The effect of dichloroacetate on health- and lifespan in C. elegans

Aging is associated with increased vulnerability to chronic, degenerative diseases and death. Strategies for promoting healthspan without necessarily affecting lifespan or aging rate have gained much interest. The mitochondrial free radical theory of aging suggests that mitochondria and, in particular, age-dependent mitochondrial decline play a central role in aging, making compounds that affect mitochondrial function a possible strategy for the modulation of healthspan and possibly the aging rate. Here we tested such a "metabolic tuning" approach in nematodes using the mitochondrial modulator dichloroacetate (DCA). We explored DCA as a proof-of-principle compound to alter mitochondrial parameters in wild-type animals and tested whether this approach is suitable for reducing reactive oxygen species (ROS) production and for improving organismal health- and lifespan. In parallel, we addressed the potential problem of operator bias by running both unblinded and blinded lifespan studies. We found that DCA treatment (1) increased ATP levels without elevating oxidative protein damage and (2) reduced ROS production in adult C. elegans. DCA treatment also significantly prolonged nematode health- and lifespan, but did not strongly impact mortality doubling time. Operator blinding resulted in considerably smaller lifespan-extending effects of DCA. Our data illustrate the promise of a "metabolic tuning" intervention strategy, emphasize the importance of mitochondria in nematode aging and highlight operator bias as a potential confounder in lifespan studies.

Molecular analysis of the selective pro-apoptotic effect of BN107 on estrogen receptor negative breast cancer cells

Abstract #3128

While advances in early detection and adjuvant therapy for breast cancer have had a favorable impact on survival, patients who develop metastatic breast cancer generally succumb to death. Hormonal, targeted or chemotherapeutic strategies largely depend on the expression of their cognate receptors and are often accompanied by toxicities and intolerable side effects. Effective and less toxic therapies against the more aggressive and hormonal therapy-resistant estrogen receptor negative (ER-) breast cancer are urgently needed.
 Botanical medicine is one of the most popular complementary and alternative medical approaches, and Chinese herbal therapies are frequently sought and used by breast cancer patients. However, the molecular mechanisms through which certain herbal extracts exert anti-breast cancer activities remain largely unknown. Bionovo Inc. has a pipeline of anti-breast cancer products (BN#) based on herbal medicine in development. Here, we present preclinical data on the potential mechanisms of the pro-apoptotic effect of BN107 on breast cancer cells.
 A panel of breast cancer cell lines was examined and the most significant cytotoxic effect was observed in the less-differentiated, more aggressive, ER- breast cancer lines. Apoptosis appeared to be the major cellular pathway mediating the cytotoxicity of BN107 as evident from Annexin V binding, dissipation of mitochondrial potential, activation of caspases, and DNA fragmentation. Transcriptomic analysis comparing sensitive (ER+) versus resistant (ER-) cell lines revealed distinct patterns of gene expression in response to BN107. ER- breast cancer cells responded to BN107 by upregulating genes involved in apoptotic responses and cholesterol synthesis pathways; while ER+ breast cancer cells did so by regulating genes involved in cell growth and IGF-1 receptor signaling pathways. Further molecular analysis showed that BN107 induced death preferentially in ER- cells via rapid inactivation of AKT/ mTOR pathways. In addition, the sensitivity to BN107 was greatly reduced when ER expression was introduced in MDA-MB-231, an ER- cell line highly sensitive to BN107.
 BN107, an extract rich in triterpenoids, caused rapid alterations in cholesterol metabolism, presumably by interfering with cell membrane permeability/integrity. Co-administration of BN107 and cholesterol abolished the pro-apoptotic effect of BN107. We found that ER- breast cancer cells rich in caveolae/lipid rafts were highly sensitive to BN107. We showed that BN107 treatment in these cells resulted in subcellular redistribution of proteins that are associated with these specialized membrane/cellular structures.
 In conclusion, BN107 exerts pro-apoptotic activity preferentially on the more aggressive, ER- breast cancer cells. The cytotoxic activity of BN107 may be attributed to its ability to modify membrane permeability/integrity. Activity-guided isolation and further mechanistic studies are underway to identify potential chemical constituents responsible for the selective cytotoxic activities against ER- breast cancer cells.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3128.

