Endocrine disruptors: Challenges and future directions in epidemiologic research.

Public concern about the impact of endocrine disrupting chemicals (EDCs) on both humans and the environment is growing steadily. Epidemiologic research provides key information towards our understanding of the relationship between environmental exposures like EDCs and human health outcomes. Intended for researchers in disciplines complementary to epidemiology, this paper highlights the importance and challenges of epidemiologic research in order to present the key elements pertaining to the design and interpretation of an epidemiologic study on EDCs. The conduct of observational studies on EDCs derives from a thoughtful research question, which will help determine the subsequent methodological choices surrounding the careful selection of the study population (including the comparison group), the adequate ascertainment of exposure(s) and outcome(s) of interest, and the application of methodological and statistical concepts more specific to epidemiology. The interpretation of epidemiologic results may be arduous due to the latency occurring between EDC exposure and certain outcome(s), the complexity in capturing EDC exposure(s), and traditional methodological and statistical issues that also deserve consideration (e.g., confounding, effect modification, non-monotonic responses). Moving forward, we strongly advocate for an integrative approach of expertise in the fields of epidemiology, exposure science, risk assessment and toxicology to adequately study the health risks associated with EDCs while tackling their challenges.

LKB1 deficiency in T cells promotes the development of gastrointestinal polyposis.

Germline mutations in STK11, which encodes the tumor suppressor liver kinase B1 (LKB1), promote Peutz-Jeghers syndrome (PJS), a cancer predisposition syndrome characterized by the development of gastrointestinal (GI) polyps. Here, we report that heterozygous deletion of Stk11 in T cells (LThet mice) is sufficient to promote GI polyposis. Polyps from LThet mice, Stk11+/- mice, and human PJS patients display hallmarks of chronic inflammation, marked by inflammatory immune-cell infiltration, signal transducer and activator of transcription 3 (STAT3) activation, and increased expression of inflammatory factors associated with cancer progression [interleukin 6 (IL-6), IL-11, and CXCL2]. Targeting either T cells, IL-6, or STAT3 signaling reduced polyp growth in Stk11+/- animals. Our results identify LKB1-mediated inflammation as a tissue-extrinsic regulator of intestinal polyposis in PJS, suggesting possible therapeutic approaches by targeting deregulated inflammation in this disease.

[Cultural diversity in Montreal: a range of public health challenges]. / La diversité culturelle montréalaise: une diversité de défis pour la santé publique.

Increasing immigration to Quebec has brought to the surface the need for adapting its public health systems and services, particularly in the area of primary care. The challenge is to take the heterogeneous nature of the population into account and to integrate diverse values, experience and know-how into the development of programmes and delivery of services, whilst simultaneously respecting the values of the various care providers and the norms of the institutions in the host country. This article addresses the question of adaptation strategies for health services, and namely the development of prevention and heath promotion programmes in public health within the framework of primary health care services within the intercultural context of Montreal. The issue of adaptation falls within the perspective and mandate of the Quebec government's policy on health and well-being (La politique de santé et du bien-être, 1992). Furthermore, it is a response to frequent demands from various health professionals and groups concerned with the adaptation of public services with respect to intercultural relationships confronted with the emerging realities associated with immigration. The article provides a reflection on specific ways of adapting prevention and health promotion initiatives targeting cultural communities and those who are undergoing immigration procedures or transitions. It also examines the development of ethno-cultural or other indicators which make it possible to capture migration experiences and their health impact. Since the Quebec health and social services system is currently in the process of major reform, it is hoped that it will seize this opportunity in order to make health and social service centres accountable for the adaptation of their programmes and services to the diversity of the populations they serve.

[Migration, ethics and public health in Quebec]. / Migration, éthique et santé publique au Québec.

