Differences in risk factors, atherosclerosis, and cardiovascular disease between ethnic groups in Canada: the Study of Health Assessment and Risk in Ethnic groups (SHARE)

BACKGROUND

Cardiovascular disease rates vary greatly between ethnic groups in Canada. To establish whether this variation can be explained by differences in disease risk factors and subclinical atherosclerosis, we undertook a population-based study of three ethnic groups in Canada: South Asians, Chinese, and Europeans.

METHODS

985 participants were recruited from three cities (Hamilton, Toronto, and Edmonton) by stratified random sampling. Clinical cardiovascular disease was defined by history or electrocardiographic findings. Carotid atherosclerosis was measured with B-mode ultrasonography. Conventional (smoking, hypertension, diabetes, raised cholesterol) and novel risk factors (markers of a prothrombotic state) were measured.

FINDINGS

Within each ethnic group and overall, the degree of carotid atherosclerosis was associated with a higher prevalence of cardiovascular disease. South Asians had the highest prevalence of this condition compared with Europeans and Chinese (11%, 5%, and 2%, respectively, p=0.0004). Despite this finding, Europeans had more atherosclerosis (mean of the maximum intimal medial thickness 0.75 [0.16] mm) than South Asians (0.72 [0.15] mm), and Chinese (0.69 [0.16] mm). South Asians had an increased prevalence of glucose intolerance, higher total and LDL cholesterol, higher triglycerides, and lower HDL cholesterol, and much greater abnormalities in novel risk factors including higher concentrations of fibrinogen, homocysteine, lipoprotein (a), and plasminogen activator inhibitor-1.

INTERPRETATION

Although there are differences in conventional and novel risk factors between ethnic groups, this variation and the degree of atherosclerosis only partly explains the higher rates of cardiovascular disease among South Asians compared with Europeans and Chinese. The increased risk of cardiovascular events could be due to factors affecting plaque rupture, the interaction between prothrombotic factors and atherosclerosis, or as yet undiscovered risk factors.

Two disparate ligand-binding sites in the human P2Y1 receptor

In response to adenosine 5'-diphosphate, the P2Y1 receptor (P2Y1R) facilitates platelet aggregation, and thus serves as an important antithrombotic drug target. Here we report the crystal structures of the human P2Y1R in complex with a nucleotide antagonist MRS2500 at 2.7 Å resolution, and with a non-nucleotide antagonist BPTU at 2.2 Å resolution. The structures reveal two distinct ligand-binding sites, providing atomic details of P2Y1R's unique ligand-binding modes. MRS2500 recognizes a binding site within the seven transmembrane bundle of P2Y1R, which is different in shape and location from the nucleotide binding site in the previously determined structure of P2Y12R, representative of another P2YR subfamily. BPTU binds to an allosteric pocket on the external receptor interface with the lipid bilayer, making it the first structurally characterized selective G-protein-coupled receptor (GPCR) ligand located entirely outside of the helical bundle. These high-resolution insights into P2Y1R should enable discovery of new orthosteric and allosteric antithrombotic drugs with reduced adverse effects.

Impact of right ventricular involvement on mortality and morbidity in patients with inferior myocardial infarction

OBJECTIVES

We sought to evaluate the prognostic impact of right ventricular (RV) myocardial involvement in patients with inferior myocardial infarction (MI).

BACKGROUND

There is uncertainty regarding the risk of major complications in patients with inferior MI complicated by RV myocardial involvement. Whether these complications are related to RV myocardial involvement itself or simply to the extent of infarction involving the left ventricle (LV) is also unknown.

METHODS

We examined the incidence of death and mechanical and electrical complications in patients with (n = 491) and without (n = 638) RV myocardial involvement and in patients with anterior MI (n = 971) in an analysis from the Collaborative Organization for RheothRx Evaluation (CORE) trial. Left ventricular infarct size was assessed by technetium-99m-sestamibi single-photon emission computed tomography and peak creatine kinase, and LV function was assessed by radionuclide angiography. We also performed a meta-analysis in which we pooled the results of our study with previous smaller studies addressing the same question.