Molecular analysis of the selective pro-apoptotic effect of the herbal extract BN108 on breast cancer cells

Abstract #3018

We present preclinical data on the potential mechanisms of the cytotoxic effect of the herbal extract BN108 towards cancer cells. Botanical medicine is one of the most popular complementary medical approaches, and herbal therapies are frequently sought and used by breast cancer patients. However, the molecular mechanisms through which certain herbal extracts exert growth inhibitory activity on breast cancer cells remain largely unknown.
 Treatment of a panel of breast cancer cell lines and normal mammary cells with BN108 induced cell death selectively in breast cancer lines. Normal mammary epithelial cells and fibroblasts were resistant to the cytotoxic effects of BN108. Breast cancer cells sensitive to BN108 underwent apoptotic death confirmed by Annexin V staining, caspase activation, cleavage of PARP and DNA fragmentation. In particular, caspases 4 and 9, whose activation is observed during apoptosis induced by endoplasmic reticulum stress, were proteolytically activated. Inhibition of caspase 4 partially protected breast cancer cells from cell death induced by BN108.
 Expression array analysis of cells treated with BN108 showed induction of expression of several known pro-apoptotic and anti-proliferative genes such as REDD1, p21CIP, cyclin G2, stratifin and more. BN108 induced rapid inactivation of AKT and mTOR kinases in breast cancer but not in non-transformed cells. Moreover, the well-defined targets of mTORC1, S6kinase and 4eBP1 were inactivated in BN108 treated cells.
 The expression array analysis also showed the induction by BN108 of numerous genes whose products code for enzymes within the cholesterol synthesis pathway. Interestingly, a transient increase in cholesterol synthesis was seen in breast cancer cells but not in normal cells following BN108 treatment. In general, cholesterol levels are higher in breast cancer cells compared to normal cells. Steroidal saponins are major components of BN108 extract, and they are known to deplete cell membrane cholesterol. Similar to BN108 extract, treatment with purified timosaponin AIII (a component of BN108 extract) also induced apoptosis and changes in cholesterol production in breast cancer cells but not in normal cells. It is possible that steroidal saponins induce a very transient depletion of cholesterol, followed by inactivation of AKT and mTOR, and negative feedback inhibition of the cholesterol synthesis pathway that is, in the end, is futile. None of these events are observed in normal cells.
 In conclusion, BN108 extract contains cytotoxic activity selective for transformed versus normal cells. These selective cytotoxic properties of BN108 could be related to its differential effects on cholesterol synthesis in breast cancer cells versus normal cells, as well as inhibition of major oncogenic pathways. Future studies will be aimed at understanding the molecular relationship between the BN1008 effect on cholesterol synthesis and induction of apoptosis, which may give rise to a unique pathway for targeting tumor cells.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3018.

Molecular basis for the cross-reactive idiotypes on human anti-IgG autoantibodies (rheumatoid factors)

High titres of anti-IgG autoantibodies (rheumatoid factors, RF) are characteristic of patients with rheumatoid arthritis, Sjögren's syndrome, and mixed cryoglobulinaemia, and may contribute to immune complex formation and tissue damage. The monoclonal RFs from cryoglobulinaemia patients frequently display cross-reactive idiotypes. The genetic basis for the cross-reactive idiotypes on RF autoantibodies has not been determined. To clarify structural and genetic relationships among RFs from unrelated subjects, a series of anti-peptide antibodies have been generated that define primary sequence-dependent idiotypes on RF heavy and light chains. Multiple monoclonal and polyclonal RFs from unrelated individuals have been probed by Western blotting with the anti-idiotypic reagents. The results show that sequences in the kappa light chain variable region represent a common structural element among RF autoantibodies. This hypothesis is confirmed by the cloning and sequencing of the conserved germline variable region gene which encodes human RF kappa chains.