This article analyses the ethical issues of migration in relation to public health in Quebec. There are two objectives: to describe the progression of analysis of the migration phenomenon in public health over the last thirty years and to state the ethical debate it raises. The progression of analysis of the migration phenomenon has been characterised by various approaches: intercultural, acculturation, transcultural, and migratory journey. Although these approaches have contributed to the development of knowledge about the reality of immigration, they have also, in spite of themselves, generated stigmatisation, discrimination and the proliferation of prejudices. Generally, findings that have emerged when migration is taken into account indicate an imbalance of power. For some, to focus on the phenomenon of migration promotes the power imbalance while for others, to disregard it masks the issue.

Prostaglandin D2 is a potent chemoattractant for human eosinophils that acts via a novel DP receptor.

Prostaglandin D2 (PGD2) is released following exposure of asthmatics to allergen and acts via the adenylyl cyclase-coupled receptor for PGD2 (DP receptor). In this study, it is reported that human eosinophils possess this receptor, which would be expected to inhibit their activation. In contrast, it was found that prostaglandin D2 is a potent stimulator of eosinophil chemotaxis, actin polymerization, CD11b expression, and L-selectin shedding. These responses are specific for eosinophils, as neutrophils display little or no response to prostaglandin D2. They were not due to interaction with receptors for other prostanoids, as prostaglandins E2 and F(2alpha), U46619 (a thromboxane A2 analogue), and carbaprostacyclin (a prostacyclin analogue) displayed little or no activity. Furthermore, they were not shared by the selective DP receptor agonist BW245C and were not prevented by the selective DP receptor antagonist BWA868C, indicating that they were not mediated by DP receptors. In contrast, the prostaglandin D2 metabolite 13,14-dihydro-15-oxoprostaglandin D2 induced eosinophil activation but did not stimulate DP receptor-mediated adenosine 3',5'-cyclic monophosphate (cAMP) formation. These results indicate that in addition to the classic inhibitory DP1 receptor, eosinophils possess a second, novel DP2 receptor that is associated with PGD2-induced cell activation. These 2 receptors appear to interact to regulate eosinophil responses to PGD2, as blockade of DP1 receptor-mediated cAMP production by BWA868C resulted in enhanced DP2 receptor-mediated stimulation of CD11b expression. The balance between DP1 and DP2 receptors could determine the degree to which prostaglandin D2 can activate eosinophils and may play a role in eosinophil recruitment in asthma.

Eotaxin and RANTES enhance 5-oxo-6,8,11,14-eicosatetraenoic acid-induced eosinophil chemotaxis.

BACKGROUND: The 5-lipoxygenase product 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a potent activator of human eosinophils and, among lipid mediators, is the most active chemoattractant for these cells. Studies have demonstrated the importance of 5-lipoxygenase products in allergen-induced pulmonary eosinophilia. Because CC chemokines such as eotaxin and RANTES also play critical roles in this phenomenon, it would seem likely that members of both classes of mediators contribute to this response. OBJECTIVE: The study was designed to directly compare the effects of 5-oxo-ETE on eosinophils with those of eotaxin and RANTES and to determine whether these chemokines could enhance the chemotactic response to 5-oxo-ETE. METHODS: Eosinophil chemotaxis was measured with microchemotaxis chambers. CD11b, L-selectin, and actin polymerization were measured by flow cytometry. Calcium mobilization was measured by fluorescence. RESULTS: 5-Oxo-ETE stimulated eosinophil chemotaxis with a potency between those of eotaxin and RANTES and a maximal response about 50% higher than that of eotaxin. Threshold concentrations of eotaxin and RANTES increased the chemotactic potency of 5-oxo-ETE by more than 4-fold. 5-Oxo-ETE and eotaxin were approximately equipotent in mobilizing cytosolic calcium in eosinophils. Eotaxin was more potent in inducing CD11b expression and actin polymerization, but the maximal responses to 5-oxo-ETE were about 50% higher. 5-Oxo-ETE strongly induced L-selectin shedding, whereas eotaxin elicited only a weak and variable response. CONCLUSION: 5-Oxo-ETE is a strong activator of human eosinophils with a chemotactic potency comparable to those of eotaxin and RANTES, both of wwhich enhance 5-oxo-ETE-induced chemotaxis. 5-Oxo-ETE and CC chemokines may combine to induce pulmonary eosinophilia in asthma.