RESULTS

Six-month mortality was 7.8% in inferior MI compared with 13.2% in anterior MI. Among patients with inferior MI, serious arrhythmias were significantly more common in patients with RV myocardial involvement who also had a trend toward higher mortality, pump failure and mechanical complications. However, this was not associated with a difference in LV infarct size or function. A meta-analysis of six studies (n = 1,198) confirmed that RV myocardial involvement was associated with an increased risk of death (odds ratio [OR] 3.2, 95% confidence interval [CI] 2.4 to 4.1), shock (OR 3.2, 95% CI 2.4 to 3.5), ventricular tachycardia or fibrillation (OR 2.7, 95% CI 2.1 to 3.5) and atrioventricular block (OR 3.4, 95% CI 2.7 to 4.2).

CONCLUSIONS

Patients with inferior MI who also have RV myocardial involvement are at increased risk of death, shock and arrhythmias. This increased risk is related to the presence of RV myocardial involvement itself rather than the extent of LV myocardial damage.

Structural basis of ligand binding modes at the neuropeptide Y Y1 receptor

Neuropeptide Y (NPY) receptors belong to the G-protein-coupled receptor superfamily and have important roles in food intake, anxiety and cancer biology 1,2 . The NPY-Y receptor system has emerged as one of the most complex networks with three peptide ligands (NPY, peptide YY and pancreatic polypeptide) binding to four receptors in most mammals, namely the Y1, Y2, Y4 and Y5 receptors, with different affinity and selectivity 3 . NPY is the most powerful stimulant of food intake and this effect is primarily mediated by the Y1 receptor (Y1R) 4 . A number of peptides and small-molecule compounds have been characterized as Y1R antagonists and have shown clinical potential in the treatment of obesity 4 , tumour 1 and bone loss 5 . However, their clinical usage has been hampered by low potency and selectivity, poor brain penetration ability or lack of oral bioavailability 6 . Here we report crystal structures of the human Y1R bound to the two selective antagonists UR-MK299 and BMS-193885 at 2.7 and 3.0 Å resolution, respectively. The structures combined with mutagenesis studies reveal the binding modes of Y1R to several structurally diverse antagonists and the determinants of ligand selectivity. The Y1R structure and molecular docking of the endogenous agonist NPY, together with nuclear magnetic resonance, photo-crosslinking and functional studies, provide insights into the binding behaviour of the agonist and for the first time, to our knowledge, determine the interaction of its N terminus with the receptor. These insights into Y1R can enable structure-based drug discovery that targets NPY receptors.

Structures of Gi-bound metabotropic glutamate receptors mGlu2 and mGlu4

The metabotropic glutamate receptors (mGlus) have key roles in modulating cell excitability and synaptic transmission in response to glutamate (the main excitatory neurotransmitter in the central nervous system)¹. It has previously been suggested that only one receptor subunit within an mGlu homodimer is responsible for coupling to G protein during receptor activation². However, the molecular mechanism that underlies the asymmetric signalling of mGlus remains unknown. Here we report two cryo-electron microscopy structures of human mGlu2 and mGlu4 bound to heterotrimeric G_i protein. The structures reveal a G-protein-binding site formed by three intracellular loops and helices III and IV that is distinct from the corresponding binding site in all of the other G-protein-coupled receptor (GPCR) structures. Furthermore, we observed an asymmetric dimer interface of the transmembrane domain of the receptor in the two mGlu-G_i structures. We confirmed that the asymmetric dimerization is crucial for receptor activation, which was supported by functional data; this dimerization may provide a molecular basis for the asymmetric signal transduction of mGlus. These findings offer insights into receptor signalling of class C GPCRs.

A clinical study of 115 patients with extranodal natural killer/T-cell lymphoma, nasal type

AIMS

To investigate the clinicopathological features, treatment outcomes, and prognostic factors in patients with extranodal natural killer (NK)/T-cell lymphoma, nasal type.

MATERIALS AND METHODS

We retrospectively reviewed the medical records of 115 patients diagnosed with extranodal NK/T-cell lymphoma, nasal type who were admitted to our hospital between January 1991 and June 2006.

