The road to recovery: translating PD-1 biology into clinical benefit

Negative immune regulation can result in the poor control of virus replication in chronic infections but is probably important to prevent tissue damage from chronic immune activation. Three recent studies have shown that programmed cell death (PD)-1 expression on T cells correlates with viral load in HIV infection, and that interrupting PD-1 signaling using an antagonistic antibody rejuvenates T-cell effector functions in vitro. These findings have important implications for potential therapies for chronic infection and, perhaps, for improved tumor immunity. Here, we discuss impending issues in the translation to clinical studies in light of recent adverse events with costimulatory antibody therapy.     

The role of basic science knowledge and clinical knowledge in diagnostic reasoning: a structural equation modeling approach.

PURPOSE: To examine four theories on the role of basic science knowledge and clinical knowledge in diagnostic reasoning. METHOD: In 2000-01, the authors tested the basic science and clinical knowledge and diagnostic performances of 59 family physicians and 184 second- to sixth-year medical students at Maastricht University, The Netherlands. Structural equation modeling was used to analyze the data. Four theoretical models were tested. In the first model only basic science knowledge is involved in diagnostic reasoning; in the second model only clinical knowledge is related to diagnostic reasoning; in the third model, clinical knowledge is related to diagnostic reasoning, but basic science knowledge is integrated in clinical knowledge; and in the fourth model, both basic science knowledge and clinical knowledge independently influence diagnostic reasoning. RESULTS: Forty-four (75%) of the family physicians and 184 (100%) of the students responded. The results indicated that the third model, which is based on the knowledge encapsulation theory, provided the best fit to the data, whereas the models that had directly related basic science knowledge with diagnostic performance did not fit the data adequately. CONCLUSION: The results generally supported the third model by Schmidt and Boshuizen of knowledge encapsulation theory suggesting that basic science knowledge is activated in expert diagnostic reasoning through its relation with clinical knowledge.     

Calorie restriction for enhanced longevity: The role of novel dietary strategies in the present obesogenic environment

Calorie restriction (CR) is a potent modulator of longevity in multiple species. A growing body of evidence shows that sustained periods of CR without malnutrition improves risk factors involved in the pathophysiology of type 2 diabetes, cardiovascular diseases, cancer, and neurological disorders in humans. Innovative dietary strategies such as intermittent fasting and protein restriction have recently emerged as alternative approaches that improve markers of aging. Some of these newer strategies might provide benefits for healthy aging with little to no CR and therefore, compared to traditional CR, may be easier to follow. Further to providing an update of CR studies in humans, the present narrative review appraises the influence of these contemporary dietary strategies on mechanisms posited to drive CR-induced longevity in humans, including those involving energy metabolism, oxidative damage, inflammation, glucose homeostasis, and functional changes in the neuroendocrine systems. The review also discusses the utilization of these diets for populations in the current obesogenic environment, and comments on whether current research can inform an optimal diet that attenuates aging, can be easily followed, and promises to improve longevity in humans.     

The role of ERK5 in T-cell signalling

The mitogen-activated protein kinase (MAPK) ERK5 plays an important role in mammary epithelial proliferation, endothelial cell survival and normal embryonic development. In nonhaematopoietic cells, mitogenic and stress signals activate the ERK5 cascade. Here, we investigated the role of the ERK5 pathway in T-cell activation and show that primary and leukaemic T cells express ERK5, whose activating phosphorylation is induced by antibodies against CD3 but not by phorbol myristate acetate treatment. ERK5 localized in the cytosol and nucleus in quiescent and activated T cells. In the latter, ERK5 phosphorylation was mainly observed in the nucleus. Selective activation of the ERK5 cascade by transfecting constitutively active MEK5 and wildtype ERK5 induced a reporter gene driven by the IL-2 promoter while barely affecting CD69 expression. These results suggest a new role for the ERK5 cascade in intracellular signalling in T cells.     