Systemic co-administration of depsipeptide selectively targets transfection enhancement to specific tissues and cell types

Depsipeptide, a histone deacetylase (HDAC) inhibitor, kills tumor cells much more effectively than normal cells, and can produce significant antitumor activity in human cancer patients. Depsipeptide also increases the expression of lipoplex-delivered genes in cultured tumor cells, as well as following direct intra-tumoral injection. We now show that co-intravenous (i.v.) injection of depsipeptide with polyethylenimine (PEI):DNA complexes significantly increases the expression of PEI-delivered genes in normal, as well as in tumor-bearing mice. At the tissue level, depsipeptide-mediated enhancement of gene expression was selectively targeted to the lung, liver and spleen. At the cellular level, depsipeptide significantly increased the expression of the i.v., PEI co-delivered wild-type human p53 gene in metastatic breast cancer cells, but not in adjacent normal cells. Thus, the ability of depsipeptide to enhance the expression of systemically delivered genes is selectively targeted at both the tissue and cellular levels, without requiring the use of ligand- or promoter-based approaches. Analyzing HDAC-based targeting of gene expression may identify host genes that control the expression of systemically delivered genes.

Immune response in silico (IRIS): immune-specific genes identified from a compendium of microarray expression data

Immune cell-specific expression is one indication of the importance of a gene's role in the immune response. We have compiled a compendium of microarray expression data for virtually all human genes from six key immune cell types and their activated and differentiated states. Immune Response In Silico (IRIS) is a collection of genes that have been selected for specific expression in immune cells. The expression pattern of IRIS genes recapitulates the phylogeny of immune cells in terms of the lineages of their differentiation. Gene Ontology assignments for IRIS genes reveal significant involvement in inflammation and immunity. Genes encoding CD antigens, cytokines, integrins and many other gene families playing key roles in the immune response are highly represented. IRIS also includes proteins of unknown function and expressed sequence tags that may not represent genes. The predicted cellular localization of IRIS proteins is evenly distributed between cell surface and intracellular compartments, indicating that immune specificity is important at many points in the signaling pathways of the immune response. IRIS provides a resource for further investigation into the function of the immune system and immune diseases.

Irrigation runoff insecticide pollution of rivers in the Imperial Valley, California (USA)

The Alamo and New Rivers located in the Imperial Valley, California receive large volumes of irrigation runoff and discharge into the ecologically sensitive Salton Sea. Between 1993 and 2002 we conducted a series of studies to assess water quality using three aquatic species: a cladoceran (Ceriodaphnia dubia), a mysid (Neomysis mercedis), and a larval fish (Pimephales promelas). Although no mortality was observed with the P. promelas, high-level toxicity to the invertebrate species was documented in samples from both rivers during many months of each year. Toxicity identifications and chemical analyses identified the organophosphorus insecticides (OP), chlorpyrifos and diazinon, as the cause of C. dubia toxicity. The extent of the C. dubia mortality was highly correlated with quantities of these OPs applied in the river watersheds. C. dubia mortality occurred during more months of our 2001/2002 study than in the 1990s investigations. During 2001/2002, the extensive C. dubia mortality observed in New River samples was caused by OP insecticide pollution that originated from Mexico. Mortality to N. mercedis in New River samples was likely caused by contaminants other than OP insecticides. Our studies document OP insecticide-caused pollution of the Alamo River over a 10-year period and provide the necessary information for remediation efforts.

Irrigation runoff insecticide pollution of rivers in the Imperial Valley, California (USA)

The Alamo and New Rivers located in the Imperial Valley, California receive large volumes of irrigation runoff and discharge into the ecologically sensitive Salton Sea. Between 1993 and 2002 we conducted a series of studies to assess water quality using three aquatic species: a cladoceran (Ceriodaphnia dubia), a mysid (Neomysis mercedis), and a larval fish (Pimephales promelas). Although no mortality was observed with the P. promelas, high-level toxicity to the invertebrate species was documented in samples from both rivers during many months of each year. Toxicity identifications and chemical analyses identified the organophosphorus insecticides (OP), chlorpyrifos and diazinon, as the cause of C. dubia toxicity. The extent of the C. dubia mortality was highly correlated with quantities of these OPs applied in the river watersheds. C. dubia mortality occurred during more months of our 2001/2002 study than in the 1990s investigations. During 2001/2002, the extensive C. dubia mortality observed in New River samples was caused by OP insecticide pollution that originated from Mexico. Mortality to N. mercedis in New River samples was likely caused by contaminants other than OP insecticides. Our studies document OP insecticide-caused pollution of the Alamo River over a 10-year period and provide the necessary information for remediation efforts.