Chronic PMA treatment of Jurkat T lymphocytes results in decreased protein tyrosine phosphorylation and inhibition of CD3- but not Ti-dependent antibody-triggered Ca2+ signaling.

We have treated Jurkat T lymphocytes with a concentration (160 nM) of phorbol myristyl acetate (PMA) that down-regulates conventional and novel protein kinase C (PKC) isozymes and we have investigated the effects on Ca2+ signaling and protein tyrosine phosphorylation using mAb (C305) directed against the beta-subunit of the Ti heterodimer or the epsilon/delta-component of the CD3 complex (mAb Leu 4 or OKT 3). The levels of expression of PKC alpha, betaI, betaII, and delta were reduced by 90% or more in PMA-treated cells, whereas the expression of PKCtheta decreased by approximately 30%. In contrast, the chronic treatment with PMA increased the expression of PKCepsilon and PKCzeta. There was a lack of Ca2+ response and myo-inositol trisphosphate (IP3) production in PMA-treated cells when they were exposed to mAb Leu 4 but the cells responded to mAb C305. The treatment with PMA did not affect the surface expression of Ti or CD3. The overall levels of tyrosine-phosphorylated proteins were markedly reduced in PMA-treated cells. We investigated whether these observations were related to defects in signal transduction related to protein tyrosine kinase (PTK) of the src and syk families. The electrophoretic mobilities of p59(fyn) or ZAP-70 were not changed in PMA-treated cells but p56(Ick) migrated as a large band of M(r) 60-62 kDa. The decreased mobility of p56(Ick) was related to a state of hyperphosphorylation. The activity of modified p56(Ick) was not up-regulated in activated Jurkat cells. Our data suggest that clonotypic Ti can trigger Ca2+ mobilization independently of conventional PKC isoforms. Our observations further suggest that conventional PKC isoforms are involved early in the cascade of events associated with Jurkat T lymphocyte activation.

The mistreatment of older adults: perpetrator-victim relationships and interventions.

ABSTRACT The characteristics of the mistreatment of older adults were investigated in a sample of 128 older adults identified as potential mistreatment cases in three community-based agencies in Quebec. Practitioners completed questionnaires to collect quantitative and qualitative data. The study also examined: (1) difficulties in identifying mistreatment, (2) interventions and outcomes, and (3) reasons for the refusal of services. The major finding (with important implications for practice) was the association between type of treatment and perpetrator relationship to victim. The harm reduction model is suggested as a useful approach to guide interventions.

Cytological and functional aspects of telomere maintenance.

The fact that eukaryotic chromosomes are linear poses a special problem for their maintenance: the natural ends of chromosomes must be distinguished from ends generated by chromosomal breakage and somehow, the chromosome ends must also be fully replicated to maintain their integrity. Telomeres, the complex structures at the ends of chromosomes are thought to be instrumental for both of these functions. However, recent insights in telomere biology suggest that these terminal structures do much more than just fulfill these two basic functions. Cytological data demonstrate that telomeres may play leading roles in chromatin organization and nuclear architecture during mitosis and meiosis. Moreover, non-functional telomeres may lead to genetic instability, a common prelude to cancer. Here, we review the basic functions of telomeres during chromosome replication and discuss the cytological aspects of telomere function during mitosis and meiosis.

Biological inactivation of 5-oxo-6,8,11,14-eicosatetraenoic acid by human platelets.