RESULTS

In total, 107 patients were available for follow-up. After the completion of treatment, 48 patients (44.9%) achieved a complete remission. By the end of the follow-up period, 60 patients (56.1%) had died from local recurrence or metastases. The mean survival duration was 70.0 months, the median survival duration was 42 months, and the 5-year survival rate was 39.4%. The mean survival durations of the three treatment groups of chemoradiotherapy, radiotherapy and palliative treatment were 91.6, 60.1 and 17.6 months, respectively. The median survival durations were 72.0, 42.0 and 10 months, respectively. Patients treated with > 50 Gy had better local control and survival than the < 50 Gy group. However, there was no significant difference between patients having fewer than four cycles of chemotherapy and patients having more than four cycles. Multifactor Cox regression model analysis showed that B symptoms, gender, International Prognostic Index (IPI) score, disease stage and therapy were all independent prognostic factors.

CONCLUSIONS

The prognosis of extranodal NK/T-cell lymphoma, nasal type is poor and significantly influenced by B symptoms, gender, IPI score, clinical staging and the method of treatment. Chemoradiotherapy should be the first choice for treatment.

miR-625 suppresses tumour migration and invasion by targeting IGF2BP1 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies and the third leading cause of cancer-related deaths worldwide. Tumour metastasis is one of the major causes of high mortality. microRNAshave been implicated in HCC metastasis. In this study, we found that miR-625 was frequently downregulated in HCC samples. A decrease in miR-625 was significantly correlated with lymph node anddistance metastasis (P=0.013), the presence of portal venous invasion (P=0.036), tumor-node-metastasis (TNM) stage (P=0.027) and unfavourable overall survival (P=0.003). Compared with primary tumours, miR-625 expression was markedly reduced in portal venous metastatic tumours. Re-expression of miR-625 in HCC cells was remarkably effective in suppressing cell migration andinvasiveness in vitro and in vivo. Mechanistically, miR-625 was confirmed to downregulate IGF2 mRNA-binding protein 1(IGF2BP1) directly, the expression of which was inversely correlated with the level of miR-625 in HCC cell lines and tissues. High expression of IGF2BP1 was frequently found in HCC samples, and associated with poor prognosis. Knockdown of endogenous IGF2BP1 by siRNA exhibited similar effects as the overexpression of miR-625, whereas overexpression of IGF2BP1 (without the 3'-UTR) abrogated miR-625-mediated metastasis inhibition. Interference of the PTEN/HSP27 pathway contributed to miR-625-mediated metastasis inhibition. Taken together, our data suggest that miR-625 might function as an antimetastatic miRNA to have an important role in HCC progression by modulating the IGF2BP1/PTEN pathway. The newly identified miR-625/IGF2BP1 axis represents a new potential therapeutic target for HCC treatment.

Accurate diagnosis of colorectal cancer based on histopathology images using artificial intelligence

BACKGROUND

Accurate and robust pathological image analysis for colorectal cancer (CRC) diagnosis is time-consuming and knowledge-intensive, but is essential for CRC patients' treatment. The current heavy workload of pathologists in clinics/hospitals may easily lead to unconscious misdiagnosis of CRC based on daily image analyses.

METHODS

Based on a state-of-the-art transfer-learned deep convolutional neural network in artificial intelligence (AI), we proposed a novel patch aggregation strategy for clinic CRC diagnosis using weakly labeled pathological whole-slide image (WSI) patches. This approach was trained and validated using an unprecedented and enormously large number of 170,099 patches, > 14,680 WSIs, from > 9631 subjects that covered diverse and representative clinical cases from multi-independent-sources across China, the USA, and Germany.

RESULTS

Our innovative AI tool consistently and nearly perfectly agreed with (average Kappa statistic 0.896) and even often better than most of the experienced expert pathologists when tested in diagnosing CRC WSIs from multicenters. The average area under the receiver operating characteristics curve (AUC) of AI was greater than that of the pathologists (0.988 vs 0.970) and achieved the best performance among the application of other AI methods to CRC diagnosis. Our AI-generated heatmap highlights the image regions of cancer tissue/cells.

CONCLUSIONS

This first-ever generalizable AI system can handle large amounts of WSIs consistently and robustly without potential bias due to fatigue commonly experienced by clinical pathologists. It will drastically alleviate the heavy clinical burden of daily pathology diagnosis and improve the treatment for CRC patients. This tool is generalizable to other cancer diagnosis based on image recognition.