Rationing HIV medications: what do patients and the public think about allocation policies?

BACKGROUND

New medications for treating HIV/AIDS are effective, but expensive, and funding shortfalls have led many state AIDS Drug Assistance Programs (ADAPs) to ration these drugs. Little is known about the views of those most directly affected by rationing policies. This study explores attitudes of patients with HIV and the general public toward specific rationing strategies.

METHODS

A Likert-style, self-administered questionnaire about rationing expensive HIV medications in the context of a budget shortfall was administered to patients with HIV and shopping mall patrons in central Pennsylvania. Subjects were asked how much they agreed or disagreed with seven drug rationing policies.

RESULTS

In all, 100 patients and 101 shoppers completed the survey (response rate = 89%). A majority in both groups "strongly" or "somewhat" disagreed with six of the seven rationing policies described, and patients more strongly disagreed with the policies than did the public. The five policies actually used by state ADAPs (first come first serve, limiting expensive medicines, limiting new patient enrollment, giving the expensive medicines to the sickest, using a spending cap) lacked support in either group.

CONCLUSIONS

HIV drug rationing policies currently in use do not reflect the preferences of patients and the public. Integrating the views of those affected by the rationing decisions would raise difficult challenges to current programs.

Ligation of alpha4ss1 integrin on human intestinal mucosal mesenchymal cells selectively Up-regulates membrane type-1 matrix metalloproteinase and confers a migratory phenotype

Human intestinal lamina propria mesenchymal cells show high surface expression of the alpha4ss1 integrin. Ligation of alpha4ss1 on mesenchymal cell lines with an activating monoclonal anti-alpha4 antibody or vascular cell adhesion molecule-immunoglobulin (VCAM-IgG) leads to the appearance of activated forms of gelatinase A in culture supernatants, and the de novo expression of activated membrane type-1-matrix metalloproteinase (MT1-MMP). In functional assays, signaling through alpha4ss1 results in an increased capacity of mesenchymal cells to migrate through an artificial extracellular matrix, an effect inhibitable by excess tissue inhibitor of metalloproteinase-2. In organ cultures of human intestine, VCAM-IgG also up-regulates MT1-MMP, and in mucosal ulcers of inflammatory bowel disease patients, MT1-MMP transcripts are abundant, coincident with expression of VCAM-1 on cells at the ulcer margin. Collectively these results suggest that alpha4ss1-induced up-regulation of MT1-MMP may be a crucial factor in the migration of mesenchymal cells into ulcer beds during restitution of diseased gut mucosa.

Characterization of huJAM: evidence for involvement in cell-cell contact and tight junction regulation

Cell-cell interactions of the mucosal epithelia are important for the maintenance and establishment of epithelial barrier function. During events of inflammation, such cell-cell interactions are often disrupted, resulting in a leaky epithelial barrier, which in turn can lead to various inflammatory and infective dysfunctions. Human junctional adhesion molecule (huJAM), found on the mucosal epithelia and vascular endothelia of many major organ systems, is a membrane glycoprotein which resolves to a doublet band of approximately 40 and approximately 37 kDa under SDS-PAGE analysis, representing differentially glycosylated forms of the same protein. huJAM was localized to the lateral membrane of Caco-2 cells (a human colonic epithelial cell line) monolayers, in an area basolateral of the epithelial tight junctions (TJ). Through functional and biochemical assays, we show huJAM to be able to homotypically associate and to participate in TJ restitution after trypsin-EDTA disruption. Furthermore, we also observed a migration of huJAM expression toward areas of cell-cell contacts during events of cell adhesion and monolayer formation. These qualities makes huJAM a likely player in the regulation of cell-cell contacts and the subsequent formation of TJs.

