Biomedical subjects

J Brett

Publications and source records attributed to J Brett.

At least 19 recordsLinked to original sources

PubMed2005

The psychological impact of mammographic screening. A systematic review.

Concerns have been raised regarding the possible negative psychological impact of the cancer screening programmes offered in the UK. This review aims to assess the extent of and factors associated with the adverse psychological consequences of mammographic screening. Fifty-four papers from 13 countries were identified, a majority of which were published after 1990, coinciding more or less with the onset of routine mammographic screening. The results report that mammographic screening does not appear to create anxiety in women who are given a clear result after a mammogram and are subsequently placed on routine recall. However, women who have further investigations following their routine mammogram experience significant anxiety in the short term, and possibly in the long term. The nature and extent of the further investigation that women are exposed to during mammographic screening determines the intensity of the psychological impact. Factors associated with the adverse psychological impact of mammographic screening included: social demographic factors of younger age, lower education, living in urban areas, manual occupation, and one or no children; cancer screening factors of dissatisfaction with information and communication during screening process, waiting time between recall letter and recall appointment, pain experienced during the mammographic screening procedures, and previous false positive result; and cancer worry factors including fear of cancer and greater perceived risk of breast cancer. Difficulties in measuring the psychological impact of screening are discussed, and methods of alleviating the negative psychological outcomes are suggested.

Age Factors↗

PubMed2003

The impact of screening on future health-promoting behaviours and health beliefs: a systematic review.

OBJECTIVES: To carry out a systematic review to examine the effects of cholesterol, breast and cervical cancer screening on actual or intended health-promoting behaviours and health-related beliefs. DATA SOURCES: Eleven electronic databases (between 1980 and 2000). REVIEW METHODS: All English language studies that investigated the impact of cholesterol, breast and cervical screening programmes on health-promoting behaviours and beliefs were assessed for inclusion. The data extraction form and quality assessment criteria were developed using the NHS Centre for Reviews and Dissemination guidelines. Data were extracted and a non-quantitative synthesis was conducted. Reviewers categorised the outcomes into those that could be considered beneficial or detrimental to health. This categorisation was based on a value judgement that considered both statistical and clinical significance. RESULTS: The cholesterol studies used prospective designs more frequently, possibly as many focused on observing changes in lifestyle following screening. Participants who went for breast or cervical screening were not offered advice on lifestyle changes and most of the research into cancer screening programmes investigated issues related to uptake of screening services, explanations of why people are or are not screened and interventions to improve uptake. All three screening programmes are associated with high levels of favourable health behaviours and beliefs that have been measured, although there is evidence that recommended follow-up after screening is often not adhered to. There was no literature on the cost-effectiveness regarding the wider implications of screening (only on reduction of disease-specific mortality/morbidity), possibly due to the outcomes being very broad and not easily categorised and classified. CONCLUSIONS: The studies reviewed suggest that cholesterol screening had a positive effect on health behaviours, although participation was voluntary and those screened were possibly more motivated to make changes. These results are therefore not generalisable to the entire population and other factors need to be taken into account. Reduction in blood cholesterol levels was reported in all but two of the studies that assessed this outcome, suggesting that successful lifestyle changes were made. However, as most of the studies only reported follow-up of those screened, some of the reduction can be attributable to regression to the mean. Whether breast and cervical screening affect future health behaviours and beliefs has not been directly measured in many studies and few studies have collected baseline measures. However, evidence suggests that women who attend breast and cervical screening once are likely to reattend and attendance is associated with several positive health behaviours, although it cannot be confirmed whether the associations observed were a result of screening or because these women have a certain set of health behaviours and beliefs irrespective of their experience of screening. Areas of further research include: measuring a much wider range of behaviours and beliefs before and after screening is accepted or declined, examining the subgroup of participants who receive 'desirable' results and the impact of this on health beliefs and health-promoting behaviour, and qualitative research into the experiences of screening and how this interacts with knowledge and beliefs about other aspects of health.

Breast Neoplasms↗

PubMed2001

Women who are recalled for further investigation for breast screening: psychological consequences 3 years after recall and factors affecting re-attendance.