Neutrophil-derived 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a potent activator of neutrophils and eosinophils. In the present study we examined the biosynthesis and metabolism of this substance by platelets. Although platelets contain an abundant amount of 5-hydroxyeicosanoid dehydrogenase, the enzyme responsible for the formation of 5-oxo-ETE, they synthesize only very small amounts of this substance from exogenous 5-hydroxyeicosatetraenoic acid (5-HETE) unless endogenous NADPH is converted to NADP+ by addition of phenazine methosulfate. Similarly, relatively small amounts of 5-oxo-ETE were formed by A23187-stimulated mixtures of platelets and neutrophils, which instead formed substantial amounts of two 12-hydroxy metabolites of this substance, 5-oxo-12-HETE and 8-trans-5-oxo-12-HETE, which were identified by comparison with authentic chemically synthesized compounds. These metabolites were also formed from 5-oxo-ETE by platelets stimulated with thrombin or A23187. In contrast, unstimulated platelets converted 5-oxo-ETE principally to 5-HETE. Neither 5-oxo-12-HETE nor 8-trans-5-oxo-12-HETE had appreciable effects on neutrophil calcium levels or platelet aggregation at concentrations as high as 10 micromol/L, but both blocked 5-oxo-ETE-induced calcium mobilization in neutrophils with IC50 values of 0.5 and 2.5 micromol/L, respectively. We conclude that platelets can biologically inactivate 5-oxo-ETE. Unstimulated platelets convert 5-oxo-ETE to 5-HETE, with a 99% loss of biological potency, whereas stimulated platelets convert this substance to 12-hydroxy metabolites, which possess antagonist properties.

5-oxo-6,8,11,14-eicosatetraenoic acid is a potent stimulator of L-selectin shedding, surface expression of CD11b, actin polymerization, and calcium mobilization in human eosinophils.

5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a metabolite of arachidonic acid formed by the oxidation of 5-hydroxy-6,8,11, 14-eicosatetraenoic acid by a highly specific dehydrogenase. 5-oxo-ETE is a chemoattractant for both neutrophils and eosinophils. Although it is not as effective as leukotriene B4 (LTB4) and platelet-activating factor (PAF) in stimulating neutrophil migration, we found that it is considerably more active than these and a variety of other lipid mediators as an eosinophil chemoattractant. Moreover, low concentrations of 5-oxo-ETE appear to enhance the responsiveness of these cells to PAF. The objectives of the current investigation were to identify rapid responses induced in eosinophils by 5-oxo-ETE that might be related to the infiltration of these cells into tissues. We found that 5-oxo-ETE is more effective than PAF and LTB4 in inducing both L-selectin shedding and actin polymerization in human eosinophils, whereas PAF is the most active of these mediators in stimulating calcium mobilization. The complementary effects of 5-oxo-ETE and PAF on actin polymerization and calcium mobilization may explain their synergistic effect on eosinophil migration. 5-oxo-ETE and PAF were equipotent in stimulating the surface expression of the beta2-integrin CD11b, but were slightly less potent than LTB4. 5-oxo-ETE- induced actin polymerization was subject to homologous but not heterologous desensitization. It was not prevented by incubation of eosinophils with inhibitors of protein kinase C (staurosporine), mitogen-activated protein kinase kinase (PD98059), or phosphatidylinositol-3-kinase (wortmannin). In conclusion, 5-oxo-ETE is a potent activator of human eosinophils and may be an important regulator of tissue infiltration of these cells.

Single-cell analysis of the t(14;18)(q32;q21) chromosomal translocation in Hodgkin's disease demonstrates the absence of this translocation in neoplastic Hodgkin and Reed-Sternberg cells.

Using the polymerase chain reaction (PCR) technique and total DNA extracts of Hodgkin's disease (HD)-involved lymph nodes, the t(14;18)(q32;q21) translocation was detected in 37 of 115 (32.2%) cases studied. No correlation was found between the presence of this translocation and bcl-2 protein expression in Hodgkin and Reed-Sternberg (HRS) cells detected by immunohistochemistry in 58 of 96 (60.4%) cases. To identify the cells carrying the t(14;18) translocation, single-cell DNA from HRS cells isolated by micromanipulation from frozen tissue sections of lymph nodes was investigated by PCR amplification. Eleven cases showing a positive band of the same size in at least two of five PCR experiments performed on the same total DNA extract were selected for single-cell PCR. We postulated that this repeated successful amplification could be indicative of the presence of the t(14;18) translocation in the neoplastic HRS cells. Single cells from frozen tumor sections of the t(14;18)-positive OCI LY8 cell line grafted into nude mice served as a positive control. The bcl-2/JH rearrangement, involved in this translocation, could be amplified from single-cell DNA of the latter tumor, whereas, in all of the HD cases, HRS cells were found to be negative. We conclude that the t(14;18) translocation is not localized in HRS cells, but in nonmalignant B bystander lymphocytes, admixed with these neoplastic cells.