The role of glutamate signalling in rheumatoid arthritis

Introduction Rheumatoid arthritis (RA) is characterized by joint inflammation and destruction mediated by enhanced secretion of degradative enzymes and cytokines. Inflammation of the joint is accompanied by elevated levels of glutamate within the synovial fluid ( McNearney et al. 2000 ). Glutamate has been shown to modulate bone cell phenotype ( Chenu et al. 1998 ). We hypothesize that the elevated glutamate in synovial fluid that accompanies RA can induce phenotypic changes associated with synovial joint destruction. Methods The mRNA expression of glutamate receptors and transporters was investigated in tissues of the rat knee joint by RT‐PCR to determine which cell types are potentially responsive to glutamate. To determine whether extracellular glutamate affects synoviocyte phenotype, we have investigated the effect of different glutamate concentrations on human, primary, RA synoviocytes' enzyme and cytokine expression. Matrix metalloproteinases (MMPs) and tissue inhibibitors of MMPs (TIMPs) protein expression was determined by zymography, and IL‐6 release by RA synoviocytes was measured using an IL‐6 ELISA (R & D systems). Results RT‐PCR has revealed glutamate transporter (GLAST‐1) and ionotropic and metabotropic receptor mRNA expression in several tissues of the rat knee joint. Pro‐MMP2, TIMP1 and TIMP2 activity were all increased in the presence of high extracellular glutamate concentrations and in the presence of glutamate transporter inhibitors. The presence of glutamate transporter inhibitors also increased production of the cytokine IL‐6 but only at low glutamate concentrations. Discussion Our data show that many cells of the synovial joint have potential for responding to glutamate signals. Primary synoviocytes from RA patients increase MMP and TIMP expression in response to high extracellular glutamate and in the presence of glutamate transporter inhibitors which also increase IL‐6 production. We postulate therefore that the high levels of glutamate present in RA synovial fluid are having a pro‐inflammatory effect on synoviocytes. This may be mediated through the cytokine IL‐6, the synovial fluid levels of which correlate with RA disease activity. We have previously shown that IL‐6 treatment of RA synoviocytes induces the glutamate transporter (GLAST‐1) expression therefore indicating a feedback mechanism between IL‐6 and GLAST‐1 expression. We are currently investigating the effect of ionotropic glutamate receptor antagonists on the pheontype of RA synoviocytes to elucidate the specific signalling mechanisms involved.     

The role of melatonin in parasite biology

Regarded as the circadian hormone in mammals, melatonin is a highly conserved molecule, present in nearly all species. In this review, we discuss the role of this indolamine and its precursors in the cell biology of parasites and the role of the molecule in the physiology of the host. In Plasmodium, melatonin can modulate intracellular concentrations of calcium and cAMP, which in turn can regulate kinase activity and cell cycle. In Trypanosoma infections, modulation of the immune system by melatonin is extremely important in controlling the parasite population. Melatonin also contributes to the inflammatory response to Toxoplasma gondii infection. Thus, there are a number of unique adaptations involving intricate connections between melatonin and the biology of the parasite-host relationship.     

The biology of haematogenous metastasis in human meal malignant melanoma

Using data on 4726 cases of uveal melanoma collected by the Registry, of Ophthalmic Pathology at the Armed Forces Institute of Pathology, my co-workers and I have been studying the biology of haematogenous metastasis. We have developed methods for evaluating separately the relationships between prognostic factors and cure-rate and median survival time for uncured patients. We have discovered that size of the tumour and size of the largest nucleoli in the cells of the uveal melanomas related equally to cure-rate and median survival time. The presence of Callender's epitheloid-type cells in the tumour and increased patient age had little effect on cure-rate but dramatically reduced the median survival time.     

Preferences towards novel foods in Cebus apella: the role of nutrients and social influences

