Behavioural Pharmacology: October 2013 - Volume 24 - Issue - p e1 doi: 10.1097/01.fbp.0000434681.66635.67

Purpose: Minimizing tip-apex distance (TAD) has been shown to reduce clinical failure of extramedullary sliding hip screws used to fix peritrochanteric fractures. There is debate regarding the optimal position of the lag screw in the femoral head when a cephalomedullary nail is used to treat a peritrochanteric fracture. Some authors suggest the TAD should be minimized as with an extramedullary sliding hip screw, while others suggest the lag screw should be placed inferior within the femoral head. The primary goal of this study was to determine which of 5 possible lag screw positions in the femoral head provides greatest mechanical stiffness and/or load-to-failure for an unstable peritrochanteric fracture treated with a cepha-clomedullary nail. The secondary goal was to determine if there is a linear correlation between implant-femur mechanical stiffness and/or load to failure (dependent variables) with a series of five radiographic measurements (independent variables) of distance from the lag screw tip to the femoral head apex. Method: Long Gamma 3 Nails (Stryker, Mahwah, NJ) were inserted into 30 left synthetic femurs (Pacific Research Laboratories, Vashon, WA). An unstable four-part fracture was created, anatomically reduced, and repaired using one of 5 lag screw placements in the femoral head: 1. superior (n=6), 2. inferior (n=6), 3. anterior (n=6), 4. posterior (n=6), 5. central (n=6). All specimens were radiographed in the anterioposterior and lateral planes, and radiographic measurements including TAD and a calcar referenced tip-apex distance (CalTAD) were calculated. All specimens were tested for axial, lateral, and torsional stiffness, and then loaded-to-failure in the axial position using an Instron 8874 (Canton, MA). ANOVA was used to compare means of the five treatment groups. Linear regression analysis was used to compare stiffness and load-to-failure (dependant variables) with radiographic measurements (independent variables). A post hoc power analysis was performed. Results: The inferior lag screw position had significantly greater mean axial stiffness than superior (p<0.01), anterior (p=0.02) and posterior (p=0.04) positions. Analysis revealed significantly less mean torsional stiffness for the superior lag screw position compared to other lag screw positions (p<0.01 all 4 pairings). No statistical differences were noted for lateral stiffness. Superior and central lag screw positions had significantly greater mean load-to-failure than anterior (p<0.01 and p=0.02) and posterior (p<0.01 and p=0.05) positions. There were significant negative linear correlations between stiffness tests with CalTAD, and load-to-failure with TAD. Power was greater than 95% for axial stiffness, torsional stiffness and load-to-failure tests. Conclusion: Position of the lag screw in the femoral head affects the biomechanical properties of the implant-femur construct. Central placement of the lag screw with minimization of TAD may provide the best combination of stiffness and load-to-failure.