Antitumor effect of sFlt-1 gene therapy system mediated by Bifidobacterium Infantis on Lewis lung cancer in mice

Soluble fms-like tyrosine kinase receptor (sFlt-1) is a soluble form of extramembrane part of vascular endothelial growth factor receptor-1 (VEGFR-1) that has antitumor effects. Bifidobacterium Infantis is a kind of non-pathogenic and anaerobic bacteria that may have specific targeting property of hypoxic environment inside of solid tumors. The aim of this study was to construct Bifidobacterium Infantis-mediated sFlt-1 gene transferring system and investigate its antitumor effect on Lewis lung cancer (LLC) in mice. Our results demonstrated that the Bifidobacterium Infantis-mediated sFlt-1 gene transferring system was constructed successfully and the system could express sFlt-1 at the levels of gene and protein. This system could not only significantly inhibit growth of human umbilical vein endothelial cells induced by VEGF in vitro, but also inhibit the tumor growth and prolong survival time of LLC C57BL/6 mice safely. These data suggest that Bifidobacterium Infantis-mediated sFlt-1 gene transferring system presents a promising therapeutic approach for the treatment of cancer.

The involvement of pineal gland and melatonin in immunity and aging. I. Thymus-mediated, immunoreconstituting and antiviral activity of thyrotropin-releasing hormone

Circadian, continued treatment with melatonin during the dark cycle produces changes in the blood level of thyroid hormones in aging mice. Thyroid-stimulating hormone (TSH) and thyrotropin-releasing hormone (TRH) antagonize the involution of the thymus produced by prednisolone. This effect of TRH does not seem thyroid dependent. TRH restores antibody production in non-responder athymic nude mice but does not exert this effect in neonatally thymectomized mice. Moreover, this activity does not correlate with thyroxine levels. TRH exerts a powerful protective effect in mice challenged with encephalomyocarditis (EMC) virus. Presumably pineal melatonin exerts its varied regulatory functions via hypothalamic TRH.

Structural basis of ligand binding modes at the human formyl peptide receptor 2

The human formyl peptide receptor 2 (FPR2) plays a crucial role in host defense and inflammation, and has been considered as a drug target for chronic inflammatory diseases. A variety of peptides with different structures and origins have been characterized as FPR2 ligands. However, the ligand-binding modes of FPR2 remain elusive, thereby limiting the development of potential drugs. Here we report the crystal structure of FPR2 bound to the potent peptide agonist WKYMVm at 2.8 Å resolution. The structure adopts an active conformation and exhibits a deep ligand-binding pocket. Combined with mutagenesis, ligand binding and signaling studies, key interactions between the agonist and FPR2 that govern ligand recognition and receptor activation are identified. Furthermore, molecular docking and functional assays reveal key factors that may define binding affinity and agonist potency of formyl peptides. These findings deepen our understanding about ligand recognition and selectivity mechanisms of the formyl peptide receptor family.

Formyl peptide receptors (FPRs) are GPCRs that play important roles in transducing chemotactic signals in phagocytes and mediating host-defense and inflammatory responses. Here the authors present the 2.8 Å crystal structure of human FPR2 in complex with the peptide agonist WKYMVm and in combination with molecular docking, ligand-binding and signalling assays provide further insights into the binding modes of FPR2 to both non-formyl and formyl peptides.

Cell growth density modulates cancer cell vascular invasion via Hippo pathway activity and CXCR2 signaling