BACKGROUND: In 1995-1996 a study was commenced investigating the experience of 'false-positive' women, i.e. who had undergone further investigations following routine breast screening and received a clear final result. These women were found to experience significantly greater adverse psychological consequences at 1 month, 5 months and 11 months after assessment compared with women who received a clear result after the initial basic mammogram. The present study follows up these 'false-positive' women 3 years later (at 35 months) just before being invited for their next routine breast screening. It investigates the effect of the previous experience of breast screening on adverse psychological consequences reported by false-positive women at this time, and explores factors that may be associated with the current adverse psychological consequences. Factors influencing attendance for the forthcoming appointment are reported, and the non-attendance rate is monitored. METHODS: Women who had previously completed a questionnaire 1 month, 5 months and 11 months after their last breast screening 3 years ago, were invited to complete a postal questionnaire just before being invited to attend for their next routine mammogram 3 years later. Attendance for this appointment was monitored. A brief questionnaire was sent to non-attenders to ascertain their reasons for not attending. RESULTS: The response rate was 77 per cent (387/505). Women who, at their last routine breast screening, had received a clear result after fine needle aspiration (FNA) at assessment, after a surgical biopsy or after a 6 month early recall appointment, all suffered significantly greater adverse psychological consequences at 1 month before returning for routine breast screening 3 years later than women who had received a clear result after the initial mammogram at their last routine breast screening. They were between 1.7 and 2 times more likely to suffer psychological consequences than women who received a clear result after their last mammogram. Women who had received a clear result at assessment without undergoing FNA reported higher psychological consequences than those who received a clear result after mammography, but the difference was not significant (relative risk 1.28, 95 per cent confidence interval 0.82-2.00). Fifteen per cent of those who had undergone assessment 3 years earlier did not attend their next routine breast screening appointment compared with 8 per cent of those who received a clear result after mammography (p = 0.035). Factors associated with adverse psychological consequences are reported. CONCLUSION: Despite having received a final clear result during their previous routine breast screening 3 years ago, women who had undergone FNA, surgical biopsy or been placed on early recall suffered significantly greater adverse psychological consequences at 1 month before their next routine breast screening appointment than women who had received a clear result after their initial mammogram at their last routine breast screening. Having undergone further investigations did not necessarily motivate women to attend for their next routine appointment, with 15 per cent of these women not returning for routine screening 3 years on.

Anxiety↗

PubMed2000

School-based HIV prevention. A promising model.

This article explores connections between the mental health and educational systems by profiling the Redefining Actions and Decisions (RAD) curriculum, a theory-based, developmentally informed HIV education program for middle and high schools. RAD was developed by Deborah R. Schoeberlein and evaluated by Dr. John Brett. RAD's public health approach, which has gained considerable attention at the national level, argues that HIV prevention, either through risk-abstinence or risk-reduction techniques, is an appropriate strategy for safeguarding community health.

Acquired Immunodeficiency Syndrome↗

PubMed1999

Endothelial-monocyte activating polypeptide II, a novel antitumor cytokine that suppresses primary and metastatic tumor growth and induces apoptosis in growing endothelial cells.

Neovascularization is essential for growth and spread of primary and metastatic tumors. We have identified a novel cytokine, endothelial-monocyte activating polypeptide (EMAP) II, that potently inhibits tumor growth, and appears to have antiangiogenic activity. Mice implanted with Matrigel showed an intense local angiogenic response, which EMAP II blocked by 76% (P < 0.001). Neovascularization of the mouse cornea was similarly prevented by EMAP II (P < 0.003). Intraperitoneally administered EMAP II suppressed the growth of primary Lewis lung carcinomas, with a reduction in tumor volume of 65% versus controls (P < 0.003). Tumors from human breast carcinoma-derived MDA-MB 468 cells were suppressed by >80% in EMAP II-treated animals (P < 0.005). In a lung metastasis model, EMAP II blocked outgrowth of Lewis lung carcinoma macrometastases; total surface metastases were diminished by 65%, and of the 35% metastases present, approximately 80% were inhibited with maximum diameter <2 mm (P < 0.002 vs. controls). In growing capillary endothelial cultures, EMAP II induced apoptosis in a time- and dose-dependent manner, whereas other cell types were unaffected. These data suggest that EMAP II is a tumor-suppressive mediator with antiangiogenic properties allowing it to target growing endothelium and limit establishment of neovasculature.