Abstract CRM1 (Xpo1) is the major export factor for proteins from the nucleus to the cytoplasm, including tumor suppressors (TSPs) and other modulators of proliferative responses such as p53, FOXO, c-Abl, pRB and IκB. Leptomycin B (LMB), a non-drug like natural product is a potent inhibitor of CRM1-mediated nucleocytoplasmic transport. LMB and related analogs trap TSPs and other proteins in the nucleus, forcing neoplastic cells into apoptosis while normal cells undergo reversible cell cycle arrest. However, LMB has limited efficacy in vivo due to its severe gastrointestinal toxicity. Here, we describe our lead compound KPT-0127 a novel small molecule, water soluble, drug-like, selective, irreversible CRM1 antagonist. Like LMB, KPT-0127 forms a covalent bond with Cys528 in the CRM1 cargo-binding pocket, abrogating most, but not all, export functions of CRM1. KPT-0127 exerts a potent (EC50 300-400nM) and prolonged inhibition of CRM1- mediated HIV-1 Rev, forkhead (FOXO), and p53 nuclear export in a variety of normal and transformed cell lines. In cytotoxicity assays, KPT-0127 showed high potency in most hematologic cancer cell lines (EC50 <500nM, with leukemia and lymphoma lines often <100nM) and variable activity in solid tumor cell lines (EC50 90-2000nM), with colon and melanoma cells being the most sensitive (EC50< 100 nM). By contrast, normal cells were largely unaffected by treatment with KPT-0127 (EC50 >5-10µM). Studies in the HCT-116 colon cancer cell line suggested that KPT-0127 dose dependently increases the nuclear levels of p53 and appears to induce cell cycle arrest at both the G1/S and G2/M checkpoints, prior to inducing apoptosis. In normal peripheral blood mononuclear cells (PBMCs) and in Hut78 leukemia cells, KPT-0127 potently increased the nuclear levels of IκB. However, KPT-0127 induced cell death of Hut78 cells with no effect on normal PBMCs. In drug combination studies, KPT-0127 showed additive or synergistic cytotoxicity activity with either 5-FU, carboplatin, or doxorubicin. Mechanism of action studies demonstrated that the Cys528 residue in the cargo-binding pocket of CRM1 is essential for the inhibitory effect of KPT-0127. Mutagenesis of Cys528 to a Ser completely abrogated KPT-0127 inhibition. KPT-0128, the transisomer of KPT-0127, shows little effect on both HIV-Rev nuclear export and in cytotoxicity assays (EC50s > 10μM), supporting the specificity of KPT-0127 for CRM1. Moreover, the selectivity of KTP-0127 was demonstrated across a panel of 37 proteins including several cysteine proteases. In single dose mouse toxicology studies, KPT-0127 was generally well tolerated (oral or SC) up to 560 mg/kg, and no deaths were observed. SC dosing daily for 5 days up to 100mg/kg (the highest dose tested) showed no behavioral, clinical chemistry, or hematogical effects in mice; Pharmacokinetics of KPT-0127 is adequate and in vivo efficacy studies are currently being performed; results will be presented. All together, these data demonstrate that KPT-0127 represents a novel, tumor selective, and well-tolerated irreversible Crm1 inhibitor which may be suitable for clinical development both as a single agent and in combination with standard therapies. Citation Information: Clin Cancer Res 2010;16(14 Suppl):A19.

RATIONALE:Various compounds believed to selectively interact with the 5-HT(2C) receptor have been demonstrated to alter the functioning of ascending dopamine systems. We postulated that this functional interaction may extend to the behavioural effects of drugs of abuse whose rewarding properties are critically dependent upon mesolimbic DA activity.OBJECTIVES:The present studies focussed on interactions between 5-HT(2C) receptor function and behaviours either supported or induced by nicotine.METHODS:The effect of Ro 60-0175, a 5-HT(2C) agonist, was assessed for its ability to modify 1) nicotine-induced locomotor activity in nicotine-treated rats, 2) lever pressing maintained by either food or IV administration of nicotine, and 3) the development of nicotine-induced hyperactivity. The specificity of this effect was further measured in locomotor activity studies by additional administration of the selective 5-HT(2C) antagonist SB 242,084.RESULTS:Ro 60-0175 (0.3-3 mg/kg SC) dose-dependently reduced nicotine-induced activity, an effect which was reversed by SB 242,084 (0.5 mg/kg IP), thus confirming receptor selectivity of the response. Responding both for food and nicotine on an FR5TO1 min schedule of reinforcement was reduced by Ro 60-0175 (0.1-1 mg/kg) with proportionally similar effects on responses for both types of reinforcer. Co-administration of Ro 60-0175 (1 mg/kg SC) and nicotine (0.4 mg/kg SC) for 10 days blocked the sensitised response that developed in subjects treated with nicotine alone.CONCLUSIONS:The present data support an involvement for the 5-HT(2C) receptor in mediating mesolimbic DA functioning as assessed by changes in behaviours indicative of nicotine reward.