Metastasis of cancer cells involves multiple steps, including their dissociation from the primary tumor and invasion through the endothelial cell barrier to enter the circulation and finding their way to distant organ sites where they extravasate and establish metastatic lesions. Deficient contact inhibition is a hallmark of invasive cancer cells, yet surprisingly the vascular invasiveness of commonly studied cancer cell lines is regulated by the density at which cells are propagated in culture. Cells grown at high density were less effective at invading an endothelial monolayer than cells grown at low density. This phenotypic difference was also observed in a zebrafish model of vascular invasion of cancer cells after injection into the yolk sac and extravasation of cancer cells into tissues from the vasculature. The vascular invasive phenotypes were reversible. A kinome-wide RNAi screen was used to identify drivers of vascular invasion by panning shRNA library transduced non-invasive cancer cell populations on endothelial monolayers. The selection of invasive subpopulations showed enrichment of shRNAs targeting the LATS1 (large tumor suppressor 1) kinase that inhibits the activity of the transcriptional coactivator YAP in the Hippo pathway. Depletion of LATS1 from non-invasive cancer cells restored the invasive phenotype. Complementary to this, inhibition or depletion of YAP inhibited invasion in vitro and in vivo. The vascular invasive phenotype was associated with a YAP-dependent up-regulation of the cytokines IL6, IL8, and CXCL1, 2, and 3. Antibody blockade of cytokine receptors inhibited invasion and confirmed that they are rate-limiting drivers that promote cancer cell vascular invasiveness and could provide therapeutic targets.

Human substance P receptor binding mode of the antagonist drug aprepitant by NMR and crystallography

Neurokinin 1 receptor (NK1R) has key regulating functions in the central and peripheral nervous systems, and NK1R antagonists such as aprepitant have been approved for treating chemotherapy-induced nausea and vomiting. However, the lack of data on NK1R structure and biochemistry has limited further drug development targeting this receptor. Here, we combine NMR spectroscopy and X-ray crystallography to provide dynamic and static characterisation of the binding mode of aprepitant in complexes with human NK1R variants. ¹⁹F-NMR showed a slow off-rate in the binding site, where aprepitant occupies multiple substates that exchange with frequencies in the millisecond range. The environment of the bound ligand is affected by the amino acid in position 2.50, which plays a key role in ligand binding and receptor signaling in class A GPCRs. Crystal structures now reveal how receptor signaling relates to the conformation of the conserved NP^7.50xxY motif in transmembrane helix VII.

The FDA approved drug aprepitant is an antagonist of the Neurokinin 1 receptor (NK1R). Here the authors present aprepitant bound NK1R crystal structures and use NMR spectroscopy to gain further insights into the dynamics of aprepitant binding, which is of interest for further drug development.

Endotoxin downregulates hepatic expression of P-glycoprotein and MRP2 in 2-acetylaminofluorene-treated rats

In liver, the ATP-dependent transporters P-glycoprotein (PGP) and multidrug resistance protein-2 (MRP2) are involved in the secretion of numerous drugs and toxins in bile. Although constitutive levels of PGP and MRP-2 are decreased in rat liver after exposure to endotoxin, it is possible that induced forms of these transporters may be alternately affected. In vitro, the hepatocarcinogen, 2-acetylaminofluorene (AAF) induces expression of PGP and MRP2. Thus, we examined the influence of endotoxin on the expression of PGP and MRP2 in AAF-treated rats. Expression of PGP and MRP2 was analyzed on Westerns and by RT-PCR in livers obtained from endotoxin and control groups. In vivo, AAF treatment significantly induced PGP/mdr1 expression and imposed a significant reduction in the expression of spgp. MRP2 protein and mRNA levels were not altered by AAF administration. Endotoxin administration to both AAF-treated and non-AAF-treated rats elicited significant reductions in the protein and mRNA expression of MRP2 and PGP (P < 0.05). Our data indicate that endotoxin suppresses the overexpression of PGP and constitutive expression of MRP2 in AAF-treated rats. Furthermore, in vivo administration of AAF, which maximally induces PGP does not induce MRP2.

Prognostic significance of thrombocytopenia during hirudin and heparin therapy in acute coronary syndrome without ST elevation: Organization to Assess Strategies for Ischemic Syndromes (OASIS-2)study

BACKGROUND

The development of thrombocytopenia in acute coronary syndromes (ACS) appears to be associated with adverse clinical outcomes. Unfractionated heparin is a recognized cause of thrombocytopenia, but the incidence, predictors, and prognostic significance of thrombocytopenia during hirudin therapy in ACS have not been reported.