Animals↗

PubMed1998

Do women who undergo further investigation for breast screening suffer adverse psychological consequences? A multi-centre follow-up study comparing different breast screening result groups five months after their last breast screening appointment.

BACKGROUND: In 1995-1996 about 53500 women aged 50-64 attending for routine breast screening were called back for further investigation after an initial mammogram. Even when women were found to be clear after further investigation, significant adverse psychological consequences (PCs) can remain one month later. This follow-up study investigates whether residual emotional effects persisted five months after women received a clear result. METHODS: Women who had previously completed a questionnaire one month after their last breast screening appointment, at which they had a clear result, were invited to complete a further postal questionnaire four months later (five months after their last appointment). We compare women who received a clear result after assessment without fine needle aspiration cytology (FNAC), after assessment with FNAC, after a benign biopsy, and those who had been placed on early recall, with those who received a clear result after mammography (reference group). RESULTS: The response rate was 76 per cent (215/284). All groups of women who went on for further investigation suffered significantly greater adverse psychological consequences (PCs) at five months than women who were given a clear result after mammography. Compared with 10 per cent (5/52) of women who received a clear result after a basic mammogram, adverse psychological consequences were experienced by 59 per cent (27/46, p<0.00001) of the women who were placed on six month early recall, 61 per cent (14/23, p<0.0001) of women who had benign surgical biopsy, 44 per cent (18/41, p<0.0001) of women who received a clear result after assessment (with FNAC), and 45 per cent (23/51, p<0.0001) of women who received a clear result after assessment (without FNAC). Whereas all groups who had gone on for further investigations had experienced a significant decrease in PCs between one month and five months, those who were placed on six month early recall showed no significant difference in PCs between these two time periods. Other factors relating to adverse experiences as a result of breast screening are reported. CONCLUSION: Despite receiving a clear final result, women who undergo further investigation suffer significantly greater adverse psychological consequences five months after their last screening appointment than women who receive a clear result after mammography.

Adaptation, Psychological↗

PubMed1997

Breast screening: adverse psychological consequences one month after placing women on early recall because of a diagnostic uncertainty. A multicentre study.

BACKGROUND: It was the original intention of the UK National Health Service Breast Screening Programme (NHSBSP) to place women who were not diagnosed with cancer on three yearly routine recall (RR). In 1994-5 approximately 16,500 women, aged 50 to 64, were placed on early recall (ER) at a shorter time interval, of which about 98% will have a normal result. This large number exceeds the expectations of the NHSBSP. OBJECTIVE: To establish the adverse psychological consequences (PCs) for women one month after placement on ER because of a diagnostic uncertainty, and if detected, to suggest practical solutions to reduce them. METHODS: Thirteen breast screening centres throughout the UK participated in the study. From March to October 1995 all women who were placed on ER because of a diagnostic uncertainty were identified and compared with groups of women placed on RR (after mammography, assessment, fine needle aspiration, and a benign biopsy). These women were invited to complete a postal questionnaire one month after they were placed on ER or RR. One reminder was sent. RESULTS: Overall 75% of women completed the questionnaire. The adverse PCs of placing women on ER because of a diagnostic uncertainty were higher (63%; n = 81 of 130) than those of women placed on RR after mammography (29%; n = 38 of 130) (P < 0.00001) or assessment (50%; n = 64 of 128) (P < 0.05), but lower than the adverse PCs of women who underwent a benign biopsy (87%; n = 26 of 30) (P < 0.05). Factors that were significantly associated with subsequent adverse PCs were identified. CONCLUSIONS: The adverse PCs of being placed on ER because of a diagnostic uncertainty were significantly higher than those of women who turned out to have a false-positive mammographic result after assessment. Possible practical solutions are discussed.

Breast Neoplasms↗

PubMed1996

A novel tumor-derived mediator that sensitizes cytokine-resistant tumors to tumor necrosis factor.