There is accumulating evidence that apolipoprotein E (apoE) plays a role in regulating the response to and outcome following brain injury. The present study compared the histological outcome and recovery following an episode of global ischaemia in apoE-deficient mice and wild-type littermates (12-week-old males, n = 8 per group). Transient global ischaemia was induced for a period of 17 min and the animals were allowed to recover for 72 h. Transient global ischaemia induced selective neuronal degeneration in several brain regions in wild-type mice. There was statistically significant increased ischaemic neuronal damage in apoE-deficient mice compared with wild-type mice in six of the seven regions examined (hippocampal regions CA1, CA3/CA4 and dentate gyrus; thalamus; cortex and caudate nucleus; P < 0.05). The data substantiate a role for apoE in modifying the response of the CNS to acute injury.

Lamotrigine is a novel anticonvulsant drug which also stabilises mood in bipolar illness via an unknown mechanism. We report the concentration-dependent inhibition of 5-hydroxytryptamine (5-HT) uptake in both human platelets and rat brain synaptosomes (IC50s were 240 and 474 μM, respectively) by lamotrigine. Synaptosomal uptake of noradrenaline (IC50 239 μM) and dopamine (IC50 322 μM) was also inhibited. Tetrodotoxin failed to modulate 5-HT uptake suggesting that sodium channel blockade does not mediate the lamotrigine effect. Lithium, sodium valproate, zonisamide, and carbamazepine all possess anti-manic activity but only the latter inhibited 5-HT uptake. The inhibition of the p-chloroamphetamine-induced 5-HT syndrome in rats suggests that lamotrigine also inhibits 5-HT uptake in vivo. These effects probably reflect an affinity for biogenic amine transporters. However, at present, it remains uncertain whether, at clinically effective doses, these effects contribute significantly to the efficacy of lamotrigine in bipolar illness.

This article provides a brief review of animal models used for the development of antipsychotic drugs. Traditionally, dopamine has been regarded as the neuro-transmitter involved in the aetiology of schizophrenia and models have evolved largely around this neurotransmitter. This tends to lead to a circular line of research: dopamine-based models tend to detect dopaminergic drugs, which are clinically efficacious but are not ideal. It is suggested that newer models which use nonpharmacological techniques to disrupt behaviour (e.g. social isolation and hippocampal lesions) and which bear some construct validity to the disease, may provide a fruitful avenue for the detection of antipsychotics that operate through novel mechanisms. Preliminary studies with these models are encouraging, although pharmacological validation is urgently required to establish whether these models have the predictive validity evident with dopamine-based models.

Using apolipoprotein E knockout mice derived from the Maeda source [Piedrahita J. A. et al. (1992) Proc. natn. Acnd. Sci U.S.A. 89, 4471-4475], we have studied the influence of apolipoprotein E gene deletion on normal CNS function by neurological tests and water maze learning, hippocampal ultrastructure assessed by quantitative immunocytochemistry and electron microscopy, CNS plasticity, i.e. hippocampal long-term potentiation and amygdaloid kindling, and CNS repair, i.e. synaptic recovery in the hippocampus following deafferentation. In each study there was little difference between the apolipoprotein E knockout mice and wild-type controls of similar age and genetic background. Apolipoprotein E knockout mice aged eight months demonstrated accurate spatial learning and normal neurological function. Synaptophysin and microtubule-associated protein 2 immunohistochemistry and electron microscopic analysis of these animals revealed that the hippocampal synaptic and dendritic densities were similar between genotypes. The induction and maintenance of kindled seizures and hippocampal long-term potentiation were indistinguishable between groups. Finally, unilateral entorhinal cortex lesions produced a marked loss of hippocampal synaptophysin immunoreactivity in both groups and a marked up-regulation of apolipoprotein E in the wild-type group. Both apolipoprotein E knockout and wild-type groups showed immunohistochemical evidence of reactive synaptogenesis, although the apolipoprotein E knockout group may have initially shown greater synaptic loss.It is suggested that either apolipoprotein E is of no importance in the maintenance of synaptic integrity and in processes of CNS plasticity and repair, or more likely, alternative (apolipo)proteins may compensate for the loss of apolipoprotein E in the knockout animals. (C) 1998 IBRO. Published by Elsevier Science Ltd.