METHODS AND RESULTS

Patients with ACS without ST elevation were randomized in a double-blind manner to receive a 72-hour intravenous infusion of unfractionated heparin or hirudin. Platelet counts were measured at baseline and within 24 hours of completion of study drug. The overall incidence of thrombocytopenia (<100x10(9)/L) was 1% and was similar in unfractionated heparin- and hirudin-treated patients (P:=0.42). Thrombocytopenia during study drug infusion was an independent predictor of 7-day outcomes, including death (OR, 6.7; 95% CI, 1.9 to 25); the composite of death, myocardial infarction, and recurrent ischemia (OR, 2.0; 95% CI, 1.0 to 1.5); revascularization (OR, 4.0; 95% CI, 2.2 to 7.1); and major bleeding (OR, 8.3; 95% CI, 3.4 to 17.7). Among patients who developed thrombocytopenia, hirudin (OR, 5.4; 95% CI, 2.6 to 11.3) but not unfractionated heparin (OR, 2.0; 95% CI, 0.3 to 14.4) therapy was associated with a significantly increased risk of major bleeding.

CONCLUSIONS

Early-onset thrombocytopenia in patients with ACS without ST elevation is strongly associated with adverse clinical outcomes, including death, ischemic events, and bleeding. The excess of major bleeding in hirudin-treated patients who develop thrombocytopenia suggests that thrombocytopenia may contribute to the increased risk of bleeding observed with hirudin.

Successful granulocyte-colony stimulating factor treatment of Crohn's disease is associated with the appearance of circulating interleukin-10-producing T cells and increased lamina propria plasmacytoid dendritic cells

Granulocyte-colony stimulating factor (G-CSF) has proved to be a successful therapy for some patients with Crohn's disease. Given the known ability of G-CSF to exert anti-T helper 1 effects and to induce interleukin (IL)-10-secreting regulatory T cells, we studied whether clinical benefit from G-CSF therapy in active Crohn's disease was associated with decreased inflammatory cytokine production and/or increased regulatory responses. Crohn's patients were treated with G-CSF (5 microg/kg/day subcutaneously) for 4 weeks and changes in cell phenotype, cytokine production and dendritic cell subsets were measured in the peripheral blood and colonic mucosal biopsies using flow cytometry, enzyme-linked immunosorbent assay and immunocytochemistry. Crohn's patients who achieved a clinical response or remission based on the decrease in the Crohn's disease activity index differed from non-responding patients in several important ways: at the end of treatment, responding patients had significantly more CD4(+) memory T cells producing IL-10 in the peripheral blood; they also had a greatly enhanced CD123(+) plasmacytoid dendritic cell infiltration of the lamina propria. Interferon-gamma production capacity was not changed significantly except in non-responders, where it increased. These data show that clinical benefit from G-CSF treatment in Crohn's disease is accompanied by significant induction of IL-10 secreting T cells as well as increases in plasmacytoid dendritic cells in the lamina propria of the inflamed gut mucosa.

Continuous in situ electrochemical monitoring of doxorubicin efflux from sensitive and drug-resistant cancer cells

One of the least well understood problems in cancer chemotherapy is the cross-resistance of certain tumor cells to a series of chemically unrelated drugs. Multidrug resistance (MDR) can be attributed to several different biophysical processes, among them increased drug efflux. This has been found to correlate with overexpression of the cell surface 170-kDa P-glycoprotein that actively excludes cytotoxic drugs against their concentration gradient. To better understand MDR, experimental methods are needed to study drug efflux from cancer cells. Continuous measurement of efflux of nonfluorescent drugs on the same cell culture in situ, or assessing efflux from a few cells or even a single cell, is beyond the capabilities of existing technologies. In this work, a carbon fiber (CF) microelectrode is used to monitor efflux of doxorubicin from a monolayer of two cell lines: an auxotrophic mutant of Chinese hamster ovary cells, AUXB1, and its MDR subline, CHRC5. Because doxorubicin is both fluorescent and electroactive, the results could be validated against existing data obtained optically and with other techniques on the same cell lines, with good agreement found. The electrochemical detection, however, is capable of in situ monitoring with high temporal resolution and is suitable for single-cell studies.