Directed evolution of D-2-keto-3-deoxy-6-phosphogluconate aldolase to new variants for the efficient synthesis of D- and L-sugars

BACKGROUND

Exploitation and improvement of enzymes as catalysts for organic synthesis is of current interest in biocatalysis. A representative enzyme for investigation is the Escherichia coli D-2-keto-3-deoxy-6-phosphogluconate (KDPG) aldolase, which catalyzes the highly specific reversible aldol reaction using the D-configurated KDPG as substrate.

RESULTS

Using in vitro evolution, the aldolase has been converted into aldolases with improved catalytic efficiency, altered substrate specificity and stereoselectivity. In particular, some evolved aldolases capable of accepting both D- and L- glyceraldehyde in the non-phosphorylated form as substrates for reversible aldol reaction have been obtained, providing a new direction to the enzymatic synthesis of both D- and L-sugars.

CONCLUSIONS

This research has demonstrated the effectiveness of using in vitro evolution to rapidly alter the properties of an aldolase to improve its utility in asymmetric synthesis. The evolved aldolases, differing from the native enzyme which is highly phosphate- and D-sugar-dependent, catalyze the efficient synthesis of both D- and L-sugars from non-phosphorylated aldehydes and pyruvate. The principles and strategies described in this study should be applicable to other aldolases to further expand the scope of their synthetic utility.

A systematic review of the effectiveness of environmental awareness interventions

PURPOSE

To evaluate and summarize evidence on the effectiveness of interventions available to public health staff regarding the protection of the public from environmental risks.

METHOD

This systematic review involved a comprehensive literature search, screening for relevance, quality assessment of relevant studies, data extraction and synthesis.

RESULTS

Fourteen of 65 relevant studies were of 'moderate' or 'strong' quality. Intervention types in these 14 studies included: mass campaign, counselling, school curriculum, educational sessions, and distribution of printed materials. Short-term improvements in awareness or knowledge were observed in 13 of the 14 studies. Eight of 13 studies that examined behavioural outcomes observed short-term improvements in self-reported behavioural outcomes.

CONCLUSIONS

Positive short-term changes in health-protective awareness, knowledge and self-reported behaviour appear to be associated with relatively intensive interventions that use multiple methods and settings, and/or are delivered over multiple sessions.

Transfer of a protein binding epitope to a minimal designed peptide

Results from protein mutagenesis and x-ray crystallographic studies of the multidomain protein Vascular Cell Adhesion Molecule (VCAM) were used to design cyclic octapeptides that retain the critical structural and binding elements of the epitope of VCAM in the interaction with the integrin alpha 4 beta 1 (VLA-4). Changes in the activities of peptide analogues correlated with the relative activities of protein mutants of VCAM, and predicted the properties of two new mutants that bound alpha 4 beta 1 with improved affinity vs wild type protein. The nmr structures of two peptides revealed a high degree of similarity to the structure of the VCAM binding epitope. These results demonstrate that a compact binding epitope identified via protein structure-function studies may be transferred to a synthetically accessible small peptide with the key structure-activity relationships intact.

A systematic review of the effectiveness of environmental awareness interventions

PURPOSE

To evaluate and summarize evidence on the effectiveness of interventions available to public health staff regarding the protection of the public from environmental risks.

METHOD

This systematic review involved a comprehensive literature search, screening for relevance, quality assessment of relevant studies, data extraction and synthesis.

RESULTS

Fourteen of 65 relevant studies were of 'moderate' or 'strong' quality. Intervention types in these 14 studies included: mass campaign, counselling, school curriculum, educational sessions, and distribution of printed materials. Short-term improvements in awareness or knowledge were observed in 13 of the 14 studies. Eight of 13 studies that examined behavioural outcomes observed short-term improvements in self-reported behavioural outcomes.