[Health promotion for immigrant women in Quebec]. / Promotion de la santé en faveur des femmes immigrant au Québec.

Over the past fifteen years, the Canadian population has undergone increasing cultural diversification. Many researchers have investigated the role of culture with respect to social and health services. Most studies confirm the fact that increased cultural diversification related to immigration challenges the public health system in many ways. Certain groups, such as economically challenged immigrant women, may pose even greater problems to the health system. While these individuals are in relatively good health upon arrival to Canada, there is a need to ensure that adequate health promotion as well as disease prevention strategies are instituted. It is important to examine the concepts of health promotion and disease prevention through a cultural perspective. Little research has been done in this area. Concepts of promotion and prevention as they are understood by immigrants may not always coincide with North American or European definitions. Therefore, it is essential to consider life conditions that surround potential health promotion and prevention behaviors of immigrants. Empowerment, economic integration and acculturation are among the many factors that need to be taken into account when studying immigrants' health promotion behavior. Here, we present a critical analysis of current knowledge in this field. This is followed by research recommendations aimed at facilitating the development of health promotion and prevention strategies that are appropriate to the needs of Canadian, and more specifically of immigrant women in Québec.

Yeast Ku as a regulator of chromosomal DNA end structure.

During telomere replication in yeast, chromosome ends acquire an S-phase-specific overhang of the guanosine-rich strand. Here it is shown that in cells lacking Ku, a heterodimeric protein involved in nonhomologous DNA end joining, these overhangs are present throughout the cell cycle. In vivo cross-linking experiments demonstrated that Ku is bound to telomeric DNA. These results show that Ku plays a direct role in establishing a normal DNA end structure on yeast chromosomes, conceivably by functioning as a terminus-binding factor. Because Ku-mediated DNA end joining involving telomeres would result in chromosome instability, our data also suggest that Ku has a distinct function when bound to telomeres.

Effects of 5-oxo-6,8,11,14-eicosatetraenoic acid on expression of CD11b, actin polymerization, and adherence in human neutrophils.

Human neutrophils contain a highly specific dehydrogenase that converts 5-hydroxy-6,8,11,14-eicosatetraenoic acid to 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE). 5-Oxo-ETE is a potent stimulator of calcium mobilization, chemotaxis, and aggregation in these cells and has similar effects on eosinophils. The primary objectives of the current study were to determine whether this compound could increase the surface expression of integrins and stimulate actin polymerization in neutrophils. 5-Oxo-ETE stimulated the expression of CD11b and, to a lesser extent, CD11c, on neutrophils, but had no significant effects on the expression of CD11a, CD16 (Fc gammaRIII), or CD32 (Fc gammaRII). Surface expression of CD11b in response to 5-oxo-ETE was maximal after 12 min and remained constant thereafter. The EC50 for this response (50 nM) was lowered to 20 nM by preincubation of neutrophils with PMA. 5-Oxo-ETE (EC50, 10 nM) also rapidly stimulated actin polymerization in neutrophils, with a maximal response at 20 s. This response was blocked by pretreatment of neutrophils with the Gi protein inhibitor, pertussis toxin, and by homologous desensitization due to preincubation with 5-oxo-ETE. However, preincubation with leukotriene B4 or platelet-activating factor had no effect on the response of neutrophils to subsequent addition of 5-oxo-ETE. The adherence of neutrophils to plasma-coated plastic was also stimulated by 5-oxo-ETE with a time course similar to that for the surface expression of CD11b. Low concentrations of PMA (0.3 nM) enhanced this response. These results raise the possibility that 5-oxo-ETE could contribute to the infiltration of neutrophils into inflammatory sites.

IgH and TcR-gamma gene rearrangements identified in Hodgkin's disease by PCR demonstrate lack of correlation between genotype, phenotype, and Epstein-Barr virus status.