Therapeutic successes following treatment of murine tumors with tumor necrosis factor-alpha (TNF) have not been easily applied to clinical oncology because the concentrations of TNF required in humans induces systemic toxicity. This has led us to identify mediators which could sensitize tumors to the effects of TNF, permitting administration of lower doses and possible realization of the therapeutic potential of this cytokine. Our study reports the ability of a novel cytokine, endothelial-monocyte-activating polypeptide II (EMAP II), to sensitize initially resistant murine and human tumors to TNF-induced regression employing a murine model. Recombinant (r) EMAP II was purified from Escherichia coli transformed with a plasmid expressing mature EMAP II. The B16 melanoma, raised in C57BL/6 mice, or a human fibrosarcoma (HT-1080), grown in immunocompromised mice, was injected intratumorally with either vehicle or rEMAP II/heat-treated EMAP II (50-100 micrograms) followed by systemic TNF/heat-treated TNF (5 micrograms) and assessed for tumor volume, hemorrhage, and histologic appearance. Both the B16 melanoma and the HT-1080 human fibrosarcoma underwent thrombohemorrhagic and acute inflammatory changes concomitant with regression or significantly slowed growth after administration of intratumor EMAP II followed by systemic TNF. Omission or inactivation of either cytokine abrogated this effect. These results demonstrate that local treatment of certain tumors with EMAP II results in enhanced susceptibility to TNF-mediated induction of thrombohemorrhage and regression.

Animals↗

PubMed1996

Cellular mechanisms of adaptation of grafts to antibody.

New, more effective, strategies of immunosuppression, including those recently designed to induce durable T cell tolerance (by grafting allogeneic or xenogeneic haematopoietic cells into T lymphocyte-depleted recipients), leave humoral rejection as the main barrier to transplantation of vascularized organs between different species. Recent experimental work indicates that hyperacute rejection can be prevented by manipulations of antibodies and complement. In this paper, we review the mechanisms governing the interaction of antibodies with cell surface antigens in vitro and in vivo, and their cellular consequences. Evidence is presented that, in appropriate conditions, antibodies can protect by effecting modification of graft antigenicity (adaptation or accommodation).

Animals↗

PubMed1996

RAGE: a novel cellular receptor for advanced glycation end products.

Exposure of proteins to reducing sugars results in nonenzymatic glycation with the ultimate formation of advanced glycation end products (AGEs). One means through which AGEs modulate cellular functions is through binding to specific cell surface acceptor molecules. The receptor for AGEs (RAGE) is such a receptor and is a newly identified member of the immunoglobulin superfamily expressed on endothelial cells (ECs), mononuclear phagocytes (MPs), and vascular smooth muscle cells (SMCs) in both vivo and in vitro. Binding of AGEs to RAGE results in induction of cellular oxidant stress, as exemplified by the generation of thiobarbituric acid-reactive substances, expression of heme oxygenase type I, and activation of the transcription factor NF-kB, with consequences for a range of cellular functions. AGEs on the surface of diabetic red cells enhance binding to endothelial RAGE and result in enhanced oxidant stress in the vessel wall. By using reagents to selectively block access to RAGE, the role of this receptor in AGE-mediated perturbation of cellular properties can be dissected in detail.

Animals↗

PubMed1996

Increased osteoclastic differentiation by PMMA particle-associated macrophages. Inhibitory effect by interleukin 4 and leukemia inhibitory factor.

To determine the influence of polymethylmethacrylate (PMMA) wear particles on macrophage-osteoclast differentiation, PMMA particles were added to mouse monocytes which were cocultured with UMR 106 osteoblast-like cells in the presence of 1,25 dihydroxy vitamin D3[1,25(OH)2D3] for up to 7 days on glass coverslips and for up to 14 days on human cortical bone slices. An increase in osteoclast differentiation, as evidenced by the expression of the osteoclast-associated enzyme tartrate-resistant acid phosphatase (TRAP) and the extent of lacunar bone resorption, was observed in monocyte cultures to which PMMA had been added. Interleukin 4 (IL-4) and Leukemia Inhibitory Factor (LIF) added to these cocultures caused considerably less expression of TRAP and significant inhibition of lacunar bone resorption. This inhibitory effect was reversed by the addition of specific neutralizing antibodies to LIF and IL-4. These findings show that PMMA-wear particle-associated macrophages exhibit an enhanced capacity for differentiation to osteoclastic bone-resorbing cells.

Acid Phosphatase↗

PubMed1995

Functional interactions of T cells with endothelial cells: the role of CD40L-CD40-mediated signals.