CONCLUSIONS

Positive short-term changes in health-protective awareness, knowledge and self-reported behaviour appear to be associated with relatively intensive interventions that use multiple methods and settings, and/or are delivered over multiple sessions.

Jembrana disease virus Tat can regulate human immunodeficiency virus (HIV) long terminal repeat-directed gene expression and can substitute for HIV Tat in viral replication

Jembrana disease virus (JDV) is a bovine lentivirus genetically similar to bovine immunodeficiency virus; it causes an acute and sometimes fatal disease in infected animals. This virus carries a very potent Tat that can strongly activate not only its own long terminal repeat (LTR) but also the human immunodeficiency virus (HIV) LTR. In contrast, HIV Tat cannot reciprocally activate the JDV LTR (H. Chen, G. E. Wilcox, G. Kertayadnya, and C. Wood, J. Virol. 73:658-666, 1999). This indicates that in transactivation JDV Tat may utilize a mechanism similar to but not the same as that of the HIV Tat. To further study the similarity of JDV and HIV tat in transactivation, we first tested the responses of a series of HIV LTR mutants to the JDV Tat. Cross-transactivation of HIV LTR by JDV Tat was impaired by mutations that disrupted the HIV type 1 transactivation response element (TAR) RNA stem-loop structure. Our results demonstrated that JDV Tat, like HIV Tat, transactivated the HIV LTR at least partially in a TAR-dependent manner. However, the sequence in the loop region of TAR was not as critical for the function of JDV Tat as it was for HIV Tat. The competitive inhibition of Tat-induced transactivation by the truncated JDV or HIV Tat, which consisted only of the activation domain, suggested that similar cellular factors were involved in both JDV and HIV Tat-induced transactivation. Based on the one-round transfection assay with HIV tat mutant proviruses, the cotransfected JDV tat plasmid can functionally complement the HIV tat defect. To further characterize the effect of JDV Tat on HIV, a stable chimeric HIV carrying the JDV tat gene was generated. This chimeric HIV replicated in a T-cell line, C8166, and in peripheral blood mononuclear cells, which suggested that JDV Tat can functionally substitute for HIV Tat. Further characterization of this chimeric virus will help to elucidate how JDV Tat functions and to explain the differences between HIV and JDV Tat transactivation.

Expression of the mucosal vascular addressin, MAdCAM-1, in inflammatory liver disease

AIMS/BACKGROUND

The integrin alpha4beta7 and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) are involved in normal recirculation of lymphocytes between the blood and the tissues of the gastrointestinal tract. In this study we have examined the expression of MAdCAM-1 in human liver.

METHODS

MAdCAM-1 expression was determined in archival human liver tissues by immunohistochemistry.

RESULTS

While MAdCAM-1 was not detected in normal fetal or adult human liver, expression was observed in association with portal tract inflammation in a variety of liver diseases. Detailed analysis of liver biopsies from patients with hepatitis C showed a positive correlation between the portal/periportal component of the histological activity index (HAI) grade and the presence or absence of MAdCAM-1 expression.

CONCLUSION

MAdCAM-1 expression may be important in the recruitment of lymphocytes to the liver during inflammation.

Safety and antitumor activity of recombinant soluble Apo2 ligand

TNF and Fas ligand induce apoptosis in tumor cells; however, their severe toxicity toward normal tissues hampers their application to cancer therapy. Apo2 ligand (Apo2L, or TRAIL) is a related molecule that triggers tumor cell apoptosis. Apo2L mRNA is expressed in many tissues, suggesting that the ligand may be nontoxic to normal cells. To investigate Apo2L's therapeutic potential, we generated in bacteria a potently active soluble version of the native human protein. Several normal cell types were resistant in vitro to apoptosis induction by Apo2L. Repeated intravenous injections of Apo2L in nonhuman primates did not cause detectable toxicity to tissues and organs examined. Apo2L exerted cytostatic or cytotoxic effects in vitro on 32 of 39 cell lines from colon, lung, breast, kidney, brain, and skin cancer. Treatment of athymic mice with Apo2L shortly after tumor xenograft injection markedly reduced tumor incidence. Apo2L treatment of mice bearing solid tumors induced tumor cell apoptosis, suppressed tumor progression, and improved survival. Apo2L cooperated synergistically with the chemotherapeutic drugs 5-fluorouracil or CPT-11, causing substantial tumor regression or complete tumor ablation. Thus, Apo2L may have potent anticancer activity without significant toxicity toward normal tissues.