Analysis of IgH and TcR-gamma genes using consensus primers identifying junctional regions of rearranged genes by polymerase chain reaction (PCR) was performed on tissues involved by Hodgkin's disease (HD) in 90 cases and was correlated with the immunophenotype of Hodgkin and Reed-Sternberg (HRS) cells and the presence of Epstein-Barr virus (EBV) within these cells. Clonal IgH gene rearrangements were found in 1/5 cases of lymphocyte predominance (LP) subtype and none was positive for EBV. In 85 cases of classic HD, no IgH or TcR-gamma gene rearrangements were found in 51 (60 per cent) cases. A similar percentage, but not the same cases, were of null (non-B, non-T) phenotype. Of 30 cases where a B phenotype was assigned to HRS cells, nine had IgH gene rearrangements, three had TcR-gamma gene rearrangements, and two had both genes rearranged. None of the five cases assigned to T phenotype of HRS cells showed rearrangement of TcR-gamma genes, but two cases showed rearranged IgH genes. Among 41 cases of null phenotype, ten had IgH gene rearrangements, five had TcR-gamma gene rearrangements, and three cases had both genes rearranged. Whereas EBV was detectable in HRS cells in 17/43 classic HD cases of assigned B phenotype, EBV was also detectable in 2/5 cases of assigned T phenotype and in 21 cases with the null phenotype. Furthermore, there was no correlation of EBV with the presence or lack or IgH or TCR-gamma gene rearrangements. Of the remainder, half (30 per cent) expressed antigens associated with lymphocytes without an appropriate genotype. The results confirm lymphocyte-lineage committed cells at the origin of HRS cells in 40 per cent of cases. Any hypothesis of a non-lymphocytic origin of HRS cells will require the inducibility of CD30 on candidate precursors and the methodology for probing genetic events in such cells to be addressed.

[Adequacy of health care services for young immigrant families]. / Adéquation des services de santé aux jeunes familles immigrantes.

This article relates the results of descriptive exploratory research conducted through interviews with 297 young immigrant families and 40 health and social workers on the primary health problems encountered by the families and on how they resolved these problems. Families and workers rank problems in different orders of priority. While families give priority to the health problems of their children, workers give priority to the problems encountered by the mothers, and in particular, mental health problems. Families and workers alike express a desire for help from the health and social service system for these problems. For families, this help would come from family doctors and nurses. These health providers are subsequently consulted; when they are not, language is determined to be the main obstacle to accessibility. Difficulties related to cultural compatibility of services are seen as more numerous by workers than by families.

Effects of metabolites of leukotriene B4 on human neutrophil migration and cytosolic calcium levels.

Leukotriene B4 (LTB4) is metabolized by beta-oxidation, omega-oxidation and the 12-hydroxyeicosanoid dehydrogenase/delta 10-reductase pathway. We have investigated the effects of metabolites formed by the latter pathway on calcium mobilization and migration in human neutrophils and have compared their potencies with those of other LTB4 derivatives. 12-Oxo-LTB4 and 10,11-dihydro-LTB4 were 60 to 100 times less potent than LTB4 in stimulating neutrophils, whereas 10,11-dihydro-12-oxo-LTB4 and 10,11-dihydro-12-epi-LTB4 exhibited still lower potencies. The 6-trans isomers of 12-oxo-LTB4 and 10,11-dihydro-12-oxo-LTB4 were much less potent than the 6-cis compounds. The EC50 values for biologically and chemically (6-cis) synthesized 12-oxo-LTB4 were similar, indicating that the 6,7-double bond is retained in the cis configuration in the biologically formed compound. Methylation of LTB4 markedly reduced its effect on cytosolic calcium levels, whereas addition of a 3-hydroxyl group had a much more modest effect. Modifications of the omega end of the molecule also resulted in lower potencies for calcium mobilization. Nearly all of the compounds tested desensitized neutrophils to LTB4-induced calcium mobilization, which suggests that their effects were mediated by receptors for the latter compound. However, modifications in the carboxyl end of the molecule had smaller effects on desensitization than on calcium mobilization, whereas the reverse was true for modifications in the omega end of the molecule. This suggests that the structural requirements for agonist-induced desensitization to LTB4 may differ to some extent from the requirements for calcium mobilization.