CD40 is expressed on a variety of cells, including B cells, monocytes, dendritic cells, and fibroblasts. CD40 interacts with CD40L, a 30-33-kD activation-induced CD4+ T cell surface molecule. CD40L-CD40 interactions are known to play key roles in B cell activation and differentiation in vitro and in vivo. We now report that normal human endothelial cells also express CD40 in situ, and CD40L-CD40 interactions induce endothelial cell activation in vitro. Frozen sections from normal spleen, thyroid, skin, muscle, kidney, lung, or umbilical cord were studied for CD40 expression by immunohistochemistry. Endothelial cells from all tissues studied express CD40 in situ. Moreover, human umbilical vein endothelial cells (HUVEC) express CD40 in vitro, and recombinant interferon gamma induces HUVEC CD40 upregulation. CD40 expression on HUVEC is functionally significant because CD40L+ Jurkat T cells or CD40L+ 293 kidney cell transfectants, but not control cells, upregulate HUVEC CD54 (intercellular adhesion molecule-1), CD62E (E-selectin), and CD106 (vascular cell adhesion molecule-1) expression in vitro. Moreover, the kinetics of CD40L-, interleukin 1-, or tumor necrosis factor alpha-induced CD54, CD62E, and CD106 upregulation on HUVEC are similar. Finally, CD40L-CD40 interactions do not induce CD80, CD86, or major histocompatibility complex class II expression on HUVEC in vitro. These results demonstrate that CD40L-CD40 interactions induce endothelial cell activation in vitro. Moreover, they suggest a mechanism by which activated CD4+ T cells may augment inflammatory responses in vivo by upregulating the expression of endothelial cell surface adhesion molecules.

Antigens, CD↗

PubMed1995

The receptor for advanced glycation end products (RAGE) is a cellular binding site for amphoterin. Mediation of neurite outgrowth and co-expression of rage and amphoterin in the developing nervous system.

The receptor for advanced glycation end products (RAGE), a newly-identified member of the immunoglobulin superfamily, mediates interactions of advanced glycation end product (AGE)-modified proteins with endothelium and other cell types. Survey of normal tissues demonstrated RAGE expression in situations in which accumulation of AGEs would be unexpected, leading to the hypothesis that under physiologic circumstances, RAGE might mediate interaction with ligands distinct from AGEs. Sequential chromatography of bovine lung extract identified polypeptides with M(r) values of approximately 12,000 (p12) and approximately 23,000 (p23) which bound RAGE. NH2-terminal and internal protein sequence data for p23 matched that reported previously for amphoterin. Amphoterin purified from rat brain or recombinant rat amphoterin bound to purified sRAGE in a saturable and dose-dependent manner, blocked by anti-RAGE IgG or a soluble form of RAGE (sRAGE). Cultured embryonic rat neurons, which express RAGE, displayed dose-dependent binding of 125I-amphoterin which was prevented by blockade of RAGE using antibody to the receptor or excess soluble receptor (sRAGE). A functional correlate of RAGE-amphoterin interaction was inhibition by anti-RAGE F(ab')2 and sRAGE of neurite formation by cortical neurons specifically on amphoterin-coated substrates. Consistent with a potential role for RAGE-amphoterin interaction in development, amphoterin and RAGE mRNA/antigen were co-localized in developing rat brain. These data indicate that RAGE has physiologically relevant ligands distinct from AGEs which are likely, via their interaction with the receptor, to participate in physiologic processes outside of the context of diabetes and accumulation of AGEs.

Animals↗

PubMed1995

Induction of interleukin 6 (IL-6) by hypoxia in vascular cells. Central role of the binding site for nuclear factor-IL-6.