Receptor-specific recognition of NPY peptides revealed by structures of NPY receptors

In response to three highly conserved neuropeptides, neuropeptide Y (NPY), peptide YY, and pancreatic polypeptide (PP), four G protein-coupled receptors mediate multiple essential physiological processes, such as food intake, vasoconstriction, sedation, and memory retention. Here, we report the structures of the human Y₁, Y₂, and Y₄ receptors in complex with NPY or PP, and the G_i1 protein. These structures reveal distinct binding poses of the peptide upon coupling to different receptors, reflecting the importance of the conformational plasticity of the peptide in recognizing the NPY receptors. The N terminus of the peptide forms extensive interactions with the Y₁ receptor, but not with the Y₂ and Y₄ receptors. Supported by mutagenesis and functional studies, subtype-specific interactions between the receptors and peptides were further observed. These findings provide insight into key factors that govern NPY signal recognition and transduction, and would enable development of selective drugs.

Structural insights into ligand recognition and selectivity of somatostatin receptors

Somatostatin receptors (SSTRs) play versatile roles in inhibiting the secretion of multiple hormones such as growth hormone and thyroid-stimulating hormone, and thus are considered as targets for treating multiple tumors. Despite great progress made in therapeutic development against this diverse receptor family, drugs that target SSTRs still show limited efficacy with preferential binding affinity and conspicuous side-effects. Here, we report five structures of SSTR2 and SSTR4 in different states, including two crystal structures of SSTR2 in complex with a selective peptide antagonist and a non-peptide agonist, respectively, a cryo-electron microscopy (cryo-EM) structure of G_i1-bound SSTR2 in the presence of the endogenous ligand SST-14, as well as two cryo-EM structures of G_i1-bound SSTR4 in complex with SST-14 and a small-molecule agonist J-2156, respectively. By comparison of the SSTR structures in different states, molecular mechanisms of agonism and antagonism were illustrated. Together with computational and functional analyses, the key determinants responsible for ligand recognition and selectivity of different SSTR subtypes and multiform binding modes of peptide and non-peptide ligands were identified. Insights gained in this study will help uncover ligand selectivity of various SSTRs and accelerate the development of new molecules with better efficacy by targeting SSTRs.

Efficacy of hirudin in reducing cardiovascular events in patients with acute coronary syndrome undergoing early percutaneous coronary intervention

AIMS

Although hirudin is superior to unfractionated heparin for prevention of death, myocardial infarction, or refractory ischaemia in patients with non-ST-elevation acute coronary syndrome, it is not clear whether hirudin is also of benefit in acute coronary syndrome patients undergoing early percutaneous coronary intervention.

METHODS AND RESULTS

In the OASIS 2 trial, 10 141 patients with non-ST-elevation acute coronary syndrome were randomized to 72 h of intravenous hirudin or unfractionated heparin. Percutaneous coronary intervention was performed at the discretion of the investigator. One hundred and seventeen patients underwent percutaneous coronary intervention within the first 72 h ("early percutaneous coronary intervention"). In patients undergoing early percutaneous coronary intervention, hirudin compared with unfractionated heparin was associated with a significantly lower incidence of death or myocardial infarction at 96 h (6.4% vs 21.4%, OR 0.30; 95% CI: 0.10-0.88) and 35 days (6.4% vs 22.9%, OR 0.25; 95% CI: 0.07-0.86). In the unfractionated heparin group, death or myocardial infarction was significantly higher at 35 days in patients undergoing early percutaneous coronary intervention compared with those managed conservatively (22.9% vs 7.3%, OR 3.14, P<0.001) but this early percutaneous coronary intervention-related hazard was not observed in hirudin-treated patients (6.4% vs 6.8%, OR 0.94 P=1.0). A time-dependent covariate for percutaneous coronary intervention was not significant in a Cox regression model, suggesting a similar treatment benefit with hirudin before and after percutaneous coronary intervention. After adjustment for percutaneous coronary intervention propensity, the benefits of hirudin remained significant. There were three major bleeds in patients undergoing early percutaneous coronary intervention, all in patients randomized to hirudin.

CONCLUSION

In patients with non-ST-elevation acute coronary syndrome undergoing early percutaneous coronary intervention, a direct thrombin inhibitor such as hirudin may be more effective than heparin in reducing the incidence of ischaemic complications.