A high-affinity, dimeric inhibitor of PSD-95 bivalently interacts with PDZ1-2 and protects against ischemic brain damage

Inhibition of the ternary protein complex of the synaptic scaffolding protein postsynaptic density protein-95 (PSD-95), neuronal nitric oxide synthase (nNOS), and the N-methyl-D-aspartate (NMDA) receptor is a potential strategy for treating ischemic brain damage, but high-affinity inhibitors are lacking. Here we report the design and synthesis of a novel dimeric inhibitor, Tat-NPEG4(IETDV)(2) (Tat-N-dimer), which binds the tandem PDZ1-2 domain of PSD-95 with an unprecedented high affinity of 4.6 nM, and displays extensive protease-resistance as evaluated in vitro by stability-measurements in human blood plasma. X-ray crystallography, NMR, and small-angle X-ray scattering (SAXS) deduced a true bivalent interaction between dimeric inhibitor and PDZ1-2, and also provided a dynamic model of the conformational changes of PDZ1-2 induced by the dimeric inhibitor. A single intravenous injection of Tat-N-dimer (3 nmol/g) to mice subjected to focal cerebral ischemia reduces infarct volume with 40% and restores motor functions. Thus, Tat-N-dimer is a highly efficacious neuroprotective agent with therapeutic potential in stroke.     

Bone marrow may be the preferable graft source in recipients homozygous for HLA-C group 2 ligands for inhibitory killer Ig-like receptors

HLA class I molecules participate in natural killer cell regulation by acting as ligands for inhibitory killer cell Ig-like receptors (KIRs). One individual may express one or more inhibitory KIR lacking the corresponding HLA ligand. The role of this 'missing KIR ligand' constellation in hematopoietic SCT (HSCT) remains controversial and depends on incompletely defined transplant variables. We have retrospectively analyzed the effects of missing HLA-C group 1/2 and Bw4 KIR ligands in the recipients on the outcome in 382 HSCT, comparing 118 BMT to 264 PBSC transplants (PBSCT). In the multivariate Cox analysis of PBSCT, poor PFS was observed in homozygous HLA-C group 2 (C2/2) recipients (risk ratio (RR), 1.59; P=0.026). In contrast, C2 homozygosity was not unfavorable after BMT (RR, 0.68; P=0.16). C2 homozygous recipients (n=68) had better PFS after BMT than after PBSCT (RR, 0.17; P=0.001), due to fewer relapses (RR, 0.27; P=0.018). Missing Bw4 favorably influenced PFS after BMT (RR, 0.56; P=0.04), but not after PBSCT. These data suggest opposite effects of missing KIR ligands in BMT vs PBSCT. Larger studies are required to reassess whether BMT should be preferred to PBSCT as an option for C2/C2 recipients.     

The Asilomar Survey: Stakeholders’ Opinions on Ethical Issues Related to Brain-Computer Interfacing

Brain-Computer Interface (BCI) research and (future) applications raise important ethical issues that need to be addressed to promote societal acceptance and adequate policies. Here we report on a survey we conducted among 145 BCI researchers at the 4^th International BCI conference, which took place in May–June 2010 in Asilomar, California. We assessed respondents’ opinions about a number of topics. First, we investigated preferences for terminology and definitions relating to BCIs. Second, we assessed respondents’ expectations on the marketability of different BCI applications (BCIs for healthy people, BCIs for assistive technology, BCIs-controlled neuroprostheses and BCIs as therapy tools). Third, we investigated opinions about ethical issues related to BCI research for the development of assistive technology: informed consent process with locked-in patients, risk-benefit analyses, team responsibility, consequences of BCI on patients’ and families’ lives, liability and personal identity and interaction with the media. Finally, we asked respondents which issues are urgent in BCI research.     

Prognostic Relevance of Number and Ratio of Metastatic Lymph Nodes in Resected Pancreatic, Ampullary, and Distal Bile Duct Carcinomas

Background

Lymph node ratio (LNR) may be more useful than nodal (N) status in prognostic subclassification of adenocarcinomas after pancreatoduodenectomy. Ampullary (AC), biliary (DBC), and pancreatic (PC) adenocarcinomas are biologically distinct, and nodal involvement may have different prognostic importance among these separate cancers.