The pathologic picture in ischemic tissue injury shares features with the inflammatory response, including production of proinflammatory cytokines. Hypoxia-mediated induction of interleukin-6 (IL-6), a cytokine with anti-inflammatory properties, could set in motion mechanisms limiting inflammation in ischemia. Exposure of cultured endothelial cells (ECs) to H (pO2 approximately 12-16 torr) increased transcription of IL-6, elevated levels of IL-6 mRNA, and induced elaboration of IL-6 antigen in a time-dependent manner. Exposure of mice to hypoxia increased IL-6 transcripts in the lung, and immunostaining revealed a striking increase in IL-6 antigen in pulmonary vasculature. Transfection of ECs with deletion chimeric IL-6 promoter-chloramphenicol acetyl-transferase (CAT) constructs showed hypoxia-mediated 9-11-fold induction with -1200/+13, -596/+13, and -225/+13 but no induction with -111/+13. Electrophoretic mobility shift assays (EMSAs) using -225/-111 as the labeled probe demonstrated enhanced binding activity in nuclear extracts of hypoxic ECs and lung; the appearance of the gel shift band was prevented by excess unlabeled probe (-225/-111), and hypoxia-mediated enhancement of the band was blocked by a probe corresponding to the nuclear factor (NF)-IL-6 site (-158/-145). The hypoxia-enhanced band on EMSA displayed a supershift with antibody to CCAAT-enhancer-binding protein beta (C/EBP-beta), but antibody to C/EBP-alpha or -delta was without effect. Transfection of ECs with a construct comprising thymidine kinase promoter, -225/-111 in either the 5' to 3' to 5' orientation, and the reporter CAT showed this region to be an enhancer (approximately 8-fold) under hypoxia. EMSA with the NF-IL-6 probe revealed a prominent induction of binding activity with nuclear extracts from hypoxic ECs and whole lung. Constructs with -158/-145 and the CAT reporter gene showed induction when transfected into hypoxic ECs, whereas a similar construct with the NF-IL-6 motif mutationally inactivated failed to display hypoxia-induced expression. Furthermore, the tumor necrosis factor (TNF) gene, whose product contributes to ischemic pathology and contains a putative regulatory NF-IL-6 site, demonstrated enhanced binding activity for its NF-IL-6 motif and induction of TNF mRNA based on analysis of hypoxic lung. These data indicate that hypoxia induces expression of IL-6, most likely a result of hypoxic activation at the NF-IL-6 site, and suggest that other genes with regulatory NF-IL-6 sites may also be induced by a similar mechanism.

Animals↗

PubMed1995

Calreticulin, an antithrombotic agent which binds to vitamin K-dependent coagulation factors, stimulates endothelial nitric oxide production, and limits thrombosis in canine coronary arteries.

Coagulation Factor IX/IXa has been shown to bind to cellular surfaces, and Factor IXa expresses its procoagulant activity by assembling into the intrinsic Factor X activating complex (Factors IXa/VIIIa/X), which also forms on membrane surfaces. This led us to identify cellular proteins which bind Factor IX/IXa; an approximately 55-kDa polypeptide was purified to homogeneity from bovine lung extracts based on its capacity to bind 125I-Factor IX in a dose-dependent and saturable manner. From protein sequence data of the amino terminus and internal peptides, the approximately 55-kDa polypeptide was identified as calreticulin, a previously identified intracellular calcium-binding protein. Recombinant calreticulin bound vitamin K-dependent coagulation factors, 125I-Factor IX, 125I-Factor X, and 125I-prothrombin (Kd values of approximately 2.7, 3.2, and 8.3 nM, respectively), via interaction with its C-domain, although it did not affect the coagulant properties of these proteins. 125I-Calreticulin also bound to endothelial cells in vitro (Kd approximately 7.4 nM), and mouse infusion studies showed an initial rapid phase of clearance in which calreticulin could be localized on the vascular endothelium. Exposure of endothelial cells to calreticulin led to dose-dependent, immediate, and sustained increase in the production of nitric oxide, as measured using a porphyrinic microsensor. In a canine electrically induced thrombosis model, intracoronary infusion of calreticulin (n = 7) prevented occlusion of the left circumflex coronary artery in a dose-dependent manner compared with vehicle-treated controls (n = 5). These results indicate that calreticulin interacts with the endothelium to stimulate release of nitric oxide and inhibit clot formation.

Animals↗

PubMed1995

TNF modulates endothelial properties by decreasing cAMP.