Metabolism and biologic effects of 5-oxoeicosanoids on human neutrophils.

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a recently discovered metabolite of arachidonic acid that activates human neutrophils by a mechanism independent of the receptor for leukotriene B4 (LTB4). The objectives of this study were to identify the major metabolites of 5-oxo-ETE in neutrophils and to compare the biologic activities of 5-oxo-ETE with those of its metabolites and other 5-oxoeicosanoids. Neutrophils rapidly converted 5-oxo-ETE to its omega-oxidation product, 5-oxo-20-hydroxy-6E,8Z,11Z,14Z- eicosatetraenoic acid. This compound was nearly 100 times less potent than 5-oxo-ETE in elevating cytosolic calcium levels in neutrophils. Methylation of the carboxyl group of 5-oxo-ETE resulted in a 20-fold loss of potency, whereas replacement of the 8,9-cis double bond by a trans double bond reduced potency by about sixfold. Similar results were obtained for the effects of the above compounds on neutrophil migration. 5-Oxo-20-hydroxy-6E,8Z,11Z,14Z- eicosatetraenoic acid, 5-oxo-8-trans-ETE, and 5-oxo-ETE methyl ester desensitized neutrophils to 5-oxo-ETE. 5-Oxo-ETE-induced calcium mobilization was inhibited by pretreatment of the cells with pertussis toxin. 5-Oxo metabolites of 6-trans-LTB4 and 12-epi-6-trans-LTB4 had weak stimulatory effects on calcium levels and migration that appeared to be mediated primarily by stimulation of LTB4 receptors. These studies indicate that the 5-oxo group, the omega-end of the molecule, and the carboxyl group are all important for the biologic activity of 5-oxo-ETE, which may be mediated by a G protein-linked receptor. The biologic activity of 5-oxo-ETE can be terminated by omega-oxidation.

Formation of a 5-oxo metabolite of 5,8,11,14,17-eicosapentaenoic acid and its effects on human neutrophils and eosinophils.

We recently showed that human neutrophils convert arachidonic acid to its 5-oxo metabolite, 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE). 5-Oxo-ETE, which is synthesized by oxidation of 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) by a highly specific microsomal dehydrogenase, is a potent stimulator of human neutrophils and eosinophils. The objective of the current investigation was to determine whether neutrophils can convert 5,8,11,14,17-eicosapentaenoic acid (EPA) to its 5-oxo metabolite, 5-oxo-6,8,11,14,17-eicosapentaenoic acid (5-oxo-EPE) and, if so, to compare the biological activities of 5-oxo-EPE and 5-oxo-ETE. The two major eicosanoids formed by neutrophils incubated with EPA in the presence of A23187 were 5-hydroxy-6,8,11,14,17-eicosapentaenoic acid (5-HEPE) and 5-oxo-EPE. Smaller amounts of LTB5 and 20-hydroxy-LTB5 were also formed. Phorbol myristate acetate stimulated the formation of 5-oxo-EPE from both EPA and 5-HEPE. 5-HEPE and 5-HETE were equally good substrates for 5-hydroxyeicosanoid dehydrogenase (Km, ca. 0.85 microM; Vmax, ca. 1.4 pmol/min per microgram protein). 5-Oxo-EPE mobilized calcium in neutrophils with an EC50 of 36 nM, about 10 times higher than that of 5-oxo-ETE. 5-Oxo-EPE was also about one-tenth as active as 5-oxo-ETE in stimulating the migration of both human neutrophils and human eosinophils. It is concluded that 5-oxo-EPE is readily formed from EPA via 5-HEPE. However, it is only about one-tenth as potent as 5-oxo-ETE in stimulating human neutrophils and eosinophils. These results support the contention that EPA can alleviate certain inflammatory diseases by reducing the contribution of arachidonate-derived eicosanoids.