Methods

We included 179 consecutive pancreatoduodenectomies for PC, AC, or DBC, and performed standardized histopathologic evaluation, including prospective registration and retrospective reevaluation of the cancer origin. Associations between histopathologic variables and LNR, N status, and number of metastatic nodes were evaluated. Unadjusted and adjusted survival analysis was performed.

Results

Overall 5 year survival was 6 % for PC (n = 72), 26 % for DBC (n = 46), and 46 % for AC (n = 61). Lymph node involvement was more frequent in PC (75 %) than in AC (48 %) and DBC (57 %). In PC, N status did not discriminate between prognostic groups (N1 vs. N0; p = 0.31). However, increasing LNR was associated with poorer survival in unadjusted analysis, as well as when adjusting for margin involvement, degree of differentiation, and tumor diameter (p = 0.032; hazard ratio 1.87, 95 % confidence interval 1.06–3.31). In AC and DBC, N status clearly discriminated between subgroups of patients with different long-term survival in unadjusted and adjusted survival analysis (N1 vs. N0; p < 0.001), whereas number of metastatic nodes and LNR did not predict survival among node-positive resections.

Conclusions

The predictive value of nodal involvement depends on the type of cancer within the pancreatic head. In AC and DBC, N status adequately discriminates between good and poor prognosis. In PC, LNR may be more powerful in prognostic subclassification.     

Muscle phenotype in patients with myotonic dystrophy type 1

Introduction: The pathogenesis of muscle involvement in patients with myotonic dystrophy type 1 (DM1) is not well understood. In this study, we characterized the muscle phenotype in patients with confirmed DM1. Methods: In 38 patients, muscle strength was tested by hand‐held dynamometry. Myotonia was evaluated by a handgrip test and by analyzing the decrement of the compound muscle action potential. Muscle biopsies were assessed for morphological changes and Na⁺‐K⁺ pump content. Results: Muscle strength correlated with a decline in Na⁺‐K⁺ pump content (r = 0.60, P < 0.001) and with CTG expansion. CTG expansion did not correlate with severity of myotonia, proximal histopathological changes, or Na⁺‐K⁺ pump content. Histopathologically, we found few centrally placed nuclei (range 0.2–6.9%). Conclusions: The main findings of this study are that muscle weakness correlated inversely with CTG expansion and that central nuclei are not a prominent feature of proximal muscles in DM1. Muscle Nerve 47:409‐415, 2013     

Impact of natural killer cell dose and donor killer-cell immunoglobulin-like receptor (KIR) genotype on outcome following human leucocyte antigen-identical haematopoietic stem cell transplantation

To define the role of quantitative graft composition and donor killer-cell immunoglobulin-like receptor (KIR) genotype in clinical outcome following unmanipulated peripheral blood stem cell transplantation (PBSCT) from human leucocyte antigen (HLA)-identical siblings, 43 consecutive transplants for haematological malignancies were analysed retrospectively. Twenty-four patients underwent myeloablative conditioning and 19 received busulphan/fludarabine-based reduced intensity conditioning (RIC). In patients with acute myelogenous leukaemia or myelodysplastic syndrome (AML/MDS; n = 18), no relapse occurred following transplants meeting both a high (above median) natural killer (NK) cell count and missing HLA-ligand(s) to donor's KIR(s), compared to all other AML/MDS patients (0% versus 44%; P = 0.049). Missing HLA-B and/or HLA-C ligand combined with missing HLA-A3/11 (KIR3DL2 unblocked) predicted for reduced relapse incidence regardless of diagnosis or conditioning type (P = 0.028). Moreover, in AML/MDS patients, this constellation predicted superior overall survival (OS) (P = 0.046). Transplants with more than two different activating donor KIRs were associated with an increased risk for non-relapse mortality (NRM), both by univariate and multivariate analysis. Quantitative graft composition had a significant impact exclusively in RIC transplants. Here, a trend towards reduced relapse incidence was found in patients receiving high numbers of NK cells (16% versus 54%; P = 0.09). In patients receiving high versus low T cell numbers, OS was superior (83% versus 37%; P = 0.01), due mainly to reduced NRM (0% versus 33%; P = 0.046). By multivariate analysis, relapse risk was decreased significantly in patients receiving high NK cell numbers (P = 0.039). These data suggest that both the number of transplanted NK cells and the donor KIR genotype play a role in graft-versus-malignancy mechanisms in HLA-identical PBSCT.