Information on the process of preference acquisition towards novel foods in nonhuman primates is lacking. This study aims to assess (1) whether nutrient and energy contents affect preferences towards novel foods encountered repeatedly by individuals when alone, (2) whether these preferences change after additional encounters with the novel foods, and (3) if the change is sensitive to social influences. We presented seven novel foods to 26 socially housed tufted capuchins. In Phase 1, each subject was presented individually with the 21 possible binary combinations of the seven novel foods. Afterwards, during treatment, 13 subjects received the novel foods ad libitum with their group members (social condition) and 13 subjects received the foods individually (individual condition); subjects assigned to the individual and social conditions had shown similar food preferences in Phase 1. Finally, in Phase 2, each subject was presented again with 21 binary choices between each of the novel foods. In Phases 1 and 2, the number of times each food was chosen differed among foods. In Phase 1, food preference correlated positively with glucose and fructose and negatively with total fiber content. In Phase 2, irrespective of social or individual prior experience in the treatment condition, food preference changed and became correlated with total energy content. Our results broaden the findings already available for familiar foods by demonstrating that individual experience based on the feedback obtained from novel foods guides the establishment of preferences towards them. Moreover, individual experience is sufficient to determine food preferences similar to those individuals may acquire when together with group members eating the same foods.     

The role of plasminogen activators in metastasis

It is proposed the tumour plasminogen activators play an essential role in the invasive and metastic process of malignancy.     

The role of hydrogen sulphide signalling in macrophage activation

Hydrogen sulphide (H₂S) is the latest identified small gaseous mediator enabled by its lipophilic nature to freely permeate the biological membranes. Initially, H₂S was recognized by its roles in neuronal activity and vascular relaxation, which makes it an important molecule involved in paracrine signalling pathways. Recently, the immune regulatory function of gasotransmitters, H₂S in particular, is increasingly being appreciated. Endogenous H₂S level has been linked to macrophage activation, polarization and inflammasome formation. Mechanistically, H₂S‐induced protein S‐sulphydration suppresses several inflammatory pathways including NF‐κB and JNK signalling. Moreover, H₂S serves as a potent cellular redox regulator to modulate epigenetic alterations and to promote mitochondrial biogenesis in macrophages. Here in this review, we intend to summarize the recent advancements of H₂S studies in macrophages, and to discuss with focus on the therapeutic potential of H₂S donors by targeting macrophages. The feasibility of H₂S signalling component as a macrophage biomarker under disease conditions would be also discussed.     

The role of membrane-associated adaptors in T cell receptor signalling

Engagement of the T cell receptor leads to activation of several tyrosine kinases and phosphorylation of many intracellular proteins. This is followed by Ca2+ mobilization and activation of multiple biochemical pathways, including the Ras/MAPK cascade, and several downstream serine/threonine kinases. Membrane-associated adaptor proteins play an important role in T cell activation by coupling TCR ligation at the membrane to distal signalling cascades. Several new membrane associated adaptors have been identified in recent years. LAT (linker for activation of T cells) is an adaptor molecule, which following its phosphorylation associates with Grb2, Gads, PLC-gamma 1, and other signalling molecules. The functional importance of this molecule has been demonstrated by the study of LAT-deficient cell lines and LAT-deficient mice. Two other recently identified adaptor proteins, TRIM (T cell receptor interacting molecule) and SIT (SHP2-interacting transmembrane adaptor protein), which constitutively associate with several surface molecules, bind to PI3K and SHP2, respectively, after T cell activation and might also function in the TCR signalling pathway.     

The role of non-antigen receptors in mast cell signalling processes

Cytophilic antibodies of the IgE class play two distinctive roles in the immunological triggering of mast cell, initially by binding to Fc receptors on the plasma membrane and secondly, by transmitting to the sensitised target cell the effects of their subsequent interaction with specific antigen (allergen). In contrast to the claim that the IgE antibody merely acts as a surrogate receptor in its latter role, evidence is presented in support of the contention that it is actively involved in mast cell triggering by providing a signal to a second “recepotr” [i.e. other than Fc()R]. Synthetic peptide studies have provided an insight into the structural characteristics of such an Fc effector site, besides beginning to suggest the manner of its interaction with the mast cell membrane. In discussing the implication of our findings, this type of immunological trigger process is contrasted with that brought about by hormone agonists. It is suggested that the cytophilic IgE antibody can be regarded as a pro-hormone, which only gains hormonal status as a result of cross-linking by specific antigen.     

