The nociceptin receptor inhibits axonal regeneration and recovery from spinal cord injury

Axonal growth after traumatic spinal cord injury is limited by endogenous inhibitors, selective blockade of which promotes partial neurological recovery. The partial repair phenotypes suggest that compensatory pathways limit improvement. Gene expression profiles of mice deficient in Ngr1, which encodes a receptor for myelin-associated inhibitors of axonal regeneration such as Nogo, revealed that trauma increased the mRNA expression of ORL1, which encodes the receptor for the opioid-related peptide nociceptin. Endogenous and overexpressed ORL1 coimmunoprecipitated with immature NgR1 protein, and ORL1 enhanced the O-linked glycosylation and surface expression of NgR1 in HEK293T and Neuro2A cells and primary neurons. ORL1 overexpression inhibited cortical neuron axon regeneration independently of NgR1. Furthermore, regeneration was inhibited by an ORL1 agonist and enhanced by the ORL1 antagonist J113397 through a ROCK-dependent mechanism. Mice treated with J113397 after dorsal hemisection of the mid-thoracic spinal cord recovered greater locomotor function and exhibited lumbar raphespinal axon sprouting. These effects were further enhanced by combined Ngr1 deletion and ORL1 inhibition. Thus, ORL1 limits neural repair directly and indirectly by enhancing NgR1 maturation, and ORL1 antagonists enhance recovery from traumatic CNS injuries in wild-type and Ngr1 null mice.

Brivaracetam, but not ethosuximide, reverses memory impairments in an Alzheimer's disease mouse model

Introduction

Recent studies have shown that several strains of transgenic Alzheimer’s disease (AD) mice overexpressing the amyloid precursor protein (APP) have cortical hyperexcitability, and their results have suggested that this aberrant network activity may be a mechanism by which amyloid-β (Aβ) causes more widespread neuronal dysfunction. Specific anticonvulsant therapy reverses memory impairments in various transgenic mouse strains, but it is not known whether reduction of epileptiform activity might serve as a surrogate marker of drug efficacy for memory improvement in AD mouse models.

Methods

Transgenic AD mice (APP/PS1 and 3xTg-AD) were chronically implanted with dural electroencephalography electrodes, and epileptiform activity was correlated with spatial memory function and transgene-specific pathology. The antiepileptic drugs ethosuximide and brivaracetam were tested for their ability to suppress epileptiform activity and to reverse memory impairments and synapse loss in APP/PS1 mice.

Results

We report that in two transgenic mouse models of AD (APP/PS1 and 3xTg-AD), the presence of spike-wave discharges (SWDs) correlated with impairments in spatial memory. Both ethosuximide and brivaracetam reduce mouse SWDs, but only brivaracetam reverses memory impairments in APP/PS1 mice.

Conclusions

Our data confirm an intriguing therapeutic role of anticonvulsant drugs targeting synaptic vesicle protein 2A across AD mouse models. Chronic ethosuximide dosing did not reverse spatial memory impairments in APP/PS1 mice, despite reduction of SWDs. Our data indicate that SWDs are not a reliable surrogate marker of appropriate target engagement for reversal of memory dysfunction in APP/PS1 mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-015-0110-9) contains supplementary material, which is available to authorized users.

A phase Ib multiple ascending dose study of the safety, tolerability, and central nervous system availability of AZD0530 (saracatinib) in Alzheimer's disease

Introduction

Despite significant progress, a disease-modifying therapy for Alzheimer’s disease (AD) has not yet been developed. Recent findings implicate soluble oligomeric amyloid beta as the most relevant protein conformation in AD pathogenesis. We recently described a signaling cascade whereby oligomeric amyloid beta binds to cellular prion protein on the neuronal cell surface, activating intracellular Fyn kinase to mediate synaptotoxicity. Fyn kinase has been implicated in AD pathophysiology both in in vitro models and in human subjects, and is a promising new therapeutic target for AD. Herein, we present a Phase Ib trial of the repurposed investigational drug AZD0530, a Src family kinase inhibitor specific for Fyn and Src kinase, for the treatment of patients with mild-to-moderate AD.

Methods

The study was a 4-week Phase Ib multiple ascending dose, randomized, double-blind, placebo-controlled trial of AZD0530 in AD patients with Mini-Mental State Examination (MMSE) scores ranging from 16 to 26. A total of 24 subjects were recruited in three sequential groups, with each randomized to receive oral AZD0530 at doses of 50 mg, 100 mg, 125 mg, or placebo daily for 4 weeks. The drug:placebo ratio was 3:1. Primary endpoints were safety, tolerability, and cerebrospinal fluid (CSF) penetration of AZD0530. Secondary endpoints included changes in clinical efficacy measures (Alzheimer’s Disease Assessment Scale – cognitive subscale, MMSE, Alzheimer’s Disease Cooperative Study – Activities of Daily Living Inventory, Neuropsychiatric Inventory, and Clinical Dementia Rating Scale – Sum of Boxes) and regional cerebral glucose metabolism measured by fluorodeoxyglucose positron emission tomography.

Results

AZD0530 was generally safe and well tolerated across doses. One subject receiving 125 mg of AZD0530 was discontinued from the study due to the development of congestive heart failure and atypical pneumonia, which were considered possibly related to the study drug. Plasma/CSF ratio of AZD0530 was 0.4. The 100 mg and 125 mg doses achieved CSF drug levels corresponding to brain levels that rescued memory deficits in transgenic mouse models. One-month treatment with AZD0530 had no significant effect on clinical efficacy measures or regional cerebral glucose metabolism.

Conclusions

AZD0530 is reasonably safe and well tolerated in patients with mild-to-moderate AD, achieving substantial central nervous system penetration with oral dosing at 100–125 mg. Targeting Fyn kinase may be a promising therapeutic approach in AD, and a larger Phase IIa clinical trial of AZD0530 for the treatment of patients with AD has recently launched.

Trial registration

ClinicalTrials.gov: NCT01864655. Registered 12 June 2014.