the initial visit. Patients were randomized either to cefixime in a dose of 8 mg/kg/day or cefaclor in a dose 40 mg/kg/day in the proportion of 2 cefixime patients to 1 cefaclor patient. Two daily doses were administered for 7 days. At day 10-12, 93.5% in the cefixime group and 90.5% in the cefaclor group (p = 0.08) were clinically cured or improved. At day 28-35 the rate of cured or improved patients had decreased, mostly due to reinfections, to 90.1% in the cefixime group and to 86.6% in the cefaclor group (p = 0.12), respectively. 375 patients (69.9%) had positive bacterial culture in the nasopharynx of at least one strain of Haemophilus influenzae, Streptococcus pneumoniae, Branhamella (Moraxella) catarrhalis or combinations of these 3.73.6% of the B. catarrhalis strains were beta-lactamase producing and 11.4% of the H. influenzae strains, respectively. All isolated bacteria were sensitive to cefixime. Adverse events were reported in 17.9% in the cefixime and 10.6% in the cefaclor group. Most reactions were of moderate or mild nature and mostly affected skin or the gastrointestinal region. No serious adverse experiences occurred. In view of the good clinical results obtained cefixime seems to be at least as effective as cefaclor in the treatment of acute otitis media in children.

Corticotropin, cortisol and beta-endorphin responses to the human corticotropin-releasing hormone during melancholia and after unilateral electroconvulsive therapy

Previous research in neuroendocrinology has evidenced that hyperactivity of the hypothalamic-pituitary-adrenal axis (HPA) depends on hypersecretion of corticotropin-releasing hormone (CRH). The aim of this study was to investigate the activity of HPA before and after recovery in depressed patients treated with electroconvulsive therapy (ECT). An h-CRH-stimulation test was performed on 2 occasions with examination of the HPA axis before ECT treatment during episodes of major depressive disorders with melancholia, and during the recovery phase after treatment. The results showed that patients during depression had significantly higher plasma levels of cortisol at 15 and 30 min after h-CRH-administration than after recovery. Depressed patients had significantly higher plasma levels of beta-endorphin 30 min after h-CRH-stimulation. The results are in agreement with previous studies, which have shown hypercortisolemia during depression. A possible hypersecretion of CRH may explain the effect on cortisol and beta-endorphin. No significant differences were found between cumulative responses of corticotropin, cortisol and beta-endorphin, calculated as the areas under the concentration curves.

The basic phospholipase A2 from Naja nigricollis venom inhibits the prothrombinase complex by a novel nonenzymatic mechanism

The three phospholipase A2 isoenzymes from Naja nigricollis venom inhibit blood coagulation with different potencies. The strongly anticoagulant basic isoenzyme CM-IV inhibits the prothrombinase complex, whereas the weakly anticoagulant isoenzymes CM-I and CM-II do not. To determine the role of enzymatic activity of the phospholipases in the inhibition of prothrombinase, we varied the time of incubation of each of these isoenzymes with the prothrombinase complex. The inhibition by CM-IV did not increase with time of incubation. CM-I and CM-II failed to inhibit the complex, even with complete hydrolysis of phospholipids in the assay mixture. After alkylation of its active-site histidine, CM-IV lost 97% of its enzymatic activity but retained 60% of its inhibitory potency on prothrombinase. CM-IV also inhibited prothrombinase activity in the absence of phospholipids, whereas CM-I and CM-II did not. The inhibition of the prothrombinase complex by CM-IV is thus not due to its binding to or hydrolysis of phospholipids. The kinetics of CM-IV inhibition of the prothrombinase complex in both the presence and absence of phospholipids was noncompetitive. This inhibition can be explained by binding of CM-IV to either factor Va or Xa, or both, to inhibit the complex. CM-IV differs from previously described nonenzymatic anticoagulants that are proteinase inhibitors or that inhibit the coagulation complexes by interfering with the binding of clotting factors to phospholipids. We conclude that the basic enzyme, CM-IV, inhibits the prothrombinase complex by a novel mechanism independent of enzymatic activity.

The inhibition of clotting complexes of the extrinsic coagulation cascade by the phospholipase A2 isoenzymes from Naja nigricollis venom

Phospholipase A2 (PLA2) isoenzymes from Naja nigricollis venom exhibit anticoagulant activity with varying potencies. To determine which complexes in the extrinsic coagulation cascade are inhibited by these PLA2 enzymes, we examined their effects on the coagulation of bovine plasma initiated by the addition of thromboplastin, Russell's viper venom (RVV) or thrombin. The weakly anticoagulant PLA2 enzymes, CM-I and CM-II, prolonged clotting initiated by thromboplastin, but not that initiated by RVV or thrombin. The strongly anticoagulant enzyme, CM-IV, prolonged clotting initiated by both thromboplastin and RVV, but not clotting initiated by thrombin. To confirm the differences in their inhibitory properties, we examined the effect of these PLA2 enzymes on reconstituted extrinsic tenase and prothrombinase complexes. The weakly anticoagulant enzymes inhibited the tenase complex, but did not inhibit the prothrombinase complex, whereas the strongly anticoagulant enzyme inhibited both complexes. Thus the enzymes showed distinct differences in their inhibition patterns in the extrinsic coagulation cascade. Their dissimilarity in inhibition of the two phospholipid dependent activation steps probably reflects the difference in phospholipid requirements and/or mechanism of inhibition between the two complexes. Inhibition of successive amplification steps in the extrinsic coagulation cascade by CM-IV is consistent with its potency as a strongly anticoagulant PLA2.