交感神经在肺泡缺氧性肺血管收缩反应中的作用

在大鼠毁髓模型上观察缺氧与不缺氧情况下电刺激肺血管的脊髓交感中枢时体、肺循环的变化。常氧时电刺激脊髓T_(1～3)节段时P_(pa)、PVR增高(P<0.05);毁髓去神经支配大鼠吸入12%O_2低氧气体后仍能引起肺血管收缩反应(HPV),但PVR上升幅度较正常大鼠降低。在缺氧基础上电刺激T_(1～3)节段引起P_(pa)、PVR大幅度增高(P<0.05),约为常氧时电刺激效应的二倍;酚妥拉明可抑制这一反应。提示交感神经兴奋对HPV的形成有一定的促进作用。缺氧时体循环对交感兴奋的反应减弱。     

The role of eosinophil major basic protein in angiogenesis

Background:  Eosinophil-derived major basic protein (MBP) plays an active role in allergic inflammation and tissue remodelling. However, its role in angiogenesis has not been established as yet. Therefore our objective was to investigate whether MBP exhibits any direct pro-angiogenic effects.
Methods:  Rat aortic endothelial cells and human umbilical vascular endothelial cells were cultured with different concentrations of MBP and their viability (Trypan blue exclusion test), proliferation (thymidine incorporation) and capillary-like structure formation (matrigel assay) were investigated in vitro . The angiogenic activity of MBP was then tested in vivo using the chick chorio allantoic membrane (CAM) assay.
Results:  Subcytotoxic concentrations of MBP induce endothelial cell proliferation and enhance the pro-mitogenic effect of vascular endothelial growth factor (VEGF), but do not affect their VEGF release. MBP promotes capillarogenesis by endothelial cells seeded on matrigel and sprouting formation in the CAM assay. Furthermore, we have shown that the pro-angiogenic effect of MBP is not due to its cationic charge since stimulation of the CAMs with the synthetic polycation, poly- l -arginine does not induce any angiogenic effects.
Conclusions:  These data demonstrate that MBP has pro-angiogenic effects in vitro and in vivo , providing a novel mechanism whereby MBP can participate in tissue inflammation and remodelling in atopic diseases.     

The role of the neural niche in brain metastasis

Cancers with neurologic metastasis are a burdensome affliction. As primary cancer care improves, the incidence of metastatic cancer increases as a result of prolonged survival time. Because of this, advances in the understanding of the mechanisms of metastasis are important for the development of continuing management strategies. Knowing how metastatic tumor cells engage, survive, and proliferate in the central nervous system (CNS) is an important first step in developing treatment paradigms. The neural niche is the soil of the CNS that accommodates tumor cells, is a microenvironment of cell signaling that exists between the tumor cell and the native neural cellular network. Elements of the neural niche have been identified as acquaintances for metastatic tumor growth. As more is known about the neural niche, treatment strategies can be developed to target these networks of metastatic tumor progression.     

The role of metastasis suppressor genes in metastatic dormancy

Metastasis suppressor genes (MSGs) are defined by their ability to inhibit overt metastasis in a secondary organ without affecting tumor growth at the primary site. Over 20 MSGs have been confirmed in vivo. This class of genes is only unified by their capacity to suppress metastasis, as they encode for proteins with a wide range of biochemical activities that are components of a variety of signaling pathways. In addition, metastasis suppressors impinge upon different stages of the metastatic cascade to manifest their suppressive effects. The MSGs KISS1, KAI1, MKK4/7 and Nm23-H1 promote tumor dormancy at the metastatic site, since tumor cells with induced expression of these MSGs disseminate, but do not form overt metastases in the secondary organ throughout the duration of a metastasis assay. Evidence suggests that KISS1 triggers dormancy in solitary, metastatic tumor cells by causing growth arrest of solitary cells at the secondary site. KAI1 induces growth arrest prior to extravasation by binding a vascular endothelial cell surface marker. MKK4, MKK7 and Nm23-H1 appear to promote dormancy of micrometastatic colonies, after disseminated tumor cells have undergone several rounds of proliferation. Other MSGs may also function in tumor dormancy, but so far their role has not been fully elucidated. Therapeutic approaches that either mimic the effects of MSGs or re-establish MSG expression in metastatic lesions may hold promise for the establishment or maintenance of dormancy.