Tumor necrosis factor-alpha (TNF-alpha), a monokine that contributes to vascular dysfunction accompanying the host response to gram-negative sepsis, has been shown to increase vascular permeability in vivo and to diminish the barrier function of cultured endothelial cell (EC) monolayers. The studies reported here indicate that a mechanism through which TNF alters EC barrier function involves a reduction in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) content, due in part to increased cyclic nucleotide phosphodiesterase (CNPDE) activities. TNF increased the diffusional transit of [3H]sorbitol, [3H]inulin, and 125I-labeled albumin across confluent bovine aortic EC monolayers. This effect of TNF was both time and dose dependent and occurred in parallel with a fall in EC cAMP. cAMP analogues, such as dibutyryl cAMP (DBcAMP), prevented TNF-induced perturbation of EC barrier function. TNF also mediated another important alteration in the EC phenotype, in that both mRNA and activity of the anticoagulant cofactor thrombomodulin were reduced after exposure of EC to TNF and were normalized by the addition of DBcAMP. EC monolayers exposed to TNF-alpha showed increased cAMP levels when exposed to 3-isobutyl-1-methylxanthine, a nonspecific CNPDE inhibitor. Ion exchange chromatography of cytosol derived from TNF-treated EC consistently showed an approximately 245% increase in phosphodiesterase (PDE) IV (high-affinity, cAMP-specific PDE) activity as identified by rolipram inhibition. PDE II activity was increased by 150% after TNF-alpha treatment of early passage EC, which was identified by cGMP-activated hydrolysis of cAMP. Western and Northern analyses, as well as activity studies, revealed that TNF treatment did not change the amount of PDE IV protein or mRNA but rather increased the specific activity of the isozyme, suggesting that a posttranslational modification had occurred. These data indicate that activation of EC CNPDE activity and decreased intracellular cAMP may represent a mechanism by which TNF increases EC permeability and promotes a procoagulant EC phenotype.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1995

Advanced glycation endproducts interacting with their endothelial receptor induce expression of vascular cell adhesion molecule-1 (VCAM-1) in cultured human endothelial cells and in mice. A potential mechanism for the accelerated vasculopathy of diabetes.

Vascular cell adhesion molecule-1 (VCAM-1), an inducible cell-cell recognition protein on the endothelial cell surface (EC), has been associated with early stages of atherosclerosis. In view of the accelerated vascular disease observed in patients with diabetes, and the enhanced expression of VCAM-1 in diabetic rabbits, we examined whether irreversible advanced glycation endproducts (AGEs), could mediate VCAM-1 expression by interacting with their endothelial cell receptor (receptor for AGE, RAGE). Exposure of cultured human ECs to AGEs induced expression of VCAM-1, increased adhesivity of the monolayer for Molt-4 cells, and was associated with increased levels of VCAM-1 transcripts. The inhibitory effect of anti-RAGE IgG, a truncated form of the receptor (soluble RAGE) or N-acetylcysteine on VCAM-1 expression indicated that AGE-RAGE-induced oxidant stress was central to VCAM-1 induction. Electrophoretic mobility shift assays on nuclear extracts from AGE-treated ECs showed induction of specific DNA binding activity for NF-kB in the VCAM-1 promoter, which was blocked by anti-RAGE IgG or N-acetylcysteine. Soluble VCAM-1 antigen was elevated in human diabetic plasma. These data are consistent with the hypothesis that AGE-RAGE interaction induces expression of VCAM-1 which can prime diabetic vasculature for enhanced interaction with circulating monocytes.

Animals↗

PubMed1995

Interaction of antibody with Forssman antigen in guinea pigs. A mechanism of adaptation to antibody- and complement-mediated injury.

Forssman antigen is a glycosphingolipid with antigenic specificity determined by extra-membrane haptenic sugars similar to blood group antigens and antigens that are the main barrier to xenogeneic organ transplantation. Herein, we describe the localization of Forssman antigen in guinea pig lungs and kidneys and the consequences of its interaction with antibodies in vitro and in vivo (Forssman reaction). Exposure of cultured guinea pig aortic endothelial cells to Forssman antibodies induced rapid redistribution of antigen-antibody complexes at the cell surface, followed by shedding that occurred by blebbing of plasma membrane as vesicles or fragments, and was associated with disappearance of antigen from the cell surface (antigenic modulation). Guinea pigs surviving frequent intravenous infections of increasing amounts of antibodies, for a total of 20 to 40 lethal doses, developed a partial or complete adaptation to generalized Forssman reaction, and adaptation was associated with partial or complete modulation of Forssman antigen at the surface of the pulmonary and, in minor degree, renal endothelial and epithelial cells. These findings support the hypothesis that modulation of endothelial carbohydrate antigens contributes to adaptation of highly vascularized organs exposed to tolerable levels of allo- or xenoantibodies.

Animals↗