Urokinase receptor antagonists: discovery and application to in vivo models of tumor growth

Urokinase receptor antagonists based on the growth factor domains of both human and murine urokinase which show sub-nanomolar affinities for their homologous receptors have been expressed as recombinant proteins. Further modification of these molecules by preparing fusions with the constant region of human IgG has led to molecules with high affinities and long in vivo half-lives. Smaller peptidic inhibitors have been obtained by a combination of bacteriophage display and peptide analog synthesis. All of these molecules inhibit the binding of the growth factor domain of uPA to the uPA receptor and enhance binding of the uPA receptor to vitronectin. Protein uPA receptor antagonists were tested in an in vivo tumor model using the human breast carcinoma MDAmb231 in immunodeficient mice. Both human and murine receptor antagonists showed significant inhibition of primary tumor growth, demonstrating that in vivo, both tumor and stromal cell uPA receptor dependent plasminogen activation can modulate tumor growth.

Blockade of both L-selectin and alpha4 integrins abrogates naive CD4 cell trafficking and responses in gut-associated lymphoid organs

The recirculation of naive lymphocytes from blood to lymph that is initiated in high endothelial venules (HEV) of secondary lymphoid organs such as lymph nodes and Peyer's patches (PP) is regulated by multiple interactions of adhesion receptor/counter-receptor pairs involving both selectins and integrins. We showed previously that blocking of only L-selectin is sufficient to ablate trafficking of naive CD4 cells and the development of their responses in peripheral lymph nodes but not in PP where alpha4beta7 integrins are thought to primarily regulate entry. However, although antibody to alpha4 integrins partially inhibited homing of naive CD4 cells to PP and not to lymph nodes, there was no effect on the development primary responses in these tissues or spleens. Since previous studies indicate that both alpha4beta7 integrins and L-selectin regulate adhesion of naive cells to PP HEV, we examined the effect a blockade of both adhesion pathways on the recirculation of naive CD4 cells. There was no detectable homing of naive CD4 cells to PP or lymph nodes when interactions with both receptors were inhibited, resulting in a profound depletion of naive CD4 cells and loss of antigen responses in these sites. In contrast, increased numbers of naive CD4 cells and responses of higher magnitude were found in the spleen. The results demonstrate recirculation of naive CD4 cells through tissues where entry is controlled through HEV is essential for the local generation of primary responses.

Characterisation of urea-denatured states of an immunoglobulin superfamily domain by heteronuclear NMR

The structural and dynamic properties of an immunoglobulin superfamily domain (IgSF), Ig 18', have been characterised by NMR at 285 K, in the presence of 4.2 M and 6.0 M urea, respectively. Analysis of chemical shift deviations, 3JHNHalpha coupling constants, sequential NOE pattern, and 15N relaxation data reveals that although the two urea-denatured states are highly disordered, some local turn-like residual structures do exist. Moreover, some distinct differences between the properties of the two denatured states are observed. In 4.2 M urea-denatured Ig 18', regions 80-83 and 86-92 adopt turn-like conformations, furthermore, region 84-93 is involved in slow exchange processes that occur on a micro- to millisecond time-scale. In the 6.0 M urea-denatured state, these turn-like conformations are less occupied, and chemical exchange processes in region 84-93 are largely reduced. In contrast, region 32-36 has persistent turn-like structures in both urea-denatured states. Some correlation between the spectral density function at 0 frequency, Jeff(0), for the urea-denatured states and the secondary structure elements of the folded state have been observed. Except for the terminal regions, residues corresponding to beta-strands have higher Jeff(0) values compared to residues corresponding to loops. The characterisation and comparison of the two urea-denatured states highlight residues that possess properties that may be crucial for the initiation of folding of this domain.